fair.c 170.6 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>
26 27 28
#include <linux/slab.h>
#include <linux/profile.h>
#include <linux/interrupt.h>
29
#include <linux/mempolicy.h>
30
#include <linux/migrate.h>
31
#include <linux/task_work.h>
32 33 34 35

#include <trace/events/sched.h>

#include "sched.h"
A
Arjan van de Ven 已提交
36

37
/*
38
 * Targeted preemption latency for CPU-bound tasks:
39
 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
40
 *
41
 * NOTE: this latency value is not the same as the concept of
I
Ingo Molnar 已提交
42 43 44
 * 'timeslice length' - timeslices in CFS are of variable length
 * and have no persistent notion like in traditional, time-slice
 * based scheduling concepts.
45
 *
I
Ingo Molnar 已提交
46 47
 * (to see the precise effective timeslice length of your workload,
 *  run vmstat and monitor the context-switches (cs) field)
48
 */
49 50
unsigned int sysctl_sched_latency = 6000000ULL;
unsigned int normalized_sysctl_sched_latency = 6000000ULL;
51

52 53 54 55 56 57 58 59 60 61 62 63
/*
 * 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;

64
/*
65
 * Minimal preemption granularity for CPU-bound tasks:
66
 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
67
 */
68 69
unsigned int sysctl_sched_min_granularity = 750000ULL;
unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
70 71

/*
72 73
 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
 */
74
static unsigned int sched_nr_latency = 8;
75 76

/*
77
 * After fork, child runs first. If set to 0 (default) then
78
 * parent will (try to) run first.
79
 */
80
unsigned int sysctl_sched_child_runs_first __read_mostly;
81 82 83

/*
 * SCHED_OTHER wake-up granularity.
84
 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
85 86 87 88 89
 *
 * This option delays the preemption effects of decoupled workloads
 * and reduces their over-scheduling. Synchronous workloads will still
 * have immediate wakeup/sleep latencies.
 */
90
unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
91
unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
92

93 94
const_debug unsigned int sysctl_sched_migration_cost = 500000UL;

95 96 97 98 99 100 101
/*
 * The exponential sliding  window over which load is averaged for shares
 * distribution.
 * (default: 10msec)
 */
unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;

102 103 104 105 106 107 108 109 110 111 112 113 114 115
#ifdef CONFIG_CFS_BANDWIDTH
/*
 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
 * each time a cfs_rq requests quota.
 *
 * Note: in the case that the slice exceeds the runtime remaining (either due
 * to consumption or the quota being specified to be smaller than the slice)
 * we will always only issue the remaining available time.
 *
 * default: 5 msec, units: microseconds
  */
unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
#endif

116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133
static inline void update_load_add(struct load_weight *lw, unsigned long inc)
{
	lw->weight += inc;
	lw->inv_weight = 0;
}

static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
{
	lw->weight -= dec;
	lw->inv_weight = 0;
}

static inline void update_load_set(struct load_weight *lw, unsigned long w)
{
	lw->weight = w;
	lw->inv_weight = 0;
}

134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237
/*
 * Increase the granularity value when there are more CPUs,
 * because with more CPUs the 'effective latency' as visible
 * to users decreases. But the relationship is not linear,
 * so pick a second-best guess by going with the log2 of the
 * number of CPUs.
 *
 * This idea comes from the SD scheduler of Con Kolivas:
 */
static int get_update_sysctl_factor(void)
{
	unsigned int cpus = min_t(int, num_online_cpus(), 8);
	unsigned int factor;

	switch (sysctl_sched_tunable_scaling) {
	case SCHED_TUNABLESCALING_NONE:
		factor = 1;
		break;
	case SCHED_TUNABLESCALING_LINEAR:
		factor = cpus;
		break;
	case SCHED_TUNABLESCALING_LOG:
	default:
		factor = 1 + ilog2(cpus);
		break;
	}

	return factor;
}

static void update_sysctl(void)
{
	unsigned int factor = get_update_sysctl_factor();

#define SET_SYSCTL(name) \
	(sysctl_##name = (factor) * normalized_sysctl_##name)
	SET_SYSCTL(sched_min_granularity);
	SET_SYSCTL(sched_latency);
	SET_SYSCTL(sched_wakeup_granularity);
#undef SET_SYSCTL
}

void sched_init_granularity(void)
{
	update_sysctl();
}

#if BITS_PER_LONG == 32
# define WMULT_CONST	(~0UL)
#else
# define WMULT_CONST	(1UL << 32)
#endif

#define WMULT_SHIFT	32

/*
 * Shift right and round:
 */
#define SRR(x, y) (((x) + (1UL << ((y) - 1))) >> (y))

/*
 * delta *= weight / lw
 */
static unsigned long
calc_delta_mine(unsigned long delta_exec, unsigned long weight,
		struct load_weight *lw)
{
	u64 tmp;

	/*
	 * weight can be less than 2^SCHED_LOAD_RESOLUTION for task group sched
	 * entities since MIN_SHARES = 2. Treat weight as 1 if less than
	 * 2^SCHED_LOAD_RESOLUTION.
	 */
	if (likely(weight > (1UL << SCHED_LOAD_RESOLUTION)))
		tmp = (u64)delta_exec * scale_load_down(weight);
	else
		tmp = (u64)delta_exec;

	if (!lw->inv_weight) {
		unsigned long w = scale_load_down(lw->weight);

		if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
			lw->inv_weight = 1;
		else if (unlikely(!w))
			lw->inv_weight = WMULT_CONST;
		else
			lw->inv_weight = WMULT_CONST / w;
	}

	/*
	 * Check whether we'd overflow the 64-bit multiplication:
	 */
	if (unlikely(tmp > WMULT_CONST))
		tmp = SRR(SRR(tmp, WMULT_SHIFT/2) * lw->inv_weight,
			WMULT_SHIFT/2);
	else
		tmp = SRR(tmp * lw->inv_weight, WMULT_SHIFT);

	return (unsigned long)min(tmp, (u64)(unsigned long)LONG_MAX);
}


const struct sched_class fair_sched_class;
238

239 240 241 242
/**************************************************************
 * CFS operations on generic schedulable entities:
 */

243
#ifdef CONFIG_FAIR_GROUP_SCHED
244

245
/* cpu runqueue to which this cfs_rq is attached */
246 247
static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
248
	return cfs_rq->rq;
249 250
}

251 252
/* An entity is a task if it doesn't "own" a runqueue */
#define entity_is_task(se)	(!se->my_q)
253

254 255 256 257 258 259 260 261
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
262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282
/* 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;
}

283 284
static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
				       int force_update);
285

286 287 288
static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
	if (!cfs_rq->on_list) {
289 290 291 292 293 294 295 296 297 298 299 300
		/*
		 * 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,
301
				&rq_of(cfs_rq)->leaf_cfs_rq_list);
302
		}
303 304

		cfs_rq->on_list = 1;
305
		/* We should have no load, but we need to update last_decay. */
306
		update_cfs_rq_blocked_load(cfs_rq, 0);
307 308 309 310 311 312 313 314 315 316 317
	}
}

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
318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336
/* 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;
}

337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379
/* 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);
	}
}

380 381 382 383 384 385
#else	/* !CONFIG_FAIR_GROUP_SCHED */

static inline struct task_struct *task_of(struct sched_entity *se)
{
	return container_of(se, struct task_struct, se);
}
386

387 388 389
static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
	return container_of(cfs_rq, struct rq, cfs);
390 391 392 393
}

#define entity_is_task(se)	1

P
Peter Zijlstra 已提交
394 395
#define for_each_sched_entity(se) \
		for (; se; se = NULL)
396

P
Peter Zijlstra 已提交
397
static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
398
{
P
Peter Zijlstra 已提交
399
	return &task_rq(p)->cfs;
400 401
}

P
Peter Zijlstra 已提交
402 403 404 405 406 407 408 409 410 411 412 413 414 415
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;
}

416 417 418 419 420 421 422 423
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
424 425 426 427 428 429 430 431 432 433 434 435 436 437
#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;
}

438 439 440 441 442
static inline void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
}

P
Peter Zijlstra 已提交
443 444
#endif	/* CONFIG_FAIR_GROUP_SCHED */

445 446
static __always_inline
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec);
447 448 449 450 451

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

452
static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
453
{
454
	s64 delta = (s64)(vruntime - max_vruntime);
455
	if (delta > 0)
456
		max_vruntime = vruntime;
457

458
	return max_vruntime;
459 460
}

461
static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
P
Peter Zijlstra 已提交
462 463 464 465 466 467 468 469
{
	s64 delta = (s64)(vruntime - min_vruntime);
	if (delta < 0)
		min_vruntime = vruntime;

	return min_vruntime;
}

470 471 472 473 474 475
static inline int entity_before(struct sched_entity *a,
				struct sched_entity *b)
{
	return (s64)(a->vruntime - b->vruntime) < 0;
}

476 477 478 479 480 481 482 483 484 485 486 487
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
488
		if (!cfs_rq->curr)
489 490 491 492 493
			vruntime = se->vruntime;
		else
			vruntime = min_vruntime(vruntime, se->vruntime);
	}

494
	/* ensure we never gain time by being placed backwards. */
495
	cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
496 497 498 499
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
500 501
}

502 503 504
/*
 * Enqueue an entity into the rb-tree:
 */
505
static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521
{
	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
	struct rb_node *parent = NULL;
	struct sched_entity *entry;
	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.
		 */
522
		if (entity_before(se, entry)) {
523 524 525 526 527 528 529 530 531 532 533
			link = &parent->rb_left;
		} else {
			link = &parent->rb_right;
			leftmost = 0;
		}
	}

	/*
	 * Maintain a cache of leftmost tree entries (it is frequently
	 * used):
	 */
534
	if (leftmost)
I
Ingo Molnar 已提交
535
		cfs_rq->rb_leftmost = &se->run_node;
536 537 538 539 540

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

541
static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
542
{
P
Peter Zijlstra 已提交
543 544 545 546 547 548
	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
549

550 551 552
	rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
}

553
struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
554
{
555 556 557 558 559 560
	struct rb_node *left = cfs_rq->rb_leftmost;

	if (!left)
		return NULL;

	return rb_entry(left, struct sched_entity, run_node);
561 562
}

563 564 565 566 567 568 569 570 571 572 573
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
574
struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
575
{
576
	struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
577

578 579
	if (!last)
		return NULL;
580 581

	return rb_entry(last, struct sched_entity, run_node);
582 583
}

584 585 586 587
/**************************************************************
 * Scheduling class statistics methods:
 */

588
int sched_proc_update_handler(struct ctl_table *table, int write,
589
		void __user *buffer, size_t *lenp,
590 591
		loff_t *ppos)
{
592
	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
593
	int factor = get_update_sysctl_factor();
594 595 596 597 598 599 600

	if (ret || !write)
		return ret;

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

601 602 603 604 605 606 607
#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

608 609 610
	return 0;
}
#endif
611

612
/*
613
 * delta /= w
614 615 616 617
 */
static inline unsigned long
calc_delta_fair(unsigned long delta, struct sched_entity *se)
{
618 619
	if (unlikely(se->load.weight != NICE_0_LOAD))
		delta = calc_delta_mine(delta, NICE_0_LOAD, &se->load);
620 621 622 623

	return delta;
}

624 625 626
/*
 * The idea is to set a period in which each task runs once.
 *
627
 * When there are too many tasks (sched_nr_latency) we have to stretch
628 629 630 631
 * this period because otherwise the slices get too small.
 *
 * p = (nr <= nl) ? l : l*nr/nl
 */
632 633 634
static u64 __sched_period(unsigned long nr_running)
{
	u64 period = sysctl_sched_latency;
635
	unsigned long nr_latency = sched_nr_latency;
636 637

	if (unlikely(nr_running > nr_latency)) {
638
		period = sysctl_sched_min_granularity;
639 640 641 642 643 644
		period *= nr_running;
	}

	return period;
}

645 646 647 648
/*
 * We calculate the wall-time slice from the period by taking a part
 * proportional to the weight.
 *
649
 * s = p*P[w/rw]
650
 */
P
Peter Zijlstra 已提交
651
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
652
{
M
Mike Galbraith 已提交
653
	u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
654

M
Mike Galbraith 已提交
655
	for_each_sched_entity(se) {
L
Lin Ming 已提交
656
		struct load_weight *load;
657
		struct load_weight lw;
L
Lin Ming 已提交
658 659 660

		cfs_rq = cfs_rq_of(se);
		load = &cfs_rq->load;
661

M
Mike Galbraith 已提交
662
		if (unlikely(!se->on_rq)) {
663
			lw = cfs_rq->load;
M
Mike Galbraith 已提交
664 665 666 667 668 669 670

			update_load_add(&lw, se->load.weight);
			load = &lw;
		}
		slice = calc_delta_mine(slice, se->load.weight, load);
	}
	return slice;
671 672
}

673
/*
A
Andrei Epure 已提交
674
 * We calculate the vruntime slice of a to-be-inserted task.
675
 *
676
 * vs = s/w
677
 */
678
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
P
Peter Zijlstra 已提交
679
{
680
	return calc_delta_fair(sched_slice(cfs_rq, se), se);
681 682
}

683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702
#ifdef CONFIG_SMP
static inline void __update_task_entity_contrib(struct sched_entity *se);

/* Give new task start runnable values to heavy its load in infant time */
void init_task_runnable_average(struct task_struct *p)
{
	u32 slice;

	p->se.avg.decay_count = 0;
	slice = sched_slice(task_cfs_rq(p), &p->se) >> 10;
	p->se.avg.runnable_avg_sum = slice;
	p->se.avg.runnable_avg_period = slice;
	__update_task_entity_contrib(&p->se);
}
#else
void init_task_runnable_average(struct task_struct *p)
{
}
#endif

703 704 705 706 707
/*
 * 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
708 709
__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
	      unsigned long delta_exec)
710
{
711
	unsigned long delta_exec_weighted;
712

713 714
	schedstat_set(curr->statistics.exec_max,
		      max((u64)delta_exec, curr->statistics.exec_max));
715 716

	curr->sum_exec_runtime += delta_exec;
717
	schedstat_add(cfs_rq, exec_clock, delta_exec);
718
	delta_exec_weighted = calc_delta_fair(delta_exec, curr);
719

I
Ingo Molnar 已提交
720
	curr->vruntime += delta_exec_weighted;
721
	update_min_vruntime(cfs_rq);
722 723
}

724
static void update_curr(struct cfs_rq *cfs_rq)
725
{
726
	struct sched_entity *curr = cfs_rq->curr;
727
	u64 now = rq_clock_task(rq_of(cfs_rq));
728 729 730 731 732 733 734 735 736 737
	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
738
	delta_exec = (unsigned long)(now - curr->exec_start);
P
Peter Zijlstra 已提交
739 740
	if (!delta_exec)
		return;
741

I
Ingo Molnar 已提交
742 743
	__update_curr(cfs_rq, curr, delta_exec);
	curr->exec_start = now;
744 745 746 747

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

748
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
749
		cpuacct_charge(curtask, delta_exec);
750
		account_group_exec_runtime(curtask, delta_exec);
751
	}
752 753

	account_cfs_rq_runtime(cfs_rq, delta_exec);
754 755 756
}

static inline void
757
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
758
{
759
	schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
760 761 762 763 764
}

/*
 * Task is being enqueued - update stats:
 */
765
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
766 767 768 769 770
{
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
771
	if (se != cfs_rq->curr)
772
		update_stats_wait_start(cfs_rq, se);
773 774 775
}

static void
776
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
777
{
778
	schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
779
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
780 781
	schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
	schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
782
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
783 784 785
#ifdef CONFIG_SCHEDSTATS
	if (entity_is_task(se)) {
		trace_sched_stat_wait(task_of(se),
786
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
787 788
	}
#endif
789
	schedstat_set(se->statistics.wait_start, 0);
790 791 792
}

static inline void
793
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
794 795 796 797 798
{
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
799
	if (se != cfs_rq->curr)
800
		update_stats_wait_end(cfs_rq, se);
801 802 803 804 805 806
}

/*
 * We are picking a new current task - update its stats:
 */
static inline void
807
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
808 809 810 811
{
	/*
	 * We are starting a new run period:
	 */
812
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
813 814 815 816 817 818
}

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

819 820
#ifdef CONFIG_NUMA_BALANCING
/*
821 822 823
 * Approximate time to scan a full NUMA task in ms. The task scan period is
 * calculated based on the tasks virtual memory size and
 * numa_balancing_scan_size.
824
 */
825 826 827
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
unsigned int sysctl_numa_balancing_scan_period_reset = 60000;
828 829 830

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
831

832 833 834
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879
static unsigned int task_nr_scan_windows(struct task_struct *p)
{
	unsigned long rss = 0;
	unsigned long nr_scan_pages;

	/*
	 * Calculations based on RSS as non-present and empty pages are skipped
	 * by the PTE scanner and NUMA hinting faults should be trapped based
	 * on resident pages
	 */
	nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
	rss = get_mm_rss(p->mm);
	if (!rss)
		rss = nr_scan_pages;

	rss = round_up(rss, nr_scan_pages);
	return rss / nr_scan_pages;
}

/* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
#define MAX_SCAN_WINDOW 2560

static unsigned int task_scan_min(struct task_struct *p)
{
	unsigned int scan, floor;
	unsigned int windows = 1;

	if (sysctl_numa_balancing_scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / sysctl_numa_balancing_scan_size;
	floor = 1000 / windows;

	scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
	return max_t(unsigned int, floor, scan);
}

static unsigned int task_scan_max(struct task_struct *p)
{
	unsigned int smin = task_scan_min(p);
	unsigned int smax;

	/* Watch for min being lower than max due to floor calculations */
	smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
	return max(smin, smax);
}

880 881 882 883 884 885 886
/*
 * Once a preferred node is selected the scheduler balancer will prefer moving
 * a task to that node for sysctl_numa_balancing_settle_count number of PTE
 * scans. This will give the process the chance to accumulate more faults on
 * the preferred node but still allow the scheduler to move the task again if
 * the nodes CPUs are overloaded.
 */
887
unsigned int sysctl_numa_balancing_settle_count __read_mostly = 4;
888

889 890 891 892 893 894 895 896 897 898 899 900 901 902
static inline int task_faults_idx(int nid, int priv)
{
	return 2 * nid + priv;
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
	if (!p->numa_faults)
		return 0;

	return p->numa_faults[task_faults_idx(nid, 0)] +
		p->numa_faults[task_faults_idx(nid, 1)];
}

903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927
static unsigned long weighted_cpuload(const int cpu);


static int
find_idlest_cpu_node(int this_cpu, int nid)
{
	unsigned long load, min_load = ULONG_MAX;
	int i, idlest_cpu = this_cpu;

	BUG_ON(cpu_to_node(this_cpu) == nid);

	rcu_read_lock();
	for_each_cpu(i, cpumask_of_node(nid)) {
		load = weighted_cpuload(i);

		if (load < min_load) {
			min_load = load;
			idlest_cpu = i;
		}
	}
	rcu_read_unlock();

	return idlest_cpu;
}

928 929
static void task_numa_placement(struct task_struct *p)
{
930 931
	int seq, nid, max_nid = -1;
	unsigned long max_faults = 0;
932

933
	seq = ACCESS_ONCE(p->mm->numa_scan_seq);
934 935 936
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
937
	p->numa_migrate_seq++;
938
	p->numa_scan_period_max = task_scan_max(p);
939

940 941
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
942
		unsigned long faults;
943
		int priv, i;
944

945 946
		for (priv = 0; priv < 2; priv++) {
			i = task_faults_idx(nid, priv);
947

948 949 950 951 952 953 954 955
			/* Decay existing window, copy faults since last scan */
			p->numa_faults[i] >>= 1;
			p->numa_faults[i] += p->numa_faults_buffer[i];
			p->numa_faults_buffer[i] = 0;
		}

		/* Find maximum private faults */
		faults = p->numa_faults[task_faults_idx(nid, 1)];
956 957 958 959 960 961
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
	}

962 963 964 965 966 967
	/*
	 * Record the preferred node as the node with the most faults,
	 * requeue the task to be running on the idlest CPU on the
	 * preferred node and reset the scanning rate to recheck
	 * the working set placement.
	 */
968
	if (max_faults && max_nid != p->numa_preferred_nid) {
969 970 971 972 973 974 975 976 977 978 979 980 981
		int preferred_cpu;

		/*
		 * If the task is not on the preferred node then find the most
		 * idle CPU to migrate to.
		 */
		preferred_cpu = task_cpu(p);
		if (cpu_to_node(preferred_cpu) != max_nid) {
			preferred_cpu = find_idlest_cpu_node(preferred_cpu,
							     max_nid);
		}

		/* Update the preferred nid and migrate task if possible */
982
		p->numa_preferred_nid = max_nid;
983
		p->numa_migrate_seq = 1;
984
		migrate_task_to(p, preferred_cpu);
985
	}
986 987 988 989 990
}

/*
 * Got a PROT_NONE fault for a page on @node.
 */
991
void task_numa_fault(int last_nidpid, int node, int pages, bool migrated)
992 993
{
	struct task_struct *p = current;
994
	int priv;
995

996
	if (!numabalancing_enabled)
997 998
		return;

999 1000 1001 1002
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

1003 1004 1005 1006 1007 1008 1009 1010
	/*
	 * First accesses are treated as private, otherwise consider accesses
	 * to be private if the accessing pid has not changed
	 */
	if (!nidpid_pid_unset(last_nidpid))
		priv = ((p->pid & LAST__PID_MASK) == nidpid_to_pid(last_nidpid));
	else
		priv = 1;
1011

1012 1013
	/* Allocate buffer to track faults on a per-node basis */
	if (unlikely(!p->numa_faults)) {
1014
		int size = sizeof(*p->numa_faults) * 2 * nr_node_ids;
1015

1016 1017
		/* numa_faults and numa_faults_buffer share the allocation */
		p->numa_faults = kzalloc(size * 2, GFP_KERNEL|__GFP_NOWARN);
1018 1019
		if (!p->numa_faults)
			return;
1020 1021

		BUG_ON(p->numa_faults_buffer);
1022
		p->numa_faults_buffer = p->numa_faults + (2 * nr_node_ids);
1023
	}
1024

1025
	/*
1026 1027
	 * If pages are properly placed (did not migrate) then scan slower.
	 * This is reset periodically in case of phase changes
1028
	 */
1029 1030 1031 1032 1033 1034 1035 1036
	if (!migrated) {
		/* Initialise if necessary */
		if (!p->numa_scan_period_max)
			p->numa_scan_period_max = task_scan_max(p);

		p->numa_scan_period = min(p->numa_scan_period_max,
			p->numa_scan_period + 10);
	}
1037

1038
	task_numa_placement(p);
1039

1040
	p->numa_faults_buffer[task_faults_idx(node, priv)] += pages;
1041 1042
}

1043 1044 1045 1046 1047 1048
static void reset_ptenuma_scan(struct task_struct *p)
{
	ACCESS_ONCE(p->mm->numa_scan_seq)++;
	p->mm->numa_scan_offset = 0;
}

1049 1050 1051 1052 1053 1054 1055 1056 1057
/*
 * The expensive part of numa migration is done from task_work context.
 * Triggered from task_tick_numa().
 */
void task_numa_work(struct callback_head *work)
{
	unsigned long migrate, next_scan, now = jiffies;
	struct task_struct *p = current;
	struct mm_struct *mm = p->mm;
1058
	struct vm_area_struct *vma;
1059
	unsigned long start, end;
1060
	unsigned long nr_pte_updates = 0;
1061
	long pages;
1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076

	WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));

	work->next = work; /* protect against double add */
	/*
	 * Who cares about NUMA placement when they're dying.
	 *
	 * NOTE: make sure not to dereference p->mm before this check,
	 * exit_task_work() happens _after_ exit_mm() so we could be called
	 * without p->mm even though we still had it when we enqueued this
	 * work.
	 */
	if (p->flags & PF_EXITING)
		return;

1077 1078 1079 1080 1081 1082 1083
	if (!mm->numa_next_reset || !mm->numa_next_scan) {
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
		mm->numa_next_reset = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_period_reset);
	}

1084 1085 1086 1087 1088 1089 1090 1091
	/*
	 * Reset the scan period if enough time has gone by. Objective is that
	 * scanning will be reduced if pages are properly placed. As tasks
	 * can enter different phases this needs to be re-examined. Lacking
	 * proper tracking of reference behaviour, this blunt hammer is used.
	 */
	migrate = mm->numa_next_reset;
	if (time_after(now, migrate)) {
1092
		p->numa_scan_period = task_scan_min(p);
1093 1094 1095 1096
		next_scan = now + msecs_to_jiffies(sysctl_numa_balancing_scan_period_reset);
		xchg(&mm->numa_next_reset, next_scan);
	}

1097 1098 1099 1100 1101 1102 1103
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

1104 1105 1106 1107
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
		p->numa_scan_period = task_scan_min(p);
	}
1108

1109
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
1110 1111 1112
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

1113 1114 1115 1116 1117 1118
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

1119 1120 1121 1122 1123
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
	if (!pages)
		return;
1124

1125
	down_read(&mm->mmap_sem);
1126
	vma = find_vma(mm, start);
1127 1128
	if (!vma) {
		reset_ptenuma_scan(p);
1129
		start = 0;
1130 1131
		vma = mm->mmap;
	}
1132
	for (; vma; vma = vma->vm_next) {
1133
		if (!vma_migratable(vma) || !vma_policy_mof(p, vma))
1134 1135
			continue;

1136 1137 1138 1139
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
1140 1141 1142 1143 1144 1145 1146 1147 1148
			nr_pte_updates += change_prot_numa(vma, start, end);

			/*
			 * Scan sysctl_numa_balancing_scan_size but ensure that
			 * at least one PTE is updated so that unused virtual
			 * address space is quickly skipped.
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
1149

1150 1151 1152 1153
			start = end;
			if (pages <= 0)
				goto out;
		} while (end != vma->vm_end);
1154
	}
1155

1156
out:
1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168
	/*
	 * If the whole process was scanned without updates then no NUMA
	 * hinting faults are being recorded and scan rate should be lower.
	 */
	if (mm->numa_scan_offset == 0 && !nr_pte_updates) {
		p->numa_scan_period = min(p->numa_scan_period_max,
			p->numa_scan_period << 1);

		next_scan = now + msecs_to_jiffies(p->numa_scan_period);
		mm->numa_next_scan = next_scan;
	}

1169
	/*
P
Peter Zijlstra 已提交
1170 1171 1172 1173
	 * It is possible to reach the end of the VMA list but the last few
	 * VMAs are not guaranteed to the vma_migratable. If they are not, we
	 * would find the !migratable VMA on the next scan but not reset the
	 * scanner to the start so check it now.
1174 1175
	 */
	if (vma)
1176
		mm->numa_scan_offset = start;
1177 1178 1179
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205
}

/*
 * Drive the periodic memory faults..
 */
void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
	struct callback_head *work = &curr->numa_work;
	u64 period, now;

	/*
	 * We don't care about NUMA placement if we don't have memory.
	 */
	if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
		return;

	/*
	 * Using runtime rather than walltime has the dual advantage that
	 * we (mostly) drive the selection from busy threads and that the
	 * task needs to have done some actual work before we bother with
	 * NUMA placement.
	 */
	now = curr->se.sum_exec_runtime;
	period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;

	if (now - curr->node_stamp > period) {
1206
		if (!curr->node_stamp)
1207
			curr->numa_scan_period = task_scan_min(curr);
1208
		curr->node_stamp += period;
1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221

		if (!time_before(jiffies, curr->mm->numa_next_scan)) {
			init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
			task_work_add(curr, work, true);
		}
	}
}
#else
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
}
#endif /* CONFIG_NUMA_BALANCING */

1222 1223 1224 1225
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
1226
	if (!parent_entity(se))
1227
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
1228 1229
#ifdef CONFIG_SMP
	if (entity_is_task(se))
1230
		list_add(&se->group_node, &rq_of(cfs_rq)->cfs_tasks);
1231
#endif
1232 1233 1234 1235 1236 1237 1238
	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);
1239
	if (!parent_entity(se))
1240
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
1241
	if (entity_is_task(se))
1242
		list_del_init(&se->group_node);
1243 1244 1245
	cfs_rq->nr_running--;
}

1246 1247
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
1248 1249 1250 1251 1252 1253 1254 1255 1256
static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
{
	long tg_weight;

	/*
	 * Use this CPU's actual weight instead of the last load_contribution
	 * to gain a more accurate current total weight. See
	 * update_cfs_rq_load_contribution().
	 */
1257
	tg_weight = atomic_long_read(&tg->load_avg);
1258
	tg_weight -= cfs_rq->tg_load_contrib;
1259 1260 1261 1262 1263
	tg_weight += cfs_rq->load.weight;

	return tg_weight;
}

1264
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1265
{
1266
	long tg_weight, load, shares;
1267

1268
	tg_weight = calc_tg_weight(tg, cfs_rq);
1269
	load = cfs_rq->load.weight;
1270 1271

	shares = (tg->shares * load);
1272 1273
	if (tg_weight)
		shares /= tg_weight;
1274 1275 1276 1277 1278 1279 1280 1281 1282

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

	return shares;
}
# else /* CONFIG_SMP */
1283
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1284 1285 1286 1287
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
P
Peter Zijlstra 已提交
1288 1289 1290
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
1291 1292 1293 1294
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
1295
		account_entity_dequeue(cfs_rq, se);
1296
	}
P
Peter Zijlstra 已提交
1297 1298 1299 1300 1301 1302 1303

	update_load_set(&se->load, weight);

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

1304 1305
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

1306
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
1307 1308 1309
{
	struct task_group *tg;
	struct sched_entity *se;
1310
	long shares;
P
Peter Zijlstra 已提交
1311 1312 1313

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
1314
	if (!se || throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
1315
		return;
1316 1317 1318 1319
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
1320
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
1321 1322 1323 1324

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
1325
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
1326 1327 1328 1329
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

1330
#ifdef CONFIG_SMP
1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358
/*
 * We choose a half-life close to 1 scheduling period.
 * Note: The tables below are dependent on this value.
 */
#define LOAD_AVG_PERIOD 32
#define LOAD_AVG_MAX 47742 /* maximum possible load avg */
#define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */

/* Precomputed fixed inverse multiplies for multiplication by y^n */
static const u32 runnable_avg_yN_inv[] = {
	0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
	0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
	0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
	0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
	0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
	0x85aac367, 0x82cd8698,
};

/*
 * Precomputed \Sum y^k { 1<=k<=n }.  These are floor(true_value) to prevent
 * over-estimates when re-combining.
 */
static const u32 runnable_avg_yN_sum[] = {
	    0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
	 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
	17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
};

1359 1360 1361 1362 1363 1364
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384
	unsigned int local_n;

	if (!n)
		return val;
	else if (unlikely(n > LOAD_AVG_PERIOD * 63))
		return 0;

	/* after bounds checking we can collapse to 32-bit */
	local_n = n;

	/*
	 * As y^PERIOD = 1/2, we can combine
	 *    y^n = 1/2^(n/PERIOD) * k^(n%PERIOD)
	 * With a look-up table which covers k^n (n<PERIOD)
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
1385 1386
	}

1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417
	val *= runnable_avg_yN_inv[local_n];
	/* We don't use SRR here since we always want to round down. */
	return val >> 32;
}

/*
 * For updates fully spanning n periods, the contribution to runnable
 * average will be: \Sum 1024*y^n
 *
 * We can compute this reasonably efficiently by combining:
 *   y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for  n <PERIOD}
 */
static u32 __compute_runnable_contrib(u64 n)
{
	u32 contrib = 0;

	if (likely(n <= LOAD_AVG_PERIOD))
		return runnable_avg_yN_sum[n];
	else if (unlikely(n >= LOAD_AVG_MAX_N))
		return LOAD_AVG_MAX;

	/* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
	do {
		contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
		contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];

		n -= LOAD_AVG_PERIOD;
	} while (n > LOAD_AVG_PERIOD);

	contrib = decay_load(contrib, n);
	return contrib + runnable_avg_yN_sum[n];
1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451
}

/*
 * We can represent the historical contribution to runnable average as the
 * coefficients of a geometric series.  To do this we sub-divide our runnable
 * history into segments of approximately 1ms (1024us); label the segment that
 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
 *
 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
 *      p0            p1           p2
 *     (now)       (~1ms ago)  (~2ms ago)
 *
 * Let u_i denote the fraction of p_i that the entity was runnable.
 *
 * We then designate the fractions u_i as our co-efficients, yielding the
 * following representation of historical load:
 *   u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
 *
 * We choose y based on the with of a reasonably scheduling period, fixing:
 *   y^32 = 0.5
 *
 * This means that the contribution to load ~32ms ago (u_32) will be weighted
 * approximately half as much as the contribution to load within the last ms
 * (u_0).
 *
 * When a period "rolls over" and we have new u_0`, multiplying the previous
 * sum again by y is sufficient to update:
 *   load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
 *            = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
 */
static __always_inline int __update_entity_runnable_avg(u64 now,
							struct sched_avg *sa,
							int runnable)
{
1452 1453
	u64 delta, periods;
	u32 runnable_contrib;
1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486
	int delta_w, decayed = 0;

	delta = now - sa->last_runnable_update;
	/*
	 * This should only happen when time goes backwards, which it
	 * unfortunately does during sched clock init when we swap over to TSC.
	 */
	if ((s64)delta < 0) {
		sa->last_runnable_update = now;
		return 0;
	}

	/*
	 * Use 1024ns as the unit of measurement since it's a reasonable
	 * approximation of 1us and fast to compute.
	 */
	delta >>= 10;
	if (!delta)
		return 0;
	sa->last_runnable_update = now;

	/* delta_w is the amount already accumulated against our next period */
	delta_w = sa->runnable_avg_period % 1024;
	if (delta + delta_w >= 1024) {
		/* period roll-over */
		decayed = 1;

		/*
		 * Now that we know we're crossing a period boundary, figure
		 * out how much from delta we need to complete the current
		 * period and accrue it.
		 */
		delta_w = 1024 - delta_w;
1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506
		if (runnable)
			sa->runnable_avg_sum += delta_w;
		sa->runnable_avg_period += delta_w;

		delta -= delta_w;

		/* Figure out how many additional periods this update spans */
		periods = delta / 1024;
		delta %= 1024;

		sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum,
						  periods + 1);
		sa->runnable_avg_period = decay_load(sa->runnable_avg_period,
						     periods + 1);

		/* Efficiently calculate \sum (1..n_period) 1024*y^i */
		runnable_contrib = __compute_runnable_contrib(periods);
		if (runnable)
			sa->runnable_avg_sum += runnable_contrib;
		sa->runnable_avg_period += runnable_contrib;
1507 1508 1509 1510 1511 1512 1513 1514 1515 1516
	}

	/* Remainder of delta accrued against u_0` */
	if (runnable)
		sa->runnable_avg_sum += delta;
	sa->runnable_avg_period += delta;

	return decayed;
}

1517
/* Synchronize an entity's decay with its parenting cfs_rq.*/
1518
static inline u64 __synchronize_entity_decay(struct sched_entity *se)
1519 1520 1521 1522 1523 1524
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 decays = atomic64_read(&cfs_rq->decay_counter);

	decays -= se->avg.decay_count;
	if (!decays)
1525
		return 0;
1526 1527 1528

	se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
	se->avg.decay_count = 0;
1529 1530

	return decays;
1531 1532
}

1533 1534 1535 1536 1537
#ifdef CONFIG_FAIR_GROUP_SCHED
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
						 int force_update)
{
	struct task_group *tg = cfs_rq->tg;
1538
	long tg_contrib;
1539 1540 1541 1542

	tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg;
	tg_contrib -= cfs_rq->tg_load_contrib;

1543 1544
	if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) {
		atomic_long_add(tg_contrib, &tg->load_avg);
1545 1546 1547
		cfs_rq->tg_load_contrib += tg_contrib;
	}
}
1548

1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569
/*
 * Aggregate cfs_rq runnable averages into an equivalent task_group
 * representation for computing load contributions.
 */
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
						  struct cfs_rq *cfs_rq)
{
	struct task_group *tg = cfs_rq->tg;
	long contrib;

	/* The fraction of a cpu used by this cfs_rq */
	contrib = div_u64(sa->runnable_avg_sum << NICE_0_SHIFT,
			  sa->runnable_avg_period + 1);
	contrib -= cfs_rq->tg_runnable_contrib;

	if (abs(contrib) > cfs_rq->tg_runnable_contrib / 64) {
		atomic_add(contrib, &tg->runnable_avg);
		cfs_rq->tg_runnable_contrib += contrib;
	}
}

1570 1571 1572 1573
static inline void __update_group_entity_contrib(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = group_cfs_rq(se);
	struct task_group *tg = cfs_rq->tg;
1574 1575
	int runnable_avg;

1576 1577 1578
	u64 contrib;

	contrib = cfs_rq->tg_load_contrib * tg->shares;
1579 1580
	se->avg.load_avg_contrib = div_u64(contrib,
				     atomic_long_read(&tg->load_avg) + 1);
1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609

	/*
	 * For group entities we need to compute a correction term in the case
	 * that they are consuming <1 cpu so that we would contribute the same
	 * load as a task of equal weight.
	 *
	 * Explicitly co-ordinating this measurement would be expensive, but
	 * fortunately the sum of each cpus contribution forms a usable
	 * lower-bound on the true value.
	 *
	 * Consider the aggregate of 2 contributions.  Either they are disjoint
	 * (and the sum represents true value) or they are disjoint and we are
	 * understating by the aggregate of their overlap.
	 *
	 * Extending this to N cpus, for a given overlap, the maximum amount we
	 * understand is then n_i(n_i+1)/2 * w_i where n_i is the number of
	 * cpus that overlap for this interval and w_i is the interval width.
	 *
	 * On a small machine; the first term is well-bounded which bounds the
	 * total error since w_i is a subset of the period.  Whereas on a
	 * larger machine, while this first term can be larger, if w_i is the
	 * of consequential size guaranteed to see n_i*w_i quickly converge to
	 * our upper bound of 1-cpu.
	 */
	runnable_avg = atomic_read(&tg->runnable_avg);
	if (runnable_avg < NICE_0_LOAD) {
		se->avg.load_avg_contrib *= runnable_avg;
		se->avg.load_avg_contrib >>= NICE_0_SHIFT;
	}
1610
}
1611 1612 1613
#else
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
						 int force_update) {}
1614 1615
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
						  struct cfs_rq *cfs_rq) {}
1616
static inline void __update_group_entity_contrib(struct sched_entity *se) {}
1617 1618
#endif

1619 1620 1621 1622 1623 1624 1625 1626 1627 1628
static inline void __update_task_entity_contrib(struct sched_entity *se)
{
	u32 contrib;

	/* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
	contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight);
	contrib /= (se->avg.runnable_avg_period + 1);
	se->avg.load_avg_contrib = scale_load(contrib);
}

1629 1630 1631 1632 1633
/* Compute the current contribution to load_avg by se, return any delta */
static long __update_entity_load_avg_contrib(struct sched_entity *se)
{
	long old_contrib = se->avg.load_avg_contrib;

1634 1635 1636
	if (entity_is_task(se)) {
		__update_task_entity_contrib(se);
	} else {
1637
		__update_tg_runnable_avg(&se->avg, group_cfs_rq(se));
1638 1639
		__update_group_entity_contrib(se);
	}
1640 1641 1642 1643

	return se->avg.load_avg_contrib - old_contrib;
}

1644 1645 1646 1647 1648 1649 1650 1651 1652
static inline void subtract_blocked_load_contrib(struct cfs_rq *cfs_rq,
						 long load_contrib)
{
	if (likely(load_contrib < cfs_rq->blocked_load_avg))
		cfs_rq->blocked_load_avg -= load_contrib;
	else
		cfs_rq->blocked_load_avg = 0;
}

1653 1654
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);

1655
/* Update a sched_entity's runnable average */
1656 1657
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq)
1658
{
1659 1660
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	long contrib_delta;
1661
	u64 now;
1662

1663 1664 1665 1666 1667 1668 1669 1670 1671 1672
	/*
	 * For a group entity we need to use their owned cfs_rq_clock_task() in
	 * case they are the parent of a throttled hierarchy.
	 */
	if (entity_is_task(se))
		now = cfs_rq_clock_task(cfs_rq);
	else
		now = cfs_rq_clock_task(group_cfs_rq(se));

	if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq))
1673 1674 1675
		return;

	contrib_delta = __update_entity_load_avg_contrib(se);
1676 1677 1678 1679

	if (!update_cfs_rq)
		return;

1680 1681
	if (se->on_rq)
		cfs_rq->runnable_load_avg += contrib_delta;
1682 1683 1684 1685 1686 1687 1688 1689
	else
		subtract_blocked_load_contrib(cfs_rq, -contrib_delta);
}

/*
 * Decay the load contributed by all blocked children and account this so that
 * their contribution may appropriately discounted when they wake up.
 */
1690
static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
1691
{
1692
	u64 now = cfs_rq_clock_task(cfs_rq) >> 20;
1693 1694 1695
	u64 decays;

	decays = now - cfs_rq->last_decay;
1696
	if (!decays && !force_update)
1697 1698
		return;

1699 1700 1701
	if (atomic_long_read(&cfs_rq->removed_load)) {
		unsigned long removed_load;
		removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0);
1702 1703
		subtract_blocked_load_contrib(cfs_rq, removed_load);
	}
1704

1705 1706 1707 1708 1709 1710
	if (decays) {
		cfs_rq->blocked_load_avg = decay_load(cfs_rq->blocked_load_avg,
						      decays);
		atomic64_add(decays, &cfs_rq->decay_counter);
		cfs_rq->last_decay = now;
	}
1711 1712

	__update_cfs_rq_tg_load_contrib(cfs_rq, force_update);
1713
}
1714 1715 1716

static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
{
1717
	__update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable);
1718
	__update_tg_runnable_avg(&rq->avg, &rq->cfs);
1719
}
1720 1721 1722

/* Add the load generated by se into cfs_rq's child load-average */
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
1723 1724
						  struct sched_entity *se,
						  int wakeup)
1725
{
1726 1727 1728 1729
	/*
	 * We track migrations using entity decay_count <= 0, on a wake-up
	 * migration we use a negative decay count to track the remote decays
	 * accumulated while sleeping.
1730 1731 1732 1733
	 *
	 * Newly forked tasks are enqueued with se->avg.decay_count == 0, they
	 * are seen by enqueue_entity_load_avg() as a migration with an already
	 * constructed load_avg_contrib.
1734 1735
	 */
	if (unlikely(se->avg.decay_count <= 0)) {
1736
		se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq));
1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751
		if (se->avg.decay_count) {
			/*
			 * In a wake-up migration we have to approximate the
			 * time sleeping.  This is because we can't synchronize
			 * clock_task between the two cpus, and it is not
			 * guaranteed to be read-safe.  Instead, we can
			 * approximate this using our carried decays, which are
			 * explicitly atomically readable.
			 */
			se->avg.last_runnable_update -= (-se->avg.decay_count)
							<< 20;
			update_entity_load_avg(se, 0);
			/* Indicate that we're now synchronized and on-rq */
			se->avg.decay_count = 0;
		}
1752 1753
		wakeup = 0;
	} else {
1754 1755 1756 1757 1758 1759 1760
		/*
		 * Task re-woke on same cpu (or else migrate_task_rq_fair()
		 * would have made count negative); we must be careful to avoid
		 * double-accounting blocked time after synchronizing decays.
		 */
		se->avg.last_runnable_update += __synchronize_entity_decay(se)
							<< 20;
1761 1762
	}

1763 1764
	/* migrated tasks did not contribute to our blocked load */
	if (wakeup) {
1765
		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
1766 1767
		update_entity_load_avg(se, 0);
	}
1768

1769
	cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
1770 1771
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !wakeup);
1772 1773
}

1774 1775 1776 1777 1778
/*
 * Remove se's load from this cfs_rq child load-average, if the entity is
 * transitioning to a blocked state we track its projected decay using
 * blocked_load_avg.
 */
1779
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
1780 1781
						  struct sched_entity *se,
						  int sleep)
1782
{
1783
	update_entity_load_avg(se, 1);
1784 1785
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !sleep);
1786

1787
	cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
1788 1789 1790 1791
	if (sleep) {
		cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
		se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
	} /* migrations, e.g. sleep=0 leave decay_count == 0 */
1792
}
1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813

/*
 * Update the rq's load with the elapsed running time before entering
 * idle. if the last scheduled task is not a CFS task, idle_enter will
 * be the only way to update the runnable statistic.
 */
void idle_enter_fair(struct rq *this_rq)
{
	update_rq_runnable_avg(this_rq, 1);
}

/*
 * Update the rq's load with the elapsed idle time before a task is
 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
 * be the only way to update the runnable statistic.
 */
void idle_exit_fair(struct rq *this_rq)
{
	update_rq_runnable_avg(this_rq, 0);
}

1814
#else
1815 1816
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq) {}
1817
static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
1818
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
1819 1820
					   struct sched_entity *se,
					   int wakeup) {}
1821
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
1822 1823
					   struct sched_entity *se,
					   int sleep) {}
1824 1825
static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
					      int force_update) {}
1826 1827
#endif

1828
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
1829 1830
{
#ifdef CONFIG_SCHEDSTATS
1831 1832 1833 1834 1835
	struct task_struct *tsk = NULL;

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

1836
	if (se->statistics.sleep_start) {
1837
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
1838 1839 1840 1841

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

1842 1843
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
1844

1845
		se->statistics.sleep_start = 0;
1846
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
1847

1848
		if (tsk) {
1849
			account_scheduler_latency(tsk, delta >> 10, 1);
1850 1851
			trace_sched_stat_sleep(tsk, delta);
		}
1852
	}
1853
	if (se->statistics.block_start) {
1854
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
1855 1856 1857 1858

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

1859 1860
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
1861

1862
		se->statistics.block_start = 0;
1863
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
1864

1865
		if (tsk) {
1866
			if (tsk->in_iowait) {
1867 1868
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
1869
				trace_sched_stat_iowait(tsk, delta);
1870 1871
			}

1872 1873
			trace_sched_stat_blocked(tsk, delta);

1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884
			/*
			 * 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
1885
		}
1886 1887 1888 1889
	}
#endif
}

P
Peter Zijlstra 已提交
1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902
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
}

1903 1904 1905
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
1906
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
1907

1908 1909 1910 1911 1912 1913
	/*
	 * 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
1914
	if (initial && sched_feat(START_DEBIT))
1915
		vruntime += sched_vslice(cfs_rq, se);
1916

1917
	/* sleeps up to a single latency don't count. */
1918
	if (!initial) {
1919
		unsigned long thresh = sysctl_sched_latency;
1920

1921 1922 1923 1924 1925 1926
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
1927

1928
		vruntime -= thresh;
1929 1930
	}

1931
	/* ensure we never gain time by being placed backwards. */
1932
	se->vruntime = max_vruntime(se->vruntime, vruntime);
1933 1934
}

1935 1936
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

1937
static void
1938
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1939
{
1940 1941
	/*
	 * Update the normalized vruntime before updating min_vruntime
1942
	 * through calling update_curr().
1943
	 */
1944
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
1945 1946
		se->vruntime += cfs_rq->min_vruntime;

1947
	/*
1948
	 * Update run-time statistics of the 'current'.
1949
	 */
1950
	update_curr(cfs_rq);
1951
	enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
1952 1953
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
1954

1955
	if (flags & ENQUEUE_WAKEUP) {
1956
		place_entity(cfs_rq, se, 0);
1957
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
1958
	}
1959

1960
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
1961
	check_spread(cfs_rq, se);
1962 1963
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
1964
	se->on_rq = 1;
1965

1966
	if (cfs_rq->nr_running == 1) {
1967
		list_add_leaf_cfs_rq(cfs_rq);
1968 1969
		check_enqueue_throttle(cfs_rq);
	}
1970 1971
}

1972
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
1973
{
1974 1975 1976 1977 1978 1979 1980 1981
	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
1982

1983 1984 1985 1986 1987 1988 1989 1990 1991
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
1992 1993
}

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
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
2005 2006
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2007 2008 2009 2010 2011
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
2012 2013 2014

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
2015 2016
}

2017
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
2018

2019
static void
2020
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2021
{
2022 2023 2024 2025
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
2026
	dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);
2027

2028
	update_stats_dequeue(cfs_rq, se);
2029
	if (flags & DEQUEUE_SLEEP) {
P
Peter Zijlstra 已提交
2030
#ifdef CONFIG_SCHEDSTATS
2031 2032 2033 2034
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
2035
				se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
2036
			if (tsk->state & TASK_UNINTERRUPTIBLE)
2037
				se->statistics.block_start = rq_clock(rq_of(cfs_rq));
2038
		}
2039
#endif
P
Peter Zijlstra 已提交
2040 2041
	}

P
Peter Zijlstra 已提交
2042
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
2043

2044
	if (se != cfs_rq->curr)
2045
		__dequeue_entity(cfs_rq, se);
2046
	se->on_rq = 0;
2047
	account_entity_dequeue(cfs_rq, se);
2048 2049 2050 2051 2052 2053

	/*
	 * 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.
	 */
2054
	if (!(flags & DEQUEUE_SLEEP))
2055
		se->vruntime -= cfs_rq->min_vruntime;
2056

2057 2058 2059
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

2060
	update_min_vruntime(cfs_rq);
2061
	update_cfs_shares(cfs_rq);
2062 2063 2064 2065 2066
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
2067
static void
I
Ingo Molnar 已提交
2068
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
2069
{
2070
	unsigned long ideal_runtime, delta_exec;
2071 2072
	struct sched_entity *se;
	s64 delta;
2073

P
Peter Zijlstra 已提交
2074
	ideal_runtime = sched_slice(cfs_rq, curr);
2075
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
2076
	if (delta_exec > ideal_runtime) {
2077
		resched_task(rq_of(cfs_rq)->curr);
2078 2079 2080 2081 2082
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093
		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 (delta_exec < sysctl_sched_min_granularity)
		return;

2094 2095
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
2096

2097 2098
	if (delta < 0)
		return;
2099

2100 2101
	if (delta > ideal_runtime)
		resched_task(rq_of(cfs_rq)->curr);
2102 2103
}

2104
static void
2105
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
2106
{
2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117
	/* '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);
	}

2118
	update_stats_curr_start(cfs_rq, se);
2119
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
2120 2121 2122 2123 2124 2125
#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):
	 */
2126
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
2127
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
2128 2129 2130
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
2131
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
2132 2133
}

2134 2135 2136
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

2137 2138 2139 2140 2141 2142 2143
/*
 * 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
 */
2144
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
2145
{
2146
	struct sched_entity *se = __pick_first_entity(cfs_rq);
2147
	struct sched_entity *left = se;
2148

2149 2150 2151 2152 2153 2154 2155 2156 2157
	/*
	 * 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;
	}
2158

2159 2160 2161 2162 2163 2164
	/*
	 * 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;

2165 2166 2167 2168 2169 2170
	/*
	 * 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;

2171
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
2172 2173

	return se;
2174 2175
}

2176 2177
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq);

2178
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
2179 2180 2181 2182 2183 2184
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
2185
		update_curr(cfs_rq);
2186

2187 2188 2189
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

P
Peter Zijlstra 已提交
2190
	check_spread(cfs_rq, prev);
2191
	if (prev->on_rq) {
2192
		update_stats_wait_start(cfs_rq, prev);
2193 2194
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
2195
		/* in !on_rq case, update occurred at dequeue */
2196
		update_entity_load_avg(prev, 1);
2197
	}
2198
	cfs_rq->curr = NULL;
2199 2200
}

P
Peter Zijlstra 已提交
2201 2202
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
2203 2204
{
	/*
2205
	 * Update run-time statistics of the 'current'.
2206
	 */
2207
	update_curr(cfs_rq);
2208

2209 2210 2211
	/*
	 * Ensure that runnable average is periodically updated.
	 */
2212
	update_entity_load_avg(curr, 1);
2213
	update_cfs_rq_blocked_load(cfs_rq, 1);
2214
	update_cfs_shares(cfs_rq);
2215

P
Peter Zijlstra 已提交
2216 2217 2218 2219 2220
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
2221 2222 2223 2224
	if (queued) {
		resched_task(rq_of(cfs_rq)->curr);
		return;
	}
P
Peter Zijlstra 已提交
2225 2226 2227 2228 2229 2230 2231 2232
	/*
	 * 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

Y
Yong Zhang 已提交
2233
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
2234
		check_preempt_tick(cfs_rq, curr);
2235 2236
}

2237 2238 2239 2240 2241 2242

/**************************************************
 * CFS bandwidth control machinery
 */

#ifdef CONFIG_CFS_BANDWIDTH
2243 2244

#ifdef HAVE_JUMP_LABEL
2245
static struct static_key __cfs_bandwidth_used;
2246 2247 2248

static inline bool cfs_bandwidth_used(void)
{
2249
	return static_key_false(&__cfs_bandwidth_used);
2250 2251 2252 2253 2254 2255
}

void account_cfs_bandwidth_used(int enabled, int was_enabled)
{
	/* only need to count groups transitioning between enabled/!enabled */
	if (enabled && !was_enabled)
2256
		static_key_slow_inc(&__cfs_bandwidth_used);
2257
	else if (!enabled && was_enabled)
2258
		static_key_slow_dec(&__cfs_bandwidth_used);
2259 2260 2261 2262 2263 2264 2265 2266 2267 2268
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

void account_cfs_bandwidth_used(int enabled, int was_enabled) {}
#endif /* HAVE_JUMP_LABEL */

2269 2270 2271 2272 2273 2274 2275 2276
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
2277 2278 2279 2280 2281 2282

static inline u64 sched_cfs_bandwidth_slice(void)
{
	return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
}

P
Paul Turner 已提交
2283 2284 2285 2286 2287 2288 2289
/*
 * Replenish runtime according to assigned quota and update expiration time.
 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
 * additional synchronization around rq->lock.
 *
 * requires cfs_b->lock
 */
2290
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301
{
	u64 now;

	if (cfs_b->quota == RUNTIME_INF)
		return;

	now = sched_clock_cpu(smp_processor_id());
	cfs_b->runtime = cfs_b->quota;
	cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
}

2302 2303 2304 2305 2306
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

2307 2308 2309 2310 2311 2312
/* rq->task_clock normalized against any time this cfs_rq has spent throttled */
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
	if (unlikely(cfs_rq->throttle_count))
		return cfs_rq->throttled_clock_task;

2313
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
2314 2315
}

2316 2317
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2318 2319 2320
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
2321
	u64 amount = 0, min_amount, expires;
2322 2323 2324 2325 2326 2327 2328

	/* note: this is a positive sum as runtime_remaining <= 0 */
	min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;

	raw_spin_lock(&cfs_b->lock);
	if (cfs_b->quota == RUNTIME_INF)
		amount = min_amount;
2329
	else {
P
Paul Turner 已提交
2330 2331 2332 2333 2334 2335 2336 2337
		/*
		 * If the bandwidth pool has become inactive, then at least one
		 * period must have elapsed since the last consumption.
		 * Refresh the global state and ensure bandwidth timer becomes
		 * active.
		 */
		if (!cfs_b->timer_active) {
			__refill_cfs_bandwidth_runtime(cfs_b);
2338
			__start_cfs_bandwidth(cfs_b);
P
Paul Turner 已提交
2339
		}
2340 2341 2342 2343 2344 2345

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
2346
	}
P
Paul Turner 已提交
2347
	expires = cfs_b->runtime_expires;
2348 2349 2350
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
2351 2352 2353 2354 2355 2356 2357
	/*
	 * we may have advanced our local expiration to account for allowed
	 * spread between our sched_clock and the one on which runtime was
	 * issued.
	 */
	if ((s64)(expires - cfs_rq->runtime_expires) > 0)
		cfs_rq->runtime_expires = expires;
2358 2359

	return cfs_rq->runtime_remaining > 0;
2360 2361
}

P
Paul Turner 已提交
2362 2363 2364 2365 2366
/*
 * Note: This depends on the synchronization provided by sched_clock and the
 * fact that rq->clock snapshots this value.
 */
static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2367
{
P
Paul Turner 已提交
2368 2369 2370
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
2371
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
2372 2373
		return;

P
Paul Turner 已提交
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
	if (cfs_rq->runtime_remaining < 0)
		return;

	/*
	 * If the local deadline has passed we have to consider the
	 * possibility that our sched_clock is 'fast' and the global deadline
	 * has not truly expired.
	 *
	 * Fortunately we can check determine whether this the case by checking
	 * whether the global deadline has advanced.
	 */

	if ((s64)(cfs_rq->runtime_expires - cfs_b->runtime_expires) >= 0) {
		/* extend local deadline, drift is bounded above by 2 ticks */
		cfs_rq->runtime_expires += TICK_NSEC;
	} else {
		/* global deadline is ahead, expiration has passed */
		cfs_rq->runtime_remaining = 0;
	}
}

static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
				     unsigned long delta_exec)
{
	/* dock delta_exec before expiring quota (as it could span periods) */
2399
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
2400 2401 2402
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
2403 2404
		return;

2405 2406 2407 2408 2409 2410
	/*
	 * if we're unable to extend our runtime we resched so that the active
	 * hierarchy can be throttled
	 */
	if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
		resched_task(rq_of(cfs_rq)->curr);
2411 2412
}

2413 2414
static __always_inline
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec)
2415
{
2416
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
2417 2418 2419 2420 2421
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

2422 2423
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
2424
	return cfs_bandwidth_used() && cfs_rq->throttled;
2425 2426
}

2427 2428 2429
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
2430
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
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
}

/*
 * Ensure that neither of the group entities corresponding to src_cpu or
 * dest_cpu are members of a throttled hierarchy when performing group
 * load-balance operations.
 */
static inline int throttled_lb_pair(struct task_group *tg,
				    int src_cpu, int dest_cpu)
{
	struct cfs_rq *src_cfs_rq, *dest_cfs_rq;

	src_cfs_rq = tg->cfs_rq[src_cpu];
	dest_cfs_rq = tg->cfs_rq[dest_cpu];

	return throttled_hierarchy(src_cfs_rq) ||
	       throttled_hierarchy(dest_cfs_rq);
}

/* updated child weight may affect parent so we have to do this bottom up */
static int tg_unthrottle_up(struct task_group *tg, void *data)
{
	struct rq *rq = data;
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];

	cfs_rq->throttle_count--;
#ifdef CONFIG_SMP
	if (!cfs_rq->throttle_count) {
2459
		/* adjust cfs_rq_clock_task() */
2460
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
2461
					     cfs_rq->throttled_clock_task;
2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472
	}
#endif

	return 0;
}

static int tg_throttle_down(struct task_group *tg, void *data)
{
	struct rq *rq = data;
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];

2473 2474
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
2475
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
2476 2477 2478 2479 2480
	cfs_rq->throttle_count++;

	return 0;
}

2481
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
2482 2483 2484 2485 2486 2487 2488 2489
{
	struct rq *rq = rq_of(cfs_rq);
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
	struct sched_entity *se;
	long task_delta, dequeue = 1;

	se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];

2490
	/* freeze hierarchy runnable averages while throttled */
2491 2492 2493
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513

	task_delta = cfs_rq->h_nr_running;
	for_each_sched_entity(se) {
		struct cfs_rq *qcfs_rq = cfs_rq_of(se);
		/* throttled entity or throttle-on-deactivate */
		if (!se->on_rq)
			break;

		if (dequeue)
			dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
		qcfs_rq->h_nr_running -= task_delta;

		if (qcfs_rq->load.weight)
			dequeue = 0;
	}

	if (!se)
		rq->nr_running -= task_delta;

	cfs_rq->throttled = 1;
2514
	cfs_rq->throttled_clock = rq_clock(rq);
2515 2516 2517 2518 2519
	raw_spin_lock(&cfs_b->lock);
	list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
	raw_spin_unlock(&cfs_b->lock);
}

2520
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
2521 2522 2523 2524 2525 2526 2527
{
	struct rq *rq = rq_of(cfs_rq);
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
	struct sched_entity *se;
	int enqueue = 1;
	long task_delta;

2528
	se = cfs_rq->tg->se[cpu_of(rq)];
2529 2530

	cfs_rq->throttled = 0;
2531 2532 2533

	update_rq_clock(rq);

2534
	raw_spin_lock(&cfs_b->lock);
2535
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
2536 2537 2538
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

2539 2540 2541
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604
	if (!cfs_rq->load.weight)
		return;

	task_delta = cfs_rq->h_nr_running;
	for_each_sched_entity(se) {
		if (se->on_rq)
			enqueue = 0;

		cfs_rq = cfs_rq_of(se);
		if (enqueue)
			enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
		cfs_rq->h_nr_running += task_delta;

		if (cfs_rq_throttled(cfs_rq))
			break;
	}

	if (!se)
		rq->nr_running += task_delta;

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
		resched_task(rq->curr);
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
	u64 runtime = remaining;

	rcu_read_lock();
	list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
				throttled_list) {
		struct rq *rq = rq_of(cfs_rq);

		raw_spin_lock(&rq->lock);
		if (!cfs_rq_throttled(cfs_rq))
			goto next;

		runtime = -cfs_rq->runtime_remaining + 1;
		if (runtime > remaining)
			runtime = remaining;
		remaining -= runtime;

		cfs_rq->runtime_remaining += runtime;
		cfs_rq->runtime_expires = expires;

		/* we check whether we're throttled above */
		if (cfs_rq->runtime_remaining > 0)
			unthrottle_cfs_rq(cfs_rq);

next:
		raw_spin_unlock(&rq->lock);

		if (!remaining)
			break;
	}
	rcu_read_unlock();

	return remaining;
}

2605 2606 2607 2608 2609 2610 2611 2612
/*
 * Responsible for refilling a task_group's bandwidth and unthrottling its
 * cfs_rqs as appropriate. If there has been no activity within the last
 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
 * used to track this state.
 */
static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
{
2613 2614
	u64 runtime, runtime_expires;
	int idle = 1, throttled;
2615 2616 2617 2618 2619 2620

	raw_spin_lock(&cfs_b->lock);
	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
		goto out_unlock;

2621 2622 2623
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
	/* idle depends on !throttled (for the case of a large deficit) */
	idle = cfs_b->idle && !throttled;
2624
	cfs_b->nr_periods += overrun;
2625

P
Paul Turner 已提交
2626 2627 2628 2629 2630 2631
	/* if we're going inactive then everything else can be deferred */
	if (idle)
		goto out_unlock;

	__refill_cfs_bandwidth_runtime(cfs_b);

2632 2633 2634 2635 2636 2637
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
		goto out_unlock;
	}

2638 2639 2640
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664
	/*
	 * There are throttled entities so we must first use the new bandwidth
	 * to unthrottle them before making it generally available.  This
	 * ensures that all existing debts will be paid before a new cfs_rq is
	 * allowed to run.
	 */
	runtime = cfs_b->runtime;
	runtime_expires = cfs_b->runtime_expires;
	cfs_b->runtime = 0;

	/*
	 * This check is repeated as we are holding onto the new bandwidth
	 * while we unthrottle.  This can potentially race with an unthrottled
	 * group trying to acquire new bandwidth from the global pool.
	 */
	while (throttled && runtime > 0) {
		raw_spin_unlock(&cfs_b->lock);
		/* we can't nest cfs_b->lock while distributing bandwidth */
		runtime = distribute_cfs_runtime(cfs_b, runtime,
						 runtime_expires);
		raw_spin_lock(&cfs_b->lock);

		throttled = !list_empty(&cfs_b->throttled_cfs_rq);
	}
2665

2666 2667 2668 2669 2670 2671 2672 2673 2674
	/* return (any) remaining runtime */
	cfs_b->runtime = runtime;
	/*
	 * While we are ensured activity in the period following an
	 * unthrottle, this also covers the case in which the new bandwidth is
	 * insufficient to cover the existing bandwidth deficit.  (Forcing the
	 * timer to remain active while there are any throttled entities.)
	 */
	cfs_b->idle = 0;
2675 2676 2677 2678 2679 2680 2681
out_unlock:
	if (idle)
		cfs_b->timer_active = 0;
	raw_spin_unlock(&cfs_b->lock);

	return idle;
}
2682

2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746
/* a cfs_rq won't donate quota below this amount */
static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
/* minimum remaining period time to redistribute slack quota */
static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
/* how long we wait to gather additional slack before distributing */
static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;

/* are we near the end of the current quota period? */
static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
{
	struct hrtimer *refresh_timer = &cfs_b->period_timer;
	u64 remaining;

	/* if the call-back is running a quota refresh is already occurring */
	if (hrtimer_callback_running(refresh_timer))
		return 1;

	/* is a quota refresh about to occur? */
	remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
	if (remaining < min_expire)
		return 1;

	return 0;
}

static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
{
	u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;

	/* if there's a quota refresh soon don't bother with slack */
	if (runtime_refresh_within(cfs_b, min_left))
		return;

	start_bandwidth_timer(&cfs_b->slack_timer,
				ns_to_ktime(cfs_bandwidth_slack_period));
}

/* we know any runtime found here is valid as update_curr() precedes return */
static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
	s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;

	if (slack_runtime <= 0)
		return;

	raw_spin_lock(&cfs_b->lock);
	if (cfs_b->quota != RUNTIME_INF &&
	    cfs_rq->runtime_expires == cfs_b->runtime_expires) {
		cfs_b->runtime += slack_runtime;

		/* we are under rq->lock, defer unthrottling using a timer */
		if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
		    !list_empty(&cfs_b->throttled_cfs_rq))
			start_cfs_slack_bandwidth(cfs_b);
	}
	raw_spin_unlock(&cfs_b->lock);

	/* even if it's not valid for return we don't want to try again */
	cfs_rq->runtime_remaining -= slack_runtime;
}

static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
2747 2748 2749
	if (!cfs_bandwidth_used())
		return;

2750
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787
		return;

	__return_cfs_rq_runtime(cfs_rq);
}

/*
 * This is done with a timer (instead of inline with bandwidth return) since
 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
 */
static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
{
	u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
	u64 expires;

	/* confirm we're still not at a refresh boundary */
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration))
		return;

	raw_spin_lock(&cfs_b->lock);
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
		runtime = cfs_b->runtime;
		cfs_b->runtime = 0;
	}
	expires = cfs_b->runtime_expires;
	raw_spin_unlock(&cfs_b->lock);

	if (!runtime)
		return;

	runtime = distribute_cfs_runtime(cfs_b, runtime, expires);

	raw_spin_lock(&cfs_b->lock);
	if (expires == cfs_b->runtime_expires)
		cfs_b->runtime = runtime;
	raw_spin_unlock(&cfs_b->lock);
}

2788 2789 2790 2791 2792 2793 2794
/*
 * When a group wakes up we want to make sure that its quota is not already
 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
 * runtime as update_curr() throttling can not not trigger until it's on-rq.
 */
static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
{
2795 2796 2797
	if (!cfs_bandwidth_used())
		return;

2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814
	/* an active group must be handled by the update_curr()->put() path */
	if (!cfs_rq->runtime_enabled || cfs_rq->curr)
		return;

	/* ensure the group is not already throttled */
	if (cfs_rq_throttled(cfs_rq))
		return;

	/* update runtime allocation */
	account_cfs_rq_runtime(cfs_rq, 0);
	if (cfs_rq->runtime_remaining <= 0)
		throttle_cfs_rq(cfs_rq);
}

/* conditionally throttle active cfs_rq's from put_prev_entity() */
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
2815 2816 2817
	if (!cfs_bandwidth_used())
		return;

2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
		return;

	/*
	 * it's possible for a throttled entity to be forced into a running
	 * state (e.g. set_curr_task), in this case we're finished.
	 */
	if (cfs_rq_throttled(cfs_rq))
		return;

	throttle_cfs_rq(cfs_rq);
}
2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910

static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
{
	struct cfs_bandwidth *cfs_b =
		container_of(timer, struct cfs_bandwidth, slack_timer);
	do_sched_cfs_slack_timer(cfs_b);

	return HRTIMER_NORESTART;
}

static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
{
	struct cfs_bandwidth *cfs_b =
		container_of(timer, struct cfs_bandwidth, period_timer);
	ktime_t now;
	int overrun;
	int idle = 0;

	for (;;) {
		now = hrtimer_cb_get_time(timer);
		overrun = hrtimer_forward(timer, now, cfs_b->period);

		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}

	return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
}

void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
	raw_spin_lock_init(&cfs_b->lock);
	cfs_b->runtime = 0;
	cfs_b->quota = RUNTIME_INF;
	cfs_b->period = ns_to_ktime(default_cfs_period());

	INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	cfs_b->period_timer.function = sched_cfs_period_timer;
	hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	cfs_b->slack_timer.function = sched_cfs_slack_timer;
}

static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
	cfs_rq->runtime_enabled = 0;
	INIT_LIST_HEAD(&cfs_rq->throttled_list);
}

/* requires cfs_b->lock, may release to reprogram timer */
void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
	/*
	 * The timer may be active because we're trying to set a new bandwidth
	 * period or because we're racing with the tear-down path
	 * (timer_active==0 becomes visible before the hrtimer call-back
	 * terminates).  In either case we ensure that it's re-programmed
	 */
	while (unlikely(hrtimer_active(&cfs_b->period_timer))) {
		raw_spin_unlock(&cfs_b->lock);
		/* ensure cfs_b->lock is available while we wait */
		hrtimer_cancel(&cfs_b->period_timer);

		raw_spin_lock(&cfs_b->lock);
		/* if someone else restarted the timer then we're done */
		if (cfs_b->timer_active)
			return;
	}

	cfs_b->timer_active = 1;
	start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period);
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

2911
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931
{
	struct cfs_rq *cfs_rq;

	for_each_leaf_cfs_rq(rq, cfs_rq) {
		struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

		if (!cfs_rq->runtime_enabled)
			continue;

		/*
		 * clock_task is not advancing so we just need to make sure
		 * there's some valid quota amount
		 */
		cfs_rq->runtime_remaining = cfs_b->quota;
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
}

#else /* CONFIG_CFS_BANDWIDTH */
2932 2933
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
2934
	return rq_clock_task(rq_of(cfs_rq));
2935 2936 2937 2938
}

static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
				     unsigned long delta_exec) {}
2939 2940
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
2941
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
2942 2943 2944 2945 2946

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957

static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
	return 0;
}

static inline int throttled_lb_pair(struct task_group *tg,
				    int src_cpu, int dest_cpu)
{
	return 0;
}
2958 2959 2960 2961 2962

void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}

#ifdef CONFIG_FAIR_GROUP_SCHED
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
2963 2964
#endif

2965 2966 2967 2968 2969
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return NULL;
}
static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
2970
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
2971 2972 2973

#endif /* CONFIG_CFS_BANDWIDTH */

2974 2975 2976 2977
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
2978 2979 2980 2981 2982 2983 2984 2985
#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);

2986
	if (cfs_rq->nr_running > 1) {
P
Peter Zijlstra 已提交
2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000
		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.
		 */
3001
		if (rq->curr != p)
3002
			delta = max_t(s64, 10000LL, delta);
P
Peter Zijlstra 已提交
3003

3004
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
3005 3006
	}
}
3007 3008 3009 3010 3011 3012 3013 3014 3015 3016

/*
 * 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;

3017
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
3018 3019 3020 3021 3022
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
3023
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
3024 3025 3026 3027
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
3028 3029 3030 3031

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
3032 3033
#endif

3034 3035 3036 3037 3038
/*
 * 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:
 */
3039
static void
3040
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
3041 3042
{
	struct cfs_rq *cfs_rq;
3043
	struct sched_entity *se = &p->se;
3044 3045

	for_each_sched_entity(se) {
3046
		if (se->on_rq)
3047 3048
			break;
		cfs_rq = cfs_rq_of(se);
3049
		enqueue_entity(cfs_rq, se, flags);
3050 3051 3052 3053 3054 3055 3056 3057 3058

		/*
		 * end evaluation on encountering a throttled cfs_rq
		 *
		 * note: in the case of encountering a throttled cfs_rq we will
		 * post the final h_nr_running increment below.
		*/
		if (cfs_rq_throttled(cfs_rq))
			break;
3059
		cfs_rq->h_nr_running++;
3060

3061
		flags = ENQUEUE_WAKEUP;
3062
	}
P
Peter Zijlstra 已提交
3063

P
Peter Zijlstra 已提交
3064
	for_each_sched_entity(se) {
3065
		cfs_rq = cfs_rq_of(se);
3066
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
3067

3068 3069 3070
		if (cfs_rq_throttled(cfs_rq))
			break;

3071
		update_cfs_shares(cfs_rq);
3072
		update_entity_load_avg(se, 1);
P
Peter Zijlstra 已提交
3073 3074
	}

3075 3076
	if (!se) {
		update_rq_runnable_avg(rq, rq->nr_running);
3077
		inc_nr_running(rq);
3078
	}
3079
	hrtick_update(rq);
3080 3081
}

3082 3083
static void set_next_buddy(struct sched_entity *se);

3084 3085 3086 3087 3088
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
3089
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
3090 3091
{
	struct cfs_rq *cfs_rq;
3092
	struct sched_entity *se = &p->se;
3093
	int task_sleep = flags & DEQUEUE_SLEEP;
3094 3095 3096

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
3097
		dequeue_entity(cfs_rq, se, flags);
3098 3099 3100 3101 3102 3103 3104 3105 3106

		/*
		 * end evaluation on encountering a throttled cfs_rq
		 *
		 * note: in the case of encountering a throttled cfs_rq we will
		 * post the final h_nr_running decrement below.
		*/
		if (cfs_rq_throttled(cfs_rq))
			break;
3107
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
3108

3109
		/* Don't dequeue parent if it has other entities besides us */
3110 3111 3112 3113 3114 3115 3116
		if (cfs_rq->load.weight) {
			/*
			 * Bias pick_next to pick a task from this cfs_rq, as
			 * p is sleeping when it is within its sched_slice.
			 */
			if (task_sleep && parent_entity(se))
				set_next_buddy(parent_entity(se));
3117 3118 3119

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
3120
			break;
3121
		}
3122
		flags |= DEQUEUE_SLEEP;
3123
	}
P
Peter Zijlstra 已提交
3124

P
Peter Zijlstra 已提交
3125
	for_each_sched_entity(se) {
3126
		cfs_rq = cfs_rq_of(se);
3127
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
3128

3129 3130 3131
		if (cfs_rq_throttled(cfs_rq))
			break;

3132
		update_cfs_shares(cfs_rq);
3133
		update_entity_load_avg(se, 1);
P
Peter Zijlstra 已提交
3134 3135
	}

3136
	if (!se) {
3137
		dec_nr_running(rq);
3138 3139
		update_rq_runnable_avg(rq, 1);
	}
3140
	hrtick_update(rq);
3141 3142
}

3143
#ifdef CONFIG_SMP
3144 3145 3146
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
3147
	return cpu_rq(cpu)->cfs.runnable_load_avg;
3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191
}

/*
 * Return a low guess at the load of a migration-source cpu weighted
 * according to the scheduling class and "nice" value.
 *
 * We want to under-estimate the load of migration sources, to
 * balance conservatively.
 */
static unsigned long source_load(int cpu, int type)
{
	struct rq *rq = cpu_rq(cpu);
	unsigned long total = weighted_cpuload(cpu);

	if (type == 0 || !sched_feat(LB_BIAS))
		return total;

	return min(rq->cpu_load[type-1], total);
}

/*
 * Return a high guess at the load of a migration-target cpu weighted
 * according to the scheduling class and "nice" value.
 */
static unsigned long target_load(int cpu, int type)
{
	struct rq *rq = cpu_rq(cpu);
	unsigned long total = weighted_cpuload(cpu);

	if (type == 0 || !sched_feat(LB_BIAS))
		return total;

	return max(rq->cpu_load[type-1], total);
}

static unsigned long power_of(int cpu)
{
	return cpu_rq(cpu)->cpu_power;
}

static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
	unsigned long nr_running = ACCESS_ONCE(rq->nr_running);
3192
	unsigned long load_avg = rq->cfs.runnable_load_avg;
3193 3194

	if (nr_running)
3195
		return load_avg / nr_running;
3196 3197 3198 3199

	return 0;
}

3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216
static void record_wakee(struct task_struct *p)
{
	/*
	 * Rough decay (wiping) for cost saving, don't worry
	 * about the boundary, really active task won't care
	 * about the loss.
	 */
	if (jiffies > current->wakee_flip_decay_ts + HZ) {
		current->wakee_flips = 0;
		current->wakee_flip_decay_ts = jiffies;
	}

	if (current->last_wakee != p) {
		current->last_wakee = p;
		current->wakee_flips++;
	}
}
3217

3218
static void task_waking_fair(struct task_struct *p)
3219 3220 3221
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
3222 3223 3224 3225
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
3226

3227 3228 3229 3230 3231 3232 3233 3234
	do {
		min_vruntime_copy = cfs_rq->min_vruntime_copy;
		smp_rmb();
		min_vruntime = cfs_rq->min_vruntime;
	} while (min_vruntime != min_vruntime_copy);
#else
	min_vruntime = cfs_rq->min_vruntime;
#endif
3235

3236
	se->vruntime -= min_vruntime;
3237
	record_wakee(p);
3238 3239
}

3240
#ifdef CONFIG_FAIR_GROUP_SCHED
3241 3242 3243 3244 3245 3246
/*
 * 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.
3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288 3289
 *
 * Calculate the effective load difference if @wl is added (subtracted) to @tg
 * on this @cpu and results in a total addition (subtraction) of @wg to the
 * total group weight.
 *
 * Given a runqueue weight distribution (rw_i) we can compute a shares
 * distribution (s_i) using:
 *
 *   s_i = rw_i / \Sum rw_j						(1)
 *
 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
 * shares distribution (s_i):
 *
 *   rw_i = {   2,   4,   1,   0 }
 *   s_i  = { 2/7, 4/7, 1/7,   0 }
 *
 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
 * task used to run on and the CPU the waker is running on), we need to
 * compute the effect of waking a task on either CPU and, in case of a sync
 * wakeup, compute the effect of the current task going to sleep.
 *
 * So for a change of @wl to the local @cpu with an overall group weight change
 * of @wl we can compute the new shares distribution (s'_i) using:
 *
 *   s'_i = (rw_i + @wl) / (@wg + \Sum rw_j)				(2)
 *
 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
 * differences in waking a task to CPU 0. The additional task changes the
 * weight and shares distributions like:
 *
 *   rw'_i = {   3,   4,   1,   0 }
 *   s'_i  = { 3/8, 4/8, 1/8,   0 }
 *
 * We can then compute the difference in effective weight by using:
 *
 *   dw_i = S * (s'_i - s_i)						(3)
 *
 * Where 'S' is the group weight as seen by its parent.
 *
 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
 * 4/7) times the weight of the group.
3290
 */
P
Peter Zijlstra 已提交
3291
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
3292
{
P
Peter Zijlstra 已提交
3293
	struct sched_entity *se = tg->se[cpu];
3294

3295
	if (!tg->parent)	/* the trivial, non-cgroup case */
3296 3297
		return wl;

P
Peter Zijlstra 已提交
3298
	for_each_sched_entity(se) {
3299
		long w, W;
P
Peter Zijlstra 已提交
3300

3301
		tg = se->my_q->tg;
3302

3303 3304 3305 3306
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
3307

3308 3309 3310 3311
		/*
		 * w = rw_i + @wl
		 */
		w = se->my_q->load.weight + wl;
3312

3313 3314 3315 3316 3317
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
			wl = (w * tg->shares) / W;
3318 3319
		else
			wl = tg->shares;
3320

3321 3322 3323 3324 3325
		/*
		 * Per the above, wl is the new se->load.weight value; since
		 * those are clipped to [MIN_SHARES, ...) do so now. See
		 * calc_cfs_shares().
		 */
3326 3327
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
3328 3329 3330 3331

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
3332
		wl -= se->load.weight;
3333 3334 3335 3336 3337 3338 3339 3340

		/*
		 * Recursively apply this logic to all parent groups to compute
		 * the final effective load change on the root group. Since
		 * only the @tg group gets extra weight, all parent groups can
		 * only redistribute existing shares. @wl is the shift in shares
		 * resulting from this level per the above.
		 */
P
Peter Zijlstra 已提交
3341 3342
		wg = 0;
	}
3343

P
Peter Zijlstra 已提交
3344
	return wl;
3345 3346
}
#else
P
Peter Zijlstra 已提交
3347

3348 3349
static inline unsigned long effective_load(struct task_group *tg, int cpu,
		unsigned long wl, unsigned long wg)
P
Peter Zijlstra 已提交
3350
{
3351
	return wl;
3352
}
P
Peter Zijlstra 已提交
3353

3354 3355
#endif

3356 3357
static int wake_wide(struct task_struct *p)
{
3358
	int factor = this_cpu_read(sd_llc_size);
3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377

	/*
	 * Yeah, it's the switching-frequency, could means many wakee or
	 * rapidly switch, use factor here will just help to automatically
	 * adjust the loose-degree, so bigger node will lead to more pull.
	 */
	if (p->wakee_flips > factor) {
		/*
		 * wakee is somewhat hot, it needs certain amount of cpu
		 * resource, so if waker is far more hot, prefer to leave
		 * it alone.
		 */
		if (current->wakee_flips > (factor * p->wakee_flips))
			return 1;
	}

	return 0;
}

3378
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
3379
{
3380
	s64 this_load, load;
3381
	int idx, this_cpu, prev_cpu;
3382
	unsigned long tl_per_task;
3383
	struct task_group *tg;
3384
	unsigned long weight;
3385
	int balanced;
3386

3387 3388 3389 3390 3391 3392 3393
	/*
	 * If we wake multiple tasks be careful to not bounce
	 * ourselves around too much.
	 */
	if (wake_wide(p))
		return 0;

3394 3395 3396 3397 3398
	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);
3399

3400 3401 3402 3403 3404
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
3405 3406 3407 3408
	if (sync) {
		tg = task_group(current);
		weight = current->se.load.weight;

3409
		this_load += effective_load(tg, this_cpu, -weight, -weight);
3410 3411
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
3412

3413 3414
	tg = task_group(p);
	weight = p->se.load.weight;
3415

3416 3417
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
3418 3419 3420
	 * 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.
3421 3422 3423 3424
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
3425 3426
	if (this_load > 0) {
		s64 this_eff_load, prev_eff_load;
3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439

		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;
3440

3441
	/*
I
Ingo Molnar 已提交
3442 3443 3444
	 * If the currently running task will sleep within
	 * a reasonable amount of time then attract this newly
	 * woken task:
3445
	 */
3446 3447
	if (sync && balanced)
		return 1;
3448

3449
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
3450 3451
	tl_per_task = cpu_avg_load_per_task(this_cpu);

3452 3453 3454
	if (balanced ||
	    (this_load <= load &&
	     this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
3455 3456 3457 3458 3459
		/*
		 * This domain has SD_WAKE_AFFINE and
		 * p is cache cold in this domain, and
		 * there is no bad imbalance.
		 */
3460
		schedstat_inc(sd, ttwu_move_affine);
3461
		schedstat_inc(p, se.statistics.nr_wakeups_affine);
3462 3463 3464 3465 3466 3467

		return 1;
	}
	return 0;
}

3468 3469 3470 3471 3472
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
3473
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
3474
		  int this_cpu, int load_idx)
3475
{
3476
	struct sched_group *idlest = NULL, *group = sd->groups;
3477 3478
	unsigned long min_load = ULONG_MAX, this_load = 0;
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
3479

3480 3481 3482 3483
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
3484

3485 3486
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
3487
					tsk_cpus_allowed(p)))
3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 3498 3499 3500 3501 3502 3503 3504 3505 3506
			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 */
3507
		avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power;
3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532

		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 */
3533
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
3534 3535 3536 3537 3538
		load = weighted_cpuload(i);

		if (load < min_load || (load == min_load && i == this_cpu)) {
			min_load = load;
			idlest = i;
3539 3540 3541
		}
	}

3542 3543
	return idlest;
}
3544

3545 3546 3547
/*
 * Try and locate an idle CPU in the sched_domain.
 */
3548
static int select_idle_sibling(struct task_struct *p, int target)
3549
{
3550
	struct sched_domain *sd;
3551
	struct sched_group *sg;
3552
	int i = task_cpu(p);
3553

3554 3555
	if (idle_cpu(target))
		return target;
3556 3557

	/*
3558
	 * If the prevous cpu is cache affine and idle, don't be stupid.
3559
	 */
3560 3561
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
3562 3563

	/*
3564
	 * Otherwise, iterate the domains and find an elegible idle cpu.
3565
	 */
3566
	sd = rcu_dereference(per_cpu(sd_llc, target));
3567
	for_each_lower_domain(sd) {
3568 3569 3570 3571 3572 3573 3574
		sg = sd->groups;
		do {
			if (!cpumask_intersects(sched_group_cpus(sg),
						tsk_cpus_allowed(p)))
				goto next;

			for_each_cpu(i, sched_group_cpus(sg)) {
3575
				if (i == target || !idle_cpu(i))
3576 3577
					goto next;
			}
3578

3579 3580 3581 3582 3583 3584 3585 3586
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
3587 3588 3589
	return target;
}

3590 3591 3592 3593 3594 3595 3596 3597 3598 3599 3600
/*
 * 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.
 */
3601
static int
3602
select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
3603
{
3604
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
3605 3606 3607
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
	int new_cpu = cpu;
3608
	int want_affine = 0;
3609
	int sync = wake_flags & WF_SYNC;
3610

3611
	if (p->nr_cpus_allowed == 1)
3612 3613
		return prev_cpu;

3614
	if (sd_flag & SD_BALANCE_WAKE) {
3615
		if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
3616 3617 3618
			want_affine = 1;
		new_cpu = prev_cpu;
	}
3619

3620
	rcu_read_lock();
3621
	for_each_domain(cpu, tmp) {
3622 3623 3624
		if (!(tmp->flags & SD_LOAD_BALANCE))
			continue;

3625
		/*
3626 3627
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
3628
		 */
3629 3630 3631
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
3632
			break;
3633
		}
3634

3635
		if (tmp->flags & sd_flag)
3636 3637 3638
			sd = tmp;
	}

3639
	if (affine_sd) {
3640
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
3641 3642 3643 3644
			prev_cpu = cpu;

		new_cpu = select_idle_sibling(p, prev_cpu);
		goto unlock;
3645
	}
3646

3647
	while (sd) {
3648
		int load_idx = sd->forkexec_idx;
3649
		struct sched_group *group;
3650
		int weight;
3651

3652
		if (!(sd->flags & sd_flag)) {
3653 3654 3655
			sd = sd->child;
			continue;
		}
3656

3657 3658
		if (sd_flag & SD_BALANCE_WAKE)
			load_idx = sd->wake_idx;
3659

3660
		group = find_idlest_group(sd, p, cpu, load_idx);
3661 3662 3663 3664
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
3665

3666
		new_cpu = find_idlest_cpu(group, p, cpu);
3667 3668 3669 3670
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
3671
		}
3672 3673 3674

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
3675
		weight = sd->span_weight;
3676 3677
		sd = NULL;
		for_each_domain(cpu, tmp) {
3678
			if (weight <= tmp->span_weight)
3679
				break;
3680
			if (tmp->flags & sd_flag)
3681 3682 3683
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
3684
	}
3685 3686
unlock:
	rcu_read_unlock();
3687

3688
	return new_cpu;
3689
}
3690 3691 3692 3693 3694 3695 3696 3697 3698 3699

/*
 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
 * cfs_rq_of(p) references at time of call are still valid and identify the
 * previous cpu.  However, the caller only guarantees p->pi_lock is held; no
 * other assumptions, including the state of rq->lock, should be made.
 */
static void
migrate_task_rq_fair(struct task_struct *p, int next_cpu)
{
3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	/*
	 * Load tracking: accumulate removed load so that it can be processed
	 * when we next update owning cfs_rq under rq->lock.  Tasks contribute
	 * to blocked load iff they have a positive decay-count.  It can never
	 * be negative here since on-rq tasks have decay-count == 0.
	 */
	if (se->avg.decay_count) {
		se->avg.decay_count = -__synchronize_entity_decay(se);
3711 3712
		atomic_long_add(se->avg.load_avg_contrib,
						&cfs_rq->removed_load);
3713
	}
3714
}
3715 3716
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
3717 3718
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
3719 3720 3721 3722
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
3723 3724
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
3725 3726 3727 3728 3729 3730 3731 3732 3733
	 *
	 * 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.
3734
	 */
3735
	return calc_delta_fair(gran, se);
3736 3737
}

3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753 3754 3755 3756 3757 3758 3759
/*
 * 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
3760
	gran = wakeup_gran(curr, se);
3761 3762 3763 3764 3765 3766
	if (vdiff > gran)
		return 1;

	return 0;
}

3767 3768
static void set_last_buddy(struct sched_entity *se)
{
3769 3770 3771 3772 3773
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
3774 3775 3776 3777
}

static void set_next_buddy(struct sched_entity *se)
{
3778 3779 3780 3781 3782
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
3783 3784
}

3785 3786
static void set_skip_buddy(struct sched_entity *se)
{
3787 3788
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
3789 3790
}

3791 3792 3793
/*
 * Preempt the current task with a newly woken task if needed:
 */
3794
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
3795 3796
{
	struct task_struct *curr = rq->curr;
3797
	struct sched_entity *se = &curr->se, *pse = &p->se;
3798
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
3799
	int scale = cfs_rq->nr_running >= sched_nr_latency;
3800
	int next_buddy_marked = 0;
3801

I
Ingo Molnar 已提交
3802 3803 3804
	if (unlikely(se == pse))
		return;

3805
	/*
3806
	 * This is possible from callers such as move_task(), in which we
3807 3808 3809 3810 3811 3812 3813
	 * unconditionally check_prempt_curr() after an enqueue (which may have
	 * lead to a throttle).  This both saves work and prevents false
	 * next-buddy nomination below.
	 */
	if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
		return;

3814
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
3815
		set_next_buddy(pse);
3816 3817
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
3818

3819 3820 3821
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
3822 3823 3824 3825 3826 3827
	 *
	 * Note: this also catches the edge-case of curr being in a throttled
	 * group (e.g. via set_curr_task), since update_curr() (in the
	 * enqueue of curr) will have resulted in resched being set.  This
	 * prevents us from potentially nominating it as a false LAST_BUDDY
	 * below.
3828 3829 3830 3831
	 */
	if (test_tsk_need_resched(curr))
		return;

3832 3833 3834 3835 3836
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

3837
	/*
3838 3839
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
3840
	 */
3841
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
3842
		return;
3843

3844
	find_matching_se(&se, &pse);
3845
	update_curr(cfs_rq_of(se));
3846
	BUG_ON(!pse);
3847 3848 3849 3850 3851 3852 3853
	if (wakeup_preempt_entity(se, pse) == 1) {
		/*
		 * Bias pick_next to pick the sched entity that is
		 * triggering this preemption.
		 */
		if (!next_buddy_marked)
			set_next_buddy(pse);
3854
		goto preempt;
3855
	}
3856

3857
	return;
3858

3859 3860 3861 3862 3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873 3874
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);
3875 3876
}

3877
static struct task_struct *pick_next_task_fair(struct rq *rq)
3878
{
P
Peter Zijlstra 已提交
3879
	struct task_struct *p;
3880 3881 3882
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;

3883
	if (!cfs_rq->nr_running)
3884 3885 3886
		return NULL;

	do {
3887
		se = pick_next_entity(cfs_rq);
3888
		set_next_entity(cfs_rq, se);
3889 3890 3891
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
3892
	p = task_of(se);
3893 3894
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
3895 3896

	return p;
3897 3898 3899 3900 3901
}

/*
 * Account for a descheduled task:
 */
3902
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
3903 3904 3905 3906 3907 3908
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
3909
		put_prev_entity(cfs_rq, se);
3910 3911 3912
	}
}

3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937
/*
 * 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);
3938 3939 3940 3941 3942 3943
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
		 rq->skip_clock_update = 1;
3944 3945 3946 3947 3948
	}

	set_skip_buddy(se);
}

3949 3950 3951 3952
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

3953 3954
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
3955 3956 3957 3958 3959 3960 3961 3962 3963 3964
		return false;

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

	yield_task_fair(rq);

	return true;
}

3965
#ifdef CONFIG_SMP
3966
/**************************************************
P
Peter Zijlstra 已提交
3967 3968 3969 3970 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 4002 4003 4004 4005 4006 4007 4008 4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019 4020 4021 4022 4023 4024 4025 4026 4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 4082
 * Fair scheduling class load-balancing methods.
 *
 * BASICS
 *
 * The purpose of load-balancing is to achieve the same basic fairness the
 * per-cpu scheduler provides, namely provide a proportional amount of compute
 * time to each task. This is expressed in the following equation:
 *
 *   W_i,n/P_i == W_j,n/P_j for all i,j                               (1)
 *
 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
 * W_i,0 is defined as:
 *
 *   W_i,0 = \Sum_j w_i,j                                             (2)
 *
 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
 * is derived from the nice value as per prio_to_weight[].
 *
 * The weight average is an exponential decay average of the instantaneous
 * weight:
 *
 *   W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0               (3)
 *
 * P_i is the cpu power (or compute capacity) of cpu i, typically it is the
 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
 * can also include other factors [XXX].
 *
 * To achieve this balance we define a measure of imbalance which follows
 * directly from (1):
 *
 *   imb_i,j = max{ avg(W/P), W_i/P_i } - min{ avg(W/P), W_j/P_j }    (4)
 *
 * We them move tasks around to minimize the imbalance. In the continuous
 * function space it is obvious this converges, in the discrete case we get
 * a few fun cases generally called infeasible weight scenarios.
 *
 * [XXX expand on:
 *     - infeasible weights;
 *     - local vs global optima in the discrete case. ]
 *
 *
 * SCHED DOMAINS
 *
 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
 * for all i,j solution, we create a tree of cpus that follows the hardware
 * topology where each level pairs two lower groups (or better). This results
 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
 * tree to only the first of the previous level and we decrease the frequency
 * of load-balance at each level inv. proportional to the number of cpus in
 * the groups.
 *
 * This yields:
 *
 *     log_2 n     1     n
 *   \Sum       { --- * --- * 2^i } = O(n)                            (5)
 *     i = 0      2^i   2^i
 *                               `- size of each group
 *         |         |     `- number of cpus doing load-balance
 *         |         `- freq
 *         `- sum over all levels
 *
 * Coupled with a limit on how many tasks we can migrate every balance pass,
 * this makes (5) the runtime complexity of the balancer.
 *
 * An important property here is that each CPU is still (indirectly) connected
 * to every other cpu in at most O(log n) steps:
 *
 * The adjacency matrix of the resulting graph is given by:
 *
 *             log_2 n     
 *   A_i,j = \Union     (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1)  (6)
 *             k = 0
 *
 * And you'll find that:
 *
 *   A^(log_2 n)_i,j != 0  for all i,j                                (7)
 *
 * Showing there's indeed a path between every cpu in at most O(log n) steps.
 * The task movement gives a factor of O(m), giving a convergence complexity
 * of:
 *
 *   O(nm log n),  n := nr_cpus, m := nr_tasks                        (8)
 *
 *
 * WORK CONSERVING
 *
 * In order to avoid CPUs going idle while there's still work to do, new idle
 * balancing is more aggressive and has the newly idle cpu iterate up the domain
 * tree itself instead of relying on other CPUs to bring it work.
 *
 * This adds some complexity to both (5) and (8) but it reduces the total idle
 * time.
 *
 * [XXX more?]
 *
 *
 * CGROUPS
 *
 * Cgroups make a horror show out of (2), instead of a simple sum we get:
 *
 *                                s_k,i
 *   W_i,0 = \Sum_j \Prod_k w_k * -----                               (9)
 *                                 S_k
 *
 * Where
 *
 *   s_k,i = \Sum_j w_i,j,k  and  S_k = \Sum_i s_k,i                 (10)
 *
 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
 *
 * The big problem is S_k, its a global sum needed to compute a local (W_i)
 * property.
 *
 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
 *      rewrite all of this once again.]
 */ 
4083

4084 4085
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

4086
#define LBF_ALL_PINNED	0x01
4087
#define LBF_NEED_BREAK	0x02
4088 4089
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
4090 4091 4092 4093 4094

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
4095
	int			src_cpu;
4096 4097 4098 4099

	int			dst_cpu;
	struct rq		*dst_rq;

4100 4101
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
4102
	enum cpu_idle_type	idle;
4103
	long			imbalance;
4104 4105 4106
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

4107
	unsigned int		flags;
4108 4109 4110 4111

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
4112 4113
};

4114
/*
4115
 * move_task - move a task from one runqueue to another runqueue.
4116 4117
 * Both runqueues must be locked.
 */
4118
static void move_task(struct task_struct *p, struct lb_env *env)
4119
{
4120 4121 4122 4123
	deactivate_task(env->src_rq, p, 0);
	set_task_cpu(p, env->dst_cpu);
	activate_task(env->dst_rq, p, 0);
	check_preempt_curr(env->dst_rq, p, 0);
4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137
#ifdef CONFIG_NUMA_BALANCING
	if (p->numa_preferred_nid != -1) {
		int src_nid = cpu_to_node(env->src_cpu);
		int dst_nid = cpu_to_node(env->dst_cpu);

		/*
		 * If the load balancer has moved the task then limit
		 * migrations from taking place in the short term in
		 * case this is a short-lived migration.
		 */
		if (src_nid != dst_nid && dst_nid != p->numa_preferred_nid)
			p->numa_migrate_seq = 0;
	}
#endif
4138 4139
}

4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4169 4170 4171
/*
 * Is this task likely cache-hot:
 */
static int
task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
{
	s64 delta;

	if (p->sched_class != &fair_sched_class)
		return 0;

	if (unlikely(p->policy == SCHED_IDLE))
		return 0;

	/*
	 * Buddy candidates are cache hot:
	 */
	if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running &&
			(&p->se == cfs_rq_of(&p->se)->next ||
			 &p->se == cfs_rq_of(&p->se)->last))
		return 1;

	if (sysctl_sched_migration_cost == -1)
		return 1;
	if (sysctl_sched_migration_cost == 0)
		return 0;

	delta = now - p->se.exec_start;

	return delta < (s64)sysctl_sched_migration_cost;
}

4172 4173 4174 4175 4176 4177 4178 4179 4180 4181 4182 4183 4184 4185 4186 4187 4188 4189 4190
#ifdef CONFIG_NUMA_BALANCING
/* Returns true if the destination node has incurred more faults */
static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
{
	int src_nid, dst_nid;

	if (!sched_feat(NUMA_FAVOUR_HIGHER) || !p->numa_faults ||
	    !(env->sd->flags & SD_NUMA)) {
		return false;
	}

	src_nid = cpu_to_node(env->src_cpu);
	dst_nid = cpu_to_node(env->dst_cpu);

	if (src_nid == dst_nid ||
	    p->numa_migrate_seq >= sysctl_numa_balancing_settle_count)
		return false;

	if (dst_nid == p->numa_preferred_nid ||
4191
	    task_faults(p, dst_nid) > task_faults(p, src_nid))
4192 4193 4194 4195
		return true;

	return false;
}
4196 4197 4198 4199 4200 4201 4202 4203 4204 4205 4206 4207 4208 4209 4210 4211 4212 4213 4214


static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
{
	int src_nid, dst_nid;

	if (!sched_feat(NUMA) || !sched_feat(NUMA_RESIST_LOWER))
		return false;

	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
		return false;

	src_nid = cpu_to_node(env->src_cpu);
	dst_nid = cpu_to_node(env->dst_cpu);

	if (src_nid == dst_nid ||
	    p->numa_migrate_seq >= sysctl_numa_balancing_settle_count)
		return false;

4215
	if (task_faults(p, dst_nid) < task_faults(p, src_nid))
4216 4217 4218 4219 4220
		return true;

	return false;
}

4221 4222 4223 4224 4225 4226
#else
static inline bool migrate_improves_locality(struct task_struct *p,
					     struct lb_env *env)
{
	return false;
}
4227 4228 4229 4230 4231 4232

static inline bool migrate_degrades_locality(struct task_struct *p,
					     struct lb_env *env)
{
	return false;
}
4233 4234
#endif

4235 4236 4237 4238
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
4239
int can_migrate_task(struct task_struct *p, struct lb_env *env)
4240 4241 4242 4243
{
	int tsk_cache_hot = 0;
	/*
	 * We do not migrate tasks that are:
4244
	 * 1) throttled_lb_pair, or
4245
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
4246 4247
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
4248
	 */
4249 4250 4251
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

4252
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
4253
		int cpu;
4254

4255
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
4256

4257 4258
		env->flags |= LBF_SOME_PINNED;

4259 4260 4261 4262 4263 4264 4265 4266
		/*
		 * Remember if this task can be migrated to any other cpu in
		 * our sched_group. We may want to revisit it if we couldn't
		 * meet load balance goals by pulling other tasks on src_cpu.
		 *
		 * Also avoid computing new_dst_cpu if we have already computed
		 * one in current iteration.
		 */
4267
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
4268 4269
			return 0;

4270 4271 4272
		/* Prevent to re-select dst_cpu via env's cpus */
		for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
			if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
4273
				env->flags |= LBF_DST_PINNED;
4274 4275 4276
				env->new_dst_cpu = cpu;
				break;
			}
4277
		}
4278

4279 4280
		return 0;
	}
4281 4282

	/* Record that we found atleast one task that could run on dst_cpu */
4283
	env->flags &= ~LBF_ALL_PINNED;
4284

4285
	if (task_running(env->src_rq, p)) {
4286
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
4287 4288 4289 4290 4291
		return 0;
	}

	/*
	 * Aggressive migration if:
4292 4293 4294
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
4295
	 */
4296
	tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq), env->sd);
4297 4298
	if (!tsk_cache_hot)
		tsk_cache_hot = migrate_degrades_locality(p, env);
4299 4300 4301 4302 4303 4304 4305 4306 4307 4308 4309

	if (migrate_improves_locality(p, env)) {
#ifdef CONFIG_SCHEDSTATS
		if (tsk_cache_hot) {
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
			schedstat_inc(p, se.statistics.nr_forced_migrations);
		}
#endif
		return 1;
	}

4310
	if (!tsk_cache_hot ||
4311
		env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
Z
Zhang Hang 已提交
4312

4313
		if (tsk_cache_hot) {
4314
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
4315
			schedstat_inc(p, se.statistics.nr_forced_migrations);
4316
		}
Z
Zhang Hang 已提交
4317

4318 4319 4320
		return 1;
	}

Z
Zhang Hang 已提交
4321 4322
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
4323 4324
}

4325 4326 4327 4328 4329 4330 4331
/*
 * 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.
 */
4332
static int move_one_task(struct lb_env *env)
4333 4334 4335
{
	struct task_struct *p, *n;

4336 4337 4338
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
4339

4340 4341 4342 4343 4344 4345 4346 4347
		move_task(p, env);
		/*
		 * Right now, this is only the second place move_task()
		 * is called, so we can safely collect move_task()
		 * stats here rather than inside move_task().
		 */
		schedstat_inc(env->sd, lb_gained[env->idle]);
		return 1;
4348 4349 4350 4351
	}
	return 0;
}

4352 4353
static unsigned long task_h_load(struct task_struct *p);

4354 4355
static const unsigned int sched_nr_migrate_break = 32;

4356
/*
4357
 * move_tasks tries to move up to imbalance weighted load from busiest to
4358 4359 4360 4361 4362 4363
 * 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 lb_env *env)
4364
{
4365 4366
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
4367 4368
	unsigned long load;
	int pulled = 0;
4369

4370
	if (env->imbalance <= 0)
4371
		return 0;
4372

4373 4374
	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
4375

4376 4377
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
4378
		if (env->loop > env->loop_max)
4379
			break;
4380 4381

		/* take a breather every nr_migrate tasks */
4382
		if (env->loop > env->loop_break) {
4383
			env->loop_break += sched_nr_migrate_break;
4384
			env->flags |= LBF_NEED_BREAK;
4385
			break;
4386
		}
4387

4388
		if (!can_migrate_task(p, env))
4389 4390 4391
			goto next;

		load = task_h_load(p);
4392

4393
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
4394 4395
			goto next;

4396
		if ((load / 2) > env->imbalance)
4397
			goto next;
4398

4399
		move_task(p, env);
4400
		pulled++;
4401
		env->imbalance -= load;
4402 4403

#ifdef CONFIG_PREEMPT
4404 4405 4406 4407 4408
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
		 * kernels will stop after the first task is pulled to minimize
		 * the critical section.
		 */
4409
		if (env->idle == CPU_NEWLY_IDLE)
4410
			break;
4411 4412
#endif

4413 4414 4415 4416
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
4417
		if (env->imbalance <= 0)
4418
			break;
4419 4420 4421

		continue;
next:
4422
		list_move_tail(&p->se.group_node, tasks);
4423
	}
4424

4425
	/*
4426 4427 4428
	 * Right now, this is one of only two places move_task() is called,
	 * so we can safely collect move_task() stats here rather than
	 * inside move_task().
4429
	 */
4430
	schedstat_add(env->sd, lb_gained[env->idle], pulled);
4431

4432
	return pulled;
4433 4434
}

P
Peter Zijlstra 已提交
4435
#ifdef CONFIG_FAIR_GROUP_SCHED
4436 4437 4438
/*
 * update tg->load_weight by folding this cpu's load_avg
 */
4439
static void __update_blocked_averages_cpu(struct task_group *tg, int cpu)
4440
{
4441 4442
	struct sched_entity *se = tg->se[cpu];
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu];
4443

4444 4445 4446
	/* throttled entities do not contribute to load */
	if (throttled_hierarchy(cfs_rq))
		return;
4447

4448
	update_cfs_rq_blocked_load(cfs_rq, 1);
4449

4450 4451 4452 4453 4454 4455 4456 4457 4458 4459 4460 4461 4462 4463
	if (se) {
		update_entity_load_avg(se, 1);
		/*
		 * We pivot on our runnable average having decayed to zero for
		 * list removal.  This generally implies that all our children
		 * have also been removed (modulo rounding error or bandwidth
		 * control); however, such cases are rare and we can fix these
		 * at enqueue.
		 *
		 * TODO: fix up out-of-order children on enqueue.
		 */
		if (!se->avg.runnable_avg_sum && !cfs_rq->nr_running)
			list_del_leaf_cfs_rq(cfs_rq);
	} else {
4464
		struct rq *rq = rq_of(cfs_rq);
4465 4466
		update_rq_runnable_avg(rq, rq->nr_running);
	}
4467 4468
}

4469
static void update_blocked_averages(int cpu)
4470 4471
{
	struct rq *rq = cpu_rq(cpu);
4472 4473
	struct cfs_rq *cfs_rq;
	unsigned long flags;
4474

4475 4476
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
4477 4478 4479 4480
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
4481
	for_each_leaf_cfs_rq(rq, cfs_rq) {
4482 4483 4484 4485 4486 4487
		/*
		 * Note: We may want to consider periodically releasing
		 * rq->lock about these updates so that creating many task
		 * groups does not result in continually extending hold time.
		 */
		__update_blocked_averages_cpu(cfs_rq->tg, rq->cpu);
4488
	}
4489 4490

	raw_spin_unlock_irqrestore(&rq->lock, flags);
4491 4492
}

4493
/*
4494
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
4495 4496 4497
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
4498
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
4499
{
4500 4501
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
4502
	unsigned long now = jiffies;
4503
	unsigned long load;
4504

4505
	if (cfs_rq->last_h_load_update == now)
4506 4507
		return;

4508 4509 4510 4511 4512 4513 4514
	cfs_rq->h_load_next = NULL;
	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
		cfs_rq->h_load_next = se;
		if (cfs_rq->last_h_load_update == now)
			break;
	}
4515

4516
	if (!se) {
4517
		cfs_rq->h_load = cfs_rq->runnable_load_avg;
4518 4519 4520 4521 4522 4523 4524 4525 4526 4527 4528
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
		load = div64_ul(load * se->avg.load_avg_contrib,
				cfs_rq->runnable_load_avg + 1);
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
4529 4530
}

4531
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
4532
{
4533
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
4534

4535
	update_cfs_rq_h_load(cfs_rq);
4536 4537
	return div64_ul(p->se.avg.load_avg_contrib * cfs_rq->h_load,
			cfs_rq->runnable_load_avg + 1);
P
Peter Zijlstra 已提交
4538 4539
}
#else
4540
static inline void update_blocked_averages(int cpu)
4541 4542 4543
{
}

4544
static unsigned long task_h_load(struct task_struct *p)
4545
{
4546
	return p->se.avg.load_avg_contrib;
4547
}
P
Peter Zijlstra 已提交
4548
#endif
4549 4550 4551 4552 4553 4554 4555 4556 4557

/********** Helpers for find_busiest_group ************************/
/*
 * 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_weighted_load; /* Weighted load of group's tasks */
J
Joonsoo Kim 已提交
4558
	unsigned long load_per_task;
4559
	unsigned long group_power;
4560 4561 4562 4563
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int group_capacity;
	unsigned int idle_cpus;
	unsigned int group_weight;
4564
	int group_imb; /* Is there an imbalance in the group ? */
4565
	int group_has_capacity; /* Is there extra capacity in the group? */
4566 4567
};

J
Joonsoo Kim 已提交
4568 4569 4570 4571 4572 4573 4574 4575 4576 4577 4578 4579
/*
 * 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 *local;	/* 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 */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
4580
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
4581 4582
};

4583 4584 4585 4586 4587 4588 4589 4590 4591 4592 4593 4594 4595 4596 4597 4598 4599 4600 4601
static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
{
	/*
	 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
	 * local_stat because update_sg_lb_stats() does a full clear/assignment.
	 * We must however clear busiest_stat::avg_load because
	 * update_sd_pick_busiest() reads this before assignment.
	 */
	*sds = (struct sd_lb_stats){
		.busiest = NULL,
		.local = NULL,
		.total_load = 0UL,
		.total_pwr = 0UL,
		.busiest_stat = {
			.avg_load = 0UL,
		},
	};
}

4602 4603 4604 4605
/**
 * 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.
4606 4607
 *
 * Return: The load index.
4608 4609 4610 4611 4612 4613 4614 4615 4616 4617 4618 4619 4620 4621 4622 4623 4624 4625 4626 4627 4628 4629
 */
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;
}

4630
static unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
4631
{
4632
	return SCHED_POWER_SCALE;
4633 4634 4635 4636 4637 4638 4639
}

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

4640
static unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
4641
{
4642
	unsigned long weight = sd->span_weight;
4643 4644 4645 4646 4647 4648 4649 4650 4651 4652 4653 4654
	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);
}

4655
static unsigned long scale_rt_power(int cpu)
4656 4657
{
	struct rq *rq = cpu_rq(cpu);
4658
	u64 total, available, age_stamp, avg;
4659

4660 4661 4662 4663 4664 4665 4666
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
	age_stamp = ACCESS_ONCE(rq->age_stamp);
	avg = ACCESS_ONCE(rq->rt_avg);

4667
	total = sched_avg_period() + (rq_clock(rq) - age_stamp);
4668

4669
	if (unlikely(total < avg)) {
4670 4671 4672
		/* Ensures that power won't end up being negative */
		available = 0;
	} else {
4673
		available = total - avg;
4674
	}
4675

4676 4677
	if (unlikely((s64)total < SCHED_POWER_SCALE))
		total = SCHED_POWER_SCALE;
4678

4679
	total >>= SCHED_POWER_SHIFT;
4680 4681 4682 4683 4684 4685

	return div_u64(available, total);
}

static void update_cpu_power(struct sched_domain *sd, int cpu)
{
4686
	unsigned long weight = sd->span_weight;
4687
	unsigned long power = SCHED_POWER_SCALE;
4688 4689 4690 4691 4692 4693 4694 4695
	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);

4696
		power >>= SCHED_POWER_SHIFT;
4697 4698
	}

4699
	sdg->sgp->power_orig = power;
4700 4701 4702 4703 4704 4705

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

4706
	power >>= SCHED_POWER_SHIFT;
4707

4708
	power *= scale_rt_power(cpu);
4709
	power >>= SCHED_POWER_SHIFT;
4710 4711 4712 4713

	if (!power)
		power = 1;

4714
	cpu_rq(cpu)->cpu_power = power;
4715
	sdg->sgp->power = power;
4716 4717
}

4718
void update_group_power(struct sched_domain *sd, int cpu)
4719 4720 4721
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
4722
	unsigned long power, power_orig;
4723 4724 4725 4726 4727
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
	sdg->sgp->next_update = jiffies + interval;
4728 4729 4730 4731 4732 4733

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

4734
	power_orig = power = 0;
4735

P
Peter Zijlstra 已提交
4736 4737 4738 4739 4740 4741
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

4742 4743 4744 4745 4746 4747
		for_each_cpu(cpu, sched_group_cpus(sdg)) {
			struct sched_group *sg = cpu_rq(cpu)->sd->groups;

			power_orig += sg->sgp->power_orig;
			power += sg->sgp->power;
		}
P
Peter Zijlstra 已提交
4748 4749 4750 4751 4752 4753 4754 4755
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
4756
			power_orig += group->sgp->power_orig;
P
Peter Zijlstra 已提交
4757 4758 4759 4760
			power += group->sgp->power;
			group = group->next;
		} while (group != child->groups);
	}
4761

4762 4763
	sdg->sgp->power_orig = power_orig;
	sdg->sgp->power = power;
4764 4765
}

4766 4767 4768 4769 4770 4771 4772 4773 4774 4775 4776
/*
 * 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)
{
	/*
4777
	 * Only siblings can have significantly less than SCHED_POWER_SCALE
4778
	 */
P
Peter Zijlstra 已提交
4779
	if (!(sd->flags & SD_SHARE_CPUPOWER))
4780 4781 4782 4783 4784
		return 0;

	/*
	 * If ~90% of the cpu_power is still there, we're good.
	 */
4785
	if (group->sgp->power * 32 > group->sgp->power_orig * 29)
4786 4787 4788 4789 4790
		return 1;

	return 0;
}

4791 4792 4793 4794 4795 4796 4797 4798 4799 4800 4801 4802 4803 4804 4805 4806
/*
 * Group imbalance indicates (and tries to solve) the problem where balancing
 * groups is inadequate due to tsk_cpus_allowed() constraints.
 *
 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
 * Something like:
 *
 * 	{ 0 1 2 3 } { 4 5 6 7 }
 * 	        *     * * *
 *
 * If we were to balance group-wise we'd place two tasks in the first group and
 * two tasks in the second group. Clearly this is undesired as it will overload
 * cpu 3 and leave one of the cpus in the second group unused.
 *
 * The current solution to this issue is detecting the skew in the first group
4807 4808
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
4809 4810 4811
 *
 * When this is so detected; this group becomes a candidate for busiest; see
 * update_sd_pick_busiest(). And calculcate_imbalance() and
4812
 * find_busiest_group() avoid some of the usual balance conditions to allow it
4813 4814 4815 4816 4817 4818 4819
 * to create an effective group imbalance.
 *
 * This is a somewhat tricky proposition since the next run might not find the
 * group imbalance and decide the groups need to be balanced again. A most
 * subtle and fragile situation.
 */

4820
static inline int sg_imbalanced(struct sched_group *group)
4821
{
4822
	return group->sgp->imbalance;
4823 4824
}

4825 4826 4827
/*
 * Compute the group capacity.
 *
4828 4829 4830
 * Avoid the issue where N*frac(smt_power) >= 1 creates 'phantom' cores by
 * first dividing out the smt factor and computing the actual number of cores
 * and limit power unit capacity with that.
4831 4832 4833
 */
static inline int sg_capacity(struct lb_env *env, struct sched_group *group)
{
4834 4835 4836 4837 4838 4839
	unsigned int capacity, smt, cpus;
	unsigned int power, power_orig;

	power = group->sgp->power;
	power_orig = group->sgp->power_orig;
	cpus = group->group_weight;
4840

4841 4842 4843
	/* smt := ceil(cpus / power), assumes: 1 < smt_power < 2 */
	smt = DIV_ROUND_UP(SCHED_POWER_SCALE * cpus, power_orig);
	capacity = cpus / smt; /* cores */
4844

4845
	capacity = min_t(unsigned, capacity, DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE));
4846 4847 4848 4849 4850 4851
	if (!capacity)
		capacity = fix_small_capacity(env->sd, group);

	return capacity;
}

4852 4853
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
4854
 * @env: The load balancing environment.
4855 4856 4857 4858 4859
 * @group: sched_group whose statistics are to be updated.
 * @load_idx: Load index of sched_domain of this_cpu for load calc.
 * @local_group: Does group contain this_cpu.
 * @sgs: variable to hold the statistics for this group.
 */
4860 4861
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
4862
			int local_group, struct sg_lb_stats *sgs)
4863
{
4864 4865
	unsigned long nr_running;
	unsigned long load;
4866
	int i;
4867

4868 4869
	memset(sgs, 0, sizeof(*sgs));

4870
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
4871 4872
		struct rq *rq = cpu_rq(i);

4873 4874
		nr_running = rq->nr_running;

4875
		/* Bias balancing toward cpus of our domain */
4876
		if (local_group)
4877
			load = target_load(i, load_idx);
4878
		else
4879 4880 4881
			load = source_load(i, load_idx);

		sgs->group_load += load;
4882
		sgs->sum_nr_running += nr_running;
4883
		sgs->sum_weighted_load += weighted_cpuload(i);
4884 4885
		if (idle_cpu(i))
			sgs->idle_cpus++;
4886 4887 4888
	}

	/* Adjust by relative CPU power of the group */
4889 4890
	sgs->group_power = group->sgp->power;
	sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / sgs->group_power;
4891

4892
	if (sgs->sum_nr_running)
4893
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
4894

4895
	sgs->group_weight = group->group_weight;
4896

4897 4898 4899
	sgs->group_imb = sg_imbalanced(group);
	sgs->group_capacity = sg_capacity(env, group);

4900 4901
	if (sgs->group_capacity > sgs->sum_nr_running)
		sgs->group_has_capacity = 1;
4902 4903
}

4904 4905
/**
 * update_sd_pick_busiest - return 1 on busiest group
4906
 * @env: The load balancing environment.
4907 4908
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
4909
 * @sgs: sched_group statistics
4910 4911 4912
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
4913 4914 4915
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
4916
 */
4917
static bool update_sd_pick_busiest(struct lb_env *env,
4918 4919
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
4920
				   struct sg_lb_stats *sgs)
4921
{
J
Joonsoo Kim 已提交
4922
	if (sgs->avg_load <= sds->busiest_stat.avg_load)
4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 4935
		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.
	 */
4936 4937
	if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
	    env->dst_cpu < group_first_cpu(sg)) {
4938 4939 4940 4941 4942 4943 4944 4945 4946 4947
		if (!sds->busiest)
			return true;

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

	return false;
}

4948
/**
4949
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
4950
 * @env: The load balancing environment.
4951 4952 4953
 * @balance: Should we balance.
 * @sds: variable to hold the statistics for this sched_domain.
 */
4954
static inline void update_sd_lb_stats(struct lb_env *env,
4955
					struct sd_lb_stats *sds)
4956
{
4957 4958
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
J
Joonsoo Kim 已提交
4959
	struct sg_lb_stats tmp_sgs;
4960 4961 4962 4963 4964
	int load_idx, prefer_sibling = 0;

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

4965
	load_idx = get_sd_load_idx(env->sd, env->idle);
4966 4967

	do {
J
Joonsoo Kim 已提交
4968
		struct sg_lb_stats *sgs = &tmp_sgs;
4969 4970
		int local_group;

4971
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
J
Joonsoo Kim 已提交
4972 4973 4974
		if (local_group) {
			sds->local = sg;
			sgs = &sds->local_stat;
4975 4976 4977 4978

			if (env->idle != CPU_NEWLY_IDLE ||
			    time_after_eq(jiffies, sg->sgp->next_update))
				update_group_power(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
4979
		}
4980

J
Joonsoo Kim 已提交
4981
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs);
4982

4983 4984 4985
		if (local_group)
			goto next_group;

4986 4987
		/*
		 * In case the child domain prefers tasks go to siblings
4988
		 * first, lower the sg capacity to one so that we'll try
4989 4990 4991 4992 4993 4994
		 * 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).
4995
		 */
4996 4997
		if (prefer_sibling && sds->local &&
		    sds->local_stat.group_has_capacity)
4998
			sgs->group_capacity = min(sgs->group_capacity, 1U);
4999

5000
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
5001
			sds->busiest = sg;
J
Joonsoo Kim 已提交
5002
			sds->busiest_stat = *sgs;
5003 5004
		}

5005 5006 5007 5008 5009
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
		sds->total_pwr += sgs->group_power;

5010
		sg = sg->next;
5011
	} while (sg != env->sd->groups);
5012 5013 5014 5015 5016 5017 5018 5019 5020 5021 5022 5023 5024 5025 5026 5027 5028 5029 5030
}

/**
 * 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.
 *
5031
 * Return: 1 when packing is required and a task should be moved to
5032 5033
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
5034
 * @env: The load balancing environment.
5035 5036
 * @sds: Statistics of the sched_domain which is to be packed
 */
5037
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
5038 5039 5040
{
	int busiest_cpu;

5041
	if (!(env->sd->flags & SD_ASYM_PACKING))
5042 5043 5044 5045 5046 5047
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
5048
	if (env->dst_cpu > busiest_cpu)
5049 5050
		return 0;

5051
	env->imbalance = DIV_ROUND_CLOSEST(
5052 5053
		sds->busiest_stat.avg_load * sds->busiest_stat.group_power,
		SCHED_POWER_SCALE);
5054

5055
	return 1;
5056 5057 5058 5059 5060 5061
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
5062
 * @env: The load balancing environment.
5063 5064
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
5065 5066
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
5067 5068 5069
{
	unsigned long tmp, pwr_now = 0, pwr_move = 0;
	unsigned int imbn = 2;
5070
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
5071
	struct sg_lb_stats *local, *busiest;
5072

J
Joonsoo Kim 已提交
5073 5074
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
5075

J
Joonsoo Kim 已提交
5076 5077 5078 5079
	if (!local->sum_nr_running)
		local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
	else if (busiest->load_per_task > local->load_per_task)
		imbn = 1;
5080

J
Joonsoo Kim 已提交
5081 5082
	scaled_busy_load_per_task =
		(busiest->load_per_task * SCHED_POWER_SCALE) /
5083
		busiest->group_power;
J
Joonsoo Kim 已提交
5084

5085 5086
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
5087
		env->imbalance = busiest->load_per_task;
5088 5089 5090 5091 5092 5093 5094 5095 5096
		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.
	 */

5097
	pwr_now += busiest->group_power *
J
Joonsoo Kim 已提交
5098
			min(busiest->load_per_task, busiest->avg_load);
5099
	pwr_now += local->group_power *
J
Joonsoo Kim 已提交
5100
			min(local->load_per_task, local->avg_load);
5101
	pwr_now /= SCHED_POWER_SCALE;
5102 5103

	/* Amount of load we'd subtract */
J
Joonsoo Kim 已提交
5104
	tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
5105
		busiest->group_power;
J
Joonsoo Kim 已提交
5106
	if (busiest->avg_load > tmp) {
5107
		pwr_move += busiest->group_power *
J
Joonsoo Kim 已提交
5108 5109 5110
			    min(busiest->load_per_task,
				busiest->avg_load - tmp);
	}
5111 5112

	/* Amount of load we'd add */
5113
	if (busiest->avg_load * busiest->group_power <
J
Joonsoo Kim 已提交
5114
	    busiest->load_per_task * SCHED_POWER_SCALE) {
5115 5116
		tmp = (busiest->avg_load * busiest->group_power) /
		      local->group_power;
J
Joonsoo Kim 已提交
5117 5118
	} else {
		tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
5119
		      local->group_power;
J
Joonsoo Kim 已提交
5120
	}
5121 5122
	pwr_move += local->group_power *
		    min(local->load_per_task, local->avg_load + tmp);
5123
	pwr_move /= SCHED_POWER_SCALE;
5124 5125 5126

	/* Move if we gain throughput */
	if (pwr_move > pwr_now)
J
Joonsoo Kim 已提交
5127
		env->imbalance = busiest->load_per_task;
5128 5129 5130 5131 5132
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
5133
 * @env: load balance environment
5134 5135
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
5136
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
5137
{
5138
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
5139 5140 5141 5142
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
5143

J
Joonsoo Kim 已提交
5144
	if (busiest->group_imb) {
5145 5146 5147 5148
		/*
		 * In the group_imb case we cannot rely on group-wide averages
		 * to ensure cpu-load equilibrium, look at wider averages. XXX
		 */
J
Joonsoo Kim 已提交
5149 5150
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
5151 5152
	}

5153 5154 5155 5156 5157
	/*
	 * 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..)
	 */
5158 5159
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
5160 5161
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
5162 5163
	}

J
Joonsoo Kim 已提交
5164
	if (!busiest->group_imb) {
5165 5166
		/*
		 * Don't want to pull so many tasks that a group would go idle.
5167 5168
		 * Except of course for the group_imb case, since then we might
		 * have to drop below capacity to reach cpu-load equilibrium.
5169
		 */
J
Joonsoo Kim 已提交
5170 5171
		load_above_capacity =
			(busiest->sum_nr_running - busiest->group_capacity);
5172

5173
		load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
5174
		load_above_capacity /= busiest->group_power;
5175 5176 5177 5178 5179 5180 5181 5182 5183 5184
	}

	/*
	 * 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.
	 */
5185
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
5186 5187

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
5188
	env->imbalance = min(
5189 5190
		max_pull * busiest->group_power,
		(sds->avg_load - local->avg_load) * local->group_power
J
Joonsoo Kim 已提交
5191
	) / SCHED_POWER_SCALE;
5192 5193 5194

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
5195
	 * there is no guarantee that any tasks will be moved so we'll have
5196 5197 5198
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
5199
	if (env->imbalance < busiest->load_per_task)
5200
		return fix_small_imbalance(env, sds);
5201
}
5202

5203 5204 5205 5206 5207 5208 5209 5210 5211 5212 5213 5214
/******* 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.
 *
5215
 * @env: The load balancing environment.
5216
 *
5217
 * Return:	- The busiest group if imbalance exists.
5218 5219 5220 5221
 *		- 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.
 */
J
Joonsoo Kim 已提交
5222
static struct sched_group *find_busiest_group(struct lb_env *env)
5223
{
J
Joonsoo Kim 已提交
5224
	struct sg_lb_stats *local, *busiest;
5225 5226
	struct sd_lb_stats sds;

5227
	init_sd_lb_stats(&sds);
5228 5229 5230 5231 5232

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
5233
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
5234 5235
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
5236

5237 5238
	if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(env, &sds))
5239 5240
		return sds.busiest;

5241
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
5242
	if (!sds.busiest || busiest->sum_nr_running == 0)
5243 5244
		goto out_balanced;

5245
	sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
5246

P
Peter Zijlstra 已提交
5247 5248
	/*
	 * If the busiest group is imbalanced the below checks don't
5249
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
5250 5251
	 * isn't true due to cpus_allowed constraints and the like.
	 */
J
Joonsoo Kim 已提交
5252
	if (busiest->group_imb)
P
Peter Zijlstra 已提交
5253 5254
		goto force_balance;

5255
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
J
Joonsoo Kim 已提交
5256 5257
	if (env->idle == CPU_NEWLY_IDLE && local->group_has_capacity &&
	    !busiest->group_has_capacity)
5258 5259
		goto force_balance;

5260 5261 5262 5263
	/*
	 * If the local group is more busy than the selected busiest group
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
5264
	if (local->avg_load >= busiest->avg_load)
5265 5266
		goto out_balanced;

5267 5268 5269 5270
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
5271
	if (local->avg_load >= sds.avg_load)
5272 5273
		goto out_balanced;

5274
	if (env->idle == CPU_IDLE) {
5275 5276 5277 5278 5279 5280
		/*
		 * 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.
		 */
J
Joonsoo Kim 已提交
5281 5282
		if ((local->idle_cpus < busiest->idle_cpus) &&
		    busiest->sum_nr_running <= busiest->group_weight)
5283
			goto out_balanced;
5284 5285 5286 5287 5288
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
5289 5290
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
5291
			goto out_balanced;
5292
	}
5293

5294
force_balance:
5295
	/* Looks like there is an imbalance. Compute it */
5296
	calculate_imbalance(env, &sds);
5297 5298 5299
	return sds.busiest;

out_balanced:
5300
	env->imbalance = 0;
5301 5302 5303 5304 5305 5306
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
5307
static struct rq *find_busiest_queue(struct lb_env *env,
5308
				     struct sched_group *group)
5309 5310
{
	struct rq *busiest = NULL, *rq;
5311
	unsigned long busiest_load = 0, busiest_power = 1;
5312 5313
	int i;

5314
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
5315
		unsigned long power = power_of(i);
5316 5317
		unsigned long capacity = DIV_ROUND_CLOSEST(power,
							   SCHED_POWER_SCALE);
5318 5319
		unsigned long wl;

5320
		if (!capacity)
5321
			capacity = fix_small_capacity(env->sd, group);
5322

5323
		rq = cpu_rq(i);
5324
		wl = weighted_cpuload(i);
5325

5326 5327 5328 5329
		/*
		 * When comparing with imbalance, use weighted_cpuload()
		 * which is not scaled with the cpu power.
		 */
5330
		if (capacity && rq->nr_running == 1 && wl > env->imbalance)
5331 5332
			continue;

5333 5334 5335 5336 5337
		/*
		 * 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.
5338 5339 5340 5341 5342
		 *
		 * Thus we're looking for max(wl_i / power_i), crosswise
		 * multiplication to rid ourselves of the division works out
		 * to: wl_i * power_j > wl_j * power_i;  where j is our
		 * previous maximum.
5343
		 */
5344 5345 5346
		if (wl * busiest_power > busiest_load * power) {
			busiest_load = wl;
			busiest_power = power;
5347 5348 5349 5350 5351 5352 5353 5354 5355 5356 5357 5358 5359 5360
			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. */
5361
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
5362

5363
static int need_active_balance(struct lb_env *env)
5364
{
5365 5366 5367
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
5368 5369 5370 5371 5372 5373

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
5374
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
5375
			return 1;
5376 5377 5378 5379 5380
	}

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

5381 5382
static int active_load_balance_cpu_stop(void *data);

5383 5384 5385 5386 5387 5388 5389 5390 5391 5392 5393 5394 5395 5396 5397 5398 5399 5400 5401 5402 5403 5404 5405 5406 5407 5408 5409 5410 5411 5412 5413
static int should_we_balance(struct lb_env *env)
{
	struct sched_group *sg = env->sd->groups;
	struct cpumask *sg_cpus, *sg_mask;
	int cpu, balance_cpu = -1;

	/*
	 * In the newly idle case, we will allow all the cpu's
	 * to do the newly idle load balance.
	 */
	if (env->idle == CPU_NEWLY_IDLE)
		return 1;

	sg_cpus = sched_group_cpus(sg);
	sg_mask = sched_group_mask(sg);
	/* Try to find first idle cpu */
	for_each_cpu_and(cpu, sg_cpus, env->cpus) {
		if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
			continue;

		balance_cpu = cpu;
		break;
	}

	if (balance_cpu == -1)
		balance_cpu = group_balance_cpu(sg);

	/*
	 * First idle cpu or the first cpu(busiest) in this sched group
	 * is eligible for doing load balancing at this and above domains.
	 */
5414
	return balance_cpu == env->dst_cpu;
5415 5416
}

5417 5418 5419 5420 5421 5422
/*
 * 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,
5423
			int *continue_balancing)
5424
{
5425
	int ld_moved, cur_ld_moved, active_balance = 0;
5426
	struct sched_domain *sd_parent = sd->parent;
5427 5428 5429
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
5430
	struct cpumask *cpus = __get_cpu_var(load_balance_mask);
5431

5432 5433
	struct lb_env env = {
		.sd		= sd,
5434 5435
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
5436
		.dst_grpmask    = sched_group_cpus(sd->groups),
5437
		.idle		= idle,
5438
		.loop_break	= sched_nr_migrate_break,
5439
		.cpus		= cpus,
5440 5441
	};

5442 5443 5444 5445
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
5446
	if (idle == CPU_NEWLY_IDLE)
5447 5448
		env.dst_grpmask = NULL;

5449 5450 5451 5452 5453
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
5454 5455
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
5456
		goto out_balanced;
5457
	}
5458

5459
	group = find_busiest_group(&env);
5460 5461 5462 5463 5464
	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

5465
	busiest = find_busiest_queue(&env, group);
5466 5467 5468 5469 5470
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

5471
	BUG_ON(busiest == env.dst_rq);
5472

5473
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
5474 5475 5476 5477 5478 5479 5480 5481 5482

	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.
		 */
5483
		env.flags |= LBF_ALL_PINNED;
5484 5485 5486
		env.src_cpu   = busiest->cpu;
		env.src_rq    = busiest;
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
5487

5488
more_balance:
5489
		local_irq_save(flags);
5490
		double_rq_lock(env.dst_rq, busiest);
5491 5492 5493 5494 5495 5496 5497

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
		cur_ld_moved = move_tasks(&env);
		ld_moved += cur_ld_moved;
5498
		double_rq_unlock(env.dst_rq, busiest);
5499 5500 5501 5502 5503
		local_irq_restore(flags);

		/*
		 * some other cpu did the load balance for us.
		 */
5504 5505 5506
		if (cur_ld_moved && env.dst_cpu != smp_processor_id())
			resched_cpu(env.dst_cpu);

5507 5508 5509 5510 5511
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

5512 5513 5514 5515 5516 5517 5518 5519 5520 5521 5522 5523 5524 5525 5526 5527 5528 5529 5530
		/*
		 * Revisit (affine) tasks on src_cpu that couldn't be moved to
		 * us and move them to an alternate dst_cpu in our sched_group
		 * where they can run. The upper limit on how many times we
		 * iterate on same src_cpu is dependent on number of cpus in our
		 * sched_group.
		 *
		 * This changes load balance semantics a bit on who can move
		 * load to a given_cpu. In addition to the given_cpu itself
		 * (or a ilb_cpu acting on its behalf where given_cpu is
		 * nohz-idle), we now have balance_cpu in a position to move
		 * load to given_cpu. In rare situations, this may cause
		 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
		 * _independently_ and at _same_ time to move some load to
		 * given_cpu) causing exceess load to be moved to given_cpu.
		 * This however should not happen so much in practice and
		 * moreover subsequent load balance cycles should correct the
		 * excess load moved.
		 */
5531
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
5532

5533 5534 5535
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

5536
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
5537
			env.dst_cpu	 = env.new_dst_cpu;
5538
			env.flags	&= ~LBF_DST_PINNED;
5539 5540
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
5541

5542 5543 5544 5545 5546 5547
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
5548

5549 5550 5551 5552 5553 5554 5555 5556 5557 5558 5559 5560
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
			int *group_imbalance = &sd_parent->groups->sgp->imbalance;

			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) {
				*group_imbalance = 1;
			} else if (*group_imbalance)
				*group_imbalance = 0;
		}

5561
		/* All tasks on this runqueue were pinned by CPU affinity */
5562
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
5563
			cpumask_clear_cpu(cpu_of(busiest), cpus);
5564 5565 5566
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
5567
				goto redo;
5568
			}
5569 5570 5571 5572 5573 5574
			goto out_balanced;
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
5575 5576 5577 5578 5579 5580 5581 5582
		/*
		 * 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++;
5583

5584
		if (need_active_balance(&env)) {
5585 5586
			raw_spin_lock_irqsave(&busiest->lock, flags);

5587 5588 5589
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
5590 5591
			 */
			if (!cpumask_test_cpu(this_cpu,
5592
					tsk_cpus_allowed(busiest->curr))) {
5593 5594
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
5595
				env.flags |= LBF_ALL_PINNED;
5596 5597 5598
				goto out_one_pinned;
			}

5599 5600 5601 5602 5603
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
5604 5605 5606 5607 5608 5609
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
5610

5611
			if (active_balance) {
5612 5613 5614
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
5615
			}
5616 5617 5618 5619 5620 5621 5622 5623 5624 5625 5626 5627 5628 5629 5630 5631 5632 5633 5634 5635 5636 5637 5638 5639 5640 5641 5642 5643 5644 5645 5646 5647 5648

			/*
			 * 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 */
5649
	if (((env.flags & LBF_ALL_PINNED) &&
5650
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
5651 5652 5653
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

5654
	ld_moved = 0;
5655 5656 5657 5658 5659 5660 5661 5662
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.
 */
5663
void idle_balance(int this_cpu, struct rq *this_rq)
5664 5665 5666 5667
{
	struct sched_domain *sd;
	int pulled_task = 0;
	unsigned long next_balance = jiffies + HZ;
5668
	u64 curr_cost = 0;
5669

5670
	this_rq->idle_stamp = rq_clock(this_rq);
5671 5672 5673 5674

	if (this_rq->avg_idle < sysctl_sched_migration_cost)
		return;

5675 5676 5677 5678 5679
	/*
	 * Drop the rq->lock, but keep IRQ/preempt disabled.
	 */
	raw_spin_unlock(&this_rq->lock);

5680
	update_blocked_averages(this_cpu);
5681
	rcu_read_lock();
5682 5683
	for_each_domain(this_cpu, sd) {
		unsigned long interval;
5684
		int continue_balancing = 1;
5685
		u64 t0, domain_cost;
5686 5687 5688 5689

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

5690 5691 5692
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost)
			break;

5693
		if (sd->flags & SD_BALANCE_NEWIDLE) {
5694 5695
			t0 = sched_clock_cpu(this_cpu);

5696
			/* If we've pulled tasks over stop searching: */
5697
			pulled_task = load_balance(this_cpu, this_rq,
5698 5699
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
5700 5701 5702 5703 5704 5705

			domain_cost = sched_clock_cpu(this_cpu) - t0;
			if (domain_cost > sd->max_newidle_lb_cost)
				sd->max_newidle_lb_cost = domain_cost;

			curr_cost += domain_cost;
5706
		}
5707 5708 5709 5710

		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
5711 5712
		if (pulled_task) {
			this_rq->idle_stamp = 0;
5713
			break;
N
Nikhil Rao 已提交
5714
		}
5715
	}
5716
	rcu_read_unlock();
5717 5718 5719

	raw_spin_lock(&this_rq->lock);

5720 5721 5722 5723 5724 5725 5726
	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;
	}
5727 5728 5729

	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;
5730 5731 5732
}

/*
5733 5734 5735 5736
 * 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.
5737
 */
5738
static int active_load_balance_cpu_stop(void *data)
5739
{
5740 5741
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
5742
	int target_cpu = busiest_rq->push_cpu;
5743
	struct rq *target_rq = cpu_rq(target_cpu);
5744
	struct sched_domain *sd;
5745 5746 5747 5748 5749 5750 5751

	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;
5752 5753 5754

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
5755
		goto out_unlock;
5756 5757 5758 5759 5760 5761 5762 5763 5764 5765 5766 5767

	/*
	 * 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. */
5768
	rcu_read_lock();
5769 5770 5771 5772 5773 5774 5775
	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)) {
5776 5777
		struct lb_env env = {
			.sd		= sd,
5778 5779 5780 5781
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
5782 5783 5784
			.idle		= CPU_IDLE,
		};

5785 5786
		schedstat_inc(sd, alb_count);

5787
		if (move_one_task(&env))
5788 5789 5790 5791
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
5792
	rcu_read_unlock();
5793
	double_unlock_balance(busiest_rq, target_rq);
5794 5795 5796 5797
out_unlock:
	busiest_rq->active_balance = 0;
	raw_spin_unlock_irq(&busiest_rq->lock);
	return 0;
5798 5799
}

5800
#ifdef CONFIG_NO_HZ_COMMON
5801 5802 5803 5804 5805 5806
/*
 * idle load balancing details
 * - 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.
 */
5807
static struct {
5808
	cpumask_var_t idle_cpus_mask;
5809
	atomic_t nr_cpus;
5810 5811
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
5812

5813
static inline int find_new_ilb(int call_cpu)
5814
{
5815
	int ilb = cpumask_first(nohz.idle_cpus_mask);
5816

5817 5818 5819 5820
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
5821 5822
}

5823 5824 5825 5826 5827 5828 5829 5830 5831 5832 5833
/*
 * 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++;

5834
	ilb_cpu = find_new_ilb(cpu);
5835

5836 5837
	if (ilb_cpu >= nr_cpu_ids)
		return;
5838

5839
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
5840 5841 5842 5843 5844 5845 5846 5847
		return;
	/*
	 * Use smp_send_reschedule() instead of resched_cpu().
	 * This way we generate a sched IPI on the target cpu which
	 * is idle. And the softirq performing nohz idle load balance
	 * will be run before returning from the IPI.
	 */
	smp_send_reschedule(ilb_cpu);
5848 5849 5850
	return;
}

5851
static inline void nohz_balance_exit_idle(int cpu)
5852 5853 5854 5855 5856 5857 5858 5859
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
		cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
		atomic_dec(&nohz.nr_cpus);
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

5860 5861 5862 5863 5864
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;

	rcu_read_lock();
N
Nathan Zimmer 已提交
5865
	sd = rcu_dereference_check_sched_domain(this_rq()->sd);
V
Vincent Guittot 已提交
5866 5867 5868 5869 5870 5871

	if (!sd || !sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 0;

	for (; sd; sd = sd->parent)
5872
		atomic_inc(&sd->groups->sgp->nr_busy_cpus);
V
Vincent Guittot 已提交
5873
unlock:
5874 5875 5876 5877 5878 5879 5880 5881
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;

	rcu_read_lock();
N
Nathan Zimmer 已提交
5882
	sd = rcu_dereference_check_sched_domain(this_rq()->sd);
V
Vincent Guittot 已提交
5883 5884 5885 5886 5887 5888

	if (!sd || sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 1;

	for (; sd; sd = sd->parent)
5889
		atomic_dec(&sd->groups->sgp->nr_busy_cpus);
V
Vincent Guittot 已提交
5890
unlock:
5891 5892 5893
	rcu_read_unlock();
}

5894
/*
5895
 * This routine will record that the cpu is going idle with tick stopped.
5896
 * This info will be used in performing idle load balancing in the future.
5897
 */
5898
void nohz_balance_enter_idle(int cpu)
5899
{
5900 5901 5902 5903 5904 5905
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

5906 5907
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
5908

5909 5910 5911
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
5912
}
5913

5914
static int sched_ilb_notifier(struct notifier_block *nfb,
5915 5916 5917 5918
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
5919
		nohz_balance_exit_idle(smp_processor_id());
5920 5921 5922 5923 5924
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
5925 5926 5927 5928
#endif

static DEFINE_SPINLOCK(balancing);

5929 5930 5931 5932
/*
 * 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.
 */
5933
void update_max_interval(void)
5934 5935 5936 5937
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

5938 5939 5940 5941
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
5942
 * Balancing parameters are set up in init_sched_domains.
5943 5944 5945
 */
static void rebalance_domains(int cpu, enum cpu_idle_type idle)
{
5946
	int continue_balancing = 1;
5947 5948
	struct rq *rq = cpu_rq(cpu);
	unsigned long interval;
5949
	struct sched_domain *sd;
5950 5951 5952
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
5953 5954
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
5955

5956
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
5957

5958
	rcu_read_lock();
5959
	for_each_domain(cpu, sd) {
5960 5961 5962 5963 5964 5965 5966 5967 5968 5969 5970 5971
		/*
		 * Decay the newidle max times here because this is a regular
		 * visit to all the domains. Decay ~1% per second.
		 */
		if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
			sd->max_newidle_lb_cost =
				(sd->max_newidle_lb_cost * 253) / 256;
			sd->next_decay_max_lb_cost = jiffies + HZ;
			need_decay = 1;
		}
		max_cost += sd->max_newidle_lb_cost;

5972 5973 5974
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

5975 5976 5977 5978 5979 5980 5981 5982 5983 5984 5985
		/*
		 * Stop the load balance at this level. There is another
		 * CPU in our sched group which is doing load balancing more
		 * actively.
		 */
		if (!continue_balancing) {
			if (need_decay)
				continue;
			break;
		}

5986 5987 5988 5989 5990 5991
		interval = sd->balance_interval;
		if (idle != CPU_IDLE)
			interval *= sd->busy_factor;

		/* scale ms to jiffies */
		interval = msecs_to_jiffies(interval);
5992
		interval = clamp(interval, 1UL, max_load_balance_interval);
5993 5994 5995 5996 5997 5998 5999 6000 6001

		need_serialize = sd->flags & SD_SERIALIZE;

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

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
6002
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
6003
				/*
6004
				 * The LBF_DST_PINNED logic could have changed
6005 6006
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
6007
				 */
6008
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
6009 6010 6011 6012 6013 6014 6015 6016 6017 6018
			}
			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;
		}
6019 6020
	}
	if (need_decay) {
6021
		/*
6022 6023
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
6024
		 */
6025 6026
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
6027
	}
6028
	rcu_read_unlock();
6029 6030 6031 6032 6033 6034 6035 6036 6037 6038

	/*
	 * 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;
}

6039
#ifdef CONFIG_NO_HZ_COMMON
6040
/*
6041
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
6042 6043
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
6044 6045 6046 6047 6048 6049
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;

6050 6051 6052
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
6053 6054

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
6055
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
6056 6057 6058 6059 6060 6061 6062
			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.
		 */
6063
		if (need_resched())
6064 6065
			break;

V
Vincent Guittot 已提交
6066 6067 6068 6069 6070 6071
		rq = cpu_rq(balance_cpu);

		raw_spin_lock_irq(&rq->lock);
		update_rq_clock(rq);
		update_idle_cpu_load(rq);
		raw_spin_unlock_irq(&rq->lock);
6072 6073 6074 6075 6076 6077 6078

		rebalance_domains(balance_cpu, CPU_IDLE);

		if (time_after(this_rq->next_balance, rq->next_balance))
			this_rq->next_balance = rq->next_balance;
	}
	nohz.next_balance = this_rq->next_balance;
6079 6080
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
6081 6082 6083
}

/*
6084 6085 6086 6087 6088 6089 6090
 * Current heuristic for kicking the idle load balancer in the presence
 * of an idle cpu is the system.
 *   - This rq has more than one task.
 *   - At any scheduler domain level, this cpu's scheduler group has multiple
 *     busy cpu's exceeding the group's power.
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
6091 6092 6093 6094
 */
static inline int nohz_kick_needed(struct rq *rq, int cpu)
{
	unsigned long now = jiffies;
6095
	struct sched_domain *sd;
6096

6097
	if (unlikely(idle_cpu(cpu)))
6098 6099
		return 0;

6100 6101 6102 6103
       /*
	* We may be recently in ticked or tickless idle mode. At the first
	* busy tick after returning from idle, we will update the busy stats.
	*/
6104
	set_cpu_sd_state_busy();
6105
	nohz_balance_exit_idle(cpu);
6106 6107 6108 6109 6110 6111 6112

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
		return 0;
6113 6114

	if (time_before(now, nohz.next_balance))
6115 6116
		return 0;

6117 6118
	if (rq->nr_running >= 2)
		goto need_kick;
6119

6120
	rcu_read_lock();
6121 6122 6123 6124
	for_each_domain(cpu, sd) {
		struct sched_group *sg = sd->groups;
		struct sched_group_power *sgp = sg->sgp;
		int nr_busy = atomic_read(&sgp->nr_busy_cpus);
6125

6126
		if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1)
6127
			goto need_kick_unlock;
6128 6129 6130 6131

		if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight
		    && (cpumask_first_and(nohz.idle_cpus_mask,
					  sched_domain_span(sd)) < cpu))
6132
			goto need_kick_unlock;
6133 6134 6135

		if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING)))
			break;
6136
	}
6137
	rcu_read_unlock();
6138
	return 0;
6139 6140 6141

need_kick_unlock:
	rcu_read_unlock();
6142 6143
need_kick:
	return 1;
6144 6145 6146 6147 6148 6149 6150 6151 6152
}
#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).
 */
6153 6154 6155 6156
static void run_rebalance_domains(struct softirq_action *h)
{
	int this_cpu = smp_processor_id();
	struct rq *this_rq = cpu_rq(this_cpu);
6157
	enum cpu_idle_type idle = this_rq->idle_balance ?
6158 6159 6160 6161 6162
						CPU_IDLE : CPU_NOT_IDLE;

	rebalance_domains(this_cpu, idle);

	/*
6163
	 * If this cpu has a pending nohz_balance_kick, then do the
6164 6165 6166
	 * balancing on behalf of the other idle cpus whose ticks are
	 * stopped.
	 */
6167
	nohz_idle_balance(this_cpu, idle);
6168 6169 6170 6171
}

static inline int on_null_domain(int cpu)
{
6172
	return !rcu_dereference_sched(cpu_rq(cpu)->sd);
6173 6174 6175 6176 6177
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
6178
void trigger_load_balance(struct rq *rq, int cpu)
6179 6180 6181 6182 6183
{
	/* 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);
6184
#ifdef CONFIG_NO_HZ_COMMON
6185
	if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
6186 6187
		nohz_balancer_kick(cpu);
#endif
6188 6189
}

6190 6191 6192 6193 6194 6195 6196 6197
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
6198 6199 6200

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
6201 6202
}

6203
#endif /* CONFIG_SMP */
6204

6205 6206 6207
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
6208
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
6209 6210 6211 6212 6213 6214
{
	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
6215
		entity_tick(cfs_rq, se, queued);
6216
	}
6217

6218
	if (numabalancing_enabled)
6219
		task_tick_numa(rq, curr);
6220

6221
	update_rq_runnable_avg(rq, 1);
6222 6223 6224
}

/*
P
Peter Zijlstra 已提交
6225 6226 6227
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
6228
 */
P
Peter Zijlstra 已提交
6229
static void task_fork_fair(struct task_struct *p)
6230
{
6231 6232
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
6233
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
6234 6235 6236
	struct rq *rq = this_rq();
	unsigned long flags;

6237
	raw_spin_lock_irqsave(&rq->lock, flags);
6238

6239 6240
	update_rq_clock(rq);

6241 6242 6243
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

6244 6245 6246 6247 6248 6249 6250 6251 6252
	/*
	 * Not only the cpu but also the task_group of the parent might have
	 * been changed after parent->se.parent,cfs_rq were copied to
	 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
	 * of child point to valid ones.
	 */
	rcu_read_lock();
	__set_task_cpu(p, this_cpu);
	rcu_read_unlock();
6253

6254
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
6255

6256 6257
	if (curr)
		se->vruntime = curr->vruntime;
6258
	place_entity(cfs_rq, se, 1);
6259

P
Peter Zijlstra 已提交
6260
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
6261
		/*
6262 6263 6264
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
6265
		swap(curr->vruntime, se->vruntime);
6266
		resched_task(rq->curr);
6267
	}
6268

6269 6270
	se->vruntime -= cfs_rq->min_vruntime;

6271
	raw_spin_unlock_irqrestore(&rq->lock, flags);
6272 6273
}

6274 6275 6276 6277
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
6278 6279
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
6280
{
P
Peter Zijlstra 已提交
6281 6282 6283
	if (!p->se.on_rq)
		return;

6284 6285 6286 6287 6288
	/*
	 * 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
6289
	if (rq->curr == p) {
6290 6291 6292
		if (p->prio > oldprio)
			resched_task(rq->curr);
	} else
6293
		check_preempt_curr(rq, p, 0);
6294 6295
}

P
Peter Zijlstra 已提交
6296 6297 6298 6299 6300 6301 6302 6303 6304 6305 6306 6307 6308 6309 6310 6311 6312 6313 6314 6315 6316 6317
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;
	}
6318

6319
#ifdef CONFIG_SMP
6320 6321 6322 6323 6324
	/*
	* Remove our load from contribution when we leave sched_fair
	* and ensure we don't carry in an old decay_count if we
	* switch back.
	*/
6325 6326 6327
	if (se->avg.decay_count) {
		__synchronize_entity_decay(se);
		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
6328 6329
	}
#endif
P
Peter Zijlstra 已提交
6330 6331
}

6332 6333 6334
/*
 * We switched to the sched_fair class.
 */
P
Peter Zijlstra 已提交
6335
static void switched_to_fair(struct rq *rq, struct task_struct *p)
6336
{
P
Peter Zijlstra 已提交
6337 6338 6339
	if (!p->se.on_rq)
		return;

6340 6341 6342 6343 6344
	/*
	 * 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
6345
	if (rq->curr == p)
6346 6347
		resched_task(rq->curr);
	else
6348
		check_preempt_curr(rq, p, 0);
6349 6350
}

6351 6352 6353 6354 6355 6356 6357 6358 6359
/* 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;

6360 6361 6362 6363 6364 6365 6366
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);

		set_next_entity(cfs_rq, se);
		/* ensure bandwidth has been allocated on our new cfs_rq */
		account_cfs_rq_runtime(cfs_rq, 0);
	}
6367 6368
}

6369 6370 6371 6372 6373 6374 6375
void init_cfs_rq(struct cfs_rq *cfs_rq)
{
	cfs_rq->tasks_timeline = RB_ROOT;
	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
#ifndef CONFIG_64BIT
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
6376
#ifdef CONFIG_SMP
6377
	atomic64_set(&cfs_rq->decay_counter, 1);
6378
	atomic_long_set(&cfs_rq->removed_load, 0);
6379
#endif
6380 6381
}

P
Peter Zijlstra 已提交
6382
#ifdef CONFIG_FAIR_GROUP_SCHED
6383
static void task_move_group_fair(struct task_struct *p, int on_rq)
P
Peter Zijlstra 已提交
6384
{
6385
	struct cfs_rq *cfs_rq;
6386 6387 6388 6389 6390 6391 6392 6393 6394 6395 6396 6397 6398
	/*
	 * 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.
	 */
6399 6400 6401 6402 6403 6404
	/*
	 * When !on_rq, vruntime of the task has usually NOT been normalized.
	 * But there are some cases where it has already been normalized:
	 *
	 * - Moving a forked child which is waiting for being woken up by
	 *   wake_up_new_task().
6405 6406
	 * - Moving a task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
6407 6408 6409 6410
	 *
	 * To prevent boost or penalty in the new cfs_rq caused by delta
	 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
	 */
6411
	if (!on_rq && (!p->se.sum_exec_runtime || p->state == TASK_WAKING))
6412 6413
		on_rq = 1;

6414 6415 6416
	if (!on_rq)
		p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime;
	set_task_rq(p, task_cpu(p));
6417 6418 6419 6420 6421 6422 6423 6424 6425 6426 6427 6428 6429
	if (!on_rq) {
		cfs_rq = cfs_rq_of(&p->se);
		p->se.vruntime += cfs_rq->min_vruntime;
#ifdef CONFIG_SMP
		/*
		 * migrate_task_rq_fair() will have removed our previous
		 * contribution, but we must synchronize for ongoing future
		 * decay.
		 */
		p->se.avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
		cfs_rq->blocked_load_avg += p->se.avg.load_avg_contrib;
#endif
	}
P
Peter Zijlstra 已提交
6430
}
6431 6432 6433 6434 6435 6436 6437 6438 6439 6440 6441 6442 6443 6444 6445 6446 6447 6448 6449 6450 6451 6452 6453 6454 6455 6456 6457 6458 6459 6460 6461 6462 6463 6464 6465 6466 6467 6468 6469 6470 6471 6472 6473 6474 6475 6476 6477 6478 6479 6480 6481 6482 6483 6484 6485 6486 6487 6488 6489 6490 6491 6492 6493 6494 6495 6496 6497 6498 6499 6500 6501 6502 6503 6504 6505 6506 6507 6508 6509 6510 6511 6512 6513 6514 6515 6516 6517 6518 6519 6520 6521 6522 6523 6524 6525 6526 6527 6528 6529 6530 6531 6532 6533 6534 6535 6536 6537 6538 6539 6540 6541 6542 6543 6544 6545 6546 6547 6548 6549 6550 6551 6552 6553 6554 6555 6556 6557 6558 6559

void free_fair_sched_group(struct task_group *tg)
{
	int i;

	destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));

	for_each_possible_cpu(i) {
		if (tg->cfs_rq)
			kfree(tg->cfs_rq[i]);
		if (tg->se)
			kfree(tg->se[i]);
	}

	kfree(tg->cfs_rq);
	kfree(tg->se);
}

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
	struct cfs_rq *cfs_rq;
	struct sched_entity *se;
	int i;

	tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
	if (!tg->cfs_rq)
		goto err;
	tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
	if (!tg->se)
		goto err;

	tg->shares = NICE_0_LOAD;

	init_cfs_bandwidth(tg_cfs_bandwidth(tg));

	for_each_possible_cpu(i) {
		cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
				      GFP_KERNEL, cpu_to_node(i));
		if (!cfs_rq)
			goto err;

		se = kzalloc_node(sizeof(struct sched_entity),
				  GFP_KERNEL, cpu_to_node(i));
		if (!se)
			goto err_free_rq;

		init_cfs_rq(cfs_rq);
		init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

void unregister_fair_sched_group(struct task_group *tg, int cpu)
{
	struct rq *rq = cpu_rq(cpu);
	unsigned long flags;

	/*
	* Only empty task groups can be destroyed; so we can speculatively
	* check on_list without danger of it being re-added.
	*/
	if (!tg->cfs_rq[cpu]->on_list)
		return;

	raw_spin_lock_irqsave(&rq->lock, flags);
	list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
	raw_spin_unlock_irqrestore(&rq->lock, flags);
}

void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
			struct sched_entity *se, int cpu,
			struct sched_entity *parent)
{
	struct rq *rq = cpu_rq(cpu);

	cfs_rq->tg = tg;
	cfs_rq->rq = rq;
	init_cfs_rq_runtime(cfs_rq);

	tg->cfs_rq[cpu] = cfs_rq;
	tg->se[cpu] = se;

	/* se could be NULL for root_task_group */
	if (!se)
		return;

	if (!parent)
		se->cfs_rq = &rq->cfs;
	else
		se->cfs_rq = parent->my_q;

	se->my_q = cfs_rq;
	update_load_set(&se->load, 0);
	se->parent = parent;
}

static DEFINE_MUTEX(shares_mutex);

int sched_group_set_shares(struct task_group *tg, unsigned long shares)
{
	int i;
	unsigned long flags;

	/*
	 * We can't change the weight of the root cgroup.
	 */
	if (!tg->se[0])
		return -EINVAL;

	shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));

	mutex_lock(&shares_mutex);
	if (tg->shares == shares)
		goto done;

	tg->shares = shares;
	for_each_possible_cpu(i) {
		struct rq *rq = cpu_rq(i);
		struct sched_entity *se;

		se = tg->se[i];
		/* Propagate contribution to hierarchy */
		raw_spin_lock_irqsave(&rq->lock, flags);
6560 6561 6562

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
6563
		for_each_sched_entity(se)
6564 6565 6566 6567 6568 6569 6570 6571 6572 6573 6574 6575 6576 6577 6578 6579 6580 6581 6582 6583 6584
			update_cfs_shares(group_cfs_rq(se));
		raw_spin_unlock_irqrestore(&rq->lock, flags);
	}

done:
	mutex_unlock(&shares_mutex);
	return 0;
}
#else /* CONFIG_FAIR_GROUP_SCHED */

void free_fair_sched_group(struct task_group *tg) { }

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
	return 1;
}

void unregister_fair_sched_group(struct task_group *tg, int cpu) { }

#endif /* CONFIG_FAIR_GROUP_SCHED */

P
Peter Zijlstra 已提交
6585

6586
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
6587 6588 6589 6590 6591 6592 6593 6594 6595
{
	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)
6596
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
6597 6598 6599 6600

	return rr_interval;
}

6601 6602 6603
/*
 * All the scheduling class methods:
 */
6604
const struct sched_class fair_sched_class = {
6605
	.next			= &idle_sched_class,
6606 6607 6608
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
6609
	.yield_to_task		= yield_to_task_fair,
6610

I
Ingo Molnar 已提交
6611
	.check_preempt_curr	= check_preempt_wakeup,
6612 6613 6614 6615

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

6616
#ifdef CONFIG_SMP
L
Li Zefan 已提交
6617
	.select_task_rq		= select_task_rq_fair,
6618
	.migrate_task_rq	= migrate_task_rq_fair,
6619

6620 6621
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
6622 6623

	.task_waking		= task_waking_fair,
6624
#endif
6625

6626
	.set_curr_task          = set_curr_task_fair,
6627
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
6628
	.task_fork		= task_fork_fair,
6629 6630

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
6631
	.switched_from		= switched_from_fair,
6632
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
6633

6634 6635
	.get_rr_interval	= get_rr_interval_fair,

P
Peter Zijlstra 已提交
6636
#ifdef CONFIG_FAIR_GROUP_SCHED
6637
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
6638
#endif
6639 6640 6641
};

#ifdef CONFIG_SCHED_DEBUG
6642
void print_cfs_stats(struct seq_file *m, int cpu)
6643 6644 6645
{
	struct cfs_rq *cfs_rq;

6646
	rcu_read_lock();
6647
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
6648
		print_cfs_rq(m, cpu, cfs_rq);
6649
	rcu_read_unlock();
6650 6651
}
#endif
6652 6653 6654 6655 6656 6657

__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

6658
#ifdef CONFIG_NO_HZ_COMMON
6659
	nohz.next_balance = jiffies;
6660
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
6661
	cpu_notifier(sched_ilb_notifier, 0);
6662 6663 6664 6665
#endif
#endif /* SMP */

}