fair.c 228.1 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
 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
20
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
21 22
 */

23
#include <linux/sched.h>
24
#include <linux/latencytop.h>
25
#include <linux/cpumask.h>
26
#include <linux/cpuidle.h>
27 28 29
#include <linux/slab.h>
#include <linux/profile.h>
#include <linux/interrupt.h>
30
#include <linux/mempolicy.h>
31
#include <linux/migrate.h>
32
#include <linux/task_work.h>
33 34 35 36

#include <trace/events/sched.h>

#include "sched.h"
A
Arjan van de Ven 已提交
37

38
/*
39
 * Targeted preemption latency for CPU-bound tasks:
40
 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
41
 *
42
 * NOTE: this latency value is not the same as the concept of
I
Ingo Molnar 已提交
43 44 45
 * 'timeslice length' - timeslices in CFS are of variable length
 * and have no persistent notion like in traditional, time-slice
 * based scheduling concepts.
46
 *
I
Ingo Molnar 已提交
47 48
 * (to see the precise effective timeslice length of your workload,
 *  run vmstat and monitor the context-switches (cs) field)
49
 */
50 51
unsigned int sysctl_sched_latency = 6000000ULL;
unsigned int normalized_sysctl_sched_latency = 6000000ULL;
52

53 54 55 56 57 58 59 60 61 62 63 64
/*
 * 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;

65
/*
66
 * Minimal preemption granularity for CPU-bound tasks:
67
 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
68
 */
69 70
unsigned int sysctl_sched_min_granularity = 750000ULL;
unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
71 72

/*
73 74
 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
 */
75
static unsigned int sched_nr_latency = 8;
76 77

/*
78
 * After fork, child runs first. If set to 0 (default) then
79
 * parent will (try to) run first.
80
 */
81
unsigned int sysctl_sched_child_runs_first __read_mostly;
82 83 84

/*
 * SCHED_OTHER wake-up granularity.
85
 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
86 87 88 89 90
 *
 * This option delays the preemption effects of decoupled workloads
 * and reduces their over-scheduling. Synchronous workloads will still
 * have immediate wakeup/sleep latencies.
 */
91
unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
92
unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
93

94 95
const_debug unsigned int sysctl_sched_migration_cost = 500000UL;

96 97 98 99 100 101 102
/*
 * The exponential sliding  window over which load is averaged for shares
 * distribution.
 * (default: 10msec)
 */
unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;

103 104 105 106 107 108 109 110 111 112 113 114 115 116
#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

117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134
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;
}

135 136 137 138 139 140 141 142 143
/*
 * 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:
 */
144
static unsigned int get_update_sysctl_factor(void)
145
{
146
	unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
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
	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();
}

182
#define WMULT_CONST	(~0U)
183 184
#define WMULT_SHIFT	32

185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200
static void __update_inv_weight(struct load_weight *lw)
{
	unsigned long w;

	if (likely(lw->inv_weight))
		return;

	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;
}
201 202

/*
203 204 205 206
 * delta_exec * weight / lw.weight
 *   OR
 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
 *
207
 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
208 209 210 211 212
 * we're guaranteed shift stays positive because inv_weight is guaranteed to
 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
 *
 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
 * weight/lw.weight <= 1, and therefore our shift will also be positive.
213
 */
214
static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
215
{
216 217
	u64 fact = scale_load_down(weight);
	int shift = WMULT_SHIFT;
218

219
	__update_inv_weight(lw);
220

221 222 223 224 225
	if (unlikely(fact >> 32)) {
		while (fact >> 32) {
			fact >>= 1;
			shift--;
		}
226 227
	}

228 229
	/* hint to use a 32x32->64 mul */
	fact = (u64)(u32)fact * lw->inv_weight;
230

231 232 233 234
	while (fact >> 32) {
		fact >>= 1;
		shift--;
	}
235

236
	return mul_u64_u32_shr(delta_exec, fact, shift);
237 238 239 240
}


const struct sched_class fair_sched_class;
241

242 243 244 245
/**************************************************************
 * CFS operations on generic schedulable entities:
 */

246
#ifdef CONFIG_FAIR_GROUP_SCHED
247

248
/* cpu runqueue to which this cfs_rq is attached */
249 250
static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
251
	return cfs_rq->rq;
252 253
}

254 255
/* An entity is a task if it doesn't "own" a runqueue */
#define entity_is_task(se)	(!se->my_q)
256

257 258 259 260 261 262 263 264
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
265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285
/* 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;
}

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
		}
303 304 305 306 307 308 309 310 311 312 313 314 315

		cfs_rq->on_list = 1;
	}
}

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

P
Peter Zijlstra 已提交
316 317 318 319 320
/* 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 ? */
P
Peter Zijlstra 已提交
321
static inline struct cfs_rq *
P
Peter Zijlstra 已提交
322 323 324
is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
	if (se->cfs_rq == pse->cfs_rq)
P
Peter Zijlstra 已提交
325
		return se->cfs_rq;
P
Peter Zijlstra 已提交
326

P
Peter Zijlstra 已提交
327
	return NULL;
P
Peter Zijlstra 已提交
328 329 330 331 332 333 334
}

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

335 336 337 338 339 340 341 342 343 344 345 346 347
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 */
P
Peter Zijlstra 已提交
348 349
	se_depth = (*se)->depth;
	pse_depth = (*pse)->depth;
350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366

	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);
	}
}

367 368 369 370 371 372
#else	/* !CONFIG_FAIR_GROUP_SCHED */

static inline struct task_struct *task_of(struct sched_entity *se)
{
	return container_of(se, struct task_struct, se);
}
373

374 375 376
static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
	return container_of(cfs_rq, struct rq, cfs);
377 378 379 380
}

#define entity_is_task(se)	1

P
Peter Zijlstra 已提交
381 382
#define for_each_sched_entity(se) \
		for (; se; se = NULL)
383

P
Peter Zijlstra 已提交
384
static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
385
{
P
Peter Zijlstra 已提交
386
	return &task_rq(p)->cfs;
387 388
}

P
Peter Zijlstra 已提交
389 390 391 392 393 394 395 396 397 398 399 400 401 402
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;
}

403 404 405 406 407 408 409 410
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
411 412 413 414 415 416 417 418
#define for_each_leaf_cfs_rq(rq, cfs_rq) \
		for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)

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

419 420 421 422 423
static inline void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
}

P
Peter Zijlstra 已提交
424 425
#endif	/* CONFIG_FAIR_GROUP_SCHED */

426
static __always_inline
427
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
428 429 430 431 432

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

433
static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
434
{
435
	s64 delta = (s64)(vruntime - max_vruntime);
436
	if (delta > 0)
437
		max_vruntime = vruntime;
438

439
	return max_vruntime;
440 441
}

442
static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
P
Peter Zijlstra 已提交
443 444 445 446 447 448 449 450
{
	s64 delta = (s64)(vruntime - min_vruntime);
	if (delta < 0)
		min_vruntime = vruntime;

	return min_vruntime;
}

451 452 453 454 455 456
static inline int entity_before(struct sched_entity *a,
				struct sched_entity *b)
{
	return (s64)(a->vruntime - b->vruntime) < 0;
}

457 458 459 460 461 462 463 464 465 466 467 468
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
469
		if (!cfs_rq->curr)
470 471 472 473 474
			vruntime = se->vruntime;
		else
			vruntime = min_vruntime(vruntime, se->vruntime);
	}

475
	/* ensure we never gain time by being placed backwards. */
476
	cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
477 478 479 480
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
481 482
}

483 484 485
/*
 * Enqueue an entity into the rb-tree:
 */
486
static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502
{
	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.
		 */
503
		if (entity_before(se, entry)) {
504 505 506 507 508 509 510 511 512 513 514
			link = &parent->rb_left;
		} else {
			link = &parent->rb_right;
			leftmost = 0;
		}
	}

	/*
	 * Maintain a cache of leftmost tree entries (it is frequently
	 * used):
	 */
515
	if (leftmost)
I
Ingo Molnar 已提交
516
		cfs_rq->rb_leftmost = &se->run_node;
517 518 519 520 521

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

522
static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
523
{
P
Peter Zijlstra 已提交
524 525 526 527 528 529
	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
530

531 532 533
	rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
}

534
struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
535
{
536 537 538 539 540 541
	struct rb_node *left = cfs_rq->rb_leftmost;

	if (!left)
		return NULL;

	return rb_entry(left, struct sched_entity, run_node);
542 543
}

544 545 546 547 548 549 550 551 552 553 554
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
555
struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
556
{
557
	struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
558

559 560
	if (!last)
		return NULL;
561 562

	return rb_entry(last, struct sched_entity, run_node);
563 564
}

565 566 567 568
/**************************************************************
 * Scheduling class statistics methods:
 */

569
int sched_proc_update_handler(struct ctl_table *table, int write,
570
		void __user *buffer, size_t *lenp,
571 572
		loff_t *ppos)
{
573
	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
574
	unsigned int factor = get_update_sysctl_factor();
575 576 577 578 579 580 581

	if (ret || !write)
		return ret;

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

582 583 584 585 586 587 588
#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

589 590 591
	return 0;
}
#endif
592

593
/*
594
 * delta /= w
595
 */
596
static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
597
{
598
	if (unlikely(se->load.weight != NICE_0_LOAD))
599
		delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
600 601 602 603

	return delta;
}

604 605 606
/*
 * The idea is to set a period in which each task runs once.
 *
607
 * When there are too many tasks (sched_nr_latency) we have to stretch
608 609 610 611
 * this period because otherwise the slices get too small.
 *
 * p = (nr <= nl) ? l : l*nr/nl
 */
612 613
static u64 __sched_period(unsigned long nr_running)
{
614 615 616 617
	if (unlikely(nr_running > sched_nr_latency))
		return nr_running * sysctl_sched_min_granularity;
	else
		return sysctl_sched_latency;
618 619
}

620 621 622 623
/*
 * We calculate the wall-time slice from the period by taking a part
 * proportional to the weight.
 *
624
 * s = p*P[w/rw]
625
 */
P
Peter Zijlstra 已提交
626
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
627
{
M
Mike Galbraith 已提交
628
	u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
629

M
Mike Galbraith 已提交
630
	for_each_sched_entity(se) {
L
Lin Ming 已提交
631
		struct load_weight *load;
632
		struct load_weight lw;
L
Lin Ming 已提交
633 634 635

		cfs_rq = cfs_rq_of(se);
		load = &cfs_rq->load;
636

M
Mike Galbraith 已提交
637
		if (unlikely(!se->on_rq)) {
638
			lw = cfs_rq->load;
M
Mike Galbraith 已提交
639 640 641 642

			update_load_add(&lw, se->load.weight);
			load = &lw;
		}
643
		slice = __calc_delta(slice, se->load.weight, load);
M
Mike Galbraith 已提交
644 645
	}
	return slice;
646 647
}

648
/*
A
Andrei Epure 已提交
649
 * We calculate the vruntime slice of a to-be-inserted task.
650
 *
651
 * vs = s/w
652
 */
653
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
P
Peter Zijlstra 已提交
654
{
655
	return calc_delta_fair(sched_slice(cfs_rq, se), se);
656 657
}

658
#ifdef CONFIG_SMP
659
static int select_idle_sibling(struct task_struct *p, int cpu);
660 661
static unsigned long task_h_load(struct task_struct *p);

662 663
/*
 * We choose a half-life close to 1 scheduling period.
664 665
 * Note: The tables runnable_avg_yN_inv and runnable_avg_yN_sum are
 * dependent on this value.
666 667 668
 */
#define LOAD_AVG_PERIOD 32
#define LOAD_AVG_MAX 47742 /* maximum possible load avg */
669
#define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_AVG_MAX */
670

671 672
/* Give new sched_entity start runnable values to heavy its load in infant time */
void init_entity_runnable_average(struct sched_entity *se)
673
{
674
	struct sched_avg *sa = &se->avg;
675

676 677 678 679 680 681 682
	sa->last_update_time = 0;
	/*
	 * sched_avg's period_contrib should be strictly less then 1024, so
	 * we give it 1023 to make sure it is almost a period (1024us), and
	 * will definitely be update (after enqueue).
	 */
	sa->period_contrib = 1023;
683
	sa->load_avg = scale_load_down(se->load.weight);
684
	sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
685 686 687 688 689
	/*
	 * At this point, util_avg won't be used in select_task_rq_fair anyway
	 */
	sa->util_avg = 0;
	sa->util_sum = 0;
690
	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
691
}
692

693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721
/*
 * With new tasks being created, their initial util_avgs are extrapolated
 * based on the cfs_rq's current util_avg:
 *
 *   util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
 *
 * However, in many cases, the above util_avg does not give a desired
 * value. Moreover, the sum of the util_avgs may be divergent, such
 * as when the series is a harmonic series.
 *
 * To solve this problem, we also cap the util_avg of successive tasks to
 * only 1/2 of the left utilization budget:
 *
 *   util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n
 *
 * where n denotes the nth task.
 *
 * For example, a simplest series from the beginning would be like:
 *
 *  task  util_avg: 512, 256, 128,  64,  32,   16,    8, ...
 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
 *
 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
 * if util_avg > util_avg_cap.
 */
void post_init_entity_util_avg(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	struct sched_avg *sa = &se->avg;
722
	long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2;
723 724 725 726 727 728 729 730 731 732 733 734 735 736 737

	if (cap > 0) {
		if (cfs_rq->avg.util_avg != 0) {
			sa->util_avg  = cfs_rq->avg.util_avg * se->load.weight;
			sa->util_avg /= (cfs_rq->avg.load_avg + 1);

			if (sa->util_avg > cap)
				sa->util_avg = cap;
		} else {
			sa->util_avg = cap;
		}
		sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
	}
}

738 739
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq);
static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq);
740
#else
741
void init_entity_runnable_average(struct sched_entity *se)
742 743
{
}
744 745 746
void post_init_entity_util_avg(struct sched_entity *se)
{
}
747 748
#endif

749
/*
750
 * Update the current task's runtime statistics.
751
 */
752
static void update_curr(struct cfs_rq *cfs_rq)
753
{
754
	struct sched_entity *curr = cfs_rq->curr;
755
	u64 now = rq_clock_task(rq_of(cfs_rq));
756
	u64 delta_exec;
757 758 759 760

	if (unlikely(!curr))
		return;

761 762
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
P
Peter Zijlstra 已提交
763
		return;
764

I
Ingo Molnar 已提交
765
	curr->exec_start = now;
766

767 768 769 770 771 772 773 774 775
	schedstat_set(curr->statistics.exec_max,
		      max(delta_exec, curr->statistics.exec_max));

	curr->sum_exec_runtime += delta_exec;
	schedstat_add(cfs_rq, exec_clock, delta_exec);

	curr->vruntime += calc_delta_fair(delta_exec, curr);
	update_min_vruntime(cfs_rq);

776 777 778
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

779
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
780
		cpuacct_charge(curtask, delta_exec);
781
		account_group_exec_runtime(curtask, delta_exec);
782
	}
783 784

	account_cfs_rq_runtime(cfs_rq, delta_exec);
785 786
}

787 788 789 790 791
static void update_curr_fair(struct rq *rq)
{
	update_curr(cfs_rq_of(&rq->curr->se));
}

792
#ifdef CONFIG_SCHEDSTATS
793
static inline void
794
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
795
{
796 797 798 799 800 801 802
	u64 wait_start = rq_clock(rq_of(cfs_rq));

	if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
	    likely(wait_start > se->statistics.wait_start))
		wait_start -= se->statistics.wait_start;

	se->statistics.wait_start = wait_start;
803 804
}

805 806 807 808
static void
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *p;
809 810 811
	u64 delta;

	delta = rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start;
812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832

	if (entity_is_task(se)) {
		p = task_of(se);
		if (task_on_rq_migrating(p)) {
			/*
			 * Preserve migrating task's wait time so wait_start
			 * time stamp can be adjusted to accumulate wait time
			 * prior to migration.
			 */
			se->statistics.wait_start = delta;
			return;
		}
		trace_sched_stat_wait(p, delta);
	}

	se->statistics.wait_max = max(se->statistics.wait_max, delta);
	se->statistics.wait_count++;
	se->statistics.wait_sum += delta;
	se->statistics.wait_start = 0;
}

833 834 835
/*
 * Task is being enqueued - update stats:
 */
836 837
static inline void
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
838 839 840 841 842
{
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
843
	if (se != cfs_rq->curr)
844
		update_stats_wait_start(cfs_rq, se);
845 846 847
}

static inline void
848
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
849 850 851 852 853
{
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
854
	if (se != cfs_rq->curr)
855
		update_stats_wait_end(cfs_rq, se);
856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887

	if (flags & DEQUEUE_SLEEP) {
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
				se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
			if (tsk->state & TASK_UNINTERRUPTIBLE)
				se->statistics.block_start = rq_clock(rq_of(cfs_rq));
		}
	}

}
#else
static inline void
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
}

static inline void
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
}

static inline void
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
}

static inline void
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
888
}
889
#endif
890 891 892 893 894

/*
 * We are picking a new current task - update its stats:
 */
static inline void
895
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
896 897 898 899
{
	/*
	 * We are starting a new run period:
	 */
900
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
901 902 903 904 905 906
}

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

907 908
#ifdef CONFIG_NUMA_BALANCING
/*
909 910 911
 * 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.
912
 */
913 914
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
915 916 917

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
918

919 920 921
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945
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)
{
946
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
947 948 949
	unsigned int scan, floor;
	unsigned int windows = 1;

950 951
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967
	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);
}

968 969 970 971 972 973 974 975 976 977 978 979
static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
{
	rq->nr_numa_running += (p->numa_preferred_nid != -1);
	rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
}

static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
{
	rq->nr_numa_running -= (p->numa_preferred_nid != -1);
	rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
}

980 981 982 983 984
struct numa_group {
	atomic_t refcount;

	spinlock_t lock; /* nr_tasks, tasks */
	int nr_tasks;
985
	pid_t gid;
986
	int active_nodes;
987 988

	struct rcu_head rcu;
989
	unsigned long total_faults;
990
	unsigned long max_faults_cpu;
991 992 993 994 995
	/*
	 * Faults_cpu is used to decide whether memory should move
	 * towards the CPU. As a consequence, these stats are weighted
	 * more by CPU use than by memory faults.
	 */
996
	unsigned long *faults_cpu;
997
	unsigned long faults[0];
998 999
};

1000 1001 1002 1003 1004 1005 1006 1007 1008
/* Shared or private faults. */
#define NR_NUMA_HINT_FAULT_TYPES 2

/* Memory and CPU locality */
#define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)

/* Averaged statistics, and temporary buffers. */
#define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)

1009 1010 1011 1012 1013
pid_t task_numa_group_id(struct task_struct *p)
{
	return p->numa_group ? p->numa_group->gid : 0;
}

1014 1015 1016 1017 1018 1019 1020
/*
 * The averaged statistics, shared & private, memory & cpu,
 * occupy the first half of the array. The second half of the
 * array is for current counters, which are averaged into the
 * first set by task_numa_placement.
 */
static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
1021
{
1022
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1023 1024 1025 1026
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
1027
	if (!p->numa_faults)
1028 1029
		return 0;

1030 1031
	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1032 1033
}

1034 1035 1036 1037 1038
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
	if (!p->numa_group)
		return 0;

1039 1040
	return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1041 1042
}

1043 1044
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
1045 1046
	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1047 1048
}

1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060
/*
 * A node triggering more than 1/3 as many NUMA faults as the maximum is
 * considered part of a numa group's pseudo-interleaving set. Migrations
 * between these nodes are slowed down, to allow things to settle down.
 */
#define ACTIVE_NODE_FRACTION 3

static bool numa_is_active_node(int nid, struct numa_group *ng)
{
	return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
}

1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125
/* Handle placement on systems where not all nodes are directly connected. */
static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
					int maxdist, bool task)
{
	unsigned long score = 0;
	int node;

	/*
	 * All nodes are directly connected, and the same distance
	 * from each other. No need for fancy placement algorithms.
	 */
	if (sched_numa_topology_type == NUMA_DIRECT)
		return 0;

	/*
	 * This code is called for each node, introducing N^2 complexity,
	 * which should be ok given the number of nodes rarely exceeds 8.
	 */
	for_each_online_node(node) {
		unsigned long faults;
		int dist = node_distance(nid, node);

		/*
		 * The furthest away nodes in the system are not interesting
		 * for placement; nid was already counted.
		 */
		if (dist == sched_max_numa_distance || node == nid)
			continue;

		/*
		 * On systems with a backplane NUMA topology, compare groups
		 * of nodes, and move tasks towards the group with the most
		 * memory accesses. When comparing two nodes at distance
		 * "hoplimit", only nodes closer by than "hoplimit" are part
		 * of each group. Skip other nodes.
		 */
		if (sched_numa_topology_type == NUMA_BACKPLANE &&
					dist > maxdist)
			continue;

		/* Add up the faults from nearby nodes. */
		if (task)
			faults = task_faults(p, node);
		else
			faults = group_faults(p, node);

		/*
		 * On systems with a glueless mesh NUMA topology, there are
		 * no fixed "groups of nodes". Instead, nodes that are not
		 * directly connected bounce traffic through intermediate
		 * nodes; a numa_group can occupy any set of nodes.
		 * The further away a node is, the less the faults count.
		 * This seems to result in good task placement.
		 */
		if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
			faults *= (sched_max_numa_distance - dist);
			faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
		}

		score += faults;
	}

	return score;
}

1126 1127 1128 1129 1130 1131
/*
 * These return the fraction of accesses done by a particular task, or
 * task group, on a particular numa node.  The group weight is given a
 * larger multiplier, in order to group tasks together that are almost
 * evenly spread out between numa nodes.
 */
1132 1133
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1134
{
1135
	unsigned long faults, total_faults;
1136

1137
	if (!p->numa_faults)
1138 1139 1140 1141 1142 1143 1144
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

1145
	faults = task_faults(p, nid);
1146 1147
	faults += score_nearby_nodes(p, nid, dist, true);

1148
	return 1000 * faults / total_faults;
1149 1150
}

1151 1152
static inline unsigned long group_weight(struct task_struct *p, int nid,
					 int dist)
1153
{
1154 1155 1156 1157 1158 1159 1160 1161
	unsigned long faults, total_faults;

	if (!p->numa_group)
		return 0;

	total_faults = p->numa_group->total_faults;

	if (!total_faults)
1162 1163
		return 0;

1164
	faults = group_faults(p, nid);
1165 1166
	faults += score_nearby_nodes(p, nid, dist, false);

1167
	return 1000 * faults / total_faults;
1168 1169
}

1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 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 1206 1207 1208 1209
bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
				int src_nid, int dst_cpu)
{
	struct numa_group *ng = p->numa_group;
	int dst_nid = cpu_to_node(dst_cpu);
	int last_cpupid, this_cpupid;

	this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);

	/*
	 * Multi-stage node selection is used in conjunction with a periodic
	 * migration fault to build a temporal task<->page relation. By using
	 * a two-stage filter we remove short/unlikely relations.
	 *
	 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
	 * a task's usage of a particular page (n_p) per total usage of this
	 * page (n_t) (in a given time-span) to a probability.
	 *
	 * Our periodic faults will sample this probability and getting the
	 * same result twice in a row, given these samples are fully
	 * independent, is then given by P(n)^2, provided our sample period
	 * is sufficiently short compared to the usage pattern.
	 *
	 * This quadric squishes small probabilities, making it less likely we
	 * act on an unlikely task<->page relation.
	 */
	last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
	if (!cpupid_pid_unset(last_cpupid) &&
				cpupid_to_nid(last_cpupid) != dst_nid)
		return false;

	/* Always allow migrate on private faults */
	if (cpupid_match_pid(p, last_cpupid))
		return true;

	/* A shared fault, but p->numa_group has not been set up yet. */
	if (!ng)
		return true;

	/*
1210 1211
	 * Destination node is much more heavily used than the source
	 * node? Allow migration.
1212
	 */
1213 1214
	if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
					ACTIVE_NODE_FRACTION)
1215 1216 1217
		return true;

	/*
1218 1219 1220 1221 1222 1223
	 * Distribute memory according to CPU & memory use on each node,
	 * with 3/4 hysteresis to avoid unnecessary memory migrations:
	 *
	 * faults_cpu(dst)   3   faults_cpu(src)
	 * --------------- * - > ---------------
	 * faults_mem(dst)   4   faults_mem(src)
1224
	 */
1225 1226
	return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
	       group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
1227 1228
}

1229
static unsigned long weighted_cpuload(const int cpu);
1230 1231
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1232
static unsigned long capacity_of(int cpu);
1233 1234
static long effective_load(struct task_group *tg, int cpu, long wl, long wg);

1235
/* Cached statistics for all CPUs within a node */
1236
struct numa_stats {
1237
	unsigned long nr_running;
1238
	unsigned long load;
1239 1240

	/* Total compute capacity of CPUs on a node */
1241
	unsigned long compute_capacity;
1242 1243

	/* Approximate capacity in terms of runnable tasks on a node */
1244
	unsigned long task_capacity;
1245
	int has_free_capacity;
1246
};
1247

1248 1249 1250 1251 1252
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1253 1254
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1255 1256 1257 1258 1259 1260 1261

	memset(ns, 0, sizeof(*ns));
	for_each_cpu(cpu, cpumask_of_node(nid)) {
		struct rq *rq = cpu_rq(cpu);

		ns->nr_running += rq->nr_running;
		ns->load += weighted_cpuload(cpu);
1262
		ns->compute_capacity += capacity_of(cpu);
1263 1264

		cpus++;
1265 1266
	}

1267 1268 1269 1270 1271
	/*
	 * If we raced with hotplug and there are no CPUs left in our mask
	 * the @ns structure is NULL'ed and task_numa_compare() will
	 * not find this node attractive.
	 *
1272 1273
	 * We'll either bail at !has_free_capacity, or we'll detect a huge
	 * imbalance and bail there.
1274 1275 1276 1277
	 */
	if (!cpus)
		return;

1278 1279 1280 1281 1282 1283
	/* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
	smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
	capacity = cpus / smt; /* cores */

	ns->task_capacity = min_t(unsigned, capacity,
		DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1284
	ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1285 1286
}

1287 1288
struct task_numa_env {
	struct task_struct *p;
1289

1290 1291
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1292

1293
	struct numa_stats src_stats, dst_stats;
1294

1295
	int imbalance_pct;
1296
	int dist;
1297 1298 1299

	struct task_struct *best_task;
	long best_imp;
1300 1301 1302
	int best_cpu;
};

1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313
static void task_numa_assign(struct task_numa_env *env,
			     struct task_struct *p, long imp)
{
	if (env->best_task)
		put_task_struct(env->best_task);

	env->best_task = p;
	env->best_imp = imp;
	env->best_cpu = env->dst_cpu;
}

1314
static bool load_too_imbalanced(long src_load, long dst_load,
1315 1316
				struct task_numa_env *env)
{
1317 1318
	long imb, old_imb;
	long orig_src_load, orig_dst_load;
1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329
	long src_capacity, dst_capacity;

	/*
	 * The load is corrected for the CPU capacity available on each node.
	 *
	 * src_load        dst_load
	 * ------------ vs ---------
	 * src_capacity    dst_capacity
	 */
	src_capacity = env->src_stats.compute_capacity;
	dst_capacity = env->dst_stats.compute_capacity;
1330 1331

	/* We care about the slope of the imbalance, not the direction. */
1332 1333
	if (dst_load < src_load)
		swap(dst_load, src_load);
1334 1335

	/* Is the difference below the threshold? */
1336 1337
	imb = dst_load * src_capacity * 100 -
	      src_load * dst_capacity * env->imbalance_pct;
1338 1339 1340 1341 1342
	if (imb <= 0)
		return false;

	/*
	 * The imbalance is above the allowed threshold.
1343
	 * Compare it with the old imbalance.
1344
	 */
1345
	orig_src_load = env->src_stats.load;
1346
	orig_dst_load = env->dst_stats.load;
1347

1348 1349
	if (orig_dst_load < orig_src_load)
		swap(orig_dst_load, orig_src_load);
1350

1351 1352 1353 1354 1355
	old_imb = orig_dst_load * src_capacity * 100 -
		  orig_src_load * dst_capacity * env->imbalance_pct;

	/* Would this change make things worse? */
	return (imb > old_imb);
1356 1357
}

1358 1359 1360 1361 1362 1363
/*
 * This checks if the overall compute and NUMA accesses of the system would
 * be improved if the source tasks was migrated to the target dst_cpu taking
 * into account that it might be best if task running on the dst_cpu should
 * be exchanged with the source task
 */
1364 1365
static void task_numa_compare(struct task_numa_env *env,
			      long taskimp, long groupimp)
1366 1367 1368 1369
{
	struct rq *src_rq = cpu_rq(env->src_cpu);
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
1370
	long src_load, dst_load;
1371
	long load;
1372
	long imp = env->p->numa_group ? groupimp : taskimp;
1373
	long moveimp = imp;
1374
	int dist = env->dist;
1375
	bool assigned = false;
1376 1377

	rcu_read_lock();
1378 1379 1380 1381

	raw_spin_lock_irq(&dst_rq->lock);
	cur = dst_rq->curr;
	/*
1382
	 * No need to move the exiting task or idle task.
1383 1384
	 */
	if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1385
		cur = NULL;
1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398
	else {
		/*
		 * The task_struct must be protected here to protect the
		 * p->numa_faults access in the task_weight since the
		 * numa_faults could already be freed in the following path:
		 * finish_task_switch()
		 *     --> put_task_struct()
		 *         --> __put_task_struct()
		 *             --> task_numa_free()
		 */
		get_task_struct(cur);
	}

1399
	raw_spin_unlock_irq(&dst_rq->lock);
1400

1401 1402 1403 1404 1405 1406 1407
	/*
	 * Because we have preemption enabled we can get migrated around and
	 * end try selecting ourselves (current == env->p) as a swap candidate.
	 */
	if (cur == env->p)
		goto unlock;

1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419
	/*
	 * "imp" is the fault differential for the source task between the
	 * source and destination node. Calculate the total differential for
	 * the source task and potential destination task. The more negative
	 * the value is, the more rmeote accesses that would be expected to
	 * be incurred if the tasks were swapped.
	 */
	if (cur) {
		/* Skip this swap candidate if cannot move to the source cpu */
		if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
			goto unlock;

1420 1421
		/*
		 * If dst and source tasks are in the same NUMA group, or not
1422
		 * in any group then look only at task weights.
1423
		 */
1424
		if (cur->numa_group == env->p->numa_group) {
1425 1426
			imp = taskimp + task_weight(cur, env->src_nid, dist) -
			      task_weight(cur, env->dst_nid, dist);
1427 1428 1429 1430 1431 1432
			/*
			 * Add some hysteresis to prevent swapping the
			 * tasks within a group over tiny differences.
			 */
			if (cur->numa_group)
				imp -= imp/16;
1433
		} else {
1434 1435 1436 1437 1438 1439
			/*
			 * Compare the group weights. If a task is all by
			 * itself (not part of a group), use the task weight
			 * instead.
			 */
			if (cur->numa_group)
1440 1441
				imp += group_weight(cur, env->src_nid, dist) -
				       group_weight(cur, env->dst_nid, dist);
1442
			else
1443 1444
				imp += task_weight(cur, env->src_nid, dist) -
				       task_weight(cur, env->dst_nid, dist);
1445
		}
1446 1447
	}

1448
	if (imp <= env->best_imp && moveimp <= env->best_imp)
1449 1450 1451 1452
		goto unlock;

	if (!cur) {
		/* Is there capacity at our destination? */
1453
		if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1454
		    !env->dst_stats.has_free_capacity)
1455 1456 1457 1458 1459 1460
			goto unlock;

		goto balance;
	}

	/* Balance doesn't matter much if we're running a task per cpu */
1461 1462
	if (imp > env->best_imp && src_rq->nr_running == 1 &&
			dst_rq->nr_running == 1)
1463 1464 1465 1466 1467 1468
		goto assign;

	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
balance:
1469 1470 1471
	load = task_h_load(env->p);
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1472

1473 1474 1475 1476 1477 1478 1479 1480 1481
	if (moveimp > imp && moveimp > env->best_imp) {
		/*
		 * If the improvement from just moving env->p direction is
		 * better than swapping tasks around, check if a move is
		 * possible. Store a slightly smaller score than moveimp,
		 * so an actually idle CPU will win.
		 */
		if (!load_too_imbalanced(src_load, dst_load, env)) {
			imp = moveimp - 1;
1482
			put_task_struct(cur);
1483 1484 1485 1486 1487 1488 1489 1490
			cur = NULL;
			goto assign;
		}
	}

	if (imp <= env->best_imp)
		goto unlock;

1491
	if (cur) {
1492 1493 1494
		load = task_h_load(cur);
		dst_load -= load;
		src_load += load;
1495 1496
	}

1497
	if (load_too_imbalanced(src_load, dst_load, env))
1498 1499
		goto unlock;

1500 1501 1502 1503 1504 1505 1506
	/*
	 * One idle CPU per node is evaluated for a task numa move.
	 * Call select_idle_sibling to maybe find a better one.
	 */
	if (!cur)
		env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);

1507
assign:
1508
	assigned = true;
1509 1510 1511
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
1512 1513 1514 1515 1516 1517
	/*
	 * The dst_rq->curr isn't assigned. The protection for task_struct is
	 * finished.
	 */
	if (cur && !assigned)
		put_task_struct(cur);
1518 1519
}

1520 1521
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1522 1523 1524 1525 1526 1527 1528 1529 1530
{
	int cpu;

	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
		/* Skip this CPU if the source task cannot migrate */
		if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
			continue;

		env->dst_cpu = cpu;
1531
		task_numa_compare(env, taskimp, groupimp);
1532 1533 1534
	}
}

1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551
/* Only move tasks to a NUMA node less busy than the current node. */
static bool numa_has_capacity(struct task_numa_env *env)
{
	struct numa_stats *src = &env->src_stats;
	struct numa_stats *dst = &env->dst_stats;

	if (src->has_free_capacity && !dst->has_free_capacity)
		return false;

	/*
	 * Only consider a task move if the source has a higher load
	 * than the destination, corrected for CPU capacity on each node.
	 *
	 *      src->load                dst->load
	 * --------------------- vs ---------------------
	 * src->compute_capacity    dst->compute_capacity
	 */
1552 1553 1554
	if (src->load * dst->compute_capacity * env->imbalance_pct >

	    dst->load * src->compute_capacity * 100)
1555 1556 1557 1558 1559
		return true;

	return false;
}

1560 1561 1562 1563
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1564

1565
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1566
		.src_nid = task_node(p),
1567 1568 1569 1570 1571

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
1572
		.best_cpu = -1,
1573 1574
	};
	struct sched_domain *sd;
1575
	unsigned long taskweight, groupweight;
1576
	int nid, ret, dist;
1577
	long taskimp, groupimp;
1578

1579
	/*
1580 1581 1582 1583 1584 1585
	 * Pick the lowest SD_NUMA domain, as that would have the smallest
	 * imbalance and would be the first to start moving tasks about.
	 *
	 * And we want to avoid any moving of tasks about, as that would create
	 * random movement of tasks -- counter the numa conditions we're trying
	 * to satisfy here.
1586 1587
	 */
	rcu_read_lock();
1588
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1589 1590
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1591 1592
	rcu_read_unlock();

1593 1594 1595 1596 1597 1598 1599
	/*
	 * Cpusets can break the scheduler domain tree into smaller
	 * balance domains, some of which do not cross NUMA boundaries.
	 * Tasks that are "trapped" in such domains cannot be migrated
	 * elsewhere, so there is no point in (re)trying.
	 */
	if (unlikely(!sd)) {
1600
		p->numa_preferred_nid = task_node(p);
1601 1602 1603
		return -EINVAL;
	}

1604
	env.dst_nid = p->numa_preferred_nid;
1605 1606 1607 1608 1609 1610
	dist = env.dist = node_distance(env.src_nid, env.dst_nid);
	taskweight = task_weight(p, env.src_nid, dist);
	groupweight = group_weight(p, env.src_nid, dist);
	update_numa_stats(&env.src_stats, env.src_nid);
	taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
	groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1611
	update_numa_stats(&env.dst_stats, env.dst_nid);
1612

1613
	/* Try to find a spot on the preferred nid. */
1614 1615
	if (numa_has_capacity(&env))
		task_numa_find_cpu(&env, taskimp, groupimp);
1616

1617 1618 1619 1620 1621 1622 1623
	/*
	 * Look at other nodes in these cases:
	 * - there is no space available on the preferred_nid
	 * - the task is part of a numa_group that is interleaved across
	 *   multiple NUMA nodes; in order to better consolidate the group,
	 *   we need to check other locations.
	 */
1624
	if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
1625 1626 1627
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1628

1629
			dist = node_distance(env.src_nid, env.dst_nid);
1630 1631 1632 1633 1634
			if (sched_numa_topology_type == NUMA_BACKPLANE &&
						dist != env.dist) {
				taskweight = task_weight(p, env.src_nid, dist);
				groupweight = group_weight(p, env.src_nid, dist);
			}
1635

1636
			/* Only consider nodes where both task and groups benefit */
1637 1638
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1639
			if (taskimp < 0 && groupimp < 0)
1640 1641
				continue;

1642
			env.dist = dist;
1643 1644
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1645 1646
			if (numa_has_capacity(&env))
				task_numa_find_cpu(&env, taskimp, groupimp);
1647 1648 1649
		}
	}

1650 1651 1652 1653 1654 1655 1656 1657
	/*
	 * If the task is part of a workload that spans multiple NUMA nodes,
	 * and is migrating into one of the workload's active nodes, remember
	 * this node as the task's preferred numa node, so the workload can
	 * settle down.
	 * A task that migrated to a second choice node will be better off
	 * trying for a better one later. Do not set the preferred node here.
	 */
1658
	if (p->numa_group) {
1659 1660
		struct numa_group *ng = p->numa_group;

1661 1662 1663 1664 1665
		if (env.best_cpu == -1)
			nid = env.src_nid;
		else
			nid = env.dst_nid;

1666
		if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng))
1667 1668 1669 1670 1671 1672
			sched_setnuma(p, env.dst_nid);
	}

	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;
1673

1674 1675 1676 1677 1678 1679
	/*
	 * Reset the scan period if the task is being rescheduled on an
	 * alternative node to recheck if the tasks is now properly placed.
	 */
	p->numa_scan_period = task_scan_min(p);

1680
	if (env.best_task == NULL) {
1681 1682 1683
		ret = migrate_task_to(p, env.best_cpu);
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1684 1685 1686 1687
		return ret;
	}

	ret = migrate_swap(p, env.best_task);
1688 1689
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1690 1691
	put_task_struct(env.best_task);
	return ret;
1692 1693
}

1694 1695 1696
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1697 1698
	unsigned long interval = HZ;

1699
	/* This task has no NUMA fault statistics yet */
1700
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1701 1702
		return;

1703
	/* Periodically retry migrating the task to the preferred node */
1704 1705
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
	p->numa_migrate_retry = jiffies + interval;
1706 1707

	/* Success if task is already running on preferred CPU */
1708
	if (task_node(p) == p->numa_preferred_nid)
1709 1710 1711
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1712
	task_numa_migrate(p);
1713 1714
}

1715
/*
1716
 * Find out how many nodes on the workload is actively running on. Do this by
1717 1718 1719 1720
 * tracking the nodes from which NUMA hinting faults are triggered. This can
 * be different from the set of nodes where the workload's memory is currently
 * located.
 */
1721
static void numa_group_count_active_nodes(struct numa_group *numa_group)
1722 1723
{
	unsigned long faults, max_faults = 0;
1724
	int nid, active_nodes = 0;
1725 1726 1727 1728 1729 1730 1731 1732 1733

	for_each_online_node(nid) {
		faults = group_faults_cpu(numa_group, nid);
		if (faults > max_faults)
			max_faults = faults;
	}

	for_each_online_node(nid) {
		faults = group_faults_cpu(numa_group, nid);
1734 1735
		if (faults * ACTIVE_NODE_FRACTION > max_faults)
			active_nodes++;
1736
	}
1737 1738 1739

	numa_group->max_faults_cpu = max_faults;
	numa_group->active_nodes = active_nodes;
1740 1741
}

1742 1743 1744
/*
 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
 * increments. The more local the fault statistics are, the higher the scan
1745 1746 1747
 * period will be for the next scan window. If local/(local+remote) ratio is
 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
 * the scan period will decrease. Aim for 70% local accesses.
1748 1749
 */
#define NUMA_PERIOD_SLOTS 10
1750
#define NUMA_PERIOD_THRESHOLD 7
1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770

/*
 * Increase the scan period (slow down scanning) if the majority of
 * our memory is already on our local node, or if the majority of
 * the page accesses are shared with other processes.
 * Otherwise, decrease the scan period.
 */
static void update_task_scan_period(struct task_struct *p,
			unsigned long shared, unsigned long private)
{
	unsigned int period_slot;
	int ratio;
	int diff;

	unsigned long remote = p->numa_faults_locality[0];
	unsigned long local = p->numa_faults_locality[1];

	/*
	 * If there were no record hinting faults then either the task is
	 * completely idle or all activity is areas that are not of interest
1771 1772 1773
	 * to automatic numa balancing. Related to that, if there were failed
	 * migration then it implies we are migrating too quickly or the local
	 * node is overloaded. In either case, scan slower
1774
	 */
1775
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808
		p->numa_scan_period = min(p->numa_scan_period_max,
			p->numa_scan_period << 1);

		p->mm->numa_next_scan = jiffies +
			msecs_to_jiffies(p->numa_scan_period);

		return;
	}

	/*
	 * Prepare to scale scan period relative to the current period.
	 *	 == NUMA_PERIOD_THRESHOLD scan period stays the same
	 *       <  NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
	 *	 >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
	 */
	period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
	ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
	if (ratio >= NUMA_PERIOD_THRESHOLD) {
		int slot = ratio - NUMA_PERIOD_THRESHOLD;
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else {
		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;

		/*
		 * Scale scan rate increases based on sharing. There is an
		 * inverse relationship between the degree of sharing and
		 * the adjustment made to the scanning period. Broadly
		 * speaking the intent is that there is little point
		 * scanning faster if shared accesses dominate as it may
		 * simply bounce migrations uselessly
		 */
1809
		ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1810 1811 1812 1813 1814 1815 1816 1817
		diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
	}

	p->numa_scan_period = clamp(p->numa_scan_period + diff,
			task_scan_min(p), task_scan_max(p));
	memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
}

1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835
/*
 * Get the fraction of time the task has been running since the last
 * NUMA placement cycle. The scheduler keeps similar statistics, but
 * decays those on a 32ms period, which is orders of magnitude off
 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
 * stats only if the task is so new there are no NUMA statistics yet.
 */
static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
{
	u64 runtime, delta, now;
	/* Use the start of this time slice to avoid calculations. */
	now = p->se.exec_start;
	runtime = p->se.sum_exec_runtime;

	if (p->last_task_numa_placement) {
		delta = runtime - p->last_sum_exec_runtime;
		*period = now - p->last_task_numa_placement;
	} else {
1836 1837
		delta = p->se.avg.load_sum / p->se.load.weight;
		*period = LOAD_AVG_MAX;
1838 1839 1840 1841 1842 1843 1844 1845
	}

	p->last_sum_exec_runtime = runtime;
	p->last_task_numa_placement = now;

	return delta;
}

1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892
/*
 * Determine the preferred nid for a task in a numa_group. This needs to
 * be done in a way that produces consistent results with group_weight,
 * otherwise workloads might not converge.
 */
static int preferred_group_nid(struct task_struct *p, int nid)
{
	nodemask_t nodes;
	int dist;

	/* Direct connections between all NUMA nodes. */
	if (sched_numa_topology_type == NUMA_DIRECT)
		return nid;

	/*
	 * On a system with glueless mesh NUMA topology, group_weight
	 * scores nodes according to the number of NUMA hinting faults on
	 * both the node itself, and on nearby nodes.
	 */
	if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
		unsigned long score, max_score = 0;
		int node, max_node = nid;

		dist = sched_max_numa_distance;

		for_each_online_node(node) {
			score = group_weight(p, node, dist);
			if (score > max_score) {
				max_score = score;
				max_node = node;
			}
		}
		return max_node;
	}

	/*
	 * Finding the preferred nid in a system with NUMA backplane
	 * interconnect topology is more involved. The goal is to locate
	 * tasks from numa_groups near each other in the system, and
	 * untangle workloads from different sides of the system. This requires
	 * searching down the hierarchy of node groups, recursively searching
	 * inside the highest scoring group of nodes. The nodemask tricks
	 * keep the complexity of the search down.
	 */
	nodes = node_online_map;
	for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
		unsigned long max_faults = 0;
1893
		nodemask_t max_group = NODE_MASK_NONE;
1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926
		int a, b;

		/* Are there nodes at this distance from each other? */
		if (!find_numa_distance(dist))
			continue;

		for_each_node_mask(a, nodes) {
			unsigned long faults = 0;
			nodemask_t this_group;
			nodes_clear(this_group);

			/* Sum group's NUMA faults; includes a==b case. */
			for_each_node_mask(b, nodes) {
				if (node_distance(a, b) < dist) {
					faults += group_faults(p, b);
					node_set(b, this_group);
					node_clear(b, nodes);
				}
			}

			/* Remember the top group. */
			if (faults > max_faults) {
				max_faults = faults;
				max_group = this_group;
				/*
				 * subtle: at the smallest distance there is
				 * just one node left in each "group", the
				 * winner is the preferred nid.
				 */
				nid = a;
			}
		}
		/* Next round, evaluate the nodes within max_group. */
1927 1928
		if (!max_faults)
			break;
1929 1930 1931 1932 1933
		nodes = max_group;
	}
	return nid;
}

1934 1935
static void task_numa_placement(struct task_struct *p)
{
1936 1937
	int seq, nid, max_nid = -1, max_group_nid = -1;
	unsigned long max_faults = 0, max_group_faults = 0;
1938
	unsigned long fault_types[2] = { 0, 0 };
1939 1940
	unsigned long total_faults;
	u64 runtime, period;
1941
	spinlock_t *group_lock = NULL;
1942

1943 1944 1945 1946 1947
	/*
	 * The p->mm->numa_scan_seq field gets updated without
	 * exclusive access. Use READ_ONCE() here to ensure
	 * that the field is read in a single access:
	 */
1948
	seq = READ_ONCE(p->mm->numa_scan_seq);
1949 1950 1951
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
1952
	p->numa_scan_period_max = task_scan_max(p);
1953

1954 1955 1956 1957
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

1958 1959 1960
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
1961
		spin_lock_irq(group_lock);
1962 1963
	}

1964 1965
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
1966 1967
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1968
		unsigned long faults = 0, group_faults = 0;
1969
		int priv;
1970

1971
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1972
			long diff, f_diff, f_weight;
1973

1974 1975 1976 1977
			mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
			membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
			cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
			cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1978

1979
			/* Decay existing window, copy faults since last scan */
1980 1981 1982
			diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
			fault_types[priv] += p->numa_faults[membuf_idx];
			p->numa_faults[membuf_idx] = 0;
1983

1984 1985 1986 1987 1988 1989 1990 1991
			/*
			 * Normalize the faults_from, so all tasks in a group
			 * count according to CPU use, instead of by the raw
			 * number of faults. Tasks with little runtime have
			 * little over-all impact on throughput, and thus their
			 * faults are less important.
			 */
			f_weight = div64_u64(runtime << 16, period + 1);
1992
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1993
				   (total_faults + 1);
1994 1995
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
1996

1997 1998 1999
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
2000
			p->total_numa_faults += diff;
2001
			if (p->numa_group) {
2002 2003 2004 2005 2006 2007 2008 2009 2010
				/*
				 * safe because we can only change our own group
				 *
				 * mem_idx represents the offset for a given
				 * nid and priv in a specific region because it
				 * is at the beginning of the numa_faults array.
				 */
				p->numa_group->faults[mem_idx] += diff;
				p->numa_group->faults_cpu[mem_idx] += f_diff;
2011
				p->numa_group->total_faults += diff;
2012
				group_faults += p->numa_group->faults[mem_idx];
2013
			}
2014 2015
		}

2016 2017 2018 2019
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
2020 2021 2022 2023 2024 2025 2026

		if (group_faults > max_group_faults) {
			max_group_faults = group_faults;
			max_group_nid = nid;
		}
	}

2027 2028
	update_task_scan_period(p, fault_types[0], fault_types[1]);

2029
	if (p->numa_group) {
2030
		numa_group_count_active_nodes(p->numa_group);
2031
		spin_unlock_irq(group_lock);
2032
		max_nid = preferred_group_nid(p, max_group_nid);
2033 2034
	}

2035 2036 2037 2038 2039 2040 2041
	if (max_faults) {
		/* Set the new preferred node */
		if (max_nid != p->numa_preferred_nid)
			sched_setnuma(p, max_nid);

		if (task_node(p) != p->numa_preferred_nid)
			numa_migrate_preferred(p);
2042
	}
2043 2044
}

2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055
static inline int get_numa_group(struct numa_group *grp)
{
	return atomic_inc_not_zero(&grp->refcount);
}

static inline void put_numa_group(struct numa_group *grp)
{
	if (atomic_dec_and_test(&grp->refcount))
		kfree_rcu(grp, rcu);
}

2056 2057
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
2058 2059 2060 2061 2062 2063 2064 2065 2066
{
	struct numa_group *grp, *my_grp;
	struct task_struct *tsk;
	bool join = false;
	int cpu = cpupid_to_cpu(cpupid);
	int i;

	if (unlikely(!p->numa_group)) {
		unsigned int size = sizeof(struct numa_group) +
2067
				    4*nr_node_ids*sizeof(unsigned long);
2068 2069 2070 2071 2072 2073

		grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
		if (!grp)
			return;

		atomic_set(&grp->refcount, 1);
2074 2075
		grp->active_nodes = 1;
		grp->max_faults_cpu = 0;
2076
		spin_lock_init(&grp->lock);
2077
		grp->gid = p->pid;
2078
		/* Second half of the array tracks nids where faults happen */
2079 2080
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
2081

2082
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2083
			grp->faults[i] = p->numa_faults[i];
2084

2085
		grp->total_faults = p->total_numa_faults;
2086

2087 2088 2089 2090 2091
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
2092
	tsk = READ_ONCE(cpu_rq(cpu)->curr);
2093 2094

	if (!cpupid_match_pid(tsk, cpupid))
2095
		goto no_join;
2096 2097 2098

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
2099
		goto no_join;
2100 2101 2102

	my_grp = p->numa_group;
	if (grp == my_grp)
2103
		goto no_join;
2104 2105 2106 2107 2108 2109

	/*
	 * Only join the other group if its bigger; if we're the bigger group,
	 * the other task will join us.
	 */
	if (my_grp->nr_tasks > grp->nr_tasks)
2110
		goto no_join;
2111 2112 2113 2114 2115

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2116
		goto no_join;
2117

2118 2119 2120 2121 2122 2123 2124
	/* Always join threads in the same process. */
	if (tsk->mm == current->mm)
		join = true;

	/* Simple filter to avoid false positives due to PID collisions */
	if (flags & TNF_SHARED)
		join = true;
2125

2126 2127 2128
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

2129
	if (join && !get_numa_group(grp))
2130
		goto no_join;
2131 2132 2133 2134 2135 2136

	rcu_read_unlock();

	if (!join)
		return;

2137 2138
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
2139

2140
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2141 2142
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
2143
	}
2144 2145
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
2146 2147 2148 2149 2150

	my_grp->nr_tasks--;
	grp->nr_tasks++;

	spin_unlock(&my_grp->lock);
2151
	spin_unlock_irq(&grp->lock);
2152 2153 2154 2155

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2156 2157 2158 2159 2160
	return;

no_join:
	rcu_read_unlock();
	return;
2161 2162 2163 2164 2165
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
2166
	void *numa_faults = p->numa_faults;
2167 2168
	unsigned long flags;
	int i;
2169 2170

	if (grp) {
2171
		spin_lock_irqsave(&grp->lock, flags);
2172
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2173
			grp->faults[i] -= p->numa_faults[i];
2174
		grp->total_faults -= p->total_numa_faults;
2175

2176
		grp->nr_tasks--;
2177
		spin_unlock_irqrestore(&grp->lock, flags);
2178
		RCU_INIT_POINTER(p->numa_group, NULL);
2179 2180 2181
		put_numa_group(grp);
	}

2182
	p->numa_faults = NULL;
2183
	kfree(numa_faults);
2184 2185
}

2186 2187 2188
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2189
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2190 2191
{
	struct task_struct *p = current;
2192
	bool migrated = flags & TNF_MIGRATED;
2193
	int cpu_node = task_node(current);
2194
	int local = !!(flags & TNF_FAULT_LOCAL);
2195
	struct numa_group *ng;
2196
	int priv;
2197

2198
	if (!static_branch_likely(&sched_numa_balancing))
2199 2200
		return;

2201 2202 2203 2204
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2205
	/* Allocate buffer to track faults on a per-node basis */
2206 2207
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2208
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2209

2210 2211
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2212
			return;
2213

2214
		p->total_numa_faults = 0;
2215
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2216
	}
2217

2218 2219 2220 2221 2222 2223 2224 2225
	/*
	 * First accesses are treated as private, otherwise consider accesses
	 * to be private if the accessing pid has not changed
	 */
	if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
		priv = 1;
	} else {
		priv = cpupid_match_pid(p, last_cpupid);
2226
		if (!priv && !(flags & TNF_NO_GROUP))
2227
			task_numa_group(p, last_cpupid, flags, &priv);
2228 2229
	}

2230 2231 2232 2233 2234 2235
	/*
	 * If a workload spans multiple NUMA nodes, a shared fault that
	 * occurs wholly within the set of nodes that the workload is
	 * actively using should be counted as local. This allows the
	 * scan rate to slow down when a workload has settled down.
	 */
2236 2237 2238 2239
	ng = p->numa_group;
	if (!priv && !local && ng && ng->active_nodes > 1 &&
				numa_is_active_node(cpu_node, ng) &&
				numa_is_active_node(mem_node, ng))
2240 2241
		local = 1;

2242
	task_numa_placement(p);
2243

2244 2245 2246 2247 2248
	/*
	 * Retry task to preferred node migration periodically, in case it
	 * case it previously failed, or the scheduler moved us.
	 */
	if (time_after(jiffies, p->numa_migrate_retry))
2249 2250
		numa_migrate_preferred(p);

I
Ingo Molnar 已提交
2251 2252
	if (migrated)
		p->numa_pages_migrated += pages;
2253 2254
	if (flags & TNF_MIGRATE_FAIL)
		p->numa_faults_locality[2] += pages;
I
Ingo Molnar 已提交
2255

2256 2257
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2258
	p->numa_faults_locality[local] += pages;
2259 2260
}

2261 2262
static void reset_ptenuma_scan(struct task_struct *p)
{
2263 2264 2265 2266 2267 2268 2269 2270
	/*
	 * We only did a read acquisition of the mmap sem, so
	 * p->mm->numa_scan_seq is written to without exclusive access
	 * and the update is not guaranteed to be atomic. That's not
	 * much of an issue though, since this is just used for
	 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
	 * expensive, to avoid any form of compiler optimizations:
	 */
2271
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2272 2273 2274
	p->mm->numa_scan_offset = 0;
}

2275 2276 2277 2278 2279 2280 2281 2282 2283
/*
 * 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;
2284
	u64 runtime = p->se.sum_exec_runtime;
2285
	struct vm_area_struct *vma;
2286
	unsigned long start, end;
2287
	unsigned long nr_pte_updates = 0;
2288
	long pages, virtpages;
2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303

	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;

2304
	if (!mm->numa_next_scan) {
2305 2306
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2307 2308
	}

2309 2310 2311 2312 2313 2314 2315
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2316 2317 2318 2319
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
		p->numa_scan_period = task_scan_min(p);
	}
2320

2321
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2322 2323 2324
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2325 2326 2327 2328 2329 2330
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2331 2332 2333
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2334
	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2335 2336
	if (!pages)
		return;
2337

2338

2339
	down_read(&mm->mmap_sem);
2340
	vma = find_vma(mm, start);
2341 2342
	if (!vma) {
		reset_ptenuma_scan(p);
2343
		start = 0;
2344 2345
		vma = mm->mmap;
	}
2346
	for (; vma; vma = vma->vm_next) {
2347
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2348
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2349
			continue;
2350
		}
2351

2352 2353 2354 2355 2356 2357 2358 2359 2360 2361
		/*
		 * Shared library pages mapped by multiple processes are not
		 * migrated as it is expected they are cache replicated. Avoid
		 * hinting faults in read-only file-backed mappings or the vdso
		 * as migrating the pages will be of marginal benefit.
		 */
		if (!vma->vm_mm ||
		    (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
			continue;

M
Mel Gorman 已提交
2362 2363 2364 2365 2366 2367
		/*
		 * Skip inaccessible VMAs to avoid any confusion between
		 * PROT_NONE and NUMA hinting ptes
		 */
		if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
			continue;
2368

2369 2370 2371 2372
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2373
			nr_pte_updates = change_prot_numa(vma, start, end);
2374 2375

			/*
2376 2377 2378 2379 2380 2381
			 * Try to scan sysctl_numa_balancing_size worth of
			 * hpages that have at least one present PTE that
			 * is not already pte-numa. If the VMA contains
			 * areas that are unused or already full of prot_numa
			 * PTEs, scan up to virtpages, to skip through those
			 * areas faster.
2382 2383 2384
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2385
			virtpages -= (end - start) >> PAGE_SHIFT;
2386

2387
			start = end;
2388
			if (pages <= 0 || virtpages <= 0)
2389
				goto out;
2390 2391

			cond_resched();
2392
		} while (end != vma->vm_end);
2393
	}
2394

2395
out:
2396
	/*
P
Peter Zijlstra 已提交
2397 2398 2399 2400
	 * 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.
2401 2402
	 */
	if (vma)
2403
		mm->numa_scan_offset = start;
2404 2405 2406
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417

	/*
	 * Make sure tasks use at least 32x as much time to run other code
	 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
	 * Usually update_task_scan_period slows down scanning enough; on an
	 * overloaded system we need to limit overhead on a per task basis.
	 */
	if (unlikely(p->se.sum_exec_runtime != runtime)) {
		u64 diff = p->se.sum_exec_runtime - runtime;
		p->node_stamp += 32 * diff;
	}
2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442
}

/*
 * 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;

2443
	if (now > curr->node_stamp + period) {
2444
		if (!curr->node_stamp)
2445
			curr->numa_scan_period = task_scan_min(curr);
2446
		curr->node_stamp += period;
2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457

		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)
{
}
2458 2459 2460 2461 2462 2463 2464 2465

static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
{
}

static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
{
}
2466 2467
#endif /* CONFIG_NUMA_BALANCING */

2468 2469 2470 2471
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2472
	if (!parent_entity(se))
2473
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2474
#ifdef CONFIG_SMP
2475 2476 2477 2478 2479 2480
	if (entity_is_task(se)) {
		struct rq *rq = rq_of(cfs_rq);

		account_numa_enqueue(rq, task_of(se));
		list_add(&se->group_node, &rq->cfs_tasks);
	}
2481
#endif
2482 2483 2484 2485 2486 2487 2488
	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);
2489
	if (!parent_entity(se))
2490
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2491
#ifdef CONFIG_SMP
2492 2493
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2494
		list_del_init(&se->group_node);
2495
	}
2496
#endif
2497 2498 2499
	cfs_rq->nr_running--;
}

2500 2501
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
2502 2503 2504 2505 2506
static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
{
	long tg_weight;

	/*
2507 2508 2509
	 * Use this CPU's real-time load instead of the last load contribution
	 * as the updating of the contribution is delayed, and we will use the
	 * the real-time load to calc the share. See update_tg_load_avg().
2510
	 */
2511
	tg_weight = atomic_long_read(&tg->load_avg);
2512
	tg_weight -= cfs_rq->tg_load_avg_contrib;
2513
	tg_weight += cfs_rq->load.weight;
2514 2515 2516 2517

	return tg_weight;
}

2518
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2519
{
2520
	long tg_weight, load, shares;
2521

2522
	tg_weight = calc_tg_weight(tg, cfs_rq);
2523
	load = cfs_rq->load.weight;
2524 2525

	shares = (tg->shares * load);
2526 2527
	if (tg_weight)
		shares /= tg_weight;
2528 2529 2530 2531 2532 2533 2534 2535 2536

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

	return shares;
}
# else /* CONFIG_SMP */
2537
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2538 2539 2540 2541
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
P
Peter Zijlstra 已提交
2542 2543 2544
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
2545 2546 2547 2548
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
2549
		account_entity_dequeue(cfs_rq, se);
2550
	}
P
Peter Zijlstra 已提交
2551 2552 2553 2554 2555 2556 2557

	update_load_set(&se->load, weight);

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

2558 2559
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

2560
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2561 2562 2563
{
	struct task_group *tg;
	struct sched_entity *se;
2564
	long shares;
P
Peter Zijlstra 已提交
2565 2566 2567

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
2568
	if (!se || throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
2569
		return;
2570 2571 2572 2573
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
2574
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
2575 2576 2577 2578

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
2579
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2580 2581 2582 2583
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

2584
#ifdef CONFIG_SMP
2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604
/* 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,
};

2605 2606 2607 2608 2609 2610 2611 2612 2613 2614
/*
 * Precomputed \Sum y^k { 1<=k<=n, where n%32=0). Values are rolled down to
 * lower integers. See Documentation/scheduler/sched-avg.txt how these
 * were generated:
 */
static const u32 __accumulated_sum_N32[] = {
	    0, 23371, 35056, 40899, 43820, 45281,
	46011, 46376, 46559, 46650, 46696, 46719,
};

2615 2616 2617 2618 2619 2620
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632
	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
2633 2634
	 *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
	 * With a look-up table which covers y^n (n<PERIOD)
2635 2636 2637 2638 2639 2640
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
2641 2642
	}

2643 2644
	val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
	return val;
2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662
}

/*
 * 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;

2663 2664 2665
	/* Since n < LOAD_AVG_MAX_N, n/LOAD_AVG_PERIOD < 11 */
	contrib = __accumulated_sum_N32[n/LOAD_AVG_PERIOD];
	n %= LOAD_AVG_PERIOD;
2666 2667
	contrib = decay_load(contrib, n);
	return contrib + runnable_avg_yN_sum[n];
2668 2669
}

2670
#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2671

2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699
/*
 * 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}]
 */
2700 2701
static __always_inline int
__update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2702
		  unsigned long weight, int running, struct cfs_rq *cfs_rq)
2703
{
2704
	u64 delta, scaled_delta, periods;
2705
	u32 contrib;
2706
	unsigned int delta_w, scaled_delta_w, decayed = 0;
2707
	unsigned long scale_freq, scale_cpu;
2708

2709
	delta = now - sa->last_update_time;
2710 2711 2712 2713 2714
	/*
	 * 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) {
2715
		sa->last_update_time = now;
2716 2717 2718 2719 2720 2721 2722 2723 2724 2725
		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;
2726
	sa->last_update_time = now;
2727

2728 2729 2730
	scale_freq = arch_scale_freq_capacity(NULL, cpu);
	scale_cpu = arch_scale_cpu_capacity(NULL, cpu);

2731
	/* delta_w is the amount already accumulated against our next period */
2732
	delta_w = sa->period_contrib;
2733 2734 2735
	if (delta + delta_w >= 1024) {
		decayed = 1;

2736 2737 2738
		/* how much left for next period will start over, we don't know yet */
		sa->period_contrib = 0;

2739 2740 2741 2742 2743 2744
		/*
		 * 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;
2745
		scaled_delta_w = cap_scale(delta_w, scale_freq);
2746
		if (weight) {
2747 2748 2749 2750 2751
			sa->load_sum += weight * scaled_delta_w;
			if (cfs_rq) {
				cfs_rq->runnable_load_sum +=
						weight * scaled_delta_w;
			}
2752
		}
2753
		if (running)
2754
			sa->util_sum += scaled_delta_w * scale_cpu;
2755 2756 2757 2758 2759 2760 2761

		delta -= delta_w;

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

2762
		sa->load_sum = decay_load(sa->load_sum, periods + 1);
2763 2764 2765 2766
		if (cfs_rq) {
			cfs_rq->runnable_load_sum =
				decay_load(cfs_rq->runnable_load_sum, periods + 1);
		}
2767
		sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2768 2769

		/* Efficiently calculate \sum (1..n_period) 1024*y^i */
2770
		contrib = __compute_runnable_contrib(periods);
2771
		contrib = cap_scale(contrib, scale_freq);
2772
		if (weight) {
2773
			sa->load_sum += weight * contrib;
2774 2775 2776
			if (cfs_rq)
				cfs_rq->runnable_load_sum += weight * contrib;
		}
2777
		if (running)
2778
			sa->util_sum += contrib * scale_cpu;
2779 2780 2781
	}

	/* Remainder of delta accrued against u_0` */
2782
	scaled_delta = cap_scale(delta, scale_freq);
2783
	if (weight) {
2784
		sa->load_sum += weight * scaled_delta;
2785
		if (cfs_rq)
2786
			cfs_rq->runnable_load_sum += weight * scaled_delta;
2787
	}
2788
	if (running)
2789
		sa->util_sum += scaled_delta * scale_cpu;
2790

2791
	sa->period_contrib += delta;
2792

2793 2794
	if (decayed) {
		sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2795 2796 2797 2798
		if (cfs_rq) {
			cfs_rq->runnable_load_avg =
				div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
		}
2799
		sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2800
	}
2801

2802
	return decayed;
2803 2804
}

2805
#ifdef CONFIG_FAIR_GROUP_SCHED
2806
/*
2807 2808
 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
 * and effective_load (which is not done because it is too costly).
2809
 */
2810
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2811
{
2812
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2813

2814 2815 2816 2817 2818 2819
	/*
	 * No need to update load_avg for root_task_group as it is not used.
	 */
	if (cfs_rq->tg == &root_task_group)
		return;

2820 2821 2822
	if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
		atomic_long_add(delta, &cfs_rq->tg->load_avg);
		cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2823
	}
2824
}
2825

2826 2827 2828 2829 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
/*
 * Called within set_task_rq() right before setting a task's cpu. The
 * caller only guarantees p->pi_lock is held; no other assumptions,
 * including the state of rq->lock, should be made.
 */
void set_task_rq_fair(struct sched_entity *se,
		      struct cfs_rq *prev, struct cfs_rq *next)
{
	if (!sched_feat(ATTACH_AGE_LOAD))
		return;

	/*
	 * We are supposed to update the task to "current" time, then its up to
	 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
	 * getting what current time is, so simply throw away the out-of-date
	 * time. This will result in the wakee task is less decayed, but giving
	 * the wakee more load sounds not bad.
	 */
	if (se->avg.last_update_time && prev) {
		u64 p_last_update_time;
		u64 n_last_update_time;

#ifndef CONFIG_64BIT
		u64 p_last_update_time_copy;
		u64 n_last_update_time_copy;

		do {
			p_last_update_time_copy = prev->load_last_update_time_copy;
			n_last_update_time_copy = next->load_last_update_time_copy;

			smp_rmb();

			p_last_update_time = prev->avg.last_update_time;
			n_last_update_time = next->avg.last_update_time;

		} while (p_last_update_time != p_last_update_time_copy ||
			 n_last_update_time != n_last_update_time_copy);
#else
		p_last_update_time = prev->avg.last_update_time;
		n_last_update_time = next->avg.last_update_time;
#endif
		__update_load_avg(p_last_update_time, cpu_of(rq_of(prev)),
				  &se->avg, 0, 0, NULL);
		se->avg.last_update_time = n_last_update_time;
	}
}
2872
#else /* CONFIG_FAIR_GROUP_SCHED */
2873
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2874
#endif /* CONFIG_FAIR_GROUP_SCHED */
2875

2876
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
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
static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)
{
	struct rq *rq = rq_of(cfs_rq);
	int cpu = cpu_of(rq);

	if (cpu == smp_processor_id() && &rq->cfs == cfs_rq) {
		unsigned long max = rq->cpu_capacity_orig;

		/*
		 * There are a few boundary cases this might miss but it should
		 * get called often enough that that should (hopefully) not be
		 * a real problem -- added to that it only calls on the local
		 * CPU, so if we enqueue remotely we'll miss an update, but
		 * the next tick/schedule should update.
		 *
		 * It will not get called when we go idle, because the idle
		 * thread is a different class (!fair), nor will the utilization
		 * number include things like RT tasks.
		 *
		 * As is, the util number is not freq-invariant (we'd have to
		 * implement arch_scale_freq_capacity() for that).
		 *
		 * See cpu_util().
		 */
		cpufreq_update_util(rq_clock(rq),
				    min(cfs_rq->avg.util_avg, max), max);
	}
}

2907
/* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2908 2909
static inline int
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
2910
{
2911
	struct sched_avg *sa = &cfs_rq->avg;
2912
	int decayed, removed_load = 0, removed_util = 0;
2913

2914
	if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2915
		s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2916 2917
		sa->load_avg = max_t(long, sa->load_avg - r, 0);
		sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
2918
		removed_load = 1;
2919
	}
2920

2921 2922 2923
	if (atomic_long_read(&cfs_rq->removed_util_avg)) {
		long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
		sa->util_avg = max_t(long, sa->util_avg - r, 0);
2924
		sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
2925
		removed_util = 1;
2926
	}
2927

2928
	decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2929
		scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2930

2931 2932 2933 2934
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
2935

2936 2937
	if (update_freq && (decayed || removed_util))
		cfs_rq_util_change(cfs_rq);
2938

2939
	return decayed || removed_load;
2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957
}

/* Update task and its cfs_rq load average */
static inline void update_load_avg(struct sched_entity *se, int update_tg)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 now = cfs_rq_clock_task(cfs_rq);
	struct rq *rq = rq_of(cfs_rq);
	int cpu = cpu_of(rq);

	/*
	 * Track task load average for carrying it to new CPU after migrated, and
	 * track group sched_entity load average for task_h_load calc in migration
	 */
	__update_load_avg(now, cpu, &se->avg,
			  se->on_rq * scale_load_down(se->load.weight),
			  cfs_rq->curr == se, NULL);

2958
	if (update_cfs_rq_load_avg(now, cfs_rq, true) && update_tg)
2959
		update_tg_load_avg(cfs_rq, 0);
2960 2961
}

2962 2963
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2964 2965 2966
	if (!sched_feat(ATTACH_AGE_LOAD))
		goto skip_aging;

2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980
	/*
	 * If we got migrated (either between CPUs or between cgroups) we'll
	 * have aged the average right before clearing @last_update_time.
	 */
	if (se->avg.last_update_time) {
		__update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
				  &se->avg, 0, 0, NULL);

		/*
		 * XXX: we could have just aged the entire load away if we've been
		 * absent from the fair class for too long.
		 */
	}

2981
skip_aging:
2982 2983 2984 2985 2986
	se->avg.last_update_time = cfs_rq->avg.last_update_time;
	cfs_rq->avg.load_avg += se->avg.load_avg;
	cfs_rq->avg.load_sum += se->avg.load_sum;
	cfs_rq->avg.util_avg += se->avg.util_avg;
	cfs_rq->avg.util_sum += se->avg.util_sum;
2987 2988

	cfs_rq_util_change(cfs_rq);
2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000
}

static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	__update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
			  &se->avg, se->on_rq * scale_load_down(se->load.weight),
			  cfs_rq->curr == se, NULL);

	cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
	cfs_rq->avg.load_sum = max_t(s64,  cfs_rq->avg.load_sum - se->avg.load_sum, 0);
	cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
	cfs_rq->avg.util_sum = max_t(s32,  cfs_rq->avg.util_sum - se->avg.util_sum, 0);
3001 3002

	cfs_rq_util_change(cfs_rq);
3003 3004
}

3005 3006 3007
/* Add the load generated by se into cfs_rq's load average */
static inline void
enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3008
{
3009 3010
	struct sched_avg *sa = &se->avg;
	u64 now = cfs_rq_clock_task(cfs_rq);
3011
	int migrated, decayed;
3012

3013 3014
	migrated = !sa->last_update_time;
	if (!migrated) {
3015
		__update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
3016 3017
			se->on_rq * scale_load_down(se->load.weight),
			cfs_rq->curr == se, NULL);
3018
	}
3019

3020
	decayed = update_cfs_rq_load_avg(now, cfs_rq, !migrated);
3021

3022 3023 3024
	cfs_rq->runnable_load_avg += sa->load_avg;
	cfs_rq->runnable_load_sum += sa->load_sum;

3025 3026
	if (migrated)
		attach_entity_load_avg(cfs_rq, se);
3027

3028 3029
	if (decayed || migrated)
		update_tg_load_avg(cfs_rq, 0);
3030 3031
}

3032 3033 3034 3035 3036 3037 3038 3039 3040
/* Remove the runnable load generated by se from cfs_rq's runnable load average */
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_avg(se, 1);

	cfs_rq->runnable_load_avg =
		max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
	cfs_rq->runnable_load_sum =
3041
		max_t(s64,  cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
3042 3043
}

3044
#ifndef CONFIG_64BIT
3045 3046
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
3047
	u64 last_update_time_copy;
3048
	u64 last_update_time;
3049

3050 3051 3052 3053 3054
	do {
		last_update_time_copy = cfs_rq->load_last_update_time_copy;
		smp_rmb();
		last_update_time = cfs_rq->avg.last_update_time;
	} while (last_update_time != last_update_time_copy);
3055 3056 3057

	return last_update_time;
}
3058
#else
3059 3060 3061 3062
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.last_update_time;
}
3063 3064
#endif

3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082
/*
 * Task first catches up with cfs_rq, and then subtract
 * itself from the cfs_rq (task must be off the queue now).
 */
void remove_entity_load_avg(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 last_update_time;

	/*
	 * Newly created task or never used group entity should not be removed
	 * from its (source) cfs_rq
	 */
	if (se->avg.last_update_time == 0)
		return;

	last_update_time = cfs_rq_last_update_time(cfs_rq);

3083
	__update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
3084 3085
	atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
	atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
3086
}
3087

3088 3089 3090 3091 3092 3093 3094 3095 3096 3097
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
{
	return cfs_rq->runnable_load_avg;
}

static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.load_avg;
}

3098 3099
static int idle_balance(struct rq *this_rq);

3100 3101
#else /* CONFIG_SMP */

3102 3103 3104 3105 3106 3107 3108 3109
static inline void update_load_avg(struct sched_entity *se, int not_used)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	struct rq *rq = rq_of(cfs_rq);

	cpufreq_trigger_update(rq_clock(rq));
}

3110 3111
static inline void
enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3112 3113
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3114
static inline void remove_entity_load_avg(struct sched_entity *se) {}
3115

3116 3117 3118 3119 3120
static inline void
attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
static inline void
detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}

3121 3122 3123 3124 3125
static inline int idle_balance(struct rq *rq)
{
	return 0;
}

3126
#endif /* CONFIG_SMP */
3127

3128
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
3129 3130
{
#ifdef CONFIG_SCHEDSTATS
3131 3132 3133 3134 3135
	struct task_struct *tsk = NULL;

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

3136
	if (se->statistics.sleep_start) {
3137
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
3138 3139 3140 3141

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

3142 3143
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
3144

3145
		se->statistics.sleep_start = 0;
3146
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
3147

3148
		if (tsk) {
3149
			account_scheduler_latency(tsk, delta >> 10, 1);
3150 3151
			trace_sched_stat_sleep(tsk, delta);
		}
3152
	}
3153
	if (se->statistics.block_start) {
3154
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
3155 3156 3157 3158

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

3159 3160
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
3161

3162
		se->statistics.block_start = 0;
3163
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
3164

3165
		if (tsk) {
3166
			if (tsk->in_iowait) {
3167 3168
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
3169
				trace_sched_stat_iowait(tsk, delta);
3170 3171
			}

3172 3173
			trace_sched_stat_blocked(tsk, delta);

3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184
			/*
			 * 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
3185
		}
3186 3187 3188 3189
	}
#endif
}

P
Peter Zijlstra 已提交
3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202
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
}

3203 3204 3205
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
3206
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
3207

3208 3209 3210 3211 3212 3213
	/*
	 * 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
3214
	if (initial && sched_feat(START_DEBIT))
3215
		vruntime += sched_vslice(cfs_rq, se);
3216

3217
	/* sleeps up to a single latency don't count. */
3218
	if (!initial) {
3219
		unsigned long thresh = sysctl_sched_latency;
3220

3221 3222 3223 3224 3225 3226
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3227

3228
		vruntime -= thresh;
3229 3230
	}

3231
	/* ensure we never gain time by being placed backwards. */
3232
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3233 3234
}

3235 3236
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256
static inline void check_schedstat_required(void)
{
#ifdef CONFIG_SCHEDSTATS
	if (schedstat_enabled())
		return;

	/* Force schedstat enabled if a dependent tracepoint is active */
	if (trace_sched_stat_wait_enabled()    ||
			trace_sched_stat_sleep_enabled()   ||
			trace_sched_stat_iowait_enabled()  ||
			trace_sched_stat_blocked_enabled() ||
			trace_sched_stat_runtime_enabled())  {
		pr_warn_once("Scheduler tracepoints stat_sleep, stat_iowait, "
			     "stat_blocked and stat_runtime require the "
			     "kernel parameter schedstats=enabled or "
			     "kernel.sched_schedstats=1\n");
	}
#endif
}

3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275

/*
 * MIGRATION
 *
 *	dequeue
 *	  update_curr()
 *	    update_min_vruntime()
 *	  vruntime -= min_vruntime
 *
 *	enqueue
 *	  update_curr()
 *	    update_min_vruntime()
 *	  vruntime += min_vruntime
 *
 * this way the vruntime transition between RQs is done when both
 * min_vruntime are up-to-date.
 *
 * WAKEUP (remote)
 *
3276
 *	->migrate_task_rq_fair() (p->state == TASK_WAKING)
3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287
 *	  vruntime -= min_vruntime
 *
 *	enqueue
 *	  update_curr()
 *	    update_min_vruntime()
 *	  vruntime += min_vruntime
 *
 * this way we don't have the most up-to-date min_vruntime on the originating
 * CPU and an up-to-date min_vruntime on the destination CPU.
 */

3288
static void
3289
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3290
{
3291 3292 3293
	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
	bool curr = cfs_rq->curr == se;

3294
	/*
3295 3296
	 * If we're the current task, we must renormalise before calling
	 * update_curr().
3297
	 */
3298
	if (renorm && curr)
3299 3300
		se->vruntime += cfs_rq->min_vruntime;

3301 3302
	update_curr(cfs_rq);

3303
	/*
3304 3305 3306 3307
	 * Otherwise, renormalise after, such that we're placed at the current
	 * moment in time, instead of some random moment in the past. Being
	 * placed in the past could significantly boost this task to the
	 * fairness detriment of existing tasks.
3308
	 */
3309 3310 3311
	if (renorm && !curr)
		se->vruntime += cfs_rq->min_vruntime;

3312
	enqueue_entity_load_avg(cfs_rq, se);
3313 3314
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
3315

3316
	if (flags & ENQUEUE_WAKEUP) {
3317
		place_entity(cfs_rq, se, 0);
3318 3319
		if (schedstat_enabled())
			enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
3320
	}
3321

3322 3323 3324 3325 3326
	check_schedstat_required();
	if (schedstat_enabled()) {
		update_stats_enqueue(cfs_rq, se);
		check_spread(cfs_rq, se);
	}
3327
	if (!curr)
3328
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
3329
	se->on_rq = 1;
3330

3331
	if (cfs_rq->nr_running == 1) {
3332
		list_add_leaf_cfs_rq(cfs_rq);
3333 3334
		check_enqueue_throttle(cfs_rq);
	}
3335 3336
}

3337
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
3338
{
3339 3340
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3341
		if (cfs_rq->last != se)
3342
			break;
3343 3344

		cfs_rq->last = NULL;
3345 3346
	}
}
P
Peter Zijlstra 已提交
3347

3348 3349 3350 3351
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3352
		if (cfs_rq->next != se)
3353
			break;
3354 3355

		cfs_rq->next = NULL;
3356
	}
P
Peter Zijlstra 已提交
3357 3358
}

3359 3360 3361 3362
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3363
		if (cfs_rq->skip != se)
3364
			break;
3365 3366

		cfs_rq->skip = NULL;
3367 3368 3369
	}
}

P
Peter Zijlstra 已提交
3370 3371
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3372 3373 3374 3375 3376
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
3377 3378 3379

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
3380 3381
}

3382
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3383

3384
static void
3385
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3386
{
3387 3388 3389 3390
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
3391
	dequeue_entity_load_avg(cfs_rq, se);
3392

3393 3394
	if (schedstat_enabled())
		update_stats_dequeue(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
3395

P
Peter Zijlstra 已提交
3396
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3397

3398
	if (se != cfs_rq->curr)
3399
		__dequeue_entity(cfs_rq, se);
3400
	se->on_rq = 0;
3401
	account_entity_dequeue(cfs_rq, se);
3402 3403 3404 3405 3406 3407

	/*
	 * 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.
	 */
3408
	if (!(flags & DEQUEUE_SLEEP))
3409
		se->vruntime -= cfs_rq->min_vruntime;
3410

3411 3412 3413
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

3414
	update_min_vruntime(cfs_rq);
3415
	update_cfs_shares(cfs_rq);
3416 3417 3418 3419 3420
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
3421
static void
I
Ingo Molnar 已提交
3422
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3423
{
3424
	unsigned long ideal_runtime, delta_exec;
3425 3426
	struct sched_entity *se;
	s64 delta;
3427

P
Peter Zijlstra 已提交
3428
	ideal_runtime = sched_slice(cfs_rq, curr);
3429
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3430
	if (delta_exec > ideal_runtime) {
3431
		resched_curr(rq_of(cfs_rq));
3432 3433 3434 3435 3436
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
3437 3438 3439 3440 3441 3442 3443 3444 3445 3446 3447
		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;

3448 3449
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
3450

3451 3452
	if (delta < 0)
		return;
3453

3454
	if (delta > ideal_runtime)
3455
		resched_curr(rq_of(cfs_rq));
3456 3457
}

3458
static void
3459
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3460
{
3461 3462 3463 3464 3465 3466 3467
	/* '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.
		 */
3468 3469
		if (schedstat_enabled())
			update_stats_wait_end(cfs_rq, se);
3470
		__dequeue_entity(cfs_rq, se);
3471
		update_load_avg(se, 1);
3472 3473
	}

3474
	update_stats_curr_start(cfs_rq, se);
3475
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
3476 3477 3478 3479 3480 3481
#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):
	 */
3482
	if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3483
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
3484 3485 3486
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
3487
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
3488 3489
}

3490 3491 3492
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

3493 3494 3495 3496 3497 3498 3499
/*
 * 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
 */
3500 3501
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3502
{
3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513
	struct sched_entity *left = __pick_first_entity(cfs_rq);
	struct sched_entity *se;

	/*
	 * If curr is set we have to see if its left of the leftmost entity
	 * still in the tree, provided there was anything in the tree at all.
	 */
	if (!left || (curr && entity_before(curr, left)))
		left = curr;

	se = left; /* ideally we run the leftmost entity */
3514

3515 3516 3517 3518 3519
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
3520 3521 3522 3523 3524 3525 3526 3527 3528 3529
		struct sched_entity *second;

		if (se == curr) {
			second = __pick_first_entity(cfs_rq);
		} else {
			second = __pick_next_entity(se);
			if (!second || (curr && entity_before(curr, second)))
				second = curr;
		}

3530 3531 3532
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
3533

3534 3535 3536 3537 3538 3539
	/*
	 * 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;

3540 3541 3542 3543 3544 3545
	/*
	 * 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;

3546
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3547 3548

	return se;
3549 3550
}

3551
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3552

3553
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3554 3555 3556 3557 3558 3559
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
3560
		update_curr(cfs_rq);
3561

3562 3563 3564
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

3565 3566 3567 3568 3569 3570
	if (schedstat_enabled()) {
		check_spread(cfs_rq, prev);
		if (prev->on_rq)
			update_stats_wait_start(cfs_rq, prev);
	}

3571 3572 3573
	if (prev->on_rq) {
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
3574
		/* in !on_rq case, update occurred at dequeue */
3575
		update_load_avg(prev, 0);
3576
	}
3577
	cfs_rq->curr = NULL;
3578 3579
}

P
Peter Zijlstra 已提交
3580 3581
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3582 3583
{
	/*
3584
	 * Update run-time statistics of the 'current'.
3585
	 */
3586
	update_curr(cfs_rq);
3587

3588 3589 3590
	/*
	 * Ensure that runnable average is periodically updated.
	 */
3591
	update_load_avg(curr, 1);
3592
	update_cfs_shares(cfs_rq);
3593

P
Peter Zijlstra 已提交
3594 3595 3596 3597 3598
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
3599
	if (queued) {
3600
		resched_curr(rq_of(cfs_rq));
3601 3602
		return;
	}
P
Peter Zijlstra 已提交
3603 3604 3605 3606 3607 3608 3609 3610
	/*
	 * 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
3611
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
3612
		check_preempt_tick(cfs_rq, curr);
3613 3614
}

3615 3616 3617 3618 3619 3620

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

#ifdef CONFIG_CFS_BANDWIDTH
3621 3622

#ifdef HAVE_JUMP_LABEL
3623
static struct static_key __cfs_bandwidth_used;
3624 3625 3626

static inline bool cfs_bandwidth_used(void)
{
3627
	return static_key_false(&__cfs_bandwidth_used);
3628 3629
}

3630
void cfs_bandwidth_usage_inc(void)
3631
{
3632 3633 3634 3635 3636 3637
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
3638 3639 3640 3641 3642 3643 3644
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

3645 3646
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
3647 3648
#endif /* HAVE_JUMP_LABEL */

3649 3650 3651 3652 3653 3654 3655 3656
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
3657 3658 3659 3660 3661 3662

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

P
Paul Turner 已提交
3663 3664 3665 3666 3667 3668 3669
/*
 * 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
 */
3670
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
3671 3672 3673 3674 3675 3676 3677 3678 3679 3680 3681
{
	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);
}

3682 3683 3684 3685 3686
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

3687 3688 3689 3690 3691 3692
/* 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;

3693
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3694 3695
}

3696 3697
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3698 3699 3700
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
3701
	u64 amount = 0, min_amount, expires;
3702 3703 3704 3705 3706 3707 3708

	/* 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;
3709
	else {
P
Peter Zijlstra 已提交
3710
		start_cfs_bandwidth(cfs_b);
3711 3712 3713 3714 3715 3716

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
3717
	}
P
Paul Turner 已提交
3718
	expires = cfs_b->runtime_expires;
3719 3720 3721
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
3722 3723 3724 3725 3726 3727 3728
	/*
	 * 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;
3729 3730

	return cfs_rq->runtime_remaining > 0;
3731 3732
}

P
Paul Turner 已提交
3733 3734 3735 3736 3737
/*
 * 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)
3738
{
P
Paul Turner 已提交
3739 3740 3741
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
3742
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3743 3744
		return;

P
Paul Turner 已提交
3745 3746 3747 3748 3749 3750 3751 3752 3753
	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
3754 3755 3756
	 * whether the global deadline has advanced. It is valid to compare
	 * cfs_b->runtime_expires without any locks since we only care about
	 * exact equality, so a partial write will still work.
P
Paul Turner 已提交
3757 3758
	 */

3759
	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
P
Paul Turner 已提交
3760 3761 3762 3763 3764 3765 3766 3767
		/* 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;
	}
}

3768
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
3769 3770
{
	/* dock delta_exec before expiring quota (as it could span periods) */
3771
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
3772 3773 3774
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
3775 3776
		return;

3777 3778 3779 3780 3781
	/*
	 * 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))
3782
		resched_curr(rq_of(cfs_rq));
3783 3784
}

3785
static __always_inline
3786
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3787
{
3788
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3789 3790 3791 3792 3793
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

3794 3795
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
3796
	return cfs_bandwidth_used() && cfs_rq->throttled;
3797 3798
}

3799 3800 3801
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
3802
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
3803 3804 3805 3806 3807 3808 3809 3810 3811 3812 3813 3814 3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829 3830
}

/*
 * 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) {
3831
		/* adjust cfs_rq_clock_task() */
3832
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3833
					     cfs_rq->throttled_clock_task;
3834 3835 3836 3837 3838 3839 3840 3841 3842 3843 3844
	}
#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)];

3845 3846
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
3847
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
3848 3849 3850 3851 3852
	cfs_rq->throttle_count++;

	return 0;
}

3853
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3854 3855 3856 3857 3858
{
	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;
P
Peter Zijlstra 已提交
3859
	bool empty;
3860 3861 3862

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

3863
	/* freeze hierarchy runnable averages while throttled */
3864 3865 3866
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
3867 3868 3869 3870 3871 3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882 3883

	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)
3884
		sub_nr_running(rq, task_delta);
3885 3886

	cfs_rq->throttled = 1;
3887
	cfs_rq->throttled_clock = rq_clock(rq);
3888
	raw_spin_lock(&cfs_b->lock);
3889
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
3890

3891 3892 3893 3894 3895
	/*
	 * Add to the _head_ of the list, so that an already-started
	 * distribute_cfs_runtime will not see us
	 */
	list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
3896 3897 3898 3899 3900 3901 3902 3903

	/*
	 * If we're the first throttled task, make sure the bandwidth
	 * timer is running.
	 */
	if (empty)
		start_cfs_bandwidth(cfs_b);

3904 3905 3906
	raw_spin_unlock(&cfs_b->lock);
}

3907
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3908 3909 3910 3911 3912 3913 3914
{
	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;

3915
	se = cfs_rq->tg->se[cpu_of(rq)];
3916 3917

	cfs_rq->throttled = 0;
3918 3919 3920

	update_rq_clock(rq);

3921
	raw_spin_lock(&cfs_b->lock);
3922
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3923 3924 3925
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

3926 3927 3928
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946
	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)
3947
		add_nr_running(rq, task_delta);
3948 3949 3950

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
3951
		resched_curr(rq);
3952 3953 3954 3955 3956 3957
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
3958 3959
	u64 runtime;
	u64 starting_runtime = remaining;
3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989

	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();

3990
	return starting_runtime - remaining;
3991 3992
}

3993 3994 3995 3996 3997 3998 3999 4000
/*
 * 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)
{
4001
	u64 runtime, runtime_expires;
4002
	int throttled;
4003 4004 4005

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
4006
		goto out_deactivate;
4007

4008
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4009
	cfs_b->nr_periods += overrun;
4010

4011 4012 4013 4014 4015 4016
	/*
	 * idle depends on !throttled (for the case of a large deficit), and if
	 * we're going inactive then everything else can be deferred
	 */
	if (cfs_b->idle && !throttled)
		goto out_deactivate;
P
Paul Turner 已提交
4017 4018 4019

	__refill_cfs_bandwidth_runtime(cfs_b);

4020 4021 4022
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
4023
		return 0;
4024 4025
	}

4026 4027 4028
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

4029 4030 4031
	runtime_expires = cfs_b->runtime_expires;

	/*
4032 4033 4034 4035 4036
	 * 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. This can result
	 * in us over-using our runtime if it is all used during this loop, but
	 * only by limited amounts in that extreme case.
4037
	 */
4038 4039
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
4040 4041 4042 4043 4044 4045 4046
		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);
4047 4048

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4049
	}
4050

4051 4052 4053 4054 4055 4056 4057
	/*
	 * 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;
4058

4059 4060 4061 4062
	return 0;

out_deactivate:
	return 1;
4063
}
4064

4065 4066 4067 4068 4069 4070 4071
/* 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;

4072 4073 4074 4075
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4076
 * hrtimer base being cleared by hrtimer_start. In the case of
4077 4078
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
4079 4080 4081 4082 4083 4084 4085 4086 4087 4088 4089 4090 4091 4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102 4103
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;

P
Peter Zijlstra 已提交
4104 4105 4106
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
4107 4108 4109 4110 4111 4112 4113 4114 4115 4116 4117 4118 4119 4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135
}

/* 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)
{
4136 4137 4138
	if (!cfs_bandwidth_used())
		return;

4139
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151 4152 4153 4154
		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 */
4155 4156 4157
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
4158
		return;
4159
	}
4160

4161
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4162
		runtime = cfs_b->runtime;
4163

4164 4165 4166 4167 4168 4169 4170 4171 4172 4173
	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)
4174
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4175 4176 4177
	raw_spin_unlock(&cfs_b->lock);
}

4178 4179 4180 4181 4182 4183 4184
/*
 * 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)
{
4185 4186 4187
	if (!cfs_bandwidth_used())
		return;

4188 4189 4190 4191 4192 4193 4194 4195 4196 4197 4198 4199 4200 4201 4202
	/* 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() */
4203
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4204
{
4205
	if (!cfs_bandwidth_used())
4206
		return false;
4207

4208
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4209
		return false;
4210 4211 4212 4213 4214 4215

	/*
	 * 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))
4216
		return true;
4217 4218

	throttle_cfs_rq(cfs_rq);
4219
	return true;
4220
}
4221 4222 4223 4224 4225

static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
{
	struct cfs_bandwidth *cfs_b =
		container_of(timer, struct cfs_bandwidth, slack_timer);
P
Peter Zijlstra 已提交
4226

4227 4228 4229 4230 4231 4232 4233 4234 4235 4236 4237 4238
	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);
	int overrun;
	int idle = 0;

4239
	raw_spin_lock(&cfs_b->lock);
4240
	for (;;) {
P
Peter Zijlstra 已提交
4241
		overrun = hrtimer_forward_now(timer, cfs_b->period);
4242 4243 4244 4245 4246
		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
P
Peter Zijlstra 已提交
4247 4248
	if (idle)
		cfs_b->period_active = 0;
4249
	raw_spin_unlock(&cfs_b->lock);
4250 4251 4252 4253 4254 4255 4256 4257 4258 4259 4260 4261

	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);
P
Peter Zijlstra 已提交
4262
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4263 4264 4265 4266 4267 4268 4269 4270 4271 4272 4273
	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);
}

P
Peter Zijlstra 已提交
4274
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4275
{
P
Peter Zijlstra 已提交
4276
	lockdep_assert_held(&cfs_b->lock);
4277

P
Peter Zijlstra 已提交
4278 4279 4280 4281 4282
	if (!cfs_b->period_active) {
		cfs_b->period_active = 1;
		hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
		hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
	}
4283 4284 4285 4286
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
4287 4288 4289 4290
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

4291 4292 4293 4294
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

4295 4296 4297 4298 4299 4300 4301 4302 4303 4304 4305 4306 4307
static void __maybe_unused update_runtime_enabled(struct rq *rq)
{
	struct cfs_rq *cfs_rq;

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

		raw_spin_lock(&cfs_b->lock);
		cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
		raw_spin_unlock(&cfs_b->lock);
	}
}

4308
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4309 4310 4311 4312 4313 4314 4315 4316 4317 4318 4319
{
	struct cfs_rq *cfs_rq;

	for_each_leaf_cfs_rq(rq, cfs_rq) {
		if (!cfs_rq->runtime_enabled)
			continue;

		/*
		 * clock_task is not advancing so we just need to make sure
		 * there's some valid quota amount
		 */
4320
		cfs_rq->runtime_remaining = 1;
4321 4322 4323 4324 4325 4326
		/*
		 * Offline rq is schedulable till cpu is completely disabled
		 * in take_cpu_down(), so we prevent new cfs throttling here.
		 */
		cfs_rq->runtime_enabled = 0;

4327 4328 4329 4330 4331 4332
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
}

#else /* CONFIG_CFS_BANDWIDTH */
4333 4334
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
4335
	return rq_clock_task(rq_of(cfs_rq));
4336 4337
}

4338
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4339
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4340
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4341
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4342 4343 4344 4345 4346

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357

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;
}
4358 4359 4360 4361 4362

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) {}
4363 4364
#endif

4365 4366 4367 4368 4369
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) {}
4370
static inline void update_runtime_enabled(struct rq *rq) {}
4371
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4372 4373 4374

#endif /* CONFIG_CFS_BANDWIDTH */

4375 4376 4377 4378
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
4379 4380 4381 4382 4383 4384 4385 4386
#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);

4387
	if (cfs_rq->nr_running > 1) {
P
Peter Zijlstra 已提交
4388 4389 4390 4391 4392 4393
		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)
4394
				resched_curr(rq);
P
Peter Zijlstra 已提交
4395 4396
			return;
		}
4397
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
4398 4399
	}
}
4400 4401 4402 4403 4404 4405 4406 4407 4408 4409

/*
 * 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;

4410
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4411 4412 4413 4414 4415
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
4416
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
4417 4418 4419 4420
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
4421 4422 4423 4424

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
4425 4426
#endif

4427 4428 4429 4430 4431
/*
 * 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:
 */
4432
static void
4433
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4434 4435
{
	struct cfs_rq *cfs_rq;
4436
	struct sched_entity *se = &p->se;
4437 4438

	for_each_sched_entity(se) {
4439
		if (se->on_rq)
4440 4441
			break;
		cfs_rq = cfs_rq_of(se);
4442
		enqueue_entity(cfs_rq, se, flags);
4443 4444 4445 4446 4447 4448 4449 4450 4451

		/*
		 * 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;
4452
		cfs_rq->h_nr_running++;
4453

4454
		flags = ENQUEUE_WAKEUP;
4455
	}
P
Peter Zijlstra 已提交
4456

P
Peter Zijlstra 已提交
4457
	for_each_sched_entity(se) {
4458
		cfs_rq = cfs_rq_of(se);
4459
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
4460

4461 4462 4463
		if (cfs_rq_throttled(cfs_rq))
			break;

4464
		update_load_avg(se, 1);
4465
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4466 4467
	}

Y
Yuyang Du 已提交
4468
	if (!se)
4469
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
4470

4471
	hrtick_update(rq);
4472 4473
}

4474 4475
static void set_next_buddy(struct sched_entity *se);

4476 4477 4478 4479 4480
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
4481
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4482 4483
{
	struct cfs_rq *cfs_rq;
4484
	struct sched_entity *se = &p->se;
4485
	int task_sleep = flags & DEQUEUE_SLEEP;
4486 4487 4488

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
4489
		dequeue_entity(cfs_rq, se, flags);
4490 4491 4492 4493 4494 4495 4496 4497 4498

		/*
		 * 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;
4499
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4500

4501
		/* Don't dequeue parent if it has other entities besides us */
4502 4503 4504 4505 4506 4507 4508
		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));
4509 4510 4511

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
4512
			break;
4513
		}
4514
		flags |= DEQUEUE_SLEEP;
4515
	}
P
Peter Zijlstra 已提交
4516

P
Peter Zijlstra 已提交
4517
	for_each_sched_entity(se) {
4518
		cfs_rq = cfs_rq_of(se);
4519
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4520

4521 4522 4523
		if (cfs_rq_throttled(cfs_rq))
			break;

4524
		update_load_avg(se, 1);
4525
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4526 4527
	}

Y
Yuyang Du 已提交
4528
	if (!se)
4529
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
4530

4531
	hrtick_update(rq);
4532 4533
}

4534
#ifdef CONFIG_SMP
4535
#ifdef CONFIG_NO_HZ_COMMON
4536 4537 4538 4539 4540
/*
 * per rq 'load' arrray crap; XXX kill this.
 */

/*
4541
 * The exact cpuload calculated at every tick would be:
4542
 *
4543 4544 4545 4546 4547 4548 4549
 *   load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
 *
 * If a cpu misses updates for n ticks (as it was idle) and update gets
 * called on the n+1-th tick when cpu may be busy, then we have:
 *
 *   load_n   = (1 - 1/2^i)^n * load_0
 *   load_n+1 = (1 - 1/2^i)   * load_n + (1/2^i) * cur_load
4550 4551 4552
 *
 * decay_load_missed() below does efficient calculation of
 *
4553 4554 4555 4556 4557 4558
 *   load' = (1 - 1/2^i)^n * load
 *
 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
 * This allows us to precompute the above in said factors, thereby allowing the
 * reduction of an arbitrary n in O(log_2 n) steps. (See also
 * fixed_power_int())
4559
 *
4560
 * The calculation is approximated on a 128 point scale.
4561 4562
 */
#define DEGRADE_SHIFT		7
4563 4564 4565 4566 4567 4568 4569 4570 4571

static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
	{   0,   0,  0,  0,  0,  0, 0, 0 },
	{  64,  32,  8,  0,  0,  0, 0, 0 },
	{  96,  72, 40, 12,  1,  0, 0, 0 },
	{ 112,  98, 75, 43, 15,  1, 0, 0 },
	{ 120, 112, 98, 76, 45, 16, 2, 0 }
};
4572 4573 4574 4575 4576 4577 4578 4579 4580 4581 4582 4583 4584 4585 4586 4587 4588 4589 4590 4591 4592 4593 4594 4595 4596 4597 4598 4599 4600

/*
 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
 * would be when CPU is idle and so we just decay the old load without
 * adding any new load.
 */
static unsigned long
decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
{
	int j = 0;

	if (!missed_updates)
		return load;

	if (missed_updates >= degrade_zero_ticks[idx])
		return 0;

	if (idx == 1)
		return load >> missed_updates;

	while (missed_updates) {
		if (missed_updates % 2)
			load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;

		missed_updates >>= 1;
		j++;
	}
	return load;
}
4601
#endif /* CONFIG_NO_HZ_COMMON */
4602

4603
/**
4604
 * __cpu_load_update - update the rq->cpu_load[] statistics
4605 4606 4607 4608
 * @this_rq: The rq to update statistics for
 * @this_load: The current load
 * @pending_updates: The number of missed updates
 *
4609
 * Update rq->cpu_load[] statistics. This function is usually called every
4610 4611 4612 4613 4614 4615 4616 4617 4618 4619 4620 4621 4622 4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635
 * scheduler tick (TICK_NSEC).
 *
 * This function computes a decaying average:
 *
 *   load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
 *
 * Because of NOHZ it might not get called on every tick which gives need for
 * the @pending_updates argument.
 *
 *   load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
 *             = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
 *             = A * (A * load[i]_n-2 + B) + B
 *             = A * (A * (A * load[i]_n-3 + B) + B) + B
 *             = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
 *             = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
 *             = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
 *             = (1 - 1/2^i)^n * (load[i]_0 - load) + load
 *
 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
 * any change in load would have resulted in the tick being turned back on.
 *
 * For regular NOHZ, this reduces to:
 *
 *   load[i]_n = (1 - 1/2^i)^n * load[i]_0
 *
 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
4636
 * term.
4637
 */
4638 4639
static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
			    unsigned long pending_updates)
4640
{
4641
	unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
4642 4643 4644 4645 4646 4647 4648 4649 4650 4651 4652
	int i, scale;

	this_rq->nr_load_updates++;

	/* Update our load: */
	this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
	for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
		unsigned long old_load, new_load;

		/* scale is effectively 1 << i now, and >> i divides by scale */

4653
		old_load = this_rq->cpu_load[i];
4654
#ifdef CONFIG_NO_HZ_COMMON
4655
		old_load = decay_load_missed(old_load, pending_updates - 1, i);
4656 4657 4658 4659 4660 4661 4662 4663 4664
		if (tickless_load) {
			old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
			/*
			 * old_load can never be a negative value because a
			 * decayed tickless_load cannot be greater than the
			 * original tickless_load.
			 */
			old_load += tickless_load;
		}
4665
#endif
4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679 4680
		new_load = this_load;
		/*
		 * Round up the averaging division if load is increasing. This
		 * prevents us from getting stuck on 9 if the load is 10, for
		 * example.
		 */
		if (new_load > old_load)
			new_load += scale - 1;

		this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
	}

	sched_avg_update(this_rq);
}

4681 4682 4683 4684 4685 4686
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
	return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
}

4687
#ifdef CONFIG_NO_HZ_COMMON
4688 4689 4690 4691 4692 4693 4694 4695 4696 4697 4698 4699 4700 4701 4702 4703 4704
/*
 * There is no sane way to deal with nohz on smp when using jiffies because the
 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
 *
 * Therefore we need to avoid the delta approach from the regular tick when
 * possible since that would seriously skew the load calculation. This is why we
 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
 * loop exit, nohz_idle_balance, nohz full exit...)
 *
 * This means we might still be one tick off for nohz periods.
 */

static void cpu_load_update_nohz(struct rq *this_rq,
				 unsigned long curr_jiffies,
				 unsigned long load)
4705 4706 4707 4708 4709 4710 4711 4712 4713 4714 4715
{
	unsigned long pending_updates;

	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
	if (pending_updates) {
		this_rq->last_load_update_tick = curr_jiffies;
		/*
		 * In the regular NOHZ case, we were idle, this means load 0.
		 * In the NOHZ_FULL case, we were non-idle, we should consider
		 * its weighted load.
		 */
4716
		cpu_load_update(this_rq, load, pending_updates);
4717 4718 4719
	}
}

4720 4721 4722 4723
/*
 * Called from nohz_idle_balance() to update the load ratings before doing the
 * idle balance.
 */
4724
static void cpu_load_update_idle(struct rq *this_rq)
4725 4726 4727 4728
{
	/*
	 * bail if there's load or we're actually up-to-date.
	 */
4729
	if (weighted_cpuload(cpu_of(this_rq)))
4730 4731
		return;

4732
	cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
4733 4734 4735
}

/*
4736 4737 4738 4739
 * Record CPU load on nohz entry so we know the tickless load to account
 * on nohz exit. cpu_load[0] happens then to be updated more frequently
 * than other cpu_load[idx] but it should be fine as cpu_load readers
 * shouldn't rely into synchronized cpu_load[*] updates.
4740
 */
4741
void cpu_load_update_nohz_start(void)
4742 4743
{
	struct rq *this_rq = this_rq();
4744 4745 4746 4747 4748 4749 4750 4751 4752 4753 4754 4755 4756 4757

	/*
	 * This is all lockless but should be fine. If weighted_cpuload changes
	 * concurrently we'll exit nohz. And cpu_load write can race with
	 * cpu_load_update_idle() but both updater would be writing the same.
	 */
	this_rq->cpu_load[0] = weighted_cpuload(cpu_of(this_rq));
}

/*
 * Account the tickless load in the end of a nohz frame.
 */
void cpu_load_update_nohz_stop(void)
{
4758
	unsigned long curr_jiffies = READ_ONCE(jiffies);
4759 4760
	struct rq *this_rq = this_rq();
	unsigned long load;
4761 4762 4763 4764

	if (curr_jiffies == this_rq->last_load_update_tick)
		return;

4765
	load = weighted_cpuload(cpu_of(this_rq));
4766
	raw_spin_lock(&this_rq->lock);
4767
	update_rq_clock(this_rq);
4768
	cpu_load_update_nohz(this_rq, curr_jiffies, load);
4769 4770
	raw_spin_unlock(&this_rq->lock);
}
4771 4772 4773 4774 4775 4776 4777 4778
#else /* !CONFIG_NO_HZ_COMMON */
static inline void cpu_load_update_nohz(struct rq *this_rq,
					unsigned long curr_jiffies,
					unsigned long load) { }
#endif /* CONFIG_NO_HZ_COMMON */

static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load)
{
4779
#ifdef CONFIG_NO_HZ_COMMON
4780 4781
	/* See the mess around cpu_load_update_nohz(). */
	this_rq->last_load_update_tick = READ_ONCE(jiffies);
4782
#endif
4783 4784
	cpu_load_update(this_rq, load, 1);
}
4785 4786 4787 4788

/*
 * Called from scheduler_tick()
 */
4789
void cpu_load_update_active(struct rq *this_rq)
4790
{
4791
	unsigned long load = weighted_cpuload(cpu_of(this_rq));
4792 4793 4794 4795 4796

	if (tick_nohz_tick_stopped())
		cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
	else
		cpu_load_update_periodic(this_rq, load);
4797 4798
}

4799 4800 4801 4802 4803 4804 4805 4806 4807 4808 4809 4810 4811 4812 4813 4814 4815 4816 4817 4818 4819 4820 4821 4822 4823 4824 4825 4826 4827 4828 4829 4830 4831
/*
 * 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);
}

4832
static unsigned long capacity_of(int cpu)
4833
{
4834
	return cpu_rq(cpu)->cpu_capacity;
4835 4836
}

4837 4838 4839 4840 4841
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

4842 4843 4844
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
4845
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4846
	unsigned long load_avg = weighted_cpuload(cpu);
4847 4848

	if (nr_running)
4849
		return load_avg / nr_running;
4850 4851 4852 4853

	return 0;
}

4854
#ifdef CONFIG_FAIR_GROUP_SCHED
4855 4856 4857 4858 4859 4860
/*
 * 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.
4861 4862 4863 4864 4865 4866 4867 4868 4869 4870 4871 4872 4873 4874 4875 4876 4877 4878 4879 4880 4881 4882 4883 4884 4885 4886 4887 4888 4889 4890 4891 4892 4893 4894 4895 4896 4897 4898 4899 4900 4901 4902 4903
 *
 * 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.
4904
 */
P
Peter Zijlstra 已提交
4905
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4906
{
P
Peter Zijlstra 已提交
4907
	struct sched_entity *se = tg->se[cpu];
4908

4909
	if (!tg->parent)	/* the trivial, non-cgroup case */
4910 4911
		return wl;

P
Peter Zijlstra 已提交
4912
	for_each_sched_entity(se) {
4913
		long w, W;
P
Peter Zijlstra 已提交
4914

4915
		tg = se->my_q->tg;
4916

4917 4918 4919 4920
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
4921

4922 4923 4924
		/*
		 * w = rw_i + @wl
		 */
4925
		w = cfs_rq_load_avg(se->my_q) + wl;
4926

4927 4928 4929 4930
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
4931
			wl = (w * (long)tg->shares) / W;
4932 4933
		else
			wl = tg->shares;
4934

4935 4936 4937 4938 4939
		/*
		 * 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().
		 */
4940 4941
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
4942 4943 4944 4945

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
4946
		wl -= se->avg.load_avg;
4947 4948 4949 4950 4951 4952 4953 4954

		/*
		 * 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
4955 4956
		wg = 0;
	}
4957

P
Peter Zijlstra 已提交
4958
	return wl;
4959 4960
}
#else
P
Peter Zijlstra 已提交
4961

4962
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
P
Peter Zijlstra 已提交
4963
{
4964
	return wl;
4965
}
P
Peter Zijlstra 已提交
4966

4967 4968
#endif

P
Peter Zijlstra 已提交
4969 4970 4971 4972 4973 4974 4975 4976 4977 4978 4979 4980 4981 4982 4983 4984 4985
static void record_wakee(struct task_struct *p)
{
	/*
	 * Only decay a single time; tasks that have less then 1 wakeup per
	 * jiffy will not have built up many flips.
	 */
	if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
		current->wakee_flips >>= 1;
		current->wakee_flip_decay_ts = jiffies;
	}

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

M
Mike Galbraith 已提交
4986 4987
/*
 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
P
Peter Zijlstra 已提交
4988
 *
M
Mike Galbraith 已提交
4989
 * A waker of many should wake a different task than the one last awakened
P
Peter Zijlstra 已提交
4990 4991 4992 4993 4994 4995 4996 4997 4998 4999 5000 5001
 * at a frequency roughly N times higher than one of its wakees.
 *
 * In order to determine whether we should let the load spread vs consolidating
 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
 * partner, and a factor of lls_size higher frequency in the other.
 *
 * With both conditions met, we can be relatively sure that the relationship is
 * non-monogamous, with partner count exceeding socket size.
 *
 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
 * whatever is irrelevant, spread criteria is apparent partner count exceeds
 * socket size.
M
Mike Galbraith 已提交
5002
 */
5003 5004
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
5005 5006
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
5007
	int factor = this_cpu_read(sd_llc_size);
5008

M
Mike Galbraith 已提交
5009 5010 5011 5012 5013
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
5014 5015
}

5016
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
5017
{
5018
	s64 this_load, load;
5019
	s64 this_eff_load, prev_eff_load;
5020 5021
	int idx, this_cpu, prev_cpu;
	struct task_group *tg;
5022
	unsigned long weight;
5023
	int balanced;
5024

5025 5026 5027 5028 5029
	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);
5030

5031 5032 5033 5034 5035
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
5036 5037
	if (sync) {
		tg = task_group(current);
5038
		weight = current->se.avg.load_avg;
5039

5040
		this_load += effective_load(tg, this_cpu, -weight, -weight);
5041 5042
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
5043

5044
	tg = task_group(p);
5045
	weight = p->se.avg.load_avg;
5046

5047 5048
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5049 5050 5051
	 * 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.
5052 5053 5054 5055
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
5056 5057
	this_eff_load = 100;
	this_eff_load *= capacity_of(prev_cpu);
5058

5059 5060
	prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
	prev_eff_load *= capacity_of(this_cpu);
5061

5062
	if (this_load > 0) {
5063 5064 5065 5066
		this_eff_load *= this_load +
			effective_load(tg, this_cpu, weight, weight);

		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
5067
	}
5068

5069
	balanced = this_eff_load <= prev_eff_load;
5070

5071
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
5072

5073 5074
	if (!balanced)
		return 0;
5075

5076 5077 5078 5079
	schedstat_inc(sd, ttwu_move_affine);
	schedstat_inc(p, se.statistics.nr_wakeups_affine);

	return 1;
5080 5081
}

5082 5083 5084 5085 5086
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
5087
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5088
		  int this_cpu, int sd_flag)
5089
{
5090
	struct sched_group *idlest = NULL, *group = sd->groups;
5091
	unsigned long min_load = ULONG_MAX, this_load = 0;
5092
	int load_idx = sd->forkexec_idx;
5093
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
5094

5095 5096 5097
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

5098 5099 5100 5101
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
5102

5103 5104
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
5105
					tsk_cpus_allowed(p)))
5106 5107 5108 5109 5110 5111 5112 5113 5114 5115 5116 5117 5118 5119 5120 5121 5122 5123
			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;
		}

5124
		/* Adjust by relative CPU capacity of the group */
5125
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
5126 5127 5128 5129 5130 5131 5132 5133 5134 5135 5136 5137 5138 5139 5140 5141 5142 5143 5144 5145 5146

		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;
5147 5148 5149 5150
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
5151 5152 5153
	int i;

	/* Traverse only the allowed CPUs */
5154
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
5155 5156 5157 5158 5159 5160 5161 5162 5163 5164 5165 5166 5167 5168 5169 5170 5171 5172 5173 5174 5175 5176
		if (idle_cpu(i)) {
			struct rq *rq = cpu_rq(i);
			struct cpuidle_state *idle = idle_get_state(rq);
			if (idle && idle->exit_latency < min_exit_latency) {
				/*
				 * We give priority to a CPU whose idle state
				 * has the smallest exit latency irrespective
				 * of any idle timestamp.
				 */
				min_exit_latency = idle->exit_latency;
				latest_idle_timestamp = rq->idle_stamp;
				shallowest_idle_cpu = i;
			} else if ((!idle || idle->exit_latency == min_exit_latency) &&
				   rq->idle_stamp > latest_idle_timestamp) {
				/*
				 * If equal or no active idle state, then
				 * the most recently idled CPU might have
				 * a warmer cache.
				 */
				latest_idle_timestamp = rq->idle_stamp;
				shallowest_idle_cpu = i;
			}
5177
		} else if (shallowest_idle_cpu == -1) {
5178 5179 5180 5181 5182
			load = weighted_cpuload(i);
			if (load < min_load || (load == min_load && i == this_cpu)) {
				min_load = load;
				least_loaded_cpu = i;
			}
5183 5184 5185
		}
	}

5186
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5187
}
5188

5189 5190 5191
/*
 * Try and locate an idle CPU in the sched_domain.
 */
5192
static int select_idle_sibling(struct task_struct *p, int target)
5193
{
5194
	struct sched_domain *sd;
5195
	struct sched_group *sg;
5196
	int i = task_cpu(p);
5197

5198 5199
	if (idle_cpu(target))
		return target;
5200 5201

	/*
5202
	 * If the prevous cpu is cache affine and idle, don't be stupid.
5203
	 */
5204 5205
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
5206 5207

	/*
5208 5209 5210 5211 5212 5213 5214 5215 5216 5217 5218 5219 5220
	 * Otherwise, iterate the domains and find an eligible idle cpu.
	 *
	 * A completely idle sched group at higher domains is more
	 * desirable than an idle group at a lower level, because lower
	 * domains have smaller groups and usually share hardware
	 * resources which causes tasks to contend on them, e.g. x86
	 * hyperthread siblings in the lowest domain (SMT) can contend
	 * on the shared cpu pipeline.
	 *
	 * However, while we prefer idle groups at higher domains
	 * finding an idle cpu at the lowest domain is still better than
	 * returning 'target', which we've already established, isn't
	 * idle.
5221
	 */
5222
	sd = rcu_dereference(per_cpu(sd_llc, target));
5223
	for_each_lower_domain(sd) {
5224 5225 5226 5227 5228 5229
		sg = sd->groups;
		do {
			if (!cpumask_intersects(sched_group_cpus(sg),
						tsk_cpus_allowed(p)))
				goto next;

5230
			/* Ensure the entire group is idle */
5231
			for_each_cpu(i, sched_group_cpus(sg)) {
5232
				if (i == target || !idle_cpu(i))
5233 5234
					goto next;
			}
5235

5236 5237 5238 5239
			/*
			 * It doesn't matter which cpu we pick, the
			 * whole group is idle.
			 */
5240 5241 5242 5243 5244 5245 5246 5247
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
5248 5249
	return target;
}
5250

5251
/*
5252
 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5253
 * tasks. The unit of the return value must be the one of capacity so we can
5254 5255
 * compare the utilization with the capacity of the CPU that is available for
 * CFS task (ie cpu_capacity).
5256 5257 5258 5259 5260 5261 5262 5263 5264 5265 5266 5267 5268 5269 5270 5271 5272 5273 5274 5275
 *
 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
 * recent utilization of currently non-runnable tasks on a CPU. It represents
 * the amount of utilization of a CPU in the range [0..capacity_orig] where
 * capacity_orig is the cpu_capacity available at the highest frequency
 * (arch_scale_freq_capacity()).
 * The utilization of a CPU converges towards a sum equal to or less than the
 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
 * the running time on this CPU scaled by capacity_curr.
 *
 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
 * higher than capacity_orig because of unfortunate rounding in
 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
 * the average stabilizes with the new running time. We need to check that the
 * utilization stays within the range of [0..capacity_orig] and cap it if
 * necessary. Without utilization capping, a group could be seen as overloaded
 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
 * available capacity. We allow utilization to overshoot capacity_curr (but not
 * capacity_orig) as it useful for predicting the capacity required after task
 * migrations (scheduler-driven DVFS).
5276
 */
5277
static int cpu_util(int cpu)
5278
{
5279
	unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
5280 5281
	unsigned long capacity = capacity_orig_of(cpu);

5282
	return (util >= capacity) ? capacity : util;
5283
}
5284

5285
/*
5286 5287 5288
 * select_task_rq_fair: Select target runqueue for the waking task in domains
 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5289
 *
5290 5291
 * Balances load by selecting the idlest cpu in the idlest group, or under
 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5292
 *
5293
 * Returns the target cpu number.
5294 5295 5296
 *
 * preempt must be disabled.
 */
5297
static int
5298
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5299
{
5300
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5301
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
5302
	int new_cpu = prev_cpu;
5303
	int want_affine = 0;
5304
	int sync = wake_flags & WF_SYNC;
5305

P
Peter Zijlstra 已提交
5306 5307
	if (sd_flag & SD_BALANCE_WAKE) {
		record_wakee(p);
M
Mike Galbraith 已提交
5308
		want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
P
Peter Zijlstra 已提交
5309
	}
5310

5311
	rcu_read_lock();
5312
	for_each_domain(cpu, tmp) {
5313
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
5314
			break;
5315

5316
		/*
5317 5318
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
5319
		 */
5320 5321 5322
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
5323
			break;
5324
		}
5325

5326
		if (tmp->flags & sd_flag)
5327
			sd = tmp;
M
Mike Galbraith 已提交
5328 5329
		else if (!want_affine)
			break;
5330 5331
	}

M
Mike Galbraith 已提交
5332 5333 5334 5335
	if (affine_sd) {
		sd = NULL; /* Prefer wake_affine over balance flags */
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
			new_cpu = cpu;
5336
	}
5337

M
Mike Galbraith 已提交
5338 5339 5340 5341 5342
	if (!sd) {
		if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
			new_cpu = select_idle_sibling(p, new_cpu);

	} else while (sd) {
5343
		struct sched_group *group;
5344
		int weight;
5345

5346
		if (!(sd->flags & sd_flag)) {
5347 5348 5349
			sd = sd->child;
			continue;
		}
5350

5351
		group = find_idlest_group(sd, p, cpu, sd_flag);
5352 5353 5354 5355
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
5356

5357
		new_cpu = find_idlest_cpu(group, p, cpu);
5358 5359 5360 5361
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
5362
		}
5363 5364 5365

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
5366
		weight = sd->span_weight;
5367 5368
		sd = NULL;
		for_each_domain(cpu, tmp) {
5369
			if (weight <= tmp->span_weight)
5370
				break;
5371
			if (tmp->flags & sd_flag)
5372 5373 5374
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
5375
	}
5376
	rcu_read_unlock();
5377

5378
	return new_cpu;
5379
}
5380 5381 5382 5383

/*
 * 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
5384
 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5385
 */
5386
static void migrate_task_rq_fair(struct task_struct *p)
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
	/*
	 * As blocked tasks retain absolute vruntime the migration needs to
	 * deal with this by subtracting the old and adding the new
	 * min_vruntime -- the latter is done by enqueue_entity() when placing
	 * the task on the new runqueue.
	 */
	if (p->state == TASK_WAKING) {
		struct sched_entity *se = &p->se;
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
		u64 min_vruntime;

#ifndef CONFIG_64BIT
		u64 min_vruntime_copy;

		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

		se->vruntime -= min_vruntime;
	}

5414
	/*
5415 5416 5417 5418 5419
	 * We are supposed to update the task to "current" time, then its up to date
	 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
	 * what current time is, so simply throw away the out-of-date time. This
	 * will result in the wakee task is less decayed, but giving the wakee more
	 * load sounds not bad.
5420
	 */
5421 5422 5423 5424
	remove_entity_load_avg(&p->se);

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
5425 5426

	/* We have migrated, no longer consider this task hot */
5427
	p->se.exec_start = 0;
5428
}
5429 5430 5431 5432 5433

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
5434 5435
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
5436 5437
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5438 5439 5440 5441
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
5442 5443
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
5444 5445 5446 5447 5448 5449 5450 5451 5452
	 *
	 * 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.
5453
	 */
5454
	return calc_delta_fair(gran, se);
5455 5456
}

5457 5458 5459 5460 5461 5462 5463 5464 5465 5466 5467 5468 5469 5470 5471 5472 5473 5474 5475 5476 5477 5478
/*
 * 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
5479
	gran = wakeup_gran(curr, se);
5480 5481 5482 5483 5484 5485
	if (vdiff > gran)
		return 1;

	return 0;
}

5486 5487
static void set_last_buddy(struct sched_entity *se)
{
5488 5489 5490 5491 5492
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
5493 5494 5495 5496
}

static void set_next_buddy(struct sched_entity *se)
{
5497 5498 5499 5500 5501
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
5502 5503
}

5504 5505
static void set_skip_buddy(struct sched_entity *se)
{
5506 5507
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
5508 5509
}

5510 5511 5512
/*
 * Preempt the current task with a newly woken task if needed:
 */
5513
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5514 5515
{
	struct task_struct *curr = rq->curr;
5516
	struct sched_entity *se = &curr->se, *pse = &p->se;
5517
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5518
	int scale = cfs_rq->nr_running >= sched_nr_latency;
5519
	int next_buddy_marked = 0;
5520

I
Ingo Molnar 已提交
5521 5522 5523
	if (unlikely(se == pse))
		return;

5524
	/*
5525
	 * This is possible from callers such as attach_tasks(), in which we
5526 5527 5528 5529 5530 5531 5532
	 * 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;

5533
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
5534
		set_next_buddy(pse);
5535 5536
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
5537

5538 5539 5540
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
5541 5542 5543 5544 5545 5546
	 *
	 * 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.
5547 5548 5549 5550
	 */
	if (test_tsk_need_resched(curr))
		return;

5551 5552 5553 5554 5555
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

5556
	/*
5557 5558
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
5559
	 */
5560
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5561
		return;
5562

5563
	find_matching_se(&se, &pse);
5564
	update_curr(cfs_rq_of(se));
5565
	BUG_ON(!pse);
5566 5567 5568 5569 5570 5571 5572
	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);
5573
		goto preempt;
5574
	}
5575

5576
	return;
5577

5578
preempt:
5579
	resched_curr(rq);
5580 5581 5582 5583 5584 5585 5586 5587 5588 5589 5590 5591 5592 5593
	/*
	 * 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);
5594 5595
}

5596
static struct task_struct *
5597
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct pin_cookie cookie)
5598 5599 5600
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
5601
	struct task_struct *p;
5602
	int new_tasks;
5603

5604
again:
5605 5606
#ifdef CONFIG_FAIR_GROUP_SCHED
	if (!cfs_rq->nr_running)
5607
		goto idle;
5608

5609
	if (prev->sched_class != &fair_sched_class)
5610 5611 5612 5613 5614 5615 5616 5617 5618 5619 5620 5621 5622 5623 5624 5625 5626 5627 5628
		goto simple;

	/*
	 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
	 * likely that a next task is from the same cgroup as the current.
	 *
	 * Therefore attempt to avoid putting and setting the entire cgroup
	 * hierarchy, only change the part that actually changes.
	 */

	do {
		struct sched_entity *curr = cfs_rq->curr;

		/*
		 * Since we got here without doing put_prev_entity() we also
		 * have to consider cfs_rq->curr. If it is still a runnable
		 * entity, update_curr() will update its vruntime, otherwise
		 * forget we've ever seen it.
		 */
5629 5630 5631 5632 5633
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
5634

5635 5636 5637 5638 5639 5640 5641 5642 5643
			/*
			 * This call to check_cfs_rq_runtime() will do the
			 * throttle and dequeue its entity in the parent(s).
			 * Therefore the 'simple' nr_running test will indeed
			 * be correct.
			 */
			if (unlikely(check_cfs_rq_runtime(cfs_rq)))
				goto simple;
		}
5644 5645 5646 5647 5648 5649 5650 5651 5652 5653 5654 5655 5656 5657 5658 5659 5660 5661 5662 5663 5664 5665 5666 5667 5668 5669 5670 5671 5672 5673 5674 5675 5676 5677 5678 5679 5680 5681 5682 5683

		se = pick_next_entity(cfs_rq, curr);
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

	p = task_of(se);

	/*
	 * Since we haven't yet done put_prev_entity and if the selected task
	 * is a different task than we started out with, try and touch the
	 * least amount of cfs_rqs.
	 */
	if (prev != p) {
		struct sched_entity *pse = &prev->se;

		while (!(cfs_rq = is_same_group(se, pse))) {
			int se_depth = se->depth;
			int pse_depth = pse->depth;

			if (se_depth <= pse_depth) {
				put_prev_entity(cfs_rq_of(pse), pse);
				pse = parent_entity(pse);
			}
			if (se_depth >= pse_depth) {
				set_next_entity(cfs_rq_of(se), se);
				se = parent_entity(se);
			}
		}

		put_prev_entity(cfs_rq, pse);
		set_next_entity(cfs_rq, se);
	}

	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);

	return p;
simple:
	cfs_rq = &rq->cfs;
#endif
5684

5685
	if (!cfs_rq->nr_running)
5686
		goto idle;
5687

5688
	put_prev_task(rq, prev);
5689

5690
	do {
5691
		se = pick_next_entity(cfs_rq, NULL);
5692
		set_next_entity(cfs_rq, se);
5693 5694 5695
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
5696
	p = task_of(se);
5697

5698 5699
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
5700 5701

	return p;
5702 5703

idle:
5704 5705 5706 5707 5708 5709
	/*
	 * This is OK, because current is on_cpu, which avoids it being picked
	 * for load-balance and preemption/IRQs are still disabled avoiding
	 * further scheduler activity on it and we're being very careful to
	 * re-start the picking loop.
	 */
5710
	lockdep_unpin_lock(&rq->lock, cookie);
5711
	new_tasks = idle_balance(rq);
5712
	lockdep_repin_lock(&rq->lock, cookie);
5713 5714 5715 5716 5717
	/*
	 * Because idle_balance() releases (and re-acquires) rq->lock, it is
	 * possible for any higher priority task to appear. In that case we
	 * must re-start the pick_next_entity() loop.
	 */
5718
	if (new_tasks < 0)
5719 5720
		return RETRY_TASK;

5721
	if (new_tasks > 0)
5722 5723 5724
		goto again;

	return NULL;
5725 5726 5727 5728 5729
}

/*
 * Account for a descheduled task:
 */
5730
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5731 5732 5733 5734 5735 5736
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5737
		put_prev_entity(cfs_rq, se);
5738 5739 5740
	}
}

5741 5742 5743 5744 5745 5746 5747 5748 5749 5750 5751 5752 5753 5754 5755 5756 5757 5758 5759 5760 5761 5762 5763 5764 5765
/*
 * 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);
5766 5767 5768 5769 5770
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
5771
		rq_clock_skip_update(rq, true);
5772 5773 5774 5775 5776
	}

	set_skip_buddy(se);
}

5777 5778 5779 5780
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

5781 5782
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5783 5784 5785 5786 5787 5788 5789 5790 5791 5792
		return false;

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

	yield_task_fair(rq);

	return true;
}

5793
#ifdef CONFIG_SMP
5794
/**************************************************
P
Peter Zijlstra 已提交
5795 5796 5797 5798 5799 5800 5801 5802 5803 5804 5805 5806 5807 5808 5809 5810
 * 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
5811
 * is derived from the nice value as per sched_prio_to_weight[].
P
Peter Zijlstra 已提交
5812 5813 5814 5815 5816 5817
 *
 * 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)
 *
5818
 * C_i is the compute capacity of cpu i, typically it is the
P
Peter Zijlstra 已提交
5819 5820 5821 5822 5823 5824
 * 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):
 *
5825
 *   imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j }    (4)
P
Peter Zijlstra 已提交
5826 5827 5828 5829 5830 5831 5832 5833 5834 5835 5836 5837 5838 5839 5840 5841 5842 5843 5844 5845 5846 5847 5848 5849 5850 5851 5852 5853 5854 5855 5856 5857 5858 5859 5860 5861 5862 5863 5864 5865 5866 5867 5868 5869 5870 5871 5872 5873 5874 5875 5876 5877 5878 5879 5880 5881 5882 5883 5884 5885 5886 5887 5888 5889 5890 5891 5892 5893 5894 5895 5896 5897 5898 5899 5900 5901 5902 5903 5904 5905 5906 5907 5908 5909 5910
 *
 * 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.]
 */ 
5911

5912 5913
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

5914 5915
enum fbq_type { regular, remote, all };

5916
#define LBF_ALL_PINNED	0x01
5917
#define LBF_NEED_BREAK	0x02
5918 5919
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
5920 5921 5922 5923 5924

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
5925
	int			src_cpu;
5926 5927 5928 5929

	int			dst_cpu;
	struct rq		*dst_rq;

5930 5931
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
5932
	enum cpu_idle_type	idle;
5933
	long			imbalance;
5934 5935 5936
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

5937
	unsigned int		flags;
5938 5939 5940 5941

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
5942 5943

	enum fbq_type		fbq_type;
5944
	struct list_head	tasks;
5945 5946
};

5947 5948 5949
/*
 * Is this task likely cache-hot:
 */
5950
static int task_hot(struct task_struct *p, struct lb_env *env)
5951 5952 5953
{
	s64 delta;

5954 5955
	lockdep_assert_held(&env->src_rq->lock);

5956 5957 5958 5959 5960 5961 5962 5963 5964
	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
5965
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5966 5967 5968 5969 5970 5971 5972 5973 5974
			(&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;

5975
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5976 5977 5978 5979

	return delta < (s64)sysctl_sched_migration_cost;
}

5980
#ifdef CONFIG_NUMA_BALANCING
5981
/*
5982 5983 5984
 * Returns 1, if task migration degrades locality
 * Returns 0, if task migration improves locality i.e migration preferred.
 * Returns -1, if task migration is not affected by locality.
5985
 */
5986
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5987
{
5988
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
5989
	unsigned long src_faults, dst_faults;
5990 5991
	int src_nid, dst_nid;

5992
	if (!static_branch_likely(&sched_numa_balancing))
5993 5994
		return -1;

5995
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5996
		return -1;
5997 5998 5999 6000

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

6001
	if (src_nid == dst_nid)
6002
		return -1;
6003

6004 6005 6006 6007 6008 6009 6010
	/* Migrating away from the preferred node is always bad. */
	if (src_nid == p->numa_preferred_nid) {
		if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
			return 1;
		else
			return -1;
	}
6011

6012 6013
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
6014
		return 0;
6015

6016 6017 6018 6019 6020 6021
	if (numa_group) {
		src_faults = group_faults(p, src_nid);
		dst_faults = group_faults(p, dst_nid);
	} else {
		src_faults = task_faults(p, src_nid);
		dst_faults = task_faults(p, dst_nid);
6022 6023
	}

6024
	return dst_faults < src_faults;
6025 6026
}

6027
#else
6028
static inline int migrate_degrades_locality(struct task_struct *p,
6029 6030
					     struct lb_env *env)
{
6031
	return -1;
6032
}
6033 6034
#endif

6035 6036 6037 6038
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
6039
int can_migrate_task(struct task_struct *p, struct lb_env *env)
6040
{
6041
	int tsk_cache_hot;
6042 6043 6044

	lockdep_assert_held(&env->src_rq->lock);

6045 6046
	/*
	 * We do not migrate tasks that are:
6047
	 * 1) throttled_lb_pair, or
6048
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6049 6050
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
6051
	 */
6052 6053 6054
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

6055
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
6056
		int cpu;
6057

6058
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
6059

6060 6061
		env->flags |= LBF_SOME_PINNED;

6062 6063 6064 6065 6066 6067 6068 6069
		/*
		 * 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.
		 */
6070
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
6071 6072
			return 0;

6073 6074 6075
		/* 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))) {
6076
				env->flags |= LBF_DST_PINNED;
6077 6078 6079
				env->new_dst_cpu = cpu;
				break;
			}
6080
		}
6081

6082 6083
		return 0;
	}
6084 6085

	/* Record that we found atleast one task that could run on dst_cpu */
6086
	env->flags &= ~LBF_ALL_PINNED;
6087

6088
	if (task_running(env->src_rq, p)) {
6089
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
6090 6091 6092 6093 6094
		return 0;
	}

	/*
	 * Aggressive migration if:
6095 6096 6097
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
6098
	 */
6099 6100 6101
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
6102

6103
	if (tsk_cache_hot <= 0 ||
6104
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6105
		if (tsk_cache_hot == 1) {
6106 6107 6108
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
			schedstat_inc(p, se.statistics.nr_forced_migrations);
		}
6109 6110 6111
		return 1;
	}

Z
Zhang Hang 已提交
6112 6113
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
6114 6115
}

6116
/*
6117 6118 6119 6120 6121 6122 6123
 * detach_task() -- detach the task for the migration specified in env
 */
static void detach_task(struct task_struct *p, struct lb_env *env)
{
	lockdep_assert_held(&env->src_rq->lock);

	p->on_rq = TASK_ON_RQ_MIGRATING;
6124
	deactivate_task(env->src_rq, p, 0);
6125 6126 6127
	set_task_cpu(p, env->dst_cpu);
}

6128
/*
6129
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6130 6131
 * part of active balancing operations within "domain".
 *
6132
 * Returns a task if successful and NULL otherwise.
6133
 */
6134
static struct task_struct *detach_one_task(struct lb_env *env)
6135 6136 6137
{
	struct task_struct *p, *n;

6138 6139
	lockdep_assert_held(&env->src_rq->lock);

6140 6141 6142
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
6143

6144
		detach_task(p, env);
6145

6146
		/*
6147
		 * Right now, this is only the second place where
6148
		 * lb_gained[env->idle] is updated (other is detach_tasks)
6149
		 * so we can safely collect stats here rather than
6150
		 * inside detach_tasks().
6151 6152
		 */
		schedstat_inc(env->sd, lb_gained[env->idle]);
6153
		return p;
6154
	}
6155
	return NULL;
6156 6157
}

6158 6159
static const unsigned int sched_nr_migrate_break = 32;

6160
/*
6161 6162
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
6163
 *
6164
 * Returns number of detached tasks if successful and 0 otherwise.
6165
 */
6166
static int detach_tasks(struct lb_env *env)
6167
{
6168 6169
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
6170
	unsigned long load;
6171 6172 6173
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
6174

6175
	if (env->imbalance <= 0)
6176
		return 0;
6177

6178
	while (!list_empty(tasks)) {
6179 6180 6181 6182 6183 6184 6185
		/*
		 * We don't want to steal all, otherwise we may be treated likewise,
		 * which could at worst lead to a livelock crash.
		 */
		if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
			break;

6186
		p = list_first_entry(tasks, struct task_struct, se.group_node);
6187

6188 6189
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
6190
		if (env->loop > env->loop_max)
6191
			break;
6192 6193

		/* take a breather every nr_migrate tasks */
6194
		if (env->loop > env->loop_break) {
6195
			env->loop_break += sched_nr_migrate_break;
6196
			env->flags |= LBF_NEED_BREAK;
6197
			break;
6198
		}
6199

6200
		if (!can_migrate_task(p, env))
6201 6202 6203
			goto next;

		load = task_h_load(p);
6204

6205
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6206 6207
			goto next;

6208
		if ((load / 2) > env->imbalance)
6209
			goto next;
6210

6211 6212 6213 6214
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
6215
		env->imbalance -= load;
6216 6217

#ifdef CONFIG_PREEMPT
6218 6219
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
6220
		 * kernels will stop after the first task is detached to minimize
6221 6222
		 * the critical section.
		 */
6223
		if (env->idle == CPU_NEWLY_IDLE)
6224
			break;
6225 6226
#endif

6227 6228 6229 6230
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
6231
		if (env->imbalance <= 0)
6232
			break;
6233 6234 6235

		continue;
next:
6236
		list_move_tail(&p->se.group_node, tasks);
6237
	}
6238

6239
	/*
6240 6241 6242
	 * Right now, this is one of only two places we collect this stat
	 * so we can safely collect detach_one_task() stats here rather
	 * than inside detach_one_task().
6243
	 */
6244
	schedstat_add(env->sd, lb_gained[env->idle], detached);
6245

6246 6247 6248 6249 6250 6251 6252 6253 6254 6255 6256 6257
	return detached;
}

/*
 * attach_task() -- attach the task detached by detach_task() to its new rq.
 */
static void attach_task(struct rq *rq, struct task_struct *p)
{
	lockdep_assert_held(&rq->lock);

	BUG_ON(task_rq(p) != rq);
	activate_task(rq, p, 0);
6258
	p->on_rq = TASK_ON_RQ_QUEUED;
6259 6260 6261 6262 6263 6264 6265 6266 6267 6268 6269 6270 6271 6272 6273 6274 6275 6276 6277 6278 6279 6280 6281 6282 6283 6284 6285 6286
	check_preempt_curr(rq, p, 0);
}

/*
 * attach_one_task() -- attaches the task returned from detach_one_task() to
 * its new rq.
 */
static void attach_one_task(struct rq *rq, struct task_struct *p)
{
	raw_spin_lock(&rq->lock);
	attach_task(rq, p);
	raw_spin_unlock(&rq->lock);
}

/*
 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
 * new rq.
 */
static void attach_tasks(struct lb_env *env)
{
	struct list_head *tasks = &env->tasks;
	struct task_struct *p;

	raw_spin_lock(&env->dst_rq->lock);

	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
		list_del_init(&p->se.group_node);
6287

6288 6289 6290 6291
		attach_task(env->dst_rq, p);
	}

	raw_spin_unlock(&env->dst_rq->lock);
6292 6293
}

P
Peter Zijlstra 已提交
6294
#ifdef CONFIG_FAIR_GROUP_SCHED
6295
static void update_blocked_averages(int cpu)
6296 6297
{
	struct rq *rq = cpu_rq(cpu);
6298 6299
	struct cfs_rq *cfs_rq;
	unsigned long flags;
6300

6301 6302
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
6303

6304 6305 6306 6307
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
6308
	for_each_leaf_cfs_rq(rq, cfs_rq) {
6309 6310 6311
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
6312

6313
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true))
6314 6315
			update_tg_load_avg(cfs_rq, 0);
	}
6316
	raw_spin_unlock_irqrestore(&rq->lock, flags);
6317 6318
}

6319
/*
6320
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6321 6322 6323
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
6324
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6325
{
6326 6327
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6328
	unsigned long now = jiffies;
6329
	unsigned long load;
6330

6331
	if (cfs_rq->last_h_load_update == now)
6332 6333
		return;

6334 6335 6336 6337 6338 6339 6340
	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;
	}
6341

6342
	if (!se) {
6343
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6344 6345 6346 6347 6348
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
6349 6350
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
6351 6352 6353 6354
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
6355 6356
}

6357
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
6358
{
6359
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
6360

6361
	update_cfs_rq_h_load(cfs_rq);
6362
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6363
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
6364 6365
}
#else
6366
static inline void update_blocked_averages(int cpu)
6367
{
6368 6369 6370 6371 6372 6373
	struct rq *rq = cpu_rq(cpu);
	struct cfs_rq *cfs_rq = &rq->cfs;
	unsigned long flags;

	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
6374
	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true);
6375
	raw_spin_unlock_irqrestore(&rq->lock, flags);
6376 6377
}

6378
static unsigned long task_h_load(struct task_struct *p)
6379
{
6380
	return p->se.avg.load_avg;
6381
}
P
Peter Zijlstra 已提交
6382
#endif
6383 6384

/********** Helpers for find_busiest_group ************************/
6385 6386 6387 6388 6389 6390 6391

enum group_type {
	group_other = 0,
	group_imbalanced,
	group_overloaded,
};

6392 6393 6394 6395 6396 6397 6398
/*
 * 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
6399
	unsigned long load_per_task;
6400
	unsigned long group_capacity;
6401
	unsigned long group_util; /* Total utilization of the group */
6402 6403 6404
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
6405
	enum group_type group_type;
6406
	int group_no_capacity;
6407 6408 6409 6410
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
6411 6412
};

J
Joonsoo Kim 已提交
6413 6414 6415 6416 6417 6418 6419 6420
/*
 * 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 */
6421
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
6422 6423 6424
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6425
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
6426 6427
};

6428 6429 6430 6431 6432 6433 6434 6435 6436 6437 6438 6439
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,
6440
		.total_capacity = 0UL,
6441 6442
		.busiest_stat = {
			.avg_load = 0UL,
6443 6444
			.sum_nr_running = 0,
			.group_type = group_other,
6445 6446 6447 6448
		},
	};
}

6449 6450 6451
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
6452
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6453 6454
 *
 * Return: The load index.
6455 6456 6457 6458 6459 6460 6461 6462 6463 6464 6465 6466 6467 6468 6469 6470 6471 6472 6473 6474 6475 6476
 */
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;
}

6477
static unsigned long scale_rt_capacity(int cpu)
6478 6479
{
	struct rq *rq = cpu_rq(cpu);
6480
	u64 total, used, age_stamp, avg;
6481
	s64 delta;
6482

6483 6484 6485 6486
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
6487 6488
	age_stamp = READ_ONCE(rq->age_stamp);
	avg = READ_ONCE(rq->rt_avg);
6489
	delta = __rq_clock_broken(rq) - age_stamp;
6490

6491 6492 6493 6494
	if (unlikely(delta < 0))
		delta = 0;

	total = sched_avg_period() + delta;
6495

6496
	used = div_u64(avg, total);
6497

6498 6499
	if (likely(used < SCHED_CAPACITY_SCALE))
		return SCHED_CAPACITY_SCALE - used;
6500

6501
	return 1;
6502 6503
}

6504
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6505
{
6506
	unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6507 6508
	struct sched_group *sdg = sd->groups;

6509
	cpu_rq(cpu)->cpu_capacity_orig = capacity;
6510

6511
	capacity *= scale_rt_capacity(cpu);
6512
	capacity >>= SCHED_CAPACITY_SHIFT;
6513

6514 6515
	if (!capacity)
		capacity = 1;
6516

6517 6518
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
6519 6520
}

6521
void update_group_capacity(struct sched_domain *sd, int cpu)
6522 6523 6524
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
6525
	unsigned long capacity;
6526 6527 6528 6529
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
6530
	sdg->sgc->next_update = jiffies + interval;
6531 6532

	if (!child) {
6533
		update_cpu_capacity(sd, cpu);
6534 6535 6536
		return;
	}

6537
	capacity = 0;
6538

P
Peter Zijlstra 已提交
6539 6540 6541 6542 6543 6544
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

6545
		for_each_cpu(cpu, sched_group_cpus(sdg)) {
6546
			struct sched_group_capacity *sgc;
6547
			struct rq *rq = cpu_rq(cpu);
6548

6549
			/*
6550
			 * build_sched_domains() -> init_sched_groups_capacity()
6551 6552 6553
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
6554 6555
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
6556
			 *
6557
			 * This avoids capacity from being 0 and
6558 6559 6560
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
6561
				capacity += capacity_of(cpu);
6562 6563
				continue;
			}
6564

6565 6566
			sgc = rq->sd->groups->sgc;
			capacity += sgc->capacity;
6567
		}
P
Peter Zijlstra 已提交
6568 6569 6570 6571 6572 6573 6574 6575
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
6576
			capacity += group->sgc->capacity;
P
Peter Zijlstra 已提交
6577 6578 6579
			group = group->next;
		} while (group != child->groups);
	}
6580

6581
	sdg->sgc->capacity = capacity;
6582 6583
}

6584
/*
6585 6586 6587
 * Check whether the capacity of the rq has been noticeably reduced by side
 * activity. The imbalance_pct is used for the threshold.
 * Return true is the capacity is reduced
6588 6589
 */
static inline int
6590
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6591
{
6592 6593
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
6594 6595
}

6596 6597 6598 6599 6600 6601 6602 6603 6604 6605 6606 6607 6608 6609 6610 6611
/*
 * 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
6612 6613
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
6614 6615
 *
 * When this is so detected; this group becomes a candidate for busiest; see
6616
 * update_sd_pick_busiest(). And calculate_imbalance() and
6617
 * find_busiest_group() avoid some of the usual balance conditions to allow it
6618 6619 6620 6621 6622 6623 6624
 * 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.
 */

6625
static inline int sg_imbalanced(struct sched_group *group)
6626
{
6627
	return group->sgc->imbalance;
6628 6629
}

6630
/*
6631 6632 6633
 * group_has_capacity returns true if the group has spare capacity that could
 * be used by some tasks.
 * We consider that a group has spare capacity if the  * number of task is
6634 6635
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
6636 6637 6638 6639 6640
 * For the latter, we use a threshold to stabilize the state, to take into
 * account the variance of the tasks' load and to return true if the available
 * capacity in meaningful for the load balancer.
 * As an example, an available capacity of 1% can appear but it doesn't make
 * any benefit for the load balance.
6641
 */
6642 6643
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6644
{
6645 6646
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
6647

6648
	if ((sgs->group_capacity * 100) >
6649
			(sgs->group_util * env->sd->imbalance_pct))
6650
		return true;
6651

6652 6653 6654 6655 6656 6657 6658 6659 6660 6661 6662 6663 6664 6665 6666 6667
	return false;
}

/*
 *  group_is_overloaded returns true if the group has more tasks than it can
 *  handle.
 *  group_is_overloaded is not equals to !group_has_capacity because a group
 *  with the exact right number of tasks, has no more spare capacity but is not
 *  overloaded so both group_has_capacity and group_is_overloaded return
 *  false.
 */
static inline bool
group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
{
	if (sgs->sum_nr_running <= sgs->group_weight)
		return false;
6668

6669
	if ((sgs->group_capacity * 100) <
6670
			(sgs->group_util * env->sd->imbalance_pct))
6671
		return true;
6672

6673
	return false;
6674 6675
}

6676 6677 6678
static inline enum
group_type group_classify(struct sched_group *group,
			  struct sg_lb_stats *sgs)
6679
{
6680
	if (sgs->group_no_capacity)
6681 6682 6683 6684 6685 6686 6687 6688
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

6689 6690
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6691
 * @env: The load balancing environment.
6692 6693 6694 6695
 * @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.
6696
 * @overload: Indicate more than one runnable task for any CPU.
6697
 */
6698 6699
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
6700 6701
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
6702
{
6703
	unsigned long load;
6704
	int i, nr_running;
6705

6706 6707
	memset(sgs, 0, sizeof(*sgs));

6708
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6709 6710 6711
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
6712
		if (local_group)
6713
			load = target_load(i, load_idx);
6714
		else
6715 6716 6717
			load = source_load(i, load_idx);

		sgs->group_load += load;
6718
		sgs->group_util += cpu_util(i);
6719
		sgs->sum_nr_running += rq->cfs.h_nr_running;
6720

6721 6722
		nr_running = rq->nr_running;
		if (nr_running > 1)
6723 6724
			*overload = true;

6725 6726 6727 6728
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
6729
		sgs->sum_weighted_load += weighted_cpuload(i);
6730 6731 6732 6733
		/*
		 * No need to call idle_cpu() if nr_running is not 0
		 */
		if (!nr_running && idle_cpu(i))
6734
			sgs->idle_cpus++;
6735 6736
	}

6737 6738
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
6739
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6740

6741
	if (sgs->sum_nr_running)
6742
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6743

6744
	sgs->group_weight = group->group_weight;
6745

6746
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
6747
	sgs->group_type = group_classify(group, sgs);
6748 6749
}

6750 6751
/**
 * update_sd_pick_busiest - return 1 on busiest group
6752
 * @env: The load balancing environment.
6753 6754
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
6755
 * @sgs: sched_group statistics
6756 6757 6758
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
6759 6760 6761
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
6762
 */
6763
static bool update_sd_pick_busiest(struct lb_env *env,
6764 6765
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
6766
				   struct sg_lb_stats *sgs)
6767
{
6768
	struct sg_lb_stats *busiest = &sds->busiest_stat;
6769

6770
	if (sgs->group_type > busiest->group_type)
6771 6772
		return true;

6773 6774 6775 6776 6777 6778 6779 6780
	if (sgs->group_type < busiest->group_type)
		return false;

	if (sgs->avg_load <= busiest->avg_load)
		return false;

	/* This is the busiest node in its class. */
	if (!(env->sd->flags & SD_ASYM_PACKING))
6781 6782
		return true;

6783 6784 6785
	/* No ASYM_PACKING if target cpu is already busy */
	if (env->idle == CPU_NOT_IDLE)
		return true;
6786 6787 6788 6789 6790
	/*
	 * 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.
	 */
6791
	if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6792 6793 6794
		if (!sds->busiest)
			return true;

6795 6796
		/* Prefer to move from highest possible cpu's work */
		if (group_first_cpu(sds->busiest) < group_first_cpu(sg))
6797 6798 6799 6800 6801 6802
			return true;
	}

	return false;
}

6803 6804 6805 6806 6807 6808 6809 6810 6811 6812 6813 6814 6815 6816 6817 6818 6819 6820 6821 6822 6823 6824 6825 6826 6827 6828 6829 6830 6831 6832
#ifdef CONFIG_NUMA_BALANCING
static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
{
	if (sgs->sum_nr_running > sgs->nr_numa_running)
		return regular;
	if (sgs->sum_nr_running > sgs->nr_preferred_running)
		return remote;
	return all;
}

static inline enum fbq_type fbq_classify_rq(struct rq *rq)
{
	if (rq->nr_running > rq->nr_numa_running)
		return regular;
	if (rq->nr_running > rq->nr_preferred_running)
		return remote;
	return all;
}
#else
static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
{
	return all;
}

static inline enum fbq_type fbq_classify_rq(struct rq *rq)
{
	return regular;
}
#endif /* CONFIG_NUMA_BALANCING */

6833
/**
6834
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6835
 * @env: The load balancing environment.
6836 6837
 * @sds: variable to hold the statistics for this sched_domain.
 */
6838
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6839
{
6840 6841
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
J
Joonsoo Kim 已提交
6842
	struct sg_lb_stats tmp_sgs;
6843
	int load_idx, prefer_sibling = 0;
6844
	bool overload = false;
6845 6846 6847 6848

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

6849
	load_idx = get_sd_load_idx(env->sd, env->idle);
6850 6851

	do {
J
Joonsoo Kim 已提交
6852
		struct sg_lb_stats *sgs = &tmp_sgs;
6853 6854
		int local_group;

6855
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
J
Joonsoo Kim 已提交
6856 6857 6858
		if (local_group) {
			sds->local = sg;
			sgs = &sds->local_stat;
6859 6860

			if (env->idle != CPU_NEWLY_IDLE ||
6861 6862
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
6863
		}
6864

6865 6866
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
6867

6868 6869 6870
		if (local_group)
			goto next_group;

6871 6872
		/*
		 * In case the child domain prefers tasks go to siblings
6873
		 * first, lower the sg capacity so that we'll try
6874 6875
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
6876 6877 6878 6879
		 * these excess tasks. 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).
6880
		 */
6881
		if (prefer_sibling && sds->local &&
6882 6883 6884
		    group_has_capacity(env, &sds->local_stat) &&
		    (sgs->sum_nr_running > 1)) {
			sgs->group_no_capacity = 1;
6885
			sgs->group_type = group_classify(sg, sgs);
6886
		}
6887

6888
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6889
			sds->busiest = sg;
J
Joonsoo Kim 已提交
6890
			sds->busiest_stat = *sgs;
6891 6892
		}

6893 6894 6895
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
6896
		sds->total_capacity += sgs->group_capacity;
6897

6898
		sg = sg->next;
6899
	} while (sg != env->sd->groups);
6900 6901 6902

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6903 6904 6905 6906 6907 6908 6909

	if (!env->sd->parent) {
		/* update overload indicator if we are at root domain */
		if (env->dst_rq->rd->overload != overload)
			env->dst_rq->rd->overload = overload;
	}

6910 6911 6912 6913 6914 6915 6916 6917 6918 6919 6920 6921 6922 6923 6924 6925 6926 6927 6928
}

/**
 * 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.
 *
6929
 * Return: 1 when packing is required and a task should be moved to
6930 6931
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
6932
 * @env: The load balancing environment.
6933 6934
 * @sds: Statistics of the sched_domain which is to be packed
 */
6935
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6936 6937 6938
{
	int busiest_cpu;

6939
	if (!(env->sd->flags & SD_ASYM_PACKING))
6940 6941
		return 0;

6942 6943 6944
	if (env->idle == CPU_NOT_IDLE)
		return 0;

6945 6946 6947 6948
	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
6949
	if (env->dst_cpu > busiest_cpu)
6950 6951
		return 0;

6952
	env->imbalance = DIV_ROUND_CLOSEST(
6953
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6954
		SCHED_CAPACITY_SCALE);
6955

6956
	return 1;
6957 6958 6959 6960 6961 6962
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
6963
 * @env: The load balancing environment.
6964 6965
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
6966 6967
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6968
{
6969
	unsigned long tmp, capa_now = 0, capa_move = 0;
6970
	unsigned int imbn = 2;
6971
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
6972
	struct sg_lb_stats *local, *busiest;
6973

J
Joonsoo Kim 已提交
6974 6975
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6976

J
Joonsoo Kim 已提交
6977 6978 6979 6980
	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;
6981

J
Joonsoo Kim 已提交
6982
	scaled_busy_load_per_task =
6983
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6984
		busiest->group_capacity;
J
Joonsoo Kim 已提交
6985

6986 6987
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
6988
		env->imbalance = busiest->load_per_task;
6989 6990 6991 6992 6993
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
6994
	 * however we may be able to increase total CPU capacity used by
6995 6996 6997
	 * moving them.
	 */

6998
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
6999
			min(busiest->load_per_task, busiest->avg_load);
7000
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
7001
			min(local->load_per_task, local->avg_load);
7002
	capa_now /= SCHED_CAPACITY_SCALE;
7003 7004

	/* Amount of load we'd subtract */
7005
	if (busiest->avg_load > scaled_busy_load_per_task) {
7006
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
7007
			    min(busiest->load_per_task,
7008
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
7009
	}
7010 7011

	/* Amount of load we'd add */
7012
	if (busiest->avg_load * busiest->group_capacity <
7013
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
7014 7015
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
7016
	} else {
7017
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7018
		      local->group_capacity;
J
Joonsoo Kim 已提交
7019
	}
7020
	capa_move += local->group_capacity *
7021
		    min(local->load_per_task, local->avg_load + tmp);
7022
	capa_move /= SCHED_CAPACITY_SCALE;
7023 7024

	/* Move if we gain throughput */
7025
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
7026
		env->imbalance = busiest->load_per_task;
7027 7028 7029 7030 7031
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
7032
 * @env: load balance environment
7033 7034
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
7035
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7036
{
7037
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
7038 7039 7040 7041
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
7042

7043
	if (busiest->group_type == group_imbalanced) {
7044 7045 7046 7047
		/*
		 * 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
7048 7049
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
7050 7051
	}

7052
	/*
7053 7054 7055 7056
	 * Avg load of busiest sg can be less and avg load of local sg can
	 * be greater than avg load across all sgs of sd because avg load
	 * factors in sg capacity and sgs with smaller group_type are
	 * skipped when updating the busiest sg:
7057
	 */
7058 7059
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
7060 7061
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
7062 7063
	}

7064 7065 7066 7067 7068
	/*
	 * If there aren't any idle cpus, avoid creating some.
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
7069
		load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
7070
		if (load_above_capacity > busiest->group_capacity) {
7071
			load_above_capacity -= busiest->group_capacity;
7072 7073 7074
			load_above_capacity *= NICE_0_LOAD;
			load_above_capacity /= busiest->group_capacity;
		} else
7075
			load_above_capacity = ~0UL;
7076 7077 7078 7079 7080 7081
	}

	/*
	 * 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,
7082 7083
	 * we also don't want to reduce the group load below the group
	 * capacity. Thus we look for the minimum possible imbalance.
7084
	 */
7085
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7086 7087

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
7088
	env->imbalance = min(
7089 7090
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
7091
	) / SCHED_CAPACITY_SCALE;
7092 7093 7094

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
7095
	 * there is no guarantee that any tasks will be moved so we'll have
7096 7097 7098
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
7099
	if (env->imbalance < busiest->load_per_task)
7100
		return fix_small_imbalance(env, sds);
7101
}
7102

7103 7104 7105 7106
/******* find_busiest_group() helpers end here *********************/

/**
 * find_busiest_group - Returns the busiest group within the sched_domain
7107
 * if there is an imbalance.
7108 7109 7110 7111
 *
 * Also calculates the amount of weighted load which should be moved
 * to restore balance.
 *
7112
 * @env: The load balancing environment.
7113
 *
7114
 * Return:	- The busiest group if imbalance exists.
7115
 */
J
Joonsoo Kim 已提交
7116
static struct sched_group *find_busiest_group(struct lb_env *env)
7117
{
J
Joonsoo Kim 已提交
7118
	struct sg_lb_stats *local, *busiest;
7119 7120
	struct sd_lb_stats sds;

7121
	init_sd_lb_stats(&sds);
7122 7123 7124 7125 7126

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
7127
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
7128 7129
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
7130

7131
	/* ASYM feature bypasses nice load balance check */
7132
	if (check_asym_packing(env, &sds))
7133 7134
		return sds.busiest;

7135
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
7136
	if (!sds.busiest || busiest->sum_nr_running == 0)
7137 7138
		goto out_balanced;

7139 7140
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
7141

P
Peter Zijlstra 已提交
7142 7143
	/*
	 * If the busiest group is imbalanced the below checks don't
7144
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
7145 7146
	 * isn't true due to cpus_allowed constraints and the like.
	 */
7147
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
7148 7149
		goto force_balance;

7150
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7151 7152
	if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
	    busiest->group_no_capacity)
7153 7154
		goto force_balance;

7155
	/*
7156
	 * If the local group is busier than the selected busiest group
7157 7158
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
7159
	if (local->avg_load >= busiest->avg_load)
7160 7161
		goto out_balanced;

7162 7163 7164 7165
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
7166
	if (local->avg_load >= sds.avg_load)
7167 7168
		goto out_balanced;

7169
	if (env->idle == CPU_IDLE) {
7170
		/*
7171 7172 7173 7174 7175
		 * This cpu is idle. If the busiest group is not overloaded
		 * and there is no imbalance between this and busiest group
		 * wrt idle cpus, it is balanced. The imbalance becomes
		 * significant if the diff is greater than 1 otherwise we
		 * might end up to just move the imbalance on another group
7176
		 */
7177 7178
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
7179
			goto out_balanced;
7180 7181 7182 7183 7184
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
7185 7186
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
7187
			goto out_balanced;
7188
	}
7189

7190
force_balance:
7191
	/* Looks like there is an imbalance. Compute it */
7192
	calculate_imbalance(env, &sds);
7193 7194 7195
	return sds.busiest;

out_balanced:
7196
	env->imbalance = 0;
7197 7198 7199 7200 7201 7202
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
7203
static struct rq *find_busiest_queue(struct lb_env *env,
7204
				     struct sched_group *group)
7205 7206
{
	struct rq *busiest = NULL, *rq;
7207
	unsigned long busiest_load = 0, busiest_capacity = 1;
7208 7209
	int i;

7210
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7211
		unsigned long capacity, wl;
7212 7213 7214 7215
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
7216

7217 7218 7219 7220 7221 7222 7223 7224 7225 7226 7227 7228 7229 7230 7231 7232 7233 7234 7235 7236 7237 7238
		/*
		 * We classify groups/runqueues into three groups:
		 *  - regular: there are !numa tasks
		 *  - remote:  there are numa tasks that run on the 'wrong' node
		 *  - all:     there is no distinction
		 *
		 * In order to avoid migrating ideally placed numa tasks,
		 * ignore those when there's better options.
		 *
		 * If we ignore the actual busiest queue to migrate another
		 * task, the next balance pass can still reduce the busiest
		 * queue by moving tasks around inside the node.
		 *
		 * If we cannot move enough load due to this classification
		 * the next pass will adjust the group classification and
		 * allow migration of more tasks.
		 *
		 * Both cases only affect the total convergence complexity.
		 */
		if (rt > env->fbq_type)
			continue;

7239
		capacity = capacity_of(i);
7240

7241
		wl = weighted_cpuload(i);
7242

7243 7244
		/*
		 * When comparing with imbalance, use weighted_cpuload()
7245
		 * which is not scaled with the cpu capacity.
7246
		 */
7247 7248 7249

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
7250 7251
			continue;

7252 7253
		/*
		 * For the load comparisons with the other cpu's, consider
7254 7255 7256
		 * the weighted_cpuload() scaled with the cpu capacity, so
		 * that the load can be moved away from the cpu that is
		 * potentially running at a lower capacity.
7257
		 *
7258
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
7259
		 * multiplication to rid ourselves of the division works out
7260 7261
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
7262
		 */
7263
		if (wl * busiest_capacity > busiest_load * capacity) {
7264
			busiest_load = wl;
7265
			busiest_capacity = capacity;
7266 7267 7268 7269 7270 7271 7272 7273 7274 7275 7276 7277 7278 7279
			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. */
7280
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
7281

7282
static int need_active_balance(struct lb_env *env)
7283
{
7284 7285 7286
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
7287 7288 7289 7290 7291 7292

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
7293
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
7294
			return 1;
7295 7296
	}

7297 7298 7299 7300 7301 7302 7303 7304 7305 7306 7307 7308 7309
	/*
	 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
	 * It's worth migrating the task if the src_cpu's capacity is reduced
	 * because of other sched_class or IRQs if more capacity stays
	 * available on dst_cpu.
	 */
	if ((env->idle != CPU_NOT_IDLE) &&
	    (env->src_rq->cfs.h_nr_running == 1)) {
		if ((check_cpu_capacity(env->src_rq, sd)) &&
		    (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
			return 1;
	}

7310 7311 7312
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

7313 7314
static int active_load_balance_cpu_stop(void *data);

7315 7316 7317 7318 7319 7320 7321 7322 7323 7324 7325 7326 7327 7328 7329 7330 7331 7332 7333 7334 7335 7336 7337 7338 7339 7340 7341 7342 7343 7344 7345
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.
	 */
7346
	return balance_cpu == env->dst_cpu;
7347 7348
}

7349 7350 7351 7352 7353 7354
/*
 * 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,
7355
			int *continue_balancing)
7356
{
7357
	int ld_moved, cur_ld_moved, active_balance = 0;
7358
	struct sched_domain *sd_parent = sd->parent;
7359 7360 7361
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
7362
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7363

7364 7365
	struct lb_env env = {
		.sd		= sd,
7366 7367
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
7368
		.dst_grpmask    = sched_group_cpus(sd->groups),
7369
		.idle		= idle,
7370
		.loop_break	= sched_nr_migrate_break,
7371
		.cpus		= cpus,
7372
		.fbq_type	= all,
7373
		.tasks		= LIST_HEAD_INIT(env.tasks),
7374 7375
	};

7376 7377 7378 7379
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
7380
	if (idle == CPU_NEWLY_IDLE)
7381 7382
		env.dst_grpmask = NULL;

7383 7384 7385 7386 7387
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
7388 7389
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
7390
		goto out_balanced;
7391
	}
7392

7393
	group = find_busiest_group(&env);
7394 7395 7396 7397 7398
	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

7399
	busiest = find_busiest_queue(&env, group);
7400 7401 7402 7403 7404
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

7405
	BUG_ON(busiest == env.dst_rq);
7406

7407
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7408

7409 7410 7411
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

7412 7413 7414 7415 7416 7417 7418 7419
	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.
		 */
7420
		env.flags |= LBF_ALL_PINNED;
7421
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
7422

7423
more_balance:
7424
		raw_spin_lock_irqsave(&busiest->lock, flags);
7425 7426 7427 7428 7429

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
7430
		cur_ld_moved = detach_tasks(&env);
7431 7432

		/*
7433 7434 7435 7436 7437
		 * We've detached some tasks from busiest_rq. Every
		 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
		 * unlock busiest->lock, and we are able to be sure
		 * that nobody can manipulate the tasks in parallel.
		 * See task_rq_lock() family for the details.
7438
		 */
7439 7440 7441 7442 7443 7444 7445 7446

		raw_spin_unlock(&busiest->lock);

		if (cur_ld_moved) {
			attach_tasks(&env);
			ld_moved += cur_ld_moved;
		}

7447
		local_irq_restore(flags);
7448

7449 7450 7451 7452 7453
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

7454 7455 7456 7457 7458 7459 7460 7461 7462 7463 7464 7465 7466 7467 7468 7469 7470 7471 7472
		/*
		 * 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.
		 */
7473
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7474

7475 7476 7477
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

7478
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
7479
			env.dst_cpu	 = env.new_dst_cpu;
7480
			env.flags	&= ~LBF_DST_PINNED;
7481 7482
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
7483

7484 7485 7486 7487 7488 7489
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
7490

7491 7492 7493 7494
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
7495
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7496

7497
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7498 7499 7500
				*group_imbalance = 1;
		}

7501
		/* All tasks on this runqueue were pinned by CPU affinity */
7502
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
7503
			cpumask_clear_cpu(cpu_of(busiest), cpus);
7504 7505 7506
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
7507
				goto redo;
7508
			}
7509
			goto out_all_pinned;
7510 7511 7512 7513 7514
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
7515 7516 7517 7518 7519 7520 7521 7522
		/*
		 * 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++;
7523

7524
		if (need_active_balance(&env)) {
7525 7526
			raw_spin_lock_irqsave(&busiest->lock, flags);

7527 7528 7529
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
7530 7531
			 */
			if (!cpumask_test_cpu(this_cpu,
7532
					tsk_cpus_allowed(busiest->curr))) {
7533 7534
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
7535
				env.flags |= LBF_ALL_PINNED;
7536 7537 7538
				goto out_one_pinned;
			}

7539 7540 7541 7542 7543
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
7544 7545 7546 7547 7548 7549
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
7550

7551
			if (active_balance) {
7552 7553 7554
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
7555
			}
7556

7557
			/* We've kicked active balancing, force task migration. */
7558 7559 7560 7561 7562 7563 7564 7565 7566 7567 7568 7569 7570
			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
7571
		 * detach_tasks).
7572 7573 7574 7575 7576 7577 7578 7579
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
7580 7581 7582 7583 7584 7585 7586 7587 7588 7589 7590 7591 7592 7593 7594 7595 7596
	/*
	 * We reach balance although we may have faced some affinity
	 * constraints. Clear the imbalance flag if it was set.
	 */
	if (sd_parent) {
		int *group_imbalance = &sd_parent->groups->sgc->imbalance;

		if (*group_imbalance)
			*group_imbalance = 0;
	}

out_all_pinned:
	/*
	 * We reach balance because all tasks are pinned at this level so
	 * we can't migrate them. Let the imbalance flag set so parent level
	 * can try to migrate them.
	 */
7597 7598 7599 7600 7601 7602
	schedstat_inc(sd, lb_balanced[idle]);

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
7603
	if (((env.flags & LBF_ALL_PINNED) &&
7604
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
7605 7606 7607
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

7608
	ld_moved = 0;
7609 7610 7611 7612
out:
	return ld_moved;
}

7613 7614 7615 7616 7617 7618 7619 7620 7621 7622 7623 7624 7625 7626 7627 7628 7629 7630 7631 7632 7633 7634 7635 7636 7637 7638 7639
static inline unsigned long
get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
{
	unsigned long interval = sd->balance_interval;

	if (cpu_busy)
		interval *= sd->busy_factor;

	/* scale ms to jiffies */
	interval = msecs_to_jiffies(interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);

	return interval;
}

static inline void
update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
{
	unsigned long interval, next;

	interval = get_sd_balance_interval(sd, cpu_busy);
	next = sd->last_balance + interval;

	if (time_after(*next_balance, next))
		*next_balance = next;
}

7640 7641 7642 7643
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
7644
static int idle_balance(struct rq *this_rq)
7645
{
7646 7647
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
7648 7649
	struct sched_domain *sd;
	int pulled_task = 0;
7650
	u64 curr_cost = 0;
7651

7652 7653 7654 7655 7656 7657
	/*
	 * We must set idle_stamp _before_ calling idle_balance(), such that we
	 * measure the duration of idle_balance() as idle time.
	 */
	this_rq->idle_stamp = rq_clock(this_rq);

7658 7659
	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
7660 7661 7662 7663 7664 7665
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
			update_next_balance(sd, 0, &next_balance);
		rcu_read_unlock();

7666
		goto out;
7667
	}
7668

7669 7670
	raw_spin_unlock(&this_rq->lock);

7671
	update_blocked_averages(this_cpu);
7672
	rcu_read_lock();
7673
	for_each_domain(this_cpu, sd) {
7674
		int continue_balancing = 1;
7675
		u64 t0, domain_cost;
7676 7677 7678 7679

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

7680 7681
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
			update_next_balance(sd, 0, &next_balance);
7682
			break;
7683
		}
7684

7685
		if (sd->flags & SD_BALANCE_NEWIDLE) {
7686 7687
			t0 = sched_clock_cpu(this_cpu);

7688
			pulled_task = load_balance(this_cpu, this_rq,
7689 7690
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
7691 7692 7693 7694 7695 7696

			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;
7697
		}
7698

7699
		update_next_balance(sd, 0, &next_balance);
7700 7701 7702 7703 7704 7705

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
7706 7707
			break;
	}
7708
	rcu_read_unlock();
7709 7710 7711

	raw_spin_lock(&this_rq->lock);

7712 7713 7714
	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

7715
	/*
7716 7717 7718
	 * While browsing the domains, we released the rq lock, a task could
	 * have been enqueued in the meantime. Since we're not going idle,
	 * pretend we pulled a task.
7719
	 */
7720
	if (this_rq->cfs.h_nr_running && !pulled_task)
7721
		pulled_task = 1;
7722

7723 7724 7725
out:
	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
7726
		this_rq->next_balance = next_balance;
7727

7728
	/* Is there a task of a high priority class? */
7729
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7730 7731
		pulled_task = -1;

7732
	if (pulled_task)
7733 7734
		this_rq->idle_stamp = 0;

7735
	return pulled_task;
7736 7737 7738
}

/*
7739 7740 7741 7742
 * 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.
7743
 */
7744
static int active_load_balance_cpu_stop(void *data)
7745
{
7746 7747
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
7748
	int target_cpu = busiest_rq->push_cpu;
7749
	struct rq *target_rq = cpu_rq(target_cpu);
7750
	struct sched_domain *sd;
7751
	struct task_struct *p = NULL;
7752 7753 7754 7755 7756 7757 7758

	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;
7759 7760 7761

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
7762
		goto out_unlock;
7763 7764 7765 7766 7767 7768 7769 7770 7771

	/*
	 * 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);

	/* Search for an sd spanning us and the target CPU. */
7772
	rcu_read_lock();
7773 7774 7775 7776 7777 7778 7779
	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)) {
7780 7781
		struct lb_env env = {
			.sd		= sd,
7782 7783 7784 7785
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
7786 7787 7788
			.idle		= CPU_IDLE,
		};

7789 7790
		schedstat_inc(sd, alb_count);

7791
		p = detach_one_task(&env);
7792
		if (p) {
7793
			schedstat_inc(sd, alb_pushed);
7794 7795 7796
			/* Active balancing done, reset the failure counter. */
			sd->nr_balance_failed = 0;
		} else {
7797
			schedstat_inc(sd, alb_failed);
7798
		}
7799
	}
7800
	rcu_read_unlock();
7801 7802
out_unlock:
	busiest_rq->active_balance = 0;
7803 7804 7805 7806 7807 7808 7809
	raw_spin_unlock(&busiest_rq->lock);

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

7810
	return 0;
7811 7812
}

7813 7814 7815 7816 7817
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

7818
#ifdef CONFIG_NO_HZ_COMMON
7819 7820 7821 7822 7823 7824
/*
 * 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.
 */
7825
static struct {
7826
	cpumask_var_t idle_cpus_mask;
7827
	atomic_t nr_cpus;
7828 7829
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
7830

7831
static inline int find_new_ilb(void)
7832
{
7833
	int ilb = cpumask_first(nohz.idle_cpus_mask);
7834

7835 7836 7837 7838
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
7839 7840
}

7841 7842 7843 7844 7845
/*
 * 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).
 */
7846
static void nohz_balancer_kick(void)
7847 7848 7849 7850 7851
{
	int ilb_cpu;

	nohz.next_balance++;

7852
	ilb_cpu = find_new_ilb();
7853

7854 7855
	if (ilb_cpu >= nr_cpu_ids)
		return;
7856

7857
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7858 7859 7860 7861 7862 7863 7864 7865
		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);
7866 7867 7868
	return;
}

7869
void nohz_balance_exit_idle(unsigned int cpu)
7870 7871
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7872 7873 7874 7875 7876 7877 7878
		/*
		 * Completely isolated CPUs don't ever set, so we must test.
		 */
		if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
			cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
			atomic_dec(&nohz.nr_cpus);
		}
7879 7880 7881 7882
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

7883 7884 7885
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
7886
	int cpu = smp_processor_id();
7887 7888

	rcu_read_lock();
7889
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7890 7891 7892 7893 7894

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

7895
	atomic_inc(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7896
unlock:
7897 7898 7899 7900 7901 7902
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;
7903
	int cpu = smp_processor_id();
7904 7905

	rcu_read_lock();
7906
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7907 7908 7909 7910 7911

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

7912
	atomic_dec(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7913
unlock:
7914 7915 7916
	rcu_read_unlock();
}

7917
/*
7918
 * This routine will record that the cpu is going idle with tick stopped.
7919
 * This info will be used in performing idle load balancing in the future.
7920
 */
7921
void nohz_balance_enter_idle(int cpu)
7922
{
7923 7924 7925 7926 7927 7928
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

7929 7930
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
7931

7932 7933 7934 7935 7936 7937
	/*
	 * If we're a completely isolated CPU, we don't play.
	 */
	if (on_null_domain(cpu_rq(cpu)))
		return;

7938 7939 7940
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7941 7942 7943 7944 7945
}
#endif

static DEFINE_SPINLOCK(balancing);

7946 7947 7948 7949
/*
 * 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.
 */
7950
void update_max_interval(void)
7951 7952 7953 7954
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

7955 7956 7957 7958
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
7959
 * Balancing parameters are set up in init_sched_domains.
7960
 */
7961
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7962
{
7963
	int continue_balancing = 1;
7964
	int cpu = rq->cpu;
7965
	unsigned long interval;
7966
	struct sched_domain *sd;
7967 7968 7969
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
7970 7971
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
7972

7973
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
7974

7975
	rcu_read_lock();
7976
	for_each_domain(cpu, sd) {
7977 7978 7979 7980 7981 7982 7983 7984 7985 7986 7987 7988
		/*
		 * 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;

7989 7990 7991
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

7992 7993 7994 7995 7996 7997 7998 7999 8000 8001 8002
		/*
		 * 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;
		}

8003
		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8004 8005 8006 8007 8008 8009 8010 8011

		need_serialize = sd->flags & SD_SERIALIZE;
		if (need_serialize) {
			if (!spin_trylock(&balancing))
				goto out;
		}

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
8012
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
8013
				/*
8014
				 * The LBF_DST_PINNED logic could have changed
8015 8016
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
8017
				 */
8018
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
8019 8020
			}
			sd->last_balance = jiffies;
8021
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8022 8023 8024 8025 8026 8027 8028 8029
		}
		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;
		}
8030 8031
	}
	if (need_decay) {
8032
		/*
8033 8034
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
8035
		 */
8036 8037
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
8038
	}
8039
	rcu_read_unlock();
8040 8041 8042 8043 8044 8045

	/*
	 * 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.
	 */
8046
	if (likely(update_next_balance)) {
8047
		rq->next_balance = next_balance;
8048 8049 8050 8051 8052 8053 8054 8055 8056 8057 8058 8059 8060 8061

#ifdef CONFIG_NO_HZ_COMMON
		/*
		 * If this CPU has been elected to perform the nohz idle
		 * balance. Other idle CPUs have already rebalanced with
		 * nohz_idle_balance() and nohz.next_balance has been
		 * updated accordingly. This CPU is now running the idle load
		 * balance for itself and we need to update the
		 * nohz.next_balance accordingly.
		 */
		if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
			nohz.next_balance = rq->next_balance;
#endif
	}
8062 8063
}

8064
#ifdef CONFIG_NO_HZ_COMMON
8065
/*
8066
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8067 8068
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
8069
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
8070
{
8071
	int this_cpu = this_rq->cpu;
8072 8073
	struct rq *rq;
	int balance_cpu;
8074 8075 8076
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
8077

8078 8079 8080
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
8081 8082

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8083
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8084 8085 8086 8087 8088 8089 8090
			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.
		 */
8091
		if (need_resched())
8092 8093
			break;

V
Vincent Guittot 已提交
8094 8095
		rq = cpu_rq(balance_cpu);

8096 8097 8098 8099 8100 8101 8102
		/*
		 * If time for next balance is due,
		 * do the balance.
		 */
		if (time_after_eq(jiffies, rq->next_balance)) {
			raw_spin_lock_irq(&rq->lock);
			update_rq_clock(rq);
8103
			cpu_load_update_idle(rq);
8104 8105 8106
			raw_spin_unlock_irq(&rq->lock);
			rebalance_domains(rq, CPU_IDLE);
		}
8107

8108 8109 8110 8111
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
8112
	}
8113 8114 8115 8116 8117 8118 8119 8120

	/*
	 * 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))
		nohz.next_balance = next_balance;
8121 8122
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
8123 8124 8125
}

/*
8126
 * Current heuristic for kicking the idle load balancer in the presence
8127
 * of an idle cpu in the system.
8128
 *   - This rq has more than one task.
8129 8130 8131 8132
 *   - This rq has at least one CFS task and the capacity of the CPU is
 *     significantly reduced because of RT tasks or IRQs.
 *   - At parent of LLC scheduler domain level, this cpu's scheduler group has
 *     multiple busy cpu.
8133 8134
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
8135
 */
8136
static inline bool nohz_kick_needed(struct rq *rq)
8137 8138
{
	unsigned long now = jiffies;
8139
	struct sched_domain *sd;
8140
	struct sched_group_capacity *sgc;
8141
	int nr_busy, cpu = rq->cpu;
8142
	bool kick = false;
8143

8144
	if (unlikely(rq->idle_balance))
8145
		return false;
8146

8147 8148 8149 8150
       /*
	* 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.
	*/
8151
	set_cpu_sd_state_busy();
8152
	nohz_balance_exit_idle(cpu);
8153 8154 8155 8156 8157 8158

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
8159
		return false;
8160 8161

	if (time_before(now, nohz.next_balance))
8162
		return false;
8163

8164
	if (rq->nr_running >= 2)
8165
		return true;
8166

8167
	rcu_read_lock();
8168 8169
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
	if (sd) {
8170 8171
		sgc = sd->groups->sgc;
		nr_busy = atomic_read(&sgc->nr_busy_cpus);
8172

8173 8174 8175 8176 8177
		if (nr_busy > 1) {
			kick = true;
			goto unlock;
		}

8178
	}
8179

8180 8181 8182 8183 8184 8185 8186 8187
	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
			kick = true;
			goto unlock;
		}
	}
8188

8189
	sd = rcu_dereference(per_cpu(sd_asym, cpu));
8190
	if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
8191 8192 8193 8194
				  sched_domain_span(sd)) < cpu)) {
		kick = true;
		goto unlock;
	}
8195

8196
unlock:
8197
	rcu_read_unlock();
8198
	return kick;
8199 8200
}
#else
8201
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8202 8203 8204 8205 8206 8207
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
8208 8209
static void run_rebalance_domains(struct softirq_action *h)
{
8210
	struct rq *this_rq = this_rq();
8211
	enum cpu_idle_type idle = this_rq->idle_balance ?
8212 8213 8214
						CPU_IDLE : CPU_NOT_IDLE;

	/*
8215
	 * If this cpu has a pending nohz_balance_kick, then do the
8216
	 * balancing on behalf of the other idle cpus whose ticks are
8217 8218 8219 8220
	 * stopped. Do nohz_idle_balance *before* rebalance_domains to
	 * give the idle cpus a chance to load balance. Else we may
	 * load balance only within the local sched_domain hierarchy
	 * and abort nohz_idle_balance altogether if we pull some load.
8221
	 */
8222
	nohz_idle_balance(this_rq, idle);
8223
	rebalance_domains(this_rq, idle);
8224 8225 8226 8227 8228
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
8229
void trigger_load_balance(struct rq *rq)
8230 8231
{
	/* Don't need to rebalance while attached to NULL domain */
8232 8233 8234 8235
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
8236
		raise_softirq(SCHED_SOFTIRQ);
8237
#ifdef CONFIG_NO_HZ_COMMON
8238
	if (nohz_kick_needed(rq))
8239
		nohz_balancer_kick();
8240
#endif
8241 8242
}

8243 8244 8245
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
8246 8247

	update_runtime_enabled(rq);
8248 8249 8250 8251 8252
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
8253 8254 8255

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
8256 8257
}

8258
#endif /* CONFIG_SMP */
8259

8260 8261 8262
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
8263
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8264 8265 8266 8267 8268 8269
{
	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
8270
		entity_tick(cfs_rq, se, queued);
8271
	}
8272

8273
	if (static_branch_unlikely(&sched_numa_balancing))
8274
		task_tick_numa(rq, curr);
8275 8276 8277
}

/*
P
Peter Zijlstra 已提交
8278 8279 8280
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
8281
 */
P
Peter Zijlstra 已提交
8282
static void task_fork_fair(struct task_struct *p)
8283
{
8284 8285
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
8286
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
8287 8288 8289
	struct rq *rq = this_rq();
	unsigned long flags;

8290
	raw_spin_lock_irqsave(&rq->lock, flags);
8291

8292 8293
	update_rq_clock(rq);

8294 8295 8296
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

8297 8298 8299 8300 8301 8302 8303 8304 8305
	/*
	 * 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();
8306

8307
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
8308

8309 8310
	if (curr)
		se->vruntime = curr->vruntime;
8311
	place_entity(cfs_rq, se, 1);
8312

P
Peter Zijlstra 已提交
8313
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
8314
		/*
8315 8316 8317
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
8318
		swap(curr->vruntime, se->vruntime);
8319
		resched_curr(rq);
8320
	}
8321

8322 8323
	se->vruntime -= cfs_rq->min_vruntime;

8324
	raw_spin_unlock_irqrestore(&rq->lock, flags);
8325 8326
}

8327 8328 8329 8330
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
8331 8332
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8333
{
8334
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
8335 8336
		return;

8337 8338 8339 8340 8341
	/*
	 * 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
8342
	if (rq->curr == p) {
8343
		if (p->prio > oldprio)
8344
			resched_curr(rq);
8345
	} else
8346
		check_preempt_curr(rq, p, 0);
8347 8348
}

8349
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
8350 8351 8352 8353
{
	struct sched_entity *se = &p->se;

	/*
8354 8355 8356 8357 8358 8359 8360 8361 8362 8363
	 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
	 * the dequeue_entity(.flags=0) will already have normalized the
	 * vruntime.
	 */
	if (p->on_rq)
		return true;

	/*
	 * When !on_rq, vruntime of the task has usually NOT been normalized.
	 * But there are some cases where it has already been normalized:
P
Peter Zijlstra 已提交
8364
	 *
8365 8366 8367 8368
	 * - A forked child which is waiting for being woken up by
	 *   wake_up_new_task().
	 * - A task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
P
Peter Zijlstra 已提交
8369
	 */
8370 8371 8372 8373 8374 8375 8376 8377 8378 8379 8380 8381
	if (!se->sum_exec_runtime || p->state == TASK_WAKING)
		return true;

	return false;
}

static void detach_task_cfs_rq(struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	if (!vruntime_normalized(p)) {
P
Peter Zijlstra 已提交
8382 8383 8384 8385 8386 8387 8388
		/*
		 * 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;
	}
8389

8390
	/* Catch up with the cfs_rq and remove our load when we leave */
8391
	detach_entity_load_avg(cfs_rq, se);
P
Peter Zijlstra 已提交
8392 8393
}

8394
static void attach_task_cfs_rq(struct task_struct *p)
8395
{
8396
	struct sched_entity *se = &p->se;
8397
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
8398 8399

#ifdef CONFIG_FAIR_GROUP_SCHED
8400 8401 8402 8403 8404 8405
	/*
	 * Since the real-depth could have been changed (only FAIR
	 * class maintain depth value), reset depth properly.
	 */
	se->depth = se->parent ? se->parent->depth + 1 : 0;
#endif
8406

8407
	/* Synchronize task with its cfs_rq */
8408 8409 8410 8411 8412
	attach_entity_load_avg(cfs_rq, se);

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
8413

8414 8415 8416 8417 8418 8419 8420 8421
static void switched_from_fair(struct rq *rq, struct task_struct *p)
{
	detach_task_cfs_rq(p);
}

static void switched_to_fair(struct rq *rq, struct task_struct *p)
{
	attach_task_cfs_rq(p);
8422

8423
	if (task_on_rq_queued(p)) {
8424
		/*
8425 8426 8427
		 * 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.
8428
		 */
8429 8430 8431 8432
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
8433
	}
8434 8435
}

8436 8437 8438 8439 8440 8441 8442 8443 8444
/* 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;

8445 8446 8447 8448 8449 8450 8451
	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);
	}
8452 8453
}

8454 8455 8456 8457 8458 8459 8460
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
8461
#ifdef CONFIG_SMP
8462 8463
	atomic_long_set(&cfs_rq->removed_load_avg, 0);
	atomic_long_set(&cfs_rq->removed_util_avg, 0);
8464
#endif
8465 8466
}

P
Peter Zijlstra 已提交
8467
#ifdef CONFIG_FAIR_GROUP_SCHED
8468
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
8469
{
8470
	detach_task_cfs_rq(p);
8471
	set_task_rq(p, task_cpu(p));
8472 8473 8474 8475 8476

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
8477
	attach_task_cfs_rq(p);
P
Peter Zijlstra 已提交
8478
}
8479 8480 8481 8482 8483 8484 8485 8486 8487 8488

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]);
8489
		if (tg->se)
8490 8491 8492 8493 8494 8495 8496 8497 8498 8499 8500 8501 8502 8503 8504 8505 8506 8507 8508 8509 8510 8511 8512 8513 8514 8515 8516 8517 8518 8519 8520 8521 8522 8523 8524 8525 8526
			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]);
8527
		init_entity_runnable_average(se);
8528
		post_init_entity_util_avg(se);
8529 8530 8531 8532 8533 8534 8535 8536 8537 8538
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

8539
void unregister_fair_sched_group(struct task_group *tg)
8540 8541
{
	unsigned long flags;
8542 8543
	struct rq *rq;
	int cpu;
8544

8545 8546 8547
	for_each_possible_cpu(cpu) {
		if (tg->se[cpu])
			remove_entity_load_avg(tg->se[cpu]);
8548

8549 8550 8551 8552 8553 8554 8555 8556 8557 8558 8559 8560 8561
		/*
		 * 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)
			continue;

		rq = cpu_rq(cpu);

		raw_spin_lock_irqsave(&rq->lock, flags);
		list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
		raw_spin_unlock_irqrestore(&rq->lock, flags);
	}
8562 8563 8564 8565 8566 8567 8568 8569 8570 8571 8572 8573 8574 8575 8576 8577 8578 8579 8580
}

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;

P
Peter Zijlstra 已提交
8581
	if (!parent) {
8582
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
8583 8584
		se->depth = 0;
	} else {
8585
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
8586 8587
		se->depth = parent->depth + 1;
	}
8588 8589

	se->my_q = cfs_rq;
8590 8591
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
8592 8593 8594 8595 8596 8597 8598 8599 8600 8601 8602 8603 8604 8605 8606 8607 8608 8609 8610 8611 8612 8613 8614 8615 8616 8617 8618 8619 8620 8621
	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);
8622 8623 8624

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
8625
		for_each_sched_entity(se)
8626 8627 8628 8629 8630 8631 8632 8633 8634 8635 8636 8637 8638 8639 8640 8641 8642
			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;
}

8643
void unregister_fair_sched_group(struct task_group *tg) { }
8644 8645 8646

#endif /* CONFIG_FAIR_GROUP_SCHED */

P
Peter Zijlstra 已提交
8647

8648
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8649 8650 8651 8652 8653 8654 8655 8656 8657
{
	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)
8658
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8659 8660 8661 8662

	return rr_interval;
}

8663 8664 8665
/*
 * All the scheduling class methods:
 */
8666
const struct sched_class fair_sched_class = {
8667
	.next			= &idle_sched_class,
8668 8669 8670
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
8671
	.yield_to_task		= yield_to_task_fair,
8672

I
Ingo Molnar 已提交
8673
	.check_preempt_curr	= check_preempt_wakeup,
8674 8675 8676 8677

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

8678
#ifdef CONFIG_SMP
L
Li Zefan 已提交
8679
	.select_task_rq		= select_task_rq_fair,
8680
	.migrate_task_rq	= migrate_task_rq_fair,
8681

8682 8683
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
8684

8685
	.task_dead		= task_dead_fair,
8686
	.set_cpus_allowed	= set_cpus_allowed_common,
8687
#endif
8688

8689
	.set_curr_task          = set_curr_task_fair,
8690
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
8691
	.task_fork		= task_fork_fair,
8692 8693

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
8694
	.switched_from		= switched_from_fair,
8695
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
8696

8697 8698
	.get_rr_interval	= get_rr_interval_fair,

8699 8700
	.update_curr		= update_curr_fair,

P
Peter Zijlstra 已提交
8701
#ifdef CONFIG_FAIR_GROUP_SCHED
8702
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
8703
#endif
8704 8705 8706
};

#ifdef CONFIG_SCHED_DEBUG
8707
void print_cfs_stats(struct seq_file *m, int cpu)
8708 8709 8710
{
	struct cfs_rq *cfs_rq;

8711
	rcu_read_lock();
8712
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8713
		print_cfs_rq(m, cpu, cfs_rq);
8714
	rcu_read_unlock();
8715
}
8716 8717 8718 8719 8720 8721 8722 8723 8724 8725 8726 8727 8728 8729 8730 8731 8732 8733 8734 8735 8736

#ifdef CONFIG_NUMA_BALANCING
void show_numa_stats(struct task_struct *p, struct seq_file *m)
{
	int node;
	unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;

	for_each_online_node(node) {
		if (p->numa_faults) {
			tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
			tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
		}
		if (p->numa_group) {
			gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
			gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
		}
		print_numa_stats(m, node, tsf, tpf, gsf, gpf);
	}
}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_SCHED_DEBUG */
8737 8738 8739 8740 8741 8742

__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

8743
#ifdef CONFIG_NO_HZ_COMMON
8744
	nohz.next_balance = jiffies;
8745 8746 8747 8748 8749
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
#endif
#endif /* SMP */

}