sched_fair.c 108.7 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
18 19 20
 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
21 22
 */

A
Arjan van de Ven 已提交
23
#include <linux/latencytop.h>
24
#include <linux/sched.h>
A
Arjan van de Ven 已提交
25

26
/*
27
 * Targeted preemption latency for CPU-bound tasks:
28
 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
29
 *
30
 * NOTE: this latency value is not the same as the concept of
I
Ingo Molnar 已提交
31 32 33
 * 'timeslice length' - timeslices in CFS are of variable length
 * and have no persistent notion like in traditional, time-slice
 * based scheduling concepts.
34
 *
I
Ingo Molnar 已提交
35 36
 * (to see the precise effective timeslice length of your workload,
 *  run vmstat and monitor the context-switches (cs) field)
37
 */
38 39
unsigned int sysctl_sched_latency = 6000000ULL;
unsigned int normalized_sysctl_sched_latency = 6000000ULL;
40

41 42 43 44 45 46 47 48 49 50 51 52
/*
 * The initial- and re-scaling of tunables is configurable
 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
 *
 * Options are:
 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
 */
enum sched_tunable_scaling sysctl_sched_tunable_scaling
	= SCHED_TUNABLESCALING_LOG;

53
/*
54
 * Minimal preemption granularity for CPU-bound tasks:
55
 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
56
 */
57 58
unsigned int sysctl_sched_min_granularity = 750000ULL;
unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
59 60

/*
61 62
 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
 */
63
static unsigned int sched_nr_latency = 8;
64 65

/*
66
 * After fork, child runs first. If set to 0 (default) then
67
 * parent will (try to) run first.
68
 */
69
unsigned int sysctl_sched_child_runs_first __read_mostly;
70

71 72 73 74 75 76 77 78
/*
 * sys_sched_yield() compat mode
 *
 * This option switches the agressive yield implementation of the
 * old scheduler back on.
 */
unsigned int __read_mostly sysctl_sched_compat_yield;

79 80
/*
 * SCHED_OTHER wake-up granularity.
81
 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
82 83 84 85 86
 *
 * This option delays the preemption effects of decoupled workloads
 * and reduces their over-scheduling. Synchronous workloads will still
 * have immediate wakeup/sleep latencies.
 */
87
unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
88
unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
89

90 91
const_debug unsigned int sysctl_sched_migration_cost = 500000UL;

92 93 94 95 96 97 98
/*
 * The exponential sliding  window over which load is averaged for shares
 * distribution.
 * (default: 10msec)
 */
unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;

99 100
static const struct sched_class fair_sched_class;

101 102 103 104
/**************************************************************
 * CFS operations on generic schedulable entities:
 */

105
#ifdef CONFIG_FAIR_GROUP_SCHED
106

107
/* cpu runqueue to which this cfs_rq is attached */
108 109
static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
110
	return cfs_rq->rq;
111 112
}

113 114
/* An entity is a task if it doesn't "own" a runqueue */
#define entity_is_task(se)	(!se->my_q)
115

116 117 118 119 120 121 122 123
static inline struct task_struct *task_of(struct sched_entity *se)
{
#ifdef CONFIG_SCHED_DEBUG
	WARN_ON_ONCE(!entity_is_task(se));
#endif
	return container_of(se, struct task_struct, se);
}

P
Peter Zijlstra 已提交
124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152
/* Walk up scheduling entities hierarchy */
#define for_each_sched_entity(se) \
		for (; se; se = se->parent)

static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
{
	return p->se.cfs_rq;
}

/* runqueue on which this entity is (to be) queued */
static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
{
	return se->cfs_rq;
}

/* runqueue "owned" by this group */
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
{
	return grp->my_q;
}

/* Given a group's cfs_rq on one cpu, return its corresponding cfs_rq on
 * another cpu ('this_cpu')
 */
static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
{
	return cfs_rq->tg->cfs_rq[this_cpu];
}

153 154 155
static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
	if (!cfs_rq->on_list) {
156 157 158 159 160 161 162 163 164 165 166 167
		/*
		 * Ensure we either appear before our parent (if already
		 * enqueued) or force our parent to appear after us when it is
		 * enqueued.  The fact that we always enqueue bottom-up
		 * reduces this to two cases.
		 */
		if (cfs_rq->tg->parent &&
		    cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
			list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
				&rq_of(cfs_rq)->leaf_cfs_rq_list);
		} else {
			list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
168
				&rq_of(cfs_rq)->leaf_cfs_rq_list);
169
		}
170 171 172 173 174 175 176 177 178 179 180 181 182

		cfs_rq->on_list = 1;
	}
}

static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
	if (cfs_rq->on_list) {
		list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
		cfs_rq->on_list = 0;
	}
}

P
Peter Zijlstra 已提交
183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201
/* Iterate thr' all leaf cfs_rq's on a runqueue */
#define for_each_leaf_cfs_rq(rq, cfs_rq) \
	list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)

/* Do the two (enqueued) entities belong to the same group ? */
static inline int
is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
	if (se->cfs_rq == pse->cfs_rq)
		return 1;

	return 0;
}

static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
	return se->parent;
}

202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244
/* return depth at which a sched entity is present in the hierarchy */
static inline int depth_se(struct sched_entity *se)
{
	int depth = 0;

	for_each_sched_entity(se)
		depth++;

	return depth;
}

static void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
	int se_depth, pse_depth;

	/*
	 * preemption test can be made between sibling entities who are in the
	 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
	 * both tasks until we find their ancestors who are siblings of common
	 * parent.
	 */

	/* First walk up until both entities are at same depth */
	se_depth = depth_se(*se);
	pse_depth = depth_se(*pse);

	while (se_depth > pse_depth) {
		se_depth--;
		*se = parent_entity(*se);
	}

	while (pse_depth > se_depth) {
		pse_depth--;
		*pse = parent_entity(*pse);
	}

	while (!is_same_group(*se, *pse)) {
		*se = parent_entity(*se);
		*pse = parent_entity(*pse);
	}
}

245 246 247 248 249 250
#else	/* !CONFIG_FAIR_GROUP_SCHED */

static inline struct task_struct *task_of(struct sched_entity *se)
{
	return container_of(se, struct task_struct, se);
}
251

252 253 254
static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
	return container_of(cfs_rq, struct rq, cfs);
255 256 257 258
}

#define entity_is_task(se)	1

P
Peter Zijlstra 已提交
259 260
#define for_each_sched_entity(se) \
		for (; se; se = NULL)
261

P
Peter Zijlstra 已提交
262
static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
263
{
P
Peter Zijlstra 已提交
264
	return &task_rq(p)->cfs;
265 266
}

P
Peter Zijlstra 已提交
267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285
static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
{
	struct task_struct *p = task_of(se);
	struct rq *rq = task_rq(p);

	return &rq->cfs;
}

/* runqueue "owned" by this group */
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
{
	return NULL;
}

static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
{
	return &cpu_rq(this_cpu)->cfs;
}

286 287 288 289 290 291 292 293
static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
}

static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
}

P
Peter Zijlstra 已提交
294 295 296 297 298 299 300 301 302 303 304 305 306 307
#define for_each_leaf_cfs_rq(rq, cfs_rq) \
		for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)

static inline int
is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
	return 1;
}

static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
	return NULL;
}

308 309 310 311 312
static inline void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
}

P
Peter Zijlstra 已提交
313 314
#endif	/* CONFIG_FAIR_GROUP_SCHED */

315 316 317 318 319

/**************************************************************
 * Scheduling class tree data structure manipulation methods:
 */

320
static inline u64 max_vruntime(u64 min_vruntime, u64 vruntime)
321
{
322 323
	s64 delta = (s64)(vruntime - min_vruntime);
	if (delta > 0)
324 325 326 327 328
		min_vruntime = vruntime;

	return min_vruntime;
}

329
static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
P
Peter Zijlstra 已提交
330 331 332 333 334 335 336 337
{
	s64 delta = (s64)(vruntime - min_vruntime);
	if (delta < 0)
		min_vruntime = vruntime;

	return min_vruntime;
}

338 339 340 341 342 343
static inline int entity_before(struct sched_entity *a,
				struct sched_entity *b)
{
	return (s64)(a->vruntime - b->vruntime) < 0;
}

344
static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
345
{
346
	return se->vruntime - cfs_rq->min_vruntime;
347 348
}

349 350 351 352 353 354 355 356 357 358 359 360
static void update_min_vruntime(struct cfs_rq *cfs_rq)
{
	u64 vruntime = cfs_rq->min_vruntime;

	if (cfs_rq->curr)
		vruntime = cfs_rq->curr->vruntime;

	if (cfs_rq->rb_leftmost) {
		struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
						   struct sched_entity,
						   run_node);

P
Peter Zijlstra 已提交
361
		if (!cfs_rq->curr)
362 363 364 365 366 367 368 369
			vruntime = se->vruntime;
		else
			vruntime = min_vruntime(vruntime, se->vruntime);
	}

	cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
}

370 371 372
/*
 * Enqueue an entity into the rb-tree:
 */
373
static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
374 375 376 377
{
	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
	struct rb_node *parent = NULL;
	struct sched_entity *entry;
378
	s64 key = entity_key(cfs_rq, se);
379 380 381 382 383 384 385 386 387 388 389 390
	int leftmost = 1;

	/*
	 * Find the right place in the rbtree:
	 */
	while (*link) {
		parent = *link;
		entry = rb_entry(parent, struct sched_entity, run_node);
		/*
		 * We dont care about collisions. Nodes with
		 * the same key stay together.
		 */
391
		if (key < entity_key(cfs_rq, entry)) {
392 393 394 395 396 397 398 399 400 401 402
			link = &parent->rb_left;
		} else {
			link = &parent->rb_right;
			leftmost = 0;
		}
	}

	/*
	 * Maintain a cache of leftmost tree entries (it is frequently
	 * used):
	 */
403
	if (leftmost)
I
Ingo Molnar 已提交
404
		cfs_rq->rb_leftmost = &se->run_node;
405 406 407 408 409

	rb_link_node(&se->run_node, parent, link);
	rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
}

410
static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
411
{
P
Peter Zijlstra 已提交
412 413 414 415 416 417
	if (cfs_rq->rb_leftmost == &se->run_node) {
		struct rb_node *next_node;

		next_node = rb_next(&se->run_node);
		cfs_rq->rb_leftmost = next_node;
	}
I
Ingo Molnar 已提交
418

419 420 421 422 423
	rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
}

static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
{
424 425 426 427 428 429
	struct rb_node *left = cfs_rq->rb_leftmost;

	if (!left)
		return NULL;

	return rb_entry(left, struct sched_entity, run_node);
430 431
}

432
static struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
433
{
434
	struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
435

436 437
	if (!last)
		return NULL;
438 439

	return rb_entry(last, struct sched_entity, run_node);
440 441
}

442 443 444 445
/**************************************************************
 * Scheduling class statistics methods:
 */

446
#ifdef CONFIG_SCHED_DEBUG
447
int sched_proc_update_handler(struct ctl_table *table, int write,
448
		void __user *buffer, size_t *lenp,
449 450
		loff_t *ppos)
{
451
	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
452
	int factor = get_update_sysctl_factor();
453 454 455 456 457 458 459

	if (ret || !write)
		return ret;

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

460 461 462 463 464 465 466
#define WRT_SYSCTL(name) \
	(normalized_sysctl_##name = sysctl_##name / (factor))
	WRT_SYSCTL(sched_min_granularity);
	WRT_SYSCTL(sched_latency);
	WRT_SYSCTL(sched_wakeup_granularity);
#undef WRT_SYSCTL

467 468 469
	return 0;
}
#endif
470

471
/*
472
 * delta /= w
473 474 475 476
 */
static inline unsigned long
calc_delta_fair(unsigned long delta, struct sched_entity *se)
{
477 478
	if (unlikely(se->load.weight != NICE_0_LOAD))
		delta = calc_delta_mine(delta, NICE_0_LOAD, &se->load);
479 480 481 482

	return delta;
}

483 484 485 486 487 488 489 490
/*
 * The idea is to set a period in which each task runs once.
 *
 * When there are too many tasks (sysctl_sched_nr_latency) we have to stretch
 * this period because otherwise the slices get too small.
 *
 * p = (nr <= nl) ? l : l*nr/nl
 */
491 492 493
static u64 __sched_period(unsigned long nr_running)
{
	u64 period = sysctl_sched_latency;
494
	unsigned long nr_latency = sched_nr_latency;
495 496

	if (unlikely(nr_running > nr_latency)) {
497
		period = sysctl_sched_min_granularity;
498 499 500 501 502 503
		period *= nr_running;
	}

	return period;
}

504 505 506 507
/*
 * We calculate the wall-time slice from the period by taking a part
 * proportional to the weight.
 *
508
 * s = p*P[w/rw]
509
 */
P
Peter Zijlstra 已提交
510
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
511
{
M
Mike Galbraith 已提交
512
	u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
513

M
Mike Galbraith 已提交
514
	for_each_sched_entity(se) {
L
Lin Ming 已提交
515
		struct load_weight *load;
516
		struct load_weight lw;
L
Lin Ming 已提交
517 518 519

		cfs_rq = cfs_rq_of(se);
		load = &cfs_rq->load;
520

M
Mike Galbraith 已提交
521
		if (unlikely(!se->on_rq)) {
522
			lw = cfs_rq->load;
M
Mike Galbraith 已提交
523 524 525 526 527 528 529

			update_load_add(&lw, se->load.weight);
			load = &lw;
		}
		slice = calc_delta_mine(slice, se->load.weight, load);
	}
	return slice;
530 531
}

532
/*
533
 * We calculate the vruntime slice of a to be inserted task
534
 *
535
 * vs = s/w
536
 */
537
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
P
Peter Zijlstra 已提交
538
{
539
	return calc_delta_fair(sched_slice(cfs_rq, se), se);
540 541
}

542
static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update);
543
static void update_cfs_shares(struct cfs_rq *cfs_rq);
544

545 546 547 548 549
/*
 * Update the current task's runtime statistics. Skip current tasks that
 * are not in our scheduling class.
 */
static inline void
I
Ingo Molnar 已提交
550 551
__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
	      unsigned long delta_exec)
552
{
553
	unsigned long delta_exec_weighted;
554

555 556
	schedstat_set(curr->statistics.exec_max,
		      max((u64)delta_exec, curr->statistics.exec_max));
557 558

	curr->sum_exec_runtime += delta_exec;
559
	schedstat_add(cfs_rq, exec_clock, delta_exec);
560
	delta_exec_weighted = calc_delta_fair(delta_exec, curr);
561

I
Ingo Molnar 已提交
562
	curr->vruntime += delta_exec_weighted;
563
	update_min_vruntime(cfs_rq);
564

P
Peter Zijlstra 已提交
565
#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
566 567
	cfs_rq->load_unacc_exec_time += delta_exec;
#endif
568 569
}

570
static void update_curr(struct cfs_rq *cfs_rq)
571
{
572
	struct sched_entity *curr = cfs_rq->curr;
573
	u64 now = rq_of(cfs_rq)->clock_task;
574 575 576 577 578 579 580 581 582 583
	unsigned long delta_exec;

	if (unlikely(!curr))
		return;

	/*
	 * Get the amount of time the current task was running
	 * since the last time we changed load (this cannot
	 * overflow on 32 bits):
	 */
I
Ingo Molnar 已提交
584
	delta_exec = (unsigned long)(now - curr->exec_start);
P
Peter Zijlstra 已提交
585 586
	if (!delta_exec)
		return;
587

I
Ingo Molnar 已提交
588 589
	__update_curr(cfs_rq, curr, delta_exec);
	curr->exec_start = now;
590 591 592 593

	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

594
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
595
		cpuacct_charge(curtask, delta_exec);
596
		account_group_exec_runtime(curtask, delta_exec);
597
	}
598 599 600
}

static inline void
601
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
602
{
603
	schedstat_set(se->statistics.wait_start, rq_of(cfs_rq)->clock);
604 605 606 607 608
}

/*
 * Task is being enqueued - update stats:
 */
609
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
610 611 612 613 614
{
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
615
	if (se != cfs_rq->curr)
616
		update_stats_wait_start(cfs_rq, se);
617 618 619
}

static void
620
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
621
{
622 623 624 625 626
	schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
			rq_of(cfs_rq)->clock - se->statistics.wait_start));
	schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
	schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
			rq_of(cfs_rq)->clock - se->statistics.wait_start);
627 628 629
#ifdef CONFIG_SCHEDSTATS
	if (entity_is_task(se)) {
		trace_sched_stat_wait(task_of(se),
630
			rq_of(cfs_rq)->clock - se->statistics.wait_start);
631 632
	}
#endif
633
	schedstat_set(se->statistics.wait_start, 0);
634 635 636
}

static inline void
637
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
638 639 640 641 642
{
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
643
	if (se != cfs_rq->curr)
644
		update_stats_wait_end(cfs_rq, se);
645 646 647 648 649 650
}

/*
 * We are picking a new current task - update its stats:
 */
static inline void
651
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
652 653 654 655
{
	/*
	 * We are starting a new run period:
	 */
656
	se->exec_start = rq_of(cfs_rq)->clock_task;
657 658 659 660 661 662
}

/**************************************************
 * Scheduling class queueing methods:
 */

663 664 665 666 667 668 669 670 671 672 673 674 675
#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
static void
add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight)
{
	cfs_rq->task_weight += weight;
}
#else
static inline void
add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight)
{
}
#endif

676 677 678 679
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
680 681
	if (!parent_entity(se))
		inc_cpu_load(rq_of(cfs_rq), se->load.weight);
682
	if (entity_is_task(se)) {
683
		add_cfs_task_weight(cfs_rq, se->load.weight);
684 685
		list_add(&se->group_node, &cfs_rq->tasks);
	}
686 687 688 689 690 691 692
	cfs_rq->nr_running++;
}

static void
account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_sub(&cfs_rq->load, se->load.weight);
693 694
	if (!parent_entity(se))
		dec_cpu_load(rq_of(cfs_rq), se->load.weight);
695
	if (entity_is_task(se)) {
696
		add_cfs_task_weight(cfs_rq, -se->load.weight);
697 698
		list_del_init(&se->group_node);
	}
699 700 701
	cfs_rq->nr_running--;
}

702 703
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719
static void update_cfs_rq_load_contribution(struct cfs_rq *cfs_rq,
					    int global_update)
{
	struct task_group *tg = cfs_rq->tg;
	long load_avg;

	load_avg = div64_u64(cfs_rq->load_avg, cfs_rq->load_period+1);
	load_avg -= cfs_rq->load_contribution;

	if (global_update || abs(load_avg) > cfs_rq->load_contribution / 8) {
		atomic_add(load_avg, &tg->load_weight);
		cfs_rq->load_contribution += load_avg;
	}
}

static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
P
Peter Zijlstra 已提交
720
{
721
	u64 period = sysctl_sched_shares_window;
P
Peter Zijlstra 已提交
722
	u64 now, delta;
723
	unsigned long load = cfs_rq->load.weight;
P
Peter Zijlstra 已提交
724

725
	if (cfs_rq->tg == &root_task_group)
P
Peter Zijlstra 已提交
726 727
		return;

728
	now = rq_of(cfs_rq)->clock_task;
P
Peter Zijlstra 已提交
729 730
	delta = now - cfs_rq->load_stamp;

731 732 733 734 735
	/* truncate load history at 4 idle periods */
	if (cfs_rq->load_stamp > cfs_rq->load_last &&
	    now - cfs_rq->load_last > 4 * period) {
		cfs_rq->load_period = 0;
		cfs_rq->load_avg = 0;
736
		delta = period - 1;
737 738
	}

P
Peter Zijlstra 已提交
739
	cfs_rq->load_stamp = now;
740
	cfs_rq->load_unacc_exec_time = 0;
P
Peter Zijlstra 已提交
741
	cfs_rq->load_period += delta;
742 743 744 745
	if (load) {
		cfs_rq->load_last = now;
		cfs_rq->load_avg += delta * load;
	}
P
Peter Zijlstra 已提交
746

747 748 749 750 751
	/* consider updating load contribution on each fold or truncate */
	if (global_update || cfs_rq->load_period > period
	    || !cfs_rq->load_period)
		update_cfs_rq_load_contribution(cfs_rq, global_update);

P
Peter Zijlstra 已提交
752 753 754 755 756 757 758 759 760 761
	while (cfs_rq->load_period > period) {
		/*
		 * Inline assembly required to prevent the compiler
		 * optimising this loop into a divmod call.
		 * See __iter_div_u64_rem() for another example of this.
		 */
		asm("" : "+rm" (cfs_rq->load_period));
		cfs_rq->load_period /= 2;
		cfs_rq->load_avg /= 2;
	}
762

763 764
	if (!cfs_rq->curr && !cfs_rq->nr_running && !cfs_rq->load_avg)
		list_del_leaf_cfs_rq(cfs_rq);
P
Peter Zijlstra 已提交
765 766
}

767
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
768 769 770
{
	long load_weight, load, shares;

771
	load = cfs_rq->load.weight;
772 773 774

	load_weight = atomic_read(&tg->load_weight);
	load_weight += load;
775
	load_weight -= cfs_rq->load_contribution;
776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792

	shares = (tg->shares * load);
	if (load_weight)
		shares /= load_weight;

	if (shares < MIN_SHARES)
		shares = MIN_SHARES;
	if (shares > tg->shares)
		shares = tg->shares;

	return shares;
}

static void update_entity_shares_tick(struct cfs_rq *cfs_rq)
{
	if (cfs_rq->load_unacc_exec_time > sysctl_sched_shares_window) {
		update_cfs_load(cfs_rq, 0);
793
		update_cfs_shares(cfs_rq);
794 795 796 797 798 799 800
	}
}
# else /* CONFIG_SMP */
static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
{
}

801
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
802 803 804 805 806 807 808 809
{
	return tg->shares;
}

static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
{
}
# endif /* CONFIG_SMP */
P
Peter Zijlstra 已提交
810 811 812
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
813 814 815 816
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
817
		account_entity_dequeue(cfs_rq, se);
818
	}
P
Peter Zijlstra 已提交
819 820 821 822 823 824 825

	update_load_set(&se->load, weight);

	if (se->on_rq)
		account_entity_enqueue(cfs_rq, se);
}

826
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
827 828 829
{
	struct task_group *tg;
	struct sched_entity *se;
830
	long shares;
P
Peter Zijlstra 已提交
831 832 833 834 835

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
	if (!se)
		return;
836 837 838 839
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
840
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
841 842 843 844

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
845
static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
P
Peter Zijlstra 已提交
846 847 848
{
}

849
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
850 851
{
}
852 853 854 855

static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
{
}
P
Peter Zijlstra 已提交
856 857
#endif /* CONFIG_FAIR_GROUP_SCHED */

858
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
859 860
{
#ifdef CONFIG_SCHEDSTATS
861 862 863 864 865
	struct task_struct *tsk = NULL;

	if (entity_is_task(se))
		tsk = task_of(se);

866 867
	if (se->statistics.sleep_start) {
		u64 delta = rq_of(cfs_rq)->clock - se->statistics.sleep_start;
868 869 870 871

		if ((s64)delta < 0)
			delta = 0;

872 873
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
874

875 876
		se->statistics.sleep_start = 0;
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
877

878
		if (tsk) {
879
			account_scheduler_latency(tsk, delta >> 10, 1);
880 881
			trace_sched_stat_sleep(tsk, delta);
		}
882
	}
883 884
	if (se->statistics.block_start) {
		u64 delta = rq_of(cfs_rq)->clock - se->statistics.block_start;
885 886 887 888

		if ((s64)delta < 0)
			delta = 0;

889 890
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
891

892 893
		se->statistics.block_start = 0;
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
894

895
		if (tsk) {
896
			if (tsk->in_iowait) {
897 898
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
899
				trace_sched_stat_iowait(tsk, delta);
900 901
			}

902 903 904 905 906 907 908 909 910 911 912
			/*
			 * Blocking time is in units of nanosecs, so shift by
			 * 20 to get a milliseconds-range estimation of the
			 * amount of time that the task spent sleeping:
			 */
			if (unlikely(prof_on == SLEEP_PROFILING)) {
				profile_hits(SLEEP_PROFILING,
						(void *)get_wchan(tsk),
						delta >> 20);
			}
			account_scheduler_latency(tsk, delta >> 10, 0);
I
Ingo Molnar 已提交
913
		}
914 915 916 917
	}
#endif
}

P
Peter Zijlstra 已提交
918 919 920 921 922 923 924 925 926 927 928 929 930
static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
#ifdef CONFIG_SCHED_DEBUG
	s64 d = se->vruntime - cfs_rq->min_vruntime;

	if (d < 0)
		d = -d;

	if (d > 3*sysctl_sched_latency)
		schedstat_inc(cfs_rq, nr_spread_over);
#endif
}

931 932 933
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
934
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
935

936 937 938 939 940 941
	/*
	 * The 'current' period is already promised to the current tasks,
	 * however the extra weight of the new task will slow them down a
	 * little, place the new task so that it fits in the slot that
	 * stays open at the end.
	 */
P
Peter Zijlstra 已提交
942
	if (initial && sched_feat(START_DEBIT))
943
		vruntime += sched_vslice(cfs_rq, se);
944

945
	/* sleeps up to a single latency don't count. */
946
	if (!initial) {
947
		unsigned long thresh = sysctl_sched_latency;
948

949 950 951 952 953 954
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
955

956
		vruntime -= thresh;
957 958
	}

959 960 961
	/* ensure we never gain time by being placed backwards. */
	vruntime = max_vruntime(se->vruntime, vruntime);

P
Peter Zijlstra 已提交
962
	se->vruntime = vruntime;
963 964
}

965
static void
966
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
967
{
968 969 970 971
	/*
	 * Update the normalized vruntime before updating min_vruntime
	 * through callig update_curr().
	 */
972
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
973 974
		se->vruntime += cfs_rq->min_vruntime;

975
	/*
976
	 * Update run-time statistics of the 'current'.
977
	 */
978
	update_curr(cfs_rq);
979
	update_cfs_load(cfs_rq, 0);
P
Peter Zijlstra 已提交
980
	account_entity_enqueue(cfs_rq, se);
981
	update_cfs_shares(cfs_rq);
982

983
	if (flags & ENQUEUE_WAKEUP) {
984
		place_entity(cfs_rq, se, 0);
985
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
986
	}
987

988
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
989
	check_spread(cfs_rq, se);
990 991
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
992
	se->on_rq = 1;
993 994 995

	if (cfs_rq->nr_running == 1)
		list_add_leaf_cfs_rq(cfs_rq);
996 997
}

998
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
999
{
1000 1001 1002 1003 1004 1005 1006 1007
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
		if (cfs_rq->last == se)
			cfs_rq->last = NULL;
		else
			break;
	}
}
P
Peter Zijlstra 已提交
1008

1009 1010 1011 1012 1013 1014 1015 1016 1017
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
		if (cfs_rq->next == se)
			cfs_rq->next = NULL;
		else
			break;
	}
P
Peter Zijlstra 已提交
1018 1019
}

P
Peter Zijlstra 已提交
1020 1021
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
1022 1023 1024 1025 1026
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
P
Peter Zijlstra 已提交
1027 1028
}

1029
static void
1030
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1031
{
1032 1033 1034 1035 1036
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);

1037
	update_stats_dequeue(cfs_rq, se);
1038
	if (flags & DEQUEUE_SLEEP) {
P
Peter Zijlstra 已提交
1039
#ifdef CONFIG_SCHEDSTATS
1040 1041 1042 1043
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
1044
				se->statistics.sleep_start = rq_of(cfs_rq)->clock;
1045
			if (tsk->state & TASK_UNINTERRUPTIBLE)
1046
				se->statistics.block_start = rq_of(cfs_rq)->clock;
1047
		}
1048
#endif
P
Peter Zijlstra 已提交
1049 1050
	}

P
Peter Zijlstra 已提交
1051
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
1052

1053
	if (se != cfs_rq->curr)
1054
		__dequeue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
1055
	se->on_rq = 0;
1056
	update_cfs_load(cfs_rq, 0);
1057
	account_entity_dequeue(cfs_rq, se);
1058
	update_min_vruntime(cfs_rq);
1059
	update_cfs_shares(cfs_rq);
1060 1061 1062 1063 1064 1065

	/*
	 * Normalize the entity after updating the min_vruntime because the
	 * update can refer to the ->curr item and we need to reflect this
	 * movement in our normalized position.
	 */
1066
	if (!(flags & DEQUEUE_SLEEP))
1067
		se->vruntime -= cfs_rq->min_vruntime;
1068 1069 1070 1071 1072
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
1073
static void
I
Ingo Molnar 已提交
1074
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
1075
{
1076 1077
	unsigned long ideal_runtime, delta_exec;

P
Peter Zijlstra 已提交
1078
	ideal_runtime = sched_slice(cfs_rq, curr);
1079
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
1080
	if (delta_exec > ideal_runtime) {
1081
		resched_task(rq_of(cfs_rq)->curr);
1082 1083 1084 1085 1086
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104
		return;
	}

	/*
	 * Ensure that a task that missed wakeup preemption by a
	 * narrow margin doesn't have to wait for a full slice.
	 * This also mitigates buddy induced latencies under load.
	 */
	if (!sched_feat(WAKEUP_PREEMPT))
		return;

	if (delta_exec < sysctl_sched_min_granularity)
		return;

	if (cfs_rq->nr_running > 1) {
		struct sched_entity *se = __pick_next_entity(cfs_rq);
		s64 delta = curr->vruntime - se->vruntime;

1105 1106 1107
		if (delta < 0)
			return;

1108 1109
		if (delta > ideal_runtime)
			resched_task(rq_of(cfs_rq)->curr);
1110
	}
1111 1112
}

1113
static void
1114
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
1115
{
1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126
	/* 'current' is not kept within the tree. */
	if (se->on_rq) {
		/*
		 * Any task has to be enqueued before it get to execute on
		 * a CPU. So account for the time it spent waiting on the
		 * runqueue.
		 */
		update_stats_wait_end(cfs_rq, se);
		__dequeue_entity(cfs_rq, se);
	}

1127
	update_stats_curr_start(cfs_rq, se);
1128
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
1129 1130 1131 1132 1133 1134
#ifdef CONFIG_SCHEDSTATS
	/*
	 * Track our maximum slice length, if the CPU's load is at
	 * least twice that of our own weight (i.e. dont track it
	 * when there are only lesser-weight tasks around):
	 */
1135
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
1136
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
1137 1138 1139
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
1140
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
1141 1142
}

1143 1144 1145
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

1146
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
1147
{
1148
	struct sched_entity *se = __pick_next_entity(cfs_rq);
1149
	struct sched_entity *left = se;
1150

1151 1152
	if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
		se = cfs_rq->next;
1153

1154 1155 1156 1157 1158 1159 1160
	/*
	 * Prefer last buddy, try to return the CPU to a preempted task.
	 */
	if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
		se = cfs_rq->last;

	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
1161 1162

	return se;
1163 1164
}

1165
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
1166 1167 1168 1169 1170 1171
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
1172
		update_curr(cfs_rq);
1173

P
Peter Zijlstra 已提交
1174
	check_spread(cfs_rq, prev);
1175
	if (prev->on_rq) {
1176
		update_stats_wait_start(cfs_rq, prev);
1177 1178 1179
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
	}
1180
	cfs_rq->curr = NULL;
1181 1182
}

P
Peter Zijlstra 已提交
1183 1184
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
1185 1186
{
	/*
1187
	 * Update run-time statistics of the 'current'.
1188
	 */
1189
	update_curr(cfs_rq);
1190

1191 1192 1193 1194 1195
	/*
	 * Update share accounting for long-running entities.
	 */
	update_entity_shares_tick(cfs_rq);

P
Peter Zijlstra 已提交
1196 1197 1198 1199 1200
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
1201 1202 1203 1204
	if (queued) {
		resched_task(rq_of(cfs_rq)->curr);
		return;
	}
P
Peter Zijlstra 已提交
1205 1206 1207 1208 1209 1210 1211 1212
	/*
	 * don't let the period tick interfere with the hrtick preemption
	 */
	if (!sched_feat(DOUBLE_TICK) &&
			hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
		return;
#endif

1213
	if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
I
Ingo Molnar 已提交
1214
		check_preempt_tick(cfs_rq, curr);
1215 1216 1217 1218 1219 1220
}

/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243
#ifdef CONFIG_SCHED_HRTICK
static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	WARN_ON(task_rq(p) != rq);

	if (hrtick_enabled(rq) && cfs_rq->nr_running > 1) {
		u64 slice = sched_slice(cfs_rq, se);
		u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
		s64 delta = slice - ran;

		if (delta < 0) {
			if (rq->curr == p)
				resched_task(p);
			return;
		}

		/*
		 * Don't schedule slices shorter than 10000ns, that just
		 * doesn't make sense. Rely on vruntime for fairness.
		 */
1244
		if (rq->curr != p)
1245
			delta = max_t(s64, 10000LL, delta);
P
Peter Zijlstra 已提交
1246

1247
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
1248 1249
	}
}
1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265

/*
 * called from enqueue/dequeue and updates the hrtick when the
 * current task is from our class and nr_running is low enough
 * to matter.
 */
static void hrtick_update(struct rq *rq)
{
	struct task_struct *curr = rq->curr;

	if (curr->sched_class != &fair_sched_class)
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
1266
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
1267 1268 1269 1270
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
1271 1272 1273 1274

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
1275 1276
#endif

1277 1278 1279 1280 1281
/*
 * The enqueue_task method is called before nr_running is
 * increased. Here we update the fair scheduling stats and
 * then put the task into the rbtree:
 */
1282
static void
1283
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
1284 1285
{
	struct cfs_rq *cfs_rq;
1286
	struct sched_entity *se = &p->se;
1287 1288

	for_each_sched_entity(se) {
1289
		if (se->on_rq)
1290 1291
			break;
		cfs_rq = cfs_rq_of(se);
1292 1293
		enqueue_entity(cfs_rq, se, flags);
		flags = ENQUEUE_WAKEUP;
1294
	}
P
Peter Zijlstra 已提交
1295

P
Peter Zijlstra 已提交
1296 1297 1298
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);

1299
		update_cfs_load(cfs_rq, 0);
1300
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
1301 1302
	}

1303
	hrtick_update(rq);
1304 1305 1306 1307 1308 1309 1310
}

/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
1311
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
1312 1313
{
	struct cfs_rq *cfs_rq;
1314
	struct sched_entity *se = &p->se;
1315 1316 1317

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
1318
		dequeue_entity(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
1319

1320
		/* Don't dequeue parent if it has other entities besides us */
1321
		if (cfs_rq->load.weight)
1322
			break;
1323
		flags |= DEQUEUE_SLEEP;
1324
	}
P
Peter Zijlstra 已提交
1325

P
Peter Zijlstra 已提交
1326 1327 1328
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);

1329
		update_cfs_load(cfs_rq, 0);
1330
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
1331 1332
	}

1333
	hrtick_update(rq);
1334 1335 1336
}

/*
1337 1338 1339
 * sched_yield() support is very simple - we dequeue and enqueue.
 *
 * If compat_yield is turned on then we requeue to the end of the tree.
1340
 */
1341
static void yield_task_fair(struct rq *rq)
1342
{
1343 1344 1345
	struct task_struct *curr = rq->curr;
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
	struct sched_entity *rightmost, *se = &curr->se;
1346 1347

	/*
1348 1349
	 * Are we the only task in the tree?
	 */
1350
	if (unlikely(rq->nr_running == 1))
1351 1352
		return;

P
Peter Zijlstra 已提交
1353 1354
	clear_buddies(cfs_rq, se);

1355
	if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) {
1356
		update_rq_clock(rq);
1357
		/*
1358
		 * Update run-time statistics of the 'current'.
1359
		 */
D
Dmitry Adamushko 已提交
1360
		update_curr(cfs_rq);
1361 1362 1363 1364 1365

		return;
	}
	/*
	 * Find the rightmost entry in the rbtree:
1366
	 */
D
Dmitry Adamushko 已提交
1367
	rightmost = __pick_last_entity(cfs_rq);
1368 1369 1370
	/*
	 * Already in the rightmost position?
	 */
1371
	if (unlikely(!rightmost || entity_before(rightmost, se)))
1372 1373 1374 1375
		return;

	/*
	 * Minimally necessary key value to be last in the tree:
D
Dmitry Adamushko 已提交
1376 1377
	 * Upon rescheduling, sched_class::put_prev_task() will place
	 * 'current' within the tree based on its new key value.
1378
	 */
1379
	se->vruntime = rightmost->vruntime + 1;
1380 1381
}

1382
#ifdef CONFIG_SMP
1383

1384 1385 1386 1387 1388 1389 1390 1391
static void task_waking_fair(struct rq *rq, struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	se->vruntime -= cfs_rq->min_vruntime;
}

1392
#ifdef CONFIG_FAIR_GROUP_SCHED
1393 1394 1395 1396 1397 1398 1399
/*
 * effective_load() calculates the load change as seen from the root_task_group
 *
 * Adding load to a group doesn't make a group heavier, but can cause movement
 * of group shares between cpus. Assuming the shares were perfectly aligned one
 * can calculate the shift in shares.
 */
P
Peter Zijlstra 已提交
1400
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
1401
{
P
Peter Zijlstra 已提交
1402
	struct sched_entity *se = tg->se[cpu];
1403 1404 1405 1406

	if (!tg->parent)
		return wl;

P
Peter Zijlstra 已提交
1407
	for_each_sched_entity(se) {
1408
		long lw, w;
P
Peter Zijlstra 已提交
1409

1410 1411
		tg = se->my_q->tg;
		w = se->my_q->load.weight;
1412

1413 1414 1415 1416
		/* use this cpu's instantaneous contribution */
		lw = atomic_read(&tg->load_weight);
		lw -= se->my_q->load_contribution;
		lw += w + wg;
P
Peter Zijlstra 已提交
1417

1418
		wl += w;
1419

1420 1421 1422 1423
		if (lw > 0 && wl < lw)
			wl = (wl * tg->shares) / lw;
		else
			wl = tg->shares;
1424

1425 1426 1427 1428
		/* zero point is MIN_SHARES */
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
		wl -= se->load.weight;
P
Peter Zijlstra 已提交
1429 1430
		wg = 0;
	}
1431

P
Peter Zijlstra 已提交
1432
	return wl;
1433
}
P
Peter Zijlstra 已提交
1434

1435
#else
P
Peter Zijlstra 已提交
1436

1437 1438
static inline unsigned long effective_load(struct task_group *tg, int cpu,
		unsigned long wl, unsigned long wg)
P
Peter Zijlstra 已提交
1439
{
1440
	return wl;
1441
}
P
Peter Zijlstra 已提交
1442

1443 1444
#endif

1445
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
1446
{
1447
	s64 this_load, load;
1448
	int idx, this_cpu, prev_cpu;
1449
	unsigned long tl_per_task;
1450
	struct task_group *tg;
1451
	unsigned long weight;
1452
	int balanced;
1453

1454 1455 1456 1457 1458
	idx	  = sd->wake_idx;
	this_cpu  = smp_processor_id();
	prev_cpu  = task_cpu(p);
	load	  = source_load(prev_cpu, idx);
	this_load = target_load(this_cpu, idx);
1459

1460 1461 1462 1463 1464
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
1465
	rcu_read_lock();
1466 1467 1468 1469
	if (sync) {
		tg = task_group(current);
		weight = current->se.load.weight;

1470
		this_load += effective_load(tg, this_cpu, -weight, -weight);
1471 1472
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
1473

1474 1475
	tg = task_group(p);
	weight = p->se.load.weight;
1476

1477 1478
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
1479 1480 1481
	 * due to the sync cause above having dropped this_load to 0, we'll
	 * always have an imbalance, but there's really nothing you can do
	 * about that, so that's good too.
1482 1483 1484 1485
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
1486 1487
	if (this_load > 0) {
		s64 this_eff_load, prev_eff_load;
1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500

		this_eff_load = 100;
		this_eff_load *= power_of(prev_cpu);
		this_eff_load *= this_load +
			effective_load(tg, this_cpu, weight, weight);

		prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
		prev_eff_load *= power_of(this_cpu);
		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);

		balanced = this_eff_load <= prev_eff_load;
	} else
		balanced = true;
1501
	rcu_read_unlock();
1502

1503
	/*
I
Ingo Molnar 已提交
1504 1505 1506
	 * If the currently running task will sleep within
	 * a reasonable amount of time then attract this newly
	 * woken task:
1507
	 */
1508 1509
	if (sync && balanced)
		return 1;
1510

1511
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
1512 1513
	tl_per_task = cpu_avg_load_per_task(this_cpu);

1514 1515 1516
	if (balanced ||
	    (this_load <= load &&
	     this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
1517 1518 1519 1520 1521
		/*
		 * This domain has SD_WAKE_AFFINE and
		 * p is cache cold in this domain, and
		 * there is no bad imbalance.
		 */
1522
		schedstat_inc(sd, ttwu_move_affine);
1523
		schedstat_inc(p, se.statistics.nr_wakeups_affine);
1524 1525 1526 1527 1528 1529

		return 1;
	}
	return 0;
}

1530 1531 1532 1533 1534
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
1535
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
1536
		  int this_cpu, int load_idx)
1537
{
1538
	struct sched_group *idlest = NULL, *group = sd->groups;
1539 1540
	unsigned long min_load = ULONG_MAX, this_load = 0;
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
1541

1542 1543 1544 1545
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
1546

1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
					&p->cpus_allowed))
			continue;

		local_group = cpumask_test_cpu(this_cpu,
					       sched_group_cpus(group));

		/* Tally up the load of all CPUs in the group */
		avg_load = 0;

		for_each_cpu(i, sched_group_cpus(group)) {
			/* Bias balancing toward cpus of our domain */
			if (local_group)
				load = source_load(i, load_idx);
			else
				load = target_load(i, load_idx);

			avg_load += load;
		}

		/* Adjust by relative CPU power of the group */
		avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;

		if (local_group) {
			this_load = avg_load;
		} else if (avg_load < min_load) {
			min_load = avg_load;
			idlest = group;
		}
	} while (group = group->next, group != sd->groups);

	if (!idlest || 100*this_load < imbalance*min_load)
		return NULL;
	return idlest;
}

/*
 * find_idlest_cpu - find the idlest cpu among the cpus in group.
 */
static int
find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
{
	unsigned long load, min_load = ULONG_MAX;
	int idlest = -1;
	int i;

	/* Traverse only the allowed CPUs */
	for_each_cpu_and(i, sched_group_cpus(group), &p->cpus_allowed) {
		load = weighted_cpuload(i);

		if (load < min_load || (load == min_load && i == this_cpu)) {
			min_load = load;
			idlest = i;
1601 1602 1603
		}
	}

1604 1605
	return idlest;
}
1606

1607 1608 1609
/*
 * Try and locate an idle CPU in the sched_domain.
 */
1610
static int select_idle_sibling(struct task_struct *p, int target)
1611 1612 1613
{
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
1614
	struct sched_domain *sd;
1615 1616 1617
	int i;

	/*
1618 1619
	 * If the task is going to be woken-up on this cpu and if it is
	 * already idle, then it is the right target.
1620
	 */
1621 1622 1623 1624 1625 1626 1627 1628
	if (target == cpu && idle_cpu(cpu))
		return cpu;

	/*
	 * If the task is going to be woken-up on the cpu where it previously
	 * ran and if it is currently idle, then it the right target.
	 */
	if (target == prev_cpu && idle_cpu(prev_cpu))
1629
		return prev_cpu;
1630 1631

	/*
1632
	 * Otherwise, iterate the domains and find an elegible idle cpu.
1633
	 */
1634 1635
	for_each_domain(target, sd) {
		if (!(sd->flags & SD_SHARE_PKG_RESOURCES))
1636
			break;
1637 1638 1639 1640 1641 1642

		for_each_cpu_and(i, sched_domain_span(sd), &p->cpus_allowed) {
			if (idle_cpu(i)) {
				target = i;
				break;
			}
1643
		}
1644 1645 1646 1647 1648 1649 1650 1651

		/*
		 * Lets stop looking for an idle sibling when we reached
		 * the domain that spans the current cpu and prev_cpu.
		 */
		if (cpumask_test_cpu(cpu, sched_domain_span(sd)) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(sd)))
			break;
1652 1653 1654 1655 1656
	}

	return target;
}

1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667
/*
 * sched_balance_self: balance the current task (running on cpu) in domains
 * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
 * SD_BALANCE_EXEC.
 *
 * Balance, ie. select the least loaded group.
 *
 * Returns the target CPU number, or the same CPU if no balancing is needed.
 *
 * preempt must be disabled.
 */
1668 1669
static int
select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_flags)
1670
{
1671
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
1672 1673 1674
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
	int new_cpu = cpu;
1675
	int want_affine = 0;
1676
	int want_sd = 1;
1677
	int sync = wake_flags & WF_SYNC;
1678

1679
	if (sd_flag & SD_BALANCE_WAKE) {
1680
		if (cpumask_test_cpu(cpu, &p->cpus_allowed))
1681 1682 1683
			want_affine = 1;
		new_cpu = prev_cpu;
	}
1684 1685

	for_each_domain(cpu, tmp) {
1686 1687 1688
		if (!(tmp->flags & SD_LOAD_BALANCE))
			continue;

1689
		/*
1690 1691
		 * If power savings logic is enabled for a domain, see if we
		 * are not overloaded, if so, don't balance wider.
1692
		 */
P
Peter Zijlstra 已提交
1693
		if (tmp->flags & (SD_POWERSAVINGS_BALANCE|SD_PREFER_LOCAL)) {
1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705
			unsigned long power = 0;
			unsigned long nr_running = 0;
			unsigned long capacity;
			int i;

			for_each_cpu(i, sched_domain_span(tmp)) {
				power += power_of(i);
				nr_running += cpu_rq(i)->cfs.nr_running;
			}

			capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);

P
Peter Zijlstra 已提交
1706 1707 1708 1709
			if (tmp->flags & SD_POWERSAVINGS_BALANCE)
				nr_running /= 2;

			if (nr_running < capacity)
1710
				want_sd = 0;
1711
		}
1712

1713
		/*
1714 1715
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
1716
		 */
1717 1718 1719 1720
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
			want_affine = 0;
1721 1722
		}

1723 1724 1725
		if (!want_sd && !want_affine)
			break;

1726
		if (!(tmp->flags & sd_flag))
1727 1728
			continue;

1729 1730 1731 1732
		if (want_sd)
			sd = tmp;
	}

1733
	if (affine_sd) {
1734 1735 1736 1737
		if (cpu == prev_cpu || wake_affine(affine_sd, p, sync))
			return select_idle_sibling(p, cpu);
		else
			return select_idle_sibling(p, prev_cpu);
1738
	}
1739

1740
	while (sd) {
1741
		int load_idx = sd->forkexec_idx;
1742
		struct sched_group *group;
1743
		int weight;
1744

1745
		if (!(sd->flags & sd_flag)) {
1746 1747 1748
			sd = sd->child;
			continue;
		}
1749

1750 1751
		if (sd_flag & SD_BALANCE_WAKE)
			load_idx = sd->wake_idx;
1752

1753
		group = find_idlest_group(sd, p, cpu, load_idx);
1754 1755 1756 1757
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
1758

1759
		new_cpu = find_idlest_cpu(group, p, cpu);
1760 1761 1762 1763
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
1764
		}
1765 1766 1767

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
1768
		weight = sd->span_weight;
1769 1770
		sd = NULL;
		for_each_domain(cpu, tmp) {
1771
			if (weight <= tmp->span_weight)
1772
				break;
1773
			if (tmp->flags & sd_flag)
1774 1775 1776
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
1777 1778
	}

1779
	return new_cpu;
1780 1781 1782
}
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
1783 1784
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
1785 1786 1787 1788
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
1789 1790
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
1791 1792 1793 1794 1795 1796 1797 1798 1799
	 *
	 * By using 'se' instead of 'curr' we penalize light tasks, so
	 * they get preempted easier. That is, if 'se' < 'curr' then
	 * the resulting gran will be larger, therefore penalizing the
	 * lighter, if otoh 'se' > 'curr' then the resulting gran will
	 * be smaller, again penalizing the lighter task.
	 *
	 * This is especially important for buddies when the leftmost
	 * task is higher priority than the buddy.
1800
	 */
M
Mike Galbraith 已提交
1801 1802
	if (unlikely(se->load.weight != NICE_0_LOAD))
		gran = calc_delta_fair(gran, se);
1803 1804 1805 1806

	return gran;
}

1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828
/*
 * Should 'se' preempt 'curr'.
 *
 *             |s1
 *        |s2
 *   |s3
 *         g
 *      |<--->|c
 *
 *  w(c, s1) = -1
 *  w(c, s2) =  0
 *  w(c, s3) =  1
 *
 */
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
{
	s64 gran, vdiff = curr->vruntime - se->vruntime;

	if (vdiff <= 0)
		return -1;

P
Peter Zijlstra 已提交
1829
	gran = wakeup_gran(curr, se);
1830 1831 1832 1833 1834 1835
	if (vdiff > gran)
		return 1;

	return 0;
}

1836 1837
static void set_last_buddy(struct sched_entity *se)
{
1838 1839 1840 1841
	if (likely(task_of(se)->policy != SCHED_IDLE)) {
		for_each_sched_entity(se)
			cfs_rq_of(se)->last = se;
	}
1842 1843 1844 1845
}

static void set_next_buddy(struct sched_entity *se)
{
1846 1847 1848 1849
	if (likely(task_of(se)->policy != SCHED_IDLE)) {
		for_each_sched_entity(se)
			cfs_rq_of(se)->next = se;
	}
1850 1851
}

1852 1853 1854
/*
 * Preempt the current task with a newly woken task if needed:
 */
1855
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
1856 1857
{
	struct task_struct *curr = rq->curr;
1858
	struct sched_entity *se = &curr->se, *pse = &p->se;
1859
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
1860
	int scale = cfs_rq->nr_running >= sched_nr_latency;
1861

I
Ingo Molnar 已提交
1862 1863 1864
	if (unlikely(se == pse))
		return;

1865
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK))
M
Mike Galbraith 已提交
1866
		set_next_buddy(pse);
P
Peter Zijlstra 已提交
1867

1868 1869 1870 1871 1872 1873 1874
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
	 */
	if (test_tsk_need_resched(curr))
		return;

1875
	/*
1876
	 * Batch and idle tasks do not preempt (their preemption is driven by
1877 1878
	 * the tick):
	 */
1879
	if (unlikely(p->policy != SCHED_NORMAL))
1880
		return;
1881

1882
	/* Idle tasks are by definition preempted by everybody. */
1883 1884
	if (unlikely(curr->policy == SCHED_IDLE))
		goto preempt;
1885

1886 1887 1888
	if (!sched_feat(WAKEUP_PREEMPT))
		return;

1889
	update_curr(cfs_rq);
1890
	find_matching_se(&se, &pse);
1891
	BUG_ON(!pse);
1892 1893
	if (wakeup_preempt_entity(se, pse) == 1)
		goto preempt;
1894

1895
	return;
1896

1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912
preempt:
	resched_task(curr);
	/*
	 * Only set the backward buddy when the current task is still
	 * on the rq. This can happen when a wakeup gets interleaved
	 * with schedule on the ->pre_schedule() or idle_balance()
	 * point, either of which can * drop the rq lock.
	 *
	 * Also, during early boot the idle thread is in the fair class,
	 * for obvious reasons its a bad idea to schedule back to it.
	 */
	if (unlikely(!se->on_rq || curr == rq->idle))
		return;

	if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
		set_last_buddy(se);
1913 1914
}

1915
static struct task_struct *pick_next_task_fair(struct rq *rq)
1916
{
P
Peter Zijlstra 已提交
1917
	struct task_struct *p;
1918 1919 1920
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;

1921
	if (!cfs_rq->nr_running)
1922 1923 1924
		return NULL;

	do {
1925
		se = pick_next_entity(cfs_rq);
1926
		set_next_entity(cfs_rq, se);
1927 1928 1929
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
1930 1931 1932 1933
	p = task_of(se);
	hrtick_start_fair(rq, p);

	return p;
1934 1935 1936 1937 1938
}

/*
 * Account for a descheduled task:
 */
1939
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
1940 1941 1942 1943 1944 1945
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
1946
		put_prev_entity(cfs_rq, se);
1947 1948 1949
	}
}

1950
#ifdef CONFIG_SMP
1951 1952 1953 1954
/**************************************************
 * Fair scheduling class load-balancing methods:
 */

1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983
/*
 * pull_task - move a task from a remote runqueue to the local runqueue.
 * Both runqueues must be locked.
 */
static void pull_task(struct rq *src_rq, struct task_struct *p,
		      struct rq *this_rq, int this_cpu)
{
	deactivate_task(src_rq, p, 0);
	set_task_cpu(p, this_cpu);
	activate_task(this_rq, p, 0);
	check_preempt_curr(this_rq, p, 0);
}

/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
		     struct sched_domain *sd, enum cpu_idle_type idle,
		     int *all_pinned)
{
	int tsk_cache_hot = 0;
	/*
	 * We do not migrate tasks that are:
	 * 1) running (obviously), or
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
	 * 3) are cache-hot on their current CPU.
	 */
	if (!cpumask_test_cpu(this_cpu, &p->cpus_allowed)) {
1984
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
1985 1986 1987 1988 1989
		return 0;
	}
	*all_pinned = 0;

	if (task_running(rq, p)) {
1990
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
1991 1992 1993 1994 1995 1996 1997 1998 1999
		return 0;
	}

	/*
	 * Aggressive migration if:
	 * 1) task is cache cold, or
	 * 2) too many balance attempts have failed.
	 */

2000
	tsk_cache_hot = task_hot(p, rq->clock_task, sd);
2001 2002 2003 2004 2005
	if (!tsk_cache_hot ||
		sd->nr_balance_failed > sd->cache_nice_tries) {
#ifdef CONFIG_SCHEDSTATS
		if (tsk_cache_hot) {
			schedstat_inc(sd, lb_hot_gained[idle]);
2006
			schedstat_inc(p, se.statistics.nr_forced_migrations);
2007 2008 2009 2010 2011 2012
		}
#endif
		return 1;
	}

	if (tsk_cache_hot) {
2013
		schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
2014 2015 2016 2017 2018
		return 0;
	}
	return 1;
}

2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054
/*
 * move_one_task tries to move exactly one task from busiest to this_rq, as
 * part of active balancing operations within "domain".
 * Returns 1 if successful and 0 otherwise.
 *
 * Called with both runqueues locked.
 */
static int
move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
	      struct sched_domain *sd, enum cpu_idle_type idle)
{
	struct task_struct *p, *n;
	struct cfs_rq *cfs_rq;
	int pinned = 0;

	for_each_leaf_cfs_rq(busiest, cfs_rq) {
		list_for_each_entry_safe(p, n, &cfs_rq->tasks, se.group_node) {

			if (!can_migrate_task(p, busiest, this_cpu,
						sd, idle, &pinned))
				continue;

			pull_task(busiest, p, this_rq, this_cpu);
			/*
			 * Right now, this is only the second place pull_task()
			 * is called, so we can safely collect pull_task()
			 * stats here rather than inside pull_task().
			 */
			schedstat_inc(sd, lb_gained[idle]);
			return 1;
		}
	}

	return 0;
}

2055 2056 2057 2058
static unsigned long
balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
	      unsigned long max_load_move, struct sched_domain *sd,
	      enum cpu_idle_type idle, int *all_pinned,
2059
	      int *this_best_prio, struct cfs_rq *busiest_cfs_rq)
2060 2061 2062
{
	int loops = 0, pulled = 0, pinned = 0;
	long rem_load_move = max_load_move;
2063
	struct task_struct *p, *n;
2064 2065 2066 2067 2068 2069

	if (max_load_move == 0)
		goto out;

	pinned = 1;

2070 2071 2072
	list_for_each_entry_safe(p, n, &busiest_cfs_rq->tasks, se.group_node) {
		if (loops++ > sysctl_sched_nr_migrate)
			break;
2073

2074 2075 2076
		if ((p->se.load.weight >> 1) > rem_load_move ||
		    !can_migrate_task(p, busiest, this_cpu, sd, idle, &pinned))
			continue;
2077

2078 2079 2080
		pull_task(busiest, p, this_rq, this_cpu);
		pulled++;
		rem_load_move -= p->se.load.weight;
2081 2082

#ifdef CONFIG_PREEMPT
2083 2084 2085 2086 2087 2088 2089
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
		 * kernels will stop after the first task is pulled to minimize
		 * the critical section.
		 */
		if (idle == CPU_NEWLY_IDLE)
			break;
2090 2091
#endif

2092 2093 2094 2095 2096 2097 2098
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
		if (rem_load_move <= 0)
			break;

2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115
		if (p->prio < *this_best_prio)
			*this_best_prio = p->prio;
	}
out:
	/*
	 * Right now, this is one of only two places pull_task() is called,
	 * so we can safely collect pull_task() stats here rather than
	 * inside pull_task().
	 */
	schedstat_add(sd, lb_gained[idle], pulled);

	if (all_pinned)
		*all_pinned = pinned;

	return max_load_move - rem_load_move;
}

P
Peter Zijlstra 已提交
2116
#ifdef CONFIG_FAIR_GROUP_SCHED
2117 2118 2119
/*
 * update tg->load_weight by folding this cpu's load_avg
 */
2120
static int update_shares_cpu(struct task_group *tg, int cpu)
2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134
{
	struct cfs_rq *cfs_rq;
	unsigned long flags;
	struct rq *rq;

	if (!tg->se[cpu])
		return 0;

	rq = cpu_rq(cpu);
	cfs_rq = tg->cfs_rq[cpu];

	raw_spin_lock_irqsave(&rq->lock, flags);

	update_rq_clock(rq);
2135
	update_cfs_load(cfs_rq, 1);
2136 2137 2138 2139 2140

	/*
	 * We need to update shares after updating tg->load_weight in
	 * order to adjust the weight of groups with long running tasks.
	 */
2141
	update_cfs_shares(cfs_rq);
2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153

	raw_spin_unlock_irqrestore(&rq->lock, flags);

	return 0;
}

static void update_shares(int cpu)
{
	struct cfs_rq *cfs_rq;
	struct rq *rq = cpu_rq(cpu);

	rcu_read_lock();
2154 2155
	for_each_leaf_cfs_rq(rq, cfs_rq)
		update_shares_cpu(cfs_rq->tg, cpu);
2156 2157 2158
	rcu_read_unlock();
}

P
Peter Zijlstra 已提交
2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205
static unsigned long
load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
		  unsigned long max_load_move,
		  struct sched_domain *sd, enum cpu_idle_type idle,
		  int *all_pinned, int *this_best_prio)
{
	long rem_load_move = max_load_move;
	int busiest_cpu = cpu_of(busiest);
	struct task_group *tg;

	rcu_read_lock();
	update_h_load(busiest_cpu);

	list_for_each_entry_rcu(tg, &task_groups, list) {
		struct cfs_rq *busiest_cfs_rq = tg->cfs_rq[busiest_cpu];
		unsigned long busiest_h_load = busiest_cfs_rq->h_load;
		unsigned long busiest_weight = busiest_cfs_rq->load.weight;
		u64 rem_load, moved_load;

		/*
		 * empty group
		 */
		if (!busiest_cfs_rq->task_weight)
			continue;

		rem_load = (u64)rem_load_move * busiest_weight;
		rem_load = div_u64(rem_load, busiest_h_load + 1);

		moved_load = balance_tasks(this_rq, this_cpu, busiest,
				rem_load, sd, idle, all_pinned, this_best_prio,
				busiest_cfs_rq);

		if (!moved_load)
			continue;

		moved_load *= busiest_h_load;
		moved_load = div_u64(moved_load, busiest_weight + 1);

		rem_load_move -= moved_load;
		if (rem_load_move < 0)
			break;
	}
	rcu_read_unlock();

	return max_load_move - rem_load_move;
}
#else
2206 2207 2208 2209
static inline void update_shares(int cpu)
{
}

P
Peter Zijlstra 已提交
2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221
static unsigned long
load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
		  unsigned long max_load_move,
		  struct sched_domain *sd, enum cpu_idle_type idle,
		  int *all_pinned, int *this_best_prio)
{
	return balance_tasks(this_rq, this_cpu, busiest,
			max_load_move, sd, idle, all_pinned,
			this_best_prio, &busiest->cfs);
}
#endif

2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233
/*
 * move_tasks tries to move up to max_load_move weighted load from busiest to
 * this_rq, as part of a balancing operation within domain "sd".
 * Returns 1 if successful and 0 otherwise.
 *
 * Called with both runqueues locked.
 */
static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
		      unsigned long max_load_move,
		      struct sched_domain *sd, enum cpu_idle_type idle,
		      int *all_pinned)
{
2234
	unsigned long total_load_moved = 0, load_moved;
2235 2236 2237
	int this_best_prio = this_rq->curr->prio;

	do {
2238
		load_moved = load_balance_fair(this_rq, this_cpu, busiest,
2239 2240
				max_load_move - total_load_moved,
				sd, idle, all_pinned, &this_best_prio);
2241 2242

		total_load_moved += load_moved;
2243 2244 2245 2246 2247 2248 2249 2250 2251

#ifdef CONFIG_PREEMPT
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
		 * kernels will stop after the first task is pulled to minimize
		 * the critical section.
		 */
		if (idle == CPU_NEWLY_IDLE && this_rq->nr_running)
			break;
2252 2253 2254 2255

		if (raw_spin_is_contended(&this_rq->lock) ||
				raw_spin_is_contended(&busiest->lock))
			break;
2256
#endif
2257
	} while (load_moved && max_load_move > total_load_moved);
2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277

	return total_load_moved > 0;
}

/********** Helpers for find_busiest_group ************************/
/*
 * sd_lb_stats - Structure to store the statistics of a sched_domain
 * 		during load balancing.
 */
struct sd_lb_stats {
	struct sched_group *busiest; /* Busiest group in this sd */
	struct sched_group *this;  /* Local group in this sd */
	unsigned long total_load;  /* Total load of all groups in sd */
	unsigned long total_pwr;   /*	Total power of all groups in sd */
	unsigned long avg_load;	   /* Average load across all groups in sd */

	/** Statistics of this group */
	unsigned long this_load;
	unsigned long this_load_per_task;
	unsigned long this_nr_running;
2278
	unsigned long this_has_capacity;
2279
	unsigned int  this_idle_cpus;
2280 2281

	/* Statistics of the busiest group */
2282
	unsigned int  busiest_idle_cpus;
2283 2284 2285
	unsigned long max_load;
	unsigned long busiest_load_per_task;
	unsigned long busiest_nr_running;
2286
	unsigned long busiest_group_capacity;
2287
	unsigned long busiest_has_capacity;
2288
	unsigned int  busiest_group_weight;
2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309

	int group_imb; /* Is there imbalance in this sd */
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
	int power_savings_balance; /* Is powersave balance needed for this sd */
	struct sched_group *group_min; /* Least loaded group in sd */
	struct sched_group *group_leader; /* Group which relieves group_min */
	unsigned long min_load_per_task; /* load_per_task in group_min */
	unsigned long leader_nr_running; /* Nr running of group_leader */
	unsigned long min_nr_running; /* Nr running of group_min */
#endif
};

/*
 * sg_lb_stats - stats of a sched_group required for load_balancing
 */
struct sg_lb_stats {
	unsigned long avg_load; /*Avg load across the CPUs of the group */
	unsigned long group_load; /* Total load over the CPUs of the group */
	unsigned long sum_nr_running; /* Nr tasks running in the group */
	unsigned long sum_weighted_load; /* Weighted load of group's tasks */
	unsigned long group_capacity;
2310 2311
	unsigned long idle_cpus;
	unsigned long group_weight;
2312
	int group_imb; /* Is there an imbalance in the group ? */
2313
	int group_has_capacity; /* Is there extra capacity in the group? */
2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504
};

/**
 * group_first_cpu - Returns the first cpu in the cpumask of a sched_group.
 * @group: The group whose first cpu is to be returned.
 */
static inline unsigned int group_first_cpu(struct sched_group *group)
{
	return cpumask_first(sched_group_cpus(group));
}

/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
 * @idle: The Idle status of the CPU for whose sd load_icx is obtained.
 */
static inline int get_sd_load_idx(struct sched_domain *sd,
					enum cpu_idle_type idle)
{
	int load_idx;

	switch (idle) {
	case CPU_NOT_IDLE:
		load_idx = sd->busy_idx;
		break;

	case CPU_NEWLY_IDLE:
		load_idx = sd->newidle_idx;
		break;
	default:
		load_idx = sd->idle_idx;
		break;
	}

	return load_idx;
}


#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
/**
 * init_sd_power_savings_stats - Initialize power savings statistics for
 * the given sched_domain, during load balancing.
 *
 * @sd: Sched domain whose power-savings statistics are to be initialized.
 * @sds: Variable containing the statistics for sd.
 * @idle: Idle status of the CPU at which we're performing load-balancing.
 */
static inline void init_sd_power_savings_stats(struct sched_domain *sd,
	struct sd_lb_stats *sds, enum cpu_idle_type idle)
{
	/*
	 * Busy processors will not participate in power savings
	 * balance.
	 */
	if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
		sds->power_savings_balance = 0;
	else {
		sds->power_savings_balance = 1;
		sds->min_nr_running = ULONG_MAX;
		sds->leader_nr_running = 0;
	}
}

/**
 * update_sd_power_savings_stats - Update the power saving stats for a
 * sched_domain while performing load balancing.
 *
 * @group: sched_group belonging to the sched_domain under consideration.
 * @sds: Variable containing the statistics of the sched_domain
 * @local_group: Does group contain the CPU for which we're performing
 * 		load balancing ?
 * @sgs: Variable containing the statistics of the group.
 */
static inline void update_sd_power_savings_stats(struct sched_group *group,
	struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)
{

	if (!sds->power_savings_balance)
		return;

	/*
	 * If the local group is idle or completely loaded
	 * no need to do power savings balance at this domain
	 */
	if (local_group && (sds->this_nr_running >= sgs->group_capacity ||
				!sds->this_nr_running))
		sds->power_savings_balance = 0;

	/*
	 * If a group is already running at full capacity or idle,
	 * don't include that group in power savings calculations
	 */
	if (!sds->power_savings_balance ||
		sgs->sum_nr_running >= sgs->group_capacity ||
		!sgs->sum_nr_running)
		return;

	/*
	 * Calculate the group which has the least non-idle load.
	 * This is the group from where we need to pick up the load
	 * for saving power
	 */
	if ((sgs->sum_nr_running < sds->min_nr_running) ||
	    (sgs->sum_nr_running == sds->min_nr_running &&
	     group_first_cpu(group) > group_first_cpu(sds->group_min))) {
		sds->group_min = group;
		sds->min_nr_running = sgs->sum_nr_running;
		sds->min_load_per_task = sgs->sum_weighted_load /
						sgs->sum_nr_running;
	}

	/*
	 * Calculate the group which is almost near its
	 * capacity but still has some space to pick up some load
	 * from other group and save more power
	 */
	if (sgs->sum_nr_running + 1 > sgs->group_capacity)
		return;

	if (sgs->sum_nr_running > sds->leader_nr_running ||
	    (sgs->sum_nr_running == sds->leader_nr_running &&
	     group_first_cpu(group) < group_first_cpu(sds->group_leader))) {
		sds->group_leader = group;
		sds->leader_nr_running = sgs->sum_nr_running;
	}
}

/**
 * check_power_save_busiest_group - see if there is potential for some power-savings balance
 * @sds: Variable containing the statistics of the sched_domain
 *	under consideration.
 * @this_cpu: Cpu at which we're currently performing load-balancing.
 * @imbalance: Variable to store the imbalance.
 *
 * Description:
 * Check if we have potential to perform some power-savings balance.
 * If yes, set the busiest group to be the least loaded group in the
 * sched_domain, so that it's CPUs can be put to idle.
 *
 * Returns 1 if there is potential to perform power-savings balance.
 * Else returns 0.
 */
static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
					int this_cpu, unsigned long *imbalance)
{
	if (!sds->power_savings_balance)
		return 0;

	if (sds->this != sds->group_leader ||
			sds->group_leader == sds->group_min)
		return 0;

	*imbalance = sds->min_load_per_task;
	sds->busiest = sds->group_min;

	return 1;

}
#else /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
static inline void init_sd_power_savings_stats(struct sched_domain *sd,
	struct sd_lb_stats *sds, enum cpu_idle_type idle)
{
	return;
}

static inline void update_sd_power_savings_stats(struct sched_group *group,
	struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)
{
	return;
}

static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
					int this_cpu, unsigned long *imbalance)
{
	return 0;
}
#endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */


unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
{
	return SCHED_LOAD_SCALE;
}

unsigned long __weak arch_scale_freq_power(struct sched_domain *sd, int cpu)
{
	return default_scale_freq_power(sd, cpu);
}

unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
{
2505
	unsigned long weight = sd->span_weight;
2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523
	unsigned long smt_gain = sd->smt_gain;

	smt_gain /= weight;

	return smt_gain;
}

unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu)
{
	return default_scale_smt_power(sd, cpu);
}

unsigned long scale_rt_power(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
	u64 total, available;

	total = sched_avg_period() + (rq->clock - rq->age_stamp);
2524 2525 2526 2527 2528 2529 2530

	if (unlikely(total < rq->rt_avg)) {
		/* Ensures that power won't end up being negative */
		available = 0;
	} else {
		available = total - rq->rt_avg;
	}
2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541

	if (unlikely((s64)total < SCHED_LOAD_SCALE))
		total = SCHED_LOAD_SCALE;

	total >>= SCHED_LOAD_SHIFT;

	return div_u64(available, total);
}

static void update_cpu_power(struct sched_domain *sd, int cpu)
{
2542
	unsigned long weight = sd->span_weight;
2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554
	unsigned long power = SCHED_LOAD_SCALE;
	struct sched_group *sdg = sd->groups;

	if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
		if (sched_feat(ARCH_POWER))
			power *= arch_scale_smt_power(sd, cpu);
		else
			power *= default_scale_smt_power(sd, cpu);

		power >>= SCHED_LOAD_SHIFT;
	}

2555 2556 2557 2558 2559 2560 2561 2562 2563
	sdg->cpu_power_orig = power;

	if (sched_feat(ARCH_POWER))
		power *= arch_scale_freq_power(sd, cpu);
	else
		power *= default_scale_freq_power(sd, cpu);

	power >>= SCHED_LOAD_SHIFT;

2564 2565 2566 2567 2568 2569
	power *= scale_rt_power(cpu);
	power >>= SCHED_LOAD_SHIFT;

	if (!power)
		power = 1;

2570
	cpu_rq(cpu)->cpu_power = power;
2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595
	sdg->cpu_power = power;
}

static void update_group_power(struct sched_domain *sd, int cpu)
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
	unsigned long power;

	if (!child) {
		update_cpu_power(sd, cpu);
		return;
	}

	power = 0;

	group = child->groups;
	do {
		power += group->cpu_power;
		group = group->next;
	} while (group != child->groups);

	sdg->cpu_power = power;
}

2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614
/*
 * Try and fix up capacity for tiny siblings, this is needed when
 * things like SD_ASYM_PACKING need f_b_g to select another sibling
 * which on its own isn't powerful enough.
 *
 * See update_sd_pick_busiest() and check_asym_packing().
 */
static inline int
fix_small_capacity(struct sched_domain *sd, struct sched_group *group)
{
	/*
	 * Only siblings can have significantly less than SCHED_LOAD_SCALE
	 */
	if (sd->level != SD_LV_SIBLING)
		return 0;

	/*
	 * If ~90% of the cpu_power is still there, we're good.
	 */
M
Michael Neuling 已提交
2615
	if (group->cpu_power * 32 > group->cpu_power_orig * 29)
2616 2617 2618 2619 2620
		return 1;

	return 0;
}

2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
 * @sd: The sched_domain whose statistics are to be updated.
 * @group: sched_group whose statistics are to be updated.
 * @this_cpu: Cpu for which load balance is currently performed.
 * @idle: Idle status of this_cpu
 * @load_idx: Load index of sched_domain of this_cpu for load calc.
 * @sd_idle: Idle status of the sched_domain containing group.
 * @local_group: Does group contain this_cpu.
 * @cpus: Set of cpus considered for load balancing.
 * @balance: Should we balance.
 * @sgs: variable to hold the statistics for this group.
 */
static inline void update_sg_lb_stats(struct sched_domain *sd,
			struct sched_group *group, int this_cpu,
			enum cpu_idle_type idle, int load_idx, int *sd_idle,
			int local_group, const struct cpumask *cpus,
			int *balance, struct sg_lb_stats *sgs)
{
2640
	unsigned long load, max_cpu_load, min_cpu_load, max_nr_running;
2641 2642
	int i;
	unsigned int balance_cpu = -1, first_idle_cpu = 0;
2643
	unsigned long avg_load_per_task = 0;
2644

2645
	if (local_group)
2646 2647 2648 2649 2650
		balance_cpu = group_first_cpu(group);

	/* Tally up the load of all CPUs in the group */
	max_cpu_load = 0;
	min_cpu_load = ~0UL;
2651
	max_nr_running = 0;
2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668

	for_each_cpu_and(i, sched_group_cpus(group), cpus) {
		struct rq *rq = cpu_rq(i);

		if (*sd_idle && rq->nr_running)
			*sd_idle = 0;

		/* Bias balancing toward cpus of our domain */
		if (local_group) {
			if (idle_cpu(i) && !first_idle_cpu) {
				first_idle_cpu = 1;
				balance_cpu = i;
			}

			load = target_load(i, load_idx);
		} else {
			load = source_load(i, load_idx);
2669
			if (load > max_cpu_load) {
2670
				max_cpu_load = load;
2671 2672
				max_nr_running = rq->nr_running;
			}
2673 2674 2675 2676 2677 2678 2679
			if (min_cpu_load > load)
				min_cpu_load = load;
		}

		sgs->group_load += load;
		sgs->sum_nr_running += rq->nr_running;
		sgs->sum_weighted_load += weighted_cpuload(i);
2680 2681
		if (idle_cpu(i))
			sgs->idle_cpus++;
2682 2683 2684 2685 2686 2687 2688 2689
	}

	/*
	 * First idle cpu or the first cpu(busiest) in this sched group
	 * is eligible for doing load balancing at this and above
	 * domains. In the newly idle case, we will allow all the cpu's
	 * to do the newly idle load balance.
	 */
2690 2691 2692 2693 2694 2695
	if (idle != CPU_NEWLY_IDLE && local_group) {
		if (balance_cpu != this_cpu) {
			*balance = 0;
			return;
		}
		update_group_power(sd, this_cpu);
2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709
	}

	/* Adjust by relative CPU power of the group */
	sgs->avg_load = (sgs->group_load * SCHED_LOAD_SCALE) / group->cpu_power;

	/*
	 * Consider the group unbalanced when the imbalance is larger
	 * than the average weight of two tasks.
	 *
	 * APZ: with cgroup the avg task weight can vary wildly and
	 *      might not be a suitable number - should we keep a
	 *      normalized nr_running number somewhere that negates
	 *      the hierarchy?
	 */
2710 2711
	if (sgs->sum_nr_running)
		avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
2712

2713
	if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task && max_nr_running > 1)
2714 2715
		sgs->group_imb = 1;

2716
	sgs->group_capacity = DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE);
2717 2718
	if (!sgs->group_capacity)
		sgs->group_capacity = fix_small_capacity(sd, group);
2719
	sgs->group_weight = group->group_weight;
2720 2721 2722

	if (sgs->group_capacity > sgs->sum_nr_running)
		sgs->group_has_capacity = 1;
2723 2724
}

2725 2726 2727 2728 2729
/**
 * update_sd_pick_busiest - return 1 on busiest group
 * @sd: sched_domain whose statistics are to be checked
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
2730 2731
 * @sgs: sched_group statistics
 * @this_cpu: the current cpu
2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
 */
static bool update_sd_pick_busiest(struct sched_domain *sd,
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
				   struct sg_lb_stats *sgs,
				   int this_cpu)
{
	if (sgs->avg_load <= sds->max_load)
		return false;

	if (sgs->sum_nr_running > sgs->group_capacity)
		return true;

	if (sgs->group_imb)
		return true;

	/*
	 * ASYM_PACKING needs to move all the work to the lowest
	 * numbered CPUs in the group, therefore mark all groups
	 * higher than ourself as busy.
	 */
	if ((sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
	    this_cpu < group_first_cpu(sg)) {
		if (!sds->busiest)
			return true;

		if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
			return true;
	}

	return false;
}

2768 2769 2770 2771 2772
/**
 * update_sd_lb_stats - Update sched_group's statistics for load balancing.
 * @sd: sched_domain whose statistics are to be updated.
 * @this_cpu: Cpu for which load balance is currently performed.
 * @idle: Idle status of this_cpu
2773
 * @sd_idle: Idle status of the sched_domain containing sg.
2774 2775 2776 2777 2778 2779 2780 2781 2782 2783
 * @cpus: Set of cpus considered for load balancing.
 * @balance: Should we balance.
 * @sds: variable to hold the statistics for this sched_domain.
 */
static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu,
			enum cpu_idle_type idle, int *sd_idle,
			const struct cpumask *cpus, int *balance,
			struct sd_lb_stats *sds)
{
	struct sched_domain *child = sd->child;
2784
	struct sched_group *sg = sd->groups;
2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796
	struct sg_lb_stats sgs;
	int load_idx, prefer_sibling = 0;

	if (child && child->flags & SD_PREFER_SIBLING)
		prefer_sibling = 1;

	init_sd_power_savings_stats(sd, sds, idle);
	load_idx = get_sd_load_idx(sd, idle);

	do {
		int local_group;

2797
		local_group = cpumask_test_cpu(this_cpu, sched_group_cpus(sg));
2798
		memset(&sgs, 0, sizeof(sgs));
2799
		update_sg_lb_stats(sd, sg, this_cpu, idle, load_idx, sd_idle,
2800 2801
				local_group, cpus, balance, &sgs);

P
Peter Zijlstra 已提交
2802
		if (local_group && !(*balance))
2803 2804 2805
			return;

		sds->total_load += sgs.group_load;
2806
		sds->total_pwr += sg->cpu_power;
2807 2808 2809

		/*
		 * In case the child domain prefers tasks go to siblings
2810
		 * first, lower the sg capacity to one so that we'll try
2811 2812 2813 2814 2815 2816
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
		 * these excess tasks, i.e. nr_running < group_capacity. The
		 * extra check prevents the case where you always pull from the
		 * heaviest group when it is already under-utilized (possible
		 * with a large weight task outweighs the tasks on the system).
2817
		 */
2818
		if (prefer_sibling && !local_group && sds->this_has_capacity)
2819 2820 2821 2822
			sgs.group_capacity = min(sgs.group_capacity, 1UL);

		if (local_group) {
			sds->this_load = sgs.avg_load;
2823
			sds->this = sg;
2824 2825
			sds->this_nr_running = sgs.sum_nr_running;
			sds->this_load_per_task = sgs.sum_weighted_load;
2826
			sds->this_has_capacity = sgs.group_has_capacity;
2827
			sds->this_idle_cpus = sgs.idle_cpus;
2828
		} else if (update_sd_pick_busiest(sd, sds, sg, &sgs, this_cpu)) {
2829
			sds->max_load = sgs.avg_load;
2830
			sds->busiest = sg;
2831
			sds->busiest_nr_running = sgs.sum_nr_running;
2832
			sds->busiest_idle_cpus = sgs.idle_cpus;
2833
			sds->busiest_group_capacity = sgs.group_capacity;
2834
			sds->busiest_load_per_task = sgs.sum_weighted_load;
2835
			sds->busiest_has_capacity = sgs.group_has_capacity;
2836
			sds->busiest_group_weight = sgs.group_weight;
2837 2838 2839
			sds->group_imb = sgs.group_imb;
		}

2840 2841 2842 2843 2844
		update_sd_power_savings_stats(sg, sds, local_group, &sgs);
		sg = sg->next;
	} while (sg != sd->groups);
}

M
Michael Neuling 已提交
2845
int __weak arch_sd_sibling_asym_packing(void)
2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866
{
       return 0*SD_ASYM_PACKING;
}

/**
 * check_asym_packing - Check to see if the group is packed into the
 *			sched doman.
 *
 * This is primarily intended to used at the sibling level.  Some
 * cores like POWER7 prefer to use lower numbered SMT threads.  In the
 * case of POWER7, it can move to lower SMT modes only when higher
 * threads are idle.  When in lower SMT modes, the threads will
 * perform better since they share less core resources.  Hence when we
 * have idle threads, we want them to be the higher ones.
 *
 * This packing function is run on idle threads.  It checks to see if
 * the busiest CPU in this domain (core in the P7 case) has a higher
 * CPU number than the packing function is being run on.  Here we are
 * assuming lower CPU number will be equivalent to lower a SMT thread
 * number.
 *
2867 2868 2869
 * Returns 1 when packing is required and a task should be moved to
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893
 * @sd: The sched_domain whose packing is to be checked.
 * @sds: Statistics of the sched_domain which is to be packed
 * @this_cpu: The cpu at whose sched_domain we're performing load-balance.
 * @imbalance: returns amount of imbalanced due to packing.
 */
static int check_asym_packing(struct sched_domain *sd,
			      struct sd_lb_stats *sds,
			      int this_cpu, unsigned long *imbalance)
{
	int busiest_cpu;

	if (!(sd->flags & SD_ASYM_PACKING))
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
	if (this_cpu > busiest_cpu)
		return 0;

	*imbalance = DIV_ROUND_CLOSEST(sds->max_load * sds->busiest->cpu_power,
				       SCHED_LOAD_SCALE);
	return 1;
2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 * @this_cpu: The cpu at whose sched_domain we're performing load-balance.
 * @imbalance: Variable to store the imbalance.
 */
static inline void fix_small_imbalance(struct sd_lb_stats *sds,
				int this_cpu, unsigned long *imbalance)
{
	unsigned long tmp, pwr_now = 0, pwr_move = 0;
	unsigned int imbn = 2;
2909
	unsigned long scaled_busy_load_per_task;
2910 2911 2912 2913 2914 2915 2916 2917 2918 2919

	if (sds->this_nr_running) {
		sds->this_load_per_task /= sds->this_nr_running;
		if (sds->busiest_load_per_task >
				sds->this_load_per_task)
			imbn = 1;
	} else
		sds->this_load_per_task =
			cpu_avg_load_per_task(this_cpu);

2920 2921 2922 2923 2924 2925
	scaled_busy_load_per_task = sds->busiest_load_per_task
						 * SCHED_LOAD_SCALE;
	scaled_busy_load_per_task /= sds->busiest->cpu_power;

	if (sds->max_load - sds->this_load + scaled_busy_load_per_task >=
			(scaled_busy_load_per_task * imbn)) {
2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975
		*imbalance = sds->busiest_load_per_task;
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
	 * however we may be able to increase total CPU power used by
	 * moving them.
	 */

	pwr_now += sds->busiest->cpu_power *
			min(sds->busiest_load_per_task, sds->max_load);
	pwr_now += sds->this->cpu_power *
			min(sds->this_load_per_task, sds->this_load);
	pwr_now /= SCHED_LOAD_SCALE;

	/* Amount of load we'd subtract */
	tmp = (sds->busiest_load_per_task * SCHED_LOAD_SCALE) /
		sds->busiest->cpu_power;
	if (sds->max_load > tmp)
		pwr_move += sds->busiest->cpu_power *
			min(sds->busiest_load_per_task, sds->max_load - tmp);

	/* Amount of load we'd add */
	if (sds->max_load * sds->busiest->cpu_power <
		sds->busiest_load_per_task * SCHED_LOAD_SCALE)
		tmp = (sds->max_load * sds->busiest->cpu_power) /
			sds->this->cpu_power;
	else
		tmp = (sds->busiest_load_per_task * SCHED_LOAD_SCALE) /
			sds->this->cpu_power;
	pwr_move += sds->this->cpu_power *
			min(sds->this_load_per_task, sds->this_load + tmp);
	pwr_move /= SCHED_LOAD_SCALE;

	/* Move if we gain throughput */
	if (pwr_move > pwr_now)
		*imbalance = sds->busiest_load_per_task;
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 * @this_cpu: Cpu for which currently load balance is being performed.
 * @imbalance: The variable to store the imbalance.
 */
static inline void calculate_imbalance(struct sd_lb_stats *sds, int this_cpu,
		unsigned long *imbalance)
{
2976 2977 2978 2979 2980 2981 2982 2983
	unsigned long max_pull, load_above_capacity = ~0UL;

	sds->busiest_load_per_task /= sds->busiest_nr_running;
	if (sds->group_imb) {
		sds->busiest_load_per_task =
			min(sds->busiest_load_per_task, sds->avg_load);
	}

2984 2985 2986 2987 2988 2989 2990 2991 2992 2993
	/*
	 * In the presence of smp nice balancing, certain scenarios can have
	 * max load less than avg load(as we skip the groups at or below
	 * its cpu_power, while calculating max_load..)
	 */
	if (sds->max_load < sds->avg_load) {
		*imbalance = 0;
		return fix_small_imbalance(sds, this_cpu, imbalance);
	}

2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016
	if (!sds->group_imb) {
		/*
		 * Don't want to pull so many tasks that a group would go idle.
		 */
		load_above_capacity = (sds->busiest_nr_running -
						sds->busiest_group_capacity);

		load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_LOAD_SCALE);

		load_above_capacity /= sds->busiest->cpu_power;
	}

	/*
	 * We're trying to get all the cpus to the average_load, so we don't
	 * want to push ourselves above the average load, nor do we wish to
	 * reduce the max loaded cpu below the average load. At the same time,
	 * we also don't want to reduce the group load below the group capacity
	 * (so that we can implement power-savings policies etc). Thus we look
	 * for the minimum possible imbalance.
	 * Be careful of negative numbers as they'll appear as very large values
	 * with unsigned longs.
	 */
	max_pull = min(sds->max_load - sds->avg_load, load_above_capacity);
3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032

	/* How much load to actually move to equalise the imbalance */
	*imbalance = min(max_pull * sds->busiest->cpu_power,
		(sds->avg_load - sds->this_load) * sds->this->cpu_power)
			/ SCHED_LOAD_SCALE;

	/*
	 * if *imbalance is less than the average load per runnable task
	 * there is no gaurantee that any tasks will be moved so we'll have
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
	if (*imbalance < sds->busiest_load_per_task)
		return fix_small_imbalance(sds, this_cpu, imbalance);

}
3033

3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084
/******* find_busiest_group() helpers end here *********************/

/**
 * find_busiest_group - Returns the busiest group within the sched_domain
 * if there is an imbalance. If there isn't an imbalance, and
 * the user has opted for power-savings, it returns a group whose
 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
 * such a group exists.
 *
 * Also calculates the amount of weighted load which should be moved
 * to restore balance.
 *
 * @sd: The sched_domain whose busiest group is to be returned.
 * @this_cpu: The cpu for which load balancing is currently being performed.
 * @imbalance: Variable which stores amount of weighted load which should
 *		be moved to restore balance/put a group to idle.
 * @idle: The idle status of this_cpu.
 * @sd_idle: The idleness of sd
 * @cpus: The set of CPUs under consideration for load-balancing.
 * @balance: Pointer to a variable indicating if this_cpu
 *	is the appropriate cpu to perform load balancing at this_level.
 *
 * Returns:	- the busiest group if imbalance exists.
 *		- If no imbalance and user has opted for power-savings balance,
 *		   return the least loaded group whose CPUs can be
 *		   put to idle by rebalancing its tasks onto our group.
 */
static struct sched_group *
find_busiest_group(struct sched_domain *sd, int this_cpu,
		   unsigned long *imbalance, enum cpu_idle_type idle,
		   int *sd_idle, const struct cpumask *cpus, int *balance)
{
	struct sd_lb_stats sds;

	memset(&sds, 0, sizeof(sds));

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
	update_sd_lb_stats(sd, this_cpu, idle, sd_idle, cpus,
					balance, &sds);

	/* Cases where imbalance does not exist from POV of this_cpu */
	/* 1) this_cpu is not the appropriate cpu to perform load balancing
	 *    at this level.
	 * 2) There is no busy sibling group to pull from.
	 * 3) This group is the busiest group.
	 * 4) This group is more busy than the avg busieness at this
	 *    sched_domain.
	 * 5) The imbalance is within the specified limit.
3085 3086 3087 3088 3089
	 *
	 * Note: when doing newidle balance, if the local group has excess
	 * capacity (i.e. nr_running < group_capacity) and the busiest group
	 * does not have any capacity, we force a load balance to pull tasks
	 * to the local group. In this case, we skip past checks 3, 4 and 5.
3090
	 */
P
Peter Zijlstra 已提交
3091
	if (!(*balance))
3092 3093
		goto ret;

3094 3095 3096 3097
	if ((idle == CPU_IDLE || idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(sd, &sds, this_cpu, imbalance))
		return sds.busiest;

3098 3099 3100
	if (!sds.busiest || sds.busiest_nr_running == 0)
		goto out_balanced;

3101 3102 3103 3104 3105
	/*  SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
	if (idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
			!sds.busiest_has_capacity)
		goto force_balance;

3106 3107 3108 3109 3110 3111 3112 3113
	if (sds.this_load >= sds.max_load)
		goto out_balanced;

	sds.avg_load = (SCHED_LOAD_SCALE * sds.total_load) / sds.total_pwr;

	if (sds.this_load >= sds.avg_load)
		goto out_balanced;

3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132 3133
	/*
	 * In the CPU_NEWLY_IDLE, use imbalance_pct to be conservative.
	 * And to check for busy balance use !idle_cpu instead of
	 * CPU_NOT_IDLE. This is because HT siblings will use CPU_NOT_IDLE
	 * even when they are idle.
	 */
	if (idle == CPU_NEWLY_IDLE || !idle_cpu(this_cpu)) {
		if (100 * sds.max_load <= sd->imbalance_pct * sds.this_load)
			goto out_balanced;
	} else {
		/*
		 * This cpu is idle. If the busiest group load doesn't
		 * have more tasks than the number of available cpu's and
		 * there is no imbalance between this and busiest group
		 * wrt to idle cpu's, it is balanced.
		 */
		if ((sds.this_idle_cpus  <= sds.busiest_idle_cpus + 1) &&
		    sds.busiest_nr_running <= sds.busiest_group_weight)
			goto out_balanced;
	}
3134

3135
force_balance:
3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155
	/* Looks like there is an imbalance. Compute it */
	calculate_imbalance(&sds, this_cpu, imbalance);
	return sds.busiest;

out_balanced:
	/*
	 * There is no obvious imbalance. But check if we can do some balancing
	 * to save power.
	 */
	if (check_power_save_busiest_group(&sds, this_cpu, imbalance))
		return sds.busiest;
ret:
	*imbalance = 0;
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
static struct rq *
3156 3157 3158
find_busiest_queue(struct sched_domain *sd, struct sched_group *group,
		   enum cpu_idle_type idle, unsigned long imbalance,
		   const struct cpumask *cpus)
3159 3160 3161 3162 3163 3164 3165 3166 3167 3168
{
	struct rq *busiest = NULL, *rq;
	unsigned long max_load = 0;
	int i;

	for_each_cpu(i, sched_group_cpus(group)) {
		unsigned long power = power_of(i);
		unsigned long capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);
		unsigned long wl;

3169 3170 3171
		if (!capacity)
			capacity = fix_small_capacity(sd, group);

3172 3173 3174 3175
		if (!cpumask_test_cpu(i, cpus))
			continue;

		rq = cpu_rq(i);
3176
		wl = weighted_cpuload(i);
3177

3178 3179 3180 3181
		/*
		 * When comparing with imbalance, use weighted_cpuload()
		 * which is not scaled with the cpu power.
		 */
3182 3183 3184
		if (capacity && rq->nr_running == 1 && wl > imbalance)
			continue;

3185 3186 3187 3188 3189 3190 3191 3192
		/*
		 * For the load comparisons with the other cpu's, consider
		 * the weighted_cpuload() scaled with the cpu power, so that
		 * the load can be moved away from the cpu that is potentially
		 * running at a lower capacity.
		 */
		wl = (wl * SCHED_LOAD_SCALE) / power;

3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210
		if (wl > max_load) {
			max_load = wl;
			busiest = rq;
		}
	}

	return busiest;
}

/*
 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
 * so long as it is large enough.
 */
#define MAX_PINNED_INTERVAL	512

/* Working cpumask for load_balance and load_balance_newidle. */
static DEFINE_PER_CPU(cpumask_var_t, load_balance_tmpmask);

3211 3212
static int need_active_balance(struct sched_domain *sd, int sd_idle, int idle,
			       int busiest_cpu, int this_cpu)
3213 3214
{
	if (idle == CPU_NEWLY_IDLE) {
3215 3216 3217 3218 3219 3220 3221 3222 3223

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
		if ((sd->flags & SD_ASYM_PACKING) && busiest_cpu > this_cpu)
			return 1;

3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253
		/*
		 * The only task running in a non-idle cpu can be moved to this
		 * cpu in an attempt to completely freeup the other CPU
		 * package.
		 *
		 * The package power saving logic comes from
		 * find_busiest_group(). If there are no imbalance, then
		 * f_b_g() will return NULL. However when sched_mc={1,2} then
		 * f_b_g() will select a group from which a running task may be
		 * pulled to this cpu in order to make the other package idle.
		 * If there is no opportunity to make a package idle and if
		 * there are no imbalance, then f_b_g() will return NULL and no
		 * action will be taken in load_balance_newidle().
		 *
		 * Under normal task pull operation due to imbalance, there
		 * will be more than one task in the source run queue and
		 * move_tasks() will succeed.  ld_moved will be true and this
		 * active balance code will not be triggered.
		 */
		if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
		    !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
			return 0;

		if (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP)
			return 0;
	}

	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

3254 3255
static int active_load_balance_cpu_stop(void *data);

3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296
/*
 * Check this_cpu to ensure it is balanced within domain. Attempt to move
 * tasks if there is an imbalance.
 */
static int load_balance(int this_cpu, struct rq *this_rq,
			struct sched_domain *sd, enum cpu_idle_type idle,
			int *balance)
{
	int ld_moved, all_pinned = 0, active_balance = 0, sd_idle = 0;
	struct sched_group *group;
	unsigned long imbalance;
	struct rq *busiest;
	unsigned long flags;
	struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);

	cpumask_copy(cpus, cpu_active_mask);

	/*
	 * When power savings policy is enabled for the parent domain, idle
	 * sibling can pick up load irrespective of busy siblings. In this case,
	 * let the state of idle sibling percolate up as CPU_IDLE, instead of
	 * portraying it as CPU_NOT_IDLE.
	 */
	if (idle != CPU_NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER &&
	    !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
		sd_idle = 1;

	schedstat_inc(sd, lb_count[idle]);

redo:
	group = find_busiest_group(sd, this_cpu, &imbalance, idle, &sd_idle,
				   cpus, balance);

	if (*balance == 0)
		goto out_balanced;

	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

3297
	busiest = find_busiest_queue(sd, group, idle, imbalance, cpus);
3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

	BUG_ON(busiest == this_rq);

	schedstat_add(sd, lb_imbalance[idle], imbalance);

	ld_moved = 0;
	if (busiest->nr_running > 1) {
		/*
		 * Attempt to move tasks. If find_busiest_group has found
		 * an imbalance but busiest->nr_running <= 1, the group is
		 * still unbalanced. ld_moved simply stays zero, so it is
		 * correctly treated as an imbalance.
		 */
		local_irq_save(flags);
		double_rq_lock(this_rq, busiest);
		ld_moved = move_tasks(this_rq, this_cpu, busiest,
				      imbalance, sd, idle, &all_pinned);
		double_rq_unlock(this_rq, busiest);
		local_irq_restore(flags);

		/*
		 * some other cpu did the load balance for us.
		 */
		if (ld_moved && this_cpu != smp_processor_id())
			resched_cpu(this_cpu);

		/* All tasks on this runqueue were pinned by CPU affinity */
		if (unlikely(all_pinned)) {
			cpumask_clear_cpu(cpu_of(busiest), cpus);
			if (!cpumask_empty(cpus))
				goto redo;
			goto out_balanced;
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
3339 3340 3341 3342 3343 3344 3345 3346
		/*
		 * Increment the failure counter only on periodic balance.
		 * We do not want newidle balance, which can be very
		 * frequent, pollute the failure counter causing
		 * excessive cache_hot migrations and active balances.
		 */
		if (idle != CPU_NEWLY_IDLE)
			sd->nr_balance_failed++;
3347

3348 3349
		if (need_active_balance(sd, sd_idle, idle, cpu_of(busiest),
					this_cpu)) {
3350 3351
			raw_spin_lock_irqsave(&busiest->lock, flags);

3352 3353 3354
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
3355 3356 3357 3358 3359 3360 3361 3362 3363
			 */
			if (!cpumask_test_cpu(this_cpu,
					      &busiest->curr->cpus_allowed)) {
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
				all_pinned = 1;
				goto out_one_pinned;
			}

3364 3365 3366 3367 3368
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
3369 3370 3371 3372 3373 3374
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
3375

3376
			if (active_balance)
3377 3378 3379
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444

			/*
			 * We've kicked active balancing, reset the failure
			 * counter.
			 */
			sd->nr_balance_failed = sd->cache_nice_tries+1;
		}
	} else
		sd->nr_balance_failed = 0;

	if (likely(!active_balance)) {
		/* We were unbalanced, so reset the balancing interval */
		sd->balance_interval = sd->min_interval;
	} else {
		/*
		 * If we've begun active balancing, start to back off. This
		 * case may not be covered by the all_pinned logic if there
		 * is only 1 task on the busy runqueue (because we don't call
		 * move_tasks).
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	if (!ld_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
	    !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
		ld_moved = -1;

	goto out;

out_balanced:
	schedstat_inc(sd, lb_balanced[idle]);

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
	if ((all_pinned && sd->balance_interval < MAX_PINNED_INTERVAL) ||
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

	if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
	    !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
		ld_moved = -1;
	else
		ld_moved = 0;
out:
	return ld_moved;
}

/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
static void idle_balance(int this_cpu, struct rq *this_rq)
{
	struct sched_domain *sd;
	int pulled_task = 0;
	unsigned long next_balance = jiffies + HZ;

	this_rq->idle_stamp = this_rq->clock;

	if (this_rq->avg_idle < sysctl_sched_migration_cost)
		return;

3445 3446 3447 3448 3449
	/*
	 * Drop the rq->lock, but keep IRQ/preempt disabled.
	 */
	raw_spin_unlock(&this_rq->lock);

P
Paul Turner 已提交
3450
	update_shares(this_cpu);
3451 3452
	for_each_domain(this_cpu, sd) {
		unsigned long interval;
3453
		int balance = 1;
3454 3455 3456 3457

		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

3458
		if (sd->flags & SD_BALANCE_NEWIDLE) {
3459
			/* If we've pulled tasks over stop searching: */
3460 3461 3462
			pulled_task = load_balance(this_cpu, this_rq,
						   sd, CPU_NEWLY_IDLE, &balance);
		}
3463 3464 3465 3466

		interval = msecs_to_jiffies(sd->balance_interval);
		if (time_after(next_balance, sd->last_balance + interval))
			next_balance = sd->last_balance + interval;
N
Nikhil Rao 已提交
3467 3468
		if (pulled_task) {
			this_rq->idle_stamp = 0;
3469
			break;
N
Nikhil Rao 已提交
3470
		}
3471
	}
3472 3473 3474

	raw_spin_lock(&this_rq->lock);

3475 3476 3477 3478 3479 3480 3481 3482 3483 3484
	if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
		/*
		 * We are going idle. next_balance may be set based on
		 * a busy processor. So reset next_balance.
		 */
		this_rq->next_balance = next_balance;
	}
}

/*
3485 3486 3487 3488
 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
 * running tasks off the busiest CPU onto idle CPUs. It requires at
 * least 1 task to be running on each physical CPU where possible, and
 * avoids physical / logical imbalances.
3489
 */
3490
static int active_load_balance_cpu_stop(void *data)
3491
{
3492 3493
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
3494
	int target_cpu = busiest_rq->push_cpu;
3495
	struct rq *target_rq = cpu_rq(target_cpu);
3496
	struct sched_domain *sd;
3497 3498 3499 3500 3501 3502 3503

	raw_spin_lock_irq(&busiest_rq->lock);

	/* make sure the requested cpu hasn't gone down in the meantime */
	if (unlikely(busiest_cpu != smp_processor_id() ||
		     !busiest_rq->active_balance))
		goto out_unlock;
3504 3505 3506

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
3507
		goto out_unlock;
3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532 3533 3534 3535

	/*
	 * This condition is "impossible", if it occurs
	 * we need to fix it. Originally reported by
	 * Bjorn Helgaas on a 128-cpu setup.
	 */
	BUG_ON(busiest_rq == target_rq);

	/* move a task from busiest_rq to target_rq */
	double_lock_balance(busiest_rq, target_rq);

	/* Search for an sd spanning us and the target CPU. */
	for_each_domain(target_cpu, sd) {
		if ((sd->flags & SD_LOAD_BALANCE) &&
		    cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
				break;
	}

	if (likely(sd)) {
		schedstat_inc(sd, alb_count);

		if (move_one_task(target_rq, target_cpu, busiest_rq,
				  sd, CPU_IDLE))
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
	double_unlock_balance(busiest_rq, target_rq);
3536 3537 3538 3539
out_unlock:
	busiest_rq->active_balance = 0;
	raw_spin_unlock_irq(&busiest_rq->lock);
	return 0;
3540 3541 3542
}

#ifdef CONFIG_NO_HZ
3543 3544 3545 3546 3547 3548 3549 3550 3551 3552 3553 3554 3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568

static DEFINE_PER_CPU(struct call_single_data, remote_sched_softirq_cb);

static void trigger_sched_softirq(void *data)
{
	raise_softirq_irqoff(SCHED_SOFTIRQ);
}

static inline void init_sched_softirq_csd(struct call_single_data *csd)
{
	csd->func = trigger_sched_softirq;
	csd->info = NULL;
	csd->flags = 0;
	csd->priv = 0;
}

/*
 * idle load balancing details
 * - One of the idle CPUs nominates itself as idle load_balancer, while
 *   entering idle.
 * - This idle load balancer CPU will also go into tickless mode when
 *   it is idle, just like all other idle CPUs
 * - When one of the busy CPUs notice that there may be an idle rebalancing
 *   needed, they will kick the idle load balancer, which then does idle
 *   load balancing for all the idle CPUs.
 */
3569 3570
static struct {
	atomic_t load_balancer;
3571 3572 3573 3574 3575 3576
	atomic_t first_pick_cpu;
	atomic_t second_pick_cpu;
	cpumask_var_t idle_cpus_mask;
	cpumask_var_t grp_idle_mask;
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629

int get_nohz_load_balancer(void)
{
	return atomic_read(&nohz.load_balancer);
}

#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
/**
 * lowest_flag_domain - Return lowest sched_domain containing flag.
 * @cpu:	The cpu whose lowest level of sched domain is to
 *		be returned.
 * @flag:	The flag to check for the lowest sched_domain
 *		for the given cpu.
 *
 * Returns the lowest sched_domain of a cpu which contains the given flag.
 */
static inline struct sched_domain *lowest_flag_domain(int cpu, int flag)
{
	struct sched_domain *sd;

	for_each_domain(cpu, sd)
		if (sd && (sd->flags & flag))
			break;

	return sd;
}

/**
 * for_each_flag_domain - Iterates over sched_domains containing the flag.
 * @cpu:	The cpu whose domains we're iterating over.
 * @sd:		variable holding the value of the power_savings_sd
 *		for cpu.
 * @flag:	The flag to filter the sched_domains to be iterated.
 *
 * Iterates over all the scheduler domains for a given cpu that has the 'flag'
 * set, starting from the lowest sched_domain to the highest.
 */
#define for_each_flag_domain(cpu, sd, flag) \
	for (sd = lowest_flag_domain(cpu, flag); \
		(sd && (sd->flags & flag)); sd = sd->parent)

/**
 * is_semi_idle_group - Checks if the given sched_group is semi-idle.
 * @ilb_group:	group to be checked for semi-idleness
 *
 * Returns:	1 if the group is semi-idle. 0 otherwise.
 *
 * We define a sched_group to be semi idle if it has atleast one idle-CPU
 * and atleast one non-idle CPU. This helper function checks if the given
 * sched_group is semi-idle or not.
 */
static inline int is_semi_idle_group(struct sched_group *ilb_group)
{
3630
	cpumask_and(nohz.grp_idle_mask, nohz.idle_cpus_mask,
3631 3632 3633 3634 3635 3636
					sched_group_cpus(ilb_group));

	/*
	 * A sched_group is semi-idle when it has atleast one busy cpu
	 * and atleast one idle cpu.
	 */
3637
	if (cpumask_empty(nohz.grp_idle_mask))
3638 3639
		return 0;

3640
	if (cpumask_equal(nohz.grp_idle_mask, sched_group_cpus(ilb_group)))
3641 3642 3643 3644 3645 3646 3647 3648 3649 3650 3651 3652 3653 3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672
		return 0;

	return 1;
}
/**
 * find_new_ilb - Finds the optimum idle load balancer for nomination.
 * @cpu:	The cpu which is nominating a new idle_load_balancer.
 *
 * Returns:	Returns the id of the idle load balancer if it exists,
 *		Else, returns >= nr_cpu_ids.
 *
 * This algorithm picks the idle load balancer such that it belongs to a
 * semi-idle powersavings sched_domain. The idea is to try and avoid
 * completely idle packages/cores just for the purpose of idle load balancing
 * when there are other idle cpu's which are better suited for that job.
 */
static int find_new_ilb(int cpu)
{
	struct sched_domain *sd;
	struct sched_group *ilb_group;

	/*
	 * Have idle load balancer selection from semi-idle packages only
	 * when power-aware load balancing is enabled
	 */
	if (!(sched_smt_power_savings || sched_mc_power_savings))
		goto out_done;

	/*
	 * Optimize for the case when we have no idle CPUs or only one
	 * idle CPU. Don't walk the sched_domain hierarchy in such cases
	 */
3673
	if (cpumask_weight(nohz.idle_cpus_mask) < 2)
3674 3675 3676 3677 3678 3679 3680
		goto out_done;

	for_each_flag_domain(cpu, sd, SD_POWERSAVINGS_BALANCE) {
		ilb_group = sd->groups;

		do {
			if (is_semi_idle_group(ilb_group))
3681
				return cpumask_first(nohz.grp_idle_mask);
3682 3683 3684 3685 3686 3687 3688

			ilb_group = ilb_group->next;

		} while (ilb_group != sd->groups);
	}

out_done:
3689
	return nr_cpu_ids;
3690 3691 3692 3693
}
#else /*  (CONFIG_SCHED_MC || CONFIG_SCHED_SMT) */
static inline int find_new_ilb(int call_cpu)
{
3694
	return nr_cpu_ids;
3695 3696 3697
}
#endif

3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726
/*
 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
 * CPU (if there is one).
 */
static void nohz_balancer_kick(int cpu)
{
	int ilb_cpu;

	nohz.next_balance++;

	ilb_cpu = get_nohz_load_balancer();

	if (ilb_cpu >= nr_cpu_ids) {
		ilb_cpu = cpumask_first(nohz.idle_cpus_mask);
		if (ilb_cpu >= nr_cpu_ids)
			return;
	}

	if (!cpu_rq(ilb_cpu)->nohz_balance_kick) {
		struct call_single_data *cp;

		cpu_rq(ilb_cpu)->nohz_balance_kick = 1;
		cp = &per_cpu(remote_sched_softirq_cb, cpu);
		__smp_call_function_single(ilb_cpu, cp, 0);
	}
	return;
}

3727 3728 3729
/*
 * This routine will try to nominate the ilb (idle load balancing)
 * owner among the cpus whose ticks are stopped. ilb owner will do the idle
3730
 * load balancing on behalf of all those cpus.
3731
 *
3732 3733 3734
 * When the ilb owner becomes busy, we will not have new ilb owner until some
 * idle CPU wakes up and goes back to idle or some busy CPU tries to kick
 * idle load balancing by kicking one of the idle CPUs.
3735
 *
3736 3737 3738
 * Ticks are stopped for the ilb owner as well, with busy CPU kicking this
 * ilb owner CPU in future (when there is a need for idle load balancing on
 * behalf of all idle CPUs).
3739
 */
3740
void select_nohz_load_balancer(int stop_tick)
3741 3742 3743 3744 3745 3746
{
	int cpu = smp_processor_id();

	if (stop_tick) {
		if (!cpu_active(cpu)) {
			if (atomic_read(&nohz.load_balancer) != cpu)
3747
				return;
3748 3749 3750 3751 3752

			/*
			 * If we are going offline and still the leader,
			 * give up!
			 */
3753 3754
			if (atomic_cmpxchg(&nohz.load_balancer, cpu,
					   nr_cpu_ids) != cpu)
3755 3756
				BUG();

3757
			return;
3758 3759
		}

3760
		cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
3761

3762 3763 3764 3765
		if (atomic_read(&nohz.first_pick_cpu) == cpu)
			atomic_cmpxchg(&nohz.first_pick_cpu, cpu, nr_cpu_ids);
		if (atomic_read(&nohz.second_pick_cpu) == cpu)
			atomic_cmpxchg(&nohz.second_pick_cpu, cpu, nr_cpu_ids);
3766

3767
		if (atomic_read(&nohz.load_balancer) >= nr_cpu_ids) {
3768 3769
			int new_ilb;

3770 3771 3772 3773 3774
			/* make me the ilb owner */
			if (atomic_cmpxchg(&nohz.load_balancer, nr_cpu_ids,
					   cpu) != nr_cpu_ids)
				return;

3775 3776 3777 3778 3779 3780
			/*
			 * Check to see if there is a more power-efficient
			 * ilb.
			 */
			new_ilb = find_new_ilb(cpu);
			if (new_ilb < nr_cpu_ids && new_ilb != cpu) {
3781
				atomic_set(&nohz.load_balancer, nr_cpu_ids);
3782
				resched_cpu(new_ilb);
3783
				return;
3784
			}
3785
			return;
3786 3787
		}
	} else {
3788 3789
		if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
			return;
3790

3791
		cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
3792 3793

		if (atomic_read(&nohz.load_balancer) == cpu)
3794 3795
			if (atomic_cmpxchg(&nohz.load_balancer, cpu,
					   nr_cpu_ids) != cpu)
3796 3797
				BUG();
	}
3798
	return;
3799 3800 3801 3802 3803 3804 3805 3806 3807 3808 3809 3810 3811 3812 3813 3814 3815 3816 3817 3818 3819 3820
}
#endif

static DEFINE_SPINLOCK(balancing);

/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
 * Balancing parameters are set up in arch_init_sched_domains.
 */
static void rebalance_domains(int cpu, enum cpu_idle_type idle)
{
	int balance = 1;
	struct rq *rq = cpu_rq(cpu);
	unsigned long interval;
	struct sched_domain *sd;
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
	int need_serialize;

P
Peter Zijlstra 已提交
3821 3822
	update_shares(cpu);

3823 3824 3825 3826 3827 3828 3829 3830 3831 3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860 3861 3862 3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873 3874 3875 3876 3877 3878 3879 3880 3881
	for_each_domain(cpu, sd) {
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

		interval = sd->balance_interval;
		if (idle != CPU_IDLE)
			interval *= sd->busy_factor;

		/* scale ms to jiffies */
		interval = msecs_to_jiffies(interval);
		if (unlikely(!interval))
			interval = 1;
		if (interval > HZ*NR_CPUS/10)
			interval = HZ*NR_CPUS/10;

		need_serialize = sd->flags & SD_SERIALIZE;

		if (need_serialize) {
			if (!spin_trylock(&balancing))
				goto out;
		}

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
			if (load_balance(cpu, rq, sd, idle, &balance)) {
				/*
				 * We've pulled tasks over so either we're no
				 * longer idle, or one of our SMT siblings is
				 * not idle.
				 */
				idle = CPU_NOT_IDLE;
			}
			sd->last_balance = jiffies;
		}
		if (need_serialize)
			spin_unlock(&balancing);
out:
		if (time_after(next_balance, sd->last_balance + interval)) {
			next_balance = sd->last_balance + interval;
			update_next_balance = 1;
		}

		/*
		 * Stop the load balance at this level. There is another
		 * CPU in our sched group which is doing load balancing more
		 * actively.
		 */
		if (!balance)
			break;
	}

	/*
	 * next_balance will be updated only when there is a need.
	 * When the cpu is attached to null domain for ex, it will not be
	 * updated.
	 */
	if (likely(update_next_balance))
		rq->next_balance = next_balance;
}

3882
#ifdef CONFIG_NO_HZ
3883
/*
3884
 * In CONFIG_NO_HZ case, the idle balance kickee will do the
3885 3886
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904 3905 3906 3907 3908 3909 3910
static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle)
{
	struct rq *this_rq = cpu_rq(this_cpu);
	struct rq *rq;
	int balance_cpu;

	if (idle != CPU_IDLE || !this_rq->nohz_balance_kick)
		return;

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
		if (balance_cpu == this_cpu)
			continue;

		/*
		 * If this cpu gets work to do, stop the load balancing
		 * work being done for other cpus. Next load
		 * balancing owner will pick it up.
		 */
		if (need_resched()) {
			this_rq->nohz_balance_kick = 0;
			break;
		}

		raw_spin_lock_irq(&this_rq->lock);
3911
		update_rq_clock(this_rq);
3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945
		update_cpu_load(this_rq);
		raw_spin_unlock_irq(&this_rq->lock);

		rebalance_domains(balance_cpu, CPU_IDLE);

		rq = cpu_rq(balance_cpu);
		if (time_after(this_rq->next_balance, rq->next_balance))
			this_rq->next_balance = rq->next_balance;
	}
	nohz.next_balance = this_rq->next_balance;
	this_rq->nohz_balance_kick = 0;
}

/*
 * Current heuristic for kicking the idle load balancer
 * - first_pick_cpu is the one of the busy CPUs. It will kick
 *   idle load balancer when it has more than one process active. This
 *   eliminates the need for idle load balancing altogether when we have
 *   only one running process in the system (common case).
 * - If there are more than one busy CPU, idle load balancer may have
 *   to run for active_load_balance to happen (i.e., two busy CPUs are
 *   SMT or core siblings and can run better if they move to different
 *   physical CPUs). So, second_pick_cpu is the second of the busy CPUs
 *   which will kick idle load balancer as soon as it has any load.
 */
static inline int nohz_kick_needed(struct rq *rq, int cpu)
{
	unsigned long now = jiffies;
	int ret;
	int first_pick_cpu, second_pick_cpu;

	if (time_before(now, nohz.next_balance))
		return 0;

S
Suresh Siddha 已提交
3946
	if (rq->idle_at_tick)
3947 3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971 3972 3973 3974 3975 3976 3977
		return 0;

	first_pick_cpu = atomic_read(&nohz.first_pick_cpu);
	second_pick_cpu = atomic_read(&nohz.second_pick_cpu);

	if (first_pick_cpu < nr_cpu_ids && first_pick_cpu != cpu &&
	    second_pick_cpu < nr_cpu_ids && second_pick_cpu != cpu)
		return 0;

	ret = atomic_cmpxchg(&nohz.first_pick_cpu, nr_cpu_ids, cpu);
	if (ret == nr_cpu_ids || ret == cpu) {
		atomic_cmpxchg(&nohz.second_pick_cpu, cpu, nr_cpu_ids);
		if (rq->nr_running > 1)
			return 1;
	} else {
		ret = atomic_cmpxchg(&nohz.second_pick_cpu, nr_cpu_ids, cpu);
		if (ret == nr_cpu_ids || ret == cpu) {
			if (rq->nr_running)
				return 1;
		}
	}
	return 0;
}
#else
static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle) { }
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
3978 3979 3980 3981 3982 3983 3984 3985 3986 3987
static void run_rebalance_domains(struct softirq_action *h)
{
	int this_cpu = smp_processor_id();
	struct rq *this_rq = cpu_rq(this_cpu);
	enum cpu_idle_type idle = this_rq->idle_at_tick ?
						CPU_IDLE : CPU_NOT_IDLE;

	rebalance_domains(this_cpu, idle);

	/*
3988
	 * If this cpu has a pending nohz_balance_kick, then do the
3989 3990 3991
	 * balancing on behalf of the other idle cpus whose ticks are
	 * stopped.
	 */
3992
	nohz_idle_balance(this_cpu, idle);
3993 3994 3995 3996
}

static inline int on_null_domain(int cpu)
{
3997
	return !rcu_dereference_sched(cpu_rq(cpu)->sd);
3998 3999 4000 4001 4002 4003 4004 4005 4006 4007 4008
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
static inline void trigger_load_balance(struct rq *rq, int cpu)
{
	/* Don't need to rebalance while attached to NULL domain */
	if (time_after_eq(jiffies, rq->next_balance) &&
	    likely(!on_null_domain(cpu)))
		raise_softirq(SCHED_SOFTIRQ);
4009 4010 4011 4012
#ifdef CONFIG_NO_HZ
	else if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
		nohz_balancer_kick(cpu);
#endif
4013 4014
}

4015 4016 4017 4018 4019 4020 4021 4022 4023 4024
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
}

4025 4026 4027 4028 4029 4030 4031 4032 4033
#else	/* CONFIG_SMP */

/*
 * on UP we do not need to balance between CPUs:
 */
static inline void idle_balance(int cpu, struct rq *rq)
{
}

4034
#endif /* CONFIG_SMP */
4035

4036 4037 4038
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
4039
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
4040 4041 4042 4043 4044 4045
{
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &curr->se;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
P
Peter Zijlstra 已提交
4046
		entity_tick(cfs_rq, se, queued);
4047 4048 4049 4050
	}
}

/*
P
Peter Zijlstra 已提交
4051 4052 4053
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
4054
 */
P
Peter Zijlstra 已提交
4055
static void task_fork_fair(struct task_struct *p)
4056
{
P
Peter Zijlstra 已提交
4057
	struct cfs_rq *cfs_rq = task_cfs_rq(current);
4058
	struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
4059
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
4060 4061 4062
	struct rq *rq = this_rq();
	unsigned long flags;

4063
	raw_spin_lock_irqsave(&rq->lock, flags);
4064

4065 4066
	update_rq_clock(rq);

4067 4068
	if (unlikely(task_cpu(p) != this_cpu)) {
		rcu_read_lock();
P
Peter Zijlstra 已提交
4069
		__set_task_cpu(p, this_cpu);
4070 4071
		rcu_read_unlock();
	}
4072

4073
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
4074

4075 4076
	if (curr)
		se->vruntime = curr->vruntime;
4077
	place_entity(cfs_rq, se, 1);
4078

P
Peter Zijlstra 已提交
4079
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
4080
		/*
4081 4082 4083
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
4084
		swap(curr->vruntime, se->vruntime);
4085
		resched_task(rq->curr);
4086
	}
4087

4088 4089
	se->vruntime -= cfs_rq->min_vruntime;

4090
	raw_spin_unlock_irqrestore(&rq->lock, flags);
4091 4092
}

4093 4094 4095 4096
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
4097 4098
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
4099
{
P
Peter Zijlstra 已提交
4100 4101 4102
	if (!p->se.on_rq)
		return;

4103 4104 4105 4106 4107
	/*
	 * Reschedule if we are currently running on this runqueue and
	 * our priority decreased, or if we are not currently running on
	 * this runqueue and our priority is higher than the current's
	 */
P
Peter Zijlstra 已提交
4108
	if (rq->curr == p) {
4109 4110 4111
		if (p->prio > oldprio)
			resched_task(rq->curr);
	} else
4112
		check_preempt_curr(rq, p, 0);
4113 4114
}

P
Peter Zijlstra 已提交
4115 4116 4117 4118 4119 4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138
static void switched_from_fair(struct rq *rq, struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	/*
	 * Ensure the task's vruntime is normalized, so that when its
	 * switched back to the fair class the enqueue_entity(.flags=0) will
	 * do the right thing.
	 *
	 * If it was on_rq, then the dequeue_entity(.flags=0) will already
	 * have normalized the vruntime, if it was !on_rq, then only when
	 * the task is sleeping will it still have non-normalized vruntime.
	 */
	if (!se->on_rq && p->state != TASK_RUNNING) {
		/*
		 * Fix up our vruntime so that the current sleep doesn't
		 * cause 'unlimited' sleep bonus.
		 */
		place_entity(cfs_rq, se, 0);
		se->vruntime -= cfs_rq->min_vruntime;
	}
}

4139 4140 4141
/*
 * We switched to the sched_fair class.
 */
P
Peter Zijlstra 已提交
4142
static void switched_to_fair(struct rq *rq, struct task_struct *p)
4143
{
P
Peter Zijlstra 已提交
4144 4145 4146
	if (!p->se.on_rq)
		return;

4147 4148 4149 4150 4151
	/*
	 * We were most likely switched from sched_rt, so
	 * kick off the schedule if running, otherwise just see
	 * if we can still preempt the current task.
	 */
P
Peter Zijlstra 已提交
4152
	if (rq->curr == p)
4153 4154
		resched_task(rq->curr);
	else
4155
		check_preempt_curr(rq, p, 0);
4156 4157
}

4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4169 4170
/* Account for a task changing its policy or group.
 *
 * This routine is mostly called to set cfs_rq->curr field when a task
 * migrates between groups/classes.
 */
static void set_curr_task_fair(struct rq *rq)
{
	struct sched_entity *se = &rq->curr->se;

	for_each_sched_entity(se)
		set_next_entity(cfs_rq_of(se), se);
}

P
Peter Zijlstra 已提交
4171
#ifdef CONFIG_FAIR_GROUP_SCHED
4172
static void task_move_group_fair(struct task_struct *p, int on_rq)
P
Peter Zijlstra 已提交
4173
{
4174 4175 4176 4177 4178 4179 4180 4181 4182 4183 4184 4185 4186 4187 4188 4189
	/*
	 * If the task was not on the rq at the time of this cgroup movement
	 * it must have been asleep, sleeping tasks keep their ->vruntime
	 * absolute on their old rq until wakeup (needed for the fair sleeper
	 * bonus in place_entity()).
	 *
	 * If it was on the rq, we've just 'preempted' it, which does convert
	 * ->vruntime to a relative base.
	 *
	 * Make sure both cases convert their relative position when migrating
	 * to another cgroup's rq. This does somewhat interfere with the
	 * fair sleeper stuff for the first placement, but who cares.
	 */
	if (!on_rq)
		p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime;
	set_task_rq(p, task_cpu(p));
4190
	if (!on_rq)
4191
		p->se.vruntime += cfs_rq_of(&p->se)->min_vruntime;
P
Peter Zijlstra 已提交
4192 4193 4194
}
#endif

4195
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
4196 4197 4198 4199 4200 4201 4202 4203 4204 4205 4206 4207 4208 4209
{
	struct sched_entity *se = &task->se;
	unsigned int rr_interval = 0;

	/*
	 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
	 * idle runqueue:
	 */
	if (rq->cfs.load.weight)
		rr_interval = NS_TO_JIFFIES(sched_slice(&rq->cfs, se));

	return rr_interval;
}

4210 4211 4212
/*
 * All the scheduling class methods:
 */
4213 4214
static const struct sched_class fair_sched_class = {
	.next			= &idle_sched_class,
4215 4216 4217 4218
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,

I
Ingo Molnar 已提交
4219
	.check_preempt_curr	= check_preempt_wakeup,
4220 4221 4222 4223

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

4224
#ifdef CONFIG_SMP
L
Li Zefan 已提交
4225 4226
	.select_task_rq		= select_task_rq_fair,

4227 4228
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
4229 4230

	.task_waking		= task_waking_fair,
4231
#endif
4232

4233
	.set_curr_task          = set_curr_task_fair,
4234
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
4235
	.task_fork		= task_fork_fair,
4236 4237

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
4238
	.switched_from		= switched_from_fair,
4239
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
4240

4241 4242
	.get_rr_interval	= get_rr_interval_fair,

P
Peter Zijlstra 已提交
4243
#ifdef CONFIG_FAIR_GROUP_SCHED
4244
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
4245
#endif
4246 4247 4248
};

#ifdef CONFIG_SCHED_DEBUG
4249
static void print_cfs_stats(struct seq_file *m, int cpu)
4250 4251 4252
{
	struct cfs_rq *cfs_rq;

4253
	rcu_read_lock();
4254
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
4255
		print_cfs_rq(m, cpu, cfs_rq);
4256
	rcu_read_unlock();
4257 4258
}
#endif