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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#include <trace/events/sched.h>
26
27/*
28 * Targeted preemption latency for CPU-bound tasks:
29 *
30 * NOTE: this latency value is not the same as the concept of
31 * 'timeslice length' - timeslices in CFS are of variable length
32 * and have no persistent notion like in traditional, time-slice
33 * based scheduling concepts.
34 *
35 * (to see the precise effective timeslice length of your workload,
36 * run vmstat and monitor the context-switches (cs) field)
37 *
38 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
39 */
40unsigned int sysctl_sched_latency = 6000000ULL;
41unsigned int normalized_sysctl_sched_latency = 6000000ULL;
42
43/*
44 * The initial- and re-scaling of tunables is configurable
45 *
46 * Options are:
47 *
48 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
49 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
50 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
51 *
52 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
53 */
54enum sched_tunable_scaling sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
55
56/*
57 * Minimal preemption granularity for CPU-bound tasks:
58 *
59 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
60 */
61unsigned int sysctl_sched_min_granularity = 750000ULL;
62unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
63
64/*
65 * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
66 */
67static unsigned int sched_nr_latency = 8;
68
69/*
70 * After fork, child runs first. If set to 0 (default) then
71 * parent will (try to) run first.
72 */
73unsigned int sysctl_sched_child_runs_first __read_mostly;
74
75/*
76 * SCHED_OTHER wake-up granularity.
77 *
78 * This option delays the preemption effects of decoupled workloads
79 * and reduces their over-scheduling. Synchronous workloads will still
80 * have immediate wakeup/sleep latencies.
81 *
82 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
83 */
84unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
85unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
86
87const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
88
89#ifdef CONFIG_SMP
90/*
91 * For asym packing, by default the lower numbered CPU has higher priority.
92 */
93int __weak arch_asym_cpu_priority(int cpu)
94{
95 return -cpu;
96}
97#endif
98
99#ifdef CONFIG_CFS_BANDWIDTH
100/*
101 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
102 * each time a cfs_rq requests quota.
103 *
104 * Note: in the case that the slice exceeds the runtime remaining (either due
105 * to consumption or the quota being specified to be smaller than the slice)
106 * we will always only issue the remaining available time.
107 *
108 * (default: 5 msec, units: microseconds)
109 */
110unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
111#endif
112
113/*
114 * The margin used when comparing utilization with CPU capacity:
115 * util * margin < capacity * 1024
116 *
117 * (default: ~20%)
118 */
119unsigned int capacity_margin = 1280;
120
121static inline void update_load_add(struct load_weight *lw, unsigned long inc)
122{
123 lw->weight += inc;
124 lw->inv_weight = 0;
125}
126
127static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
128{
129 lw->weight -= dec;
130 lw->inv_weight = 0;
131}
132
133static inline void update_load_set(struct load_weight *lw, unsigned long w)
134{
135 lw->weight = w;
136 lw->inv_weight = 0;
137}
138
139/*
140 * Increase the granularity value when there are more CPUs,
141 * because with more CPUs the 'effective latency' as visible
142 * to users decreases. But the relationship is not linear,
143 * so pick a second-best guess by going with the log2 of the
144 * number of CPUs.
145 *
146 * This idea comes from the SD scheduler of Con Kolivas:
147 */
148static unsigned int get_update_sysctl_factor(void)
149{
150 unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
151 unsigned int factor;
152
153 switch (sysctl_sched_tunable_scaling) {
154 case SCHED_TUNABLESCALING_NONE:
155 factor = 1;
156 break;
157 case SCHED_TUNABLESCALING_LINEAR:
158 factor = cpus;
159 break;
160 case SCHED_TUNABLESCALING_LOG:
161 default:
162 factor = 1 + ilog2(cpus);
163 break;
164 }
165
166 return factor;
167}
168
169static void update_sysctl(void)
170{
171 unsigned int factor = get_update_sysctl_factor();
172
173#define SET_SYSCTL(name) \
174 (sysctl_##name = (factor) * normalized_sysctl_##name)
175 SET_SYSCTL(sched_min_granularity);
176 SET_SYSCTL(sched_latency);
177 SET_SYSCTL(sched_wakeup_granularity);
178#undef SET_SYSCTL
179}
180
181void sched_init_granularity(void)
182{
183 update_sysctl();
184}
185
186#define WMULT_CONST (~0U)
187#define WMULT_SHIFT 32
188
189static void __update_inv_weight(struct load_weight *lw)
190{
191 unsigned long w;
192
193 if (likely(lw->inv_weight))
194 return;
195
196 w = scale_load_down(lw->weight);
197
198 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
199 lw->inv_weight = 1;
200 else if (unlikely(!w))
201 lw->inv_weight = WMULT_CONST;
202 else
203 lw->inv_weight = WMULT_CONST / w;
204}
205
206/*
207 * delta_exec * weight / lw.weight
208 * OR
209 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
210 *
211 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
212 * we're guaranteed shift stays positive because inv_weight is guaranteed to
213 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
214 *
215 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
216 * weight/lw.weight <= 1, and therefore our shift will also be positive.
217 */
218static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
219{
220 u64 fact = scale_load_down(weight);
221 int shift = WMULT_SHIFT;
222
223 __update_inv_weight(lw);
224
225 if (unlikely(fact >> 32)) {
226 while (fact >> 32) {
227 fact >>= 1;
228 shift--;
229 }
230 }
231
232 /* hint to use a 32x32->64 mul */
233 fact = (u64)(u32)fact * lw->inv_weight;
234
235 while (fact >> 32) {
236 fact >>= 1;
237 shift--;
238 }
239
240 return mul_u64_u32_shr(delta_exec, fact, shift);
241}
242
243
244const struct sched_class fair_sched_class;
245
246/**************************************************************
247 * CFS operations on generic schedulable entities:
248 */
249
250#ifdef CONFIG_FAIR_GROUP_SCHED
251
252/* cpu runqueue to which this cfs_rq is attached */
253static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
254{
255 return cfs_rq->rq;
256}
257
258/* An entity is a task if it doesn't "own" a runqueue */
259#define entity_is_task(se) (!se->my_q)
260
261static inline struct task_struct *task_of(struct sched_entity *se)
262{
263 SCHED_WARN_ON(!entity_is_task(se));
264 return container_of(se, struct task_struct, se);
265}
266
267/* Walk up scheduling entities hierarchy */
268#define for_each_sched_entity(se) \
269 for (; se; se = se->parent)
270
271static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
272{
273 return p->se.cfs_rq;
274}
275
276/* runqueue on which this entity is (to be) queued */
277static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
278{
279 return se->cfs_rq;
280}
281
282/* runqueue "owned" by this group */
283static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
284{
285 return grp->my_q;
286}
287
288static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
289{
290 if (!cfs_rq->on_list) {
291 struct rq *rq = rq_of(cfs_rq);
292 int cpu = cpu_of(rq);
293 /*
294 * Ensure we either appear before our parent (if already
295 * enqueued) or force our parent to appear after us when it is
296 * enqueued. The fact that we always enqueue bottom-up
297 * reduces this to two cases and a special case for the root
298 * cfs_rq. Furthermore, it also means that we will always reset
299 * tmp_alone_branch either when the branch is connected
300 * to a tree or when we reach the beg of the tree
301 */
302 if (cfs_rq->tg->parent &&
303 cfs_rq->tg->parent->cfs_rq[cpu]->on_list) {
304 /*
305 * If parent is already on the list, we add the child
306 * just before. Thanks to circular linked property of
307 * the list, this means to put the child at the tail
308 * of the list that starts by parent.
309 */
310 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
311 &(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list));
312 /*
313 * The branch is now connected to its tree so we can
314 * reset tmp_alone_branch to the beginning of the
315 * list.
316 */
317 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
318 } else if (!cfs_rq->tg->parent) {
319 /*
320 * cfs rq without parent should be put
321 * at the tail of the list.
322 */
323 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
324 &rq->leaf_cfs_rq_list);
325 /*
326 * We have reach the beg of a tree so we can reset
327 * tmp_alone_branch to the beginning of the list.
328 */
329 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
330 } else {
331 /*
332 * The parent has not already been added so we want to
333 * make sure that it will be put after us.
334 * tmp_alone_branch points to the beg of the branch
335 * where we will add parent.
336 */
337 list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
338 rq->tmp_alone_branch);
339 /*
340 * update tmp_alone_branch to points to the new beg
341 * of the branch
342 */
343 rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list;
344 }
345
346 cfs_rq->on_list = 1;
347 }
348}
349
350static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
351{
352 if (cfs_rq->on_list) {
353 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
354 cfs_rq->on_list = 0;
355 }
356}
357
358/* Iterate thr' all leaf cfs_rq's on a runqueue */
359#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
360 list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list, \
361 leaf_cfs_rq_list)
362
363/* Do the two (enqueued) entities belong to the same group ? */
364static inline struct cfs_rq *
365is_same_group(struct sched_entity *se, struct sched_entity *pse)
366{
367 if (se->cfs_rq == pse->cfs_rq)
368 return se->cfs_rq;
369
370 return NULL;
371}
372
373static inline struct sched_entity *parent_entity(struct sched_entity *se)
374{
375 return se->parent;
376}
377
378static void
379find_matching_se(struct sched_entity **se, struct sched_entity **pse)
380{
381 int se_depth, pse_depth;
382
383 /*
384 * preemption test can be made between sibling entities who are in the
385 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
386 * both tasks until we find their ancestors who are siblings of common
387 * parent.
388 */
389
390 /* First walk up until both entities are at same depth */
391 se_depth = (*se)->depth;
392 pse_depth = (*pse)->depth;
393
394 while (se_depth > pse_depth) {
395 se_depth--;
396 *se = parent_entity(*se);
397 }
398
399 while (pse_depth > se_depth) {
400 pse_depth--;
401 *pse = parent_entity(*pse);
402 }
403
404 while (!is_same_group(*se, *pse)) {
405 *se = parent_entity(*se);
406 *pse = parent_entity(*pse);
407 }
408}
409
410#else /* !CONFIG_FAIR_GROUP_SCHED */
411
412static inline struct task_struct *task_of(struct sched_entity *se)
413{
414 return container_of(se, struct task_struct, se);
415}
416
417static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
418{
419 return container_of(cfs_rq, struct rq, cfs);
420}
421
422#define entity_is_task(se) 1
423
424#define for_each_sched_entity(se) \
425 for (; se; se = NULL)
426
427static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
428{
429 return &task_rq(p)->cfs;
430}
431
432static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
433{
434 struct task_struct *p = task_of(se);
435 struct rq *rq = task_rq(p);
436
437 return &rq->cfs;
438}
439
440/* runqueue "owned" by this group */
441static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
442{
443 return NULL;
444}
445
446static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
447{
448}
449
450static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
451{
452}
453
454#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
455 for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
456
457static inline struct sched_entity *parent_entity(struct sched_entity *se)
458{
459 return NULL;
460}
461
462static inline void
463find_matching_se(struct sched_entity **se, struct sched_entity **pse)
464{
465}
466
467#endif /* CONFIG_FAIR_GROUP_SCHED */
468
469static __always_inline
470void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
471
472/**************************************************************
473 * Scheduling class tree data structure manipulation methods:
474 */
475
476static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
477{
478 s64 delta = (s64)(vruntime - max_vruntime);
479 if (delta > 0)
480 max_vruntime = vruntime;
481
482 return max_vruntime;
483}
484
485static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
486{
487 s64 delta = (s64)(vruntime - min_vruntime);
488 if (delta < 0)
489 min_vruntime = vruntime;
490
491 return min_vruntime;
492}
493
494static inline int entity_before(struct sched_entity *a,
495 struct sched_entity *b)
496{
497 return (s64)(a->vruntime - b->vruntime) < 0;
498}
499
500static void update_min_vruntime(struct cfs_rq *cfs_rq)
501{
502 struct sched_entity *curr = cfs_rq->curr;
503 struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline);
504
505 u64 vruntime = cfs_rq->min_vruntime;
506
507 if (curr) {
508 if (curr->on_rq)
509 vruntime = curr->vruntime;
510 else
511 curr = NULL;
512 }
513
514 if (leftmost) { /* non-empty tree */
515 struct sched_entity *se;
516 se = rb_entry(leftmost, struct sched_entity, run_node);
517
518 if (!curr)
519 vruntime = se->vruntime;
520 else
521 vruntime = min_vruntime(vruntime, se->vruntime);
522 }
523
524 /* ensure we never gain time by being placed backwards. */
525 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
526#ifndef CONFIG_64BIT
527 smp_wmb();
528 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
529#endif
530}
531
532/*
533 * Enqueue an entity into the rb-tree:
534 */
535static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
536{
537 struct rb_node **link = &cfs_rq->tasks_timeline.rb_root.rb_node;
538 struct rb_node *parent = NULL;
539 struct sched_entity *entry;
540 bool leftmost = true;
541
542 /*
543 * Find the right place in the rbtree:
544 */
545 while (*link) {
546 parent = *link;
547 entry = rb_entry(parent, struct sched_entity, run_node);
548 /*
549 * We dont care about collisions. Nodes with
550 * the same key stay together.
551 */
552 if (entity_before(se, entry)) {
553 link = &parent->rb_left;
554 } else {
555 link = &parent->rb_right;
556 leftmost = false;
557 }
558 }
559
560 rb_link_node(&se->run_node, parent, link);
561 rb_insert_color_cached(&se->run_node,
562 &cfs_rq->tasks_timeline, leftmost);
563}
564
565static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
566{
567 rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
568}
569
570struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
571{
572 struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline);
573
574 if (!left)
575 return NULL;
576
577 return rb_entry(left, struct sched_entity, run_node);
578}
579
580static struct sched_entity *__pick_next_entity(struct sched_entity *se)
581{
582 struct rb_node *next = rb_next(&se->run_node);
583
584 if (!next)
585 return NULL;
586
587 return rb_entry(next, struct sched_entity, run_node);
588}
589
590#ifdef CONFIG_SCHED_DEBUG
591struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
592{
593 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);
594
595 if (!last)
596 return NULL;
597
598 return rb_entry(last, struct sched_entity, run_node);
599}
600
601/**************************************************************
602 * Scheduling class statistics methods:
603 */
604
605int sched_proc_update_handler(struct ctl_table *table, int write,
606 void __user *buffer, size_t *lenp,
607 loff_t *ppos)
608{
609 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
610 unsigned int factor = get_update_sysctl_factor();
611
612 if (ret || !write)
613 return ret;
614
615 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
616 sysctl_sched_min_granularity);
617
618#define WRT_SYSCTL(name) \
619 (normalized_sysctl_##name = sysctl_##name / (factor))
620 WRT_SYSCTL(sched_min_granularity);
621 WRT_SYSCTL(sched_latency);
622 WRT_SYSCTL(sched_wakeup_granularity);
623#undef WRT_SYSCTL
624
625 return 0;
626}
627#endif
628
629/*
630 * delta /= w
631 */
632static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
633{
634 if (unlikely(se->load.weight != NICE_0_LOAD))
635 delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
636
637 return delta;
638}
639
640/*
641 * The idea is to set a period in which each task runs once.
642 *
643 * When there are too many tasks (sched_nr_latency) we have to stretch
644 * this period because otherwise the slices get too small.
645 *
646 * p = (nr <= nl) ? l : l*nr/nl
647 */
648static u64 __sched_period(unsigned long nr_running)
649{
650 if (unlikely(nr_running > sched_nr_latency))
651 return nr_running * sysctl_sched_min_granularity;
652 else
653 return sysctl_sched_latency;
654}
655
656/*
657 * We calculate the wall-time slice from the period by taking a part
658 * proportional to the weight.
659 *
660 * s = p*P[w/rw]
661 */
662static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
663{
664 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
665
666 for_each_sched_entity(se) {
667 struct load_weight *load;
668 struct load_weight lw;
669
670 cfs_rq = cfs_rq_of(se);
671 load = &cfs_rq->load;
672
673 if (unlikely(!se->on_rq)) {
674 lw = cfs_rq->load;
675
676 update_load_add(&lw, se->load.weight);
677 load = &lw;
678 }
679 slice = __calc_delta(slice, se->load.weight, load);
680 }
681 return slice;
682}
683
684/*
685 * We calculate the vruntime slice of a to-be-inserted task.
686 *
687 * vs = s/w
688 */
689static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
690{
691 return calc_delta_fair(sched_slice(cfs_rq, se), se);
692}
693
694#ifdef CONFIG_SMP
695
696#include "sched-pelt.h"
697
698static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
699static unsigned long task_h_load(struct task_struct *p);
700
701/* Give new sched_entity start runnable values to heavy its load in infant time */
702void init_entity_runnable_average(struct sched_entity *se)
703{
704 struct sched_avg *sa = &se->avg;
705
706 memset(sa, 0, sizeof(*sa));
707
708 /*
709 * Tasks are intialized with full load to be seen as heavy tasks until
710 * they get a chance to stabilize to their real load level.
711 * Group entities are intialized with zero load to reflect the fact that
712 * nothing has been attached to the task group yet.
713 */
714 if (entity_is_task(se))
715 sa->runnable_load_avg = sa->load_avg = scale_load_down(se->load.weight);
716
717 se->runnable_weight = se->load.weight;
718
719 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
720}
721
722static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
723static void attach_entity_cfs_rq(struct sched_entity *se);
724
725/*
726 * With new tasks being created, their initial util_avgs are extrapolated
727 * based on the cfs_rq's current util_avg:
728 *
729 * util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
730 *
731 * However, in many cases, the above util_avg does not give a desired
732 * value. Moreover, the sum of the util_avgs may be divergent, such
733 * as when the series is a harmonic series.
734 *
735 * To solve this problem, we also cap the util_avg of successive tasks to
736 * only 1/2 of the left utilization budget:
737 *
738 * util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n
739 *
740 * where n denotes the nth task.
741 *
742 * For example, a simplest series from the beginning would be like:
743 *
744 * task util_avg: 512, 256, 128, 64, 32, 16, 8, ...
745 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
746 *
747 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
748 * if util_avg > util_avg_cap.
749 */
750void post_init_entity_util_avg(struct sched_entity *se)
751{
752 struct cfs_rq *cfs_rq = cfs_rq_of(se);
753 struct sched_avg *sa = &se->avg;
754 long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2;
755
756 if (cap > 0) {
757 if (cfs_rq->avg.util_avg != 0) {
758 sa->util_avg = cfs_rq->avg.util_avg * se->load.weight;
759 sa->util_avg /= (cfs_rq->avg.load_avg + 1);
760
761 if (sa->util_avg > cap)
762 sa->util_avg = cap;
763 } else {
764 sa->util_avg = cap;
765 }
766 }
767
768 if (entity_is_task(se)) {
769 struct task_struct *p = task_of(se);
770 if (p->sched_class != &fair_sched_class) {
771 /*
772 * For !fair tasks do:
773 *
774 update_cfs_rq_load_avg(now, cfs_rq);
775 attach_entity_load_avg(cfs_rq, se, 0);
776 switched_from_fair(rq, p);
777 *
778 * such that the next switched_to_fair() has the
779 * expected state.
780 */
781 se->avg.last_update_time = cfs_rq_clock_task(cfs_rq);
782 return;
783 }
784 }
785
786 attach_entity_cfs_rq(se);
787}
788
789#else /* !CONFIG_SMP */
790void init_entity_runnable_average(struct sched_entity *se)
791{
792}
793void post_init_entity_util_avg(struct sched_entity *se)
794{
795}
796static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
797{
798}
799#endif /* CONFIG_SMP */
800
801/*
802 * Update the current task's runtime statistics.
803 */
804static void update_curr(struct cfs_rq *cfs_rq)
805{
806 struct sched_entity *curr = cfs_rq->curr;
807 u64 now = rq_clock_task(rq_of(cfs_rq));
808 u64 delta_exec;
809
810 if (unlikely(!curr))
811 return;
812
813 delta_exec = now - curr->exec_start;
814 if (unlikely((s64)delta_exec <= 0))
815 return;
816
817 curr->exec_start = now;
818
819 schedstat_set(curr->statistics.exec_max,
820 max(delta_exec, curr->statistics.exec_max));
821
822 curr->sum_exec_runtime += delta_exec;
823 schedstat_add(cfs_rq->exec_clock, delta_exec);
824
825 curr->vruntime += calc_delta_fair(delta_exec, curr);
826 update_min_vruntime(cfs_rq);
827
828 if (entity_is_task(curr)) {
829 struct task_struct *curtask = task_of(curr);
830
831 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
832 cgroup_account_cputime(curtask, delta_exec);
833 account_group_exec_runtime(curtask, delta_exec);
834 }
835
836 account_cfs_rq_runtime(cfs_rq, delta_exec);
837}
838
839static void update_curr_fair(struct rq *rq)
840{
841 update_curr(cfs_rq_of(&rq->curr->se));
842}
843
844static inline void
845update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
846{
847 u64 wait_start, prev_wait_start;
848
849 if (!schedstat_enabled())
850 return;
851
852 wait_start = rq_clock(rq_of(cfs_rq));
853 prev_wait_start = schedstat_val(se->statistics.wait_start);
854
855 if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
856 likely(wait_start > prev_wait_start))
857 wait_start -= prev_wait_start;
858
859 __schedstat_set(se->statistics.wait_start, wait_start);
860}
861
862static inline void
863update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
864{
865 struct task_struct *p;
866 u64 delta;
867
868 if (!schedstat_enabled())
869 return;
870
871 delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
872
873 if (entity_is_task(se)) {
874 p = task_of(se);
875 if (task_on_rq_migrating(p)) {
876 /*
877 * Preserve migrating task's wait time so wait_start
878 * time stamp can be adjusted to accumulate wait time
879 * prior to migration.
880 */
881 __schedstat_set(se->statistics.wait_start, delta);
882 return;
883 }
884 trace_sched_stat_wait(p, delta);
885 }
886
887 __schedstat_set(se->statistics.wait_max,
888 max(schedstat_val(se->statistics.wait_max), delta));
889 __schedstat_inc(se->statistics.wait_count);
890 __schedstat_add(se->statistics.wait_sum, delta);
891 __schedstat_set(se->statistics.wait_start, 0);
892}
893
894static inline void
895update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
896{
897 struct task_struct *tsk = NULL;
898 u64 sleep_start, block_start;
899
900 if (!schedstat_enabled())
901 return;
902
903 sleep_start = schedstat_val(se->statistics.sleep_start);
904 block_start = schedstat_val(se->statistics.block_start);
905
906 if (entity_is_task(se))
907 tsk = task_of(se);
908
909 if (sleep_start) {
910 u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
911
912 if ((s64)delta < 0)
913 delta = 0;
914
915 if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
916 __schedstat_set(se->statistics.sleep_max, delta);
917
918 __schedstat_set(se->statistics.sleep_start, 0);
919 __schedstat_add(se->statistics.sum_sleep_runtime, delta);
920
921 if (tsk) {
922 account_scheduler_latency(tsk, delta >> 10, 1);
923 trace_sched_stat_sleep(tsk, delta);
924 }
925 }
926 if (block_start) {
927 u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
928
929 if ((s64)delta < 0)
930 delta = 0;
931
932 if (unlikely(delta > schedstat_val(se->statistics.block_max)))
933 __schedstat_set(se->statistics.block_max, delta);
934
935 __schedstat_set(se->statistics.block_start, 0);
936 __schedstat_add(se->statistics.sum_sleep_runtime, delta);
937
938 if (tsk) {
939 if (tsk->in_iowait) {
940 __schedstat_add(se->statistics.iowait_sum, delta);
941 __schedstat_inc(se->statistics.iowait_count);
942 trace_sched_stat_iowait(tsk, delta);
943 }
944
945 trace_sched_stat_blocked(tsk, delta);
946
947 /*
948 * Blocking time is in units of nanosecs, so shift by
949 * 20 to get a milliseconds-range estimation of the
950 * amount of time that the task spent sleeping:
951 */
952 if (unlikely(prof_on == SLEEP_PROFILING)) {
953 profile_hits(SLEEP_PROFILING,
954 (void *)get_wchan(tsk),
955 delta >> 20);
956 }
957 account_scheduler_latency(tsk, delta >> 10, 0);
958 }
959 }
960}
961
962/*
963 * Task is being enqueued - update stats:
964 */
965static inline void
966update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
967{
968 if (!schedstat_enabled())
969 return;
970
971 /*
972 * Are we enqueueing a waiting task? (for current tasks
973 * a dequeue/enqueue event is a NOP)
974 */
975 if (se != cfs_rq->curr)
976 update_stats_wait_start(cfs_rq, se);
977
978 if (flags & ENQUEUE_WAKEUP)
979 update_stats_enqueue_sleeper(cfs_rq, se);
980}
981
982static inline void
983update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
984{
985
986 if (!schedstat_enabled())
987 return;
988
989 /*
990 * Mark the end of the wait period if dequeueing a
991 * waiting task:
992 */
993 if (se != cfs_rq->curr)
994 update_stats_wait_end(cfs_rq, se);
995
996 if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
997 struct task_struct *tsk = task_of(se);
998
999 if (tsk->state & TASK_INTERRUPTIBLE)
1000 __schedstat_set(se->statistics.sleep_start,
1001 rq_clock(rq_of(cfs_rq)));
1002 if (tsk->state & TASK_UNINTERRUPTIBLE)
1003 __schedstat_set(se->statistics.block_start,
1004 rq_clock(rq_of(cfs_rq)));
1005 }
1006}
1007
1008/*
1009 * We are picking a new current task - update its stats:
1010 */
1011static inline void
1012update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
1013{
1014 /*
1015 * We are starting a new run period:
1016 */
1017 se->exec_start = rq_clock_task(rq_of(cfs_rq));
1018}
1019
1020/**************************************************
1021 * Scheduling class queueing methods:
1022 */
1023
1024#ifdef CONFIG_NUMA_BALANCING
1025/*
1026 * Approximate time to scan a full NUMA task in ms. The task scan period is
1027 * calculated based on the tasks virtual memory size and
1028 * numa_balancing_scan_size.
1029 */
1030unsigned int sysctl_numa_balancing_scan_period_min = 1000;
1031unsigned int sysctl_numa_balancing_scan_period_max = 60000;
1032
1033/* Portion of address space to scan in MB */
1034unsigned int sysctl_numa_balancing_scan_size = 256;
1035
1036/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
1037unsigned int sysctl_numa_balancing_scan_delay = 1000;
1038
1039struct numa_group {
1040 atomic_t refcount;
1041
1042 spinlock_t lock; /* nr_tasks, tasks */
1043 int nr_tasks;
1044 pid_t gid;
1045 int active_nodes;
1046
1047 struct rcu_head rcu;
1048 unsigned long total_faults;
1049 unsigned long max_faults_cpu;
1050 /*
1051 * Faults_cpu is used to decide whether memory should move
1052 * towards the CPU. As a consequence, these stats are weighted
1053 * more by CPU use than by memory faults.
1054 */
1055 unsigned long *faults_cpu;
1056 unsigned long faults[0];
1057};
1058
1059static inline unsigned long group_faults_priv(struct numa_group *ng);
1060static inline unsigned long group_faults_shared(struct numa_group *ng);
1061
1062static unsigned int task_nr_scan_windows(struct task_struct *p)
1063{
1064 unsigned long rss = 0;
1065 unsigned long nr_scan_pages;
1066
1067 /*
1068 * Calculations based on RSS as non-present and empty pages are skipped
1069 * by the PTE scanner and NUMA hinting faults should be trapped based
1070 * on resident pages
1071 */
1072 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
1073 rss = get_mm_rss(p->mm);
1074 if (!rss)
1075 rss = nr_scan_pages;
1076
1077 rss = round_up(rss, nr_scan_pages);
1078 return rss / nr_scan_pages;
1079}
1080
1081/* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
1082#define MAX_SCAN_WINDOW 2560
1083
1084static unsigned int task_scan_min(struct task_struct *p)
1085{
1086 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
1087 unsigned int scan, floor;
1088 unsigned int windows = 1;
1089
1090 if (scan_size < MAX_SCAN_WINDOW)
1091 windows = MAX_SCAN_WINDOW / scan_size;
1092 floor = 1000 / windows;
1093
1094 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
1095 return max_t(unsigned int, floor, scan);
1096}
1097
1098static unsigned int task_scan_start(struct task_struct *p)
1099{
1100 unsigned long smin = task_scan_min(p);
1101 unsigned long period = smin;
1102
1103 /* Scale the maximum scan period with the amount of shared memory. */
1104 if (p->numa_group) {
1105 struct numa_group *ng = p->numa_group;
1106 unsigned long shared = group_faults_shared(ng);
1107 unsigned long private = group_faults_priv(ng);
1108
1109 period *= atomic_read(&ng->refcount);
1110 period *= shared + 1;
1111 period /= private + shared + 1;
1112 }
1113
1114 return max(smin, period);
1115}
1116
1117static unsigned int task_scan_max(struct task_struct *p)
1118{
1119 unsigned long smin = task_scan_min(p);
1120 unsigned long smax;
1121
1122 /* Watch for min being lower than max due to floor calculations */
1123 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
1124
1125 /* Scale the maximum scan period with the amount of shared memory. */
1126 if (p->numa_group) {
1127 struct numa_group *ng = p->numa_group;
1128 unsigned long shared = group_faults_shared(ng);
1129 unsigned long private = group_faults_priv(ng);
1130 unsigned long period = smax;
1131
1132 period *= atomic_read(&ng->refcount);
1133 period *= shared + 1;
1134 period /= private + shared + 1;
1135
1136 smax = max(smax, period);
1137 }
1138
1139 return max(smin, smax);
1140}
1141
1142static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
1143{
1144 rq->nr_numa_running += (p->numa_preferred_nid != -1);
1145 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
1146}
1147
1148static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
1149{
1150 rq->nr_numa_running -= (p->numa_preferred_nid != -1);
1151 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
1152}
1153
1154/* Shared or private faults. */
1155#define NR_NUMA_HINT_FAULT_TYPES 2
1156
1157/* Memory and CPU locality */
1158#define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
1159
1160/* Averaged statistics, and temporary buffers. */
1161#define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
1162
1163pid_t task_numa_group_id(struct task_struct *p)
1164{
1165 return p->numa_group ? p->numa_group->gid : 0;
1166}
1167
1168/*
1169 * The averaged statistics, shared & private, memory & CPU,
1170 * occupy the first half of the array. The second half of the
1171 * array is for current counters, which are averaged into the
1172 * first set by task_numa_placement.
1173 */
1174static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
1175{
1176 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1177}
1178
1179static inline unsigned long task_faults(struct task_struct *p, int nid)
1180{
1181 if (!p->numa_faults)
1182 return 0;
1183
1184 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1185 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1186}
1187
1188static inline unsigned long group_faults(struct task_struct *p, int nid)
1189{
1190 if (!p->numa_group)
1191 return 0;
1192
1193 return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1194 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1195}
1196
1197static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
1198{
1199 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
1200 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1201}
1202
1203static inline unsigned long group_faults_priv(struct numa_group *ng)
1204{
1205 unsigned long faults = 0;
1206 int node;
1207
1208 for_each_online_node(node) {
1209 faults += ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
1210 }
1211
1212 return faults;
1213}
1214
1215static inline unsigned long group_faults_shared(struct numa_group *ng)
1216{
1217 unsigned long faults = 0;
1218 int node;
1219
1220 for_each_online_node(node) {
1221 faults += ng->faults[task_faults_idx(NUMA_MEM, node, 0)];
1222 }
1223
1224 return faults;
1225}
1226
1227/*
1228 * A node triggering more than 1/3 as many NUMA faults as the maximum is
1229 * considered part of a numa group's pseudo-interleaving set. Migrations
1230 * between these nodes are slowed down, to allow things to settle down.
1231 */
1232#define ACTIVE_NODE_FRACTION 3
1233
1234static bool numa_is_active_node(int nid, struct numa_group *ng)
1235{
1236 return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
1237}
1238
1239/* Handle placement on systems where not all nodes are directly connected. */
1240static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
1241 int maxdist, bool task)
1242{
1243 unsigned long score = 0;
1244 int node;
1245
1246 /*
1247 * All nodes are directly connected, and the same distance
1248 * from each other. No need for fancy placement algorithms.
1249 */
1250 if (sched_numa_topology_type == NUMA_DIRECT)
1251 return 0;
1252
1253 /*
1254 * This code is called for each node, introducing N^2 complexity,
1255 * which should be ok given the number of nodes rarely exceeds 8.
1256 */
1257 for_each_online_node(node) {
1258 unsigned long faults;
1259 int dist = node_distance(nid, node);
1260
1261 /*
1262 * The furthest away nodes in the system are not interesting
1263 * for placement; nid was already counted.
1264 */
1265 if (dist == sched_max_numa_distance || node == nid)
1266 continue;
1267
1268 /*
1269 * On systems with a backplane NUMA topology, compare groups
1270 * of nodes, and move tasks towards the group with the most
1271 * memory accesses. When comparing two nodes at distance
1272 * "hoplimit", only nodes closer by than "hoplimit" are part
1273 * of each group. Skip other nodes.
1274 */
1275 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1276 dist > maxdist)
1277 continue;
1278
1279 /* Add up the faults from nearby nodes. */
1280 if (task)
1281 faults = task_faults(p, node);
1282 else
1283 faults = group_faults(p, node);
1284
1285 /*
1286 * On systems with a glueless mesh NUMA topology, there are
1287 * no fixed "groups of nodes". Instead, nodes that are not
1288 * directly connected bounce traffic through intermediate
1289 * nodes; a numa_group can occupy any set of nodes.
1290 * The further away a node is, the less the faults count.
1291 * This seems to result in good task placement.
1292 */
1293 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1294 faults *= (sched_max_numa_distance - dist);
1295 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1296 }
1297
1298 score += faults;
1299 }
1300
1301 return score;
1302}
1303
1304/*
1305 * These return the fraction of accesses done by a particular task, or
1306 * task group, on a particular numa node. The group weight is given a
1307 * larger multiplier, in order to group tasks together that are almost
1308 * evenly spread out between numa nodes.
1309 */
1310static inline unsigned long task_weight(struct task_struct *p, int nid,
1311 int dist)
1312{
1313 unsigned long faults, total_faults;
1314
1315 if (!p->numa_faults)
1316 return 0;
1317
1318 total_faults = p->total_numa_faults;
1319
1320 if (!total_faults)
1321 return 0;
1322
1323 faults = task_faults(p, nid);
1324 faults += score_nearby_nodes(p, nid, dist, true);
1325
1326 return 1000 * faults / total_faults;
1327}
1328
1329static inline unsigned long group_weight(struct task_struct *p, int nid,
1330 int dist)
1331{
1332 unsigned long faults, total_faults;
1333
1334 if (!p->numa_group)
1335 return 0;
1336
1337 total_faults = p->numa_group->total_faults;
1338
1339 if (!total_faults)
1340 return 0;
1341
1342 faults = group_faults(p, nid);
1343 faults += score_nearby_nodes(p, nid, dist, false);
1344
1345 return 1000 * faults / total_faults;
1346}
1347
1348bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1349 int src_nid, int dst_cpu)
1350{
1351 struct numa_group *ng = p->numa_group;
1352 int dst_nid = cpu_to_node(dst_cpu);
1353 int last_cpupid, this_cpupid;
1354
1355 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1356
1357 /*
1358 * Multi-stage node selection is used in conjunction with a periodic
1359 * migration fault to build a temporal task<->page relation. By using
1360 * a two-stage filter we remove short/unlikely relations.
1361 *
1362 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1363 * a task's usage of a particular page (n_p) per total usage of this
1364 * page (n_t) (in a given time-span) to a probability.
1365 *
1366 * Our periodic faults will sample this probability and getting the
1367 * same result twice in a row, given these samples are fully
1368 * independent, is then given by P(n)^2, provided our sample period
1369 * is sufficiently short compared to the usage pattern.
1370 *
1371 * This quadric squishes small probabilities, making it less likely we
1372 * act on an unlikely task<->page relation.
1373 */
1374 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1375 if (!cpupid_pid_unset(last_cpupid) &&
1376 cpupid_to_nid(last_cpupid) != dst_nid)
1377 return false;
1378
1379 /* Always allow migrate on private faults */
1380 if (cpupid_match_pid(p, last_cpupid))
1381 return true;
1382
1383 /* A shared fault, but p->numa_group has not been set up yet. */
1384 if (!ng)
1385 return true;
1386
1387 /*
1388 * Destination node is much more heavily used than the source
1389 * node? Allow migration.
1390 */
1391 if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
1392 ACTIVE_NODE_FRACTION)
1393 return true;
1394
1395 /*
1396 * Distribute memory according to CPU & memory use on each node,
1397 * with 3/4 hysteresis to avoid unnecessary memory migrations:
1398 *
1399 * faults_cpu(dst) 3 faults_cpu(src)
1400 * --------------- * - > ---------------
1401 * faults_mem(dst) 4 faults_mem(src)
1402 */
1403 return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
1404 group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
1405}
1406
1407static unsigned long weighted_cpuload(struct rq *rq);
1408static unsigned long source_load(int cpu, int type);
1409static unsigned long target_load(int cpu, int type);
1410static unsigned long capacity_of(int cpu);
1411
1412/* Cached statistics for all CPUs within a node */
1413struct numa_stats {
1414 unsigned long nr_running;
1415 unsigned long load;
1416
1417 /* Total compute capacity of CPUs on a node */
1418 unsigned long compute_capacity;
1419
1420 /* Approximate capacity in terms of runnable tasks on a node */
1421 unsigned long task_capacity;
1422 int has_free_capacity;
1423};
1424
1425/*
1426 * XXX borrowed from update_sg_lb_stats
1427 */
1428static void update_numa_stats(struct numa_stats *ns, int nid)
1429{
1430 int smt, cpu, cpus = 0;
1431 unsigned long capacity;
1432
1433 memset(ns, 0, sizeof(*ns));
1434 for_each_cpu(cpu, cpumask_of_node(nid)) {
1435 struct rq *rq = cpu_rq(cpu);
1436
1437 ns->nr_running += rq->nr_running;
1438 ns->load += weighted_cpuload(rq);
1439 ns->compute_capacity += capacity_of(cpu);
1440
1441 cpus++;
1442 }
1443
1444 /*
1445 * If we raced with hotplug and there are no CPUs left in our mask
1446 * the @ns structure is NULL'ed and task_numa_compare() will
1447 * not find this node attractive.
1448 *
1449 * We'll either bail at !has_free_capacity, or we'll detect a huge
1450 * imbalance and bail there.
1451 */
1452 if (!cpus)
1453 return;
1454
1455 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1456 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1457 capacity = cpus / smt; /* cores */
1458
1459 ns->task_capacity = min_t(unsigned, capacity,
1460 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1461 ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1462}
1463
1464struct task_numa_env {
1465 struct task_struct *p;
1466
1467 int src_cpu, src_nid;
1468 int dst_cpu, dst_nid;
1469
1470 struct numa_stats src_stats, dst_stats;
1471
1472 int imbalance_pct;
1473 int dist;
1474
1475 struct task_struct *best_task;
1476 long best_imp;
1477 int best_cpu;
1478};
1479
1480static void task_numa_assign(struct task_numa_env *env,
1481 struct task_struct *p, long imp)
1482{
1483 if (env->best_task)
1484 put_task_struct(env->best_task);
1485 if (p)
1486 get_task_struct(p);
1487
1488 env->best_task = p;
1489 env->best_imp = imp;
1490 env->best_cpu = env->dst_cpu;
1491}
1492
1493static bool load_too_imbalanced(long src_load, long dst_load,
1494 struct task_numa_env *env)
1495{
1496 long imb, old_imb;
1497 long orig_src_load, orig_dst_load;
1498 long src_capacity, dst_capacity;
1499
1500 /*
1501 * The load is corrected for the CPU capacity available on each node.
1502 *
1503 * src_load dst_load
1504 * ------------ vs ---------
1505 * src_capacity dst_capacity
1506 */
1507 src_capacity = env->src_stats.compute_capacity;
1508 dst_capacity = env->dst_stats.compute_capacity;
1509
1510 /* We care about the slope of the imbalance, not the direction. */
1511 if (dst_load < src_load)
1512 swap(dst_load, src_load);
1513
1514 /* Is the difference below the threshold? */
1515 imb = dst_load * src_capacity * 100 -
1516 src_load * dst_capacity * env->imbalance_pct;
1517 if (imb <= 0)
1518 return false;
1519
1520 /*
1521 * The imbalance is above the allowed threshold.
1522 * Compare it with the old imbalance.
1523 */
1524 orig_src_load = env->src_stats.load;
1525 orig_dst_load = env->dst_stats.load;
1526
1527 if (orig_dst_load < orig_src_load)
1528 swap(orig_dst_load, orig_src_load);
1529
1530 old_imb = orig_dst_load * src_capacity * 100 -
1531 orig_src_load * dst_capacity * env->imbalance_pct;
1532
1533 /* Would this change make things worse? */
1534 return (imb > old_imb);
1535}
1536
1537/*
1538 * This checks if the overall compute and NUMA accesses of the system would
1539 * be improved if the source tasks was migrated to the target dst_cpu taking
1540 * into account that it might be best if task running on the dst_cpu should
1541 * be exchanged with the source task
1542 */
1543static void task_numa_compare(struct task_numa_env *env,
1544 long taskimp, long groupimp)
1545{
1546 struct rq *src_rq = cpu_rq(env->src_cpu);
1547 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1548 struct task_struct *cur;
1549 long src_load, dst_load;
1550 long load;
1551 long imp = env->p->numa_group ? groupimp : taskimp;
1552 long moveimp = imp;
1553 int dist = env->dist;
1554
1555 rcu_read_lock();
1556 cur = task_rcu_dereference(&dst_rq->curr);
1557 if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1558 cur = NULL;
1559
1560 /*
1561 * Because we have preemption enabled we can get migrated around and
1562 * end try selecting ourselves (current == env->p) as a swap candidate.
1563 */
1564 if (cur == env->p)
1565 goto unlock;
1566
1567 /*
1568 * "imp" is the fault differential for the source task between the
1569 * source and destination node. Calculate the total differential for
1570 * the source task and potential destination task. The more negative
1571 * the value is, the more rmeote accesses that would be expected to
1572 * be incurred if the tasks were swapped.
1573 */
1574 if (cur) {
1575 /* Skip this swap candidate if cannot move to the source CPU: */
1576 if (!cpumask_test_cpu(env->src_cpu, &cur->cpus_allowed))
1577 goto unlock;
1578
1579 /*
1580 * If dst and source tasks are in the same NUMA group, or not
1581 * in any group then look only at task weights.
1582 */
1583 if (cur->numa_group == env->p->numa_group) {
1584 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1585 task_weight(cur, env->dst_nid, dist);
1586 /*
1587 * Add some hysteresis to prevent swapping the
1588 * tasks within a group over tiny differences.
1589 */
1590 if (cur->numa_group)
1591 imp -= imp/16;
1592 } else {
1593 /*
1594 * Compare the group weights. If a task is all by
1595 * itself (not part of a group), use the task weight
1596 * instead.
1597 */
1598 if (cur->numa_group)
1599 imp += group_weight(cur, env->src_nid, dist) -
1600 group_weight(cur, env->dst_nid, dist);
1601 else
1602 imp += task_weight(cur, env->src_nid, dist) -
1603 task_weight(cur, env->dst_nid, dist);
1604 }
1605 }
1606
1607 if (imp <= env->best_imp && moveimp <= env->best_imp)
1608 goto unlock;
1609
1610 if (!cur) {
1611 /* Is there capacity at our destination? */
1612 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1613 !env->dst_stats.has_free_capacity)
1614 goto unlock;
1615
1616 goto balance;
1617 }
1618
1619 /* Balance doesn't matter much if we're running a task per CPU: */
1620 if (imp > env->best_imp && src_rq->nr_running == 1 &&
1621 dst_rq->nr_running == 1)
1622 goto assign;
1623
1624 /*
1625 * In the overloaded case, try and keep the load balanced.
1626 */
1627balance:
1628 load = task_h_load(env->p);
1629 dst_load = env->dst_stats.load + load;
1630 src_load = env->src_stats.load - load;
1631
1632 if (moveimp > imp && moveimp > env->best_imp) {
1633 /*
1634 * If the improvement from just moving env->p direction is
1635 * better than swapping tasks around, check if a move is
1636 * possible. Store a slightly smaller score than moveimp,
1637 * so an actually idle CPU will win.
1638 */
1639 if (!load_too_imbalanced(src_load, dst_load, env)) {
1640 imp = moveimp - 1;
1641 cur = NULL;
1642 goto assign;
1643 }
1644 }
1645
1646 if (imp <= env->best_imp)
1647 goto unlock;
1648
1649 if (cur) {
1650 load = task_h_load(cur);
1651 dst_load -= load;
1652 src_load += load;
1653 }
1654
1655 if (load_too_imbalanced(src_load, dst_load, env))
1656 goto unlock;
1657
1658 /*
1659 * One idle CPU per node is evaluated for a task numa move.
1660 * Call select_idle_sibling to maybe find a better one.
1661 */
1662 if (!cur) {
1663 /*
1664 * select_idle_siblings() uses an per-CPU cpumask that
1665 * can be used from IRQ context.
1666 */
1667 local_irq_disable();
1668 env->dst_cpu = select_idle_sibling(env->p, env->src_cpu,
1669 env->dst_cpu);
1670 local_irq_enable();
1671 }
1672
1673assign:
1674 task_numa_assign(env, cur, imp);
1675unlock:
1676 rcu_read_unlock();
1677}
1678
1679static void task_numa_find_cpu(struct task_numa_env *env,
1680 long taskimp, long groupimp)
1681{
1682 int cpu;
1683
1684 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1685 /* Skip this CPU if the source task cannot migrate */
1686 if (!cpumask_test_cpu(cpu, &env->p->cpus_allowed))
1687 continue;
1688
1689 env->dst_cpu = cpu;
1690 task_numa_compare(env, taskimp, groupimp);
1691 }
1692}
1693
1694/* Only move tasks to a NUMA node less busy than the current node. */
1695static bool numa_has_capacity(struct task_numa_env *env)
1696{
1697 struct numa_stats *src = &env->src_stats;
1698 struct numa_stats *dst = &env->dst_stats;
1699
1700 if (src->has_free_capacity && !dst->has_free_capacity)
1701 return false;
1702
1703 /*
1704 * Only consider a task move if the source has a higher load
1705 * than the destination, corrected for CPU capacity on each node.
1706 *
1707 * src->load dst->load
1708 * --------------------- vs ---------------------
1709 * src->compute_capacity dst->compute_capacity
1710 */
1711 if (src->load * dst->compute_capacity * env->imbalance_pct >
1712
1713 dst->load * src->compute_capacity * 100)
1714 return true;
1715
1716 return false;
1717}
1718
1719static int task_numa_migrate(struct task_struct *p)
1720{
1721 struct task_numa_env env = {
1722 .p = p,
1723
1724 .src_cpu = task_cpu(p),
1725 .src_nid = task_node(p),
1726
1727 .imbalance_pct = 112,
1728
1729 .best_task = NULL,
1730 .best_imp = 0,
1731 .best_cpu = -1,
1732 };
1733 struct sched_domain *sd;
1734 unsigned long taskweight, groupweight;
1735 int nid, ret, dist;
1736 long taskimp, groupimp;
1737
1738 /*
1739 * Pick the lowest SD_NUMA domain, as that would have the smallest
1740 * imbalance and would be the first to start moving tasks about.
1741 *
1742 * And we want to avoid any moving of tasks about, as that would create
1743 * random movement of tasks -- counter the numa conditions we're trying
1744 * to satisfy here.
1745 */
1746 rcu_read_lock();
1747 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1748 if (sd)
1749 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1750 rcu_read_unlock();
1751
1752 /*
1753 * Cpusets can break the scheduler domain tree into smaller
1754 * balance domains, some of which do not cross NUMA boundaries.
1755 * Tasks that are "trapped" in such domains cannot be migrated
1756 * elsewhere, so there is no point in (re)trying.
1757 */
1758 if (unlikely(!sd)) {
1759 p->numa_preferred_nid = task_node(p);
1760 return -EINVAL;
1761 }
1762
1763 env.dst_nid = p->numa_preferred_nid;
1764 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1765 taskweight = task_weight(p, env.src_nid, dist);
1766 groupweight = group_weight(p, env.src_nid, dist);
1767 update_numa_stats(&env.src_stats, env.src_nid);
1768 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1769 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1770 update_numa_stats(&env.dst_stats, env.dst_nid);
1771
1772 /* Try to find a spot on the preferred nid. */
1773 if (numa_has_capacity(&env))
1774 task_numa_find_cpu(&env, taskimp, groupimp);
1775
1776 /*
1777 * Look at other nodes in these cases:
1778 * - there is no space available on the preferred_nid
1779 * - the task is part of a numa_group that is interleaved across
1780 * multiple NUMA nodes; in order to better consolidate the group,
1781 * we need to check other locations.
1782 */
1783 if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
1784 for_each_online_node(nid) {
1785 if (nid == env.src_nid || nid == p->numa_preferred_nid)
1786 continue;
1787
1788 dist = node_distance(env.src_nid, env.dst_nid);
1789 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1790 dist != env.dist) {
1791 taskweight = task_weight(p, env.src_nid, dist);
1792 groupweight = group_weight(p, env.src_nid, dist);
1793 }
1794
1795 /* Only consider nodes where both task and groups benefit */
1796 taskimp = task_weight(p, nid, dist) - taskweight;
1797 groupimp = group_weight(p, nid, dist) - groupweight;
1798 if (taskimp < 0 && groupimp < 0)
1799 continue;
1800
1801 env.dist = dist;
1802 env.dst_nid = nid;
1803 update_numa_stats(&env.dst_stats, env.dst_nid);
1804 if (numa_has_capacity(&env))
1805 task_numa_find_cpu(&env, taskimp, groupimp);
1806 }
1807 }
1808
1809 /*
1810 * If the task is part of a workload that spans multiple NUMA nodes,
1811 * and is migrating into one of the workload's active nodes, remember
1812 * this node as the task's preferred numa node, so the workload can
1813 * settle down.
1814 * A task that migrated to a second choice node will be better off
1815 * trying for a better one later. Do not set the preferred node here.
1816 */
1817 if (p->numa_group) {
1818 struct numa_group *ng = p->numa_group;
1819
1820 if (env.best_cpu == -1)
1821 nid = env.src_nid;
1822 else
1823 nid = env.dst_nid;
1824
1825 if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng))
1826 sched_setnuma(p, env.dst_nid);
1827 }
1828
1829 /* No better CPU than the current one was found. */
1830 if (env.best_cpu == -1)
1831 return -EAGAIN;
1832
1833 /*
1834 * Reset the scan period if the task is being rescheduled on an
1835 * alternative node to recheck if the tasks is now properly placed.
1836 */
1837 p->numa_scan_period = task_scan_start(p);
1838
1839 if (env.best_task == NULL) {
1840 ret = migrate_task_to(p, env.best_cpu);
1841 if (ret != 0)
1842 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1843 return ret;
1844 }
1845
1846 ret = migrate_swap(p, env.best_task);
1847 if (ret != 0)
1848 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1849 put_task_struct(env.best_task);
1850 return ret;
1851}
1852
1853/* Attempt to migrate a task to a CPU on the preferred node. */
1854static void numa_migrate_preferred(struct task_struct *p)
1855{
1856 unsigned long interval = HZ;
1857
1858 /* This task has no NUMA fault statistics yet */
1859 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1860 return;
1861
1862 /* Periodically retry migrating the task to the preferred node */
1863 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1864 p->numa_migrate_retry = jiffies + interval;
1865
1866 /* Success if task is already running on preferred CPU */
1867 if (task_node(p) == p->numa_preferred_nid)
1868 return;
1869
1870 /* Otherwise, try migrate to a CPU on the preferred node */
1871 task_numa_migrate(p);
1872}
1873
1874/*
1875 * Find out how many nodes on the workload is actively running on. Do this by
1876 * tracking the nodes from which NUMA hinting faults are triggered. This can
1877 * be different from the set of nodes where the workload's memory is currently
1878 * located.
1879 */
1880static void numa_group_count_active_nodes(struct numa_group *numa_group)
1881{
1882 unsigned long faults, max_faults = 0;
1883 int nid, active_nodes = 0;
1884
1885 for_each_online_node(nid) {
1886 faults = group_faults_cpu(numa_group, nid);
1887 if (faults > max_faults)
1888 max_faults = faults;
1889 }
1890
1891 for_each_online_node(nid) {
1892 faults = group_faults_cpu(numa_group, nid);
1893 if (faults * ACTIVE_NODE_FRACTION > max_faults)
1894 active_nodes++;
1895 }
1896
1897 numa_group->max_faults_cpu = max_faults;
1898 numa_group->active_nodes = active_nodes;
1899}
1900
1901/*
1902 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1903 * increments. The more local the fault statistics are, the higher the scan
1904 * period will be for the next scan window. If local/(local+remote) ratio is
1905 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1906 * the scan period will decrease. Aim for 70% local accesses.
1907 */
1908#define NUMA_PERIOD_SLOTS 10
1909#define NUMA_PERIOD_THRESHOLD 7
1910
1911/*
1912 * Increase the scan period (slow down scanning) if the majority of
1913 * our memory is already on our local node, or if the majority of
1914 * the page accesses are shared with other processes.
1915 * Otherwise, decrease the scan period.
1916 */
1917static void update_task_scan_period(struct task_struct *p,
1918 unsigned long shared, unsigned long private)
1919{
1920 unsigned int period_slot;
1921 int lr_ratio, ps_ratio;
1922 int diff;
1923
1924 unsigned long remote = p->numa_faults_locality[0];
1925 unsigned long local = p->numa_faults_locality[1];
1926
1927 /*
1928 * If there were no record hinting faults then either the task is
1929 * completely idle or all activity is areas that are not of interest
1930 * to automatic numa balancing. Related to that, if there were failed
1931 * migration then it implies we are migrating too quickly or the local
1932 * node is overloaded. In either case, scan slower
1933 */
1934 if (local + shared == 0 || p->numa_faults_locality[2]) {
1935 p->numa_scan_period = min(p->numa_scan_period_max,
1936 p->numa_scan_period << 1);
1937
1938 p->mm->numa_next_scan = jiffies +
1939 msecs_to_jiffies(p->numa_scan_period);
1940
1941 return;
1942 }
1943
1944 /*
1945 * Prepare to scale scan period relative to the current period.
1946 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1947 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1948 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1949 */
1950 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1951 lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1952 ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);
1953
1954 if (ps_ratio >= NUMA_PERIOD_THRESHOLD) {
1955 /*
1956 * Most memory accesses are local. There is no need to
1957 * do fast NUMA scanning, since memory is already local.
1958 */
1959 int slot = ps_ratio - NUMA_PERIOD_THRESHOLD;
1960 if (!slot)
1961 slot = 1;
1962 diff = slot * period_slot;
1963 } else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
1964 /*
1965 * Most memory accesses are shared with other tasks.
1966 * There is no point in continuing fast NUMA scanning,
1967 * since other tasks may just move the memory elsewhere.
1968 */
1969 int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
1970 if (!slot)
1971 slot = 1;
1972 diff = slot * period_slot;
1973 } else {
1974 /*
1975 * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
1976 * yet they are not on the local NUMA node. Speed up
1977 * NUMA scanning to get the memory moved over.
1978 */
1979 int ratio = max(lr_ratio, ps_ratio);
1980 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1981 }
1982
1983 p->numa_scan_period = clamp(p->numa_scan_period + diff,
1984 task_scan_min(p), task_scan_max(p));
1985 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1986}
1987
1988/*
1989 * Get the fraction of time the task has been running since the last
1990 * NUMA placement cycle. The scheduler keeps similar statistics, but
1991 * decays those on a 32ms period, which is orders of magnitude off
1992 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1993 * stats only if the task is so new there are no NUMA statistics yet.
1994 */
1995static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1996{
1997 u64 runtime, delta, now;
1998 /* Use the start of this time slice to avoid calculations. */
1999 now = p->se.exec_start;
2000 runtime = p->se.sum_exec_runtime;
2001
2002 if (p->last_task_numa_placement) {
2003 delta = runtime - p->last_sum_exec_runtime;
2004 *period = now - p->last_task_numa_placement;
2005 } else {
2006 delta = p->se.avg.load_sum;
2007 *period = LOAD_AVG_MAX;
2008 }
2009
2010 p->last_sum_exec_runtime = runtime;
2011 p->last_task_numa_placement = now;
2012
2013 return delta;
2014}
2015
2016/*
2017 * Determine the preferred nid for a task in a numa_group. This needs to
2018 * be done in a way that produces consistent results with group_weight,
2019 * otherwise workloads might not converge.
2020 */
2021static int preferred_group_nid(struct task_struct *p, int nid)
2022{
2023 nodemask_t nodes;
2024 int dist;
2025
2026 /* Direct connections between all NUMA nodes. */
2027 if (sched_numa_topology_type == NUMA_DIRECT)
2028 return nid;
2029
2030 /*
2031 * On a system with glueless mesh NUMA topology, group_weight
2032 * scores nodes according to the number of NUMA hinting faults on
2033 * both the node itself, and on nearby nodes.
2034 */
2035 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
2036 unsigned long score, max_score = 0;
2037 int node, max_node = nid;
2038
2039 dist = sched_max_numa_distance;
2040
2041 for_each_online_node(node) {
2042 score = group_weight(p, node, dist);
2043 if (score > max_score) {
2044 max_score = score;
2045 max_node = node;
2046 }
2047 }
2048 return max_node;
2049 }
2050
2051 /*
2052 * Finding the preferred nid in a system with NUMA backplane
2053 * interconnect topology is more involved. The goal is to locate
2054 * tasks from numa_groups near each other in the system, and
2055 * untangle workloads from different sides of the system. This requires
2056 * searching down the hierarchy of node groups, recursively searching
2057 * inside the highest scoring group of nodes. The nodemask tricks
2058 * keep the complexity of the search down.
2059 */
2060 nodes = node_online_map;
2061 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
2062 unsigned long max_faults = 0;
2063 nodemask_t max_group = NODE_MASK_NONE;
2064 int a, b;
2065
2066 /* Are there nodes at this distance from each other? */
2067 if (!find_numa_distance(dist))
2068 continue;
2069
2070 for_each_node_mask(a, nodes) {
2071 unsigned long faults = 0;
2072 nodemask_t this_group;
2073 nodes_clear(this_group);
2074
2075 /* Sum group's NUMA faults; includes a==b case. */
2076 for_each_node_mask(b, nodes) {
2077 if (node_distance(a, b) < dist) {
2078 faults += group_faults(p, b);
2079 node_set(b, this_group);
2080 node_clear(b, nodes);
2081 }
2082 }
2083
2084 /* Remember the top group. */
2085 if (faults > max_faults) {
2086 max_faults = faults;
2087 max_group = this_group;
2088 /*
2089 * subtle: at the smallest distance there is
2090 * just one node left in each "group", the
2091 * winner is the preferred nid.
2092 */
2093 nid = a;
2094 }
2095 }
2096 /* Next round, evaluate the nodes within max_group. */
2097 if (!max_faults)
2098 break;
2099 nodes = max_group;
2100 }
2101 return nid;
2102}
2103
2104static void task_numa_placement(struct task_struct *p)
2105{
2106 int seq, nid, max_nid = -1, max_group_nid = -1;
2107 unsigned long max_faults = 0, max_group_faults = 0;
2108 unsigned long fault_types[2] = { 0, 0 };
2109 unsigned long total_faults;
2110 u64 runtime, period;
2111 spinlock_t *group_lock = NULL;
2112
2113 /*
2114 * The p->mm->numa_scan_seq field gets updated without
2115 * exclusive access. Use READ_ONCE() here to ensure
2116 * that the field is read in a single access:
2117 */
2118 seq = READ_ONCE(p->mm->numa_scan_seq);
2119 if (p->numa_scan_seq == seq)
2120 return;
2121 p->numa_scan_seq = seq;
2122 p->numa_scan_period_max = task_scan_max(p);
2123
2124 total_faults = p->numa_faults_locality[0] +
2125 p->numa_faults_locality[1];
2126 runtime = numa_get_avg_runtime(p, &period);
2127
2128 /* If the task is part of a group prevent parallel updates to group stats */
2129 if (p->numa_group) {
2130 group_lock = &p->numa_group->lock;
2131 spin_lock_irq(group_lock);
2132 }
2133
2134 /* Find the node with the highest number of faults */
2135 for_each_online_node(nid) {
2136 /* Keep track of the offsets in numa_faults array */
2137 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
2138 unsigned long faults = 0, group_faults = 0;
2139 int priv;
2140
2141 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
2142 long diff, f_diff, f_weight;
2143
2144 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
2145 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
2146 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
2147 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
2148
2149 /* Decay existing window, copy faults since last scan */
2150 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
2151 fault_types[priv] += p->numa_faults[membuf_idx];
2152 p->numa_faults[membuf_idx] = 0;
2153
2154 /*
2155 * Normalize the faults_from, so all tasks in a group
2156 * count according to CPU use, instead of by the raw
2157 * number of faults. Tasks with little runtime have
2158 * little over-all impact on throughput, and thus their
2159 * faults are less important.
2160 */
2161 f_weight = div64_u64(runtime << 16, period + 1);
2162 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
2163 (total_faults + 1);
2164 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
2165 p->numa_faults[cpubuf_idx] = 0;
2166
2167 p->numa_faults[mem_idx] += diff;
2168 p->numa_faults[cpu_idx] += f_diff;
2169 faults += p->numa_faults[mem_idx];
2170 p->total_numa_faults += diff;
2171 if (p->numa_group) {
2172 /*
2173 * safe because we can only change our own group
2174 *
2175 * mem_idx represents the offset for a given
2176 * nid and priv in a specific region because it
2177 * is at the beginning of the numa_faults array.
2178 */
2179 p->numa_group->faults[mem_idx] += diff;
2180 p->numa_group->faults_cpu[mem_idx] += f_diff;
2181 p->numa_group->total_faults += diff;
2182 group_faults += p->numa_group->faults[mem_idx];
2183 }
2184 }
2185
2186 if (faults > max_faults) {
2187 max_faults = faults;
2188 max_nid = nid;
2189 }
2190
2191 if (group_faults > max_group_faults) {
2192 max_group_faults = group_faults;
2193 max_group_nid = nid;
2194 }
2195 }
2196
2197 update_task_scan_period(p, fault_types[0], fault_types[1]);
2198
2199 if (p->numa_group) {
2200 numa_group_count_active_nodes(p->numa_group);
2201 spin_unlock_irq(group_lock);
2202 max_nid = preferred_group_nid(p, max_group_nid);
2203 }
2204
2205 if (max_faults) {
2206 /* Set the new preferred node */
2207 if (max_nid != p->numa_preferred_nid)
2208 sched_setnuma(p, max_nid);
2209
2210 if (task_node(p) != p->numa_preferred_nid)
2211 numa_migrate_preferred(p);
2212 }
2213}
2214
2215static inline int get_numa_group(struct numa_group *grp)
2216{
2217 return atomic_inc_not_zero(&grp->refcount);
2218}
2219
2220static inline void put_numa_group(struct numa_group *grp)
2221{
2222 if (atomic_dec_and_test(&grp->refcount))
2223 kfree_rcu(grp, rcu);
2224}
2225
2226static void task_numa_group(struct task_struct *p, int cpupid, int flags,
2227 int *priv)
2228{
2229 struct numa_group *grp, *my_grp;
2230 struct task_struct *tsk;
2231 bool join = false;
2232 int cpu = cpupid_to_cpu(cpupid);
2233 int i;
2234
2235 if (unlikely(!p->numa_group)) {
2236 unsigned int size = sizeof(struct numa_group) +
2237 4*nr_node_ids*sizeof(unsigned long);
2238
2239 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
2240 if (!grp)
2241 return;
2242
2243 atomic_set(&grp->refcount, 1);
2244 grp->active_nodes = 1;
2245 grp->max_faults_cpu = 0;
2246 spin_lock_init(&grp->lock);
2247 grp->gid = p->pid;
2248 /* Second half of the array tracks nids where faults happen */
2249 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
2250 nr_node_ids;
2251
2252 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2253 grp->faults[i] = p->numa_faults[i];
2254
2255 grp->total_faults = p->total_numa_faults;
2256
2257 grp->nr_tasks++;
2258 rcu_assign_pointer(p->numa_group, grp);
2259 }
2260
2261 rcu_read_lock();
2262 tsk = READ_ONCE(cpu_rq(cpu)->curr);
2263
2264 if (!cpupid_match_pid(tsk, cpupid))
2265 goto no_join;
2266
2267 grp = rcu_dereference(tsk->numa_group);
2268 if (!grp)
2269 goto no_join;
2270
2271 my_grp = p->numa_group;
2272 if (grp == my_grp)
2273 goto no_join;
2274
2275 /*
2276 * Only join the other group if its bigger; if we're the bigger group,
2277 * the other task will join us.
2278 */
2279 if (my_grp->nr_tasks > grp->nr_tasks)
2280 goto no_join;
2281
2282 /*
2283 * Tie-break on the grp address.
2284 */
2285 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2286 goto no_join;
2287
2288 /* Always join threads in the same process. */
2289 if (tsk->mm == current->mm)
2290 join = true;
2291
2292 /* Simple filter to avoid false positives due to PID collisions */
2293 if (flags & TNF_SHARED)
2294 join = true;
2295
2296 /* Update priv based on whether false sharing was detected */
2297 *priv = !join;
2298
2299 if (join && !get_numa_group(grp))
2300 goto no_join;
2301
2302 rcu_read_unlock();
2303
2304 if (!join)
2305 return;
2306
2307 BUG_ON(irqs_disabled());
2308 double_lock_irq(&my_grp->lock, &grp->lock);
2309
2310 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2311 my_grp->faults[i] -= p->numa_faults[i];
2312 grp->faults[i] += p->numa_faults[i];
2313 }
2314 my_grp->total_faults -= p->total_numa_faults;
2315 grp->total_faults += p->total_numa_faults;
2316
2317 my_grp->nr_tasks--;
2318 grp->nr_tasks++;
2319
2320 spin_unlock(&my_grp->lock);
2321 spin_unlock_irq(&grp->lock);
2322
2323 rcu_assign_pointer(p->numa_group, grp);
2324
2325 put_numa_group(my_grp);
2326 return;
2327
2328no_join:
2329 rcu_read_unlock();
2330 return;
2331}
2332
2333void task_numa_free(struct task_struct *p)
2334{
2335 struct numa_group *grp = p->numa_group;
2336 void *numa_faults = p->numa_faults;
2337 unsigned long flags;
2338 int i;
2339
2340 if (grp) {
2341 spin_lock_irqsave(&grp->lock, flags);
2342 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2343 grp->faults[i] -= p->numa_faults[i];
2344 grp->total_faults -= p->total_numa_faults;
2345
2346 grp->nr_tasks--;
2347 spin_unlock_irqrestore(&grp->lock, flags);
2348 RCU_INIT_POINTER(p->numa_group, NULL);
2349 put_numa_group(grp);
2350 }
2351
2352 p->numa_faults = NULL;
2353 kfree(numa_faults);
2354}
2355
2356/*
2357 * Got a PROT_NONE fault for a page on @node.
2358 */
2359void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2360{
2361 struct task_struct *p = current;
2362 bool migrated = flags & TNF_MIGRATED;
2363 int cpu_node = task_node(current);
2364 int local = !!(flags & TNF_FAULT_LOCAL);
2365 struct numa_group *ng;
2366 int priv;
2367
2368 if (!static_branch_likely(&sched_numa_balancing))
2369 return;
2370
2371 /* for example, ksmd faulting in a user's mm */
2372 if (!p->mm)
2373 return;
2374
2375 /* Allocate buffer to track faults on a per-node basis */
2376 if (unlikely(!p->numa_faults)) {
2377 int size = sizeof(*p->numa_faults) *
2378 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2379
2380 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2381 if (!p->numa_faults)
2382 return;
2383
2384 p->total_numa_faults = 0;
2385 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2386 }
2387
2388 /*
2389 * First accesses are treated as private, otherwise consider accesses
2390 * to be private if the accessing pid has not changed
2391 */
2392 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2393 priv = 1;
2394 } else {
2395 priv = cpupid_match_pid(p, last_cpupid);
2396 if (!priv && !(flags & TNF_NO_GROUP))
2397 task_numa_group(p, last_cpupid, flags, &priv);
2398 }
2399
2400 /*
2401 * If a workload spans multiple NUMA nodes, a shared fault that
2402 * occurs wholly within the set of nodes that the workload is
2403 * actively using should be counted as local. This allows the
2404 * scan rate to slow down when a workload has settled down.
2405 */
2406 ng = p->numa_group;
2407 if (!priv && !local && ng && ng->active_nodes > 1 &&
2408 numa_is_active_node(cpu_node, ng) &&
2409 numa_is_active_node(mem_node, ng))
2410 local = 1;
2411
2412 task_numa_placement(p);
2413
2414 /*
2415 * Retry task to preferred node migration periodically, in case it
2416 * case it previously failed, or the scheduler moved us.
2417 */
2418 if (time_after(jiffies, p->numa_migrate_retry))
2419 numa_migrate_preferred(p);
2420
2421 if (migrated)
2422 p->numa_pages_migrated += pages;
2423 if (flags & TNF_MIGRATE_FAIL)
2424 p->numa_faults_locality[2] += pages;
2425
2426 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2427 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2428 p->numa_faults_locality[local] += pages;
2429}
2430
2431static void reset_ptenuma_scan(struct task_struct *p)
2432{
2433 /*
2434 * We only did a read acquisition of the mmap sem, so
2435 * p->mm->numa_scan_seq is written to without exclusive access
2436 * and the update is not guaranteed to be atomic. That's not
2437 * much of an issue though, since this is just used for
2438 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2439 * expensive, to avoid any form of compiler optimizations:
2440 */
2441 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2442 p->mm->numa_scan_offset = 0;
2443}
2444
2445/*
2446 * The expensive part of numa migration is done from task_work context.
2447 * Triggered from task_tick_numa().
2448 */
2449void task_numa_work(struct callback_head *work)
2450{
2451 unsigned long migrate, next_scan, now = jiffies;
2452 struct task_struct *p = current;
2453 struct mm_struct *mm = p->mm;
2454 u64 runtime = p->se.sum_exec_runtime;
2455 struct vm_area_struct *vma;
2456 unsigned long start, end;
2457 unsigned long nr_pte_updates = 0;
2458 long pages, virtpages;
2459
2460 SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
2461
2462 work->next = work; /* protect against double add */
2463 /*
2464 * Who cares about NUMA placement when they're dying.
2465 *
2466 * NOTE: make sure not to dereference p->mm before this check,
2467 * exit_task_work() happens _after_ exit_mm() so we could be called
2468 * without p->mm even though we still had it when we enqueued this
2469 * work.
2470 */
2471 if (p->flags & PF_EXITING)
2472 return;
2473
2474 if (!mm->numa_next_scan) {
2475 mm->numa_next_scan = now +
2476 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2477 }
2478
2479 /*
2480 * Enforce maximal scan/migration frequency..
2481 */
2482 migrate = mm->numa_next_scan;
2483 if (time_before(now, migrate))
2484 return;
2485
2486 if (p->numa_scan_period == 0) {
2487 p->numa_scan_period_max = task_scan_max(p);
2488 p->numa_scan_period = task_scan_start(p);
2489 }
2490
2491 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2492 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2493 return;
2494
2495 /*
2496 * Delay this task enough that another task of this mm will likely win
2497 * the next time around.
2498 */
2499 p->node_stamp += 2 * TICK_NSEC;
2500
2501 start = mm->numa_scan_offset;
2502 pages = sysctl_numa_balancing_scan_size;
2503 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2504 virtpages = pages * 8; /* Scan up to this much virtual space */
2505 if (!pages)
2506 return;
2507
2508
2509 if (!down_read_trylock(&mm->mmap_sem))
2510 return;
2511 vma = find_vma(mm, start);
2512 if (!vma) {
2513 reset_ptenuma_scan(p);
2514 start = 0;
2515 vma = mm->mmap;
2516 }
2517 for (; vma; vma = vma->vm_next) {
2518 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2519 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2520 continue;
2521 }
2522
2523 /*
2524 * Shared library pages mapped by multiple processes are not
2525 * migrated as it is expected they are cache replicated. Avoid
2526 * hinting faults in read-only file-backed mappings or the vdso
2527 * as migrating the pages will be of marginal benefit.
2528 */
2529 if (!vma->vm_mm ||
2530 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2531 continue;
2532
2533 /*
2534 * Skip inaccessible VMAs to avoid any confusion between
2535 * PROT_NONE and NUMA hinting ptes
2536 */
2537 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2538 continue;
2539
2540 do {
2541 start = max(start, vma->vm_start);
2542 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2543 end = min(end, vma->vm_end);
2544 nr_pte_updates = change_prot_numa(vma, start, end);
2545
2546 /*
2547 * Try to scan sysctl_numa_balancing_size worth of
2548 * hpages that have at least one present PTE that
2549 * is not already pte-numa. If the VMA contains
2550 * areas that are unused or already full of prot_numa
2551 * PTEs, scan up to virtpages, to skip through those
2552 * areas faster.
2553 */
2554 if (nr_pte_updates)
2555 pages -= (end - start) >> PAGE_SHIFT;
2556 virtpages -= (end - start) >> PAGE_SHIFT;
2557
2558 start = end;
2559 if (pages <= 0 || virtpages <= 0)
2560 goto out;
2561
2562 cond_resched();
2563 } while (end != vma->vm_end);
2564 }
2565
2566out:
2567 /*
2568 * It is possible to reach the end of the VMA list but the last few
2569 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2570 * would find the !migratable VMA on the next scan but not reset the
2571 * scanner to the start so check it now.
2572 */
2573 if (vma)
2574 mm->numa_scan_offset = start;
2575 else
2576 reset_ptenuma_scan(p);
2577 up_read(&mm->mmap_sem);
2578
2579 /*
2580 * Make sure tasks use at least 32x as much time to run other code
2581 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2582 * Usually update_task_scan_period slows down scanning enough; on an
2583 * overloaded system we need to limit overhead on a per task basis.
2584 */
2585 if (unlikely(p->se.sum_exec_runtime != runtime)) {
2586 u64 diff = p->se.sum_exec_runtime - runtime;
2587 p->node_stamp += 32 * diff;
2588 }
2589}
2590
2591/*
2592 * Drive the periodic memory faults..
2593 */
2594void task_tick_numa(struct rq *rq, struct task_struct *curr)
2595{
2596 struct callback_head *work = &curr->numa_work;
2597 u64 period, now;
2598
2599 /*
2600 * We don't care about NUMA placement if we don't have memory.
2601 */
2602 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2603 return;
2604
2605 /*
2606 * Using runtime rather than walltime has the dual advantage that
2607 * we (mostly) drive the selection from busy threads and that the
2608 * task needs to have done some actual work before we bother with
2609 * NUMA placement.
2610 */
2611 now = curr->se.sum_exec_runtime;
2612 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2613
2614 if (now > curr->node_stamp + period) {
2615 if (!curr->node_stamp)
2616 curr->numa_scan_period = task_scan_start(curr);
2617 curr->node_stamp += period;
2618
2619 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2620 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2621 task_work_add(curr, work, true);
2622 }
2623 }
2624}
2625
2626#else
2627static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2628{
2629}
2630
2631static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2632{
2633}
2634
2635static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2636{
2637}
2638
2639#endif /* CONFIG_NUMA_BALANCING */
2640
2641static void
2642account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2643{
2644 update_load_add(&cfs_rq->load, se->load.weight);
2645 if (!parent_entity(se))
2646 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2647#ifdef CONFIG_SMP
2648 if (entity_is_task(se)) {
2649 struct rq *rq = rq_of(cfs_rq);
2650
2651 account_numa_enqueue(rq, task_of(se));
2652 list_add(&se->group_node, &rq->cfs_tasks);
2653 }
2654#endif
2655 cfs_rq->nr_running++;
2656}
2657
2658static void
2659account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2660{
2661 update_load_sub(&cfs_rq->load, se->load.weight);
2662 if (!parent_entity(se))
2663 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2664#ifdef CONFIG_SMP
2665 if (entity_is_task(se)) {
2666 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2667 list_del_init(&se->group_node);
2668 }
2669#endif
2670 cfs_rq->nr_running--;
2671}
2672
2673/*
2674 * Signed add and clamp on underflow.
2675 *
2676 * Explicitly do a load-store to ensure the intermediate value never hits
2677 * memory. This allows lockless observations without ever seeing the negative
2678 * values.
2679 */
2680#define add_positive(_ptr, _val) do { \
2681 typeof(_ptr) ptr = (_ptr); \
2682 typeof(_val) val = (_val); \
2683 typeof(*ptr) res, var = READ_ONCE(*ptr); \
2684 \
2685 res = var + val; \
2686 \
2687 if (val < 0 && res > var) \
2688 res = 0; \
2689 \
2690 WRITE_ONCE(*ptr, res); \
2691} while (0)
2692
2693/*
2694 * Unsigned subtract and clamp on underflow.
2695 *
2696 * Explicitly do a load-store to ensure the intermediate value never hits
2697 * memory. This allows lockless observations without ever seeing the negative
2698 * values.
2699 */
2700#define sub_positive(_ptr, _val) do { \
2701 typeof(_ptr) ptr = (_ptr); \
2702 typeof(*ptr) val = (_val); \
2703 typeof(*ptr) res, var = READ_ONCE(*ptr); \
2704 res = var - val; \
2705 if (res > var) \
2706 res = 0; \
2707 WRITE_ONCE(*ptr, res); \
2708} while (0)
2709
2710#ifdef CONFIG_SMP
2711/*
2712 * XXX we want to get rid of these helpers and use the full load resolution.
2713 */
2714static inline long se_weight(struct sched_entity *se)
2715{
2716 return scale_load_down(se->load.weight);
2717}
2718
2719static inline long se_runnable(struct sched_entity *se)
2720{
2721 return scale_load_down(se->runnable_weight);
2722}
2723
2724static inline void
2725enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2726{
2727 cfs_rq->runnable_weight += se->runnable_weight;
2728
2729 cfs_rq->avg.runnable_load_avg += se->avg.runnable_load_avg;
2730 cfs_rq->avg.runnable_load_sum += se_runnable(se) * se->avg.runnable_load_sum;
2731}
2732
2733static inline void
2734dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2735{
2736 cfs_rq->runnable_weight -= se->runnable_weight;
2737
2738 sub_positive(&cfs_rq->avg.runnable_load_avg, se->avg.runnable_load_avg);
2739 sub_positive(&cfs_rq->avg.runnable_load_sum,
2740 se_runnable(se) * se->avg.runnable_load_sum);
2741}
2742
2743static inline void
2744enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2745{
2746 cfs_rq->avg.load_avg += se->avg.load_avg;
2747 cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
2748}
2749
2750static inline void
2751dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2752{
2753 sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
2754 sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum);
2755}
2756#else
2757static inline void
2758enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
2759static inline void
2760dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
2761static inline void
2762enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
2763static inline void
2764dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
2765#endif
2766
2767static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2768 unsigned long weight, unsigned long runnable)
2769{
2770 if (se->on_rq) {
2771 /* commit outstanding execution time */
2772 if (cfs_rq->curr == se)
2773 update_curr(cfs_rq);
2774 account_entity_dequeue(cfs_rq, se);
2775 dequeue_runnable_load_avg(cfs_rq, se);
2776 }
2777 dequeue_load_avg(cfs_rq, se);
2778
2779 se->runnable_weight = runnable;
2780 update_load_set(&se->load, weight);
2781
2782#ifdef CONFIG_SMP
2783 do {
2784 u32 divider = LOAD_AVG_MAX - 1024 + se->avg.period_contrib;
2785
2786 se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider);
2787 se->avg.runnable_load_avg =
2788 div_u64(se_runnable(se) * se->avg.runnable_load_sum, divider);
2789 } while (0);
2790#endif
2791
2792 enqueue_load_avg(cfs_rq, se);
2793 if (se->on_rq) {
2794 account_entity_enqueue(cfs_rq, se);
2795 enqueue_runnable_load_avg(cfs_rq, se);
2796 }
2797}
2798
2799void reweight_task(struct task_struct *p, int prio)
2800{
2801 struct sched_entity *se = &p->se;
2802 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2803 struct load_weight *load = &se->load;
2804 unsigned long weight = scale_load(sched_prio_to_weight[prio]);
2805
2806 reweight_entity(cfs_rq, se, weight, weight);
2807 load->inv_weight = sched_prio_to_wmult[prio];
2808}
2809
2810#ifdef CONFIG_FAIR_GROUP_SCHED
2811#ifdef CONFIG_SMP
2812/*
2813 * All this does is approximate the hierarchical proportion which includes that
2814 * global sum we all love to hate.
2815 *
2816 * That is, the weight of a group entity, is the proportional share of the
2817 * group weight based on the group runqueue weights. That is:
2818 *
2819 * tg->weight * grq->load.weight
2820 * ge->load.weight = ----------------------------- (1)
2821 * \Sum grq->load.weight
2822 *
2823 * Now, because computing that sum is prohibitively expensive to compute (been
2824 * there, done that) we approximate it with this average stuff. The average
2825 * moves slower and therefore the approximation is cheaper and more stable.
2826 *
2827 * So instead of the above, we substitute:
2828 *
2829 * grq->load.weight -> grq->avg.load_avg (2)
2830 *
2831 * which yields the following:
2832 *
2833 * tg->weight * grq->avg.load_avg
2834 * ge->load.weight = ------------------------------ (3)
2835 * tg->load_avg
2836 *
2837 * Where: tg->load_avg ~= \Sum grq->avg.load_avg
2838 *
2839 * That is shares_avg, and it is right (given the approximation (2)).
2840 *
2841 * The problem with it is that because the average is slow -- it was designed
2842 * to be exactly that of course -- this leads to transients in boundary
2843 * conditions. In specific, the case where the group was idle and we start the
2844 * one task. It takes time for our CPU's grq->avg.load_avg to build up,
2845 * yielding bad latency etc..
2846 *
2847 * Now, in that special case (1) reduces to:
2848 *
2849 * tg->weight * grq->load.weight
2850 * ge->load.weight = ----------------------------- = tg->weight (4)
2851 * grp->load.weight
2852 *
2853 * That is, the sum collapses because all other CPUs are idle; the UP scenario.
2854 *
2855 * So what we do is modify our approximation (3) to approach (4) in the (near)
2856 * UP case, like:
2857 *
2858 * ge->load.weight =
2859 *
2860 * tg->weight * grq->load.weight
2861 * --------------------------------------------------- (5)
2862 * tg->load_avg - grq->avg.load_avg + grq->load.weight
2863 *
2864 * But because grq->load.weight can drop to 0, resulting in a divide by zero,
2865 * we need to use grq->avg.load_avg as its lower bound, which then gives:
2866 *
2867 *
2868 * tg->weight * grq->load.weight
2869 * ge->load.weight = ----------------------------- (6)
2870 * tg_load_avg'
2871 *
2872 * Where:
2873 *
2874 * tg_load_avg' = tg->load_avg - grq->avg.load_avg +
2875 * max(grq->load.weight, grq->avg.load_avg)
2876 *
2877 * And that is shares_weight and is icky. In the (near) UP case it approaches
2878 * (4) while in the normal case it approaches (3). It consistently
2879 * overestimates the ge->load.weight and therefore:
2880 *
2881 * \Sum ge->load.weight >= tg->weight
2882 *
2883 * hence icky!
2884 */
2885static long calc_group_shares(struct cfs_rq *cfs_rq)
2886{
2887 long tg_weight, tg_shares, load, shares;
2888 struct task_group *tg = cfs_rq->tg;
2889
2890 tg_shares = READ_ONCE(tg->shares);
2891
2892 load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
2893
2894 tg_weight = atomic_long_read(&tg->load_avg);
2895
2896 /* Ensure tg_weight >= load */
2897 tg_weight -= cfs_rq->tg_load_avg_contrib;
2898 tg_weight += load;
2899
2900 shares = (tg_shares * load);
2901 if (tg_weight)
2902 shares /= tg_weight;
2903
2904 /*
2905 * MIN_SHARES has to be unscaled here to support per-CPU partitioning
2906 * of a group with small tg->shares value. It is a floor value which is
2907 * assigned as a minimum load.weight to the sched_entity representing
2908 * the group on a CPU.
2909 *
2910 * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024
2911 * on an 8-core system with 8 tasks each runnable on one CPU shares has
2912 * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In
2913 * case no task is runnable on a CPU MIN_SHARES=2 should be returned
2914 * instead of 0.
2915 */
2916 return clamp_t(long, shares, MIN_SHARES, tg_shares);
2917}
2918
2919/*
2920 * This calculates the effective runnable weight for a group entity based on
2921 * the group entity weight calculated above.
2922 *
2923 * Because of the above approximation (2), our group entity weight is
2924 * an load_avg based ratio (3). This means that it includes blocked load and
2925 * does not represent the runnable weight.
2926 *
2927 * Approximate the group entity's runnable weight per ratio from the group
2928 * runqueue:
2929 *
2930 * grq->avg.runnable_load_avg
2931 * ge->runnable_weight = ge->load.weight * -------------------------- (7)
2932 * grq->avg.load_avg
2933 *
2934 * However, analogous to above, since the avg numbers are slow, this leads to
2935 * transients in the from-idle case. Instead we use:
2936 *
2937 * ge->runnable_weight = ge->load.weight *
2938 *
2939 * max(grq->avg.runnable_load_avg, grq->runnable_weight)
2940 * ----------------------------------------------------- (8)
2941 * max(grq->avg.load_avg, grq->load.weight)
2942 *
2943 * Where these max() serve both to use the 'instant' values to fix the slow
2944 * from-idle and avoid the /0 on to-idle, similar to (6).
2945 */
2946static long calc_group_runnable(struct cfs_rq *cfs_rq, long shares)
2947{
2948 long runnable, load_avg;
2949
2950 load_avg = max(cfs_rq->avg.load_avg,
2951 scale_load_down(cfs_rq->load.weight));
2952
2953 runnable = max(cfs_rq->avg.runnable_load_avg,
2954 scale_load_down(cfs_rq->runnable_weight));
2955
2956 runnable *= shares;
2957 if (load_avg)
2958 runnable /= load_avg;
2959
2960 return clamp_t(long, runnable, MIN_SHARES, shares);
2961}
2962#endif /* CONFIG_SMP */
2963
2964static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2965
2966/*
2967 * Recomputes the group entity based on the current state of its group
2968 * runqueue.
2969 */
2970static void update_cfs_group(struct sched_entity *se)
2971{
2972 struct cfs_rq *gcfs_rq = group_cfs_rq(se);
2973 long shares, runnable;
2974
2975 if (!gcfs_rq)
2976 return;
2977
2978 if (throttled_hierarchy(gcfs_rq))
2979 return;
2980
2981#ifndef CONFIG_SMP
2982 runnable = shares = READ_ONCE(gcfs_rq->tg->shares);
2983
2984 if (likely(se->load.weight == shares))
2985 return;
2986#else
2987 shares = calc_group_shares(gcfs_rq);
2988 runnable = calc_group_runnable(gcfs_rq, shares);
2989#endif
2990
2991 reweight_entity(cfs_rq_of(se), se, shares, runnable);
2992}
2993
2994#else /* CONFIG_FAIR_GROUP_SCHED */
2995static inline void update_cfs_group(struct sched_entity *se)
2996{
2997}
2998#endif /* CONFIG_FAIR_GROUP_SCHED */
2999
3000static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
3001{
3002 struct rq *rq = rq_of(cfs_rq);
3003
3004 if (&rq->cfs == cfs_rq || (flags & SCHED_CPUFREQ_MIGRATION)) {
3005 /*
3006 * There are a few boundary cases this might miss but it should
3007 * get called often enough that that should (hopefully) not be
3008 * a real problem.
3009 *
3010 * It will not get called when we go idle, because the idle
3011 * thread is a different class (!fair), nor will the utilization
3012 * number include things like RT tasks.
3013 *
3014 * As is, the util number is not freq-invariant (we'd have to
3015 * implement arch_scale_freq_capacity() for that).
3016 *
3017 * See cpu_util().
3018 */
3019 cpufreq_update_util(rq, flags);
3020 }
3021}
3022
3023#ifdef CONFIG_SMP
3024/*
3025 * Approximate:
3026 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
3027 */
3028static u64 decay_load(u64 val, u64 n)
3029{
3030 unsigned int local_n;
3031
3032 if (unlikely(n > LOAD_AVG_PERIOD * 63))
3033 return 0;
3034
3035 /* after bounds checking we can collapse to 32-bit */
3036 local_n = n;
3037
3038 /*
3039 * As y^PERIOD = 1/2, we can combine
3040 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
3041 * With a look-up table which covers y^n (n<PERIOD)
3042 *
3043 * To achieve constant time decay_load.
3044 */
3045 if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
3046 val >>= local_n / LOAD_AVG_PERIOD;
3047 local_n %= LOAD_AVG_PERIOD;
3048 }
3049
3050 val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
3051 return val;
3052}
3053
3054static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3)
3055{
3056 u32 c1, c2, c3 = d3; /* y^0 == 1 */
3057
3058 /*
3059 * c1 = d1 y^p
3060 */
3061 c1 = decay_load((u64)d1, periods);
3062
3063 /*
3064 * p-1
3065 * c2 = 1024 \Sum y^n
3066 * n=1
3067 *
3068 * inf inf
3069 * = 1024 ( \Sum y^n - \Sum y^n - y^0 )
3070 * n=0 n=p
3071 */
3072 c2 = LOAD_AVG_MAX - decay_load(LOAD_AVG_MAX, periods) - 1024;
3073
3074 return c1 + c2 + c3;
3075}
3076
3077/*
3078 * Accumulate the three separate parts of the sum; d1 the remainder
3079 * of the last (incomplete) period, d2 the span of full periods and d3
3080 * the remainder of the (incomplete) current period.
3081 *
3082 * d1 d2 d3
3083 * ^ ^ ^
3084 * | | |
3085 * |<->|<----------------->|<--->|
3086 * ... |---x---|------| ... |------|-----x (now)
3087 *
3088 * p-1
3089 * u' = (u + d1) y^p + 1024 \Sum y^n + d3 y^0
3090 * n=1
3091 *
3092 * = u y^p + (Step 1)
3093 *
3094 * p-1
3095 * d1 y^p + 1024 \Sum y^n + d3 y^0 (Step 2)
3096 * n=1
3097 */
3098static __always_inline u32
3099accumulate_sum(u64 delta, int cpu, struct sched_avg *sa,
3100 unsigned long load, unsigned long runnable, int running)
3101{
3102 unsigned long scale_freq, scale_cpu;
3103 u32 contrib = (u32)delta; /* p == 0 -> delta < 1024 */
3104 u64 periods;
3105
3106 scale_freq = arch_scale_freq_capacity(cpu);
3107 scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
3108
3109 delta += sa->period_contrib;
3110 periods = delta / 1024; /* A period is 1024us (~1ms) */
3111
3112 /*
3113 * Step 1: decay old *_sum if we crossed period boundaries.
3114 */
3115 if (periods) {
3116 sa->load_sum = decay_load(sa->load_sum, periods);
3117 sa->runnable_load_sum =
3118 decay_load(sa->runnable_load_sum, periods);
3119 sa->util_sum = decay_load((u64)(sa->util_sum), periods);
3120
3121 /*
3122 * Step 2
3123 */
3124 delta %= 1024;
3125 contrib = __accumulate_pelt_segments(periods,
3126 1024 - sa->period_contrib, delta);
3127 }
3128 sa->period_contrib = delta;
3129
3130 contrib = cap_scale(contrib, scale_freq);
3131 if (load)
3132 sa->load_sum += load * contrib;
3133 if (runnable)
3134 sa->runnable_load_sum += runnable * contrib;
3135 if (running)
3136 sa->util_sum += contrib * scale_cpu;
3137
3138 return periods;
3139}
3140
3141/*
3142 * We can represent the historical contribution to runnable average as the
3143 * coefficients of a geometric series. To do this we sub-divide our runnable
3144 * history into segments of approximately 1ms (1024us); label the segment that
3145 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
3146 *
3147 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
3148 * p0 p1 p2
3149 * (now) (~1ms ago) (~2ms ago)
3150 *
3151 * Let u_i denote the fraction of p_i that the entity was runnable.
3152 *
3153 * We then designate the fractions u_i as our co-efficients, yielding the
3154 * following representation of historical load:
3155 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
3156 *
3157 * We choose y based on the with of a reasonably scheduling period, fixing:
3158 * y^32 = 0.5
3159 *
3160 * This means that the contribution to load ~32ms ago (u_32) will be weighted
3161 * approximately half as much as the contribution to load within the last ms
3162 * (u_0).
3163 *
3164 * When a period "rolls over" and we have new u_0`, multiplying the previous
3165 * sum again by y is sufficient to update:
3166 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
3167 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
3168 */
3169static __always_inline int
3170___update_load_sum(u64 now, int cpu, struct sched_avg *sa,
3171 unsigned long load, unsigned long runnable, int running)
3172{
3173 u64 delta;
3174
3175 delta = now - sa->last_update_time;
3176 /*
3177 * This should only happen when time goes backwards, which it
3178 * unfortunately does during sched clock init when we swap over to TSC.
3179 */
3180 if ((s64)delta < 0) {
3181 sa->last_update_time = now;
3182 return 0;
3183 }
3184
3185 /*
3186 * Use 1024ns as the unit of measurement since it's a reasonable
3187 * approximation of 1us and fast to compute.
3188 */
3189 delta >>= 10;
3190 if (!delta)
3191 return 0;
3192
3193 sa->last_update_time += delta << 10;
3194
3195 /*
3196 * running is a subset of runnable (weight) so running can't be set if
3197 * runnable is clear. But there are some corner cases where the current
3198 * se has been already dequeued but cfs_rq->curr still points to it.
3199 * This means that weight will be 0 but not running for a sched_entity
3200 * but also for a cfs_rq if the latter becomes idle. As an example,
3201 * this happens during idle_balance() which calls
3202 * update_blocked_averages()
3203 */
3204 if (!load)
3205 runnable = running = 0;
3206
3207 /*
3208 * Now we know we crossed measurement unit boundaries. The *_avg
3209 * accrues by two steps:
3210 *
3211 * Step 1: accumulate *_sum since last_update_time. If we haven't
3212 * crossed period boundaries, finish.
3213 */
3214 if (!accumulate_sum(delta, cpu, sa, load, runnable, running))
3215 return 0;
3216
3217 return 1;
3218}
3219
3220static __always_inline void
3221___update_load_avg(struct sched_avg *sa, unsigned long load, unsigned long runnable)
3222{
3223 u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
3224
3225 /*
3226 * Step 2: update *_avg.
3227 */
3228 sa->load_avg = div_u64(load * sa->load_sum, divider);
3229 sa->runnable_load_avg = div_u64(runnable * sa->runnable_load_sum, divider);
3230 sa->util_avg = sa->util_sum / divider;
3231}
3232
3233/*
3234 * When a task is dequeued, its estimated utilization should not be update if
3235 * its util_avg has not been updated at least once.
3236 * This flag is used to synchronize util_avg updates with util_est updates.
3237 * We map this information into the LSB bit of the utilization saved at
3238 * dequeue time (i.e. util_est.dequeued).
3239 */
3240#define UTIL_AVG_UNCHANGED 0x1
3241
3242static inline void cfs_se_util_change(struct sched_avg *avg)
3243{
3244 unsigned int enqueued;
3245
3246 if (!sched_feat(UTIL_EST))
3247 return;
3248
3249 /* Avoid store if the flag has been already set */
3250 enqueued = avg->util_est.enqueued;
3251 if (!(enqueued & UTIL_AVG_UNCHANGED))
3252 return;
3253
3254 /* Reset flag to report util_avg has been updated */
3255 enqueued &= ~UTIL_AVG_UNCHANGED;
3256 WRITE_ONCE(avg->util_est.enqueued, enqueued);
3257}
3258
3259/*
3260 * sched_entity:
3261 *
3262 * task:
3263 * se_runnable() == se_weight()
3264 *
3265 * group: [ see update_cfs_group() ]
3266 * se_weight() = tg->weight * grq->load_avg / tg->load_avg
3267 * se_runnable() = se_weight(se) * grq->runnable_load_avg / grq->load_avg
3268 *
3269 * load_sum := runnable_sum
3270 * load_avg = se_weight(se) * runnable_avg
3271 *
3272 * runnable_load_sum := runnable_sum
3273 * runnable_load_avg = se_runnable(se) * runnable_avg
3274 *
3275 * XXX collapse load_sum and runnable_load_sum
3276 *
3277 * cfq_rs:
3278 *
3279 * load_sum = \Sum se_weight(se) * se->avg.load_sum
3280 * load_avg = \Sum se->avg.load_avg
3281 *
3282 * runnable_load_sum = \Sum se_runnable(se) * se->avg.runnable_load_sum
3283 * runnable_load_avg = \Sum se->avg.runable_load_avg
3284 */
3285
3286static int
3287__update_load_avg_blocked_se(u64 now, int cpu, struct sched_entity *se)
3288{
3289 if (entity_is_task(se))
3290 se->runnable_weight = se->load.weight;
3291
3292 if (___update_load_sum(now, cpu, &se->avg, 0, 0, 0)) {
3293 ___update_load_avg(&se->avg, se_weight(se), se_runnable(se));
3294 return 1;
3295 }
3296
3297 return 0;
3298}
3299
3300static int
3301__update_load_avg_se(u64 now, int cpu, struct cfs_rq *cfs_rq, struct sched_entity *se)
3302{
3303 if (entity_is_task(se))
3304 se->runnable_weight = se->load.weight;
3305
3306 if (___update_load_sum(now, cpu, &se->avg, !!se->on_rq, !!se->on_rq,
3307 cfs_rq->curr == se)) {
3308
3309 ___update_load_avg(&se->avg, se_weight(se), se_runnable(se));
3310 cfs_se_util_change(&se->avg);
3311 return 1;
3312 }
3313
3314 return 0;
3315}
3316
3317static int
3318__update_load_avg_cfs_rq(u64 now, int cpu, struct cfs_rq *cfs_rq)
3319{
3320 if (___update_load_sum(now, cpu, &cfs_rq->avg,
3321 scale_load_down(cfs_rq->load.weight),
3322 scale_load_down(cfs_rq->runnable_weight),
3323 cfs_rq->curr != NULL)) {
3324
3325 ___update_load_avg(&cfs_rq->avg, 1, 1);
3326 return 1;
3327 }
3328
3329 return 0;
3330}
3331
3332#ifdef CONFIG_FAIR_GROUP_SCHED
3333/**
3334 * update_tg_load_avg - update the tg's load avg
3335 * @cfs_rq: the cfs_rq whose avg changed
3336 * @force: update regardless of how small the difference
3337 *
3338 * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
3339 * However, because tg->load_avg is a global value there are performance
3340 * considerations.
3341 *
3342 * In order to avoid having to look at the other cfs_rq's, we use a
3343 * differential update where we store the last value we propagated. This in
3344 * turn allows skipping updates if the differential is 'small'.
3345 *
3346 * Updating tg's load_avg is necessary before update_cfs_share().
3347 */
3348static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
3349{
3350 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
3351
3352 /*
3353 * No need to update load_avg for root_task_group as it is not used.
3354 */
3355 if (cfs_rq->tg == &root_task_group)
3356 return;
3357
3358 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
3359 atomic_long_add(delta, &cfs_rq->tg->load_avg);
3360 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
3361 }
3362}
3363
3364/*
3365 * Called within set_task_rq() right before setting a task's CPU. The
3366 * caller only guarantees p->pi_lock is held; no other assumptions,
3367 * including the state of rq->lock, should be made.
3368 */
3369void set_task_rq_fair(struct sched_entity *se,
3370 struct cfs_rq *prev, struct cfs_rq *next)
3371{
3372 u64 p_last_update_time;
3373 u64 n_last_update_time;
3374
3375 if (!sched_feat(ATTACH_AGE_LOAD))
3376 return;
3377
3378 /*
3379 * We are supposed to update the task to "current" time, then its up to
3380 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
3381 * getting what current time is, so simply throw away the out-of-date
3382 * time. This will result in the wakee task is less decayed, but giving
3383 * the wakee more load sounds not bad.
3384 */
3385 if (!(se->avg.last_update_time && prev))
3386 return;
3387
3388#ifndef CONFIG_64BIT
3389 {
3390 u64 p_last_update_time_copy;
3391 u64 n_last_update_time_copy;
3392
3393 do {
3394 p_last_update_time_copy = prev->load_last_update_time_copy;
3395 n_last_update_time_copy = next->load_last_update_time_copy;
3396
3397 smp_rmb();
3398
3399 p_last_update_time = prev->avg.last_update_time;
3400 n_last_update_time = next->avg.last_update_time;
3401
3402 } while (p_last_update_time != p_last_update_time_copy ||
3403 n_last_update_time != n_last_update_time_copy);
3404 }
3405#else
3406 p_last_update_time = prev->avg.last_update_time;
3407 n_last_update_time = next->avg.last_update_time;
3408#endif
3409 __update_load_avg_blocked_se(p_last_update_time, cpu_of(rq_of(prev)), se);
3410 se->avg.last_update_time = n_last_update_time;
3411}
3412
3413
3414/*
3415 * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
3416 * propagate its contribution. The key to this propagation is the invariant
3417 * that for each group:
3418 *
3419 * ge->avg == grq->avg (1)
3420 *
3421 * _IFF_ we look at the pure running and runnable sums. Because they
3422 * represent the very same entity, just at different points in the hierarchy.
3423 *
3424 * Per the above update_tg_cfs_util() is trivial and simply copies the running
3425 * sum over (but still wrong, because the group entity and group rq do not have
3426 * their PELT windows aligned).
3427 *
3428 * However, update_tg_cfs_runnable() is more complex. So we have:
3429 *
3430 * ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg (2)
3431 *
3432 * And since, like util, the runnable part should be directly transferable,
3433 * the following would _appear_ to be the straight forward approach:
3434 *
3435 * grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg (3)
3436 *
3437 * And per (1) we have:
3438 *
3439 * ge->avg.runnable_avg == grq->avg.runnable_avg
3440 *
3441 * Which gives:
3442 *
3443 * ge->load.weight * grq->avg.load_avg
3444 * ge->avg.load_avg = ----------------------------------- (4)
3445 * grq->load.weight
3446 *
3447 * Except that is wrong!
3448 *
3449 * Because while for entities historical weight is not important and we
3450 * really only care about our future and therefore can consider a pure
3451 * runnable sum, runqueues can NOT do this.
3452 *
3453 * We specifically want runqueues to have a load_avg that includes
3454 * historical weights. Those represent the blocked load, the load we expect
3455 * to (shortly) return to us. This only works by keeping the weights as
3456 * integral part of the sum. We therefore cannot decompose as per (3).
3457 *
3458 * Another reason this doesn't work is that runnable isn't a 0-sum entity.
3459 * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
3460 * rq itself is runnable anywhere between 2/3 and 1 depending on how the
3461 * runnable section of these tasks overlap (or not). If they were to perfectly
3462 * align the rq as a whole would be runnable 2/3 of the time. If however we
3463 * always have at least 1 runnable task, the rq as a whole is always runnable.
3464 *
3465 * So we'll have to approximate.. :/
3466 *
3467 * Given the constraint:
3468 *
3469 * ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
3470 *
3471 * We can construct a rule that adds runnable to a rq by assuming minimal
3472 * overlap.
3473 *
3474 * On removal, we'll assume each task is equally runnable; which yields:
3475 *
3476 * grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
3477 *
3478 * XXX: only do this for the part of runnable > running ?
3479 *
3480 */
3481
3482static inline void
3483update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3484{
3485 long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;
3486
3487 /* Nothing to update */
3488 if (!delta)
3489 return;
3490
3491 /*
3492 * The relation between sum and avg is:
3493 *
3494 * LOAD_AVG_MAX - 1024 + sa->period_contrib
3495 *
3496 * however, the PELT windows are not aligned between grq and gse.
3497 */
3498
3499 /* Set new sched_entity's utilization */
3500 se->avg.util_avg = gcfs_rq->avg.util_avg;
3501 se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX;
3502
3503 /* Update parent cfs_rq utilization */
3504 add_positive(&cfs_rq->avg.util_avg, delta);
3505 cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX;
3506}
3507
3508static inline void
3509update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3510{
3511 long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum;
3512 unsigned long runnable_load_avg, load_avg;
3513 u64 runnable_load_sum, load_sum = 0;
3514 s64 delta_sum;
3515
3516 if (!runnable_sum)
3517 return;
3518
3519 gcfs_rq->prop_runnable_sum = 0;
3520
3521 if (runnable_sum >= 0) {
3522 /*
3523 * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
3524 * the CPU is saturated running == runnable.
3525 */
3526 runnable_sum += se->avg.load_sum;
3527 runnable_sum = min(runnable_sum, (long)LOAD_AVG_MAX);
3528 } else {
3529 /*
3530 * Estimate the new unweighted runnable_sum of the gcfs_rq by
3531 * assuming all tasks are equally runnable.
3532 */
3533 if (scale_load_down(gcfs_rq->load.weight)) {
3534 load_sum = div_s64(gcfs_rq->avg.load_sum,
3535 scale_load_down(gcfs_rq->load.weight));
3536 }
3537
3538 /* But make sure to not inflate se's runnable */
3539 runnable_sum = min(se->avg.load_sum, load_sum);
3540 }
3541
3542 /*
3543 * runnable_sum can't be lower than running_sum
3544 * As running sum is scale with CPU capacity wehreas the runnable sum
3545 * is not we rescale running_sum 1st
3546 */
3547 running_sum = se->avg.util_sum /
3548 arch_scale_cpu_capacity(NULL, cpu_of(rq_of(cfs_rq)));
3549 runnable_sum = max(runnable_sum, running_sum);
3550
3551 load_sum = (s64)se_weight(se) * runnable_sum;
3552 load_avg = div_s64(load_sum, LOAD_AVG_MAX);
3553
3554 delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum;
3555 delta_avg = load_avg - se->avg.load_avg;
3556
3557 se->avg.load_sum = runnable_sum;
3558 se->avg.load_avg = load_avg;
3559 add_positive(&cfs_rq->avg.load_avg, delta_avg);
3560 add_positive(&cfs_rq->avg.load_sum, delta_sum);
3561
3562 runnable_load_sum = (s64)se_runnable(se) * runnable_sum;
3563 runnable_load_avg = div_s64(runnable_load_sum, LOAD_AVG_MAX);
3564 delta_sum = runnable_load_sum - se_weight(se) * se->avg.runnable_load_sum;
3565 delta_avg = runnable_load_avg - se->avg.runnable_load_avg;
3566
3567 se->avg.runnable_load_sum = runnable_sum;
3568 se->avg.runnable_load_avg = runnable_load_avg;
3569
3570 if (se->on_rq) {
3571 add_positive(&cfs_rq->avg.runnable_load_avg, delta_avg);
3572 add_positive(&cfs_rq->avg.runnable_load_sum, delta_sum);
3573 }
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
3603 return 1;
3604}
3605
3606/*
3607 * Check if we need to update the load and the utilization of a blocked
3608 * group_entity:
3609 */
3610static inline bool skip_blocked_update(struct sched_entity *se)
3611{
3612 struct cfs_rq *gcfs_rq = group_cfs_rq(se);
3613
3614 /*
3615 * If sched_entity still have not zero load or utilization, we have to
3616 * decay it:
3617 */
3618 if (se->avg.load_avg || se->avg.util_avg)
3619 return false;
3620
3621 /*
3622 * If there is a pending propagation, we have to update the load and
3623 * the utilization of the sched_entity:
3624 */
3625 if (gcfs_rq->propagate)
3626 return false;
3627
3628 /*
3629 * Otherwise, the load and the utilization of the sched_entity is
3630 * already zero and there is no pending propagation, so it will be a
3631 * waste of time to try to decay it:
3632 */
3633 return true;
3634}
3635
3636#else /* CONFIG_FAIR_GROUP_SCHED */
3637
3638static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
3639
3640static inline int propagate_entity_load_avg(struct sched_entity *se)
3641{
3642 return 0;
3643}
3644
3645static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
3646
3647#endif /* CONFIG_FAIR_GROUP_SCHED */
3648
3649/**
3650 * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
3651 * @now: current time, as per cfs_rq_clock_task()
3652 * @cfs_rq: cfs_rq to update
3653 *
3654 * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
3655 * avg. The immediate corollary is that all (fair) tasks must be attached, see
3656 * post_init_entity_util_avg().
3657 *
3658 * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
3659 *
3660 * Returns true if the load decayed or we removed load.
3661 *
3662 * Since both these conditions indicate a changed cfs_rq->avg.load we should
3663 * call update_tg_load_avg() when this function returns true.
3664 */
3665static inline int
3666update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3667{
3668 unsigned long removed_load = 0, removed_util = 0, removed_runnable_sum = 0;
3669 struct sched_avg *sa = &cfs_rq->avg;
3670 int decayed = 0;
3671
3672 if (cfs_rq->removed.nr) {
3673 unsigned long r;
3674 u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
3675
3676 raw_spin_lock(&cfs_rq->removed.lock);
3677 swap(cfs_rq->removed.util_avg, removed_util);
3678 swap(cfs_rq->removed.load_avg, removed_load);
3679 swap(cfs_rq->removed.runnable_sum, removed_runnable_sum);
3680 cfs_rq->removed.nr = 0;
3681 raw_spin_unlock(&cfs_rq->removed.lock);
3682
3683 r = removed_load;
3684 sub_positive(&sa->load_avg, r);
3685 sub_positive(&sa->load_sum, r * divider);
3686
3687 r = removed_util;
3688 sub_positive(&sa->util_avg, r);
3689 sub_positive(&sa->util_sum, r * divider);
3690
3691 add_tg_cfs_propagate(cfs_rq, -(long)removed_runnable_sum);
3692
3693 decayed = 1;
3694 }
3695
3696 decayed |= __update_load_avg_cfs_rq(now, cpu_of(rq_of(cfs_rq)), cfs_rq);
3697
3698#ifndef CONFIG_64BIT
3699 smp_wmb();
3700 cfs_rq->load_last_update_time_copy = sa->last_update_time;
3701#endif
3702
3703 if (decayed)
3704 cfs_rq_util_change(cfs_rq, 0);
3705
3706 return decayed;
3707}
3708
3709/**
3710 * attach_entity_load_avg - attach this entity to its cfs_rq load avg
3711 * @cfs_rq: cfs_rq to attach to
3712 * @se: sched_entity to attach
3713 *
3714 * Must call update_cfs_rq_load_avg() before this, since we rely on
3715 * cfs_rq->avg.last_update_time being current.
3716 */
3717static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3718{
3719 u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib;
3720
3721 /*
3722 * When we attach the @se to the @cfs_rq, we must align the decay
3723 * window because without that, really weird and wonderful things can
3724 * happen.
3725 *
3726 * XXX illustrate
3727 */
3728 se->avg.last_update_time = cfs_rq->avg.last_update_time;
3729 se->avg.period_contrib = cfs_rq->avg.period_contrib;
3730
3731 /*
3732 * Hell(o) Nasty stuff.. we need to recompute _sum based on the new
3733 * period_contrib. This isn't strictly correct, but since we're
3734 * entirely outside of the PELT hierarchy, nobody cares if we truncate
3735 * _sum a little.
3736 */
3737 se->avg.util_sum = se->avg.util_avg * divider;
3738
3739 se->avg.load_sum = divider;
3740 if (se_weight(se)) {
3741 se->avg.load_sum =
3742 div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se));
3743 }
3744
3745 se->avg.runnable_load_sum = se->avg.load_sum;
3746
3747 enqueue_load_avg(cfs_rq, se);
3748 cfs_rq->avg.util_avg += se->avg.util_avg;
3749 cfs_rq->avg.util_sum += se->avg.util_sum;
3750
3751 add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
3752
3753 cfs_rq_util_change(cfs_rq, flags);
3754}
3755
3756/**
3757 * detach_entity_load_avg - detach this entity from its cfs_rq load avg
3758 * @cfs_rq: cfs_rq to detach from
3759 * @se: sched_entity to detach
3760 *
3761 * Must call update_cfs_rq_load_avg() before this, since we rely on
3762 * cfs_rq->avg.last_update_time being current.
3763 */
3764static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3765{
3766 dequeue_load_avg(cfs_rq, se);
3767 sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
3768 sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
3769
3770 add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
3771
3772 cfs_rq_util_change(cfs_rq, 0);
3773}
3774
3775/*
3776 * Optional action to be done while updating the load average
3777 */
3778#define UPDATE_TG 0x1
3779#define SKIP_AGE_LOAD 0x2
3780#define DO_ATTACH 0x4
3781
3782/* Update task and its cfs_rq load average */
3783static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3784{
3785 u64 now = cfs_rq_clock_task(cfs_rq);
3786 struct rq *rq = rq_of(cfs_rq);
3787 int cpu = cpu_of(rq);
3788 int decayed;
3789
3790 /*
3791 * Track task load average for carrying it to new CPU after migrated, and
3792 * track group sched_entity load average for task_h_load calc in migration
3793 */
3794 if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
3795 __update_load_avg_se(now, cpu, cfs_rq, se);
3796
3797 decayed = update_cfs_rq_load_avg(now, cfs_rq);
3798 decayed |= propagate_entity_load_avg(se);
3799
3800 if (!se->avg.last_update_time && (flags & DO_ATTACH)) {
3801
3802 /*
3803 * DO_ATTACH means we're here from enqueue_entity().
3804 * !last_update_time means we've passed through
3805 * migrate_task_rq_fair() indicating we migrated.
3806 *
3807 * IOW we're enqueueing a task on a new CPU.
3808 */
3809 attach_entity_load_avg(cfs_rq, se, SCHED_CPUFREQ_MIGRATION);
3810 update_tg_load_avg(cfs_rq, 0);
3811
3812 } else if (decayed && (flags & UPDATE_TG))
3813 update_tg_load_avg(cfs_rq, 0);
3814}
3815
3816#ifndef CONFIG_64BIT
3817static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3818{
3819 u64 last_update_time_copy;
3820 u64 last_update_time;
3821
3822 do {
3823 last_update_time_copy = cfs_rq->load_last_update_time_copy;
3824 smp_rmb();
3825 last_update_time = cfs_rq->avg.last_update_time;
3826 } while (last_update_time != last_update_time_copy);
3827
3828 return last_update_time;
3829}
3830#else
3831static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3832{
3833 return cfs_rq->avg.last_update_time;
3834}
3835#endif
3836
3837/*
3838 * Synchronize entity load avg of dequeued entity without locking
3839 * the previous rq.
3840 */
3841void sync_entity_load_avg(struct sched_entity *se)
3842{
3843 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3844 u64 last_update_time;
3845
3846 last_update_time = cfs_rq_last_update_time(cfs_rq);
3847 __update_load_avg_blocked_se(last_update_time, cpu_of(rq_of(cfs_rq)), se);
3848}
3849
3850/*
3851 * Task first catches up with cfs_rq, and then subtract
3852 * itself from the cfs_rq (task must be off the queue now).
3853 */
3854void remove_entity_load_avg(struct sched_entity *se)
3855{
3856 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3857 unsigned long flags;
3858
3859 /*
3860 * tasks cannot exit without having gone through wake_up_new_task() ->
3861 * post_init_entity_util_avg() which will have added things to the
3862 * cfs_rq, so we can remove unconditionally.
3863 *
3864 * Similarly for groups, they will have passed through
3865 * post_init_entity_util_avg() before unregister_sched_fair_group()
3866 * calls this.
3867 */
3868
3869 sync_entity_load_avg(se);
3870
3871 raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags);
3872 ++cfs_rq->removed.nr;
3873 cfs_rq->removed.util_avg += se->avg.util_avg;
3874 cfs_rq->removed.load_avg += se->avg.load_avg;
3875 cfs_rq->removed.runnable_sum += se->avg.load_sum; /* == runnable_sum */
3876 raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
3877}
3878
3879static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
3880{
3881 return cfs_rq->avg.runnable_load_avg;
3882}
3883
3884static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
3885{
3886 return cfs_rq->avg.load_avg;
3887}
3888
3889static int idle_balance(struct rq *this_rq, struct rq_flags *rf);
3890
3891static inline unsigned long task_util(struct task_struct *p)
3892{
3893 return READ_ONCE(p->se.avg.util_avg);
3894}
3895
3896static inline unsigned long _task_util_est(struct task_struct *p)
3897{
3898 struct util_est ue = READ_ONCE(p->se.avg.util_est);
3899
3900 return max(ue.ewma, ue.enqueued);
3901}
3902
3903static inline unsigned long task_util_est(struct task_struct *p)
3904{
3905 return max(task_util(p), _task_util_est(p));
3906}
3907
3908static inline void util_est_enqueue(struct cfs_rq *cfs_rq,
3909 struct task_struct *p)
3910{
3911 unsigned int enqueued;
3912
3913 if (!sched_feat(UTIL_EST))
3914 return;
3915
3916 /* Update root cfs_rq's estimated utilization */
3917 enqueued = cfs_rq->avg.util_est.enqueued;
3918 enqueued += (_task_util_est(p) | UTIL_AVG_UNCHANGED);
3919 WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
3920}
3921
3922/*
3923 * Check if a (signed) value is within a specified (unsigned) margin,
3924 * based on the observation that:
3925 *
3926 * abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1)
3927 *
3928 * NOTE: this only works when value + maring < INT_MAX.
3929 */
3930static inline bool within_margin(int value, int margin)
3931{
3932 return ((unsigned int)(value + margin - 1) < (2 * margin - 1));
3933}
3934
3935static void
3936util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep)
3937{
3938 long last_ewma_diff;
3939 struct util_est ue;
3940
3941 if (!sched_feat(UTIL_EST))
3942 return;
3943
3944 /*
3945 * Update root cfs_rq's estimated utilization
3946 *
3947 * If *p is the last task then the root cfs_rq's estimated utilization
3948 * of a CPU is 0 by definition.
3949 */
3950 ue.enqueued = 0;
3951 if (cfs_rq->nr_running) {
3952 ue.enqueued = cfs_rq->avg.util_est.enqueued;
3953 ue.enqueued -= min_t(unsigned int, ue.enqueued,
3954 (_task_util_est(p) | UTIL_AVG_UNCHANGED));
3955 }
3956 WRITE_ONCE(cfs_rq->avg.util_est.enqueued, ue.enqueued);
3957
3958 /*
3959 * Skip update of task's estimated utilization when the task has not
3960 * yet completed an activation, e.g. being migrated.
3961 */
3962 if (!task_sleep)
3963 return;
3964
3965 /*
3966 * If the PELT values haven't changed since enqueue time,
3967 * skip the util_est update.
3968 */
3969 ue = p->se.avg.util_est;
3970 if (ue.enqueued & UTIL_AVG_UNCHANGED)
3971 return;
3972
3973 /*
3974 * Skip update of task's estimated utilization when its EWMA is
3975 * already ~1% close to its last activation value.
3976 */
3977 ue.enqueued = (task_util(p) | UTIL_AVG_UNCHANGED);
3978 last_ewma_diff = ue.enqueued - ue.ewma;
3979 if (within_margin(last_ewma_diff, (SCHED_CAPACITY_SCALE / 100)))
3980 return;
3981
3982 /*
3983 * Update Task's estimated utilization
3984 *
3985 * When *p completes an activation we can consolidate another sample
3986 * of the task size. This is done by storing the current PELT value
3987 * as ue.enqueued and by using this value to update the Exponential
3988 * Weighted Moving Average (EWMA):
3989 *
3990 * ewma(t) = w * task_util(p) + (1-w) * ewma(t-1)
3991 * = w * task_util(p) + ewma(t-1) - w * ewma(t-1)
3992 * = w * (task_util(p) - ewma(t-1)) + ewma(t-1)
3993 * = w * ( last_ewma_diff ) + ewma(t-1)
3994 * = w * (last_ewma_diff + ewma(t-1) / w)
3995 *
3996 * Where 'w' is the weight of new samples, which is configured to be
3997 * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
3998 */
3999 ue.ewma <<= UTIL_EST_WEIGHT_SHIFT;
4000 ue.ewma += last_ewma_diff;
4001 ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
4002 WRITE_ONCE(p->se.avg.util_est, ue);
4003}
4004
4005#else /* CONFIG_SMP */
4006
4007static inline int
4008update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
4009{
4010 return 0;
4011}
4012
4013#define UPDATE_TG 0x0
4014#define SKIP_AGE_LOAD 0x0
4015#define DO_ATTACH 0x0
4016
4017static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
4018{
4019 cfs_rq_util_change(cfs_rq, 0);
4020}
4021
4022static inline void remove_entity_load_avg(struct sched_entity *se) {}
4023
4024static inline void
4025attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) {}
4026static inline void
4027detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
4028
4029static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
4030{
4031 return 0;
4032}
4033
4034static inline void
4035util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
4036
4037static inline void
4038util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p,
4039 bool task_sleep) {}
4040
4041#endif /* CONFIG_SMP */
4042
4043static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
4044{
4045#ifdef CONFIG_SCHED_DEBUG
4046 s64 d = se->vruntime - cfs_rq->min_vruntime;
4047
4048 if (d < 0)
4049 d = -d;
4050
4051 if (d > 3*sysctl_sched_latency)
4052 schedstat_inc(cfs_rq->nr_spread_over);
4053#endif
4054}
4055
4056static void
4057place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
4058{
4059 u64 vruntime = cfs_rq->min_vruntime;
4060
4061 /*
4062 * The 'current' period is already promised to the current tasks,
4063 * however the extra weight of the new task will slow them down a
4064 * little, place the new task so that it fits in the slot that
4065 * stays open at the end.
4066 */
4067 if (initial && sched_feat(START_DEBIT))
4068 vruntime += sched_vslice(cfs_rq, se);
4069
4070 /* sleeps up to a single latency don't count. */
4071 if (!initial) {
4072 unsigned long thresh = sysctl_sched_latency;
4073
4074 /*
4075 * Halve their sleep time's effect, to allow
4076 * for a gentler effect of sleepers:
4077 */
4078 if (sched_feat(GENTLE_FAIR_SLEEPERS))
4079 thresh >>= 1;
4080
4081 vruntime -= thresh;
4082 }
4083
4084 /* ensure we never gain time by being placed backwards. */
4085 se->vruntime = max_vruntime(se->vruntime, vruntime);
4086}
4087
4088static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
4089
4090static inline void check_schedstat_required(void)
4091{
4092#ifdef CONFIG_SCHEDSTATS
4093 if (schedstat_enabled())
4094 return;
4095
4096 /* Force schedstat enabled if a dependent tracepoint is active */
4097 if (trace_sched_stat_wait_enabled() ||
4098 trace_sched_stat_sleep_enabled() ||
4099 trace_sched_stat_iowait_enabled() ||
4100 trace_sched_stat_blocked_enabled() ||
4101 trace_sched_stat_runtime_enabled()) {
4102 printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
4103 "stat_blocked and stat_runtime require the "
4104 "kernel parameter schedstats=enable or "
4105 "kernel.sched_schedstats=1\n");
4106 }
4107#endif
4108}
4109
4110
4111/*
4112 * MIGRATION
4113 *
4114 * dequeue
4115 * update_curr()
4116 * update_min_vruntime()
4117 * vruntime -= min_vruntime
4118 *
4119 * enqueue
4120 * update_curr()
4121 * update_min_vruntime()
4122 * vruntime += min_vruntime
4123 *
4124 * this way the vruntime transition between RQs is done when both
4125 * min_vruntime are up-to-date.
4126 *
4127 * WAKEUP (remote)
4128 *
4129 * ->migrate_task_rq_fair() (p->state == TASK_WAKING)
4130 * vruntime -= min_vruntime
4131 *
4132 * enqueue
4133 * update_curr()
4134 * update_min_vruntime()
4135 * vruntime += min_vruntime
4136 *
4137 * this way we don't have the most up-to-date min_vruntime on the originating
4138 * CPU and an up-to-date min_vruntime on the destination CPU.
4139 */
4140
4141static void
4142enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
4143{
4144 bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
4145 bool curr = cfs_rq->curr == se;
4146
4147 /*
4148 * If we're the current task, we must renormalise before calling
4149 * update_curr().
4150 */
4151 if (renorm && curr)
4152 se->vruntime += cfs_rq->min_vruntime;
4153
4154 update_curr(cfs_rq);
4155
4156 /*
4157 * Otherwise, renormalise after, such that we're placed at the current
4158 * moment in time, instead of some random moment in the past. Being
4159 * placed in the past could significantly boost this task to the
4160 * fairness detriment of existing tasks.
4161 */
4162 if (renorm && !curr)
4163 se->vruntime += cfs_rq->min_vruntime;
4164
4165 /*
4166 * When enqueuing a sched_entity, we must:
4167 * - Update loads to have both entity and cfs_rq synced with now.
4168 * - Add its load to cfs_rq->runnable_avg
4169 * - For group_entity, update its weight to reflect the new share of
4170 * its group cfs_rq
4171 * - Add its new weight to cfs_rq->load.weight
4172 */
4173 update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
4174 update_cfs_group(se);
4175 enqueue_runnable_load_avg(cfs_rq, se);
4176 account_entity_enqueue(cfs_rq, se);
4177
4178 if (flags & ENQUEUE_WAKEUP)
4179 place_entity(cfs_rq, se, 0);
4180
4181 check_schedstat_required();
4182 update_stats_enqueue(cfs_rq, se, flags);
4183 check_spread(cfs_rq, se);
4184 if (!curr)
4185 __enqueue_entity(cfs_rq, se);
4186 se->on_rq = 1;
4187
4188 if (cfs_rq->nr_running == 1) {
4189 list_add_leaf_cfs_rq(cfs_rq);
4190 check_enqueue_throttle(cfs_rq);
4191 }
4192}
4193
4194static void __clear_buddies_last(struct sched_entity *se)
4195{
4196 for_each_sched_entity(se) {
4197 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4198 if (cfs_rq->last != se)
4199 break;
4200
4201 cfs_rq->last = NULL;
4202 }
4203}
4204
4205static void __clear_buddies_next(struct sched_entity *se)
4206{
4207 for_each_sched_entity(se) {
4208 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4209 if (cfs_rq->next != se)
4210 break;
4211
4212 cfs_rq->next = NULL;
4213 }
4214}
4215
4216static void __clear_buddies_skip(struct sched_entity *se)
4217{
4218 for_each_sched_entity(se) {
4219 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4220 if (cfs_rq->skip != se)
4221 break;
4222
4223 cfs_rq->skip = NULL;
4224 }
4225}
4226
4227static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
4228{
4229 if (cfs_rq->last == se)
4230 __clear_buddies_last(se);
4231
4232 if (cfs_rq->next == se)
4233 __clear_buddies_next(se);
4234
4235 if (cfs_rq->skip == se)
4236 __clear_buddies_skip(se);
4237}
4238
4239static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4240
4241static void
4242dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
4243{
4244 /*
4245 * Update run-time statistics of the 'current'.
4246 */
4247 update_curr(cfs_rq);
4248
4249 /*
4250 * When dequeuing a sched_entity, we must:
4251 * - Update loads to have both entity and cfs_rq synced with now.
4252 * - Substract its load from the cfs_rq->runnable_avg.
4253 * - Substract its previous weight from cfs_rq->load.weight.
4254 * - For group entity, update its weight to reflect the new share
4255 * of its group cfs_rq.
4256 */
4257 update_load_avg(cfs_rq, se, UPDATE_TG);
4258 dequeue_runnable_load_avg(cfs_rq, se);
4259
4260 update_stats_dequeue(cfs_rq, se, flags);
4261
4262 clear_buddies(cfs_rq, se);
4263
4264 if (se != cfs_rq->curr)
4265 __dequeue_entity(cfs_rq, se);
4266 se->on_rq = 0;
4267 account_entity_dequeue(cfs_rq, se);
4268
4269 /*
4270 * Normalize after update_curr(); which will also have moved
4271 * min_vruntime if @se is the one holding it back. But before doing
4272 * update_min_vruntime() again, which will discount @se's position and
4273 * can move min_vruntime forward still more.
4274 */
4275 if (!(flags & DEQUEUE_SLEEP))
4276 se->vruntime -= cfs_rq->min_vruntime;
4277
4278 /* return excess runtime on last dequeue */
4279 return_cfs_rq_runtime(cfs_rq);
4280
4281 update_cfs_group(se);
4282
4283 /*
4284 * Now advance min_vruntime if @se was the entity holding it back,
4285 * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
4286 * put back on, and if we advance min_vruntime, we'll be placed back
4287 * further than we started -- ie. we'll be penalized.
4288 */
4289 if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE)
4290 update_min_vruntime(cfs_rq);
4291}
4292
4293/*
4294 * Preempt the current task with a newly woken task if needed:
4295 */
4296static void
4297check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4298{
4299 unsigned long ideal_runtime, delta_exec;
4300 struct sched_entity *se;
4301 s64 delta;
4302
4303 ideal_runtime = sched_slice(cfs_rq, curr);
4304 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
4305 if (delta_exec > ideal_runtime) {
4306 resched_curr(rq_of(cfs_rq));
4307 /*
4308 * The current task ran long enough, ensure it doesn't get
4309 * re-elected due to buddy favours.
4310 */
4311 clear_buddies(cfs_rq, curr);
4312 return;
4313 }
4314
4315 /*
4316 * Ensure that a task that missed wakeup preemption by a
4317 * narrow margin doesn't have to wait for a full slice.
4318 * This also mitigates buddy induced latencies under load.
4319 */
4320 if (delta_exec < sysctl_sched_min_granularity)
4321 return;
4322
4323 se = __pick_first_entity(cfs_rq);
4324 delta = curr->vruntime - se->vruntime;
4325
4326 if (delta < 0)
4327 return;
4328
4329 if (delta > ideal_runtime)
4330 resched_curr(rq_of(cfs_rq));
4331}
4332
4333static void
4334set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
4335{
4336 /* 'current' is not kept within the tree. */
4337 if (se->on_rq) {
4338 /*
4339 * Any task has to be enqueued before it get to execute on
4340 * a CPU. So account for the time it spent waiting on the
4341 * runqueue.
4342 */
4343 update_stats_wait_end(cfs_rq, se);
4344 __dequeue_entity(cfs_rq, se);
4345 update_load_avg(cfs_rq, se, UPDATE_TG);
4346 }
4347
4348 update_stats_curr_start(cfs_rq, se);
4349 cfs_rq->curr = se;
4350
4351 /*
4352 * Track our maximum slice length, if the CPU's load is at
4353 * least twice that of our own weight (i.e. dont track it
4354 * when there are only lesser-weight tasks around):
4355 */
4356 if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
4357 schedstat_set(se->statistics.slice_max,
4358 max((u64)schedstat_val(se->statistics.slice_max),
4359 se->sum_exec_runtime - se->prev_sum_exec_runtime));
4360 }
4361
4362 se->prev_sum_exec_runtime = se->sum_exec_runtime;
4363}
4364
4365static int
4366wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
4367
4368/*
4369 * Pick the next process, keeping these things in mind, in this order:
4370 * 1) keep things fair between processes/task groups
4371 * 2) pick the "next" process, since someone really wants that to run
4372 * 3) pick the "last" process, for cache locality
4373 * 4) do not run the "skip" process, if something else is available
4374 */
4375static struct sched_entity *
4376pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4377{
4378 struct sched_entity *left = __pick_first_entity(cfs_rq);
4379 struct sched_entity *se;
4380
4381 /*
4382 * If curr is set we have to see if its left of the leftmost entity
4383 * still in the tree, provided there was anything in the tree at all.
4384 */
4385 if (!left || (curr && entity_before(curr, left)))
4386 left = curr;
4387
4388 se = left; /* ideally we run the leftmost entity */
4389
4390 /*
4391 * Avoid running the skip buddy, if running something else can
4392 * be done without getting too unfair.
4393 */
4394 if (cfs_rq->skip == se) {
4395 struct sched_entity *second;
4396
4397 if (se == curr) {
4398 second = __pick_first_entity(cfs_rq);
4399 } else {
4400 second = __pick_next_entity(se);
4401 if (!second || (curr && entity_before(curr, second)))
4402 second = curr;
4403 }
4404
4405 if (second && wakeup_preempt_entity(second, left) < 1)
4406 se = second;
4407 }
4408
4409 /*
4410 * Prefer last buddy, try to return the CPU to a preempted task.
4411 */
4412 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
4413 se = cfs_rq->last;
4414
4415 /*
4416 * Someone really wants this to run. If it's not unfair, run it.
4417 */
4418 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
4419 se = cfs_rq->next;
4420
4421 clear_buddies(cfs_rq, se);
4422
4423 return se;
4424}
4425
4426static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4427
4428static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
4429{
4430 /*
4431 * If still on the runqueue then deactivate_task()
4432 * was not called and update_curr() has to be done:
4433 */
4434 if (prev->on_rq)
4435 update_curr(cfs_rq);
4436
4437 /* throttle cfs_rqs exceeding runtime */
4438 check_cfs_rq_runtime(cfs_rq);
4439
4440 check_spread(cfs_rq, prev);
4441
4442 if (prev->on_rq) {
4443 update_stats_wait_start(cfs_rq, prev);
4444 /* Put 'current' back into the tree. */
4445 __enqueue_entity(cfs_rq, prev);
4446 /* in !on_rq case, update occurred at dequeue */
4447 update_load_avg(cfs_rq, prev, 0);
4448 }
4449 cfs_rq->curr = NULL;
4450}
4451
4452static void
4453entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
4454{
4455 /*
4456 * Update run-time statistics of the 'current'.
4457 */
4458 update_curr(cfs_rq);
4459
4460 /*
4461 * Ensure that runnable average is periodically updated.
4462 */
4463 update_load_avg(cfs_rq, curr, UPDATE_TG);
4464 update_cfs_group(curr);
4465
4466#ifdef CONFIG_SCHED_HRTICK
4467 /*
4468 * queued ticks are scheduled to match the slice, so don't bother
4469 * validating it and just reschedule.
4470 */
4471 if (queued) {
4472 resched_curr(rq_of(cfs_rq));
4473 return;
4474 }
4475 /*
4476 * don't let the period tick interfere with the hrtick preemption
4477 */
4478 if (!sched_feat(DOUBLE_TICK) &&
4479 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
4480 return;
4481#endif
4482
4483 if (cfs_rq->nr_running > 1)
4484 check_preempt_tick(cfs_rq, curr);
4485}
4486
4487
4488/**************************************************
4489 * CFS bandwidth control machinery
4490 */
4491
4492#ifdef CONFIG_CFS_BANDWIDTH
4493
4494#ifdef HAVE_JUMP_LABEL
4495static struct static_key __cfs_bandwidth_used;
4496
4497static inline bool cfs_bandwidth_used(void)
4498{
4499 return static_key_false(&__cfs_bandwidth_used);
4500}
4501
4502void cfs_bandwidth_usage_inc(void)
4503{
4504 static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
4505}
4506
4507void cfs_bandwidth_usage_dec(void)
4508{
4509 static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
4510}
4511#else /* HAVE_JUMP_LABEL */
4512static bool cfs_bandwidth_used(void)
4513{
4514 return true;
4515}
4516
4517void cfs_bandwidth_usage_inc(void) {}
4518void cfs_bandwidth_usage_dec(void) {}
4519#endif /* HAVE_JUMP_LABEL */
4520
4521/*
4522 * default period for cfs group bandwidth.
4523 * default: 0.1s, units: nanoseconds
4524 */
4525static inline u64 default_cfs_period(void)
4526{
4527 return 100000000ULL;
4528}
4529
4530static inline u64 sched_cfs_bandwidth_slice(void)
4531{
4532 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
4533}
4534
4535/*
4536 * Replenish runtime according to assigned quota and update expiration time.
4537 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
4538 * additional synchronization around rq->lock.
4539 *
4540 * requires cfs_b->lock
4541 */
4542void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
4543{
4544 u64 now;
4545
4546 if (cfs_b->quota == RUNTIME_INF)
4547 return;
4548
4549 now = sched_clock_cpu(smp_processor_id());
4550 cfs_b->runtime = cfs_b->quota;
4551 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
4552}
4553
4554static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4555{
4556 return &tg->cfs_bandwidth;
4557}
4558
4559/* rq->task_clock normalized against any time this cfs_rq has spent throttled */
4560static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
4561{
4562 if (unlikely(cfs_rq->throttle_count))
4563 return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
4564
4565 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
4566}
4567
4568/* returns 0 on failure to allocate runtime */
4569static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4570{
4571 struct task_group *tg = cfs_rq->tg;
4572 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
4573 u64 amount = 0, min_amount, expires;
4574
4575 /* note: this is a positive sum as runtime_remaining <= 0 */
4576 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
4577
4578 raw_spin_lock(&cfs_b->lock);
4579 if (cfs_b->quota == RUNTIME_INF)
4580 amount = min_amount;
4581 else {
4582 start_cfs_bandwidth(cfs_b);
4583
4584 if (cfs_b->runtime > 0) {
4585 amount = min(cfs_b->runtime, min_amount);
4586 cfs_b->runtime -= amount;
4587 cfs_b->idle = 0;
4588 }
4589 }
4590 expires = cfs_b->runtime_expires;
4591 raw_spin_unlock(&cfs_b->lock);
4592
4593 cfs_rq->runtime_remaining += amount;
4594 /*
4595 * we may have advanced our local expiration to account for allowed
4596 * spread between our sched_clock and the one on which runtime was
4597 * issued.
4598 */
4599 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
4600 cfs_rq->runtime_expires = expires;
4601
4602 return cfs_rq->runtime_remaining > 0;
4603}
4604
4605/*
4606 * Note: This depends on the synchronization provided by sched_clock and the
4607 * fact that rq->clock snapshots this value.
4608 */
4609static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4610{
4611 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4612
4613 /* if the deadline is ahead of our clock, nothing to do */
4614 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
4615 return;
4616
4617 if (cfs_rq->runtime_remaining < 0)
4618 return;
4619
4620 /*
4621 * If the local deadline has passed we have to consider the
4622 * possibility that our sched_clock is 'fast' and the global deadline
4623 * has not truly expired.
4624 *
4625 * Fortunately we can check determine whether this the case by checking
4626 * whether the global deadline has advanced. It is valid to compare
4627 * cfs_b->runtime_expires without any locks since we only care about
4628 * exact equality, so a partial write will still work.
4629 */
4630
4631 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
4632 /* extend local deadline, drift is bounded above by 2 ticks */
4633 cfs_rq->runtime_expires += TICK_NSEC;
4634 } else {
4635 /* global deadline is ahead, expiration has passed */
4636 cfs_rq->runtime_remaining = 0;
4637 }
4638}
4639
4640static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4641{
4642 /* dock delta_exec before expiring quota (as it could span periods) */
4643 cfs_rq->runtime_remaining -= delta_exec;
4644 expire_cfs_rq_runtime(cfs_rq);
4645
4646 if (likely(cfs_rq->runtime_remaining > 0))
4647 return;
4648
4649 /*
4650 * if we're unable to extend our runtime we resched so that the active
4651 * hierarchy can be throttled
4652 */
4653 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
4654 resched_curr(rq_of(cfs_rq));
4655}
4656
4657static __always_inline
4658void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4659{
4660 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
4661 return;
4662
4663 __account_cfs_rq_runtime(cfs_rq, delta_exec);
4664}
4665
4666static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4667{
4668 return cfs_bandwidth_used() && cfs_rq->throttled;
4669}
4670
4671/* check whether cfs_rq, or any parent, is throttled */
4672static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4673{
4674 return cfs_bandwidth_used() && cfs_rq->throttle_count;
4675}
4676
4677/*
4678 * Ensure that neither of the group entities corresponding to src_cpu or
4679 * dest_cpu are members of a throttled hierarchy when performing group
4680 * load-balance operations.
4681 */
4682static inline int throttled_lb_pair(struct task_group *tg,
4683 int src_cpu, int dest_cpu)
4684{
4685 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
4686
4687 src_cfs_rq = tg->cfs_rq[src_cpu];
4688 dest_cfs_rq = tg->cfs_rq[dest_cpu];
4689
4690 return throttled_hierarchy(src_cfs_rq) ||
4691 throttled_hierarchy(dest_cfs_rq);
4692}
4693
4694/* updated child weight may affect parent so we have to do this bottom up */
4695static int tg_unthrottle_up(struct task_group *tg, void *data)
4696{
4697 struct rq *rq = data;
4698 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4699
4700 cfs_rq->throttle_count--;
4701 if (!cfs_rq->throttle_count) {
4702 /* adjust cfs_rq_clock_task() */
4703 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
4704 cfs_rq->throttled_clock_task;
4705 }
4706
4707 return 0;
4708}
4709
4710static int tg_throttle_down(struct task_group *tg, void *data)
4711{
4712 struct rq *rq = data;
4713 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4714
4715 /* group is entering throttled state, stop time */
4716 if (!cfs_rq->throttle_count)
4717 cfs_rq->throttled_clock_task = rq_clock_task(rq);
4718 cfs_rq->throttle_count++;
4719
4720 return 0;
4721}
4722
4723static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
4724{
4725 struct rq *rq = rq_of(cfs_rq);
4726 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4727 struct sched_entity *se;
4728 long task_delta, dequeue = 1;
4729 bool empty;
4730
4731 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
4732
4733 /* freeze hierarchy runnable averages while throttled */
4734 rcu_read_lock();
4735 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
4736 rcu_read_unlock();
4737
4738 task_delta = cfs_rq->h_nr_running;
4739 for_each_sched_entity(se) {
4740 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
4741 /* throttled entity or throttle-on-deactivate */
4742 if (!se->on_rq)
4743 break;
4744
4745 if (dequeue)
4746 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
4747 qcfs_rq->h_nr_running -= task_delta;
4748
4749 if (qcfs_rq->load.weight)
4750 dequeue = 0;
4751 }
4752
4753 if (!se)
4754 sub_nr_running(rq, task_delta);
4755
4756 cfs_rq->throttled = 1;
4757 cfs_rq->throttled_clock = rq_clock(rq);
4758 raw_spin_lock(&cfs_b->lock);
4759 empty = list_empty(&cfs_b->throttled_cfs_rq);
4760
4761 /*
4762 * Add to the _head_ of the list, so that an already-started
4763 * distribute_cfs_runtime will not see us
4764 */
4765 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
4766
4767 /*
4768 * If we're the first throttled task, make sure the bandwidth
4769 * timer is running.
4770 */
4771 if (empty)
4772 start_cfs_bandwidth(cfs_b);
4773
4774 raw_spin_unlock(&cfs_b->lock);
4775}
4776
4777void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
4778{
4779 struct rq *rq = rq_of(cfs_rq);
4780 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4781 struct sched_entity *se;
4782 int enqueue = 1;
4783 long task_delta;
4784
4785 se = cfs_rq->tg->se[cpu_of(rq)];
4786
4787 cfs_rq->throttled = 0;
4788
4789 update_rq_clock(rq);
4790
4791 raw_spin_lock(&cfs_b->lock);
4792 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
4793 list_del_rcu(&cfs_rq->throttled_list);
4794 raw_spin_unlock(&cfs_b->lock);
4795
4796 /* update hierarchical throttle state */
4797 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
4798
4799 if (!cfs_rq->load.weight)
4800 return;
4801
4802 task_delta = cfs_rq->h_nr_running;
4803 for_each_sched_entity(se) {
4804 if (se->on_rq)
4805 enqueue = 0;
4806
4807 cfs_rq = cfs_rq_of(se);
4808 if (enqueue)
4809 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
4810 cfs_rq->h_nr_running += task_delta;
4811
4812 if (cfs_rq_throttled(cfs_rq))
4813 break;
4814 }
4815
4816 if (!se)
4817 add_nr_running(rq, task_delta);
4818
4819 /* Determine whether we need to wake up potentially idle CPU: */
4820 if (rq->curr == rq->idle && rq->cfs.nr_running)
4821 resched_curr(rq);
4822}
4823
4824static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
4825 u64 remaining, u64 expires)
4826{
4827 struct cfs_rq *cfs_rq;
4828 u64 runtime;
4829 u64 starting_runtime = remaining;
4830
4831 rcu_read_lock();
4832 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
4833 throttled_list) {
4834 struct rq *rq = rq_of(cfs_rq);
4835 struct rq_flags rf;
4836
4837 rq_lock(rq, &rf);
4838 if (!cfs_rq_throttled(cfs_rq))
4839 goto next;
4840
4841 runtime = -cfs_rq->runtime_remaining + 1;
4842 if (runtime > remaining)
4843 runtime = remaining;
4844 remaining -= runtime;
4845
4846 cfs_rq->runtime_remaining += runtime;
4847 cfs_rq->runtime_expires = expires;
4848
4849 /* we check whether we're throttled above */
4850 if (cfs_rq->runtime_remaining > 0)
4851 unthrottle_cfs_rq(cfs_rq);
4852
4853next:
4854 rq_unlock(rq, &rf);
4855
4856 if (!remaining)
4857 break;
4858 }
4859 rcu_read_unlock();
4860
4861 return starting_runtime - remaining;
4862}
4863
4864/*
4865 * Responsible for refilling a task_group's bandwidth and unthrottling its
4866 * cfs_rqs as appropriate. If there has been no activity within the last
4867 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
4868 * used to track this state.
4869 */
4870static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
4871{
4872 u64 runtime, runtime_expires;
4873 int throttled;
4874
4875 /* no need to continue the timer with no bandwidth constraint */
4876 if (cfs_b->quota == RUNTIME_INF)
4877 goto out_deactivate;
4878
4879 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4880 cfs_b->nr_periods += overrun;
4881
4882 /*
4883 * idle depends on !throttled (for the case of a large deficit), and if
4884 * we're going inactive then everything else can be deferred
4885 */
4886 if (cfs_b->idle && !throttled)
4887 goto out_deactivate;
4888
4889 __refill_cfs_bandwidth_runtime(cfs_b);
4890
4891 if (!throttled) {
4892 /* mark as potentially idle for the upcoming period */
4893 cfs_b->idle = 1;
4894 return 0;
4895 }
4896
4897 /* account preceding periods in which throttling occurred */
4898 cfs_b->nr_throttled += overrun;
4899
4900 runtime_expires = cfs_b->runtime_expires;
4901
4902 /*
4903 * This check is repeated as we are holding onto the new bandwidth while
4904 * we unthrottle. This can potentially race with an unthrottled group
4905 * trying to acquire new bandwidth from the global pool. This can result
4906 * in us over-using our runtime if it is all used during this loop, but
4907 * only by limited amounts in that extreme case.
4908 */
4909 while (throttled && cfs_b->runtime > 0) {
4910 runtime = cfs_b->runtime;
4911 raw_spin_unlock(&cfs_b->lock);
4912 /* we can't nest cfs_b->lock while distributing bandwidth */
4913 runtime = distribute_cfs_runtime(cfs_b, runtime,
4914 runtime_expires);
4915 raw_spin_lock(&cfs_b->lock);
4916
4917 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4918
4919 cfs_b->runtime -= min(runtime, cfs_b->runtime);
4920 }
4921
4922 /*
4923 * While we are ensured activity in the period following an
4924 * unthrottle, this also covers the case in which the new bandwidth is
4925 * insufficient to cover the existing bandwidth deficit. (Forcing the
4926 * timer to remain active while there are any throttled entities.)
4927 */
4928 cfs_b->idle = 0;
4929
4930 return 0;
4931
4932out_deactivate:
4933 return 1;
4934}
4935
4936/* a cfs_rq won't donate quota below this amount */
4937static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
4938/* minimum remaining period time to redistribute slack quota */
4939static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
4940/* how long we wait to gather additional slack before distributing */
4941static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
4942
4943/*
4944 * Are we near the end of the current quota period?
4945 *
4946 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4947 * hrtimer base being cleared by hrtimer_start. In the case of
4948 * migrate_hrtimers, base is never cleared, so we are fine.
4949 */
4950static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
4951{
4952 struct hrtimer *refresh_timer = &cfs_b->period_timer;
4953 u64 remaining;
4954
4955 /* if the call-back is running a quota refresh is already occurring */
4956 if (hrtimer_callback_running(refresh_timer))
4957 return 1;
4958
4959 /* is a quota refresh about to occur? */
4960 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
4961 if (remaining < min_expire)
4962 return 1;
4963
4964 return 0;
4965}
4966
4967static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
4968{
4969 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
4970
4971 /* if there's a quota refresh soon don't bother with slack */
4972 if (runtime_refresh_within(cfs_b, min_left))
4973 return;
4974
4975 hrtimer_start(&cfs_b->slack_timer,
4976 ns_to_ktime(cfs_bandwidth_slack_period),
4977 HRTIMER_MODE_REL);
4978}
4979
4980/* we know any runtime found here is valid as update_curr() precedes return */
4981static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4982{
4983 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4984 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
4985
4986 if (slack_runtime <= 0)
4987 return;
4988
4989 raw_spin_lock(&cfs_b->lock);
4990 if (cfs_b->quota != RUNTIME_INF &&
4991 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
4992 cfs_b->runtime += slack_runtime;
4993
4994 /* we are under rq->lock, defer unthrottling using a timer */
4995 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
4996 !list_empty(&cfs_b->throttled_cfs_rq))
4997 start_cfs_slack_bandwidth(cfs_b);
4998 }
4999 raw_spin_unlock(&cfs_b->lock);
5000
5001 /* even if it's not valid for return we don't want to try again */
5002 cfs_rq->runtime_remaining -= slack_runtime;
5003}
5004
5005static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5006{
5007 if (!cfs_bandwidth_used())
5008 return;
5009
5010 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
5011 return;
5012
5013 __return_cfs_rq_runtime(cfs_rq);
5014}
5015
5016/*
5017 * This is done with a timer (instead of inline with bandwidth return) since
5018 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
5019 */
5020static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
5021{
5022 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
5023 u64 expires;
5024
5025 /* confirm we're still not at a refresh boundary */
5026 raw_spin_lock(&cfs_b->lock);
5027 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
5028 raw_spin_unlock(&cfs_b->lock);
5029 return;
5030 }
5031
5032 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
5033 runtime = cfs_b->runtime;
5034
5035 expires = cfs_b->runtime_expires;
5036 raw_spin_unlock(&cfs_b->lock);
5037
5038 if (!runtime)
5039 return;
5040
5041 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
5042
5043 raw_spin_lock(&cfs_b->lock);
5044 if (expires == cfs_b->runtime_expires)
5045 cfs_b->runtime -= min(runtime, cfs_b->runtime);
5046 raw_spin_unlock(&cfs_b->lock);
5047}
5048
5049/*
5050 * When a group wakes up we want to make sure that its quota is not already
5051 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
5052 * runtime as update_curr() throttling can not not trigger until it's on-rq.
5053 */
5054static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
5055{
5056 if (!cfs_bandwidth_used())
5057 return;
5058
5059 /* an active group must be handled by the update_curr()->put() path */
5060 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
5061 return;
5062
5063 /* ensure the group is not already throttled */
5064 if (cfs_rq_throttled(cfs_rq))
5065 return;
5066
5067 /* update runtime allocation */
5068 account_cfs_rq_runtime(cfs_rq, 0);
5069 if (cfs_rq->runtime_remaining <= 0)
5070 throttle_cfs_rq(cfs_rq);
5071}
5072
5073static void sync_throttle(struct task_group *tg, int cpu)
5074{
5075 struct cfs_rq *pcfs_rq, *cfs_rq;
5076
5077 if (!cfs_bandwidth_used())
5078 return;
5079
5080 if (!tg->parent)
5081 return;
5082
5083 cfs_rq = tg->cfs_rq[cpu];
5084 pcfs_rq = tg->parent->cfs_rq[cpu];
5085
5086 cfs_rq->throttle_count = pcfs_rq->throttle_count;
5087 cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
5088}
5089
5090/* conditionally throttle active cfs_rq's from put_prev_entity() */
5091static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5092{
5093 if (!cfs_bandwidth_used())
5094 return false;
5095
5096 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
5097 return false;
5098
5099 /*
5100 * it's possible for a throttled entity to be forced into a running
5101 * state (e.g. set_curr_task), in this case we're finished.
5102 */
5103 if (cfs_rq_throttled(cfs_rq))
5104 return true;
5105
5106 throttle_cfs_rq(cfs_rq);
5107 return true;
5108}
5109
5110static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
5111{
5112 struct cfs_bandwidth *cfs_b =
5113 container_of(timer, struct cfs_bandwidth, slack_timer);
5114
5115 do_sched_cfs_slack_timer(cfs_b);
5116
5117 return HRTIMER_NORESTART;
5118}
5119
5120static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
5121{
5122 struct cfs_bandwidth *cfs_b =
5123 container_of(timer, struct cfs_bandwidth, period_timer);
5124 int overrun;
5125 int idle = 0;
5126
5127 raw_spin_lock(&cfs_b->lock);
5128 for (;;) {
5129 overrun = hrtimer_forward_now(timer, cfs_b->period);
5130 if (!overrun)
5131 break;
5132
5133 idle = do_sched_cfs_period_timer(cfs_b, overrun);
5134 }
5135 if (idle)
5136 cfs_b->period_active = 0;
5137 raw_spin_unlock(&cfs_b->lock);
5138
5139 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
5140}
5141
5142void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5143{
5144 raw_spin_lock_init(&cfs_b->lock);
5145 cfs_b->runtime = 0;
5146 cfs_b->quota = RUNTIME_INF;
5147 cfs_b->period = ns_to_ktime(default_cfs_period());
5148
5149 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
5150 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
5151 cfs_b->period_timer.function = sched_cfs_period_timer;
5152 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
5153 cfs_b->slack_timer.function = sched_cfs_slack_timer;
5154}
5155
5156static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5157{
5158 cfs_rq->runtime_enabled = 0;
5159 INIT_LIST_HEAD(&cfs_rq->throttled_list);
5160}
5161
5162void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5163{
5164 lockdep_assert_held(&cfs_b->lock);
5165
5166 if (!cfs_b->period_active) {
5167 cfs_b->period_active = 1;
5168 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
5169 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
5170 }
5171}
5172
5173static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5174{
5175 /* init_cfs_bandwidth() was not called */
5176 if (!cfs_b->throttled_cfs_rq.next)
5177 return;
5178
5179 hrtimer_cancel(&cfs_b->period_timer);
5180 hrtimer_cancel(&cfs_b->slack_timer);
5181}
5182
5183/*
5184 * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
5185 *
5186 * The race is harmless, since modifying bandwidth settings of unhooked group
5187 * bits doesn't do much.
5188 */
5189
5190/* cpu online calback */
5191static void __maybe_unused update_runtime_enabled(struct rq *rq)
5192{
5193 struct task_group *tg;
5194
5195 lockdep_assert_held(&rq->lock);
5196
5197 rcu_read_lock();
5198 list_for_each_entry_rcu(tg, &task_groups, list) {
5199 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
5200 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
5201
5202 raw_spin_lock(&cfs_b->lock);
5203 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
5204 raw_spin_unlock(&cfs_b->lock);
5205 }
5206 rcu_read_unlock();
5207}
5208
5209/* cpu offline callback */
5210static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
5211{
5212 struct task_group *tg;
5213
5214 lockdep_assert_held(&rq->lock);
5215
5216 rcu_read_lock();
5217 list_for_each_entry_rcu(tg, &task_groups, list) {
5218 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
5219
5220 if (!cfs_rq->runtime_enabled)
5221 continue;
5222
5223 /*
5224 * clock_task is not advancing so we just need to make sure
5225 * there's some valid quota amount
5226 */
5227 cfs_rq->runtime_remaining = 1;
5228 /*
5229 * Offline rq is schedulable till CPU is completely disabled
5230 * in take_cpu_down(), so we prevent new cfs throttling here.
5231 */
5232 cfs_rq->runtime_enabled = 0;
5233
5234 if (cfs_rq_throttled(cfs_rq))
5235 unthrottle_cfs_rq(cfs_rq);
5236 }
5237 rcu_read_unlock();
5238}
5239
5240#else /* CONFIG_CFS_BANDWIDTH */
5241static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
5242{
5243 return rq_clock_task(rq_of(cfs_rq));
5244}
5245
5246static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
5247static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
5248static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
5249static inline void sync_throttle(struct task_group *tg, int cpu) {}
5250static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5251
5252static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
5253{
5254 return 0;
5255}
5256
5257static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
5258{
5259 return 0;
5260}
5261
5262static inline int throttled_lb_pair(struct task_group *tg,
5263 int src_cpu, int dest_cpu)
5264{
5265 return 0;
5266}
5267
5268void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
5269
5270#ifdef CONFIG_FAIR_GROUP_SCHED
5271static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5272#endif
5273
5274static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
5275{
5276 return NULL;
5277}
5278static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
5279static inline void update_runtime_enabled(struct rq *rq) {}
5280static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
5281
5282#endif /* CONFIG_CFS_BANDWIDTH */
5283
5284/**************************************************
5285 * CFS operations on tasks:
5286 */
5287
5288#ifdef CONFIG_SCHED_HRTICK
5289static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
5290{
5291 struct sched_entity *se = &p->se;
5292 struct cfs_rq *cfs_rq = cfs_rq_of(se);
5293
5294 SCHED_WARN_ON(task_rq(p) != rq);
5295
5296 if (rq->cfs.h_nr_running > 1) {
5297 u64 slice = sched_slice(cfs_rq, se);
5298 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
5299 s64 delta = slice - ran;
5300
5301 if (delta < 0) {
5302 if (rq->curr == p)
5303 resched_curr(rq);
5304 return;
5305 }
5306 hrtick_start(rq, delta);
5307 }
5308}
5309
5310/*
5311 * called from enqueue/dequeue and updates the hrtick when the
5312 * current task is from our class and nr_running is low enough
5313 * to matter.
5314 */
5315static void hrtick_update(struct rq *rq)
5316{
5317 struct task_struct *curr = rq->curr;
5318
5319 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
5320 return;
5321
5322 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
5323 hrtick_start_fair(rq, curr);
5324}
5325#else /* !CONFIG_SCHED_HRTICK */
5326static inline void
5327hrtick_start_fair(struct rq *rq, struct task_struct *p)
5328{
5329}
5330
5331static inline void hrtick_update(struct rq *rq)
5332{
5333}
5334#endif
5335
5336/*
5337 * The enqueue_task method is called before nr_running is
5338 * increased. Here we update the fair scheduling stats and
5339 * then put the task into the rbtree:
5340 */
5341static void
5342enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5343{
5344 struct cfs_rq *cfs_rq;
5345 struct sched_entity *se = &p->se;
5346
5347 /*
5348 * If in_iowait is set, the code below may not trigger any cpufreq
5349 * utilization updates, so do it here explicitly with the IOWAIT flag
5350 * passed.
5351 */
5352 if (p->in_iowait)
5353 cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
5354
5355 for_each_sched_entity(se) {
5356 if (se->on_rq)
5357 break;
5358 cfs_rq = cfs_rq_of(se);
5359 enqueue_entity(cfs_rq, se, flags);
5360
5361 /*
5362 * end evaluation on encountering a throttled cfs_rq
5363 *
5364 * note: in the case of encountering a throttled cfs_rq we will
5365 * post the final h_nr_running increment below.
5366 */
5367 if (cfs_rq_throttled(cfs_rq))
5368 break;
5369 cfs_rq->h_nr_running++;
5370
5371 flags = ENQUEUE_WAKEUP;
5372 }
5373
5374 for_each_sched_entity(se) {
5375 cfs_rq = cfs_rq_of(se);
5376 cfs_rq->h_nr_running++;
5377
5378 if (cfs_rq_throttled(cfs_rq))
5379 break;
5380
5381 update_load_avg(cfs_rq, se, UPDATE_TG);
5382 update_cfs_group(se);
5383 }
5384
5385 if (!se)
5386 add_nr_running(rq, 1);
5387
5388 util_est_enqueue(&rq->cfs, p);
5389 hrtick_update(rq);
5390}
5391
5392static void set_next_buddy(struct sched_entity *se);
5393
5394/*
5395 * The dequeue_task method is called before nr_running is
5396 * decreased. We remove the task from the rbtree and
5397 * update the fair scheduling stats:
5398 */
5399static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5400{
5401 struct cfs_rq *cfs_rq;
5402 struct sched_entity *se = &p->se;
5403 int task_sleep = flags & DEQUEUE_SLEEP;
5404
5405 for_each_sched_entity(se) {
5406 cfs_rq = cfs_rq_of(se);
5407 dequeue_entity(cfs_rq, se, flags);
5408
5409 /*
5410 * end evaluation on encountering a throttled cfs_rq
5411 *
5412 * note: in the case of encountering a throttled cfs_rq we will
5413 * post the final h_nr_running decrement below.
5414 */
5415 if (cfs_rq_throttled(cfs_rq))
5416 break;
5417 cfs_rq->h_nr_running--;
5418
5419 /* Don't dequeue parent if it has other entities besides us */
5420 if (cfs_rq->load.weight) {
5421 /* Avoid re-evaluating load for this entity: */
5422 se = parent_entity(se);
5423 /*
5424 * Bias pick_next to pick a task from this cfs_rq, as
5425 * p is sleeping when it is within its sched_slice.
5426 */
5427 if (task_sleep && se && !throttled_hierarchy(cfs_rq))
5428 set_next_buddy(se);
5429 break;
5430 }
5431 flags |= DEQUEUE_SLEEP;
5432 }
5433
5434 for_each_sched_entity(se) {
5435 cfs_rq = cfs_rq_of(se);
5436 cfs_rq->h_nr_running--;
5437
5438 if (cfs_rq_throttled(cfs_rq))
5439 break;
5440
5441 update_load_avg(cfs_rq, se, UPDATE_TG);
5442 update_cfs_group(se);
5443 }
5444
5445 if (!se)
5446 sub_nr_running(rq, 1);
5447
5448 util_est_dequeue(&rq->cfs, p, task_sleep);
5449 hrtick_update(rq);
5450}
5451
5452#ifdef CONFIG_SMP
5453
5454/* Working cpumask for: load_balance, load_balance_newidle. */
5455DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
5456DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
5457
5458#ifdef CONFIG_NO_HZ_COMMON
5459/*
5460 * per rq 'load' arrray crap; XXX kill this.
5461 */
5462
5463/*
5464 * The exact cpuload calculated at every tick would be:
5465 *
5466 * load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
5467 *
5468 * If a CPU misses updates for n ticks (as it was idle) and update gets
5469 * called on the n+1-th tick when CPU may be busy, then we have:
5470 *
5471 * load_n = (1 - 1/2^i)^n * load_0
5472 * load_n+1 = (1 - 1/2^i) * load_n + (1/2^i) * cur_load
5473 *
5474 * decay_load_missed() below does efficient calculation of
5475 *
5476 * load' = (1 - 1/2^i)^n * load
5477 *
5478 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
5479 * This allows us to precompute the above in said factors, thereby allowing the
5480 * reduction of an arbitrary n in O(log_2 n) steps. (See also
5481 * fixed_power_int())
5482 *
5483 * The calculation is approximated on a 128 point scale.
5484 */
5485#define DEGRADE_SHIFT 7
5486
5487static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
5488static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
5489 { 0, 0, 0, 0, 0, 0, 0, 0 },
5490 { 64, 32, 8, 0, 0, 0, 0, 0 },
5491 { 96, 72, 40, 12, 1, 0, 0, 0 },
5492 { 112, 98, 75, 43, 15, 1, 0, 0 },
5493 { 120, 112, 98, 76, 45, 16, 2, 0 }
5494};
5495
5496/*
5497 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
5498 * would be when CPU is idle and so we just decay the old load without
5499 * adding any new load.
5500 */
5501static unsigned long
5502decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
5503{
5504 int j = 0;
5505
5506 if (!missed_updates)
5507 return load;
5508
5509 if (missed_updates >= degrade_zero_ticks[idx])
5510 return 0;
5511
5512 if (idx == 1)
5513 return load >> missed_updates;
5514
5515 while (missed_updates) {
5516 if (missed_updates % 2)
5517 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
5518
5519 missed_updates >>= 1;
5520 j++;
5521 }
5522 return load;
5523}
5524
5525static struct {
5526 cpumask_var_t idle_cpus_mask;
5527 atomic_t nr_cpus;
5528 int has_blocked; /* Idle CPUS has blocked load */
5529 unsigned long next_balance; /* in jiffy units */
5530 unsigned long next_blocked; /* Next update of blocked load in jiffies */
5531} nohz ____cacheline_aligned;
5532
5533#endif /* CONFIG_NO_HZ_COMMON */
5534
5535/**
5536 * __cpu_load_update - update the rq->cpu_load[] statistics
5537 * @this_rq: The rq to update statistics for
5538 * @this_load: The current load
5539 * @pending_updates: The number of missed updates
5540 *
5541 * Update rq->cpu_load[] statistics. This function is usually called every
5542 * scheduler tick (TICK_NSEC).
5543 *
5544 * This function computes a decaying average:
5545 *
5546 * load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
5547 *
5548 * Because of NOHZ it might not get called on every tick which gives need for
5549 * the @pending_updates argument.
5550 *
5551 * load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
5552 * = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
5553 * = A * (A * load[i]_n-2 + B) + B
5554 * = A * (A * (A * load[i]_n-3 + B) + B) + B
5555 * = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
5556 * = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
5557 * = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
5558 * = (1 - 1/2^i)^n * (load[i]_0 - load) + load
5559 *
5560 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
5561 * any change in load would have resulted in the tick being turned back on.
5562 *
5563 * For regular NOHZ, this reduces to:
5564 *
5565 * load[i]_n = (1 - 1/2^i)^n * load[i]_0
5566 *
5567 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
5568 * term.
5569 */
5570static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
5571 unsigned long pending_updates)
5572{
5573 unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
5574 int i, scale;
5575
5576 this_rq->nr_load_updates++;
5577
5578 /* Update our load: */
5579 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
5580 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
5581 unsigned long old_load, new_load;
5582
5583 /* scale is effectively 1 << i now, and >> i divides by scale */
5584
5585 old_load = this_rq->cpu_load[i];
5586#ifdef CONFIG_NO_HZ_COMMON
5587 old_load = decay_load_missed(old_load, pending_updates - 1, i);
5588 if (tickless_load) {
5589 old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
5590 /*
5591 * old_load can never be a negative value because a
5592 * decayed tickless_load cannot be greater than the
5593 * original tickless_load.
5594 */
5595 old_load += tickless_load;
5596 }
5597#endif
5598 new_load = this_load;
5599 /*
5600 * Round up the averaging division if load is increasing. This
5601 * prevents us from getting stuck on 9 if the load is 10, for
5602 * example.
5603 */
5604 if (new_load > old_load)
5605 new_load += scale - 1;
5606
5607 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
5608 }
5609
5610 sched_avg_update(this_rq);
5611}
5612
5613/* Used instead of source_load when we know the type == 0 */
5614static unsigned long weighted_cpuload(struct rq *rq)
5615{
5616 return cfs_rq_runnable_load_avg(&rq->cfs);
5617}
5618
5619#ifdef CONFIG_NO_HZ_COMMON
5620/*
5621 * There is no sane way to deal with nohz on smp when using jiffies because the
5622 * CPU doing the jiffies update might drift wrt the CPU doing the jiffy reading
5623 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
5624 *
5625 * Therefore we need to avoid the delta approach from the regular tick when
5626 * possible since that would seriously skew the load calculation. This is why we
5627 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
5628 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
5629 * loop exit, nohz_idle_balance, nohz full exit...)
5630 *
5631 * This means we might still be one tick off for nohz periods.
5632 */
5633
5634static void cpu_load_update_nohz(struct rq *this_rq,
5635 unsigned long curr_jiffies,
5636 unsigned long load)
5637{
5638 unsigned long pending_updates;
5639
5640 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
5641 if (pending_updates) {
5642 this_rq->last_load_update_tick = curr_jiffies;
5643 /*
5644 * In the regular NOHZ case, we were idle, this means load 0.
5645 * In the NOHZ_FULL case, we were non-idle, we should consider
5646 * its weighted load.
5647 */
5648 cpu_load_update(this_rq, load, pending_updates);
5649 }
5650}
5651
5652/*
5653 * Called from nohz_idle_balance() to update the load ratings before doing the
5654 * idle balance.
5655 */
5656static void cpu_load_update_idle(struct rq *this_rq)
5657{
5658 /*
5659 * bail if there's load or we're actually up-to-date.
5660 */
5661 if (weighted_cpuload(this_rq))
5662 return;
5663
5664 cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
5665}
5666
5667/*
5668 * Record CPU load on nohz entry so we know the tickless load to account
5669 * on nohz exit. cpu_load[0] happens then to be updated more frequently
5670 * than other cpu_load[idx] but it should be fine as cpu_load readers
5671 * shouldn't rely into synchronized cpu_load[*] updates.
5672 */
5673void cpu_load_update_nohz_start(void)
5674{
5675 struct rq *this_rq = this_rq();
5676
5677 /*
5678 * This is all lockless but should be fine. If weighted_cpuload changes
5679 * concurrently we'll exit nohz. And cpu_load write can race with
5680 * cpu_load_update_idle() but both updater would be writing the same.
5681 */
5682 this_rq->cpu_load[0] = weighted_cpuload(this_rq);
5683}
5684
5685/*
5686 * Account the tickless load in the end of a nohz frame.
5687 */
5688void cpu_load_update_nohz_stop(void)
5689{
5690 unsigned long curr_jiffies = READ_ONCE(jiffies);
5691 struct rq *this_rq = this_rq();
5692 unsigned long load;
5693 struct rq_flags rf;
5694
5695 if (curr_jiffies == this_rq->last_load_update_tick)
5696 return;
5697
5698 load = weighted_cpuload(this_rq);
5699 rq_lock(this_rq, &rf);
5700 update_rq_clock(this_rq);
5701 cpu_load_update_nohz(this_rq, curr_jiffies, load);
5702 rq_unlock(this_rq, &rf);
5703}
5704#else /* !CONFIG_NO_HZ_COMMON */
5705static inline void cpu_load_update_nohz(struct rq *this_rq,
5706 unsigned long curr_jiffies,
5707 unsigned long load) { }
5708#endif /* CONFIG_NO_HZ_COMMON */
5709
5710static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load)
5711{
5712#ifdef CONFIG_NO_HZ_COMMON
5713 /* See the mess around cpu_load_update_nohz(). */
5714 this_rq->last_load_update_tick = READ_ONCE(jiffies);
5715#endif
5716 cpu_load_update(this_rq, load, 1);
5717}
5718
5719/*
5720 * Called from scheduler_tick()
5721 */
5722void cpu_load_update_active(struct rq *this_rq)
5723{
5724 unsigned long load = weighted_cpuload(this_rq);
5725
5726 if (tick_nohz_tick_stopped())
5727 cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
5728 else
5729 cpu_load_update_periodic(this_rq, load);
5730}
5731
5732/*
5733 * Return a low guess at the load of a migration-source CPU weighted
5734 * according to the scheduling class and "nice" value.
5735 *
5736 * We want to under-estimate the load of migration sources, to
5737 * balance conservatively.
5738 */
5739static unsigned long source_load(int cpu, int type)
5740{
5741 struct rq *rq = cpu_rq(cpu);
5742 unsigned long total = weighted_cpuload(rq);
5743
5744 if (type == 0 || !sched_feat(LB_BIAS))
5745 return total;
5746
5747 return min(rq->cpu_load[type-1], total);
5748}
5749
5750/*
5751 * Return a high guess at the load of a migration-target CPU weighted
5752 * according to the scheduling class and "nice" value.
5753 */
5754static unsigned long target_load(int cpu, int type)
5755{
5756 struct rq *rq = cpu_rq(cpu);
5757 unsigned long total = weighted_cpuload(rq);
5758
5759 if (type == 0 || !sched_feat(LB_BIAS))
5760 return total;
5761
5762 return max(rq->cpu_load[type-1], total);
5763}
5764
5765static unsigned long capacity_of(int cpu)
5766{
5767 return cpu_rq(cpu)->cpu_capacity;
5768}
5769
5770static unsigned long capacity_orig_of(int cpu)
5771{
5772 return cpu_rq(cpu)->cpu_capacity_orig;
5773}
5774
5775static unsigned long cpu_avg_load_per_task(int cpu)
5776{
5777 struct rq *rq = cpu_rq(cpu);
5778 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
5779 unsigned long load_avg = weighted_cpuload(rq);
5780
5781 if (nr_running)
5782 return load_avg / nr_running;
5783
5784 return 0;
5785}
5786
5787static void record_wakee(struct task_struct *p)
5788{
5789 /*
5790 * Only decay a single time; tasks that have less then 1 wakeup per
5791 * jiffy will not have built up many flips.
5792 */
5793 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
5794 current->wakee_flips >>= 1;
5795 current->wakee_flip_decay_ts = jiffies;
5796 }
5797
5798 if (current->last_wakee != p) {
5799 current->last_wakee = p;
5800 current->wakee_flips++;
5801 }
5802}
5803
5804/*
5805 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5806 *
5807 * A waker of many should wake a different task than the one last awakened
5808 * at a frequency roughly N times higher than one of its wakees.
5809 *
5810 * In order to determine whether we should let the load spread vs consolidating
5811 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
5812 * partner, and a factor of lls_size higher frequency in the other.
5813 *
5814 * With both conditions met, we can be relatively sure that the relationship is
5815 * non-monogamous, with partner count exceeding socket size.
5816 *
5817 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
5818 * whatever is irrelevant, spread criteria is apparent partner count exceeds
5819 * socket size.
5820 */
5821static int wake_wide(struct task_struct *p)
5822{
5823 unsigned int master = current->wakee_flips;
5824 unsigned int slave = p->wakee_flips;
5825 int factor = this_cpu_read(sd_llc_size);
5826
5827 if (master < slave)
5828 swap(master, slave);
5829 if (slave < factor || master < slave * factor)
5830 return 0;
5831 return 1;
5832}
5833
5834/*
5835 * The purpose of wake_affine() is to quickly determine on which CPU we can run
5836 * soonest. For the purpose of speed we only consider the waking and previous
5837 * CPU.
5838 *
5839 * wake_affine_idle() - only considers 'now', it check if the waking CPU is
5840 * cache-affine and is (or will be) idle.
5841 *
5842 * wake_affine_weight() - considers the weight to reflect the average
5843 * scheduling latency of the CPUs. This seems to work
5844 * for the overloaded case.
5845 */
5846static int
5847wake_affine_idle(int this_cpu, int prev_cpu, int sync)
5848{
5849 /*
5850 * If this_cpu is idle, it implies the wakeup is from interrupt
5851 * context. Only allow the move if cache is shared. Otherwise an
5852 * interrupt intensive workload could force all tasks onto one
5853 * node depending on the IO topology or IRQ affinity settings.
5854 *
5855 * If the prev_cpu is idle and cache affine then avoid a migration.
5856 * There is no guarantee that the cache hot data from an interrupt
5857 * is more important than cache hot data on the prev_cpu and from
5858 * a cpufreq perspective, it's better to have higher utilisation
5859 * on one CPU.
5860 */
5861 if (idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
5862 return idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
5863
5864 if (sync && cpu_rq(this_cpu)->nr_running == 1)
5865 return this_cpu;
5866
5867 return nr_cpumask_bits;
5868}
5869
5870static int
5871wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
5872 int this_cpu, int prev_cpu, int sync)
5873{
5874 s64 this_eff_load, prev_eff_load;
5875 unsigned long task_load;
5876
5877 this_eff_load = target_load(this_cpu, sd->wake_idx);
5878
5879 if (sync) {
5880 unsigned long current_load = task_h_load(current);
5881
5882 if (current_load > this_eff_load)
5883 return this_cpu;
5884
5885 this_eff_load -= current_load;
5886 }
5887
5888 task_load = task_h_load(p);
5889
5890 this_eff_load += task_load;
5891 if (sched_feat(WA_BIAS))
5892 this_eff_load *= 100;
5893 this_eff_load *= capacity_of(prev_cpu);
5894
5895 prev_eff_load = source_load(prev_cpu, sd->wake_idx);
5896 prev_eff_load -= task_load;
5897 if (sched_feat(WA_BIAS))
5898 prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2;
5899 prev_eff_load *= capacity_of(this_cpu);
5900
5901 /*
5902 * If sync, adjust the weight of prev_eff_load such that if
5903 * prev_eff == this_eff that select_idle_sibling() will consider
5904 * stacking the wakee on top of the waker if no other CPU is
5905 * idle.
5906 */
5907 if (sync)
5908 prev_eff_load += 1;
5909
5910 return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
5911}
5912
5913static int wake_affine(struct sched_domain *sd, struct task_struct *p,
5914 int this_cpu, int prev_cpu, int sync)
5915{
5916 int target = nr_cpumask_bits;
5917
5918 if (sched_feat(WA_IDLE))
5919 target = wake_affine_idle(this_cpu, prev_cpu, sync);
5920
5921 if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
5922 target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
5923
5924 schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
5925 if (target == nr_cpumask_bits)
5926 return prev_cpu;
5927
5928 schedstat_inc(sd->ttwu_move_affine);
5929 schedstat_inc(p->se.statistics.nr_wakeups_affine);
5930 return target;
5931}
5932
5933static unsigned long cpu_util_wake(int cpu, struct task_struct *p);
5934
5935static unsigned long capacity_spare_wake(int cpu, struct task_struct *p)
5936{
5937 return max_t(long, capacity_of(cpu) - cpu_util_wake(cpu, p), 0);
5938}
5939
5940/*
5941 * find_idlest_group finds and returns the least busy CPU group within the
5942 * domain.
5943 *
5944 * Assumes p is allowed on at least one CPU in sd.
5945 */
5946static struct sched_group *
5947find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5948 int this_cpu, int sd_flag)
5949{
5950 struct sched_group *idlest = NULL, *group = sd->groups;
5951 struct sched_group *most_spare_sg = NULL;
5952 unsigned long min_runnable_load = ULONG_MAX;
5953 unsigned long this_runnable_load = ULONG_MAX;
5954 unsigned long min_avg_load = ULONG_MAX, this_avg_load = ULONG_MAX;
5955 unsigned long most_spare = 0, this_spare = 0;
5956 int load_idx = sd->forkexec_idx;
5957 int imbalance_scale = 100 + (sd->imbalance_pct-100)/2;
5958 unsigned long imbalance = scale_load_down(NICE_0_LOAD) *
5959 (sd->imbalance_pct-100) / 100;
5960
5961 if (sd_flag & SD_BALANCE_WAKE)
5962 load_idx = sd->wake_idx;
5963
5964 do {
5965 unsigned long load, avg_load, runnable_load;
5966 unsigned long spare_cap, max_spare_cap;
5967 int local_group;
5968 int i;
5969
5970 /* Skip over this group if it has no CPUs allowed */
5971 if (!cpumask_intersects(sched_group_span(group),
5972 &p->cpus_allowed))
5973 continue;
5974
5975 local_group = cpumask_test_cpu(this_cpu,
5976 sched_group_span(group));
5977
5978 /*
5979 * Tally up the load of all CPUs in the group and find
5980 * the group containing the CPU with most spare capacity.
5981 */
5982 avg_load = 0;
5983 runnable_load = 0;
5984 max_spare_cap = 0;
5985
5986 for_each_cpu(i, sched_group_span(group)) {
5987 /* Bias balancing toward CPUs of our domain */
5988 if (local_group)
5989 load = source_load(i, load_idx);
5990 else
5991 load = target_load(i, load_idx);
5992
5993 runnable_load += load;
5994
5995 avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs);
5996
5997 spare_cap = capacity_spare_wake(i, p);
5998
5999 if (spare_cap > max_spare_cap)
6000 max_spare_cap = spare_cap;
6001 }
6002
6003 /* Adjust by relative CPU capacity of the group */
6004 avg_load = (avg_load * SCHED_CAPACITY_SCALE) /
6005 group->sgc->capacity;
6006 runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) /
6007 group->sgc->capacity;
6008
6009 if (local_group) {
6010 this_runnable_load = runnable_load;
6011 this_avg_load = avg_load;
6012 this_spare = max_spare_cap;
6013 } else {
6014 if (min_runnable_load > (runnable_load + imbalance)) {
6015 /*
6016 * The runnable load is significantly smaller
6017 * so we can pick this new CPU:
6018 */
6019 min_runnable_load = runnable_load;
6020 min_avg_load = avg_load;
6021 idlest = group;
6022 } else if ((runnable_load < (min_runnable_load + imbalance)) &&
6023 (100*min_avg_load > imbalance_scale*avg_load)) {
6024 /*
6025 * The runnable loads are close so take the
6026 * blocked load into account through avg_load:
6027 */
6028 min_avg_load = avg_load;
6029 idlest = group;
6030 }
6031
6032 if (most_spare < max_spare_cap) {
6033 most_spare = max_spare_cap;
6034 most_spare_sg = group;
6035 }
6036 }
6037 } while (group = group->next, group != sd->groups);
6038
6039 /*
6040 * The cross-over point between using spare capacity or least load
6041 * is too conservative for high utilization tasks on partially
6042 * utilized systems if we require spare_capacity > task_util(p),
6043 * so we allow for some task stuffing by using
6044 * spare_capacity > task_util(p)/2.
6045 *
6046 * Spare capacity can't be used for fork because the utilization has
6047 * not been set yet, we must first select a rq to compute the initial
6048 * utilization.
6049 */
6050 if (sd_flag & SD_BALANCE_FORK)
6051 goto skip_spare;
6052
6053 if (this_spare > task_util(p) / 2 &&
6054 imbalance_scale*this_spare > 100*most_spare)
6055 return NULL;
6056
6057 if (most_spare > task_util(p) / 2)
6058 return most_spare_sg;
6059
6060skip_spare:
6061 if (!idlest)
6062 return NULL;
6063
6064 /*
6065 * When comparing groups across NUMA domains, it's possible for the
6066 * local domain to be very lightly loaded relative to the remote
6067 * domains but "imbalance" skews the comparison making remote CPUs
6068 * look much more favourable. When considering cross-domain, add
6069 * imbalance to the runnable load on the remote node and consider
6070 * staying local.
6071 */
6072 if ((sd->flags & SD_NUMA) &&
6073 min_runnable_load + imbalance >= this_runnable_load)
6074 return NULL;
6075
6076 if (min_runnable_load > (this_runnable_load + imbalance))
6077 return NULL;
6078
6079 if ((this_runnable_load < (min_runnable_load + imbalance)) &&
6080 (100*this_avg_load < imbalance_scale*min_avg_load))
6081 return NULL;
6082
6083 return idlest;
6084}
6085
6086/*
6087 * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
6088 */
6089static int
6090find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
6091{
6092 unsigned long load, min_load = ULONG_MAX;
6093 unsigned int min_exit_latency = UINT_MAX;
6094 u64 latest_idle_timestamp = 0;
6095 int least_loaded_cpu = this_cpu;
6096 int shallowest_idle_cpu = -1;
6097 int i;
6098
6099 /* Check if we have any choice: */
6100 if (group->group_weight == 1)
6101 return cpumask_first(sched_group_span(group));
6102
6103 /* Traverse only the allowed CPUs */
6104 for_each_cpu_and(i, sched_group_span(group), &p->cpus_allowed) {
6105 if (idle_cpu(i)) {
6106 struct rq *rq = cpu_rq(i);
6107 struct cpuidle_state *idle = idle_get_state(rq);
6108 if (idle && idle->exit_latency < min_exit_latency) {
6109 /*
6110 * We give priority to a CPU whose idle state
6111 * has the smallest exit latency irrespective
6112 * of any idle timestamp.
6113 */
6114 min_exit_latency = idle->exit_latency;
6115 latest_idle_timestamp = rq->idle_stamp;
6116 shallowest_idle_cpu = i;
6117 } else if ((!idle || idle->exit_latency == min_exit_latency) &&
6118 rq->idle_stamp > latest_idle_timestamp) {
6119 /*
6120 * If equal or no active idle state, then
6121 * the most recently idled CPU might have
6122 * a warmer cache.
6123 */
6124 latest_idle_timestamp = rq->idle_stamp;
6125 shallowest_idle_cpu = i;
6126 }
6127 } else if (shallowest_idle_cpu == -1) {
6128 load = weighted_cpuload(cpu_rq(i));
6129 if (load < min_load) {
6130 min_load = load;
6131 least_loaded_cpu = i;
6132 }
6133 }
6134 }
6135
6136 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
6137}
6138
6139static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
6140 int cpu, int prev_cpu, int sd_flag)
6141{
6142 int new_cpu = cpu;
6143
6144 if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed))
6145 return prev_cpu;
6146
6147 while (sd) {
6148 struct sched_group *group;
6149 struct sched_domain *tmp;
6150 int weight;
6151
6152 if (!(sd->flags & sd_flag)) {
6153 sd = sd->child;
6154 continue;
6155 }
6156
6157 group = find_idlest_group(sd, p, cpu, sd_flag);
6158 if (!group) {
6159 sd = sd->child;
6160 continue;
6161 }
6162
6163 new_cpu = find_idlest_group_cpu(group, p, cpu);
6164 if (new_cpu == cpu) {
6165 /* Now try balancing at a lower domain level of 'cpu': */
6166 sd = sd->child;
6167 continue;
6168 }
6169
6170 /* Now try balancing at a lower domain level of 'new_cpu': */
6171 cpu = new_cpu;
6172 weight = sd->span_weight;
6173 sd = NULL;
6174 for_each_domain(cpu, tmp) {
6175 if (weight <= tmp->span_weight)
6176 break;
6177 if (tmp->flags & sd_flag)
6178 sd = tmp;
6179 }
6180 }
6181
6182 return new_cpu;
6183}
6184
6185#ifdef CONFIG_SCHED_SMT
6186
6187static inline void set_idle_cores(int cpu, int val)
6188{
6189 struct sched_domain_shared *sds;
6190
6191 sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
6192 if (sds)
6193 WRITE_ONCE(sds->has_idle_cores, val);
6194}
6195
6196static inline bool test_idle_cores(int cpu, bool def)
6197{
6198 struct sched_domain_shared *sds;
6199
6200 sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
6201 if (sds)
6202 return READ_ONCE(sds->has_idle_cores);
6203
6204 return def;
6205}
6206
6207/*
6208 * Scans the local SMT mask to see if the entire core is idle, and records this
6209 * information in sd_llc_shared->has_idle_cores.
6210 *
6211 * Since SMT siblings share all cache levels, inspecting this limited remote
6212 * state should be fairly cheap.
6213 */
6214void __update_idle_core(struct rq *rq)
6215{
6216 int core = cpu_of(rq);
6217 int cpu;
6218
6219 rcu_read_lock();
6220 if (test_idle_cores(core, true))
6221 goto unlock;
6222
6223 for_each_cpu(cpu, cpu_smt_mask(core)) {
6224 if (cpu == core)
6225 continue;
6226
6227 if (!idle_cpu(cpu))
6228 goto unlock;
6229 }
6230
6231 set_idle_cores(core, 1);
6232unlock:
6233 rcu_read_unlock();
6234}
6235
6236/*
6237 * Scan the entire LLC domain for idle cores; this dynamically switches off if
6238 * there are no idle cores left in the system; tracked through
6239 * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
6240 */
6241static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
6242{
6243 struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
6244 int core, cpu;
6245
6246 if (!static_branch_likely(&sched_smt_present))
6247 return -1;
6248
6249 if (!test_idle_cores(target, false))
6250 return -1;
6251
6252 cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed);
6253
6254 for_each_cpu_wrap(core, cpus, target) {
6255 bool idle = true;
6256
6257 for_each_cpu(cpu, cpu_smt_mask(core)) {
6258 cpumask_clear_cpu(cpu, cpus);
6259 if (!idle_cpu(cpu))
6260 idle = false;
6261 }
6262
6263 if (idle)
6264 return core;
6265 }
6266
6267 /*
6268 * Failed to find an idle core; stop looking for one.
6269 */
6270 set_idle_cores(target, 0);
6271
6272 return -1;
6273}
6274
6275/*
6276 * Scan the local SMT mask for idle CPUs.
6277 */
6278static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
6279{
6280 int cpu;
6281
6282 if (!static_branch_likely(&sched_smt_present))
6283 return -1;
6284
6285 for_each_cpu(cpu, cpu_smt_mask(target)) {
6286 if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
6287 continue;
6288 if (idle_cpu(cpu))
6289 return cpu;
6290 }
6291
6292 return -1;
6293}
6294
6295#else /* CONFIG_SCHED_SMT */
6296
6297static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
6298{
6299 return -1;
6300}
6301
6302static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
6303{
6304 return -1;
6305}
6306
6307#endif /* CONFIG_SCHED_SMT */
6308
6309/*
6310 * Scan the LLC domain for idle CPUs; this is dynamically regulated by
6311 * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
6312 * average idle time for this rq (as found in rq->avg_idle).
6313 */
6314static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
6315{
6316 struct sched_domain *this_sd;
6317 u64 avg_cost, avg_idle;
6318 u64 time, cost;
6319 s64 delta;
6320 int cpu, nr = INT_MAX;
6321
6322 this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
6323 if (!this_sd)
6324 return -1;
6325
6326 /*
6327 * Due to large variance we need a large fuzz factor; hackbench in
6328 * particularly is sensitive here.
6329 */
6330 avg_idle = this_rq()->avg_idle / 512;
6331 avg_cost = this_sd->avg_scan_cost + 1;
6332
6333 if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost)
6334 return -1;
6335
6336 if (sched_feat(SIS_PROP)) {
6337 u64 span_avg = sd->span_weight * avg_idle;
6338 if (span_avg > 4*avg_cost)
6339 nr = div_u64(span_avg, avg_cost);
6340 else
6341 nr = 4;
6342 }
6343
6344 time = local_clock();
6345
6346 for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
6347 if (!--nr)
6348 return -1;
6349 if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
6350 continue;
6351 if (idle_cpu(cpu))
6352 break;
6353 }
6354
6355 time = local_clock() - time;
6356 cost = this_sd->avg_scan_cost;
6357 delta = (s64)(time - cost) / 8;
6358 this_sd->avg_scan_cost += delta;
6359
6360 return cpu;
6361}
6362
6363/*
6364 * Try and locate an idle core/thread in the LLC cache domain.
6365 */
6366static int select_idle_sibling(struct task_struct *p, int prev, int target)
6367{
6368 struct sched_domain *sd;
6369 int i, recent_used_cpu;
6370
6371 if (idle_cpu(target))
6372 return target;
6373
6374 /*
6375 * If the previous CPU is cache affine and idle, don't be stupid:
6376 */
6377 if (prev != target && cpus_share_cache(prev, target) && idle_cpu(prev))
6378 return prev;
6379
6380 /* Check a recently used CPU as a potential idle candidate: */
6381 recent_used_cpu = p->recent_used_cpu;
6382 if (recent_used_cpu != prev &&
6383 recent_used_cpu != target &&
6384 cpus_share_cache(recent_used_cpu, target) &&
6385 idle_cpu(recent_used_cpu) &&
6386 cpumask_test_cpu(p->recent_used_cpu, &p->cpus_allowed)) {
6387 /*
6388 * Replace recent_used_cpu with prev as it is a potential
6389 * candidate for the next wake:
6390 */
6391 p->recent_used_cpu = prev;
6392 return recent_used_cpu;
6393 }
6394
6395 sd = rcu_dereference(per_cpu(sd_llc, target));
6396 if (!sd)
6397 return target;
6398
6399 i = select_idle_core(p, sd, target);
6400 if ((unsigned)i < nr_cpumask_bits)
6401 return i;
6402
6403 i = select_idle_cpu(p, sd, target);
6404 if ((unsigned)i < nr_cpumask_bits)
6405 return i;
6406
6407 i = select_idle_smt(p, sd, target);
6408 if ((unsigned)i < nr_cpumask_bits)
6409 return i;
6410
6411 return target;
6412}
6413
6414/**
6415 * Amount of capacity of a CPU that is (estimated to be) used by CFS tasks
6416 * @cpu: the CPU to get the utilization of
6417 *
6418 * The unit of the return value must be the one of capacity so we can compare
6419 * the utilization with the capacity of the CPU that is available for CFS task
6420 * (ie cpu_capacity).
6421 *
6422 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
6423 * recent utilization of currently non-runnable tasks on a CPU. It represents
6424 * the amount of utilization of a CPU in the range [0..capacity_orig] where
6425 * capacity_orig is the cpu_capacity available at the highest frequency
6426 * (arch_scale_freq_capacity()).
6427 * The utilization of a CPU converges towards a sum equal to or less than the
6428 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
6429 * the running time on this CPU scaled by capacity_curr.
6430 *
6431 * The estimated utilization of a CPU is defined to be the maximum between its
6432 * cfs_rq.avg.util_avg and the sum of the estimated utilization of the tasks
6433 * currently RUNNABLE on that CPU.
6434 * This allows to properly represent the expected utilization of a CPU which
6435 * has just got a big task running since a long sleep period. At the same time
6436 * however it preserves the benefits of the "blocked utilization" in
6437 * describing the potential for other tasks waking up on the same CPU.
6438 *
6439 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
6440 * higher than capacity_orig because of unfortunate rounding in
6441 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
6442 * the average stabilizes with the new running time. We need to check that the
6443 * utilization stays within the range of [0..capacity_orig] and cap it if
6444 * necessary. Without utilization capping, a group could be seen as overloaded
6445 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
6446 * available capacity. We allow utilization to overshoot capacity_curr (but not
6447 * capacity_orig) as it useful for predicting the capacity required after task
6448 * migrations (scheduler-driven DVFS).
6449 *
6450 * Return: the (estimated) utilization for the specified CPU
6451 */
6452static inline unsigned long cpu_util(int cpu)
6453{
6454 struct cfs_rq *cfs_rq;
6455 unsigned int util;
6456
6457 cfs_rq = &cpu_rq(cpu)->cfs;
6458 util = READ_ONCE(cfs_rq->avg.util_avg);
6459
6460 if (sched_feat(UTIL_EST))
6461 util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued));
6462
6463 return min_t(unsigned long, util, capacity_orig_of(cpu));
6464}
6465
6466/*
6467 * cpu_util_wake: Compute CPU utilization with any contributions from
6468 * the waking task p removed.
6469 */
6470static unsigned long cpu_util_wake(int cpu, struct task_struct *p)
6471{
6472 struct cfs_rq *cfs_rq;
6473 unsigned int util;
6474
6475 /* Task has no contribution or is new */
6476 if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
6477 return cpu_util(cpu);
6478
6479 cfs_rq = &cpu_rq(cpu)->cfs;
6480 util = READ_ONCE(cfs_rq->avg.util_avg);
6481
6482 /* Discount task's blocked util from CPU's util */
6483 util -= min_t(unsigned int, util, task_util(p));
6484
6485 /*
6486 * Covered cases:
6487 *
6488 * a) if *p is the only task sleeping on this CPU, then:
6489 * cpu_util (== task_util) > util_est (== 0)
6490 * and thus we return:
6491 * cpu_util_wake = (cpu_util - task_util) = 0
6492 *
6493 * b) if other tasks are SLEEPING on this CPU, which is now exiting
6494 * IDLE, then:
6495 * cpu_util >= task_util
6496 * cpu_util > util_est (== 0)
6497 * and thus we discount *p's blocked utilization to return:
6498 * cpu_util_wake = (cpu_util - task_util) >= 0
6499 *
6500 * c) if other tasks are RUNNABLE on that CPU and
6501 * util_est > cpu_util
6502 * then we use util_est since it returns a more restrictive
6503 * estimation of the spare capacity on that CPU, by just
6504 * considering the expected utilization of tasks already
6505 * runnable on that CPU.
6506 *
6507 * Cases a) and b) are covered by the above code, while case c) is
6508 * covered by the following code when estimated utilization is
6509 * enabled.
6510 */
6511 if (sched_feat(UTIL_EST))
6512 util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued));
6513
6514 /*
6515 * Utilization (estimated) can exceed the CPU capacity, thus let's
6516 * clamp to the maximum CPU capacity to ensure consistency with
6517 * the cpu_util call.
6518 */
6519 return min_t(unsigned long, util, capacity_orig_of(cpu));
6520}
6521
6522/*
6523 * Disable WAKE_AFFINE in the case where task @p doesn't fit in the
6524 * capacity of either the waking CPU @cpu or the previous CPU @prev_cpu.
6525 *
6526 * In that case WAKE_AFFINE doesn't make sense and we'll let
6527 * BALANCE_WAKE sort things out.
6528 */
6529static int wake_cap(struct task_struct *p, int cpu, int prev_cpu)
6530{
6531 long min_cap, max_cap;
6532
6533 min_cap = min(capacity_orig_of(prev_cpu), capacity_orig_of(cpu));
6534 max_cap = cpu_rq(cpu)->rd->max_cpu_capacity;
6535
6536 /* Minimum capacity is close to max, no need to abort wake_affine */
6537 if (max_cap - min_cap < max_cap >> 3)
6538 return 0;
6539
6540 /* Bring task utilization in sync with prev_cpu */
6541 sync_entity_load_avg(&p->se);
6542
6543 return min_cap * 1024 < task_util(p) * capacity_margin;
6544}
6545
6546/*
6547 * select_task_rq_fair: Select target runqueue for the waking task in domains
6548 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
6549 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
6550 *
6551 * Balances load by selecting the idlest CPU in the idlest group, or under
6552 * certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set.
6553 *
6554 * Returns the target CPU number.
6555 *
6556 * preempt must be disabled.
6557 */
6558static int
6559select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
6560{
6561 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
6562 int cpu = smp_processor_id();
6563 int new_cpu = prev_cpu;
6564 int want_affine = 0;
6565 int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
6566
6567 if (sd_flag & SD_BALANCE_WAKE) {
6568 record_wakee(p);
6569 want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu)
6570 && cpumask_test_cpu(cpu, &p->cpus_allowed);
6571 }
6572
6573 rcu_read_lock();
6574 for_each_domain(cpu, tmp) {
6575 if (!(tmp->flags & SD_LOAD_BALANCE))
6576 break;
6577
6578 /*
6579 * If both 'cpu' and 'prev_cpu' are part of this domain,
6580 * cpu is a valid SD_WAKE_AFFINE target.
6581 */
6582 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
6583 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
6584 affine_sd = tmp;
6585 break;
6586 }
6587
6588 if (tmp->flags & sd_flag)
6589 sd = tmp;
6590 else if (!want_affine)
6591 break;
6592 }
6593
6594 if (affine_sd) {
6595 sd = NULL; /* Prefer wake_affine over balance flags */
6596 if (cpu == prev_cpu)
6597 goto pick_cpu;
6598
6599 new_cpu = wake_affine(affine_sd, p, cpu, prev_cpu, sync);
6600 }
6601
6602 if (sd && !(sd_flag & SD_BALANCE_FORK)) {
6603 /*
6604 * We're going to need the task's util for capacity_spare_wake
6605 * in find_idlest_group. Sync it up to prev_cpu's
6606 * last_update_time.
6607 */
6608 sync_entity_load_avg(&p->se);
6609 }
6610
6611 if (!sd) {
6612pick_cpu:
6613 if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */
6614 new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
6615
6616 if (want_affine)
6617 current->recent_used_cpu = cpu;
6618 }
6619 } else {
6620 new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
6621 }
6622 rcu_read_unlock();
6623
6624 return new_cpu;
6625}
6626
6627static void detach_entity_cfs_rq(struct sched_entity *se);
6628
6629/*
6630 * Called immediately before a task is migrated to a new CPU; task_cpu(p) and
6631 * cfs_rq_of(p) references at time of call are still valid and identify the
6632 * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6633 */
6634static void migrate_task_rq_fair(struct task_struct *p)
6635{
6636 /*
6637 * As blocked tasks retain absolute vruntime the migration needs to
6638 * deal with this by subtracting the old and adding the new
6639 * min_vruntime -- the latter is done by enqueue_entity() when placing
6640 * the task on the new runqueue.
6641 */
6642 if (p->state == TASK_WAKING) {
6643 struct sched_entity *se = &p->se;
6644 struct cfs_rq *cfs_rq = cfs_rq_of(se);
6645 u64 min_vruntime;
6646
6647#ifndef CONFIG_64BIT
6648 u64 min_vruntime_copy;
6649
6650 do {
6651 min_vruntime_copy = cfs_rq->min_vruntime_copy;
6652 smp_rmb();
6653 min_vruntime = cfs_rq->min_vruntime;
6654 } while (min_vruntime != min_vruntime_copy);
6655#else
6656 min_vruntime = cfs_rq->min_vruntime;
6657#endif
6658
6659 se->vruntime -= min_vruntime;
6660 }
6661
6662 if (p->on_rq == TASK_ON_RQ_MIGRATING) {
6663 /*
6664 * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old'
6665 * rq->lock and can modify state directly.
6666 */
6667 lockdep_assert_held(&task_rq(p)->lock);
6668 detach_entity_cfs_rq(&p->se);
6669
6670 } else {
6671 /*
6672 * We are supposed to update the task to "current" time, then
6673 * its up to date and ready to go to new CPU/cfs_rq. But we
6674 * have difficulty in getting what current time is, so simply
6675 * throw away the out-of-date time. This will result in the
6676 * wakee task is less decayed, but giving the wakee more load
6677 * sounds not bad.
6678 */
6679 remove_entity_load_avg(&p->se);
6680 }
6681
6682 /* Tell new CPU we are migrated */
6683 p->se.avg.last_update_time = 0;
6684
6685 /* We have migrated, no longer consider this task hot */
6686 p->se.exec_start = 0;
6687}
6688
6689static void task_dead_fair(struct task_struct *p)
6690{
6691 remove_entity_load_avg(&p->se);
6692}
6693#endif /* CONFIG_SMP */
6694
6695static unsigned long wakeup_gran(struct sched_entity *se)
6696{
6697 unsigned long gran = sysctl_sched_wakeup_granularity;
6698
6699 /*
6700 * Since its curr running now, convert the gran from real-time
6701 * to virtual-time in his units.
6702 *
6703 * By using 'se' instead of 'curr' we penalize light tasks, so
6704 * they get preempted easier. That is, if 'se' < 'curr' then
6705 * the resulting gran will be larger, therefore penalizing the
6706 * lighter, if otoh 'se' > 'curr' then the resulting gran will
6707 * be smaller, again penalizing the lighter task.
6708 *
6709 * This is especially important for buddies when the leftmost
6710 * task is higher priority than the buddy.
6711 */
6712 return calc_delta_fair(gran, se);
6713}
6714
6715/*
6716 * Should 'se' preempt 'curr'.
6717 *
6718 * |s1
6719 * |s2
6720 * |s3
6721 * g
6722 * |<--->|c
6723 *
6724 * w(c, s1) = -1
6725 * w(c, s2) = 0
6726 * w(c, s3) = 1
6727 *
6728 */
6729static int
6730wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
6731{
6732 s64 gran, vdiff = curr->vruntime - se->vruntime;
6733
6734 if (vdiff <= 0)
6735 return -1;
6736
6737 gran = wakeup_gran(se);
6738 if (vdiff > gran)
6739 return 1;
6740
6741 return 0;
6742}
6743
6744static void set_last_buddy(struct sched_entity *se)
6745{
6746 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
6747 return;
6748
6749 for_each_sched_entity(se) {
6750 if (SCHED_WARN_ON(!se->on_rq))
6751 return;
6752 cfs_rq_of(se)->last = se;
6753 }
6754}
6755
6756static void set_next_buddy(struct sched_entity *se)
6757{
6758 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
6759 return;
6760
6761 for_each_sched_entity(se) {
6762 if (SCHED_WARN_ON(!se->on_rq))
6763 return;
6764 cfs_rq_of(se)->next = se;
6765 }
6766}
6767
6768static void set_skip_buddy(struct sched_entity *se)
6769{
6770 for_each_sched_entity(se)
6771 cfs_rq_of(se)->skip = se;
6772}
6773
6774/*
6775 * Preempt the current task with a newly woken task if needed:
6776 */
6777static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
6778{
6779 struct task_struct *curr = rq->curr;
6780 struct sched_entity *se = &curr->se, *pse = &p->se;
6781 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6782 int scale = cfs_rq->nr_running >= sched_nr_latency;
6783 int next_buddy_marked = 0;
6784
6785 if (unlikely(se == pse))
6786 return;
6787
6788 /*
6789 * This is possible from callers such as attach_tasks(), in which we
6790 * unconditionally check_prempt_curr() after an enqueue (which may have
6791 * lead to a throttle). This both saves work and prevents false
6792 * next-buddy nomination below.
6793 */
6794 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
6795 return;
6796
6797 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
6798 set_next_buddy(pse);
6799 next_buddy_marked = 1;
6800 }
6801
6802 /*
6803 * We can come here with TIF_NEED_RESCHED already set from new task
6804 * wake up path.
6805 *
6806 * Note: this also catches the edge-case of curr being in a throttled
6807 * group (e.g. via set_curr_task), since update_curr() (in the
6808 * enqueue of curr) will have resulted in resched being set. This
6809 * prevents us from potentially nominating it as a false LAST_BUDDY
6810 * below.
6811 */
6812 if (test_tsk_need_resched(curr))
6813 return;
6814
6815 /* Idle tasks are by definition preempted by non-idle tasks. */
6816 if (unlikely(curr->policy == SCHED_IDLE) &&
6817 likely(p->policy != SCHED_IDLE))
6818 goto preempt;
6819
6820 /*
6821 * Batch and idle tasks do not preempt non-idle tasks (their preemption
6822 * is driven by the tick):
6823 */
6824 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
6825 return;
6826
6827 find_matching_se(&se, &pse);
6828 update_curr(cfs_rq_of(se));
6829 BUG_ON(!pse);
6830 if (wakeup_preempt_entity(se, pse) == 1) {
6831 /*
6832 * Bias pick_next to pick the sched entity that is
6833 * triggering this preemption.
6834 */
6835 if (!next_buddy_marked)
6836 set_next_buddy(pse);
6837 goto preempt;
6838 }
6839
6840 return;
6841
6842preempt:
6843 resched_curr(rq);
6844 /*
6845 * Only set the backward buddy when the current task is still
6846 * on the rq. This can happen when a wakeup gets interleaved
6847 * with schedule on the ->pre_schedule() or idle_balance()
6848 * point, either of which can * drop the rq lock.
6849 *
6850 * Also, during early boot the idle thread is in the fair class,
6851 * for obvious reasons its a bad idea to schedule back to it.
6852 */
6853 if (unlikely(!se->on_rq || curr == rq->idle))
6854 return;
6855
6856 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
6857 set_last_buddy(se);
6858}
6859
6860static struct task_struct *
6861pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6862{
6863 struct cfs_rq *cfs_rq = &rq->cfs;
6864 struct sched_entity *se;
6865 struct task_struct *p;
6866 int new_tasks;
6867
6868again:
6869 if (!cfs_rq->nr_running)
6870 goto idle;
6871
6872#ifdef CONFIG_FAIR_GROUP_SCHED
6873 if (prev->sched_class != &fair_sched_class)
6874 goto simple;
6875
6876 /*
6877 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
6878 * likely that a next task is from the same cgroup as the current.
6879 *
6880 * Therefore attempt to avoid putting and setting the entire cgroup
6881 * hierarchy, only change the part that actually changes.
6882 */
6883
6884 do {
6885 struct sched_entity *curr = cfs_rq->curr;
6886
6887 /*
6888 * Since we got here without doing put_prev_entity() we also
6889 * have to consider cfs_rq->curr. If it is still a runnable
6890 * entity, update_curr() will update its vruntime, otherwise
6891 * forget we've ever seen it.
6892 */
6893 if (curr) {
6894 if (curr->on_rq)
6895 update_curr(cfs_rq);
6896 else
6897 curr = NULL;
6898
6899 /*
6900 * This call to check_cfs_rq_runtime() will do the
6901 * throttle and dequeue its entity in the parent(s).
6902 * Therefore the nr_running test will indeed
6903 * be correct.
6904 */
6905 if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
6906 cfs_rq = &rq->cfs;
6907
6908 if (!cfs_rq->nr_running)
6909 goto idle;
6910
6911 goto simple;
6912 }
6913 }
6914
6915 se = pick_next_entity(cfs_rq, curr);
6916 cfs_rq = group_cfs_rq(se);
6917 } while (cfs_rq);
6918
6919 p = task_of(se);
6920
6921 /*
6922 * Since we haven't yet done put_prev_entity and if the selected task
6923 * is a different task than we started out with, try and touch the
6924 * least amount of cfs_rqs.
6925 */
6926 if (prev != p) {
6927 struct sched_entity *pse = &prev->se;
6928
6929 while (!(cfs_rq = is_same_group(se, pse))) {
6930 int se_depth = se->depth;
6931 int pse_depth = pse->depth;
6932
6933 if (se_depth <= pse_depth) {
6934 put_prev_entity(cfs_rq_of(pse), pse);
6935 pse = parent_entity(pse);
6936 }
6937 if (se_depth >= pse_depth) {
6938 set_next_entity(cfs_rq_of(se), se);
6939 se = parent_entity(se);
6940 }
6941 }
6942
6943 put_prev_entity(cfs_rq, pse);
6944 set_next_entity(cfs_rq, se);
6945 }
6946
6947 goto done;
6948simple:
6949#endif
6950
6951 put_prev_task(rq, prev);
6952
6953 do {
6954 se = pick_next_entity(cfs_rq, NULL);
6955 set_next_entity(cfs_rq, se);
6956 cfs_rq = group_cfs_rq(se);
6957 } while (cfs_rq);
6958
6959 p = task_of(se);
6960
6961done: __maybe_unused;
6962#ifdef CONFIG_SMP
6963 /*
6964 * Move the next running task to the front of
6965 * the list, so our cfs_tasks list becomes MRU
6966 * one.
6967 */
6968 list_move(&p->se.group_node, &rq->cfs_tasks);
6969#endif
6970
6971 if (hrtick_enabled(rq))
6972 hrtick_start_fair(rq, p);
6973
6974 return p;
6975
6976idle:
6977 new_tasks = idle_balance(rq, rf);
6978
6979 /*
6980 * Because idle_balance() releases (and re-acquires) rq->lock, it is
6981 * possible for any higher priority task to appear. In that case we
6982 * must re-start the pick_next_entity() loop.
6983 */
6984 if (new_tasks < 0)
6985 return RETRY_TASK;
6986
6987 if (new_tasks > 0)
6988 goto again;
6989
6990 return NULL;
6991}
6992
6993/*
6994 * Account for a descheduled task:
6995 */
6996static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
6997{
6998 struct sched_entity *se = &prev->se;
6999 struct cfs_rq *cfs_rq;
7000
7001 for_each_sched_entity(se) {
7002 cfs_rq = cfs_rq_of(se);
7003 put_prev_entity(cfs_rq, se);
7004 }
7005}
7006
7007/*
7008 * sched_yield() is very simple
7009 *
7010 * The magic of dealing with the ->skip buddy is in pick_next_entity.
7011 */
7012static void yield_task_fair(struct rq *rq)
7013{
7014 struct task_struct *curr = rq->curr;
7015 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
7016 struct sched_entity *se = &curr->se;
7017
7018 /*
7019 * Are we the only task in the tree?
7020 */
7021 if (unlikely(rq->nr_running == 1))
7022 return;
7023
7024 clear_buddies(cfs_rq, se);
7025
7026 if (curr->policy != SCHED_BATCH) {
7027 update_rq_clock(rq);
7028 /*
7029 * Update run-time statistics of the 'current'.
7030 */
7031 update_curr(cfs_rq);
7032 /*
7033 * Tell update_rq_clock() that we've just updated,
7034 * so we don't do microscopic update in schedule()
7035 * and double the fastpath cost.
7036 */
7037 rq_clock_skip_update(rq);
7038 }
7039
7040 set_skip_buddy(se);
7041}
7042
7043static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
7044{
7045 struct sched_entity *se = &p->se;
7046
7047 /* throttled hierarchies are not runnable */
7048 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
7049 return false;
7050
7051 /* Tell the scheduler that we'd really like pse to run next. */
7052 set_next_buddy(se);
7053
7054 yield_task_fair(rq);
7055
7056 return true;
7057}
7058
7059#ifdef CONFIG_SMP
7060/**************************************************
7061 * Fair scheduling class load-balancing methods.
7062 *
7063 * BASICS
7064 *
7065 * The purpose of load-balancing is to achieve the same basic fairness the
7066 * per-CPU scheduler provides, namely provide a proportional amount of compute
7067 * time to each task. This is expressed in the following equation:
7068 *
7069 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
7070 *
7071 * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
7072 * W_i,0 is defined as:
7073 *
7074 * W_i,0 = \Sum_j w_i,j (2)
7075 *
7076 * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
7077 * is derived from the nice value as per sched_prio_to_weight[].
7078 *
7079 * The weight average is an exponential decay average of the instantaneous
7080 * weight:
7081 *
7082 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
7083 *
7084 * C_i is the compute capacity of CPU i, typically it is the
7085 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
7086 * can also include other factors [XXX].
7087 *
7088 * To achieve this balance we define a measure of imbalance which follows
7089 * directly from (1):
7090 *
7091 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
7092 *
7093 * We them move tasks around to minimize the imbalance. In the continuous
7094 * function space it is obvious this converges, in the discrete case we get
7095 * a few fun cases generally called infeasible weight scenarios.
7096 *
7097 * [XXX expand on:
7098 * - infeasible weights;
7099 * - local vs global optima in the discrete case. ]
7100 *
7101 *
7102 * SCHED DOMAINS
7103 *
7104 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
7105 * for all i,j solution, we create a tree of CPUs that follows the hardware
7106 * topology where each level pairs two lower groups (or better). This results
7107 * in O(log n) layers. Furthermore we reduce the number of CPUs going up the
7108 * tree to only the first of the previous level and we decrease the frequency
7109 * of load-balance at each level inv. proportional to the number of CPUs in
7110 * the groups.
7111 *
7112 * This yields:
7113 *
7114 * log_2 n 1 n
7115 * \Sum { --- * --- * 2^i } = O(n) (5)
7116 * i = 0 2^i 2^i
7117 * `- size of each group
7118 * | | `- number of CPUs doing load-balance
7119 * | `- freq
7120 * `- sum over all levels
7121 *
7122 * Coupled with a limit on how many tasks we can migrate every balance pass,
7123 * this makes (5) the runtime complexity of the balancer.
7124 *
7125 * An important property here is that each CPU is still (indirectly) connected
7126 * to every other CPU in at most O(log n) steps:
7127 *
7128 * The adjacency matrix of the resulting graph is given by:
7129 *
7130 * log_2 n
7131 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
7132 * k = 0
7133 *
7134 * And you'll find that:
7135 *
7136 * A^(log_2 n)_i,j != 0 for all i,j (7)
7137 *
7138 * Showing there's indeed a path between every CPU in at most O(log n) steps.
7139 * The task movement gives a factor of O(m), giving a convergence complexity
7140 * of:
7141 *
7142 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
7143 *
7144 *
7145 * WORK CONSERVING
7146 *
7147 * In order to avoid CPUs going idle while there's still work to do, new idle
7148 * balancing is more aggressive and has the newly idle CPU iterate up the domain
7149 * tree itself instead of relying on other CPUs to bring it work.
7150 *
7151 * This adds some complexity to both (5) and (8) but it reduces the total idle
7152 * time.
7153 *
7154 * [XXX more?]
7155 *
7156 *
7157 * CGROUPS
7158 *
7159 * Cgroups make a horror show out of (2), instead of a simple sum we get:
7160 *
7161 * s_k,i
7162 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
7163 * S_k
7164 *
7165 * Where
7166 *
7167 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
7168 *
7169 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i.
7170 *
7171 * The big problem is S_k, its a global sum needed to compute a local (W_i)
7172 * property.
7173 *
7174 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
7175 * rewrite all of this once again.]
7176 */
7177
7178static unsigned long __read_mostly max_load_balance_interval = HZ/10;
7179
7180enum fbq_type { regular, remote, all };
7181
7182#define LBF_ALL_PINNED 0x01
7183#define LBF_NEED_BREAK 0x02
7184#define LBF_DST_PINNED 0x04
7185#define LBF_SOME_PINNED 0x08
7186#define LBF_NOHZ_STATS 0x10
7187#define LBF_NOHZ_AGAIN 0x20
7188
7189struct lb_env {
7190 struct sched_domain *sd;
7191
7192 struct rq *src_rq;
7193 int src_cpu;
7194
7195 int dst_cpu;
7196 struct rq *dst_rq;
7197
7198 struct cpumask *dst_grpmask;
7199 int new_dst_cpu;
7200 enum cpu_idle_type idle;
7201 long imbalance;
7202 /* The set of CPUs under consideration for load-balancing */
7203 struct cpumask *cpus;
7204
7205 unsigned int flags;
7206
7207 unsigned int loop;
7208 unsigned int loop_break;
7209 unsigned int loop_max;
7210
7211 enum fbq_type fbq_type;
7212 struct list_head tasks;
7213};
7214
7215/*
7216 * Is this task likely cache-hot:
7217 */
7218static int task_hot(struct task_struct *p, struct lb_env *env)
7219{
7220 s64 delta;
7221
7222 lockdep_assert_held(&env->src_rq->lock);
7223
7224 if (p->sched_class != &fair_sched_class)
7225 return 0;
7226
7227 if (unlikely(p->policy == SCHED_IDLE))
7228 return 0;
7229
7230 /*
7231 * Buddy candidates are cache hot:
7232 */
7233 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
7234 (&p->se == cfs_rq_of(&p->se)->next ||
7235 &p->se == cfs_rq_of(&p->se)->last))
7236 return 1;
7237
7238 if (sysctl_sched_migration_cost == -1)
7239 return 1;
7240 if (sysctl_sched_migration_cost == 0)
7241 return 0;
7242
7243 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
7244
7245 return delta < (s64)sysctl_sched_migration_cost;
7246}
7247
7248#ifdef CONFIG_NUMA_BALANCING
7249/*
7250 * Returns 1, if task migration degrades locality
7251 * Returns 0, if task migration improves locality i.e migration preferred.
7252 * Returns -1, if task migration is not affected by locality.
7253 */
7254static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
7255{
7256 struct numa_group *numa_group = rcu_dereference(p->numa_group);
7257 unsigned long src_faults, dst_faults;
7258 int src_nid, dst_nid;
7259
7260 if (!static_branch_likely(&sched_numa_balancing))
7261 return -1;
7262
7263 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
7264 return -1;
7265
7266 src_nid = cpu_to_node(env->src_cpu);
7267 dst_nid = cpu_to_node(env->dst_cpu);
7268
7269 if (src_nid == dst_nid)
7270 return -1;
7271
7272 /* Migrating away from the preferred node is always bad. */
7273 if (src_nid == p->numa_preferred_nid) {
7274 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
7275 return 1;
7276 else
7277 return -1;
7278 }
7279
7280 /* Encourage migration to the preferred node. */
7281 if (dst_nid == p->numa_preferred_nid)
7282 return 0;
7283
7284 /* Leaving a core idle is often worse than degrading locality. */
7285 if (env->idle != CPU_NOT_IDLE)
7286 return -1;
7287
7288 if (numa_group) {
7289 src_faults = group_faults(p, src_nid);
7290 dst_faults = group_faults(p, dst_nid);
7291 } else {
7292 src_faults = task_faults(p, src_nid);
7293 dst_faults = task_faults(p, dst_nid);
7294 }
7295
7296 return dst_faults < src_faults;
7297}
7298
7299#else
7300static inline int migrate_degrades_locality(struct task_struct *p,
7301 struct lb_env *env)
7302{
7303 return -1;
7304}
7305#endif
7306
7307/*
7308 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
7309 */
7310static
7311int can_migrate_task(struct task_struct *p, struct lb_env *env)
7312{
7313 int tsk_cache_hot;
7314
7315 lockdep_assert_held(&env->src_rq->lock);
7316
7317 /*
7318 * We do not migrate tasks that are:
7319 * 1) throttled_lb_pair, or
7320 * 2) cannot be migrated to this CPU due to cpus_allowed, or
7321 * 3) running (obviously), or
7322 * 4) are cache-hot on their current CPU.
7323 */
7324 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
7325 return 0;
7326
7327 if (!cpumask_test_cpu(env->dst_cpu, &p->cpus_allowed)) {
7328 int cpu;
7329
7330 schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
7331
7332 env->flags |= LBF_SOME_PINNED;
7333
7334 /*
7335 * Remember if this task can be migrated to any other CPU in
7336 * our sched_group. We may want to revisit it if we couldn't
7337 * meet load balance goals by pulling other tasks on src_cpu.
7338 *
7339 * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have
7340 * already computed one in current iteration.
7341 */
7342 if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED))
7343 return 0;
7344
7345 /* Prevent to re-select dst_cpu via env's CPUs: */
7346 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
7347 if (cpumask_test_cpu(cpu, &p->cpus_allowed)) {
7348 env->flags |= LBF_DST_PINNED;
7349 env->new_dst_cpu = cpu;
7350 break;
7351 }
7352 }
7353
7354 return 0;
7355 }
7356
7357 /* Record that we found atleast one task that could run on dst_cpu */
7358 env->flags &= ~LBF_ALL_PINNED;
7359
7360 if (task_running(env->src_rq, p)) {
7361 schedstat_inc(p->se.statistics.nr_failed_migrations_running);
7362 return 0;
7363 }
7364
7365 /*
7366 * Aggressive migration if:
7367 * 1) destination numa is preferred
7368 * 2) task is cache cold, or
7369 * 3) too many balance attempts have failed.
7370 */
7371 tsk_cache_hot = migrate_degrades_locality(p, env);
7372 if (tsk_cache_hot == -1)
7373 tsk_cache_hot = task_hot(p, env);
7374
7375 if (tsk_cache_hot <= 0 ||
7376 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
7377 if (tsk_cache_hot == 1) {
7378 schedstat_inc(env->sd->lb_hot_gained[env->idle]);
7379 schedstat_inc(p->se.statistics.nr_forced_migrations);
7380 }
7381 return 1;
7382 }
7383
7384 schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
7385 return 0;
7386}
7387
7388/*
7389 * detach_task() -- detach the task for the migration specified in env
7390 */
7391static void detach_task(struct task_struct *p, struct lb_env *env)
7392{
7393 lockdep_assert_held(&env->src_rq->lock);
7394
7395 p->on_rq = TASK_ON_RQ_MIGRATING;
7396 deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
7397 set_task_cpu(p, env->dst_cpu);
7398}
7399
7400/*
7401 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
7402 * part of active balancing operations within "domain".
7403 *
7404 * Returns a task if successful and NULL otherwise.
7405 */
7406static struct task_struct *detach_one_task(struct lb_env *env)
7407{
7408 struct task_struct *p;
7409
7410 lockdep_assert_held(&env->src_rq->lock);
7411
7412 list_for_each_entry_reverse(p,
7413 &env->src_rq->cfs_tasks, se.group_node) {
7414 if (!can_migrate_task(p, env))
7415 continue;
7416
7417 detach_task(p, env);
7418
7419 /*
7420 * Right now, this is only the second place where
7421 * lb_gained[env->idle] is updated (other is detach_tasks)
7422 * so we can safely collect stats here rather than
7423 * inside detach_tasks().
7424 */
7425 schedstat_inc(env->sd->lb_gained[env->idle]);
7426 return p;
7427 }
7428 return NULL;
7429}
7430
7431static const unsigned int sched_nr_migrate_break = 32;
7432
7433/*
7434 * detach_tasks() -- tries to detach up to imbalance weighted load from
7435 * busiest_rq, as part of a balancing operation within domain "sd".
7436 *
7437 * Returns number of detached tasks if successful and 0 otherwise.
7438 */
7439static int detach_tasks(struct lb_env *env)
7440{
7441 struct list_head *tasks = &env->src_rq->cfs_tasks;
7442 struct task_struct *p;
7443 unsigned long load;
7444 int detached = 0;
7445
7446 lockdep_assert_held(&env->src_rq->lock);
7447
7448 if (env->imbalance <= 0)
7449 return 0;
7450
7451 while (!list_empty(tasks)) {
7452 /*
7453 * We don't want to steal all, otherwise we may be treated likewise,
7454 * which could at worst lead to a livelock crash.
7455 */
7456 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
7457 break;
7458
7459 p = list_last_entry(tasks, struct task_struct, se.group_node);
7460
7461 env->loop++;
7462 /* We've more or less seen every task there is, call it quits */
7463 if (env->loop > env->loop_max)
7464 break;
7465
7466 /* take a breather every nr_migrate tasks */
7467 if (env->loop > env->loop_break) {
7468 env->loop_break += sched_nr_migrate_break;
7469 env->flags |= LBF_NEED_BREAK;
7470 break;
7471 }
7472
7473 if (!can_migrate_task(p, env))
7474 goto next;
7475
7476 load = task_h_load(p);
7477
7478 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
7479 goto next;
7480
7481 if ((load / 2) > env->imbalance)
7482 goto next;
7483
7484 detach_task(p, env);
7485 list_add(&p->se.group_node, &env->tasks);
7486
7487 detached++;
7488 env->imbalance -= load;
7489
7490#ifdef CONFIG_PREEMPT
7491 /*
7492 * NEWIDLE balancing is a source of latency, so preemptible
7493 * kernels will stop after the first task is detached to minimize
7494 * the critical section.
7495 */
7496 if (env->idle == CPU_NEWLY_IDLE)
7497 break;
7498#endif
7499
7500 /*
7501 * We only want to steal up to the prescribed amount of
7502 * weighted load.
7503 */
7504 if (env->imbalance <= 0)
7505 break;
7506
7507 continue;
7508next:
7509 list_move(&p->se.group_node, tasks);
7510 }
7511
7512 /*
7513 * Right now, this is one of only two places we collect this stat
7514 * so we can safely collect detach_one_task() stats here rather
7515 * than inside detach_one_task().
7516 */
7517 schedstat_add(env->sd->lb_gained[env->idle], detached);
7518
7519 return detached;
7520}
7521
7522/*
7523 * attach_task() -- attach the task detached by detach_task() to its new rq.
7524 */
7525static void attach_task(struct rq *rq, struct task_struct *p)
7526{
7527 lockdep_assert_held(&rq->lock);
7528
7529 BUG_ON(task_rq(p) != rq);
7530 activate_task(rq, p, ENQUEUE_NOCLOCK);
7531 p->on_rq = TASK_ON_RQ_QUEUED;
7532 check_preempt_curr(rq, p, 0);
7533}
7534
7535/*
7536 * attach_one_task() -- attaches the task returned from detach_one_task() to
7537 * its new rq.
7538 */
7539static void attach_one_task(struct rq *rq, struct task_struct *p)
7540{
7541 struct rq_flags rf;
7542
7543 rq_lock(rq, &rf);
7544 update_rq_clock(rq);
7545 attach_task(rq, p);
7546 rq_unlock(rq, &rf);
7547}
7548
7549/*
7550 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
7551 * new rq.
7552 */
7553static void attach_tasks(struct lb_env *env)
7554{
7555 struct list_head *tasks = &env->tasks;
7556 struct task_struct *p;
7557 struct rq_flags rf;
7558
7559 rq_lock(env->dst_rq, &rf);
7560 update_rq_clock(env->dst_rq);
7561
7562 while (!list_empty(tasks)) {
7563 p = list_first_entry(tasks, struct task_struct, se.group_node);
7564 list_del_init(&p->se.group_node);
7565
7566 attach_task(env->dst_rq, p);
7567 }
7568
7569 rq_unlock(env->dst_rq, &rf);
7570}
7571
7572static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
7573{
7574 if (cfs_rq->avg.load_avg)
7575 return true;
7576
7577 if (cfs_rq->avg.util_avg)
7578 return true;
7579
7580 return false;
7581}
7582
7583#ifdef CONFIG_FAIR_GROUP_SCHED
7584
7585static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
7586{
7587 if (cfs_rq->load.weight)
7588 return false;
7589
7590 if (cfs_rq->avg.load_sum)
7591 return false;
7592
7593 if (cfs_rq->avg.util_sum)
7594 return false;
7595
7596 if (cfs_rq->avg.runnable_load_sum)
7597 return false;
7598
7599 return true;
7600}
7601
7602static void update_blocked_averages(int cpu)
7603{
7604 struct rq *rq = cpu_rq(cpu);
7605 struct cfs_rq *cfs_rq, *pos;
7606 struct rq_flags rf;
7607 bool done = true;
7608
7609 rq_lock_irqsave(rq, &rf);
7610 update_rq_clock(rq);
7611
7612 /*
7613 * Iterates the task_group tree in a bottom up fashion, see
7614 * list_add_leaf_cfs_rq() for details.
7615 */
7616 for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
7617 struct sched_entity *se;
7618
7619 /* throttled entities do not contribute to load */
7620 if (throttled_hierarchy(cfs_rq))
7621 continue;
7622
7623 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
7624 update_tg_load_avg(cfs_rq, 0);
7625
7626 /* Propagate pending load changes to the parent, if any: */
7627 se = cfs_rq->tg->se[cpu];
7628 if (se && !skip_blocked_update(se))
7629 update_load_avg(cfs_rq_of(se), se, 0);
7630
7631 /*
7632 * There can be a lot of idle CPU cgroups. Don't let fully
7633 * decayed cfs_rqs linger on the list.
7634 */
7635 if (cfs_rq_is_decayed(cfs_rq))
7636 list_del_leaf_cfs_rq(cfs_rq);
7637
7638 /* Don't need periodic decay once load/util_avg are null */
7639 if (cfs_rq_has_blocked(cfs_rq))
7640 done = false;
7641 }
7642
7643#ifdef CONFIG_NO_HZ_COMMON
7644 rq->last_blocked_load_update_tick = jiffies;
7645 if (done)
7646 rq->has_blocked_load = 0;
7647#endif
7648 rq_unlock_irqrestore(rq, &rf);
7649}
7650
7651/*
7652 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
7653 * This needs to be done in a top-down fashion because the load of a child
7654 * group is a fraction of its parents load.
7655 */
7656static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
7657{
7658 struct rq *rq = rq_of(cfs_rq);
7659 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
7660 unsigned long now = jiffies;
7661 unsigned long load;
7662
7663 if (cfs_rq->last_h_load_update == now)
7664 return;
7665
7666 cfs_rq->h_load_next = NULL;
7667 for_each_sched_entity(se) {
7668 cfs_rq = cfs_rq_of(se);
7669 cfs_rq->h_load_next = se;
7670 if (cfs_rq->last_h_load_update == now)
7671 break;
7672 }
7673
7674 if (!se) {
7675 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
7676 cfs_rq->last_h_load_update = now;
7677 }
7678
7679 while ((se = cfs_rq->h_load_next) != NULL) {
7680 load = cfs_rq->h_load;
7681 load = div64_ul(load * se->avg.load_avg,
7682 cfs_rq_load_avg(cfs_rq) + 1);
7683 cfs_rq = group_cfs_rq(se);
7684 cfs_rq->h_load = load;
7685 cfs_rq->last_h_load_update = now;
7686 }
7687}
7688
7689static unsigned long task_h_load(struct task_struct *p)
7690{
7691 struct cfs_rq *cfs_rq = task_cfs_rq(p);
7692
7693 update_cfs_rq_h_load(cfs_rq);
7694 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
7695 cfs_rq_load_avg(cfs_rq) + 1);
7696}
7697#else
7698static inline void update_blocked_averages(int cpu)
7699{
7700 struct rq *rq = cpu_rq(cpu);
7701 struct cfs_rq *cfs_rq = &rq->cfs;
7702 struct rq_flags rf;
7703
7704 rq_lock_irqsave(rq, &rf);
7705 update_rq_clock(rq);
7706 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
7707#ifdef CONFIG_NO_HZ_COMMON
7708 rq->last_blocked_load_update_tick = jiffies;
7709 if (!cfs_rq_has_blocked(cfs_rq))
7710 rq->has_blocked_load = 0;
7711#endif
7712 rq_unlock_irqrestore(rq, &rf);
7713}
7714
7715static unsigned long task_h_load(struct task_struct *p)
7716{
7717 return p->se.avg.load_avg;
7718}
7719#endif
7720
7721/********** Helpers for find_busiest_group ************************/
7722
7723enum group_type {
7724 group_other = 0,
7725 group_imbalanced,
7726 group_overloaded,
7727};
7728
7729/*
7730 * sg_lb_stats - stats of a sched_group required for load_balancing
7731 */
7732struct sg_lb_stats {
7733 unsigned long avg_load; /*Avg load across the CPUs of the group */
7734 unsigned long group_load; /* Total load over the CPUs of the group */
7735 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
7736 unsigned long load_per_task;
7737 unsigned long group_capacity;
7738 unsigned long group_util; /* Total utilization of the group */
7739 unsigned int sum_nr_running; /* Nr tasks running in the group */
7740 unsigned int idle_cpus;
7741 unsigned int group_weight;
7742 enum group_type group_type;
7743 int group_no_capacity;
7744#ifdef CONFIG_NUMA_BALANCING
7745 unsigned int nr_numa_running;
7746 unsigned int nr_preferred_running;
7747#endif
7748};
7749
7750/*
7751 * sd_lb_stats - Structure to store the statistics of a sched_domain
7752 * during load balancing.
7753 */
7754struct sd_lb_stats {
7755 struct sched_group *busiest; /* Busiest group in this sd */
7756 struct sched_group *local; /* Local group in this sd */
7757 unsigned long total_running;
7758 unsigned long total_load; /* Total load of all groups in sd */
7759 unsigned long total_capacity; /* Total capacity of all groups in sd */
7760 unsigned long avg_load; /* Average load across all groups in sd */
7761
7762 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
7763 struct sg_lb_stats local_stat; /* Statistics of the local group */
7764};
7765
7766static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
7767{
7768 /*
7769 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
7770 * local_stat because update_sg_lb_stats() does a full clear/assignment.
7771 * We must however clear busiest_stat::avg_load because
7772 * update_sd_pick_busiest() reads this before assignment.
7773 */
7774 *sds = (struct sd_lb_stats){
7775 .busiest = NULL,
7776 .local = NULL,
7777 .total_running = 0UL,
7778 .total_load = 0UL,
7779 .total_capacity = 0UL,
7780 .busiest_stat = {
7781 .avg_load = 0UL,
7782 .sum_nr_running = 0,
7783 .group_type = group_other,
7784 },
7785 };
7786}
7787
7788/**
7789 * get_sd_load_idx - Obtain the load index for a given sched domain.
7790 * @sd: The sched_domain whose load_idx is to be obtained.
7791 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
7792 *
7793 * Return: The load index.
7794 */
7795static inline int get_sd_load_idx(struct sched_domain *sd,
7796 enum cpu_idle_type idle)
7797{
7798 int load_idx;
7799
7800 switch (idle) {
7801 case CPU_NOT_IDLE:
7802 load_idx = sd->busy_idx;
7803 break;
7804
7805 case CPU_NEWLY_IDLE:
7806 load_idx = sd->newidle_idx;
7807 break;
7808 default:
7809 load_idx = sd->idle_idx;
7810 break;
7811 }
7812
7813 return load_idx;
7814}
7815
7816static unsigned long scale_rt_capacity(int cpu)
7817{
7818 struct rq *rq = cpu_rq(cpu);
7819 u64 total, used, age_stamp, avg;
7820 s64 delta;
7821
7822 /*
7823 * Since we're reading these variables without serialization make sure
7824 * we read them once before doing sanity checks on them.
7825 */
7826 age_stamp = READ_ONCE(rq->age_stamp);
7827 avg = READ_ONCE(rq->rt_avg);
7828 delta = __rq_clock_broken(rq) - age_stamp;
7829
7830 if (unlikely(delta < 0))
7831 delta = 0;
7832
7833 total = sched_avg_period() + delta;
7834
7835 used = div_u64(avg, total);
7836
7837 if (likely(used < SCHED_CAPACITY_SCALE))
7838 return SCHED_CAPACITY_SCALE - used;
7839
7840 return 1;
7841}
7842
7843static void update_cpu_capacity(struct sched_domain *sd, int cpu)
7844{
7845 unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
7846 struct sched_group *sdg = sd->groups;
7847
7848 cpu_rq(cpu)->cpu_capacity_orig = capacity;
7849
7850 capacity *= scale_rt_capacity(cpu);
7851 capacity >>= SCHED_CAPACITY_SHIFT;
7852
7853 if (!capacity)
7854 capacity = 1;
7855
7856 cpu_rq(cpu)->cpu_capacity = capacity;
7857 sdg->sgc->capacity = capacity;
7858 sdg->sgc->min_capacity = capacity;
7859}
7860
7861void update_group_capacity(struct sched_domain *sd, int cpu)
7862{
7863 struct sched_domain *child = sd->child;
7864 struct sched_group *group, *sdg = sd->groups;
7865 unsigned long capacity, min_capacity;
7866 unsigned long interval;
7867
7868 interval = msecs_to_jiffies(sd->balance_interval);
7869 interval = clamp(interval, 1UL, max_load_balance_interval);
7870 sdg->sgc->next_update = jiffies + interval;
7871
7872 if (!child) {
7873 update_cpu_capacity(sd, cpu);
7874 return;
7875 }
7876
7877 capacity = 0;
7878 min_capacity = ULONG_MAX;
7879
7880 if (child->flags & SD_OVERLAP) {
7881 /*
7882 * SD_OVERLAP domains cannot assume that child groups
7883 * span the current group.
7884 */
7885
7886 for_each_cpu(cpu, sched_group_span(sdg)) {
7887 struct sched_group_capacity *sgc;
7888 struct rq *rq = cpu_rq(cpu);
7889
7890 /*
7891 * build_sched_domains() -> init_sched_groups_capacity()
7892 * gets here before we've attached the domains to the
7893 * runqueues.
7894 *
7895 * Use capacity_of(), which is set irrespective of domains
7896 * in update_cpu_capacity().
7897 *
7898 * This avoids capacity from being 0 and
7899 * causing divide-by-zero issues on boot.
7900 */
7901 if (unlikely(!rq->sd)) {
7902 capacity += capacity_of(cpu);
7903 } else {
7904 sgc = rq->sd->groups->sgc;
7905 capacity += sgc->capacity;
7906 }
7907
7908 min_capacity = min(capacity, min_capacity);
7909 }
7910 } else {
7911 /*
7912 * !SD_OVERLAP domains can assume that child groups
7913 * span the current group.
7914 */
7915
7916 group = child->groups;
7917 do {
7918 struct sched_group_capacity *sgc = group->sgc;
7919
7920 capacity += sgc->capacity;
7921 min_capacity = min(sgc->min_capacity, min_capacity);
7922 group = group->next;
7923 } while (group != child->groups);
7924 }
7925
7926 sdg->sgc->capacity = capacity;
7927 sdg->sgc->min_capacity = min_capacity;
7928}
7929
7930/*
7931 * Check whether the capacity of the rq has been noticeably reduced by side
7932 * activity. The imbalance_pct is used for the threshold.
7933 * Return true is the capacity is reduced
7934 */
7935static inline int
7936check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
7937{
7938 return ((rq->cpu_capacity * sd->imbalance_pct) <
7939 (rq->cpu_capacity_orig * 100));
7940}
7941
7942/*
7943 * Group imbalance indicates (and tries to solve) the problem where balancing
7944 * groups is inadequate due to ->cpus_allowed constraints.
7945 *
7946 * Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a
7947 * cpumask covering 1 CPU of the first group and 3 CPUs of the second group.
7948 * Something like:
7949 *
7950 * { 0 1 2 3 } { 4 5 6 7 }
7951 * * * * *
7952 *
7953 * If we were to balance group-wise we'd place two tasks in the first group and
7954 * two tasks in the second group. Clearly this is undesired as it will overload
7955 * cpu 3 and leave one of the CPUs in the second group unused.
7956 *
7957 * The current solution to this issue is detecting the skew in the first group
7958 * by noticing the lower domain failed to reach balance and had difficulty
7959 * moving tasks due to affinity constraints.
7960 *
7961 * When this is so detected; this group becomes a candidate for busiest; see
7962 * update_sd_pick_busiest(). And calculate_imbalance() and
7963 * find_busiest_group() avoid some of the usual balance conditions to allow it
7964 * to create an effective group imbalance.
7965 *
7966 * This is a somewhat tricky proposition since the next run might not find the
7967 * group imbalance and decide the groups need to be balanced again. A most
7968 * subtle and fragile situation.
7969 */
7970
7971static inline int sg_imbalanced(struct sched_group *group)
7972{
7973 return group->sgc->imbalance;
7974}
7975
7976/*
7977 * group_has_capacity returns true if the group has spare capacity that could
7978 * be used by some tasks.
7979 * We consider that a group has spare capacity if the * number of task is
7980 * smaller than the number of CPUs or if the utilization is lower than the
7981 * available capacity for CFS tasks.
7982 * For the latter, we use a threshold to stabilize the state, to take into
7983 * account the variance of the tasks' load and to return true if the available
7984 * capacity in meaningful for the load balancer.
7985 * As an example, an available capacity of 1% can appear but it doesn't make
7986 * any benefit for the load balance.
7987 */
7988static inline bool
7989group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
7990{
7991 if (sgs->sum_nr_running < sgs->group_weight)
7992 return true;
7993
7994 if ((sgs->group_capacity * 100) >
7995 (sgs->group_util * env->sd->imbalance_pct))
7996 return true;
7997
7998 return false;
7999}
8000
8001/*
8002 * group_is_overloaded returns true if the group has more tasks than it can
8003 * handle.
8004 * group_is_overloaded is not equals to !group_has_capacity because a group
8005 * with the exact right number of tasks, has no more spare capacity but is not
8006 * overloaded so both group_has_capacity and group_is_overloaded return
8007 * false.
8008 */
8009static inline bool
8010group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
8011{
8012 if (sgs->sum_nr_running <= sgs->group_weight)
8013 return false;
8014
8015 if ((sgs->group_capacity * 100) <
8016 (sgs->group_util * env->sd->imbalance_pct))
8017 return true;
8018
8019 return false;
8020}
8021
8022/*
8023 * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller
8024 * per-CPU capacity than sched_group ref.
8025 */
8026static inline bool
8027group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
8028{
8029 return sg->sgc->min_capacity * capacity_margin <
8030 ref->sgc->min_capacity * 1024;
8031}
8032
8033static inline enum
8034group_type group_classify(struct sched_group *group,
8035 struct sg_lb_stats *sgs)
8036{
8037 if (sgs->group_no_capacity)
8038 return group_overloaded;
8039
8040 if (sg_imbalanced(group))
8041 return group_imbalanced;
8042
8043 return group_other;
8044}
8045
8046static bool update_nohz_stats(struct rq *rq, bool force)
8047{
8048#ifdef CONFIG_NO_HZ_COMMON
8049 unsigned int cpu = rq->cpu;
8050
8051 if (!rq->has_blocked_load)
8052 return false;
8053
8054 if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
8055 return false;
8056
8057 if (!force && !time_after(jiffies, rq->last_blocked_load_update_tick))
8058 return true;
8059
8060 update_blocked_averages(cpu);
8061
8062 return rq->has_blocked_load;
8063#else
8064 return false;
8065#endif
8066}
8067
8068/**
8069 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
8070 * @env: The load balancing environment.
8071 * @group: sched_group whose statistics are to be updated.
8072 * @load_idx: Load index of sched_domain of this_cpu for load calc.
8073 * @local_group: Does group contain this_cpu.
8074 * @sgs: variable to hold the statistics for this group.
8075 * @overload: Indicate more than one runnable task for any CPU.
8076 */
8077static inline void update_sg_lb_stats(struct lb_env *env,
8078 struct sched_group *group, int load_idx,
8079 int local_group, struct sg_lb_stats *sgs,
8080 bool *overload)
8081{
8082 unsigned long load;
8083 int i, nr_running;
8084
8085 memset(sgs, 0, sizeof(*sgs));
8086
8087 for_each_cpu_and(i, sched_group_span(group), env->cpus) {
8088 struct rq *rq = cpu_rq(i);
8089
8090 if ((env->flags & LBF_NOHZ_STATS) && update_nohz_stats(rq, false))
8091 env->flags |= LBF_NOHZ_AGAIN;
8092
8093 /* Bias balancing toward CPUs of our domain: */
8094 if (local_group)
8095 load = target_load(i, load_idx);
8096 else
8097 load = source_load(i, load_idx);
8098
8099 sgs->group_load += load;
8100 sgs->group_util += cpu_util(i);
8101 sgs->sum_nr_running += rq->cfs.h_nr_running;
8102
8103 nr_running = rq->nr_running;
8104 if (nr_running > 1)
8105 *overload = true;
8106
8107#ifdef CONFIG_NUMA_BALANCING
8108 sgs->nr_numa_running += rq->nr_numa_running;
8109 sgs->nr_preferred_running += rq->nr_preferred_running;
8110#endif
8111 sgs->sum_weighted_load += weighted_cpuload(rq);
8112 /*
8113 * No need to call idle_cpu() if nr_running is not 0
8114 */
8115 if (!nr_running && idle_cpu(i))
8116 sgs->idle_cpus++;
8117 }
8118
8119 /* Adjust by relative CPU capacity of the group */
8120 sgs->group_capacity = group->sgc->capacity;
8121 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
8122
8123 if (sgs->sum_nr_running)
8124 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
8125
8126 sgs->group_weight = group->group_weight;
8127
8128 sgs->group_no_capacity = group_is_overloaded(env, sgs);
8129 sgs->group_type = group_classify(group, sgs);
8130}
8131
8132/**
8133 * update_sd_pick_busiest - return 1 on busiest group
8134 * @env: The load balancing environment.
8135 * @sds: sched_domain statistics
8136 * @sg: sched_group candidate to be checked for being the busiest
8137 * @sgs: sched_group statistics
8138 *
8139 * Determine if @sg is a busier group than the previously selected
8140 * busiest group.
8141 *
8142 * Return: %true if @sg is a busier group than the previously selected
8143 * busiest group. %false otherwise.
8144 */
8145static bool update_sd_pick_busiest(struct lb_env *env,
8146 struct sd_lb_stats *sds,
8147 struct sched_group *sg,
8148 struct sg_lb_stats *sgs)
8149{
8150 struct sg_lb_stats *busiest = &sds->busiest_stat;
8151
8152 if (sgs->group_type > busiest->group_type)
8153 return true;
8154
8155 if (sgs->group_type < busiest->group_type)
8156 return false;
8157
8158 if (sgs->avg_load <= busiest->avg_load)
8159 return false;
8160
8161 if (!(env->sd->flags & SD_ASYM_CPUCAPACITY))
8162 goto asym_packing;
8163
8164 /*
8165 * Candidate sg has no more than one task per CPU and
8166 * has higher per-CPU capacity. Migrating tasks to less
8167 * capable CPUs may harm throughput. Maximize throughput,
8168 * power/energy consequences are not considered.
8169 */
8170 if (sgs->sum_nr_running <= sgs->group_weight &&
8171 group_smaller_cpu_capacity(sds->local, sg))
8172 return false;
8173
8174asym_packing:
8175 /* This is the busiest node in its class. */
8176 if (!(env->sd->flags & SD_ASYM_PACKING))
8177 return true;
8178
8179 /* No ASYM_PACKING if target CPU is already busy */
8180 if (env->idle == CPU_NOT_IDLE)
8181 return true;
8182 /*
8183 * ASYM_PACKING needs to move all the work to the highest
8184 * prority CPUs in the group, therefore mark all groups
8185 * of lower priority than ourself as busy.
8186 */
8187 if (sgs->sum_nr_running &&
8188 sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) {
8189 if (!sds->busiest)
8190 return true;
8191
8192 /* Prefer to move from lowest priority CPU's work */
8193 if (sched_asym_prefer(sds->busiest->asym_prefer_cpu,
8194 sg->asym_prefer_cpu))
8195 return true;
8196 }
8197
8198 return false;
8199}
8200
8201#ifdef CONFIG_NUMA_BALANCING
8202static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
8203{
8204 if (sgs->sum_nr_running > sgs->nr_numa_running)
8205 return regular;
8206 if (sgs->sum_nr_running > sgs->nr_preferred_running)
8207 return remote;
8208 return all;
8209}
8210
8211static inline enum fbq_type fbq_classify_rq(struct rq *rq)
8212{
8213 if (rq->nr_running > rq->nr_numa_running)
8214 return regular;
8215 if (rq->nr_running > rq->nr_preferred_running)
8216 return remote;
8217 return all;
8218}
8219#else
8220static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
8221{
8222 return all;
8223}
8224
8225static inline enum fbq_type fbq_classify_rq(struct rq *rq)
8226{
8227 return regular;
8228}
8229#endif /* CONFIG_NUMA_BALANCING */
8230
8231/**
8232 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
8233 * @env: The load balancing environment.
8234 * @sds: variable to hold the statistics for this sched_domain.
8235 */
8236static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
8237{
8238 struct sched_domain *child = env->sd->child;
8239 struct sched_group *sg = env->sd->groups;
8240 struct sg_lb_stats *local = &sds->local_stat;
8241 struct sg_lb_stats tmp_sgs;
8242 int load_idx, prefer_sibling = 0;
8243 bool overload = false;
8244
8245 if (child && child->flags & SD_PREFER_SIBLING)
8246 prefer_sibling = 1;
8247
8248#ifdef CONFIG_NO_HZ_COMMON
8249 if (env->idle == CPU_NEWLY_IDLE && READ_ONCE(nohz.has_blocked))
8250 env->flags |= LBF_NOHZ_STATS;
8251#endif
8252
8253 load_idx = get_sd_load_idx(env->sd, env->idle);
8254
8255 do {
8256 struct sg_lb_stats *sgs = &tmp_sgs;
8257 int local_group;
8258
8259 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
8260 if (local_group) {
8261 sds->local = sg;
8262 sgs = local;
8263
8264 if (env->idle != CPU_NEWLY_IDLE ||
8265 time_after_eq(jiffies, sg->sgc->next_update))
8266 update_group_capacity(env->sd, env->dst_cpu);
8267 }
8268
8269 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
8270 &overload);
8271
8272 if (local_group)
8273 goto next_group;
8274
8275 /*
8276 * In case the child domain prefers tasks go to siblings
8277 * first, lower the sg capacity so that we'll try
8278 * and move all the excess tasks away. We lower the capacity
8279 * of a group only if the local group has the capacity to fit
8280 * these excess tasks. The extra check prevents the case where
8281 * you always pull from the heaviest group when it is already
8282 * under-utilized (possible with a large weight task outweighs
8283 * the tasks on the system).
8284 */
8285 if (prefer_sibling && sds->local &&
8286 group_has_capacity(env, local) &&
8287 (sgs->sum_nr_running > local->sum_nr_running + 1)) {
8288 sgs->group_no_capacity = 1;
8289 sgs->group_type = group_classify(sg, sgs);
8290 }
8291
8292 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
8293 sds->busiest = sg;
8294 sds->busiest_stat = *sgs;
8295 }
8296
8297next_group:
8298 /* Now, start updating sd_lb_stats */
8299 sds->total_running += sgs->sum_nr_running;
8300 sds->total_load += sgs->group_load;
8301 sds->total_capacity += sgs->group_capacity;
8302
8303 sg = sg->next;
8304 } while (sg != env->sd->groups);
8305
8306#ifdef CONFIG_NO_HZ_COMMON
8307 if ((env->flags & LBF_NOHZ_AGAIN) &&
8308 cpumask_subset(nohz.idle_cpus_mask, sched_domain_span(env->sd))) {
8309
8310 WRITE_ONCE(nohz.next_blocked,
8311 jiffies + msecs_to_jiffies(LOAD_AVG_PERIOD));
8312 }
8313#endif
8314
8315 if (env->sd->flags & SD_NUMA)
8316 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
8317
8318 if (!env->sd->parent) {
8319 /* update overload indicator if we are at root domain */
8320 if (env->dst_rq->rd->overload != overload)
8321 env->dst_rq->rd->overload = overload;
8322 }
8323}
8324
8325/**
8326 * check_asym_packing - Check to see if the group is packed into the
8327 * sched domain.
8328 *
8329 * This is primarily intended to used at the sibling level. Some
8330 * cores like POWER7 prefer to use lower numbered SMT threads. In the
8331 * case of POWER7, it can move to lower SMT modes only when higher
8332 * threads are idle. When in lower SMT modes, the threads will
8333 * perform better since they share less core resources. Hence when we
8334 * have idle threads, we want them to be the higher ones.
8335 *
8336 * This packing function is run on idle threads. It checks to see if
8337 * the busiest CPU in this domain (core in the P7 case) has a higher
8338 * CPU number than the packing function is being run on. Here we are
8339 * assuming lower CPU number will be equivalent to lower a SMT thread
8340 * number.
8341 *
8342 * Return: 1 when packing is required and a task should be moved to
8343 * this CPU. The amount of the imbalance is returned in env->imbalance.
8344 *
8345 * @env: The load balancing environment.
8346 * @sds: Statistics of the sched_domain which is to be packed
8347 */
8348static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
8349{
8350 int busiest_cpu;
8351
8352 if (!(env->sd->flags & SD_ASYM_PACKING))
8353 return 0;
8354
8355 if (env->idle == CPU_NOT_IDLE)
8356 return 0;
8357
8358 if (!sds->busiest)
8359 return 0;
8360
8361 busiest_cpu = sds->busiest->asym_prefer_cpu;
8362 if (sched_asym_prefer(busiest_cpu, env->dst_cpu))
8363 return 0;
8364
8365 env->imbalance = DIV_ROUND_CLOSEST(
8366 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
8367 SCHED_CAPACITY_SCALE);
8368
8369 return 1;
8370}
8371
8372/**
8373 * fix_small_imbalance - Calculate the minor imbalance that exists
8374 * amongst the groups of a sched_domain, during
8375 * load balancing.
8376 * @env: The load balancing environment.
8377 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
8378 */
8379static inline
8380void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8381{
8382 unsigned long tmp, capa_now = 0, capa_move = 0;
8383 unsigned int imbn = 2;
8384 unsigned long scaled_busy_load_per_task;
8385 struct sg_lb_stats *local, *busiest;
8386
8387 local = &sds->local_stat;
8388 busiest = &sds->busiest_stat;
8389
8390 if (!local->sum_nr_running)
8391 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
8392 else if (busiest->load_per_task > local->load_per_task)
8393 imbn = 1;
8394
8395 scaled_busy_load_per_task =
8396 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
8397 busiest->group_capacity;
8398
8399 if (busiest->avg_load + scaled_busy_load_per_task >=
8400 local->avg_load + (scaled_busy_load_per_task * imbn)) {
8401 env->imbalance = busiest->load_per_task;
8402 return;
8403 }
8404
8405 /*
8406 * OK, we don't have enough imbalance to justify moving tasks,
8407 * however we may be able to increase total CPU capacity used by
8408 * moving them.
8409 */
8410
8411 capa_now += busiest->group_capacity *
8412 min(busiest->load_per_task, busiest->avg_load);
8413 capa_now += local->group_capacity *
8414 min(local->load_per_task, local->avg_load);
8415 capa_now /= SCHED_CAPACITY_SCALE;
8416
8417 /* Amount of load we'd subtract */
8418 if (busiest->avg_load > scaled_busy_load_per_task) {
8419 capa_move += busiest->group_capacity *
8420 min(busiest->load_per_task,
8421 busiest->avg_load - scaled_busy_load_per_task);
8422 }
8423
8424 /* Amount of load we'd add */
8425 if (busiest->avg_load * busiest->group_capacity <
8426 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
8427 tmp = (busiest->avg_load * busiest->group_capacity) /
8428 local->group_capacity;
8429 } else {
8430 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
8431 local->group_capacity;
8432 }
8433 capa_move += local->group_capacity *
8434 min(local->load_per_task, local->avg_load + tmp);
8435 capa_move /= SCHED_CAPACITY_SCALE;
8436
8437 /* Move if we gain throughput */
8438 if (capa_move > capa_now)
8439 env->imbalance = busiest->load_per_task;
8440}
8441
8442/**
8443 * calculate_imbalance - Calculate the amount of imbalance present within the
8444 * groups of a given sched_domain during load balance.
8445 * @env: load balance environment
8446 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
8447 */
8448static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8449{
8450 unsigned long max_pull, load_above_capacity = ~0UL;
8451 struct sg_lb_stats *local, *busiest;
8452
8453 local = &sds->local_stat;
8454 busiest = &sds->busiest_stat;
8455
8456 if (busiest->group_type == group_imbalanced) {
8457 /*
8458 * In the group_imb case we cannot rely on group-wide averages
8459 * to ensure CPU-load equilibrium, look at wider averages. XXX
8460 */
8461 busiest->load_per_task =
8462 min(busiest->load_per_task, sds->avg_load);
8463 }
8464
8465 /*
8466 * Avg load of busiest sg can be less and avg load of local sg can
8467 * be greater than avg load across all sgs of sd because avg load
8468 * factors in sg capacity and sgs with smaller group_type are
8469 * skipped when updating the busiest sg:
8470 */
8471 if (busiest->avg_load <= sds->avg_load ||
8472 local->avg_load >= sds->avg_load) {
8473 env->imbalance = 0;
8474 return fix_small_imbalance(env, sds);
8475 }
8476
8477 /*
8478 * If there aren't any idle CPUs, avoid creating some.
8479 */
8480 if (busiest->group_type == group_overloaded &&
8481 local->group_type == group_overloaded) {
8482 load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
8483 if (load_above_capacity > busiest->group_capacity) {
8484 load_above_capacity -= busiest->group_capacity;
8485 load_above_capacity *= scale_load_down(NICE_0_LOAD);
8486 load_above_capacity /= busiest->group_capacity;
8487 } else
8488 load_above_capacity = ~0UL;
8489 }
8490
8491 /*
8492 * We're trying to get all the CPUs to the average_load, so we don't
8493 * want to push ourselves above the average load, nor do we wish to
8494 * reduce the max loaded CPU below the average load. At the same time,
8495 * we also don't want to reduce the group load below the group
8496 * capacity. Thus we look for the minimum possible imbalance.
8497 */
8498 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
8499
8500 /* How much load to actually move to equalise the imbalance */
8501 env->imbalance = min(
8502 max_pull * busiest->group_capacity,
8503 (sds->avg_load - local->avg_load) * local->group_capacity
8504 ) / SCHED_CAPACITY_SCALE;
8505
8506 /*
8507 * if *imbalance is less than the average load per runnable task
8508 * there is no guarantee that any tasks will be moved so we'll have
8509 * a think about bumping its value to force at least one task to be
8510 * moved
8511 */
8512 if (env->imbalance < busiest->load_per_task)
8513 return fix_small_imbalance(env, sds);
8514}
8515
8516/******* find_busiest_group() helpers end here *********************/
8517
8518/**
8519 * find_busiest_group - Returns the busiest group within the sched_domain
8520 * if there is an imbalance.
8521 *
8522 * Also calculates the amount of weighted load which should be moved
8523 * to restore balance.
8524 *
8525 * @env: The load balancing environment.
8526 *
8527 * Return: - The busiest group if imbalance exists.
8528 */
8529static struct sched_group *find_busiest_group(struct lb_env *env)
8530{
8531 struct sg_lb_stats *local, *busiest;
8532 struct sd_lb_stats sds;
8533
8534 init_sd_lb_stats(&sds);
8535
8536 /*
8537 * Compute the various statistics relavent for load balancing at
8538 * this level.
8539 */
8540 update_sd_lb_stats(env, &sds);
8541 local = &sds.local_stat;
8542 busiest = &sds.busiest_stat;
8543
8544 /* ASYM feature bypasses nice load balance check */
8545 if (check_asym_packing(env, &sds))
8546 return sds.busiest;
8547
8548 /* There is no busy sibling group to pull tasks from */
8549 if (!sds.busiest || busiest->sum_nr_running == 0)
8550 goto out_balanced;
8551
8552 /* XXX broken for overlapping NUMA groups */
8553 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
8554 / sds.total_capacity;
8555
8556 /*
8557 * If the busiest group is imbalanced the below checks don't
8558 * work because they assume all things are equal, which typically
8559 * isn't true due to cpus_allowed constraints and the like.
8560 */
8561 if (busiest->group_type == group_imbalanced)
8562 goto force_balance;
8563
8564 /*
8565 * When dst_cpu is idle, prevent SMP nice and/or asymmetric group
8566 * capacities from resulting in underutilization due to avg_load.
8567 */
8568 if (env->idle != CPU_NOT_IDLE && group_has_capacity(env, local) &&
8569 busiest->group_no_capacity)
8570 goto force_balance;
8571
8572 /*
8573 * If the local group is busier than the selected busiest group
8574 * don't try and pull any tasks.
8575 */
8576 if (local->avg_load >= busiest->avg_load)
8577 goto out_balanced;
8578
8579 /*
8580 * Don't pull any tasks if this group is already above the domain
8581 * average load.
8582 */
8583 if (local->avg_load >= sds.avg_load)
8584 goto out_balanced;
8585
8586 if (env->idle == CPU_IDLE) {
8587 /*
8588 * This CPU is idle. If the busiest group is not overloaded
8589 * and there is no imbalance between this and busiest group
8590 * wrt idle CPUs, it is balanced. The imbalance becomes
8591 * significant if the diff is greater than 1 otherwise we
8592 * might end up to just move the imbalance on another group
8593 */
8594 if ((busiest->group_type != group_overloaded) &&
8595 (local->idle_cpus <= (busiest->idle_cpus + 1)))
8596 goto out_balanced;
8597 } else {
8598 /*
8599 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
8600 * imbalance_pct to be conservative.
8601 */
8602 if (100 * busiest->avg_load <=
8603 env->sd->imbalance_pct * local->avg_load)
8604 goto out_balanced;
8605 }
8606
8607force_balance:
8608 /* Looks like there is an imbalance. Compute it */
8609 calculate_imbalance(env, &sds);
8610 return sds.busiest;
8611
8612out_balanced:
8613 env->imbalance = 0;
8614 return NULL;
8615}
8616
8617/*
8618 * find_busiest_queue - find the busiest runqueue among the CPUs in the group.
8619 */
8620static struct rq *find_busiest_queue(struct lb_env *env,
8621 struct sched_group *group)
8622{
8623 struct rq *busiest = NULL, *rq;
8624 unsigned long busiest_load = 0, busiest_capacity = 1;
8625 int i;
8626
8627 for_each_cpu_and(i, sched_group_span(group), env->cpus) {
8628 unsigned long capacity, wl;
8629 enum fbq_type rt;
8630
8631 rq = cpu_rq(i);
8632 rt = fbq_classify_rq(rq);
8633
8634 /*
8635 * We classify groups/runqueues into three groups:
8636 * - regular: there are !numa tasks
8637 * - remote: there are numa tasks that run on the 'wrong' node
8638 * - all: there is no distinction
8639 *
8640 * In order to avoid migrating ideally placed numa tasks,
8641 * ignore those when there's better options.
8642 *
8643 * If we ignore the actual busiest queue to migrate another
8644 * task, the next balance pass can still reduce the busiest
8645 * queue by moving tasks around inside the node.
8646 *
8647 * If we cannot move enough load due to this classification
8648 * the next pass will adjust the group classification and
8649 * allow migration of more tasks.
8650 *
8651 * Both cases only affect the total convergence complexity.
8652 */
8653 if (rt > env->fbq_type)
8654 continue;
8655
8656 capacity = capacity_of(i);
8657
8658 wl = weighted_cpuload(rq);
8659
8660 /*
8661 * When comparing with imbalance, use weighted_cpuload()
8662 * which is not scaled with the CPU capacity.
8663 */
8664
8665 if (rq->nr_running == 1 && wl > env->imbalance &&
8666 !check_cpu_capacity(rq, env->sd))
8667 continue;
8668
8669 /*
8670 * For the load comparisons with the other CPU's, consider
8671 * the weighted_cpuload() scaled with the CPU capacity, so
8672 * that the load can be moved away from the CPU that is
8673 * potentially running at a lower capacity.
8674 *
8675 * Thus we're looking for max(wl_i / capacity_i), crosswise
8676 * multiplication to rid ourselves of the division works out
8677 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
8678 * our previous maximum.
8679 */
8680 if (wl * busiest_capacity > busiest_load * capacity) {
8681 busiest_load = wl;
8682 busiest_capacity = capacity;
8683 busiest = rq;
8684 }
8685 }
8686
8687 return busiest;
8688}
8689
8690/*
8691 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
8692 * so long as it is large enough.
8693 */
8694#define MAX_PINNED_INTERVAL 512
8695
8696static int need_active_balance(struct lb_env *env)
8697{
8698 struct sched_domain *sd = env->sd;
8699
8700 if (env->idle == CPU_NEWLY_IDLE) {
8701
8702 /*
8703 * ASYM_PACKING needs to force migrate tasks from busy but
8704 * lower priority CPUs in order to pack all tasks in the
8705 * highest priority CPUs.
8706 */
8707 if ((sd->flags & SD_ASYM_PACKING) &&
8708 sched_asym_prefer(env->dst_cpu, env->src_cpu))
8709 return 1;
8710 }
8711
8712 /*
8713 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
8714 * It's worth migrating the task if the src_cpu's capacity is reduced
8715 * because of other sched_class or IRQs if more capacity stays
8716 * available on dst_cpu.
8717 */
8718 if ((env->idle != CPU_NOT_IDLE) &&
8719 (env->src_rq->cfs.h_nr_running == 1)) {
8720 if ((check_cpu_capacity(env->src_rq, sd)) &&
8721 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
8722 return 1;
8723 }
8724
8725 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
8726}
8727
8728static int active_load_balance_cpu_stop(void *data);
8729
8730static int should_we_balance(struct lb_env *env)
8731{
8732 struct sched_group *sg = env->sd->groups;
8733 int cpu, balance_cpu = -1;
8734
8735 /*
8736 * Ensure the balancing environment is consistent; can happen
8737 * when the softirq triggers 'during' hotplug.
8738 */
8739 if (!cpumask_test_cpu(env->dst_cpu, env->cpus))
8740 return 0;
8741
8742 /*
8743 * In the newly idle case, we will allow all the CPUs
8744 * to do the newly idle load balance.
8745 */
8746 if (env->idle == CPU_NEWLY_IDLE)
8747 return 1;
8748
8749 /* Try to find first idle CPU */
8750 for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
8751 if (!idle_cpu(cpu))
8752 continue;
8753
8754 balance_cpu = cpu;
8755 break;
8756 }
8757
8758 if (balance_cpu == -1)
8759 balance_cpu = group_balance_cpu(sg);
8760
8761 /*
8762 * First idle CPU or the first CPU(busiest) in this sched group
8763 * is eligible for doing load balancing at this and above domains.
8764 */
8765 return balance_cpu == env->dst_cpu;
8766}
8767
8768/*
8769 * Check this_cpu to ensure it is balanced within domain. Attempt to move
8770 * tasks if there is an imbalance.
8771 */
8772static int load_balance(int this_cpu, struct rq *this_rq,
8773 struct sched_domain *sd, enum cpu_idle_type idle,
8774 int *continue_balancing)
8775{
8776 int ld_moved, cur_ld_moved, active_balance = 0;
8777 struct sched_domain *sd_parent = sd->parent;
8778 struct sched_group *group;
8779 struct rq *busiest;
8780 struct rq_flags rf;
8781 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
8782
8783 struct lb_env env = {
8784 .sd = sd,
8785 .dst_cpu = this_cpu,
8786 .dst_rq = this_rq,
8787 .dst_grpmask = sched_group_span(sd->groups),
8788 .idle = idle,
8789 .loop_break = sched_nr_migrate_break,
8790 .cpus = cpus,
8791 .fbq_type = all,
8792 .tasks = LIST_HEAD_INIT(env.tasks),
8793 };
8794
8795 cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
8796
8797 schedstat_inc(sd->lb_count[idle]);
8798
8799redo:
8800 if (!should_we_balance(&env)) {
8801 *continue_balancing = 0;
8802 goto out_balanced;
8803 }
8804
8805 group = find_busiest_group(&env);
8806 if (!group) {
8807 schedstat_inc(sd->lb_nobusyg[idle]);
8808 goto out_balanced;
8809 }
8810
8811 busiest = find_busiest_queue(&env, group);
8812 if (!busiest) {
8813 schedstat_inc(sd->lb_nobusyq[idle]);
8814 goto out_balanced;
8815 }
8816
8817 BUG_ON(busiest == env.dst_rq);
8818
8819 schedstat_add(sd->lb_imbalance[idle], env.imbalance);
8820
8821 env.src_cpu = busiest->cpu;
8822 env.src_rq = busiest;
8823
8824 ld_moved = 0;
8825 if (busiest->nr_running > 1) {
8826 /*
8827 * Attempt to move tasks. If find_busiest_group has found
8828 * an imbalance but busiest->nr_running <= 1, the group is
8829 * still unbalanced. ld_moved simply stays zero, so it is
8830 * correctly treated as an imbalance.
8831 */
8832 env.flags |= LBF_ALL_PINNED;
8833 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
8834
8835more_balance:
8836 rq_lock_irqsave(busiest, &rf);
8837 update_rq_clock(busiest);
8838
8839 /*
8840 * cur_ld_moved - load moved in current iteration
8841 * ld_moved - cumulative load moved across iterations
8842 */
8843 cur_ld_moved = detach_tasks(&env);
8844
8845 /*
8846 * We've detached some tasks from busiest_rq. Every
8847 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
8848 * unlock busiest->lock, and we are able to be sure
8849 * that nobody can manipulate the tasks in parallel.
8850 * See task_rq_lock() family for the details.
8851 */
8852
8853 rq_unlock(busiest, &rf);
8854
8855 if (cur_ld_moved) {
8856 attach_tasks(&env);
8857 ld_moved += cur_ld_moved;
8858 }
8859
8860 local_irq_restore(rf.flags);
8861
8862 if (env.flags & LBF_NEED_BREAK) {
8863 env.flags &= ~LBF_NEED_BREAK;
8864 goto more_balance;
8865 }
8866
8867 /*
8868 * Revisit (affine) tasks on src_cpu that couldn't be moved to
8869 * us and move them to an alternate dst_cpu in our sched_group
8870 * where they can run. The upper limit on how many times we
8871 * iterate on same src_cpu is dependent on number of CPUs in our
8872 * sched_group.
8873 *
8874 * This changes load balance semantics a bit on who can move
8875 * load to a given_cpu. In addition to the given_cpu itself
8876 * (or a ilb_cpu acting on its behalf where given_cpu is
8877 * nohz-idle), we now have balance_cpu in a position to move
8878 * load to given_cpu. In rare situations, this may cause
8879 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
8880 * _independently_ and at _same_ time to move some load to
8881 * given_cpu) causing exceess load to be moved to given_cpu.
8882 * This however should not happen so much in practice and
8883 * moreover subsequent load balance cycles should correct the
8884 * excess load moved.
8885 */
8886 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
8887
8888 /* Prevent to re-select dst_cpu via env's CPUs */
8889 cpumask_clear_cpu(env.dst_cpu, env.cpus);
8890
8891 env.dst_rq = cpu_rq(env.new_dst_cpu);
8892 env.dst_cpu = env.new_dst_cpu;
8893 env.flags &= ~LBF_DST_PINNED;
8894 env.loop = 0;
8895 env.loop_break = sched_nr_migrate_break;
8896
8897 /*
8898 * Go back to "more_balance" rather than "redo" since we
8899 * need to continue with same src_cpu.
8900 */
8901 goto more_balance;
8902 }
8903
8904 /*
8905 * We failed to reach balance because of affinity.
8906 */
8907 if (sd_parent) {
8908 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
8909
8910 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
8911 *group_imbalance = 1;
8912 }
8913
8914 /* All tasks on this runqueue were pinned by CPU affinity */
8915 if (unlikely(env.flags & LBF_ALL_PINNED)) {
8916 cpumask_clear_cpu(cpu_of(busiest), cpus);
8917 /*
8918 * Attempting to continue load balancing at the current
8919 * sched_domain level only makes sense if there are
8920 * active CPUs remaining as possible busiest CPUs to
8921 * pull load from which are not contained within the
8922 * destination group that is receiving any migrated
8923 * load.
8924 */
8925 if (!cpumask_subset(cpus, env.dst_grpmask)) {
8926 env.loop = 0;
8927 env.loop_break = sched_nr_migrate_break;
8928 goto redo;
8929 }
8930 goto out_all_pinned;
8931 }
8932 }
8933
8934 if (!ld_moved) {
8935 schedstat_inc(sd->lb_failed[idle]);
8936 /*
8937 * Increment the failure counter only on periodic balance.
8938 * We do not want newidle balance, which can be very
8939 * frequent, pollute the failure counter causing
8940 * excessive cache_hot migrations and active balances.
8941 */
8942 if (idle != CPU_NEWLY_IDLE)
8943 sd->nr_balance_failed++;
8944
8945 if (need_active_balance(&env)) {
8946 unsigned long flags;
8947
8948 raw_spin_lock_irqsave(&busiest->lock, flags);
8949
8950 /*
8951 * Don't kick the active_load_balance_cpu_stop,
8952 * if the curr task on busiest CPU can't be
8953 * moved to this_cpu:
8954 */
8955 if (!cpumask_test_cpu(this_cpu, &busiest->curr->cpus_allowed)) {
8956 raw_spin_unlock_irqrestore(&busiest->lock,
8957 flags);
8958 env.flags |= LBF_ALL_PINNED;
8959 goto out_one_pinned;
8960 }
8961
8962 /*
8963 * ->active_balance synchronizes accesses to
8964 * ->active_balance_work. Once set, it's cleared
8965 * only after active load balance is finished.
8966 */
8967 if (!busiest->active_balance) {
8968 busiest->active_balance = 1;
8969 busiest->push_cpu = this_cpu;
8970 active_balance = 1;
8971 }
8972 raw_spin_unlock_irqrestore(&busiest->lock, flags);
8973
8974 if (active_balance) {
8975 stop_one_cpu_nowait(cpu_of(busiest),
8976 active_load_balance_cpu_stop, busiest,
8977 &busiest->active_balance_work);
8978 }
8979
8980 /* We've kicked active balancing, force task migration. */
8981 sd->nr_balance_failed = sd->cache_nice_tries+1;
8982 }
8983 } else
8984 sd->nr_balance_failed = 0;
8985
8986 if (likely(!active_balance)) {
8987 /* We were unbalanced, so reset the balancing interval */
8988 sd->balance_interval = sd->min_interval;
8989 } else {
8990 /*
8991 * If we've begun active balancing, start to back off. This
8992 * case may not be covered by the all_pinned logic if there
8993 * is only 1 task on the busy runqueue (because we don't call
8994 * detach_tasks).
8995 */
8996 if (sd->balance_interval < sd->max_interval)
8997 sd->balance_interval *= 2;
8998 }
8999
9000 goto out;
9001
9002out_balanced:
9003 /*
9004 * We reach balance although we may have faced some affinity
9005 * constraints. Clear the imbalance flag if it was set.
9006 */
9007 if (sd_parent) {
9008 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
9009
9010 if (*group_imbalance)
9011 *group_imbalance = 0;
9012 }
9013
9014out_all_pinned:
9015 /*
9016 * We reach balance because all tasks are pinned at this level so
9017 * we can't migrate them. Let the imbalance flag set so parent level
9018 * can try to migrate them.
9019 */
9020 schedstat_inc(sd->lb_balanced[idle]);
9021
9022 sd->nr_balance_failed = 0;
9023
9024out_one_pinned:
9025 /* tune up the balancing interval */
9026 if (((env.flags & LBF_ALL_PINNED) &&
9027 sd->balance_interval < MAX_PINNED_INTERVAL) ||
9028 (sd->balance_interval < sd->max_interval))
9029 sd->balance_interval *= 2;
9030
9031 ld_moved = 0;
9032out:
9033 return ld_moved;
9034}
9035
9036static inline unsigned long
9037get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
9038{
9039 unsigned long interval = sd->balance_interval;
9040
9041 if (cpu_busy)
9042 interval *= sd->busy_factor;
9043
9044 /* scale ms to jiffies */
9045 interval = msecs_to_jiffies(interval);
9046 interval = clamp(interval, 1UL, max_load_balance_interval);
9047
9048 return interval;
9049}
9050
9051static inline void
9052update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
9053{
9054 unsigned long interval, next;
9055
9056 /* used by idle balance, so cpu_busy = 0 */
9057 interval = get_sd_balance_interval(sd, 0);
9058 next = sd->last_balance + interval;
9059
9060 if (time_after(*next_balance, next))
9061 *next_balance = next;
9062}
9063
9064/*
9065 * active_load_balance_cpu_stop is run by the CPU stopper. It pushes
9066 * running tasks off the busiest CPU onto idle CPUs. It requires at
9067 * least 1 task to be running on each physical CPU where possible, and
9068 * avoids physical / logical imbalances.
9069 */
9070static int active_load_balance_cpu_stop(void *data)
9071{
9072 struct rq *busiest_rq = data;
9073 int busiest_cpu = cpu_of(busiest_rq);
9074 int target_cpu = busiest_rq->push_cpu;
9075 struct rq *target_rq = cpu_rq(target_cpu);
9076 struct sched_domain *sd;
9077 struct task_struct *p = NULL;
9078 struct rq_flags rf;
9079
9080 rq_lock_irq(busiest_rq, &rf);
9081 /*
9082 * Between queueing the stop-work and running it is a hole in which
9083 * CPUs can become inactive. We should not move tasks from or to
9084 * inactive CPUs.
9085 */
9086 if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu))
9087 goto out_unlock;
9088
9089 /* Make sure the requested CPU hasn't gone down in the meantime: */
9090 if (unlikely(busiest_cpu != smp_processor_id() ||
9091 !busiest_rq->active_balance))
9092 goto out_unlock;
9093
9094 /* Is there any task to move? */
9095 if (busiest_rq->nr_running <= 1)
9096 goto out_unlock;
9097
9098 /*
9099 * This condition is "impossible", if it occurs
9100 * we need to fix it. Originally reported by
9101 * Bjorn Helgaas on a 128-CPU setup.
9102 */
9103 BUG_ON(busiest_rq == target_rq);
9104
9105 /* Search for an sd spanning us and the target CPU. */
9106 rcu_read_lock();
9107 for_each_domain(target_cpu, sd) {
9108 if ((sd->flags & SD_LOAD_BALANCE) &&
9109 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
9110 break;
9111 }
9112
9113 if (likely(sd)) {
9114 struct lb_env env = {
9115 .sd = sd,
9116 .dst_cpu = target_cpu,
9117 .dst_rq = target_rq,
9118 .src_cpu = busiest_rq->cpu,
9119 .src_rq = busiest_rq,
9120 .idle = CPU_IDLE,
9121 /*
9122 * can_migrate_task() doesn't need to compute new_dst_cpu
9123 * for active balancing. Since we have CPU_IDLE, but no
9124 * @dst_grpmask we need to make that test go away with lying
9125 * about DST_PINNED.
9126 */
9127 .flags = LBF_DST_PINNED,
9128 };
9129
9130 schedstat_inc(sd->alb_count);
9131 update_rq_clock(busiest_rq);
9132
9133 p = detach_one_task(&env);
9134 if (p) {
9135 schedstat_inc(sd->alb_pushed);
9136 /* Active balancing done, reset the failure counter. */
9137 sd->nr_balance_failed = 0;
9138 } else {
9139 schedstat_inc(sd->alb_failed);
9140 }
9141 }
9142 rcu_read_unlock();
9143out_unlock:
9144 busiest_rq->active_balance = 0;
9145 rq_unlock(busiest_rq, &rf);
9146
9147 if (p)
9148 attach_one_task(target_rq, p);
9149
9150 local_irq_enable();
9151
9152 return 0;
9153}
9154
9155static DEFINE_SPINLOCK(balancing);
9156
9157/*
9158 * Scale the max load_balance interval with the number of CPUs in the system.
9159 * This trades load-balance latency on larger machines for less cross talk.
9160 */
9161void update_max_interval(void)
9162{
9163 max_load_balance_interval = HZ*num_online_cpus()/10;
9164}
9165
9166/*
9167 * It checks each scheduling domain to see if it is due to be balanced,
9168 * and initiates a balancing operation if so.
9169 *
9170 * Balancing parameters are set up in init_sched_domains.
9171 */
9172static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
9173{
9174 int continue_balancing = 1;
9175 int cpu = rq->cpu;
9176 unsigned long interval;
9177 struct sched_domain *sd;
9178 /* Earliest time when we have to do rebalance again */
9179 unsigned long next_balance = jiffies + 60*HZ;
9180 int update_next_balance = 0;
9181 int need_serialize, need_decay = 0;
9182 u64 max_cost = 0;
9183
9184 rcu_read_lock();
9185 for_each_domain(cpu, sd) {
9186 /*
9187 * Decay the newidle max times here because this is a regular
9188 * visit to all the domains. Decay ~1% per second.
9189 */
9190 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
9191 sd->max_newidle_lb_cost =
9192 (sd->max_newidle_lb_cost * 253) / 256;
9193 sd->next_decay_max_lb_cost = jiffies + HZ;
9194 need_decay = 1;
9195 }
9196 max_cost += sd->max_newidle_lb_cost;
9197
9198 if (!(sd->flags & SD_LOAD_BALANCE))
9199 continue;
9200
9201 /*
9202 * Stop the load balance at this level. There is another
9203 * CPU in our sched group which is doing load balancing more
9204 * actively.
9205 */
9206 if (!continue_balancing) {
9207 if (need_decay)
9208 continue;
9209 break;
9210 }
9211
9212 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
9213
9214 need_serialize = sd->flags & SD_SERIALIZE;
9215 if (need_serialize) {
9216 if (!spin_trylock(&balancing))
9217 goto out;
9218 }
9219
9220 if (time_after_eq(jiffies, sd->last_balance + interval)) {
9221 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
9222 /*
9223 * The LBF_DST_PINNED logic could have changed
9224 * env->dst_cpu, so we can't know our idle
9225 * state even if we migrated tasks. Update it.
9226 */
9227 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
9228 }
9229 sd->last_balance = jiffies;
9230 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
9231 }
9232 if (need_serialize)
9233 spin_unlock(&balancing);
9234out:
9235 if (time_after(next_balance, sd->last_balance + interval)) {
9236 next_balance = sd->last_balance + interval;
9237 update_next_balance = 1;
9238 }
9239 }
9240 if (need_decay) {
9241 /*
9242 * Ensure the rq-wide value also decays but keep it at a
9243 * reasonable floor to avoid funnies with rq->avg_idle.
9244 */
9245 rq->max_idle_balance_cost =
9246 max((u64)sysctl_sched_migration_cost, max_cost);
9247 }
9248 rcu_read_unlock();
9249
9250 /*
9251 * next_balance will be updated only when there is a need.
9252 * When the cpu is attached to null domain for ex, it will not be
9253 * updated.
9254 */
9255 if (likely(update_next_balance)) {
9256 rq->next_balance = next_balance;
9257
9258#ifdef CONFIG_NO_HZ_COMMON
9259 /*
9260 * If this CPU has been elected to perform the nohz idle
9261 * balance. Other idle CPUs have already rebalanced with
9262 * nohz_idle_balance() and nohz.next_balance has been
9263 * updated accordingly. This CPU is now running the idle load
9264 * balance for itself and we need to update the
9265 * nohz.next_balance accordingly.
9266 */
9267 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
9268 nohz.next_balance = rq->next_balance;
9269#endif
9270 }
9271}
9272
9273static inline int on_null_domain(struct rq *rq)
9274{
9275 return unlikely(!rcu_dereference_sched(rq->sd));
9276}
9277
9278#ifdef CONFIG_NO_HZ_COMMON
9279/*
9280 * idle load balancing details
9281 * - When one of the busy CPUs notice that there may be an idle rebalancing
9282 * needed, they will kick the idle load balancer, which then does idle
9283 * load balancing for all the idle CPUs.
9284 */
9285
9286static inline int find_new_ilb(void)
9287{
9288 int ilb = cpumask_first(nohz.idle_cpus_mask);
9289
9290 if (ilb < nr_cpu_ids && idle_cpu(ilb))
9291 return ilb;
9292
9293 return nr_cpu_ids;
9294}
9295
9296/*
9297 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
9298 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
9299 * CPU (if there is one).
9300 */
9301static void kick_ilb(unsigned int flags)
9302{
9303 int ilb_cpu;
9304
9305 nohz.next_balance++;
9306
9307 ilb_cpu = find_new_ilb();
9308
9309 if (ilb_cpu >= nr_cpu_ids)
9310 return;
9311
9312 flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
9313 if (flags & NOHZ_KICK_MASK)
9314 return;
9315
9316 /*
9317 * Use smp_send_reschedule() instead of resched_cpu().
9318 * This way we generate a sched IPI on the target CPU which
9319 * is idle. And the softirq performing nohz idle load balance
9320 * will be run before returning from the IPI.
9321 */
9322 smp_send_reschedule(ilb_cpu);
9323}
9324
9325/*
9326 * Current heuristic for kicking the idle load balancer in the presence
9327 * of an idle cpu in the system.
9328 * - This rq has more than one task.
9329 * - This rq has at least one CFS task and the capacity of the CPU is
9330 * significantly reduced because of RT tasks or IRQs.
9331 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
9332 * multiple busy cpu.
9333 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
9334 * domain span are idle.
9335 */
9336static void nohz_balancer_kick(struct rq *rq)
9337{
9338 unsigned long now = jiffies;
9339 struct sched_domain_shared *sds;
9340 struct sched_domain *sd;
9341 int nr_busy, i, cpu = rq->cpu;
9342 unsigned int flags = 0;
9343
9344 if (unlikely(rq->idle_balance))
9345 return;
9346
9347 /*
9348 * We may be recently in ticked or tickless idle mode. At the first
9349 * busy tick after returning from idle, we will update the busy stats.
9350 */
9351 nohz_balance_exit_idle(rq);
9352
9353 /*
9354 * None are in tickless mode and hence no need for NOHZ idle load
9355 * balancing.
9356 */
9357 if (likely(!atomic_read(&nohz.nr_cpus)))
9358 return;
9359
9360 if (READ_ONCE(nohz.has_blocked) &&
9361 time_after(now, READ_ONCE(nohz.next_blocked)))
9362 flags = NOHZ_STATS_KICK;
9363
9364 if (time_before(now, nohz.next_balance))
9365 goto out;
9366
9367 if (rq->nr_running >= 2) {
9368 flags = NOHZ_KICK_MASK;
9369 goto out;
9370 }
9371
9372 rcu_read_lock();
9373 sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
9374 if (sds) {
9375 /*
9376 * XXX: write a coherent comment on why we do this.
9377 * See also: http://lkml.kernel.org/r/20111202010832.602203411@sbsiddha-desk.sc.intel.com
9378 */
9379 nr_busy = atomic_read(&sds->nr_busy_cpus);
9380 if (nr_busy > 1) {
9381 flags = NOHZ_KICK_MASK;
9382 goto unlock;
9383 }
9384
9385 }
9386
9387 sd = rcu_dereference(rq->sd);
9388 if (sd) {
9389 if ((rq->cfs.h_nr_running >= 1) &&
9390 check_cpu_capacity(rq, sd)) {
9391 flags = NOHZ_KICK_MASK;
9392 goto unlock;
9393 }
9394 }
9395
9396 sd = rcu_dereference(per_cpu(sd_asym, cpu));
9397 if (sd) {
9398 for_each_cpu(i, sched_domain_span(sd)) {
9399 if (i == cpu ||
9400 !cpumask_test_cpu(i, nohz.idle_cpus_mask))
9401 continue;
9402
9403 if (sched_asym_prefer(i, cpu)) {
9404 flags = NOHZ_KICK_MASK;
9405 goto unlock;
9406 }
9407 }
9408 }
9409unlock:
9410 rcu_read_unlock();
9411out:
9412 if (flags)
9413 kick_ilb(flags);
9414}
9415
9416static void set_cpu_sd_state_busy(int cpu)
9417{
9418 struct sched_domain *sd;
9419
9420 rcu_read_lock();
9421 sd = rcu_dereference(per_cpu(sd_llc, cpu));
9422
9423 if (!sd || !sd->nohz_idle)
9424 goto unlock;
9425 sd->nohz_idle = 0;
9426
9427 atomic_inc(&sd->shared->nr_busy_cpus);
9428unlock:
9429 rcu_read_unlock();
9430}
9431
9432void nohz_balance_exit_idle(struct rq *rq)
9433{
9434 SCHED_WARN_ON(rq != this_rq());
9435
9436 if (likely(!rq->nohz_tick_stopped))
9437 return;
9438
9439 rq->nohz_tick_stopped = 0;
9440 cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask);
9441 atomic_dec(&nohz.nr_cpus);
9442
9443 set_cpu_sd_state_busy(rq->cpu);
9444}
9445
9446static void set_cpu_sd_state_idle(int cpu)
9447{
9448 struct sched_domain *sd;
9449
9450 rcu_read_lock();
9451 sd = rcu_dereference(per_cpu(sd_llc, cpu));
9452
9453 if (!sd || sd->nohz_idle)
9454 goto unlock;
9455 sd->nohz_idle = 1;
9456
9457 atomic_dec(&sd->shared->nr_busy_cpus);
9458unlock:
9459 rcu_read_unlock();
9460}
9461
9462/*
9463 * This routine will record that the CPU is going idle with tick stopped.
9464 * This info will be used in performing idle load balancing in the future.
9465 */
9466void nohz_balance_enter_idle(int cpu)
9467{
9468 struct rq *rq = cpu_rq(cpu);
9469
9470 SCHED_WARN_ON(cpu != smp_processor_id());
9471
9472 /* If this CPU is going down, then nothing needs to be done: */
9473 if (!cpu_active(cpu))
9474 return;
9475
9476 /* Spare idle load balancing on CPUs that don't want to be disturbed: */
9477 if (!housekeeping_cpu(cpu, HK_FLAG_SCHED))
9478 return;
9479
9480 /*
9481 * Can be set safely without rq->lock held
9482 * If a clear happens, it will have evaluated last additions because
9483 * rq->lock is held during the check and the clear
9484 */
9485 rq->has_blocked_load = 1;
9486
9487 /*
9488 * The tick is still stopped but load could have been added in the
9489 * meantime. We set the nohz.has_blocked flag to trig a check of the
9490 * *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear
9491 * of nohz.has_blocked can only happen after checking the new load
9492 */
9493 if (rq->nohz_tick_stopped)
9494 goto out;
9495
9496 /* If we're a completely isolated CPU, we don't play: */
9497 if (on_null_domain(rq))
9498 return;
9499
9500 rq->nohz_tick_stopped = 1;
9501
9502 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
9503 atomic_inc(&nohz.nr_cpus);
9504
9505 /*
9506 * Ensures that if nohz_idle_balance() fails to observe our
9507 * @idle_cpus_mask store, it must observe the @has_blocked
9508 * store.
9509 */
9510 smp_mb__after_atomic();
9511
9512 set_cpu_sd_state_idle(cpu);
9513
9514out:
9515 /*
9516 * Each time a cpu enter idle, we assume that it has blocked load and
9517 * enable the periodic update of the load of idle cpus
9518 */
9519 WRITE_ONCE(nohz.has_blocked, 1);
9520}
9521
9522/*
9523 * Internal function that runs load balance for all idle cpus. The load balance
9524 * can be a simple update of blocked load or a complete load balance with
9525 * tasks movement depending of flags.
9526 * The function returns false if the loop has stopped before running
9527 * through all idle CPUs.
9528 */
9529static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags,
9530 enum cpu_idle_type idle)
9531{
9532 /* Earliest time when we have to do rebalance again */
9533 unsigned long now = jiffies;
9534 unsigned long next_balance = now + 60*HZ;
9535 bool has_blocked_load = false;
9536 int update_next_balance = 0;
9537 int this_cpu = this_rq->cpu;
9538 int balance_cpu;
9539 int ret = false;
9540 struct rq *rq;
9541
9542 SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);
9543
9544 /*
9545 * We assume there will be no idle load after this update and clear
9546 * the has_blocked flag. If a cpu enters idle in the mean time, it will
9547 * set the has_blocked flag and trig another update of idle load.
9548 * Because a cpu that becomes idle, is added to idle_cpus_mask before
9549 * setting the flag, we are sure to not clear the state and not
9550 * check the load of an idle cpu.
9551 */
9552 WRITE_ONCE(nohz.has_blocked, 0);
9553
9554 /*
9555 * Ensures that if we miss the CPU, we must see the has_blocked
9556 * store from nohz_balance_enter_idle().
9557 */
9558 smp_mb();
9559
9560 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
9561 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
9562 continue;
9563
9564 /*
9565 * If this CPU gets work to do, stop the load balancing
9566 * work being done for other CPUs. Next load
9567 * balancing owner will pick it up.
9568 */
9569 if (need_resched()) {
9570 has_blocked_load = true;
9571 goto abort;
9572 }
9573
9574 rq = cpu_rq(balance_cpu);
9575
9576 has_blocked_load |= update_nohz_stats(rq, true);
9577
9578 /*
9579 * If time for next balance is due,
9580 * do the balance.
9581 */
9582 if (time_after_eq(jiffies, rq->next_balance)) {
9583 struct rq_flags rf;
9584
9585 rq_lock_irqsave(rq, &rf);
9586 update_rq_clock(rq);
9587 cpu_load_update_idle(rq);
9588 rq_unlock_irqrestore(rq, &rf);
9589
9590 if (flags & NOHZ_BALANCE_KICK)
9591 rebalance_domains(rq, CPU_IDLE);
9592 }
9593
9594 if (time_after(next_balance, rq->next_balance)) {
9595 next_balance = rq->next_balance;
9596 update_next_balance = 1;
9597 }
9598 }
9599
9600 /* Newly idle CPU doesn't need an update */
9601 if (idle != CPU_NEWLY_IDLE) {
9602 update_blocked_averages(this_cpu);
9603 has_blocked_load |= this_rq->has_blocked_load;
9604 }
9605
9606 if (flags & NOHZ_BALANCE_KICK)
9607 rebalance_domains(this_rq, CPU_IDLE);
9608
9609 WRITE_ONCE(nohz.next_blocked,
9610 now + msecs_to_jiffies(LOAD_AVG_PERIOD));
9611
9612 /* The full idle balance loop has been done */
9613 ret = true;
9614
9615abort:
9616 /* There is still blocked load, enable periodic update */
9617 if (has_blocked_load)
9618 WRITE_ONCE(nohz.has_blocked, 1);
9619
9620 /*
9621 * next_balance will be updated only when there is a need.
9622 * When the CPU is attached to null domain for ex, it will not be
9623 * updated.
9624 */
9625 if (likely(update_next_balance))
9626 nohz.next_balance = next_balance;
9627
9628 return ret;
9629}
9630
9631/*
9632 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
9633 * rebalancing for all the cpus for whom scheduler ticks are stopped.
9634 */
9635static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
9636{
9637 int this_cpu = this_rq->cpu;
9638 unsigned int flags;
9639
9640 if (!(atomic_read(nohz_flags(this_cpu)) & NOHZ_KICK_MASK))
9641 return false;
9642
9643 if (idle != CPU_IDLE) {
9644 atomic_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));
9645 return false;
9646 }
9647
9648 /*
9649 * barrier, pairs with nohz_balance_enter_idle(), ensures ...
9650 */
9651 flags = atomic_fetch_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));
9652 if (!(flags & NOHZ_KICK_MASK))
9653 return false;
9654
9655 _nohz_idle_balance(this_rq, flags, idle);
9656
9657 return true;
9658}
9659
9660static void nohz_newidle_balance(struct rq *this_rq)
9661{
9662 int this_cpu = this_rq->cpu;
9663
9664 /*
9665 * This CPU doesn't want to be disturbed by scheduler
9666 * housekeeping
9667 */
9668 if (!housekeeping_cpu(this_cpu, HK_FLAG_SCHED))
9669 return;
9670
9671 /* Will wake up very soon. No time for doing anything else*/
9672 if (this_rq->avg_idle < sysctl_sched_migration_cost)
9673 return;
9674
9675 /* Don't need to update blocked load of idle CPUs*/
9676 if (!READ_ONCE(nohz.has_blocked) ||
9677 time_before(jiffies, READ_ONCE(nohz.next_blocked)))
9678 return;
9679
9680 raw_spin_unlock(&this_rq->lock);
9681 /*
9682 * This CPU is going to be idle and blocked load of idle CPUs
9683 * need to be updated. Run the ilb locally as it is a good
9684 * candidate for ilb instead of waking up another idle CPU.
9685 * Kick an normal ilb if we failed to do the update.
9686 */
9687 if (!_nohz_idle_balance(this_rq, NOHZ_STATS_KICK, CPU_NEWLY_IDLE))
9688 kick_ilb(NOHZ_STATS_KICK);
9689 raw_spin_lock(&this_rq->lock);
9690}
9691
9692#else /* !CONFIG_NO_HZ_COMMON */
9693static inline void nohz_balancer_kick(struct rq *rq) { }
9694
9695static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
9696{
9697 return false;
9698}
9699
9700static inline void nohz_newidle_balance(struct rq *this_rq) { }
9701#endif /* CONFIG_NO_HZ_COMMON */
9702
9703/*
9704 * idle_balance is called by schedule() if this_cpu is about to become
9705 * idle. Attempts to pull tasks from other CPUs.
9706 */
9707static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
9708{
9709 unsigned long next_balance = jiffies + HZ;
9710 int this_cpu = this_rq->cpu;
9711 struct sched_domain *sd;
9712 int pulled_task = 0;
9713 u64 curr_cost = 0;
9714
9715 /*
9716 * We must set idle_stamp _before_ calling idle_balance(), such that we
9717 * measure the duration of idle_balance() as idle time.
9718 */
9719 this_rq->idle_stamp = rq_clock(this_rq);
9720
9721 /*
9722 * Do not pull tasks towards !active CPUs...
9723 */
9724 if (!cpu_active(this_cpu))
9725 return 0;
9726
9727 /*
9728 * This is OK, because current is on_cpu, which avoids it being picked
9729 * for load-balance and preemption/IRQs are still disabled avoiding
9730 * further scheduler activity on it and we're being very careful to
9731 * re-start the picking loop.
9732 */
9733 rq_unpin_lock(this_rq, rf);
9734
9735 if (this_rq->avg_idle < sysctl_sched_migration_cost ||
9736 !this_rq->rd->overload) {
9737
9738 rcu_read_lock();
9739 sd = rcu_dereference_check_sched_domain(this_rq->sd);
9740 if (sd)
9741 update_next_balance(sd, &next_balance);
9742 rcu_read_unlock();
9743
9744 nohz_newidle_balance(this_rq);
9745
9746 goto out;
9747 }
9748
9749 raw_spin_unlock(&this_rq->lock);
9750
9751 update_blocked_averages(this_cpu);
9752 rcu_read_lock();
9753 for_each_domain(this_cpu, sd) {
9754 int continue_balancing = 1;
9755 u64 t0, domain_cost;
9756
9757 if (!(sd->flags & SD_LOAD_BALANCE))
9758 continue;
9759
9760 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
9761 update_next_balance(sd, &next_balance);
9762 break;
9763 }
9764
9765 if (sd->flags & SD_BALANCE_NEWIDLE) {
9766 t0 = sched_clock_cpu(this_cpu);
9767
9768 pulled_task = load_balance(this_cpu, this_rq,
9769 sd, CPU_NEWLY_IDLE,
9770 &continue_balancing);
9771
9772 domain_cost = sched_clock_cpu(this_cpu) - t0;
9773 if (domain_cost > sd->max_newidle_lb_cost)
9774 sd->max_newidle_lb_cost = domain_cost;
9775
9776 curr_cost += domain_cost;
9777 }
9778
9779 update_next_balance(sd, &next_balance);
9780
9781 /*
9782 * Stop searching for tasks to pull if there are
9783 * now runnable tasks on this rq.
9784 */
9785 if (pulled_task || this_rq->nr_running > 0)
9786 break;
9787 }
9788 rcu_read_unlock();
9789
9790 raw_spin_lock(&this_rq->lock);
9791
9792 if (curr_cost > this_rq->max_idle_balance_cost)
9793 this_rq->max_idle_balance_cost = curr_cost;
9794
9795out:
9796 /*
9797 * While browsing the domains, we released the rq lock, a task could
9798 * have been enqueued in the meantime. Since we're not going idle,
9799 * pretend we pulled a task.
9800 */
9801 if (this_rq->cfs.h_nr_running && !pulled_task)
9802 pulled_task = 1;
9803
9804 /* Move the next balance forward */
9805 if (time_after(this_rq->next_balance, next_balance))
9806 this_rq->next_balance = next_balance;
9807
9808 /* Is there a task of a high priority class? */
9809 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
9810 pulled_task = -1;
9811
9812 if (pulled_task)
9813 this_rq->idle_stamp = 0;
9814
9815 rq_repin_lock(this_rq, rf);
9816
9817 return pulled_task;
9818}
9819
9820/*
9821 * run_rebalance_domains is triggered when needed from the scheduler tick.
9822 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
9823 */
9824static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
9825{
9826 struct rq *this_rq = this_rq();
9827 enum cpu_idle_type idle = this_rq->idle_balance ?
9828 CPU_IDLE : CPU_NOT_IDLE;
9829
9830 /*
9831 * If this CPU has a pending nohz_balance_kick, then do the
9832 * balancing on behalf of the other idle CPUs whose ticks are
9833 * stopped. Do nohz_idle_balance *before* rebalance_domains to
9834 * give the idle CPUs a chance to load balance. Else we may
9835 * load balance only within the local sched_domain hierarchy
9836 * and abort nohz_idle_balance altogether if we pull some load.
9837 */
9838 if (nohz_idle_balance(this_rq, idle))
9839 return;
9840
9841 /* normal load balance */
9842 update_blocked_averages(this_rq->cpu);
9843 rebalance_domains(this_rq, idle);
9844}
9845
9846/*
9847 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
9848 */
9849void trigger_load_balance(struct rq *rq)
9850{
9851 /* Don't need to rebalance while attached to NULL domain */
9852 if (unlikely(on_null_domain(rq)))
9853 return;
9854
9855 if (time_after_eq(jiffies, rq->next_balance))
9856 raise_softirq(SCHED_SOFTIRQ);
9857
9858 nohz_balancer_kick(rq);
9859}
9860
9861static void rq_online_fair(struct rq *rq)
9862{
9863 update_sysctl();
9864
9865 update_runtime_enabled(rq);
9866}
9867
9868static void rq_offline_fair(struct rq *rq)
9869{
9870 update_sysctl();
9871
9872 /* Ensure any throttled groups are reachable by pick_next_task */
9873 unthrottle_offline_cfs_rqs(rq);
9874}
9875
9876#endif /* CONFIG_SMP */
9877
9878/*
9879 * scheduler tick hitting a task of our scheduling class.
9880 *
9881 * NOTE: This function can be called remotely by the tick offload that
9882 * goes along full dynticks. Therefore no local assumption can be made
9883 * and everything must be accessed through the @rq and @curr passed in
9884 * parameters.
9885 */
9886static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
9887{
9888 struct cfs_rq *cfs_rq;
9889 struct sched_entity *se = &curr->se;
9890
9891 for_each_sched_entity(se) {
9892 cfs_rq = cfs_rq_of(se);
9893 entity_tick(cfs_rq, se, queued);
9894 }
9895
9896 if (static_branch_unlikely(&sched_numa_balancing))
9897 task_tick_numa(rq, curr);
9898}
9899
9900/*
9901 * called on fork with the child task as argument from the parent's context
9902 * - child not yet on the tasklist
9903 * - preemption disabled
9904 */
9905static void task_fork_fair(struct task_struct *p)
9906{
9907 struct cfs_rq *cfs_rq;
9908 struct sched_entity *se = &p->se, *curr;
9909 struct rq *rq = this_rq();
9910 struct rq_flags rf;
9911
9912 rq_lock(rq, &rf);
9913 update_rq_clock(rq);
9914
9915 cfs_rq = task_cfs_rq(current);
9916 curr = cfs_rq->curr;
9917 if (curr) {
9918 update_curr(cfs_rq);
9919 se->vruntime = curr->vruntime;
9920 }
9921 place_entity(cfs_rq, se, 1);
9922
9923 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
9924 /*
9925 * Upon rescheduling, sched_class::put_prev_task() will place
9926 * 'current' within the tree based on its new key value.
9927 */
9928 swap(curr->vruntime, se->vruntime);
9929 resched_curr(rq);
9930 }
9931
9932 se->vruntime -= cfs_rq->min_vruntime;
9933 rq_unlock(rq, &rf);
9934}
9935
9936/*
9937 * Priority of the task has changed. Check to see if we preempt
9938 * the current task.
9939 */
9940static void
9941prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
9942{
9943 if (!task_on_rq_queued(p))
9944 return;
9945
9946 /*
9947 * Reschedule if we are currently running on this runqueue and
9948 * our priority decreased, or if we are not currently running on
9949 * this runqueue and our priority is higher than the current's
9950 */
9951 if (rq->curr == p) {
9952 if (p->prio > oldprio)
9953 resched_curr(rq);
9954 } else
9955 check_preempt_curr(rq, p, 0);
9956}
9957
9958static inline bool vruntime_normalized(struct task_struct *p)
9959{
9960 struct sched_entity *se = &p->se;
9961
9962 /*
9963 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
9964 * the dequeue_entity(.flags=0) will already have normalized the
9965 * vruntime.
9966 */
9967 if (p->on_rq)
9968 return true;
9969
9970 /*
9971 * When !on_rq, vruntime of the task has usually NOT been normalized.
9972 * But there are some cases where it has already been normalized:
9973 *
9974 * - A forked child which is waiting for being woken up by
9975 * wake_up_new_task().
9976 * - A task which has been woken up by try_to_wake_up() and
9977 * waiting for actually being woken up by sched_ttwu_pending().
9978 */
9979 if (!se->sum_exec_runtime || p->state == TASK_WAKING)
9980 return true;
9981
9982 return false;
9983}
9984
9985#ifdef CONFIG_FAIR_GROUP_SCHED
9986/*
9987 * Propagate the changes of the sched_entity across the tg tree to make it
9988 * visible to the root
9989 */
9990static void propagate_entity_cfs_rq(struct sched_entity *se)
9991{
9992 struct cfs_rq *cfs_rq;
9993
9994 /* Start to propagate at parent */
9995 se = se->parent;
9996
9997 for_each_sched_entity(se) {
9998 cfs_rq = cfs_rq_of(se);
9999
10000 if (cfs_rq_throttled(cfs_rq))
10001 break;
10002
10003 update_load_avg(cfs_rq, se, UPDATE_TG);
10004 }
10005}
10006#else
10007static void propagate_entity_cfs_rq(struct sched_entity *se) { }
10008#endif
10009
10010static void detach_entity_cfs_rq(struct sched_entity *se)
10011{
10012 struct cfs_rq *cfs_rq = cfs_rq_of(se);
10013
10014 /* Catch up with the cfs_rq and remove our load when we leave */
10015 update_load_avg(cfs_rq, se, 0);
10016 detach_entity_load_avg(cfs_rq, se);
10017 update_tg_load_avg(cfs_rq, false);
10018 propagate_entity_cfs_rq(se);
10019}
10020
10021static void attach_entity_cfs_rq(struct sched_entity *se)
10022{
10023 struct cfs_rq *cfs_rq = cfs_rq_of(se);
10024
10025#ifdef CONFIG_FAIR_GROUP_SCHED
10026 /*
10027 * Since the real-depth could have been changed (only FAIR
10028 * class maintain depth value), reset depth properly.
10029 */
10030 se->depth = se->parent ? se->parent->depth + 1 : 0;
10031#endif
10032
10033 /* Synchronize entity with its cfs_rq */
10034 update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
10035 attach_entity_load_avg(cfs_rq, se, 0);
10036 update_tg_load_avg(cfs_rq, false);
10037 propagate_entity_cfs_rq(se);
10038}
10039
10040static void detach_task_cfs_rq(struct task_struct *p)
10041{
10042 struct sched_entity *se = &p->se;
10043 struct cfs_rq *cfs_rq = cfs_rq_of(se);
10044
10045 if (!vruntime_normalized(p)) {
10046 /*
10047 * Fix up our vruntime so that the current sleep doesn't
10048 * cause 'unlimited' sleep bonus.
10049 */
10050 place_entity(cfs_rq, se, 0);
10051 se->vruntime -= cfs_rq->min_vruntime;
10052 }
10053
10054 detach_entity_cfs_rq(se);
10055}
10056
10057static void attach_task_cfs_rq(struct task_struct *p)
10058{
10059 struct sched_entity *se = &p->se;
10060 struct cfs_rq *cfs_rq = cfs_rq_of(se);
10061
10062 attach_entity_cfs_rq(se);
10063
10064 if (!vruntime_normalized(p))
10065 se->vruntime += cfs_rq->min_vruntime;
10066}
10067
10068static void switched_from_fair(struct rq *rq, struct task_struct *p)
10069{
10070 detach_task_cfs_rq(p);
10071}
10072
10073static void switched_to_fair(struct rq *rq, struct task_struct *p)
10074{
10075 attach_task_cfs_rq(p);
10076
10077 if (task_on_rq_queued(p)) {
10078 /*
10079 * We were most likely switched from sched_rt, so
10080 * kick off the schedule if running, otherwise just see
10081 * if we can still preempt the current task.
10082 */
10083 if (rq->curr == p)
10084 resched_curr(rq);
10085 else
10086 check_preempt_curr(rq, p, 0);
10087 }
10088}
10089
10090/* Account for a task changing its policy or group.
10091 *
10092 * This routine is mostly called to set cfs_rq->curr field when a task
10093 * migrates between groups/classes.
10094 */
10095static void set_curr_task_fair(struct rq *rq)
10096{
10097 struct sched_entity *se = &rq->curr->se;
10098
10099 for_each_sched_entity(se) {
10100 struct cfs_rq *cfs_rq = cfs_rq_of(se);
10101
10102 set_next_entity(cfs_rq, se);
10103 /* ensure bandwidth has been allocated on our new cfs_rq */
10104 account_cfs_rq_runtime(cfs_rq, 0);
10105 }
10106}
10107
10108void init_cfs_rq(struct cfs_rq *cfs_rq)
10109{
10110 cfs_rq->tasks_timeline = RB_ROOT_CACHED;
10111 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
10112#ifndef CONFIG_64BIT
10113 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
10114#endif
10115#ifdef CONFIG_SMP
10116 raw_spin_lock_init(&cfs_rq->removed.lock);
10117#endif
10118}
10119
10120#ifdef CONFIG_FAIR_GROUP_SCHED
10121static void task_set_group_fair(struct task_struct *p)
10122{
10123 struct sched_entity *se = &p->se;
10124
10125 set_task_rq(p, task_cpu(p));
10126 se->depth = se->parent ? se->parent->depth + 1 : 0;
10127}
10128
10129static void task_move_group_fair(struct task_struct *p)
10130{
10131 detach_task_cfs_rq(p);
10132 set_task_rq(p, task_cpu(p));
10133
10134#ifdef CONFIG_SMP
10135 /* Tell se's cfs_rq has been changed -- migrated */
10136 p->se.avg.last_update_time = 0;
10137#endif
10138 attach_task_cfs_rq(p);
10139}
10140
10141static void task_change_group_fair(struct task_struct *p, int type)
10142{
10143 switch (type) {
10144 case TASK_SET_GROUP:
10145 task_set_group_fair(p);
10146 break;
10147
10148 case TASK_MOVE_GROUP:
10149 task_move_group_fair(p);
10150 break;
10151 }
10152}
10153
10154void free_fair_sched_group(struct task_group *tg)
10155{
10156 int i;
10157
10158 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
10159
10160 for_each_possible_cpu(i) {
10161 if (tg->cfs_rq)
10162 kfree(tg->cfs_rq[i]);
10163 if (tg->se)
10164 kfree(tg->se[i]);
10165 }
10166
10167 kfree(tg->cfs_rq);
10168 kfree(tg->se);
10169}
10170
10171int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
10172{
10173 struct sched_entity *se;
10174 struct cfs_rq *cfs_rq;
10175 int i;
10176
10177 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
10178 if (!tg->cfs_rq)
10179 goto err;
10180 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
10181 if (!tg->se)
10182 goto err;
10183
10184 tg->shares = NICE_0_LOAD;
10185
10186 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
10187
10188 for_each_possible_cpu(i) {
10189 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
10190 GFP_KERNEL, cpu_to_node(i));
10191 if (!cfs_rq)
10192 goto err;
10193
10194 se = kzalloc_node(sizeof(struct sched_entity),
10195 GFP_KERNEL, cpu_to_node(i));
10196 if (!se)
10197 goto err_free_rq;
10198
10199 init_cfs_rq(cfs_rq);
10200 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
10201 init_entity_runnable_average(se);
10202 }
10203
10204 return 1;
10205
10206err_free_rq:
10207 kfree(cfs_rq);
10208err:
10209 return 0;
10210}
10211
10212void online_fair_sched_group(struct task_group *tg)
10213{
10214 struct sched_entity *se;
10215 struct rq *rq;
10216 int i;
10217
10218 for_each_possible_cpu(i) {
10219 rq = cpu_rq(i);
10220 se = tg->se[i];
10221
10222 raw_spin_lock_irq(&rq->lock);
10223 update_rq_clock(rq);
10224 attach_entity_cfs_rq(se);
10225 sync_throttle(tg, i);
10226 raw_spin_unlock_irq(&rq->lock);
10227 }
10228}
10229
10230void unregister_fair_sched_group(struct task_group *tg)
10231{
10232 unsigned long flags;
10233 struct rq *rq;
10234 int cpu;
10235
10236 for_each_possible_cpu(cpu) {
10237 if (tg->se[cpu])
10238 remove_entity_load_avg(tg->se[cpu]);
10239
10240 /*
10241 * Only empty task groups can be destroyed; so we can speculatively
10242 * check on_list without danger of it being re-added.
10243 */
10244 if (!tg->cfs_rq[cpu]->on_list)
10245 continue;
10246
10247 rq = cpu_rq(cpu);
10248
10249 raw_spin_lock_irqsave(&rq->lock, flags);
10250 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
10251 raw_spin_unlock_irqrestore(&rq->lock, flags);
10252 }
10253}
10254
10255void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
10256 struct sched_entity *se, int cpu,
10257 struct sched_entity *parent)
10258{
10259 struct rq *rq = cpu_rq(cpu);
10260
10261 cfs_rq->tg = tg;
10262 cfs_rq->rq = rq;
10263 init_cfs_rq_runtime(cfs_rq);
10264
10265 tg->cfs_rq[cpu] = cfs_rq;
10266 tg->se[cpu] = se;
10267
10268 /* se could be NULL for root_task_group */
10269 if (!se)
10270 return;
10271
10272 if (!parent) {
10273 se->cfs_rq = &rq->cfs;
10274 se->depth = 0;
10275 } else {
10276 se->cfs_rq = parent->my_q;
10277 se->depth = parent->depth + 1;
10278 }
10279
10280 se->my_q = cfs_rq;
10281 /* guarantee group entities always have weight */
10282 update_load_set(&se->load, NICE_0_LOAD);
10283 se->parent = parent;
10284}
10285
10286static DEFINE_MUTEX(shares_mutex);
10287
10288int sched_group_set_shares(struct task_group *tg, unsigned long shares)
10289{
10290 int i;
10291
10292 /*
10293 * We can't change the weight of the root cgroup.
10294 */
10295 if (!tg->se[0])
10296 return -EINVAL;
10297
10298 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
10299
10300 mutex_lock(&shares_mutex);
10301 if (tg->shares == shares)
10302 goto done;
10303
10304 tg->shares = shares;
10305 for_each_possible_cpu(i) {
10306 struct rq *rq = cpu_rq(i);
10307 struct sched_entity *se = tg->se[i];
10308 struct rq_flags rf;
10309
10310 /* Propagate contribution to hierarchy */
10311 rq_lock_irqsave(rq, &rf);
10312 update_rq_clock(rq);
10313 for_each_sched_entity(se) {
10314 update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
10315 update_cfs_group(se);
10316 }
10317 rq_unlock_irqrestore(rq, &rf);
10318 }
10319
10320done:
10321 mutex_unlock(&shares_mutex);
10322 return 0;
10323}
10324#else /* CONFIG_FAIR_GROUP_SCHED */
10325
10326void free_fair_sched_group(struct task_group *tg) { }
10327
10328int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
10329{
10330 return 1;
10331}
10332
10333void online_fair_sched_group(struct task_group *tg) { }
10334
10335void unregister_fair_sched_group(struct task_group *tg) { }
10336
10337#endif /* CONFIG_FAIR_GROUP_SCHED */
10338
10339
10340static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
10341{
10342 struct sched_entity *se = &task->se;
10343 unsigned int rr_interval = 0;
10344
10345 /*
10346 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
10347 * idle runqueue:
10348 */
10349 if (rq->cfs.load.weight)
10350 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
10351
10352 return rr_interval;
10353}
10354
10355/*
10356 * All the scheduling class methods:
10357 */
10358const struct sched_class fair_sched_class = {
10359 .next = &idle_sched_class,
10360 .enqueue_task = enqueue_task_fair,
10361 .dequeue_task = dequeue_task_fair,
10362 .yield_task = yield_task_fair,
10363 .yield_to_task = yield_to_task_fair,
10364
10365 .check_preempt_curr = check_preempt_wakeup,
10366
10367 .pick_next_task = pick_next_task_fair,
10368 .put_prev_task = put_prev_task_fair,
10369
10370#ifdef CONFIG_SMP
10371 .select_task_rq = select_task_rq_fair,
10372 .migrate_task_rq = migrate_task_rq_fair,
10373
10374 .rq_online = rq_online_fair,
10375 .rq_offline = rq_offline_fair,
10376
10377 .task_dead = task_dead_fair,
10378 .set_cpus_allowed = set_cpus_allowed_common,
10379#endif
10380
10381 .set_curr_task = set_curr_task_fair,
10382 .task_tick = task_tick_fair,
10383 .task_fork = task_fork_fair,
10384
10385 .prio_changed = prio_changed_fair,
10386 .switched_from = switched_from_fair,
10387 .switched_to = switched_to_fair,
10388
10389 .get_rr_interval = get_rr_interval_fair,
10390
10391 .update_curr = update_curr_fair,
10392
10393#ifdef CONFIG_FAIR_GROUP_SCHED
10394 .task_change_group = task_change_group_fair,
10395#endif
10396};
10397
10398#ifdef CONFIG_SCHED_DEBUG
10399void print_cfs_stats(struct seq_file *m, int cpu)
10400{
10401 struct cfs_rq *cfs_rq, *pos;
10402
10403 rcu_read_lock();
10404 for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos)
10405 print_cfs_rq(m, cpu, cfs_rq);
10406 rcu_read_unlock();
10407}
10408
10409#ifdef CONFIG_NUMA_BALANCING
10410void show_numa_stats(struct task_struct *p, struct seq_file *m)
10411{
10412 int node;
10413 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
10414
10415 for_each_online_node(node) {
10416 if (p->numa_faults) {
10417 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
10418 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
10419 }
10420 if (p->numa_group) {
10421 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
10422 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
10423 }
10424 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
10425 }
10426}
10427#endif /* CONFIG_NUMA_BALANCING */
10428#endif /* CONFIG_SCHED_DEBUG */
10429
10430__init void init_sched_fair_class(void)
10431{
10432#ifdef CONFIG_SMP
10433 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
10434
10435#ifdef CONFIG_NO_HZ_COMMON
10436 nohz.next_balance = jiffies;
10437 nohz.next_blocked = jiffies;
10438 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
10439#endif
10440#endif /* SMP */
10441
10442}