1/*
   2 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
   3 *
   4 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
   5 *
   6 *  Interactivity improvements by Mike Galbraith
   7 *  (C) 2007 Mike Galbraith <efault@gmx.de>
   8 *
   9 *  Various enhancements by Dmitry Adamushko.
  10 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
  11 *
  12 *  Group scheduling enhancements by Srivatsa Vaddagiri
  13 *  Copyright IBM Corporation, 2007
  14 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
  15 *
  16 *  Scaled math optimizations by Thomas Gleixner
  17 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
  18 *
  19 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
  20 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
  21 */
  22
  23#include <linux/latencytop.h>
  24#include <linux/sched.h>
 
  25#include <linux/cpumask.h>
 
  26#include <linux/slab.h>
  27#include <linux/profile.h>
  28#include <linux/interrupt.h>
  29#include <linux/mempolicy.h>
  30#include <linux/migrate.h>
  31#include <linux/task_work.h>
  32
  33#include <trace/events/sched.h>
  34
  35#include "sched.h"
  36
  37/*
  38 * Targeted preemption latency for CPU-bound tasks:
  39 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
  40 *
  41 * NOTE: this latency value is not the same as the concept of
  42 * 'timeslice length' - timeslices in CFS are of variable length
  43 * and have no persistent notion like in traditional, time-slice
  44 * based scheduling concepts.
  45 *
  46 * (to see the precise effective timeslice length of your workload,
  47 *  run vmstat and monitor the context-switches (cs) field)
  48 */
  49unsigned int sysctl_sched_latency = 6000000ULL;
  50unsigned int normalized_sysctl_sched_latency = 6000000ULL;
  51
  52/*
  53 * The initial- and re-scaling of tunables is configurable
  54 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
  55 *
  56 * Options are:
  57 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
  58 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
  59 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
  60 */
  61enum sched_tunable_scaling sysctl_sched_tunable_scaling
  62	= SCHED_TUNABLESCALING_LOG;
  63
  64/*
  65 * Minimal preemption granularity for CPU-bound tasks:
  66 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
  67 */
  68unsigned int sysctl_sched_min_granularity = 750000ULL;
  69unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
  70
  71/*
  72 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
  73 */
  74static unsigned int sched_nr_latency = 8;
  75
  76/*
  77 * After fork, child runs first. If set to 0 (default) then
  78 * parent will (try to) run first.
  79 */
  80unsigned int sysctl_sched_child_runs_first __read_mostly;
  81
  82/*
  83 * SCHED_OTHER wake-up granularity.
  84 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
  85 *
  86 * This option delays the preemption effects of decoupled workloads
  87 * and reduces their over-scheduling. Synchronous workloads will still
  88 * have immediate wakeup/sleep latencies.
  89 */
  90unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
  91unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
  92
  93const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
  94
  95/*
  96 * The exponential sliding  window over which load is averaged for shares
  97 * distribution.
  98 * (default: 10msec)
  99 */
 100unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
 101
 102#ifdef CONFIG_CFS_BANDWIDTH
 103/*
 104 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
 105 * each time a cfs_rq requests quota.
 106 *
 107 * Note: in the case that the slice exceeds the runtime remaining (either due
 108 * to consumption or the quota being specified to be smaller than the slice)
 109 * we will always only issue the remaining available time.
 110 *
 111 * default: 5 msec, units: microseconds
 112  */
 113unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
 114#endif
 115
 116static inline void update_load_add(struct load_weight *lw, unsigned long inc)
 117{
 118	lw->weight += inc;
 119	lw->inv_weight = 0;
 120}
 121
 122static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
 123{
 124	lw->weight -= dec;
 125	lw->inv_weight = 0;
 126}
 127
 128static inline void update_load_set(struct load_weight *lw, unsigned long w)
 129{
 130	lw->weight = w;
 131	lw->inv_weight = 0;
 132}
 133
 134/*
 135 * Increase the granularity value when there are more CPUs,
 136 * because with more CPUs the 'effective latency' as visible
 137 * to users decreases. But the relationship is not linear,
 138 * so pick a second-best guess by going with the log2 of the
 139 * number of CPUs.
 140 *
 141 * This idea comes from the SD scheduler of Con Kolivas:
 142 */
 143static int get_update_sysctl_factor(void)
 144{
 145	unsigned int cpus = min_t(int, num_online_cpus(), 8);
 146	unsigned int factor;
 147
 148	switch (sysctl_sched_tunable_scaling) {
 149	case SCHED_TUNABLESCALING_NONE:
 150		factor = 1;
 151		break;
 152	case SCHED_TUNABLESCALING_LINEAR:
 153		factor = cpus;
 154		break;
 155	case SCHED_TUNABLESCALING_LOG:
 156	default:
 157		factor = 1 + ilog2(cpus);
 158		break;
 159	}
 160
 161	return factor;
 162}
 163
 164static void update_sysctl(void)
 165{
 166	unsigned int factor = get_update_sysctl_factor();
 167
 168#define SET_SYSCTL(name) \
 169	(sysctl_##name = (factor) * normalized_sysctl_##name)
 170	SET_SYSCTL(sched_min_granularity);
 171	SET_SYSCTL(sched_latency);
 172	SET_SYSCTL(sched_wakeup_granularity);
 173#undef SET_SYSCTL
 174}
 175
 176void sched_init_granularity(void)
 177{
 178	update_sysctl();
 179}
 180
 181#define WMULT_CONST	(~0U)
 182#define WMULT_SHIFT	32
 183
 184static void __update_inv_weight(struct load_weight *lw)
 185{
 186	unsigned long w;
 187
 188	if (likely(lw->inv_weight))
 189		return;
 190
 191	w = scale_load_down(lw->weight);
 192
 193	if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
 194		lw->inv_weight = 1;
 195	else if (unlikely(!w))
 196		lw->inv_weight = WMULT_CONST;
 197	else
 198		lw->inv_weight = WMULT_CONST / w;
 199}
 200
 201/*
 202 * delta_exec * weight / lw.weight
 203 *   OR
 204 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
 205 *
 206 * Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case
 207 * we're guaranteed shift stays positive because inv_weight is guaranteed to
 208 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
 209 *
 210 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
 211 * weight/lw.weight <= 1, and therefore our shift will also be positive.
 212 */
 213static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
 214{
 215	u64 fact = scale_load_down(weight);
 216	int shift = WMULT_SHIFT;
 217
 218	__update_inv_weight(lw);
 219
 220	if (unlikely(fact >> 32)) {
 221		while (fact >> 32) {
 222			fact >>= 1;
 223			shift--;
 224		}
 225	}
 226
 227	/* hint to use a 32x32->64 mul */
 228	fact = (u64)(u32)fact * lw->inv_weight;
 229
 230	while (fact >> 32) {
 231		fact >>= 1;
 232		shift--;
 233	}
 234
 235	return mul_u64_u32_shr(delta_exec, fact, shift);
 236}
 237
 238
 239const struct sched_class fair_sched_class;
 240
 241/**************************************************************
 242 * CFS operations on generic schedulable entities:
 243 */
 244
 245#ifdef CONFIG_FAIR_GROUP_SCHED
 246
 247/* cpu runqueue to which this cfs_rq is attached */
 248static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
 249{
 250	return cfs_rq->rq;
 251}
 252
 253/* An entity is a task if it doesn't "own" a runqueue */
 254#define entity_is_task(se)	(!se->my_q)
 255
 256static inline struct task_struct *task_of(struct sched_entity *se)
 257{
 258#ifdef CONFIG_SCHED_DEBUG
 259	WARN_ON_ONCE(!entity_is_task(se));
 260#endif
 261	return container_of(se, struct task_struct, se);
 262}
 263
 264/* Walk up scheduling entities hierarchy */
 265#define for_each_sched_entity(se) \
 266		for (; se; se = se->parent)
 267
 268static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
 269{
 270	return p->se.cfs_rq;
 271}
 272
 273/* runqueue on which this entity is (to be) queued */
 274static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
 275{
 276	return se->cfs_rq;
 277}
 278
 279/* runqueue "owned" by this group */
 280static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
 281{
 282	return grp->my_q;
 283}
 284
 285static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
 286				       int force_update);
 287
 288static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 289{
 290	if (!cfs_rq->on_list) {
 291		/*
 292		 * Ensure we either appear before our parent (if already
 293		 * enqueued) or force our parent to appear after us when it is
 294		 * enqueued.  The fact that we always enqueue bottom-up
 295		 * reduces this to two cases.
 296		 */
 297		if (cfs_rq->tg->parent &&
 298		    cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
 299			list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
 300				&rq_of(cfs_rq)->leaf_cfs_rq_list);
 301		} else {
 302			list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
 303				&rq_of(cfs_rq)->leaf_cfs_rq_list);
 304		}
 305
 306		cfs_rq->on_list = 1;
 307		/* We should have no load, but we need to update last_decay. */
 308		update_cfs_rq_blocked_load(cfs_rq, 0);
 309	}
 310}
 311
 312static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 313{
 314	if (cfs_rq->on_list) {
 315		list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
 316		cfs_rq->on_list = 0;
 317	}
 318}
 319
 320/* Iterate thr' all leaf cfs_rq's on a runqueue */
 321#define for_each_leaf_cfs_rq(rq, cfs_rq) \
 322	list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
 323
 324/* Do the two (enqueued) entities belong to the same group ? */
 325static inline struct cfs_rq *
 326is_same_group(struct sched_entity *se, struct sched_entity *pse)
 327{
 328	if (se->cfs_rq == pse->cfs_rq)
 329		return se->cfs_rq;
 330
 331	return NULL;
 332}
 333
 334static inline struct sched_entity *parent_entity(struct sched_entity *se)
 335{
 336	return se->parent;
 337}
 338
 339static void
 340find_matching_se(struct sched_entity **se, struct sched_entity **pse)
 341{
 342	int se_depth, pse_depth;
 343
 344	/*
 345	 * preemption test can be made between sibling entities who are in the
 346	 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
 347	 * both tasks until we find their ancestors who are siblings of common
 348	 * parent.
 349	 */
 350
 351	/* First walk up until both entities are at same depth */
 352	se_depth = (*se)->depth;
 353	pse_depth = (*pse)->depth;
 354
 355	while (se_depth > pse_depth) {
 356		se_depth--;
 357		*se = parent_entity(*se);
 358	}
 359
 360	while (pse_depth > se_depth) {
 361		pse_depth--;
 362		*pse = parent_entity(*pse);
 363	}
 364
 365	while (!is_same_group(*se, *pse)) {
 366		*se = parent_entity(*se);
 367		*pse = parent_entity(*pse);
 368	}
 369}
 370
 371#else	/* !CONFIG_FAIR_GROUP_SCHED */
 372
 373static inline struct task_struct *task_of(struct sched_entity *se)
 374{
 375	return container_of(se, struct task_struct, se);
 376}
 377
 378static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
 379{
 380	return container_of(cfs_rq, struct rq, cfs);
 381}
 382
 383#define entity_is_task(se)	1
 384
 385#define for_each_sched_entity(se) \
 386		for (; se; se = NULL)
 387
 388static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
 389{
 390	return &task_rq(p)->cfs;
 391}
 392
 393static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
 394{
 395	struct task_struct *p = task_of(se);
 396	struct rq *rq = task_rq(p);
 397
 398	return &rq->cfs;
 399}
 400
 401/* runqueue "owned" by this group */
 402static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
 403{
 404	return NULL;
 405}
 406
 407static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 408{
 409}
 410
 411static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 412{
 413}
 414
 415#define for_each_leaf_cfs_rq(rq, cfs_rq) \
 416		for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
 417
 418static inline struct sched_entity *parent_entity(struct sched_entity *se)
 419{
 420	return NULL;
 421}
 422
 423static inline void
 424find_matching_se(struct sched_entity **se, struct sched_entity **pse)
 425{
 426}
 427
 428#endif	/* CONFIG_FAIR_GROUP_SCHED */
 429
 430static __always_inline
 431void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
 432
 433/**************************************************************
 434 * Scheduling class tree data structure manipulation methods:
 435 */
 436
 437static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
 438{
 439	s64 delta = (s64)(vruntime - max_vruntime);
 440	if (delta > 0)
 441		max_vruntime = vruntime;
 442
 443	return max_vruntime;
 444}
 445
 446static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
 447{
 448	s64 delta = (s64)(vruntime - min_vruntime);
 449	if (delta < 0)
 450		min_vruntime = vruntime;
 451
 452	return min_vruntime;
 453}
 454
 455static inline int entity_before(struct sched_entity *a,
 456				struct sched_entity *b)
 457{
 458	return (s64)(a->vruntime - b->vruntime) < 0;
 459}
 460
 461static void update_min_vruntime(struct cfs_rq *cfs_rq)
 462{
 463	u64 vruntime = cfs_rq->min_vruntime;
 464
 465	if (cfs_rq->curr)
 466		vruntime = cfs_rq->curr->vruntime;
 467
 468	if (cfs_rq->rb_leftmost) {
 469		struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
 470						   struct sched_entity,
 471						   run_node);
 472
 473		if (!cfs_rq->curr)
 474			vruntime = se->vruntime;
 475		else
 476			vruntime = min_vruntime(vruntime, se->vruntime);
 477	}
 478
 479	/* ensure we never gain time by being placed backwards. */
 480	cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
 481#ifndef CONFIG_64BIT
 482	smp_wmb();
 483	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
 484#endif
 485}
 486
 487/*
 488 * Enqueue an entity into the rb-tree:
 489 */
 490static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 491{
 492	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
 493	struct rb_node *parent = NULL;
 494	struct sched_entity *entry;
 495	int leftmost = 1;
 496
 497	/*
 498	 * Find the right place in the rbtree:
 499	 */
 500	while (*link) {
 501		parent = *link;
 502		entry = rb_entry(parent, struct sched_entity, run_node);
 503		/*
 504		 * We dont care about collisions. Nodes with
 505		 * the same key stay together.
 506		 */
 507		if (entity_before(se, entry)) {
 508			link = &parent->rb_left;
 509		} else {
 510			link = &parent->rb_right;
 511			leftmost = 0;
 512		}
 513	}
 514
 515	/*
 516	 * Maintain a cache of leftmost tree entries (it is frequently
 517	 * used):
 518	 */
 519	if (leftmost)
 520		cfs_rq->rb_leftmost = &se->run_node;
 521
 522	rb_link_node(&se->run_node, parent, link);
 523	rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
 524}
 525
 526static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 527{
 528	if (cfs_rq->rb_leftmost == &se->run_node) {
 529		struct rb_node *next_node;
 530
 531		next_node = rb_next(&se->run_node);
 532		cfs_rq->rb_leftmost = next_node;
 533	}
 534
 535	rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
 536}
 537
 538struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
 539{
 540	struct rb_node *left = cfs_rq->rb_leftmost;
 541
 542	if (!left)
 543		return NULL;
 544
 545	return rb_entry(left, struct sched_entity, run_node);
 546}
 547
 548static struct sched_entity *__pick_next_entity(struct sched_entity *se)
 549{
 550	struct rb_node *next = rb_next(&se->run_node);
 551
 552	if (!next)
 553		return NULL;
 554
 555	return rb_entry(next, struct sched_entity, run_node);
 556}
 557
 558#ifdef CONFIG_SCHED_DEBUG
 559struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
 560{
 561	struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
 562
 563	if (!last)
 564		return NULL;
 565
 566	return rb_entry(last, struct sched_entity, run_node);
 567}
 568
 569/**************************************************************
 570 * Scheduling class statistics methods:
 571 */
 572
 573int sched_proc_update_handler(struct ctl_table *table, int write,
 574		void __user *buffer, size_t *lenp,
 575		loff_t *ppos)
 576{
 577	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 578	int factor = get_update_sysctl_factor();
 579
 580	if (ret || !write)
 581		return ret;
 582
 583	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
 584					sysctl_sched_min_granularity);
 585
 586#define WRT_SYSCTL(name) \
 587	(normalized_sysctl_##name = sysctl_##name / (factor))
 588	WRT_SYSCTL(sched_min_granularity);
 589	WRT_SYSCTL(sched_latency);
 590	WRT_SYSCTL(sched_wakeup_granularity);
 591#undef WRT_SYSCTL
 592
 593	return 0;
 594}
 595#endif
 596
 597/*
 598 * delta /= w
 599 */
 600static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
 601{
 602	if (unlikely(se->load.weight != NICE_0_LOAD))
 603		delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
 604
 605	return delta;
 606}
 607
 608/*
 609 * The idea is to set a period in which each task runs once.
 610 *
 611 * When there are too many tasks (sched_nr_latency) we have to stretch
 612 * this period because otherwise the slices get too small.
 613 *
 614 * p = (nr <= nl) ? l : l*nr/nl
 615 */
 616static u64 __sched_period(unsigned long nr_running)
 617{
 618	u64 period = sysctl_sched_latency;
 619	unsigned long nr_latency = sched_nr_latency;
 620
 621	if (unlikely(nr_running > nr_latency)) {
 622		period = sysctl_sched_min_granularity;
 623		period *= nr_running;
 624	}
 625
 626	return period;
 627}
 628
 629/*
 630 * We calculate the wall-time slice from the period by taking a part
 631 * proportional to the weight.
 632 *
 633 * s = p*P[w/rw]
 634 */
 635static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
 636{
 637	u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
 638
 639	for_each_sched_entity(se) {
 640		struct load_weight *load;
 641		struct load_weight lw;
 642
 643		cfs_rq = cfs_rq_of(se);
 644		load = &cfs_rq->load;
 645
 646		if (unlikely(!se->on_rq)) {
 647			lw = cfs_rq->load;
 648
 649			update_load_add(&lw, se->load.weight);
 650			load = &lw;
 651		}
 652		slice = __calc_delta(slice, se->load.weight, load);
 653	}
 654	return slice;
 655}
 656
 657/*
 658 * We calculate the vruntime slice of a to-be-inserted task.
 659 *
 660 * vs = s/w
 661 */
 662static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
 663{
 664	return calc_delta_fair(sched_slice(cfs_rq, se), se);
 665}
 666
 667#ifdef CONFIG_SMP
 
 668static unsigned long task_h_load(struct task_struct *p);
 669
 670static inline void __update_task_entity_contrib(struct sched_entity *se);
 
 
 
 
 
 
 
 671
 672/* Give new task start runnable values to heavy its load in infant time */
 673void init_task_runnable_average(struct task_struct *p)
 674{
 675	u32 slice;
 676
 677	p->se.avg.decay_count = 0;
 678	slice = sched_slice(task_cfs_rq(p), &p->se) >> 10;
 679	p->se.avg.runnable_avg_sum = slice;
 680	p->se.avg.runnable_avg_period = slice;
 681	__update_task_entity_contrib(&p->se);
 
 
 
 
 
 
 
 682}
 
 
 
 683#else
 684void init_task_runnable_average(struct task_struct *p)
 685{
 686}
 687#endif
 688
 689/*
 690 * Update the current task's runtime statistics.
 691 */
 692static void update_curr(struct cfs_rq *cfs_rq)
 693{
 694	struct sched_entity *curr = cfs_rq->curr;
 695	u64 now = rq_clock_task(rq_of(cfs_rq));
 696	u64 delta_exec;
 697
 698	if (unlikely(!curr))
 699		return;
 700
 701	delta_exec = now - curr->exec_start;
 702	if (unlikely((s64)delta_exec <= 0))
 703		return;
 704
 705	curr->exec_start = now;
 706
 707	schedstat_set(curr->statistics.exec_max,
 708		      max(delta_exec, curr->statistics.exec_max));
 709
 710	curr->sum_exec_runtime += delta_exec;
 711	schedstat_add(cfs_rq, exec_clock, delta_exec);
 712
 713	curr->vruntime += calc_delta_fair(delta_exec, curr);
 714	update_min_vruntime(cfs_rq);
 715
 716	if (entity_is_task(curr)) {
 717		struct task_struct *curtask = task_of(curr);
 718
 719		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
 720		cpuacct_charge(curtask, delta_exec);
 721		account_group_exec_runtime(curtask, delta_exec);
 722	}
 723
 724	account_cfs_rq_runtime(cfs_rq, delta_exec);
 725}
 726
 
 
 
 
 
 
 727static inline void
 728update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
 729{
 730	schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 731}
 732
 733/*
 734 * Task is being enqueued - update stats:
 735 */
 736static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
 
 737{
 738	/*
 739	 * Are we enqueueing a waiting task? (for current tasks
 740	 * a dequeue/enqueue event is a NOP)
 741	 */
 742	if (se != cfs_rq->curr)
 743		update_stats_wait_start(cfs_rq, se);
 744}
 745
 746static void
 747update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
 748{
 749	schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
 750			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
 751	schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
 752	schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
 753			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
 754#ifdef CONFIG_SCHEDSTATS
 755	if (entity_is_task(se)) {
 756		trace_sched_stat_wait(task_of(se),
 757			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
 758	}
 759#endif
 760	schedstat_set(se->statistics.wait_start, 0);
 761}
 762
 763static inline void
 764update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
 765{
 766	/*
 767	 * Mark the end of the wait period if dequeueing a
 768	 * waiting task:
 769	 */
 770	if (se != cfs_rq->curr)
 771		update_stats_wait_end(cfs_rq, se);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 772}
 773
 
 
 
 
 
 
 
 
 
 
 
 774/*
 775 * We are picking a new current task - update its stats:
 776 */
 777static inline void
 778update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
 779{
 780	/*
 781	 * We are starting a new run period:
 782	 */
 783	se->exec_start = rq_clock_task(rq_of(cfs_rq));
 784}
 785
 786/**************************************************
 787 * Scheduling class queueing methods:
 788 */
 789
 790#ifdef CONFIG_NUMA_BALANCING
 791/*
 792 * Approximate time to scan a full NUMA task in ms. The task scan period is
 793 * calculated based on the tasks virtual memory size and
 794 * numa_balancing_scan_size.
 795 */
 796unsigned int sysctl_numa_balancing_scan_period_min = 1000;
 797unsigned int sysctl_numa_balancing_scan_period_max = 60000;
 798
 799/* Portion of address space to scan in MB */
 800unsigned int sysctl_numa_balancing_scan_size = 256;
 801
 802/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
 803unsigned int sysctl_numa_balancing_scan_delay = 1000;
 804
 805static unsigned int task_nr_scan_windows(struct task_struct *p)
 806{
 807	unsigned long rss = 0;
 808	unsigned long nr_scan_pages;
 809
 810	/*
 811	 * Calculations based on RSS as non-present and empty pages are skipped
 812	 * by the PTE scanner and NUMA hinting faults should be trapped based
 813	 * on resident pages
 814	 */
 815	nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
 816	rss = get_mm_rss(p->mm);
 817	if (!rss)
 818		rss = nr_scan_pages;
 819
 820	rss = round_up(rss, nr_scan_pages);
 821	return rss / nr_scan_pages;
 822}
 823
 824/* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
 825#define MAX_SCAN_WINDOW 2560
 826
 827static unsigned int task_scan_min(struct task_struct *p)
 828{
 
 829	unsigned int scan, floor;
 830	unsigned int windows = 1;
 831
 832	if (sysctl_numa_balancing_scan_size < MAX_SCAN_WINDOW)
 833		windows = MAX_SCAN_WINDOW / sysctl_numa_balancing_scan_size;
 834	floor = 1000 / windows;
 835
 836	scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
 837	return max_t(unsigned int, floor, scan);
 838}
 839
 840static unsigned int task_scan_max(struct task_struct *p)
 841{
 842	unsigned int smin = task_scan_min(p);
 843	unsigned int smax;
 844
 845	/* Watch for min being lower than max due to floor calculations */
 846	smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
 847	return max(smin, smax);
 848}
 849
 850static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
 851{
 852	rq->nr_numa_running += (p->numa_preferred_nid != -1);
 853	rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
 854}
 855
 856static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
 857{
 858	rq->nr_numa_running -= (p->numa_preferred_nid != -1);
 859	rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
 860}
 861
 862struct numa_group {
 863	atomic_t refcount;
 864
 865	spinlock_t lock; /* nr_tasks, tasks */
 866	int nr_tasks;
 867	pid_t gid;
 868	struct list_head task_list;
 869
 870	struct rcu_head rcu;
 871	nodemask_t active_nodes;
 872	unsigned long total_faults;
 
 873	/*
 874	 * Faults_cpu is used to decide whether memory should move
 875	 * towards the CPU. As a consequence, these stats are weighted
 876	 * more by CPU use than by memory faults.
 877	 */
 878	unsigned long *faults_cpu;
 879	unsigned long faults[0];
 880};
 881
 882/* Shared or private faults. */
 883#define NR_NUMA_HINT_FAULT_TYPES 2
 884
 885/* Memory and CPU locality */
 886#define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
 887
 888/* Averaged statistics, and temporary buffers. */
 889#define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
 890
 891pid_t task_numa_group_id(struct task_struct *p)
 892{
 893	return p->numa_group ? p->numa_group->gid : 0;
 894}
 895
 896static inline int task_faults_idx(int nid, int priv)
 
 
 
 
 
 
 897{
 898	return NR_NUMA_HINT_FAULT_TYPES * nid + priv;
 899}
 900
 901static inline unsigned long task_faults(struct task_struct *p, int nid)
 902{
 903	if (!p->numa_faults_memory)
 904		return 0;
 905
 906	return p->numa_faults_memory[task_faults_idx(nid, 0)] +
 907		p->numa_faults_memory[task_faults_idx(nid, 1)];
 908}
 909
 910static inline unsigned long group_faults(struct task_struct *p, int nid)
 911{
 912	if (!p->numa_group)
 913		return 0;
 914
 915	return p->numa_group->faults[task_faults_idx(nid, 0)] +
 916		p->numa_group->faults[task_faults_idx(nid, 1)];
 917}
 918
 919static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
 920{
 921	return group->faults_cpu[task_faults_idx(nid, 0)] +
 922		group->faults_cpu[task_faults_idx(nid, 1)];
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 923}
 924
 925/*
 926 * These return the fraction of accesses done by a particular task, or
 927 * task group, on a particular numa node.  The group weight is given a
 928 * larger multiplier, in order to group tasks together that are almost
 929 * evenly spread out between numa nodes.
 930 */
 931static inline unsigned long task_weight(struct task_struct *p, int nid)
 
 932{
 933	unsigned long total_faults;
 934
 935	if (!p->numa_faults_memory)
 936		return 0;
 937
 938	total_faults = p->total_numa_faults;
 939
 940	if (!total_faults)
 941		return 0;
 942
 943	return 1000 * task_faults(p, nid) / total_faults;
 
 
 
 944}
 945
 946static inline unsigned long group_weight(struct task_struct *p, int nid)
 
 947{
 948	if (!p->numa_group || !p->numa_group->total_faults)
 
 
 
 
 
 
 
 949		return 0;
 950
 951	return 1000 * group_faults(p, nid) / p->numa_group->total_faults;
 
 
 
 952}
 953
 954bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
 955				int src_nid, int dst_cpu)
 956{
 957	struct numa_group *ng = p->numa_group;
 958	int dst_nid = cpu_to_node(dst_cpu);
 959	int last_cpupid, this_cpupid;
 960
 961	this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
 962
 963	/*
 964	 * Multi-stage node selection is used in conjunction with a periodic
 965	 * migration fault to build a temporal task<->page relation. By using
 966	 * a two-stage filter we remove short/unlikely relations.
 967	 *
 968	 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
 969	 * a task's usage of a particular page (n_p) per total usage of this
 970	 * page (n_t) (in a given time-span) to a probability.
 971	 *
 972	 * Our periodic faults will sample this probability and getting the
 973	 * same result twice in a row, given these samples are fully
 974	 * independent, is then given by P(n)^2, provided our sample period
 975	 * is sufficiently short compared to the usage pattern.
 976	 *
 977	 * This quadric squishes small probabilities, making it less likely we
 978	 * act on an unlikely task<->page relation.
 979	 */
 980	last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
 981	if (!cpupid_pid_unset(last_cpupid) &&
 982				cpupid_to_nid(last_cpupid) != dst_nid)
 983		return false;
 984
 985	/* Always allow migrate on private faults */
 986	if (cpupid_match_pid(p, last_cpupid))
 987		return true;
 988
 989	/* A shared fault, but p->numa_group has not been set up yet. */
 990	if (!ng)
 991		return true;
 992
 993	/*
 994	 * Do not migrate if the destination is not a node that
 995	 * is actively used by this numa group.
 996	 */
 997	if (!node_isset(dst_nid, ng->active_nodes))
 998		return false;
 999
1000	/*
1001	 * Source is a node that is not actively used by this
1002	 * numa group, while the destination is. Migrate.
1003	 */
1004	if (!node_isset(src_nid, ng->active_nodes))
 
1005		return true;
1006
1007	/*
1008	 * Both source and destination are nodes in active
1009	 * use by this numa group. Maximize memory bandwidth
1010	 * by migrating from more heavily used groups, to less
1011	 * heavily used ones, spreading the load around.
1012	 * Use a 1/4 hysteresis to avoid spurious page movement.
 
1013	 */
1014	return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4);
 
1015}
1016
1017static unsigned long weighted_cpuload(const int cpu);
1018static unsigned long source_load(int cpu, int type);
1019static unsigned long target_load(int cpu, int type);
1020static unsigned long power_of(int cpu);
1021static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1022
1023/* Cached statistics for all CPUs within a node */
1024struct numa_stats {
1025	unsigned long nr_running;
1026	unsigned long load;
1027
1028	/* Total compute capacity of CPUs on a node */
1029	unsigned long power;
1030
1031	/* Approximate capacity in terms of runnable tasks on a node */
1032	unsigned long capacity;
1033	int has_capacity;
1034};
1035
1036/*
1037 * XXX borrowed from update_sg_lb_stats
1038 */
1039static void update_numa_stats(struct numa_stats *ns, int nid)
1040{
1041	int cpu, cpus = 0;
 
1042
1043	memset(ns, 0, sizeof(*ns));
1044	for_each_cpu(cpu, cpumask_of_node(nid)) {
1045		struct rq *rq = cpu_rq(cpu);
1046
1047		ns->nr_running += rq->nr_running;
1048		ns->load += weighted_cpuload(cpu);
1049		ns->power += power_of(cpu);
1050
1051		cpus++;
1052	}
1053
1054	/*
1055	 * If we raced with hotplug and there are no CPUs left in our mask
1056	 * the @ns structure is NULL'ed and task_numa_compare() will
1057	 * not find this node attractive.
1058	 *
1059	 * We'll either bail at !has_capacity, or we'll detect a huge imbalance
1060	 * and bail there.
1061	 */
1062	if (!cpus)
1063		return;
1064
1065	ns->load = (ns->load * SCHED_POWER_SCALE) / ns->power;
1066	ns->capacity = DIV_ROUND_CLOSEST(ns->power, SCHED_POWER_SCALE);
1067	ns->has_capacity = (ns->nr_running < ns->capacity);
 
 
 
 
1068}
1069
1070struct task_numa_env {
1071	struct task_struct *p;
1072
1073	int src_cpu, src_nid;
1074	int dst_cpu, dst_nid;
1075
1076	struct numa_stats src_stats, dst_stats;
1077
1078	int imbalance_pct;
 
1079
1080	struct task_struct *best_task;
1081	long best_imp;
1082	int best_cpu;
1083};
1084
1085static void task_numa_assign(struct task_numa_env *env,
1086			     struct task_struct *p, long imp)
1087{
1088	if (env->best_task)
1089		put_task_struct(env->best_task);
1090	if (p)
1091		get_task_struct(p);
1092
1093	env->best_task = p;
1094	env->best_imp = imp;
1095	env->best_cpu = env->dst_cpu;
1096}
1097
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1098/*
1099 * This checks if the overall compute and NUMA accesses of the system would
1100 * be improved if the source tasks was migrated to the target dst_cpu taking
1101 * into account that it might be best if task running on the dst_cpu should
1102 * be exchanged with the source task
1103 */
1104static void task_numa_compare(struct task_numa_env *env,
1105			      long taskimp, long groupimp)
1106{
1107	struct rq *src_rq = cpu_rq(env->src_cpu);
1108	struct rq *dst_rq = cpu_rq(env->dst_cpu);
1109	struct task_struct *cur;
1110	long dst_load, src_load;
1111	long load;
1112	long imp = (groupimp > 0) ? groupimp : taskimp;
 
 
 
1113
1114	rcu_read_lock();
1115	cur = ACCESS_ONCE(dst_rq->curr);
1116	if (cur->pid == 0) /* idle */
 
 
 
 
 
1117		cur = NULL;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1118
1119	/*
1120	 * "imp" is the fault differential for the source task between the
1121	 * source and destination node. Calculate the total differential for
1122	 * the source task and potential destination task. The more negative
1123	 * the value is, the more rmeote accesses that would be expected to
1124	 * be incurred if the tasks were swapped.
1125	 */
1126	if (cur) {
1127		/* Skip this swap candidate if cannot move to the source cpu */
1128		if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1129			goto unlock;
1130
1131		/*
1132		 * If dst and source tasks are in the same NUMA group, or not
1133		 * in any group then look only at task weights.
1134		 */
1135		if (cur->numa_group == env->p->numa_group) {
1136			imp = taskimp + task_weight(cur, env->src_nid) -
1137			      task_weight(cur, env->dst_nid);
1138			/*
1139			 * Add some hysteresis to prevent swapping the
1140			 * tasks within a group over tiny differences.
1141			 */
1142			if (cur->numa_group)
1143				imp -= imp/16;
1144		} else {
1145			/*
1146			 * Compare the group weights. If a task is all by
1147			 * itself (not part of a group), use the task weight
1148			 * instead.
1149			 */
1150			if (env->p->numa_group)
1151				imp = groupimp;
1152			else
1153				imp = taskimp;
1154
1155			if (cur->numa_group)
1156				imp += group_weight(cur, env->src_nid) -
1157				       group_weight(cur, env->dst_nid);
1158			else
1159				imp += task_weight(cur, env->src_nid) -
1160				       task_weight(cur, env->dst_nid);
1161		}
1162	}
1163
1164	if (imp < env->best_imp)
1165		goto unlock;
1166
1167	if (!cur) {
1168		/* Is there capacity at our destination? */
1169		if (env->src_stats.has_capacity &&
1170		    !env->dst_stats.has_capacity)
1171			goto unlock;
1172
1173		goto balance;
1174	}
1175
1176	/* Balance doesn't matter much if we're running a task per cpu */
1177	if (src_rq->nr_running == 1 && dst_rq->nr_running == 1)
 
1178		goto assign;
1179
1180	/*
1181	 * In the overloaded case, try and keep the load balanced.
1182	 */
1183balance:
1184	dst_load = env->dst_stats.load;
1185	src_load = env->src_stats.load;
1186
1187	/* XXX missing power terms */
1188	load = task_h_load(env->p);
1189	dst_load += load;
1190	src_load -= load;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1191
1192	if (cur) {
1193		load = task_h_load(cur);
1194		dst_load -= load;
1195		src_load += load;
1196	}
1197
1198	/* make src_load the smaller */
1199	if (dst_load < src_load)
1200		swap(dst_load, src_load);
1201
1202	if (src_load * env->imbalance_pct < dst_load * 100)
1203		goto unlock;
1204
 
 
 
 
 
 
 
1205assign:
 
1206	task_numa_assign(env, cur, imp);
1207unlock:
1208	rcu_read_unlock();
 
 
 
 
 
 
1209}
1210
1211static void task_numa_find_cpu(struct task_numa_env *env,
1212				long taskimp, long groupimp)
1213{
1214	int cpu;
1215
1216	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1217		/* Skip this CPU if the source task cannot migrate */
1218		if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1219			continue;
1220
1221		env->dst_cpu = cpu;
1222		task_numa_compare(env, taskimp, groupimp);
1223	}
1224}
1225
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1226static int task_numa_migrate(struct task_struct *p)
1227{
1228	struct task_numa_env env = {
1229		.p = p,
1230
1231		.src_cpu = task_cpu(p),
1232		.src_nid = task_node(p),
1233
1234		.imbalance_pct = 112,
1235
1236		.best_task = NULL,
1237		.best_imp = 0,
1238		.best_cpu = -1
1239	};
1240	struct sched_domain *sd;
1241	unsigned long taskweight, groupweight;
1242	int nid, ret;
1243	long taskimp, groupimp;
1244
1245	/*
1246	 * Pick the lowest SD_NUMA domain, as that would have the smallest
1247	 * imbalance and would be the first to start moving tasks about.
1248	 *
1249	 * And we want to avoid any moving of tasks about, as that would create
1250	 * random movement of tasks -- counter the numa conditions we're trying
1251	 * to satisfy here.
1252	 */
1253	rcu_read_lock();
1254	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1255	if (sd)
1256		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1257	rcu_read_unlock();
1258
1259	/*
1260	 * Cpusets can break the scheduler domain tree into smaller
1261	 * balance domains, some of which do not cross NUMA boundaries.
1262	 * Tasks that are "trapped" in such domains cannot be migrated
1263	 * elsewhere, so there is no point in (re)trying.
1264	 */
1265	if (unlikely(!sd)) {
1266		p->numa_preferred_nid = task_node(p);
1267		return -EINVAL;
1268	}
1269
1270	taskweight = task_weight(p, env.src_nid);
1271	groupweight = group_weight(p, env.src_nid);
1272	update_numa_stats(&env.src_stats, env.src_nid);
1273	env.dst_nid = p->numa_preferred_nid;
1274	taskimp = task_weight(p, env.dst_nid) - taskweight;
1275	groupimp = group_weight(p, env.dst_nid) - groupweight;
 
 
 
 
1276	update_numa_stats(&env.dst_stats, env.dst_nid);
1277
1278	/* If the preferred nid has capacity, try to use it. */
1279	if (env.dst_stats.has_capacity)
1280		task_numa_find_cpu(&env, taskimp, groupimp);
1281
1282	/* No space available on the preferred nid. Look elsewhere. */
1283	if (env.best_cpu == -1) {
 
 
 
 
 
 
1284		for_each_online_node(nid) {
1285			if (nid == env.src_nid || nid == p->numa_preferred_nid)
1286				continue;
1287
 
 
 
 
 
 
 
1288			/* Only consider nodes where both task and groups benefit */
1289			taskimp = task_weight(p, nid) - taskweight;
1290			groupimp = group_weight(p, nid) - groupweight;
1291			if (taskimp < 0 && groupimp < 0)
1292				continue;
1293
 
1294			env.dst_nid = nid;
1295			update_numa_stats(&env.dst_stats, env.dst_nid);
1296			task_numa_find_cpu(&env, taskimp, groupimp);
 
1297		}
1298	}
1299
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1300	/* No better CPU than the current one was found. */
1301	if (env.best_cpu == -1)
1302		return -EAGAIN;
1303
1304	sched_setnuma(p, env.dst_nid);
1305
1306	/*
1307	 * Reset the scan period if the task is being rescheduled on an
1308	 * alternative node to recheck if the tasks is now properly placed.
1309	 */
1310	p->numa_scan_period = task_scan_min(p);
1311
1312	if (env.best_task == NULL) {
1313		ret = migrate_task_to(p, env.best_cpu);
1314		if (ret != 0)
1315			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1316		return ret;
1317	}
1318
1319	ret = migrate_swap(p, env.best_task);
1320	if (ret != 0)
1321		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1322	put_task_struct(env.best_task);
1323	return ret;
1324}
1325
1326/* Attempt to migrate a task to a CPU on the preferred node. */
1327static void numa_migrate_preferred(struct task_struct *p)
1328{
 
 
1329	/* This task has no NUMA fault statistics yet */
1330	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults_memory))
1331		return;
1332
1333	/* Periodically retry migrating the task to the preferred node */
1334	p->numa_migrate_retry = jiffies + HZ;
 
1335
1336	/* Success if task is already running on preferred CPU */
1337	if (task_node(p) == p->numa_preferred_nid)
1338		return;
1339
1340	/* Otherwise, try migrate to a CPU on the preferred node */
1341	task_numa_migrate(p);
1342}
1343
1344/*
1345 * Find the nodes on which the workload is actively running. We do this by
1346 * tracking the nodes from which NUMA hinting faults are triggered. This can
1347 * be different from the set of nodes where the workload's memory is currently
1348 * located.
1349 *
1350 * The bitmask is used to make smarter decisions on when to do NUMA page
1351 * migrations, To prevent flip-flopping, and excessive page migrations, nodes
1352 * are added when they cause over 6/16 of the maximum number of faults, but
1353 * only removed when they drop below 3/16.
1354 */
1355static void update_numa_active_node_mask(struct numa_group *numa_group)
1356{
1357	unsigned long faults, max_faults = 0;
1358	int nid;
1359
1360	for_each_online_node(nid) {
1361		faults = group_faults_cpu(numa_group, nid);
1362		if (faults > max_faults)
1363			max_faults = faults;
1364	}
1365
1366	for_each_online_node(nid) {
1367		faults = group_faults_cpu(numa_group, nid);
1368		if (!node_isset(nid, numa_group->active_nodes)) {
1369			if (faults > max_faults * 6 / 16)
1370				node_set(nid, numa_group->active_nodes);
1371		} else if (faults < max_faults * 3 / 16)
1372			node_clear(nid, numa_group->active_nodes);
1373	}
 
 
 
1374}
1375
1376/*
1377 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1378 * increments. The more local the fault statistics are, the higher the scan
1379 * period will be for the next scan window. If local/remote ratio is below
1380 * NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) the
1381 * scan period will decrease
1382 */
1383#define NUMA_PERIOD_SLOTS 10
1384#define NUMA_PERIOD_THRESHOLD 3
1385
1386/*
1387 * Increase the scan period (slow down scanning) if the majority of
1388 * our memory is already on our local node, or if the majority of
1389 * the page accesses are shared with other processes.
1390 * Otherwise, decrease the scan period.
1391 */
1392static void update_task_scan_period(struct task_struct *p,
1393			unsigned long shared, unsigned long private)
1394{
1395	unsigned int period_slot;
1396	int ratio;
1397	int diff;
1398
1399	unsigned long remote = p->numa_faults_locality[0];
1400	unsigned long local = p->numa_faults_locality[1];
1401
1402	/*
1403	 * If there were no record hinting faults then either the task is
1404	 * completely idle or all activity is areas that are not of interest
1405	 * to automatic numa balancing. Scan slower
 
 
1406	 */
1407	if (local + shared == 0) {
1408		p->numa_scan_period = min(p->numa_scan_period_max,
1409			p->numa_scan_period << 1);
1410
1411		p->mm->numa_next_scan = jiffies +
1412			msecs_to_jiffies(p->numa_scan_period);
1413
1414		return;
1415	}
1416
1417	/*
1418	 * Prepare to scale scan period relative to the current period.
1419	 *	 == NUMA_PERIOD_THRESHOLD scan period stays the same
1420	 *       <  NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1421	 *	 >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1422	 */
1423	period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1424	ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1425	if (ratio >= NUMA_PERIOD_THRESHOLD) {
1426		int slot = ratio - NUMA_PERIOD_THRESHOLD;
1427		if (!slot)
1428			slot = 1;
1429		diff = slot * period_slot;
1430	} else {
1431		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1432
1433		/*
1434		 * Scale scan rate increases based on sharing. There is an
1435		 * inverse relationship between the degree of sharing and
1436		 * the adjustment made to the scanning period. Broadly
1437		 * speaking the intent is that there is little point
1438		 * scanning faster if shared accesses dominate as it may
1439		 * simply bounce migrations uselessly
1440		 */
1441		ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared));
1442		diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1443	}
1444
1445	p->numa_scan_period = clamp(p->numa_scan_period + diff,
1446			task_scan_min(p), task_scan_max(p));
1447	memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1448}
1449
1450/*
1451 * Get the fraction of time the task has been running since the last
1452 * NUMA placement cycle. The scheduler keeps similar statistics, but
1453 * decays those on a 32ms period, which is orders of magnitude off
1454 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1455 * stats only if the task is so new there are no NUMA statistics yet.
1456 */
1457static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1458{
1459	u64 runtime, delta, now;
1460	/* Use the start of this time slice to avoid calculations. */
1461	now = p->se.exec_start;
1462	runtime = p->se.sum_exec_runtime;
1463
1464	if (p->last_task_numa_placement) {
1465		delta = runtime - p->last_sum_exec_runtime;
1466		*period = now - p->last_task_numa_placement;
1467	} else {
1468		delta = p->se.avg.runnable_avg_sum;
1469		*period = p->se.avg.runnable_avg_period;
1470	}
1471
1472	p->last_sum_exec_runtime = runtime;
1473	p->last_task_numa_placement = now;
1474
1475	return delta;
1476}
1477
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1478static void task_numa_placement(struct task_struct *p)
1479{
1480	int seq, nid, max_nid = -1, max_group_nid = -1;
1481	unsigned long max_faults = 0, max_group_faults = 0;
1482	unsigned long fault_types[2] = { 0, 0 };
1483	unsigned long total_faults;
1484	u64 runtime, period;
1485	spinlock_t *group_lock = NULL;
1486
1487	seq = ACCESS_ONCE(p->mm->numa_scan_seq);
 
 
 
 
 
1488	if (p->numa_scan_seq == seq)
1489		return;
1490	p->numa_scan_seq = seq;
1491	p->numa_scan_period_max = task_scan_max(p);
1492
1493	total_faults = p->numa_faults_locality[0] +
1494		       p->numa_faults_locality[1];
1495	runtime = numa_get_avg_runtime(p, &period);
1496
1497	/* If the task is part of a group prevent parallel updates to group stats */
1498	if (p->numa_group) {
1499		group_lock = &p->numa_group->lock;
1500		spin_lock_irq(group_lock);
1501	}
1502
1503	/* Find the node with the highest number of faults */
1504	for_each_online_node(nid) {
 
 
1505		unsigned long faults = 0, group_faults = 0;
1506		int priv, i;
1507
1508		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1509			long diff, f_diff, f_weight;
1510
1511			i = task_faults_idx(nid, priv);
 
 
 
1512
1513			/* Decay existing window, copy faults since last scan */
1514			diff = p->numa_faults_buffer_memory[i] - p->numa_faults_memory[i] / 2;
1515			fault_types[priv] += p->numa_faults_buffer_memory[i];
1516			p->numa_faults_buffer_memory[i] = 0;
1517
1518			/*
1519			 * Normalize the faults_from, so all tasks in a group
1520			 * count according to CPU use, instead of by the raw
1521			 * number of faults. Tasks with little runtime have
1522			 * little over-all impact on throughput, and thus their
1523			 * faults are less important.
1524			 */
1525			f_weight = div64_u64(runtime << 16, period + 1);
1526			f_weight = (f_weight * p->numa_faults_buffer_cpu[i]) /
1527				   (total_faults + 1);
1528			f_diff = f_weight - p->numa_faults_cpu[i] / 2;
1529			p->numa_faults_buffer_cpu[i] = 0;
1530
1531			p->numa_faults_memory[i] += diff;
1532			p->numa_faults_cpu[i] += f_diff;
1533			faults += p->numa_faults_memory[i];
1534			p->total_numa_faults += diff;
1535			if (p->numa_group) {
1536				/* safe because we can only change our own group */
1537				p->numa_group->faults[i] += diff;
1538				p->numa_group->faults_cpu[i] += f_diff;
 
 
 
 
 
 
1539				p->numa_group->total_faults += diff;
1540				group_faults += p->numa_group->faults[i];
1541			}
1542		}
1543
1544		if (faults > max_faults) {
1545			max_faults = faults;
1546			max_nid = nid;
1547		}
1548
1549		if (group_faults > max_group_faults) {
1550			max_group_faults = group_faults;
1551			max_group_nid = nid;
1552		}
1553	}
1554
1555	update_task_scan_period(p, fault_types[0], fault_types[1]);
1556
1557	if (p->numa_group) {
1558		update_numa_active_node_mask(p->numa_group);
1559		/*
1560		 * If the preferred task and group nids are different,
1561		 * iterate over the nodes again to find the best place.
1562		 */
1563		if (max_nid != max_group_nid) {
1564			unsigned long weight, max_weight = 0;
1565
1566			for_each_online_node(nid) {
1567				weight = task_weight(p, nid) + group_weight(p, nid);
1568				if (weight > max_weight) {
1569					max_weight = weight;
1570					max_nid = nid;
1571				}
1572			}
1573		}
1574
1575		spin_unlock_irq(group_lock);
 
1576	}
1577
1578	/* Preferred node as the node with the most faults */
1579	if (max_faults && max_nid != p->numa_preferred_nid) {
1580		/* Update the preferred nid and migrate task if possible */
1581		sched_setnuma(p, max_nid);
1582		numa_migrate_preferred(p);
 
 
1583	}
1584}
1585
1586static inline int get_numa_group(struct numa_group *grp)
1587{
1588	return atomic_inc_not_zero(&grp->refcount);
1589}
1590
1591static inline void put_numa_group(struct numa_group *grp)
1592{
1593	if (atomic_dec_and_test(&grp->refcount))
1594		kfree_rcu(grp, rcu);
1595}
1596
1597static void task_numa_group(struct task_struct *p, int cpupid, int flags,
1598			int *priv)
1599{
1600	struct numa_group *grp, *my_grp;
1601	struct task_struct *tsk;
1602	bool join = false;
1603	int cpu = cpupid_to_cpu(cpupid);
1604	int i;
1605
1606	if (unlikely(!p->numa_group)) {
1607		unsigned int size = sizeof(struct numa_group) +
1608				    4*nr_node_ids*sizeof(unsigned long);
1609
1610		grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
1611		if (!grp)
1612			return;
1613
1614		atomic_set(&grp->refcount, 1);
 
 
1615		spin_lock_init(&grp->lock);
1616		INIT_LIST_HEAD(&grp->task_list);
1617		grp->gid = p->pid;
1618		/* Second half of the array tracks nids where faults happen */
1619		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
1620						nr_node_ids;
1621
1622		node_set(task_node(current), grp->active_nodes);
1623
1624		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1625			grp->faults[i] = p->numa_faults_memory[i];
1626
1627		grp->total_faults = p->total_numa_faults;
1628
1629		list_add(&p->numa_entry, &grp->task_list);
1630		grp->nr_tasks++;
1631		rcu_assign_pointer(p->numa_group, grp);
1632	}
1633
1634	rcu_read_lock();
1635	tsk = ACCESS_ONCE(cpu_rq(cpu)->curr);
1636
1637	if (!cpupid_match_pid(tsk, cpupid))
1638		goto no_join;
1639
1640	grp = rcu_dereference(tsk->numa_group);
1641	if (!grp)
1642		goto no_join;
1643
1644	my_grp = p->numa_group;
1645	if (grp == my_grp)
1646		goto no_join;
1647
1648	/*
1649	 * Only join the other group if its bigger; if we're the bigger group,
1650	 * the other task will join us.
1651	 */
1652	if (my_grp->nr_tasks > grp->nr_tasks)
1653		goto no_join;
1654
1655	/*
1656	 * Tie-break on the grp address.
1657	 */
1658	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1659		goto no_join;
1660
1661	/* Always join threads in the same process. */
1662	if (tsk->mm == current->mm)
1663		join = true;
1664
1665	/* Simple filter to avoid false positives due to PID collisions */
1666	if (flags & TNF_SHARED)
1667		join = true;
1668
1669	/* Update priv based on whether false sharing was detected */
1670	*priv = !join;
1671
1672	if (join && !get_numa_group(grp))
1673		goto no_join;
1674
1675	rcu_read_unlock();
1676
1677	if (!join)
1678		return;
1679
1680	BUG_ON(irqs_disabled());
1681	double_lock_irq(&my_grp->lock, &grp->lock);
1682
1683	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
1684		my_grp->faults[i] -= p->numa_faults_memory[i];
1685		grp->faults[i] += p->numa_faults_memory[i];
1686	}
1687	my_grp->total_faults -= p->total_numa_faults;
1688	grp->total_faults += p->total_numa_faults;
1689
1690	list_move(&p->numa_entry, &grp->task_list);
1691	my_grp->nr_tasks--;
1692	grp->nr_tasks++;
1693
1694	spin_unlock(&my_grp->lock);
1695	spin_unlock_irq(&grp->lock);
1696
1697	rcu_assign_pointer(p->numa_group, grp);
1698
1699	put_numa_group(my_grp);
1700	return;
1701
1702no_join:
1703	rcu_read_unlock();
1704	return;
1705}
1706
1707void task_numa_free(struct task_struct *p)
1708{
1709	struct numa_group *grp = p->numa_group;
1710	void *numa_faults = p->numa_faults_memory;
1711	unsigned long flags;
1712	int i;
1713
1714	if (grp) {
1715		spin_lock_irqsave(&grp->lock, flags);
1716		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1717			grp->faults[i] -= p->numa_faults_memory[i];
1718		grp->total_faults -= p->total_numa_faults;
1719
1720		list_del(&p->numa_entry);
1721		grp->nr_tasks--;
1722		spin_unlock_irqrestore(&grp->lock, flags);
1723		rcu_assign_pointer(p->numa_group, NULL);
1724		put_numa_group(grp);
1725	}
1726
1727	p->numa_faults_memory = NULL;
1728	p->numa_faults_buffer_memory = NULL;
1729	p->numa_faults_cpu= NULL;
1730	p->numa_faults_buffer_cpu = NULL;
1731	kfree(numa_faults);
1732}
1733
1734/*
1735 * Got a PROT_NONE fault for a page on @node.
1736 */
1737void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
1738{
1739	struct task_struct *p = current;
1740	bool migrated = flags & TNF_MIGRATED;
1741	int cpu_node = task_node(current);
 
 
1742	int priv;
1743
1744	if (!numabalancing_enabled)
1745		return;
1746
1747	/* for example, ksmd faulting in a user's mm */
1748	if (!p->mm)
1749		return;
1750
1751	/* Do not worry about placement if exiting */
1752	if (p->state == TASK_DEAD)
1753		return;
1754
1755	/* Allocate buffer to track faults on a per-node basis */
1756	if (unlikely(!p->numa_faults_memory)) {
1757		int size = sizeof(*p->numa_faults_memory) *
1758			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
1759
1760		p->numa_faults_memory = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
1761		if (!p->numa_faults_memory)
1762			return;
1763
1764		BUG_ON(p->numa_faults_buffer_memory);
1765		/*
1766		 * The averaged statistics, shared & private, memory & cpu,
1767		 * occupy the first half of the array. The second half of the
1768		 * array is for current counters, which are averaged into the
1769		 * first set by task_numa_placement.
1770		 */
1771		p->numa_faults_cpu = p->numa_faults_memory + (2 * nr_node_ids);
1772		p->numa_faults_buffer_memory = p->numa_faults_memory + (4 * nr_node_ids);
1773		p->numa_faults_buffer_cpu = p->numa_faults_memory + (6 * nr_node_ids);
1774		p->total_numa_faults = 0;
1775		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1776	}
1777
1778	/*
1779	 * First accesses are treated as private, otherwise consider accesses
1780	 * to be private if the accessing pid has not changed
1781	 */
1782	if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
1783		priv = 1;
1784	} else {
1785		priv = cpupid_match_pid(p, last_cpupid);
1786		if (!priv && !(flags & TNF_NO_GROUP))
1787			task_numa_group(p, last_cpupid, flags, &priv);
1788	}
1789
 
 
 
 
 
 
 
 
 
 
 
 
1790	task_numa_placement(p);
1791
1792	/*
1793	 * Retry task to preferred node migration periodically, in case it
1794	 * case it previously failed, or the scheduler moved us.
1795	 */
1796	if (time_after(jiffies, p->numa_migrate_retry))
1797		numa_migrate_preferred(p);
1798
1799	if (migrated)
1800		p->numa_pages_migrated += pages;
 
 
1801
1802	p->numa_faults_buffer_memory[task_faults_idx(mem_node, priv)] += pages;
1803	p->numa_faults_buffer_cpu[task_faults_idx(cpu_node, priv)] += pages;
1804	p->numa_faults_locality[!!(flags & TNF_FAULT_LOCAL)] += pages;
1805}
1806
1807static void reset_ptenuma_scan(struct task_struct *p)
1808{
1809	ACCESS_ONCE(p->mm->numa_scan_seq)++;
 
 
 
 
 
 
 
 
1810	p->mm->numa_scan_offset = 0;
1811}
1812
1813/*
1814 * The expensive part of numa migration is done from task_work context.
1815 * Triggered from task_tick_numa().
1816 */
1817void task_numa_work(struct callback_head *work)
1818{
1819	unsigned long migrate, next_scan, now = jiffies;
1820	struct task_struct *p = current;
1821	struct mm_struct *mm = p->mm;
 
1822	struct vm_area_struct *vma;
1823	unsigned long start, end;
1824	unsigned long nr_pte_updates = 0;
1825	long pages;
1826
1827	WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
1828
1829	work->next = work; /* protect against double add */
1830	/*
1831	 * Who cares about NUMA placement when they're dying.
1832	 *
1833	 * NOTE: make sure not to dereference p->mm before this check,
1834	 * exit_task_work() happens _after_ exit_mm() so we could be called
1835	 * without p->mm even though we still had it when we enqueued this
1836	 * work.
1837	 */
1838	if (p->flags & PF_EXITING)
1839		return;
1840
1841	if (!mm->numa_next_scan) {
1842		mm->numa_next_scan = now +
1843			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
1844	}
1845
1846	/*
1847	 * Enforce maximal scan/migration frequency..
1848	 */
1849	migrate = mm->numa_next_scan;
1850	if (time_before(now, migrate))
1851		return;
1852
1853	if (p->numa_scan_period == 0) {
1854		p->numa_scan_period_max = task_scan_max(p);
1855		p->numa_scan_period = task_scan_min(p);
1856	}
1857
1858	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
1859	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
1860		return;
1861
1862	/*
1863	 * Delay this task enough that another task of this mm will likely win
1864	 * the next time around.
1865	 */
1866	p->node_stamp += 2 * TICK_NSEC;
1867
1868	start = mm->numa_scan_offset;
1869	pages = sysctl_numa_balancing_scan_size;
1870	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
 
1871	if (!pages)
1872		return;
1873
 
1874	down_read(&mm->mmap_sem);
1875	vma = find_vma(mm, start);
1876	if (!vma) {
1877		reset_ptenuma_scan(p);
1878		start = 0;
1879		vma = mm->mmap;
1880	}
1881	for (; vma; vma = vma->vm_next) {
1882		if (!vma_migratable(vma) || !vma_policy_mof(p, vma))
 
1883			continue;
 
1884
1885		/*
1886		 * Shared library pages mapped by multiple processes are not
1887		 * migrated as it is expected they are cache replicated. Avoid
1888		 * hinting faults in read-only file-backed mappings or the vdso
1889		 * as migrating the pages will be of marginal benefit.
1890		 */
1891		if (!vma->vm_mm ||
1892		    (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
1893			continue;
1894
1895		/*
1896		 * Skip inaccessible VMAs to avoid any confusion between
1897		 * PROT_NONE and NUMA hinting ptes
1898		 */
1899		if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
1900			continue;
1901
1902		do {
1903			start = max(start, vma->vm_start);
1904			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
1905			end = min(end, vma->vm_end);
1906			nr_pte_updates += change_prot_numa(vma, start, end);
1907
1908			/*
1909			 * Scan sysctl_numa_balancing_scan_size but ensure that
1910			 * at least one PTE is updated so that unused virtual
1911			 * address space is quickly skipped.
 
 
 
1912			 */
1913			if (nr_pte_updates)
1914				pages -= (end - start) >> PAGE_SHIFT;
 
1915
1916			start = end;
1917			if (pages <= 0)
1918				goto out;
1919
1920			cond_resched();
1921		} while (end != vma->vm_end);
1922	}
1923
1924out:
1925	/*
1926	 * It is possible to reach the end of the VMA list but the last few
1927	 * VMAs are not guaranteed to the vma_migratable. If they are not, we
1928	 * would find the !migratable VMA on the next scan but not reset the
1929	 * scanner to the start so check it now.
1930	 */
1931	if (vma)
1932		mm->numa_scan_offset = start;
1933	else
1934		reset_ptenuma_scan(p);
1935	up_read(&mm->mmap_sem);
 
 
 
 
 
 
 
 
 
 
 
1936}
1937
1938/*
1939 * Drive the periodic memory faults..
1940 */
1941void task_tick_numa(struct rq *rq, struct task_struct *curr)
1942{
1943	struct callback_head *work = &curr->numa_work;
1944	u64 period, now;
1945
1946	/*
1947	 * We don't care about NUMA placement if we don't have memory.
1948	 */
1949	if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
1950		return;
1951
1952	/*
1953	 * Using runtime rather than walltime has the dual advantage that
1954	 * we (mostly) drive the selection from busy threads and that the
1955	 * task needs to have done some actual work before we bother with
1956	 * NUMA placement.
1957	 */
1958	now = curr->se.sum_exec_runtime;
1959	period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
1960
1961	if (now - curr->node_stamp > period) {
1962		if (!curr->node_stamp)
1963			curr->numa_scan_period = task_scan_min(curr);
1964		curr->node_stamp += period;
1965
1966		if (!time_before(jiffies, curr->mm->numa_next_scan)) {
1967			init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
1968			task_work_add(curr, work, true);
1969		}
1970	}
1971}
1972#else
1973static void task_tick_numa(struct rq *rq, struct task_struct *curr)
1974{
1975}
1976
1977static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
1978{
1979}
1980
1981static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
1982{
1983}
1984#endif /* CONFIG_NUMA_BALANCING */
1985
1986static void
1987account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
1988{
1989	update_load_add(&cfs_rq->load, se->load.weight);
1990	if (!parent_entity(se))
1991		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
1992#ifdef CONFIG_SMP
1993	if (entity_is_task(se)) {
1994		struct rq *rq = rq_of(cfs_rq);
1995
1996		account_numa_enqueue(rq, task_of(se));
1997		list_add(&se->group_node, &rq->cfs_tasks);
1998	}
1999#endif
2000	cfs_rq->nr_running++;
2001}
2002
2003static void
2004account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2005{
2006	update_load_sub(&cfs_rq->load, se->load.weight);
2007	if (!parent_entity(se))
2008		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2009	if (entity_is_task(se)) {
2010		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2011		list_del_init(&se->group_node);
2012	}
2013	cfs_rq->nr_running--;
2014}
2015
2016#ifdef CONFIG_FAIR_GROUP_SCHED
2017# ifdef CONFIG_SMP
2018static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
2019{
2020	long tg_weight;
2021
2022	/*
2023	 * Use this CPU's actual weight instead of the last load_contribution
2024	 * to gain a more accurate current total weight. See
2025	 * update_cfs_rq_load_contribution().
2026	 */
2027	tg_weight = atomic_long_read(&tg->load_avg);
2028	tg_weight -= cfs_rq->tg_load_contrib;
2029	tg_weight += cfs_rq->load.weight;
2030
2031	return tg_weight;
2032}
2033
2034static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2035{
2036	long tg_weight, load, shares;
2037
2038	tg_weight = calc_tg_weight(tg, cfs_rq);
2039	load = cfs_rq->load.weight;
2040
2041	shares = (tg->shares * load);
2042	if (tg_weight)
2043		shares /= tg_weight;
2044
2045	if (shares < MIN_SHARES)
2046		shares = MIN_SHARES;
2047	if (shares > tg->shares)
2048		shares = tg->shares;
2049
2050	return shares;
2051}
2052# else /* CONFIG_SMP */
2053static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2054{
2055	return tg->shares;
2056}
2057# endif /* CONFIG_SMP */
2058static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2059			    unsigned long weight)
2060{
2061	if (se->on_rq) {
2062		/* commit outstanding execution time */
2063		if (cfs_rq->curr == se)
2064			update_curr(cfs_rq);
2065		account_entity_dequeue(cfs_rq, se);
2066	}
2067
2068	update_load_set(&se->load, weight);
2069
2070	if (se->on_rq)
2071		account_entity_enqueue(cfs_rq, se);
2072}
2073
2074static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2075
2076static void update_cfs_shares(struct cfs_rq *cfs_rq)
2077{
2078	struct task_group *tg;
2079	struct sched_entity *se;
2080	long shares;
2081
2082	tg = cfs_rq->tg;
2083	se = tg->se[cpu_of(rq_of(cfs_rq))];
2084	if (!se || throttled_hierarchy(cfs_rq))
2085		return;
2086#ifndef CONFIG_SMP
2087	if (likely(se->load.weight == tg->shares))
2088		return;
2089#endif
2090	shares = calc_cfs_shares(cfs_rq, tg);
2091
2092	reweight_entity(cfs_rq_of(se), se, shares);
2093}
2094#else /* CONFIG_FAIR_GROUP_SCHED */
2095static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2096{
2097}
2098#endif /* CONFIG_FAIR_GROUP_SCHED */
2099
2100#ifdef CONFIG_SMP
2101/*
2102 * We choose a half-life close to 1 scheduling period.
2103 * Note: The tables below are dependent on this value.
2104 */
2105#define LOAD_AVG_PERIOD 32
2106#define LOAD_AVG_MAX 47742 /* maximum possible load avg */
2107#define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */
2108
2109/* Precomputed fixed inverse multiplies for multiplication by y^n */
2110static const u32 runnable_avg_yN_inv[] = {
2111	0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2112	0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2113	0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2114	0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2115	0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2116	0x85aac367, 0x82cd8698,
2117};
2118
2119/*
2120 * Precomputed \Sum y^k { 1<=k<=n }.  These are floor(true_value) to prevent
2121 * over-estimates when re-combining.
2122 */
2123static const u32 runnable_avg_yN_sum[] = {
2124	    0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2125	 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2126	17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2127};
2128
2129/*
2130 * Approximate:
2131 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
2132 */
2133static __always_inline u64 decay_load(u64 val, u64 n)
2134{
2135	unsigned int local_n;
2136
2137	if (!n)
2138		return val;
2139	else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2140		return 0;
2141
2142	/* after bounds checking we can collapse to 32-bit */
2143	local_n = n;
2144
2145	/*
2146	 * As y^PERIOD = 1/2, we can combine
2147	 *    y^n = 1/2^(n/PERIOD) * k^(n%PERIOD)
2148	 * With a look-up table which covers k^n (n<PERIOD)
2149	 *
2150	 * To achieve constant time decay_load.
2151	 */
2152	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2153		val >>= local_n / LOAD_AVG_PERIOD;
2154		local_n %= LOAD_AVG_PERIOD;
2155	}
2156
2157	val *= runnable_avg_yN_inv[local_n];
2158	/* We don't use SRR here since we always want to round down. */
2159	return val >> 32;
2160}
2161
2162/*
2163 * For updates fully spanning n periods, the contribution to runnable
2164 * average will be: \Sum 1024*y^n
2165 *
2166 * We can compute this reasonably efficiently by combining:
2167 *   y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for  n <PERIOD}
2168 */
2169static u32 __compute_runnable_contrib(u64 n)
2170{
2171	u32 contrib = 0;
2172
2173	if (likely(n <= LOAD_AVG_PERIOD))
2174		return runnable_avg_yN_sum[n];
2175	else if (unlikely(n >= LOAD_AVG_MAX_N))
2176		return LOAD_AVG_MAX;
2177
2178	/* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2179	do {
2180		contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2181		contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
2182
2183		n -= LOAD_AVG_PERIOD;
2184	} while (n > LOAD_AVG_PERIOD);
2185
2186	contrib = decay_load(contrib, n);
2187	return contrib + runnable_avg_yN_sum[n];
2188}
2189
 
 
 
 
 
 
2190/*
2191 * We can represent the historical contribution to runnable average as the
2192 * coefficients of a geometric series.  To do this we sub-divide our runnable
2193 * history into segments of approximately 1ms (1024us); label the segment that
2194 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2195 *
2196 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2197 *      p0            p1           p2
2198 *     (now)       (~1ms ago)  (~2ms ago)
2199 *
2200 * Let u_i denote the fraction of p_i that the entity was runnable.
2201 *
2202 * We then designate the fractions u_i as our co-efficients, yielding the
2203 * following representation of historical load:
2204 *   u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2205 *
2206 * We choose y based on the with of a reasonably scheduling period, fixing:
2207 *   y^32 = 0.5
2208 *
2209 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2210 * approximately half as much as the contribution to load within the last ms
2211 * (u_0).
2212 *
2213 * When a period "rolls over" and we have new u_0`, multiplying the previous
2214 * sum again by y is sufficient to update:
2215 *   load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2216 *            = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2217 */
2218static __always_inline int __update_entity_runnable_avg(u64 now,
2219							struct sched_avg *sa,
2220							int runnable)
2221{
2222	u64 delta, periods;
2223	u32 runnable_contrib;
2224	int delta_w, decayed = 0;
 
2225
2226	delta = now - sa->last_runnable_update;
2227	/*
2228	 * This should only happen when time goes backwards, which it
2229	 * unfortunately does during sched clock init when we swap over to TSC.
2230	 */
2231	if ((s64)delta < 0) {
2232		sa->last_runnable_update = now;
2233		return 0;
2234	}
2235
2236	/*
2237	 * Use 1024ns as the unit of measurement since it's a reasonable
2238	 * approximation of 1us and fast to compute.
2239	 */
2240	delta >>= 10;
2241	if (!delta)
2242		return 0;
2243	sa->last_runnable_update = now;
 
 
 
2244
2245	/* delta_w is the amount already accumulated against our next period */
2246	delta_w = sa->runnable_avg_period % 1024;
2247	if (delta + delta_w >= 1024) {
2248		/* period roll-over */
2249		decayed = 1;
2250
 
 
 
2251		/*
2252		 * Now that we know we're crossing a period boundary, figure
2253		 * out how much from delta we need to complete the current
2254		 * period and accrue it.
2255		 */
2256		delta_w = 1024 - delta_w;
2257		if (runnable)
2258			sa->runnable_avg_sum += delta_w;
2259		sa->runnable_avg_period += delta_w;
 
 
 
 
 
 
 
2260
2261		delta -= delta_w;
2262
2263		/* Figure out how many additional periods this update spans */
2264		periods = delta / 1024;
2265		delta %= 1024;
2266
2267		sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum,
2268						  periods + 1);
2269		sa->runnable_avg_period = decay_load(sa->runnable_avg_period,
2270						     periods + 1);
 
 
2271
2272		/* Efficiently calculate \sum (1..n_period) 1024*y^i */
2273		runnable_contrib = __compute_runnable_contrib(periods);
2274		if (runnable)
2275			sa->runnable_avg_sum += runnable_contrib;
2276		sa->runnable_avg_period += runnable_contrib;
 
 
 
 
 
2277	}
2278
2279	/* Remainder of delta accrued against u_0` */
2280	if (runnable)
2281		sa->runnable_avg_sum += delta;
2282	sa->runnable_avg_period += delta;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2283
2284	return decayed;
2285}
2286
2287/* Synchronize an entity's decay with its parenting cfs_rq.*/
2288static inline u64 __synchronize_entity_decay(struct sched_entity *se)
2289{
2290	struct cfs_rq *cfs_rq = cfs_rq_of(se);
2291	u64 decays = atomic64_read(&cfs_rq->decay_counter);
2292
2293	decays -= se->avg.decay_count;
2294	if (!decays)
2295		return 0;
2296
2297	se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
2298	se->avg.decay_count = 0;
2299
2300	return decays;
2301}
2302
2303#ifdef CONFIG_FAIR_GROUP_SCHED
2304static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
2305						 int force_update)
 
 
 
2306{
2307	struct task_group *tg = cfs_rq->tg;
2308	long tg_contrib;
2309
2310	tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg;
2311	tg_contrib -= cfs_rq->tg_load_contrib;
 
 
 
2312
2313	if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) {
2314		atomic_long_add(tg_contrib, &tg->load_avg);
2315		cfs_rq->tg_load_contrib += tg_contrib;
2316	}
2317}
2318
2319/*
2320 * Aggregate cfs_rq runnable averages into an equivalent task_group
2321 * representation for computing load contributions.
 
2322 */
2323static inline void __update_tg_runnable_avg(struct sched_avg *sa,
2324						  struct cfs_rq *cfs_rq)
2325{
2326	struct task_group *tg = cfs_rq->tg;
2327	long contrib;
2328
2329	/* The fraction of a cpu used by this cfs_rq */
2330	contrib = div_u64((u64)sa->runnable_avg_sum << NICE_0_SHIFT,
2331			  sa->runnable_avg_period + 1);
2332	contrib -= cfs_rq->tg_runnable_contrib;
 
 
 
 
 
 
2333
2334	if (abs(contrib) > cfs_rq->tg_runnable_contrib / 64) {
2335		atomic_add(contrib, &tg->runnable_avg);
2336		cfs_rq->tg_runnable_contrib += contrib;
2337	}
2338}
2339
2340static inline void __update_group_entity_contrib(struct sched_entity *se)
2341{
2342	struct cfs_rq *cfs_rq = group_cfs_rq(se);
2343	struct task_group *tg = cfs_rq->tg;
2344	int runnable_avg;
2345
2346	u64 contrib;
2347
2348	contrib = cfs_rq->tg_load_contrib * tg->shares;
2349	se->avg.load_avg_contrib = div_u64(contrib,
2350				     atomic_long_read(&tg->load_avg) + 1);
2351
2352	/*
2353	 * For group entities we need to compute a correction term in the case
2354	 * that they are consuming <1 cpu so that we would contribute the same
2355	 * load as a task of equal weight.
2356	 *
2357	 * Explicitly co-ordinating this measurement would be expensive, but
2358	 * fortunately the sum of each cpus contribution forms a usable
2359	 * lower-bound on the true value.
2360	 *
2361	 * Consider the aggregate of 2 contributions.  Either they are disjoint
2362	 * (and the sum represents true value) or they are disjoint and we are
2363	 * understating by the aggregate of their overlap.
2364	 *
2365	 * Extending this to N cpus, for a given overlap, the maximum amount we
2366	 * understand is then n_i(n_i+1)/2 * w_i where n_i is the number of
2367	 * cpus that overlap for this interval and w_i is the interval width.
2368	 *
2369	 * On a small machine; the first term is well-bounded which bounds the
2370	 * total error since w_i is a subset of the period.  Whereas on a
2371	 * larger machine, while this first term can be larger, if w_i is the
2372	 * of consequential size guaranteed to see n_i*w_i quickly converge to
2373	 * our upper bound of 1-cpu.
2374	 */
2375	runnable_avg = atomic_read(&tg->runnable_avg);
2376	if (runnable_avg < NICE_0_LOAD) {
2377		se->avg.load_avg_contrib *= runnable_avg;
2378		se->avg.load_avg_contrib >>= NICE_0_SHIFT;
2379	}
2380}
2381
2382static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
2383{
2384	__update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable);
2385	__update_tg_runnable_avg(&rq->avg, &rq->cfs);
2386}
2387#else /* CONFIG_FAIR_GROUP_SCHED */
2388static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
2389						 int force_update) {}
2390static inline void __update_tg_runnable_avg(struct sched_avg *sa,
2391						  struct cfs_rq *cfs_rq) {}
2392static inline void __update_group_entity_contrib(struct sched_entity *se) {}
2393static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
2394#endif /* CONFIG_FAIR_GROUP_SCHED */
2395
2396static inline void __update_task_entity_contrib(struct sched_entity *se)
2397{
2398	u32 contrib;
2399
2400	/* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
2401	contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight);
2402	contrib /= (se->avg.runnable_avg_period + 1);
2403	se->avg.load_avg_contrib = scale_load(contrib);
2404}
2405
2406/* Compute the current contribution to load_avg by se, return any delta */
2407static long __update_entity_load_avg_contrib(struct sched_entity *se)
2408{
2409	long old_contrib = se->avg.load_avg_contrib;
 
2410
2411	if (entity_is_task(se)) {
2412		__update_task_entity_contrib(se);
2413	} else {
2414		__update_tg_runnable_avg(&se->avg, group_cfs_rq(se));
2415		__update_group_entity_contrib(se);
2416	}
2417
2418	return se->avg.load_avg_contrib - old_contrib;
2419}
 
 
 
2420
2421static inline void subtract_blocked_load_contrib(struct cfs_rq *cfs_rq,
2422						 long load_contrib)
2423{
2424	if (likely(load_contrib < cfs_rq->blocked_load_avg))
2425		cfs_rq->blocked_load_avg -= load_contrib;
2426	else
2427		cfs_rq->blocked_load_avg = 0;
2428}
2429
2430static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
 
 
 
2431
2432/* Update a sched_entity's runnable average */
2433static inline void update_entity_load_avg(struct sched_entity *se,
2434					  int update_cfs_rq)
 
 
2435{
2436	struct cfs_rq *cfs_rq = cfs_rq_of(se);
2437	long contrib_delta;
2438	u64 now;
 
2439
2440	/*
2441	 * For a group entity we need to use their owned cfs_rq_clock_task() in
2442	 * case they are the parent of a throttled hierarchy.
2443	 */
2444	if (entity_is_task(se))
2445		now = cfs_rq_clock_task(cfs_rq);
2446	else
2447		now = cfs_rq_clock_task(group_cfs_rq(se));
2448
2449	if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq))
2450		return;
2451
2452	contrib_delta = __update_entity_load_avg_contrib(se);
 
2453
2454	if (!update_cfs_rq)
2455		return;
2456
2457	if (se->on_rq)
2458		cfs_rq->runnable_load_avg += contrib_delta;
2459	else
2460		subtract_blocked_load_contrib(cfs_rq, -contrib_delta);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2461}
2462
2463/*
2464 * Decay the load contributed by all blocked children and account this so that
2465 * their contribution may appropriately discounted when they wake up.
2466 */
2467static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
2468{
2469	u64 now = cfs_rq_clock_task(cfs_rq) >> 20;
2470	u64 decays;
2471
2472	decays = now - cfs_rq->last_decay;
2473	if (!decays && !force_update)
2474		return;
 
 
 
 
2475
2476	if (atomic_long_read(&cfs_rq->removed_load)) {
2477		unsigned long removed_load;
2478		removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0);
2479		subtract_blocked_load_contrib(cfs_rq, removed_load);
2480	}
2481
2482	if (decays) {
2483		cfs_rq->blocked_load_avg = decay_load(cfs_rq->blocked_load_avg,
2484						      decays);
2485		atomic64_add(decays, &cfs_rq->decay_counter);
2486		cfs_rq->last_decay = now;
2487	}
 
2488
2489	__update_cfs_rq_tg_load_contrib(cfs_rq, force_update);
 
 
 
 
 
 
 
 
 
2490}
2491
2492/* Add the load generated by se into cfs_rq's child load-average */
2493static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
2494						  struct sched_entity *se,
2495						  int wakeup)
2496{
2497	/*
2498	 * We track migrations using entity decay_count <= 0, on a wake-up
2499	 * migration we use a negative decay count to track the remote decays
2500	 * accumulated while sleeping.
2501	 *
2502	 * Newly forked tasks are enqueued with se->avg.decay_count == 0, they
2503	 * are seen by enqueue_entity_load_avg() as a migration with an already
2504	 * constructed load_avg_contrib.
2505	 */
2506	if (unlikely(se->avg.decay_count <= 0)) {
2507		se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq));
2508		if (se->avg.decay_count) {
2509			/*
2510			 * In a wake-up migration we have to approximate the
2511			 * time sleeping.  This is because we can't synchronize
2512			 * clock_task between the two cpus, and it is not
2513			 * guaranteed to be read-safe.  Instead, we can
2514			 * approximate this using our carried decays, which are
2515			 * explicitly atomically readable.
2516			 */
2517			se->avg.last_runnable_update -= (-se->avg.decay_count)
2518							<< 20;
2519			update_entity_load_avg(se, 0);
2520			/* Indicate that we're now synchronized and on-rq */
2521			se->avg.decay_count = 0;
2522		}
2523		wakeup = 0;
2524	} else {
2525		__synchronize_entity_decay(se);
2526	}
2527
2528	/* migrated tasks did not contribute to our blocked load */
2529	if (wakeup) {
2530		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
2531		update_entity_load_avg(se, 0);
 
2532	}
2533
2534	cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
2535	/* we force update consideration on load-balancer moves */
2536	update_cfs_rq_blocked_load(cfs_rq, !wakeup);
 
 
 
 
 
 
 
2537}
2538
2539/*
2540 * Remove se's load from this cfs_rq child load-average, if the entity is
2541 * transitioning to a blocked state we track its projected decay using
2542 * blocked_load_avg.
2543 */
2544static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
2545						  struct sched_entity *se,
2546						  int sleep)
2547{
2548	update_entity_load_avg(se, 1);
2549	/* we force update consideration on load-balancer moves */
2550	update_cfs_rq_blocked_load(cfs_rq, !sleep);
2551
2552	cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
2553	if (sleep) {
2554		cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
2555		se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
2556	} /* migrations, e.g. sleep=0 leave decay_count == 0 */
2557}
2558
2559/*
2560 * Update the rq's load with the elapsed running time before entering
2561 * idle. if the last scheduled task is not a CFS task, idle_enter will
2562 * be the only way to update the runnable statistic.
2563 */
2564void idle_enter_fair(struct rq *this_rq)
 
 
 
 
 
 
 
 
 
 
2565{
2566	update_rq_runnable_avg(this_rq, 1);
2567}
 
2568
2569/*
2570 * Update the rq's load with the elapsed idle time before a task is
2571 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2572 * be the only way to update the runnable statistic.
2573 */
2574void idle_exit_fair(struct rq *this_rq)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2575{
2576	update_rq_runnable_avg(this_rq, 0);
 
 
 
 
 
2577}
2578
2579static int idle_balance(struct rq *this_rq);
2580
2581#else /* CONFIG_SMP */
2582
2583static inline void update_entity_load_avg(struct sched_entity *se,
2584					  int update_cfs_rq) {}
2585static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
2586static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
2587					   struct sched_entity *se,
2588					   int wakeup) {}
2589static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
2590					   struct sched_entity *se,
2591					   int sleep) {}
2592static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
2593					      int force_update) {}
 
 
 
 
 
 
 
2594
2595static inline int idle_balance(struct rq *rq)
2596{
2597	return 0;
2598}
2599
2600#endif /* CONFIG_SMP */
2601
2602static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2603{
2604#ifdef CONFIG_SCHEDSTATS
2605	struct task_struct *tsk = NULL;
2606
2607	if (entity_is_task(se))
2608		tsk = task_of(se);
2609
2610	if (se->statistics.sleep_start) {
2611		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2612
2613		if ((s64)delta < 0)
2614			delta = 0;
2615
2616		if (unlikely(delta > se->statistics.sleep_max))
2617			se->statistics.sleep_max = delta;
2618
2619		se->statistics.sleep_start = 0;
2620		se->statistics.sum_sleep_runtime += delta;
2621
2622		if (tsk) {
2623			account_scheduler_latency(tsk, delta >> 10, 1);
2624			trace_sched_stat_sleep(tsk, delta);
2625		}
2626	}
2627	if (se->statistics.block_start) {
2628		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2629
2630		if ((s64)delta < 0)
2631			delta = 0;
2632
2633		if (unlikely(delta > se->statistics.block_max))
2634			se->statistics.block_max = delta;
2635
2636		se->statistics.block_start = 0;
2637		se->statistics.sum_sleep_runtime += delta;
2638
2639		if (tsk) {
2640			if (tsk->in_iowait) {
2641				se->statistics.iowait_sum += delta;
2642				se->statistics.iowait_count++;
2643				trace_sched_stat_iowait(tsk, delta);
2644			}
2645
2646			trace_sched_stat_blocked(tsk, delta);
2647
2648			/*
2649			 * Blocking time is in units of nanosecs, so shift by
2650			 * 20 to get a milliseconds-range estimation of the
2651			 * amount of time that the task spent sleeping:
2652			 */
2653			if (unlikely(prof_on == SLEEP_PROFILING)) {
2654				profile_hits(SLEEP_PROFILING,
2655						(void *)get_wchan(tsk),
2656						delta >> 20);
2657			}
2658			account_scheduler_latency(tsk, delta >> 10, 0);
2659		}
2660	}
2661#endif
2662}
2663
2664static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
2665{
2666#ifdef CONFIG_SCHED_DEBUG
2667	s64 d = se->vruntime - cfs_rq->min_vruntime;
2668
2669	if (d < 0)
2670		d = -d;
2671
2672	if (d > 3*sysctl_sched_latency)
2673		schedstat_inc(cfs_rq, nr_spread_over);
2674#endif
2675}
2676
2677static void
2678place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
2679{
2680	u64 vruntime = cfs_rq->min_vruntime;
2681
2682	/*
2683	 * The 'current' period is already promised to the current tasks,
2684	 * however the extra weight of the new task will slow them down a
2685	 * little, place the new task so that it fits in the slot that
2686	 * stays open at the end.
2687	 */
2688	if (initial && sched_feat(START_DEBIT))
2689		vruntime += sched_vslice(cfs_rq, se);
2690
2691	/* sleeps up to a single latency don't count. */
2692	if (!initial) {
2693		unsigned long thresh = sysctl_sched_latency;
2694
2695		/*
2696		 * Halve their sleep time's effect, to allow
2697		 * for a gentler effect of sleepers:
2698		 */
2699		if (sched_feat(GENTLE_FAIR_SLEEPERS))
2700			thresh >>= 1;
2701
2702		vruntime -= thresh;
2703	}
2704
2705	/* ensure we never gain time by being placed backwards. */
2706	se->vruntime = max_vruntime(se->vruntime, vruntime);
2707}
2708
2709static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
2710
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2711static void
2712enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2713{
2714	/*
2715	 * Update the normalized vruntime before updating min_vruntime
2716	 * through calling update_curr().
2717	 */
2718	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
2719		se->vruntime += cfs_rq->min_vruntime;
2720
2721	/*
2722	 * Update run-time statistics of the 'current'.
2723	 */
2724	update_curr(cfs_rq);
2725	enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
2726	account_entity_enqueue(cfs_rq, se);
2727	update_cfs_shares(cfs_rq);
2728
2729	if (flags & ENQUEUE_WAKEUP) {
2730		place_entity(cfs_rq, se, 0);
2731		enqueue_sleeper(cfs_rq, se);
 
2732	}
2733
2734	update_stats_enqueue(cfs_rq, se);
2735	check_spread(cfs_rq, se);
 
 
 
2736	if (se != cfs_rq->curr)
2737		__enqueue_entity(cfs_rq, se);
2738	se->on_rq = 1;
2739
2740	if (cfs_rq->nr_running == 1) {
2741		list_add_leaf_cfs_rq(cfs_rq);
2742		check_enqueue_throttle(cfs_rq);
2743	}
2744}
2745
2746static void __clear_buddies_last(struct sched_entity *se)
2747{
2748	for_each_sched_entity(se) {
2749		struct cfs_rq *cfs_rq = cfs_rq_of(se);
2750		if (cfs_rq->last != se)
2751			break;
2752
2753		cfs_rq->last = NULL;
2754	}
2755}
2756
2757static void __clear_buddies_next(struct sched_entity *se)
2758{
2759	for_each_sched_entity(se) {
2760		struct cfs_rq *cfs_rq = cfs_rq_of(se);
2761		if (cfs_rq->next != se)
2762			break;
2763
2764		cfs_rq->next = NULL;
2765	}
2766}
2767
2768static void __clear_buddies_skip(struct sched_entity *se)
2769{
2770	for_each_sched_entity(se) {
2771		struct cfs_rq *cfs_rq = cfs_rq_of(se);
2772		if (cfs_rq->skip != se)
2773			break;
2774
2775		cfs_rq->skip = NULL;
2776	}
2777}
2778
2779static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
2780{
2781	if (cfs_rq->last == se)
2782		__clear_buddies_last(se);
2783
2784	if (cfs_rq->next == se)
2785		__clear_buddies_next(se);
2786
2787	if (cfs_rq->skip == se)
2788		__clear_buddies_skip(se);
2789}
2790
2791static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
2792
2793static void
2794dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2795{
2796	/*
2797	 * Update run-time statistics of the 'current'.
2798	 */
2799	update_curr(cfs_rq);
2800	dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);
2801
2802	update_stats_dequeue(cfs_rq, se);
2803	if (flags & DEQUEUE_SLEEP) {
2804#ifdef CONFIG_SCHEDSTATS
2805		if (entity_is_task(se)) {
2806			struct task_struct *tsk = task_of(se);
2807
2808			if (tsk->state & TASK_INTERRUPTIBLE)
2809				se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
2810			if (tsk->state & TASK_UNINTERRUPTIBLE)
2811				se->statistics.block_start = rq_clock(rq_of(cfs_rq));
2812		}
2813#endif
2814	}
2815
2816	clear_buddies(cfs_rq, se);
2817
2818	if (se != cfs_rq->curr)
2819		__dequeue_entity(cfs_rq, se);
2820	se->on_rq = 0;
2821	account_entity_dequeue(cfs_rq, se);
2822
2823	/*
2824	 * Normalize the entity after updating the min_vruntime because the
2825	 * update can refer to the ->curr item and we need to reflect this
2826	 * movement in our normalized position.
2827	 */
2828	if (!(flags & DEQUEUE_SLEEP))
2829		se->vruntime -= cfs_rq->min_vruntime;
2830
2831	/* return excess runtime on last dequeue */
2832	return_cfs_rq_runtime(cfs_rq);
2833
2834	update_min_vruntime(cfs_rq);
2835	update_cfs_shares(cfs_rq);
2836}
2837
2838/*
2839 * Preempt the current task with a newly woken task if needed:
2840 */
2841static void
2842check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
2843{
2844	unsigned long ideal_runtime, delta_exec;
2845	struct sched_entity *se;
2846	s64 delta;
2847
2848	ideal_runtime = sched_slice(cfs_rq, curr);
2849	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
2850	if (delta_exec > ideal_runtime) {
2851		resched_task(rq_of(cfs_rq)->curr);
2852		/*
2853		 * The current task ran long enough, ensure it doesn't get
2854		 * re-elected due to buddy favours.
2855		 */
2856		clear_buddies(cfs_rq, curr);
2857		return;
2858	}
2859
2860	/*
2861	 * Ensure that a task that missed wakeup preemption by a
2862	 * narrow margin doesn't have to wait for a full slice.
2863	 * This also mitigates buddy induced latencies under load.
2864	 */
2865	if (delta_exec < sysctl_sched_min_granularity)
2866		return;
2867
2868	se = __pick_first_entity(cfs_rq);
2869	delta = curr->vruntime - se->vruntime;
2870
2871	if (delta < 0)
2872		return;
2873
2874	if (delta > ideal_runtime)
2875		resched_task(rq_of(cfs_rq)->curr);
2876}
2877
2878static void
2879set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
2880{
2881	/* 'current' is not kept within the tree. */
2882	if (se->on_rq) {
2883		/*
2884		 * Any task has to be enqueued before it get to execute on
2885		 * a CPU. So account for the time it spent waiting on the
2886		 * runqueue.
2887		 */
2888		update_stats_wait_end(cfs_rq, se);
 
2889		__dequeue_entity(cfs_rq, se);
 
2890	}
2891
2892	update_stats_curr_start(cfs_rq, se);
2893	cfs_rq->curr = se;
2894#ifdef CONFIG_SCHEDSTATS
2895	/*
2896	 * Track our maximum slice length, if the CPU's load is at
2897	 * least twice that of our own weight (i.e. dont track it
2898	 * when there are only lesser-weight tasks around):
2899	 */
2900	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
2901		se->statistics.slice_max = max(se->statistics.slice_max,
2902			se->sum_exec_runtime - se->prev_sum_exec_runtime);
2903	}
2904#endif
2905	se->prev_sum_exec_runtime = se->sum_exec_runtime;
2906}
2907
2908static int
2909wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
2910
2911/*
2912 * Pick the next process, keeping these things in mind, in this order:
2913 * 1) keep things fair between processes/task groups
2914 * 2) pick the "next" process, since someone really wants that to run
2915 * 3) pick the "last" process, for cache locality
2916 * 4) do not run the "skip" process, if something else is available
2917 */
2918static struct sched_entity *
2919pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
2920{
2921	struct sched_entity *left = __pick_first_entity(cfs_rq);
2922	struct sched_entity *se;
2923
2924	/*
2925	 * If curr is set we have to see if its left of the leftmost entity
2926	 * still in the tree, provided there was anything in the tree at all.
2927	 */
2928	if (!left || (curr && entity_before(curr, left)))
2929		left = curr;
2930
2931	se = left; /* ideally we run the leftmost entity */
2932
2933	/*
2934	 * Avoid running the skip buddy, if running something else can
2935	 * be done without getting too unfair.
2936	 */
2937	if (cfs_rq->skip == se) {
2938		struct sched_entity *second;
2939
2940		if (se == curr) {
2941			second = __pick_first_entity(cfs_rq);
2942		} else {
2943			second = __pick_next_entity(se);
2944			if (!second || (curr && entity_before(curr, second)))
2945				second = curr;
2946		}
2947
2948		if (second && wakeup_preempt_entity(second, left) < 1)
2949			se = second;
2950	}
2951
2952	/*
2953	 * Prefer last buddy, try to return the CPU to a preempted task.
2954	 */
2955	if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
2956		se = cfs_rq->last;
2957
2958	/*
2959	 * Someone really wants this to run. If it's not unfair, run it.
2960	 */
2961	if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
2962		se = cfs_rq->next;
2963
2964	clear_buddies(cfs_rq, se);
2965
2966	return se;
2967}
2968
2969static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
2970
2971static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
2972{
2973	/*
2974	 * If still on the runqueue then deactivate_task()
2975	 * was not called and update_curr() has to be done:
2976	 */
2977	if (prev->on_rq)
2978		update_curr(cfs_rq);
2979
2980	/* throttle cfs_rqs exceeding runtime */
2981	check_cfs_rq_runtime(cfs_rq);
2982
2983	check_spread(cfs_rq, prev);
 
 
 
 
 
2984	if (prev->on_rq) {
2985		update_stats_wait_start(cfs_rq, prev);
2986		/* Put 'current' back into the tree. */
2987		__enqueue_entity(cfs_rq, prev);
2988		/* in !on_rq case, update occurred at dequeue */
2989		update_entity_load_avg(prev, 1);
2990	}
2991	cfs_rq->curr = NULL;
2992}
2993
2994static void
2995entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
2996{
2997	/*
2998	 * Update run-time statistics of the 'current'.
2999	 */
3000	update_curr(cfs_rq);
3001
3002	/*
3003	 * Ensure that runnable average is periodically updated.
3004	 */
3005	update_entity_load_avg(curr, 1);
3006	update_cfs_rq_blocked_load(cfs_rq, 1);
3007	update_cfs_shares(cfs_rq);
3008
3009#ifdef CONFIG_SCHED_HRTICK
3010	/*
3011	 * queued ticks are scheduled to match the slice, so don't bother
3012	 * validating it and just reschedule.
3013	 */
3014	if (queued) {
3015		resched_task(rq_of(cfs_rq)->curr);
3016		return;
3017	}
3018	/*
3019	 * don't let the period tick interfere with the hrtick preemption
3020	 */
3021	if (!sched_feat(DOUBLE_TICK) &&
3022			hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3023		return;
3024#endif
3025
3026	if (cfs_rq->nr_running > 1)
3027		check_preempt_tick(cfs_rq, curr);
3028}
3029
3030
3031/**************************************************
3032 * CFS bandwidth control machinery
3033 */
3034
3035#ifdef CONFIG_CFS_BANDWIDTH
3036
3037#ifdef HAVE_JUMP_LABEL
3038static struct static_key __cfs_bandwidth_used;
3039
3040static inline bool cfs_bandwidth_used(void)
3041{
3042	return static_key_false(&__cfs_bandwidth_used);
3043}
3044
3045void cfs_bandwidth_usage_inc(void)
3046{
3047	static_key_slow_inc(&__cfs_bandwidth_used);
3048}
3049
3050void cfs_bandwidth_usage_dec(void)
3051{
3052	static_key_slow_dec(&__cfs_bandwidth_used);
3053}
3054#else /* HAVE_JUMP_LABEL */
3055static bool cfs_bandwidth_used(void)
3056{
3057	return true;
3058}
3059
3060void cfs_bandwidth_usage_inc(void) {}
3061void cfs_bandwidth_usage_dec(void) {}
3062#endif /* HAVE_JUMP_LABEL */
3063
3064/*
3065 * default period for cfs group bandwidth.
3066 * default: 0.1s, units: nanoseconds
3067 */
3068static inline u64 default_cfs_period(void)
3069{
3070	return 100000000ULL;
3071}
3072
3073static inline u64 sched_cfs_bandwidth_slice(void)
3074{
3075	return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3076}
3077
3078/*
3079 * Replenish runtime according to assigned quota and update expiration time.
3080 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3081 * additional synchronization around rq->lock.
3082 *
3083 * requires cfs_b->lock
3084 */
3085void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3086{
3087	u64 now;
3088
3089	if (cfs_b->quota == RUNTIME_INF)
3090		return;
3091
3092	now = sched_clock_cpu(smp_processor_id());
3093	cfs_b->runtime = cfs_b->quota;
3094	cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3095}
3096
3097static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3098{
3099	return &tg->cfs_bandwidth;
3100}
3101
3102/* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3103static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3104{
3105	if (unlikely(cfs_rq->throttle_count))
3106		return cfs_rq->throttled_clock_task;
3107
3108	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3109}
3110
3111/* returns 0 on failure to allocate runtime */
3112static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3113{
3114	struct task_group *tg = cfs_rq->tg;
3115	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3116	u64 amount = 0, min_amount, expires;
3117
3118	/* note: this is a positive sum as runtime_remaining <= 0 */
3119	min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3120
3121	raw_spin_lock(&cfs_b->lock);
3122	if (cfs_b->quota == RUNTIME_INF)
3123		amount = min_amount;
3124	else {
3125		/*
3126		 * If the bandwidth pool has become inactive, then at least one
3127		 * period must have elapsed since the last consumption.
3128		 * Refresh the global state and ensure bandwidth timer becomes
3129		 * active.
3130		 */
3131		if (!cfs_b->timer_active) {
3132			__refill_cfs_bandwidth_runtime(cfs_b);
3133			__start_cfs_bandwidth(cfs_b, false);
3134		}
3135
3136		if (cfs_b->runtime > 0) {
3137			amount = min(cfs_b->runtime, min_amount);
3138			cfs_b->runtime -= amount;
3139			cfs_b->idle = 0;
3140		}
3141	}
3142	expires = cfs_b->runtime_expires;
3143	raw_spin_unlock(&cfs_b->lock);
3144
3145	cfs_rq->runtime_remaining += amount;
3146	/*
3147	 * we may have advanced our local expiration to account for allowed
3148	 * spread between our sched_clock and the one on which runtime was
3149	 * issued.
3150	 */
3151	if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3152		cfs_rq->runtime_expires = expires;
3153
3154	return cfs_rq->runtime_remaining > 0;
3155}
3156
3157/*
3158 * Note: This depends on the synchronization provided by sched_clock and the
3159 * fact that rq->clock snapshots this value.
3160 */
3161static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3162{
3163	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3164
3165	/* if the deadline is ahead of our clock, nothing to do */
3166	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3167		return;
3168
3169	if (cfs_rq->runtime_remaining < 0)
3170		return;
3171
3172	/*
3173	 * If the local deadline has passed we have to consider the
3174	 * possibility that our sched_clock is 'fast' and the global deadline
3175	 * has not truly expired.
3176	 *
3177	 * Fortunately we can check determine whether this the case by checking
3178	 * whether the global deadline has advanced.
 
 
3179	 */
3180
3181	if ((s64)(cfs_rq->runtime_expires - cfs_b->runtime_expires) >= 0) {
3182		/* extend local deadline, drift is bounded above by 2 ticks */
3183		cfs_rq->runtime_expires += TICK_NSEC;
3184	} else {
3185		/* global deadline is ahead, expiration has passed */
3186		cfs_rq->runtime_remaining = 0;
3187	}
3188}
3189
3190static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3191{
3192	/* dock delta_exec before expiring quota (as it could span periods) */
3193	cfs_rq->runtime_remaining -= delta_exec;
3194	expire_cfs_rq_runtime(cfs_rq);
3195
3196	if (likely(cfs_rq->runtime_remaining > 0))
3197		return;
3198
3199	/*
3200	 * if we're unable to extend our runtime we resched so that the active
3201	 * hierarchy can be throttled
3202	 */
3203	if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3204		resched_task(rq_of(cfs_rq)->curr);
3205}
3206
3207static __always_inline
3208void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3209{
3210	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3211		return;
3212
3213	__account_cfs_rq_runtime(cfs_rq, delta_exec);
3214}
3215
3216static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3217{
3218	return cfs_bandwidth_used() && cfs_rq->throttled;
3219}
3220
3221/* check whether cfs_rq, or any parent, is throttled */
3222static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3223{
3224	return cfs_bandwidth_used() && cfs_rq->throttle_count;
3225}
3226
3227/*
3228 * Ensure that neither of the group entities corresponding to src_cpu or
3229 * dest_cpu are members of a throttled hierarchy when performing group
3230 * load-balance operations.
3231 */
3232static inline int throttled_lb_pair(struct task_group *tg,
3233				    int src_cpu, int dest_cpu)
3234{
3235	struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3236
3237	src_cfs_rq = tg->cfs_rq[src_cpu];
3238	dest_cfs_rq = tg->cfs_rq[dest_cpu];
3239
3240	return throttled_hierarchy(src_cfs_rq) ||
3241	       throttled_hierarchy(dest_cfs_rq);
3242}
3243
3244/* updated child weight may affect parent so we have to do this bottom up */
3245static int tg_unthrottle_up(struct task_group *tg, void *data)
3246{
3247	struct rq *rq = data;
3248	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3249
3250	cfs_rq->throttle_count--;
3251#ifdef CONFIG_SMP
3252	if (!cfs_rq->throttle_count) {
3253		/* adjust cfs_rq_clock_task() */
3254		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3255					     cfs_rq->throttled_clock_task;
3256	}
3257#endif
3258
3259	return 0;
3260}
3261
3262static int tg_throttle_down(struct task_group *tg, void *data)
3263{
3264	struct rq *rq = data;
3265	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3266
3267	/* group is entering throttled state, stop time */
3268	if (!cfs_rq->throttle_count)
3269		cfs_rq->throttled_clock_task = rq_clock_task(rq);
3270	cfs_rq->throttle_count++;
3271
3272	return 0;
3273}
3274
3275static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3276{
3277	struct rq *rq = rq_of(cfs_rq);
3278	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3279	struct sched_entity *se;
3280	long task_delta, dequeue = 1;
 
3281
3282	se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3283
3284	/* freeze hierarchy runnable averages while throttled */
3285	rcu_read_lock();
3286	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3287	rcu_read_unlock();
3288
3289	task_delta = cfs_rq->h_nr_running;
3290	for_each_sched_entity(se) {
3291		struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3292		/* throttled entity or throttle-on-deactivate */
3293		if (!se->on_rq)
3294			break;
3295
3296		if (dequeue)
3297			dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3298		qcfs_rq->h_nr_running -= task_delta;
3299
3300		if (qcfs_rq->load.weight)
3301			dequeue = 0;
3302	}
3303
3304	if (!se)
3305		rq->nr_running -= task_delta;
3306
3307	cfs_rq->throttled = 1;
3308	cfs_rq->throttled_clock = rq_clock(rq);
3309	raw_spin_lock(&cfs_b->lock);
3310	list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3311	if (!cfs_b->timer_active)
3312		__start_cfs_bandwidth(cfs_b, false);
 
 
 
 
 
 
 
 
 
 
 
 
3313	raw_spin_unlock(&cfs_b->lock);
3314}
3315
3316void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3317{
3318	struct rq *rq = rq_of(cfs_rq);
3319	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3320	struct sched_entity *se;
3321	int enqueue = 1;
3322	long task_delta;
3323
3324	se = cfs_rq->tg->se[cpu_of(rq)];
3325
3326	cfs_rq->throttled = 0;
3327
3328	update_rq_clock(rq);
3329
3330	raw_spin_lock(&cfs_b->lock);
3331	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3332	list_del_rcu(&cfs_rq->throttled_list);
3333	raw_spin_unlock(&cfs_b->lock);
3334
3335	/* update hierarchical throttle state */
3336	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3337
3338	if (!cfs_rq->load.weight)
3339		return;
3340
3341	task_delta = cfs_rq->h_nr_running;
3342	for_each_sched_entity(se) {
3343		if (se->on_rq)
3344			enqueue = 0;
3345
3346		cfs_rq = cfs_rq_of(se);
3347		if (enqueue)
3348			enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3349		cfs_rq->h_nr_running += task_delta;
3350
3351		if (cfs_rq_throttled(cfs_rq))
3352			break;
3353	}
3354
3355	if (!se)
3356		rq->nr_running += task_delta;
3357
3358	/* determine whether we need to wake up potentially idle cpu */
3359	if (rq->curr == rq->idle && rq->cfs.nr_running)
3360		resched_task(rq->curr);
3361}
3362
3363static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3364		u64 remaining, u64 expires)
3365{
3366	struct cfs_rq *cfs_rq;
3367	u64 runtime = remaining;
 
3368
3369	rcu_read_lock();
3370	list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3371				throttled_list) {
3372		struct rq *rq = rq_of(cfs_rq);
3373
3374		raw_spin_lock(&rq->lock);
3375		if (!cfs_rq_throttled(cfs_rq))
3376			goto next;
3377
3378		runtime = -cfs_rq->runtime_remaining + 1;
3379		if (runtime > remaining)
3380			runtime = remaining;
3381		remaining -= runtime;
3382
3383		cfs_rq->runtime_remaining += runtime;
3384		cfs_rq->runtime_expires = expires;
3385
3386		/* we check whether we're throttled above */
3387		if (cfs_rq->runtime_remaining > 0)
3388			unthrottle_cfs_rq(cfs_rq);
3389
3390next:
3391		raw_spin_unlock(&rq->lock);
3392
3393		if (!remaining)
3394			break;
3395	}
3396	rcu_read_unlock();
3397
3398	return remaining;
3399}
3400
3401/*
3402 * Responsible for refilling a task_group's bandwidth and unthrottling its
3403 * cfs_rqs as appropriate. If there has been no activity within the last
3404 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3405 * used to track this state.
3406 */
3407static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3408{
3409	u64 runtime, runtime_expires;
3410	int idle = 1, throttled;
3411
3412	raw_spin_lock(&cfs_b->lock);
3413	/* no need to continue the timer with no bandwidth constraint */
3414	if (cfs_b->quota == RUNTIME_INF)
3415		goto out_unlock;
3416
3417	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3418	/* idle depends on !throttled (for the case of a large deficit) */
3419	idle = cfs_b->idle && !throttled;
3420	cfs_b->nr_periods += overrun;
3421
3422	/* if we're going inactive then everything else can be deferred */
3423	if (idle)
3424		goto out_unlock;
3425
3426	/*
3427	 * if we have relooped after returning idle once, we need to update our
3428	 * status as actually running, so that other cpus doing
3429	 * __start_cfs_bandwidth will stop trying to cancel us.
3430	 */
3431	cfs_b->timer_active = 1;
 
3432
3433	__refill_cfs_bandwidth_runtime(cfs_b);
3434
3435	if (!throttled) {
3436		/* mark as potentially idle for the upcoming period */
3437		cfs_b->idle = 1;
3438		goto out_unlock;
3439	}
3440
3441	/* account preceding periods in which throttling occurred */
3442	cfs_b->nr_throttled += overrun;
3443
3444	/*
3445	 * There are throttled entities so we must first use the new bandwidth
3446	 * to unthrottle them before making it generally available.  This
3447	 * ensures that all existing debts will be paid before a new cfs_rq is
3448	 * allowed to run.
3449	 */
3450	runtime = cfs_b->runtime;
3451	runtime_expires = cfs_b->runtime_expires;
3452	cfs_b->runtime = 0;
3453
3454	/*
3455	 * This check is repeated as we are holding onto the new bandwidth
3456	 * while we unthrottle.  This can potentially race with an unthrottled
3457	 * group trying to acquire new bandwidth from the global pool.
 
 
3458	 */
3459	while (throttled && runtime > 0) {
 
3460		raw_spin_unlock(&cfs_b->lock);
3461		/* we can't nest cfs_b->lock while distributing bandwidth */
3462		runtime = distribute_cfs_runtime(cfs_b, runtime,
3463						 runtime_expires);
3464		raw_spin_lock(&cfs_b->lock);
3465
3466		throttled = !list_empty(&cfs_b->throttled_cfs_rq);
 
 
3467	}
3468
3469	/* return (any) remaining runtime */
3470	cfs_b->runtime = runtime;
3471	/*
3472	 * While we are ensured activity in the period following an
3473	 * unthrottle, this also covers the case in which the new bandwidth is
3474	 * insufficient to cover the existing bandwidth deficit.  (Forcing the
3475	 * timer to remain active while there are any throttled entities.)
3476	 */
3477	cfs_b->idle = 0;
3478out_unlock:
3479	if (idle)
3480		cfs_b->timer_active = 0;
3481	raw_spin_unlock(&cfs_b->lock);
3482
3483	return idle;
 
 
 
3484}
3485
3486/* a cfs_rq won't donate quota below this amount */
3487static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3488/* minimum remaining period time to redistribute slack quota */
3489static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3490/* how long we wait to gather additional slack before distributing */
3491static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3492
3493/*
3494 * Are we near the end of the current quota period?
3495 *
3496 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3497 * hrtimer base being cleared by __hrtimer_start_range_ns. In the case of
3498 * migrate_hrtimers, base is never cleared, so we are fine.
3499 */
3500static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3501{
3502	struct hrtimer *refresh_timer = &cfs_b->period_timer;
3503	u64 remaining;
3504
3505	/* if the call-back is running a quota refresh is already occurring */
3506	if (hrtimer_callback_running(refresh_timer))
3507		return 1;
3508
3509	/* is a quota refresh about to occur? */
3510	remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3511	if (remaining < min_expire)
3512		return 1;
3513
3514	return 0;
3515}
3516
3517static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3518{
3519	u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3520
3521	/* if there's a quota refresh soon don't bother with slack */
3522	if (runtime_refresh_within(cfs_b, min_left))
3523		return;
3524
3525	start_bandwidth_timer(&cfs_b->slack_timer,
3526				ns_to_ktime(cfs_bandwidth_slack_period));
 
3527}
3528
3529/* we know any runtime found here is valid as update_curr() precedes return */
3530static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3531{
3532	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3533	s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3534
3535	if (slack_runtime <= 0)
3536		return;
3537
3538	raw_spin_lock(&cfs_b->lock);
3539	if (cfs_b->quota != RUNTIME_INF &&
3540	    cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3541		cfs_b->runtime += slack_runtime;
3542
3543		/* we are under rq->lock, defer unthrottling using a timer */
3544		if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3545		    !list_empty(&cfs_b->throttled_cfs_rq))
3546			start_cfs_slack_bandwidth(cfs_b);
3547	}
3548	raw_spin_unlock(&cfs_b->lock);
3549
3550	/* even if it's not valid for return we don't want to try again */
3551	cfs_rq->runtime_remaining -= slack_runtime;
3552}
3553
3554static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3555{
3556	if (!cfs_bandwidth_used())
3557		return;
3558
3559	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3560		return;
3561
3562	__return_cfs_rq_runtime(cfs_rq);
3563}
3564
3565/*
3566 * This is done with a timer (instead of inline with bandwidth return) since
3567 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3568 */
3569static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
3570{
3571	u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
3572	u64 expires;
3573
3574	/* confirm we're still not at a refresh boundary */
3575	raw_spin_lock(&cfs_b->lock);
3576	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
3577		raw_spin_unlock(&cfs_b->lock);
3578		return;
3579	}
3580
3581	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
3582		runtime = cfs_b->runtime;
3583		cfs_b->runtime = 0;
3584	}
3585	expires = cfs_b->runtime_expires;
3586	raw_spin_unlock(&cfs_b->lock);
3587
3588	if (!runtime)
3589		return;
3590
3591	runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
3592
3593	raw_spin_lock(&cfs_b->lock);
3594	if (expires == cfs_b->runtime_expires)
3595		cfs_b->runtime = runtime;
3596	raw_spin_unlock(&cfs_b->lock);
3597}
3598
3599/*
3600 * When a group wakes up we want to make sure that its quota is not already
3601 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3602 * runtime as update_curr() throttling can not not trigger until it's on-rq.
3603 */
3604static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
3605{
3606	if (!cfs_bandwidth_used())
3607		return;
3608
3609	/* an active group must be handled by the update_curr()->put() path */
3610	if (!cfs_rq->runtime_enabled || cfs_rq->curr)
3611		return;
3612
3613	/* ensure the group is not already throttled */
3614	if (cfs_rq_throttled(cfs_rq))
3615		return;
3616
3617	/* update runtime allocation */
3618	account_cfs_rq_runtime(cfs_rq, 0);
3619	if (cfs_rq->runtime_remaining <= 0)
3620		throttle_cfs_rq(cfs_rq);
3621}
3622
3623/* conditionally throttle active cfs_rq's from put_prev_entity() */
3624static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3625{
3626	if (!cfs_bandwidth_used())
3627		return false;
3628
3629	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3630		return false;
3631
3632	/*
3633	 * it's possible for a throttled entity to be forced into a running
3634	 * state (e.g. set_curr_task), in this case we're finished.
3635	 */
3636	if (cfs_rq_throttled(cfs_rq))
3637		return true;
3638
3639	throttle_cfs_rq(cfs_rq);
3640	return true;
3641}
3642
3643static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
3644{
3645	struct cfs_bandwidth *cfs_b =
3646		container_of(timer, struct cfs_bandwidth, slack_timer);
 
3647	do_sched_cfs_slack_timer(cfs_b);
3648
3649	return HRTIMER_NORESTART;
3650}
3651
3652static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
3653{
3654	struct cfs_bandwidth *cfs_b =
3655		container_of(timer, struct cfs_bandwidth, period_timer);
3656	ktime_t now;
3657	int overrun;
3658	int idle = 0;
3659
 
3660	for (;;) {
3661		now = hrtimer_cb_get_time(timer);
3662		overrun = hrtimer_forward(timer, now, cfs_b->period);
3663
3664		if (!overrun)
3665			break;
3666
3667		idle = do_sched_cfs_period_timer(cfs_b, overrun);
3668	}
 
 
 
3669
3670	return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
3671}
3672
3673void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3674{
3675	raw_spin_lock_init(&cfs_b->lock);
3676	cfs_b->runtime = 0;
3677	cfs_b->quota = RUNTIME_INF;
3678	cfs_b->period = ns_to_ktime(default_cfs_period());
3679
3680	INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
3681	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
3682	cfs_b->period_timer.function = sched_cfs_period_timer;
3683	hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
3684	cfs_b->slack_timer.function = sched_cfs_slack_timer;
3685}
3686
3687static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3688{
3689	cfs_rq->runtime_enabled = 0;
3690	INIT_LIST_HEAD(&cfs_rq->throttled_list);
3691}
3692
3693/* requires cfs_b->lock, may release to reprogram timer */
3694void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b, bool force)
3695{
3696	/*
3697	 * The timer may be active because we're trying to set a new bandwidth
3698	 * period or because we're racing with the tear-down path
3699	 * (timer_active==0 becomes visible before the hrtimer call-back
3700	 * terminates).  In either case we ensure that it's re-programmed
3701	 */
3702	while (unlikely(hrtimer_active(&cfs_b->period_timer)) &&
3703	       hrtimer_try_to_cancel(&cfs_b->period_timer) < 0) {
3704		/* bounce the lock to allow do_sched_cfs_period_timer to run */
3705		raw_spin_unlock(&cfs_b->lock);
3706		cpu_relax();
3707		raw_spin_lock(&cfs_b->lock);
3708		/* if someone else restarted the timer then we're done */
3709		if (!force && cfs_b->timer_active)
3710			return;
3711	}
3712
3713	cfs_b->timer_active = 1;
3714	start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period);
 
 
 
3715}
3716
3717static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3718{
 
 
 
 
3719	hrtimer_cancel(&cfs_b->period_timer);
3720	hrtimer_cancel(&cfs_b->slack_timer);
3721}
3722
3723static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
3724{
3725	struct cfs_rq *cfs_rq;
3726
3727	for_each_leaf_cfs_rq(rq, cfs_rq) {
3728		struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3729
 
 
 
 
 
 
 
 
 
 
 
3730		if (!cfs_rq->runtime_enabled)
3731			continue;
3732
3733		/*
3734		 * clock_task is not advancing so we just need to make sure
3735		 * there's some valid quota amount
3736		 */
3737		cfs_rq->runtime_remaining = cfs_b->quota;
 
 
 
 
 
 
3738		if (cfs_rq_throttled(cfs_rq))
3739			unthrottle_cfs_rq(cfs_rq);
3740	}
3741}
3742
3743#else /* CONFIG_CFS_BANDWIDTH */
3744static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3745{
3746	return rq_clock_task(rq_of(cfs_rq));
3747}
3748
3749static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
3750static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
3751static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
3752static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
3753
3754static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3755{
3756	return 0;
3757}
3758
3759static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3760{
3761	return 0;
3762}
3763
3764static inline int throttled_lb_pair(struct task_group *tg,
3765				    int src_cpu, int dest_cpu)
3766{
3767	return 0;
3768}
3769
3770void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
3771
3772#ifdef CONFIG_FAIR_GROUP_SCHED
3773static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
3774#endif
3775
3776static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3777{
3778	return NULL;
3779}
3780static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
 
3781static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
3782
3783#endif /* CONFIG_CFS_BANDWIDTH */
3784
3785/**************************************************
3786 * CFS operations on tasks:
3787 */
3788
3789#ifdef CONFIG_SCHED_HRTICK
3790static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
3791{
3792	struct sched_entity *se = &p->se;
3793	struct cfs_rq *cfs_rq = cfs_rq_of(se);
3794
3795	WARN_ON(task_rq(p) != rq);
3796
3797	if (cfs_rq->nr_running > 1) {
3798		u64 slice = sched_slice(cfs_rq, se);
3799		u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
3800		s64 delta = slice - ran;
3801
3802		if (delta < 0) {
3803			if (rq->curr == p)
3804				resched_task(p);
3805			return;
3806		}
3807
3808		/*
3809		 * Don't schedule slices shorter than 10000ns, that just
3810		 * doesn't make sense. Rely on vruntime for fairness.
3811		 */
3812		if (rq->curr != p)
3813			delta = max_t(s64, 10000LL, delta);
3814
3815		hrtick_start(rq, delta);
3816	}
3817}
3818
3819/*
3820 * called from enqueue/dequeue and updates the hrtick when the
3821 * current task is from our class and nr_running is low enough
3822 * to matter.
3823 */
3824static void hrtick_update(struct rq *rq)
3825{
3826	struct task_struct *curr = rq->curr;
3827
3828	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
3829		return;
3830
3831	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
3832		hrtick_start_fair(rq, curr);
3833}
3834#else /* !CONFIG_SCHED_HRTICK */
3835static inline void
3836hrtick_start_fair(struct rq *rq, struct task_struct *p)
3837{
3838}
3839
3840static inline void hrtick_update(struct rq *rq)
3841{
3842}
3843#endif
3844
3845/*
3846 * The enqueue_task method is called before nr_running is
3847 * increased. Here we update the fair scheduling stats and
3848 * then put the task into the rbtree:
3849 */
3850static void
3851enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
3852{
3853	struct cfs_rq *cfs_rq;
3854	struct sched_entity *se = &p->se;
3855
3856	for_each_sched_entity(se) {
3857		if (se->on_rq)
3858			break;
3859		cfs_rq = cfs_rq_of(se);
3860		enqueue_entity(cfs_rq, se, flags);
3861
3862		/*
3863		 * end evaluation on encountering a throttled cfs_rq
3864		 *
3865		 * note: in the case of encountering a throttled cfs_rq we will
3866		 * post the final h_nr_running increment below.
3867		*/
3868		if (cfs_rq_throttled(cfs_rq))
3869			break;
3870		cfs_rq->h_nr_running++;
3871
3872		flags = ENQUEUE_WAKEUP;
3873	}
3874
3875	for_each_sched_entity(se) {
3876		cfs_rq = cfs_rq_of(se);
3877		cfs_rq->h_nr_running++;
3878
3879		if (cfs_rq_throttled(cfs_rq))
3880			break;
3881
 
3882		update_cfs_shares(cfs_rq);
3883		update_entity_load_avg(se, 1);
3884	}
3885
3886	if (!se) {
3887		update_rq_runnable_avg(rq, rq->nr_running);
3888		inc_nr_running(rq);
3889	}
3890	hrtick_update(rq);
3891}
3892
3893static void set_next_buddy(struct sched_entity *se);
3894
3895/*
3896 * The dequeue_task method is called before nr_running is
3897 * decreased. We remove the task from the rbtree and
3898 * update the fair scheduling stats:
3899 */
3900static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
3901{
3902	struct cfs_rq *cfs_rq;
3903	struct sched_entity *se = &p->se;
3904	int task_sleep = flags & DEQUEUE_SLEEP;
3905
3906	for_each_sched_entity(se) {
3907		cfs_rq = cfs_rq_of(se);
3908		dequeue_entity(cfs_rq, se, flags);
3909
3910		/*
3911		 * end evaluation on encountering a throttled cfs_rq
3912		 *
3913		 * note: in the case of encountering a throttled cfs_rq we will
3914		 * post the final h_nr_running decrement below.
3915		*/
3916		if (cfs_rq_throttled(cfs_rq))
3917			break;
3918		cfs_rq->h_nr_running--;
3919
3920		/* Don't dequeue parent if it has other entities besides us */
3921		if (cfs_rq->load.weight) {
3922			/*
3923			 * Bias pick_next to pick a task from this cfs_rq, as
3924			 * p is sleeping when it is within its sched_slice.
3925			 */
3926			if (task_sleep && parent_entity(se))
3927				set_next_buddy(parent_entity(se));
3928
3929			/* avoid re-evaluating load for this entity */
3930			se = parent_entity(se);
3931			break;
3932		}
3933		flags |= DEQUEUE_SLEEP;
3934	}
3935
3936	for_each_sched_entity(se) {
3937		cfs_rq = cfs_rq_of(se);
3938		cfs_rq->h_nr_running--;
3939
3940		if (cfs_rq_throttled(cfs_rq))
3941			break;
3942
 
3943		update_cfs_shares(cfs_rq);
3944		update_entity_load_avg(se, 1);
3945	}
3946
3947	if (!se) {
3948		dec_nr_running(rq);
3949		update_rq_runnable_avg(rq, 1);
3950	}
3951	hrtick_update(rq);
3952}
3953
3954#ifdef CONFIG_SMP
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3955/* Used instead of source_load when we know the type == 0 */
3956static unsigned long weighted_cpuload(const int cpu)
3957{
3958	return cpu_rq(cpu)->cfs.runnable_load_avg;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3959}
3960
3961/*
3962 * Return a low guess at the load of a migration-source cpu weighted
3963 * according to the scheduling class and "nice" value.
3964 *
3965 * We want to under-estimate the load of migration sources, to
3966 * balance conservatively.
3967 */
3968static unsigned long source_load(int cpu, int type)
3969{
3970	struct rq *rq = cpu_rq(cpu);
3971	unsigned long total = weighted_cpuload(cpu);
3972
3973	if (type == 0 || !sched_feat(LB_BIAS))
3974		return total;
3975
3976	return min(rq->cpu_load[type-1], total);
3977}
3978
3979/*
3980 * Return a high guess at the load of a migration-target cpu weighted
3981 * according to the scheduling class and "nice" value.
3982 */
3983static unsigned long target_load(int cpu, int type)
3984{
3985	struct rq *rq = cpu_rq(cpu);
3986	unsigned long total = weighted_cpuload(cpu);
3987
3988	if (type == 0 || !sched_feat(LB_BIAS))
3989		return total;
3990
3991	return max(rq->cpu_load[type-1], total);
3992}
3993
3994static unsigned long power_of(int cpu)
 
 
 
 
 
3995{
3996	return cpu_rq(cpu)->cpu_power;
3997}
3998
3999static unsigned long cpu_avg_load_per_task(int cpu)
4000{
4001	struct rq *rq = cpu_rq(cpu);
4002	unsigned long nr_running = ACCESS_ONCE(rq->nr_running);
4003	unsigned long load_avg = rq->cfs.runnable_load_avg;
4004
4005	if (nr_running)
4006		return load_avg / nr_running;
4007
4008	return 0;
4009}
4010
4011static void record_wakee(struct task_struct *p)
4012{
4013	/*
4014	 * Rough decay (wiping) for cost saving, don't worry
4015	 * about the boundary, really active task won't care
4016	 * about the loss.
4017	 */
4018	if (jiffies > current->wakee_flip_decay_ts + HZ) {
4019		current->wakee_flips = 0;
4020		current->wakee_flip_decay_ts = jiffies;
4021	}
4022
4023	if (current->last_wakee != p) {
4024		current->last_wakee = p;
4025		current->wakee_flips++;
4026	}
4027}
4028
4029static void task_waking_fair(struct task_struct *p)
4030{
4031	struct sched_entity *se = &p->se;
4032	struct cfs_rq *cfs_rq = cfs_rq_of(se);
4033	u64 min_vruntime;
4034
4035#ifndef CONFIG_64BIT
4036	u64 min_vruntime_copy;
4037
4038	do {
4039		min_vruntime_copy = cfs_rq->min_vruntime_copy;
4040		smp_rmb();
4041		min_vruntime = cfs_rq->min_vruntime;
4042	} while (min_vruntime != min_vruntime_copy);
4043#else
4044	min_vruntime = cfs_rq->min_vruntime;
4045#endif
4046
4047	se->vruntime -= min_vruntime;
4048	record_wakee(p);
4049}
4050
4051#ifdef CONFIG_FAIR_GROUP_SCHED
4052/*
4053 * effective_load() calculates the load change as seen from the root_task_group
4054 *
4055 * Adding load to a group doesn't make a group heavier, but can cause movement
4056 * of group shares between cpus. Assuming the shares were perfectly aligned one
4057 * can calculate the shift in shares.
4058 *
4059 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4060 * on this @cpu and results in a total addition (subtraction) of @wg to the
4061 * total group weight.
4062 *
4063 * Given a runqueue weight distribution (rw_i) we can compute a shares
4064 * distribution (s_i) using:
4065 *
4066 *   s_i = rw_i / \Sum rw_j						(1)
4067 *
4068 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4069 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4070 * shares distribution (s_i):
4071 *
4072 *   rw_i = {   2,   4,   1,   0 }
4073 *   s_i  = { 2/7, 4/7, 1/7,   0 }
4074 *
4075 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4076 * task used to run on and the CPU the waker is running on), we need to
4077 * compute the effect of waking a task on either CPU and, in case of a sync
4078 * wakeup, compute the effect of the current task going to sleep.
4079 *
4080 * So for a change of @wl to the local @cpu with an overall group weight change
4081 * of @wl we can compute the new shares distribution (s'_i) using:
4082 *
4083 *   s'_i = (rw_i + @wl) / (@wg + \Sum rw_j)				(2)
4084 *
4085 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4086 * differences in waking a task to CPU 0. The additional task changes the
4087 * weight and shares distributions like:
4088 *
4089 *   rw'_i = {   3,   4,   1,   0 }
4090 *   s'_i  = { 3/8, 4/8, 1/8,   0 }
4091 *
4092 * We can then compute the difference in effective weight by using:
4093 *
4094 *   dw_i = S * (s'_i - s_i)						(3)
4095 *
4096 * Where 'S' is the group weight as seen by its parent.
4097 *
4098 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4099 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4100 * 4/7) times the weight of the group.
4101 */
4102static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4103{
4104	struct sched_entity *se = tg->se[cpu];
4105
4106	if (!tg->parent)	/* the trivial, non-cgroup case */
4107		return wl;
4108
4109	for_each_sched_entity(se) {
4110		long w, W;
4111
4112		tg = se->my_q->tg;
4113
4114		/*
4115		 * W = @wg + \Sum rw_j
4116		 */
4117		W = wg + calc_tg_weight(tg, se->my_q);
4118
4119		/*
4120		 * w = rw_i + @wl
4121		 */
4122		w = se->my_q->load.weight + wl;
4123
4124		/*
4125		 * wl = S * s'_i; see (2)
4126		 */
4127		if (W > 0 && w < W)
4128			wl = (w * tg->shares) / W;
4129		else
4130			wl = tg->shares;
4131
4132		/*
4133		 * Per the above, wl is the new se->load.weight value; since
4134		 * those are clipped to [MIN_SHARES, ...) do so now. See
4135		 * calc_cfs_shares().
4136		 */
4137		if (wl < MIN_SHARES)
4138			wl = MIN_SHARES;
4139
4140		/*
4141		 * wl = dw_i = S * (s'_i - s_i); see (3)
4142		 */
4143		wl -= se->load.weight;
4144
4145		/*
4146		 * Recursively apply this logic to all parent groups to compute
4147		 * the final effective load change on the root group. Since
4148		 * only the @tg group gets extra weight, all parent groups can
4149		 * only redistribute existing shares. @wl is the shift in shares
4150		 * resulting from this level per the above.
4151		 */
4152		wg = 0;
4153	}
4154
4155	return wl;
4156}
4157#else
4158
4159static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4160{
4161	return wl;
4162}
4163
4164#endif
4165
 
 
 
 
 
 
 
 
 
 
 
 
4166static int wake_wide(struct task_struct *p)
4167{
 
 
4168	int factor = this_cpu_read(sd_llc_size);
4169
4170	/*
4171	 * Yeah, it's the switching-frequency, could means many wakee or
4172	 * rapidly switch, use factor here will just help to automatically
4173	 * adjust the loose-degree, so bigger node will lead to more pull.
4174	 */
4175	if (p->wakee_flips > factor) {
4176		/*
4177		 * wakee is somewhat hot, it needs certain amount of cpu
4178		 * resource, so if waker is far more hot, prefer to leave
4179		 * it alone.
4180		 */
4181		if (current->wakee_flips > (factor * p->wakee_flips))
4182			return 1;
4183	}
4184
4185	return 0;
4186}
4187
4188static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4189{
4190	s64 this_load, load;
 
4191	int idx, this_cpu, prev_cpu;
4192	unsigned long tl_per_task;
4193	struct task_group *tg;
4194	unsigned long weight;
4195	int balanced;
4196
4197	/*
4198	 * If we wake multiple tasks be careful to not bounce
4199	 * ourselves around too much.
4200	 */
4201	if (wake_wide(p))
4202		return 0;
4203
4204	idx	  = sd->wake_idx;
4205	this_cpu  = smp_processor_id();
4206	prev_cpu  = task_cpu(p);
4207	load	  = source_load(prev_cpu, idx);
4208	this_load = target_load(this_cpu, idx);
4209
4210	/*
4211	 * If sync wakeup then subtract the (maximum possible)
4212	 * effect of the currently running task from the load
4213	 * of the current CPU:
4214	 */
4215	if (sync) {
4216		tg = task_group(current);
4217		weight = current->se.load.weight;
4218
4219		this_load += effective_load(tg, this_cpu, -weight, -weight);
4220		load += effective_load(tg, prev_cpu, 0, -weight);
4221	}
4222
4223	tg = task_group(p);
4224	weight = p->se.load.weight;
4225
4226	/*
4227	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4228	 * due to the sync cause above having dropped this_load to 0, we'll
4229	 * always have an imbalance, but there's really nothing you can do
4230	 * about that, so that's good too.
4231	 *
4232	 * Otherwise check if either cpus are near enough in load to allow this
4233	 * task to be woken on this_cpu.
4234	 */
4235	if (this_load > 0) {
4236		s64 this_eff_load, prev_eff_load;
 
 
 
4237
4238		this_eff_load = 100;
4239		this_eff_load *= power_of(prev_cpu);
4240		this_eff_load *= this_load +
4241			effective_load(tg, this_cpu, weight, weight);
4242
4243		prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
4244		prev_eff_load *= power_of(this_cpu);
4245		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
 
4246
4247		balanced = this_eff_load <= prev_eff_load;
4248	} else
4249		balanced = true;
4250
4251	/*
4252	 * If the currently running task will sleep within
4253	 * a reasonable amount of time then attract this newly
4254	 * woken task:
4255	 */
4256	if (sync && balanced)
4257		return 1;
4258
4259	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4260	tl_per_task = cpu_avg_load_per_task(this_cpu);
4261
4262	if (balanced ||
4263	    (this_load <= load &&
4264	     this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
4265		/*
4266		 * This domain has SD_WAKE_AFFINE and
4267		 * p is cache cold in this domain, and
4268		 * there is no bad imbalance.
4269		 */
4270		schedstat_inc(sd, ttwu_move_affine);
4271		schedstat_inc(p, se.statistics.nr_wakeups_affine);
4272
4273		return 1;
4274	}
4275	return 0;
 
4276}
4277
4278/*
4279 * find_idlest_group finds and returns the least busy CPU group within the
4280 * domain.
4281 */
4282static struct sched_group *
4283find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4284		  int this_cpu, int sd_flag)
4285{
4286	struct sched_group *idlest = NULL, *group = sd->groups;
4287	unsigned long min_load = ULONG_MAX, this_load = 0;
4288	int load_idx = sd->forkexec_idx;
4289	int imbalance = 100 + (sd->imbalance_pct-100)/2;
4290
4291	if (sd_flag & SD_BALANCE_WAKE)
4292		load_idx = sd->wake_idx;
4293
4294	do {
4295		unsigned long load, avg_load;
4296		int local_group;
4297		int i;
4298
4299		/* Skip over this group if it has no CPUs allowed */
4300		if (!cpumask_intersects(sched_group_cpus(group),
4301					tsk_cpus_allowed(p)))
4302			continue;
4303
4304		local_group = cpumask_test_cpu(this_cpu,
4305					       sched_group_cpus(group));
4306
4307		/* Tally up the load of all CPUs in the group */
4308		avg_load = 0;
4309
4310		for_each_cpu(i, sched_group_cpus(group)) {
4311			/* Bias balancing toward cpus of our domain */
4312			if (local_group)
4313				load = source_load(i, load_idx);
4314			else
4315				load = target_load(i, load_idx);
4316
4317			avg_load += load;
4318		}
4319
4320		/* Adjust by relative CPU power of the group */
4321		avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power;
4322
4323		if (local_group) {
4324			this_load = avg_load;
4325		} else if (avg_load < min_load) {
4326			min_load = avg_load;
4327			idlest = group;
4328		}
4329	} while (group = group->next, group != sd->groups);
4330
4331	if (!idlest || 100*this_load < imbalance*min_load)
4332		return NULL;
4333	return idlest;
4334}
4335
4336/*
4337 * find_idlest_cpu - find the idlest cpu among the cpus in group.
4338 */
4339static int
4340find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
4341{
4342	unsigned long load, min_load = ULONG_MAX;
4343	int idlest = -1;
 
 
 
4344	int i;
4345
4346	/* Traverse only the allowed CPUs */
4347	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4348		load = weighted_cpuload(i);
4349
4350		if (load < min_load || (load == min_load && i == this_cpu)) {
4351			min_load = load;
4352			idlest = i;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4353		}
4354	}
4355
4356	return idlest;
4357}
4358
4359/*
4360 * Try and locate an idle CPU in the sched_domain.
4361 */
4362static int select_idle_sibling(struct task_struct *p, int target)
4363{
4364	struct sched_domain *sd;
4365	struct sched_group *sg;
4366	int i = task_cpu(p);
4367
4368	if (idle_cpu(target))
4369		return target;
4370
4371	/*
4372	 * If the prevous cpu is cache affine and idle, don't be stupid.
4373	 */
4374	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
4375		return i;
4376
4377	/*
4378	 * Otherwise, iterate the domains and find an elegible idle cpu.
 
 
 
 
 
 
 
 
 
 
 
 
4379	 */
4380	sd = rcu_dereference(per_cpu(sd_llc, target));
4381	for_each_lower_domain(sd) {
4382		sg = sd->groups;
4383		do {
4384			if (!cpumask_intersects(sched_group_cpus(sg),
4385						tsk_cpus_allowed(p)))
4386				goto next;
4387
 
4388			for_each_cpu(i, sched_group_cpus(sg)) {
4389				if (i == target || !idle_cpu(i))
4390					goto next;
4391			}
4392
 
 
 
 
4393			target = cpumask_first_and(sched_group_cpus(sg),
4394					tsk_cpus_allowed(p));
4395			goto done;
4396next:
4397			sg = sg->next;
4398		} while (sg != sd->groups);
4399	}
4400done:
4401	return target;
4402}
4403
4404/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4405 * select_task_rq_fair: Select target runqueue for the waking task in domains
4406 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
4407 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
4408 *
4409 * Balances load by selecting the idlest cpu in the idlest group, or under
4410 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
4411 *
4412 * Returns the target cpu number.
4413 *
4414 * preempt must be disabled.
4415 */
4416static int
4417select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
4418{
4419	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
4420	int cpu = smp_processor_id();
4421	int new_cpu = cpu;
4422	int want_affine = 0;
4423	int sync = wake_flags & WF_SYNC;
4424
4425	if (p->nr_cpus_allowed == 1)
4426		return prev_cpu;
4427
4428	if (sd_flag & SD_BALANCE_WAKE) {
4429		if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
4430			want_affine = 1;
4431		new_cpu = prev_cpu;
4432	}
4433
4434	rcu_read_lock();
4435	for_each_domain(cpu, tmp) {
4436		if (!(tmp->flags & SD_LOAD_BALANCE))
4437			continue;
4438
4439		/*
4440		 * If both cpu and prev_cpu are part of this domain,
4441		 * cpu is a valid SD_WAKE_AFFINE target.
4442		 */
4443		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
4444		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
4445			affine_sd = tmp;
4446			break;
4447		}
4448
4449		if (tmp->flags & sd_flag)
4450			sd = tmp;
 
 
4451	}
4452
4453	if (affine_sd) {
 
4454		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
4455			prev_cpu = cpu;
4456
4457		new_cpu = select_idle_sibling(p, prev_cpu);
4458		goto unlock;
4459	}
4460
4461	while (sd) {
 
 
 
 
4462		struct sched_group *group;
4463		int weight;
4464
4465		if (!(sd->flags & sd_flag)) {
4466			sd = sd->child;
4467			continue;
4468		}
4469
4470		group = find_idlest_group(sd, p, cpu, sd_flag);
4471		if (!group) {
4472			sd = sd->child;
4473			continue;
4474		}
4475
4476		new_cpu = find_idlest_cpu(group, p, cpu);
4477		if (new_cpu == -1 || new_cpu == cpu) {
4478			/* Now try balancing at a lower domain level of cpu */
4479			sd = sd->child;
4480			continue;
4481		}
4482
4483		/* Now try balancing at a lower domain level of new_cpu */
4484		cpu = new_cpu;
4485		weight = sd->span_weight;
4486		sd = NULL;
4487		for_each_domain(cpu, tmp) {
4488			if (weight <= tmp->span_weight)
4489				break;
4490			if (tmp->flags & sd_flag)
4491				sd = tmp;
4492		}
4493		/* while loop will break here if sd == NULL */
4494	}
4495unlock:
4496	rcu_read_unlock();
4497
4498	return new_cpu;
4499}
4500
4501/*
4502 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
4503 * cfs_rq_of(p) references at time of call are still valid and identify the
4504 * previous cpu.  However, the caller only guarantees p->pi_lock is held; no
4505 * other assumptions, including the state of rq->lock, should be made.
4506 */
4507static void
4508migrate_task_rq_fair(struct task_struct *p, int next_cpu)
4509{
4510	struct sched_entity *se = &p->se;
4511	struct cfs_rq *cfs_rq = cfs_rq_of(se);
4512
4513	/*
4514	 * Load tracking: accumulate removed load so that it can be processed
4515	 * when we next update owning cfs_rq under rq->lock.  Tasks contribute
4516	 * to blocked load iff they have a positive decay-count.  It can never
4517	 * be negative here since on-rq tasks have decay-count == 0.
4518	 */
4519	if (se->avg.decay_count) {
4520		se->avg.decay_count = -__synchronize_entity_decay(se);
4521		atomic_long_add(se->avg.load_avg_contrib,
4522						&cfs_rq->removed_load);
4523	}
 
 
 
 
 
 
 
 
4524}
4525#endif /* CONFIG_SMP */
4526
4527static unsigned long
4528wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
4529{
4530	unsigned long gran = sysctl_sched_wakeup_granularity;
4531
4532	/*
4533	 * Since its curr running now, convert the gran from real-time
4534	 * to virtual-time in his units.
4535	 *
4536	 * By using 'se' instead of 'curr' we penalize light tasks, so
4537	 * they get preempted easier. That is, if 'se' < 'curr' then
4538	 * the resulting gran will be larger, therefore penalizing the
4539	 * lighter, if otoh 'se' > 'curr' then the resulting gran will
4540	 * be smaller, again penalizing the lighter task.
4541	 *
4542	 * This is especially important for buddies when the leftmost
4543	 * task is higher priority than the buddy.
4544	 */
4545	return calc_delta_fair(gran, se);
4546}
4547
4548/*
4549 * Should 'se' preempt 'curr'.
4550 *
4551 *             |s1
4552 *        |s2
4553 *   |s3
4554 *         g
4555 *      |<--->|c
4556 *
4557 *  w(c, s1) = -1
4558 *  w(c, s2) =  0
4559 *  w(c, s3) =  1
4560 *
4561 */
4562static int
4563wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
4564{
4565	s64 gran, vdiff = curr->vruntime - se->vruntime;
4566
4567	if (vdiff <= 0)
4568		return -1;
4569
4570	gran = wakeup_gran(curr, se);
4571	if (vdiff > gran)
4572		return 1;
4573
4574	return 0;
4575}
4576
4577static void set_last_buddy(struct sched_entity *se)
4578{
4579	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
4580		return;
4581
4582	for_each_sched_entity(se)
4583		cfs_rq_of(se)->last = se;
4584}
4585
4586static void set_next_buddy(struct sched_entity *se)
4587{
4588	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
4589		return;
4590
4591	for_each_sched_entity(se)
4592		cfs_rq_of(se)->next = se;
4593}
4594
4595static void set_skip_buddy(struct sched_entity *se)
4596{
4597	for_each_sched_entity(se)
4598		cfs_rq_of(se)->skip = se;
4599}
4600
4601/*
4602 * Preempt the current task with a newly woken task if needed:
4603 */
4604static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
4605{
4606	struct task_struct *curr = rq->curr;
4607	struct sched_entity *se = &curr->se, *pse = &p->se;
4608	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
4609	int scale = cfs_rq->nr_running >= sched_nr_latency;
4610	int next_buddy_marked = 0;
4611
4612	if (unlikely(se == pse))
4613		return;
4614
4615	/*
4616	 * This is possible from callers such as move_task(), in which we
4617	 * unconditionally check_prempt_curr() after an enqueue (which may have
4618	 * lead to a throttle).  This both saves work and prevents false
4619	 * next-buddy nomination below.
4620	 */
4621	if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
4622		return;
4623
4624	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
4625		set_next_buddy(pse);
4626		next_buddy_marked = 1;
4627	}
4628
4629	/*
4630	 * We can come here with TIF_NEED_RESCHED already set from new task
4631	 * wake up path.
4632	 *
4633	 * Note: this also catches the edge-case of curr being in a throttled
4634	 * group (e.g. via set_curr_task), since update_curr() (in the
4635	 * enqueue of curr) will have resulted in resched being set.  This
4636	 * prevents us from potentially nominating it as a false LAST_BUDDY
4637	 * below.
4638	 */
4639	if (test_tsk_need_resched(curr))
4640		return;
4641
4642	/* Idle tasks are by definition preempted by non-idle tasks. */
4643	if (unlikely(curr->policy == SCHED_IDLE) &&
4644	    likely(p->policy != SCHED_IDLE))
4645		goto preempt;
4646
4647	/*
4648	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
4649	 * is driven by the tick):
4650	 */
4651	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
4652		return;
4653
4654	find_matching_se(&se, &pse);
4655	update_curr(cfs_rq_of(se));
4656	BUG_ON(!pse);
4657	if (wakeup_preempt_entity(se, pse) == 1) {
4658		/*
4659		 * Bias pick_next to pick the sched entity that is
4660		 * triggering this preemption.
4661		 */
4662		if (!next_buddy_marked)
4663			set_next_buddy(pse);
4664		goto preempt;
4665	}
4666
4667	return;
4668
4669preempt:
4670	resched_task(curr);
4671	/*
4672	 * Only set the backward buddy when the current task is still
4673	 * on the rq. This can happen when a wakeup gets interleaved
4674	 * with schedule on the ->pre_schedule() or idle_balance()
4675	 * point, either of which can * drop the rq lock.
4676	 *
4677	 * Also, during early boot the idle thread is in the fair class,
4678	 * for obvious reasons its a bad idea to schedule back to it.
4679	 */
4680	if (unlikely(!se->on_rq || curr == rq->idle))
4681		return;
4682
4683	if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
4684		set_last_buddy(se);
4685}
4686
4687static struct task_struct *
4688pick_next_task_fair(struct rq *rq, struct task_struct *prev)
4689{
4690	struct cfs_rq *cfs_rq = &rq->cfs;
4691	struct sched_entity *se;
4692	struct task_struct *p;
4693	int new_tasks;
4694
4695again:
4696#ifdef CONFIG_FAIR_GROUP_SCHED
4697	if (!cfs_rq->nr_running)
4698		goto idle;
4699
4700	if (prev->sched_class != &fair_sched_class)
4701		goto simple;
4702
4703	/*
4704	 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
4705	 * likely that a next task is from the same cgroup as the current.
4706	 *
4707	 * Therefore attempt to avoid putting and setting the entire cgroup
4708	 * hierarchy, only change the part that actually changes.
4709	 */
4710
4711	do {
4712		struct sched_entity *curr = cfs_rq->curr;
4713
4714		/*
4715		 * Since we got here without doing put_prev_entity() we also
4716		 * have to consider cfs_rq->curr. If it is still a runnable
4717		 * entity, update_curr() will update its vruntime, otherwise
4718		 * forget we've ever seen it.
4719		 */
4720		if (curr && curr->on_rq)
4721			update_curr(cfs_rq);
4722		else
4723			curr = NULL;
 
4724
4725		/*
4726		 * This call to check_cfs_rq_runtime() will do the throttle and
4727		 * dequeue its entity in the parent(s). Therefore the 'simple'
4728		 * nr_running test will indeed be correct.
4729		 */
4730		if (unlikely(check_cfs_rq_runtime(cfs_rq)))
4731			goto simple;
 
 
4732
4733		se = pick_next_entity(cfs_rq, curr);
4734		cfs_rq = group_cfs_rq(se);
4735	} while (cfs_rq);
4736
4737	p = task_of(se);
4738
4739	/*
4740	 * Since we haven't yet done put_prev_entity and if the selected task
4741	 * is a different task than we started out with, try and touch the
4742	 * least amount of cfs_rqs.
4743	 */
4744	if (prev != p) {
4745		struct sched_entity *pse = &prev->se;
4746
4747		while (!(cfs_rq = is_same_group(se, pse))) {
4748			int se_depth = se->depth;
4749			int pse_depth = pse->depth;
4750
4751			if (se_depth <= pse_depth) {
4752				put_prev_entity(cfs_rq_of(pse), pse);
4753				pse = parent_entity(pse);
4754			}
4755			if (se_depth >= pse_depth) {
4756				set_next_entity(cfs_rq_of(se), se);
4757				se = parent_entity(se);
4758			}
4759		}
4760
4761		put_prev_entity(cfs_rq, pse);
4762		set_next_entity(cfs_rq, se);
4763	}
4764
4765	if (hrtick_enabled(rq))
4766		hrtick_start_fair(rq, p);
4767
4768	return p;
4769simple:
4770	cfs_rq = &rq->cfs;
4771#endif
4772
4773	if (!cfs_rq->nr_running)
4774		goto idle;
4775
4776	put_prev_task(rq, prev);
4777
4778	do {
4779		se = pick_next_entity(cfs_rq, NULL);
4780		set_next_entity(cfs_rq, se);
4781		cfs_rq = group_cfs_rq(se);
4782	} while (cfs_rq);
4783
4784	p = task_of(se);
4785
4786	if (hrtick_enabled(rq))
4787		hrtick_start_fair(rq, p);
4788
4789	return p;
4790
4791idle:
 
 
 
 
 
 
 
4792	new_tasks = idle_balance(rq);
 
4793	/*
4794	 * Because idle_balance() releases (and re-acquires) rq->lock, it is
4795	 * possible for any higher priority task to appear. In that case we
4796	 * must re-start the pick_next_entity() loop.
4797	 */
4798	if (new_tasks < 0)
4799		return RETRY_TASK;
4800
4801	if (new_tasks > 0)
4802		goto again;
4803
4804	return NULL;
4805}
4806
4807/*
4808 * Account for a descheduled task:
4809 */
4810static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
4811{
4812	struct sched_entity *se = &prev->se;
4813	struct cfs_rq *cfs_rq;
4814
4815	for_each_sched_entity(se) {
4816		cfs_rq = cfs_rq_of(se);
4817		put_prev_entity(cfs_rq, se);
4818	}
4819}
4820
4821/*
4822 * sched_yield() is very simple
4823 *
4824 * The magic of dealing with the ->skip buddy is in pick_next_entity.
4825 */
4826static void yield_task_fair(struct rq *rq)
4827{
4828	struct task_struct *curr = rq->curr;
4829	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
4830	struct sched_entity *se = &curr->se;
4831
4832	/*
4833	 * Are we the only task in the tree?
4834	 */
4835	if (unlikely(rq->nr_running == 1))
4836		return;
4837
4838	clear_buddies(cfs_rq, se);
4839
4840	if (curr->policy != SCHED_BATCH) {
4841		update_rq_clock(rq);
4842		/*
4843		 * Update run-time statistics of the 'current'.
4844		 */
4845		update_curr(cfs_rq);
4846		/*
4847		 * Tell update_rq_clock() that we've just updated,
4848		 * so we don't do microscopic update in schedule()
4849		 * and double the fastpath cost.
4850		 */
4851		 rq->skip_clock_update = 1;
4852	}
4853
4854	set_skip_buddy(se);
4855}
4856
4857static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
4858{
4859	struct sched_entity *se = &p->se;
4860
4861	/* throttled hierarchies are not runnable */
4862	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
4863		return false;
4864
4865	/* Tell the scheduler that we'd really like pse to run next. */
4866	set_next_buddy(se);
4867
4868	yield_task_fair(rq);
4869
4870	return true;
4871}
4872
4873#ifdef CONFIG_SMP
4874/**************************************************
4875 * Fair scheduling class load-balancing methods.
4876 *
4877 * BASICS
4878 *
4879 * The purpose of load-balancing is to achieve the same basic fairness the
4880 * per-cpu scheduler provides, namely provide a proportional amount of compute
4881 * time to each task. This is expressed in the following equation:
4882 *
4883 *   W_i,n/P_i == W_j,n/P_j for all i,j                               (1)
4884 *
4885 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
4886 * W_i,0 is defined as:
4887 *
4888 *   W_i,0 = \Sum_j w_i,j                                             (2)
4889 *
4890 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
4891 * is derived from the nice value as per prio_to_weight[].
4892 *
4893 * The weight average is an exponential decay average of the instantaneous
4894 * weight:
4895 *
4896 *   W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0               (3)
4897 *
4898 * P_i is the cpu power (or compute capacity) of cpu i, typically it is the
4899 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
4900 * can also include other factors [XXX].
4901 *
4902 * To achieve this balance we define a measure of imbalance which follows
4903 * directly from (1):
4904 *
4905 *   imb_i,j = max{ avg(W/P), W_i/P_i } - min{ avg(W/P), W_j/P_j }    (4)
4906 *
4907 * We them move tasks around to minimize the imbalance. In the continuous
4908 * function space it is obvious this converges, in the discrete case we get
4909 * a few fun cases generally called infeasible weight scenarios.
4910 *
4911 * [XXX expand on:
4912 *     - infeasible weights;
4913 *     - local vs global optima in the discrete case. ]
4914 *
4915 *
4916 * SCHED DOMAINS
4917 *
4918 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
4919 * for all i,j solution, we create a tree of cpus that follows the hardware
4920 * topology where each level pairs two lower groups (or better). This results
4921 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
4922 * tree to only the first of the previous level and we decrease the frequency
4923 * of load-balance at each level inv. proportional to the number of cpus in
4924 * the groups.
4925 *
4926 * This yields:
4927 *
4928 *     log_2 n     1     n
4929 *   \Sum       { --- * --- * 2^i } = O(n)                            (5)
4930 *     i = 0      2^i   2^i
4931 *                               `- size of each group
4932 *         |         |     `- number of cpus doing load-balance
4933 *         |         `- freq
4934 *         `- sum over all levels
4935 *
4936 * Coupled with a limit on how many tasks we can migrate every balance pass,
4937 * this makes (5) the runtime complexity of the balancer.
4938 *
4939 * An important property here is that each CPU is still (indirectly) connected
4940 * to every other cpu in at most O(log n) steps:
4941 *
4942 * The adjacency matrix of the resulting graph is given by:
4943 *
4944 *             log_2 n     
4945 *   A_i,j = \Union     (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1)  (6)
4946 *             k = 0
4947 *
4948 * And you'll find that:
4949 *
4950 *   A^(log_2 n)_i,j != 0  for all i,j                                (7)
4951 *
4952 * Showing there's indeed a path between every cpu in at most O(log n) steps.
4953 * The task movement gives a factor of O(m), giving a convergence complexity
4954 * of:
4955 *
4956 *   O(nm log n),  n := nr_cpus, m := nr_tasks                        (8)
4957 *
4958 *
4959 * WORK CONSERVING
4960 *
4961 * In order to avoid CPUs going idle while there's still work to do, new idle
4962 * balancing is more aggressive and has the newly idle cpu iterate up the domain
4963 * tree itself instead of relying on other CPUs to bring it work.
4964 *
4965 * This adds some complexity to both (5) and (8) but it reduces the total idle
4966 * time.
4967 *
4968 * [XXX more?]
4969 *
4970 *
4971 * CGROUPS
4972 *
4973 * Cgroups make a horror show out of (2), instead of a simple sum we get:
4974 *
4975 *                                s_k,i
4976 *   W_i,0 = \Sum_j \Prod_k w_k * -----                               (9)
4977 *                                 S_k
4978 *
4979 * Where
4980 *
4981 *   s_k,i = \Sum_j w_i,j,k  and  S_k = \Sum_i s_k,i                 (10)
4982 *
4983 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
4984 *
4985 * The big problem is S_k, its a global sum needed to compute a local (W_i)
4986 * property.
4987 *
4988 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
4989 *      rewrite all of this once again.]
4990 */ 
4991
4992static unsigned long __read_mostly max_load_balance_interval = HZ/10;
4993
4994enum fbq_type { regular, remote, all };
4995
4996#define LBF_ALL_PINNED	0x01
4997#define LBF_NEED_BREAK	0x02
4998#define LBF_DST_PINNED  0x04
4999#define LBF_SOME_PINNED	0x08
5000
5001struct lb_env {
5002	struct sched_domain	*sd;
5003
5004	struct rq		*src_rq;
5005	int			src_cpu;
5006
5007	int			dst_cpu;
5008	struct rq		*dst_rq;
5009
5010	struct cpumask		*dst_grpmask;
5011	int			new_dst_cpu;
5012	enum cpu_idle_type	idle;
5013	long			imbalance;
5014	/* The set of CPUs under consideration for load-balancing */
5015	struct cpumask		*cpus;
5016
5017	unsigned int		flags;
5018
5019	unsigned int		loop;
5020	unsigned int		loop_break;
5021	unsigned int		loop_max;
5022
5023	enum fbq_type		fbq_type;
 
5024};
5025
5026/*
5027 * move_task - move a task from one runqueue to another runqueue.
5028 * Both runqueues must be locked.
5029 */
5030static void move_task(struct task_struct *p, struct lb_env *env)
5031{
5032	deactivate_task(env->src_rq, p, 0);
5033	set_task_cpu(p, env->dst_cpu);
5034	activate_task(env->dst_rq, p, 0);
5035	check_preempt_curr(env->dst_rq, p, 0);
5036}
5037
5038/*
5039 * Is this task likely cache-hot:
5040 */
5041static int
5042task_hot(struct task_struct *p, u64 now)
5043{
5044	s64 delta;
5045
 
 
5046	if (p->sched_class != &fair_sched_class)
5047		return 0;
5048
5049	if (unlikely(p->policy == SCHED_IDLE))
5050		return 0;
5051
5052	/*
5053	 * Buddy candidates are cache hot:
5054	 */
5055	if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running &&
5056			(&p->se == cfs_rq_of(&p->se)->next ||
5057			 &p->se == cfs_rq_of(&p->se)->last))
5058		return 1;
5059
5060	if (sysctl_sched_migration_cost == -1)
5061		return 1;
5062	if (sysctl_sched_migration_cost == 0)
5063		return 0;
5064
5065	delta = now - p->se.exec_start;
5066
5067	return delta < (s64)sysctl_sched_migration_cost;
5068}
5069
5070#ifdef CONFIG_NUMA_BALANCING
5071/* Returns true if the destination node has incurred more faults */
5072static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
5073{
5074	int src_nid, dst_nid;
5075
5076	if (!sched_feat(NUMA_FAVOUR_HIGHER) || !p->numa_faults_memory ||
5077	    !(env->sd->flags & SD_NUMA)) {
5078		return false;
5079	}
5080
5081	src_nid = cpu_to_node(env->src_cpu);
5082	dst_nid = cpu_to_node(env->dst_cpu);
5083
5084	if (src_nid == dst_nid)
5085		return false;
5086
5087	/* Always encourage migration to the preferred node. */
5088	if (dst_nid == p->numa_preferred_nid)
5089		return true;
5090
5091	/* If both task and group weight improve, this move is a winner. */
5092	if (task_weight(p, dst_nid) > task_weight(p, src_nid) &&
5093	    group_weight(p, dst_nid) > group_weight(p, src_nid))
5094		return true;
5095
5096	return false;
5097}
5098
5099
5100static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5101{
 
 
5102	int src_nid, dst_nid;
5103
5104	if (!sched_feat(NUMA) || !sched_feat(NUMA_RESIST_LOWER))
5105		return false;
5106
5107	if (!p->numa_faults_memory || !(env->sd->flags & SD_NUMA))
5108		return false;
5109
5110	src_nid = cpu_to_node(env->src_cpu);
5111	dst_nid = cpu_to_node(env->dst_cpu);
5112
5113	if (src_nid == dst_nid)
5114		return false;
5115
5116	/* Migrating away from the preferred node is always bad. */
5117	if (src_nid == p->numa_preferred_nid)
5118		return true;
 
 
 
 
5119
5120	/* If either task or group weight get worse, don't do it. */
5121	if (task_weight(p, dst_nid) < task_weight(p, src_nid) ||
5122	    group_weight(p, dst_nid) < group_weight(p, src_nid))
5123		return true;
5124
5125	return false;
5126}
 
 
 
 
 
5127
5128#else
5129static inline bool migrate_improves_locality(struct task_struct *p,
5130					     struct lb_env *env)
5131{
5132	return false;
5133}
5134
5135static inline bool migrate_degrades_locality(struct task_struct *p,
 
5136					     struct lb_env *env)
5137{
5138	return false;
5139}
5140#endif
5141
5142/*
5143 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
5144 */
5145static
5146int can_migrate_task(struct task_struct *p, struct lb_env *env)
5147{
5148	int tsk_cache_hot = 0;
 
 
 
5149	/*
5150	 * We do not migrate tasks that are:
5151	 * 1) throttled_lb_pair, or
5152	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5153	 * 3) running (obviously), or
5154	 * 4) are cache-hot on their current CPU.
5155	 */
5156	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
5157		return 0;
5158
5159	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5160		int cpu;
5161
5162		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5163
5164		env->flags |= LBF_SOME_PINNED;
5165
5166		/*
5167		 * Remember if this task can be migrated to any other cpu in
5168		 * our sched_group. We may want to revisit it if we couldn't
5169		 * meet load balance goals by pulling other tasks on src_cpu.
5170		 *
5171		 * Also avoid computing new_dst_cpu if we have already computed
5172		 * one in current iteration.
5173		 */
5174		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5175			return 0;
5176
5177		/* Prevent to re-select dst_cpu via env's cpus */
5178		for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
5179			if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
5180				env->flags |= LBF_DST_PINNED;
5181				env->new_dst_cpu = cpu;
5182				break;
5183			}
5184		}
5185
5186		return 0;
5187	}
5188
5189	/* Record that we found atleast one task that could run on dst_cpu */
5190	env->flags &= ~LBF_ALL_PINNED;
5191
5192	if (task_running(env->src_rq, p)) {
5193		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5194		return 0;
5195	}
5196
5197	/*
5198	 * Aggressive migration if:
5199	 * 1) destination numa is preferred
5200	 * 2) task is cache cold, or
5201	 * 3) too many balance attempts have failed.
5202	 */
5203	tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq));
5204	if (!tsk_cache_hot)
5205		tsk_cache_hot = migrate_degrades_locality(p, env);
5206
5207	if (migrate_improves_locality(p, env)) {
5208#ifdef CONFIG_SCHEDSTATS
5209		if (tsk_cache_hot) {
5210			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
5211			schedstat_inc(p, se.statistics.nr_forced_migrations);
5212		}
5213#endif
5214		return 1;
5215	}
5216
5217	if (!tsk_cache_hot ||
5218		env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5219
5220		if (tsk_cache_hot) {
5221			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
5222			schedstat_inc(p, se.statistics.nr_forced_migrations);
5223		}
5224
5225		return 1;
5226	}
5227
5228	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
5229	return 0;
5230}
5231
5232/*
5233 * move_one_task tries to move exactly one task from busiest to this_rq, as
 
 
 
 
 
 
 
 
 
 
 
 
5234 * part of active balancing operations within "domain".
5235 * Returns 1 if successful and 0 otherwise.
5236 *
5237 * Called with both runqueues locked.
5238 */
5239static int move_one_task(struct lb_env *env)
5240{
5241	struct task_struct *p, *n;
5242
 
 
5243	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
5244		if (!can_migrate_task(p, env))
5245			continue;
5246
5247		move_task(p, env);
 
5248		/*
5249		 * Right now, this is only the second place move_task()
5250		 * is called, so we can safely collect move_task()
5251		 * stats here rather than inside move_task().
 
5252		 */
5253		schedstat_inc(env->sd, lb_gained[env->idle]);
5254		return 1;
5255	}
5256	return 0;
5257}
5258
5259static const unsigned int sched_nr_migrate_break = 32;
5260
5261/*
5262 * move_tasks tries to move up to imbalance weighted load from busiest to
5263 * this_rq, as part of a balancing operation within domain "sd".
5264 * Returns 1 if successful and 0 otherwise.
5265 *
5266 * Called with both runqueues locked.
5267 */
5268static int move_tasks(struct lb_env *env)
5269{
5270	struct list_head *tasks = &env->src_rq->cfs_tasks;
5271	struct task_struct *p;
5272	unsigned long load;
5273	int pulled = 0;
 
 
5274
5275	if (env->imbalance <= 0)
5276		return 0;
5277
5278	while (!list_empty(tasks)) {
 
 
 
 
 
 
 
5279		p = list_first_entry(tasks, struct task_struct, se.group_node);
5280
5281		env->loop++;
5282		/* We've more or less seen every task there is, call it quits */
5283		if (env->loop > env->loop_max)
5284			break;
5285
5286		/* take a breather every nr_migrate tasks */
5287		if (env->loop > env->loop_break) {
5288			env->loop_break += sched_nr_migrate_break;
5289			env->flags |= LBF_NEED_BREAK;
5290			break;
5291		}
5292
5293		if (!can_migrate_task(p, env))
5294			goto next;
5295
5296		load = task_h_load(p);
5297
5298		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5299			goto next;
5300
5301		if ((load / 2) > env->imbalance)
5302			goto next;
5303
5304		move_task(p, env);
5305		pulled++;
 
 
5306		env->imbalance -= load;
5307
5308#ifdef CONFIG_PREEMPT
5309		/*
5310		 * NEWIDLE balancing is a source of latency, so preemptible
5311		 * kernels will stop after the first task is pulled to minimize
5312		 * the critical section.
5313		 */
5314		if (env->idle == CPU_NEWLY_IDLE)
5315			break;
5316#endif
5317
5318		/*
5319		 * We only want to steal up to the prescribed amount of
5320		 * weighted load.
5321		 */
5322		if (env->imbalance <= 0)
5323			break;
5324
5325		continue;
5326next:
5327		list_move_tail(&p->se.group_node, tasks);
5328	}
5329
5330	/*
5331	 * Right now, this is one of only two places move_task() is called,
5332	 * so we can safely collect move_task() stats here rather than
5333	 * inside move_task().
5334	 */
5335	schedstat_add(env->sd, lb_gained[env->idle], pulled);
5336
5337	return pulled;
5338}
5339
5340#ifdef CONFIG_FAIR_GROUP_SCHED
5341/*
5342 * update tg->load_weight by folding this cpu's load_avg
5343 */
5344static void __update_blocked_averages_cpu(struct task_group *tg, int cpu)
5345{
5346	struct sched_entity *se = tg->se[cpu];
5347	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu];
5348
5349	/* throttled entities do not contribute to load */
5350	if (throttled_hierarchy(cfs_rq))
5351		return;
 
 
5352
5353	update_cfs_rq_blocked_load(cfs_rq, 1);
 
 
 
 
 
 
 
 
 
5354
5355	if (se) {
5356		update_entity_load_avg(se, 1);
5357		/*
5358		 * We pivot on our runnable average having decayed to zero for
5359		 * list removal.  This generally implies that all our children
5360		 * have also been removed (modulo rounding error or bandwidth
5361		 * control); however, such cases are rare and we can fix these
5362		 * at enqueue.
5363		 *
5364		 * TODO: fix up out-of-order children on enqueue.
5365		 */
5366		if (!se->avg.runnable_avg_sum && !cfs_rq->nr_running)
5367			list_del_leaf_cfs_rq(cfs_rq);
5368	} else {
5369		struct rq *rq = rq_of(cfs_rq);
5370		update_rq_runnable_avg(rq, rq->nr_running);
5371	}
 
 
5372}
5373
 
5374static void update_blocked_averages(int cpu)
5375{
5376	struct rq *rq = cpu_rq(cpu);
5377	struct cfs_rq *cfs_rq;
5378	unsigned long flags;
5379
5380	raw_spin_lock_irqsave(&rq->lock, flags);
5381	update_rq_clock(rq);
 
5382	/*
5383	 * Iterates the task_group tree in a bottom up fashion, see
5384	 * list_add_leaf_cfs_rq() for details.
5385	 */
5386	for_each_leaf_cfs_rq(rq, cfs_rq) {
5387		/*
5388		 * Note: We may want to consider periodically releasing
5389		 * rq->lock about these updates so that creating many task
5390		 * groups does not result in continually extending hold time.
5391		 */
5392		__update_blocked_averages_cpu(cfs_rq->tg, rq->cpu);
5393	}
5394
 
 
 
5395	raw_spin_unlock_irqrestore(&rq->lock, flags);
5396}
5397
5398/*
5399 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5400 * This needs to be done in a top-down fashion because the load of a child
5401 * group is a fraction of its parents load.
5402 */
5403static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
5404{
5405	struct rq *rq = rq_of(cfs_rq);
5406	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
5407	unsigned long now = jiffies;
5408	unsigned long load;
5409
5410	if (cfs_rq->last_h_load_update == now)
5411		return;
5412
5413	cfs_rq->h_load_next = NULL;
5414	for_each_sched_entity(se) {
5415		cfs_rq = cfs_rq_of(se);
5416		cfs_rq->h_load_next = se;
5417		if (cfs_rq->last_h_load_update == now)
5418			break;
5419	}
5420
5421	if (!se) {
5422		cfs_rq->h_load = cfs_rq->runnable_load_avg;
5423		cfs_rq->last_h_load_update = now;
5424	}
5425
5426	while ((se = cfs_rq->h_load_next) != NULL) {
5427		load = cfs_rq->h_load;
5428		load = div64_ul(load * se->avg.load_avg_contrib,
5429				cfs_rq->runnable_load_avg + 1);
5430		cfs_rq = group_cfs_rq(se);
5431		cfs_rq->h_load = load;
5432		cfs_rq->last_h_load_update = now;
5433	}
5434}
5435
5436static unsigned long task_h_load(struct task_struct *p)
5437{
5438	struct cfs_rq *cfs_rq = task_cfs_rq(p);
5439
5440	update_cfs_rq_h_load(cfs_rq);
5441	return div64_ul(p->se.avg.load_avg_contrib * cfs_rq->h_load,
5442			cfs_rq->runnable_load_avg + 1);
5443}
5444#else
5445static inline void update_blocked_averages(int cpu)
5446{
 
 
 
 
 
 
 
 
5447}
5448
5449static unsigned long task_h_load(struct task_struct *p)
5450{
5451	return p->se.avg.load_avg_contrib;
5452}
5453#endif
5454
5455/********** Helpers for find_busiest_group ************************/
 
 
 
 
 
 
 
5456/*
5457 * sg_lb_stats - stats of a sched_group required for load_balancing
5458 */
5459struct sg_lb_stats {
5460	unsigned long avg_load; /*Avg load across the CPUs of the group */
5461	unsigned long group_load; /* Total load over the CPUs of the group */
5462	unsigned long sum_weighted_load; /* Weighted load of group's tasks */
5463	unsigned long load_per_task;
5464	unsigned long group_power;
 
5465	unsigned int sum_nr_running; /* Nr tasks running in the group */
5466	unsigned int group_capacity;
5467	unsigned int idle_cpus;
5468	unsigned int group_weight;
5469	int group_imb; /* Is there an imbalance in the group ? */
5470	int group_has_capacity; /* Is there extra capacity in the group? */
5471#ifdef CONFIG_NUMA_BALANCING
5472	unsigned int nr_numa_running;
5473	unsigned int nr_preferred_running;
5474#endif
5475};
5476
5477/*
5478 * sd_lb_stats - Structure to store the statistics of a sched_domain
5479 *		 during load balancing.
5480 */
5481struct sd_lb_stats {
5482	struct sched_group *busiest;	/* Busiest group in this sd */
5483	struct sched_group *local;	/* Local group in this sd */
5484	unsigned long total_load;	/* Total load of all groups in sd */
5485	unsigned long total_pwr;	/* Total power of all groups in sd */
5486	unsigned long avg_load;	/* Average load across all groups in sd */
5487
5488	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
5489	struct sg_lb_stats local_stat;	/* Statistics of the local group */
5490};
5491
5492static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
5493{
5494	/*
5495	 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
5496	 * local_stat because update_sg_lb_stats() does a full clear/assignment.
5497	 * We must however clear busiest_stat::avg_load because
5498	 * update_sd_pick_busiest() reads this before assignment.
5499	 */
5500	*sds = (struct sd_lb_stats){
5501		.busiest = NULL,
5502		.local = NULL,
5503		.total_load = 0UL,
5504		.total_pwr = 0UL,
5505		.busiest_stat = {
5506			.avg_load = 0UL,
 
 
5507		},
5508	};
5509}
5510
5511/**
5512 * get_sd_load_idx - Obtain the load index for a given sched domain.
5513 * @sd: The sched_domain whose load_idx is to be obtained.
5514 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
5515 *
5516 * Return: The load index.
5517 */
5518static inline int get_sd_load_idx(struct sched_domain *sd,
5519					enum cpu_idle_type idle)
5520{
5521	int load_idx;
5522
5523	switch (idle) {
5524	case CPU_NOT_IDLE:
5525		load_idx = sd->busy_idx;
5526		break;
5527
5528	case CPU_NEWLY_IDLE:
5529		load_idx = sd->newidle_idx;
5530		break;
5531	default:
5532		load_idx = sd->idle_idx;
5533		break;
5534	}
5535
5536	return load_idx;
5537}
5538
5539static unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
5540{
5541	return SCHED_POWER_SCALE;
5542}
5543
5544unsigned long __weak arch_scale_freq_power(struct sched_domain *sd, int cpu)
5545{
5546	return default_scale_freq_power(sd, cpu);
5547}
5548
5549static unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
5550{
5551	unsigned long weight = sd->span_weight;
5552	unsigned long smt_gain = sd->smt_gain;
5553
5554	smt_gain /= weight;
5555
5556	return smt_gain;
5557}
5558
5559unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu)
5560{
5561	return default_scale_smt_power(sd, cpu);
5562}
5563
5564static unsigned long scale_rt_power(int cpu)
5565{
5566	struct rq *rq = cpu_rq(cpu);
5567	u64 total, available, age_stamp, avg;
 
5568
5569	/*
5570	 * Since we're reading these variables without serialization make sure
5571	 * we read them once before doing sanity checks on them.
5572	 */
5573	age_stamp = ACCESS_ONCE(rq->age_stamp);
5574	avg = ACCESS_ONCE(rq->rt_avg);
 
5575
5576	total = sched_avg_period() + (rq_clock(rq) - age_stamp);
 
5577
5578	if (unlikely(total < avg)) {
5579		/* Ensures that power won't end up being negative */
5580		available = 0;
5581	} else {
5582		available = total - avg;
5583	}
5584
5585	if (unlikely((s64)total < SCHED_POWER_SCALE))
5586		total = SCHED_POWER_SCALE;
5587
5588	total >>= SCHED_POWER_SHIFT;
 
5589
5590	return div_u64(available, total);
5591}
5592
5593static void update_cpu_power(struct sched_domain *sd, int cpu)
5594{
5595	unsigned long weight = sd->span_weight;
5596	unsigned long power = SCHED_POWER_SCALE;
5597	struct sched_group *sdg = sd->groups;
5598
5599	if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
5600		if (sched_feat(ARCH_POWER))
5601			power *= arch_scale_smt_power(sd, cpu);
5602		else
5603			power *= default_scale_smt_power(sd, cpu);
5604
5605		power >>= SCHED_POWER_SHIFT;
5606	}
5607
5608	sdg->sgp->power_orig = power;
5609
5610	if (sched_feat(ARCH_POWER))
5611		power *= arch_scale_freq_power(sd, cpu);
5612	else
5613		power *= default_scale_freq_power(sd, cpu);
5614
5615	power >>= SCHED_POWER_SHIFT;
5616
5617	power *= scale_rt_power(cpu);
5618	power >>= SCHED_POWER_SHIFT;
5619
5620	if (!power)
5621		power = 1;
5622
5623	cpu_rq(cpu)->cpu_power = power;
5624	sdg->sgp->power = power;
5625}
5626
5627void update_group_power(struct sched_domain *sd, int cpu)
5628{
5629	struct sched_domain *child = sd->child;
5630	struct sched_group *group, *sdg = sd->groups;
5631	unsigned long power, power_orig;
5632	unsigned long interval;
5633
5634	interval = msecs_to_jiffies(sd->balance_interval);
5635	interval = clamp(interval, 1UL, max_load_balance_interval);
5636	sdg->sgp->next_update = jiffies + interval;
5637
5638	if (!child) {
5639		update_cpu_power(sd, cpu);
5640		return;
5641	}
5642
5643	power_orig = power = 0;
5644
5645	if (child->flags & SD_OVERLAP) {
5646		/*
5647		 * SD_OVERLAP domains cannot assume that child groups
5648		 * span the current group.
5649		 */
5650
5651		for_each_cpu(cpu, sched_group_cpus(sdg)) {
5652			struct sched_group_power *sgp;
5653			struct rq *rq = cpu_rq(cpu);
5654
5655			/*
5656			 * build_sched_domains() -> init_sched_groups_power()
5657			 * gets here before we've attached the domains to the
5658			 * runqueues.
5659			 *
5660			 * Use power_of(), which is set irrespective of domains
5661			 * in update_cpu_power().
5662			 *
5663			 * This avoids power/power_orig from being 0 and
5664			 * causing divide-by-zero issues on boot.
5665			 *
5666			 * Runtime updates will correct power_orig.
5667			 */
5668			if (unlikely(!rq->sd)) {
5669				power_orig += power_of(cpu);
5670				power += power_of(cpu);
5671				continue;
5672			}
5673
5674			sgp = rq->sd->groups->sgp;
5675			power_orig += sgp->power_orig;
5676			power += sgp->power;
5677		}
5678	} else  {
5679		/*
5680		 * !SD_OVERLAP domains can assume that child groups
5681		 * span the current group.
5682		 */ 
5683
5684		group = child->groups;
5685		do {
5686			power_orig += group->sgp->power_orig;
5687			power += group->sgp->power;
5688			group = group->next;
5689		} while (group != child->groups);
5690	}
5691
5692	sdg->sgp->power_orig = power_orig;
5693	sdg->sgp->power = power;
5694}
5695
5696/*
5697 * Try and fix up capacity for tiny siblings, this is needed when
5698 * things like SD_ASYM_PACKING need f_b_g to select another sibling
5699 * which on its own isn't powerful enough.
5700 *
5701 * See update_sd_pick_busiest() and check_asym_packing().
5702 */
5703static inline int
5704fix_small_capacity(struct sched_domain *sd, struct sched_group *group)
5705{
5706	/*
5707	 * Only siblings can have significantly less than SCHED_POWER_SCALE
5708	 */
5709	if (!(sd->flags & SD_SHARE_CPUPOWER))
5710		return 0;
5711
5712	/*
5713	 * If ~90% of the cpu_power is still there, we're good.
5714	 */
5715	if (group->sgp->power * 32 > group->sgp->power_orig * 29)
5716		return 1;
5717
5718	return 0;
5719}
5720
5721/*
5722 * Group imbalance indicates (and tries to solve) the problem where balancing
5723 * groups is inadequate due to tsk_cpus_allowed() constraints.
5724 *
5725 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
5726 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
5727 * Something like:
5728 *
5729 * 	{ 0 1 2 3 } { 4 5 6 7 }
5730 * 	        *     * * *
5731 *
5732 * If we were to balance group-wise we'd place two tasks in the first group and
5733 * two tasks in the second group. Clearly this is undesired as it will overload
5734 * cpu 3 and leave one of the cpus in the second group unused.
5735 *
5736 * The current solution to this issue is detecting the skew in the first group
5737 * by noticing the lower domain failed to reach balance and had difficulty
5738 * moving tasks due to affinity constraints.
5739 *
5740 * When this is so detected; this group becomes a candidate for busiest; see
5741 * update_sd_pick_busiest(). And calculate_imbalance() and
5742 * find_busiest_group() avoid some of the usual balance conditions to allow it
5743 * to create an effective group imbalance.
5744 *
5745 * This is a somewhat tricky proposition since the next run might not find the
5746 * group imbalance and decide the groups need to be balanced again. A most
5747 * subtle and fragile situation.
5748 */
5749
5750static inline int sg_imbalanced(struct sched_group *group)
5751{
5752	return group->sgp->imbalance;
5753}
5754
5755/*
5756 * Compute the group capacity.
5757 *
5758 * Avoid the issue where N*frac(smt_power) >= 1 creates 'phantom' cores by
5759 * first dividing out the smt factor and computing the actual number of cores
5760 * and limit power unit capacity with that.
 
 
 
 
 
5761 */
5762static inline int sg_capacity(struct lb_env *env, struct sched_group *group)
 
5763{
5764	unsigned int capacity, smt, cpus;
5765	unsigned int power, power_orig;
5766
5767	power = group->sgp->power;
5768	power_orig = group->sgp->power_orig;
5769	cpus = group->group_weight;
5770
5771	/* smt := ceil(cpus / power), assumes: 1 < smt_power < 2 */
5772	smt = DIV_ROUND_UP(SCHED_POWER_SCALE * cpus, power_orig);
5773	capacity = cpus / smt; /* cores */
5774
5775	capacity = min_t(unsigned, capacity, DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE));
5776	if (!capacity)
5777		capacity = fix_small_capacity(env->sd, group);
 
 
 
 
 
 
 
 
 
 
5778
5779	return capacity;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5780}
5781
5782/**
5783 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
5784 * @env: The load balancing environment.
5785 * @group: sched_group whose statistics are to be updated.
5786 * @load_idx: Load index of sched_domain of this_cpu for load calc.
5787 * @local_group: Does group contain this_cpu.
5788 * @sgs: variable to hold the statistics for this group.
 
5789 */
5790static inline void update_sg_lb_stats(struct lb_env *env,
5791			struct sched_group *group, int load_idx,
5792			int local_group, struct sg_lb_stats *sgs)
 
5793{
5794	unsigned long load;
5795	int i;
5796
5797	memset(sgs, 0, sizeof(*sgs));
5798
5799	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
5800		struct rq *rq = cpu_rq(i);
5801
5802		/* Bias balancing toward cpus of our domain */
5803		if (local_group)
5804			load = target_load(i, load_idx);
5805		else
5806			load = source_load(i, load_idx);
5807
5808		sgs->group_load += load;
5809		sgs->sum_nr_running += rq->nr_running;
 
 
 
 
 
 
5810#ifdef CONFIG_NUMA_BALANCING
5811		sgs->nr_numa_running += rq->nr_numa_running;
5812		sgs->nr_preferred_running += rq->nr_preferred_running;
5813#endif
5814		sgs->sum_weighted_load += weighted_cpuload(i);
5815		if (idle_cpu(i))
 
 
 
5816			sgs->idle_cpus++;
5817	}
5818
5819	/* Adjust by relative CPU power of the group */
5820	sgs->group_power = group->sgp->power;
5821	sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / sgs->group_power;
5822
5823	if (sgs->sum_nr_running)
5824		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
5825
5826	sgs->group_weight = group->group_weight;
5827
5828	sgs->group_imb = sg_imbalanced(group);
5829	sgs->group_capacity = sg_capacity(env, group);
5830
5831	if (sgs->group_capacity > sgs->sum_nr_running)
5832		sgs->group_has_capacity = 1;
5833}
5834
5835/**
5836 * update_sd_pick_busiest - return 1 on busiest group
5837 * @env: The load balancing environment.
5838 * @sds: sched_domain statistics
5839 * @sg: sched_group candidate to be checked for being the busiest
5840 * @sgs: sched_group statistics
5841 *
5842 * Determine if @sg is a busier group than the previously selected
5843 * busiest group.
5844 *
5845 * Return: %true if @sg is a busier group than the previously selected
5846 * busiest group. %false otherwise.
5847 */
5848static bool update_sd_pick_busiest(struct lb_env *env,
5849				   struct sd_lb_stats *sds,
5850				   struct sched_group *sg,
5851				   struct sg_lb_stats *sgs)
5852{
5853	if (sgs->avg_load <= sds->busiest_stat.avg_load)
5854		return false;
5855
5856	if (sgs->sum_nr_running > sgs->group_capacity)
5857		return true;
5858
5859	if (sgs->group_imb)
 
 
 
 
 
 
 
5860		return true;
5861
5862	/*
5863	 * ASYM_PACKING needs to move all the work to the lowest
5864	 * numbered CPUs in the group, therefore mark all groups
5865	 * higher than ourself as busy.
5866	 */
5867	if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
5868	    env->dst_cpu < group_first_cpu(sg)) {
5869		if (!sds->busiest)
5870			return true;
5871
5872		if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
5873			return true;
5874	}
5875
5876	return false;
5877}
5878
5879#ifdef CONFIG_NUMA_BALANCING
5880static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
5881{
5882	if (sgs->sum_nr_running > sgs->nr_numa_running)
5883		return regular;
5884	if (sgs->sum_nr_running > sgs->nr_preferred_running)
5885		return remote;
5886	return all;
5887}
5888
5889static inline enum fbq_type fbq_classify_rq(struct rq *rq)
5890{
5891	if (rq->nr_running > rq->nr_numa_running)
5892		return regular;
5893	if (rq->nr_running > rq->nr_preferred_running)
5894		return remote;
5895	return all;
5896}
5897#else
5898static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
5899{
5900	return all;
5901}
5902
5903static inline enum fbq_type fbq_classify_rq(struct rq *rq)
5904{
5905	return regular;
5906}
5907#endif /* CONFIG_NUMA_BALANCING */
5908
5909/**
5910 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
5911 * @env: The load balancing environment.
5912 * @sds: variable to hold the statistics for this sched_domain.
5913 */
5914static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
5915{
5916	struct sched_domain *child = env->sd->child;
5917	struct sched_group *sg = env->sd->groups;
5918	struct sg_lb_stats tmp_sgs;
5919	int load_idx, prefer_sibling = 0;
 
5920
5921	if (child && child->flags & SD_PREFER_SIBLING)
5922		prefer_sibling = 1;
5923
5924	load_idx = get_sd_load_idx(env->sd, env->idle);
5925
5926	do {
5927		struct sg_lb_stats *sgs = &tmp_sgs;
5928		int local_group;
5929
5930		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
5931		if (local_group) {
5932			sds->local = sg;
5933			sgs = &sds->local_stat;
5934
5935			if (env->idle != CPU_NEWLY_IDLE ||
5936			    time_after_eq(jiffies, sg->sgp->next_update))
5937				update_group_power(env->sd, env->dst_cpu);
5938		}
5939
5940		update_sg_lb_stats(env, sg, load_idx, local_group, sgs);
 
5941
5942		if (local_group)
5943			goto next_group;
5944
5945		/*
5946		 * In case the child domain prefers tasks go to siblings
5947		 * first, lower the sg capacity to one so that we'll try
5948		 * and move all the excess tasks away. We lower the capacity
5949		 * of a group only if the local group has the capacity to fit
5950		 * these excess tasks, i.e. nr_running < group_capacity. The
5951		 * extra check prevents the case where you always pull from the
5952		 * heaviest group when it is already under-utilized (possible
5953		 * with a large weight task outweighs the tasks on the system).
5954		 */
5955		if (prefer_sibling && sds->local &&
5956		    sds->local_stat.group_has_capacity)
5957			sgs->group_capacity = min(sgs->group_capacity, 1U);
 
 
 
5958
5959		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
5960			sds->busiest = sg;
5961			sds->busiest_stat = *sgs;
5962		}
5963
5964next_group:
5965		/* Now, start updating sd_lb_stats */
5966		sds->total_load += sgs->group_load;
5967		sds->total_pwr += sgs->group_power;
5968
5969		sg = sg->next;
5970	} while (sg != env->sd->groups);
5971
5972	if (env->sd->flags & SD_NUMA)
5973		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
 
 
 
 
 
 
 
5974}
5975
5976/**
5977 * check_asym_packing - Check to see if the group is packed into the
5978 *			sched doman.
5979 *
5980 * This is primarily intended to used at the sibling level.  Some
5981 * cores like POWER7 prefer to use lower numbered SMT threads.  In the
5982 * case of POWER7, it can move to lower SMT modes only when higher
5983 * threads are idle.  When in lower SMT modes, the threads will
5984 * perform better since they share less core resources.  Hence when we
5985 * have idle threads, we want them to be the higher ones.
5986 *
5987 * This packing function is run on idle threads.  It checks to see if
5988 * the busiest CPU in this domain (core in the P7 case) has a higher
5989 * CPU number than the packing function is being run on.  Here we are
5990 * assuming lower CPU number will be equivalent to lower a SMT thread
5991 * number.
5992 *
5993 * Return: 1 when packing is required and a task should be moved to
5994 * this CPU.  The amount of the imbalance is returned in *imbalance.
5995 *
5996 * @env: The load balancing environment.
5997 * @sds: Statistics of the sched_domain which is to be packed
5998 */
5999static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6000{
6001	int busiest_cpu;
6002
6003	if (!(env->sd->flags & SD_ASYM_PACKING))
6004		return 0;
6005
6006	if (!sds->busiest)
6007		return 0;
6008
6009	busiest_cpu = group_first_cpu(sds->busiest);
6010	if (env->dst_cpu > busiest_cpu)
6011		return 0;
6012
6013	env->imbalance = DIV_ROUND_CLOSEST(
6014		sds->busiest_stat.avg_load * sds->busiest_stat.group_power,
6015		SCHED_POWER_SCALE);
6016
6017	return 1;
6018}
6019
6020/**
6021 * fix_small_imbalance - Calculate the minor imbalance that exists
6022 *			amongst the groups of a sched_domain, during
6023 *			load balancing.
6024 * @env: The load balancing environment.
6025 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6026 */
6027static inline
6028void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6029{
6030	unsigned long tmp, pwr_now = 0, pwr_move = 0;
6031	unsigned int imbn = 2;
6032	unsigned long scaled_busy_load_per_task;
6033	struct sg_lb_stats *local, *busiest;
6034
6035	local = &sds->local_stat;
6036	busiest = &sds->busiest_stat;
6037
6038	if (!local->sum_nr_running)
6039		local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
6040	else if (busiest->load_per_task > local->load_per_task)
6041		imbn = 1;
6042
6043	scaled_busy_load_per_task =
6044		(busiest->load_per_task * SCHED_POWER_SCALE) /
6045		busiest->group_power;
6046
6047	if (busiest->avg_load + scaled_busy_load_per_task >=
6048	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
6049		env->imbalance = busiest->load_per_task;
6050		return;
6051	}
6052
6053	/*
6054	 * OK, we don't have enough imbalance to justify moving tasks,
6055	 * however we may be able to increase total CPU power used by
6056	 * moving them.
6057	 */
6058
6059	pwr_now += busiest->group_power *
6060			min(busiest->load_per_task, busiest->avg_load);
6061	pwr_now += local->group_power *
6062			min(local->load_per_task, local->avg_load);
6063	pwr_now /= SCHED_POWER_SCALE;
6064
6065	/* Amount of load we'd subtract */
6066	if (busiest->avg_load > scaled_busy_load_per_task) {
6067		pwr_move += busiest->group_power *
6068			    min(busiest->load_per_task,
6069				busiest->avg_load - scaled_busy_load_per_task);
6070	}
6071
6072	/* Amount of load we'd add */
6073	if (busiest->avg_load * busiest->group_power <
6074	    busiest->load_per_task * SCHED_POWER_SCALE) {
6075		tmp = (busiest->avg_load * busiest->group_power) /
6076		      local->group_power;
6077	} else {
6078		tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
6079		      local->group_power;
6080	}
6081	pwr_move += local->group_power *
6082		    min(local->load_per_task, local->avg_load + tmp);
6083	pwr_move /= SCHED_POWER_SCALE;
6084
6085	/* Move if we gain throughput */
6086	if (pwr_move > pwr_now)
6087		env->imbalance = busiest->load_per_task;
6088}
6089
6090/**
6091 * calculate_imbalance - Calculate the amount of imbalance present within the
6092 *			 groups of a given sched_domain during load balance.
6093 * @env: load balance environment
6094 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
6095 */
6096static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6097{
6098	unsigned long max_pull, load_above_capacity = ~0UL;
6099	struct sg_lb_stats *local, *busiest;
6100
6101	local = &sds->local_stat;
6102	busiest = &sds->busiest_stat;
6103
6104	if (busiest->group_imb) {
6105		/*
6106		 * In the group_imb case we cannot rely on group-wide averages
6107		 * to ensure cpu-load equilibrium, look at wider averages. XXX
6108		 */
6109		busiest->load_per_task =
6110			min(busiest->load_per_task, sds->avg_load);
6111	}
6112
6113	/*
6114	 * In the presence of smp nice balancing, certain scenarios can have
6115	 * max load less than avg load(as we skip the groups at or below
6116	 * its cpu_power, while calculating max_load..)
6117	 */
6118	if (busiest->avg_load <= sds->avg_load ||
6119	    local->avg_load >= sds->avg_load) {
6120		env->imbalance = 0;
6121		return fix_small_imbalance(env, sds);
6122	}
6123
6124	if (!busiest->group_imb) {
6125		/*
6126		 * Don't want to pull so many tasks that a group would go idle.
6127		 * Except of course for the group_imb case, since then we might
6128		 * have to drop below capacity to reach cpu-load equilibrium.
6129		 */
6130		load_above_capacity =
6131			(busiest->sum_nr_running - busiest->group_capacity);
6132
6133		load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
6134		load_above_capacity /= busiest->group_power;
6135	}
6136
6137	/*
6138	 * We're trying to get all the cpus to the average_load, so we don't
6139	 * want to push ourselves above the average load, nor do we wish to
6140	 * reduce the max loaded cpu below the average load. At the same time,
6141	 * we also don't want to reduce the group load below the group capacity
6142	 * (so that we can implement power-savings policies etc). Thus we look
6143	 * for the minimum possible imbalance.
6144	 */
6145	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6146
6147	/* How much load to actually move to equalise the imbalance */
6148	env->imbalance = min(
6149		max_pull * busiest->group_power,
6150		(sds->avg_load - local->avg_load) * local->group_power
6151	) / SCHED_POWER_SCALE;
6152
6153	/*
6154	 * if *imbalance is less than the average load per runnable task
6155	 * there is no guarantee that any tasks will be moved so we'll have
6156	 * a think about bumping its value to force at least one task to be
6157	 * moved
6158	 */
6159	if (env->imbalance < busiest->load_per_task)
6160		return fix_small_imbalance(env, sds);
6161}
6162
6163/******* find_busiest_group() helpers end here *********************/
6164
6165/**
6166 * find_busiest_group - Returns the busiest group within the sched_domain
6167 * if there is an imbalance. If there isn't an imbalance, and
6168 * the user has opted for power-savings, it returns a group whose
6169 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
6170 * such a group exists.
6171 *
6172 * Also calculates the amount of weighted load which should be moved
6173 * to restore balance.
6174 *
6175 * @env: The load balancing environment.
6176 *
6177 * Return:	- The busiest group if imbalance exists.
6178 *		- If no imbalance and user has opted for power-savings balance,
6179 *		   return the least loaded group whose CPUs can be
6180 *		   put to idle by rebalancing its tasks onto our group.
6181 */
6182static struct sched_group *find_busiest_group(struct lb_env *env)
6183{
6184	struct sg_lb_stats *local, *busiest;
6185	struct sd_lb_stats sds;
6186
6187	init_sd_lb_stats(&sds);
6188
6189	/*
6190	 * Compute the various statistics relavent for load balancing at
6191	 * this level.
6192	 */
6193	update_sd_lb_stats(env, &sds);
6194	local = &sds.local_stat;
6195	busiest = &sds.busiest_stat;
6196
 
6197	if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
6198	    check_asym_packing(env, &sds))
6199		return sds.busiest;
6200
6201	/* There is no busy sibling group to pull tasks from */
6202	if (!sds.busiest || busiest->sum_nr_running == 0)
6203		goto out_balanced;
6204
6205	sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
 
6206
6207	/*
6208	 * If the busiest group is imbalanced the below checks don't
6209	 * work because they assume all things are equal, which typically
6210	 * isn't true due to cpus_allowed constraints and the like.
6211	 */
6212	if (busiest->group_imb)
6213		goto force_balance;
6214
6215	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6216	if (env->idle == CPU_NEWLY_IDLE && local->group_has_capacity &&
6217	    !busiest->group_has_capacity)
6218		goto force_balance;
6219
6220	/*
6221	 * If the local group is more busy than the selected busiest group
6222	 * don't try and pull any tasks.
6223	 */
6224	if (local->avg_load >= busiest->avg_load)
6225		goto out_balanced;
6226
6227	/*
6228	 * Don't pull any tasks if this group is already above the domain
6229	 * average load.
6230	 */
6231	if (local->avg_load >= sds.avg_load)
6232		goto out_balanced;
6233
6234	if (env->idle == CPU_IDLE) {
6235		/*
6236		 * This cpu is idle. If the busiest group load doesn't
6237		 * have more tasks than the number of available cpu's and
6238		 * there is no imbalance between this and busiest group
6239		 * wrt to idle cpu's, it is balanced.
 
6240		 */
6241		if ((local->idle_cpus < busiest->idle_cpus) &&
6242		    busiest->sum_nr_running <= busiest->group_weight)
6243			goto out_balanced;
6244	} else {
6245		/*
6246		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
6247		 * imbalance_pct to be conservative.
6248		 */
6249		if (100 * busiest->avg_load <=
6250				env->sd->imbalance_pct * local->avg_load)
6251			goto out_balanced;
6252	}
6253
6254force_balance:
6255	/* Looks like there is an imbalance. Compute it */
6256	calculate_imbalance(env, &sds);
6257	return sds.busiest;
6258
6259out_balanced:
6260	env->imbalance = 0;
6261	return NULL;
6262}
6263
6264/*
6265 * find_busiest_queue - find the busiest runqueue among the cpus in group.
6266 */
6267static struct rq *find_busiest_queue(struct lb_env *env,
6268				     struct sched_group *group)
6269{
6270	struct rq *busiest = NULL, *rq;
6271	unsigned long busiest_load = 0, busiest_power = 1;
6272	int i;
6273
6274	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6275		unsigned long power, capacity, wl;
6276		enum fbq_type rt;
6277
6278		rq = cpu_rq(i);
6279		rt = fbq_classify_rq(rq);
6280
6281		/*
6282		 * We classify groups/runqueues into three groups:
6283		 *  - regular: there are !numa tasks
6284		 *  - remote:  there are numa tasks that run on the 'wrong' node
6285		 *  - all:     there is no distinction
6286		 *
6287		 * In order to avoid migrating ideally placed numa tasks,
6288		 * ignore those when there's better options.
6289		 *
6290		 * If we ignore the actual busiest queue to migrate another
6291		 * task, the next balance pass can still reduce the busiest
6292		 * queue by moving tasks around inside the node.
6293		 *
6294		 * If we cannot move enough load due to this classification
6295		 * the next pass will adjust the group classification and
6296		 * allow migration of more tasks.
6297		 *
6298		 * Both cases only affect the total convergence complexity.
6299		 */
6300		if (rt > env->fbq_type)
6301			continue;
6302
6303		power = power_of(i);
6304		capacity = DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE);
6305		if (!capacity)
6306			capacity = fix_small_capacity(env->sd, group);
6307
6308		wl = weighted_cpuload(i);
6309
6310		/*
6311		 * When comparing with imbalance, use weighted_cpuload()
6312		 * which is not scaled with the cpu power.
6313		 */
6314		if (capacity && rq->nr_running == 1 && wl > env->imbalance)
 
 
6315			continue;
6316
6317		/*
6318		 * For the load comparisons with the other cpu's, consider
6319		 * the weighted_cpuload() scaled with the cpu power, so that
6320		 * the load can be moved away from the cpu that is potentially
6321		 * running at a lower capacity.
6322		 *
6323		 * Thus we're looking for max(wl_i / power_i), crosswise
6324		 * multiplication to rid ourselves of the division works out
6325		 * to: wl_i * power_j > wl_j * power_i;  where j is our
6326		 * previous maximum.
6327		 */
6328		if (wl * busiest_power > busiest_load * power) {
6329			busiest_load = wl;
6330			busiest_power = power;
6331			busiest = rq;
6332		}
6333	}
6334
6335	return busiest;
6336}
6337
6338/*
6339 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
6340 * so long as it is large enough.
6341 */
6342#define MAX_PINNED_INTERVAL	512
6343
6344/* Working cpumask for load_balance and load_balance_newidle. */
6345DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6346
6347static int need_active_balance(struct lb_env *env)
6348{
6349	struct sched_domain *sd = env->sd;
6350
6351	if (env->idle == CPU_NEWLY_IDLE) {
6352
6353		/*
6354		 * ASYM_PACKING needs to force migrate tasks from busy but
6355		 * higher numbered CPUs in order to pack all tasks in the
6356		 * lowest numbered CPUs.
6357		 */
6358		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
6359			return 1;
6360	}
6361
 
 
 
 
 
 
 
 
 
 
 
 
 
6362	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
6363}
6364
6365static int active_load_balance_cpu_stop(void *data);
6366
6367static int should_we_balance(struct lb_env *env)
6368{
6369	struct sched_group *sg = env->sd->groups;
6370	struct cpumask *sg_cpus, *sg_mask;
6371	int cpu, balance_cpu = -1;
6372
6373	/*
6374	 * In the newly idle case, we will allow all the cpu's
6375	 * to do the newly idle load balance.
6376	 */
6377	if (env->idle == CPU_NEWLY_IDLE)
6378		return 1;
6379
6380	sg_cpus = sched_group_cpus(sg);
6381	sg_mask = sched_group_mask(sg);
6382	/* Try to find first idle cpu */
6383	for_each_cpu_and(cpu, sg_cpus, env->cpus) {
6384		if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
6385			continue;
6386
6387		balance_cpu = cpu;
6388		break;
6389	}
6390
6391	if (balance_cpu == -1)
6392		balance_cpu = group_balance_cpu(sg);
6393
6394	/*
6395	 * First idle cpu or the first cpu(busiest) in this sched group
6396	 * is eligible for doing load balancing at this and above domains.
6397	 */
6398	return balance_cpu == env->dst_cpu;
6399}
6400
6401/*
6402 * Check this_cpu to ensure it is balanced within domain. Attempt to move
6403 * tasks if there is an imbalance.
6404 */
6405static int load_balance(int this_cpu, struct rq *this_rq,
6406			struct sched_domain *sd, enum cpu_idle_type idle,
6407			int *continue_balancing)
6408{
6409	int ld_moved, cur_ld_moved, active_balance = 0;
6410	struct sched_domain *sd_parent = sd->parent;
6411	struct sched_group *group;
6412	struct rq *busiest;
6413	unsigned long flags;
6414	struct cpumask *cpus = __get_cpu_var(load_balance_mask);
6415
6416	struct lb_env env = {
6417		.sd		= sd,
6418		.dst_cpu	= this_cpu,
6419		.dst_rq		= this_rq,
6420		.dst_grpmask    = sched_group_cpus(sd->groups),
6421		.idle		= idle,
6422		.loop_break	= sched_nr_migrate_break,
6423		.cpus		= cpus,
6424		.fbq_type	= all,
 
6425	};
6426
6427	/*
6428	 * For NEWLY_IDLE load_balancing, we don't need to consider
6429	 * other cpus in our group
6430	 */
6431	if (idle == CPU_NEWLY_IDLE)
6432		env.dst_grpmask = NULL;
6433
6434	cpumask_copy(cpus, cpu_active_mask);
6435
6436	schedstat_inc(sd, lb_count[idle]);
6437
6438redo:
6439	if (!should_we_balance(&env)) {
6440		*continue_balancing = 0;
6441		goto out_balanced;
6442	}
6443
6444	group = find_busiest_group(&env);
6445	if (!group) {
6446		schedstat_inc(sd, lb_nobusyg[idle]);
6447		goto out_balanced;
6448	}
6449
6450	busiest = find_busiest_queue(&env, group);
6451	if (!busiest) {
6452		schedstat_inc(sd, lb_nobusyq[idle]);
6453		goto out_balanced;
6454	}
6455
6456	BUG_ON(busiest == env.dst_rq);
6457
6458	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
6459
 
 
 
6460	ld_moved = 0;
6461	if (busiest->nr_running > 1) {
6462		/*
6463		 * Attempt to move tasks. If find_busiest_group has found
6464		 * an imbalance but busiest->nr_running <= 1, the group is
6465		 * still unbalanced. ld_moved simply stays zero, so it is
6466		 * correctly treated as an imbalance.
6467		 */
6468		env.flags |= LBF_ALL_PINNED;
6469		env.src_cpu   = busiest->cpu;
6470		env.src_rq    = busiest;
6471		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
6472
6473more_balance:
6474		local_irq_save(flags);
6475		double_rq_lock(env.dst_rq, busiest);
6476
6477		/*
6478		 * cur_ld_moved - load moved in current iteration
6479		 * ld_moved     - cumulative load moved across iterations
6480		 */
6481		cur_ld_moved = move_tasks(&env);
6482		ld_moved += cur_ld_moved;
6483		double_rq_unlock(env.dst_rq, busiest);
6484		local_irq_restore(flags);
6485
6486		/*
6487		 * some other cpu did the load balance for us.
 
 
 
 
6488		 */
6489		if (cur_ld_moved && env.dst_cpu != smp_processor_id())
6490			resched_cpu(env.dst_cpu);
 
 
 
 
 
 
 
6491
6492		if (env.flags & LBF_NEED_BREAK) {
6493			env.flags &= ~LBF_NEED_BREAK;
6494			goto more_balance;
6495		}
6496
6497		/*
6498		 * Revisit (affine) tasks on src_cpu that couldn't be moved to
6499		 * us and move them to an alternate dst_cpu in our sched_group
6500		 * where they can run. The upper limit on how many times we
6501		 * iterate on same src_cpu is dependent on number of cpus in our
6502		 * sched_group.
6503		 *
6504		 * This changes load balance semantics a bit on who can move
6505		 * load to a given_cpu. In addition to the given_cpu itself
6506		 * (or a ilb_cpu acting on its behalf where given_cpu is
6507		 * nohz-idle), we now have balance_cpu in a position to move
6508		 * load to given_cpu. In rare situations, this may cause
6509		 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
6510		 * _independently_ and at _same_ time to move some load to
6511		 * given_cpu) causing exceess load to be moved to given_cpu.
6512		 * This however should not happen so much in practice and
6513		 * moreover subsequent load balance cycles should correct the
6514		 * excess load moved.
6515		 */
6516		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
6517
6518			/* Prevent to re-select dst_cpu via env's cpus */
6519			cpumask_clear_cpu(env.dst_cpu, env.cpus);
6520
6521			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
6522			env.dst_cpu	 = env.new_dst_cpu;
6523			env.flags	&= ~LBF_DST_PINNED;
6524			env.loop	 = 0;
6525			env.loop_break	 = sched_nr_migrate_break;
6526
6527			/*
6528			 * Go back to "more_balance" rather than "redo" since we
6529			 * need to continue with same src_cpu.
6530			 */
6531			goto more_balance;
6532		}
6533
6534		/*
6535		 * We failed to reach balance because of affinity.
6536		 */
6537		if (sd_parent) {
6538			int *group_imbalance = &sd_parent->groups->sgp->imbalance;
6539
6540			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) {
6541				*group_imbalance = 1;
6542			} else if (*group_imbalance)
6543				*group_imbalance = 0;
6544		}
6545
6546		/* All tasks on this runqueue were pinned by CPU affinity */
6547		if (unlikely(env.flags & LBF_ALL_PINNED)) {
6548			cpumask_clear_cpu(cpu_of(busiest), cpus);
6549			if (!cpumask_empty(cpus)) {
6550				env.loop = 0;
6551				env.loop_break = sched_nr_migrate_break;
6552				goto redo;
6553			}
6554			goto out_balanced;
6555		}
6556	}
6557
6558	if (!ld_moved) {
6559		schedstat_inc(sd, lb_failed[idle]);
6560		/*
6561		 * Increment the failure counter only on periodic balance.
6562		 * We do not want newidle balance, which can be very
6563		 * frequent, pollute the failure counter causing
6564		 * excessive cache_hot migrations and active balances.
6565		 */
6566		if (idle != CPU_NEWLY_IDLE)
6567			sd->nr_balance_failed++;
6568
6569		if (need_active_balance(&env)) {
6570			raw_spin_lock_irqsave(&busiest->lock, flags);
6571
6572			/* don't kick the active_load_balance_cpu_stop,
6573			 * if the curr task on busiest cpu can't be
6574			 * moved to this_cpu
6575			 */
6576			if (!cpumask_test_cpu(this_cpu,
6577					tsk_cpus_allowed(busiest->curr))) {
6578				raw_spin_unlock_irqrestore(&busiest->lock,
6579							    flags);
6580				env.flags |= LBF_ALL_PINNED;
6581				goto out_one_pinned;
6582			}
6583
6584			/*
6585			 * ->active_balance synchronizes accesses to
6586			 * ->active_balance_work.  Once set, it's cleared
6587			 * only after active load balance is finished.
6588			 */
6589			if (!busiest->active_balance) {
6590				busiest->active_balance = 1;
6591				busiest->push_cpu = this_cpu;
6592				active_balance = 1;
6593			}
6594			raw_spin_unlock_irqrestore(&busiest->lock, flags);
6595
6596			if (active_balance) {
6597				stop_one_cpu_nowait(cpu_of(busiest),
6598					active_load_balance_cpu_stop, busiest,
6599					&busiest->active_balance_work);
6600			}
6601
6602			/*
6603			 * We've kicked active balancing, reset the failure
6604			 * counter.
6605			 */
6606			sd->nr_balance_failed = sd->cache_nice_tries+1;
6607		}
6608	} else
6609		sd->nr_balance_failed = 0;
6610
6611	if (likely(!active_balance)) {
6612		/* We were unbalanced, so reset the balancing interval */
6613		sd->balance_interval = sd->min_interval;
6614	} else {
6615		/*
6616		 * If we've begun active balancing, start to back off. This
6617		 * case may not be covered by the all_pinned logic if there
6618		 * is only 1 task on the busy runqueue (because we don't call
6619		 * move_tasks).
6620		 */
6621		if (sd->balance_interval < sd->max_interval)
6622			sd->balance_interval *= 2;
6623	}
6624
6625	goto out;
6626
6627out_balanced:
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6628	schedstat_inc(sd, lb_balanced[idle]);
6629
6630	sd->nr_balance_failed = 0;
6631
6632out_one_pinned:
6633	/* tune up the balancing interval */
6634	if (((env.flags & LBF_ALL_PINNED) &&
6635			sd->balance_interval < MAX_PINNED_INTERVAL) ||
6636			(sd->balance_interval < sd->max_interval))
6637		sd->balance_interval *= 2;
6638
6639	ld_moved = 0;
6640out:
6641	return ld_moved;
6642}
6643
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6644/*
6645 * idle_balance is called by schedule() if this_cpu is about to become
6646 * idle. Attempts to pull tasks from other CPUs.
6647 */
6648static int idle_balance(struct rq *this_rq)
6649{
 
 
6650	struct sched_domain *sd;
6651	int pulled_task = 0;
6652	unsigned long next_balance = jiffies + HZ;
6653	u64 curr_cost = 0;
6654	int this_cpu = this_rq->cpu;
6655
6656	idle_enter_fair(this_rq);
6657
6658	/*
6659	 * We must set idle_stamp _before_ calling idle_balance(), such that we
6660	 * measure the duration of idle_balance() as idle time.
6661	 */
6662	this_rq->idle_stamp = rq_clock(this_rq);
6663
6664	if (this_rq->avg_idle < sysctl_sched_migration_cost)
 
 
 
 
 
 
 
6665		goto out;
 
6666
6667	/*
6668	 * Drop the rq->lock, but keep IRQ/preempt disabled.
6669	 */
6670	raw_spin_unlock(&this_rq->lock);
6671
6672	update_blocked_averages(this_cpu);
6673	rcu_read_lock();
6674	for_each_domain(this_cpu, sd) {
6675		unsigned long interval;
6676		int continue_balancing = 1;
6677		u64 t0, domain_cost;
6678
6679		if (!(sd->flags & SD_LOAD_BALANCE))
6680			continue;
6681
6682		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost)
 
6683			break;
 
6684
6685		if (sd->flags & SD_BALANCE_NEWIDLE) {
6686			t0 = sched_clock_cpu(this_cpu);
6687
6688			/* If we've pulled tasks over stop searching: */
6689			pulled_task = load_balance(this_cpu, this_rq,
6690						   sd, CPU_NEWLY_IDLE,
6691						   &continue_balancing);
6692
6693			domain_cost = sched_clock_cpu(this_cpu) - t0;
6694			if (domain_cost > sd->max_newidle_lb_cost)
6695				sd->max_newidle_lb_cost = domain_cost;
6696
6697			curr_cost += domain_cost;
6698		}
6699
6700		interval = msecs_to_jiffies(sd->balance_interval);
6701		if (time_after(next_balance, sd->last_balance + interval))
6702			next_balance = sd->last_balance + interval;
6703		if (pulled_task)
 
 
 
6704			break;
6705	}
6706	rcu_read_unlock();
6707
6708	raw_spin_lock(&this_rq->lock);
6709
6710	if (curr_cost > this_rq->max_idle_balance_cost)
6711		this_rq->max_idle_balance_cost = curr_cost;
6712
6713	/*
6714	 * While browsing the domains, we released the rq lock, a task could
6715	 * have been enqueued in the meantime. Since we're not going idle,
6716	 * pretend we pulled a task.
6717	 */
6718	if (this_rq->cfs.h_nr_running && !pulled_task)
6719		pulled_task = 1;
6720
6721	if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
6722		/*
6723		 * We are going idle. next_balance may be set based on
6724		 * a busy processor. So reset next_balance.
6725		 */
6726		this_rq->next_balance = next_balance;
6727	}
6728
6729out:
6730	/* Is there a task of a high priority class? */
6731	if (this_rq->nr_running != this_rq->cfs.h_nr_running &&
6732	    ((this_rq->stop && this_rq->stop->on_rq) ||
6733	     this_rq->dl.dl_nr_running ||
6734	     (this_rq->rt.rt_nr_running && !rt_rq_throttled(&this_rq->rt))))
6735		pulled_task = -1;
6736
6737	if (pulled_task) {
6738		idle_exit_fair(this_rq);
6739		this_rq->idle_stamp = 0;
6740	}
6741
6742	return pulled_task;
6743}
6744
6745/*
6746 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
6747 * running tasks off the busiest CPU onto idle CPUs. It requires at
6748 * least 1 task to be running on each physical CPU where possible, and
6749 * avoids physical / logical imbalances.
6750 */
6751static int active_load_balance_cpu_stop(void *data)
6752{
6753	struct rq *busiest_rq = data;
6754	int busiest_cpu = cpu_of(busiest_rq);
6755	int target_cpu = busiest_rq->push_cpu;
6756	struct rq *target_rq = cpu_rq(target_cpu);
6757	struct sched_domain *sd;
 
6758
6759	raw_spin_lock_irq(&busiest_rq->lock);
6760
6761	/* make sure the requested cpu hasn't gone down in the meantime */
6762	if (unlikely(busiest_cpu != smp_processor_id() ||
6763		     !busiest_rq->active_balance))
6764		goto out_unlock;
6765
6766	/* Is there any task to move? */
6767	if (busiest_rq->nr_running <= 1)
6768		goto out_unlock;
6769
6770	/*
6771	 * This condition is "impossible", if it occurs
6772	 * we need to fix it. Originally reported by
6773	 * Bjorn Helgaas on a 128-cpu setup.
6774	 */
6775	BUG_ON(busiest_rq == target_rq);
6776
6777	/* move a task from busiest_rq to target_rq */
6778	double_lock_balance(busiest_rq, target_rq);
6779
6780	/* Search for an sd spanning us and the target CPU. */
6781	rcu_read_lock();
6782	for_each_domain(target_cpu, sd) {
6783		if ((sd->flags & SD_LOAD_BALANCE) &&
6784		    cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
6785				break;
6786	}
6787
6788	if (likely(sd)) {
6789		struct lb_env env = {
6790			.sd		= sd,
6791			.dst_cpu	= target_cpu,
6792			.dst_rq		= target_rq,
6793			.src_cpu	= busiest_rq->cpu,
6794			.src_rq		= busiest_rq,
6795			.idle		= CPU_IDLE,
6796		};
6797
6798		schedstat_inc(sd, alb_count);
6799
6800		if (move_one_task(&env))
 
6801			schedstat_inc(sd, alb_pushed);
6802		else
6803			schedstat_inc(sd, alb_failed);
6804	}
6805	rcu_read_unlock();
6806	double_unlock_balance(busiest_rq, target_rq);
6807out_unlock:
6808	busiest_rq->active_balance = 0;
6809	raw_spin_unlock_irq(&busiest_rq->lock);
 
 
 
 
 
 
6810	return 0;
6811}
6812
6813static inline int on_null_domain(struct rq *rq)
6814{
6815	return unlikely(!rcu_dereference_sched(rq->sd));
6816}
6817
6818#ifdef CONFIG_NO_HZ_COMMON
6819/*
6820 * idle load balancing details
6821 * - When one of the busy CPUs notice that there may be an idle rebalancing
6822 *   needed, they will kick the idle load balancer, which then does idle
6823 *   load balancing for all the idle CPUs.
6824 */
6825static struct {
6826	cpumask_var_t idle_cpus_mask;
6827	atomic_t nr_cpus;
6828	unsigned long next_balance;     /* in jiffy units */
6829} nohz ____cacheline_aligned;
6830
6831static inline int find_new_ilb(void)
6832{
6833	int ilb = cpumask_first(nohz.idle_cpus_mask);
6834
6835	if (ilb < nr_cpu_ids && idle_cpu(ilb))
6836		return ilb;
6837
6838	return nr_cpu_ids;
6839}
6840
6841/*
6842 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
6843 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
6844 * CPU (if there is one).
6845 */
6846static void nohz_balancer_kick(void)
6847{
6848	int ilb_cpu;
6849
6850	nohz.next_balance++;
6851
6852	ilb_cpu = find_new_ilb();
6853
6854	if (ilb_cpu >= nr_cpu_ids)
6855		return;
6856
6857	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
6858		return;
6859	/*
6860	 * Use smp_send_reschedule() instead of resched_cpu().
6861	 * This way we generate a sched IPI on the target cpu which
6862	 * is idle. And the softirq performing nohz idle load balance
6863	 * will be run before returning from the IPI.
6864	 */
6865	smp_send_reschedule(ilb_cpu);
6866	return;
6867}
6868
6869static inline void nohz_balance_exit_idle(int cpu)
6870{
6871	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
6872		/*
6873		 * Completely isolated CPUs don't ever set, so we must test.
6874		 */
6875		if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
6876			cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
6877			atomic_dec(&nohz.nr_cpus);
6878		}
6879		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
6880	}
6881}
6882
6883static inline void set_cpu_sd_state_busy(void)
6884{
6885	struct sched_domain *sd;
6886	int cpu = smp_processor_id();
6887
6888	rcu_read_lock();
6889	sd = rcu_dereference(per_cpu(sd_busy, cpu));
6890
6891	if (!sd || !sd->nohz_idle)
6892		goto unlock;
6893	sd->nohz_idle = 0;
6894
6895	atomic_inc(&sd->groups->sgp->nr_busy_cpus);
6896unlock:
6897	rcu_read_unlock();
6898}
6899
6900void set_cpu_sd_state_idle(void)
6901{
6902	struct sched_domain *sd;
6903	int cpu = smp_processor_id();
6904
6905	rcu_read_lock();
6906	sd = rcu_dereference(per_cpu(sd_busy, cpu));
6907
6908	if (!sd || sd->nohz_idle)
6909		goto unlock;
6910	sd->nohz_idle = 1;
6911
6912	atomic_dec(&sd->groups->sgp->nr_busy_cpus);
6913unlock:
6914	rcu_read_unlock();
6915}
6916
6917/*
6918 * This routine will record that the cpu is going idle with tick stopped.
6919 * This info will be used in performing idle load balancing in the future.
6920 */
6921void nohz_balance_enter_idle(int cpu)
6922{
6923	/*
6924	 * If this cpu is going down, then nothing needs to be done.
6925	 */
6926	if (!cpu_active(cpu))
6927		return;
6928
6929	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
6930		return;
6931
6932	/*
6933	 * If we're a completely isolated CPU, we don't play.
6934	 */
6935	if (on_null_domain(cpu_rq(cpu)))
6936		return;
6937
6938	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
6939	atomic_inc(&nohz.nr_cpus);
6940	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
6941}
6942
6943static int sched_ilb_notifier(struct notifier_block *nfb,
6944					unsigned long action, void *hcpu)
6945{
6946	switch (action & ~CPU_TASKS_FROZEN) {
6947	case CPU_DYING:
6948		nohz_balance_exit_idle(smp_processor_id());
6949		return NOTIFY_OK;
6950	default:
6951		return NOTIFY_DONE;
6952	}
6953}
6954#endif
6955
6956static DEFINE_SPINLOCK(balancing);
6957
6958/*
6959 * Scale the max load_balance interval with the number of CPUs in the system.
6960 * This trades load-balance latency on larger machines for less cross talk.
6961 */
6962void update_max_interval(void)
6963{
6964	max_load_balance_interval = HZ*num_online_cpus()/10;
6965}
6966
6967/*
6968 * It checks each scheduling domain to see if it is due to be balanced,
6969 * and initiates a balancing operation if so.
6970 *
6971 * Balancing parameters are set up in init_sched_domains.
6972 */
6973static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
6974{
6975	int continue_balancing = 1;
6976	int cpu = rq->cpu;
6977	unsigned long interval;
6978	struct sched_domain *sd;
6979	/* Earliest time when we have to do rebalance again */
6980	unsigned long next_balance = jiffies + 60*HZ;
6981	int update_next_balance = 0;
6982	int need_serialize, need_decay = 0;
6983	u64 max_cost = 0;
6984
6985	update_blocked_averages(cpu);
6986
6987	rcu_read_lock();
6988	for_each_domain(cpu, sd) {
6989		/*
6990		 * Decay the newidle max times here because this is a regular
6991		 * visit to all the domains. Decay ~1% per second.
6992		 */
6993		if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
6994			sd->max_newidle_lb_cost =
6995				(sd->max_newidle_lb_cost * 253) / 256;
6996			sd->next_decay_max_lb_cost = jiffies + HZ;
6997			need_decay = 1;
6998		}
6999		max_cost += sd->max_newidle_lb_cost;
7000
7001		if (!(sd->flags & SD_LOAD_BALANCE))
7002			continue;
7003
7004		/*
7005		 * Stop the load balance at this level. There is another
7006		 * CPU in our sched group which is doing load balancing more
7007		 * actively.
7008		 */
7009		if (!continue_balancing) {
7010			if (need_decay)
7011				continue;
7012			break;
7013		}
7014
7015		interval = sd->balance_interval;
7016		if (idle != CPU_IDLE)
7017			interval *= sd->busy_factor;
7018
7019		/* scale ms to jiffies */
7020		interval = msecs_to_jiffies(interval);
7021		interval = clamp(interval, 1UL, max_load_balance_interval);
7022
7023		need_serialize = sd->flags & SD_SERIALIZE;
7024
7025		if (need_serialize) {
7026			if (!spin_trylock(&balancing))
7027				goto out;
7028		}
7029
7030		if (time_after_eq(jiffies, sd->last_balance + interval)) {
7031			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7032				/*
7033				 * The LBF_DST_PINNED logic could have changed
7034				 * env->dst_cpu, so we can't know our idle
7035				 * state even if we migrated tasks. Update it.
7036				 */
7037				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7038			}
7039			sd->last_balance = jiffies;
 
7040		}
7041		if (need_serialize)
7042			spin_unlock(&balancing);
7043out:
7044		if (time_after(next_balance, sd->last_balance + interval)) {
7045			next_balance = sd->last_balance + interval;
7046			update_next_balance = 1;
7047		}
7048	}
7049	if (need_decay) {
7050		/*
7051		 * Ensure the rq-wide value also decays but keep it at a
7052		 * reasonable floor to avoid funnies with rq->avg_idle.
7053		 */
7054		rq->max_idle_balance_cost =
7055			max((u64)sysctl_sched_migration_cost, max_cost);
7056	}
7057	rcu_read_unlock();
7058
7059	/*
7060	 * next_balance will be updated only when there is a need.
7061	 * When the cpu is attached to null domain for ex, it will not be
7062	 * updated.
7063	 */
7064	if (likely(update_next_balance))
7065		rq->next_balance = next_balance;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7066}
7067
7068#ifdef CONFIG_NO_HZ_COMMON
7069/*
7070 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7071 * rebalancing for all the cpus for whom scheduler ticks are stopped.
7072 */
7073static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7074{
7075	int this_cpu = this_rq->cpu;
7076	struct rq *rq;
7077	int balance_cpu;
 
 
 
7078
7079	if (idle != CPU_IDLE ||
7080	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
7081		goto end;
7082
7083	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7084		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7085			continue;
7086
7087		/*
7088		 * If this cpu gets work to do, stop the load balancing
7089		 * work being done for other cpus. Next load
7090		 * balancing owner will pick it up.
7091		 */
7092		if (need_resched())
7093			break;
7094
7095		rq = cpu_rq(balance_cpu);
7096
7097		raw_spin_lock_irq(&rq->lock);
7098		update_rq_clock(rq);
7099		update_idle_cpu_load(rq);
7100		raw_spin_unlock_irq(&rq->lock);
7101
7102		rebalance_domains(rq, CPU_IDLE);
 
 
 
 
 
7103
7104		if (time_after(this_rq->next_balance, rq->next_balance))
7105			this_rq->next_balance = rq->next_balance;
 
 
7106	}
7107	nohz.next_balance = this_rq->next_balance;
 
 
 
 
 
 
 
7108end:
7109	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7110}
7111
7112/*
7113 * Current heuristic for kicking the idle load balancer in the presence
7114 * of an idle cpu is the system.
7115 *   - This rq has more than one task.
7116 *   - At any scheduler domain level, this cpu's scheduler group has multiple
7117 *     busy cpu's exceeding the group's power.
 
 
7118 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
7119 *     domain span are idle.
7120 */
7121static inline int nohz_kick_needed(struct rq *rq)
7122{
7123	unsigned long now = jiffies;
7124	struct sched_domain *sd;
7125	struct sched_group_power *sgp;
7126	int nr_busy, cpu = rq->cpu;
 
7127
7128	if (unlikely(rq->idle_balance))
7129		return 0;
7130
7131       /*
7132	* We may be recently in ticked or tickless idle mode. At the first
7133	* busy tick after returning from idle, we will update the busy stats.
7134	*/
7135	set_cpu_sd_state_busy();
7136	nohz_balance_exit_idle(cpu);
7137
7138	/*
7139	 * None are in tickless mode and hence no need for NOHZ idle load
7140	 * balancing.
7141	 */
7142	if (likely(!atomic_read(&nohz.nr_cpus)))
7143		return 0;
7144
7145	if (time_before(now, nohz.next_balance))
7146		return 0;
7147
7148	if (rq->nr_running >= 2)
7149		goto need_kick;
7150
7151	rcu_read_lock();
7152	sd = rcu_dereference(per_cpu(sd_busy, cpu));
7153
7154	if (sd) {
7155		sgp = sd->groups->sgp;
7156		nr_busy = atomic_read(&sgp->nr_busy_cpus);
 
 
 
 
 
7157
7158		if (nr_busy > 1)
7159			goto need_kick_unlock;
7160	}
7161
7162	sd = rcu_dereference(per_cpu(sd_asym, cpu));
 
 
 
 
 
 
 
7163
 
7164	if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
7165				  sched_domain_span(sd)) < cpu))
7166		goto need_kick_unlock;
7167
7168	rcu_read_unlock();
7169	return 0;
7170
7171need_kick_unlock:
7172	rcu_read_unlock();
7173need_kick:
7174	return 1;
7175}
7176#else
7177static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7178#endif
7179
7180/*
7181 * run_rebalance_domains is triggered when needed from the scheduler tick.
7182 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
7183 */
7184static void run_rebalance_domains(struct softirq_action *h)
7185{
7186	struct rq *this_rq = this_rq();
7187	enum cpu_idle_type idle = this_rq->idle_balance ?
7188						CPU_IDLE : CPU_NOT_IDLE;
7189
7190	rebalance_domains(this_rq, idle);
7191
7192	/*
7193	 * If this cpu has a pending nohz_balance_kick, then do the
7194	 * balancing on behalf of the other idle cpus whose ticks are
7195	 * stopped.
 
 
 
7196	 */
7197	nohz_idle_balance(this_rq, idle);
 
7198}
7199
7200/*
7201 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
7202 */
7203void trigger_load_balance(struct rq *rq)
7204{
7205	/* Don't need to rebalance while attached to NULL domain */
7206	if (unlikely(on_null_domain(rq)))
7207		return;
7208
7209	if (time_after_eq(jiffies, rq->next_balance))
7210		raise_softirq(SCHED_SOFTIRQ);
7211#ifdef CONFIG_NO_HZ_COMMON
7212	if (nohz_kick_needed(rq))
7213		nohz_balancer_kick();
7214#endif
7215}
7216
7217static void rq_online_fair(struct rq *rq)
7218{
7219	update_sysctl();
 
 
7220}
7221
7222static void rq_offline_fair(struct rq *rq)
7223{
7224	update_sysctl();
7225
7226	/* Ensure any throttled groups are reachable by pick_next_task */
7227	unthrottle_offline_cfs_rqs(rq);
7228}
7229
7230#endif /* CONFIG_SMP */
7231
7232/*
7233 * scheduler tick hitting a task of our scheduling class:
7234 */
7235static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
7236{
7237	struct cfs_rq *cfs_rq;
7238	struct sched_entity *se = &curr->se;
7239
7240	for_each_sched_entity(se) {
7241		cfs_rq = cfs_rq_of(se);
7242		entity_tick(cfs_rq, se, queued);
7243	}
7244
7245	if (numabalancing_enabled)
7246		task_tick_numa(rq, curr);
7247
7248	update_rq_runnable_avg(rq, 1);
7249}
7250
7251/*
7252 * called on fork with the child task as argument from the parent's context
7253 *  - child not yet on the tasklist
7254 *  - preemption disabled
7255 */
7256static void task_fork_fair(struct task_struct *p)
7257{
7258	struct cfs_rq *cfs_rq;
7259	struct sched_entity *se = &p->se, *curr;
7260	int this_cpu = smp_processor_id();
7261	struct rq *rq = this_rq();
7262	unsigned long flags;
7263
7264	raw_spin_lock_irqsave(&rq->lock, flags);
7265
7266	update_rq_clock(rq);
7267
7268	cfs_rq = task_cfs_rq(current);
7269	curr = cfs_rq->curr;
7270
7271	/*
7272	 * Not only the cpu but also the task_group of the parent might have
7273	 * been changed after parent->se.parent,cfs_rq were copied to
7274	 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
7275	 * of child point to valid ones.
7276	 */
7277	rcu_read_lock();
7278	__set_task_cpu(p, this_cpu);
7279	rcu_read_unlock();
7280
7281	update_curr(cfs_rq);
7282
7283	if (curr)
7284		se->vruntime = curr->vruntime;
7285	place_entity(cfs_rq, se, 1);
7286
7287	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
7288		/*
7289		 * Upon rescheduling, sched_class::put_prev_task() will place
7290		 * 'current' within the tree based on its new key value.
7291		 */
7292		swap(curr->vruntime, se->vruntime);
7293		resched_task(rq->curr);
7294	}
7295
7296	se->vruntime -= cfs_rq->min_vruntime;
7297
7298	raw_spin_unlock_irqrestore(&rq->lock, flags);
7299}
7300
7301/*
7302 * Priority of the task has changed. Check to see if we preempt
7303 * the current task.
7304 */
7305static void
7306prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
7307{
7308	if (!p->se.on_rq)
7309		return;
7310
7311	/*
7312	 * Reschedule if we are currently running on this runqueue and
7313	 * our priority decreased, or if we are not currently running on
7314	 * this runqueue and our priority is higher than the current's
7315	 */
7316	if (rq->curr == p) {
7317		if (p->prio > oldprio)
7318			resched_task(rq->curr);
7319	} else
7320		check_preempt_curr(rq, p, 0);
7321}
7322
7323static void switched_from_fair(struct rq *rq, struct task_struct *p)
7324{
7325	struct sched_entity *se = &p->se;
7326	struct cfs_rq *cfs_rq = cfs_rq_of(se);
7327
7328	/*
7329	 * Ensure the task's vruntime is normalized, so that when it's
7330	 * switched back to the fair class the enqueue_entity(.flags=0) will
7331	 * do the right thing.
 
 
 
 
 
 
 
7332	 *
7333	 * If it's on_rq, then the dequeue_entity(.flags=0) will already
7334	 * have normalized the vruntime, if it's !on_rq, then only when
7335	 * the task is sleeping will it still have non-normalized vruntime.
 
7336	 */
7337	if (!p->on_rq && p->state != TASK_RUNNING) {
 
 
 
 
 
 
 
 
 
 
 
7338		/*
7339		 * Fix up our vruntime so that the current sleep doesn't
7340		 * cause 'unlimited' sleep bonus.
7341		 */
7342		place_entity(cfs_rq, se, 0);
7343		se->vruntime -= cfs_rq->min_vruntime;
7344	}
7345
7346#ifdef CONFIG_SMP
7347	/*
7348	* Remove our load from contribution when we leave sched_fair
7349	* and ensure we don't carry in an old decay_count if we
7350	* switch back.
7351	*/
7352	if (se->avg.decay_count) {
7353		__synchronize_entity_decay(se);
7354		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
7355	}
7356#endif
7357}
7358
7359/*
7360 * We switched to the sched_fair class.
7361 */
7362static void switched_to_fair(struct rq *rq, struct task_struct *p)
7363{
7364	struct sched_entity *se = &p->se;
 
 
7365#ifdef CONFIG_FAIR_GROUP_SCHED
7366	/*
7367	 * Since the real-depth could have been changed (only FAIR
7368	 * class maintain depth value), reset depth properly.
7369	 */
7370	se->depth = se->parent ? se->parent->depth + 1 : 0;
7371#endif
7372	if (!se->on_rq)
7373		return;
7374
7375	/*
7376	 * We were most likely switched from sched_rt, so
7377	 * kick off the schedule if running, otherwise just see
7378	 * if we can still preempt the current task.
7379	 */
7380	if (rq->curr == p)
7381		resched_task(rq->curr);
7382	else
7383		check_preempt_curr(rq, p, 0);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7384}
7385
7386/* Account for a task changing its policy or group.
7387 *
7388 * This routine is mostly called to set cfs_rq->curr field when a task
7389 * migrates between groups/classes.
7390 */
7391static void set_curr_task_fair(struct rq *rq)
7392{
7393	struct sched_entity *se = &rq->curr->se;
7394
7395	for_each_sched_entity(se) {
7396		struct cfs_rq *cfs_rq = cfs_rq_of(se);
7397
7398		set_next_entity(cfs_rq, se);
7399		/* ensure bandwidth has been allocated on our new cfs_rq */
7400		account_cfs_rq_runtime(cfs_rq, 0);
7401	}
7402}
7403
7404void init_cfs_rq(struct cfs_rq *cfs_rq)
7405{
7406	cfs_rq->tasks_timeline = RB_ROOT;
7407	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
7408#ifndef CONFIG_64BIT
7409	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
7410#endif
7411#ifdef CONFIG_SMP
7412	atomic64_set(&cfs_rq->decay_counter, 1);
7413	atomic_long_set(&cfs_rq->removed_load, 0);
7414#endif
7415}
7416
7417#ifdef CONFIG_FAIR_GROUP_SCHED
7418static void task_move_group_fair(struct task_struct *p, int on_rq)
7419{
7420	struct sched_entity *se = &p->se;
7421	struct cfs_rq *cfs_rq;
7422
7423	/*
7424	 * If the task was not on the rq at the time of this cgroup movement
7425	 * it must have been asleep, sleeping tasks keep their ->vruntime
7426	 * absolute on their old rq until wakeup (needed for the fair sleeper
7427	 * bonus in place_entity()).
7428	 *
7429	 * If it was on the rq, we've just 'preempted' it, which does convert
7430	 * ->vruntime to a relative base.
7431	 *
7432	 * Make sure both cases convert their relative position when migrating
7433	 * to another cgroup's rq. This does somewhat interfere with the
7434	 * fair sleeper stuff for the first placement, but who cares.
7435	 */
7436	/*
7437	 * When !on_rq, vruntime of the task has usually NOT been normalized.
7438	 * But there are some cases where it has already been normalized:
7439	 *
7440	 * - Moving a forked child which is waiting for being woken up by
7441	 *   wake_up_new_task().
7442	 * - Moving a task which has been woken up by try_to_wake_up() and
7443	 *   waiting for actually being woken up by sched_ttwu_pending().
7444	 *
7445	 * To prevent boost or penalty in the new cfs_rq caused by delta
7446	 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
7447	 */
7448	if (!on_rq && (!se->sum_exec_runtime || p->state == TASK_WAKING))
7449		on_rq = 1;
7450
7451	if (!on_rq)
7452		se->vruntime -= cfs_rq_of(se)->min_vruntime;
7453	set_task_rq(p, task_cpu(p));
7454	se->depth = se->parent ? se->parent->depth + 1 : 0;
7455	if (!on_rq) {
7456		cfs_rq = cfs_rq_of(se);
7457		se->vruntime += cfs_rq->min_vruntime;
7458#ifdef CONFIG_SMP
7459		/*
7460		 * migrate_task_rq_fair() will have removed our previous
7461		 * contribution, but we must synchronize for ongoing future
7462		 * decay.
7463		 */
7464		se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
7465		cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
7466#endif
7467	}
7468}
7469
7470void free_fair_sched_group(struct task_group *tg)
7471{
7472	int i;
7473
7474	destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
7475
7476	for_each_possible_cpu(i) {
7477		if (tg->cfs_rq)
7478			kfree(tg->cfs_rq[i]);
7479		if (tg->se)
7480			kfree(tg->se[i]);
7481	}
7482
7483	kfree(tg->cfs_rq);
7484	kfree(tg->se);
7485}
7486
7487int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
7488{
7489	struct cfs_rq *cfs_rq;
7490	struct sched_entity *se;
7491	int i;
7492
7493	tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
7494	if (!tg->cfs_rq)
7495		goto err;
7496	tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
7497	if (!tg->se)
7498		goto err;
7499
7500	tg->shares = NICE_0_LOAD;
7501
7502	init_cfs_bandwidth(tg_cfs_bandwidth(tg));
7503
7504	for_each_possible_cpu(i) {
7505		cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
7506				      GFP_KERNEL, cpu_to_node(i));
7507		if (!cfs_rq)
7508			goto err;
7509
7510		se = kzalloc_node(sizeof(struct sched_entity),
7511				  GFP_KERNEL, cpu_to_node(i));
7512		if (!se)
7513			goto err_free_rq;
7514
7515		init_cfs_rq(cfs_rq);
7516		init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
 
7517	}
7518
7519	return 1;
7520
7521err_free_rq:
7522	kfree(cfs_rq);
7523err:
7524	return 0;
7525}
7526
7527void unregister_fair_sched_group(struct task_group *tg, int cpu)
7528{
7529	struct rq *rq = cpu_rq(cpu);
7530	unsigned long flags;
 
 
7531
7532	/*
7533	* Only empty task groups can be destroyed; so we can speculatively
7534	* check on_list without danger of it being re-added.
7535	*/
7536	if (!tg->cfs_rq[cpu]->on_list)
7537		return;
7538
7539	raw_spin_lock_irqsave(&rq->lock, flags);
7540	list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
7541	raw_spin_unlock_irqrestore(&rq->lock, flags);
 
 
 
 
 
 
 
 
 
 
7542}
7543
7544void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
7545			struct sched_entity *se, int cpu,
7546			struct sched_entity *parent)
7547{
7548	struct rq *rq = cpu_rq(cpu);
7549
7550	cfs_rq->tg = tg;
7551	cfs_rq->rq = rq;
7552	init_cfs_rq_runtime(cfs_rq);
7553
7554	tg->cfs_rq[cpu] = cfs_rq;
7555	tg->se[cpu] = se;
7556
7557	/* se could be NULL for root_task_group */
7558	if (!se)
7559		return;
7560
7561	if (!parent) {
7562		se->cfs_rq = &rq->cfs;
7563		se->depth = 0;
7564	} else {
7565		se->cfs_rq = parent->my_q;
7566		se->depth = parent->depth + 1;
7567	}
7568
7569	se->my_q = cfs_rq;
7570	/* guarantee group entities always have weight */
7571	update_load_set(&se->load, NICE_0_LOAD);
7572	se->parent = parent;
7573}
7574
7575static DEFINE_MUTEX(shares_mutex);
7576
7577int sched_group_set_shares(struct task_group *tg, unsigned long shares)
7578{
7579	int i;
7580	unsigned long flags;
7581
7582	/*
7583	 * We can't change the weight of the root cgroup.
7584	 */
7585	if (!tg->se[0])
7586		return -EINVAL;
7587
7588	shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
7589
7590	mutex_lock(&shares_mutex);
7591	if (tg->shares == shares)
7592		goto done;
7593
7594	tg->shares = shares;
7595	for_each_possible_cpu(i) {
7596		struct rq *rq = cpu_rq(i);
7597		struct sched_entity *se;
7598
7599		se = tg->se[i];
7600		/* Propagate contribution to hierarchy */
7601		raw_spin_lock_irqsave(&rq->lock, flags);
7602
7603		/* Possible calls to update_curr() need rq clock */
7604		update_rq_clock(rq);
7605		for_each_sched_entity(se)
7606			update_cfs_shares(group_cfs_rq(se));
7607		raw_spin_unlock_irqrestore(&rq->lock, flags);
7608	}
7609
7610done:
7611	mutex_unlock(&shares_mutex);
7612	return 0;
7613}
7614#else /* CONFIG_FAIR_GROUP_SCHED */
7615
7616void free_fair_sched_group(struct task_group *tg) { }
7617
7618int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
7619{
7620	return 1;
7621}
7622
7623void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
7624
7625#endif /* CONFIG_FAIR_GROUP_SCHED */
7626
7627
7628static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
7629{
7630	struct sched_entity *se = &task->se;
7631	unsigned int rr_interval = 0;
7632
7633	/*
7634	 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
7635	 * idle runqueue:
7636	 */
7637	if (rq->cfs.load.weight)
7638		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
7639
7640	return rr_interval;
7641}
7642
7643/*
7644 * All the scheduling class methods:
7645 */
7646const struct sched_class fair_sched_class = {
7647	.next			= &idle_sched_class,
7648	.enqueue_task		= enqueue_task_fair,
7649	.dequeue_task		= dequeue_task_fair,
7650	.yield_task		= yield_task_fair,
7651	.yield_to_task		= yield_to_task_fair,
7652
7653	.check_preempt_curr	= check_preempt_wakeup,
7654
7655	.pick_next_task		= pick_next_task_fair,
7656	.put_prev_task		= put_prev_task_fair,
7657
7658#ifdef CONFIG_SMP
7659	.select_task_rq		= select_task_rq_fair,
7660	.migrate_task_rq	= migrate_task_rq_fair,
7661
7662	.rq_online		= rq_online_fair,
7663	.rq_offline		= rq_offline_fair,
7664
7665	.task_waking		= task_waking_fair,
 
 
7666#endif
7667
7668	.set_curr_task          = set_curr_task_fair,
7669	.task_tick		= task_tick_fair,
7670	.task_fork		= task_fork_fair,
7671
7672	.prio_changed		= prio_changed_fair,
7673	.switched_from		= switched_from_fair,
7674	.switched_to		= switched_to_fair,
7675
7676	.get_rr_interval	= get_rr_interval_fair,
7677
 
 
7678#ifdef CONFIG_FAIR_GROUP_SCHED
7679	.task_move_group	= task_move_group_fair,
7680#endif
7681};
7682
7683#ifdef CONFIG_SCHED_DEBUG
7684void print_cfs_stats(struct seq_file *m, int cpu)
7685{
7686	struct cfs_rq *cfs_rq;
7687
7688	rcu_read_lock();
7689	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
7690		print_cfs_rq(m, cpu, cfs_rq);
7691	rcu_read_unlock();
7692}
7693#endif
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7694
7695__init void init_sched_fair_class(void)
7696{
7697#ifdef CONFIG_SMP
7698	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
7699
7700#ifdef CONFIG_NO_HZ_COMMON
7701	nohz.next_balance = jiffies;
7702	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
7703	cpu_notifier(sched_ilb_notifier, 0);
7704#endif
7705#endif /* SMP */
7706
7707}