sched_fair.c 108.6 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>
25
#include <linux/cpumask.h>
A
Arjan van de Ven 已提交
26

27
/*
28
 * Targeted preemption latency for CPU-bound tasks:
29
 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
30
 *
31
 * NOTE: this latency value is not the same as the concept of
I
Ingo Molnar 已提交
32 33 34
 * 'timeslice length' - timeslices in CFS are of variable length
 * and have no persistent notion like in traditional, time-slice
 * based scheduling concepts.
35
 *
I
Ingo Molnar 已提交
36 37
 * (to see the precise effective timeslice length of your workload,
 *  run vmstat and monitor the context-switches (cs) field)
38
 */
39 40
unsigned int sysctl_sched_latency = 6000000ULL;
unsigned int normalized_sysctl_sched_latency = 6000000ULL;
41

42 43 44 45 46 47 48 49 50 51 52 53
/*
 * 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;

54
/*
55
 * Minimal preemption granularity for CPU-bound tasks:
56
 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
57
 */
58 59
unsigned int sysctl_sched_min_granularity = 750000ULL;
unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
60 61

/*
62 63
 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
 */
64
static unsigned int sched_nr_latency = 8;
65 66

/*
67
 * After fork, child runs first. If set to 0 (default) then
68
 * parent will (try to) run first.
69
 */
70
unsigned int sysctl_sched_child_runs_first __read_mostly;
71 72 73

/*
 * SCHED_OTHER wake-up granularity.
74
 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
75 76 77 78 79
 *
 * This option delays the preemption effects of decoupled workloads
 * and reduces their over-scheduling. Synchronous workloads will still
 * have immediate wakeup/sleep latencies.
 */
80
unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
81
unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
82

83 84
const_debug unsigned int sysctl_sched_migration_cost = 500000UL;

85 86 87 88 89 90 91
/*
 * The exponential sliding  window over which load is averaged for shares
 * distribution.
 * (default: 10msec)
 */
unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;

92 93
static const struct sched_class fair_sched_class;

94 95 96 97
/**************************************************************
 * CFS operations on generic schedulable entities:
 */

98
#ifdef CONFIG_FAIR_GROUP_SCHED
99

100
/* cpu runqueue to which this cfs_rq is attached */
101 102
static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
103
	return cfs_rq->rq;
104 105
}

106 107
/* An entity is a task if it doesn't "own" a runqueue */
#define entity_is_task(se)	(!se->my_q)
108

109 110 111 112 113 114 115 116
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
117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145
/* 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];
}

146 147 148
static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
	if (!cfs_rq->on_list) {
149 150 151 152 153 154 155 156 157 158 159 160
		/*
		 * 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,
161
				&rq_of(cfs_rq)->leaf_cfs_rq_list);
162
		}
163 164 165 166 167 168 169 170 171 172 173 174 175

		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
176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194
/* 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;
}

195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237
/* 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);
	}
}

238 239 240 241 242 243
#else	/* !CONFIG_FAIR_GROUP_SCHED */

static inline struct task_struct *task_of(struct sched_entity *se)
{
	return container_of(se, struct task_struct, se);
}
244

245 246 247
static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
	return container_of(cfs_rq, struct rq, cfs);
248 249 250 251
}

#define entity_is_task(se)	1

P
Peter Zijlstra 已提交
252 253
#define for_each_sched_entity(se) \
		for (; se; se = NULL)
254

P
Peter Zijlstra 已提交
255
static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
256
{
P
Peter Zijlstra 已提交
257
	return &task_rq(p)->cfs;
258 259
}

P
Peter Zijlstra 已提交
260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278
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;
}

279 280 281 282 283 284 285 286
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
287 288 289 290 291 292 293 294 295 296 297 298 299 300
#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;
}

301 302 303 304 305
static inline void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
}

P
Peter Zijlstra 已提交
306 307
#endif	/* CONFIG_FAIR_GROUP_SCHED */

308 309 310 311 312

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

313
static inline u64 max_vruntime(u64 min_vruntime, u64 vruntime)
314
{
315 316
	s64 delta = (s64)(vruntime - min_vruntime);
	if (delta > 0)
317 318 319 320 321
		min_vruntime = vruntime;

	return min_vruntime;
}

322
static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
P
Peter Zijlstra 已提交
323 324 325 326 327 328 329 330
{
	s64 delta = (s64)(vruntime - min_vruntime);
	if (delta < 0)
		min_vruntime = vruntime;

	return min_vruntime;
}

331 332 333 334 335 336
static inline int entity_before(struct sched_entity *a,
				struct sched_entity *b)
{
	return (s64)(a->vruntime - b->vruntime) < 0;
}

337
static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
338
{
339
	return se->vruntime - cfs_rq->min_vruntime;
340 341
}

342 343 344 345 346 347 348 349 350 351 352 353
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
354
		if (!cfs_rq->curr)
355 356 357 358 359 360 361 362
			vruntime = se->vruntime;
		else
			vruntime = min_vruntime(vruntime, se->vruntime);
	}

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

363 364 365
/*
 * Enqueue an entity into the rb-tree:
 */
366
static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
367 368 369 370
{
	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
	struct rb_node *parent = NULL;
	struct sched_entity *entry;
371
	s64 key = entity_key(cfs_rq, se);
372 373 374 375 376 377 378 379 380 381 382 383
	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.
		 */
384
		if (key < entity_key(cfs_rq, entry)) {
385 386 387 388 389 390 391 392 393 394 395
			link = &parent->rb_left;
		} else {
			link = &parent->rb_right;
			leftmost = 0;
		}
	}

	/*
	 * Maintain a cache of leftmost tree entries (it is frequently
	 * used):
	 */
396
	if (leftmost)
I
Ingo Molnar 已提交
397
		cfs_rq->rb_leftmost = &se->run_node;
398 399 400 401 402

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

403
static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
404
{
P
Peter Zijlstra 已提交
405 406 407 408 409 410
	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
411

412 413 414
	rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
}

415
static struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
416
{
417 418 419 420 421 422
	struct rb_node *left = cfs_rq->rb_leftmost;

	if (!left)
		return NULL;

	return rb_entry(left, struct sched_entity, run_node);
423 424
}

425 426 427 428 429 430 431 432 433 434 435
static struct sched_entity *__pick_next_entity(struct sched_entity *se)
{
	struct rb_node *next = rb_next(&se->run_node);

	if (!next)
		return NULL;

	return rb_entry(next, struct sched_entity, run_node);
}

#ifdef CONFIG_SCHED_DEBUG
436
static struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
437
{
438
	struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
439

440 441
	if (!last)
		return NULL;
442 443

	return rb_entry(last, struct sched_entity, run_node);
444 445
}

446 447 448 449
/**************************************************************
 * Scheduling class statistics methods:
 */

450
int sched_proc_update_handler(struct ctl_table *table, int write,
451
		void __user *buffer, size_t *lenp,
452 453
		loff_t *ppos)
{
454
	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
455
	int factor = get_update_sysctl_factor();
456 457 458 459 460 461 462

	if (ret || !write)
		return ret;

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

463 464 465 466 467 468 469
#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

470 471 472
	return 0;
}
#endif
473

474
/*
475
 * delta /= w
476 477 478 479
 */
static inline unsigned long
calc_delta_fair(unsigned long delta, struct sched_entity *se)
{
480 481
	if (unlikely(se->load.weight != NICE_0_LOAD))
		delta = calc_delta_mine(delta, NICE_0_LOAD, &se->load);
482 483 484 485

	return delta;
}

486 487 488 489 490 491 492 493
/*
 * 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
 */
494 495 496
static u64 __sched_period(unsigned long nr_running)
{
	u64 period = sysctl_sched_latency;
497
	unsigned long nr_latency = sched_nr_latency;
498 499

	if (unlikely(nr_running > nr_latency)) {
500
		period = sysctl_sched_min_granularity;
501 502 503 504 505 506
		period *= nr_running;
	}

	return period;
}

507 508 509 510
/*
 * We calculate the wall-time slice from the period by taking a part
 * proportional to the weight.
 *
511
 * s = p*P[w/rw]
512
 */
P
Peter Zijlstra 已提交
513
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
514
{
M
Mike Galbraith 已提交
515
	u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
516

M
Mike Galbraith 已提交
517
	for_each_sched_entity(se) {
L
Lin Ming 已提交
518
		struct load_weight *load;
519
		struct load_weight lw;
L
Lin Ming 已提交
520 521 522

		cfs_rq = cfs_rq_of(se);
		load = &cfs_rq->load;
523

M
Mike Galbraith 已提交
524
		if (unlikely(!se->on_rq)) {
525
			lw = cfs_rq->load;
M
Mike Galbraith 已提交
526 527 528 529 530 531 532

			update_load_add(&lw, se->load.weight);
			load = &lw;
		}
		slice = calc_delta_mine(slice, se->load.weight, load);
	}
	return slice;
533 534
}

535
/*
536
 * We calculate the vruntime slice of a to be inserted task
537
 *
538
 * vs = s/w
539
 */
540
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
P
Peter Zijlstra 已提交
541
{
542
	return calc_delta_fair(sched_slice(cfs_rq, se), se);
543 544
}

545
static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update);
546
static void update_cfs_shares(struct cfs_rq *cfs_rq);
547

548 549 550 551 552
/*
 * 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
553 554
__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
	      unsigned long delta_exec)
555
{
556
	unsigned long delta_exec_weighted;
557

558 559
	schedstat_set(curr->statistics.exec_max,
		      max((u64)delta_exec, curr->statistics.exec_max));
560 561

	curr->sum_exec_runtime += delta_exec;
562
	schedstat_add(cfs_rq, exec_clock, delta_exec);
563
	delta_exec_weighted = calc_delta_fair(delta_exec, curr);
564

I
Ingo Molnar 已提交
565
	curr->vruntime += delta_exec_weighted;
566
	update_min_vruntime(cfs_rq);
567

P
Peter Zijlstra 已提交
568
#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
569 570
	cfs_rq->load_unacc_exec_time += delta_exec;
#endif
571 572
}

573
static void update_curr(struct cfs_rq *cfs_rq)
574
{
575
	struct sched_entity *curr = cfs_rq->curr;
576
	u64 now = rq_of(cfs_rq)->clock_task;
577 578 579 580 581 582 583 584 585 586
	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
587
	delta_exec = (unsigned long)(now - curr->exec_start);
P
Peter Zijlstra 已提交
588 589
	if (!delta_exec)
		return;
590

I
Ingo Molnar 已提交
591 592
	__update_curr(cfs_rq, curr, delta_exec);
	curr->exec_start = now;
593 594 595 596

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

597
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
598
		cpuacct_charge(curtask, delta_exec);
599
		account_group_exec_runtime(curtask, delta_exec);
600
	}
601 602 603
}

static inline void
604
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
605
{
606
	schedstat_set(se->statistics.wait_start, rq_of(cfs_rq)->clock);
607 608 609 610 611
}

/*
 * Task is being enqueued - update stats:
 */
612
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
613 614 615 616 617
{
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
618
	if (se != cfs_rq->curr)
619
		update_stats_wait_start(cfs_rq, se);
620 621 622
}

static void
623
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
624
{
625 626 627 628 629
	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);
630 631 632
#ifdef CONFIG_SCHEDSTATS
	if (entity_is_task(se)) {
		trace_sched_stat_wait(task_of(se),
633
			rq_of(cfs_rq)->clock - se->statistics.wait_start);
634 635
	}
#endif
636
	schedstat_set(se->statistics.wait_start, 0);
637 638 639
}

static inline void
640
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
641 642 643 644 645
{
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
646
	if (se != cfs_rq->curr)
647
		update_stats_wait_end(cfs_rq, se);
648 649 650 651 652 653
}

/*
 * We are picking a new current task - update its stats:
 */
static inline void
654
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
655 656 657 658
{
	/*
	 * We are starting a new run period:
	 */
659
	se->exec_start = rq_of(cfs_rq)->clock_task;
660 661 662 663 664 665
}

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

666 667 668 669 670 671 672 673 674 675 676 677 678
#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

679 680 681 682
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
683 684
	if (!parent_entity(se))
		inc_cpu_load(rq_of(cfs_rq), se->load.weight);
685
	if (entity_is_task(se)) {
686
		add_cfs_task_weight(cfs_rq, se->load.weight);
687 688
		list_add(&se->group_node, &cfs_rq->tasks);
	}
689 690 691 692 693 694 695
	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);
696 697
	if (!parent_entity(se))
		dec_cpu_load(rq_of(cfs_rq), se->load.weight);
698
	if (entity_is_task(se)) {
699
		add_cfs_task_weight(cfs_rq, -se->load.weight);
700 701
		list_del_init(&se->group_node);
	}
702 703 704
	cfs_rq->nr_running--;
}

705 706
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722
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
723
{
724
	u64 period = sysctl_sched_shares_window;
P
Peter Zijlstra 已提交
725
	u64 now, delta;
726
	unsigned long load = cfs_rq->load.weight;
P
Peter Zijlstra 已提交
727

728
	if (cfs_rq->tg == &root_task_group)
P
Peter Zijlstra 已提交
729 730
		return;

731
	now = rq_of(cfs_rq)->clock_task;
P
Peter Zijlstra 已提交
732 733
	delta = now - cfs_rq->load_stamp;

734 735 736 737 738
	/* 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;
739
		delta = period - 1;
740 741
	}

P
Peter Zijlstra 已提交
742
	cfs_rq->load_stamp = now;
743
	cfs_rq->load_unacc_exec_time = 0;
P
Peter Zijlstra 已提交
744
	cfs_rq->load_period += delta;
745 746 747 748
	if (load) {
		cfs_rq->load_last = now;
		cfs_rq->load_avg += delta * load;
	}
P
Peter Zijlstra 已提交
749

750 751 752 753 754
	/* 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
755 756 757 758 759 760 761 762 763 764
	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;
	}
765

766 767
	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
768 769
}

770
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
771 772 773
{
	long load_weight, load, shares;

774
	load = cfs_rq->load.weight;
775 776 777

	load_weight = atomic_read(&tg->load_weight);
	load_weight += load;
778
	load_weight -= cfs_rq->load_contribution;
779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795

	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);
796
		update_cfs_shares(cfs_rq);
797 798 799 800 801 802 803
	}
}
# else /* CONFIG_SMP */
static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
{
}

804
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
805 806 807 808 809 810 811 812
{
	return tg->shares;
}

static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
{
}
# endif /* CONFIG_SMP */
P
Peter Zijlstra 已提交
813 814 815
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
816 817 818 819
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
820
		account_entity_dequeue(cfs_rq, se);
821
	}
P
Peter Zijlstra 已提交
822 823 824 825 826 827 828

	update_load_set(&se->load, weight);

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

829
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
830 831 832
{
	struct task_group *tg;
	struct sched_entity *se;
833
	long shares;
P
Peter Zijlstra 已提交
834 835 836 837 838

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
	if (!se)
		return;
839 840 841 842
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
843
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
844 845 846 847

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
848
static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
P
Peter Zijlstra 已提交
849 850 851
{
}

852
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
853 854
{
}
855 856 857 858

static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
{
}
P
Peter Zijlstra 已提交
859 860
#endif /* CONFIG_FAIR_GROUP_SCHED */

861
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
862 863
{
#ifdef CONFIG_SCHEDSTATS
864 865 866 867 868
	struct task_struct *tsk = NULL;

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

869 870
	if (se->statistics.sleep_start) {
		u64 delta = rq_of(cfs_rq)->clock - se->statistics.sleep_start;
871 872 873 874

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

875 876
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
877

878 879
		se->statistics.sleep_start = 0;
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
880

881
		if (tsk) {
882
			account_scheduler_latency(tsk, delta >> 10, 1);
883 884
			trace_sched_stat_sleep(tsk, delta);
		}
885
	}
886 887
	if (se->statistics.block_start) {
		u64 delta = rq_of(cfs_rq)->clock - se->statistics.block_start;
888 889 890 891

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

892 893
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
894

895 896
		se->statistics.block_start = 0;
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
897

898
		if (tsk) {
899
			if (tsk->in_iowait) {
900 901
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
902
				trace_sched_stat_iowait(tsk, delta);
903 904
			}

905 906 907 908 909 910 911 912 913 914 915
			/*
			 * 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
916
		}
917 918 919 920
	}
#endif
}

P
Peter Zijlstra 已提交
921 922 923 924 925 926 927 928 929 930 931 932 933
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
}

934 935 936
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
937
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
938

939 940 941 942 943 944
	/*
	 * 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
945
	if (initial && sched_feat(START_DEBIT))
946
		vruntime += sched_vslice(cfs_rq, se);
947

948
	/* sleeps up to a single latency don't count. */
949
	if (!initial) {
950
		unsigned long thresh = sysctl_sched_latency;
951

952 953 954 955 956 957
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
958

959
		vruntime -= thresh;
960 961
	}

962 963 964
	/* ensure we never gain time by being placed backwards. */
	vruntime = max_vruntime(se->vruntime, vruntime);

P
Peter Zijlstra 已提交
965
	se->vruntime = vruntime;
966 967
}

968
static void
969
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
970
{
971 972 973 974
	/*
	 * Update the normalized vruntime before updating min_vruntime
	 * through callig update_curr().
	 */
975
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
976 977
		se->vruntime += cfs_rq->min_vruntime;

978
	/*
979
	 * Update run-time statistics of the 'current'.
980
	 */
981
	update_curr(cfs_rq);
982
	update_cfs_load(cfs_rq, 0);
P
Peter Zijlstra 已提交
983
	account_entity_enqueue(cfs_rq, se);
984
	update_cfs_shares(cfs_rq);
985

986
	if (flags & ENQUEUE_WAKEUP) {
987
		place_entity(cfs_rq, se, 0);
988
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
989
	}
990

991
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
992
	check_spread(cfs_rq, se);
993 994
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
995
	se->on_rq = 1;
996 997 998

	if (cfs_rq->nr_running == 1)
		list_add_leaf_cfs_rq(cfs_rq);
999 1000
}

1001
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
1002
{
1003 1004 1005 1006 1007 1008 1009 1010
	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
1011

1012 1013 1014 1015 1016 1017 1018 1019 1020
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
1021 1022
}

1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
		if (cfs_rq->skip == se)
			cfs_rq->skip = NULL;
		else
			break;
	}
}

P
Peter Zijlstra 已提交
1034 1035
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
1036 1037 1038 1039 1040
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
1041 1042 1043

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
1044 1045
}

1046
static void
1047
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1048
{
1049 1050 1051 1052 1053
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);

1054
	update_stats_dequeue(cfs_rq, se);
1055
	if (flags & DEQUEUE_SLEEP) {
P
Peter Zijlstra 已提交
1056
#ifdef CONFIG_SCHEDSTATS
1057 1058 1059 1060
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
1061
				se->statistics.sleep_start = rq_of(cfs_rq)->clock;
1062
			if (tsk->state & TASK_UNINTERRUPTIBLE)
1063
				se->statistics.block_start = rq_of(cfs_rq)->clock;
1064
		}
1065
#endif
P
Peter Zijlstra 已提交
1066 1067
	}

P
Peter Zijlstra 已提交
1068
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
1069

1070
	if (se != cfs_rq->curr)
1071
		__dequeue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
1072
	se->on_rq = 0;
1073
	update_cfs_load(cfs_rq, 0);
1074
	account_entity_dequeue(cfs_rq, se);
1075
	update_min_vruntime(cfs_rq);
1076
	update_cfs_shares(cfs_rq);
1077 1078 1079 1080 1081 1082

	/*
	 * 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.
	 */
1083
	if (!(flags & DEQUEUE_SLEEP))
1084
		se->vruntime -= cfs_rq->min_vruntime;
1085 1086 1087 1088 1089
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
1090
static void
I
Ingo Molnar 已提交
1091
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
1092
{
1093 1094
	unsigned long ideal_runtime, delta_exec;

P
Peter Zijlstra 已提交
1095
	ideal_runtime = sched_slice(cfs_rq, curr);
1096
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
1097
	if (delta_exec > ideal_runtime) {
1098
		resched_task(rq_of(cfs_rq)->curr);
1099 1100 1101 1102 1103
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118
		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) {
1119
		struct sched_entity *se = __pick_first_entity(cfs_rq);
1120 1121
		s64 delta = curr->vruntime - se->vruntime;

1122 1123 1124
		if (delta < 0)
			return;

1125 1126
		if (delta > ideal_runtime)
			resched_task(rq_of(cfs_rq)->curr);
1127
	}
1128 1129
}

1130
static void
1131
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
1132
{
1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143
	/* '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);
	}

1144
	update_stats_curr_start(cfs_rq, se);
1145
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
1146 1147 1148 1149 1150 1151
#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):
	 */
1152
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
1153
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
1154 1155 1156
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
1157
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
1158 1159
}

1160 1161 1162
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

1163 1164 1165 1166 1167 1168 1169
/*
 * Pick the next process, keeping these things in mind, in this order:
 * 1) keep things fair between processes/task groups
 * 2) pick the "next" process, since someone really wants that to run
 * 3) pick the "last" process, for cache locality
 * 4) do not run the "skip" process, if something else is available
 */
1170
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
1171
{
1172
	struct sched_entity *se = __pick_first_entity(cfs_rq);
1173
	struct sched_entity *left = se;
1174

1175 1176 1177 1178 1179 1180 1181 1182 1183
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
		struct sched_entity *second = __pick_next_entity(se);
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
1184

1185 1186 1187 1188 1189 1190
	/*
	 * 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;

1191 1192 1193 1194 1195 1196
	/*
	 * Someone really wants this to run. If it's not unfair, run it.
	 */
	if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
		se = cfs_rq->next;

1197
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
1198 1199

	return se;
1200 1201
}

1202
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
1203 1204 1205 1206 1207 1208
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
1209
		update_curr(cfs_rq);
1210

P
Peter Zijlstra 已提交
1211
	check_spread(cfs_rq, prev);
1212
	if (prev->on_rq) {
1213
		update_stats_wait_start(cfs_rq, prev);
1214 1215 1216
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
	}
1217
	cfs_rq->curr = NULL;
1218 1219
}

P
Peter Zijlstra 已提交
1220 1221
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
1222 1223
{
	/*
1224
	 * Update run-time statistics of the 'current'.
1225
	 */
1226
	update_curr(cfs_rq);
1227

1228 1229 1230 1231 1232
	/*
	 * Update share accounting for long-running entities.
	 */
	update_entity_shares_tick(cfs_rq);

P
Peter Zijlstra 已提交
1233 1234 1235 1236 1237
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
1238 1239 1240 1241
	if (queued) {
		resched_task(rq_of(cfs_rq)->curr);
		return;
	}
P
Peter Zijlstra 已提交
1242 1243 1244 1245 1246 1247 1248 1249
	/*
	 * 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

1250
	if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
I
Ingo Molnar 已提交
1251
		check_preempt_tick(cfs_rq, curr);
1252 1253 1254 1255 1256 1257
}

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

P
Peter Zijlstra 已提交
1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280
#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.
		 */
1281
		if (rq->curr != p)
1282
			delta = max_t(s64, 10000LL, delta);
P
Peter Zijlstra 已提交
1283

1284
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
1285 1286
	}
}
1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302

/*
 * 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);
}
1303
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
1304 1305 1306 1307
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
1308 1309 1310 1311

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
1312 1313
#endif

1314 1315 1316 1317 1318
/*
 * 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:
 */
1319
static void
1320
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
1321 1322
{
	struct cfs_rq *cfs_rq;
1323
	struct sched_entity *se = &p->se;
1324 1325

	for_each_sched_entity(se) {
1326
		if (se->on_rq)
1327 1328
			break;
		cfs_rq = cfs_rq_of(se);
1329 1330
		enqueue_entity(cfs_rq, se, flags);
		flags = ENQUEUE_WAKEUP;
1331
	}
P
Peter Zijlstra 已提交
1332

P
Peter Zijlstra 已提交
1333 1334 1335
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);

1336
		update_cfs_load(cfs_rq, 0);
1337
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
1338 1339
	}

1340
	hrtick_update(rq);
1341 1342 1343 1344 1345 1346 1347
}

/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
1348
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
1349 1350
{
	struct cfs_rq *cfs_rq;
1351
	struct sched_entity *se = &p->se;
1352 1353 1354

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
1355
		dequeue_entity(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
1356

1357
		/* Don't dequeue parent if it has other entities besides us */
1358
		if (cfs_rq->load.weight)
1359
			break;
1360
		flags |= DEQUEUE_SLEEP;
1361
	}
P
Peter Zijlstra 已提交
1362

P
Peter Zijlstra 已提交
1363 1364 1365
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);

1366
		update_cfs_load(cfs_rq, 0);
1367
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
1368 1369
	}

1370
	hrtick_update(rq);
1371 1372
}

1373
#ifdef CONFIG_SMP
1374

1375 1376 1377 1378 1379 1380 1381 1382
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;
}

1383
#ifdef CONFIG_FAIR_GROUP_SCHED
1384 1385 1386 1387 1388 1389 1390
/*
 * 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
1391
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
1392
{
P
Peter Zijlstra 已提交
1393
	struct sched_entity *se = tg->se[cpu];
1394 1395 1396 1397

	if (!tg->parent)
		return wl;

P
Peter Zijlstra 已提交
1398
	for_each_sched_entity(se) {
1399
		long lw, w;
P
Peter Zijlstra 已提交
1400

1401 1402
		tg = se->my_q->tg;
		w = se->my_q->load.weight;
1403

1404 1405 1406 1407
		/* 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
1408

1409
		wl += w;
1410

1411 1412 1413 1414
		if (lw > 0 && wl < lw)
			wl = (wl * tg->shares) / lw;
		else
			wl = tg->shares;
1415

1416 1417 1418 1419
		/* zero point is MIN_SHARES */
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
		wl -= se->load.weight;
P
Peter Zijlstra 已提交
1420 1421
		wg = 0;
	}
1422

P
Peter Zijlstra 已提交
1423
	return wl;
1424
}
P
Peter Zijlstra 已提交
1425

1426
#else
P
Peter Zijlstra 已提交
1427

1428 1429
static inline unsigned long effective_load(struct task_group *tg, int cpu,
		unsigned long wl, unsigned long wg)
P
Peter Zijlstra 已提交
1430
{
1431
	return wl;
1432
}
P
Peter Zijlstra 已提交
1433

1434 1435
#endif

1436
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
1437
{
1438
	s64 this_load, load;
1439
	int idx, this_cpu, prev_cpu;
1440
	unsigned long tl_per_task;
1441
	struct task_group *tg;
1442
	unsigned long weight;
1443
	int balanced;
1444

1445 1446 1447 1448 1449
	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);
1450

1451 1452 1453 1454 1455
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
1456
	rcu_read_lock();
1457 1458 1459 1460
	if (sync) {
		tg = task_group(current);
		weight = current->se.load.weight;

1461
		this_load += effective_load(tg, this_cpu, -weight, -weight);
1462 1463
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
1464

1465 1466
	tg = task_group(p);
	weight = p->se.load.weight;
1467

1468 1469
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
1470 1471 1472
	 * 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.
1473 1474 1475 1476
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
1477 1478
	if (this_load > 0) {
		s64 this_eff_load, prev_eff_load;
1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491

		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;
1492
	rcu_read_unlock();
1493

1494
	/*
I
Ingo Molnar 已提交
1495 1496 1497
	 * If the currently running task will sleep within
	 * a reasonable amount of time then attract this newly
	 * woken task:
1498
	 */
1499 1500
	if (sync && balanced)
		return 1;
1501

1502
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
1503 1504
	tl_per_task = cpu_avg_load_per_task(this_cpu);

1505 1506 1507
	if (balanced ||
	    (this_load <= load &&
	     this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
1508 1509 1510 1511 1512
		/*
		 * This domain has SD_WAKE_AFFINE and
		 * p is cache cold in this domain, and
		 * there is no bad imbalance.
		 */
1513
		schedstat_inc(sd, ttwu_move_affine);
1514
		schedstat_inc(p, se.statistics.nr_wakeups_affine);
1515 1516 1517 1518 1519 1520

		return 1;
	}
	return 0;
}

1521 1522 1523 1524 1525
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
1526
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
1527
		  int this_cpu, int load_idx)
1528
{
1529
	struct sched_group *idlest = NULL, *group = sd->groups;
1530 1531
	unsigned long min_load = ULONG_MAX, this_load = 0;
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
1532

1533 1534 1535 1536
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
1537

1538 1539 1540 1541 1542 1543 1544 1545 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
		/* 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;
1592 1593 1594
		}
	}

1595 1596
	return idlest;
}
1597

1598 1599 1600
/*
 * Try and locate an idle CPU in the sched_domain.
 */
1601
static int select_idle_sibling(struct task_struct *p, int target)
1602 1603 1604
{
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
1605
	struct sched_domain *sd;
1606 1607 1608
	int i;

	/*
1609 1610
	 * If the task is going to be woken-up on this cpu and if it is
	 * already idle, then it is the right target.
1611
	 */
1612 1613 1614 1615 1616 1617 1618 1619
	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))
1620
		return prev_cpu;
1621 1622

	/*
1623
	 * Otherwise, iterate the domains and find an elegible idle cpu.
1624
	 */
1625 1626
	for_each_domain(target, sd) {
		if (!(sd->flags & SD_SHARE_PKG_RESOURCES))
1627
			break;
1628 1629 1630 1631 1632 1633

		for_each_cpu_and(i, sched_domain_span(sd), &p->cpus_allowed) {
			if (idle_cpu(i)) {
				target = i;
				break;
			}
1634
		}
1635 1636 1637 1638 1639 1640 1641 1642

		/*
		 * 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;
1643 1644 1645 1646 1647
	}

	return target;
}

1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658
/*
 * 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.
 */
1659 1660
static int
select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_flags)
1661
{
1662
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
1663 1664 1665
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
	int new_cpu = cpu;
1666
	int want_affine = 0;
1667
	int want_sd = 1;
1668
	int sync = wake_flags & WF_SYNC;
1669

1670
	if (sd_flag & SD_BALANCE_WAKE) {
1671
		if (cpumask_test_cpu(cpu, &p->cpus_allowed))
1672 1673 1674
			want_affine = 1;
		new_cpu = prev_cpu;
	}
1675 1676

	for_each_domain(cpu, tmp) {
1677 1678 1679
		if (!(tmp->flags & SD_LOAD_BALANCE))
			continue;

1680
		/*
1681 1682
		 * If power savings logic is enabled for a domain, see if we
		 * are not overloaded, if so, don't balance wider.
1683
		 */
P
Peter Zijlstra 已提交
1684
		if (tmp->flags & (SD_POWERSAVINGS_BALANCE|SD_PREFER_LOCAL)) {
1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696
			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
1697 1698 1699 1700
			if (tmp->flags & SD_POWERSAVINGS_BALANCE)
				nr_running /= 2;

			if (nr_running < capacity)
1701
				want_sd = 0;
1702
		}
1703

1704
		/*
1705 1706
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
1707
		 */
1708 1709 1710 1711
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
			want_affine = 0;
1712 1713
		}

1714 1715 1716
		if (!want_sd && !want_affine)
			break;

1717
		if (!(tmp->flags & sd_flag))
1718 1719
			continue;

1720 1721 1722 1723
		if (want_sd)
			sd = tmp;
	}

1724
	if (affine_sd) {
1725 1726 1727 1728
		if (cpu == prev_cpu || wake_affine(affine_sd, p, sync))
			return select_idle_sibling(p, cpu);
		else
			return select_idle_sibling(p, prev_cpu);
1729
	}
1730

1731
	while (sd) {
1732
		int load_idx = sd->forkexec_idx;
1733
		struct sched_group *group;
1734
		int weight;
1735

1736
		if (!(sd->flags & sd_flag)) {
1737 1738 1739
			sd = sd->child;
			continue;
		}
1740

1741 1742
		if (sd_flag & SD_BALANCE_WAKE)
			load_idx = sd->wake_idx;
1743

1744
		group = find_idlest_group(sd, p, cpu, load_idx);
1745 1746 1747 1748
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
1749

1750
		new_cpu = find_idlest_cpu(group, p, cpu);
1751 1752 1753 1754
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
1755
		}
1756 1757 1758

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
1759
		weight = sd->span_weight;
1760 1761
		sd = NULL;
		for_each_domain(cpu, tmp) {
1762
			if (weight <= tmp->span_weight)
1763
				break;
1764
			if (tmp->flags & sd_flag)
1765 1766 1767
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
1768 1769
	}

1770
	return new_cpu;
1771 1772 1773
}
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
1774 1775
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
1776 1777 1778 1779
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
1780 1781
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
1782 1783 1784 1785 1786 1787 1788 1789 1790
	 *
	 * 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.
1791
	 */
M
Mike Galbraith 已提交
1792 1793
	if (unlikely(se->load.weight != NICE_0_LOAD))
		gran = calc_delta_fair(gran, se);
1794 1795 1796 1797

	return gran;
}

1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819
/*
 * 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
1820
	gran = wakeup_gran(curr, se);
1821 1822 1823 1824 1825 1826
	if (vdiff > gran)
		return 1;

	return 0;
}

1827 1828
static void set_last_buddy(struct sched_entity *se)
{
1829 1830 1831 1832
	if (likely(task_of(se)->policy != SCHED_IDLE)) {
		for_each_sched_entity(se)
			cfs_rq_of(se)->last = se;
	}
1833 1834 1835 1836
}

static void set_next_buddy(struct sched_entity *se)
{
1837 1838 1839 1840
	if (likely(task_of(se)->policy != SCHED_IDLE)) {
		for_each_sched_entity(se)
			cfs_rq_of(se)->next = se;
	}
1841 1842
}

1843 1844 1845 1846 1847 1848 1849 1850
static void set_skip_buddy(struct sched_entity *se)
{
	if (likely(task_of(se)->policy != SCHED_IDLE)) {
		for_each_sched_entity(se)
			cfs_rq_of(se)->skip = se;
	}
}

1851 1852 1853
/*
 * Preempt the current task with a newly woken task if needed:
 */
1854
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
1855 1856
{
	struct task_struct *curr = rq->curr;
1857
	struct sched_entity *se = &curr->se, *pse = &p->se;
1858
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
1859
	int scale = cfs_rq->nr_running >= sched_nr_latency;
1860

I
Ingo Molnar 已提交
1861 1862 1863
	if (unlikely(se == pse))
		return;

1864
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK))
M
Mike Galbraith 已提交
1865
		set_next_buddy(pse);
P
Peter Zijlstra 已提交
1866

1867 1868 1869 1870 1871 1872 1873
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
	 */
	if (test_tsk_need_resched(curr))
		return;

1874 1875 1876 1877 1878
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

1879
	/*
1880 1881
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
1882
	 */
1883
	if (unlikely(p->policy != SCHED_NORMAL))
1884
		return;
1885 1886


1887 1888 1889
	if (!sched_feat(WAKEUP_PREEMPT))
		return;

1890
	update_curr(cfs_rq);
1891
	find_matching_se(&se, &pse);
1892
	BUG_ON(!pse);
1893 1894
	if (wakeup_preempt_entity(se, pse) == 1)
		goto preempt;
1895

1896
	return;
1897

1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913
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);
1914 1915
}

1916
static struct task_struct *pick_next_task_fair(struct rq *rq)
1917
{
P
Peter Zijlstra 已提交
1918
	struct task_struct *p;
1919 1920 1921
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;

1922
	if (!cfs_rq->nr_running)
1923 1924 1925
		return NULL;

	do {
1926
		se = pick_next_entity(cfs_rq);
1927
		set_next_entity(cfs_rq, se);
1928 1929 1930
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
1931 1932 1933 1934
	p = task_of(se);
	hrtick_start_fair(rq, p);

	return p;
1935 1936 1937 1938 1939
}

/*
 * Account for a descheduled task:
 */
1940
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
1941 1942 1943 1944 1945 1946
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
1947
		put_prev_entity(cfs_rq, se);
1948 1949 1950
	}
}

1951 1952 1953 1954 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
/*
 * sched_yield() is very simple
 *
 * The magic of dealing with the ->skip buddy is in pick_next_entity.
 */
static void yield_task_fair(struct rq *rq)
{
	struct task_struct *curr = rq->curr;
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
	struct sched_entity *se = &curr->se;

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

	clear_buddies(cfs_rq, se);

	if (curr->policy != SCHED_BATCH) {
		update_rq_clock(rq);
		/*
		 * Update run-time statistics of the 'current'.
		 */
		update_curr(cfs_rq);
	}

	set_skip_buddy(se);
}

1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

	if (!se->on_rq)
		return false;

	/* Tell the scheduler that we'd really like pse to run next. */
	set_next_buddy(se);

	yield_task_fair(rq);

	return true;
}

1996
#ifdef CONFIG_SMP
1997 1998 1999 2000
/**************************************************
 * Fair scheduling class load-balancing methods:
 */

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029
/*
 * 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)) {
2030
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
2031 2032 2033 2034 2035
		return 0;
	}
	*all_pinned = 0;

	if (task_running(rq, p)) {
2036
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
2037 2038 2039 2040 2041 2042 2043 2044 2045
		return 0;
	}

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

2046
	tsk_cache_hot = task_hot(p, rq->clock_task, sd);
2047 2048 2049 2050 2051
	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]);
2052
			schedstat_inc(p, se.statistics.nr_forced_migrations);
2053 2054 2055 2056 2057 2058
		}
#endif
		return 1;
	}

	if (tsk_cache_hot) {
2059
		schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
2060 2061 2062 2063 2064
		return 0;
	}
	return 1;
}

2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100
/*
 * 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;
}

2101 2102 2103 2104
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,
2105
	      int *this_best_prio, struct cfs_rq *busiest_cfs_rq)
2106
{
K
Ken Chen 已提交
2107
	int loops = 0, pulled = 0;
2108
	long rem_load_move = max_load_move;
2109
	struct task_struct *p, *n;
2110 2111 2112 2113

	if (max_load_move == 0)
		goto out;

2114 2115 2116
	list_for_each_entry_safe(p, n, &busiest_cfs_rq->tasks, se.group_node) {
		if (loops++ > sysctl_sched_nr_migrate)
			break;
2117

2118
		if ((p->se.load.weight >> 1) > rem_load_move ||
K
Ken Chen 已提交
2119 2120
		    !can_migrate_task(p, busiest, this_cpu, sd, idle,
				      all_pinned))
2121
			continue;
2122

2123 2124 2125
		pull_task(busiest, p, this_rq, this_cpu);
		pulled++;
		rem_load_move -= p->se.load.weight;
2126 2127

#ifdef CONFIG_PREEMPT
2128 2129 2130 2131 2132 2133 2134
		/*
		 * 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;
2135 2136
#endif

2137 2138 2139 2140 2141 2142 2143
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
		if (rem_load_move <= 0)
			break;

2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157
		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);

	return max_load_move - rem_load_move;
}

P
Peter Zijlstra 已提交
2158
#ifdef CONFIG_FAIR_GROUP_SCHED
2159 2160 2161
/*
 * update tg->load_weight by folding this cpu's load_avg
 */
2162
static int update_shares_cpu(struct task_group *tg, int cpu)
2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176
{
	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);
2177
	update_cfs_load(cfs_rq, 1);
2178 2179 2180 2181 2182

	/*
	 * We need to update shares after updating tg->load_weight in
	 * order to adjust the weight of groups with long running tasks.
	 */
2183
	update_cfs_shares(cfs_rq);
2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195

	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();
2196 2197
	for_each_leaf_cfs_rq(rq, cfs_rq)
		update_shares_cpu(cfs_rq->tg, cpu);
2198 2199 2200
	rcu_read_unlock();
}

P
Peter Zijlstra 已提交
2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247
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
2248 2249 2250 2251
static inline void update_shares(int cpu)
{
}

P
Peter Zijlstra 已提交
2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263
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

2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275
/*
 * 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)
{
2276
	unsigned long total_load_moved = 0, load_moved;
2277 2278 2279
	int this_best_prio = this_rq->curr->prio;

	do {
2280
		load_moved = load_balance_fair(this_rq, this_cpu, busiest,
2281 2282
				max_load_move - total_load_moved,
				sd, idle, all_pinned, &this_best_prio);
2283 2284

		total_load_moved += load_moved;
2285 2286 2287 2288 2289 2290 2291 2292 2293

#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;
2294 2295 2296 2297

		if (raw_spin_is_contended(&this_rq->lock) ||
				raw_spin_is_contended(&busiest->lock))
			break;
2298
#endif
2299
	} while (load_moved && max_load_move > total_load_moved);
2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319

	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;
2320
	unsigned long this_has_capacity;
2321
	unsigned int  this_idle_cpus;
2322 2323

	/* Statistics of the busiest group */
2324
	unsigned int  busiest_idle_cpus;
2325 2326 2327
	unsigned long max_load;
	unsigned long busiest_load_per_task;
	unsigned long busiest_nr_running;
2328
	unsigned long busiest_group_capacity;
2329
	unsigned long busiest_has_capacity;
2330
	unsigned int  busiest_group_weight;
2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351

	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;
2352 2353
	unsigned long idle_cpus;
	unsigned long group_weight;
2354
	int group_imb; /* Is there an imbalance in the group ? */
2355
	int group_has_capacity; /* Is there extra capacity in the group? */
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 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546
};

/**
 * 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)
{
2547
	unsigned long weight = sd->span_weight;
2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565
	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);
2566 2567 2568 2569 2570 2571 2572

	if (unlikely(total < rq->rt_avg)) {
		/* Ensures that power won't end up being negative */
		available = 0;
	} else {
		available = total - rq->rt_avg;
	}
2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583

	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)
{
2584
	unsigned long weight = sd->span_weight;
2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596
	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;
	}

2597 2598 2599 2600 2601 2602 2603 2604 2605
	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;

2606 2607 2608 2609 2610 2611
	power *= scale_rt_power(cpu);
	power >>= SCHED_LOAD_SHIFT;

	if (!power)
		power = 1;

2612
	cpu_rq(cpu)->cpu_power = power;
2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637
	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;
}

2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656
/*
 * 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
2657
	if (group->cpu_power * 32 > group->cpu_power_orig * 29)
2658 2659 2660 2661 2662
		return 1;

	return 0;
}

2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676
/**
 * 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.
 * @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,
2677
			enum cpu_idle_type idle, int load_idx,
2678 2679 2680
			int local_group, const struct cpumask *cpus,
			int *balance, struct sg_lb_stats *sgs)
{
2681
	unsigned long load, max_cpu_load, min_cpu_load, max_nr_running;
2682 2683
	int i;
	unsigned int balance_cpu = -1, first_idle_cpu = 0;
2684
	unsigned long avg_load_per_task = 0;
2685

2686
	if (local_group)
2687 2688 2689 2690 2691
		balance_cpu = group_first_cpu(group);

	/* Tally up the load of all CPUs in the group */
	max_cpu_load = 0;
	min_cpu_load = ~0UL;
2692
	max_nr_running = 0;
2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706

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

		/* 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);
2707
			if (load > max_cpu_load) {
2708
				max_cpu_load = load;
2709 2710
				max_nr_running = rq->nr_running;
			}
2711 2712 2713 2714 2715 2716 2717
			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);
2718 2719
		if (idle_cpu(i))
			sgs->idle_cpus++;
2720 2721 2722 2723 2724 2725 2726 2727
	}

	/*
	 * 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.
	 */
2728 2729 2730 2731 2732 2733
	if (idle != CPU_NEWLY_IDLE && local_group) {
		if (balance_cpu != this_cpu) {
			*balance = 0;
			return;
		}
		update_group_power(sd, this_cpu);
2734 2735 2736 2737 2738 2739 2740
	}

	/* 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
P
Peter Zijlstra 已提交
2741
	 * than the average weight of a task.
2742 2743 2744 2745 2746 2747
	 *
	 * 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?
	 */
2748 2749
	if (sgs->sum_nr_running)
		avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
2750

P
Peter Zijlstra 已提交
2751
	if ((max_cpu_load - min_cpu_load) >= avg_load_per_task && max_nr_running > 1)
2752 2753
		sgs->group_imb = 1;

2754
	sgs->group_capacity = DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE);
2755 2756
	if (!sgs->group_capacity)
		sgs->group_capacity = fix_small_capacity(sd, group);
2757
	sgs->group_weight = group->group_weight;
2758 2759 2760

	if (sgs->group_capacity > sgs->sum_nr_running)
		sgs->group_has_capacity = 1;
2761 2762
}

2763 2764 2765 2766 2767
/**
 * 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
2768 2769
 * @sgs: sched_group statistics
 * @this_cpu: the current cpu
2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805
 *
 * 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;
}

2806 2807 2808 2809 2810 2811 2812 2813 2814 2815
/**
 * 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
 * @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,
2816 2817
			enum cpu_idle_type idle, const struct cpumask *cpus,
			int *balance, struct sd_lb_stats *sds)
2818 2819
{
	struct sched_domain *child = sd->child;
2820
	struct sched_group *sg = sd->groups;
2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832
	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;

2833
		local_group = cpumask_test_cpu(this_cpu, sched_group_cpus(sg));
2834
		memset(&sgs, 0, sizeof(sgs));
2835
		update_sg_lb_stats(sd, sg, this_cpu, idle, load_idx,
2836 2837
				local_group, cpus, balance, &sgs);

P
Peter Zijlstra 已提交
2838
		if (local_group && !(*balance))
2839 2840 2841
			return;

		sds->total_load += sgs.group_load;
2842
		sds->total_pwr += sg->cpu_power;
2843 2844 2845

		/*
		 * In case the child domain prefers tasks go to siblings
2846
		 * first, lower the sg capacity to one so that we'll try
2847 2848 2849 2850 2851 2852
		 * 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).
2853
		 */
2854
		if (prefer_sibling && !local_group && sds->this_has_capacity)
2855 2856 2857 2858
			sgs.group_capacity = min(sgs.group_capacity, 1UL);

		if (local_group) {
			sds->this_load = sgs.avg_load;
2859
			sds->this = sg;
2860 2861
			sds->this_nr_running = sgs.sum_nr_running;
			sds->this_load_per_task = sgs.sum_weighted_load;
2862
			sds->this_has_capacity = sgs.group_has_capacity;
2863
			sds->this_idle_cpus = sgs.idle_cpus;
2864
		} else if (update_sd_pick_busiest(sd, sds, sg, &sgs, this_cpu)) {
2865
			sds->max_load = sgs.avg_load;
2866
			sds->busiest = sg;
2867
			sds->busiest_nr_running = sgs.sum_nr_running;
2868
			sds->busiest_idle_cpus = sgs.idle_cpus;
2869
			sds->busiest_group_capacity = sgs.group_capacity;
2870
			sds->busiest_load_per_task = sgs.sum_weighted_load;
2871
			sds->busiest_has_capacity = sgs.group_has_capacity;
2872
			sds->busiest_group_weight = sgs.group_weight;
2873 2874 2875
			sds->group_imb = sgs.group_imb;
		}

2876 2877 2878 2879 2880
		update_sd_power_savings_stats(sg, sds, local_group, &sgs);
		sg = sg->next;
	} while (sg != sd->groups);
}

M
Michael Neuling 已提交
2881
int __weak arch_sd_sibling_asym_packing(void)
2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902
{
       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.
 *
2903 2904 2905
 * Returns 1 when packing is required and a task should be moved to
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929
 * @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;
2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944
}

/**
 * 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;
2945
	unsigned long scaled_busy_load_per_task;
2946 2947 2948 2949 2950 2951 2952 2953 2954 2955

	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);

2956 2957 2958 2959 2960 2961
	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)) {
2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011
		*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)
{
3012 3013 3014 3015 3016 3017 3018 3019
	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);
	}

3020 3021 3022 3023 3024 3025 3026 3027 3028 3029
	/*
	 * 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);
	}

3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052
	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);
3053 3054 3055 3056 3057 3058 3059 3060

	/* 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
L
Lucas De Marchi 已提交
3061
	 * there is no guarantee that any tasks will be moved so we'll have
3062 3063 3064 3065 3066 3067 3068
	 * 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);

}
3069

3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098
/******* 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.
 * @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,
3099
		   const struct cpumask *cpus, int *balance)
3100 3101 3102 3103 3104 3105 3106 3107 3108
{
	struct sd_lb_stats sds;

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

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
3109
	update_sd_lb_stats(sd, this_cpu, idle, cpus, balance, &sds);
3110

3111 3112 3113
	/*
	 * this_cpu is not the appropriate cpu to perform load balancing at
	 * this level.
3114
	 */
P
Peter Zijlstra 已提交
3115
	if (!(*balance))
3116 3117
		goto ret;

3118 3119 3120 3121
	if ((idle == CPU_IDLE || idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(sd, &sds, this_cpu, imbalance))
		return sds.busiest;

3122
	/* There is no busy sibling group to pull tasks from */
3123 3124 3125
	if (!sds.busiest || sds.busiest_nr_running == 0)
		goto out_balanced;

3126 3127
	sds.avg_load = (SCHED_LOAD_SCALE * sds.total_load) / sds.total_pwr;

P
Peter Zijlstra 已提交
3128 3129 3130 3131 3132 3133 3134 3135
	/*
	 * If the busiest group is imbalanced the below checks don't
	 * work because they assumes all things are equal, which typically
	 * isn't true due to cpus_allowed constraints and the like.
	 */
	if (sds.group_imb)
		goto force_balance;

3136
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
3137 3138 3139 3140
	if (idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
			!sds.busiest_has_capacity)
		goto force_balance;

3141 3142 3143 3144
	/*
	 * If the local group is more busy than the selected busiest group
	 * don't try and pull any tasks.
	 */
3145 3146 3147
	if (sds.this_load >= sds.max_load)
		goto out_balanced;

3148 3149 3150 3151
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
3152 3153 3154
	if (sds.this_load >= sds.avg_load)
		goto out_balanced;

3155
	if (idle == CPU_IDLE) {
3156 3157 3158 3159 3160 3161
		/*
		 * 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.
		 */
3162
		if ((sds.this_idle_cpus <= sds.busiest_idle_cpus + 1) &&
3163 3164
		    sds.busiest_nr_running <= sds.busiest_group_weight)
			goto out_balanced;
3165 3166 3167 3168 3169 3170 3171
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
		if (100 * sds.max_load <= sd->imbalance_pct * sds.this_load)
			goto out_balanced;
3172
	}
3173

3174
force_balance:
3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194
	/* 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 *
3195 3196 3197
find_busiest_queue(struct sched_domain *sd, struct sched_group *group,
		   enum cpu_idle_type idle, unsigned long imbalance,
		   const struct cpumask *cpus)
3198 3199 3200 3201 3202 3203 3204 3205 3206 3207
{
	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;

3208 3209 3210
		if (!capacity)
			capacity = fix_small_capacity(sd, group);

3211 3212 3213 3214
		if (!cpumask_test_cpu(i, cpus))
			continue;

		rq = cpu_rq(i);
3215
		wl = weighted_cpuload(i);
3216

3217 3218 3219 3220
		/*
		 * When comparing with imbalance, use weighted_cpuload()
		 * which is not scaled with the cpu power.
		 */
3221 3222 3223
		if (capacity && rq->nr_running == 1 && wl > imbalance)
			continue;

3224 3225 3226 3227 3228 3229 3230 3231
		/*
		 * 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;

3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249
		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);

3250
static int need_active_balance(struct sched_domain *sd, int idle,
3251
			       int busiest_cpu, int this_cpu)
3252 3253
{
	if (idle == CPU_NEWLY_IDLE) {
3254 3255 3256 3257 3258 3259 3260 3261 3262

		/*
		 * 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;

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
		/*
		 * 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 (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP)
			return 0;
	}

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

3289 3290
static int active_load_balance_cpu_stop(void *data);

3291 3292 3293 3294 3295 3296 3297 3298
/*
 * 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)
{
3299
	int ld_moved, all_pinned = 0, active_balance = 0;
3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310
	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);

	schedstat_inc(sd, lb_count[idle]);

redo:
3311
	group = find_busiest_group(sd, this_cpu, &imbalance, idle,
3312 3313 3314 3315 3316 3317 3318 3319 3320 3321
				   cpus, balance);

	if (*balance == 0)
		goto out_balanced;

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

3322
	busiest = find_busiest_queue(sd, group, idle, imbalance, cpus);
3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339
	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.
		 */
K
Ken Chen 已提交
3340
		all_pinned = 1;
3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364
		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]);
3365 3366 3367 3368 3369 3370 3371 3372
		/*
		 * 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++;
3373

3374
		if (need_active_balance(sd, idle, cpu_of(busiest), this_cpu)) {
3375 3376
			raw_spin_lock_irqsave(&busiest->lock, flags);

3377 3378 3379
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
3380 3381 3382 3383 3384 3385 3386 3387 3388
			 */
			if (!cpumask_test_cpu(this_cpu,
					      &busiest->curr->cpus_allowed)) {
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
				all_pinned = 1;
				goto out_one_pinned;
			}

3389 3390 3391 3392 3393
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
3394 3395 3396 3397 3398 3399
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
3400

3401
			if (active_balance)
3402 3403 3404
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
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

			/*
			 * 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;
	}

	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;

3442
	ld_moved = 0;
3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461
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;

3462 3463 3464 3465 3466
	/*
	 * Drop the rq->lock, but keep IRQ/preempt disabled.
	 */
	raw_spin_unlock(&this_rq->lock);

P
Paul Turner 已提交
3467
	update_shares(this_cpu);
3468 3469
	for_each_domain(this_cpu, sd) {
		unsigned long interval;
3470
		int balance = 1;
3471 3472 3473 3474

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

3475
		if (sd->flags & SD_BALANCE_NEWIDLE) {
3476
			/* If we've pulled tasks over stop searching: */
3477 3478 3479
			pulled_task = load_balance(this_cpu, this_rq,
						   sd, CPU_NEWLY_IDLE, &balance);
		}
3480 3481 3482 3483

		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
3484 3485
		if (pulled_task) {
			this_rq->idle_stamp = 0;
3486
			break;
N
Nikhil Rao 已提交
3487
		}
3488
	}
3489 3490 3491

	raw_spin_lock(&this_rq->lock);

3492 3493 3494 3495 3496 3497 3498 3499 3500 3501
	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;
	}
}

/*
3502 3503 3504 3505
 * 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.
3506
 */
3507
static int active_load_balance_cpu_stop(void *data)
3508
{
3509 3510
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
3511
	int target_cpu = busiest_rq->push_cpu;
3512
	struct rq *target_rq = cpu_rq(target_cpu);
3513
	struct sched_domain *sd;
3514 3515 3516 3517 3518 3519 3520

	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;
3521 3522 3523

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
3524
		goto out_unlock;
3525 3526 3527 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545 3546 3547 3548 3549 3550 3551 3552

	/*
	 * 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);
3553 3554 3555 3556
out_unlock:
	busiest_rq->active_balance = 0;
	raw_spin_unlock_irq(&busiest_rq->lock);
	return 0;
3557 3558 3559
}

#ifdef CONFIG_NO_HZ
3560 3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585

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.
 */
3586 3587
static struct {
	atomic_t load_balancer;
3588 3589 3590 3591 3592 3593
	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;
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 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646

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)
{
3647
	cpumask_and(nohz.grp_idle_mask, nohz.idle_cpus_mask,
3648 3649 3650 3651 3652 3653
					sched_group_cpus(ilb_group));

	/*
	 * A sched_group is semi-idle when it has atleast one busy cpu
	 * and atleast one idle cpu.
	 */
3654
	if (cpumask_empty(nohz.grp_idle_mask))
3655 3656
		return 0;

3657
	if (cpumask_equal(nohz.grp_idle_mask, sched_group_cpus(ilb_group)))
3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675 3676 3677 3678 3679 3680 3681 3682 3683 3684 3685 3686 3687 3688 3689
		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
	 */
3690
	if (cpumask_weight(nohz.idle_cpus_mask) < 2)
3691 3692 3693 3694 3695 3696 3697
		goto out_done;

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

		do {
			if (is_semi_idle_group(ilb_group))
3698
				return cpumask_first(nohz.grp_idle_mask);
3699 3700 3701 3702 3703 3704 3705

			ilb_group = ilb_group->next;

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

out_done:
3706
	return nr_cpu_ids;
3707 3708 3709 3710
}
#else /*  (CONFIG_SCHED_MC || CONFIG_SCHED_SMT) */
static inline int find_new_ilb(int call_cpu)
{
3711
	return nr_cpu_ids;
3712 3713 3714
}
#endif

3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742 3743
/*
 * 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;
}

3744 3745 3746
/*
 * 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
3747
 * load balancing on behalf of all those cpus.
3748
 *
3749 3750 3751
 * 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.
3752
 *
3753 3754 3755
 * 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).
3756
 */
3757
void select_nohz_load_balancer(int stop_tick)
3758 3759 3760 3761 3762 3763
{
	int cpu = smp_processor_id();

	if (stop_tick) {
		if (!cpu_active(cpu)) {
			if (atomic_read(&nohz.load_balancer) != cpu)
3764
				return;
3765 3766 3767 3768 3769

			/*
			 * If we are going offline and still the leader,
			 * give up!
			 */
3770 3771
			if (atomic_cmpxchg(&nohz.load_balancer, cpu,
					   nr_cpu_ids) != cpu)
3772 3773
				BUG();

3774
			return;
3775 3776
		}

3777
		cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
3778

3779 3780 3781 3782
		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);
3783

3784
		if (atomic_read(&nohz.load_balancer) >= nr_cpu_ids) {
3785 3786
			int new_ilb;

3787 3788 3789 3790 3791
			/* make me the ilb owner */
			if (atomic_cmpxchg(&nohz.load_balancer, nr_cpu_ids,
					   cpu) != nr_cpu_ids)
				return;

3792 3793 3794 3795 3796 3797
			/*
			 * 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) {
3798
				atomic_set(&nohz.load_balancer, nr_cpu_ids);
3799
				resched_cpu(new_ilb);
3800
				return;
3801
			}
3802
			return;
3803 3804
		}
	} else {
3805 3806
		if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
			return;
3807

3808
		cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
3809 3810

		if (atomic_read(&nohz.load_balancer) == cpu)
3811 3812
			if (atomic_cmpxchg(&nohz.load_balancer, cpu,
					   nr_cpu_ids) != cpu)
3813 3814
				BUG();
	}
3815
	return;
3816 3817 3818 3819 3820
}
#endif

static DEFINE_SPINLOCK(balancing);

3821 3822 3823 3824 3825 3826 3827 3828 3829 3830 3831
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

/*
 * Scale the max load_balance interval with the number of CPUs in the system.
 * This trades load-balance latency on larger machines for less cross talk.
 */
static void update_max_interval(void)
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 3846 3847 3848
/*
 * 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
3849 3850
	update_shares(cpu);

3851 3852 3853 3854 3855 3856 3857 3858 3859 3860
	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);
3861
		interval = clamp(interval, 1UL, max_load_balance_interval);
3862 3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873

		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
3874
				 * longer idle.
3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904 3905
				 */
				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;
}

3906
#ifdef CONFIG_NO_HZ
3907
/*
3908
 * In CONFIG_NO_HZ case, the idle balance kickee will do the
3909 3910
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934
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);
3935
		update_rq_clock(this_rq);
3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946 3947 3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969
		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
3970
	if (rq->idle_at_tick)
3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989 3990 3991 3992 3993 3994 3995 3996 3997 3998 3999 4000 4001
		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).
 */
4002 4003 4004 4005 4006 4007 4008 4009 4010 4011
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);

	/*
4012
	 * If this cpu has a pending nohz_balance_kick, then do the
4013 4014 4015
	 * balancing on behalf of the other idle cpus whose ticks are
	 * stopped.
	 */
4016
	nohz_idle_balance(this_cpu, idle);
4017 4018 4019 4020
}

static inline int on_null_domain(int cpu)
{
4021
	return !rcu_dereference_sched(cpu_rq(cpu)->sd);
4022 4023 4024 4025 4026 4027 4028 4029 4030 4031 4032
}

/*
 * 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);
4033 4034 4035 4036
#ifdef CONFIG_NO_HZ
	else if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
		nohz_balancer_kick(cpu);
#endif
4037 4038
}

4039 4040 4041 4042 4043 4044 4045 4046 4047 4048
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
}

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

4049 4050 4051 4052 4053 4054 4055 4056 4057
#else	/* CONFIG_SMP */

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

4058
#endif /* CONFIG_SMP */
4059

4060 4061 4062
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
4063
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
4064 4065 4066 4067 4068 4069
{
	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
4070
		entity_tick(cfs_rq, se, queued);
4071 4072 4073 4074
	}
}

/*
P
Peter Zijlstra 已提交
4075 4076 4077
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
4078
 */
P
Peter Zijlstra 已提交
4079
static void task_fork_fair(struct task_struct *p)
4080
{
P
Peter Zijlstra 已提交
4081
	struct cfs_rq *cfs_rq = task_cfs_rq(current);
4082
	struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
4083
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
4084 4085 4086
	struct rq *rq = this_rq();
	unsigned long flags;

4087
	raw_spin_lock_irqsave(&rq->lock, flags);
4088

4089 4090
	update_rq_clock(rq);

4091 4092
	if (unlikely(task_cpu(p) != this_cpu)) {
		rcu_read_lock();
P
Peter Zijlstra 已提交
4093
		__set_task_cpu(p, this_cpu);
4094 4095
		rcu_read_unlock();
	}
4096

4097
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
4098

4099 4100
	if (curr)
		se->vruntime = curr->vruntime;
4101
	place_entity(cfs_rq, se, 1);
4102

P
Peter Zijlstra 已提交
4103
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
4104
		/*
4105 4106 4107
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
4108
		swap(curr->vruntime, se->vruntime);
4109
		resched_task(rq->curr);
4110
	}
4111

4112 4113
	se->vruntime -= cfs_rq->min_vruntime;

4114
	raw_spin_unlock_irqrestore(&rq->lock, flags);
4115 4116
}

4117 4118 4119 4120
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
4121 4122
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
4123
{
P
Peter Zijlstra 已提交
4124 4125 4126
	if (!p->se.on_rq)
		return;

4127 4128 4129 4130 4131
	/*
	 * 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
4132
	if (rq->curr == p) {
4133 4134 4135
		if (p->prio > oldprio)
			resched_task(rq->curr);
	} else
4136
		check_preempt_curr(rq, p, 0);
4137 4138
}

P
Peter Zijlstra 已提交
4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161 4162
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;
	}
}

4163 4164 4165
/*
 * We switched to the sched_fair class.
 */
P
Peter Zijlstra 已提交
4166
static void switched_to_fair(struct rq *rq, struct task_struct *p)
4167
{
P
Peter Zijlstra 已提交
4168 4169 4170
	if (!p->se.on_rq)
		return;

4171 4172 4173 4174 4175
	/*
	 * 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
4176
	if (rq->curr == p)
4177 4178
		resched_task(rq->curr);
	else
4179
		check_preempt_curr(rq, p, 0);
4180 4181
}

4182 4183 4184 4185 4186 4187 4188 4189 4190 4191 4192 4193 4194
/* 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
4195
#ifdef CONFIG_FAIR_GROUP_SCHED
4196
static void task_move_group_fair(struct task_struct *p, int on_rq)
P
Peter Zijlstra 已提交
4197
{
4198 4199 4200 4201 4202 4203 4204 4205 4206 4207 4208 4209 4210 4211 4212 4213
	/*
	 * 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));
4214
	if (!on_rq)
4215
		p->se.vruntime += cfs_rq_of(&p->se)->min_vruntime;
P
Peter Zijlstra 已提交
4216 4217 4218
}
#endif

4219
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
4220 4221 4222 4223 4224 4225 4226 4227 4228 4229 4230 4231 4232 4233
{
	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;
}

4234 4235 4236
/*
 * All the scheduling class methods:
 */
4237 4238
static const struct sched_class fair_sched_class = {
	.next			= &idle_sched_class,
4239 4240 4241
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
4242
	.yield_to_task		= yield_to_task_fair,
4243

I
Ingo Molnar 已提交
4244
	.check_preempt_curr	= check_preempt_wakeup,
4245 4246 4247 4248

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

4249
#ifdef CONFIG_SMP
L
Li Zefan 已提交
4250 4251
	.select_task_rq		= select_task_rq_fair,

4252 4253
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
4254 4255

	.task_waking		= task_waking_fair,
4256
#endif
4257

4258
	.set_curr_task          = set_curr_task_fair,
4259
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
4260
	.task_fork		= task_fork_fair,
4261 4262

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
4263
	.switched_from		= switched_from_fair,
4264
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
4265

4266 4267
	.get_rr_interval	= get_rr_interval_fair,

P
Peter Zijlstra 已提交
4268
#ifdef CONFIG_FAIR_GROUP_SCHED
4269
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
4270
#endif
4271 4272 4273
};

#ifdef CONFIG_SCHED_DEBUG
4274
static void print_cfs_stats(struct seq_file *m, int cpu)
4275 4276 4277
{
	struct cfs_rq *cfs_rq;

4278
	rcu_read_lock();
4279
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
4280
		print_cfs_rq(m, cpu, cfs_rq);
4281
	rcu_read_unlock();
4282 4283
}
#endif