Loading...
Note: File does not exist in v3.1.
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
4 *
5 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
6 *
7 * Interactivity improvements by Mike Galbraith
8 * (C) 2007 Mike Galbraith <efault@gmx.de>
9 *
10 * Various enhancements by Dmitry Adamushko.
11 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
12 *
13 * Group scheduling enhancements by Srivatsa Vaddagiri
14 * Copyright IBM Corporation, 2007
15 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
16 *
17 * Scaled math optimizations by Thomas Gleixner
18 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
19 *
20 * Adaptive scheduling granularity, math enhancements by Peter Zijlstra
21 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
22 */
23#include "sched.h"
24
25/*
26 * Targeted preemption latency for CPU-bound tasks:
27 *
28 * NOTE: this latency value is not the same as the concept of
29 * 'timeslice length' - timeslices in CFS are of variable length
30 * and have no persistent notion like in traditional, time-slice
31 * based scheduling concepts.
32 *
33 * (to see the precise effective timeslice length of your workload,
34 * run vmstat and monitor the context-switches (cs) field)
35 *
36 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
37 */
38unsigned int sysctl_sched_latency = 6000000ULL;
39static unsigned int normalized_sysctl_sched_latency = 6000000ULL;
40
41/*
42 * The initial- and re-scaling of tunables is configurable
43 *
44 * Options are:
45 *
46 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
47 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
48 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
49 *
50 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
51 */
52unsigned int sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
53
54/*
55 * Minimal preemption granularity for CPU-bound tasks:
56 *
57 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
58 */
59unsigned int sysctl_sched_min_granularity = 750000ULL;
60static unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
61
62/*
63 * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
64 */
65static unsigned int sched_nr_latency = 8;
66
67/*
68 * After fork, child runs first. If set to 0 (default) then
69 * parent will (try to) run first.
70 */
71unsigned int sysctl_sched_child_runs_first __read_mostly;
72
73/*
74 * SCHED_OTHER wake-up granularity.
75 *
76 * This option delays the preemption effects of decoupled workloads
77 * and reduces their over-scheduling. Synchronous workloads will still
78 * have immediate wakeup/sleep latencies.
79 *
80 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
81 */
82unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
83static unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
84
85const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
86
87int sched_thermal_decay_shift;
88static int __init setup_sched_thermal_decay_shift(char *str)
89{
90 int _shift = 0;
91
92 if (kstrtoint(str, 0, &_shift))
93 pr_warn("Unable to set scheduler thermal pressure decay shift parameter\n");
94
95 sched_thermal_decay_shift = clamp(_shift, 0, 10);
96 return 1;
97}
98__setup("sched_thermal_decay_shift=", setup_sched_thermal_decay_shift);
99
100#ifdef CONFIG_SMP
101/*
102 * For asym packing, by default the lower numbered CPU has higher priority.
103 */
104int __weak arch_asym_cpu_priority(int cpu)
105{
106 return -cpu;
107}
108
109/*
110 * The margin used when comparing utilization with CPU capacity.
111 *
112 * (default: ~20%)
113 */
114#define fits_capacity(cap, max) ((cap) * 1280 < (max) * 1024)
115
116/*
117 * The margin used when comparing CPU capacities.
118 * is 'cap1' noticeably greater than 'cap2'
119 *
120 * (default: ~5%)
121 */
122#define capacity_greater(cap1, cap2) ((cap1) * 1024 > (cap2) * 1078)
123#endif
124
125#ifdef CONFIG_CFS_BANDWIDTH
126/*
127 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
128 * each time a cfs_rq requests quota.
129 *
130 * Note: in the case that the slice exceeds the runtime remaining (either due
131 * to consumption or the quota being specified to be smaller than the slice)
132 * we will always only issue the remaining available time.
133 *
134 * (default: 5 msec, units: microseconds)
135 */
136unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
137#endif
138
139static inline void update_load_add(struct load_weight *lw, unsigned long inc)
140{
141 lw->weight += inc;
142 lw->inv_weight = 0;
143}
144
145static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
146{
147 lw->weight -= dec;
148 lw->inv_weight = 0;
149}
150
151static inline void update_load_set(struct load_weight *lw, unsigned long w)
152{
153 lw->weight = w;
154 lw->inv_weight = 0;
155}
156
157/*
158 * Increase the granularity value when there are more CPUs,
159 * because with more CPUs the 'effective latency' as visible
160 * to users decreases. But the relationship is not linear,
161 * so pick a second-best guess by going with the log2 of the
162 * number of CPUs.
163 *
164 * This idea comes from the SD scheduler of Con Kolivas:
165 */
166static unsigned int get_update_sysctl_factor(void)
167{
168 unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
169 unsigned int factor;
170
171 switch (sysctl_sched_tunable_scaling) {
172 case SCHED_TUNABLESCALING_NONE:
173 factor = 1;
174 break;
175 case SCHED_TUNABLESCALING_LINEAR:
176 factor = cpus;
177 break;
178 case SCHED_TUNABLESCALING_LOG:
179 default:
180 factor = 1 + ilog2(cpus);
181 break;
182 }
183
184 return factor;
185}
186
187static void update_sysctl(void)
188{
189 unsigned int factor = get_update_sysctl_factor();
190
191#define SET_SYSCTL(name) \
192 (sysctl_##name = (factor) * normalized_sysctl_##name)
193 SET_SYSCTL(sched_min_granularity);
194 SET_SYSCTL(sched_latency);
195 SET_SYSCTL(sched_wakeup_granularity);
196#undef SET_SYSCTL
197}
198
199void __init sched_init_granularity(void)
200{
201 update_sysctl();
202}
203
204#define WMULT_CONST (~0U)
205#define WMULT_SHIFT 32
206
207static void __update_inv_weight(struct load_weight *lw)
208{
209 unsigned long w;
210
211 if (likely(lw->inv_weight))
212 return;
213
214 w = scale_load_down(lw->weight);
215
216 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
217 lw->inv_weight = 1;
218 else if (unlikely(!w))
219 lw->inv_weight = WMULT_CONST;
220 else
221 lw->inv_weight = WMULT_CONST / w;
222}
223
224/*
225 * delta_exec * weight / lw.weight
226 * OR
227 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
228 *
229 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
230 * we're guaranteed shift stays positive because inv_weight is guaranteed to
231 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
232 *
233 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
234 * weight/lw.weight <= 1, and therefore our shift will also be positive.
235 */
236static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
237{
238 u64 fact = scale_load_down(weight);
239 u32 fact_hi = (u32)(fact >> 32);
240 int shift = WMULT_SHIFT;
241 int fs;
242
243 __update_inv_weight(lw);
244
245 if (unlikely(fact_hi)) {
246 fs = fls(fact_hi);
247 shift -= fs;
248 fact >>= fs;
249 }
250
251 fact = mul_u32_u32(fact, lw->inv_weight);
252
253 fact_hi = (u32)(fact >> 32);
254 if (fact_hi) {
255 fs = fls(fact_hi);
256 shift -= fs;
257 fact >>= fs;
258 }
259
260 return mul_u64_u32_shr(delta_exec, fact, shift);
261}
262
263
264const struct sched_class fair_sched_class;
265
266/**************************************************************
267 * CFS operations on generic schedulable entities:
268 */
269
270#ifdef CONFIG_FAIR_GROUP_SCHED
271
272/* Walk up scheduling entities hierarchy */
273#define for_each_sched_entity(se) \
274 for (; se; se = se->parent)
275
276static inline void cfs_rq_tg_path(struct cfs_rq *cfs_rq, char *path, int len)
277{
278 if (!path)
279 return;
280
281 if (cfs_rq && task_group_is_autogroup(cfs_rq->tg))
282 autogroup_path(cfs_rq->tg, path, len);
283 else if (cfs_rq && cfs_rq->tg->css.cgroup)
284 cgroup_path(cfs_rq->tg->css.cgroup, path, len);
285 else
286 strlcpy(path, "(null)", len);
287}
288
289static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
290{
291 struct rq *rq = rq_of(cfs_rq);
292 int cpu = cpu_of(rq);
293
294 if (cfs_rq->on_list)
295 return rq->tmp_alone_branch == &rq->leaf_cfs_rq_list;
296
297 cfs_rq->on_list = 1;
298
299 /*
300 * Ensure we either appear before our parent (if already
301 * enqueued) or force our parent to appear after us when it is
302 * enqueued. The fact that we always enqueue bottom-up
303 * reduces this to two cases and a special case for the root
304 * cfs_rq. Furthermore, it also means that we will always reset
305 * tmp_alone_branch either when the branch is connected
306 * to a tree or when we reach the top of the tree
307 */
308 if (cfs_rq->tg->parent &&
309 cfs_rq->tg->parent->cfs_rq[cpu]->on_list) {
310 /*
311 * If parent is already on the list, we add the child
312 * just before. Thanks to circular linked property of
313 * the list, this means to put the child at the tail
314 * of the list that starts by parent.
315 */
316 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
317 &(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list));
318 /*
319 * The branch is now connected to its tree so we can
320 * reset tmp_alone_branch to the beginning of the
321 * list.
322 */
323 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
324 return true;
325 }
326
327 if (!cfs_rq->tg->parent) {
328 /*
329 * cfs rq without parent should be put
330 * at the tail of the list.
331 */
332 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
333 &rq->leaf_cfs_rq_list);
334 /*
335 * We have reach the top of a tree so we can reset
336 * tmp_alone_branch to the beginning of the list.
337 */
338 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
339 return true;
340 }
341
342 /*
343 * The parent has not already been added so we want to
344 * make sure that it will be put after us.
345 * tmp_alone_branch points to the begin of the branch
346 * where we will add parent.
347 */
348 list_add_rcu(&cfs_rq->leaf_cfs_rq_list, rq->tmp_alone_branch);
349 /*
350 * update tmp_alone_branch to points to the new begin
351 * of the branch
352 */
353 rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list;
354 return false;
355}
356
357static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
358{
359 if (cfs_rq->on_list) {
360 struct rq *rq = rq_of(cfs_rq);
361
362 /*
363 * With cfs_rq being unthrottled/throttled during an enqueue,
364 * it can happen the tmp_alone_branch points the a leaf that
365 * we finally want to del. In this case, tmp_alone_branch moves
366 * to the prev element but it will point to rq->leaf_cfs_rq_list
367 * at the end of the enqueue.
368 */
369 if (rq->tmp_alone_branch == &cfs_rq->leaf_cfs_rq_list)
370 rq->tmp_alone_branch = cfs_rq->leaf_cfs_rq_list.prev;
371
372 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
373 cfs_rq->on_list = 0;
374 }
375}
376
377static inline void assert_list_leaf_cfs_rq(struct rq *rq)
378{
379 SCHED_WARN_ON(rq->tmp_alone_branch != &rq->leaf_cfs_rq_list);
380}
381
382/* Iterate thr' all leaf cfs_rq's on a runqueue */
383#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
384 list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list, \
385 leaf_cfs_rq_list)
386
387/* Do the two (enqueued) entities belong to the same group ? */
388static inline struct cfs_rq *
389is_same_group(struct sched_entity *se, struct sched_entity *pse)
390{
391 if (se->cfs_rq == pse->cfs_rq)
392 return se->cfs_rq;
393
394 return NULL;
395}
396
397static inline struct sched_entity *parent_entity(struct sched_entity *se)
398{
399 return se->parent;
400}
401
402static void
403find_matching_se(struct sched_entity **se, struct sched_entity **pse)
404{
405 int se_depth, pse_depth;
406
407 /*
408 * preemption test can be made between sibling entities who are in the
409 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
410 * both tasks until we find their ancestors who are siblings of common
411 * parent.
412 */
413
414 /* First walk up until both entities are at same depth */
415 se_depth = (*se)->depth;
416 pse_depth = (*pse)->depth;
417
418 while (se_depth > pse_depth) {
419 se_depth--;
420 *se = parent_entity(*se);
421 }
422
423 while (pse_depth > se_depth) {
424 pse_depth--;
425 *pse = parent_entity(*pse);
426 }
427
428 while (!is_same_group(*se, *pse)) {
429 *se = parent_entity(*se);
430 *pse = parent_entity(*pse);
431 }
432}
433
434#else /* !CONFIG_FAIR_GROUP_SCHED */
435
436#define for_each_sched_entity(se) \
437 for (; se; se = NULL)
438
439static inline void cfs_rq_tg_path(struct cfs_rq *cfs_rq, char *path, int len)
440{
441 if (path)
442 strlcpy(path, "(null)", len);
443}
444
445static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
446{
447 return true;
448}
449
450static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
451{
452}
453
454static inline void assert_list_leaf_cfs_rq(struct rq *rq)
455{
456}
457
458#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
459 for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
460
461static inline struct sched_entity *parent_entity(struct sched_entity *se)
462{
463 return NULL;
464}
465
466static inline void
467find_matching_se(struct sched_entity **se, struct sched_entity **pse)
468{
469}
470
471#endif /* CONFIG_FAIR_GROUP_SCHED */
472
473static __always_inline
474void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
475
476/**************************************************************
477 * Scheduling class tree data structure manipulation methods:
478 */
479
480static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
481{
482 s64 delta = (s64)(vruntime - max_vruntime);
483 if (delta > 0)
484 max_vruntime = vruntime;
485
486 return max_vruntime;
487}
488
489static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
490{
491 s64 delta = (s64)(vruntime - min_vruntime);
492 if (delta < 0)
493 min_vruntime = vruntime;
494
495 return min_vruntime;
496}
497
498static inline bool entity_before(struct sched_entity *a,
499 struct sched_entity *b)
500{
501 return (s64)(a->vruntime - b->vruntime) < 0;
502}
503
504#define __node_2_se(node) \
505 rb_entry((node), struct sched_entity, run_node)
506
507static void update_min_vruntime(struct cfs_rq *cfs_rq)
508{
509 struct sched_entity *curr = cfs_rq->curr;
510 struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline);
511
512 u64 vruntime = cfs_rq->min_vruntime;
513
514 if (curr) {
515 if (curr->on_rq)
516 vruntime = curr->vruntime;
517 else
518 curr = NULL;
519 }
520
521 if (leftmost) { /* non-empty tree */
522 struct sched_entity *se = __node_2_se(leftmost);
523
524 if (!curr)
525 vruntime = se->vruntime;
526 else
527 vruntime = min_vruntime(vruntime, se->vruntime);
528 }
529
530 /* ensure we never gain time by being placed backwards. */
531 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
532#ifndef CONFIG_64BIT
533 smp_wmb();
534 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
535#endif
536}
537
538static inline bool __entity_less(struct rb_node *a, const struct rb_node *b)
539{
540 return entity_before(__node_2_se(a), __node_2_se(b));
541}
542
543/*
544 * Enqueue an entity into the rb-tree:
545 */
546static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
547{
548 rb_add_cached(&se->run_node, &cfs_rq->tasks_timeline, __entity_less);
549}
550
551static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
552{
553 rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
554}
555
556struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
557{
558 struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline);
559
560 if (!left)
561 return NULL;
562
563 return __node_2_se(left);
564}
565
566static struct sched_entity *__pick_next_entity(struct sched_entity *se)
567{
568 struct rb_node *next = rb_next(&se->run_node);
569
570 if (!next)
571 return NULL;
572
573 return __node_2_se(next);
574}
575
576#ifdef CONFIG_SCHED_DEBUG
577struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
578{
579 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);
580
581 if (!last)
582 return NULL;
583
584 return __node_2_se(last);
585}
586
587/**************************************************************
588 * Scheduling class statistics methods:
589 */
590
591int sched_update_scaling(void)
592{
593 unsigned int factor = get_update_sysctl_factor();
594
595 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
596 sysctl_sched_min_granularity);
597
598#define WRT_SYSCTL(name) \
599 (normalized_sysctl_##name = sysctl_##name / (factor))
600 WRT_SYSCTL(sched_min_granularity);
601 WRT_SYSCTL(sched_latency);
602 WRT_SYSCTL(sched_wakeup_granularity);
603#undef WRT_SYSCTL
604
605 return 0;
606}
607#endif
608
609/*
610 * delta /= w
611 */
612static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
613{
614 if (unlikely(se->load.weight != NICE_0_LOAD))
615 delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
616
617 return delta;
618}
619
620/*
621 * The idea is to set a period in which each task runs once.
622 *
623 * When there are too many tasks (sched_nr_latency) we have to stretch
624 * this period because otherwise the slices get too small.
625 *
626 * p = (nr <= nl) ? l : l*nr/nl
627 */
628static u64 __sched_period(unsigned long nr_running)
629{
630 if (unlikely(nr_running > sched_nr_latency))
631 return nr_running * sysctl_sched_min_granularity;
632 else
633 return sysctl_sched_latency;
634}
635
636/*
637 * We calculate the wall-time slice from the period by taking a part
638 * proportional to the weight.
639 *
640 * s = p*P[w/rw]
641 */
642static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
643{
644 unsigned int nr_running = cfs_rq->nr_running;
645 u64 slice;
646
647 if (sched_feat(ALT_PERIOD))
648 nr_running = rq_of(cfs_rq)->cfs.h_nr_running;
649
650 slice = __sched_period(nr_running + !se->on_rq);
651
652 for_each_sched_entity(se) {
653 struct load_weight *load;
654 struct load_weight lw;
655
656 cfs_rq = cfs_rq_of(se);
657 load = &cfs_rq->load;
658
659 if (unlikely(!se->on_rq)) {
660 lw = cfs_rq->load;
661
662 update_load_add(&lw, se->load.weight);
663 load = &lw;
664 }
665 slice = __calc_delta(slice, se->load.weight, load);
666 }
667
668 if (sched_feat(BASE_SLICE))
669 slice = max(slice, (u64)sysctl_sched_min_granularity);
670
671 return slice;
672}
673
674/*
675 * We calculate the vruntime slice of a to-be-inserted task.
676 *
677 * vs = s/w
678 */
679static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
680{
681 return calc_delta_fair(sched_slice(cfs_rq, se), se);
682}
683
684#include "pelt.h"
685#ifdef CONFIG_SMP
686
687static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
688static unsigned long task_h_load(struct task_struct *p);
689static unsigned long capacity_of(int cpu);
690
691/* Give new sched_entity start runnable values to heavy its load in infant time */
692void init_entity_runnable_average(struct sched_entity *se)
693{
694 struct sched_avg *sa = &se->avg;
695
696 memset(sa, 0, sizeof(*sa));
697
698 /*
699 * Tasks are initialized with full load to be seen as heavy tasks until
700 * they get a chance to stabilize to their real load level.
701 * Group entities are initialized with zero load to reflect the fact that
702 * nothing has been attached to the task group yet.
703 */
704 if (entity_is_task(se))
705 sa->load_avg = scale_load_down(se->load.weight);
706
707 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
708}
709
710static void attach_entity_cfs_rq(struct sched_entity *se);
711
712/*
713 * With new tasks being created, their initial util_avgs are extrapolated
714 * based on the cfs_rq's current util_avg:
715 *
716 * util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
717 *
718 * However, in many cases, the above util_avg does not give a desired
719 * value. Moreover, the sum of the util_avgs may be divergent, such
720 * as when the series is a harmonic series.
721 *
722 * To solve this problem, we also cap the util_avg of successive tasks to
723 * only 1/2 of the left utilization budget:
724 *
725 * util_avg_cap = (cpu_scale - cfs_rq->avg.util_avg) / 2^n
726 *
727 * where n denotes the nth task and cpu_scale the CPU capacity.
728 *
729 * For example, for a CPU with 1024 of capacity, a simplest series from
730 * the beginning would be like:
731 *
732 * task util_avg: 512, 256, 128, 64, 32, 16, 8, ...
733 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
734 *
735 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
736 * if util_avg > util_avg_cap.
737 */
738void post_init_entity_util_avg(struct task_struct *p)
739{
740 struct sched_entity *se = &p->se;
741 struct cfs_rq *cfs_rq = cfs_rq_of(se);
742 struct sched_avg *sa = &se->avg;
743 long cpu_scale = arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq)));
744 long cap = (long)(cpu_scale - cfs_rq->avg.util_avg) / 2;
745
746 if (cap > 0) {
747 if (cfs_rq->avg.util_avg != 0) {
748 sa->util_avg = cfs_rq->avg.util_avg * se->load.weight;
749 sa->util_avg /= (cfs_rq->avg.load_avg + 1);
750
751 if (sa->util_avg > cap)
752 sa->util_avg = cap;
753 } else {
754 sa->util_avg = cap;
755 }
756 }
757
758 sa->runnable_avg = sa->util_avg;
759
760 if (p->sched_class != &fair_sched_class) {
761 /*
762 * For !fair tasks do:
763 *
764 update_cfs_rq_load_avg(now, cfs_rq);
765 attach_entity_load_avg(cfs_rq, se);
766 switched_from_fair(rq, p);
767 *
768 * such that the next switched_to_fair() has the
769 * expected state.
770 */
771 se->avg.last_update_time = cfs_rq_clock_pelt(cfs_rq);
772 return;
773 }
774
775 attach_entity_cfs_rq(se);
776}
777
778#else /* !CONFIG_SMP */
779void init_entity_runnable_average(struct sched_entity *se)
780{
781}
782void post_init_entity_util_avg(struct task_struct *p)
783{
784}
785static void update_tg_load_avg(struct cfs_rq *cfs_rq)
786{
787}
788#endif /* CONFIG_SMP */
789
790/*
791 * Update the current task's runtime statistics.
792 */
793static void update_curr(struct cfs_rq *cfs_rq)
794{
795 struct sched_entity *curr = cfs_rq->curr;
796 u64 now = rq_clock_task(rq_of(cfs_rq));
797 u64 delta_exec;
798
799 if (unlikely(!curr))
800 return;
801
802 delta_exec = now - curr->exec_start;
803 if (unlikely((s64)delta_exec <= 0))
804 return;
805
806 curr->exec_start = now;
807
808 schedstat_set(curr->statistics.exec_max,
809 max(delta_exec, curr->statistics.exec_max));
810
811 curr->sum_exec_runtime += delta_exec;
812 schedstat_add(cfs_rq->exec_clock, delta_exec);
813
814 curr->vruntime += calc_delta_fair(delta_exec, curr);
815 update_min_vruntime(cfs_rq);
816
817 if (entity_is_task(curr)) {
818 struct task_struct *curtask = task_of(curr);
819
820 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
821 cgroup_account_cputime(curtask, delta_exec);
822 account_group_exec_runtime(curtask, delta_exec);
823 }
824
825 account_cfs_rq_runtime(cfs_rq, delta_exec);
826}
827
828static void update_curr_fair(struct rq *rq)
829{
830 update_curr(cfs_rq_of(&rq->curr->se));
831}
832
833static inline void
834update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
835{
836 u64 wait_start, prev_wait_start;
837
838 if (!schedstat_enabled())
839 return;
840
841 wait_start = rq_clock(rq_of(cfs_rq));
842 prev_wait_start = schedstat_val(se->statistics.wait_start);
843
844 if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
845 likely(wait_start > prev_wait_start))
846 wait_start -= prev_wait_start;
847
848 __schedstat_set(se->statistics.wait_start, wait_start);
849}
850
851static inline void
852update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
853{
854 struct task_struct *p;
855 u64 delta;
856
857 if (!schedstat_enabled())
858 return;
859
860 /*
861 * When the sched_schedstat changes from 0 to 1, some sched se
862 * maybe already in the runqueue, the se->statistics.wait_start
863 * will be 0.So it will let the delta wrong. We need to avoid this
864 * scenario.
865 */
866 if (unlikely(!schedstat_val(se->statistics.wait_start)))
867 return;
868
869 delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
870
871 if (entity_is_task(se)) {
872 p = task_of(se);
873 if (task_on_rq_migrating(p)) {
874 /*
875 * Preserve migrating task's wait time so wait_start
876 * time stamp can be adjusted to accumulate wait time
877 * prior to migration.
878 */
879 __schedstat_set(se->statistics.wait_start, delta);
880 return;
881 }
882 trace_sched_stat_wait(p, delta);
883 }
884
885 __schedstat_set(se->statistics.wait_max,
886 max(schedstat_val(se->statistics.wait_max), delta));
887 __schedstat_inc(se->statistics.wait_count);
888 __schedstat_add(se->statistics.wait_sum, delta);
889 __schedstat_set(se->statistics.wait_start, 0);
890}
891
892static inline void
893update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
894{
895 struct task_struct *tsk = NULL;
896 u64 sleep_start, block_start;
897
898 if (!schedstat_enabled())
899 return;
900
901 sleep_start = schedstat_val(se->statistics.sleep_start);
902 block_start = schedstat_val(se->statistics.block_start);
903
904 if (entity_is_task(se))
905 tsk = task_of(se);
906
907 if (sleep_start) {
908 u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
909
910 if ((s64)delta < 0)
911 delta = 0;
912
913 if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
914 __schedstat_set(se->statistics.sleep_max, delta);
915
916 __schedstat_set(se->statistics.sleep_start, 0);
917 __schedstat_add(se->statistics.sum_sleep_runtime, delta);
918
919 if (tsk) {
920 account_scheduler_latency(tsk, delta >> 10, 1);
921 trace_sched_stat_sleep(tsk, delta);
922 }
923 }
924 if (block_start) {
925 u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
926
927 if ((s64)delta < 0)
928 delta = 0;
929
930 if (unlikely(delta > schedstat_val(se->statistics.block_max)))
931 __schedstat_set(se->statistics.block_max, delta);
932
933 __schedstat_set(se->statistics.block_start, 0);
934 __schedstat_add(se->statistics.sum_sleep_runtime, delta);
935
936 if (tsk) {
937 if (tsk->in_iowait) {
938 __schedstat_add(se->statistics.iowait_sum, delta);
939 __schedstat_inc(se->statistics.iowait_count);
940 trace_sched_stat_iowait(tsk, delta);
941 }
942
943 trace_sched_stat_blocked(tsk, delta);
944
945 /*
946 * Blocking time is in units of nanosecs, so shift by
947 * 20 to get a milliseconds-range estimation of the
948 * amount of time that the task spent sleeping:
949 */
950 if (unlikely(prof_on == SLEEP_PROFILING)) {
951 profile_hits(SLEEP_PROFILING,
952 (void *)get_wchan(tsk),
953 delta >> 20);
954 }
955 account_scheduler_latency(tsk, delta >> 10, 0);
956 }
957 }
958}
959
960/*
961 * Task is being enqueued - update stats:
962 */
963static inline void
964update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
965{
966 if (!schedstat_enabled())
967 return;
968
969 /*
970 * Are we enqueueing a waiting task? (for current tasks
971 * a dequeue/enqueue event is a NOP)
972 */
973 if (se != cfs_rq->curr)
974 update_stats_wait_start(cfs_rq, se);
975
976 if (flags & ENQUEUE_WAKEUP)
977 update_stats_enqueue_sleeper(cfs_rq, se);
978}
979
980static inline void
981update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
982{
983
984 if (!schedstat_enabled())
985 return;
986
987 /*
988 * Mark the end of the wait period if dequeueing a
989 * waiting task:
990 */
991 if (se != cfs_rq->curr)
992 update_stats_wait_end(cfs_rq, se);
993
994 if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
995 struct task_struct *tsk = task_of(se);
996 unsigned int state;
997
998 /* XXX racy against TTWU */
999 state = READ_ONCE(tsk->__state);
1000 if (state & TASK_INTERRUPTIBLE)
1001 __schedstat_set(se->statistics.sleep_start,
1002 rq_clock(rq_of(cfs_rq)));
1003 if (state & TASK_UNINTERRUPTIBLE)
1004 __schedstat_set(se->statistics.block_start,
1005 rq_clock(rq_of(cfs_rq)));
1006 }
1007}
1008
1009/*
1010 * We are picking a new current task - update its stats:
1011 */
1012static inline void
1013update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
1014{
1015 /*
1016 * We are starting a new run period:
1017 */
1018 se->exec_start = rq_clock_task(rq_of(cfs_rq));
1019}
1020
1021/**************************************************
1022 * Scheduling class queueing methods:
1023 */
1024
1025#ifdef CONFIG_NUMA_BALANCING
1026/*
1027 * Approximate time to scan a full NUMA task in ms. The task scan period is
1028 * calculated based on the tasks virtual memory size and
1029 * numa_balancing_scan_size.
1030 */
1031unsigned int sysctl_numa_balancing_scan_period_min = 1000;
1032unsigned int sysctl_numa_balancing_scan_period_max = 60000;
1033
1034/* Portion of address space to scan in MB */
1035unsigned int sysctl_numa_balancing_scan_size = 256;
1036
1037/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
1038unsigned int sysctl_numa_balancing_scan_delay = 1000;
1039
1040struct numa_group {
1041 refcount_t refcount;
1042
1043 spinlock_t lock; /* nr_tasks, tasks */
1044 int nr_tasks;
1045 pid_t gid;
1046 int active_nodes;
1047
1048 struct rcu_head rcu;
1049 unsigned long total_faults;
1050 unsigned long max_faults_cpu;
1051 /*
1052 * Faults_cpu is used to decide whether memory should move
1053 * towards the CPU. As a consequence, these stats are weighted
1054 * more by CPU use than by memory faults.
1055 */
1056 unsigned long *faults_cpu;
1057 unsigned long faults[];
1058};
1059
1060/*
1061 * For functions that can be called in multiple contexts that permit reading
1062 * ->numa_group (see struct task_struct for locking rules).
1063 */
1064static struct numa_group *deref_task_numa_group(struct task_struct *p)
1065{
1066 return rcu_dereference_check(p->numa_group, p == current ||
1067 (lockdep_is_held(__rq_lockp(task_rq(p))) && !READ_ONCE(p->on_cpu)));
1068}
1069
1070static struct numa_group *deref_curr_numa_group(struct task_struct *p)
1071{
1072 return rcu_dereference_protected(p->numa_group, p == current);
1073}
1074
1075static inline unsigned long group_faults_priv(struct numa_group *ng);
1076static inline unsigned long group_faults_shared(struct numa_group *ng);
1077
1078static unsigned int task_nr_scan_windows(struct task_struct *p)
1079{
1080 unsigned long rss = 0;
1081 unsigned long nr_scan_pages;
1082
1083 /*
1084 * Calculations based on RSS as non-present and empty pages are skipped
1085 * by the PTE scanner and NUMA hinting faults should be trapped based
1086 * on resident pages
1087 */
1088 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
1089 rss = get_mm_rss(p->mm);
1090 if (!rss)
1091 rss = nr_scan_pages;
1092
1093 rss = round_up(rss, nr_scan_pages);
1094 return rss / nr_scan_pages;
1095}
1096
1097/* For sanity's sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
1098#define MAX_SCAN_WINDOW 2560
1099
1100static unsigned int task_scan_min(struct task_struct *p)
1101{
1102 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
1103 unsigned int scan, floor;
1104 unsigned int windows = 1;
1105
1106 if (scan_size < MAX_SCAN_WINDOW)
1107 windows = MAX_SCAN_WINDOW / scan_size;
1108 floor = 1000 / windows;
1109
1110 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
1111 return max_t(unsigned int, floor, scan);
1112}
1113
1114static unsigned int task_scan_start(struct task_struct *p)
1115{
1116 unsigned long smin = task_scan_min(p);
1117 unsigned long period = smin;
1118 struct numa_group *ng;
1119
1120 /* Scale the maximum scan period with the amount of shared memory. */
1121 rcu_read_lock();
1122 ng = rcu_dereference(p->numa_group);
1123 if (ng) {
1124 unsigned long shared = group_faults_shared(ng);
1125 unsigned long private = group_faults_priv(ng);
1126
1127 period *= refcount_read(&ng->refcount);
1128 period *= shared + 1;
1129 period /= private + shared + 1;
1130 }
1131 rcu_read_unlock();
1132
1133 return max(smin, period);
1134}
1135
1136static unsigned int task_scan_max(struct task_struct *p)
1137{
1138 unsigned long smin = task_scan_min(p);
1139 unsigned long smax;
1140 struct numa_group *ng;
1141
1142 /* Watch for min being lower than max due to floor calculations */
1143 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
1144
1145 /* Scale the maximum scan period with the amount of shared memory. */
1146 ng = deref_curr_numa_group(p);
1147 if (ng) {
1148 unsigned long shared = group_faults_shared(ng);
1149 unsigned long private = group_faults_priv(ng);
1150 unsigned long period = smax;
1151
1152 period *= refcount_read(&ng->refcount);
1153 period *= shared + 1;
1154 period /= private + shared + 1;
1155
1156 smax = max(smax, period);
1157 }
1158
1159 return max(smin, smax);
1160}
1161
1162static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
1163{
1164 rq->nr_numa_running += (p->numa_preferred_nid != NUMA_NO_NODE);
1165 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
1166}
1167
1168static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
1169{
1170 rq->nr_numa_running -= (p->numa_preferred_nid != NUMA_NO_NODE);
1171 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
1172}
1173
1174/* Shared or private faults. */
1175#define NR_NUMA_HINT_FAULT_TYPES 2
1176
1177/* Memory and CPU locality */
1178#define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
1179
1180/* Averaged statistics, and temporary buffers. */
1181#define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
1182
1183pid_t task_numa_group_id(struct task_struct *p)
1184{
1185 struct numa_group *ng;
1186 pid_t gid = 0;
1187
1188 rcu_read_lock();
1189 ng = rcu_dereference(p->numa_group);
1190 if (ng)
1191 gid = ng->gid;
1192 rcu_read_unlock();
1193
1194 return gid;
1195}
1196
1197/*
1198 * The averaged statistics, shared & private, memory & CPU,
1199 * occupy the first half of the array. The second half of the
1200 * array is for current counters, which are averaged into the
1201 * first set by task_numa_placement.
1202 */
1203static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
1204{
1205 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1206}
1207
1208static inline unsigned long task_faults(struct task_struct *p, int nid)
1209{
1210 if (!p->numa_faults)
1211 return 0;
1212
1213 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1214 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1215}
1216
1217static inline unsigned long group_faults(struct task_struct *p, int nid)
1218{
1219 struct numa_group *ng = deref_task_numa_group(p);
1220
1221 if (!ng)
1222 return 0;
1223
1224 return ng->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1225 ng->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1226}
1227
1228static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
1229{
1230 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
1231 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1232}
1233
1234static inline unsigned long group_faults_priv(struct numa_group *ng)
1235{
1236 unsigned long faults = 0;
1237 int node;
1238
1239 for_each_online_node(node) {
1240 faults += ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
1241 }
1242
1243 return faults;
1244}
1245
1246static inline unsigned long group_faults_shared(struct numa_group *ng)
1247{
1248 unsigned long faults = 0;
1249 int node;
1250
1251 for_each_online_node(node) {
1252 faults += ng->faults[task_faults_idx(NUMA_MEM, node, 0)];
1253 }
1254
1255 return faults;
1256}
1257
1258/*
1259 * A node triggering more than 1/3 as many NUMA faults as the maximum is
1260 * considered part of a numa group's pseudo-interleaving set. Migrations
1261 * between these nodes are slowed down, to allow things to settle down.
1262 */
1263#define ACTIVE_NODE_FRACTION 3
1264
1265static bool numa_is_active_node(int nid, struct numa_group *ng)
1266{
1267 return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
1268}
1269
1270/* Handle placement on systems where not all nodes are directly connected. */
1271static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
1272 int maxdist, bool task)
1273{
1274 unsigned long score = 0;
1275 int node;
1276
1277 /*
1278 * All nodes are directly connected, and the same distance
1279 * from each other. No need for fancy placement algorithms.
1280 */
1281 if (sched_numa_topology_type == NUMA_DIRECT)
1282 return 0;
1283
1284 /*
1285 * This code is called for each node, introducing N^2 complexity,
1286 * which should be ok given the number of nodes rarely exceeds 8.
1287 */
1288 for_each_online_node(node) {
1289 unsigned long faults;
1290 int dist = node_distance(nid, node);
1291
1292 /*
1293 * The furthest away nodes in the system are not interesting
1294 * for placement; nid was already counted.
1295 */
1296 if (dist == sched_max_numa_distance || node == nid)
1297 continue;
1298
1299 /*
1300 * On systems with a backplane NUMA topology, compare groups
1301 * of nodes, and move tasks towards the group with the most
1302 * memory accesses. When comparing two nodes at distance
1303 * "hoplimit", only nodes closer by than "hoplimit" are part
1304 * of each group. Skip other nodes.
1305 */
1306 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1307 dist >= maxdist)
1308 continue;
1309
1310 /* Add up the faults from nearby nodes. */
1311 if (task)
1312 faults = task_faults(p, node);
1313 else
1314 faults = group_faults(p, node);
1315
1316 /*
1317 * On systems with a glueless mesh NUMA topology, there are
1318 * no fixed "groups of nodes". Instead, nodes that are not
1319 * directly connected bounce traffic through intermediate
1320 * nodes; a numa_group can occupy any set of nodes.
1321 * The further away a node is, the less the faults count.
1322 * This seems to result in good task placement.
1323 */
1324 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1325 faults *= (sched_max_numa_distance - dist);
1326 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1327 }
1328
1329 score += faults;
1330 }
1331
1332 return score;
1333}
1334
1335/*
1336 * These return the fraction of accesses done by a particular task, or
1337 * task group, on a particular numa node. The group weight is given a
1338 * larger multiplier, in order to group tasks together that are almost
1339 * evenly spread out between numa nodes.
1340 */
1341static inline unsigned long task_weight(struct task_struct *p, int nid,
1342 int dist)
1343{
1344 unsigned long faults, total_faults;
1345
1346 if (!p->numa_faults)
1347 return 0;
1348
1349 total_faults = p->total_numa_faults;
1350
1351 if (!total_faults)
1352 return 0;
1353
1354 faults = task_faults(p, nid);
1355 faults += score_nearby_nodes(p, nid, dist, true);
1356
1357 return 1000 * faults / total_faults;
1358}
1359
1360static inline unsigned long group_weight(struct task_struct *p, int nid,
1361 int dist)
1362{
1363 struct numa_group *ng = deref_task_numa_group(p);
1364 unsigned long faults, total_faults;
1365
1366 if (!ng)
1367 return 0;
1368
1369 total_faults = ng->total_faults;
1370
1371 if (!total_faults)
1372 return 0;
1373
1374 faults = group_faults(p, nid);
1375 faults += score_nearby_nodes(p, nid, dist, false);
1376
1377 return 1000 * faults / total_faults;
1378}
1379
1380bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1381 int src_nid, int dst_cpu)
1382{
1383 struct numa_group *ng = deref_curr_numa_group(p);
1384 int dst_nid = cpu_to_node(dst_cpu);
1385 int last_cpupid, this_cpupid;
1386
1387 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1388 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1389
1390 /*
1391 * Allow first faults or private faults to migrate immediately early in
1392 * the lifetime of a task. The magic number 4 is based on waiting for
1393 * two full passes of the "multi-stage node selection" test that is
1394 * executed below.
1395 */
1396 if ((p->numa_preferred_nid == NUMA_NO_NODE || p->numa_scan_seq <= 4) &&
1397 (cpupid_pid_unset(last_cpupid) || cpupid_match_pid(p, last_cpupid)))
1398 return true;
1399
1400 /*
1401 * Multi-stage node selection is used in conjunction with a periodic
1402 * migration fault to build a temporal task<->page relation. By using
1403 * a two-stage filter we remove short/unlikely relations.
1404 *
1405 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1406 * a task's usage of a particular page (n_p) per total usage of this
1407 * page (n_t) (in a given time-span) to a probability.
1408 *
1409 * Our periodic faults will sample this probability and getting the
1410 * same result twice in a row, given these samples are fully
1411 * independent, is then given by P(n)^2, provided our sample period
1412 * is sufficiently short compared to the usage pattern.
1413 *
1414 * This quadric squishes small probabilities, making it less likely we
1415 * act on an unlikely task<->page relation.
1416 */
1417 if (!cpupid_pid_unset(last_cpupid) &&
1418 cpupid_to_nid(last_cpupid) != dst_nid)
1419 return false;
1420
1421 /* Always allow migrate on private faults */
1422 if (cpupid_match_pid(p, last_cpupid))
1423 return true;
1424
1425 /* A shared fault, but p->numa_group has not been set up yet. */
1426 if (!ng)
1427 return true;
1428
1429 /*
1430 * Destination node is much more heavily used than the source
1431 * node? Allow migration.
1432 */
1433 if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
1434 ACTIVE_NODE_FRACTION)
1435 return true;
1436
1437 /*
1438 * Distribute memory according to CPU & memory use on each node,
1439 * with 3/4 hysteresis to avoid unnecessary memory migrations:
1440 *
1441 * faults_cpu(dst) 3 faults_cpu(src)
1442 * --------------- * - > ---------------
1443 * faults_mem(dst) 4 faults_mem(src)
1444 */
1445 return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
1446 group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
1447}
1448
1449/*
1450 * 'numa_type' describes the node at the moment of load balancing.
1451 */
1452enum numa_type {
1453 /* The node has spare capacity that can be used to run more tasks. */
1454 node_has_spare = 0,
1455 /*
1456 * The node is fully used and the tasks don't compete for more CPU
1457 * cycles. Nevertheless, some tasks might wait before running.
1458 */
1459 node_fully_busy,
1460 /*
1461 * The node is overloaded and can't provide expected CPU cycles to all
1462 * tasks.
1463 */
1464 node_overloaded
1465};
1466
1467/* Cached statistics for all CPUs within a node */
1468struct numa_stats {
1469 unsigned long load;
1470 unsigned long runnable;
1471 unsigned long util;
1472 /* Total compute capacity of CPUs on a node */
1473 unsigned long compute_capacity;
1474 unsigned int nr_running;
1475 unsigned int weight;
1476 enum numa_type node_type;
1477 int idle_cpu;
1478};
1479
1480static inline bool is_core_idle(int cpu)
1481{
1482#ifdef CONFIG_SCHED_SMT
1483 int sibling;
1484
1485 for_each_cpu(sibling, cpu_smt_mask(cpu)) {
1486 if (cpu == sibling)
1487 continue;
1488
1489 if (!idle_cpu(sibling))
1490 return false;
1491 }
1492#endif
1493
1494 return true;
1495}
1496
1497struct task_numa_env {
1498 struct task_struct *p;
1499
1500 int src_cpu, src_nid;
1501 int dst_cpu, dst_nid;
1502
1503 struct numa_stats src_stats, dst_stats;
1504
1505 int imbalance_pct;
1506 int dist;
1507
1508 struct task_struct *best_task;
1509 long best_imp;
1510 int best_cpu;
1511};
1512
1513static unsigned long cpu_load(struct rq *rq);
1514static unsigned long cpu_runnable(struct rq *rq);
1515static unsigned long cpu_util(int cpu);
1516static inline long adjust_numa_imbalance(int imbalance,
1517 int dst_running, int dst_weight);
1518
1519static inline enum
1520numa_type numa_classify(unsigned int imbalance_pct,
1521 struct numa_stats *ns)
1522{
1523 if ((ns->nr_running > ns->weight) &&
1524 (((ns->compute_capacity * 100) < (ns->util * imbalance_pct)) ||
1525 ((ns->compute_capacity * imbalance_pct) < (ns->runnable * 100))))
1526 return node_overloaded;
1527
1528 if ((ns->nr_running < ns->weight) ||
1529 (((ns->compute_capacity * 100) > (ns->util * imbalance_pct)) &&
1530 ((ns->compute_capacity * imbalance_pct) > (ns->runnable * 100))))
1531 return node_has_spare;
1532
1533 return node_fully_busy;
1534}
1535
1536#ifdef CONFIG_SCHED_SMT
1537/* Forward declarations of select_idle_sibling helpers */
1538static inline bool test_idle_cores(int cpu, bool def);
1539static inline int numa_idle_core(int idle_core, int cpu)
1540{
1541 if (!static_branch_likely(&sched_smt_present) ||
1542 idle_core >= 0 || !test_idle_cores(cpu, false))
1543 return idle_core;
1544
1545 /*
1546 * Prefer cores instead of packing HT siblings
1547 * and triggering future load balancing.
1548 */
1549 if (is_core_idle(cpu))
1550 idle_core = cpu;
1551
1552 return idle_core;
1553}
1554#else
1555static inline int numa_idle_core(int idle_core, int cpu)
1556{
1557 return idle_core;
1558}
1559#endif
1560
1561/*
1562 * Gather all necessary information to make NUMA balancing placement
1563 * decisions that are compatible with standard load balancer. This
1564 * borrows code and logic from update_sg_lb_stats but sharing a
1565 * common implementation is impractical.
1566 */
1567static void update_numa_stats(struct task_numa_env *env,
1568 struct numa_stats *ns, int nid,
1569 bool find_idle)
1570{
1571 int cpu, idle_core = -1;
1572
1573 memset(ns, 0, sizeof(*ns));
1574 ns->idle_cpu = -1;
1575
1576 rcu_read_lock();
1577 for_each_cpu(cpu, cpumask_of_node(nid)) {
1578 struct rq *rq = cpu_rq(cpu);
1579
1580 ns->load += cpu_load(rq);
1581 ns->runnable += cpu_runnable(rq);
1582 ns->util += cpu_util(cpu);
1583 ns->nr_running += rq->cfs.h_nr_running;
1584 ns->compute_capacity += capacity_of(cpu);
1585
1586 if (find_idle && !rq->nr_running && idle_cpu(cpu)) {
1587 if (READ_ONCE(rq->numa_migrate_on) ||
1588 !cpumask_test_cpu(cpu, env->p->cpus_ptr))
1589 continue;
1590
1591 if (ns->idle_cpu == -1)
1592 ns->idle_cpu = cpu;
1593
1594 idle_core = numa_idle_core(idle_core, cpu);
1595 }
1596 }
1597 rcu_read_unlock();
1598
1599 ns->weight = cpumask_weight(cpumask_of_node(nid));
1600
1601 ns->node_type = numa_classify(env->imbalance_pct, ns);
1602
1603 if (idle_core >= 0)
1604 ns->idle_cpu = idle_core;
1605}
1606
1607static void task_numa_assign(struct task_numa_env *env,
1608 struct task_struct *p, long imp)
1609{
1610 struct rq *rq = cpu_rq(env->dst_cpu);
1611
1612 /* Check if run-queue part of active NUMA balance. */
1613 if (env->best_cpu != env->dst_cpu && xchg(&rq->numa_migrate_on, 1)) {
1614 int cpu;
1615 int start = env->dst_cpu;
1616
1617 /* Find alternative idle CPU. */
1618 for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), start) {
1619 if (cpu == env->best_cpu || !idle_cpu(cpu) ||
1620 !cpumask_test_cpu(cpu, env->p->cpus_ptr)) {
1621 continue;
1622 }
1623
1624 env->dst_cpu = cpu;
1625 rq = cpu_rq(env->dst_cpu);
1626 if (!xchg(&rq->numa_migrate_on, 1))
1627 goto assign;
1628 }
1629
1630 /* Failed to find an alternative idle CPU */
1631 return;
1632 }
1633
1634assign:
1635 /*
1636 * Clear previous best_cpu/rq numa-migrate flag, since task now
1637 * found a better CPU to move/swap.
1638 */
1639 if (env->best_cpu != -1 && env->best_cpu != env->dst_cpu) {
1640 rq = cpu_rq(env->best_cpu);
1641 WRITE_ONCE(rq->numa_migrate_on, 0);
1642 }
1643
1644 if (env->best_task)
1645 put_task_struct(env->best_task);
1646 if (p)
1647 get_task_struct(p);
1648
1649 env->best_task = p;
1650 env->best_imp = imp;
1651 env->best_cpu = env->dst_cpu;
1652}
1653
1654static bool load_too_imbalanced(long src_load, long dst_load,
1655 struct task_numa_env *env)
1656{
1657 long imb, old_imb;
1658 long orig_src_load, orig_dst_load;
1659 long src_capacity, dst_capacity;
1660
1661 /*
1662 * The load is corrected for the CPU capacity available on each node.
1663 *
1664 * src_load dst_load
1665 * ------------ vs ---------
1666 * src_capacity dst_capacity
1667 */
1668 src_capacity = env->src_stats.compute_capacity;
1669 dst_capacity = env->dst_stats.compute_capacity;
1670
1671 imb = abs(dst_load * src_capacity - src_load * dst_capacity);
1672
1673 orig_src_load = env->src_stats.load;
1674 orig_dst_load = env->dst_stats.load;
1675
1676 old_imb = abs(orig_dst_load * src_capacity - orig_src_load * dst_capacity);
1677
1678 /* Would this change make things worse? */
1679 return (imb > old_imb);
1680}
1681
1682/*
1683 * Maximum NUMA importance can be 1998 (2*999);
1684 * SMALLIMP @ 30 would be close to 1998/64.
1685 * Used to deter task migration.
1686 */
1687#define SMALLIMP 30
1688
1689/*
1690 * This checks if the overall compute and NUMA accesses of the system would
1691 * be improved if the source tasks was migrated to the target dst_cpu taking
1692 * into account that it might be best if task running on the dst_cpu should
1693 * be exchanged with the source task
1694 */
1695static bool task_numa_compare(struct task_numa_env *env,
1696 long taskimp, long groupimp, bool maymove)
1697{
1698 struct numa_group *cur_ng, *p_ng = deref_curr_numa_group(env->p);
1699 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1700 long imp = p_ng ? groupimp : taskimp;
1701 struct task_struct *cur;
1702 long src_load, dst_load;
1703 int dist = env->dist;
1704 long moveimp = imp;
1705 long load;
1706 bool stopsearch = false;
1707
1708 if (READ_ONCE(dst_rq->numa_migrate_on))
1709 return false;
1710
1711 rcu_read_lock();
1712 cur = rcu_dereference(dst_rq->curr);
1713 if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1714 cur = NULL;
1715
1716 /*
1717 * Because we have preemption enabled we can get migrated around and
1718 * end try selecting ourselves (current == env->p) as a swap candidate.
1719 */
1720 if (cur == env->p) {
1721 stopsearch = true;
1722 goto unlock;
1723 }
1724
1725 if (!cur) {
1726 if (maymove && moveimp >= env->best_imp)
1727 goto assign;
1728 else
1729 goto unlock;
1730 }
1731
1732 /* Skip this swap candidate if cannot move to the source cpu. */
1733 if (!cpumask_test_cpu(env->src_cpu, cur->cpus_ptr))
1734 goto unlock;
1735
1736 /*
1737 * Skip this swap candidate if it is not moving to its preferred
1738 * node and the best task is.
1739 */
1740 if (env->best_task &&
1741 env->best_task->numa_preferred_nid == env->src_nid &&
1742 cur->numa_preferred_nid != env->src_nid) {
1743 goto unlock;
1744 }
1745
1746 /*
1747 * "imp" is the fault differential for the source task between the
1748 * source and destination node. Calculate the total differential for
1749 * the source task and potential destination task. The more negative
1750 * the value is, the more remote accesses that would be expected to
1751 * be incurred if the tasks were swapped.
1752 *
1753 * If dst and source tasks are in the same NUMA group, or not
1754 * in any group then look only at task weights.
1755 */
1756 cur_ng = rcu_dereference(cur->numa_group);
1757 if (cur_ng == p_ng) {
1758 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1759 task_weight(cur, env->dst_nid, dist);
1760 /*
1761 * Add some hysteresis to prevent swapping the
1762 * tasks within a group over tiny differences.
1763 */
1764 if (cur_ng)
1765 imp -= imp / 16;
1766 } else {
1767 /*
1768 * Compare the group weights. If a task is all by itself
1769 * (not part of a group), use the task weight instead.
1770 */
1771 if (cur_ng && p_ng)
1772 imp += group_weight(cur, env->src_nid, dist) -
1773 group_weight(cur, env->dst_nid, dist);
1774 else
1775 imp += task_weight(cur, env->src_nid, dist) -
1776 task_weight(cur, env->dst_nid, dist);
1777 }
1778
1779 /* Discourage picking a task already on its preferred node */
1780 if (cur->numa_preferred_nid == env->dst_nid)
1781 imp -= imp / 16;
1782
1783 /*
1784 * Encourage picking a task that moves to its preferred node.
1785 * This potentially makes imp larger than it's maximum of
1786 * 1998 (see SMALLIMP and task_weight for why) but in this
1787 * case, it does not matter.
1788 */
1789 if (cur->numa_preferred_nid == env->src_nid)
1790 imp += imp / 8;
1791
1792 if (maymove && moveimp > imp && moveimp > env->best_imp) {
1793 imp = moveimp;
1794 cur = NULL;
1795 goto assign;
1796 }
1797
1798 /*
1799 * Prefer swapping with a task moving to its preferred node over a
1800 * task that is not.
1801 */
1802 if (env->best_task && cur->numa_preferred_nid == env->src_nid &&
1803 env->best_task->numa_preferred_nid != env->src_nid) {
1804 goto assign;
1805 }
1806
1807 /*
1808 * If the NUMA importance is less than SMALLIMP,
1809 * task migration might only result in ping pong
1810 * of tasks and also hurt performance due to cache
1811 * misses.
1812 */
1813 if (imp < SMALLIMP || imp <= env->best_imp + SMALLIMP / 2)
1814 goto unlock;
1815
1816 /*
1817 * In the overloaded case, try and keep the load balanced.
1818 */
1819 load = task_h_load(env->p) - task_h_load(cur);
1820 if (!load)
1821 goto assign;
1822
1823 dst_load = env->dst_stats.load + load;
1824 src_load = env->src_stats.load - load;
1825
1826 if (load_too_imbalanced(src_load, dst_load, env))
1827 goto unlock;
1828
1829assign:
1830 /* Evaluate an idle CPU for a task numa move. */
1831 if (!cur) {
1832 int cpu = env->dst_stats.idle_cpu;
1833
1834 /* Nothing cached so current CPU went idle since the search. */
1835 if (cpu < 0)
1836 cpu = env->dst_cpu;
1837
1838 /*
1839 * If the CPU is no longer truly idle and the previous best CPU
1840 * is, keep using it.
1841 */
1842 if (!idle_cpu(cpu) && env->best_cpu >= 0 &&
1843 idle_cpu(env->best_cpu)) {
1844 cpu = env->best_cpu;
1845 }
1846
1847 env->dst_cpu = cpu;
1848 }
1849
1850 task_numa_assign(env, cur, imp);
1851
1852 /*
1853 * If a move to idle is allowed because there is capacity or load
1854 * balance improves then stop the search. While a better swap
1855 * candidate may exist, a search is not free.
1856 */
1857 if (maymove && !cur && env->best_cpu >= 0 && idle_cpu(env->best_cpu))
1858 stopsearch = true;
1859
1860 /*
1861 * If a swap candidate must be identified and the current best task
1862 * moves its preferred node then stop the search.
1863 */
1864 if (!maymove && env->best_task &&
1865 env->best_task->numa_preferred_nid == env->src_nid) {
1866 stopsearch = true;
1867 }
1868unlock:
1869 rcu_read_unlock();
1870
1871 return stopsearch;
1872}
1873
1874static void task_numa_find_cpu(struct task_numa_env *env,
1875 long taskimp, long groupimp)
1876{
1877 bool maymove = false;
1878 int cpu;
1879
1880 /*
1881 * If dst node has spare capacity, then check if there is an
1882 * imbalance that would be overruled by the load balancer.
1883 */
1884 if (env->dst_stats.node_type == node_has_spare) {
1885 unsigned int imbalance;
1886 int src_running, dst_running;
1887
1888 /*
1889 * Would movement cause an imbalance? Note that if src has
1890 * more running tasks that the imbalance is ignored as the
1891 * move improves the imbalance from the perspective of the
1892 * CPU load balancer.
1893 * */
1894 src_running = env->src_stats.nr_running - 1;
1895 dst_running = env->dst_stats.nr_running + 1;
1896 imbalance = max(0, dst_running - src_running);
1897 imbalance = adjust_numa_imbalance(imbalance, dst_running,
1898 env->dst_stats.weight);
1899
1900 /* Use idle CPU if there is no imbalance */
1901 if (!imbalance) {
1902 maymove = true;
1903 if (env->dst_stats.idle_cpu >= 0) {
1904 env->dst_cpu = env->dst_stats.idle_cpu;
1905 task_numa_assign(env, NULL, 0);
1906 return;
1907 }
1908 }
1909 } else {
1910 long src_load, dst_load, load;
1911 /*
1912 * If the improvement from just moving env->p direction is better
1913 * than swapping tasks around, check if a move is possible.
1914 */
1915 load = task_h_load(env->p);
1916 dst_load = env->dst_stats.load + load;
1917 src_load = env->src_stats.load - load;
1918 maymove = !load_too_imbalanced(src_load, dst_load, env);
1919 }
1920
1921 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1922 /* Skip this CPU if the source task cannot migrate */
1923 if (!cpumask_test_cpu(cpu, env->p->cpus_ptr))
1924 continue;
1925
1926 env->dst_cpu = cpu;
1927 if (task_numa_compare(env, taskimp, groupimp, maymove))
1928 break;
1929 }
1930}
1931
1932static int task_numa_migrate(struct task_struct *p)
1933{
1934 struct task_numa_env env = {
1935 .p = p,
1936
1937 .src_cpu = task_cpu(p),
1938 .src_nid = task_node(p),
1939
1940 .imbalance_pct = 112,
1941
1942 .best_task = NULL,
1943 .best_imp = 0,
1944 .best_cpu = -1,
1945 };
1946 unsigned long taskweight, groupweight;
1947 struct sched_domain *sd;
1948 long taskimp, groupimp;
1949 struct numa_group *ng;
1950 struct rq *best_rq;
1951 int nid, ret, dist;
1952
1953 /*
1954 * Pick the lowest SD_NUMA domain, as that would have the smallest
1955 * imbalance and would be the first to start moving tasks about.
1956 *
1957 * And we want to avoid any moving of tasks about, as that would create
1958 * random movement of tasks -- counter the numa conditions we're trying
1959 * to satisfy here.
1960 */
1961 rcu_read_lock();
1962 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1963 if (sd)
1964 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1965 rcu_read_unlock();
1966
1967 /*
1968 * Cpusets can break the scheduler domain tree into smaller
1969 * balance domains, some of which do not cross NUMA boundaries.
1970 * Tasks that are "trapped" in such domains cannot be migrated
1971 * elsewhere, so there is no point in (re)trying.
1972 */
1973 if (unlikely(!sd)) {
1974 sched_setnuma(p, task_node(p));
1975 return -EINVAL;
1976 }
1977
1978 env.dst_nid = p->numa_preferred_nid;
1979 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1980 taskweight = task_weight(p, env.src_nid, dist);
1981 groupweight = group_weight(p, env.src_nid, dist);
1982 update_numa_stats(&env, &env.src_stats, env.src_nid, false);
1983 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1984 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1985 update_numa_stats(&env, &env.dst_stats, env.dst_nid, true);
1986
1987 /* Try to find a spot on the preferred nid. */
1988 task_numa_find_cpu(&env, taskimp, groupimp);
1989
1990 /*
1991 * Look at other nodes in these cases:
1992 * - there is no space available on the preferred_nid
1993 * - the task is part of a numa_group that is interleaved across
1994 * multiple NUMA nodes; in order to better consolidate the group,
1995 * we need to check other locations.
1996 */
1997 ng = deref_curr_numa_group(p);
1998 if (env.best_cpu == -1 || (ng && ng->active_nodes > 1)) {
1999 for_each_online_node(nid) {
2000 if (nid == env.src_nid || nid == p->numa_preferred_nid)
2001 continue;
2002
2003 dist = node_distance(env.src_nid, env.dst_nid);
2004 if (sched_numa_topology_type == NUMA_BACKPLANE &&
2005 dist != env.dist) {
2006 taskweight = task_weight(p, env.src_nid, dist);
2007 groupweight = group_weight(p, env.src_nid, dist);
2008 }
2009
2010 /* Only consider nodes where both task and groups benefit */
2011 taskimp = task_weight(p, nid, dist) - taskweight;
2012 groupimp = group_weight(p, nid, dist) - groupweight;
2013 if (taskimp < 0 && groupimp < 0)
2014 continue;
2015
2016 env.dist = dist;
2017 env.dst_nid = nid;
2018 update_numa_stats(&env, &env.dst_stats, env.dst_nid, true);
2019 task_numa_find_cpu(&env, taskimp, groupimp);
2020 }
2021 }
2022
2023 /*
2024 * If the task is part of a workload that spans multiple NUMA nodes,
2025 * and is migrating into one of the workload's active nodes, remember
2026 * this node as the task's preferred numa node, so the workload can
2027 * settle down.
2028 * A task that migrated to a second choice node will be better off
2029 * trying for a better one later. Do not set the preferred node here.
2030 */
2031 if (ng) {
2032 if (env.best_cpu == -1)
2033 nid = env.src_nid;
2034 else
2035 nid = cpu_to_node(env.best_cpu);
2036
2037 if (nid != p->numa_preferred_nid)
2038 sched_setnuma(p, nid);
2039 }
2040
2041 /* No better CPU than the current one was found. */
2042 if (env.best_cpu == -1) {
2043 trace_sched_stick_numa(p, env.src_cpu, NULL, -1);
2044 return -EAGAIN;
2045 }
2046
2047 best_rq = cpu_rq(env.best_cpu);
2048 if (env.best_task == NULL) {
2049 ret = migrate_task_to(p, env.best_cpu);
2050 WRITE_ONCE(best_rq->numa_migrate_on, 0);
2051 if (ret != 0)
2052 trace_sched_stick_numa(p, env.src_cpu, NULL, env.best_cpu);
2053 return ret;
2054 }
2055
2056 ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu);
2057 WRITE_ONCE(best_rq->numa_migrate_on, 0);
2058
2059 if (ret != 0)
2060 trace_sched_stick_numa(p, env.src_cpu, env.best_task, env.best_cpu);
2061 put_task_struct(env.best_task);
2062 return ret;
2063}
2064
2065/* Attempt to migrate a task to a CPU on the preferred node. */
2066static void numa_migrate_preferred(struct task_struct *p)
2067{
2068 unsigned long interval = HZ;
2069
2070 /* This task has no NUMA fault statistics yet */
2071 if (unlikely(p->numa_preferred_nid == NUMA_NO_NODE || !p->numa_faults))
2072 return;
2073
2074 /* Periodically retry migrating the task to the preferred node */
2075 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
2076 p->numa_migrate_retry = jiffies + interval;
2077
2078 /* Success if task is already running on preferred CPU */
2079 if (task_node(p) == p->numa_preferred_nid)
2080 return;
2081
2082 /* Otherwise, try migrate to a CPU on the preferred node */
2083 task_numa_migrate(p);
2084}
2085
2086/*
2087 * Find out how many nodes on the workload is actively running on. Do this by
2088 * tracking the nodes from which NUMA hinting faults are triggered. This can
2089 * be different from the set of nodes where the workload's memory is currently
2090 * located.
2091 */
2092static void numa_group_count_active_nodes(struct numa_group *numa_group)
2093{
2094 unsigned long faults, max_faults = 0;
2095 int nid, active_nodes = 0;
2096
2097 for_each_online_node(nid) {
2098 faults = group_faults_cpu(numa_group, nid);
2099 if (faults > max_faults)
2100 max_faults = faults;
2101 }
2102
2103 for_each_online_node(nid) {
2104 faults = group_faults_cpu(numa_group, nid);
2105 if (faults * ACTIVE_NODE_FRACTION > max_faults)
2106 active_nodes++;
2107 }
2108
2109 numa_group->max_faults_cpu = max_faults;
2110 numa_group->active_nodes = active_nodes;
2111}
2112
2113/*
2114 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
2115 * increments. The more local the fault statistics are, the higher the scan
2116 * period will be for the next scan window. If local/(local+remote) ratio is
2117 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
2118 * the scan period will decrease. Aim for 70% local accesses.
2119 */
2120#define NUMA_PERIOD_SLOTS 10
2121#define NUMA_PERIOD_THRESHOLD 7
2122
2123/*
2124 * Increase the scan period (slow down scanning) if the majority of
2125 * our memory is already on our local node, or if the majority of
2126 * the page accesses are shared with other processes.
2127 * Otherwise, decrease the scan period.
2128 */
2129static void update_task_scan_period(struct task_struct *p,
2130 unsigned long shared, unsigned long private)
2131{
2132 unsigned int period_slot;
2133 int lr_ratio, ps_ratio;
2134 int diff;
2135
2136 unsigned long remote = p->numa_faults_locality[0];
2137 unsigned long local = p->numa_faults_locality[1];
2138
2139 /*
2140 * If there were no record hinting faults then either the task is
2141 * completely idle or all activity is areas that are not of interest
2142 * to automatic numa balancing. Related to that, if there were failed
2143 * migration then it implies we are migrating too quickly or the local
2144 * node is overloaded. In either case, scan slower
2145 */
2146 if (local + shared == 0 || p->numa_faults_locality[2]) {
2147 p->numa_scan_period = min(p->numa_scan_period_max,
2148 p->numa_scan_period << 1);
2149
2150 p->mm->numa_next_scan = jiffies +
2151 msecs_to_jiffies(p->numa_scan_period);
2152
2153 return;
2154 }
2155
2156 /*
2157 * Prepare to scale scan period relative to the current period.
2158 * == NUMA_PERIOD_THRESHOLD scan period stays the same
2159 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
2160 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
2161 */
2162 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
2163 lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
2164 ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);
2165
2166 if (ps_ratio >= NUMA_PERIOD_THRESHOLD) {
2167 /*
2168 * Most memory accesses are local. There is no need to
2169 * do fast NUMA scanning, since memory is already local.
2170 */
2171 int slot = ps_ratio - NUMA_PERIOD_THRESHOLD;
2172 if (!slot)
2173 slot = 1;
2174 diff = slot * period_slot;
2175 } else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
2176 /*
2177 * Most memory accesses are shared with other tasks.
2178 * There is no point in continuing fast NUMA scanning,
2179 * since other tasks may just move the memory elsewhere.
2180 */
2181 int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
2182 if (!slot)
2183 slot = 1;
2184 diff = slot * period_slot;
2185 } else {
2186 /*
2187 * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
2188 * yet they are not on the local NUMA node. Speed up
2189 * NUMA scanning to get the memory moved over.
2190 */
2191 int ratio = max(lr_ratio, ps_ratio);
2192 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
2193 }
2194
2195 p->numa_scan_period = clamp(p->numa_scan_period + diff,
2196 task_scan_min(p), task_scan_max(p));
2197 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2198}
2199
2200/*
2201 * Get the fraction of time the task has been running since the last
2202 * NUMA placement cycle. The scheduler keeps similar statistics, but
2203 * decays those on a 32ms period, which is orders of magnitude off
2204 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
2205 * stats only if the task is so new there are no NUMA statistics yet.
2206 */
2207static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
2208{
2209 u64 runtime, delta, now;
2210 /* Use the start of this time slice to avoid calculations. */
2211 now = p->se.exec_start;
2212 runtime = p->se.sum_exec_runtime;
2213
2214 if (p->last_task_numa_placement) {
2215 delta = runtime - p->last_sum_exec_runtime;
2216 *period = now - p->last_task_numa_placement;
2217
2218 /* Avoid time going backwards, prevent potential divide error: */
2219 if (unlikely((s64)*period < 0))
2220 *period = 0;
2221 } else {
2222 delta = p->se.avg.load_sum;
2223 *period = LOAD_AVG_MAX;
2224 }
2225
2226 p->last_sum_exec_runtime = runtime;
2227 p->last_task_numa_placement = now;
2228
2229 return delta;
2230}
2231
2232/*
2233 * Determine the preferred nid for a task in a numa_group. This needs to
2234 * be done in a way that produces consistent results with group_weight,
2235 * otherwise workloads might not converge.
2236 */
2237static int preferred_group_nid(struct task_struct *p, int nid)
2238{
2239 nodemask_t nodes;
2240 int dist;
2241
2242 /* Direct connections between all NUMA nodes. */
2243 if (sched_numa_topology_type == NUMA_DIRECT)
2244 return nid;
2245
2246 /*
2247 * On a system with glueless mesh NUMA topology, group_weight
2248 * scores nodes according to the number of NUMA hinting faults on
2249 * both the node itself, and on nearby nodes.
2250 */
2251 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
2252 unsigned long score, max_score = 0;
2253 int node, max_node = nid;
2254
2255 dist = sched_max_numa_distance;
2256
2257 for_each_online_node(node) {
2258 score = group_weight(p, node, dist);
2259 if (score > max_score) {
2260 max_score = score;
2261 max_node = node;
2262 }
2263 }
2264 return max_node;
2265 }
2266
2267 /*
2268 * Finding the preferred nid in a system with NUMA backplane
2269 * interconnect topology is more involved. The goal is to locate
2270 * tasks from numa_groups near each other in the system, and
2271 * untangle workloads from different sides of the system. This requires
2272 * searching down the hierarchy of node groups, recursively searching
2273 * inside the highest scoring group of nodes. The nodemask tricks
2274 * keep the complexity of the search down.
2275 */
2276 nodes = node_online_map;
2277 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
2278 unsigned long max_faults = 0;
2279 nodemask_t max_group = NODE_MASK_NONE;
2280 int a, b;
2281
2282 /* Are there nodes at this distance from each other? */
2283 if (!find_numa_distance(dist))
2284 continue;
2285
2286 for_each_node_mask(a, nodes) {
2287 unsigned long faults = 0;
2288 nodemask_t this_group;
2289 nodes_clear(this_group);
2290
2291 /* Sum group's NUMA faults; includes a==b case. */
2292 for_each_node_mask(b, nodes) {
2293 if (node_distance(a, b) < dist) {
2294 faults += group_faults(p, b);
2295 node_set(b, this_group);
2296 node_clear(b, nodes);
2297 }
2298 }
2299
2300 /* Remember the top group. */
2301 if (faults > max_faults) {
2302 max_faults = faults;
2303 max_group = this_group;
2304 /*
2305 * subtle: at the smallest distance there is
2306 * just one node left in each "group", the
2307 * winner is the preferred nid.
2308 */
2309 nid = a;
2310 }
2311 }
2312 /* Next round, evaluate the nodes within max_group. */
2313 if (!max_faults)
2314 break;
2315 nodes = max_group;
2316 }
2317 return nid;
2318}
2319
2320static void task_numa_placement(struct task_struct *p)
2321{
2322 int seq, nid, max_nid = NUMA_NO_NODE;
2323 unsigned long max_faults = 0;
2324 unsigned long fault_types[2] = { 0, 0 };
2325 unsigned long total_faults;
2326 u64 runtime, period;
2327 spinlock_t *group_lock = NULL;
2328 struct numa_group *ng;
2329
2330 /*
2331 * The p->mm->numa_scan_seq field gets updated without
2332 * exclusive access. Use READ_ONCE() here to ensure
2333 * that the field is read in a single access:
2334 */
2335 seq = READ_ONCE(p->mm->numa_scan_seq);
2336 if (p->numa_scan_seq == seq)
2337 return;
2338 p->numa_scan_seq = seq;
2339 p->numa_scan_period_max = task_scan_max(p);
2340
2341 total_faults = p->numa_faults_locality[0] +
2342 p->numa_faults_locality[1];
2343 runtime = numa_get_avg_runtime(p, &period);
2344
2345 /* If the task is part of a group prevent parallel updates to group stats */
2346 ng = deref_curr_numa_group(p);
2347 if (ng) {
2348 group_lock = &ng->lock;
2349 spin_lock_irq(group_lock);
2350 }
2351
2352 /* Find the node with the highest number of faults */
2353 for_each_online_node(nid) {
2354 /* Keep track of the offsets in numa_faults array */
2355 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
2356 unsigned long faults = 0, group_faults = 0;
2357 int priv;
2358
2359 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
2360 long diff, f_diff, f_weight;
2361
2362 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
2363 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
2364 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
2365 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
2366
2367 /* Decay existing window, copy faults since last scan */
2368 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
2369 fault_types[priv] += p->numa_faults[membuf_idx];
2370 p->numa_faults[membuf_idx] = 0;
2371
2372 /*
2373 * Normalize the faults_from, so all tasks in a group
2374 * count according to CPU use, instead of by the raw
2375 * number of faults. Tasks with little runtime have
2376 * little over-all impact on throughput, and thus their
2377 * faults are less important.
2378 */
2379 f_weight = div64_u64(runtime << 16, period + 1);
2380 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
2381 (total_faults + 1);
2382 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
2383 p->numa_faults[cpubuf_idx] = 0;
2384
2385 p->numa_faults[mem_idx] += diff;
2386 p->numa_faults[cpu_idx] += f_diff;
2387 faults += p->numa_faults[mem_idx];
2388 p->total_numa_faults += diff;
2389 if (ng) {
2390 /*
2391 * safe because we can only change our own group
2392 *
2393 * mem_idx represents the offset for a given
2394 * nid and priv in a specific region because it
2395 * is at the beginning of the numa_faults array.
2396 */
2397 ng->faults[mem_idx] += diff;
2398 ng->faults_cpu[mem_idx] += f_diff;
2399 ng->total_faults += diff;
2400 group_faults += ng->faults[mem_idx];
2401 }
2402 }
2403
2404 if (!ng) {
2405 if (faults > max_faults) {
2406 max_faults = faults;
2407 max_nid = nid;
2408 }
2409 } else if (group_faults > max_faults) {
2410 max_faults = group_faults;
2411 max_nid = nid;
2412 }
2413 }
2414
2415 if (ng) {
2416 numa_group_count_active_nodes(ng);
2417 spin_unlock_irq(group_lock);
2418 max_nid = preferred_group_nid(p, max_nid);
2419 }
2420
2421 if (max_faults) {
2422 /* Set the new preferred node */
2423 if (max_nid != p->numa_preferred_nid)
2424 sched_setnuma(p, max_nid);
2425 }
2426
2427 update_task_scan_period(p, fault_types[0], fault_types[1]);
2428}
2429
2430static inline int get_numa_group(struct numa_group *grp)
2431{
2432 return refcount_inc_not_zero(&grp->refcount);
2433}
2434
2435static inline void put_numa_group(struct numa_group *grp)
2436{
2437 if (refcount_dec_and_test(&grp->refcount))
2438 kfree_rcu(grp, rcu);
2439}
2440
2441static void task_numa_group(struct task_struct *p, int cpupid, int flags,
2442 int *priv)
2443{
2444 struct numa_group *grp, *my_grp;
2445 struct task_struct *tsk;
2446 bool join = false;
2447 int cpu = cpupid_to_cpu(cpupid);
2448 int i;
2449
2450 if (unlikely(!deref_curr_numa_group(p))) {
2451 unsigned int size = sizeof(struct numa_group) +
2452 4*nr_node_ids*sizeof(unsigned long);
2453
2454 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
2455 if (!grp)
2456 return;
2457
2458 refcount_set(&grp->refcount, 1);
2459 grp->active_nodes = 1;
2460 grp->max_faults_cpu = 0;
2461 spin_lock_init(&grp->lock);
2462 grp->gid = p->pid;
2463 /* Second half of the array tracks nids where faults happen */
2464 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
2465 nr_node_ids;
2466
2467 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2468 grp->faults[i] = p->numa_faults[i];
2469
2470 grp->total_faults = p->total_numa_faults;
2471
2472 grp->nr_tasks++;
2473 rcu_assign_pointer(p->numa_group, grp);
2474 }
2475
2476 rcu_read_lock();
2477 tsk = READ_ONCE(cpu_rq(cpu)->curr);
2478
2479 if (!cpupid_match_pid(tsk, cpupid))
2480 goto no_join;
2481
2482 grp = rcu_dereference(tsk->numa_group);
2483 if (!grp)
2484 goto no_join;
2485
2486 my_grp = deref_curr_numa_group(p);
2487 if (grp == my_grp)
2488 goto no_join;
2489
2490 /*
2491 * Only join the other group if its bigger; if we're the bigger group,
2492 * the other task will join us.
2493 */
2494 if (my_grp->nr_tasks > grp->nr_tasks)
2495 goto no_join;
2496
2497 /*
2498 * Tie-break on the grp address.
2499 */
2500 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2501 goto no_join;
2502
2503 /* Always join threads in the same process. */
2504 if (tsk->mm == current->mm)
2505 join = true;
2506
2507 /* Simple filter to avoid false positives due to PID collisions */
2508 if (flags & TNF_SHARED)
2509 join = true;
2510
2511 /* Update priv based on whether false sharing was detected */
2512 *priv = !join;
2513
2514 if (join && !get_numa_group(grp))
2515 goto no_join;
2516
2517 rcu_read_unlock();
2518
2519 if (!join)
2520 return;
2521
2522 BUG_ON(irqs_disabled());
2523 double_lock_irq(&my_grp->lock, &grp->lock);
2524
2525 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2526 my_grp->faults[i] -= p->numa_faults[i];
2527 grp->faults[i] += p->numa_faults[i];
2528 }
2529 my_grp->total_faults -= p->total_numa_faults;
2530 grp->total_faults += p->total_numa_faults;
2531
2532 my_grp->nr_tasks--;
2533 grp->nr_tasks++;
2534
2535 spin_unlock(&my_grp->lock);
2536 spin_unlock_irq(&grp->lock);
2537
2538 rcu_assign_pointer(p->numa_group, grp);
2539
2540 put_numa_group(my_grp);
2541 return;
2542
2543no_join:
2544 rcu_read_unlock();
2545 return;
2546}
2547
2548/*
2549 * Get rid of NUMA statistics associated with a task (either current or dead).
2550 * If @final is set, the task is dead and has reached refcount zero, so we can
2551 * safely free all relevant data structures. Otherwise, there might be
2552 * concurrent reads from places like load balancing and procfs, and we should
2553 * reset the data back to default state without freeing ->numa_faults.
2554 */
2555void task_numa_free(struct task_struct *p, bool final)
2556{
2557 /* safe: p either is current or is being freed by current */
2558 struct numa_group *grp = rcu_dereference_raw(p->numa_group);
2559 unsigned long *numa_faults = p->numa_faults;
2560 unsigned long flags;
2561 int i;
2562
2563 if (!numa_faults)
2564 return;
2565
2566 if (grp) {
2567 spin_lock_irqsave(&grp->lock, flags);
2568 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2569 grp->faults[i] -= p->numa_faults[i];
2570 grp->total_faults -= p->total_numa_faults;
2571
2572 grp->nr_tasks--;
2573 spin_unlock_irqrestore(&grp->lock, flags);
2574 RCU_INIT_POINTER(p->numa_group, NULL);
2575 put_numa_group(grp);
2576 }
2577
2578 if (final) {
2579 p->numa_faults = NULL;
2580 kfree(numa_faults);
2581 } else {
2582 p->total_numa_faults = 0;
2583 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2584 numa_faults[i] = 0;
2585 }
2586}
2587
2588/*
2589 * Got a PROT_NONE fault for a page on @node.
2590 */
2591void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2592{
2593 struct task_struct *p = current;
2594 bool migrated = flags & TNF_MIGRATED;
2595 int cpu_node = task_node(current);
2596 int local = !!(flags & TNF_FAULT_LOCAL);
2597 struct numa_group *ng;
2598 int priv;
2599
2600 if (!static_branch_likely(&sched_numa_balancing))
2601 return;
2602
2603 /* for example, ksmd faulting in a user's mm */
2604 if (!p->mm)
2605 return;
2606
2607 /* Allocate buffer to track faults on a per-node basis */
2608 if (unlikely(!p->numa_faults)) {
2609 int size = sizeof(*p->numa_faults) *
2610 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2611
2612 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2613 if (!p->numa_faults)
2614 return;
2615
2616 p->total_numa_faults = 0;
2617 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2618 }
2619
2620 /*
2621 * First accesses are treated as private, otherwise consider accesses
2622 * to be private if the accessing pid has not changed
2623 */
2624 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2625 priv = 1;
2626 } else {
2627 priv = cpupid_match_pid(p, last_cpupid);
2628 if (!priv && !(flags & TNF_NO_GROUP))
2629 task_numa_group(p, last_cpupid, flags, &priv);
2630 }
2631
2632 /*
2633 * If a workload spans multiple NUMA nodes, a shared fault that
2634 * occurs wholly within the set of nodes that the workload is
2635 * actively using should be counted as local. This allows the
2636 * scan rate to slow down when a workload has settled down.
2637 */
2638 ng = deref_curr_numa_group(p);
2639 if (!priv && !local && ng && ng->active_nodes > 1 &&
2640 numa_is_active_node(cpu_node, ng) &&
2641 numa_is_active_node(mem_node, ng))
2642 local = 1;
2643
2644 /*
2645 * Retry to migrate task to preferred node periodically, in case it
2646 * previously failed, or the scheduler moved us.
2647 */
2648 if (time_after(jiffies, p->numa_migrate_retry)) {
2649 task_numa_placement(p);
2650 numa_migrate_preferred(p);
2651 }
2652
2653 if (migrated)
2654 p->numa_pages_migrated += pages;
2655 if (flags & TNF_MIGRATE_FAIL)
2656 p->numa_faults_locality[2] += pages;
2657
2658 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2659 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2660 p->numa_faults_locality[local] += pages;
2661}
2662
2663static void reset_ptenuma_scan(struct task_struct *p)
2664{
2665 /*
2666 * We only did a read acquisition of the mmap sem, so
2667 * p->mm->numa_scan_seq is written to without exclusive access
2668 * and the update is not guaranteed to be atomic. That's not
2669 * much of an issue though, since this is just used for
2670 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2671 * expensive, to avoid any form of compiler optimizations:
2672 */
2673 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2674 p->mm->numa_scan_offset = 0;
2675}
2676
2677/*
2678 * The expensive part of numa migration is done from task_work context.
2679 * Triggered from task_tick_numa().
2680 */
2681static void task_numa_work(struct callback_head *work)
2682{
2683 unsigned long migrate, next_scan, now = jiffies;
2684 struct task_struct *p = current;
2685 struct mm_struct *mm = p->mm;
2686 u64 runtime = p->se.sum_exec_runtime;
2687 struct vm_area_struct *vma;
2688 unsigned long start, end;
2689 unsigned long nr_pte_updates = 0;
2690 long pages, virtpages;
2691
2692 SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
2693
2694 work->next = work;
2695 /*
2696 * Who cares about NUMA placement when they're dying.
2697 *
2698 * NOTE: make sure not to dereference p->mm before this check,
2699 * exit_task_work() happens _after_ exit_mm() so we could be called
2700 * without p->mm even though we still had it when we enqueued this
2701 * work.
2702 */
2703 if (p->flags & PF_EXITING)
2704 return;
2705
2706 if (!mm->numa_next_scan) {
2707 mm->numa_next_scan = now +
2708 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2709 }
2710
2711 /*
2712 * Enforce maximal scan/migration frequency..
2713 */
2714 migrate = mm->numa_next_scan;
2715 if (time_before(now, migrate))
2716 return;
2717
2718 if (p->numa_scan_period == 0) {
2719 p->numa_scan_period_max = task_scan_max(p);
2720 p->numa_scan_period = task_scan_start(p);
2721 }
2722
2723 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2724 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2725 return;
2726
2727 /*
2728 * Delay this task enough that another task of this mm will likely win
2729 * the next time around.
2730 */
2731 p->node_stamp += 2 * TICK_NSEC;
2732
2733 start = mm->numa_scan_offset;
2734 pages = sysctl_numa_balancing_scan_size;
2735 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2736 virtpages = pages * 8; /* Scan up to this much virtual space */
2737 if (!pages)
2738 return;
2739
2740
2741 if (!mmap_read_trylock(mm))
2742 return;
2743 vma = find_vma(mm, start);
2744 if (!vma) {
2745 reset_ptenuma_scan(p);
2746 start = 0;
2747 vma = mm->mmap;
2748 }
2749 for (; vma; vma = vma->vm_next) {
2750 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2751 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2752 continue;
2753 }
2754
2755 /*
2756 * Shared library pages mapped by multiple processes are not
2757 * migrated as it is expected they are cache replicated. Avoid
2758 * hinting faults in read-only file-backed mappings or the vdso
2759 * as migrating the pages will be of marginal benefit.
2760 */
2761 if (!vma->vm_mm ||
2762 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2763 continue;
2764
2765 /*
2766 * Skip inaccessible VMAs to avoid any confusion between
2767 * PROT_NONE and NUMA hinting ptes
2768 */
2769 if (!vma_is_accessible(vma))
2770 continue;
2771
2772 do {
2773 start = max(start, vma->vm_start);
2774 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2775 end = min(end, vma->vm_end);
2776 nr_pte_updates = change_prot_numa(vma, start, end);
2777
2778 /*
2779 * Try to scan sysctl_numa_balancing_size worth of
2780 * hpages that have at least one present PTE that
2781 * is not already pte-numa. If the VMA contains
2782 * areas that are unused or already full of prot_numa
2783 * PTEs, scan up to virtpages, to skip through those
2784 * areas faster.
2785 */
2786 if (nr_pte_updates)
2787 pages -= (end - start) >> PAGE_SHIFT;
2788 virtpages -= (end - start) >> PAGE_SHIFT;
2789
2790 start = end;
2791 if (pages <= 0 || virtpages <= 0)
2792 goto out;
2793
2794 cond_resched();
2795 } while (end != vma->vm_end);
2796 }
2797
2798out:
2799 /*
2800 * It is possible to reach the end of the VMA list but the last few
2801 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2802 * would find the !migratable VMA on the next scan but not reset the
2803 * scanner to the start so check it now.
2804 */
2805 if (vma)
2806 mm->numa_scan_offset = start;
2807 else
2808 reset_ptenuma_scan(p);
2809 mmap_read_unlock(mm);
2810
2811 /*
2812 * Make sure tasks use at least 32x as much time to run other code
2813 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2814 * Usually update_task_scan_period slows down scanning enough; on an
2815 * overloaded system we need to limit overhead on a per task basis.
2816 */
2817 if (unlikely(p->se.sum_exec_runtime != runtime)) {
2818 u64 diff = p->se.sum_exec_runtime - runtime;
2819 p->node_stamp += 32 * diff;
2820 }
2821}
2822
2823void init_numa_balancing(unsigned long clone_flags, struct task_struct *p)
2824{
2825 int mm_users = 0;
2826 struct mm_struct *mm = p->mm;
2827
2828 if (mm) {
2829 mm_users = atomic_read(&mm->mm_users);
2830 if (mm_users == 1) {
2831 mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2832 mm->numa_scan_seq = 0;
2833 }
2834 }
2835 p->node_stamp = 0;
2836 p->numa_scan_seq = mm ? mm->numa_scan_seq : 0;
2837 p->numa_scan_period = sysctl_numa_balancing_scan_delay;
2838 /* Protect against double add, see task_tick_numa and task_numa_work */
2839 p->numa_work.next = &p->numa_work;
2840 p->numa_faults = NULL;
2841 RCU_INIT_POINTER(p->numa_group, NULL);
2842 p->last_task_numa_placement = 0;
2843 p->last_sum_exec_runtime = 0;
2844
2845 init_task_work(&p->numa_work, task_numa_work);
2846
2847 /* New address space, reset the preferred nid */
2848 if (!(clone_flags & CLONE_VM)) {
2849 p->numa_preferred_nid = NUMA_NO_NODE;
2850 return;
2851 }
2852
2853 /*
2854 * New thread, keep existing numa_preferred_nid which should be copied
2855 * already by arch_dup_task_struct but stagger when scans start.
2856 */
2857 if (mm) {
2858 unsigned int delay;
2859
2860 delay = min_t(unsigned int, task_scan_max(current),
2861 current->numa_scan_period * mm_users * NSEC_PER_MSEC);
2862 delay += 2 * TICK_NSEC;
2863 p->node_stamp = delay;
2864 }
2865}
2866
2867/*
2868 * Drive the periodic memory faults..
2869 */
2870static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2871{
2872 struct callback_head *work = &curr->numa_work;
2873 u64 period, now;
2874
2875 /*
2876 * We don't care about NUMA placement if we don't have memory.
2877 */
2878 if ((curr->flags & (PF_EXITING | PF_KTHREAD)) || work->next != work)
2879 return;
2880
2881 /*
2882 * Using runtime rather than walltime has the dual advantage that
2883 * we (mostly) drive the selection from busy threads and that the
2884 * task needs to have done some actual work before we bother with
2885 * NUMA placement.
2886 */
2887 now = curr->se.sum_exec_runtime;
2888 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2889
2890 if (now > curr->node_stamp + period) {
2891 if (!curr->node_stamp)
2892 curr->numa_scan_period = task_scan_start(curr);
2893 curr->node_stamp += period;
2894
2895 if (!time_before(jiffies, curr->mm->numa_next_scan))
2896 task_work_add(curr, work, TWA_RESUME);
2897 }
2898}
2899
2900static void update_scan_period(struct task_struct *p, int new_cpu)
2901{
2902 int src_nid = cpu_to_node(task_cpu(p));
2903 int dst_nid = cpu_to_node(new_cpu);
2904
2905 if (!static_branch_likely(&sched_numa_balancing))
2906 return;
2907
2908 if (!p->mm || !p->numa_faults || (p->flags & PF_EXITING))
2909 return;
2910
2911 if (src_nid == dst_nid)
2912 return;
2913
2914 /*
2915 * Allow resets if faults have been trapped before one scan
2916 * has completed. This is most likely due to a new task that
2917 * is pulled cross-node due to wakeups or load balancing.
2918 */
2919 if (p->numa_scan_seq) {
2920 /*
2921 * Avoid scan adjustments if moving to the preferred
2922 * node or if the task was not previously running on
2923 * the preferred node.
2924 */
2925 if (dst_nid == p->numa_preferred_nid ||
2926 (p->numa_preferred_nid != NUMA_NO_NODE &&
2927 src_nid != p->numa_preferred_nid))
2928 return;
2929 }
2930
2931 p->numa_scan_period = task_scan_start(p);
2932}
2933
2934#else
2935static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2936{
2937}
2938
2939static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2940{
2941}
2942
2943static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2944{
2945}
2946
2947static inline void update_scan_period(struct task_struct *p, int new_cpu)
2948{
2949}
2950
2951#endif /* CONFIG_NUMA_BALANCING */
2952
2953static void
2954account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2955{
2956 update_load_add(&cfs_rq->load, se->load.weight);
2957#ifdef CONFIG_SMP
2958 if (entity_is_task(se)) {
2959 struct rq *rq = rq_of(cfs_rq);
2960
2961 account_numa_enqueue(rq, task_of(se));
2962 list_add(&se->group_node, &rq->cfs_tasks);
2963 }
2964#endif
2965 cfs_rq->nr_running++;
2966}
2967
2968static void
2969account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2970{
2971 update_load_sub(&cfs_rq->load, se->load.weight);
2972#ifdef CONFIG_SMP
2973 if (entity_is_task(se)) {
2974 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2975 list_del_init(&se->group_node);
2976 }
2977#endif
2978 cfs_rq->nr_running--;
2979}
2980
2981/*
2982 * Signed add and clamp on underflow.
2983 *
2984 * Explicitly do a load-store to ensure the intermediate value never hits
2985 * memory. This allows lockless observations without ever seeing the negative
2986 * values.
2987 */
2988#define add_positive(_ptr, _val) do { \
2989 typeof(_ptr) ptr = (_ptr); \
2990 typeof(_val) val = (_val); \
2991 typeof(*ptr) res, var = READ_ONCE(*ptr); \
2992 \
2993 res = var + val; \
2994 \
2995 if (val < 0 && res > var) \
2996 res = 0; \
2997 \
2998 WRITE_ONCE(*ptr, res); \
2999} while (0)
3000
3001/*
3002 * Unsigned subtract and clamp on underflow.
3003 *
3004 * Explicitly do a load-store to ensure the intermediate value never hits
3005 * memory. This allows lockless observations without ever seeing the negative
3006 * values.
3007 */
3008#define sub_positive(_ptr, _val) do { \
3009 typeof(_ptr) ptr = (_ptr); \
3010 typeof(*ptr) val = (_val); \
3011 typeof(*ptr) res, var = READ_ONCE(*ptr); \
3012 res = var - val; \
3013 if (res > var) \
3014 res = 0; \
3015 WRITE_ONCE(*ptr, res); \
3016} while (0)
3017
3018/*
3019 * Remove and clamp on negative, from a local variable.
3020 *
3021 * A variant of sub_positive(), which does not use explicit load-store
3022 * and is thus optimized for local variable updates.
3023 */
3024#define lsub_positive(_ptr, _val) do { \
3025 typeof(_ptr) ptr = (_ptr); \
3026 *ptr -= min_t(typeof(*ptr), *ptr, _val); \
3027} while (0)
3028
3029#ifdef CONFIG_SMP
3030static inline void
3031enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3032{
3033 cfs_rq->avg.load_avg += se->avg.load_avg;
3034 cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
3035}
3036
3037static inline void
3038dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3039{
3040 u32 divider = get_pelt_divider(&se->avg);
3041 sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
3042 cfs_rq->avg.load_sum = cfs_rq->avg.load_avg * divider;
3043}
3044#else
3045static inline void
3046enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
3047static inline void
3048dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
3049#endif
3050
3051static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
3052 unsigned long weight)
3053{
3054 if (se->on_rq) {
3055 /* commit outstanding execution time */
3056 if (cfs_rq->curr == se)
3057 update_curr(cfs_rq);
3058 update_load_sub(&cfs_rq->load, se->load.weight);
3059 }
3060 dequeue_load_avg(cfs_rq, se);
3061
3062 update_load_set(&se->load, weight);
3063
3064#ifdef CONFIG_SMP
3065 do {
3066 u32 divider = get_pelt_divider(&se->avg);
3067
3068 se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider);
3069 } while (0);
3070#endif
3071
3072 enqueue_load_avg(cfs_rq, se);
3073 if (se->on_rq)
3074 update_load_add(&cfs_rq->load, se->load.weight);
3075
3076}
3077
3078void reweight_task(struct task_struct *p, int prio)
3079{
3080 struct sched_entity *se = &p->se;
3081 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3082 struct load_weight *load = &se->load;
3083 unsigned long weight = scale_load(sched_prio_to_weight[prio]);
3084
3085 reweight_entity(cfs_rq, se, weight);
3086 load->inv_weight = sched_prio_to_wmult[prio];
3087}
3088
3089#ifdef CONFIG_FAIR_GROUP_SCHED
3090#ifdef CONFIG_SMP
3091/*
3092 * All this does is approximate the hierarchical proportion which includes that
3093 * global sum we all love to hate.
3094 *
3095 * That is, the weight of a group entity, is the proportional share of the
3096 * group weight based on the group runqueue weights. That is:
3097 *
3098 * tg->weight * grq->load.weight
3099 * ge->load.weight = ----------------------------- (1)
3100 * \Sum grq->load.weight
3101 *
3102 * Now, because computing that sum is prohibitively expensive to compute (been
3103 * there, done that) we approximate it with this average stuff. The average
3104 * moves slower and therefore the approximation is cheaper and more stable.
3105 *
3106 * So instead of the above, we substitute:
3107 *
3108 * grq->load.weight -> grq->avg.load_avg (2)
3109 *
3110 * which yields the following:
3111 *
3112 * tg->weight * grq->avg.load_avg
3113 * ge->load.weight = ------------------------------ (3)
3114 * tg->load_avg
3115 *
3116 * Where: tg->load_avg ~= \Sum grq->avg.load_avg
3117 *
3118 * That is shares_avg, and it is right (given the approximation (2)).
3119 *
3120 * The problem with it is that because the average is slow -- it was designed
3121 * to be exactly that of course -- this leads to transients in boundary
3122 * conditions. In specific, the case where the group was idle and we start the
3123 * one task. It takes time for our CPU's grq->avg.load_avg to build up,
3124 * yielding bad latency etc..
3125 *
3126 * Now, in that special case (1) reduces to:
3127 *
3128 * tg->weight * grq->load.weight
3129 * ge->load.weight = ----------------------------- = tg->weight (4)
3130 * grp->load.weight
3131 *
3132 * That is, the sum collapses because all other CPUs are idle; the UP scenario.
3133 *
3134 * So what we do is modify our approximation (3) to approach (4) in the (near)
3135 * UP case, like:
3136 *
3137 * ge->load.weight =
3138 *
3139 * tg->weight * grq->load.weight
3140 * --------------------------------------------------- (5)
3141 * tg->load_avg - grq->avg.load_avg + grq->load.weight
3142 *
3143 * But because grq->load.weight can drop to 0, resulting in a divide by zero,
3144 * we need to use grq->avg.load_avg as its lower bound, which then gives:
3145 *
3146 *
3147 * tg->weight * grq->load.weight
3148 * ge->load.weight = ----------------------------- (6)
3149 * tg_load_avg'
3150 *
3151 * Where:
3152 *
3153 * tg_load_avg' = tg->load_avg - grq->avg.load_avg +
3154 * max(grq->load.weight, grq->avg.load_avg)
3155 *
3156 * And that is shares_weight and is icky. In the (near) UP case it approaches
3157 * (4) while in the normal case it approaches (3). It consistently
3158 * overestimates the ge->load.weight and therefore:
3159 *
3160 * \Sum ge->load.weight >= tg->weight
3161 *
3162 * hence icky!
3163 */
3164static long calc_group_shares(struct cfs_rq *cfs_rq)
3165{
3166 long tg_weight, tg_shares, load, shares;
3167 struct task_group *tg = cfs_rq->tg;
3168
3169 tg_shares = READ_ONCE(tg->shares);
3170
3171 load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
3172
3173 tg_weight = atomic_long_read(&tg->load_avg);
3174
3175 /* Ensure tg_weight >= load */
3176 tg_weight -= cfs_rq->tg_load_avg_contrib;
3177 tg_weight += load;
3178
3179 shares = (tg_shares * load);
3180 if (tg_weight)
3181 shares /= tg_weight;
3182
3183 /*
3184 * MIN_SHARES has to be unscaled here to support per-CPU partitioning
3185 * of a group with small tg->shares value. It is a floor value which is
3186 * assigned as a minimum load.weight to the sched_entity representing
3187 * the group on a CPU.
3188 *
3189 * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024
3190 * on an 8-core system with 8 tasks each runnable on one CPU shares has
3191 * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In
3192 * case no task is runnable on a CPU MIN_SHARES=2 should be returned
3193 * instead of 0.
3194 */
3195 return clamp_t(long, shares, MIN_SHARES, tg_shares);
3196}
3197#endif /* CONFIG_SMP */
3198
3199static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
3200
3201/*
3202 * Recomputes the group entity based on the current state of its group
3203 * runqueue.
3204 */
3205static void update_cfs_group(struct sched_entity *se)
3206{
3207 struct cfs_rq *gcfs_rq = group_cfs_rq(se);
3208 long shares;
3209
3210 if (!gcfs_rq)
3211 return;
3212
3213 if (throttled_hierarchy(gcfs_rq))
3214 return;
3215
3216#ifndef CONFIG_SMP
3217 shares = READ_ONCE(gcfs_rq->tg->shares);
3218
3219 if (likely(se->load.weight == shares))
3220 return;
3221#else
3222 shares = calc_group_shares(gcfs_rq);
3223#endif
3224
3225 reweight_entity(cfs_rq_of(se), se, shares);
3226}
3227
3228#else /* CONFIG_FAIR_GROUP_SCHED */
3229static inline void update_cfs_group(struct sched_entity *se)
3230{
3231}
3232#endif /* CONFIG_FAIR_GROUP_SCHED */
3233
3234static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
3235{
3236 struct rq *rq = rq_of(cfs_rq);
3237
3238 if (&rq->cfs == cfs_rq) {
3239 /*
3240 * There are a few boundary cases this might miss but it should
3241 * get called often enough that that should (hopefully) not be
3242 * a real problem.
3243 *
3244 * It will not get called when we go idle, because the idle
3245 * thread is a different class (!fair), nor will the utilization
3246 * number include things like RT tasks.
3247 *
3248 * As is, the util number is not freq-invariant (we'd have to
3249 * implement arch_scale_freq_capacity() for that).
3250 *
3251 * See cpu_util().
3252 */
3253 cpufreq_update_util(rq, flags);
3254 }
3255}
3256
3257#ifdef CONFIG_SMP
3258#ifdef CONFIG_FAIR_GROUP_SCHED
3259/*
3260 * Because list_add_leaf_cfs_rq always places a child cfs_rq on the list
3261 * immediately before a parent cfs_rq, and cfs_rqs are removed from the list
3262 * bottom-up, we only have to test whether the cfs_rq before us on the list
3263 * is our child.
3264 * If cfs_rq is not on the list, test whether a child needs its to be added to
3265 * connect a branch to the tree * (see list_add_leaf_cfs_rq() for details).
3266 */
3267static inline bool child_cfs_rq_on_list(struct cfs_rq *cfs_rq)
3268{
3269 struct cfs_rq *prev_cfs_rq;
3270 struct list_head *prev;
3271
3272 if (cfs_rq->on_list) {
3273 prev = cfs_rq->leaf_cfs_rq_list.prev;
3274 } else {
3275 struct rq *rq = rq_of(cfs_rq);
3276
3277 prev = rq->tmp_alone_branch;
3278 }
3279
3280 prev_cfs_rq = container_of(prev, struct cfs_rq, leaf_cfs_rq_list);
3281
3282 return (prev_cfs_rq->tg->parent == cfs_rq->tg);
3283}
3284
3285static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
3286{
3287 if (cfs_rq->load.weight)
3288 return false;
3289
3290 if (cfs_rq->avg.load_sum)
3291 return false;
3292
3293 if (cfs_rq->avg.util_sum)
3294 return false;
3295
3296 if (cfs_rq->avg.runnable_sum)
3297 return false;
3298
3299 if (child_cfs_rq_on_list(cfs_rq))
3300 return false;
3301
3302 /*
3303 * _avg must be null when _sum are null because _avg = _sum / divider
3304 * Make sure that rounding and/or propagation of PELT values never
3305 * break this.
3306 */
3307 SCHED_WARN_ON(cfs_rq->avg.load_avg ||
3308 cfs_rq->avg.util_avg ||
3309 cfs_rq->avg.runnable_avg);
3310
3311 return true;
3312}
3313
3314/**
3315 * update_tg_load_avg - update the tg's load avg
3316 * @cfs_rq: the cfs_rq whose avg changed
3317 *
3318 * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
3319 * However, because tg->load_avg is a global value there are performance
3320 * considerations.
3321 *
3322 * In order to avoid having to look at the other cfs_rq's, we use a
3323 * differential update where we store the last value we propagated. This in
3324 * turn allows skipping updates if the differential is 'small'.
3325 *
3326 * Updating tg's load_avg is necessary before update_cfs_share().
3327 */
3328static inline void update_tg_load_avg(struct cfs_rq *cfs_rq)
3329{
3330 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
3331
3332 /*
3333 * No need to update load_avg for root_task_group as it is not used.
3334 */
3335 if (cfs_rq->tg == &root_task_group)
3336 return;
3337
3338 if (abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
3339 atomic_long_add(delta, &cfs_rq->tg->load_avg);
3340 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
3341 }
3342}
3343
3344/*
3345 * Called within set_task_rq() right before setting a task's CPU. The
3346 * caller only guarantees p->pi_lock is held; no other assumptions,
3347 * including the state of rq->lock, should be made.
3348 */
3349void set_task_rq_fair(struct sched_entity *se,
3350 struct cfs_rq *prev, struct cfs_rq *next)
3351{
3352 u64 p_last_update_time;
3353 u64 n_last_update_time;
3354
3355 if (!sched_feat(ATTACH_AGE_LOAD))
3356 return;
3357
3358 /*
3359 * We are supposed to update the task to "current" time, then its up to
3360 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
3361 * getting what current time is, so simply throw away the out-of-date
3362 * time. This will result in the wakee task is less decayed, but giving
3363 * the wakee more load sounds not bad.
3364 */
3365 if (!(se->avg.last_update_time && prev))
3366 return;
3367
3368#ifndef CONFIG_64BIT
3369 {
3370 u64 p_last_update_time_copy;
3371 u64 n_last_update_time_copy;
3372
3373 do {
3374 p_last_update_time_copy = prev->load_last_update_time_copy;
3375 n_last_update_time_copy = next->load_last_update_time_copy;
3376
3377 smp_rmb();
3378
3379 p_last_update_time = prev->avg.last_update_time;
3380 n_last_update_time = next->avg.last_update_time;
3381
3382 } while (p_last_update_time != p_last_update_time_copy ||
3383 n_last_update_time != n_last_update_time_copy);
3384 }
3385#else
3386 p_last_update_time = prev->avg.last_update_time;
3387 n_last_update_time = next->avg.last_update_time;
3388#endif
3389 __update_load_avg_blocked_se(p_last_update_time, se);
3390 se->avg.last_update_time = n_last_update_time;
3391}
3392
3393
3394/*
3395 * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
3396 * propagate its contribution. The key to this propagation is the invariant
3397 * that for each group:
3398 *
3399 * ge->avg == grq->avg (1)
3400 *
3401 * _IFF_ we look at the pure running and runnable sums. Because they
3402 * represent the very same entity, just at different points in the hierarchy.
3403 *
3404 * Per the above update_tg_cfs_util() and update_tg_cfs_runnable() are trivial
3405 * and simply copies the running/runnable sum over (but still wrong, because
3406 * the group entity and group rq do not have their PELT windows aligned).
3407 *
3408 * However, update_tg_cfs_load() is more complex. So we have:
3409 *
3410 * ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg (2)
3411 *
3412 * And since, like util, the runnable part should be directly transferable,
3413 * the following would _appear_ to be the straight forward approach:
3414 *
3415 * grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg (3)
3416 *
3417 * And per (1) we have:
3418 *
3419 * ge->avg.runnable_avg == grq->avg.runnable_avg
3420 *
3421 * Which gives:
3422 *
3423 * ge->load.weight * grq->avg.load_avg
3424 * ge->avg.load_avg = ----------------------------------- (4)
3425 * grq->load.weight
3426 *
3427 * Except that is wrong!
3428 *
3429 * Because while for entities historical weight is not important and we
3430 * really only care about our future and therefore can consider a pure
3431 * runnable sum, runqueues can NOT do this.
3432 *
3433 * We specifically want runqueues to have a load_avg that includes
3434 * historical weights. Those represent the blocked load, the load we expect
3435 * to (shortly) return to us. This only works by keeping the weights as
3436 * integral part of the sum. We therefore cannot decompose as per (3).
3437 *
3438 * Another reason this doesn't work is that runnable isn't a 0-sum entity.
3439 * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
3440 * rq itself is runnable anywhere between 2/3 and 1 depending on how the
3441 * runnable section of these tasks overlap (or not). If they were to perfectly
3442 * align the rq as a whole would be runnable 2/3 of the time. If however we
3443 * always have at least 1 runnable task, the rq as a whole is always runnable.
3444 *
3445 * So we'll have to approximate.. :/
3446 *
3447 * Given the constraint:
3448 *
3449 * ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
3450 *
3451 * We can construct a rule that adds runnable to a rq by assuming minimal
3452 * overlap.
3453 *
3454 * On removal, we'll assume each task is equally runnable; which yields:
3455 *
3456 * grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
3457 *
3458 * XXX: only do this for the part of runnable > running ?
3459 *
3460 */
3461
3462static inline void
3463update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3464{
3465 long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;
3466 u32 divider;
3467
3468 /* Nothing to update */
3469 if (!delta)
3470 return;
3471
3472 /*
3473 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
3474 * See ___update_load_avg() for details.
3475 */
3476 divider = get_pelt_divider(&cfs_rq->avg);
3477
3478 /* Set new sched_entity's utilization */
3479 se->avg.util_avg = gcfs_rq->avg.util_avg;
3480 se->avg.util_sum = se->avg.util_avg * divider;
3481
3482 /* Update parent cfs_rq utilization */
3483 add_positive(&cfs_rq->avg.util_avg, delta);
3484 cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * divider;
3485}
3486
3487static inline void
3488update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3489{
3490 long delta = gcfs_rq->avg.runnable_avg - se->avg.runnable_avg;
3491 u32 divider;
3492
3493 /* Nothing to update */
3494 if (!delta)
3495 return;
3496
3497 /*
3498 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
3499 * See ___update_load_avg() for details.
3500 */
3501 divider = get_pelt_divider(&cfs_rq->avg);
3502
3503 /* Set new sched_entity's runnable */
3504 se->avg.runnable_avg = gcfs_rq->avg.runnable_avg;
3505 se->avg.runnable_sum = se->avg.runnable_avg * divider;
3506
3507 /* Update parent cfs_rq runnable */
3508 add_positive(&cfs_rq->avg.runnable_avg, delta);
3509 cfs_rq->avg.runnable_sum = cfs_rq->avg.runnable_avg * divider;
3510}
3511
3512static inline void
3513update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3514{
3515 long delta, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum;
3516 unsigned long load_avg;
3517 u64 load_sum = 0;
3518 u32 divider;
3519
3520 if (!runnable_sum)
3521 return;
3522
3523 gcfs_rq->prop_runnable_sum = 0;
3524
3525 /*
3526 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
3527 * See ___update_load_avg() for details.
3528 */
3529 divider = get_pelt_divider(&cfs_rq->avg);
3530
3531 if (runnable_sum >= 0) {
3532 /*
3533 * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
3534 * the CPU is saturated running == runnable.
3535 */
3536 runnable_sum += se->avg.load_sum;
3537 runnable_sum = min_t(long, runnable_sum, divider);
3538 } else {
3539 /*
3540 * Estimate the new unweighted runnable_sum of the gcfs_rq by
3541 * assuming all tasks are equally runnable.
3542 */
3543 if (scale_load_down(gcfs_rq->load.weight)) {
3544 load_sum = div_s64(gcfs_rq->avg.load_sum,
3545 scale_load_down(gcfs_rq->load.weight));
3546 }
3547
3548 /* But make sure to not inflate se's runnable */
3549 runnable_sum = min(se->avg.load_sum, load_sum);
3550 }
3551
3552 /*
3553 * runnable_sum can't be lower than running_sum
3554 * Rescale running sum to be in the same range as runnable sum
3555 * running_sum is in [0 : LOAD_AVG_MAX << SCHED_CAPACITY_SHIFT]
3556 * runnable_sum is in [0 : LOAD_AVG_MAX]
3557 */
3558 running_sum = se->avg.util_sum >> SCHED_CAPACITY_SHIFT;
3559 runnable_sum = max(runnable_sum, running_sum);
3560
3561 load_sum = (s64)se_weight(se) * runnable_sum;
3562 load_avg = div_s64(load_sum, divider);
3563
3564 se->avg.load_sum = runnable_sum;
3565
3566 delta = load_avg - se->avg.load_avg;
3567 if (!delta)
3568 return;
3569
3570 se->avg.load_avg = load_avg;
3571
3572 add_positive(&cfs_rq->avg.load_avg, delta);
3573 cfs_rq->avg.load_sum = cfs_rq->avg.load_avg * divider;
3574}
3575
3576static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
3577{
3578 cfs_rq->propagate = 1;
3579 cfs_rq->prop_runnable_sum += runnable_sum;
3580}
3581
3582/* Update task and its cfs_rq load average */
3583static inline int propagate_entity_load_avg(struct sched_entity *se)
3584{
3585 struct cfs_rq *cfs_rq, *gcfs_rq;
3586
3587 if (entity_is_task(se))
3588 return 0;
3589
3590 gcfs_rq = group_cfs_rq(se);
3591 if (!gcfs_rq->propagate)
3592 return 0;
3593
3594 gcfs_rq->propagate = 0;
3595
3596 cfs_rq = cfs_rq_of(se);
3597
3598 add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
3599
3600 update_tg_cfs_util(cfs_rq, se, gcfs_rq);
3601 update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
3602 update_tg_cfs_load(cfs_rq, se, gcfs_rq);
3603
3604 trace_pelt_cfs_tp(cfs_rq);
3605 trace_pelt_se_tp(se);
3606
3607 return 1;
3608}
3609
3610/*
3611 * Check if we need to update the load and the utilization of a blocked
3612 * group_entity:
3613 */
3614static inline bool skip_blocked_update(struct sched_entity *se)
3615{
3616 struct cfs_rq *gcfs_rq = group_cfs_rq(se);
3617
3618 /*
3619 * If sched_entity still have not zero load or utilization, we have to
3620 * decay it:
3621 */
3622 if (se->avg.load_avg || se->avg.util_avg)
3623 return false;
3624
3625 /*
3626 * If there is a pending propagation, we have to update the load and
3627 * the utilization of the sched_entity:
3628 */
3629 if (gcfs_rq->propagate)
3630 return false;
3631
3632 /*
3633 * Otherwise, the load and the utilization of the sched_entity is
3634 * already zero and there is no pending propagation, so it will be a
3635 * waste of time to try to decay it:
3636 */
3637 return true;
3638}
3639
3640#else /* CONFIG_FAIR_GROUP_SCHED */
3641
3642static inline void update_tg_load_avg(struct cfs_rq *cfs_rq) {}
3643
3644static inline int propagate_entity_load_avg(struct sched_entity *se)
3645{
3646 return 0;
3647}
3648
3649static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
3650
3651#endif /* CONFIG_FAIR_GROUP_SCHED */
3652
3653/**
3654 * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
3655 * @now: current time, as per cfs_rq_clock_pelt()
3656 * @cfs_rq: cfs_rq to update
3657 *
3658 * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
3659 * avg. The immediate corollary is that all (fair) tasks must be attached, see
3660 * post_init_entity_util_avg().
3661 *
3662 * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
3663 *
3664 * Returns true if the load decayed or we removed load.
3665 *
3666 * Since both these conditions indicate a changed cfs_rq->avg.load we should
3667 * call update_tg_load_avg() when this function returns true.
3668 */
3669static inline int
3670update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3671{
3672 unsigned long removed_load = 0, removed_util = 0, removed_runnable = 0;
3673 struct sched_avg *sa = &cfs_rq->avg;
3674 int decayed = 0;
3675
3676 if (cfs_rq->removed.nr) {
3677 unsigned long r;
3678 u32 divider = get_pelt_divider(&cfs_rq->avg);
3679
3680 raw_spin_lock(&cfs_rq->removed.lock);
3681 swap(cfs_rq->removed.util_avg, removed_util);
3682 swap(cfs_rq->removed.load_avg, removed_load);
3683 swap(cfs_rq->removed.runnable_avg, removed_runnable);
3684 cfs_rq->removed.nr = 0;
3685 raw_spin_unlock(&cfs_rq->removed.lock);
3686
3687 r = removed_load;
3688 sub_positive(&sa->load_avg, r);
3689 sa->load_sum = sa->load_avg * divider;
3690
3691 r = removed_util;
3692 sub_positive(&sa->util_avg, r);
3693 sa->util_sum = sa->util_avg * divider;
3694
3695 r = removed_runnable;
3696 sub_positive(&sa->runnable_avg, r);
3697 sa->runnable_sum = sa->runnable_avg * divider;
3698
3699 /*
3700 * removed_runnable is the unweighted version of removed_load so we
3701 * can use it to estimate removed_load_sum.
3702 */
3703 add_tg_cfs_propagate(cfs_rq,
3704 -(long)(removed_runnable * divider) >> SCHED_CAPACITY_SHIFT);
3705
3706 decayed = 1;
3707 }
3708
3709 decayed |= __update_load_avg_cfs_rq(now, cfs_rq);
3710
3711#ifndef CONFIG_64BIT
3712 smp_wmb();
3713 cfs_rq->load_last_update_time_copy = sa->last_update_time;
3714#endif
3715
3716 return decayed;
3717}
3718
3719/**
3720 * attach_entity_load_avg - attach this entity to its cfs_rq load avg
3721 * @cfs_rq: cfs_rq to attach to
3722 * @se: sched_entity to attach
3723 *
3724 * Must call update_cfs_rq_load_avg() before this, since we rely on
3725 * cfs_rq->avg.last_update_time being current.
3726 */
3727static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3728{
3729 /*
3730 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
3731 * See ___update_load_avg() for details.
3732 */
3733 u32 divider = get_pelt_divider(&cfs_rq->avg);
3734
3735 /*
3736 * When we attach the @se to the @cfs_rq, we must align the decay
3737 * window because without that, really weird and wonderful things can
3738 * happen.
3739 *
3740 * XXX illustrate
3741 */
3742 se->avg.last_update_time = cfs_rq->avg.last_update_time;
3743 se->avg.period_contrib = cfs_rq->avg.period_contrib;
3744
3745 /*
3746 * Hell(o) Nasty stuff.. we need to recompute _sum based on the new
3747 * period_contrib. This isn't strictly correct, but since we're
3748 * entirely outside of the PELT hierarchy, nobody cares if we truncate
3749 * _sum a little.
3750 */
3751 se->avg.util_sum = se->avg.util_avg * divider;
3752
3753 se->avg.runnable_sum = se->avg.runnable_avg * divider;
3754
3755 se->avg.load_sum = divider;
3756 if (se_weight(se)) {
3757 se->avg.load_sum =
3758 div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se));
3759 }
3760
3761 enqueue_load_avg(cfs_rq, se);
3762 cfs_rq->avg.util_avg += se->avg.util_avg;
3763 cfs_rq->avg.util_sum += se->avg.util_sum;
3764 cfs_rq->avg.runnable_avg += se->avg.runnable_avg;
3765 cfs_rq->avg.runnable_sum += se->avg.runnable_sum;
3766
3767 add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
3768
3769 cfs_rq_util_change(cfs_rq, 0);
3770
3771 trace_pelt_cfs_tp(cfs_rq);
3772}
3773
3774/**
3775 * detach_entity_load_avg - detach this entity from its cfs_rq load avg
3776 * @cfs_rq: cfs_rq to detach from
3777 * @se: sched_entity to detach
3778 *
3779 * Must call update_cfs_rq_load_avg() before this, since we rely on
3780 * cfs_rq->avg.last_update_time being current.
3781 */
3782static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3783{
3784 /*
3785 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
3786 * See ___update_load_avg() for details.
3787 */
3788 u32 divider = get_pelt_divider(&cfs_rq->avg);
3789
3790 dequeue_load_avg(cfs_rq, se);
3791 sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
3792 cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * divider;
3793 sub_positive(&cfs_rq->avg.runnable_avg, se->avg.runnable_avg);
3794 cfs_rq->avg.runnable_sum = cfs_rq->avg.runnable_avg * divider;
3795
3796 add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
3797
3798 cfs_rq_util_change(cfs_rq, 0);
3799
3800 trace_pelt_cfs_tp(cfs_rq);
3801}
3802
3803/*
3804 * Optional action to be done while updating the load average
3805 */
3806#define UPDATE_TG 0x1
3807#define SKIP_AGE_LOAD 0x2
3808#define DO_ATTACH 0x4
3809
3810/* Update task and its cfs_rq load average */
3811static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3812{
3813 u64 now = cfs_rq_clock_pelt(cfs_rq);
3814 int decayed;
3815
3816 /*
3817 * Track task load average for carrying it to new CPU after migrated, and
3818 * track group sched_entity load average for task_h_load calc in migration
3819 */
3820 if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
3821 __update_load_avg_se(now, cfs_rq, se);
3822
3823 decayed = update_cfs_rq_load_avg(now, cfs_rq);
3824 decayed |= propagate_entity_load_avg(se);
3825
3826 if (!se->avg.last_update_time && (flags & DO_ATTACH)) {
3827
3828 /*
3829 * DO_ATTACH means we're here from enqueue_entity().
3830 * !last_update_time means we've passed through
3831 * migrate_task_rq_fair() indicating we migrated.
3832 *
3833 * IOW we're enqueueing a task on a new CPU.
3834 */
3835 attach_entity_load_avg(cfs_rq, se);
3836 update_tg_load_avg(cfs_rq);
3837
3838 } else if (decayed) {
3839 cfs_rq_util_change(cfs_rq, 0);
3840
3841 if (flags & UPDATE_TG)
3842 update_tg_load_avg(cfs_rq);
3843 }
3844}
3845
3846#ifndef CONFIG_64BIT
3847static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3848{
3849 u64 last_update_time_copy;
3850 u64 last_update_time;
3851
3852 do {
3853 last_update_time_copy = cfs_rq->load_last_update_time_copy;
3854 smp_rmb();
3855 last_update_time = cfs_rq->avg.last_update_time;
3856 } while (last_update_time != last_update_time_copy);
3857
3858 return last_update_time;
3859}
3860#else
3861static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3862{
3863 return cfs_rq->avg.last_update_time;
3864}
3865#endif
3866
3867/*
3868 * Synchronize entity load avg of dequeued entity without locking
3869 * the previous rq.
3870 */
3871static void sync_entity_load_avg(struct sched_entity *se)
3872{
3873 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3874 u64 last_update_time;
3875
3876 last_update_time = cfs_rq_last_update_time(cfs_rq);
3877 __update_load_avg_blocked_se(last_update_time, se);
3878}
3879
3880/*
3881 * Task first catches up with cfs_rq, and then subtract
3882 * itself from the cfs_rq (task must be off the queue now).
3883 */
3884static void remove_entity_load_avg(struct sched_entity *se)
3885{
3886 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3887 unsigned long flags;
3888
3889 /*
3890 * tasks cannot exit without having gone through wake_up_new_task() ->
3891 * post_init_entity_util_avg() which will have added things to the
3892 * cfs_rq, so we can remove unconditionally.
3893 */
3894
3895 sync_entity_load_avg(se);
3896
3897 raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags);
3898 ++cfs_rq->removed.nr;
3899 cfs_rq->removed.util_avg += se->avg.util_avg;
3900 cfs_rq->removed.load_avg += se->avg.load_avg;
3901 cfs_rq->removed.runnable_avg += se->avg.runnable_avg;
3902 raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
3903}
3904
3905static inline unsigned long cfs_rq_runnable_avg(struct cfs_rq *cfs_rq)
3906{
3907 return cfs_rq->avg.runnable_avg;
3908}
3909
3910static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
3911{
3912 return cfs_rq->avg.load_avg;
3913}
3914
3915static int newidle_balance(struct rq *this_rq, struct rq_flags *rf);
3916
3917static inline unsigned long task_util(struct task_struct *p)
3918{
3919 return READ_ONCE(p->se.avg.util_avg);
3920}
3921
3922static inline unsigned long _task_util_est(struct task_struct *p)
3923{
3924 struct util_est ue = READ_ONCE(p->se.avg.util_est);
3925
3926 return max(ue.ewma, (ue.enqueued & ~UTIL_AVG_UNCHANGED));
3927}
3928
3929static inline unsigned long task_util_est(struct task_struct *p)
3930{
3931 return max(task_util(p), _task_util_est(p));
3932}
3933
3934#ifdef CONFIG_UCLAMP_TASK
3935static inline unsigned long uclamp_task_util(struct task_struct *p)
3936{
3937 return clamp(task_util_est(p),
3938 uclamp_eff_value(p, UCLAMP_MIN),
3939 uclamp_eff_value(p, UCLAMP_MAX));
3940}
3941#else
3942static inline unsigned long uclamp_task_util(struct task_struct *p)
3943{
3944 return task_util_est(p);
3945}
3946#endif
3947
3948static inline void util_est_enqueue(struct cfs_rq *cfs_rq,
3949 struct task_struct *p)
3950{
3951 unsigned int enqueued;
3952
3953 if (!sched_feat(UTIL_EST))
3954 return;
3955
3956 /* Update root cfs_rq's estimated utilization */
3957 enqueued = cfs_rq->avg.util_est.enqueued;
3958 enqueued += _task_util_est(p);
3959 WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
3960
3961 trace_sched_util_est_cfs_tp(cfs_rq);
3962}
3963
3964static inline void util_est_dequeue(struct cfs_rq *cfs_rq,
3965 struct task_struct *p)
3966{
3967 unsigned int enqueued;
3968
3969 if (!sched_feat(UTIL_EST))
3970 return;
3971
3972 /* Update root cfs_rq's estimated utilization */
3973 enqueued = cfs_rq->avg.util_est.enqueued;
3974 enqueued -= min_t(unsigned int, enqueued, _task_util_est(p));
3975 WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
3976
3977 trace_sched_util_est_cfs_tp(cfs_rq);
3978}
3979
3980#define UTIL_EST_MARGIN (SCHED_CAPACITY_SCALE / 100)
3981
3982/*
3983 * Check if a (signed) value is within a specified (unsigned) margin,
3984 * based on the observation that:
3985 *
3986 * abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1)
3987 *
3988 * NOTE: this only works when value + margin < INT_MAX.
3989 */
3990static inline bool within_margin(int value, int margin)
3991{
3992 return ((unsigned int)(value + margin - 1) < (2 * margin - 1));
3993}
3994
3995static inline void util_est_update(struct cfs_rq *cfs_rq,
3996 struct task_struct *p,
3997 bool task_sleep)
3998{
3999 long last_ewma_diff, last_enqueued_diff;
4000 struct util_est ue;
4001
4002 if (!sched_feat(UTIL_EST))
4003 return;
4004
4005 /*
4006 * Skip update of task's estimated utilization when the task has not
4007 * yet completed an activation, e.g. being migrated.
4008 */
4009 if (!task_sleep)
4010 return;
4011
4012 /*
4013 * If the PELT values haven't changed since enqueue time,
4014 * skip the util_est update.
4015 */
4016 ue = p->se.avg.util_est;
4017 if (ue.enqueued & UTIL_AVG_UNCHANGED)
4018 return;
4019
4020 last_enqueued_diff = ue.enqueued;
4021
4022 /*
4023 * Reset EWMA on utilization increases, the moving average is used only
4024 * to smooth utilization decreases.
4025 */
4026 ue.enqueued = task_util(p);
4027 if (sched_feat(UTIL_EST_FASTUP)) {
4028 if (ue.ewma < ue.enqueued) {
4029 ue.ewma = ue.enqueued;
4030 goto done;
4031 }
4032 }
4033
4034 /*
4035 * Skip update of task's estimated utilization when its members are
4036 * already ~1% close to its last activation value.
4037 */
4038 last_ewma_diff = ue.enqueued - ue.ewma;
4039 last_enqueued_diff -= ue.enqueued;
4040 if (within_margin(last_ewma_diff, UTIL_EST_MARGIN)) {
4041 if (!within_margin(last_enqueued_diff, UTIL_EST_MARGIN))
4042 goto done;
4043
4044 return;
4045 }
4046
4047 /*
4048 * To avoid overestimation of actual task utilization, skip updates if
4049 * we cannot grant there is idle time in this CPU.
4050 */
4051 if (task_util(p) > capacity_orig_of(cpu_of(rq_of(cfs_rq))))
4052 return;
4053
4054 /*
4055 * Update Task's estimated utilization
4056 *
4057 * When *p completes an activation we can consolidate another sample
4058 * of the task size. This is done by storing the current PELT value
4059 * as ue.enqueued and by using this value to update the Exponential
4060 * Weighted Moving Average (EWMA):
4061 *
4062 * ewma(t) = w * task_util(p) + (1-w) * ewma(t-1)
4063 * = w * task_util(p) + ewma(t-1) - w * ewma(t-1)
4064 * = w * (task_util(p) - ewma(t-1)) + ewma(t-1)
4065 * = w * ( last_ewma_diff ) + ewma(t-1)
4066 * = w * (last_ewma_diff + ewma(t-1) / w)
4067 *
4068 * Where 'w' is the weight of new samples, which is configured to be
4069 * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
4070 */
4071 ue.ewma <<= UTIL_EST_WEIGHT_SHIFT;
4072 ue.ewma += last_ewma_diff;
4073 ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
4074done:
4075 ue.enqueued |= UTIL_AVG_UNCHANGED;
4076 WRITE_ONCE(p->se.avg.util_est, ue);
4077
4078 trace_sched_util_est_se_tp(&p->se);
4079}
4080
4081static inline int task_fits_capacity(struct task_struct *p, long capacity)
4082{
4083 return fits_capacity(uclamp_task_util(p), capacity);
4084}
4085
4086static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
4087{
4088 if (!static_branch_unlikely(&sched_asym_cpucapacity))
4089 return;
4090
4091 if (!p || p->nr_cpus_allowed == 1) {
4092 rq->misfit_task_load = 0;
4093 return;
4094 }
4095
4096 if (task_fits_capacity(p, capacity_of(cpu_of(rq)))) {
4097 rq->misfit_task_load = 0;
4098 return;
4099 }
4100
4101 /*
4102 * Make sure that misfit_task_load will not be null even if
4103 * task_h_load() returns 0.
4104 */
4105 rq->misfit_task_load = max_t(unsigned long, task_h_load(p), 1);
4106}
4107
4108#else /* CONFIG_SMP */
4109
4110static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
4111{
4112 return true;
4113}
4114
4115#define UPDATE_TG 0x0
4116#define SKIP_AGE_LOAD 0x0
4117#define DO_ATTACH 0x0
4118
4119static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
4120{
4121 cfs_rq_util_change(cfs_rq, 0);
4122}
4123
4124static inline void remove_entity_load_avg(struct sched_entity *se) {}
4125
4126static inline void
4127attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
4128static inline void
4129detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
4130
4131static inline int newidle_balance(struct rq *rq, struct rq_flags *rf)
4132{
4133 return 0;
4134}
4135
4136static inline void
4137util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
4138
4139static inline void
4140util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
4141
4142static inline void
4143util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p,
4144 bool task_sleep) {}
4145static inline void update_misfit_status(struct task_struct *p, struct rq *rq) {}
4146
4147#endif /* CONFIG_SMP */
4148
4149static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
4150{
4151#ifdef CONFIG_SCHED_DEBUG
4152 s64 d = se->vruntime - cfs_rq->min_vruntime;
4153
4154 if (d < 0)
4155 d = -d;
4156
4157 if (d > 3*sysctl_sched_latency)
4158 schedstat_inc(cfs_rq->nr_spread_over);
4159#endif
4160}
4161
4162static void
4163place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
4164{
4165 u64 vruntime = cfs_rq->min_vruntime;
4166
4167 /*
4168 * The 'current' period is already promised to the current tasks,
4169 * however the extra weight of the new task will slow them down a
4170 * little, place the new task so that it fits in the slot that
4171 * stays open at the end.
4172 */
4173 if (initial && sched_feat(START_DEBIT))
4174 vruntime += sched_vslice(cfs_rq, se);
4175
4176 /* sleeps up to a single latency don't count. */
4177 if (!initial) {
4178 unsigned long thresh = sysctl_sched_latency;
4179
4180 /*
4181 * Halve their sleep time's effect, to allow
4182 * for a gentler effect of sleepers:
4183 */
4184 if (sched_feat(GENTLE_FAIR_SLEEPERS))
4185 thresh >>= 1;
4186
4187 vruntime -= thresh;
4188 }
4189
4190 /* ensure we never gain time by being placed backwards. */
4191 se->vruntime = max_vruntime(se->vruntime, vruntime);
4192}
4193
4194static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
4195
4196static inline void check_schedstat_required(void)
4197{
4198#ifdef CONFIG_SCHEDSTATS
4199 if (schedstat_enabled())
4200 return;
4201
4202 /* Force schedstat enabled if a dependent tracepoint is active */
4203 if (trace_sched_stat_wait_enabled() ||
4204 trace_sched_stat_sleep_enabled() ||
4205 trace_sched_stat_iowait_enabled() ||
4206 trace_sched_stat_blocked_enabled() ||
4207 trace_sched_stat_runtime_enabled()) {
4208 printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
4209 "stat_blocked and stat_runtime require the "
4210 "kernel parameter schedstats=enable or "
4211 "kernel.sched_schedstats=1\n");
4212 }
4213#endif
4214}
4215
4216static inline bool cfs_bandwidth_used(void);
4217
4218/*
4219 * MIGRATION
4220 *
4221 * dequeue
4222 * update_curr()
4223 * update_min_vruntime()
4224 * vruntime -= min_vruntime
4225 *
4226 * enqueue
4227 * update_curr()
4228 * update_min_vruntime()
4229 * vruntime += min_vruntime
4230 *
4231 * this way the vruntime transition between RQs is done when both
4232 * min_vruntime are up-to-date.
4233 *
4234 * WAKEUP (remote)
4235 *
4236 * ->migrate_task_rq_fair() (p->state == TASK_WAKING)
4237 * vruntime -= min_vruntime
4238 *
4239 * enqueue
4240 * update_curr()
4241 * update_min_vruntime()
4242 * vruntime += min_vruntime
4243 *
4244 * this way we don't have the most up-to-date min_vruntime on the originating
4245 * CPU and an up-to-date min_vruntime on the destination CPU.
4246 */
4247
4248static void
4249enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
4250{
4251 bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
4252 bool curr = cfs_rq->curr == se;
4253
4254 /*
4255 * If we're the current task, we must renormalise before calling
4256 * update_curr().
4257 */
4258 if (renorm && curr)
4259 se->vruntime += cfs_rq->min_vruntime;
4260
4261 update_curr(cfs_rq);
4262
4263 /*
4264 * Otherwise, renormalise after, such that we're placed at the current
4265 * moment in time, instead of some random moment in the past. Being
4266 * placed in the past could significantly boost this task to the
4267 * fairness detriment of existing tasks.
4268 */
4269 if (renorm && !curr)
4270 se->vruntime += cfs_rq->min_vruntime;
4271
4272 /*
4273 * When enqueuing a sched_entity, we must:
4274 * - Update loads to have both entity and cfs_rq synced with now.
4275 * - Add its load to cfs_rq->runnable_avg
4276 * - For group_entity, update its weight to reflect the new share of
4277 * its group cfs_rq
4278 * - Add its new weight to cfs_rq->load.weight
4279 */
4280 update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
4281 se_update_runnable(se);
4282 update_cfs_group(se);
4283 account_entity_enqueue(cfs_rq, se);
4284
4285 if (flags & ENQUEUE_WAKEUP)
4286 place_entity(cfs_rq, se, 0);
4287
4288 check_schedstat_required();
4289 update_stats_enqueue(cfs_rq, se, flags);
4290 check_spread(cfs_rq, se);
4291 if (!curr)
4292 __enqueue_entity(cfs_rq, se);
4293 se->on_rq = 1;
4294
4295 /*
4296 * When bandwidth control is enabled, cfs might have been removed
4297 * because of a parent been throttled but cfs->nr_running > 1. Try to
4298 * add it unconditionally.
4299 */
4300 if (cfs_rq->nr_running == 1 || cfs_bandwidth_used())
4301 list_add_leaf_cfs_rq(cfs_rq);
4302
4303 if (cfs_rq->nr_running == 1)
4304 check_enqueue_throttle(cfs_rq);
4305}
4306
4307static void __clear_buddies_last(struct sched_entity *se)
4308{
4309 for_each_sched_entity(se) {
4310 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4311 if (cfs_rq->last != se)
4312 break;
4313
4314 cfs_rq->last = NULL;
4315 }
4316}
4317
4318static void __clear_buddies_next(struct sched_entity *se)
4319{
4320 for_each_sched_entity(se) {
4321 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4322 if (cfs_rq->next != se)
4323 break;
4324
4325 cfs_rq->next = NULL;
4326 }
4327}
4328
4329static void __clear_buddies_skip(struct sched_entity *se)
4330{
4331 for_each_sched_entity(se) {
4332 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4333 if (cfs_rq->skip != se)
4334 break;
4335
4336 cfs_rq->skip = NULL;
4337 }
4338}
4339
4340static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
4341{
4342 if (cfs_rq->last == se)
4343 __clear_buddies_last(se);
4344
4345 if (cfs_rq->next == se)
4346 __clear_buddies_next(se);
4347
4348 if (cfs_rq->skip == se)
4349 __clear_buddies_skip(se);
4350}
4351
4352static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4353
4354static void
4355dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
4356{
4357 /*
4358 * Update run-time statistics of the 'current'.
4359 */
4360 update_curr(cfs_rq);
4361
4362 /*
4363 * When dequeuing a sched_entity, we must:
4364 * - Update loads to have both entity and cfs_rq synced with now.
4365 * - Subtract its load from the cfs_rq->runnable_avg.
4366 * - Subtract its previous weight from cfs_rq->load.weight.
4367 * - For group entity, update its weight to reflect the new share
4368 * of its group cfs_rq.
4369 */
4370 update_load_avg(cfs_rq, se, UPDATE_TG);
4371 se_update_runnable(se);
4372
4373 update_stats_dequeue(cfs_rq, se, flags);
4374
4375 clear_buddies(cfs_rq, se);
4376
4377 if (se != cfs_rq->curr)
4378 __dequeue_entity(cfs_rq, se);
4379 se->on_rq = 0;
4380 account_entity_dequeue(cfs_rq, se);
4381
4382 /*
4383 * Normalize after update_curr(); which will also have moved
4384 * min_vruntime if @se is the one holding it back. But before doing
4385 * update_min_vruntime() again, which will discount @se's position and
4386 * can move min_vruntime forward still more.
4387 */
4388 if (!(flags & DEQUEUE_SLEEP))
4389 se->vruntime -= cfs_rq->min_vruntime;
4390
4391 /* return excess runtime on last dequeue */
4392 return_cfs_rq_runtime(cfs_rq);
4393
4394 update_cfs_group(se);
4395
4396 /*
4397 * Now advance min_vruntime if @se was the entity holding it back,
4398 * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
4399 * put back on, and if we advance min_vruntime, we'll be placed back
4400 * further than we started -- ie. we'll be penalized.
4401 */
4402 if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
4403 update_min_vruntime(cfs_rq);
4404}
4405
4406/*
4407 * Preempt the current task with a newly woken task if needed:
4408 */
4409static void
4410check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4411{
4412 unsigned long ideal_runtime, delta_exec;
4413 struct sched_entity *se;
4414 s64 delta;
4415
4416 ideal_runtime = sched_slice(cfs_rq, curr);
4417 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
4418 if (delta_exec > ideal_runtime) {
4419 resched_curr(rq_of(cfs_rq));
4420 /*
4421 * The current task ran long enough, ensure it doesn't get
4422 * re-elected due to buddy favours.
4423 */
4424 clear_buddies(cfs_rq, curr);
4425 return;
4426 }
4427
4428 /*
4429 * Ensure that a task that missed wakeup preemption by a
4430 * narrow margin doesn't have to wait for a full slice.
4431 * This also mitigates buddy induced latencies under load.
4432 */
4433 if (delta_exec < sysctl_sched_min_granularity)
4434 return;
4435
4436 se = __pick_first_entity(cfs_rq);
4437 delta = curr->vruntime - se->vruntime;
4438
4439 if (delta < 0)
4440 return;
4441
4442 if (delta > ideal_runtime)
4443 resched_curr(rq_of(cfs_rq));
4444}
4445
4446static void
4447set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
4448{
4449 clear_buddies(cfs_rq, se);
4450
4451 /* 'current' is not kept within the tree. */
4452 if (se->on_rq) {
4453 /*
4454 * Any task has to be enqueued before it get to execute on
4455 * a CPU. So account for the time it spent waiting on the
4456 * runqueue.
4457 */
4458 update_stats_wait_end(cfs_rq, se);
4459 __dequeue_entity(cfs_rq, se);
4460 update_load_avg(cfs_rq, se, UPDATE_TG);
4461 }
4462
4463 update_stats_curr_start(cfs_rq, se);
4464 cfs_rq->curr = se;
4465
4466 /*
4467 * Track our maximum slice length, if the CPU's load is at
4468 * least twice that of our own weight (i.e. dont track it
4469 * when there are only lesser-weight tasks around):
4470 */
4471 if (schedstat_enabled() &&
4472 rq_of(cfs_rq)->cfs.load.weight >= 2*se->load.weight) {
4473 schedstat_set(se->statistics.slice_max,
4474 max((u64)schedstat_val(se->statistics.slice_max),
4475 se->sum_exec_runtime - se->prev_sum_exec_runtime));
4476 }
4477
4478 se->prev_sum_exec_runtime = se->sum_exec_runtime;
4479}
4480
4481static int
4482wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
4483
4484/*
4485 * Pick the next process, keeping these things in mind, in this order:
4486 * 1) keep things fair between processes/task groups
4487 * 2) pick the "next" process, since someone really wants that to run
4488 * 3) pick the "last" process, for cache locality
4489 * 4) do not run the "skip" process, if something else is available
4490 */
4491static struct sched_entity *
4492pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4493{
4494 struct sched_entity *left = __pick_first_entity(cfs_rq);
4495 struct sched_entity *se;
4496
4497 /*
4498 * If curr is set we have to see if its left of the leftmost entity
4499 * still in the tree, provided there was anything in the tree at all.
4500 */
4501 if (!left || (curr && entity_before(curr, left)))
4502 left = curr;
4503
4504 se = left; /* ideally we run the leftmost entity */
4505
4506 /*
4507 * Avoid running the skip buddy, if running something else can
4508 * be done without getting too unfair.
4509 */
4510 if (cfs_rq->skip && cfs_rq->skip == se) {
4511 struct sched_entity *second;
4512
4513 if (se == curr) {
4514 second = __pick_first_entity(cfs_rq);
4515 } else {
4516 second = __pick_next_entity(se);
4517 if (!second || (curr && entity_before(curr, second)))
4518 second = curr;
4519 }
4520
4521 if (second && wakeup_preempt_entity(second, left) < 1)
4522 se = second;
4523 }
4524
4525 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) {
4526 /*
4527 * Someone really wants this to run. If it's not unfair, run it.
4528 */
4529 se = cfs_rq->next;
4530 } else if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) {
4531 /*
4532 * Prefer last buddy, try to return the CPU to a preempted task.
4533 */
4534 se = cfs_rq->last;
4535 }
4536
4537 return se;
4538}
4539
4540static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4541
4542static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
4543{
4544 /*
4545 * If still on the runqueue then deactivate_task()
4546 * was not called and update_curr() has to be done:
4547 */
4548 if (prev->on_rq)
4549 update_curr(cfs_rq);
4550
4551 /* throttle cfs_rqs exceeding runtime */
4552 check_cfs_rq_runtime(cfs_rq);
4553
4554 check_spread(cfs_rq, prev);
4555
4556 if (prev->on_rq) {
4557 update_stats_wait_start(cfs_rq, prev);
4558 /* Put 'current' back into the tree. */
4559 __enqueue_entity(cfs_rq, prev);
4560 /* in !on_rq case, update occurred at dequeue */
4561 update_load_avg(cfs_rq, prev, 0);
4562 }
4563 cfs_rq->curr = NULL;
4564}
4565
4566static void
4567entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
4568{
4569 /*
4570 * Update run-time statistics of the 'current'.
4571 */
4572 update_curr(cfs_rq);
4573
4574 /*
4575 * Ensure that runnable average is periodically updated.
4576 */
4577 update_load_avg(cfs_rq, curr, UPDATE_TG);
4578 update_cfs_group(curr);
4579
4580#ifdef CONFIG_SCHED_HRTICK
4581 /*
4582 * queued ticks are scheduled to match the slice, so don't bother
4583 * validating it and just reschedule.
4584 */
4585 if (queued) {
4586 resched_curr(rq_of(cfs_rq));
4587 return;
4588 }
4589 /*
4590 * don't let the period tick interfere with the hrtick preemption
4591 */
4592 if (!sched_feat(DOUBLE_TICK) &&
4593 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
4594 return;
4595#endif
4596
4597 if (cfs_rq->nr_running > 1)
4598 check_preempt_tick(cfs_rq, curr);
4599}
4600
4601
4602/**************************************************
4603 * CFS bandwidth control machinery
4604 */
4605
4606#ifdef CONFIG_CFS_BANDWIDTH
4607
4608#ifdef CONFIG_JUMP_LABEL
4609static struct static_key __cfs_bandwidth_used;
4610
4611static inline bool cfs_bandwidth_used(void)
4612{
4613 return static_key_false(&__cfs_bandwidth_used);
4614}
4615
4616void cfs_bandwidth_usage_inc(void)
4617{
4618 static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
4619}
4620
4621void cfs_bandwidth_usage_dec(void)
4622{
4623 static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
4624}
4625#else /* CONFIG_JUMP_LABEL */
4626static bool cfs_bandwidth_used(void)
4627{
4628 return true;
4629}
4630
4631void cfs_bandwidth_usage_inc(void) {}
4632void cfs_bandwidth_usage_dec(void) {}
4633#endif /* CONFIG_JUMP_LABEL */
4634
4635/*
4636 * default period for cfs group bandwidth.
4637 * default: 0.1s, units: nanoseconds
4638 */
4639static inline u64 default_cfs_period(void)
4640{
4641 return 100000000ULL;
4642}
4643
4644static inline u64 sched_cfs_bandwidth_slice(void)
4645{
4646 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
4647}
4648
4649/*
4650 * Replenish runtime according to assigned quota. We use sched_clock_cpu
4651 * directly instead of rq->clock to avoid adding additional synchronization
4652 * around rq->lock.
4653 *
4654 * requires cfs_b->lock
4655 */
4656void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
4657{
4658 if (unlikely(cfs_b->quota == RUNTIME_INF))
4659 return;
4660
4661 cfs_b->runtime += cfs_b->quota;
4662 cfs_b->runtime = min(cfs_b->runtime, cfs_b->quota + cfs_b->burst);
4663}
4664
4665static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4666{
4667 return &tg->cfs_bandwidth;
4668}
4669
4670/* returns 0 on failure to allocate runtime */
4671static int __assign_cfs_rq_runtime(struct cfs_bandwidth *cfs_b,
4672 struct cfs_rq *cfs_rq, u64 target_runtime)
4673{
4674 u64 min_amount, amount = 0;
4675
4676 lockdep_assert_held(&cfs_b->lock);
4677
4678 /* note: this is a positive sum as runtime_remaining <= 0 */
4679 min_amount = target_runtime - cfs_rq->runtime_remaining;
4680
4681 if (cfs_b->quota == RUNTIME_INF)
4682 amount = min_amount;
4683 else {
4684 start_cfs_bandwidth(cfs_b);
4685
4686 if (cfs_b->runtime > 0) {
4687 amount = min(cfs_b->runtime, min_amount);
4688 cfs_b->runtime -= amount;
4689 cfs_b->idle = 0;
4690 }
4691 }
4692
4693 cfs_rq->runtime_remaining += amount;
4694
4695 return cfs_rq->runtime_remaining > 0;
4696}
4697
4698/* returns 0 on failure to allocate runtime */
4699static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4700{
4701 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4702 int ret;
4703
4704 raw_spin_lock(&cfs_b->lock);
4705 ret = __assign_cfs_rq_runtime(cfs_b, cfs_rq, sched_cfs_bandwidth_slice());
4706 raw_spin_unlock(&cfs_b->lock);
4707
4708 return ret;
4709}
4710
4711static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4712{
4713 /* dock delta_exec before expiring quota (as it could span periods) */
4714 cfs_rq->runtime_remaining -= delta_exec;
4715
4716 if (likely(cfs_rq->runtime_remaining > 0))
4717 return;
4718
4719 if (cfs_rq->throttled)
4720 return;
4721 /*
4722 * if we're unable to extend our runtime we resched so that the active
4723 * hierarchy can be throttled
4724 */
4725 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
4726 resched_curr(rq_of(cfs_rq));
4727}
4728
4729static __always_inline
4730void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4731{
4732 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
4733 return;
4734
4735 __account_cfs_rq_runtime(cfs_rq, delta_exec);
4736}
4737
4738static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4739{
4740 return cfs_bandwidth_used() && cfs_rq->throttled;
4741}
4742
4743/* check whether cfs_rq, or any parent, is throttled */
4744static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4745{
4746 return cfs_bandwidth_used() && cfs_rq->throttle_count;
4747}
4748
4749/*
4750 * Ensure that neither of the group entities corresponding to src_cpu or
4751 * dest_cpu are members of a throttled hierarchy when performing group
4752 * load-balance operations.
4753 */
4754static inline int throttled_lb_pair(struct task_group *tg,
4755 int src_cpu, int dest_cpu)
4756{
4757 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
4758
4759 src_cfs_rq = tg->cfs_rq[src_cpu];
4760 dest_cfs_rq = tg->cfs_rq[dest_cpu];
4761
4762 return throttled_hierarchy(src_cfs_rq) ||
4763 throttled_hierarchy(dest_cfs_rq);
4764}
4765
4766static int tg_unthrottle_up(struct task_group *tg, void *data)
4767{
4768 struct rq *rq = data;
4769 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4770
4771 cfs_rq->throttle_count--;
4772 if (!cfs_rq->throttle_count) {
4773 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
4774 cfs_rq->throttled_clock_task;
4775
4776 /* Add cfs_rq with load or one or more already running entities to the list */
4777 if (!cfs_rq_is_decayed(cfs_rq) || cfs_rq->nr_running)
4778 list_add_leaf_cfs_rq(cfs_rq);
4779 }
4780
4781 return 0;
4782}
4783
4784static int tg_throttle_down(struct task_group *tg, void *data)
4785{
4786 struct rq *rq = data;
4787 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4788
4789 /* group is entering throttled state, stop time */
4790 if (!cfs_rq->throttle_count) {
4791 cfs_rq->throttled_clock_task = rq_clock_task(rq);
4792 list_del_leaf_cfs_rq(cfs_rq);
4793 }
4794 cfs_rq->throttle_count++;
4795
4796 return 0;
4797}
4798
4799static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
4800{
4801 struct rq *rq = rq_of(cfs_rq);
4802 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4803 struct sched_entity *se;
4804 long task_delta, idle_task_delta, dequeue = 1;
4805
4806 raw_spin_lock(&cfs_b->lock);
4807 /* This will start the period timer if necessary */
4808 if (__assign_cfs_rq_runtime(cfs_b, cfs_rq, 1)) {
4809 /*
4810 * We have raced with bandwidth becoming available, and if we
4811 * actually throttled the timer might not unthrottle us for an
4812 * entire period. We additionally needed to make sure that any
4813 * subsequent check_cfs_rq_runtime calls agree not to throttle
4814 * us, as we may commit to do cfs put_prev+pick_next, so we ask
4815 * for 1ns of runtime rather than just check cfs_b.
4816 */
4817 dequeue = 0;
4818 } else {
4819 list_add_tail_rcu(&cfs_rq->throttled_list,
4820 &cfs_b->throttled_cfs_rq);
4821 }
4822 raw_spin_unlock(&cfs_b->lock);
4823
4824 if (!dequeue)
4825 return false; /* Throttle no longer required. */
4826
4827 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
4828
4829 /* freeze hierarchy runnable averages while throttled */
4830 rcu_read_lock();
4831 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
4832 rcu_read_unlock();
4833
4834 task_delta = cfs_rq->h_nr_running;
4835 idle_task_delta = cfs_rq->idle_h_nr_running;
4836 for_each_sched_entity(se) {
4837 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
4838 /* throttled entity or throttle-on-deactivate */
4839 if (!se->on_rq)
4840 goto done;
4841
4842 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
4843
4844 qcfs_rq->h_nr_running -= task_delta;
4845 qcfs_rq->idle_h_nr_running -= idle_task_delta;
4846
4847 if (qcfs_rq->load.weight) {
4848 /* Avoid re-evaluating load for this entity: */
4849 se = parent_entity(se);
4850 break;
4851 }
4852 }
4853
4854 for_each_sched_entity(se) {
4855 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
4856 /* throttled entity or throttle-on-deactivate */
4857 if (!se->on_rq)
4858 goto done;
4859
4860 update_load_avg(qcfs_rq, se, 0);
4861 se_update_runnable(se);
4862
4863 qcfs_rq->h_nr_running -= task_delta;
4864 qcfs_rq->idle_h_nr_running -= idle_task_delta;
4865 }
4866
4867 /* At this point se is NULL and we are at root level*/
4868 sub_nr_running(rq, task_delta);
4869
4870done:
4871 /*
4872 * Note: distribution will already see us throttled via the
4873 * throttled-list. rq->lock protects completion.
4874 */
4875 cfs_rq->throttled = 1;
4876 cfs_rq->throttled_clock = rq_clock(rq);
4877 return true;
4878}
4879
4880void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
4881{
4882 struct rq *rq = rq_of(cfs_rq);
4883 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4884 struct sched_entity *se;
4885 long task_delta, idle_task_delta;
4886
4887 se = cfs_rq->tg->se[cpu_of(rq)];
4888
4889 cfs_rq->throttled = 0;
4890
4891 update_rq_clock(rq);
4892
4893 raw_spin_lock(&cfs_b->lock);
4894 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
4895 list_del_rcu(&cfs_rq->throttled_list);
4896 raw_spin_unlock(&cfs_b->lock);
4897
4898 /* update hierarchical throttle state */
4899 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
4900
4901 /* Nothing to run but something to decay (on_list)? Complete the branch */
4902 if (!cfs_rq->load.weight) {
4903 if (cfs_rq->on_list)
4904 goto unthrottle_throttle;
4905 return;
4906 }
4907
4908 task_delta = cfs_rq->h_nr_running;
4909 idle_task_delta = cfs_rq->idle_h_nr_running;
4910 for_each_sched_entity(se) {
4911 if (se->on_rq)
4912 break;
4913 cfs_rq = cfs_rq_of(se);
4914 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
4915
4916 cfs_rq->h_nr_running += task_delta;
4917 cfs_rq->idle_h_nr_running += idle_task_delta;
4918
4919 /* end evaluation on encountering a throttled cfs_rq */
4920 if (cfs_rq_throttled(cfs_rq))
4921 goto unthrottle_throttle;
4922 }
4923
4924 for_each_sched_entity(se) {
4925 cfs_rq = cfs_rq_of(se);
4926
4927 update_load_avg(cfs_rq, se, UPDATE_TG);
4928 se_update_runnable(se);
4929
4930 cfs_rq->h_nr_running += task_delta;
4931 cfs_rq->idle_h_nr_running += idle_task_delta;
4932
4933
4934 /* end evaluation on encountering a throttled cfs_rq */
4935 if (cfs_rq_throttled(cfs_rq))
4936 goto unthrottle_throttle;
4937
4938 /*
4939 * One parent has been throttled and cfs_rq removed from the
4940 * list. Add it back to not break the leaf list.
4941 */
4942 if (throttled_hierarchy(cfs_rq))
4943 list_add_leaf_cfs_rq(cfs_rq);
4944 }
4945
4946 /* At this point se is NULL and we are at root level*/
4947 add_nr_running(rq, task_delta);
4948
4949unthrottle_throttle:
4950 /*
4951 * The cfs_rq_throttled() breaks in the above iteration can result in
4952 * incomplete leaf list maintenance, resulting in triggering the
4953 * assertion below.
4954 */
4955 for_each_sched_entity(se) {
4956 cfs_rq = cfs_rq_of(se);
4957
4958 if (list_add_leaf_cfs_rq(cfs_rq))
4959 break;
4960 }
4961
4962 assert_list_leaf_cfs_rq(rq);
4963
4964 /* Determine whether we need to wake up potentially idle CPU: */
4965 if (rq->curr == rq->idle && rq->cfs.nr_running)
4966 resched_curr(rq);
4967}
4968
4969static void distribute_cfs_runtime(struct cfs_bandwidth *cfs_b)
4970{
4971 struct cfs_rq *cfs_rq;
4972 u64 runtime, remaining = 1;
4973
4974 rcu_read_lock();
4975 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
4976 throttled_list) {
4977 struct rq *rq = rq_of(cfs_rq);
4978 struct rq_flags rf;
4979
4980 rq_lock_irqsave(rq, &rf);
4981 if (!cfs_rq_throttled(cfs_rq))
4982 goto next;
4983
4984 /* By the above check, this should never be true */
4985 SCHED_WARN_ON(cfs_rq->runtime_remaining > 0);
4986
4987 raw_spin_lock(&cfs_b->lock);
4988 runtime = -cfs_rq->runtime_remaining + 1;
4989 if (runtime > cfs_b->runtime)
4990 runtime = cfs_b->runtime;
4991 cfs_b->runtime -= runtime;
4992 remaining = cfs_b->runtime;
4993 raw_spin_unlock(&cfs_b->lock);
4994
4995 cfs_rq->runtime_remaining += runtime;
4996
4997 /* we check whether we're throttled above */
4998 if (cfs_rq->runtime_remaining > 0)
4999 unthrottle_cfs_rq(cfs_rq);
5000
5001next:
5002 rq_unlock_irqrestore(rq, &rf);
5003
5004 if (!remaining)
5005 break;
5006 }
5007 rcu_read_unlock();
5008}
5009
5010/*
5011 * Responsible for refilling a task_group's bandwidth and unthrottling its
5012 * cfs_rqs as appropriate. If there has been no activity within the last
5013 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
5014 * used to track this state.
5015 */
5016static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, unsigned long flags)
5017{
5018 int throttled;
5019
5020 /* no need to continue the timer with no bandwidth constraint */
5021 if (cfs_b->quota == RUNTIME_INF)
5022 goto out_deactivate;
5023
5024 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
5025 cfs_b->nr_periods += overrun;
5026
5027 /* Refill extra burst quota even if cfs_b->idle */
5028 __refill_cfs_bandwidth_runtime(cfs_b);
5029
5030 /*
5031 * idle depends on !throttled (for the case of a large deficit), and if
5032 * we're going inactive then everything else can be deferred
5033 */
5034 if (cfs_b->idle && !throttled)
5035 goto out_deactivate;
5036
5037 if (!throttled) {
5038 /* mark as potentially idle for the upcoming period */
5039 cfs_b->idle = 1;
5040 return 0;
5041 }
5042
5043 /* account preceding periods in which throttling occurred */
5044 cfs_b->nr_throttled += overrun;
5045
5046 /*
5047 * This check is repeated as we release cfs_b->lock while we unthrottle.
5048 */
5049 while (throttled && cfs_b->runtime > 0) {
5050 raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5051 /* we can't nest cfs_b->lock while distributing bandwidth */
5052 distribute_cfs_runtime(cfs_b);
5053 raw_spin_lock_irqsave(&cfs_b->lock, flags);
5054
5055 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
5056 }
5057
5058 /*
5059 * While we are ensured activity in the period following an
5060 * unthrottle, this also covers the case in which the new bandwidth is
5061 * insufficient to cover the existing bandwidth deficit. (Forcing the
5062 * timer to remain active while there are any throttled entities.)
5063 */
5064 cfs_b->idle = 0;
5065
5066 return 0;
5067
5068out_deactivate:
5069 return 1;
5070}
5071
5072/* a cfs_rq won't donate quota below this amount */
5073static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
5074/* minimum remaining period time to redistribute slack quota */
5075static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
5076/* how long we wait to gather additional slack before distributing */
5077static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
5078
5079/*
5080 * Are we near the end of the current quota period?
5081 *
5082 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
5083 * hrtimer base being cleared by hrtimer_start. In the case of
5084 * migrate_hrtimers, base is never cleared, so we are fine.
5085 */
5086static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
5087{
5088 struct hrtimer *refresh_timer = &cfs_b->period_timer;
5089 s64 remaining;
5090
5091 /* if the call-back is running a quota refresh is already occurring */
5092 if (hrtimer_callback_running(refresh_timer))
5093 return 1;
5094
5095 /* is a quota refresh about to occur? */
5096 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
5097 if (remaining < (s64)min_expire)
5098 return 1;
5099
5100 return 0;
5101}
5102
5103static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
5104{
5105 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
5106
5107 /* if there's a quota refresh soon don't bother with slack */
5108 if (runtime_refresh_within(cfs_b, min_left))
5109 return;
5110
5111 /* don't push forwards an existing deferred unthrottle */
5112 if (cfs_b->slack_started)
5113 return;
5114 cfs_b->slack_started = true;
5115
5116 hrtimer_start(&cfs_b->slack_timer,
5117 ns_to_ktime(cfs_bandwidth_slack_period),
5118 HRTIMER_MODE_REL);
5119}
5120
5121/* we know any runtime found here is valid as update_curr() precedes return */
5122static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5123{
5124 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
5125 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
5126
5127 if (slack_runtime <= 0)
5128 return;
5129
5130 raw_spin_lock(&cfs_b->lock);
5131 if (cfs_b->quota != RUNTIME_INF) {
5132 cfs_b->runtime += slack_runtime;
5133
5134 /* we are under rq->lock, defer unthrottling using a timer */
5135 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
5136 !list_empty(&cfs_b->throttled_cfs_rq))
5137 start_cfs_slack_bandwidth(cfs_b);
5138 }
5139 raw_spin_unlock(&cfs_b->lock);
5140
5141 /* even if it's not valid for return we don't want to try again */
5142 cfs_rq->runtime_remaining -= slack_runtime;
5143}
5144
5145static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5146{
5147 if (!cfs_bandwidth_used())
5148 return;
5149
5150 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
5151 return;
5152
5153 __return_cfs_rq_runtime(cfs_rq);
5154}
5155
5156/*
5157 * This is done with a timer (instead of inline with bandwidth return) since
5158 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
5159 */
5160static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
5161{
5162 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
5163 unsigned long flags;
5164
5165 /* confirm we're still not at a refresh boundary */
5166 raw_spin_lock_irqsave(&cfs_b->lock, flags);
5167 cfs_b->slack_started = false;
5168
5169 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
5170 raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5171 return;
5172 }
5173
5174 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
5175 runtime = cfs_b->runtime;
5176
5177 raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5178
5179 if (!runtime)
5180 return;
5181
5182 distribute_cfs_runtime(cfs_b);
5183}
5184
5185/*
5186 * When a group wakes up we want to make sure that its quota is not already
5187 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
5188 * runtime as update_curr() throttling can not trigger until it's on-rq.
5189 */
5190static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
5191{
5192 if (!cfs_bandwidth_used())
5193 return;
5194
5195 /* an active group must be handled by the update_curr()->put() path */
5196 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
5197 return;
5198
5199 /* ensure the group is not already throttled */
5200 if (cfs_rq_throttled(cfs_rq))
5201 return;
5202
5203 /* update runtime allocation */
5204 account_cfs_rq_runtime(cfs_rq, 0);
5205 if (cfs_rq->runtime_remaining <= 0)
5206 throttle_cfs_rq(cfs_rq);
5207}
5208
5209static void sync_throttle(struct task_group *tg, int cpu)
5210{
5211 struct cfs_rq *pcfs_rq, *cfs_rq;
5212
5213 if (!cfs_bandwidth_used())
5214 return;
5215
5216 if (!tg->parent)
5217 return;
5218
5219 cfs_rq = tg->cfs_rq[cpu];
5220 pcfs_rq = tg->parent->cfs_rq[cpu];
5221
5222 cfs_rq->throttle_count = pcfs_rq->throttle_count;
5223 cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
5224}
5225
5226/* conditionally throttle active cfs_rq's from put_prev_entity() */
5227static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5228{
5229 if (!cfs_bandwidth_used())
5230 return false;
5231
5232 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
5233 return false;
5234
5235 /*
5236 * it's possible for a throttled entity to be forced into a running
5237 * state (e.g. set_curr_task), in this case we're finished.
5238 */
5239 if (cfs_rq_throttled(cfs_rq))
5240 return true;
5241
5242 return throttle_cfs_rq(cfs_rq);
5243}
5244
5245static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
5246{
5247 struct cfs_bandwidth *cfs_b =
5248 container_of(timer, struct cfs_bandwidth, slack_timer);
5249
5250 do_sched_cfs_slack_timer(cfs_b);
5251
5252 return HRTIMER_NORESTART;
5253}
5254
5255extern const u64 max_cfs_quota_period;
5256
5257static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
5258{
5259 struct cfs_bandwidth *cfs_b =
5260 container_of(timer, struct cfs_bandwidth, period_timer);
5261 unsigned long flags;
5262 int overrun;
5263 int idle = 0;
5264 int count = 0;
5265
5266 raw_spin_lock_irqsave(&cfs_b->lock, flags);
5267 for (;;) {
5268 overrun = hrtimer_forward_now(timer, cfs_b->period);
5269 if (!overrun)
5270 break;
5271
5272 idle = do_sched_cfs_period_timer(cfs_b, overrun, flags);
5273
5274 if (++count > 3) {
5275 u64 new, old = ktime_to_ns(cfs_b->period);
5276
5277 /*
5278 * Grow period by a factor of 2 to avoid losing precision.
5279 * Precision loss in the quota/period ratio can cause __cfs_schedulable
5280 * to fail.
5281 */
5282 new = old * 2;
5283 if (new < max_cfs_quota_period) {
5284 cfs_b->period = ns_to_ktime(new);
5285 cfs_b->quota *= 2;
5286 cfs_b->burst *= 2;
5287
5288 pr_warn_ratelimited(
5289 "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n",
5290 smp_processor_id(),
5291 div_u64(new, NSEC_PER_USEC),
5292 div_u64(cfs_b->quota, NSEC_PER_USEC));
5293 } else {
5294 pr_warn_ratelimited(
5295 "cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n",
5296 smp_processor_id(),
5297 div_u64(old, NSEC_PER_USEC),
5298 div_u64(cfs_b->quota, NSEC_PER_USEC));
5299 }
5300
5301 /* reset count so we don't come right back in here */
5302 count = 0;
5303 }
5304 }
5305 if (idle)
5306 cfs_b->period_active = 0;
5307 raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5308
5309 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
5310}
5311
5312void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5313{
5314 raw_spin_lock_init(&cfs_b->lock);
5315 cfs_b->runtime = 0;
5316 cfs_b->quota = RUNTIME_INF;
5317 cfs_b->period = ns_to_ktime(default_cfs_period());
5318 cfs_b->burst = 0;
5319
5320 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
5321 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
5322 cfs_b->period_timer.function = sched_cfs_period_timer;
5323 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
5324 cfs_b->slack_timer.function = sched_cfs_slack_timer;
5325 cfs_b->slack_started = false;
5326}
5327
5328static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5329{
5330 cfs_rq->runtime_enabled = 0;
5331 INIT_LIST_HEAD(&cfs_rq->throttled_list);
5332}
5333
5334void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5335{
5336 lockdep_assert_held(&cfs_b->lock);
5337
5338 if (cfs_b->period_active)
5339 return;
5340
5341 cfs_b->period_active = 1;
5342 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
5343 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
5344}
5345
5346static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5347{
5348 /* init_cfs_bandwidth() was not called */
5349 if (!cfs_b->throttled_cfs_rq.next)
5350 return;
5351
5352 hrtimer_cancel(&cfs_b->period_timer);
5353 hrtimer_cancel(&cfs_b->slack_timer);
5354}
5355
5356/*
5357 * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
5358 *
5359 * The race is harmless, since modifying bandwidth settings of unhooked group
5360 * bits doesn't do much.
5361 */
5362
5363/* cpu online callback */
5364static void __maybe_unused update_runtime_enabled(struct rq *rq)
5365{
5366 struct task_group *tg;
5367
5368 lockdep_assert_rq_held(rq);
5369
5370 rcu_read_lock();
5371 list_for_each_entry_rcu(tg, &task_groups, list) {
5372 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
5373 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
5374
5375 raw_spin_lock(&cfs_b->lock);
5376 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
5377 raw_spin_unlock(&cfs_b->lock);
5378 }
5379 rcu_read_unlock();
5380}
5381
5382/* cpu offline callback */
5383static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
5384{
5385 struct task_group *tg;
5386
5387 lockdep_assert_rq_held(rq);
5388
5389 rcu_read_lock();
5390 list_for_each_entry_rcu(tg, &task_groups, list) {
5391 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
5392
5393 if (!cfs_rq->runtime_enabled)
5394 continue;
5395
5396 /*
5397 * clock_task is not advancing so we just need to make sure
5398 * there's some valid quota amount
5399 */
5400 cfs_rq->runtime_remaining = 1;
5401 /*
5402 * Offline rq is schedulable till CPU is completely disabled
5403 * in take_cpu_down(), so we prevent new cfs throttling here.
5404 */
5405 cfs_rq->runtime_enabled = 0;
5406
5407 if (cfs_rq_throttled(cfs_rq))
5408 unthrottle_cfs_rq(cfs_rq);
5409 }
5410 rcu_read_unlock();
5411}
5412
5413#else /* CONFIG_CFS_BANDWIDTH */
5414
5415static inline bool cfs_bandwidth_used(void)
5416{
5417 return false;
5418}
5419
5420static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
5421static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
5422static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
5423static inline void sync_throttle(struct task_group *tg, int cpu) {}
5424static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5425
5426static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
5427{
5428 return 0;
5429}
5430
5431static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
5432{
5433 return 0;
5434}
5435
5436static inline int throttled_lb_pair(struct task_group *tg,
5437 int src_cpu, int dest_cpu)
5438{
5439 return 0;
5440}
5441
5442void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
5443
5444#ifdef CONFIG_FAIR_GROUP_SCHED
5445static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5446#endif
5447
5448static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
5449{
5450 return NULL;
5451}
5452static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
5453static inline void update_runtime_enabled(struct rq *rq) {}
5454static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
5455
5456#endif /* CONFIG_CFS_BANDWIDTH */
5457
5458/**************************************************
5459 * CFS operations on tasks:
5460 */
5461
5462#ifdef CONFIG_SCHED_HRTICK
5463static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
5464{
5465 struct sched_entity *se = &p->se;
5466 struct cfs_rq *cfs_rq = cfs_rq_of(se);
5467
5468 SCHED_WARN_ON(task_rq(p) != rq);
5469
5470 if (rq->cfs.h_nr_running > 1) {
5471 u64 slice = sched_slice(cfs_rq, se);
5472 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
5473 s64 delta = slice - ran;
5474
5475 if (delta < 0) {
5476 if (task_current(rq, p))
5477 resched_curr(rq);
5478 return;
5479 }
5480 hrtick_start(rq, delta);
5481 }
5482}
5483
5484/*
5485 * called from enqueue/dequeue and updates the hrtick when the
5486 * current task is from our class and nr_running is low enough
5487 * to matter.
5488 */
5489static void hrtick_update(struct rq *rq)
5490{
5491 struct task_struct *curr = rq->curr;
5492
5493 if (!hrtick_enabled_fair(rq) || curr->sched_class != &fair_sched_class)
5494 return;
5495
5496 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
5497 hrtick_start_fair(rq, curr);
5498}
5499#else /* !CONFIG_SCHED_HRTICK */
5500static inline void
5501hrtick_start_fair(struct rq *rq, struct task_struct *p)
5502{
5503}
5504
5505static inline void hrtick_update(struct rq *rq)
5506{
5507}
5508#endif
5509
5510#ifdef CONFIG_SMP
5511static inline unsigned long cpu_util(int cpu);
5512
5513static inline bool cpu_overutilized(int cpu)
5514{
5515 return !fits_capacity(cpu_util(cpu), capacity_of(cpu));
5516}
5517
5518static inline void update_overutilized_status(struct rq *rq)
5519{
5520 if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu)) {
5521 WRITE_ONCE(rq->rd->overutilized, SG_OVERUTILIZED);
5522 trace_sched_overutilized_tp(rq->rd, SG_OVERUTILIZED);
5523 }
5524}
5525#else
5526static inline void update_overutilized_status(struct rq *rq) { }
5527#endif
5528
5529/* Runqueue only has SCHED_IDLE tasks enqueued */
5530static int sched_idle_rq(struct rq *rq)
5531{
5532 return unlikely(rq->nr_running == rq->cfs.idle_h_nr_running &&
5533 rq->nr_running);
5534}
5535
5536#ifdef CONFIG_SMP
5537static int sched_idle_cpu(int cpu)
5538{
5539 return sched_idle_rq(cpu_rq(cpu));
5540}
5541#endif
5542
5543/*
5544 * The enqueue_task method is called before nr_running is
5545 * increased. Here we update the fair scheduling stats and
5546 * then put the task into the rbtree:
5547 */
5548static void
5549enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5550{
5551 struct cfs_rq *cfs_rq;
5552 struct sched_entity *se = &p->se;
5553 int idle_h_nr_running = task_has_idle_policy(p);
5554 int task_new = !(flags & ENQUEUE_WAKEUP);
5555
5556 /*
5557 * The code below (indirectly) updates schedutil which looks at
5558 * the cfs_rq utilization to select a frequency.
5559 * Let's add the task's estimated utilization to the cfs_rq's
5560 * estimated utilization, before we update schedutil.
5561 */
5562 util_est_enqueue(&rq->cfs, p);
5563
5564 /*
5565 * If in_iowait is set, the code below may not trigger any cpufreq
5566 * utilization updates, so do it here explicitly with the IOWAIT flag
5567 * passed.
5568 */
5569 if (p->in_iowait)
5570 cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
5571
5572 for_each_sched_entity(se) {
5573 if (se->on_rq)
5574 break;
5575 cfs_rq = cfs_rq_of(se);
5576 enqueue_entity(cfs_rq, se, flags);
5577
5578 cfs_rq->h_nr_running++;
5579 cfs_rq->idle_h_nr_running += idle_h_nr_running;
5580
5581 /* end evaluation on encountering a throttled cfs_rq */
5582 if (cfs_rq_throttled(cfs_rq))
5583 goto enqueue_throttle;
5584
5585 flags = ENQUEUE_WAKEUP;
5586 }
5587
5588 for_each_sched_entity(se) {
5589 cfs_rq = cfs_rq_of(se);
5590
5591 update_load_avg(cfs_rq, se, UPDATE_TG);
5592 se_update_runnable(se);
5593 update_cfs_group(se);
5594
5595 cfs_rq->h_nr_running++;
5596 cfs_rq->idle_h_nr_running += idle_h_nr_running;
5597
5598 /* end evaluation on encountering a throttled cfs_rq */
5599 if (cfs_rq_throttled(cfs_rq))
5600 goto enqueue_throttle;
5601
5602 /*
5603 * One parent has been throttled and cfs_rq removed from the
5604 * list. Add it back to not break the leaf list.
5605 */
5606 if (throttled_hierarchy(cfs_rq))
5607 list_add_leaf_cfs_rq(cfs_rq);
5608 }
5609
5610 /* At this point se is NULL and we are at root level*/
5611 add_nr_running(rq, 1);
5612
5613 /*
5614 * Since new tasks are assigned an initial util_avg equal to
5615 * half of the spare capacity of their CPU, tiny tasks have the
5616 * ability to cross the overutilized threshold, which will
5617 * result in the load balancer ruining all the task placement
5618 * done by EAS. As a way to mitigate that effect, do not account
5619 * for the first enqueue operation of new tasks during the
5620 * overutilized flag detection.
5621 *
5622 * A better way of solving this problem would be to wait for
5623 * the PELT signals of tasks to converge before taking them
5624 * into account, but that is not straightforward to implement,
5625 * and the following generally works well enough in practice.
5626 */
5627 if (!task_new)
5628 update_overutilized_status(rq);
5629
5630enqueue_throttle:
5631 if (cfs_bandwidth_used()) {
5632 /*
5633 * When bandwidth control is enabled; the cfs_rq_throttled()
5634 * breaks in the above iteration can result in incomplete
5635 * leaf list maintenance, resulting in triggering the assertion
5636 * below.
5637 */
5638 for_each_sched_entity(se) {
5639 cfs_rq = cfs_rq_of(se);
5640
5641 if (list_add_leaf_cfs_rq(cfs_rq))
5642 break;
5643 }
5644 }
5645
5646 assert_list_leaf_cfs_rq(rq);
5647
5648 hrtick_update(rq);
5649}
5650
5651static void set_next_buddy(struct sched_entity *se);
5652
5653/*
5654 * The dequeue_task method is called before nr_running is
5655 * decreased. We remove the task from the rbtree and
5656 * update the fair scheduling stats:
5657 */
5658static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5659{
5660 struct cfs_rq *cfs_rq;
5661 struct sched_entity *se = &p->se;
5662 int task_sleep = flags & DEQUEUE_SLEEP;
5663 int idle_h_nr_running = task_has_idle_policy(p);
5664 bool was_sched_idle = sched_idle_rq(rq);
5665
5666 util_est_dequeue(&rq->cfs, p);
5667
5668 for_each_sched_entity(se) {
5669 cfs_rq = cfs_rq_of(se);
5670 dequeue_entity(cfs_rq, se, flags);
5671
5672 cfs_rq->h_nr_running--;
5673 cfs_rq->idle_h_nr_running -= idle_h_nr_running;
5674
5675 /* end evaluation on encountering a throttled cfs_rq */
5676 if (cfs_rq_throttled(cfs_rq))
5677 goto dequeue_throttle;
5678
5679 /* Don't dequeue parent if it has other entities besides us */
5680 if (cfs_rq->load.weight) {
5681 /* Avoid re-evaluating load for this entity: */
5682 se = parent_entity(se);
5683 /*
5684 * Bias pick_next to pick a task from this cfs_rq, as
5685 * p is sleeping when it is within its sched_slice.
5686 */
5687 if (task_sleep && se && !throttled_hierarchy(cfs_rq))
5688 set_next_buddy(se);
5689 break;
5690 }
5691 flags |= DEQUEUE_SLEEP;
5692 }
5693
5694 for_each_sched_entity(se) {
5695 cfs_rq = cfs_rq_of(se);
5696
5697 update_load_avg(cfs_rq, se, UPDATE_TG);
5698 se_update_runnable(se);
5699 update_cfs_group(se);
5700
5701 cfs_rq->h_nr_running--;
5702 cfs_rq->idle_h_nr_running -= idle_h_nr_running;
5703
5704 /* end evaluation on encountering a throttled cfs_rq */
5705 if (cfs_rq_throttled(cfs_rq))
5706 goto dequeue_throttle;
5707
5708 }
5709
5710 /* At this point se is NULL and we are at root level*/
5711 sub_nr_running(rq, 1);
5712
5713 /* balance early to pull high priority tasks */
5714 if (unlikely(!was_sched_idle && sched_idle_rq(rq)))
5715 rq->next_balance = jiffies;
5716
5717dequeue_throttle:
5718 util_est_update(&rq->cfs, p, task_sleep);
5719 hrtick_update(rq);
5720}
5721
5722#ifdef CONFIG_SMP
5723
5724/* Working cpumask for: load_balance, load_balance_newidle. */
5725DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
5726DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
5727
5728#ifdef CONFIG_NO_HZ_COMMON
5729
5730static struct {
5731 cpumask_var_t idle_cpus_mask;
5732 atomic_t nr_cpus;
5733 int has_blocked; /* Idle CPUS has blocked load */
5734 unsigned long next_balance; /* in jiffy units */
5735 unsigned long next_blocked; /* Next update of blocked load in jiffies */
5736} nohz ____cacheline_aligned;
5737
5738#endif /* CONFIG_NO_HZ_COMMON */
5739
5740static unsigned long cpu_load(struct rq *rq)
5741{
5742 return cfs_rq_load_avg(&rq->cfs);
5743}
5744
5745/*
5746 * cpu_load_without - compute CPU load without any contributions from *p
5747 * @cpu: the CPU which load is requested
5748 * @p: the task which load should be discounted
5749 *
5750 * The load of a CPU is defined by the load of tasks currently enqueued on that
5751 * CPU as well as tasks which are currently sleeping after an execution on that
5752 * CPU.
5753 *
5754 * This method returns the load of the specified CPU by discounting the load of
5755 * the specified task, whenever the task is currently contributing to the CPU
5756 * load.
5757 */
5758static unsigned long cpu_load_without(struct rq *rq, struct task_struct *p)
5759{
5760 struct cfs_rq *cfs_rq;
5761 unsigned int load;
5762
5763 /* Task has no contribution or is new */
5764 if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
5765 return cpu_load(rq);
5766
5767 cfs_rq = &rq->cfs;
5768 load = READ_ONCE(cfs_rq->avg.load_avg);
5769
5770 /* Discount task's util from CPU's util */
5771 lsub_positive(&load, task_h_load(p));
5772
5773 return load;
5774}
5775
5776static unsigned long cpu_runnable(struct rq *rq)
5777{
5778 return cfs_rq_runnable_avg(&rq->cfs);
5779}
5780
5781static unsigned long cpu_runnable_without(struct rq *rq, struct task_struct *p)
5782{
5783 struct cfs_rq *cfs_rq;
5784 unsigned int runnable;
5785
5786 /* Task has no contribution or is new */
5787 if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
5788 return cpu_runnable(rq);
5789
5790 cfs_rq = &rq->cfs;
5791 runnable = READ_ONCE(cfs_rq->avg.runnable_avg);
5792
5793 /* Discount task's runnable from CPU's runnable */
5794 lsub_positive(&runnable, p->se.avg.runnable_avg);
5795
5796 return runnable;
5797}
5798
5799static unsigned long capacity_of(int cpu)
5800{
5801 return cpu_rq(cpu)->cpu_capacity;
5802}
5803
5804static void record_wakee(struct task_struct *p)
5805{
5806 /*
5807 * Only decay a single time; tasks that have less then 1 wakeup per
5808 * jiffy will not have built up many flips.
5809 */
5810 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
5811 current->wakee_flips >>= 1;
5812 current->wakee_flip_decay_ts = jiffies;
5813 }
5814
5815 if (current->last_wakee != p) {
5816 current->last_wakee = p;
5817 current->wakee_flips++;
5818 }
5819}
5820
5821/*
5822 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5823 *
5824 * A waker of many should wake a different task than the one last awakened
5825 * at a frequency roughly N times higher than one of its wakees.
5826 *
5827 * In order to determine whether we should let the load spread vs consolidating
5828 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
5829 * partner, and a factor of lls_size higher frequency in the other.
5830 *
5831 * With both conditions met, we can be relatively sure that the relationship is
5832 * non-monogamous, with partner count exceeding socket size.
5833 *
5834 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
5835 * whatever is irrelevant, spread criteria is apparent partner count exceeds
5836 * socket size.
5837 */
5838static int wake_wide(struct task_struct *p)
5839{
5840 unsigned int master = current->wakee_flips;
5841 unsigned int slave = p->wakee_flips;
5842 int factor = __this_cpu_read(sd_llc_size);
5843
5844 if (master < slave)
5845 swap(master, slave);
5846 if (slave < factor || master < slave * factor)
5847 return 0;
5848 return 1;
5849}
5850
5851/*
5852 * The purpose of wake_affine() is to quickly determine on which CPU we can run
5853 * soonest. For the purpose of speed we only consider the waking and previous
5854 * CPU.
5855 *
5856 * wake_affine_idle() - only considers 'now', it check if the waking CPU is
5857 * cache-affine and is (or will be) idle.
5858 *
5859 * wake_affine_weight() - considers the weight to reflect the average
5860 * scheduling latency of the CPUs. This seems to work
5861 * for the overloaded case.
5862 */
5863static int
5864wake_affine_idle(int this_cpu, int prev_cpu, int sync)
5865{
5866 /*
5867 * If this_cpu is idle, it implies the wakeup is from interrupt
5868 * context. Only allow the move if cache is shared. Otherwise an
5869 * interrupt intensive workload could force all tasks onto one
5870 * node depending on the IO topology or IRQ affinity settings.
5871 *
5872 * If the prev_cpu is idle and cache affine then avoid a migration.
5873 * There is no guarantee that the cache hot data from an interrupt
5874 * is more important than cache hot data on the prev_cpu and from
5875 * a cpufreq perspective, it's better to have higher utilisation
5876 * on one CPU.
5877 */
5878 if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
5879 return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
5880
5881 if (sync && cpu_rq(this_cpu)->nr_running == 1)
5882 return this_cpu;
5883
5884 if (available_idle_cpu(prev_cpu))
5885 return prev_cpu;
5886
5887 return nr_cpumask_bits;
5888}
5889
5890static int
5891wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
5892 int this_cpu, int prev_cpu, int sync)
5893{
5894 s64 this_eff_load, prev_eff_load;
5895 unsigned long task_load;
5896
5897 this_eff_load = cpu_load(cpu_rq(this_cpu));
5898
5899 if (sync) {
5900 unsigned long current_load = task_h_load(current);
5901
5902 if (current_load > this_eff_load)
5903 return this_cpu;
5904
5905 this_eff_load -= current_load;
5906 }
5907
5908 task_load = task_h_load(p);
5909
5910 this_eff_load += task_load;
5911 if (sched_feat(WA_BIAS))
5912 this_eff_load *= 100;
5913 this_eff_load *= capacity_of(prev_cpu);
5914
5915 prev_eff_load = cpu_load(cpu_rq(prev_cpu));
5916 prev_eff_load -= task_load;
5917 if (sched_feat(WA_BIAS))
5918 prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2;
5919 prev_eff_load *= capacity_of(this_cpu);
5920
5921 /*
5922 * If sync, adjust the weight of prev_eff_load such that if
5923 * prev_eff == this_eff that select_idle_sibling() will consider
5924 * stacking the wakee on top of the waker if no other CPU is
5925 * idle.
5926 */
5927 if (sync)
5928 prev_eff_load += 1;
5929
5930 return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
5931}
5932
5933static int wake_affine(struct sched_domain *sd, struct task_struct *p,
5934 int this_cpu, int prev_cpu, int sync)
5935{
5936 int target = nr_cpumask_bits;
5937
5938 if (sched_feat(WA_IDLE))
5939 target = wake_affine_idle(this_cpu, prev_cpu, sync);
5940
5941 if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
5942 target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
5943
5944 schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
5945 if (target == nr_cpumask_bits)
5946 return prev_cpu;
5947
5948 schedstat_inc(sd->ttwu_move_affine);
5949 schedstat_inc(p->se.statistics.nr_wakeups_affine);
5950 return target;
5951}
5952
5953static struct sched_group *
5954find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu);
5955
5956/*
5957 * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
5958 */
5959static int
5960find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5961{
5962 unsigned long load, min_load = ULONG_MAX;
5963 unsigned int min_exit_latency = UINT_MAX;
5964 u64 latest_idle_timestamp = 0;
5965 int least_loaded_cpu = this_cpu;
5966 int shallowest_idle_cpu = -1;
5967 int i;
5968
5969 /* Check if we have any choice: */
5970 if (group->group_weight == 1)
5971 return cpumask_first(sched_group_span(group));
5972
5973 /* Traverse only the allowed CPUs */
5974 for_each_cpu_and(i, sched_group_span(group), p->cpus_ptr) {
5975 struct rq *rq = cpu_rq(i);
5976
5977 if (!sched_core_cookie_match(rq, p))
5978 continue;
5979
5980 if (sched_idle_cpu(i))
5981 return i;
5982
5983 if (available_idle_cpu(i)) {
5984 struct cpuidle_state *idle = idle_get_state(rq);
5985 if (idle && idle->exit_latency < min_exit_latency) {
5986 /*
5987 * We give priority to a CPU whose idle state
5988 * has the smallest exit latency irrespective
5989 * of any idle timestamp.
5990 */
5991 min_exit_latency = idle->exit_latency;
5992 latest_idle_timestamp = rq->idle_stamp;
5993 shallowest_idle_cpu = i;
5994 } else if ((!idle || idle->exit_latency == min_exit_latency) &&
5995 rq->idle_stamp > latest_idle_timestamp) {
5996 /*
5997 * If equal or no active idle state, then
5998 * the most recently idled CPU might have
5999 * a warmer cache.
6000 */
6001 latest_idle_timestamp = rq->idle_stamp;
6002 shallowest_idle_cpu = i;
6003 }
6004 } else if (shallowest_idle_cpu == -1) {
6005 load = cpu_load(cpu_rq(i));
6006 if (load < min_load) {
6007 min_load = load;
6008 least_loaded_cpu = i;
6009 }
6010 }
6011 }
6012
6013 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
6014}
6015
6016static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
6017 int cpu, int prev_cpu, int sd_flag)
6018{
6019 int new_cpu = cpu;
6020
6021 if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr))
6022 return prev_cpu;
6023
6024 /*
6025 * We need task's util for cpu_util_without, sync it up to
6026 * prev_cpu's last_update_time.
6027 */
6028 if (!(sd_flag & SD_BALANCE_FORK))
6029 sync_entity_load_avg(&p->se);
6030
6031 while (sd) {
6032 struct sched_group *group;
6033 struct sched_domain *tmp;
6034 int weight;
6035
6036 if (!(sd->flags & sd_flag)) {
6037 sd = sd->child;
6038 continue;
6039 }
6040
6041 group = find_idlest_group(sd, p, cpu);
6042 if (!group) {
6043 sd = sd->child;
6044 continue;
6045 }
6046
6047 new_cpu = find_idlest_group_cpu(group, p, cpu);
6048 if (new_cpu == cpu) {
6049 /* Now try balancing at a lower domain level of 'cpu': */
6050 sd = sd->child;
6051 continue;
6052 }
6053
6054 /* Now try balancing at a lower domain level of 'new_cpu': */
6055 cpu = new_cpu;
6056 weight = sd->span_weight;
6057 sd = NULL;
6058 for_each_domain(cpu, tmp) {
6059 if (weight <= tmp->span_weight)
6060 break;
6061 if (tmp->flags & sd_flag)
6062 sd = tmp;
6063 }
6064 }
6065
6066 return new_cpu;
6067}
6068
6069static inline int __select_idle_cpu(int cpu, struct task_struct *p)
6070{
6071 if ((available_idle_cpu(cpu) || sched_idle_cpu(cpu)) &&
6072 sched_cpu_cookie_match(cpu_rq(cpu), p))
6073 return cpu;
6074
6075 return -1;
6076}
6077
6078#ifdef CONFIG_SCHED_SMT
6079DEFINE_STATIC_KEY_FALSE(sched_smt_present);
6080EXPORT_SYMBOL_GPL(sched_smt_present);
6081
6082static inline void set_idle_cores(int cpu, int val)
6083{
6084 struct sched_domain_shared *sds;
6085
6086 sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
6087 if (sds)
6088 WRITE_ONCE(sds->has_idle_cores, val);
6089}
6090
6091static inline bool test_idle_cores(int cpu, bool def)
6092{
6093 struct sched_domain_shared *sds;
6094
6095 sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
6096 if (sds)
6097 return READ_ONCE(sds->has_idle_cores);
6098
6099 return def;
6100}
6101
6102/*
6103 * Scans the local SMT mask to see if the entire core is idle, and records this
6104 * information in sd_llc_shared->has_idle_cores.
6105 *
6106 * Since SMT siblings share all cache levels, inspecting this limited remote
6107 * state should be fairly cheap.
6108 */
6109void __update_idle_core(struct rq *rq)
6110{
6111 int core = cpu_of(rq);
6112 int cpu;
6113
6114 rcu_read_lock();
6115 if (test_idle_cores(core, true))
6116 goto unlock;
6117
6118 for_each_cpu(cpu, cpu_smt_mask(core)) {
6119 if (cpu == core)
6120 continue;
6121
6122 if (!available_idle_cpu(cpu))
6123 goto unlock;
6124 }
6125
6126 set_idle_cores(core, 1);
6127unlock:
6128 rcu_read_unlock();
6129}
6130
6131/*
6132 * Scan the entire LLC domain for idle cores; this dynamically switches off if
6133 * there are no idle cores left in the system; tracked through
6134 * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
6135 */
6136static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
6137{
6138 bool idle = true;
6139 int cpu;
6140
6141 if (!static_branch_likely(&sched_smt_present))
6142 return __select_idle_cpu(core, p);
6143
6144 for_each_cpu(cpu, cpu_smt_mask(core)) {
6145 if (!available_idle_cpu(cpu)) {
6146 idle = false;
6147 if (*idle_cpu == -1) {
6148 if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, p->cpus_ptr)) {
6149 *idle_cpu = cpu;
6150 break;
6151 }
6152 continue;
6153 }
6154 break;
6155 }
6156 if (*idle_cpu == -1 && cpumask_test_cpu(cpu, p->cpus_ptr))
6157 *idle_cpu = cpu;
6158 }
6159
6160 if (idle)
6161 return core;
6162
6163 cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
6164 return -1;
6165}
6166
6167/*
6168 * Scan the local SMT mask for idle CPUs.
6169 */
6170static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
6171{
6172 int cpu;
6173
6174 for_each_cpu(cpu, cpu_smt_mask(target)) {
6175 if (!cpumask_test_cpu(cpu, p->cpus_ptr) ||
6176 !cpumask_test_cpu(cpu, sched_domain_span(sd)))
6177 continue;
6178 if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
6179 return cpu;
6180 }
6181
6182 return -1;
6183}
6184
6185#else /* CONFIG_SCHED_SMT */
6186
6187static inline void set_idle_cores(int cpu, int val)
6188{
6189}
6190
6191static inline bool test_idle_cores(int cpu, bool def)
6192{
6193 return def;
6194}
6195
6196static inline int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
6197{
6198 return __select_idle_cpu(core, p);
6199}
6200
6201static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
6202{
6203 return -1;
6204}
6205
6206#endif /* CONFIG_SCHED_SMT */
6207
6208/*
6209 * Scan the LLC domain for idle CPUs; this is dynamically regulated by
6210 * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
6211 * average idle time for this rq (as found in rq->avg_idle).
6212 */
6213static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool has_idle_core, int target)
6214{
6215 struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
6216 int i, cpu, idle_cpu = -1, nr = INT_MAX;
6217 struct rq *this_rq = this_rq();
6218 int this = smp_processor_id();
6219 struct sched_domain *this_sd;
6220 u64 time = 0;
6221
6222 this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
6223 if (!this_sd)
6224 return -1;
6225
6226 cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
6227
6228 if (sched_feat(SIS_PROP) && !has_idle_core) {
6229 u64 avg_cost, avg_idle, span_avg;
6230 unsigned long now = jiffies;
6231
6232 /*
6233 * If we're busy, the assumption that the last idle period
6234 * predicts the future is flawed; age away the remaining
6235 * predicted idle time.
6236 */
6237 if (unlikely(this_rq->wake_stamp < now)) {
6238 while (this_rq->wake_stamp < now && this_rq->wake_avg_idle) {
6239 this_rq->wake_stamp++;
6240 this_rq->wake_avg_idle >>= 1;
6241 }
6242 }
6243
6244 avg_idle = this_rq->wake_avg_idle;
6245 avg_cost = this_sd->avg_scan_cost + 1;
6246
6247 span_avg = sd->span_weight * avg_idle;
6248 if (span_avg > 4*avg_cost)
6249 nr = div_u64(span_avg, avg_cost);
6250 else
6251 nr = 4;
6252
6253 time = cpu_clock(this);
6254 }
6255
6256 for_each_cpu_wrap(cpu, cpus, target) {
6257 if (has_idle_core) {
6258 i = select_idle_core(p, cpu, cpus, &idle_cpu);
6259 if ((unsigned int)i < nr_cpumask_bits)
6260 return i;
6261
6262 } else {
6263 if (!--nr)
6264 return -1;
6265 idle_cpu = __select_idle_cpu(cpu, p);
6266 if ((unsigned int)idle_cpu < nr_cpumask_bits)
6267 break;
6268 }
6269 }
6270
6271 if (has_idle_core)
6272 set_idle_cores(target, false);
6273
6274 if (sched_feat(SIS_PROP) && !has_idle_core) {
6275 time = cpu_clock(this) - time;
6276
6277 /*
6278 * Account for the scan cost of wakeups against the average
6279 * idle time.
6280 */
6281 this_rq->wake_avg_idle -= min(this_rq->wake_avg_idle, time);
6282
6283 update_avg(&this_sd->avg_scan_cost, time);
6284 }
6285
6286 return idle_cpu;
6287}
6288
6289/*
6290 * Scan the asym_capacity domain for idle CPUs; pick the first idle one on which
6291 * the task fits. If no CPU is big enough, but there are idle ones, try to
6292 * maximize capacity.
6293 */
6294static int
6295select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
6296{
6297 unsigned long task_util, best_cap = 0;
6298 int cpu, best_cpu = -1;
6299 struct cpumask *cpus;
6300
6301 cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
6302 cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
6303
6304 task_util = uclamp_task_util(p);
6305
6306 for_each_cpu_wrap(cpu, cpus, target) {
6307 unsigned long cpu_cap = capacity_of(cpu);
6308
6309 if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu))
6310 continue;
6311 if (fits_capacity(task_util, cpu_cap))
6312 return cpu;
6313
6314 if (cpu_cap > best_cap) {
6315 best_cap = cpu_cap;
6316 best_cpu = cpu;
6317 }
6318 }
6319
6320 return best_cpu;
6321}
6322
6323static inline bool asym_fits_capacity(int task_util, int cpu)
6324{
6325 if (static_branch_unlikely(&sched_asym_cpucapacity))
6326 return fits_capacity(task_util, capacity_of(cpu));
6327
6328 return true;
6329}
6330
6331/*
6332 * Try and locate an idle core/thread in the LLC cache domain.
6333 */
6334static int select_idle_sibling(struct task_struct *p, int prev, int target)
6335{
6336 bool has_idle_core = false;
6337 struct sched_domain *sd;
6338 unsigned long task_util;
6339 int i, recent_used_cpu;
6340
6341 /*
6342 * On asymmetric system, update task utilization because we will check
6343 * that the task fits with cpu's capacity.
6344 */
6345 if (static_branch_unlikely(&sched_asym_cpucapacity)) {
6346 sync_entity_load_avg(&p->se);
6347 task_util = uclamp_task_util(p);
6348 }
6349
6350 /*
6351 * per-cpu select_idle_mask usage
6352 */
6353 lockdep_assert_irqs_disabled();
6354
6355 if ((available_idle_cpu(target) || sched_idle_cpu(target)) &&
6356 asym_fits_capacity(task_util, target))
6357 return target;
6358
6359 /*
6360 * If the previous CPU is cache affine and idle, don't be stupid:
6361 */
6362 if (prev != target && cpus_share_cache(prev, target) &&
6363 (available_idle_cpu(prev) || sched_idle_cpu(prev)) &&
6364 asym_fits_capacity(task_util, prev))
6365 return prev;
6366
6367 /*
6368 * Allow a per-cpu kthread to stack with the wakee if the
6369 * kworker thread and the tasks previous CPUs are the same.
6370 * The assumption is that the wakee queued work for the
6371 * per-cpu kthread that is now complete and the wakeup is
6372 * essentially a sync wakeup. An obvious example of this
6373 * pattern is IO completions.
6374 */
6375 if (is_per_cpu_kthread(current) &&
6376 prev == smp_processor_id() &&
6377 this_rq()->nr_running <= 1) {
6378 return prev;
6379 }
6380
6381 /* Check a recently used CPU as a potential idle candidate: */
6382 recent_used_cpu = p->recent_used_cpu;
6383 if (recent_used_cpu != prev &&
6384 recent_used_cpu != target &&
6385 cpus_share_cache(recent_used_cpu, target) &&
6386 (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) &&
6387 cpumask_test_cpu(p->recent_used_cpu, p->cpus_ptr) &&
6388 asym_fits_capacity(task_util, recent_used_cpu)) {
6389 /*
6390 * Replace recent_used_cpu with prev as it is a potential
6391 * candidate for the next wake:
6392 */
6393 p->recent_used_cpu = prev;
6394 return recent_used_cpu;
6395 }
6396
6397 /*
6398 * For asymmetric CPU capacity systems, our domain of interest is
6399 * sd_asym_cpucapacity rather than sd_llc.
6400 */
6401 if (static_branch_unlikely(&sched_asym_cpucapacity)) {
6402 sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, target));
6403 /*
6404 * On an asymmetric CPU capacity system where an exclusive
6405 * cpuset defines a symmetric island (i.e. one unique
6406 * capacity_orig value through the cpuset), the key will be set
6407 * but the CPUs within that cpuset will not have a domain with
6408 * SD_ASYM_CPUCAPACITY. These should follow the usual symmetric
6409 * capacity path.
6410 */
6411 if (sd) {
6412 i = select_idle_capacity(p, sd, target);
6413 return ((unsigned)i < nr_cpumask_bits) ? i : target;
6414 }
6415 }
6416
6417 sd = rcu_dereference(per_cpu(sd_llc, target));
6418 if (!sd)
6419 return target;
6420
6421 if (sched_smt_active()) {
6422 has_idle_core = test_idle_cores(target, false);
6423
6424 if (!has_idle_core && cpus_share_cache(prev, target)) {
6425 i = select_idle_smt(p, sd, prev);
6426 if ((unsigned int)i < nr_cpumask_bits)
6427 return i;
6428 }
6429 }
6430
6431 i = select_idle_cpu(p, sd, has_idle_core, target);
6432 if ((unsigned)i < nr_cpumask_bits)
6433 return i;
6434
6435 return target;
6436}
6437
6438/**
6439 * cpu_util - Estimates the amount of capacity of a CPU used by CFS tasks.
6440 * @cpu: the CPU to get the utilization of
6441 *
6442 * The unit of the return value must be the one of capacity so we can compare
6443 * the utilization with the capacity of the CPU that is available for CFS task
6444 * (ie cpu_capacity).
6445 *
6446 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
6447 * recent utilization of currently non-runnable tasks on a CPU. It represents
6448 * the amount of utilization of a CPU in the range [0..capacity_orig] where
6449 * capacity_orig is the cpu_capacity available at the highest frequency
6450 * (arch_scale_freq_capacity()).
6451 * The utilization of a CPU converges towards a sum equal to or less than the
6452 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
6453 * the running time on this CPU scaled by capacity_curr.
6454 *
6455 * The estimated utilization of a CPU is defined to be the maximum between its
6456 * cfs_rq.avg.util_avg and the sum of the estimated utilization of the tasks
6457 * currently RUNNABLE on that CPU.
6458 * This allows to properly represent the expected utilization of a CPU which
6459 * has just got a big task running since a long sleep period. At the same time
6460 * however it preserves the benefits of the "blocked utilization" in
6461 * describing the potential for other tasks waking up on the same CPU.
6462 *
6463 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
6464 * higher than capacity_orig because of unfortunate rounding in
6465 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
6466 * the average stabilizes with the new running time. We need to check that the
6467 * utilization stays within the range of [0..capacity_orig] and cap it if
6468 * necessary. Without utilization capping, a group could be seen as overloaded
6469 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
6470 * available capacity. We allow utilization to overshoot capacity_curr (but not
6471 * capacity_orig) as it useful for predicting the capacity required after task
6472 * migrations (scheduler-driven DVFS).
6473 *
6474 * Return: the (estimated) utilization for the specified CPU
6475 */
6476static inline unsigned long cpu_util(int cpu)
6477{
6478 struct cfs_rq *cfs_rq;
6479 unsigned int util;
6480
6481 cfs_rq = &cpu_rq(cpu)->cfs;
6482 util = READ_ONCE(cfs_rq->avg.util_avg);
6483
6484 if (sched_feat(UTIL_EST))
6485 util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued));
6486
6487 return min_t(unsigned long, util, capacity_orig_of(cpu));
6488}
6489
6490/*
6491 * cpu_util_without: compute cpu utilization without any contributions from *p
6492 * @cpu: the CPU which utilization is requested
6493 * @p: the task which utilization should be discounted
6494 *
6495 * The utilization of a CPU is defined by the utilization of tasks currently
6496 * enqueued on that CPU as well as tasks which are currently sleeping after an
6497 * execution on that CPU.
6498 *
6499 * This method returns the utilization of the specified CPU by discounting the
6500 * utilization of the specified task, whenever the task is currently
6501 * contributing to the CPU utilization.
6502 */
6503static unsigned long cpu_util_without(int cpu, struct task_struct *p)
6504{
6505 struct cfs_rq *cfs_rq;
6506 unsigned int util;
6507
6508 /* Task has no contribution or is new */
6509 if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
6510 return cpu_util(cpu);
6511
6512 cfs_rq = &cpu_rq(cpu)->cfs;
6513 util = READ_ONCE(cfs_rq->avg.util_avg);
6514
6515 /* Discount task's util from CPU's util */
6516 lsub_positive(&util, task_util(p));
6517
6518 /*
6519 * Covered cases:
6520 *
6521 * a) if *p is the only task sleeping on this CPU, then:
6522 * cpu_util (== task_util) > util_est (== 0)
6523 * and thus we return:
6524 * cpu_util_without = (cpu_util - task_util) = 0
6525 *
6526 * b) if other tasks are SLEEPING on this CPU, which is now exiting
6527 * IDLE, then:
6528 * cpu_util >= task_util
6529 * cpu_util > util_est (== 0)
6530 * and thus we discount *p's blocked utilization to return:
6531 * cpu_util_without = (cpu_util - task_util) >= 0
6532 *
6533 * c) if other tasks are RUNNABLE on that CPU and
6534 * util_est > cpu_util
6535 * then we use util_est since it returns a more restrictive
6536 * estimation of the spare capacity on that CPU, by just
6537 * considering the expected utilization of tasks already
6538 * runnable on that CPU.
6539 *
6540 * Cases a) and b) are covered by the above code, while case c) is
6541 * covered by the following code when estimated utilization is
6542 * enabled.
6543 */
6544 if (sched_feat(UTIL_EST)) {
6545 unsigned int estimated =
6546 READ_ONCE(cfs_rq->avg.util_est.enqueued);
6547
6548 /*
6549 * Despite the following checks we still have a small window
6550 * for a possible race, when an execl's select_task_rq_fair()
6551 * races with LB's detach_task():
6552 *
6553 * detach_task()
6554 * p->on_rq = TASK_ON_RQ_MIGRATING;
6555 * ---------------------------------- A
6556 * deactivate_task() \
6557 * dequeue_task() + RaceTime
6558 * util_est_dequeue() /
6559 * ---------------------------------- B
6560 *
6561 * The additional check on "current == p" it's required to
6562 * properly fix the execl regression and it helps in further
6563 * reducing the chances for the above race.
6564 */
6565 if (unlikely(task_on_rq_queued(p) || current == p))
6566 lsub_positive(&estimated, _task_util_est(p));
6567
6568 util = max(util, estimated);
6569 }
6570
6571 /*
6572 * Utilization (estimated) can exceed the CPU capacity, thus let's
6573 * clamp to the maximum CPU capacity to ensure consistency with
6574 * the cpu_util call.
6575 */
6576 return min_t(unsigned long, util, capacity_orig_of(cpu));
6577}
6578
6579/*
6580 * Predicts what cpu_util(@cpu) would return if @p was migrated (and enqueued)
6581 * to @dst_cpu.
6582 */
6583static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
6584{
6585 struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs;
6586 unsigned long util_est, util = READ_ONCE(cfs_rq->avg.util_avg);
6587
6588 /*
6589 * If @p migrates from @cpu to another, remove its contribution. Or,
6590 * if @p migrates from another CPU to @cpu, add its contribution. In
6591 * the other cases, @cpu is not impacted by the migration, so the
6592 * util_avg should already be correct.
6593 */
6594 if (task_cpu(p) == cpu && dst_cpu != cpu)
6595 lsub_positive(&util, task_util(p));
6596 else if (task_cpu(p) != cpu && dst_cpu == cpu)
6597 util += task_util(p);
6598
6599 if (sched_feat(UTIL_EST)) {
6600 util_est = READ_ONCE(cfs_rq->avg.util_est.enqueued);
6601
6602 /*
6603 * During wake-up, the task isn't enqueued yet and doesn't
6604 * appear in the cfs_rq->avg.util_est.enqueued of any rq,
6605 * so just add it (if needed) to "simulate" what will be
6606 * cpu_util() after the task has been enqueued.
6607 */
6608 if (dst_cpu == cpu)
6609 util_est += _task_util_est(p);
6610
6611 util = max(util, util_est);
6612 }
6613
6614 return min(util, capacity_orig_of(cpu));
6615}
6616
6617/*
6618 * compute_energy(): Estimates the energy that @pd would consume if @p was
6619 * migrated to @dst_cpu. compute_energy() predicts what will be the utilization
6620 * landscape of @pd's CPUs after the task migration, and uses the Energy Model
6621 * to compute what would be the energy if we decided to actually migrate that
6622 * task.
6623 */
6624static long
6625compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
6626{
6627 struct cpumask *pd_mask = perf_domain_span(pd);
6628 unsigned long cpu_cap = arch_scale_cpu_capacity(cpumask_first(pd_mask));
6629 unsigned long max_util = 0, sum_util = 0;
6630 unsigned long _cpu_cap = cpu_cap;
6631 int cpu;
6632
6633 _cpu_cap -= arch_scale_thermal_pressure(cpumask_first(pd_mask));
6634
6635 /*
6636 * The capacity state of CPUs of the current rd can be driven by CPUs
6637 * of another rd if they belong to the same pd. So, account for the
6638 * utilization of these CPUs too by masking pd with cpu_online_mask
6639 * instead of the rd span.
6640 *
6641 * If an entire pd is outside of the current rd, it will not appear in
6642 * its pd list and will not be accounted by compute_energy().
6643 */
6644 for_each_cpu_and(cpu, pd_mask, cpu_online_mask) {
6645 unsigned long util_freq = cpu_util_next(cpu, p, dst_cpu);
6646 unsigned long cpu_util, util_running = util_freq;
6647 struct task_struct *tsk = NULL;
6648
6649 /*
6650 * When @p is placed on @cpu:
6651 *
6652 * util_running = max(cpu_util, cpu_util_est) +
6653 * max(task_util, _task_util_est)
6654 *
6655 * while cpu_util_next is: max(cpu_util + task_util,
6656 * cpu_util_est + _task_util_est)
6657 */
6658 if (cpu == dst_cpu) {
6659 tsk = p;
6660 util_running =
6661 cpu_util_next(cpu, p, -1) + task_util_est(p);
6662 }
6663
6664 /*
6665 * Busy time computation: utilization clamping is not
6666 * required since the ratio (sum_util / cpu_capacity)
6667 * is already enough to scale the EM reported power
6668 * consumption at the (eventually clamped) cpu_capacity.
6669 */
6670 cpu_util = effective_cpu_util(cpu, util_running, cpu_cap,
6671 ENERGY_UTIL, NULL);
6672
6673 sum_util += min(cpu_util, _cpu_cap);
6674
6675 /*
6676 * Performance domain frequency: utilization clamping
6677 * must be considered since it affects the selection
6678 * of the performance domain frequency.
6679 * NOTE: in case RT tasks are running, by default the
6680 * FREQUENCY_UTIL's utilization can be max OPP.
6681 */
6682 cpu_util = effective_cpu_util(cpu, util_freq, cpu_cap,
6683 FREQUENCY_UTIL, tsk);
6684 max_util = max(max_util, min(cpu_util, _cpu_cap));
6685 }
6686
6687 return em_cpu_energy(pd->em_pd, max_util, sum_util, _cpu_cap);
6688}
6689
6690/*
6691 * find_energy_efficient_cpu(): Find most energy-efficient target CPU for the
6692 * waking task. find_energy_efficient_cpu() looks for the CPU with maximum
6693 * spare capacity in each performance domain and uses it as a potential
6694 * candidate to execute the task. Then, it uses the Energy Model to figure
6695 * out which of the CPU candidates is the most energy-efficient.
6696 *
6697 * The rationale for this heuristic is as follows. In a performance domain,
6698 * all the most energy efficient CPU candidates (according to the Energy
6699 * Model) are those for which we'll request a low frequency. When there are
6700 * several CPUs for which the frequency request will be the same, we don't
6701 * have enough data to break the tie between them, because the Energy Model
6702 * only includes active power costs. With this model, if we assume that
6703 * frequency requests follow utilization (e.g. using schedutil), the CPU with
6704 * the maximum spare capacity in a performance domain is guaranteed to be among
6705 * the best candidates of the performance domain.
6706 *
6707 * In practice, it could be preferable from an energy standpoint to pack
6708 * small tasks on a CPU in order to let other CPUs go in deeper idle states,
6709 * but that could also hurt our chances to go cluster idle, and we have no
6710 * ways to tell with the current Energy Model if this is actually a good
6711 * idea or not. So, find_energy_efficient_cpu() basically favors
6712 * cluster-packing, and spreading inside a cluster. That should at least be
6713 * a good thing for latency, and this is consistent with the idea that most
6714 * of the energy savings of EAS come from the asymmetry of the system, and
6715 * not so much from breaking the tie between identical CPUs. That's also the
6716 * reason why EAS is enabled in the topology code only for systems where
6717 * SD_ASYM_CPUCAPACITY is set.
6718 *
6719 * NOTE: Forkees are not accepted in the energy-aware wake-up path because
6720 * they don't have any useful utilization data yet and it's not possible to
6721 * forecast their impact on energy consumption. Consequently, they will be
6722 * placed by find_idlest_cpu() on the least loaded CPU, which might turn out
6723 * to be energy-inefficient in some use-cases. The alternative would be to
6724 * bias new tasks towards specific types of CPUs first, or to try to infer
6725 * their util_avg from the parent task, but those heuristics could hurt
6726 * other use-cases too. So, until someone finds a better way to solve this,
6727 * let's keep things simple by re-using the existing slow path.
6728 */
6729static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
6730{
6731 unsigned long prev_delta = ULONG_MAX, best_delta = ULONG_MAX;
6732 struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
6733 int cpu, best_energy_cpu = prev_cpu, target = -1;
6734 unsigned long cpu_cap, util, base_energy = 0;
6735 struct sched_domain *sd;
6736 struct perf_domain *pd;
6737
6738 rcu_read_lock();
6739 pd = rcu_dereference(rd->pd);
6740 if (!pd || READ_ONCE(rd->overutilized))
6741 goto unlock;
6742
6743 /*
6744 * Energy-aware wake-up happens on the lowest sched_domain starting
6745 * from sd_asym_cpucapacity spanning over this_cpu and prev_cpu.
6746 */
6747 sd = rcu_dereference(*this_cpu_ptr(&sd_asym_cpucapacity));
6748 while (sd && !cpumask_test_cpu(prev_cpu, sched_domain_span(sd)))
6749 sd = sd->parent;
6750 if (!sd)
6751 goto unlock;
6752
6753 target = prev_cpu;
6754
6755 sync_entity_load_avg(&p->se);
6756 if (!task_util_est(p))
6757 goto unlock;
6758
6759 for (; pd; pd = pd->next) {
6760 unsigned long cur_delta, spare_cap, max_spare_cap = 0;
6761 bool compute_prev_delta = false;
6762 unsigned long base_energy_pd;
6763 int max_spare_cap_cpu = -1;
6764
6765 for_each_cpu_and(cpu, perf_domain_span(pd), sched_domain_span(sd)) {
6766 if (!cpumask_test_cpu(cpu, p->cpus_ptr))
6767 continue;
6768
6769 util = cpu_util_next(cpu, p, cpu);
6770 cpu_cap = capacity_of(cpu);
6771 spare_cap = cpu_cap;
6772 lsub_positive(&spare_cap, util);
6773
6774 /*
6775 * Skip CPUs that cannot satisfy the capacity request.
6776 * IOW, placing the task there would make the CPU
6777 * overutilized. Take uclamp into account to see how
6778 * much capacity we can get out of the CPU; this is
6779 * aligned with sched_cpu_util().
6780 */
6781 util = uclamp_rq_util_with(cpu_rq(cpu), util, p);
6782 if (!fits_capacity(util, cpu_cap))
6783 continue;
6784
6785 if (cpu == prev_cpu) {
6786 /* Always use prev_cpu as a candidate. */
6787 compute_prev_delta = true;
6788 } else if (spare_cap > max_spare_cap) {
6789 /*
6790 * Find the CPU with the maximum spare capacity
6791 * in the performance domain.
6792 */
6793 max_spare_cap = spare_cap;
6794 max_spare_cap_cpu = cpu;
6795 }
6796 }
6797
6798 if (max_spare_cap_cpu < 0 && !compute_prev_delta)
6799 continue;
6800
6801 /* Compute the 'base' energy of the pd, without @p */
6802 base_energy_pd = compute_energy(p, -1, pd);
6803 base_energy += base_energy_pd;
6804
6805 /* Evaluate the energy impact of using prev_cpu. */
6806 if (compute_prev_delta) {
6807 prev_delta = compute_energy(p, prev_cpu, pd);
6808 if (prev_delta < base_energy_pd)
6809 goto unlock;
6810 prev_delta -= base_energy_pd;
6811 best_delta = min(best_delta, prev_delta);
6812 }
6813
6814 /* Evaluate the energy impact of using max_spare_cap_cpu. */
6815 if (max_spare_cap_cpu >= 0) {
6816 cur_delta = compute_energy(p, max_spare_cap_cpu, pd);
6817 if (cur_delta < base_energy_pd)
6818 goto unlock;
6819 cur_delta -= base_energy_pd;
6820 if (cur_delta < best_delta) {
6821 best_delta = cur_delta;
6822 best_energy_cpu = max_spare_cap_cpu;
6823 }
6824 }
6825 }
6826 rcu_read_unlock();
6827
6828 /*
6829 * Pick the best CPU if prev_cpu cannot be used, or if it saves at
6830 * least 6% of the energy used by prev_cpu.
6831 */
6832 if ((prev_delta == ULONG_MAX) ||
6833 (prev_delta - best_delta) > ((prev_delta + base_energy) >> 4))
6834 target = best_energy_cpu;
6835
6836 return target;
6837
6838unlock:
6839 rcu_read_unlock();
6840
6841 return target;
6842}
6843
6844/*
6845 * select_task_rq_fair: Select target runqueue for the waking task in domains
6846 * that have the relevant SD flag set. In practice, this is SD_BALANCE_WAKE,
6847 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
6848 *
6849 * Balances load by selecting the idlest CPU in the idlest group, or under
6850 * certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set.
6851 *
6852 * Returns the target CPU number.
6853 */
6854static int
6855select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
6856{
6857 int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
6858 struct sched_domain *tmp, *sd = NULL;
6859 int cpu = smp_processor_id();
6860 int new_cpu = prev_cpu;
6861 int want_affine = 0;
6862 /* SD_flags and WF_flags share the first nibble */
6863 int sd_flag = wake_flags & 0xF;
6864
6865 /*
6866 * required for stable ->cpus_allowed
6867 */
6868 lockdep_assert_held(&p->pi_lock);
6869 if (wake_flags & WF_TTWU) {
6870 record_wakee(p);
6871
6872 if (sched_energy_enabled()) {
6873 new_cpu = find_energy_efficient_cpu(p, prev_cpu);
6874 if (new_cpu >= 0)
6875 return new_cpu;
6876 new_cpu = prev_cpu;
6877 }
6878
6879 want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, p->cpus_ptr);
6880 }
6881
6882 rcu_read_lock();
6883 for_each_domain(cpu, tmp) {
6884 /*
6885 * If both 'cpu' and 'prev_cpu' are part of this domain,
6886 * cpu is a valid SD_WAKE_AFFINE target.
6887 */
6888 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
6889 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
6890 if (cpu != prev_cpu)
6891 new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync);
6892
6893 sd = NULL; /* Prefer wake_affine over balance flags */
6894 break;
6895 }
6896
6897 if (tmp->flags & sd_flag)
6898 sd = tmp;
6899 else if (!want_affine)
6900 break;
6901 }
6902
6903 if (unlikely(sd)) {
6904 /* Slow path */
6905 new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
6906 } else if (wake_flags & WF_TTWU) { /* XXX always ? */
6907 /* Fast path */
6908 new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
6909
6910 if (want_affine)
6911 current->recent_used_cpu = cpu;
6912 }
6913 rcu_read_unlock();
6914
6915 return new_cpu;
6916}
6917
6918static void detach_entity_cfs_rq(struct sched_entity *se);
6919
6920/*
6921 * Called immediately before a task is migrated to a new CPU; task_cpu(p) and
6922 * cfs_rq_of(p) references at time of call are still valid and identify the
6923 * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6924 */
6925static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
6926{
6927 /*
6928 * As blocked tasks retain absolute vruntime the migration needs to
6929 * deal with this by subtracting the old and adding the new
6930 * min_vruntime -- the latter is done by enqueue_entity() when placing
6931 * the task on the new runqueue.
6932 */
6933 if (READ_ONCE(p->__state) == TASK_WAKING) {
6934 struct sched_entity *se = &p->se;
6935 struct cfs_rq *cfs_rq = cfs_rq_of(se);
6936 u64 min_vruntime;
6937
6938#ifndef CONFIG_64BIT
6939 u64 min_vruntime_copy;
6940
6941 do {
6942 min_vruntime_copy = cfs_rq->min_vruntime_copy;
6943 smp_rmb();
6944 min_vruntime = cfs_rq->min_vruntime;
6945 } while (min_vruntime != min_vruntime_copy);
6946#else
6947 min_vruntime = cfs_rq->min_vruntime;
6948#endif
6949
6950 se->vruntime -= min_vruntime;
6951 }
6952
6953 if (p->on_rq == TASK_ON_RQ_MIGRATING) {
6954 /*
6955 * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old'
6956 * rq->lock and can modify state directly.
6957 */
6958 lockdep_assert_rq_held(task_rq(p));
6959 detach_entity_cfs_rq(&p->se);
6960
6961 } else {
6962 /*
6963 * We are supposed to update the task to "current" time, then
6964 * its up to date and ready to go to new CPU/cfs_rq. But we
6965 * have difficulty in getting what current time is, so simply
6966 * throw away the out-of-date time. This will result in the
6967 * wakee task is less decayed, but giving the wakee more load
6968 * sounds not bad.
6969 */
6970 remove_entity_load_avg(&p->se);
6971 }
6972
6973 /* Tell new CPU we are migrated */
6974 p->se.avg.last_update_time = 0;
6975
6976 /* We have migrated, no longer consider this task hot */
6977 p->se.exec_start = 0;
6978
6979 update_scan_period(p, new_cpu);
6980}
6981
6982static void task_dead_fair(struct task_struct *p)
6983{
6984 remove_entity_load_avg(&p->se);
6985}
6986
6987static int
6988balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6989{
6990 if (rq->nr_running)
6991 return 1;
6992
6993 return newidle_balance(rq, rf) != 0;
6994}
6995#endif /* CONFIG_SMP */
6996
6997static unsigned long wakeup_gran(struct sched_entity *se)
6998{
6999 unsigned long gran = sysctl_sched_wakeup_granularity;
7000
7001 /*
7002 * Since its curr running now, convert the gran from real-time
7003 * to virtual-time in his units.
7004 *
7005 * By using 'se' instead of 'curr' we penalize light tasks, so
7006 * they get preempted easier. That is, if 'se' < 'curr' then
7007 * the resulting gran will be larger, therefore penalizing the
7008 * lighter, if otoh 'se' > 'curr' then the resulting gran will
7009 * be smaller, again penalizing the lighter task.
7010 *
7011 * This is especially important for buddies when the leftmost
7012 * task is higher priority than the buddy.
7013 */
7014 return calc_delta_fair(gran, se);
7015}
7016
7017/*
7018 * Should 'se' preempt 'curr'.
7019 *
7020 * |s1
7021 * |s2
7022 * |s3
7023 * g
7024 * |<--->|c
7025 *
7026 * w(c, s1) = -1
7027 * w(c, s2) = 0
7028 * w(c, s3) = 1
7029 *
7030 */
7031static int
7032wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
7033{
7034 s64 gran, vdiff = curr->vruntime - se->vruntime;
7035
7036 if (vdiff <= 0)
7037 return -1;
7038
7039 gran = wakeup_gran(se);
7040 if (vdiff > gran)
7041 return 1;
7042
7043 return 0;
7044}
7045
7046static void set_last_buddy(struct sched_entity *se)
7047{
7048 if (entity_is_task(se) && unlikely(task_has_idle_policy(task_of(se))))
7049 return;
7050
7051 for_each_sched_entity(se) {
7052 if (SCHED_WARN_ON(!se->on_rq))
7053 return;
7054 cfs_rq_of(se)->last = se;
7055 }
7056}
7057
7058static void set_next_buddy(struct sched_entity *se)
7059{
7060 if (entity_is_task(se) && unlikely(task_has_idle_policy(task_of(se))))
7061 return;
7062
7063 for_each_sched_entity(se) {
7064 if (SCHED_WARN_ON(!se->on_rq))
7065 return;
7066 cfs_rq_of(se)->next = se;
7067 }
7068}
7069
7070static void set_skip_buddy(struct sched_entity *se)
7071{
7072 for_each_sched_entity(se)
7073 cfs_rq_of(se)->skip = se;
7074}
7075
7076/*
7077 * Preempt the current task with a newly woken task if needed:
7078 */
7079static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
7080{
7081 struct task_struct *curr = rq->curr;
7082 struct sched_entity *se = &curr->se, *pse = &p->se;
7083 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
7084 int scale = cfs_rq->nr_running >= sched_nr_latency;
7085 int next_buddy_marked = 0;
7086
7087 if (unlikely(se == pse))
7088 return;
7089
7090 /*
7091 * This is possible from callers such as attach_tasks(), in which we
7092 * unconditionally check_preempt_curr() after an enqueue (which may have
7093 * lead to a throttle). This both saves work and prevents false
7094 * next-buddy nomination below.
7095 */
7096 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
7097 return;
7098
7099 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
7100 set_next_buddy(pse);
7101 next_buddy_marked = 1;
7102 }
7103
7104 /*
7105 * We can come here with TIF_NEED_RESCHED already set from new task
7106 * wake up path.
7107 *
7108 * Note: this also catches the edge-case of curr being in a throttled
7109 * group (e.g. via set_curr_task), since update_curr() (in the
7110 * enqueue of curr) will have resulted in resched being set. This
7111 * prevents us from potentially nominating it as a false LAST_BUDDY
7112 * below.
7113 */
7114 if (test_tsk_need_resched(curr))
7115 return;
7116
7117 /* Idle tasks are by definition preempted by non-idle tasks. */
7118 if (unlikely(task_has_idle_policy(curr)) &&
7119 likely(!task_has_idle_policy(p)))
7120 goto preempt;
7121
7122 /*
7123 * Batch and idle tasks do not preempt non-idle tasks (their preemption
7124 * is driven by the tick):
7125 */
7126 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
7127 return;
7128
7129 find_matching_se(&se, &pse);
7130 update_curr(cfs_rq_of(se));
7131 BUG_ON(!pse);
7132 if (wakeup_preempt_entity(se, pse) == 1) {
7133 /*
7134 * Bias pick_next to pick the sched entity that is
7135 * triggering this preemption.
7136 */
7137 if (!next_buddy_marked)
7138 set_next_buddy(pse);
7139 goto preempt;
7140 }
7141
7142 return;
7143
7144preempt:
7145 resched_curr(rq);
7146 /*
7147 * Only set the backward buddy when the current task is still
7148 * on the rq. This can happen when a wakeup gets interleaved
7149 * with schedule on the ->pre_schedule() or idle_balance()
7150 * point, either of which can * drop the rq lock.
7151 *
7152 * Also, during early boot the idle thread is in the fair class,
7153 * for obvious reasons its a bad idea to schedule back to it.
7154 */
7155 if (unlikely(!se->on_rq || curr == rq->idle))
7156 return;
7157
7158 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
7159 set_last_buddy(se);
7160}
7161
7162#ifdef CONFIG_SMP
7163static struct task_struct *pick_task_fair(struct rq *rq)
7164{
7165 struct sched_entity *se;
7166 struct cfs_rq *cfs_rq;
7167
7168again:
7169 cfs_rq = &rq->cfs;
7170 if (!cfs_rq->nr_running)
7171 return NULL;
7172
7173 do {
7174 struct sched_entity *curr = cfs_rq->curr;
7175
7176 /* When we pick for a remote RQ, we'll not have done put_prev_entity() */
7177 if (curr) {
7178 if (curr->on_rq)
7179 update_curr(cfs_rq);
7180 else
7181 curr = NULL;
7182
7183 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
7184 goto again;
7185 }
7186
7187 se = pick_next_entity(cfs_rq, curr);
7188 cfs_rq = group_cfs_rq(se);
7189 } while (cfs_rq);
7190
7191 return task_of(se);
7192}
7193#endif
7194
7195struct task_struct *
7196pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
7197{
7198 struct cfs_rq *cfs_rq = &rq->cfs;
7199 struct sched_entity *se;
7200 struct task_struct *p;
7201 int new_tasks;
7202
7203again:
7204 if (!sched_fair_runnable(rq))
7205 goto idle;
7206
7207#ifdef CONFIG_FAIR_GROUP_SCHED
7208 if (!prev || prev->sched_class != &fair_sched_class)
7209 goto simple;
7210
7211 /*
7212 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
7213 * likely that a next task is from the same cgroup as the current.
7214 *
7215 * Therefore attempt to avoid putting and setting the entire cgroup
7216 * hierarchy, only change the part that actually changes.
7217 */
7218
7219 do {
7220 struct sched_entity *curr = cfs_rq->curr;
7221
7222 /*
7223 * Since we got here without doing put_prev_entity() we also
7224 * have to consider cfs_rq->curr. If it is still a runnable
7225 * entity, update_curr() will update its vruntime, otherwise
7226 * forget we've ever seen it.
7227 */
7228 if (curr) {
7229 if (curr->on_rq)
7230 update_curr(cfs_rq);
7231 else
7232 curr = NULL;
7233
7234 /*
7235 * This call to check_cfs_rq_runtime() will do the
7236 * throttle and dequeue its entity in the parent(s).
7237 * Therefore the nr_running test will indeed
7238 * be correct.
7239 */
7240 if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
7241 cfs_rq = &rq->cfs;
7242
7243 if (!cfs_rq->nr_running)
7244 goto idle;
7245
7246 goto simple;
7247 }
7248 }
7249
7250 se = pick_next_entity(cfs_rq, curr);
7251 cfs_rq = group_cfs_rq(se);
7252 } while (cfs_rq);
7253
7254 p = task_of(se);
7255
7256 /*
7257 * Since we haven't yet done put_prev_entity and if the selected task
7258 * is a different task than we started out with, try and touch the
7259 * least amount of cfs_rqs.
7260 */
7261 if (prev != p) {
7262 struct sched_entity *pse = &prev->se;
7263
7264 while (!(cfs_rq = is_same_group(se, pse))) {
7265 int se_depth = se->depth;
7266 int pse_depth = pse->depth;
7267
7268 if (se_depth <= pse_depth) {
7269 put_prev_entity(cfs_rq_of(pse), pse);
7270 pse = parent_entity(pse);
7271 }
7272 if (se_depth >= pse_depth) {
7273 set_next_entity(cfs_rq_of(se), se);
7274 se = parent_entity(se);
7275 }
7276 }
7277
7278 put_prev_entity(cfs_rq, pse);
7279 set_next_entity(cfs_rq, se);
7280 }
7281
7282 goto done;
7283simple:
7284#endif
7285 if (prev)
7286 put_prev_task(rq, prev);
7287
7288 do {
7289 se = pick_next_entity(cfs_rq, NULL);
7290 set_next_entity(cfs_rq, se);
7291 cfs_rq = group_cfs_rq(se);
7292 } while (cfs_rq);
7293
7294 p = task_of(se);
7295
7296done: __maybe_unused;
7297#ifdef CONFIG_SMP
7298 /*
7299 * Move the next running task to the front of
7300 * the list, so our cfs_tasks list becomes MRU
7301 * one.
7302 */
7303 list_move(&p->se.group_node, &rq->cfs_tasks);
7304#endif
7305
7306 if (hrtick_enabled_fair(rq))
7307 hrtick_start_fair(rq, p);
7308
7309 update_misfit_status(p, rq);
7310
7311 return p;
7312
7313idle:
7314 if (!rf)
7315 return NULL;
7316
7317 new_tasks = newidle_balance(rq, rf);
7318
7319 /*
7320 * Because newidle_balance() releases (and re-acquires) rq->lock, it is
7321 * possible for any higher priority task to appear. In that case we
7322 * must re-start the pick_next_entity() loop.
7323 */
7324 if (new_tasks < 0)
7325 return RETRY_TASK;
7326
7327 if (new_tasks > 0)
7328 goto again;
7329
7330 /*
7331 * rq is about to be idle, check if we need to update the
7332 * lost_idle_time of clock_pelt
7333 */
7334 update_idle_rq_clock_pelt(rq);
7335
7336 return NULL;
7337}
7338
7339static struct task_struct *__pick_next_task_fair(struct rq *rq)
7340{
7341 return pick_next_task_fair(rq, NULL, NULL);
7342}
7343
7344/*
7345 * Account for a descheduled task:
7346 */
7347static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
7348{
7349 struct sched_entity *se = &prev->se;
7350 struct cfs_rq *cfs_rq;
7351
7352 for_each_sched_entity(se) {
7353 cfs_rq = cfs_rq_of(se);
7354 put_prev_entity(cfs_rq, se);
7355 }
7356}
7357
7358/*
7359 * sched_yield() is very simple
7360 *
7361 * The magic of dealing with the ->skip buddy is in pick_next_entity.
7362 */
7363static void yield_task_fair(struct rq *rq)
7364{
7365 struct task_struct *curr = rq->curr;
7366 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
7367 struct sched_entity *se = &curr->se;
7368
7369 /*
7370 * Are we the only task in the tree?
7371 */
7372 if (unlikely(rq->nr_running == 1))
7373 return;
7374
7375 clear_buddies(cfs_rq, se);
7376
7377 if (curr->policy != SCHED_BATCH) {
7378 update_rq_clock(rq);
7379 /*
7380 * Update run-time statistics of the 'current'.
7381 */
7382 update_curr(cfs_rq);
7383 /*
7384 * Tell update_rq_clock() that we've just updated,
7385 * so we don't do microscopic update in schedule()
7386 * and double the fastpath cost.
7387 */
7388 rq_clock_skip_update(rq);
7389 }
7390
7391 set_skip_buddy(se);
7392}
7393
7394static bool yield_to_task_fair(struct rq *rq, struct task_struct *p)
7395{
7396 struct sched_entity *se = &p->se;
7397
7398 /* throttled hierarchies are not runnable */
7399 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
7400 return false;
7401
7402 /* Tell the scheduler that we'd really like pse to run next. */
7403 set_next_buddy(se);
7404
7405 yield_task_fair(rq);
7406
7407 return true;
7408}
7409
7410#ifdef CONFIG_SMP
7411/**************************************************
7412 * Fair scheduling class load-balancing methods.
7413 *
7414 * BASICS
7415 *
7416 * The purpose of load-balancing is to achieve the same basic fairness the
7417 * per-CPU scheduler provides, namely provide a proportional amount of compute
7418 * time to each task. This is expressed in the following equation:
7419 *
7420 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
7421 *
7422 * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
7423 * W_i,0 is defined as:
7424 *
7425 * W_i,0 = \Sum_j w_i,j (2)
7426 *
7427 * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
7428 * is derived from the nice value as per sched_prio_to_weight[].
7429 *
7430 * The weight average is an exponential decay average of the instantaneous
7431 * weight:
7432 *
7433 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
7434 *
7435 * C_i is the compute capacity of CPU i, typically it is the
7436 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
7437 * can also include other factors [XXX].
7438 *
7439 * To achieve this balance we define a measure of imbalance which follows
7440 * directly from (1):
7441 *
7442 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
7443 *
7444 * We them move tasks around to minimize the imbalance. In the continuous
7445 * function space it is obvious this converges, in the discrete case we get
7446 * a few fun cases generally called infeasible weight scenarios.
7447 *
7448 * [XXX expand on:
7449 * - infeasible weights;
7450 * - local vs global optima in the discrete case. ]
7451 *
7452 *
7453 * SCHED DOMAINS
7454 *
7455 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
7456 * for all i,j solution, we create a tree of CPUs that follows the hardware
7457 * topology where each level pairs two lower groups (or better). This results
7458 * in O(log n) layers. Furthermore we reduce the number of CPUs going up the
7459 * tree to only the first of the previous level and we decrease the frequency
7460 * of load-balance at each level inv. proportional to the number of CPUs in
7461 * the groups.
7462 *
7463 * This yields:
7464 *
7465 * log_2 n 1 n
7466 * \Sum { --- * --- * 2^i } = O(n) (5)
7467 * i = 0 2^i 2^i
7468 * `- size of each group
7469 * | | `- number of CPUs doing load-balance
7470 * | `- freq
7471 * `- sum over all levels
7472 *
7473 * Coupled with a limit on how many tasks we can migrate every balance pass,
7474 * this makes (5) the runtime complexity of the balancer.
7475 *
7476 * An important property here is that each CPU is still (indirectly) connected
7477 * to every other CPU in at most O(log n) steps:
7478 *
7479 * The adjacency matrix of the resulting graph is given by:
7480 *
7481 * log_2 n
7482 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
7483 * k = 0
7484 *
7485 * And you'll find that:
7486 *
7487 * A^(log_2 n)_i,j != 0 for all i,j (7)
7488 *
7489 * Showing there's indeed a path between every CPU in at most O(log n) steps.
7490 * The task movement gives a factor of O(m), giving a convergence complexity
7491 * of:
7492 *
7493 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
7494 *
7495 *
7496 * WORK CONSERVING
7497 *
7498 * In order to avoid CPUs going idle while there's still work to do, new idle
7499 * balancing is more aggressive and has the newly idle CPU iterate up the domain
7500 * tree itself instead of relying on other CPUs to bring it work.
7501 *
7502 * This adds some complexity to both (5) and (8) but it reduces the total idle
7503 * time.
7504 *
7505 * [XXX more?]
7506 *
7507 *
7508 * CGROUPS
7509 *
7510 * Cgroups make a horror show out of (2), instead of a simple sum we get:
7511 *
7512 * s_k,i
7513 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
7514 * S_k
7515 *
7516 * Where
7517 *
7518 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
7519 *
7520 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i.
7521 *
7522 * The big problem is S_k, its a global sum needed to compute a local (W_i)
7523 * property.
7524 *
7525 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
7526 * rewrite all of this once again.]
7527 */
7528
7529static unsigned long __read_mostly max_load_balance_interval = HZ/10;
7530
7531enum fbq_type { regular, remote, all };
7532
7533/*
7534 * 'group_type' describes the group of CPUs at the moment of load balancing.
7535 *
7536 * The enum is ordered by pulling priority, with the group with lowest priority
7537 * first so the group_type can simply be compared when selecting the busiest
7538 * group. See update_sd_pick_busiest().
7539 */
7540enum group_type {
7541 /* The group has spare capacity that can be used to run more tasks. */
7542 group_has_spare = 0,
7543 /*
7544 * The group is fully used and the tasks don't compete for more CPU
7545 * cycles. Nevertheless, some tasks might wait before running.
7546 */
7547 group_fully_busy,
7548 /*
7549 * SD_ASYM_CPUCAPACITY only: One task doesn't fit with CPU's capacity
7550 * and must be migrated to a more powerful CPU.
7551 */
7552 group_misfit_task,
7553 /*
7554 * SD_ASYM_PACKING only: One local CPU with higher capacity is available,
7555 * and the task should be migrated to it instead of running on the
7556 * current CPU.
7557 */
7558 group_asym_packing,
7559 /*
7560 * The tasks' affinity constraints previously prevented the scheduler
7561 * from balancing the load across the system.
7562 */
7563 group_imbalanced,
7564 /*
7565 * The CPU is overloaded and can't provide expected CPU cycles to all
7566 * tasks.
7567 */
7568 group_overloaded
7569};
7570
7571enum migration_type {
7572 migrate_load = 0,
7573 migrate_util,
7574 migrate_task,
7575 migrate_misfit
7576};
7577
7578#define LBF_ALL_PINNED 0x01
7579#define LBF_NEED_BREAK 0x02
7580#define LBF_DST_PINNED 0x04
7581#define LBF_SOME_PINNED 0x08
7582#define LBF_ACTIVE_LB 0x10
7583
7584struct lb_env {
7585 struct sched_domain *sd;
7586
7587 struct rq *src_rq;
7588 int src_cpu;
7589
7590 int dst_cpu;
7591 struct rq *dst_rq;
7592
7593 struct cpumask *dst_grpmask;
7594 int new_dst_cpu;
7595 enum cpu_idle_type idle;
7596 long imbalance;
7597 /* The set of CPUs under consideration for load-balancing */
7598 struct cpumask *cpus;
7599
7600 unsigned int flags;
7601
7602 unsigned int loop;
7603 unsigned int loop_break;
7604 unsigned int loop_max;
7605
7606 enum fbq_type fbq_type;
7607 enum migration_type migration_type;
7608 struct list_head tasks;
7609};
7610
7611/*
7612 * Is this task likely cache-hot:
7613 */
7614static int task_hot(struct task_struct *p, struct lb_env *env)
7615{
7616 s64 delta;
7617
7618 lockdep_assert_rq_held(env->src_rq);
7619
7620 if (p->sched_class != &fair_sched_class)
7621 return 0;
7622
7623 if (unlikely(task_has_idle_policy(p)))
7624 return 0;
7625
7626 /* SMT siblings share cache */
7627 if (env->sd->flags & SD_SHARE_CPUCAPACITY)
7628 return 0;
7629
7630 /*
7631 * Buddy candidates are cache hot:
7632 */
7633 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
7634 (&p->se == cfs_rq_of(&p->se)->next ||
7635 &p->se == cfs_rq_of(&p->se)->last))
7636 return 1;
7637
7638 if (sysctl_sched_migration_cost == -1)
7639 return 1;
7640
7641 /*
7642 * Don't migrate task if the task's cookie does not match
7643 * with the destination CPU's core cookie.
7644 */
7645 if (!sched_core_cookie_match(cpu_rq(env->dst_cpu), p))
7646 return 1;
7647
7648 if (sysctl_sched_migration_cost == 0)
7649 return 0;
7650
7651 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
7652
7653 return delta < (s64)sysctl_sched_migration_cost;
7654}
7655
7656#ifdef CONFIG_NUMA_BALANCING
7657/*
7658 * Returns 1, if task migration degrades locality
7659 * Returns 0, if task migration improves locality i.e migration preferred.
7660 * Returns -1, if task migration is not affected by locality.
7661 */
7662static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
7663{
7664 struct numa_group *numa_group = rcu_dereference(p->numa_group);
7665 unsigned long src_weight, dst_weight;
7666 int src_nid, dst_nid, dist;
7667
7668 if (!static_branch_likely(&sched_numa_balancing))
7669 return -1;
7670
7671 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
7672 return -1;
7673
7674 src_nid = cpu_to_node(env->src_cpu);
7675 dst_nid = cpu_to_node(env->dst_cpu);
7676
7677 if (src_nid == dst_nid)
7678 return -1;
7679
7680 /* Migrating away from the preferred node is always bad. */
7681 if (src_nid == p->numa_preferred_nid) {
7682 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
7683 return 1;
7684 else
7685 return -1;
7686 }
7687
7688 /* Encourage migration to the preferred node. */
7689 if (dst_nid == p->numa_preferred_nid)
7690 return 0;
7691
7692 /* Leaving a core idle is often worse than degrading locality. */
7693 if (env->idle == CPU_IDLE)
7694 return -1;
7695
7696 dist = node_distance(src_nid, dst_nid);
7697 if (numa_group) {
7698 src_weight = group_weight(p, src_nid, dist);
7699 dst_weight = group_weight(p, dst_nid, dist);
7700 } else {
7701 src_weight = task_weight(p, src_nid, dist);
7702 dst_weight = task_weight(p, dst_nid, dist);
7703 }
7704
7705 return dst_weight < src_weight;
7706}
7707
7708#else
7709static inline int migrate_degrades_locality(struct task_struct *p,
7710 struct lb_env *env)
7711{
7712 return -1;
7713}
7714#endif
7715
7716/*
7717 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
7718 */
7719static
7720int can_migrate_task(struct task_struct *p, struct lb_env *env)
7721{
7722 int tsk_cache_hot;
7723
7724 lockdep_assert_rq_held(env->src_rq);
7725
7726 /*
7727 * We do not migrate tasks that are:
7728 * 1) throttled_lb_pair, or
7729 * 2) cannot be migrated to this CPU due to cpus_ptr, or
7730 * 3) running (obviously), or
7731 * 4) are cache-hot on their current CPU.
7732 */
7733 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
7734 return 0;
7735
7736 /* Disregard pcpu kthreads; they are where they need to be. */
7737 if (kthread_is_per_cpu(p))
7738 return 0;
7739
7740 if (!cpumask_test_cpu(env->dst_cpu, p->cpus_ptr)) {
7741 int cpu;
7742
7743 schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
7744
7745 env->flags |= LBF_SOME_PINNED;
7746
7747 /*
7748 * Remember if this task can be migrated to any other CPU in
7749 * our sched_group. We may want to revisit it if we couldn't
7750 * meet load balance goals by pulling other tasks on src_cpu.
7751 *
7752 * Avoid computing new_dst_cpu
7753 * - for NEWLY_IDLE
7754 * - if we have already computed one in current iteration
7755 * - if it's an active balance
7756 */
7757 if (env->idle == CPU_NEWLY_IDLE ||
7758 env->flags & (LBF_DST_PINNED | LBF_ACTIVE_LB))
7759 return 0;
7760
7761 /* Prevent to re-select dst_cpu via env's CPUs: */
7762 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
7763 if (cpumask_test_cpu(cpu, p->cpus_ptr)) {
7764 env->flags |= LBF_DST_PINNED;
7765 env->new_dst_cpu = cpu;
7766 break;
7767 }
7768 }
7769
7770 return 0;
7771 }
7772
7773 /* Record that we found at least one task that could run on dst_cpu */
7774 env->flags &= ~LBF_ALL_PINNED;
7775
7776 if (task_running(env->src_rq, p)) {
7777 schedstat_inc(p->se.statistics.nr_failed_migrations_running);
7778 return 0;
7779 }
7780
7781 /*
7782 * Aggressive migration if:
7783 * 1) active balance
7784 * 2) destination numa is preferred
7785 * 3) task is cache cold, or
7786 * 4) too many balance attempts have failed.
7787 */
7788 if (env->flags & LBF_ACTIVE_LB)
7789 return 1;
7790
7791 tsk_cache_hot = migrate_degrades_locality(p, env);
7792 if (tsk_cache_hot == -1)
7793 tsk_cache_hot = task_hot(p, env);
7794
7795 if (tsk_cache_hot <= 0 ||
7796 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
7797 if (tsk_cache_hot == 1) {
7798 schedstat_inc(env->sd->lb_hot_gained[env->idle]);
7799 schedstat_inc(p->se.statistics.nr_forced_migrations);
7800 }
7801 return 1;
7802 }
7803
7804 schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
7805 return 0;
7806}
7807
7808/*
7809 * detach_task() -- detach the task for the migration specified in env
7810 */
7811static void detach_task(struct task_struct *p, struct lb_env *env)
7812{
7813 lockdep_assert_rq_held(env->src_rq);
7814
7815 deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
7816 set_task_cpu(p, env->dst_cpu);
7817}
7818
7819/*
7820 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
7821 * part of active balancing operations within "domain".
7822 *
7823 * Returns a task if successful and NULL otherwise.
7824 */
7825static struct task_struct *detach_one_task(struct lb_env *env)
7826{
7827 struct task_struct *p;
7828
7829 lockdep_assert_rq_held(env->src_rq);
7830
7831 list_for_each_entry_reverse(p,
7832 &env->src_rq->cfs_tasks, se.group_node) {
7833 if (!can_migrate_task(p, env))
7834 continue;
7835
7836 detach_task(p, env);
7837
7838 /*
7839 * Right now, this is only the second place where
7840 * lb_gained[env->idle] is updated (other is detach_tasks)
7841 * so we can safely collect stats here rather than
7842 * inside detach_tasks().
7843 */
7844 schedstat_inc(env->sd->lb_gained[env->idle]);
7845 return p;
7846 }
7847 return NULL;
7848}
7849
7850static const unsigned int sched_nr_migrate_break = 32;
7851
7852/*
7853 * detach_tasks() -- tries to detach up to imbalance load/util/tasks from
7854 * busiest_rq, as part of a balancing operation within domain "sd".
7855 *
7856 * Returns number of detached tasks if successful and 0 otherwise.
7857 */
7858static int detach_tasks(struct lb_env *env)
7859{
7860 struct list_head *tasks = &env->src_rq->cfs_tasks;
7861 unsigned long util, load;
7862 struct task_struct *p;
7863 int detached = 0;
7864
7865 lockdep_assert_rq_held(env->src_rq);
7866
7867 /*
7868 * Source run queue has been emptied by another CPU, clear
7869 * LBF_ALL_PINNED flag as we will not test any task.
7870 */
7871 if (env->src_rq->nr_running <= 1) {
7872 env->flags &= ~LBF_ALL_PINNED;
7873 return 0;
7874 }
7875
7876 if (env->imbalance <= 0)
7877 return 0;
7878
7879 while (!list_empty(tasks)) {
7880 /*
7881 * We don't want to steal all, otherwise we may be treated likewise,
7882 * which could at worst lead to a livelock crash.
7883 */
7884 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
7885 break;
7886
7887 p = list_last_entry(tasks, struct task_struct, se.group_node);
7888
7889 env->loop++;
7890 /* We've more or less seen every task there is, call it quits */
7891 if (env->loop > env->loop_max)
7892 break;
7893
7894 /* take a breather every nr_migrate tasks */
7895 if (env->loop > env->loop_break) {
7896 env->loop_break += sched_nr_migrate_break;
7897 env->flags |= LBF_NEED_BREAK;
7898 break;
7899 }
7900
7901 if (!can_migrate_task(p, env))
7902 goto next;
7903
7904 switch (env->migration_type) {
7905 case migrate_load:
7906 /*
7907 * Depending of the number of CPUs and tasks and the
7908 * cgroup hierarchy, task_h_load() can return a null
7909 * value. Make sure that env->imbalance decreases
7910 * otherwise detach_tasks() will stop only after
7911 * detaching up to loop_max tasks.
7912 */
7913 load = max_t(unsigned long, task_h_load(p), 1);
7914
7915 if (sched_feat(LB_MIN) &&
7916 load < 16 && !env->sd->nr_balance_failed)
7917 goto next;
7918
7919 /*
7920 * Make sure that we don't migrate too much load.
7921 * Nevertheless, let relax the constraint if
7922 * scheduler fails to find a good waiting task to
7923 * migrate.
7924 */
7925 if (shr_bound(load, env->sd->nr_balance_failed) > env->imbalance)
7926 goto next;
7927
7928 env->imbalance -= load;
7929 break;
7930
7931 case migrate_util:
7932 util = task_util_est(p);
7933
7934 if (util > env->imbalance)
7935 goto next;
7936
7937 env->imbalance -= util;
7938 break;
7939
7940 case migrate_task:
7941 env->imbalance--;
7942 break;
7943
7944 case migrate_misfit:
7945 /* This is not a misfit task */
7946 if (task_fits_capacity(p, capacity_of(env->src_cpu)))
7947 goto next;
7948
7949 env->imbalance = 0;
7950 break;
7951 }
7952
7953 detach_task(p, env);
7954 list_add(&p->se.group_node, &env->tasks);
7955
7956 detached++;
7957
7958#ifdef CONFIG_PREEMPTION
7959 /*
7960 * NEWIDLE balancing is a source of latency, so preemptible
7961 * kernels will stop after the first task is detached to minimize
7962 * the critical section.
7963 */
7964 if (env->idle == CPU_NEWLY_IDLE)
7965 break;
7966#endif
7967
7968 /*
7969 * We only want to steal up to the prescribed amount of
7970 * load/util/tasks.
7971 */
7972 if (env->imbalance <= 0)
7973 break;
7974
7975 continue;
7976next:
7977 list_move(&p->se.group_node, tasks);
7978 }
7979
7980 /*
7981 * Right now, this is one of only two places we collect this stat
7982 * so we can safely collect detach_one_task() stats here rather
7983 * than inside detach_one_task().
7984 */
7985 schedstat_add(env->sd->lb_gained[env->idle], detached);
7986
7987 return detached;
7988}
7989
7990/*
7991 * attach_task() -- attach the task detached by detach_task() to its new rq.
7992 */
7993static void attach_task(struct rq *rq, struct task_struct *p)
7994{
7995 lockdep_assert_rq_held(rq);
7996
7997 BUG_ON(task_rq(p) != rq);
7998 activate_task(rq, p, ENQUEUE_NOCLOCK);
7999 check_preempt_curr(rq, p, 0);
8000}
8001
8002/*
8003 * attach_one_task() -- attaches the task returned from detach_one_task() to
8004 * its new rq.
8005 */
8006static void attach_one_task(struct rq *rq, struct task_struct *p)
8007{
8008 struct rq_flags rf;
8009
8010 rq_lock(rq, &rf);
8011 update_rq_clock(rq);
8012 attach_task(rq, p);
8013 rq_unlock(rq, &rf);
8014}
8015
8016/*
8017 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
8018 * new rq.
8019 */
8020static void attach_tasks(struct lb_env *env)
8021{
8022 struct list_head *tasks = &env->tasks;
8023 struct task_struct *p;
8024 struct rq_flags rf;
8025
8026 rq_lock(env->dst_rq, &rf);
8027 update_rq_clock(env->dst_rq);
8028
8029 while (!list_empty(tasks)) {
8030 p = list_first_entry(tasks, struct task_struct, se.group_node);
8031 list_del_init(&p->se.group_node);
8032
8033 attach_task(env->dst_rq, p);
8034 }
8035
8036 rq_unlock(env->dst_rq, &rf);
8037}
8038
8039#ifdef CONFIG_NO_HZ_COMMON
8040static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
8041{
8042 if (cfs_rq->avg.load_avg)
8043 return true;
8044
8045 if (cfs_rq->avg.util_avg)
8046 return true;
8047
8048 return false;
8049}
8050
8051static inline bool others_have_blocked(struct rq *rq)
8052{
8053 if (READ_ONCE(rq->avg_rt.util_avg))
8054 return true;
8055
8056 if (READ_ONCE(rq->avg_dl.util_avg))
8057 return true;
8058
8059 if (thermal_load_avg(rq))
8060 return true;
8061
8062#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
8063 if (READ_ONCE(rq->avg_irq.util_avg))
8064 return true;
8065#endif
8066
8067 return false;
8068}
8069
8070static inline void update_blocked_load_tick(struct rq *rq)
8071{
8072 WRITE_ONCE(rq->last_blocked_load_update_tick, jiffies);
8073}
8074
8075static inline void update_blocked_load_status(struct rq *rq, bool has_blocked)
8076{
8077 if (!has_blocked)
8078 rq->has_blocked_load = 0;
8079}
8080#else
8081static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq) { return false; }
8082static inline bool others_have_blocked(struct rq *rq) { return false; }
8083static inline void update_blocked_load_tick(struct rq *rq) {}
8084static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) {}
8085#endif
8086
8087static bool __update_blocked_others(struct rq *rq, bool *done)
8088{
8089 const struct sched_class *curr_class;
8090 u64 now = rq_clock_pelt(rq);
8091 unsigned long thermal_pressure;
8092 bool decayed;
8093
8094 /*
8095 * update_load_avg() can call cpufreq_update_util(). Make sure that RT,
8096 * DL and IRQ signals have been updated before updating CFS.
8097 */
8098 curr_class = rq->curr->sched_class;
8099
8100 thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
8101
8102 decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
8103 update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
8104 update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure) |
8105 update_irq_load_avg(rq, 0);
8106
8107 if (others_have_blocked(rq))
8108 *done = false;
8109
8110 return decayed;
8111}
8112
8113#ifdef CONFIG_FAIR_GROUP_SCHED
8114
8115static bool __update_blocked_fair(struct rq *rq, bool *done)
8116{
8117 struct cfs_rq *cfs_rq, *pos;
8118 bool decayed = false;
8119 int cpu = cpu_of(rq);
8120
8121 /*
8122 * Iterates the task_group tree in a bottom up fashion, see
8123 * list_add_leaf_cfs_rq() for details.
8124 */
8125 for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
8126 struct sched_entity *se;
8127
8128 if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq)) {
8129 update_tg_load_avg(cfs_rq);
8130
8131 if (cfs_rq == &rq->cfs)
8132 decayed = true;
8133 }
8134
8135 /* Propagate pending load changes to the parent, if any: */
8136 se = cfs_rq->tg->se[cpu];
8137 if (se && !skip_blocked_update(se))
8138 update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
8139
8140 /*
8141 * There can be a lot of idle CPU cgroups. Don't let fully
8142 * decayed cfs_rqs linger on the list.
8143 */
8144 if (cfs_rq_is_decayed(cfs_rq))
8145 list_del_leaf_cfs_rq(cfs_rq);
8146
8147 /* Don't need periodic decay once load/util_avg are null */
8148 if (cfs_rq_has_blocked(cfs_rq))
8149 *done = false;
8150 }
8151
8152 return decayed;
8153}
8154
8155/*
8156 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
8157 * This needs to be done in a top-down fashion because the load of a child
8158 * group is a fraction of its parents load.
8159 */
8160static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
8161{
8162 struct rq *rq = rq_of(cfs_rq);
8163 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
8164 unsigned long now = jiffies;
8165 unsigned long load;
8166
8167 if (cfs_rq->last_h_load_update == now)
8168 return;
8169
8170 WRITE_ONCE(cfs_rq->h_load_next, NULL);
8171 for_each_sched_entity(se) {
8172 cfs_rq = cfs_rq_of(se);
8173 WRITE_ONCE(cfs_rq->h_load_next, se);
8174 if (cfs_rq->last_h_load_update == now)
8175 break;
8176 }
8177
8178 if (!se) {
8179 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
8180 cfs_rq->last_h_load_update = now;
8181 }
8182
8183 while ((se = READ_ONCE(cfs_rq->h_load_next)) != NULL) {
8184 load = cfs_rq->h_load;
8185 load = div64_ul(load * se->avg.load_avg,
8186 cfs_rq_load_avg(cfs_rq) + 1);
8187 cfs_rq = group_cfs_rq(se);
8188 cfs_rq->h_load = load;
8189 cfs_rq->last_h_load_update = now;
8190 }
8191}
8192
8193static unsigned long task_h_load(struct task_struct *p)
8194{
8195 struct cfs_rq *cfs_rq = task_cfs_rq(p);
8196
8197 update_cfs_rq_h_load(cfs_rq);
8198 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
8199 cfs_rq_load_avg(cfs_rq) + 1);
8200}
8201#else
8202static bool __update_blocked_fair(struct rq *rq, bool *done)
8203{
8204 struct cfs_rq *cfs_rq = &rq->cfs;
8205 bool decayed;
8206
8207 decayed = update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq);
8208 if (cfs_rq_has_blocked(cfs_rq))
8209 *done = false;
8210
8211 return decayed;
8212}
8213
8214static unsigned long task_h_load(struct task_struct *p)
8215{
8216 return p->se.avg.load_avg;
8217}
8218#endif
8219
8220static void update_blocked_averages(int cpu)
8221{
8222 bool decayed = false, done = true;
8223 struct rq *rq = cpu_rq(cpu);
8224 struct rq_flags rf;
8225
8226 rq_lock_irqsave(rq, &rf);
8227 update_blocked_load_tick(rq);
8228 update_rq_clock(rq);
8229
8230 decayed |= __update_blocked_others(rq, &done);
8231 decayed |= __update_blocked_fair(rq, &done);
8232
8233 update_blocked_load_status(rq, !done);
8234 if (decayed)
8235 cpufreq_update_util(rq, 0);
8236 rq_unlock_irqrestore(rq, &rf);
8237}
8238
8239/********** Helpers for find_busiest_group ************************/
8240
8241/*
8242 * sg_lb_stats - stats of a sched_group required for load_balancing
8243 */
8244struct sg_lb_stats {
8245 unsigned long avg_load; /*Avg load across the CPUs of the group */
8246 unsigned long group_load; /* Total load over the CPUs of the group */
8247 unsigned long group_capacity;
8248 unsigned long group_util; /* Total utilization over the CPUs of the group */
8249 unsigned long group_runnable; /* Total runnable time over the CPUs of the group */
8250 unsigned int sum_nr_running; /* Nr of tasks running in the group */
8251 unsigned int sum_h_nr_running; /* Nr of CFS tasks running in the group */
8252 unsigned int idle_cpus;
8253 unsigned int group_weight;
8254 enum group_type group_type;
8255 unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */
8256 unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */
8257#ifdef CONFIG_NUMA_BALANCING
8258 unsigned int nr_numa_running;
8259 unsigned int nr_preferred_running;
8260#endif
8261};
8262
8263/*
8264 * sd_lb_stats - Structure to store the statistics of a sched_domain
8265 * during load balancing.
8266 */
8267struct sd_lb_stats {
8268 struct sched_group *busiest; /* Busiest group in this sd */
8269 struct sched_group *local; /* Local group in this sd */
8270 unsigned long total_load; /* Total load of all groups in sd */
8271 unsigned long total_capacity; /* Total capacity of all groups in sd */
8272 unsigned long avg_load; /* Average load across all groups in sd */
8273 unsigned int prefer_sibling; /* tasks should go to sibling first */
8274
8275 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
8276 struct sg_lb_stats local_stat; /* Statistics of the local group */
8277};
8278
8279static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
8280{
8281 /*
8282 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
8283 * local_stat because update_sg_lb_stats() does a full clear/assignment.
8284 * We must however set busiest_stat::group_type and
8285 * busiest_stat::idle_cpus to the worst busiest group because
8286 * update_sd_pick_busiest() reads these before assignment.
8287 */
8288 *sds = (struct sd_lb_stats){
8289 .busiest = NULL,
8290 .local = NULL,
8291 .total_load = 0UL,
8292 .total_capacity = 0UL,
8293 .busiest_stat = {
8294 .idle_cpus = UINT_MAX,
8295 .group_type = group_has_spare,
8296 },
8297 };
8298}
8299
8300static unsigned long scale_rt_capacity(int cpu)
8301{
8302 struct rq *rq = cpu_rq(cpu);
8303 unsigned long max = arch_scale_cpu_capacity(cpu);
8304 unsigned long used, free;
8305 unsigned long irq;
8306
8307 irq = cpu_util_irq(rq);
8308
8309 if (unlikely(irq >= max))
8310 return 1;
8311
8312 /*
8313 * avg_rt.util_avg and avg_dl.util_avg track binary signals
8314 * (running and not running) with weights 0 and 1024 respectively.
8315 * avg_thermal.load_avg tracks thermal pressure and the weighted
8316 * average uses the actual delta max capacity(load).
8317 */
8318 used = READ_ONCE(rq->avg_rt.util_avg);
8319 used += READ_ONCE(rq->avg_dl.util_avg);
8320 used += thermal_load_avg(rq);
8321
8322 if (unlikely(used >= max))
8323 return 1;
8324
8325 free = max - used;
8326
8327 return scale_irq_capacity(free, irq, max);
8328}
8329
8330static void update_cpu_capacity(struct sched_domain *sd, int cpu)
8331{
8332 unsigned long capacity = scale_rt_capacity(cpu);
8333 struct sched_group *sdg = sd->groups;
8334
8335 cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(cpu);
8336
8337 if (!capacity)
8338 capacity = 1;
8339
8340 cpu_rq(cpu)->cpu_capacity = capacity;
8341 trace_sched_cpu_capacity_tp(cpu_rq(cpu));
8342
8343 sdg->sgc->capacity = capacity;
8344 sdg->sgc->min_capacity = capacity;
8345 sdg->sgc->max_capacity = capacity;
8346}
8347
8348void update_group_capacity(struct sched_domain *sd, int cpu)
8349{
8350 struct sched_domain *child = sd->child;
8351 struct sched_group *group, *sdg = sd->groups;
8352 unsigned long capacity, min_capacity, max_capacity;
8353 unsigned long interval;
8354
8355 interval = msecs_to_jiffies(sd->balance_interval);
8356 interval = clamp(interval, 1UL, max_load_balance_interval);
8357 sdg->sgc->next_update = jiffies + interval;
8358
8359 if (!child) {
8360 update_cpu_capacity(sd, cpu);
8361 return;
8362 }
8363
8364 capacity = 0;
8365 min_capacity = ULONG_MAX;
8366 max_capacity = 0;
8367
8368 if (child->flags & SD_OVERLAP) {
8369 /*
8370 * SD_OVERLAP domains cannot assume that child groups
8371 * span the current group.
8372 */
8373
8374 for_each_cpu(cpu, sched_group_span(sdg)) {
8375 unsigned long cpu_cap = capacity_of(cpu);
8376
8377 capacity += cpu_cap;
8378 min_capacity = min(cpu_cap, min_capacity);
8379 max_capacity = max(cpu_cap, max_capacity);
8380 }
8381 } else {
8382 /*
8383 * !SD_OVERLAP domains can assume that child groups
8384 * span the current group.
8385 */
8386
8387 group = child->groups;
8388 do {
8389 struct sched_group_capacity *sgc = group->sgc;
8390
8391 capacity += sgc->capacity;
8392 min_capacity = min(sgc->min_capacity, min_capacity);
8393 max_capacity = max(sgc->max_capacity, max_capacity);
8394 group = group->next;
8395 } while (group != child->groups);
8396 }
8397
8398 sdg->sgc->capacity = capacity;
8399 sdg->sgc->min_capacity = min_capacity;
8400 sdg->sgc->max_capacity = max_capacity;
8401}
8402
8403/*
8404 * Check whether the capacity of the rq has been noticeably reduced by side
8405 * activity. The imbalance_pct is used for the threshold.
8406 * Return true is the capacity is reduced
8407 */
8408static inline int
8409check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
8410{
8411 return ((rq->cpu_capacity * sd->imbalance_pct) <
8412 (rq->cpu_capacity_orig * 100));
8413}
8414
8415/*
8416 * Check whether a rq has a misfit task and if it looks like we can actually
8417 * help that task: we can migrate the task to a CPU of higher capacity, or
8418 * the task's current CPU is heavily pressured.
8419 */
8420static inline int check_misfit_status(struct rq *rq, struct sched_domain *sd)
8421{
8422 return rq->misfit_task_load &&
8423 (rq->cpu_capacity_orig < rq->rd->max_cpu_capacity ||
8424 check_cpu_capacity(rq, sd));
8425}
8426
8427/*
8428 * Group imbalance indicates (and tries to solve) the problem where balancing
8429 * groups is inadequate due to ->cpus_ptr constraints.
8430 *
8431 * Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a
8432 * cpumask covering 1 CPU of the first group and 3 CPUs of the second group.
8433 * Something like:
8434 *
8435 * { 0 1 2 3 } { 4 5 6 7 }
8436 * * * * *
8437 *
8438 * If we were to balance group-wise we'd place two tasks in the first group and
8439 * two tasks in the second group. Clearly this is undesired as it will overload
8440 * cpu 3 and leave one of the CPUs in the second group unused.
8441 *
8442 * The current solution to this issue is detecting the skew in the first group
8443 * by noticing the lower domain failed to reach balance and had difficulty
8444 * moving tasks due to affinity constraints.
8445 *
8446 * When this is so detected; this group becomes a candidate for busiest; see
8447 * update_sd_pick_busiest(). And calculate_imbalance() and
8448 * find_busiest_group() avoid some of the usual balance conditions to allow it
8449 * to create an effective group imbalance.
8450 *
8451 * This is a somewhat tricky proposition since the next run might not find the
8452 * group imbalance and decide the groups need to be balanced again. A most
8453 * subtle and fragile situation.
8454 */
8455
8456static inline int sg_imbalanced(struct sched_group *group)
8457{
8458 return group->sgc->imbalance;
8459}
8460
8461/*
8462 * group_has_capacity returns true if the group has spare capacity that could
8463 * be used by some tasks.
8464 * We consider that a group has spare capacity if the * number of task is
8465 * smaller than the number of CPUs or if the utilization is lower than the
8466 * available capacity for CFS tasks.
8467 * For the latter, we use a threshold to stabilize the state, to take into
8468 * account the variance of the tasks' load and to return true if the available
8469 * capacity in meaningful for the load balancer.
8470 * As an example, an available capacity of 1% can appear but it doesn't make
8471 * any benefit for the load balance.
8472 */
8473static inline bool
8474group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
8475{
8476 if (sgs->sum_nr_running < sgs->group_weight)
8477 return true;
8478
8479 if ((sgs->group_capacity * imbalance_pct) <
8480 (sgs->group_runnable * 100))
8481 return false;
8482
8483 if ((sgs->group_capacity * 100) >
8484 (sgs->group_util * imbalance_pct))
8485 return true;
8486
8487 return false;
8488}
8489
8490/*
8491 * group_is_overloaded returns true if the group has more tasks than it can
8492 * handle.
8493 * group_is_overloaded is not equals to !group_has_capacity because a group
8494 * with the exact right number of tasks, has no more spare capacity but is not
8495 * overloaded so both group_has_capacity and group_is_overloaded return
8496 * false.
8497 */
8498static inline bool
8499group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
8500{
8501 if (sgs->sum_nr_running <= sgs->group_weight)
8502 return false;
8503
8504 if ((sgs->group_capacity * 100) <
8505 (sgs->group_util * imbalance_pct))
8506 return true;
8507
8508 if ((sgs->group_capacity * imbalance_pct) <
8509 (sgs->group_runnable * 100))
8510 return true;
8511
8512 return false;
8513}
8514
8515static inline enum
8516group_type group_classify(unsigned int imbalance_pct,
8517 struct sched_group *group,
8518 struct sg_lb_stats *sgs)
8519{
8520 if (group_is_overloaded(imbalance_pct, sgs))
8521 return group_overloaded;
8522
8523 if (sg_imbalanced(group))
8524 return group_imbalanced;
8525
8526 if (sgs->group_asym_packing)
8527 return group_asym_packing;
8528
8529 if (sgs->group_misfit_task_load)
8530 return group_misfit_task;
8531
8532 if (!group_has_capacity(imbalance_pct, sgs))
8533 return group_fully_busy;
8534
8535 return group_has_spare;
8536}
8537
8538/**
8539 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
8540 * @env: The load balancing environment.
8541 * @group: sched_group whose statistics are to be updated.
8542 * @sgs: variable to hold the statistics for this group.
8543 * @sg_status: Holds flag indicating the status of the sched_group
8544 */
8545static inline void update_sg_lb_stats(struct lb_env *env,
8546 struct sched_group *group,
8547 struct sg_lb_stats *sgs,
8548 int *sg_status)
8549{
8550 int i, nr_running, local_group;
8551
8552 memset(sgs, 0, sizeof(*sgs));
8553
8554 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(group));
8555
8556 for_each_cpu_and(i, sched_group_span(group), env->cpus) {
8557 struct rq *rq = cpu_rq(i);
8558
8559 sgs->group_load += cpu_load(rq);
8560 sgs->group_util += cpu_util(i);
8561 sgs->group_runnable += cpu_runnable(rq);
8562 sgs->sum_h_nr_running += rq->cfs.h_nr_running;
8563
8564 nr_running = rq->nr_running;
8565 sgs->sum_nr_running += nr_running;
8566
8567 if (nr_running > 1)
8568 *sg_status |= SG_OVERLOAD;
8569
8570 if (cpu_overutilized(i))
8571 *sg_status |= SG_OVERUTILIZED;
8572
8573#ifdef CONFIG_NUMA_BALANCING
8574 sgs->nr_numa_running += rq->nr_numa_running;
8575 sgs->nr_preferred_running += rq->nr_preferred_running;
8576#endif
8577 /*
8578 * No need to call idle_cpu() if nr_running is not 0
8579 */
8580 if (!nr_running && idle_cpu(i)) {
8581 sgs->idle_cpus++;
8582 /* Idle cpu can't have misfit task */
8583 continue;
8584 }
8585
8586 if (local_group)
8587 continue;
8588
8589 /* Check for a misfit task on the cpu */
8590 if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
8591 sgs->group_misfit_task_load < rq->misfit_task_load) {
8592 sgs->group_misfit_task_load = rq->misfit_task_load;
8593 *sg_status |= SG_OVERLOAD;
8594 }
8595 }
8596
8597 /* Check if dst CPU is idle and preferred to this group */
8598 if (env->sd->flags & SD_ASYM_PACKING &&
8599 env->idle != CPU_NOT_IDLE &&
8600 sgs->sum_h_nr_running &&
8601 sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu)) {
8602 sgs->group_asym_packing = 1;
8603 }
8604
8605 sgs->group_capacity = group->sgc->capacity;
8606
8607 sgs->group_weight = group->group_weight;
8608
8609 sgs->group_type = group_classify(env->sd->imbalance_pct, group, sgs);
8610
8611 /* Computing avg_load makes sense only when group is overloaded */
8612 if (sgs->group_type == group_overloaded)
8613 sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
8614 sgs->group_capacity;
8615}
8616
8617/**
8618 * update_sd_pick_busiest - return 1 on busiest group
8619 * @env: The load balancing environment.
8620 * @sds: sched_domain statistics
8621 * @sg: sched_group candidate to be checked for being the busiest
8622 * @sgs: sched_group statistics
8623 *
8624 * Determine if @sg is a busier group than the previously selected
8625 * busiest group.
8626 *
8627 * Return: %true if @sg is a busier group than the previously selected
8628 * busiest group. %false otherwise.
8629 */
8630static bool update_sd_pick_busiest(struct lb_env *env,
8631 struct sd_lb_stats *sds,
8632 struct sched_group *sg,
8633 struct sg_lb_stats *sgs)
8634{
8635 struct sg_lb_stats *busiest = &sds->busiest_stat;
8636
8637 /* Make sure that there is at least one task to pull */
8638 if (!sgs->sum_h_nr_running)
8639 return false;
8640
8641 /*
8642 * Don't try to pull misfit tasks we can't help.
8643 * We can use max_capacity here as reduction in capacity on some
8644 * CPUs in the group should either be possible to resolve
8645 * internally or be covered by avg_load imbalance (eventually).
8646 */
8647 if (sgs->group_type == group_misfit_task &&
8648 (!capacity_greater(capacity_of(env->dst_cpu), sg->sgc->max_capacity) ||
8649 sds->local_stat.group_type != group_has_spare))
8650 return false;
8651
8652 if (sgs->group_type > busiest->group_type)
8653 return true;
8654
8655 if (sgs->group_type < busiest->group_type)
8656 return false;
8657
8658 /*
8659 * The candidate and the current busiest group are the same type of
8660 * group. Let check which one is the busiest according to the type.
8661 */
8662
8663 switch (sgs->group_type) {
8664 case group_overloaded:
8665 /* Select the overloaded group with highest avg_load. */
8666 if (sgs->avg_load <= busiest->avg_load)
8667 return false;
8668 break;
8669
8670 case group_imbalanced:
8671 /*
8672 * Select the 1st imbalanced group as we don't have any way to
8673 * choose one more than another.
8674 */
8675 return false;
8676
8677 case group_asym_packing:
8678 /* Prefer to move from lowest priority CPU's work */
8679 if (sched_asym_prefer(sg->asym_prefer_cpu, sds->busiest->asym_prefer_cpu))
8680 return false;
8681 break;
8682
8683 case group_misfit_task:
8684 /*
8685 * If we have more than one misfit sg go with the biggest
8686 * misfit.
8687 */
8688 if (sgs->group_misfit_task_load < busiest->group_misfit_task_load)
8689 return false;
8690 break;
8691
8692 case group_fully_busy:
8693 /*
8694 * Select the fully busy group with highest avg_load. In
8695 * theory, there is no need to pull task from such kind of
8696 * group because tasks have all compute capacity that they need
8697 * but we can still improve the overall throughput by reducing
8698 * contention when accessing shared HW resources.
8699 *
8700 * XXX for now avg_load is not computed and always 0 so we
8701 * select the 1st one.
8702 */
8703 if (sgs->avg_load <= busiest->avg_load)
8704 return false;
8705 break;
8706
8707 case group_has_spare:
8708 /*
8709 * Select not overloaded group with lowest number of idle cpus
8710 * and highest number of running tasks. We could also compare
8711 * the spare capacity which is more stable but it can end up
8712 * that the group has less spare capacity but finally more idle
8713 * CPUs which means less opportunity to pull tasks.
8714 */
8715 if (sgs->idle_cpus > busiest->idle_cpus)
8716 return false;
8717 else if ((sgs->idle_cpus == busiest->idle_cpus) &&
8718 (sgs->sum_nr_running <= busiest->sum_nr_running))
8719 return false;
8720
8721 break;
8722 }
8723
8724 /*
8725 * Candidate sg has no more than one task per CPU and has higher
8726 * per-CPU capacity. Migrating tasks to less capable CPUs may harm
8727 * throughput. Maximize throughput, power/energy consequences are not
8728 * considered.
8729 */
8730 if ((env->sd->flags & SD_ASYM_CPUCAPACITY) &&
8731 (sgs->group_type <= group_fully_busy) &&
8732 (capacity_greater(sg->sgc->min_capacity, capacity_of(env->dst_cpu))))
8733 return false;
8734
8735 return true;
8736}
8737
8738#ifdef CONFIG_NUMA_BALANCING
8739static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
8740{
8741 if (sgs->sum_h_nr_running > sgs->nr_numa_running)
8742 return regular;
8743 if (sgs->sum_h_nr_running > sgs->nr_preferred_running)
8744 return remote;
8745 return all;
8746}
8747
8748static inline enum fbq_type fbq_classify_rq(struct rq *rq)
8749{
8750 if (rq->nr_running > rq->nr_numa_running)
8751 return regular;
8752 if (rq->nr_running > rq->nr_preferred_running)
8753 return remote;
8754 return all;
8755}
8756#else
8757static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
8758{
8759 return all;
8760}
8761
8762static inline enum fbq_type fbq_classify_rq(struct rq *rq)
8763{
8764 return regular;
8765}
8766#endif /* CONFIG_NUMA_BALANCING */
8767
8768
8769struct sg_lb_stats;
8770
8771/*
8772 * task_running_on_cpu - return 1 if @p is running on @cpu.
8773 */
8774
8775static unsigned int task_running_on_cpu(int cpu, struct task_struct *p)
8776{
8777 /* Task has no contribution or is new */
8778 if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
8779 return 0;
8780
8781 if (task_on_rq_queued(p))
8782 return 1;
8783
8784 return 0;
8785}
8786
8787/**
8788 * idle_cpu_without - would a given CPU be idle without p ?
8789 * @cpu: the processor on which idleness is tested.
8790 * @p: task which should be ignored.
8791 *
8792 * Return: 1 if the CPU would be idle. 0 otherwise.
8793 */
8794static int idle_cpu_without(int cpu, struct task_struct *p)
8795{
8796 struct rq *rq = cpu_rq(cpu);
8797
8798 if (rq->curr != rq->idle && rq->curr != p)
8799 return 0;
8800
8801 /*
8802 * rq->nr_running can't be used but an updated version without the
8803 * impact of p on cpu must be used instead. The updated nr_running
8804 * be computed and tested before calling idle_cpu_without().
8805 */
8806
8807#ifdef CONFIG_SMP
8808 if (rq->ttwu_pending)
8809 return 0;
8810#endif
8811
8812 return 1;
8813}
8814
8815/*
8816 * update_sg_wakeup_stats - Update sched_group's statistics for wakeup.
8817 * @sd: The sched_domain level to look for idlest group.
8818 * @group: sched_group whose statistics are to be updated.
8819 * @sgs: variable to hold the statistics for this group.
8820 * @p: The task for which we look for the idlest group/CPU.
8821 */
8822static inline void update_sg_wakeup_stats(struct sched_domain *sd,
8823 struct sched_group *group,
8824 struct sg_lb_stats *sgs,
8825 struct task_struct *p)
8826{
8827 int i, nr_running;
8828
8829 memset(sgs, 0, sizeof(*sgs));
8830
8831 for_each_cpu(i, sched_group_span(group)) {
8832 struct rq *rq = cpu_rq(i);
8833 unsigned int local;
8834
8835 sgs->group_load += cpu_load_without(rq, p);
8836 sgs->group_util += cpu_util_without(i, p);
8837 sgs->group_runnable += cpu_runnable_without(rq, p);
8838 local = task_running_on_cpu(i, p);
8839 sgs->sum_h_nr_running += rq->cfs.h_nr_running - local;
8840
8841 nr_running = rq->nr_running - local;
8842 sgs->sum_nr_running += nr_running;
8843
8844 /*
8845 * No need to call idle_cpu_without() if nr_running is not 0
8846 */
8847 if (!nr_running && idle_cpu_without(i, p))
8848 sgs->idle_cpus++;
8849
8850 }
8851
8852 /* Check if task fits in the group */
8853 if (sd->flags & SD_ASYM_CPUCAPACITY &&
8854 !task_fits_capacity(p, group->sgc->max_capacity)) {
8855 sgs->group_misfit_task_load = 1;
8856 }
8857
8858 sgs->group_capacity = group->sgc->capacity;
8859
8860 sgs->group_weight = group->group_weight;
8861
8862 sgs->group_type = group_classify(sd->imbalance_pct, group, sgs);
8863
8864 /*
8865 * Computing avg_load makes sense only when group is fully busy or
8866 * overloaded
8867 */
8868 if (sgs->group_type == group_fully_busy ||
8869 sgs->group_type == group_overloaded)
8870 sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
8871 sgs->group_capacity;
8872}
8873
8874static bool update_pick_idlest(struct sched_group *idlest,
8875 struct sg_lb_stats *idlest_sgs,
8876 struct sched_group *group,
8877 struct sg_lb_stats *sgs)
8878{
8879 if (sgs->group_type < idlest_sgs->group_type)
8880 return true;
8881
8882 if (sgs->group_type > idlest_sgs->group_type)
8883 return false;
8884
8885 /*
8886 * The candidate and the current idlest group are the same type of
8887 * group. Let check which one is the idlest according to the type.
8888 */
8889
8890 switch (sgs->group_type) {
8891 case group_overloaded:
8892 case group_fully_busy:
8893 /* Select the group with lowest avg_load. */
8894 if (idlest_sgs->avg_load <= sgs->avg_load)
8895 return false;
8896 break;
8897
8898 case group_imbalanced:
8899 case group_asym_packing:
8900 /* Those types are not used in the slow wakeup path */
8901 return false;
8902
8903 case group_misfit_task:
8904 /* Select group with the highest max capacity */
8905 if (idlest->sgc->max_capacity >= group->sgc->max_capacity)
8906 return false;
8907 break;
8908
8909 case group_has_spare:
8910 /* Select group with most idle CPUs */
8911 if (idlest_sgs->idle_cpus > sgs->idle_cpus)
8912 return false;
8913
8914 /* Select group with lowest group_util */
8915 if (idlest_sgs->idle_cpus == sgs->idle_cpus &&
8916 idlest_sgs->group_util <= sgs->group_util)
8917 return false;
8918
8919 break;
8920 }
8921
8922 return true;
8923}
8924
8925/*
8926 * Allow a NUMA imbalance if busy CPUs is less than 25% of the domain.
8927 * This is an approximation as the number of running tasks may not be
8928 * related to the number of busy CPUs due to sched_setaffinity.
8929 */
8930static inline bool allow_numa_imbalance(int dst_running, int dst_weight)
8931{
8932 return (dst_running < (dst_weight >> 2));
8933}
8934
8935/*
8936 * find_idlest_group() finds and returns the least busy CPU group within the
8937 * domain.
8938 *
8939 * Assumes p is allowed on at least one CPU in sd.
8940 */
8941static struct sched_group *
8942find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
8943{
8944 struct sched_group *idlest = NULL, *local = NULL, *group = sd->groups;
8945 struct sg_lb_stats local_sgs, tmp_sgs;
8946 struct sg_lb_stats *sgs;
8947 unsigned long imbalance;
8948 struct sg_lb_stats idlest_sgs = {
8949 .avg_load = UINT_MAX,
8950 .group_type = group_overloaded,
8951 };
8952
8953 do {
8954 int local_group;
8955
8956 /* Skip over this group if it has no CPUs allowed */
8957 if (!cpumask_intersects(sched_group_span(group),
8958 p->cpus_ptr))
8959 continue;
8960
8961 /* Skip over this group if no cookie matched */
8962 if (!sched_group_cookie_match(cpu_rq(this_cpu), p, group))
8963 continue;
8964
8965 local_group = cpumask_test_cpu(this_cpu,
8966 sched_group_span(group));
8967
8968 if (local_group) {
8969 sgs = &local_sgs;
8970 local = group;
8971 } else {
8972 sgs = &tmp_sgs;
8973 }
8974
8975 update_sg_wakeup_stats(sd, group, sgs, p);
8976
8977 if (!local_group && update_pick_idlest(idlest, &idlest_sgs, group, sgs)) {
8978 idlest = group;
8979 idlest_sgs = *sgs;
8980 }
8981
8982 } while (group = group->next, group != sd->groups);
8983
8984
8985 /* There is no idlest group to push tasks to */
8986 if (!idlest)
8987 return NULL;
8988
8989 /* The local group has been skipped because of CPU affinity */
8990 if (!local)
8991 return idlest;
8992
8993 /*
8994 * If the local group is idler than the selected idlest group
8995 * don't try and push the task.
8996 */
8997 if (local_sgs.group_type < idlest_sgs.group_type)
8998 return NULL;
8999
9000 /*
9001 * If the local group is busier than the selected idlest group
9002 * try and push the task.
9003 */
9004 if (local_sgs.group_type > idlest_sgs.group_type)
9005 return idlest;
9006
9007 switch (local_sgs.group_type) {
9008 case group_overloaded:
9009 case group_fully_busy:
9010
9011 /* Calculate allowed imbalance based on load */
9012 imbalance = scale_load_down(NICE_0_LOAD) *
9013 (sd->imbalance_pct-100) / 100;
9014
9015 /*
9016 * When comparing groups across NUMA domains, it's possible for
9017 * the local domain to be very lightly loaded relative to the
9018 * remote domains but "imbalance" skews the comparison making
9019 * remote CPUs look much more favourable. When considering
9020 * cross-domain, add imbalance to the load on the remote node
9021 * and consider staying local.
9022 */
9023
9024 if ((sd->flags & SD_NUMA) &&
9025 ((idlest_sgs.avg_load + imbalance) >= local_sgs.avg_load))
9026 return NULL;
9027
9028 /*
9029 * If the local group is less loaded than the selected
9030 * idlest group don't try and push any tasks.
9031 */
9032 if (idlest_sgs.avg_load >= (local_sgs.avg_load + imbalance))
9033 return NULL;
9034
9035 if (100 * local_sgs.avg_load <= sd->imbalance_pct * idlest_sgs.avg_load)
9036 return NULL;
9037 break;
9038
9039 case group_imbalanced:
9040 case group_asym_packing:
9041 /* Those type are not used in the slow wakeup path */
9042 return NULL;
9043
9044 case group_misfit_task:
9045 /* Select group with the highest max capacity */
9046 if (local->sgc->max_capacity >= idlest->sgc->max_capacity)
9047 return NULL;
9048 break;
9049
9050 case group_has_spare:
9051 if (sd->flags & SD_NUMA) {
9052#ifdef CONFIG_NUMA_BALANCING
9053 int idlest_cpu;
9054 /*
9055 * If there is spare capacity at NUMA, try to select
9056 * the preferred node
9057 */
9058 if (cpu_to_node(this_cpu) == p->numa_preferred_nid)
9059 return NULL;
9060
9061 idlest_cpu = cpumask_first(sched_group_span(idlest));
9062 if (cpu_to_node(idlest_cpu) == p->numa_preferred_nid)
9063 return idlest;
9064#endif
9065 /*
9066 * Otherwise, keep the task on this node to stay close
9067 * its wakeup source and improve locality. If there is
9068 * a real need of migration, periodic load balance will
9069 * take care of it.
9070 */
9071 if (allow_numa_imbalance(local_sgs.sum_nr_running, sd->span_weight))
9072 return NULL;
9073 }
9074
9075 /*
9076 * Select group with highest number of idle CPUs. We could also
9077 * compare the utilization which is more stable but it can end
9078 * up that the group has less spare capacity but finally more
9079 * idle CPUs which means more opportunity to run task.
9080 */
9081 if (local_sgs.idle_cpus >= idlest_sgs.idle_cpus)
9082 return NULL;
9083 break;
9084 }
9085
9086 return idlest;
9087}
9088
9089/**
9090 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
9091 * @env: The load balancing environment.
9092 * @sds: variable to hold the statistics for this sched_domain.
9093 */
9094
9095static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
9096{
9097 struct sched_domain *child = env->sd->child;
9098 struct sched_group *sg = env->sd->groups;
9099 struct sg_lb_stats *local = &sds->local_stat;
9100 struct sg_lb_stats tmp_sgs;
9101 int sg_status = 0;
9102
9103 do {
9104 struct sg_lb_stats *sgs = &tmp_sgs;
9105 int local_group;
9106
9107 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
9108 if (local_group) {
9109 sds->local = sg;
9110 sgs = local;
9111
9112 if (env->idle != CPU_NEWLY_IDLE ||
9113 time_after_eq(jiffies, sg->sgc->next_update))
9114 update_group_capacity(env->sd, env->dst_cpu);
9115 }
9116
9117 update_sg_lb_stats(env, sg, sgs, &sg_status);
9118
9119 if (local_group)
9120 goto next_group;
9121
9122
9123 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
9124 sds->busiest = sg;
9125 sds->busiest_stat = *sgs;
9126 }
9127
9128next_group:
9129 /* Now, start updating sd_lb_stats */
9130 sds->total_load += sgs->group_load;
9131 sds->total_capacity += sgs->group_capacity;
9132
9133 sg = sg->next;
9134 } while (sg != env->sd->groups);
9135
9136 /* Tag domain that child domain prefers tasks go to siblings first */
9137 sds->prefer_sibling = child && child->flags & SD_PREFER_SIBLING;
9138
9139
9140 if (env->sd->flags & SD_NUMA)
9141 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
9142
9143 if (!env->sd->parent) {
9144 struct root_domain *rd = env->dst_rq->rd;
9145
9146 /* update overload indicator if we are at root domain */
9147 WRITE_ONCE(rd->overload, sg_status & SG_OVERLOAD);
9148
9149 /* Update over-utilization (tipping point, U >= 0) indicator */
9150 WRITE_ONCE(rd->overutilized, sg_status & SG_OVERUTILIZED);
9151 trace_sched_overutilized_tp(rd, sg_status & SG_OVERUTILIZED);
9152 } else if (sg_status & SG_OVERUTILIZED) {
9153 struct root_domain *rd = env->dst_rq->rd;
9154
9155 WRITE_ONCE(rd->overutilized, SG_OVERUTILIZED);
9156 trace_sched_overutilized_tp(rd, SG_OVERUTILIZED);
9157 }
9158}
9159
9160#define NUMA_IMBALANCE_MIN 2
9161
9162static inline long adjust_numa_imbalance(int imbalance,
9163 int dst_running, int dst_weight)
9164{
9165 if (!allow_numa_imbalance(dst_running, dst_weight))
9166 return imbalance;
9167
9168 /*
9169 * Allow a small imbalance based on a simple pair of communicating
9170 * tasks that remain local when the destination is lightly loaded.
9171 */
9172 if (imbalance <= NUMA_IMBALANCE_MIN)
9173 return 0;
9174
9175 return imbalance;
9176}
9177
9178/**
9179 * calculate_imbalance - Calculate the amount of imbalance present within the
9180 * groups of a given sched_domain during load balance.
9181 * @env: load balance environment
9182 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
9183 */
9184static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
9185{
9186 struct sg_lb_stats *local, *busiest;
9187
9188 local = &sds->local_stat;
9189 busiest = &sds->busiest_stat;
9190
9191 if (busiest->group_type == group_misfit_task) {
9192 /* Set imbalance to allow misfit tasks to be balanced. */
9193 env->migration_type = migrate_misfit;
9194 env->imbalance = 1;
9195 return;
9196 }
9197
9198 if (busiest->group_type == group_asym_packing) {
9199 /*
9200 * In case of asym capacity, we will try to migrate all load to
9201 * the preferred CPU.
9202 */
9203 env->migration_type = migrate_task;
9204 env->imbalance = busiest->sum_h_nr_running;
9205 return;
9206 }
9207
9208 if (busiest->group_type == group_imbalanced) {
9209 /*
9210 * In the group_imb case we cannot rely on group-wide averages
9211 * to ensure CPU-load equilibrium, try to move any task to fix
9212 * the imbalance. The next load balance will take care of
9213 * balancing back the system.
9214 */
9215 env->migration_type = migrate_task;
9216 env->imbalance = 1;
9217 return;
9218 }
9219
9220 /*
9221 * Try to use spare capacity of local group without overloading it or
9222 * emptying busiest.
9223 */
9224 if (local->group_type == group_has_spare) {
9225 if ((busiest->group_type > group_fully_busy) &&
9226 !(env->sd->flags & SD_SHARE_PKG_RESOURCES)) {
9227 /*
9228 * If busiest is overloaded, try to fill spare
9229 * capacity. This might end up creating spare capacity
9230 * in busiest or busiest still being overloaded but
9231 * there is no simple way to directly compute the
9232 * amount of load to migrate in order to balance the
9233 * system.
9234 */
9235 env->migration_type = migrate_util;
9236 env->imbalance = max(local->group_capacity, local->group_util) -
9237 local->group_util;
9238
9239 /*
9240 * In some cases, the group's utilization is max or even
9241 * higher than capacity because of migrations but the
9242 * local CPU is (newly) idle. There is at least one
9243 * waiting task in this overloaded busiest group. Let's
9244 * try to pull it.
9245 */
9246 if (env->idle != CPU_NOT_IDLE && env->imbalance == 0) {
9247 env->migration_type = migrate_task;
9248 env->imbalance = 1;
9249 }
9250
9251 return;
9252 }
9253
9254 if (busiest->group_weight == 1 || sds->prefer_sibling) {
9255 unsigned int nr_diff = busiest->sum_nr_running;
9256 /*
9257 * When prefer sibling, evenly spread running tasks on
9258 * groups.
9259 */
9260 env->migration_type = migrate_task;
9261 lsub_positive(&nr_diff, local->sum_nr_running);
9262 env->imbalance = nr_diff >> 1;
9263 } else {
9264
9265 /*
9266 * If there is no overload, we just want to even the number of
9267 * idle cpus.
9268 */
9269 env->migration_type = migrate_task;
9270 env->imbalance = max_t(long, 0, (local->idle_cpus -
9271 busiest->idle_cpus) >> 1);
9272 }
9273
9274 /* Consider allowing a small imbalance between NUMA groups */
9275 if (env->sd->flags & SD_NUMA) {
9276 env->imbalance = adjust_numa_imbalance(env->imbalance,
9277 busiest->sum_nr_running, busiest->group_weight);
9278 }
9279
9280 return;
9281 }
9282
9283 /*
9284 * Local is fully busy but has to take more load to relieve the
9285 * busiest group
9286 */
9287 if (local->group_type < group_overloaded) {
9288 /*
9289 * Local will become overloaded so the avg_load metrics are
9290 * finally needed.
9291 */
9292
9293 local->avg_load = (local->group_load * SCHED_CAPACITY_SCALE) /
9294 local->group_capacity;
9295
9296 sds->avg_load = (sds->total_load * SCHED_CAPACITY_SCALE) /
9297 sds->total_capacity;
9298 /*
9299 * If the local group is more loaded than the selected
9300 * busiest group don't try to pull any tasks.
9301 */
9302 if (local->avg_load >= busiest->avg_load) {
9303 env->imbalance = 0;
9304 return;
9305 }
9306 }
9307
9308 /*
9309 * Both group are or will become overloaded and we're trying to get all
9310 * the CPUs to the average_load, so we don't want to push ourselves
9311 * above the average load, nor do we wish to reduce the max loaded CPU
9312 * below the average load. At the same time, we also don't want to
9313 * reduce the group load below the group capacity. Thus we look for
9314 * the minimum possible imbalance.
9315 */
9316 env->migration_type = migrate_load;
9317 env->imbalance = min(
9318 (busiest->avg_load - sds->avg_load) * busiest->group_capacity,
9319 (sds->avg_load - local->avg_load) * local->group_capacity
9320 ) / SCHED_CAPACITY_SCALE;
9321}
9322
9323/******* find_busiest_group() helpers end here *********************/
9324
9325/*
9326 * Decision matrix according to the local and busiest group type:
9327 *
9328 * busiest \ local has_spare fully_busy misfit asym imbalanced overloaded
9329 * has_spare nr_idle balanced N/A N/A balanced balanced
9330 * fully_busy nr_idle nr_idle N/A N/A balanced balanced
9331 * misfit_task force N/A N/A N/A force force
9332 * asym_packing force force N/A N/A force force
9333 * imbalanced force force N/A N/A force force
9334 * overloaded force force N/A N/A force avg_load
9335 *
9336 * N/A : Not Applicable because already filtered while updating
9337 * statistics.
9338 * balanced : The system is balanced for these 2 groups.
9339 * force : Calculate the imbalance as load migration is probably needed.
9340 * avg_load : Only if imbalance is significant enough.
9341 * nr_idle : dst_cpu is not busy and the number of idle CPUs is quite
9342 * different in groups.
9343 */
9344
9345/**
9346 * find_busiest_group - Returns the busiest group within the sched_domain
9347 * if there is an imbalance.
9348 *
9349 * Also calculates the amount of runnable load which should be moved
9350 * to restore balance.
9351 *
9352 * @env: The load balancing environment.
9353 *
9354 * Return: - The busiest group if imbalance exists.
9355 */
9356static struct sched_group *find_busiest_group(struct lb_env *env)
9357{
9358 struct sg_lb_stats *local, *busiest;
9359 struct sd_lb_stats sds;
9360
9361 init_sd_lb_stats(&sds);
9362
9363 /*
9364 * Compute the various statistics relevant for load balancing at
9365 * this level.
9366 */
9367 update_sd_lb_stats(env, &sds);
9368
9369 if (sched_energy_enabled()) {
9370 struct root_domain *rd = env->dst_rq->rd;
9371
9372 if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))
9373 goto out_balanced;
9374 }
9375
9376 local = &sds.local_stat;
9377 busiest = &sds.busiest_stat;
9378
9379 /* There is no busy sibling group to pull tasks from */
9380 if (!sds.busiest)
9381 goto out_balanced;
9382
9383 /* Misfit tasks should be dealt with regardless of the avg load */
9384 if (busiest->group_type == group_misfit_task)
9385 goto force_balance;
9386
9387 /* ASYM feature bypasses nice load balance check */
9388 if (busiest->group_type == group_asym_packing)
9389 goto force_balance;
9390
9391 /*
9392 * If the busiest group is imbalanced the below checks don't
9393 * work because they assume all things are equal, which typically
9394 * isn't true due to cpus_ptr constraints and the like.
9395 */
9396 if (busiest->group_type == group_imbalanced)
9397 goto force_balance;
9398
9399 /*
9400 * If the local group is busier than the selected busiest group
9401 * don't try and pull any tasks.
9402 */
9403 if (local->group_type > busiest->group_type)
9404 goto out_balanced;
9405
9406 /*
9407 * When groups are overloaded, use the avg_load to ensure fairness
9408 * between tasks.
9409 */
9410 if (local->group_type == group_overloaded) {
9411 /*
9412 * If the local group is more loaded than the selected
9413 * busiest group don't try to pull any tasks.
9414 */
9415 if (local->avg_load >= busiest->avg_load)
9416 goto out_balanced;
9417
9418 /* XXX broken for overlapping NUMA groups */
9419 sds.avg_load = (sds.total_load * SCHED_CAPACITY_SCALE) /
9420 sds.total_capacity;
9421
9422 /*
9423 * Don't pull any tasks if this group is already above the
9424 * domain average load.
9425 */
9426 if (local->avg_load >= sds.avg_load)
9427 goto out_balanced;
9428
9429 /*
9430 * If the busiest group is more loaded, use imbalance_pct to be
9431 * conservative.
9432 */
9433 if (100 * busiest->avg_load <=
9434 env->sd->imbalance_pct * local->avg_load)
9435 goto out_balanced;
9436 }
9437
9438 /* Try to move all excess tasks to child's sibling domain */
9439 if (sds.prefer_sibling && local->group_type == group_has_spare &&
9440 busiest->sum_nr_running > local->sum_nr_running + 1)
9441 goto force_balance;
9442
9443 if (busiest->group_type != group_overloaded) {
9444 if (env->idle == CPU_NOT_IDLE)
9445 /*
9446 * If the busiest group is not overloaded (and as a
9447 * result the local one too) but this CPU is already
9448 * busy, let another idle CPU try to pull task.
9449 */
9450 goto out_balanced;
9451
9452 if (busiest->group_weight > 1 &&
9453 local->idle_cpus <= (busiest->idle_cpus + 1))
9454 /*
9455 * If the busiest group is not overloaded
9456 * and there is no imbalance between this and busiest
9457 * group wrt idle CPUs, it is balanced. The imbalance
9458 * becomes significant if the diff is greater than 1
9459 * otherwise we might end up to just move the imbalance
9460 * on another group. Of course this applies only if
9461 * there is more than 1 CPU per group.
9462 */
9463 goto out_balanced;
9464
9465 if (busiest->sum_h_nr_running == 1)
9466 /*
9467 * busiest doesn't have any tasks waiting to run
9468 */
9469 goto out_balanced;
9470 }
9471
9472force_balance:
9473 /* Looks like there is an imbalance. Compute it */
9474 calculate_imbalance(env, &sds);
9475 return env->imbalance ? sds.busiest : NULL;
9476
9477out_balanced:
9478 env->imbalance = 0;
9479 return NULL;
9480}
9481
9482/*
9483 * find_busiest_queue - find the busiest runqueue among the CPUs in the group.
9484 */
9485static struct rq *find_busiest_queue(struct lb_env *env,
9486 struct sched_group *group)
9487{
9488 struct rq *busiest = NULL, *rq;
9489 unsigned long busiest_util = 0, busiest_load = 0, busiest_capacity = 1;
9490 unsigned int busiest_nr = 0;
9491 int i;
9492
9493 for_each_cpu_and(i, sched_group_span(group), env->cpus) {
9494 unsigned long capacity, load, util;
9495 unsigned int nr_running;
9496 enum fbq_type rt;
9497
9498 rq = cpu_rq(i);
9499 rt = fbq_classify_rq(rq);
9500
9501 /*
9502 * We classify groups/runqueues into three groups:
9503 * - regular: there are !numa tasks
9504 * - remote: there are numa tasks that run on the 'wrong' node
9505 * - all: there is no distinction
9506 *
9507 * In order to avoid migrating ideally placed numa tasks,
9508 * ignore those when there's better options.
9509 *
9510 * If we ignore the actual busiest queue to migrate another
9511 * task, the next balance pass can still reduce the busiest
9512 * queue by moving tasks around inside the node.
9513 *
9514 * If we cannot move enough load due to this classification
9515 * the next pass will adjust the group classification and
9516 * allow migration of more tasks.
9517 *
9518 * Both cases only affect the total convergence complexity.
9519 */
9520 if (rt > env->fbq_type)
9521 continue;
9522
9523 nr_running = rq->cfs.h_nr_running;
9524 if (!nr_running)
9525 continue;
9526
9527 capacity = capacity_of(i);
9528
9529 /*
9530 * For ASYM_CPUCAPACITY domains, don't pick a CPU that could
9531 * eventually lead to active_balancing high->low capacity.
9532 * Higher per-CPU capacity is considered better than balancing
9533 * average load.
9534 */
9535 if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
9536 !capacity_greater(capacity_of(env->dst_cpu), capacity) &&
9537 nr_running == 1)
9538 continue;
9539
9540 switch (env->migration_type) {
9541 case migrate_load:
9542 /*
9543 * When comparing with load imbalance, use cpu_load()
9544 * which is not scaled with the CPU capacity.
9545 */
9546 load = cpu_load(rq);
9547
9548 if (nr_running == 1 && load > env->imbalance &&
9549 !check_cpu_capacity(rq, env->sd))
9550 break;
9551
9552 /*
9553 * For the load comparisons with the other CPUs,
9554 * consider the cpu_load() scaled with the CPU
9555 * capacity, so that the load can be moved away
9556 * from the CPU that is potentially running at a
9557 * lower capacity.
9558 *
9559 * Thus we're looking for max(load_i / capacity_i),
9560 * crosswise multiplication to rid ourselves of the
9561 * division works out to:
9562 * load_i * capacity_j > load_j * capacity_i;
9563 * where j is our previous maximum.
9564 */
9565 if (load * busiest_capacity > busiest_load * capacity) {
9566 busiest_load = load;
9567 busiest_capacity = capacity;
9568 busiest = rq;
9569 }
9570 break;
9571
9572 case migrate_util:
9573 util = cpu_util(cpu_of(rq));
9574
9575 /*
9576 * Don't try to pull utilization from a CPU with one
9577 * running task. Whatever its utilization, we will fail
9578 * detach the task.
9579 */
9580 if (nr_running <= 1)
9581 continue;
9582
9583 if (busiest_util < util) {
9584 busiest_util = util;
9585 busiest = rq;
9586 }
9587 break;
9588
9589 case migrate_task:
9590 if (busiest_nr < nr_running) {
9591 busiest_nr = nr_running;
9592 busiest = rq;
9593 }
9594 break;
9595
9596 case migrate_misfit:
9597 /*
9598 * For ASYM_CPUCAPACITY domains with misfit tasks we
9599 * simply seek the "biggest" misfit task.
9600 */
9601 if (rq->misfit_task_load > busiest_load) {
9602 busiest_load = rq->misfit_task_load;
9603 busiest = rq;
9604 }
9605
9606 break;
9607
9608 }
9609 }
9610
9611 return busiest;
9612}
9613
9614/*
9615 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
9616 * so long as it is large enough.
9617 */
9618#define MAX_PINNED_INTERVAL 512
9619
9620static inline bool
9621asym_active_balance(struct lb_env *env)
9622{
9623 /*
9624 * ASYM_PACKING needs to force migrate tasks from busy but
9625 * lower priority CPUs in order to pack all tasks in the
9626 * highest priority CPUs.
9627 */
9628 return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) &&
9629 sched_asym_prefer(env->dst_cpu, env->src_cpu);
9630}
9631
9632static inline bool
9633imbalanced_active_balance(struct lb_env *env)
9634{
9635 struct sched_domain *sd = env->sd;
9636
9637 /*
9638 * The imbalanced case includes the case of pinned tasks preventing a fair
9639 * distribution of the load on the system but also the even distribution of the
9640 * threads on a system with spare capacity
9641 */
9642 if ((env->migration_type == migrate_task) &&
9643 (sd->nr_balance_failed > sd->cache_nice_tries+2))
9644 return 1;
9645
9646 return 0;
9647}
9648
9649static int need_active_balance(struct lb_env *env)
9650{
9651 struct sched_domain *sd = env->sd;
9652
9653 if (asym_active_balance(env))
9654 return 1;
9655
9656 if (imbalanced_active_balance(env))
9657 return 1;
9658
9659 /*
9660 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
9661 * It's worth migrating the task if the src_cpu's capacity is reduced
9662 * because of other sched_class or IRQs if more capacity stays
9663 * available on dst_cpu.
9664 */
9665 if ((env->idle != CPU_NOT_IDLE) &&
9666 (env->src_rq->cfs.h_nr_running == 1)) {
9667 if ((check_cpu_capacity(env->src_rq, sd)) &&
9668 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
9669 return 1;
9670 }
9671
9672 if (env->migration_type == migrate_misfit)
9673 return 1;
9674
9675 return 0;
9676}
9677
9678static int active_load_balance_cpu_stop(void *data);
9679
9680static int should_we_balance(struct lb_env *env)
9681{
9682 struct sched_group *sg = env->sd->groups;
9683 int cpu;
9684
9685 /*
9686 * Ensure the balancing environment is consistent; can happen
9687 * when the softirq triggers 'during' hotplug.
9688 */
9689 if (!cpumask_test_cpu(env->dst_cpu, env->cpus))
9690 return 0;
9691
9692 /*
9693 * In the newly idle case, we will allow all the CPUs
9694 * to do the newly idle load balance.
9695 */
9696 if (env->idle == CPU_NEWLY_IDLE)
9697 return 1;
9698
9699 /* Try to find first idle CPU */
9700 for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
9701 if (!idle_cpu(cpu))
9702 continue;
9703
9704 /* Are we the first idle CPU? */
9705 return cpu == env->dst_cpu;
9706 }
9707
9708 /* Are we the first CPU of this group ? */
9709 return group_balance_cpu(sg) == env->dst_cpu;
9710}
9711
9712/*
9713 * Check this_cpu to ensure it is balanced within domain. Attempt to move
9714 * tasks if there is an imbalance.
9715 */
9716static int load_balance(int this_cpu, struct rq *this_rq,
9717 struct sched_domain *sd, enum cpu_idle_type idle,
9718 int *continue_balancing)
9719{
9720 int ld_moved, cur_ld_moved, active_balance = 0;
9721 struct sched_domain *sd_parent = sd->parent;
9722 struct sched_group *group;
9723 struct rq *busiest;
9724 struct rq_flags rf;
9725 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
9726
9727 struct lb_env env = {
9728 .sd = sd,
9729 .dst_cpu = this_cpu,
9730 .dst_rq = this_rq,
9731 .dst_grpmask = sched_group_span(sd->groups),
9732 .idle = idle,
9733 .loop_break = sched_nr_migrate_break,
9734 .cpus = cpus,
9735 .fbq_type = all,
9736 .tasks = LIST_HEAD_INIT(env.tasks),
9737 };
9738
9739 cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
9740
9741 schedstat_inc(sd->lb_count[idle]);
9742
9743redo:
9744 if (!should_we_balance(&env)) {
9745 *continue_balancing = 0;
9746 goto out_balanced;
9747 }
9748
9749 group = find_busiest_group(&env);
9750 if (!group) {
9751 schedstat_inc(sd->lb_nobusyg[idle]);
9752 goto out_balanced;
9753 }
9754
9755 busiest = find_busiest_queue(&env, group);
9756 if (!busiest) {
9757 schedstat_inc(sd->lb_nobusyq[idle]);
9758 goto out_balanced;
9759 }
9760
9761 BUG_ON(busiest == env.dst_rq);
9762
9763 schedstat_add(sd->lb_imbalance[idle], env.imbalance);
9764
9765 env.src_cpu = busiest->cpu;
9766 env.src_rq = busiest;
9767
9768 ld_moved = 0;
9769 /* Clear this flag as soon as we find a pullable task */
9770 env.flags |= LBF_ALL_PINNED;
9771 if (busiest->nr_running > 1) {
9772 /*
9773 * Attempt to move tasks. If find_busiest_group has found
9774 * an imbalance but busiest->nr_running <= 1, the group is
9775 * still unbalanced. ld_moved simply stays zero, so it is
9776 * correctly treated as an imbalance.
9777 */
9778 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
9779
9780more_balance:
9781 rq_lock_irqsave(busiest, &rf);
9782 update_rq_clock(busiest);
9783
9784 /*
9785 * cur_ld_moved - load moved in current iteration
9786 * ld_moved - cumulative load moved across iterations
9787 */
9788 cur_ld_moved = detach_tasks(&env);
9789
9790 /*
9791 * We've detached some tasks from busiest_rq. Every
9792 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
9793 * unlock busiest->lock, and we are able to be sure
9794 * that nobody can manipulate the tasks in parallel.
9795 * See task_rq_lock() family for the details.
9796 */
9797
9798 rq_unlock(busiest, &rf);
9799
9800 if (cur_ld_moved) {
9801 attach_tasks(&env);
9802 ld_moved += cur_ld_moved;
9803 }
9804
9805 local_irq_restore(rf.flags);
9806
9807 if (env.flags & LBF_NEED_BREAK) {
9808 env.flags &= ~LBF_NEED_BREAK;
9809 goto more_balance;
9810 }
9811
9812 /*
9813 * Revisit (affine) tasks on src_cpu that couldn't be moved to
9814 * us and move them to an alternate dst_cpu in our sched_group
9815 * where they can run. The upper limit on how many times we
9816 * iterate on same src_cpu is dependent on number of CPUs in our
9817 * sched_group.
9818 *
9819 * This changes load balance semantics a bit on who can move
9820 * load to a given_cpu. In addition to the given_cpu itself
9821 * (or a ilb_cpu acting on its behalf where given_cpu is
9822 * nohz-idle), we now have balance_cpu in a position to move
9823 * load to given_cpu. In rare situations, this may cause
9824 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
9825 * _independently_ and at _same_ time to move some load to
9826 * given_cpu) causing excess load to be moved to given_cpu.
9827 * This however should not happen so much in practice and
9828 * moreover subsequent load balance cycles should correct the
9829 * excess load moved.
9830 */
9831 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
9832
9833 /* Prevent to re-select dst_cpu via env's CPUs */
9834 __cpumask_clear_cpu(env.dst_cpu, env.cpus);
9835
9836 env.dst_rq = cpu_rq(env.new_dst_cpu);
9837 env.dst_cpu = env.new_dst_cpu;
9838 env.flags &= ~LBF_DST_PINNED;
9839 env.loop = 0;
9840 env.loop_break = sched_nr_migrate_break;
9841
9842 /*
9843 * Go back to "more_balance" rather than "redo" since we
9844 * need to continue with same src_cpu.
9845 */
9846 goto more_balance;
9847 }
9848
9849 /*
9850 * We failed to reach balance because of affinity.
9851 */
9852 if (sd_parent) {
9853 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
9854
9855 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
9856 *group_imbalance = 1;
9857 }
9858
9859 /* All tasks on this runqueue were pinned by CPU affinity */
9860 if (unlikely(env.flags & LBF_ALL_PINNED)) {
9861 __cpumask_clear_cpu(cpu_of(busiest), cpus);
9862 /*
9863 * Attempting to continue load balancing at the current
9864 * sched_domain level only makes sense if there are
9865 * active CPUs remaining as possible busiest CPUs to
9866 * pull load from which are not contained within the
9867 * destination group that is receiving any migrated
9868 * load.
9869 */
9870 if (!cpumask_subset(cpus, env.dst_grpmask)) {
9871 env.loop = 0;
9872 env.loop_break = sched_nr_migrate_break;
9873 goto redo;
9874 }
9875 goto out_all_pinned;
9876 }
9877 }
9878
9879 if (!ld_moved) {
9880 schedstat_inc(sd->lb_failed[idle]);
9881 /*
9882 * Increment the failure counter only on periodic balance.
9883 * We do not want newidle balance, which can be very
9884 * frequent, pollute the failure counter causing
9885 * excessive cache_hot migrations and active balances.
9886 */
9887 if (idle != CPU_NEWLY_IDLE)
9888 sd->nr_balance_failed++;
9889
9890 if (need_active_balance(&env)) {
9891 unsigned long flags;
9892
9893 raw_spin_rq_lock_irqsave(busiest, flags);
9894
9895 /*
9896 * Don't kick the active_load_balance_cpu_stop,
9897 * if the curr task on busiest CPU can't be
9898 * moved to this_cpu:
9899 */
9900 if (!cpumask_test_cpu(this_cpu, busiest->curr->cpus_ptr)) {
9901 raw_spin_rq_unlock_irqrestore(busiest, flags);
9902 goto out_one_pinned;
9903 }
9904
9905 /* Record that we found at least one task that could run on this_cpu */
9906 env.flags &= ~LBF_ALL_PINNED;
9907
9908 /*
9909 * ->active_balance synchronizes accesses to
9910 * ->active_balance_work. Once set, it's cleared
9911 * only after active load balance is finished.
9912 */
9913 if (!busiest->active_balance) {
9914 busiest->active_balance = 1;
9915 busiest->push_cpu = this_cpu;
9916 active_balance = 1;
9917 }
9918 raw_spin_rq_unlock_irqrestore(busiest, flags);
9919
9920 if (active_balance) {
9921 stop_one_cpu_nowait(cpu_of(busiest),
9922 active_load_balance_cpu_stop, busiest,
9923 &busiest->active_balance_work);
9924 }
9925 }
9926 } else {
9927 sd->nr_balance_failed = 0;
9928 }
9929
9930 if (likely(!active_balance) || need_active_balance(&env)) {
9931 /* We were unbalanced, so reset the balancing interval */
9932 sd->balance_interval = sd->min_interval;
9933 }
9934
9935 goto out;
9936
9937out_balanced:
9938 /*
9939 * We reach balance although we may have faced some affinity
9940 * constraints. Clear the imbalance flag only if other tasks got
9941 * a chance to move and fix the imbalance.
9942 */
9943 if (sd_parent && !(env.flags & LBF_ALL_PINNED)) {
9944 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
9945
9946 if (*group_imbalance)
9947 *group_imbalance = 0;
9948 }
9949
9950out_all_pinned:
9951 /*
9952 * We reach balance because all tasks are pinned at this level so
9953 * we can't migrate them. Let the imbalance flag set so parent level
9954 * can try to migrate them.
9955 */
9956 schedstat_inc(sd->lb_balanced[idle]);
9957
9958 sd->nr_balance_failed = 0;
9959
9960out_one_pinned:
9961 ld_moved = 0;
9962
9963 /*
9964 * newidle_balance() disregards balance intervals, so we could
9965 * repeatedly reach this code, which would lead to balance_interval
9966 * skyrocketing in a short amount of time. Skip the balance_interval
9967 * increase logic to avoid that.
9968 */
9969 if (env.idle == CPU_NEWLY_IDLE)
9970 goto out;
9971
9972 /* tune up the balancing interval */
9973 if ((env.flags & LBF_ALL_PINNED &&
9974 sd->balance_interval < MAX_PINNED_INTERVAL) ||
9975 sd->balance_interval < sd->max_interval)
9976 sd->balance_interval *= 2;
9977out:
9978 return ld_moved;
9979}
9980
9981static inline unsigned long
9982get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
9983{
9984 unsigned long interval = sd->balance_interval;
9985
9986 if (cpu_busy)
9987 interval *= sd->busy_factor;
9988
9989 /* scale ms to jiffies */
9990 interval = msecs_to_jiffies(interval);
9991
9992 /*
9993 * Reduce likelihood of busy balancing at higher domains racing with
9994 * balancing at lower domains by preventing their balancing periods
9995 * from being multiples of each other.
9996 */
9997 if (cpu_busy)
9998 interval -= 1;
9999
10000 interval = clamp(interval, 1UL, max_load_balance_interval);
10001
10002 return interval;
10003}
10004
10005static inline void
10006update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
10007{
10008 unsigned long interval, next;
10009
10010 /* used by idle balance, so cpu_busy = 0 */
10011 interval = get_sd_balance_interval(sd, 0);
10012 next = sd->last_balance + interval;
10013
10014 if (time_after(*next_balance, next))
10015 *next_balance = next;
10016}
10017
10018/*
10019 * active_load_balance_cpu_stop is run by the CPU stopper. It pushes
10020 * running tasks off the busiest CPU onto idle CPUs. It requires at
10021 * least 1 task to be running on each physical CPU where possible, and
10022 * avoids physical / logical imbalances.
10023 */
10024static int active_load_balance_cpu_stop(void *data)
10025{
10026 struct rq *busiest_rq = data;
10027 int busiest_cpu = cpu_of(busiest_rq);
10028 int target_cpu = busiest_rq->push_cpu;
10029 struct rq *target_rq = cpu_rq(target_cpu);
10030 struct sched_domain *sd;
10031 struct task_struct *p = NULL;
10032 struct rq_flags rf;
10033
10034 rq_lock_irq(busiest_rq, &rf);
10035 /*
10036 * Between queueing the stop-work and running it is a hole in which
10037 * CPUs can become inactive. We should not move tasks from or to
10038 * inactive CPUs.
10039 */
10040 if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu))
10041 goto out_unlock;
10042
10043 /* Make sure the requested CPU hasn't gone down in the meantime: */
10044 if (unlikely(busiest_cpu != smp_processor_id() ||
10045 !busiest_rq->active_balance))
10046 goto out_unlock;
10047
10048 /* Is there any task to move? */
10049 if (busiest_rq->nr_running <= 1)
10050 goto out_unlock;
10051
10052 /*
10053 * This condition is "impossible", if it occurs
10054 * we need to fix it. Originally reported by
10055 * Bjorn Helgaas on a 128-CPU setup.
10056 */
10057 BUG_ON(busiest_rq == target_rq);
10058
10059 /* Search for an sd spanning us and the target CPU. */
10060 rcu_read_lock();
10061 for_each_domain(target_cpu, sd) {
10062 if (cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
10063 break;
10064 }
10065
10066 if (likely(sd)) {
10067 struct lb_env env = {
10068 .sd = sd,
10069 .dst_cpu = target_cpu,
10070 .dst_rq = target_rq,
10071 .src_cpu = busiest_rq->cpu,
10072 .src_rq = busiest_rq,
10073 .idle = CPU_IDLE,
10074 .flags = LBF_ACTIVE_LB,
10075 };
10076
10077 schedstat_inc(sd->alb_count);
10078 update_rq_clock(busiest_rq);
10079
10080 p = detach_one_task(&env);
10081 if (p) {
10082 schedstat_inc(sd->alb_pushed);
10083 /* Active balancing done, reset the failure counter. */
10084 sd->nr_balance_failed = 0;
10085 } else {
10086 schedstat_inc(sd->alb_failed);
10087 }
10088 }
10089 rcu_read_unlock();
10090out_unlock:
10091 busiest_rq->active_balance = 0;
10092 rq_unlock(busiest_rq, &rf);
10093
10094 if (p)
10095 attach_one_task(target_rq, p);
10096
10097 local_irq_enable();
10098
10099 return 0;
10100}
10101
10102static DEFINE_SPINLOCK(balancing);
10103
10104/*
10105 * Scale the max load_balance interval with the number of CPUs in the system.
10106 * This trades load-balance latency on larger machines for less cross talk.
10107 */
10108void update_max_interval(void)
10109{
10110 max_load_balance_interval = HZ*num_online_cpus()/10;
10111}
10112
10113/*
10114 * It checks each scheduling domain to see if it is due to be balanced,
10115 * and initiates a balancing operation if so.
10116 *
10117 * Balancing parameters are set up in init_sched_domains.
10118 */
10119static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
10120{
10121 int continue_balancing = 1;
10122 int cpu = rq->cpu;
10123 int busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
10124 unsigned long interval;
10125 struct sched_domain *sd;
10126 /* Earliest time when we have to do rebalance again */
10127 unsigned long next_balance = jiffies + 60*HZ;
10128 int update_next_balance = 0;
10129 int need_serialize, need_decay = 0;
10130 u64 max_cost = 0;
10131
10132 rcu_read_lock();
10133 for_each_domain(cpu, sd) {
10134 /*
10135 * Decay the newidle max times here because this is a regular
10136 * visit to all the domains. Decay ~1% per second.
10137 */
10138 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
10139 sd->max_newidle_lb_cost =
10140 (sd->max_newidle_lb_cost * 253) / 256;
10141 sd->next_decay_max_lb_cost = jiffies + HZ;
10142 need_decay = 1;
10143 }
10144 max_cost += sd->max_newidle_lb_cost;
10145
10146 /*
10147 * Stop the load balance at this level. There is another
10148 * CPU in our sched group which is doing load balancing more
10149 * actively.
10150 */
10151 if (!continue_balancing) {
10152 if (need_decay)
10153 continue;
10154 break;
10155 }
10156
10157 interval = get_sd_balance_interval(sd, busy);
10158
10159 need_serialize = sd->flags & SD_SERIALIZE;
10160 if (need_serialize) {
10161 if (!spin_trylock(&balancing))
10162 goto out;
10163 }
10164
10165 if (time_after_eq(jiffies, sd->last_balance + interval)) {
10166 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
10167 /*
10168 * The LBF_DST_PINNED logic could have changed
10169 * env->dst_cpu, so we can't know our idle
10170 * state even if we migrated tasks. Update it.
10171 */
10172 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
10173 busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
10174 }
10175 sd->last_balance = jiffies;
10176 interval = get_sd_balance_interval(sd, busy);
10177 }
10178 if (need_serialize)
10179 spin_unlock(&balancing);
10180out:
10181 if (time_after(next_balance, sd->last_balance + interval)) {
10182 next_balance = sd->last_balance + interval;
10183 update_next_balance = 1;
10184 }
10185 }
10186 if (need_decay) {
10187 /*
10188 * Ensure the rq-wide value also decays but keep it at a
10189 * reasonable floor to avoid funnies with rq->avg_idle.
10190 */
10191 rq->max_idle_balance_cost =
10192 max((u64)sysctl_sched_migration_cost, max_cost);
10193 }
10194 rcu_read_unlock();
10195
10196 /*
10197 * next_balance will be updated only when there is a need.
10198 * When the cpu is attached to null domain for ex, it will not be
10199 * updated.
10200 */
10201 if (likely(update_next_balance))
10202 rq->next_balance = next_balance;
10203
10204}
10205
10206static inline int on_null_domain(struct rq *rq)
10207{
10208 return unlikely(!rcu_dereference_sched(rq->sd));
10209}
10210
10211#ifdef CONFIG_NO_HZ_COMMON
10212/*
10213 * idle load balancing details
10214 * - When one of the busy CPUs notice that there may be an idle rebalancing
10215 * needed, they will kick the idle load balancer, which then does idle
10216 * load balancing for all the idle CPUs.
10217 * - HK_FLAG_MISC CPUs are used for this task, because HK_FLAG_SCHED not set
10218 * anywhere yet.
10219 */
10220
10221static inline int find_new_ilb(void)
10222{
10223 int ilb;
10224
10225 for_each_cpu_and(ilb, nohz.idle_cpus_mask,
10226 housekeeping_cpumask(HK_FLAG_MISC)) {
10227
10228 if (ilb == smp_processor_id())
10229 continue;
10230
10231 if (idle_cpu(ilb))
10232 return ilb;
10233 }
10234
10235 return nr_cpu_ids;
10236}
10237
10238/*
10239 * Kick a CPU to do the nohz balancing, if it is time for it. We pick any
10240 * idle CPU in the HK_FLAG_MISC housekeeping set (if there is one).
10241 */
10242static void kick_ilb(unsigned int flags)
10243{
10244 int ilb_cpu;
10245
10246 /*
10247 * Increase nohz.next_balance only when if full ilb is triggered but
10248 * not if we only update stats.
10249 */
10250 if (flags & NOHZ_BALANCE_KICK)
10251 nohz.next_balance = jiffies+1;
10252
10253 ilb_cpu = find_new_ilb();
10254
10255 if (ilb_cpu >= nr_cpu_ids)
10256 return;
10257
10258 /*
10259 * Access to rq::nohz_csd is serialized by NOHZ_KICK_MASK; he who sets
10260 * the first flag owns it; cleared by nohz_csd_func().
10261 */
10262 flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
10263 if (flags & NOHZ_KICK_MASK)
10264 return;
10265
10266 /*
10267 * This way we generate an IPI on the target CPU which
10268 * is idle. And the softirq performing nohz idle load balance
10269 * will be run before returning from the IPI.
10270 */
10271 smp_call_function_single_async(ilb_cpu, &cpu_rq(ilb_cpu)->nohz_csd);
10272}
10273
10274/*
10275 * Current decision point for kicking the idle load balancer in the presence
10276 * of idle CPUs in the system.
10277 */
10278static void nohz_balancer_kick(struct rq *rq)
10279{
10280 unsigned long now = jiffies;
10281 struct sched_domain_shared *sds;
10282 struct sched_domain *sd;
10283 int nr_busy, i, cpu = rq->cpu;
10284 unsigned int flags = 0;
10285
10286 if (unlikely(rq->idle_balance))
10287 return;
10288
10289 /*
10290 * We may be recently in ticked or tickless idle mode. At the first
10291 * busy tick after returning from idle, we will update the busy stats.
10292 */
10293 nohz_balance_exit_idle(rq);
10294
10295 /*
10296 * None are in tickless mode and hence no need for NOHZ idle load
10297 * balancing.
10298 */
10299 if (likely(!atomic_read(&nohz.nr_cpus)))
10300 return;
10301
10302 if (READ_ONCE(nohz.has_blocked) &&
10303 time_after(now, READ_ONCE(nohz.next_blocked)))
10304 flags = NOHZ_STATS_KICK;
10305
10306 if (time_before(now, nohz.next_balance))
10307 goto out;
10308
10309 if (rq->nr_running >= 2) {
10310 flags = NOHZ_KICK_MASK;
10311 goto out;
10312 }
10313
10314 rcu_read_lock();
10315
10316 sd = rcu_dereference(rq->sd);
10317 if (sd) {
10318 /*
10319 * If there's a CFS task and the current CPU has reduced
10320 * capacity; kick the ILB to see if there's a better CPU to run
10321 * on.
10322 */
10323 if (rq->cfs.h_nr_running >= 1 && check_cpu_capacity(rq, sd)) {
10324 flags = NOHZ_KICK_MASK;
10325 goto unlock;
10326 }
10327 }
10328
10329 sd = rcu_dereference(per_cpu(sd_asym_packing, cpu));
10330 if (sd) {
10331 /*
10332 * When ASYM_PACKING; see if there's a more preferred CPU
10333 * currently idle; in which case, kick the ILB to move tasks
10334 * around.
10335 */
10336 for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) {
10337 if (sched_asym_prefer(i, cpu)) {
10338 flags = NOHZ_KICK_MASK;
10339 goto unlock;
10340 }
10341 }
10342 }
10343
10344 sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, cpu));
10345 if (sd) {
10346 /*
10347 * When ASYM_CPUCAPACITY; see if there's a higher capacity CPU
10348 * to run the misfit task on.
10349 */
10350 if (check_misfit_status(rq, sd)) {
10351 flags = NOHZ_KICK_MASK;
10352 goto unlock;
10353 }
10354
10355 /*
10356 * For asymmetric systems, we do not want to nicely balance
10357 * cache use, instead we want to embrace asymmetry and only
10358 * ensure tasks have enough CPU capacity.
10359 *
10360 * Skip the LLC logic because it's not relevant in that case.
10361 */
10362 goto unlock;
10363 }
10364
10365 sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
10366 if (sds) {
10367 /*
10368 * If there is an imbalance between LLC domains (IOW we could
10369 * increase the overall cache use), we need some less-loaded LLC
10370 * domain to pull some load. Likewise, we may need to spread
10371 * load within the current LLC domain (e.g. packed SMT cores but
10372 * other CPUs are idle). We can't really know from here how busy
10373 * the others are - so just get a nohz balance going if it looks
10374 * like this LLC domain has tasks we could move.
10375 */
10376 nr_busy = atomic_read(&sds->nr_busy_cpus);
10377 if (nr_busy > 1) {
10378 flags = NOHZ_KICK_MASK;
10379 goto unlock;
10380 }
10381 }
10382unlock:
10383 rcu_read_unlock();
10384out:
10385 if (flags)
10386 kick_ilb(flags);
10387}
10388
10389static void set_cpu_sd_state_busy(int cpu)
10390{
10391 struct sched_domain *sd;
10392
10393 rcu_read_lock();
10394 sd = rcu_dereference(per_cpu(sd_llc, cpu));
10395
10396 if (!sd || !sd->nohz_idle)
10397 goto unlock;
10398 sd->nohz_idle = 0;
10399
10400 atomic_inc(&sd->shared->nr_busy_cpus);
10401unlock:
10402 rcu_read_unlock();
10403}
10404
10405void nohz_balance_exit_idle(struct rq *rq)
10406{
10407 SCHED_WARN_ON(rq != this_rq());
10408
10409 if (likely(!rq->nohz_tick_stopped))
10410 return;
10411
10412 rq->nohz_tick_stopped = 0;
10413 cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask);
10414 atomic_dec(&nohz.nr_cpus);
10415
10416 set_cpu_sd_state_busy(rq->cpu);
10417}
10418
10419static void set_cpu_sd_state_idle(int cpu)
10420{
10421 struct sched_domain *sd;
10422
10423 rcu_read_lock();
10424 sd = rcu_dereference(per_cpu(sd_llc, cpu));
10425
10426 if (!sd || sd->nohz_idle)
10427 goto unlock;
10428 sd->nohz_idle = 1;
10429
10430 atomic_dec(&sd->shared->nr_busy_cpus);
10431unlock:
10432 rcu_read_unlock();
10433}
10434
10435/*
10436 * This routine will record that the CPU is going idle with tick stopped.
10437 * This info will be used in performing idle load balancing in the future.
10438 */
10439void nohz_balance_enter_idle(int cpu)
10440{
10441 struct rq *rq = cpu_rq(cpu);
10442
10443 SCHED_WARN_ON(cpu != smp_processor_id());
10444
10445 /* If this CPU is going down, then nothing needs to be done: */
10446 if (!cpu_active(cpu))
10447 return;
10448
10449 /* Spare idle load balancing on CPUs that don't want to be disturbed: */
10450 if (!housekeeping_cpu(cpu, HK_FLAG_SCHED))
10451 return;
10452
10453 /*
10454 * Can be set safely without rq->lock held
10455 * If a clear happens, it will have evaluated last additions because
10456 * rq->lock is held during the check and the clear
10457 */
10458 rq->has_blocked_load = 1;
10459
10460 /*
10461 * The tick is still stopped but load could have been added in the
10462 * meantime. We set the nohz.has_blocked flag to trig a check of the
10463 * *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear
10464 * of nohz.has_blocked can only happen after checking the new load
10465 */
10466 if (rq->nohz_tick_stopped)
10467 goto out;
10468
10469 /* If we're a completely isolated CPU, we don't play: */
10470 if (on_null_domain(rq))
10471 return;
10472
10473 rq->nohz_tick_stopped = 1;
10474
10475 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
10476 atomic_inc(&nohz.nr_cpus);
10477
10478 /*
10479 * Ensures that if nohz_idle_balance() fails to observe our
10480 * @idle_cpus_mask store, it must observe the @has_blocked
10481 * store.
10482 */
10483 smp_mb__after_atomic();
10484
10485 set_cpu_sd_state_idle(cpu);
10486
10487out:
10488 /*
10489 * Each time a cpu enter idle, we assume that it has blocked load and
10490 * enable the periodic update of the load of idle cpus
10491 */
10492 WRITE_ONCE(nohz.has_blocked, 1);
10493}
10494
10495static bool update_nohz_stats(struct rq *rq)
10496{
10497 unsigned int cpu = rq->cpu;
10498
10499 if (!rq->has_blocked_load)
10500 return false;
10501
10502 if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
10503 return false;
10504
10505 if (!time_after(jiffies, READ_ONCE(rq->last_blocked_load_update_tick)))
10506 return true;
10507
10508 update_blocked_averages(cpu);
10509
10510 return rq->has_blocked_load;
10511}
10512
10513/*
10514 * Internal function that runs load balance for all idle cpus. The load balance
10515 * can be a simple update of blocked load or a complete load balance with
10516 * tasks movement depending of flags.
10517 */
10518static void _nohz_idle_balance(struct rq *this_rq, unsigned int flags,
10519 enum cpu_idle_type idle)
10520{
10521 /* Earliest time when we have to do rebalance again */
10522 unsigned long now = jiffies;
10523 unsigned long next_balance = now + 60*HZ;
10524 bool has_blocked_load = false;
10525 int update_next_balance = 0;
10526 int this_cpu = this_rq->cpu;
10527 int balance_cpu;
10528 struct rq *rq;
10529
10530 SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);
10531
10532 /*
10533 * We assume there will be no idle load after this update and clear
10534 * the has_blocked flag. If a cpu enters idle in the mean time, it will
10535 * set the has_blocked flag and trig another update of idle load.
10536 * Because a cpu that becomes idle, is added to idle_cpus_mask before
10537 * setting the flag, we are sure to not clear the state and not
10538 * check the load of an idle cpu.
10539 */
10540 WRITE_ONCE(nohz.has_blocked, 0);
10541
10542 /*
10543 * Ensures that if we miss the CPU, we must see the has_blocked
10544 * store from nohz_balance_enter_idle().
10545 */
10546 smp_mb();
10547
10548 /*
10549 * Start with the next CPU after this_cpu so we will end with this_cpu and let a
10550 * chance for other idle cpu to pull load.
10551 */
10552 for_each_cpu_wrap(balance_cpu, nohz.idle_cpus_mask, this_cpu+1) {
10553 if (!idle_cpu(balance_cpu))
10554 continue;
10555
10556 /*
10557 * If this CPU gets work to do, stop the load balancing
10558 * work being done for other CPUs. Next load
10559 * balancing owner will pick it up.
10560 */
10561 if (need_resched()) {
10562 has_blocked_load = true;
10563 goto abort;
10564 }
10565
10566 rq = cpu_rq(balance_cpu);
10567
10568 has_blocked_load |= update_nohz_stats(rq);
10569
10570 /*
10571 * If time for next balance is due,
10572 * do the balance.
10573 */
10574 if (time_after_eq(jiffies, rq->next_balance)) {
10575 struct rq_flags rf;
10576
10577 rq_lock_irqsave(rq, &rf);
10578 update_rq_clock(rq);
10579 rq_unlock_irqrestore(rq, &rf);
10580
10581 if (flags & NOHZ_BALANCE_KICK)
10582 rebalance_domains(rq, CPU_IDLE);
10583 }
10584
10585 if (time_after(next_balance, rq->next_balance)) {
10586 next_balance = rq->next_balance;
10587 update_next_balance = 1;
10588 }
10589 }
10590
10591 /*
10592 * next_balance will be updated only when there is a need.
10593 * When the CPU is attached to null domain for ex, it will not be
10594 * updated.
10595 */
10596 if (likely(update_next_balance))
10597 nohz.next_balance = next_balance;
10598
10599 WRITE_ONCE(nohz.next_blocked,
10600 now + msecs_to_jiffies(LOAD_AVG_PERIOD));
10601
10602abort:
10603 /* There is still blocked load, enable periodic update */
10604 if (has_blocked_load)
10605 WRITE_ONCE(nohz.has_blocked, 1);
10606}
10607
10608/*
10609 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
10610 * rebalancing for all the cpus for whom scheduler ticks are stopped.
10611 */
10612static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
10613{
10614 unsigned int flags = this_rq->nohz_idle_balance;
10615
10616 if (!flags)
10617 return false;
10618
10619 this_rq->nohz_idle_balance = 0;
10620
10621 if (idle != CPU_IDLE)
10622 return false;
10623
10624 _nohz_idle_balance(this_rq, flags, idle);
10625
10626 return true;
10627}
10628
10629/*
10630 * Check if we need to run the ILB for updating blocked load before entering
10631 * idle state.
10632 */
10633void nohz_run_idle_balance(int cpu)
10634{
10635 unsigned int flags;
10636
10637 flags = atomic_fetch_andnot(NOHZ_NEWILB_KICK, nohz_flags(cpu));
10638
10639 /*
10640 * Update the blocked load only if no SCHED_SOFTIRQ is about to happen
10641 * (ie NOHZ_STATS_KICK set) and will do the same.
10642 */
10643 if ((flags == NOHZ_NEWILB_KICK) && !need_resched())
10644 _nohz_idle_balance(cpu_rq(cpu), NOHZ_STATS_KICK, CPU_IDLE);
10645}
10646
10647static void nohz_newidle_balance(struct rq *this_rq)
10648{
10649 int this_cpu = this_rq->cpu;
10650
10651 /*
10652 * This CPU doesn't want to be disturbed by scheduler
10653 * housekeeping
10654 */
10655 if (!housekeeping_cpu(this_cpu, HK_FLAG_SCHED))
10656 return;
10657
10658 /* Will wake up very soon. No time for doing anything else*/
10659 if (this_rq->avg_idle < sysctl_sched_migration_cost)
10660 return;
10661
10662 /* Don't need to update blocked load of idle CPUs*/
10663 if (!READ_ONCE(nohz.has_blocked) ||
10664 time_before(jiffies, READ_ONCE(nohz.next_blocked)))
10665 return;
10666
10667 /*
10668 * Set the need to trigger ILB in order to update blocked load
10669 * before entering idle state.
10670 */
10671 atomic_or(NOHZ_NEWILB_KICK, nohz_flags(this_cpu));
10672}
10673
10674#else /* !CONFIG_NO_HZ_COMMON */
10675static inline void nohz_balancer_kick(struct rq *rq) { }
10676
10677static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
10678{
10679 return false;
10680}
10681
10682static inline void nohz_newidle_balance(struct rq *this_rq) { }
10683#endif /* CONFIG_NO_HZ_COMMON */
10684
10685/*
10686 * newidle_balance is called by schedule() if this_cpu is about to become
10687 * idle. Attempts to pull tasks from other CPUs.
10688 *
10689 * Returns:
10690 * < 0 - we released the lock and there are !fair tasks present
10691 * 0 - failed, no new tasks
10692 * > 0 - success, new (fair) tasks present
10693 */
10694static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
10695{
10696 unsigned long next_balance = jiffies + HZ;
10697 int this_cpu = this_rq->cpu;
10698 struct sched_domain *sd;
10699 int pulled_task = 0;
10700 u64 curr_cost = 0;
10701
10702 update_misfit_status(NULL, this_rq);
10703
10704 /*
10705 * There is a task waiting to run. No need to search for one.
10706 * Return 0; the task will be enqueued when switching to idle.
10707 */
10708 if (this_rq->ttwu_pending)
10709 return 0;
10710
10711 /*
10712 * We must set idle_stamp _before_ calling idle_balance(), such that we
10713 * measure the duration of idle_balance() as idle time.
10714 */
10715 this_rq->idle_stamp = rq_clock(this_rq);
10716
10717 /*
10718 * Do not pull tasks towards !active CPUs...
10719 */
10720 if (!cpu_active(this_cpu))
10721 return 0;
10722
10723 /*
10724 * This is OK, because current is on_cpu, which avoids it being picked
10725 * for load-balance and preemption/IRQs are still disabled avoiding
10726 * further scheduler activity on it and we're being very careful to
10727 * re-start the picking loop.
10728 */
10729 rq_unpin_lock(this_rq, rf);
10730
10731 if (this_rq->avg_idle < sysctl_sched_migration_cost ||
10732 !READ_ONCE(this_rq->rd->overload)) {
10733
10734 rcu_read_lock();
10735 sd = rcu_dereference_check_sched_domain(this_rq->sd);
10736 if (sd)
10737 update_next_balance(sd, &next_balance);
10738 rcu_read_unlock();
10739
10740 goto out;
10741 }
10742
10743 raw_spin_rq_unlock(this_rq);
10744
10745 update_blocked_averages(this_cpu);
10746 rcu_read_lock();
10747 for_each_domain(this_cpu, sd) {
10748 int continue_balancing = 1;
10749 u64 t0, domain_cost;
10750
10751 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
10752 update_next_balance(sd, &next_balance);
10753 break;
10754 }
10755
10756 if (sd->flags & SD_BALANCE_NEWIDLE) {
10757 t0 = sched_clock_cpu(this_cpu);
10758
10759 pulled_task = load_balance(this_cpu, this_rq,
10760 sd, CPU_NEWLY_IDLE,
10761 &continue_balancing);
10762
10763 domain_cost = sched_clock_cpu(this_cpu) - t0;
10764 if (domain_cost > sd->max_newidle_lb_cost)
10765 sd->max_newidle_lb_cost = domain_cost;
10766
10767 curr_cost += domain_cost;
10768 }
10769
10770 update_next_balance(sd, &next_balance);
10771
10772 /*
10773 * Stop searching for tasks to pull if there are
10774 * now runnable tasks on this rq.
10775 */
10776 if (pulled_task || this_rq->nr_running > 0 ||
10777 this_rq->ttwu_pending)
10778 break;
10779 }
10780 rcu_read_unlock();
10781
10782 raw_spin_rq_lock(this_rq);
10783
10784 if (curr_cost > this_rq->max_idle_balance_cost)
10785 this_rq->max_idle_balance_cost = curr_cost;
10786
10787 /*
10788 * While browsing the domains, we released the rq lock, a task could
10789 * have been enqueued in the meantime. Since we're not going idle,
10790 * pretend we pulled a task.
10791 */
10792 if (this_rq->cfs.h_nr_running && !pulled_task)
10793 pulled_task = 1;
10794
10795 /* Is there a task of a high priority class? */
10796 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
10797 pulled_task = -1;
10798
10799out:
10800 /* Move the next balance forward */
10801 if (time_after(this_rq->next_balance, next_balance))
10802 this_rq->next_balance = next_balance;
10803
10804 if (pulled_task)
10805 this_rq->idle_stamp = 0;
10806 else
10807 nohz_newidle_balance(this_rq);
10808
10809 rq_repin_lock(this_rq, rf);
10810
10811 return pulled_task;
10812}
10813
10814/*
10815 * run_rebalance_domains is triggered when needed from the scheduler tick.
10816 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
10817 */
10818static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
10819{
10820 struct rq *this_rq = this_rq();
10821 enum cpu_idle_type idle = this_rq->idle_balance ?
10822 CPU_IDLE : CPU_NOT_IDLE;
10823
10824 /*
10825 * If this CPU has a pending nohz_balance_kick, then do the
10826 * balancing on behalf of the other idle CPUs whose ticks are
10827 * stopped. Do nohz_idle_balance *before* rebalance_domains to
10828 * give the idle CPUs a chance to load balance. Else we may
10829 * load balance only within the local sched_domain hierarchy
10830 * and abort nohz_idle_balance altogether if we pull some load.
10831 */
10832 if (nohz_idle_balance(this_rq, idle))
10833 return;
10834
10835 /* normal load balance */
10836 update_blocked_averages(this_rq->cpu);
10837 rebalance_domains(this_rq, idle);
10838}
10839
10840/*
10841 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
10842 */
10843void trigger_load_balance(struct rq *rq)
10844{
10845 /*
10846 * Don't need to rebalance while attached to NULL domain or
10847 * runqueue CPU is not active
10848 */
10849 if (unlikely(on_null_domain(rq) || !cpu_active(cpu_of(rq))))
10850 return;
10851
10852 if (time_after_eq(jiffies, rq->next_balance))
10853 raise_softirq(SCHED_SOFTIRQ);
10854
10855 nohz_balancer_kick(rq);
10856}
10857
10858static void rq_online_fair(struct rq *rq)
10859{
10860 update_sysctl();
10861
10862 update_runtime_enabled(rq);
10863}
10864
10865static void rq_offline_fair(struct rq *rq)
10866{
10867 update_sysctl();
10868
10869 /* Ensure any throttled groups are reachable by pick_next_task */
10870 unthrottle_offline_cfs_rqs(rq);
10871}
10872
10873#endif /* CONFIG_SMP */
10874
10875#ifdef CONFIG_SCHED_CORE
10876static inline bool
10877__entity_slice_used(struct sched_entity *se, int min_nr_tasks)
10878{
10879 u64 slice = sched_slice(cfs_rq_of(se), se);
10880 u64 rtime = se->sum_exec_runtime - se->prev_sum_exec_runtime;
10881
10882 return (rtime * min_nr_tasks > slice);
10883}
10884
10885#define MIN_NR_TASKS_DURING_FORCEIDLE 2
10886static inline void task_tick_core(struct rq *rq, struct task_struct *curr)
10887{
10888 if (!sched_core_enabled(rq))
10889 return;
10890
10891 /*
10892 * If runqueue has only one task which used up its slice and
10893 * if the sibling is forced idle, then trigger schedule to
10894 * give forced idle task a chance.
10895 *
10896 * sched_slice() considers only this active rq and it gets the
10897 * whole slice. But during force idle, we have siblings acting
10898 * like a single runqueue and hence we need to consider runnable
10899 * tasks on this CPU and the forced idle CPU. Ideally, we should
10900 * go through the forced idle rq, but that would be a perf hit.
10901 * We can assume that the forced idle CPU has at least
10902 * MIN_NR_TASKS_DURING_FORCEIDLE - 1 tasks and use that to check
10903 * if we need to give up the CPU.
10904 */
10905 if (rq->core->core_forceidle && rq->cfs.nr_running == 1 &&
10906 __entity_slice_used(&curr->se, MIN_NR_TASKS_DURING_FORCEIDLE))
10907 resched_curr(rq);
10908}
10909
10910/*
10911 * se_fi_update - Update the cfs_rq->min_vruntime_fi in a CFS hierarchy if needed.
10912 */
10913static void se_fi_update(struct sched_entity *se, unsigned int fi_seq, bool forceidle)
10914{
10915 for_each_sched_entity(se) {
10916 struct cfs_rq *cfs_rq = cfs_rq_of(se);
10917
10918 if (forceidle) {
10919 if (cfs_rq->forceidle_seq == fi_seq)
10920 break;
10921 cfs_rq->forceidle_seq = fi_seq;
10922 }
10923
10924 cfs_rq->min_vruntime_fi = cfs_rq->min_vruntime;
10925 }
10926}
10927
10928void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi)
10929{
10930 struct sched_entity *se = &p->se;
10931
10932 if (p->sched_class != &fair_sched_class)
10933 return;
10934
10935 se_fi_update(se, rq->core->core_forceidle_seq, in_fi);
10936}
10937
10938bool cfs_prio_less(struct task_struct *a, struct task_struct *b, bool in_fi)
10939{
10940 struct rq *rq = task_rq(a);
10941 struct sched_entity *sea = &a->se;
10942 struct sched_entity *seb = &b->se;
10943 struct cfs_rq *cfs_rqa;
10944 struct cfs_rq *cfs_rqb;
10945 s64 delta;
10946
10947 SCHED_WARN_ON(task_rq(b)->core != rq->core);
10948
10949#ifdef CONFIG_FAIR_GROUP_SCHED
10950 /*
10951 * Find an se in the hierarchy for tasks a and b, such that the se's
10952 * are immediate siblings.
10953 */
10954 while (sea->cfs_rq->tg != seb->cfs_rq->tg) {
10955 int sea_depth = sea->depth;
10956 int seb_depth = seb->depth;
10957
10958 if (sea_depth >= seb_depth)
10959 sea = parent_entity(sea);
10960 if (sea_depth <= seb_depth)
10961 seb = parent_entity(seb);
10962 }
10963
10964 se_fi_update(sea, rq->core->core_forceidle_seq, in_fi);
10965 se_fi_update(seb, rq->core->core_forceidle_seq, in_fi);
10966
10967 cfs_rqa = sea->cfs_rq;
10968 cfs_rqb = seb->cfs_rq;
10969#else
10970 cfs_rqa = &task_rq(a)->cfs;
10971 cfs_rqb = &task_rq(b)->cfs;
10972#endif
10973
10974 /*
10975 * Find delta after normalizing se's vruntime with its cfs_rq's
10976 * min_vruntime_fi, which would have been updated in prior calls
10977 * to se_fi_update().
10978 */
10979 delta = (s64)(sea->vruntime - seb->vruntime) +
10980 (s64)(cfs_rqb->min_vruntime_fi - cfs_rqa->min_vruntime_fi);
10981
10982 return delta > 0;
10983}
10984#else
10985static inline void task_tick_core(struct rq *rq, struct task_struct *curr) {}
10986#endif
10987
10988/*
10989 * scheduler tick hitting a task of our scheduling class.
10990 *
10991 * NOTE: This function can be called remotely by the tick offload that
10992 * goes along full dynticks. Therefore no local assumption can be made
10993 * and everything must be accessed through the @rq and @curr passed in
10994 * parameters.
10995 */
10996static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
10997{
10998 struct cfs_rq *cfs_rq;
10999 struct sched_entity *se = &curr->se;
11000
11001 for_each_sched_entity(se) {
11002 cfs_rq = cfs_rq_of(se);
11003 entity_tick(cfs_rq, se, queued);
11004 }
11005
11006 if (static_branch_unlikely(&sched_numa_balancing))
11007 task_tick_numa(rq, curr);
11008
11009 update_misfit_status(curr, rq);
11010 update_overutilized_status(task_rq(curr));
11011
11012 task_tick_core(rq, curr);
11013}
11014
11015/*
11016 * called on fork with the child task as argument from the parent's context
11017 * - child not yet on the tasklist
11018 * - preemption disabled
11019 */
11020static void task_fork_fair(struct task_struct *p)
11021{
11022 struct cfs_rq *cfs_rq;
11023 struct sched_entity *se = &p->se, *curr;
11024 struct rq *rq = this_rq();
11025 struct rq_flags rf;
11026
11027 rq_lock(rq, &rf);
11028 update_rq_clock(rq);
11029
11030 cfs_rq = task_cfs_rq(current);
11031 curr = cfs_rq->curr;
11032 if (curr) {
11033 update_curr(cfs_rq);
11034 se->vruntime = curr->vruntime;
11035 }
11036 place_entity(cfs_rq, se, 1);
11037
11038 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
11039 /*
11040 * Upon rescheduling, sched_class::put_prev_task() will place
11041 * 'current' within the tree based on its new key value.
11042 */
11043 swap(curr->vruntime, se->vruntime);
11044 resched_curr(rq);
11045 }
11046
11047 se->vruntime -= cfs_rq->min_vruntime;
11048 rq_unlock(rq, &rf);
11049}
11050
11051/*
11052 * Priority of the task has changed. Check to see if we preempt
11053 * the current task.
11054 */
11055static void
11056prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
11057{
11058 if (!task_on_rq_queued(p))
11059 return;
11060
11061 if (rq->cfs.nr_running == 1)
11062 return;
11063
11064 /*
11065 * Reschedule if we are currently running on this runqueue and
11066 * our priority decreased, or if we are not currently running on
11067 * this runqueue and our priority is higher than the current's
11068 */
11069 if (task_current(rq, p)) {
11070 if (p->prio > oldprio)
11071 resched_curr(rq);
11072 } else
11073 check_preempt_curr(rq, p, 0);
11074}
11075
11076static inline bool vruntime_normalized(struct task_struct *p)
11077{
11078 struct sched_entity *se = &p->se;
11079
11080 /*
11081 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
11082 * the dequeue_entity(.flags=0) will already have normalized the
11083 * vruntime.
11084 */
11085 if (p->on_rq)
11086 return true;
11087
11088 /*
11089 * When !on_rq, vruntime of the task has usually NOT been normalized.
11090 * But there are some cases where it has already been normalized:
11091 *
11092 * - A forked child which is waiting for being woken up by
11093 * wake_up_new_task().
11094 * - A task which has been woken up by try_to_wake_up() and
11095 * waiting for actually being woken up by sched_ttwu_pending().
11096 */
11097 if (!se->sum_exec_runtime ||
11098 (READ_ONCE(p->__state) == TASK_WAKING && p->sched_remote_wakeup))
11099 return true;
11100
11101 return false;
11102}
11103
11104#ifdef CONFIG_FAIR_GROUP_SCHED
11105/*
11106 * Propagate the changes of the sched_entity across the tg tree to make it
11107 * visible to the root
11108 */
11109static void propagate_entity_cfs_rq(struct sched_entity *se)
11110{
11111 struct cfs_rq *cfs_rq;
11112
11113 list_add_leaf_cfs_rq(cfs_rq_of(se));
11114
11115 /* Start to propagate at parent */
11116 se = se->parent;
11117
11118 for_each_sched_entity(se) {
11119 cfs_rq = cfs_rq_of(se);
11120
11121 if (!cfs_rq_throttled(cfs_rq)){
11122 update_load_avg(cfs_rq, se, UPDATE_TG);
11123 list_add_leaf_cfs_rq(cfs_rq);
11124 continue;
11125 }
11126
11127 if (list_add_leaf_cfs_rq(cfs_rq))
11128 break;
11129 }
11130}
11131#else
11132static void propagate_entity_cfs_rq(struct sched_entity *se) { }
11133#endif
11134
11135static void detach_entity_cfs_rq(struct sched_entity *se)
11136{
11137 struct cfs_rq *cfs_rq = cfs_rq_of(se);
11138
11139 /* Catch up with the cfs_rq and remove our load when we leave */
11140 update_load_avg(cfs_rq, se, 0);
11141 detach_entity_load_avg(cfs_rq, se);
11142 update_tg_load_avg(cfs_rq);
11143 propagate_entity_cfs_rq(se);
11144}
11145
11146static void attach_entity_cfs_rq(struct sched_entity *se)
11147{
11148 struct cfs_rq *cfs_rq = cfs_rq_of(se);
11149
11150#ifdef CONFIG_FAIR_GROUP_SCHED
11151 /*
11152 * Since the real-depth could have been changed (only FAIR
11153 * class maintain depth value), reset depth properly.
11154 */
11155 se->depth = se->parent ? se->parent->depth + 1 : 0;
11156#endif
11157
11158 /* Synchronize entity with its cfs_rq */
11159 update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
11160 attach_entity_load_avg(cfs_rq, se);
11161 update_tg_load_avg(cfs_rq);
11162 propagate_entity_cfs_rq(se);
11163}
11164
11165static void detach_task_cfs_rq(struct task_struct *p)
11166{
11167 struct sched_entity *se = &p->se;
11168 struct cfs_rq *cfs_rq = cfs_rq_of(se);
11169
11170 if (!vruntime_normalized(p)) {
11171 /*
11172 * Fix up our vruntime so that the current sleep doesn't
11173 * cause 'unlimited' sleep bonus.
11174 */
11175 place_entity(cfs_rq, se, 0);
11176 se->vruntime -= cfs_rq->min_vruntime;
11177 }
11178
11179 detach_entity_cfs_rq(se);
11180}
11181
11182static void attach_task_cfs_rq(struct task_struct *p)
11183{
11184 struct sched_entity *se = &p->se;
11185 struct cfs_rq *cfs_rq = cfs_rq_of(se);
11186
11187 attach_entity_cfs_rq(se);
11188
11189 if (!vruntime_normalized(p))
11190 se->vruntime += cfs_rq->min_vruntime;
11191}
11192
11193static void switched_from_fair(struct rq *rq, struct task_struct *p)
11194{
11195 detach_task_cfs_rq(p);
11196}
11197
11198static void switched_to_fair(struct rq *rq, struct task_struct *p)
11199{
11200 attach_task_cfs_rq(p);
11201
11202 if (task_on_rq_queued(p)) {
11203 /*
11204 * We were most likely switched from sched_rt, so
11205 * kick off the schedule if running, otherwise just see
11206 * if we can still preempt the current task.
11207 */
11208 if (task_current(rq, p))
11209 resched_curr(rq);
11210 else
11211 check_preempt_curr(rq, p, 0);
11212 }
11213}
11214
11215/* Account for a task changing its policy or group.
11216 *
11217 * This routine is mostly called to set cfs_rq->curr field when a task
11218 * migrates between groups/classes.
11219 */
11220static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first)
11221{
11222 struct sched_entity *se = &p->se;
11223
11224#ifdef CONFIG_SMP
11225 if (task_on_rq_queued(p)) {
11226 /*
11227 * Move the next running task to the front of the list, so our
11228 * cfs_tasks list becomes MRU one.
11229 */
11230 list_move(&se->group_node, &rq->cfs_tasks);
11231 }
11232#endif
11233
11234 for_each_sched_entity(se) {
11235 struct cfs_rq *cfs_rq = cfs_rq_of(se);
11236
11237 set_next_entity(cfs_rq, se);
11238 /* ensure bandwidth has been allocated on our new cfs_rq */
11239 account_cfs_rq_runtime(cfs_rq, 0);
11240 }
11241}
11242
11243void init_cfs_rq(struct cfs_rq *cfs_rq)
11244{
11245 cfs_rq->tasks_timeline = RB_ROOT_CACHED;
11246 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
11247#ifndef CONFIG_64BIT
11248 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
11249#endif
11250#ifdef CONFIG_SMP
11251 raw_spin_lock_init(&cfs_rq->removed.lock);
11252#endif
11253}
11254
11255#ifdef CONFIG_FAIR_GROUP_SCHED
11256static void task_set_group_fair(struct task_struct *p)
11257{
11258 struct sched_entity *se = &p->se;
11259
11260 set_task_rq(p, task_cpu(p));
11261 se->depth = se->parent ? se->parent->depth + 1 : 0;
11262}
11263
11264static void task_move_group_fair(struct task_struct *p)
11265{
11266 detach_task_cfs_rq(p);
11267 set_task_rq(p, task_cpu(p));
11268
11269#ifdef CONFIG_SMP
11270 /* Tell se's cfs_rq has been changed -- migrated */
11271 p->se.avg.last_update_time = 0;
11272#endif
11273 attach_task_cfs_rq(p);
11274}
11275
11276static void task_change_group_fair(struct task_struct *p, int type)
11277{
11278 switch (type) {
11279 case TASK_SET_GROUP:
11280 task_set_group_fair(p);
11281 break;
11282
11283 case TASK_MOVE_GROUP:
11284 task_move_group_fair(p);
11285 break;
11286 }
11287}
11288
11289void free_fair_sched_group(struct task_group *tg)
11290{
11291 int i;
11292
11293 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
11294
11295 for_each_possible_cpu(i) {
11296 if (tg->cfs_rq)
11297 kfree(tg->cfs_rq[i]);
11298 if (tg->se)
11299 kfree(tg->se[i]);
11300 }
11301
11302 kfree(tg->cfs_rq);
11303 kfree(tg->se);
11304}
11305
11306int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
11307{
11308 struct sched_entity *se;
11309 struct cfs_rq *cfs_rq;
11310 int i;
11311
11312 tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL);
11313 if (!tg->cfs_rq)
11314 goto err;
11315 tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL);
11316 if (!tg->se)
11317 goto err;
11318
11319 tg->shares = NICE_0_LOAD;
11320
11321 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
11322
11323 for_each_possible_cpu(i) {
11324 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
11325 GFP_KERNEL, cpu_to_node(i));
11326 if (!cfs_rq)
11327 goto err;
11328
11329 se = kzalloc_node(sizeof(struct sched_entity),
11330 GFP_KERNEL, cpu_to_node(i));
11331 if (!se)
11332 goto err_free_rq;
11333
11334 init_cfs_rq(cfs_rq);
11335 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
11336 init_entity_runnable_average(se);
11337 }
11338
11339 return 1;
11340
11341err_free_rq:
11342 kfree(cfs_rq);
11343err:
11344 return 0;
11345}
11346
11347void online_fair_sched_group(struct task_group *tg)
11348{
11349 struct sched_entity *se;
11350 struct rq_flags rf;
11351 struct rq *rq;
11352 int i;
11353
11354 for_each_possible_cpu(i) {
11355 rq = cpu_rq(i);
11356 se = tg->se[i];
11357 rq_lock_irq(rq, &rf);
11358 update_rq_clock(rq);
11359 attach_entity_cfs_rq(se);
11360 sync_throttle(tg, i);
11361 rq_unlock_irq(rq, &rf);
11362 }
11363}
11364
11365void unregister_fair_sched_group(struct task_group *tg)
11366{
11367 unsigned long flags;
11368 struct rq *rq;
11369 int cpu;
11370
11371 for_each_possible_cpu(cpu) {
11372 if (tg->se[cpu])
11373 remove_entity_load_avg(tg->se[cpu]);
11374
11375 /*
11376 * Only empty task groups can be destroyed; so we can speculatively
11377 * check on_list without danger of it being re-added.
11378 */
11379 if (!tg->cfs_rq[cpu]->on_list)
11380 continue;
11381
11382 rq = cpu_rq(cpu);
11383
11384 raw_spin_rq_lock_irqsave(rq, flags);
11385 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
11386 raw_spin_rq_unlock_irqrestore(rq, flags);
11387 }
11388}
11389
11390void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
11391 struct sched_entity *se, int cpu,
11392 struct sched_entity *parent)
11393{
11394 struct rq *rq = cpu_rq(cpu);
11395
11396 cfs_rq->tg = tg;
11397 cfs_rq->rq = rq;
11398 init_cfs_rq_runtime(cfs_rq);
11399
11400 tg->cfs_rq[cpu] = cfs_rq;
11401 tg->se[cpu] = se;
11402
11403 /* se could be NULL for root_task_group */
11404 if (!se)
11405 return;
11406
11407 if (!parent) {
11408 se->cfs_rq = &rq->cfs;
11409 se->depth = 0;
11410 } else {
11411 se->cfs_rq = parent->my_q;
11412 se->depth = parent->depth + 1;
11413 }
11414
11415 se->my_q = cfs_rq;
11416 /* guarantee group entities always have weight */
11417 update_load_set(&se->load, NICE_0_LOAD);
11418 se->parent = parent;
11419}
11420
11421static DEFINE_MUTEX(shares_mutex);
11422
11423int sched_group_set_shares(struct task_group *tg, unsigned long shares)
11424{
11425 int i;
11426
11427 /*
11428 * We can't change the weight of the root cgroup.
11429 */
11430 if (!tg->se[0])
11431 return -EINVAL;
11432
11433 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
11434
11435 mutex_lock(&shares_mutex);
11436 if (tg->shares == shares)
11437 goto done;
11438
11439 tg->shares = shares;
11440 for_each_possible_cpu(i) {
11441 struct rq *rq = cpu_rq(i);
11442 struct sched_entity *se = tg->se[i];
11443 struct rq_flags rf;
11444
11445 /* Propagate contribution to hierarchy */
11446 rq_lock_irqsave(rq, &rf);
11447 update_rq_clock(rq);
11448 for_each_sched_entity(se) {
11449 update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
11450 update_cfs_group(se);
11451 }
11452 rq_unlock_irqrestore(rq, &rf);
11453 }
11454
11455done:
11456 mutex_unlock(&shares_mutex);
11457 return 0;
11458}
11459#else /* CONFIG_FAIR_GROUP_SCHED */
11460
11461void free_fair_sched_group(struct task_group *tg) { }
11462
11463int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
11464{
11465 return 1;
11466}
11467
11468void online_fair_sched_group(struct task_group *tg) { }
11469
11470void unregister_fair_sched_group(struct task_group *tg) { }
11471
11472#endif /* CONFIG_FAIR_GROUP_SCHED */
11473
11474
11475static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
11476{
11477 struct sched_entity *se = &task->se;
11478 unsigned int rr_interval = 0;
11479
11480 /*
11481 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
11482 * idle runqueue:
11483 */
11484 if (rq->cfs.load.weight)
11485 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
11486
11487 return rr_interval;
11488}
11489
11490/*
11491 * All the scheduling class methods:
11492 */
11493DEFINE_SCHED_CLASS(fair) = {
11494
11495 .enqueue_task = enqueue_task_fair,
11496 .dequeue_task = dequeue_task_fair,
11497 .yield_task = yield_task_fair,
11498 .yield_to_task = yield_to_task_fair,
11499
11500 .check_preempt_curr = check_preempt_wakeup,
11501
11502 .pick_next_task = __pick_next_task_fair,
11503 .put_prev_task = put_prev_task_fair,
11504 .set_next_task = set_next_task_fair,
11505
11506#ifdef CONFIG_SMP
11507 .balance = balance_fair,
11508 .pick_task = pick_task_fair,
11509 .select_task_rq = select_task_rq_fair,
11510 .migrate_task_rq = migrate_task_rq_fair,
11511
11512 .rq_online = rq_online_fair,
11513 .rq_offline = rq_offline_fair,
11514
11515 .task_dead = task_dead_fair,
11516 .set_cpus_allowed = set_cpus_allowed_common,
11517#endif
11518
11519 .task_tick = task_tick_fair,
11520 .task_fork = task_fork_fair,
11521
11522 .prio_changed = prio_changed_fair,
11523 .switched_from = switched_from_fair,
11524 .switched_to = switched_to_fair,
11525
11526 .get_rr_interval = get_rr_interval_fair,
11527
11528 .update_curr = update_curr_fair,
11529
11530#ifdef CONFIG_FAIR_GROUP_SCHED
11531 .task_change_group = task_change_group_fair,
11532#endif
11533
11534#ifdef CONFIG_UCLAMP_TASK
11535 .uclamp_enabled = 1,
11536#endif
11537};
11538
11539#ifdef CONFIG_SCHED_DEBUG
11540void print_cfs_stats(struct seq_file *m, int cpu)
11541{
11542 struct cfs_rq *cfs_rq, *pos;
11543
11544 rcu_read_lock();
11545 for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos)
11546 print_cfs_rq(m, cpu, cfs_rq);
11547 rcu_read_unlock();
11548}
11549
11550#ifdef CONFIG_NUMA_BALANCING
11551void show_numa_stats(struct task_struct *p, struct seq_file *m)
11552{
11553 int node;
11554 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
11555 struct numa_group *ng;
11556
11557 rcu_read_lock();
11558 ng = rcu_dereference(p->numa_group);
11559 for_each_online_node(node) {
11560 if (p->numa_faults) {
11561 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
11562 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
11563 }
11564 if (ng) {
11565 gsf = ng->faults[task_faults_idx(NUMA_MEM, node, 0)],
11566 gpf = ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
11567 }
11568 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
11569 }
11570 rcu_read_unlock();
11571}
11572#endif /* CONFIG_NUMA_BALANCING */
11573#endif /* CONFIG_SCHED_DEBUG */
11574
11575__init void init_sched_fair_class(void)
11576{
11577#ifdef CONFIG_SMP
11578 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
11579
11580#ifdef CONFIG_NO_HZ_COMMON
11581 nohz.next_balance = jiffies;
11582 nohz.next_blocked = jiffies;
11583 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
11584#endif
11585#endif /* SMP */
11586
11587}
11588
11589/*
11590 * Helper functions to facilitate extracting info from tracepoints.
11591 */
11592
11593const struct sched_avg *sched_trace_cfs_rq_avg(struct cfs_rq *cfs_rq)
11594{
11595#ifdef CONFIG_SMP
11596 return cfs_rq ? &cfs_rq->avg : NULL;
11597#else
11598 return NULL;
11599#endif
11600}
11601EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_avg);
11602
11603char *sched_trace_cfs_rq_path(struct cfs_rq *cfs_rq, char *str, int len)
11604{
11605 if (!cfs_rq) {
11606 if (str)
11607 strlcpy(str, "(null)", len);
11608 else
11609 return NULL;
11610 }
11611
11612 cfs_rq_tg_path(cfs_rq, str, len);
11613 return str;
11614}
11615EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_path);
11616
11617int sched_trace_cfs_rq_cpu(struct cfs_rq *cfs_rq)
11618{
11619 return cfs_rq ? cpu_of(rq_of(cfs_rq)) : -1;
11620}
11621EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_cpu);
11622
11623const struct sched_avg *sched_trace_rq_avg_rt(struct rq *rq)
11624{
11625#ifdef CONFIG_SMP
11626 return rq ? &rq->avg_rt : NULL;
11627#else
11628 return NULL;
11629#endif
11630}
11631EXPORT_SYMBOL_GPL(sched_trace_rq_avg_rt);
11632
11633const struct sched_avg *sched_trace_rq_avg_dl(struct rq *rq)
11634{
11635#ifdef CONFIG_SMP
11636 return rq ? &rq->avg_dl : NULL;
11637#else
11638 return NULL;
11639#endif
11640}
11641EXPORT_SYMBOL_GPL(sched_trace_rq_avg_dl);
11642
11643const struct sched_avg *sched_trace_rq_avg_irq(struct rq *rq)
11644{
11645#if defined(CONFIG_SMP) && defined(CONFIG_HAVE_SCHED_AVG_IRQ)
11646 return rq ? &rq->avg_irq : NULL;
11647#else
11648 return NULL;
11649#endif
11650}
11651EXPORT_SYMBOL_GPL(sched_trace_rq_avg_irq);
11652
11653int sched_trace_rq_cpu(struct rq *rq)
11654{
11655 return rq ? cpu_of(rq) : -1;
11656}
11657EXPORT_SYMBOL_GPL(sched_trace_rq_cpu);
11658
11659int sched_trace_rq_cpu_capacity(struct rq *rq)
11660{
11661 return rq ?
11662#ifdef CONFIG_SMP
11663 rq->cpu_capacity
11664#else
11665 SCHED_CAPACITY_SCALE
11666#endif
11667 : -1;
11668}
11669EXPORT_SYMBOL_GPL(sched_trace_rq_cpu_capacity);
11670
11671const struct cpumask *sched_trace_rd_span(struct root_domain *rd)
11672{
11673#ifdef CONFIG_SMP
11674 return rd ? rd->span : NULL;
11675#else
11676 return NULL;
11677#endif
11678}
11679EXPORT_SYMBOL_GPL(sched_trace_rd_span);
11680
11681int sched_trace_rq_nr_running(struct rq *rq)
11682{
11683 return rq ? rq->nr_running : -1;
11684}
11685EXPORT_SYMBOL_GPL(sched_trace_rq_nr_running);