fair.c 269.6 KB
Newer Older
1
// SPDX-License-Identifier: GPL-2.0
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
/*
 * 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>
19 20
 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
21
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
22
 */
23
#include "sched.h"
24 25 26

#include <trace/events/sched.h>

27
/*
28
 * Targeted preemption latency for CPU-bound tasks:
29
 *
30
 * NOTE: this latency value is not the same as the concept of
I
Ingo Molnar 已提交
31 32 33
 * 'timeslice length' - timeslices in CFS are of variable length
 * and have no persistent notion like in traditional, time-slice
 * based scheduling concepts.
34
 *
I
Ingo Molnar 已提交
35 36
 * (to see the precise effective timeslice length of your workload,
 *  run vmstat and monitor the context-switches (cs) field)
37 38
 *
 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
39
 */
40 41
unsigned int sysctl_sched_latency			= 6000000ULL;
unsigned int normalized_sysctl_sched_latency		= 6000000ULL;
42

43 44 45 46
/*
 * The initial- and re-scaling of tunables is configurable
 *
 * Options are:
47 48 49 50 51 52
 *
 *   SCHED_TUNABLESCALING_NONE - unscaled, always *1
 *   SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
 *   SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
 *
 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
53
 */
54
enum sched_tunable_scaling sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
55

56
/*
57
 * Minimal preemption granularity for CPU-bound tasks:
58
 *
59
 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
60
 */
61 62
unsigned int sysctl_sched_min_granularity		= 750000ULL;
unsigned int normalized_sysctl_sched_min_granularity	= 750000ULL;
63 64

/*
65
 * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
66
 */
67
static unsigned int sched_nr_latency = 8;
68 69

/*
70
 * After fork, child runs first. If set to 0 (default) then
71
 * parent will (try to) run first.
72
 */
73
unsigned int sysctl_sched_child_runs_first __read_mostly;
74 75 76 77 78 79 80

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

87
const_debug unsigned int sysctl_sched_migration_cost	= 500000UL;
88

T
Tim Chen 已提交
89 90
#ifdef CONFIG_SMP
/*
91
 * For asym packing, by default the lower numbered CPU has higher priority.
T
Tim Chen 已提交
92 93 94 95 96 97 98
 */
int __weak arch_asym_cpu_priority(int cpu)
{
	return -cpu;
}
#endif

99 100 101 102 103 104 105 106 107
#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.
 *
108 109 110
 * (default: 5 msec, units: microseconds)
 */
unsigned int sysctl_sched_cfs_bandwidth_slice		= 5000UL;
111 112
#endif

113 114
/*
 * The margin used when comparing utilization with CPU capacity:
115
 * util * margin < capacity * 1024
116 117
 *
 * (default: ~20%)
118
 */
119
unsigned int capacity_margin				= 1280;
120

121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138
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;
}

139 140 141 142 143 144 145 146 147
/*
 * 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:
 */
148
static unsigned int get_update_sysctl_factor(void)
149
{
150
	unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185
	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();
}

186
#define WMULT_CONST	(~0U)
187 188
#define WMULT_SHIFT	32

189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204
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;
}
205 206

/*
207 208 209 210
 * delta_exec * weight / lw.weight
 *   OR
 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
 *
211
 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
212 213 214 215 216
 * 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.
217
 */
218
static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
219
{
220 221
	u64 fact = scale_load_down(weight);
	int shift = WMULT_SHIFT;
222

223
	__update_inv_weight(lw);
224

225 226 227 228 229
	if (unlikely(fact >> 32)) {
		while (fact >> 32) {
			fact >>= 1;
			shift--;
		}
230 231
	}

232 233
	/* hint to use a 32x32->64 mul */
	fact = (u64)(u32)fact * lw->inv_weight;
234

235 236 237 238
	while (fact >> 32) {
		fact >>= 1;
		shift--;
	}
239

240
	return mul_u64_u32_shr(delta_exec, fact, shift);
241 242 243 244
}


const struct sched_class fair_sched_class;
245

246 247 248 249
/**************************************************************
 * CFS operations on generic schedulable entities:
 */

250
#ifdef CONFIG_FAIR_GROUP_SCHED
251

252
/* cpu runqueue to which this cfs_rq is attached */
253 254
static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
255
	return cfs_rq->rq;
256 257
}

258 259
static inline struct task_struct *task_of(struct sched_entity *se)
{
260
	SCHED_WARN_ON(!entity_is_task(se));
261 262 263
	return container_of(se, struct task_struct, se);
}

P
Peter Zijlstra 已提交
264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284
/* 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;
}

285 286 287
static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
	if (!cfs_rq->on_list) {
288 289
		struct rq *rq = rq_of(cfs_rq);
		int cpu = cpu_of(rq);
290 291 292
		/*
		 * Ensure we either appear before our parent (if already
		 * enqueued) or force our parent to appear after us when it is
293 294 295 296 297
		 * enqueued. The fact that we always enqueue bottom-up
		 * reduces this to two cases and a special case for the root
		 * cfs_rq. Furthermore, it also means that we will always reset
		 * tmp_alone_branch either when the branch is connected
		 * to a tree or when we reach the beg of the tree
298 299
		 */
		if (cfs_rq->tg->parent &&
300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319
		    cfs_rq->tg->parent->cfs_rq[cpu]->on_list) {
			/*
			 * If parent is already on the list, we add the child
			 * just before. Thanks to circular linked property of
			 * the list, this means to put the child at the tail
			 * of the list that starts by parent.
			 */
			list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
				&(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list));
			/*
			 * The branch is now connected to its tree so we can
			 * reset tmp_alone_branch to the beginning of the
			 * list.
			 */
			rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
		} else if (!cfs_rq->tg->parent) {
			/*
			 * cfs rq without parent should be put
			 * at the tail of the list.
			 */
320
			list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340
				&rq->leaf_cfs_rq_list);
			/*
			 * We have reach the beg of a tree so we can reset
			 * tmp_alone_branch to the beginning of the list.
			 */
			rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
		} else {
			/*
			 * The parent has not already been added so we want to
			 * make sure that it will be put after us.
			 * tmp_alone_branch points to the beg of the branch
			 * where we will add parent.
			 */
			list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
				rq->tmp_alone_branch);
			/*
			 * update tmp_alone_branch to points to the new beg
			 * of the branch
			 */
			rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list;
341
		}
342 343 344 345 346 347 348 349 350 351 352 353 354

		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;
	}
}

355 356 357
/* Iterate through 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)
P
Peter Zijlstra 已提交
358 359

/* Do the two (enqueued) entities belong to the same group ? */
P
Peter Zijlstra 已提交
360
static inline struct cfs_rq *
P
Peter Zijlstra 已提交
361 362 363
is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
	if (se->cfs_rq == pse->cfs_rq)
P
Peter Zijlstra 已提交
364
		return se->cfs_rq;
P
Peter Zijlstra 已提交
365

P
Peter Zijlstra 已提交
366
	return NULL;
P
Peter Zijlstra 已提交
367 368 369 370 371 372 373
}

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

374 375 376 377 378 379 380 381 382 383 384 385 386
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
387 388
	se_depth = (*se)->depth;
	pse_depth = (*pse)->depth;
389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405

	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);
	}
}

406 407 408 409 410 411
#else	/* !CONFIG_FAIR_GROUP_SCHED */

static inline struct task_struct *task_of(struct sched_entity *se)
{
	return container_of(se, struct task_struct, se);
}
412

413 414 415
static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
	return container_of(cfs_rq, struct rq, cfs);
416 417 418
}


P
Peter Zijlstra 已提交
419 420
#define for_each_sched_entity(se) \
		for (; se; se = NULL)
421

P
Peter Zijlstra 已提交
422
static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
423
{
P
Peter Zijlstra 已提交
424
	return &task_rq(p)->cfs;
425 426
}

P
Peter Zijlstra 已提交
427 428 429 430 431 432 433 434 435 436 437 438 439 440
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;
}

441 442 443 444 445 446 447 448
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)
{
}

449 450
#define for_each_leaf_cfs_rq(rq, cfs_rq)	\
		for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
P
Peter Zijlstra 已提交
451 452 453 454 455 456

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

457 458 459 460 461
static inline void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
}

P
Peter Zijlstra 已提交
462 463
#endif	/* CONFIG_FAIR_GROUP_SCHED */

464
static __always_inline
465
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
466 467 468 469 470

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

471
static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
472
{
473
	s64 delta = (s64)(vruntime - max_vruntime);
474
	if (delta > 0)
475
		max_vruntime = vruntime;
476

477
	return max_vruntime;
478 479
}

480
static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
P
Peter Zijlstra 已提交
481 482 483 484 485 486 487 488
{
	s64 delta = (s64)(vruntime - min_vruntime);
	if (delta < 0)
		min_vruntime = vruntime;

	return min_vruntime;
}

489 490 491 492 493 494
static inline int entity_before(struct sched_entity *a,
				struct sched_entity *b)
{
	return (s64)(a->vruntime - b->vruntime) < 0;
}

495 496
static void update_min_vruntime(struct cfs_rq *cfs_rq)
{
497
	struct sched_entity *curr = cfs_rq->curr;
498
	struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline);
499

500 501
	u64 vruntime = cfs_rq->min_vruntime;

502 503 504 505 506 507
	if (curr) {
		if (curr->on_rq)
			vruntime = curr->vruntime;
		else
			curr = NULL;
	}
508

509 510 511
	if (leftmost) { /* non-empty tree */
		struct sched_entity *se;
		se = rb_entry(leftmost, struct sched_entity, run_node);
512

513
		if (!curr)
514 515 516 517 518
			vruntime = se->vruntime;
		else
			vruntime = min_vruntime(vruntime, se->vruntime);
	}

519
	/* ensure we never gain time by being placed backwards. */
520
	cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
521 522 523 524
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
525 526
}

527 528 529
/*
 * Enqueue an entity into the rb-tree:
 */
530
static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
531
{
532
	struct rb_node **link = &cfs_rq->tasks_timeline.rb_root.rb_node;
533 534
	struct rb_node *parent = NULL;
	struct sched_entity *entry;
535
	bool leftmost = true;
536 537 538 539 540 541 542 543 544 545 546

	/*
	 * 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.
		 */
547
		if (entity_before(se, entry)) {
548 549 550
			link = &parent->rb_left;
		} else {
			link = &parent->rb_right;
551
			leftmost = false;
552 553 554 555
		}
	}

	rb_link_node(&se->run_node, parent, link);
556 557
	rb_insert_color_cached(&se->run_node,
			       &cfs_rq->tasks_timeline, leftmost);
558 559
}

560
static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
561
{
562
	rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
563 564
}

565
struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
566
{
567
	struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline);
568 569 570 571 572

	if (!left)
		return NULL;

	return rb_entry(left, struct sched_entity, run_node);
573 574
}

575 576 577 578 579 580 581 582 583 584 585
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
586
struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
587
{
588
	struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);
589

590 591
	if (!last)
		return NULL;
592 593

	return rb_entry(last, struct sched_entity, run_node);
594 595
}

596 597 598 599
/**************************************************************
 * Scheduling class statistics methods:
 */

600
int sched_proc_update_handler(struct ctl_table *table, int write,
601
		void __user *buffer, size_t *lenp,
602 603
		loff_t *ppos)
{
604
	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
605
	unsigned int factor = get_update_sysctl_factor();
606 607 608 609 610 611 612

	if (ret || !write)
		return ret;

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

613 614 615 616 617 618 619
#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

620 621 622
	return 0;
}
#endif
623

624
/*
625
 * delta /= w
626
 */
627
static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
628
{
629
	if (unlikely(se->load.weight != NICE_0_LOAD))
630
		delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
631 632 633 634

	return delta;
}

635 636 637
/*
 * The idea is to set a period in which each task runs once.
 *
638
 * When there are too many tasks (sched_nr_latency) we have to stretch
639 640 641 642
 * this period because otherwise the slices get too small.
 *
 * p = (nr <= nl) ? l : l*nr/nl
 */
643 644
static u64 __sched_period(unsigned long nr_running)
{
645 646 647 648
	if (unlikely(nr_running > sched_nr_latency))
		return nr_running * sysctl_sched_min_granularity;
	else
		return sysctl_sched_latency;
649 650
}

651 652 653 654
/*
 * We calculate the wall-time slice from the period by taking a part
 * proportional to the weight.
 *
655
 * s = p*P[w/rw]
656
 */
P
Peter Zijlstra 已提交
657
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
658
{
M
Mike Galbraith 已提交
659
	u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
660

M
Mike Galbraith 已提交
661
	for_each_sched_entity(se) {
L
Lin Ming 已提交
662
		struct load_weight *load;
663
		struct load_weight lw;
L
Lin Ming 已提交
664 665 666

		cfs_rq = cfs_rq_of(se);
		load = &cfs_rq->load;
667

M
Mike Galbraith 已提交
668
		if (unlikely(!se->on_rq)) {
669
			lw = cfs_rq->load;
M
Mike Galbraith 已提交
670 671 672 673

			update_load_add(&lw, se->load.weight);
			load = &lw;
		}
674
		slice = __calc_delta(slice, se->load.weight, load);
M
Mike Galbraith 已提交
675 676
	}
	return slice;
677 678
}

679
/*
A
Andrei Epure 已提交
680
 * We calculate the vruntime slice of a to-be-inserted task.
681
 *
682
 * vs = s/w
683
 */
684
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
P
Peter Zijlstra 已提交
685
{
686
	return calc_delta_fair(sched_slice(cfs_rq, se), se);
687 688
}

689
#ifdef CONFIG_SMP
690
#include "pelt.h"
691 692
#include "sched-pelt.h"

693
static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
694 695
static unsigned long task_h_load(struct task_struct *p);

696 697
/* Give new sched_entity start runnable values to heavy its load in infant time */
void init_entity_runnable_average(struct sched_entity *se)
698
{
699
	struct sched_avg *sa = &se->avg;
700

701 702
	memset(sa, 0, sizeof(*sa));

703 704 705 706 707 708 709
	/*
	 * Tasks are intialized with full load to be seen as heavy tasks until
	 * they get a chance to stabilize to their real load level.
	 * Group entities are intialized with zero load to reflect the fact that
	 * nothing has been attached to the task group yet.
	 */
	if (entity_is_task(se))
710 711
		sa->runnable_load_avg = sa->load_avg = scale_load_down(se->load.weight);

712 713
	se->runnable_weight = se->load.weight;

714
	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
715
}
716

717
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
718
static void attach_entity_cfs_rq(struct sched_entity *se);
719

720 721 722 723 724 725 726 727 728 729 730 731 732
/*
 * 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:
 *
733
 *   util_avg_cap = (cpu_scale - cfs_rq->avg.util_avg) / 2^n
734
 *
735
 * where n denotes the nth task and cpu_scale the CPU capacity.
736
 *
737 738
 * For example, for a CPU with 1024 of capacity, a simplest series from
 * the beginning would be like:
739 740 741 742 743 744 745 746 747 748 749
 *
 *  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;
750 751
	long cpu_scale = arch_scale_cpu_capacity(NULL, cpu_of(rq_of(cfs_rq)));
	long cap = (long)(cpu_scale - cfs_rq->avg.util_avg) / 2;
752 753 754 755 756 757 758 759 760 761 762 763

	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;
		}
	}
764 765 766 767 768 769 770

	if (entity_is_task(se)) {
		struct task_struct *p = task_of(se);
		if (p->sched_class != &fair_sched_class) {
			/*
			 * For !fair tasks do:
			 *
771
			update_cfs_rq_load_avg(now, cfs_rq);
772
			attach_entity_load_avg(cfs_rq, se, 0);
773 774 775 776 777
			switched_from_fair(rq, p);
			 *
			 * such that the next switched_to_fair() has the
			 * expected state.
			 */
778
			se->avg.last_update_time = cfs_rq_clock_task(cfs_rq);
779 780 781 782
			return;
		}
	}

783
	attach_entity_cfs_rq(se);
784 785
}

786
#else /* !CONFIG_SMP */
787
void init_entity_runnable_average(struct sched_entity *se)
788 789
{
}
790 791 792
void post_init_entity_util_avg(struct sched_entity *se)
{
}
793 794 795
static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
{
}
796
#endif /* CONFIG_SMP */
797

798
/*
799
 * Update the current task's runtime statistics.
800
 */
801
static void update_curr(struct cfs_rq *cfs_rq)
802
{
803
	struct sched_entity *curr = cfs_rq->curr;
804
	u64 now = rq_clock_task(rq_of(cfs_rq));
805
	u64 delta_exec;
806 807 808 809

	if (unlikely(!curr))
		return;

810 811
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
P
Peter Zijlstra 已提交
812
		return;
813

I
Ingo Molnar 已提交
814
	curr->exec_start = now;
815

816 817 818 819
	schedstat_set(curr->statistics.exec_max,
		      max(delta_exec, curr->statistics.exec_max));

	curr->sum_exec_runtime += delta_exec;
820
	schedstat_add(cfs_rq->exec_clock, delta_exec);
821 822 823 824

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

825 826 827
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

828
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
829
		cgroup_account_cputime(curtask, delta_exec);
830
		account_group_exec_runtime(curtask, delta_exec);
831
	}
832 833

	account_cfs_rq_runtime(cfs_rq, delta_exec);
834 835
}

836 837 838 839 840
static void update_curr_fair(struct rq *rq)
{
	update_curr(cfs_rq_of(&rq->curr->se));
}

841
static inline void
842
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
843
{
844 845 846 847 848 849 850
	u64 wait_start, prev_wait_start;

	if (!schedstat_enabled())
		return;

	wait_start = rq_clock(rq_of(cfs_rq));
	prev_wait_start = schedstat_val(se->statistics.wait_start);
851 852

	if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
853 854
	    likely(wait_start > prev_wait_start))
		wait_start -= prev_wait_start;
855

856
	__schedstat_set(se->statistics.wait_start, wait_start);
857 858
}

859
static inline void
860 861 862
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *p;
863 864
	u64 delta;

865 866 867 868
	if (!schedstat_enabled())
		return;

	delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
869 870 871 872 873 874 875 876 877

	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.
			 */
878
			__schedstat_set(se->statistics.wait_start, delta);
879 880 881 882 883
			return;
		}
		trace_sched_stat_wait(p, delta);
	}

884
	__schedstat_set(se->statistics.wait_max,
885
		      max(schedstat_val(se->statistics.wait_max), delta));
886 887 888
	__schedstat_inc(se->statistics.wait_count);
	__schedstat_add(se->statistics.wait_sum, delta);
	__schedstat_set(se->statistics.wait_start, 0);
889 890
}

891
static inline void
892 893 894
update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *tsk = NULL;
895 896 897 898 899 900 901
	u64 sleep_start, block_start;

	if (!schedstat_enabled())
		return;

	sleep_start = schedstat_val(se->statistics.sleep_start);
	block_start = schedstat_val(se->statistics.block_start);
902 903 904 905

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

906 907
	if (sleep_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
908 909 910 911

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

912
		if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
913
			__schedstat_set(se->statistics.sleep_max, delta);
914

915 916
		__schedstat_set(se->statistics.sleep_start, 0);
		__schedstat_add(se->statistics.sum_sleep_runtime, delta);
917 918 919 920 921 922

		if (tsk) {
			account_scheduler_latency(tsk, delta >> 10, 1);
			trace_sched_stat_sleep(tsk, delta);
		}
	}
923 924
	if (block_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
925 926 927 928

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

929
		if (unlikely(delta > schedstat_val(se->statistics.block_max)))
930
			__schedstat_set(se->statistics.block_max, delta);
931

932 933
		__schedstat_set(se->statistics.block_start, 0);
		__schedstat_add(se->statistics.sum_sleep_runtime, delta);
934 935 936

		if (tsk) {
			if (tsk->in_iowait) {
937 938
				__schedstat_add(se->statistics.iowait_sum, delta);
				__schedstat_inc(se->statistics.iowait_count);
939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956
				trace_sched_stat_iowait(tsk, delta);
			}

			trace_sched_stat_blocked(tsk, delta);

			/*
			 * 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);
		}
	}
957 958
}

959 960 961
/*
 * Task is being enqueued - update stats:
 */
962
static inline void
963
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
964
{
965 966 967
	if (!schedstat_enabled())
		return;

968 969 970 971
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
972
	if (se != cfs_rq->curr)
973
		update_stats_wait_start(cfs_rq, se);
974 975 976

	if (flags & ENQUEUE_WAKEUP)
		update_stats_enqueue_sleeper(cfs_rq, se);
977 978 979
}

static inline void
980
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
981
{
982 983 984 985

	if (!schedstat_enabled())
		return;

986 987 988 989
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
990
	if (se != cfs_rq->curr)
991
		update_stats_wait_end(cfs_rq, se);
992

993 994
	if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
		struct task_struct *tsk = task_of(se);
995

996
		if (tsk->state & TASK_INTERRUPTIBLE)
997
			__schedstat_set(se->statistics.sleep_start,
998 999
				      rq_clock(rq_of(cfs_rq)));
		if (tsk->state & TASK_UNINTERRUPTIBLE)
1000
			__schedstat_set(se->statistics.block_start,
1001
				      rq_clock(rq_of(cfs_rq)));
1002 1003 1004
	}
}

1005 1006 1007 1008
/*
 * We are picking a new current task - update its stats:
 */
static inline void
1009
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
1010 1011 1012 1013
{
	/*
	 * We are starting a new run period:
	 */
1014
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
1015 1016 1017 1018 1019 1020
}

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

1021 1022
#ifdef CONFIG_NUMA_BALANCING
/*
1023 1024 1025
 * 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.
1026
 */
1027 1028
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
1029 1030 1031

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
1032

1033 1034 1035
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058
struct numa_group {
	atomic_t refcount;

	spinlock_t lock; /* nr_tasks, tasks */
	int nr_tasks;
	pid_t gid;
	int active_nodes;

	struct rcu_head rcu;
	unsigned long total_faults;
	unsigned long max_faults_cpu;
	/*
	 * 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.
	 */
	unsigned long *faults_cpu;
	unsigned long faults[0];
};

static inline unsigned long group_faults_priv(struct numa_group *ng);
static inline unsigned long group_faults_shared(struct numa_group *ng);

1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082
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)
{
1083
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
1084 1085 1086
	unsigned int scan, floor;
	unsigned int windows = 1;

1087 1088
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
1089 1090 1091 1092 1093 1094
	floor = 1000 / windows;

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

1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113
static unsigned int task_scan_start(struct task_struct *p)
{
	unsigned long smin = task_scan_min(p);
	unsigned long period = smin;

	/* Scale the maximum scan period with the amount of shared memory. */
	if (p->numa_group) {
		struct numa_group *ng = p->numa_group;
		unsigned long shared = group_faults_shared(ng);
		unsigned long private = group_faults_priv(ng);

		period *= atomic_read(&ng->refcount);
		period *= shared + 1;
		period /= private + shared + 1;
	}

	return max(smin, period);
}

1114 1115
static unsigned int task_scan_max(struct task_struct *p)
{
1116 1117
	unsigned long smin = task_scan_min(p);
	unsigned long smax;
1118 1119 1120

	/* Watch for min being lower than max due to floor calculations */
	smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135

	/* Scale the maximum scan period with the amount of shared memory. */
	if (p->numa_group) {
		struct numa_group *ng = p->numa_group;
		unsigned long shared = group_faults_shared(ng);
		unsigned long private = group_faults_priv(ng);
		unsigned long period = smax;

		period *= atomic_read(&ng->refcount);
		period *= shared + 1;
		period /= private + shared + 1;

		smax = max(smax, period);
	}

1136 1137 1138
	return max(smin, smax);
}

1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179
void init_numa_balancing(unsigned long clone_flags, struct task_struct *p)
{
	int mm_users = 0;
	struct mm_struct *mm = p->mm;

	if (mm) {
		mm_users = atomic_read(&mm->mm_users);
		if (mm_users == 1) {
			mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
			mm->numa_scan_seq = 0;
		}
	}
	p->node_stamp			= 0;
	p->numa_scan_seq		= mm ? mm->numa_scan_seq : 0;
	p->numa_scan_period		= sysctl_numa_balancing_scan_delay;
	p->numa_work.next		= &p->numa_work;
	p->numa_faults			= NULL;
	p->numa_group			= NULL;
	p->last_task_numa_placement	= 0;
	p->last_sum_exec_runtime	= 0;

	/* New address space, reset the preferred nid */
	if (!(clone_flags & CLONE_VM)) {
		p->numa_preferred_nid = -1;
		return;
	}

	/*
	 * New thread, keep existing numa_preferred_nid which should be copied
	 * already by arch_dup_task_struct but stagger when scans start.
	 */
	if (mm) {
		unsigned int delay;

		delay = min_t(unsigned int, task_scan_max(current),
			current->numa_scan_period * mm_users * NSEC_PER_MSEC);
		delay += 2 * TICK_NSEC;
		p->node_stamp = delay;
	}
}

1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191
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));
}

1192 1193 1194 1195 1196 1197 1198 1199 1200
/* 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)

1201 1202 1203 1204 1205
pid_t task_numa_group_id(struct task_struct *p)
{
	return p->numa_group ? p->numa_group->gid : 0;
}

1206
/*
1207
 * The averaged statistics, shared & private, memory & CPU,
1208 1209 1210 1211 1212
 * 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)
1213
{
1214
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1215 1216 1217 1218
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
1219
	if (!p->numa_faults)
1220 1221
		return 0;

1222 1223
	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1224 1225
}

1226 1227 1228 1229 1230
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
	if (!p->numa_group)
		return 0;

1231 1232
	return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1233 1234
}

1235 1236
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
1237 1238
	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1239 1240
}

1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264
static inline unsigned long group_faults_priv(struct numa_group *ng)
{
	unsigned long faults = 0;
	int node;

	for_each_online_node(node) {
		faults += ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
	}

	return faults;
}

static inline unsigned long group_faults_shared(struct numa_group *ng)
{
	unsigned long faults = 0;
	int node;

	for_each_online_node(node) {
		faults += ng->faults[task_faults_idx(NUMA_MEM, node, 0)];
	}

	return faults;
}

1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276
/*
 * 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;
}

1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313
/* 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 &&
1314
					dist >= maxdist)
1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341
			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;
}

1342 1343 1344 1345 1346 1347
/*
 * 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.
 */
1348 1349
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1350
{
1351
	unsigned long faults, total_faults;
1352

1353
	if (!p->numa_faults)
1354 1355 1356 1357 1358 1359 1360
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

1361
	faults = task_faults(p, nid);
1362 1363
	faults += score_nearby_nodes(p, nid, dist, true);

1364
	return 1000 * faults / total_faults;
1365 1366
}

1367 1368
static inline unsigned long group_weight(struct task_struct *p, int nid,
					 int dist)
1369
{
1370 1371 1372 1373 1374 1375 1376 1377
	unsigned long faults, total_faults;

	if (!p->numa_group)
		return 0;

	total_faults = p->numa_group->total_faults;

	if (!total_faults)
1378 1379
		return 0;

1380
	faults = group_faults(p, nid);
1381 1382
	faults += score_nearby_nodes(p, nid, dist, false);

1383
	return 1000 * faults / total_faults;
1384 1385
}

1386 1387 1388 1389 1390 1391 1392 1393
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);
1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404
	last_cpupid = page_cpupid_xchg_last(page, this_cpupid);

	/*
	 * Allow first faults or private faults to migrate immediately early in
	 * the lifetime of a task. The magic number 4 is based on waiting for
	 * two full passes of the "multi-stage node selection" test that is
	 * executed below.
	 */
	if ((p->numa_preferred_nid == -1 || p->numa_scan_seq <= 4) &&
	    (cpupid_pid_unset(last_cpupid) || cpupid_match_pid(p, last_cpupid)))
		return true;
1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435

	/*
	 * 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.
	 */
	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;

	/*
1436 1437
	 * Destination node is much more heavily used than the source
	 * node? Allow migration.
1438
	 */
1439 1440
	if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
					ACTIVE_NODE_FRACTION)
1441 1442 1443
		return true;

	/*
1444 1445 1446 1447 1448 1449
	 * 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)
1450
	 */
1451 1452
	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;
1453 1454
}

1455
static unsigned long weighted_cpuload(struct rq *rq);
1456 1457
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1458
static unsigned long capacity_of(int cpu);
1459

1460
/* Cached statistics for all CPUs within a node */
1461 1462
struct numa_stats {
	unsigned long load;
1463 1464

	/* Total compute capacity of CPUs on a node */
1465
	unsigned long compute_capacity;
1466

1467
	unsigned int nr_running;
1468
};
1469

1470 1471 1472 1473 1474
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1475 1476
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1477 1478 1479 1480 1481 1482

	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;
1483
		ns->load += weighted_cpuload(rq);
1484
		ns->compute_capacity += capacity_of(cpu);
1485 1486

		cpus++;
1487 1488
	}

1489 1490 1491 1492 1493
	/*
	 * 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.
	 *
1494
	 * We'll detect a huge imbalance and bail there.
1495 1496 1497 1498
	 */
	if (!cpus)
		return;

1499 1500 1501 1502
	/* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
	smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
	capacity = cpus / smt; /* cores */

1503
	capacity = min_t(unsigned, capacity,
1504
		DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1505 1506
}

1507 1508
struct task_numa_env {
	struct task_struct *p;
1509

1510 1511
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1512

1513
	struct numa_stats src_stats, dst_stats;
1514

1515
	int imbalance_pct;
1516
	int dist;
1517 1518 1519

	struct task_struct *best_task;
	long best_imp;
1520 1521 1522
	int best_cpu;
};

1523 1524 1525
static void task_numa_assign(struct task_numa_env *env,
			     struct task_struct *p, long imp)
{
1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540
	struct rq *rq = cpu_rq(env->dst_cpu);

	/* Bail out if run-queue part of active NUMA balance. */
	if (xchg(&rq->numa_migrate_on, 1))
		return;

	/*
	 * Clear previous best_cpu/rq numa-migrate flag, since task now
	 * found a better CPU to move/swap.
	 */
	if (env->best_cpu != -1) {
		rq = cpu_rq(env->best_cpu);
		WRITE_ONCE(rq->numa_migrate_on, 0);
	}

1541 1542
	if (env->best_task)
		put_task_struct(env->best_task);
1543 1544
	if (p)
		get_task_struct(p);
1545 1546 1547 1548 1549 1550

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

1551
static bool load_too_imbalanced(long src_load, long dst_load,
1552 1553
				struct task_numa_env *env)
{
1554 1555
	long imb, old_imb;
	long orig_src_load, orig_dst_load;
1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566
	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;
1567

1568
	imb = abs(dst_load * src_capacity - src_load * dst_capacity);
1569

1570
	orig_src_load = env->src_stats.load;
1571
	orig_dst_load = env->dst_stats.load;
1572

1573
	old_imb = abs(orig_dst_load * src_capacity - orig_src_load * dst_capacity);
1574 1575 1576

	/* Would this change make things worse? */
	return (imb > old_imb);
1577 1578
}

1579 1580 1581 1582 1583 1584 1585
/*
 * Maximum NUMA importance can be 1998 (2*999);
 * SMALLIMP @ 30 would be close to 1998/64.
 * Used to deter task migration.
 */
#define SMALLIMP	30

1586 1587 1588 1589 1590 1591
/*
 * 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
 */
1592
static void task_numa_compare(struct task_numa_env *env,
1593
			      long taskimp, long groupimp, bool maymove)
1594 1595 1596
{
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
1597
	long src_load, dst_load;
1598
	long load;
1599
	long imp = env->p->numa_group ? groupimp : taskimp;
1600
	long moveimp = imp;
1601
	int dist = env->dist;
1602

1603 1604 1605
	if (READ_ONCE(dst_rq->numa_migrate_on))
		return;

1606
	rcu_read_lock();
1607 1608
	cur = task_rcu_dereference(&dst_rq->curr);
	if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1609 1610
		cur = NULL;

1611 1612 1613 1614 1615 1616 1617
	/*
	 * 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;

1618
	if (!cur) {
1619
		if (maymove && moveimp >= env->best_imp)
1620 1621 1622 1623 1624
			goto assign;
		else
			goto unlock;
	}

1625 1626 1627 1628
	/*
	 * "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
1629
	 * the value is, the more remote accesses that would be expected to
1630 1631
	 * be incurred if the tasks were swapped.
	 */
1632 1633 1634
	/* Skip this swap candidate if cannot move to the source cpu */
	if (!cpumask_test_cpu(env->src_cpu, &cur->cpus_allowed))
		goto unlock;
1635

1636 1637 1638 1639 1640 1641 1642
	/*
	 * If dst and source tasks are in the same NUMA group, or not
	 * in any group then look only at task weights.
	 */
	if (cur->numa_group == env->p->numa_group) {
		imp = taskimp + task_weight(cur, env->src_nid, dist) -
		      task_weight(cur, env->dst_nid, dist);
1643
		/*
1644 1645
		 * Add some hysteresis to prevent swapping the
		 * tasks within a group over tiny differences.
1646
		 */
1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659
		if (cur->numa_group)
			imp -= imp / 16;
	} else {
		/*
		 * 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 && env->p->numa_group)
			imp += group_weight(cur, env->src_nid, dist) -
			       group_weight(cur, env->dst_nid, dist);
		else
			imp += task_weight(cur, env->src_nid, dist) -
			       task_weight(cur, env->dst_nid, dist);
1660 1661
	}

1662
	if (maymove && moveimp > imp && moveimp > env->best_imp) {
1663
		imp = moveimp;
1664
		cur = NULL;
1665
		goto assign;
1666
	}
1667

1668 1669 1670 1671 1672 1673 1674 1675 1676
	/*
	 * If the NUMA importance is less than SMALLIMP,
	 * task migration might only result in ping pong
	 * of tasks and also hurt performance due to cache
	 * misses.
	 */
	if (imp < SMALLIMP || imp <= env->best_imp + SMALLIMP / 2)
		goto unlock;

1677 1678 1679
	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
1680 1681 1682 1683
	load = task_h_load(env->p) - task_h_load(cur);
	if (!load)
		goto assign;

1684 1685
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1686

1687
	if (load_too_imbalanced(src_load, dst_load, env))
1688 1689
		goto unlock;

1690
assign:
1691 1692 1693 1694
	/*
	 * One idle CPU per node is evaluated for a task numa move.
	 * Call select_idle_sibling to maybe find a better one.
	 */
1695 1696
	if (!cur) {
		/*
1697
		 * select_idle_siblings() uses an per-CPU cpumask that
1698 1699 1700
		 * can be used from IRQ context.
		 */
		local_irq_disable();
1701 1702
		env->dst_cpu = select_idle_sibling(env->p, env->src_cpu,
						   env->dst_cpu);
1703 1704
		local_irq_enable();
	}
1705

1706 1707 1708 1709 1710
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1711 1712
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1713
{
1714 1715
	long src_load, dst_load, load;
	bool maymove = false;
1716 1717
	int cpu;

1718 1719 1720 1721 1722 1723 1724 1725 1726 1727
	load = task_h_load(env->p);
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;

	/*
	 * If the improvement from just moving env->p direction is better
	 * than swapping tasks around, check if a move is possible.
	 */
	maymove = !load_too_imbalanced(src_load, dst_load, env);

1728 1729
	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
		/* Skip this CPU if the source task cannot migrate */
1730
		if (!cpumask_test_cpu(cpu, &env->p->cpus_allowed))
1731 1732 1733
			continue;

		env->dst_cpu = cpu;
1734
		task_numa_compare(env, taskimp, groupimp, maymove);
1735 1736 1737
	}
}

1738 1739 1740 1741
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1742

1743
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1744
		.src_nid = task_node(p),
1745 1746 1747 1748 1749

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
1750
		.best_cpu = -1,
1751 1752
	};
	struct sched_domain *sd;
1753
	struct rq *best_rq;
1754
	unsigned long taskweight, groupweight;
1755
	int nid, ret, dist;
1756
	long taskimp, groupimp;
1757

1758
	/*
1759 1760 1761 1762 1763 1764
	 * 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.
1765 1766
	 */
	rcu_read_lock();
1767
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1768 1769
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1770 1771
	rcu_read_unlock();

1772 1773 1774 1775 1776 1777 1778
	/*
	 * 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)) {
1779
		sched_setnuma(p, task_node(p));
1780 1781 1782
		return -EINVAL;
	}

1783
	env.dst_nid = p->numa_preferred_nid;
1784 1785 1786 1787 1788 1789
	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;
1790
	update_numa_stats(&env.dst_stats, env.dst_nid);
1791

1792
	/* Try to find a spot on the preferred nid. */
1793
	task_numa_find_cpu(&env, taskimp, groupimp);
1794

1795 1796 1797 1798 1799 1800 1801
	/*
	 * 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.
	 */
1802
	if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
1803 1804 1805
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1806

1807
			dist = node_distance(env.src_nid, env.dst_nid);
1808 1809 1810 1811 1812
			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);
			}
1813

1814
			/* Only consider nodes where both task and groups benefit */
1815 1816
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1817
			if (taskimp < 0 && groupimp < 0)
1818 1819
				continue;

1820
			env.dist = dist;
1821 1822
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1823
			task_numa_find_cpu(&env, taskimp, groupimp);
1824 1825 1826
		}
	}

1827 1828 1829 1830 1831 1832 1833 1834
	/*
	 * 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.
	 */
1835 1836 1837 1838
	if (p->numa_group) {
		if (env.best_cpu == -1)
			nid = env.src_nid;
		else
1839
			nid = cpu_to_node(env.best_cpu);
1840

1841 1842
		if (nid != p->numa_preferred_nid)
			sched_setnuma(p, nid);
1843 1844 1845 1846 1847
	}

	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;
1848

1849
	best_rq = cpu_rq(env.best_cpu);
1850
	if (env.best_task == NULL) {
1851
		ret = migrate_task_to(p, env.best_cpu);
1852
		WRITE_ONCE(best_rq->numa_migrate_on, 0);
1853 1854
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1855 1856 1857
		return ret;
	}

1858
	ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu);
1859
	WRITE_ONCE(best_rq->numa_migrate_on, 0);
1860

1861 1862
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1863 1864
	put_task_struct(env.best_task);
	return ret;
1865 1866
}

1867 1868 1869
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1870 1871
	unsigned long interval = HZ;

1872
	/* This task has no NUMA fault statistics yet */
1873
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1874 1875
		return;

1876
	/* Periodically retry migrating the task to the preferred node */
1877
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1878
	p->numa_migrate_retry = jiffies + interval;
1879 1880

	/* Success if task is already running on preferred CPU */
1881
	if (task_node(p) == p->numa_preferred_nid)
1882 1883 1884
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1885
	task_numa_migrate(p);
1886 1887
}

1888
/*
1889
 * Find out how many nodes on the workload is actively running on. Do this by
1890 1891 1892 1893
 * 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.
 */
1894
static void numa_group_count_active_nodes(struct numa_group *numa_group)
1895 1896
{
	unsigned long faults, max_faults = 0;
1897
	int nid, active_nodes = 0;
1898 1899 1900 1901 1902 1903 1904 1905 1906

	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);
1907 1908
		if (faults * ACTIVE_NODE_FRACTION > max_faults)
			active_nodes++;
1909
	}
1910 1911 1912

	numa_group->max_faults_cpu = max_faults;
	numa_group->active_nodes = active_nodes;
1913 1914
}

1915 1916 1917
/*
 * 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
1918 1919 1920
 * 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.
1921 1922
 */
#define NUMA_PERIOD_SLOTS 10
1923
#define NUMA_PERIOD_THRESHOLD 7
1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934

/*
 * 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;
1935
	int lr_ratio, ps_ratio;
1936 1937 1938 1939 1940 1941 1942 1943
	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
1944 1945 1946
	 * 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
1947
	 */
1948
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964
		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);
1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983
	lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
	ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);

	if (ps_ratio >= NUMA_PERIOD_THRESHOLD) {
		/*
		 * Most memory accesses are local. There is no need to
		 * do fast NUMA scanning, since memory is already local.
		 */
		int slot = ps_ratio - NUMA_PERIOD_THRESHOLD;
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
		/*
		 * Most memory accesses are shared with other tasks.
		 * There is no point in continuing fast NUMA scanning,
		 * since other tasks may just move the memory elsewhere.
		 */
		int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
1984 1985 1986 1987 1988
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else {
		/*
1989 1990 1991
		 * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
		 * yet they are not on the local NUMA node. Speed up
		 * NUMA scanning to get the memory moved over.
1992
		 */
1993 1994
		int ratio = max(lr_ratio, ps_ratio);
		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1995 1996 1997 1998 1999 2000 2001
	}

	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));
}

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018
/*
 * 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;
2019 2020 2021 2022

		/* Avoid time going backwards, prevent potential divide error: */
		if (unlikely((s64)*period < 0))
			*period = 0;
2023
	} else {
2024
		delta = p->se.avg.load_sum;
2025
		*period = LOAD_AVG_MAX;
2026 2027 2028 2029 2030 2031 2032 2033
	}

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

	return delta;
}

2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080
/*
 * 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;
2081
		nodemask_t max_group = NODE_MASK_NONE;
2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114
		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. */
2115 2116
		if (!max_faults)
			break;
2117 2118 2119 2120 2121
		nodes = max_group;
	}
	return nid;
}

2122 2123
static void task_numa_placement(struct task_struct *p)
{
2124 2125
	int seq, nid, max_nid = -1;
	unsigned long max_faults = 0;
2126
	unsigned long fault_types[2] = { 0, 0 };
2127 2128
	unsigned long total_faults;
	u64 runtime, period;
2129
	spinlock_t *group_lock = NULL;
2130

2131 2132 2133 2134 2135
	/*
	 * 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:
	 */
2136
	seq = READ_ONCE(p->mm->numa_scan_seq);
2137 2138 2139
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
2140
	p->numa_scan_period_max = task_scan_max(p);
2141

2142 2143 2144 2145
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

2146 2147 2148
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
2149
		spin_lock_irq(group_lock);
2150 2151
	}

2152 2153
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
2154 2155
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
2156
		unsigned long faults = 0, group_faults = 0;
2157
		int priv;
2158

2159
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
2160
			long diff, f_diff, f_weight;
2161

2162 2163 2164 2165
			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);
2166

2167
			/* Decay existing window, copy faults since last scan */
2168 2169 2170
			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;
2171

2172 2173 2174 2175 2176 2177 2178 2179
			/*
			 * 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);
2180
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
2181
				   (total_faults + 1);
2182 2183
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
2184

2185 2186 2187
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
2188
			p->total_numa_faults += diff;
2189
			if (p->numa_group) {
2190 2191 2192 2193 2194 2195 2196 2197 2198
				/*
				 * 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;
2199
				p->numa_group->total_faults += diff;
2200
				group_faults += p->numa_group->faults[mem_idx];
2201
			}
2202 2203
		}

2204 2205 2206 2207 2208 2209 2210
		if (!p->numa_group) {
			if (faults > max_faults) {
				max_faults = faults;
				max_nid = nid;
			}
		} else if (group_faults > max_faults) {
			max_faults = group_faults;
2211 2212
			max_nid = nid;
		}
2213 2214
	}

2215
	if (p->numa_group) {
2216
		numa_group_count_active_nodes(p->numa_group);
2217
		spin_unlock_irq(group_lock);
2218
		max_nid = preferred_group_nid(p, max_nid);
2219 2220
	}

2221 2222 2223 2224
	if (max_faults) {
		/* Set the new preferred node */
		if (max_nid != p->numa_preferred_nid)
			sched_setnuma(p, max_nid);
2225
	}
2226 2227

	update_task_scan_period(p, fault_types[0], fault_types[1]);
2228 2229
}

2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240
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);
}

2241 2242
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
2243 2244 2245 2246 2247 2248 2249 2250 2251
{
	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) +
2252
				    4*nr_node_ids*sizeof(unsigned long);
2253 2254 2255 2256 2257 2258

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

		atomic_set(&grp->refcount, 1);
2259 2260
		grp->active_nodes = 1;
		grp->max_faults_cpu = 0;
2261
		spin_lock_init(&grp->lock);
2262
		grp->gid = p->pid;
2263
		/* Second half of the array tracks nids where faults happen */
2264 2265
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
2266

2267
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2268
			grp->faults[i] = p->numa_faults[i];
2269

2270
		grp->total_faults = p->total_numa_faults;
2271

2272 2273 2274 2275 2276
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
2277
	tsk = READ_ONCE(cpu_rq(cpu)->curr);
2278 2279

	if (!cpupid_match_pid(tsk, cpupid))
2280
		goto no_join;
2281 2282 2283

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
2284
		goto no_join;
2285 2286 2287

	my_grp = p->numa_group;
	if (grp == my_grp)
2288
		goto no_join;
2289 2290 2291 2292 2293 2294

	/*
	 * 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)
2295
		goto no_join;
2296 2297 2298 2299 2300

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2301
		goto no_join;
2302

2303 2304 2305 2306 2307 2308 2309
	/* 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;
2310

2311 2312 2313
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

2314
	if (join && !get_numa_group(grp))
2315
		goto no_join;
2316 2317 2318 2319 2320 2321

	rcu_read_unlock();

	if (!join)
		return;

2322 2323
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
2324

2325
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2326 2327
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
2328
	}
2329 2330
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
2331 2332 2333 2334 2335

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

	spin_unlock(&my_grp->lock);
2336
	spin_unlock_irq(&grp->lock);
2337 2338 2339 2340

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2341 2342 2343 2344 2345
	return;

no_join:
	rcu_read_unlock();
	return;
2346 2347 2348 2349 2350
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
2351
	void *numa_faults = p->numa_faults;
2352 2353
	unsigned long flags;
	int i;
2354 2355

	if (grp) {
2356
		spin_lock_irqsave(&grp->lock, flags);
2357
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2358
			grp->faults[i] -= p->numa_faults[i];
2359
		grp->total_faults -= p->total_numa_faults;
2360

2361
		grp->nr_tasks--;
2362
		spin_unlock_irqrestore(&grp->lock, flags);
2363
		RCU_INIT_POINTER(p->numa_group, NULL);
2364 2365 2366
		put_numa_group(grp);
	}

2367
	p->numa_faults = NULL;
2368
	kfree(numa_faults);
2369 2370
}

2371 2372 2373
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2374
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2375 2376
{
	struct task_struct *p = current;
2377
	bool migrated = flags & TNF_MIGRATED;
2378
	int cpu_node = task_node(current);
2379
	int local = !!(flags & TNF_FAULT_LOCAL);
2380
	struct numa_group *ng;
2381
	int priv;
2382

2383
	if (!static_branch_likely(&sched_numa_balancing))
2384 2385
		return;

2386 2387 2388 2389
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2390
	/* Allocate buffer to track faults on a per-node basis */
2391 2392
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2393
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2394

2395 2396
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2397
			return;
2398

2399
		p->total_numa_faults = 0;
2400
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2401
	}
2402

2403 2404 2405 2406 2407 2408 2409 2410
	/*
	 * 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);
2411
		if (!priv && !(flags & TNF_NO_GROUP))
2412
			task_numa_group(p, last_cpupid, flags, &priv);
2413 2414
	}

2415 2416 2417 2418 2419 2420
	/*
	 * 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.
	 */
2421 2422 2423 2424
	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))
2425 2426
		local = 1;

2427 2428 2429 2430
	/*
	 * Retry task to preferred node migration periodically, in case it
	 * case it previously failed, or the scheduler moved us.
	 */
2431 2432
	if (time_after(jiffies, p->numa_migrate_retry)) {
		task_numa_placement(p);
2433
		numa_migrate_preferred(p);
2434
	}
2435

I
Ingo Molnar 已提交
2436 2437
	if (migrated)
		p->numa_pages_migrated += pages;
2438 2439
	if (flags & TNF_MIGRATE_FAIL)
		p->numa_faults_locality[2] += pages;
I
Ingo Molnar 已提交
2440

2441 2442
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2443
	p->numa_faults_locality[local] += pages;
2444 2445
}

2446 2447
static void reset_ptenuma_scan(struct task_struct *p)
{
2448 2449 2450 2451 2452 2453 2454 2455
	/*
	 * 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:
	 */
2456
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2457 2458 2459
	p->mm->numa_scan_offset = 0;
}

2460 2461 2462 2463 2464 2465 2466 2467 2468
/*
 * 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;
2469
	u64 runtime = p->se.sum_exec_runtime;
2470
	struct vm_area_struct *vma;
2471
	unsigned long start, end;
2472
	unsigned long nr_pte_updates = 0;
2473
	long pages, virtpages;
2474

2475
	SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488

	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;

2489
	if (!mm->numa_next_scan) {
2490 2491
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2492 2493
	}

2494 2495 2496 2497 2498 2499 2500
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2501 2502
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
2503
		p->numa_scan_period = task_scan_start(p);
2504
	}
2505

2506
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2507 2508 2509
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2510 2511 2512 2513 2514 2515
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2516 2517 2518
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2519
	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2520 2521
	if (!pages)
		return;
2522

2523

2524 2525
	if (!down_read_trylock(&mm->mmap_sem))
		return;
2526
	vma = find_vma(mm, start);
2527 2528
	if (!vma) {
		reset_ptenuma_scan(p);
2529
		start = 0;
2530 2531
		vma = mm->mmap;
	}
2532
	for (; vma; vma = vma->vm_next) {
2533
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2534
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2535
			continue;
2536
		}
2537

2538 2539 2540 2541 2542 2543 2544 2545 2546 2547
		/*
		 * 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
2548 2549 2550 2551 2552 2553
		/*
		 * 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;
2554

2555 2556 2557 2558
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2559
			nr_pte_updates = change_prot_numa(vma, start, end);
2560 2561

			/*
2562 2563 2564 2565 2566 2567
			 * 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.
2568 2569 2570
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2571
			virtpages -= (end - start) >> PAGE_SHIFT;
2572

2573
			start = end;
2574
			if (pages <= 0 || virtpages <= 0)
2575
				goto out;
2576 2577

			cond_resched();
2578
		} while (end != vma->vm_end);
2579
	}
2580

2581
out:
2582
	/*
P
Peter Zijlstra 已提交
2583 2584 2585 2586
	 * 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.
2587 2588
	 */
	if (vma)
2589
		mm->numa_scan_offset = start;
2590 2591 2592
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603

	/*
	 * 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;
	}
2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628
}

/*
 * 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;

2629
	if (now > curr->node_stamp + period) {
2630
		if (!curr->node_stamp)
2631
			curr->numa_scan_period = task_scan_start(curr);
2632
		curr->node_stamp += period;
2633 2634 2635 2636 2637 2638 2639

		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);
		}
	}
}
2640

2641 2642 2643 2644 2645
static void update_scan_period(struct task_struct *p, int new_cpu)
{
	int src_nid = cpu_to_node(task_cpu(p));
	int dst_nid = cpu_to_node(new_cpu);

2646 2647 2648
	if (!static_branch_likely(&sched_numa_balancing))
		return;

2649 2650 2651
	if (!p->mm || !p->numa_faults || (p->flags & PF_EXITING))
		return;

2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671
	if (src_nid == dst_nid)
		return;

	/*
	 * Allow resets if faults have been trapped before one scan
	 * has completed. This is most likely due to a new task that
	 * is pulled cross-node due to wakeups or load balancing.
	 */
	if (p->numa_scan_seq) {
		/*
		 * Avoid scan adjustments if moving to the preferred
		 * node or if the task was not previously running on
		 * the preferred node.
		 */
		if (dst_nid == p->numa_preferred_nid ||
		    (p->numa_preferred_nid != -1 && src_nid != p->numa_preferred_nid))
			return;
	}

	p->numa_scan_period = task_scan_start(p);
2672 2673
}

2674 2675 2676 2677
#else
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
}
2678 2679 2680 2681 2682 2683 2684 2685

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)
{
}
2686

2687 2688 2689 2690
static inline void update_scan_period(struct task_struct *p, int new_cpu)
{
}

2691 2692
#endif /* CONFIG_NUMA_BALANCING */

2693 2694 2695 2696
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2697
	if (!parent_entity(se))
2698
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2699
#ifdef CONFIG_SMP
2700 2701 2702 2703 2704 2705
	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);
	}
2706
#endif
2707 2708 2709 2710 2711 2712 2713
	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);
2714
	if (!parent_entity(se))
2715
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2716
#ifdef CONFIG_SMP
2717 2718
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2719
		list_del_init(&se->group_node);
2720
	}
2721
#endif
2722 2723 2724
	cfs_rq->nr_running--;
}

2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765
/*
 * Signed add and clamp on underflow.
 *
 * Explicitly do a load-store to ensure the intermediate value never hits
 * memory. This allows lockless observations without ever seeing the negative
 * values.
 */
#define add_positive(_ptr, _val) do {                           \
	typeof(_ptr) ptr = (_ptr);                              \
	typeof(_val) val = (_val);                              \
	typeof(*ptr) res, var = READ_ONCE(*ptr);                \
								\
	res = var + val;                                        \
								\
	if (val < 0 && res > var)                               \
		res = 0;                                        \
								\
	WRITE_ONCE(*ptr, res);                                  \
} while (0)

/*
 * Unsigned subtract and clamp on underflow.
 *
 * Explicitly do a load-store to ensure the intermediate value never hits
 * memory. This allows lockless observations without ever seeing the negative
 * values.
 */
#define sub_positive(_ptr, _val) do {				\
	typeof(_ptr) ptr = (_ptr);				\
	typeof(*ptr) val = (_val);				\
	typeof(*ptr) res, var = READ_ONCE(*ptr);		\
	res = var - val;					\
	if (res > var)						\
		res = 0;					\
	WRITE_ONCE(*ptr, res);					\
} while (0)

#ifdef CONFIG_SMP
static inline void
enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2766 2767 2768 2769
	cfs_rq->runnable_weight += se->runnable_weight;

	cfs_rq->avg.runnable_load_avg += se->avg.runnable_load_avg;
	cfs_rq->avg.runnable_load_sum += se_runnable(se) * se->avg.runnable_load_sum;
2770 2771 2772 2773 2774
}

static inline void
dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2775 2776 2777 2778 2779
	cfs_rq->runnable_weight -= se->runnable_weight;

	sub_positive(&cfs_rq->avg.runnable_load_avg, se->avg.runnable_load_avg);
	sub_positive(&cfs_rq->avg.runnable_load_sum,
		     se_runnable(se) * se->avg.runnable_load_sum);
2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805
}

static inline void
enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	cfs_rq->avg.load_avg += se->avg.load_avg;
	cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
}

static inline void
dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
	sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum);
}
#else
static inline void
enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
static inline void
dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
static inline void
enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
static inline void
dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
#endif

2806
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2807
			    unsigned long weight, unsigned long runnable)
2808 2809 2810 2811 2812 2813 2814 2815 2816 2817
{
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
		account_entity_dequeue(cfs_rq, se);
		dequeue_runnable_load_avg(cfs_rq, se);
	}
	dequeue_load_avg(cfs_rq, se);

2818
	se->runnable_weight = runnable;
2819 2820 2821
	update_load_set(&se->load, weight);

#ifdef CONFIG_SMP
2822 2823 2824 2825 2826 2827 2828
	do {
		u32 divider = LOAD_AVG_MAX - 1024 + se->avg.period_contrib;

		se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider);
		se->avg.runnable_load_avg =
			div_u64(se_runnable(se) * se->avg.runnable_load_sum, divider);
	} while (0);
2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844
#endif

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

void reweight_task(struct task_struct *p, int prio)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	struct load_weight *load = &se->load;
	unsigned long weight = scale_load(sched_prio_to_weight[prio]);

2845
	reweight_entity(cfs_rq, se, weight, weight);
2846 2847 2848
	load->inv_weight = sched_prio_to_wmult[prio];
}

2849
#ifdef CONFIG_FAIR_GROUP_SCHED
2850
#ifdef CONFIG_SMP
2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888
/*
 * All this does is approximate the hierarchical proportion which includes that
 * global sum we all love to hate.
 *
 * That is, the weight of a group entity, is the proportional share of the
 * group weight based on the group runqueue weights. That is:
 *
 *                     tg->weight * grq->load.weight
 *   ge->load.weight = -----------------------------               (1)
 *			  \Sum grq->load.weight
 *
 * Now, because computing that sum is prohibitively expensive to compute (been
 * there, done that) we approximate it with this average stuff. The average
 * moves slower and therefore the approximation is cheaper and more stable.
 *
 * So instead of the above, we substitute:
 *
 *   grq->load.weight -> grq->avg.load_avg                         (2)
 *
 * which yields the following:
 *
 *                     tg->weight * grq->avg.load_avg
 *   ge->load.weight = ------------------------------              (3)
 *				tg->load_avg
 *
 * Where: tg->load_avg ~= \Sum grq->avg.load_avg
 *
 * That is shares_avg, and it is right (given the approximation (2)).
 *
 * The problem with it is that because the average is slow -- it was designed
 * to be exactly that of course -- this leads to transients in boundary
 * conditions. In specific, the case where the group was idle and we start the
 * one task. It takes time for our CPU's grq->avg.load_avg to build up,
 * yielding bad latency etc..
 *
 * Now, in that special case (1) reduces to:
 *
 *                     tg->weight * grq->load.weight
2889
 *   ge->load.weight = ----------------------------- = tg->weight   (4)
2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902
 *			    grp->load.weight
 *
 * That is, the sum collapses because all other CPUs are idle; the UP scenario.
 *
 * So what we do is modify our approximation (3) to approach (4) in the (near)
 * UP case, like:
 *
 *   ge->load.weight =
 *
 *              tg->weight * grq->load.weight
 *     ---------------------------------------------------         (5)
 *     tg->load_avg - grq->avg.load_avg + grq->load.weight
 *
2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914
 * But because grq->load.weight can drop to 0, resulting in a divide by zero,
 * we need to use grq->avg.load_avg as its lower bound, which then gives:
 *
 *
 *                     tg->weight * grq->load.weight
 *   ge->load.weight = -----------------------------		   (6)
 *				tg_load_avg'
 *
 * Where:
 *
 *   tg_load_avg' = tg->load_avg - grq->avg.load_avg +
 *                  max(grq->load.weight, grq->avg.load_avg)
2915 2916 2917 2918 2919 2920 2921 2922 2923
 *
 * And that is shares_weight and is icky. In the (near) UP case it approaches
 * (4) while in the normal case it approaches (3). It consistently
 * overestimates the ge->load.weight and therefore:
 *
 *   \Sum ge->load.weight >= tg->weight
 *
 * hence icky!
 */
2924
static long calc_group_shares(struct cfs_rq *cfs_rq)
2925
{
2926 2927 2928 2929
	long tg_weight, tg_shares, load, shares;
	struct task_group *tg = cfs_rq->tg;

	tg_shares = READ_ONCE(tg->shares);
2930

2931
	load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
2932

2933
	tg_weight = atomic_long_read(&tg->load_avg);
2934

2935 2936 2937
	/* Ensure tg_weight >= load */
	tg_weight -= cfs_rq->tg_load_avg_contrib;
	tg_weight += load;
2938

2939
	shares = (tg_shares * load);
2940 2941
	if (tg_weight)
		shares /= tg_weight;
2942

2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954
	/*
	 * MIN_SHARES has to be unscaled here to support per-CPU partitioning
	 * of a group with small tg->shares value. It is a floor value which is
	 * assigned as a minimum load.weight to the sched_entity representing
	 * the group on a CPU.
	 *
	 * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024
	 * on an 8-core system with 8 tasks each runnable on one CPU shares has
	 * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In
	 * case no task is runnable on a CPU MIN_SHARES=2 should be returned
	 * instead of 0.
	 */
2955
	return clamp_t(long, shares, MIN_SHARES, tg_shares);
2956
}
2957 2958

/*
2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983
 * This calculates the effective runnable weight for a group entity based on
 * the group entity weight calculated above.
 *
 * Because of the above approximation (2), our group entity weight is
 * an load_avg based ratio (3). This means that it includes blocked load and
 * does not represent the runnable weight.
 *
 * Approximate the group entity's runnable weight per ratio from the group
 * runqueue:
 *
 *					     grq->avg.runnable_load_avg
 *   ge->runnable_weight = ge->load.weight * -------------------------- (7)
 *						 grq->avg.load_avg
 *
 * However, analogous to above, since the avg numbers are slow, this leads to
 * transients in the from-idle case. Instead we use:
 *
 *   ge->runnable_weight = ge->load.weight *
 *
 *		max(grq->avg.runnable_load_avg, grq->runnable_weight)
 *		-----------------------------------------------------	(8)
 *		      max(grq->avg.load_avg, grq->load.weight)
 *
 * Where these max() serve both to use the 'instant' values to fix the slow
 * from-idle and avoid the /0 on to-idle, similar to (6).
2984 2985 2986
 */
static long calc_group_runnable(struct cfs_rq *cfs_rq, long shares)
{
2987 2988 2989 2990 2991 2992 2993
	long runnable, load_avg;

	load_avg = max(cfs_rq->avg.load_avg,
		       scale_load_down(cfs_rq->load.weight));

	runnable = max(cfs_rq->avg.runnable_load_avg,
		       scale_load_down(cfs_rq->runnable_weight));
2994 2995 2996 2997

	runnable *= shares;
	if (load_avg)
		runnable /= load_avg;
2998

2999 3000
	return clamp_t(long, runnable, MIN_SHARES, shares);
}
3001
#endif /* CONFIG_SMP */
3002

3003 3004
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

3005 3006 3007 3008 3009
/*
 * Recomputes the group entity based on the current state of its group
 * runqueue.
 */
static void update_cfs_group(struct sched_entity *se)
P
Peter Zijlstra 已提交
3010
{
3011 3012
	struct cfs_rq *gcfs_rq = group_cfs_rq(se);
	long shares, runnable;
P
Peter Zijlstra 已提交
3013

3014
	if (!gcfs_rq)
3015 3016
		return;

3017
	if (throttled_hierarchy(gcfs_rq))
P
Peter Zijlstra 已提交
3018
		return;
3019

3020
#ifndef CONFIG_SMP
3021
	runnable = shares = READ_ONCE(gcfs_rq->tg->shares);
3022 3023

	if (likely(se->load.weight == shares))
3024
		return;
3025
#else
3026 3027
	shares   = calc_group_shares(gcfs_rq);
	runnable = calc_group_runnable(gcfs_rq, shares);
3028
#endif
P
Peter Zijlstra 已提交
3029

3030
	reweight_entity(cfs_rq_of(se), se, shares, runnable);
P
Peter Zijlstra 已提交
3031
}
3032

P
Peter Zijlstra 已提交
3033
#else /* CONFIG_FAIR_GROUP_SCHED */
3034
static inline void update_cfs_group(struct sched_entity *se)
P
Peter Zijlstra 已提交
3035 3036 3037 3038
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

3039
static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
3040
{
3041 3042
	struct rq *rq = rq_of(cfs_rq);

3043
	if (&rq->cfs == cfs_rq || (flags & SCHED_CPUFREQ_MIGRATION)) {
3044 3045 3046
		/*
		 * There are a few boundary cases this might miss but it should
		 * get called often enough that that should (hopefully) not be
3047
		 * a real problem.
3048 3049 3050 3051 3052 3053 3054 3055 3056 3057
		 *
		 * 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().
		 */
3058
		cpufreq_update_util(rq, flags);
3059 3060 3061
	}
}

3062
#ifdef CONFIG_SMP
3063
#ifdef CONFIG_FAIR_GROUP_SCHED
3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076
/**
 * update_tg_load_avg - update the tg's load avg
 * @cfs_rq: the cfs_rq whose avg changed
 * @force: update regardless of how small the difference
 *
 * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
 * However, because tg->load_avg is a global value there are performance
 * considerations.
 *
 * In order to avoid having to look at the other cfs_rq's, we use a
 * differential update where we store the last value we propagated. This in
 * turn allows skipping updates if the differential is 'small'.
 *
3077
 * Updating tg's load_avg is necessary before update_cfs_share().
3078
 */
3079
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
3080
{
3081
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
3082

3083 3084 3085 3086 3087 3088
	/*
	 * No need to update load_avg for root_task_group as it is not used.
	 */
	if (cfs_rq->tg == &root_task_group)
		return;

3089 3090 3091
	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;
3092
	}
3093
}
3094

3095
/*
3096
 * Called within set_task_rq() right before setting a task's CPU. The
3097 3098 3099 3100 3101 3102
 * 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)
{
3103 3104 3105
	u64 p_last_update_time;
	u64 n_last_update_time;

3106 3107 3108 3109 3110 3111 3112 3113 3114 3115
	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.
	 */
3116 3117
	if (!(se->avg.last_update_time && prev))
		return;
3118 3119

#ifndef CONFIG_64BIT
3120
	{
3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132 3133 3134
		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);
3135
	}
3136
#else
3137 3138
	p_last_update_time = prev->avg.last_update_time;
	n_last_update_time = next->avg.last_update_time;
3139
#endif
3140 3141
	__update_load_avg_blocked_se(p_last_update_time, cpu_of(rq_of(prev)), se);
	se->avg.last_update_time = n_last_update_time;
3142
}
3143

3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154

/*
 * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
 * propagate its contribution. The key to this propagation is the invariant
 * that for each group:
 *
 *   ge->avg == grq->avg						(1)
 *
 * _IFF_ we look at the pure running and runnable sums. Because they
 * represent the very same entity, just at different points in the hierarchy.
 *
3155 3156 3157
 * Per the above update_tg_cfs_util() is trivial and simply copies the running
 * sum over (but still wrong, because the group entity and group rq do not have
 * their PELT windows aligned).
3158 3159 3160 3161 3162 3163 3164 3165
 *
 * However, update_tg_cfs_runnable() is more complex. So we have:
 *
 *   ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg		(2)
 *
 * And since, like util, the runnable part should be directly transferable,
 * the following would _appear_ to be the straight forward approach:
 *
3166
 *   grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg	(3)
3167 3168 3169
 *
 * And per (1) we have:
 *
3170
 *   ge->avg.runnable_avg == grq->avg.runnable_avg
3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188
 *
 * Which gives:
 *
 *                      ge->load.weight * grq->avg.load_avg
 *   ge->avg.load_avg = -----------------------------------		(4)
 *                               grq->load.weight
 *
 * Except that is wrong!
 *
 * Because while for entities historical weight is not important and we
 * really only care about our future and therefore can consider a pure
 * runnable sum, runqueues can NOT do this.
 *
 * We specifically want runqueues to have a load_avg that includes
 * historical weights. Those represent the blocked load, the load we expect
 * to (shortly) return to us. This only works by keeping the weights as
 * integral part of the sum. We therefore cannot decompose as per (3).
 *
3189 3190 3191 3192 3193 3194
 * Another reason this doesn't work is that runnable isn't a 0-sum entity.
 * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
 * rq itself is runnable anywhere between 2/3 and 1 depending on how the
 * runnable section of these tasks overlap (or not). If they were to perfectly
 * align the rq as a whole would be runnable 2/3 of the time. If however we
 * always have at least 1 runnable task, the rq as a whole is always runnable.
3195
 *
3196
 * So we'll have to approximate.. :/
3197
 *
3198
 * Given the constraint:
3199
 *
3200
 *   ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
3201
 *
3202 3203
 * We can construct a rule that adds runnable to a rq by assuming minimal
 * overlap.
3204
 *
3205
 * On removal, we'll assume each task is equally runnable; which yields:
3206
 *
3207
 *   grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
3208
 *
3209
 * XXX: only do this for the part of runnable > running ?
3210 3211 3212
 *
 */

3213
static inline void
3214
update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3215 3216 3217 3218 3219 3220 3221
{
	long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;

	/* Nothing to update */
	if (!delta)
		return;

3222 3223 3224 3225 3226 3227 3228 3229
	/*
	 * The relation between sum and avg is:
	 *
	 *   LOAD_AVG_MAX - 1024 + sa->period_contrib
	 *
	 * however, the PELT windows are not aligned between grq and gse.
	 */

3230 3231 3232 3233 3234 3235 3236 3237 3238 3239
	/* Set new sched_entity's utilization */
	se->avg.util_avg = gcfs_rq->avg.util_avg;
	se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX;

	/* Update parent cfs_rq utilization */
	add_positive(&cfs_rq->avg.util_avg, delta);
	cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX;
}

static inline void
3240
update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3241
{
3242 3243 3244 3245
	long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum;
	unsigned long runnable_load_avg, load_avg;
	u64 runnable_load_sum, load_sum = 0;
	s64 delta_sum;
3246

3247 3248
	if (!runnable_sum)
		return;
3249

3250
	gcfs_rq->prop_runnable_sum = 0;
3251

3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274
	if (runnable_sum >= 0) {
		/*
		 * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
		 * the CPU is saturated running == runnable.
		 */
		runnable_sum += se->avg.load_sum;
		runnable_sum = min(runnable_sum, (long)LOAD_AVG_MAX);
	} else {
		/*
		 * Estimate the new unweighted runnable_sum of the gcfs_rq by
		 * assuming all tasks are equally runnable.
		 */
		if (scale_load_down(gcfs_rq->load.weight)) {
			load_sum = div_s64(gcfs_rq->avg.load_sum,
				scale_load_down(gcfs_rq->load.weight));
		}

		/* But make sure to not inflate se's runnable */
		runnable_sum = min(se->avg.load_sum, load_sum);
	}

	/*
	 * runnable_sum can't be lower than running_sum
3275
	 * As running sum is scale with CPU capacity wehreas the runnable sum
3276 3277 3278 3279 3280 3281
	 * is not we rescale running_sum 1st
	 */
	running_sum = se->avg.util_sum /
		arch_scale_cpu_capacity(NULL, cpu_of(rq_of(cfs_rq)));
	runnable_sum = max(runnable_sum, running_sum);

3282 3283
	load_sum = (s64)se_weight(se) * runnable_sum;
	load_avg = div_s64(load_sum, LOAD_AVG_MAX);
3284

3285 3286
	delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum;
	delta_avg = load_avg - se->avg.load_avg;
3287

3288 3289 3290 3291
	se->avg.load_sum = runnable_sum;
	se->avg.load_avg = load_avg;
	add_positive(&cfs_rq->avg.load_avg, delta_avg);
	add_positive(&cfs_rq->avg.load_sum, delta_sum);
3292

3293 3294
	runnable_load_sum = (s64)se_runnable(se) * runnable_sum;
	runnable_load_avg = div_s64(runnable_load_sum, LOAD_AVG_MAX);
3295 3296
	delta_sum = runnable_load_sum - se_weight(se) * se->avg.runnable_load_sum;
	delta_avg = runnable_load_avg - se->avg.runnable_load_avg;
3297

3298 3299
	se->avg.runnable_load_sum = runnable_sum;
	se->avg.runnable_load_avg = runnable_load_avg;
3300

3301
	if (se->on_rq) {
3302 3303
		add_positive(&cfs_rq->avg.runnable_load_avg, delta_avg);
		add_positive(&cfs_rq->avg.runnable_load_sum, delta_sum);
3304 3305 3306
	}
}

3307
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
3308
{
3309 3310
	cfs_rq->propagate = 1;
	cfs_rq->prop_runnable_sum += runnable_sum;
3311 3312 3313 3314 3315
}

/* Update task and its cfs_rq load average */
static inline int propagate_entity_load_avg(struct sched_entity *se)
{
3316
	struct cfs_rq *cfs_rq, *gcfs_rq;
3317 3318 3319 3320

	if (entity_is_task(se))
		return 0;

3321 3322
	gcfs_rq = group_cfs_rq(se);
	if (!gcfs_rq->propagate)
3323 3324
		return 0;

3325 3326
	gcfs_rq->propagate = 0;

3327 3328
	cfs_rq = cfs_rq_of(se);

3329
	add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
3330

3331 3332
	update_tg_cfs_util(cfs_rq, se, gcfs_rq);
	update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
3333 3334 3335 3336

	return 1;
}

3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355
/*
 * Check if we need to update the load and the utilization of a blocked
 * group_entity:
 */
static inline bool skip_blocked_update(struct sched_entity *se)
{
	struct cfs_rq *gcfs_rq = group_cfs_rq(se);

	/*
	 * If sched_entity still have not zero load or utilization, we have to
	 * decay it:
	 */
	if (se->avg.load_avg || se->avg.util_avg)
		return false;

	/*
	 * If there is a pending propagation, we have to update the load and
	 * the utilization of the sched_entity:
	 */
3356
	if (gcfs_rq->propagate)
3357 3358 3359 3360 3361 3362 3363 3364 3365 3366
		return false;

	/*
	 * Otherwise, the load and the utilization of the sched_entity is
	 * already zero and there is no pending propagation, so it will be a
	 * waste of time to try to decay it:
	 */
	return true;
}

3367
#else /* CONFIG_FAIR_GROUP_SCHED */
3368

3369
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
3370 3371 3372 3373 3374 3375

static inline int propagate_entity_load_avg(struct sched_entity *se)
{
	return 0;
}

3376
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
3377

3378
#endif /* CONFIG_FAIR_GROUP_SCHED */
3379

3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390
/**
 * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
 * @now: current time, as per cfs_rq_clock_task()
 * @cfs_rq: cfs_rq to update
 *
 * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
 * avg. The immediate corollary is that all (fair) tasks must be attached, see
 * post_init_entity_util_avg().
 *
 * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
 *
3391 3392 3393 3394
 * Returns true if the load decayed or we removed load.
 *
 * Since both these conditions indicate a changed cfs_rq->avg.load we should
 * call update_tg_load_avg() when this function returns true.
3395
 */
3396
static inline int
3397
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3398
{
3399
	unsigned long removed_load = 0, removed_util = 0, removed_runnable_sum = 0;
3400
	struct sched_avg *sa = &cfs_rq->avg;
3401
	int decayed = 0;
3402

3403 3404
	if (cfs_rq->removed.nr) {
		unsigned long r;
3405
		u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
3406 3407 3408 3409

		raw_spin_lock(&cfs_rq->removed.lock);
		swap(cfs_rq->removed.util_avg, removed_util);
		swap(cfs_rq->removed.load_avg, removed_load);
3410
		swap(cfs_rq->removed.runnable_sum, removed_runnable_sum);
3411 3412 3413 3414
		cfs_rq->removed.nr = 0;
		raw_spin_unlock(&cfs_rq->removed.lock);

		r = removed_load;
3415
		sub_positive(&sa->load_avg, r);
3416
		sub_positive(&sa->load_sum, r * divider);
3417

3418
		r = removed_util;
3419
		sub_positive(&sa->util_avg, r);
3420
		sub_positive(&sa->util_sum, r * divider);
3421

3422
		add_tg_cfs_propagate(cfs_rq, -(long)removed_runnable_sum);
3423 3424

		decayed = 1;
3425
	}
3426

3427
	decayed |= __update_load_avg_cfs_rq(now, cpu_of(rq_of(cfs_rq)), cfs_rq);
3428

3429 3430 3431 3432
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
3433

3434
	if (decayed)
3435
		cfs_rq_util_change(cfs_rq, 0);
3436

3437
	return decayed;
3438 3439
}

3440 3441 3442 3443
/**
 * attach_entity_load_avg - attach this entity to its cfs_rq load avg
 * @cfs_rq: cfs_rq to attach to
 * @se: sched_entity to attach
3444
 * @flags: migration hints
3445 3446 3447 3448
 *
 * Must call update_cfs_rq_load_avg() before this, since we rely on
 * cfs_rq->avg.last_update_time being current.
 */
3449
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3450
{
3451 3452 3453 3454 3455 3456 3457 3458 3459
	u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib;

	/*
	 * When we attach the @se to the @cfs_rq, we must align the decay
	 * window because without that, really weird and wonderful things can
	 * happen.
	 *
	 * XXX illustrate
	 */
3460
	se->avg.last_update_time = cfs_rq->avg.last_update_time;
3461 3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473 3474 3475 3476 3477 3478
	se->avg.period_contrib = cfs_rq->avg.period_contrib;

	/*
	 * Hell(o) Nasty stuff.. we need to recompute _sum based on the new
	 * period_contrib. This isn't strictly correct, but since we're
	 * entirely outside of the PELT hierarchy, nobody cares if we truncate
	 * _sum a little.
	 */
	se->avg.util_sum = se->avg.util_avg * divider;

	se->avg.load_sum = divider;
	if (se_weight(se)) {
		se->avg.load_sum =
			div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se));
	}

	se->avg.runnable_load_sum = se->avg.load_sum;

3479
	enqueue_load_avg(cfs_rq, se);
3480 3481
	cfs_rq->avg.util_avg += se->avg.util_avg;
	cfs_rq->avg.util_sum += se->avg.util_sum;
3482 3483

	add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
3484

3485
	cfs_rq_util_change(cfs_rq, flags);
3486 3487
}

3488 3489 3490 3491 3492 3493 3494 3495
/**
 * detach_entity_load_avg - detach this entity from its cfs_rq load avg
 * @cfs_rq: cfs_rq to detach from
 * @se: sched_entity to detach
 *
 * Must call update_cfs_rq_load_avg() before this, since we rely on
 * cfs_rq->avg.last_update_time being current.
 */
3496 3497
static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3498
	dequeue_load_avg(cfs_rq, se);
3499 3500
	sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
	sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
3501 3502

	add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
3503

3504
	cfs_rq_util_change(cfs_rq, 0);
3505 3506
}

3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532 3533
/*
 * Optional action to be done while updating the load average
 */
#define UPDATE_TG	0x1
#define SKIP_AGE_LOAD	0x2
#define DO_ATTACH	0x4

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

	/*
	 * 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
	 */
	if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
		__update_load_avg_se(now, cpu, cfs_rq, se);

	decayed  = update_cfs_rq_load_avg(now, cfs_rq);
	decayed |= propagate_entity_load_avg(se);

	if (!se->avg.last_update_time && (flags & DO_ATTACH)) {

3534 3535 3536 3537 3538 3539 3540 3541
		/*
		 * DO_ATTACH means we're here from enqueue_entity().
		 * !last_update_time means we've passed through
		 * migrate_task_rq_fair() indicating we migrated.
		 *
		 * IOW we're enqueueing a task on a new CPU.
		 */
		attach_entity_load_avg(cfs_rq, se, SCHED_CPUFREQ_MIGRATION);
3542 3543 3544 3545 3546 3547
		update_tg_load_avg(cfs_rq, 0);

	} else if (decayed && (flags & UPDATE_TG))
		update_tg_load_avg(cfs_rq, 0);
}

3548
#ifndef CONFIG_64BIT
3549 3550
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
3551
	u64 last_update_time_copy;
3552
	u64 last_update_time;
3553

3554 3555 3556 3557 3558
	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);
3559 3560 3561

	return last_update_time;
}
3562
#else
3563 3564 3565 3566
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.last_update_time;
}
3567 3568
#endif

3569 3570 3571 3572 3573 3574 3575 3576 3577 3578
/*
 * Synchronize entity load avg of dequeued entity without locking
 * the previous rq.
 */
void sync_entity_load_avg(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 last_update_time;

	last_update_time = cfs_rq_last_update_time(cfs_rq);
3579
	__update_load_avg_blocked_se(last_update_time, cpu_of(rq_of(cfs_rq)), se);
3580 3581
}

3582 3583 3584 3585 3586 3587 3588
/*
 * 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);
3589
	unsigned long flags;
3590 3591

	/*
3592 3593 3594 3595 3596 3597 3598
	 * tasks cannot exit without having gone through wake_up_new_task() ->
	 * post_init_entity_util_avg() which will have added things to the
	 * cfs_rq, so we can remove unconditionally.
	 *
	 * Similarly for groups, they will have passed through
	 * post_init_entity_util_avg() before unregister_sched_fair_group()
	 * calls this.
3599 3600
	 */

3601
	sync_entity_load_avg(se);
3602 3603 3604 3605 3606

	raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags);
	++cfs_rq->removed.nr;
	cfs_rq->removed.util_avg	+= se->avg.util_avg;
	cfs_rq->removed.load_avg	+= se->avg.load_avg;
3607
	cfs_rq->removed.runnable_sum	+= se->avg.load_sum; /* == runnable_sum */
3608
	raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
3609
}
3610

3611 3612
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
{
3613
	return cfs_rq->avg.runnable_load_avg;
3614 3615 3616 3617 3618 3619 3620
}

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

3621
static int idle_balance(struct rq *this_rq, struct rq_flags *rf);
3622

3623 3624 3625 3626 3627 3628 3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649
static inline unsigned long task_util(struct task_struct *p)
{
	return READ_ONCE(p->se.avg.util_avg);
}

static inline unsigned long _task_util_est(struct task_struct *p)
{
	struct util_est ue = READ_ONCE(p->se.avg.util_est);

	return max(ue.ewma, ue.enqueued);
}

static inline unsigned long task_util_est(struct task_struct *p)
{
	return max(task_util(p), _task_util_est(p));
}

static inline void util_est_enqueue(struct cfs_rq *cfs_rq,
				    struct task_struct *p)
{
	unsigned int enqueued;

	if (!sched_feat(UTIL_EST))
		return;

	/* Update root cfs_rq's estimated utilization */
	enqueued  = cfs_rq->avg.util_est.enqueued;
3650
	enqueued += (_task_util_est(p) | UTIL_AVG_UNCHANGED);
3651 3652 3653 3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675
	WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
}

/*
 * Check if a (signed) value is within a specified (unsigned) margin,
 * based on the observation that:
 *
 *     abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1)
 *
 * NOTE: this only works when value + maring < INT_MAX.
 */
static inline bool within_margin(int value, int margin)
{
	return ((unsigned int)(value + margin - 1) < (2 * margin - 1));
}

static void
util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep)
{
	long last_ewma_diff;
	struct util_est ue;

	if (!sched_feat(UTIL_EST))
		return;

3676 3677 3678 3679
	/* Update root cfs_rq's estimated utilization */
	ue.enqueued  = cfs_rq->avg.util_est.enqueued;
	ue.enqueued -= min_t(unsigned int, ue.enqueued,
			     (_task_util_est(p) | UTIL_AVG_UNCHANGED));
3680 3681 3682 3683 3684 3685 3686 3687 3688
	WRITE_ONCE(cfs_rq->avg.util_est.enqueued, ue.enqueued);

	/*
	 * Skip update of task's estimated utilization when the task has not
	 * yet completed an activation, e.g. being migrated.
	 */
	if (!task_sleep)
		return;

3689 3690 3691 3692 3693 3694 3695 3696
	/*
	 * If the PELT values haven't changed since enqueue time,
	 * skip the util_est update.
	 */
	ue = p->se.avg.util_est;
	if (ue.enqueued & UTIL_AVG_UNCHANGED)
		return;

3697 3698 3699 3700
	/*
	 * Skip update of task's estimated utilization when its EWMA is
	 * already ~1% close to its last activation value.
	 */
3701
	ue.enqueued = (task_util(p) | UTIL_AVG_UNCHANGED);
3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728
	last_ewma_diff = ue.enqueued - ue.ewma;
	if (within_margin(last_ewma_diff, (SCHED_CAPACITY_SCALE / 100)))
		return;

	/*
	 * Update Task's estimated utilization
	 *
	 * When *p completes an activation we can consolidate another sample
	 * of the task size. This is done by storing the current PELT value
	 * as ue.enqueued and by using this value to update the Exponential
	 * Weighted Moving Average (EWMA):
	 *
	 *  ewma(t) = w *  task_util(p) + (1-w) * ewma(t-1)
	 *          = w *  task_util(p) +         ewma(t-1)  - w * ewma(t-1)
	 *          = w * (task_util(p) -         ewma(t-1)) +     ewma(t-1)
	 *          = w * (      last_ewma_diff            ) +     ewma(t-1)
	 *          = w * (last_ewma_diff  +  ewma(t-1) / w)
	 *
	 * Where 'w' is the weight of new samples, which is configured to be
	 * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
	 */
	ue.ewma <<= UTIL_EST_WEIGHT_SHIFT;
	ue.ewma  += last_ewma_diff;
	ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
	WRITE_ONCE(p->se.avg.util_est, ue);
}

3729 3730
#else /* CONFIG_SMP */

3731 3732
#define UPDATE_TG	0x0
#define SKIP_AGE_LOAD	0x0
3733
#define DO_ATTACH	0x0
3734

3735
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
3736
{
3737
	cfs_rq_util_change(cfs_rq, 0);
3738 3739
}

3740
static inline void remove_entity_load_avg(struct sched_entity *se) {}
3741

3742
static inline void
3743
attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) {}
3744 3745 3746
static inline void
detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}

3747
static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
3748 3749 3750 3751
{
	return 0;
}

3752 3753 3754 3755 3756 3757 3758
static inline void
util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {}

static inline void
util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p,
		 bool task_sleep) {}

3759
#endif /* CONFIG_SMP */
3760

P
Peter Zijlstra 已提交
3761 3762 3763 3764 3765 3766 3767 3768 3769
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)
3770
		schedstat_inc(cfs_rq->nr_spread_over);
P
Peter Zijlstra 已提交
3771 3772 3773
#endif
}

3774 3775 3776
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
3777
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
3778

3779 3780 3781 3782 3783 3784
	/*
	 * 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
3785
	if (initial && sched_feat(START_DEBIT))
3786
		vruntime += sched_vslice(cfs_rq, se);
3787

3788
	/* sleeps up to a single latency don't count. */
3789
	if (!initial) {
3790
		unsigned long thresh = sysctl_sched_latency;
3791

3792 3793 3794 3795 3796 3797
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3798

3799
		vruntime -= thresh;
3800 3801
	}

3802
	/* ensure we never gain time by being placed backwards. */
3803
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3804 3805
}

3806 3807
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3808 3809 3810 3811 3812 3813 3814 3815 3816 3817 3818 3819
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())  {
3820
		printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3821
			     "stat_blocked and stat_runtime require the "
3822
			     "kernel parameter schedstats=enable or "
3823 3824 3825 3826 3827
			     "kernel.sched_schedstats=1\n");
	}
#endif
}

3828 3829 3830 3831 3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 3846

/*
 * 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)
 *
3847
 *	->migrate_task_rq_fair() (p->state == TASK_WAKING)
3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858
 *	  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.
 */

3859
static void
3860
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3861
{
3862 3863 3864
	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
	bool curr = cfs_rq->curr == se;

3865
	/*
3866 3867
	 * If we're the current task, we must renormalise before calling
	 * update_curr().
3868
	 */
3869
	if (renorm && curr)
3870 3871
		se->vruntime += cfs_rq->min_vruntime;

3872 3873
	update_curr(cfs_rq);

3874
	/*
3875 3876 3877 3878
	 * 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.
3879
	 */
3880 3881 3882
	if (renorm && !curr)
		se->vruntime += cfs_rq->min_vruntime;

3883 3884 3885 3886 3887 3888 3889 3890
	/*
	 * When enqueuing a sched_entity, we must:
	 *   - Update loads to have both entity and cfs_rq synced with now.
	 *   - Add its load to cfs_rq->runnable_avg
	 *   - For group_entity, update its weight to reflect the new share of
	 *     its group cfs_rq
	 *   - Add its new weight to cfs_rq->load.weight
	 */
3891
	update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
3892
	update_cfs_group(se);
3893
	enqueue_runnable_load_avg(cfs_rq, se);
3894
	account_entity_enqueue(cfs_rq, se);
3895

3896
	if (flags & ENQUEUE_WAKEUP)
3897
		place_entity(cfs_rq, se, 0);
3898

3899
	check_schedstat_required();
3900 3901
	update_stats_enqueue(cfs_rq, se, flags);
	check_spread(cfs_rq, se);
3902
	if (!curr)
3903
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
3904
	se->on_rq = 1;
3905

3906
	if (cfs_rq->nr_running == 1) {
3907
		list_add_leaf_cfs_rq(cfs_rq);
3908 3909
		check_enqueue_throttle(cfs_rq);
	}
3910 3911
}

3912
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
3913
{
3914 3915
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3916
		if (cfs_rq->last != se)
3917
			break;
3918 3919

		cfs_rq->last = NULL;
3920 3921
	}
}
P
Peter Zijlstra 已提交
3922

3923 3924 3925 3926
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3927
		if (cfs_rq->next != se)
3928
			break;
3929 3930

		cfs_rq->next = NULL;
3931
	}
P
Peter Zijlstra 已提交
3932 3933
}

3934 3935 3936 3937
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3938
		if (cfs_rq->skip != se)
3939
			break;
3940 3941

		cfs_rq->skip = NULL;
3942 3943 3944
	}
}

P
Peter Zijlstra 已提交
3945 3946
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3947 3948 3949 3950 3951
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
3952 3953 3954

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
3955 3956
}

3957
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3958

3959
static void
3960
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3961
{
3962 3963 3964 3965
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
3966 3967 3968 3969 3970 3971 3972 3973 3974

	/*
	 * When dequeuing a sched_entity, we must:
	 *   - Update loads to have both entity and cfs_rq synced with now.
	 *   - Substract its load from the cfs_rq->runnable_avg.
	 *   - Substract its previous weight from cfs_rq->load.weight.
	 *   - For group entity, update its weight to reflect the new share
	 *     of its group cfs_rq.
	 */
3975
	update_load_avg(cfs_rq, se, UPDATE_TG);
3976
	dequeue_runnable_load_avg(cfs_rq, se);
3977

3978
	update_stats_dequeue(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
3979

P
Peter Zijlstra 已提交
3980
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3981

3982
	if (se != cfs_rq->curr)
3983
		__dequeue_entity(cfs_rq, se);
3984
	se->on_rq = 0;
3985
	account_entity_dequeue(cfs_rq, se);
3986 3987

	/*
3988 3989 3990 3991
	 * Normalize after update_curr(); which will also have moved
	 * min_vruntime if @se is the one holding it back. But before doing
	 * update_min_vruntime() again, which will discount @se's position and
	 * can move min_vruntime forward still more.
3992
	 */
3993
	if (!(flags & DEQUEUE_SLEEP))
3994
		se->vruntime -= cfs_rq->min_vruntime;
3995

3996 3997 3998
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

3999
	update_cfs_group(se);
4000 4001 4002 4003 4004 4005 4006

	/*
	 * Now advance min_vruntime if @se was the entity holding it back,
	 * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
	 * put back on, and if we advance min_vruntime, we'll be placed back
	 * further than we started -- ie. we'll be penalized.
	 */
4007
	if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
4008
		update_min_vruntime(cfs_rq);
4009 4010 4011 4012 4013
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
4014
static void
I
Ingo Molnar 已提交
4015
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4016
{
4017
	unsigned long ideal_runtime, delta_exec;
4018 4019
	struct sched_entity *se;
	s64 delta;
4020

P
Peter Zijlstra 已提交
4021
	ideal_runtime = sched_slice(cfs_rq, curr);
4022
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
4023
	if (delta_exec > ideal_runtime) {
4024
		resched_curr(rq_of(cfs_rq));
4025 4026 4027 4028 4029
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 4040
		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;

4041 4042
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
4043

4044 4045
	if (delta < 0)
		return;
4046

4047
	if (delta > ideal_runtime)
4048
		resched_curr(rq_of(cfs_rq));
4049 4050
}

4051
static void
4052
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
4053
{
4054 4055 4056 4057 4058 4059 4060
	/* '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.
		 */
4061
		update_stats_wait_end(cfs_rq, se);
4062
		__dequeue_entity(cfs_rq, se);
4063
		update_load_avg(cfs_rq, se, UPDATE_TG);
4064 4065
	}

4066
	update_stats_curr_start(cfs_rq, se);
4067
	cfs_rq->curr = se;
4068

I
Ingo Molnar 已提交
4069 4070 4071 4072 4073
	/*
	 * 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):
	 */
4074
	if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
4075 4076 4077
		schedstat_set(se->statistics.slice_max,
			max((u64)schedstat_val(se->statistics.slice_max),
			    se->sum_exec_runtime - se->prev_sum_exec_runtime));
I
Ingo Molnar 已提交
4078
	}
4079

4080
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
4081 4082
}

4083 4084 4085
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

4086 4087 4088 4089 4090 4091 4092
/*
 * 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
 */
4093 4094
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4095
{
4096 4097 4098 4099 4100 4101 4102 4103 4104 4105 4106
	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 */
4107

4108 4109 4110 4111 4112
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
4113 4114 4115 4116 4117 4118 4119 4120 4121 4122
		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;
		}

4123 4124 4125
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
4126

4127 4128 4129 4130 4131 4132
	/*
	 * 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;

4133 4134 4135 4136 4137 4138
	/*
	 * 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;

4139
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
4140 4141

	return se;
4142 4143
}

4144
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4145

4146
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
4147 4148 4149 4150 4151 4152
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
4153
		update_curr(cfs_rq);
4154

4155 4156 4157
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

4158
	check_spread(cfs_rq, prev);
4159

4160
	if (prev->on_rq) {
4161
		update_stats_wait_start(cfs_rq, prev);
4162 4163
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
4164
		/* in !on_rq case, update occurred at dequeue */
4165
		update_load_avg(cfs_rq, prev, 0);
4166
	}
4167
	cfs_rq->curr = NULL;
4168 4169
}

P
Peter Zijlstra 已提交
4170 4171
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
4172 4173
{
	/*
4174
	 * Update run-time statistics of the 'current'.
4175
	 */
4176
	update_curr(cfs_rq);
4177

4178 4179 4180
	/*
	 * Ensure that runnable average is periodically updated.
	 */
4181
	update_load_avg(cfs_rq, curr, UPDATE_TG);
4182
	update_cfs_group(curr);
4183

P
Peter Zijlstra 已提交
4184 4185 4186 4187 4188
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
4189
	if (queued) {
4190
		resched_curr(rq_of(cfs_rq));
4191 4192
		return;
	}
P
Peter Zijlstra 已提交
4193 4194 4195 4196 4197 4198 4199 4200
	/*
	 * 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
4201
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
4202
		check_preempt_tick(cfs_rq, curr);
4203 4204
}

4205 4206 4207 4208 4209 4210

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

#ifdef CONFIG_CFS_BANDWIDTH
4211 4212

#ifdef HAVE_JUMP_LABEL
4213
static struct static_key __cfs_bandwidth_used;
4214 4215 4216

static inline bool cfs_bandwidth_used(void)
{
4217
	return static_key_false(&__cfs_bandwidth_used);
4218 4219
}

4220
void cfs_bandwidth_usage_inc(void)
4221
{
4222
	static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
4223 4224 4225 4226
}

void cfs_bandwidth_usage_dec(void)
{
4227
	static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
4228 4229 4230 4231 4232 4233 4234
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

4235 4236
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
4237 4238
#endif /* HAVE_JUMP_LABEL */

4239 4240 4241 4242 4243 4244 4245 4246
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
4247 4248 4249 4250 4251 4252

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

P
Paul Turner 已提交
4253 4254 4255 4256 4257 4258 4259
/*
 * 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
 */
4260
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
4261 4262 4263 4264 4265 4266 4267 4268 4269
{
	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);
4270
	cfs_b->expires_seq++;
P
Paul Turner 已提交
4271 4272
}

4273 4274 4275 4276 4277
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

4278 4279 4280 4281
/* 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))
4282
		return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
4283

4284
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
4285 4286
}

4287 4288
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4289 4290 4291
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
4292
	u64 amount = 0, min_amount, expires;
4293
	int expires_seq;
4294 4295 4296 4297 4298 4299 4300

	/* 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;
4301
	else {
P
Peter Zijlstra 已提交
4302
		start_cfs_bandwidth(cfs_b);
4303 4304 4305 4306 4307 4308

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
4309
	}
4310
	expires_seq = cfs_b->expires_seq;
P
Paul Turner 已提交
4311
	expires = cfs_b->runtime_expires;
4312 4313 4314
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
4315 4316 4317 4318 4319
	/*
	 * we may have advanced our local expiration to account for allowed
	 * spread between our sched_clock and the one on which runtime was
	 * issued.
	 */
4320 4321
	if (cfs_rq->expires_seq != expires_seq) {
		cfs_rq->expires_seq = expires_seq;
P
Paul Turner 已提交
4322
		cfs_rq->runtime_expires = expires;
4323
	}
4324 4325

	return cfs_rq->runtime_remaining > 0;
4326 4327
}

P
Paul Turner 已提交
4328 4329 4330 4331 4332
/*
 * 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)
4333
{
P
Paul Turner 已提交
4334 4335 4336
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
4337
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
4338 4339
		return;

P
Paul Turner 已提交
4340 4341 4342 4343 4344 4345 4346 4347 4348
	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
4349
	 * whether the global deadline(cfs_b->expires_seq) has advanced.
P
Paul Turner 已提交
4350
	 */
4351
	if (cfs_rq->expires_seq == cfs_b->expires_seq) {
P
Paul Turner 已提交
4352 4353 4354 4355 4356 4357 4358 4359
		/* 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;
	}
}

4360
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
4361 4362
{
	/* dock delta_exec before expiring quota (as it could span periods) */
4363
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
4364 4365 4366
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
4367 4368
		return;

4369 4370 4371 4372 4373
	/*
	 * 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))
4374
		resched_curr(rq_of(cfs_rq));
4375 4376
}

4377
static __always_inline
4378
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4379
{
4380
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
4381 4382 4383 4384 4385
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

4386 4387
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
4388
	return cfs_bandwidth_used() && cfs_rq->throttled;
4389 4390
}

4391 4392 4393
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
4394
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
4395 4396 4397 4398 4399 4400 4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414 4415 4416 4417 4418 4419 4420
}

/*
 * 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);
}

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--;
	if (!cfs_rq->throttle_count) {
4421
		/* adjust cfs_rq_clock_task() */
4422
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
4423
					     cfs_rq->throttled_clock_task;
4424 4425 4426 4427 4428 4429 4430 4431 4432 4433
	}

	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)];

4434 4435
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
4436
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
4437 4438 4439 4440 4441
	cfs_rq->throttle_count++;

	return 0;
}

4442
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
4443 4444 4445 4446 4447
{
	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
4448
	bool empty;
4449 4450 4451

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

4452
	/* freeze hierarchy runnable averages while throttled */
4453 4454 4455
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
4456 4457 4458 4459 4460 4461 4462 4463 4464 4465 4466 4467 4468 4469 4470 4471 4472

	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)
4473
		sub_nr_running(rq, task_delta);
4474 4475

	cfs_rq->throttled = 1;
4476
	cfs_rq->throttled_clock = rq_clock(rq);
4477
	raw_spin_lock(&cfs_b->lock);
4478
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4479

4480 4481
	/*
	 * Add to the _head_ of the list, so that an already-started
4482 4483
	 * distribute_cfs_runtime will not see us. If disribute_cfs_runtime is
	 * not running add to the tail so that later runqueues don't get starved.
4484
	 */
4485 4486 4487 4488
	if (cfs_b->distribute_running)
		list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
	else
		list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4489 4490 4491 4492 4493 4494 4495 4496

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

4497 4498 4499
	raw_spin_unlock(&cfs_b->lock);
}

4500
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
4501 4502 4503 4504 4505 4506 4507
{
	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;

4508
	se = cfs_rq->tg->se[cpu_of(rq)];
4509 4510

	cfs_rq->throttled = 0;
4511 4512 4513

	update_rq_clock(rq);

4514
	raw_spin_lock(&cfs_b->lock);
4515
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
4516 4517 4518
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

4519 4520 4521
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

4522 4523 4524 4525 4526 4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539
	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)
4540
		add_nr_running(rq, task_delta);
4541

4542
	/* Determine whether we need to wake up potentially idle CPU: */
4543
	if (rq->curr == rq->idle && rq->cfs.nr_running)
4544
		resched_curr(rq);
4545 4546 4547 4548 4549 4550
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
4551 4552
	u64 runtime;
	u64 starting_runtime = remaining;
4553 4554 4555 4556 4557

	rcu_read_lock();
	list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
				throttled_list) {
		struct rq *rq = rq_of(cfs_rq);
4558
		struct rq_flags rf;
4559

4560
		rq_lock(rq, &rf);
4561 4562 4563 4564 4565 4566 4567 4568 4569 4570 4571 4572 4573 4574 4575 4576
		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:
4577
		rq_unlock(rq, &rf);
4578 4579 4580 4581 4582 4583

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

4584
	return starting_runtime - remaining;
4585 4586
}

4587 4588 4589 4590 4591 4592 4593 4594
/*
 * 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)
{
4595
	u64 runtime, runtime_expires;
4596
	int throttled;
4597 4598 4599

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
4600
		goto out_deactivate;
4601

4602
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4603
	cfs_b->nr_periods += overrun;
4604

4605 4606 4607 4608 4609 4610
	/*
	 * 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
4611 4612 4613

	__refill_cfs_bandwidth_runtime(cfs_b);

4614 4615 4616
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
4617
		return 0;
4618 4619
	}

4620 4621 4622
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

4623 4624 4625
	runtime_expires = cfs_b->runtime_expires;

	/*
4626 4627 4628 4629 4630
	 * 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.
4631
	 */
4632
	while (throttled && cfs_b->runtime > 0 && !cfs_b->distribute_running) {
4633
		runtime = cfs_b->runtime;
4634
		cfs_b->distribute_running = 1;
4635 4636 4637 4638 4639 4640
		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);

4641
		cfs_b->distribute_running = 0;
4642
		throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4643 4644

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4645
	}
4646

4647 4648 4649 4650 4651 4652 4653
	/*
	 * 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;
4654

4655 4656 4657 4658
	return 0;

out_deactivate:
	return 1;
4659
}
4660

4661 4662 4663 4664 4665 4666 4667
/* 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;

4668 4669 4670 4671
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4672
 * hrtimer base being cleared by hrtimer_start. In the case of
4673 4674
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
4675 4676 4677 4678 4679 4680 4681 4682 4683 4684 4685 4686 4687 4688 4689 4690 4691 4692 4693 4694 4695 4696 4697 4698 4699
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
4700 4701 4702
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
4703 4704 4705 4706 4707 4708 4709 4710 4711 4712 4713 4714 4715 4716 4717 4718 4719 4720 4721 4722 4723 4724 4725 4726 4727 4728 4729 4730 4731
}

/* 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)
{
4732 4733 4734
	if (!cfs_bandwidth_used())
		return;

4735
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4736 4737 4738 4739 4740 4741 4742 4743 4744 4745 4746 4747 4748 4749 4750
		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 */
4751
	raw_spin_lock(&cfs_b->lock);
4752 4753 4754 4755 4756
	if (cfs_b->distribute_running) {
		raw_spin_unlock(&cfs_b->lock);
		return;
	}

4757 4758
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
4759
		return;
4760
	}
4761

4762
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4763
		runtime = cfs_b->runtime;
4764

4765
	expires = cfs_b->runtime_expires;
4766 4767 4768
	if (runtime)
		cfs_b->distribute_running = 1;

4769 4770 4771 4772 4773 4774 4775 4776 4777
	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)
4778
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4779
	cfs_b->distribute_running = 0;
4780 4781 4782
	raw_spin_unlock(&cfs_b->lock);
}

4783 4784 4785 4786 4787 4788 4789
/*
 * 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)
{
4790 4791 4792
	if (!cfs_bandwidth_used())
		return;

4793 4794 4795 4796 4797 4798 4799 4800 4801 4802 4803 4804 4805 4806
	/* 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);
}

4807 4808 4809 4810 4811 4812 4813 4814 4815 4816 4817 4818 4819 4820
static void sync_throttle(struct task_group *tg, int cpu)
{
	struct cfs_rq *pcfs_rq, *cfs_rq;

	if (!cfs_bandwidth_used())
		return;

	if (!tg->parent)
		return;

	cfs_rq = tg->cfs_rq[cpu];
	pcfs_rq = tg->parent->cfs_rq[cpu];

	cfs_rq->throttle_count = pcfs_rq->throttle_count;
4821
	cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
4822 4823
}

4824
/* conditionally throttle active cfs_rq's from put_prev_entity() */
4825
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4826
{
4827
	if (!cfs_bandwidth_used())
4828
		return false;
4829

4830
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4831
		return false;
4832 4833 4834 4835 4836 4837

	/*
	 * 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))
4838
		return true;
4839 4840

	throttle_cfs_rq(cfs_rq);
4841
	return true;
4842
}
4843 4844 4845 4846 4847

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
4848

4849 4850 4851 4852 4853
	do_sched_cfs_slack_timer(cfs_b);

	return HRTIMER_NORESTART;
}

4854 4855
extern const u64 max_cfs_quota_period;

4856 4857 4858 4859 4860 4861
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;
4862
	int count = 0;
4863

4864
	raw_spin_lock(&cfs_b->lock);
4865
	for (;;) {
P
Peter Zijlstra 已提交
4866
		overrun = hrtimer_forward_now(timer, cfs_b->period);
4867 4868 4869
		if (!overrun)
			break;

4870 4871 4872 4873 4874 4875 4876 4877 4878 4879 4880 4881 4882 4883 4884 4885 4886 4887 4888 4889 4890 4891
		if (++count > 3) {
			u64 new, old = ktime_to_ns(cfs_b->period);

			new = (old * 147) / 128; /* ~115% */
			new = min(new, max_cfs_quota_period);

			cfs_b->period = ns_to_ktime(new);

			/* since max is 1s, this is limited to 1e9^2, which fits in u64 */
			cfs_b->quota *= new;
			cfs_b->quota = div64_u64(cfs_b->quota, old);

			pr_warn_ratelimited(
        "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us %lld, cfs_quota_us = %lld)\n",
	                        smp_processor_id(),
	                        div_u64(new, NSEC_PER_USEC),
                                div_u64(cfs_b->quota, NSEC_PER_USEC));

			/* reset count so we don't come right back in here */
			count = 0;
		}

4892 4893
		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
P
Peter Zijlstra 已提交
4894 4895
	if (idle)
		cfs_b->period_active = 0;
4896
	raw_spin_unlock(&cfs_b->lock);
4897 4898 4899 4900 4901 4902 4903 4904 4905 4906 4907 4908

	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
4909
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4910 4911 4912
	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;
4913
	cfs_b->distribute_running = 0;
4914 4915 4916 4917 4918 4919 4920 4921
}

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
4922
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4923
{
4924 4925
	u64 overrun;

P
Peter Zijlstra 已提交
4926
	lockdep_assert_held(&cfs_b->lock);
4927

4928 4929 4930 4931 4932 4933 4934 4935
	if (cfs_b->period_active)
		return;

	cfs_b->period_active = 1;
	overrun = hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
	cfs_b->runtime_expires += (overrun + 1) * ktime_to_ns(cfs_b->period);
	cfs_b->expires_seq++;
	hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4936 4937 4938 4939
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
4940 4941 4942 4943
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

4944 4945 4946 4947
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

4948
/*
4949
 * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
4950 4951 4952 4953 4954 4955
 *
 * The race is harmless, since modifying bandwidth settings of unhooked group
 * bits doesn't do much.
 */

/* cpu online calback */
4956 4957
static void __maybe_unused update_runtime_enabled(struct rq *rq)
{
4958
	struct task_group *tg;
4959

4960 4961 4962 4963 4964 4965
	lockdep_assert_held(&rq->lock);

	rcu_read_lock();
	list_for_each_entry_rcu(tg, &task_groups, list) {
		struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
		struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4966 4967 4968 4969 4970

		raw_spin_lock(&cfs_b->lock);
		cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
		raw_spin_unlock(&cfs_b->lock);
	}
4971
	rcu_read_unlock();
4972 4973
}

4974
/* cpu offline callback */
4975
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4976
{
4977 4978 4979 4980 4981 4982 4983
	struct task_group *tg;

	lockdep_assert_held(&rq->lock);

	rcu_read_lock();
	list_for_each_entry_rcu(tg, &task_groups, list) {
		struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4984 4985 4986 4987 4988 4989 4990 4991

		if (!cfs_rq->runtime_enabled)
			continue;

		/*
		 * clock_task is not advancing so we just need to make sure
		 * there's some valid quota amount
		 */
4992
		cfs_rq->runtime_remaining = 1;
4993
		/*
4994
		 * Offline rq is schedulable till CPU is completely disabled
4995 4996 4997 4998
		 * in take_cpu_down(), so we prevent new cfs throttling here.
		 */
		cfs_rq->runtime_enabled = 0;

4999 5000 5001
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
5002
	rcu_read_unlock();
5003 5004 5005
}

#else /* CONFIG_CFS_BANDWIDTH */
5006 5007
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
5008
	return rq_clock_task(rq_of(cfs_rq));
5009 5010
}

5011
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
5012
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
5013
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
5014
static inline void sync_throttle(struct task_group *tg, int cpu) {}
5015
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5016 5017 5018 5019 5020

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
5021 5022 5023 5024 5025 5026 5027 5028 5029 5030 5031

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;
}
5032 5033 5034 5035 5036

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) {}
5037 5038
#endif

5039 5040 5041 5042 5043
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) {}
5044
static inline void update_runtime_enabled(struct rq *rq) {}
5045
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
5046 5047 5048

#endif /* CONFIG_CFS_BANDWIDTH */

5049 5050 5051 5052
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
5053 5054 5055 5056 5057 5058
#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);

5059
	SCHED_WARN_ON(task_rq(p) != rq);
P
Peter Zijlstra 已提交
5060

5061
	if (rq->cfs.h_nr_running > 1) {
P
Peter Zijlstra 已提交
5062 5063 5064 5065 5066 5067
		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)
5068
				resched_curr(rq);
P
Peter Zijlstra 已提交
5069 5070
			return;
		}
5071
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
5072 5073
	}
}
5074 5075 5076 5077 5078 5079 5080 5081 5082 5083

/*
 * 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;

5084
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
5085 5086 5087 5088 5089
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
5090
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
5091 5092 5093 5094
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
5095 5096 5097 5098

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
5099 5100
#endif

5101 5102 5103 5104 5105
/*
 * 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:
 */
5106
static void
5107
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5108 5109
{
	struct cfs_rq *cfs_rq;
5110
	struct sched_entity *se = &p->se;
5111

5112 5113 5114 5115 5116 5117 5118 5119
	/*
	 * The code below (indirectly) updates schedutil which looks at
	 * the cfs_rq utilization to select a frequency.
	 * Let's add the task's estimated utilization to the cfs_rq's
	 * estimated utilization, before we update schedutil.
	 */
	util_est_enqueue(&rq->cfs, p);

5120 5121 5122 5123 5124 5125
	/*
	 * If in_iowait is set, the code below may not trigger any cpufreq
	 * utilization updates, so do it here explicitly with the IOWAIT flag
	 * passed.
	 */
	if (p->in_iowait)
5126
		cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
5127

5128
	for_each_sched_entity(se) {
5129
		if (se->on_rq)
5130 5131
			break;
		cfs_rq = cfs_rq_of(se);
5132
		enqueue_entity(cfs_rq, se, flags);
5133 5134 5135 5136 5137 5138

		/*
		 * 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.
5139
		 */
5140 5141
		if (cfs_rq_throttled(cfs_rq))
			break;
5142
		cfs_rq->h_nr_running++;
5143

5144
		flags = ENQUEUE_WAKEUP;
5145
	}
P
Peter Zijlstra 已提交
5146

P
Peter Zijlstra 已提交
5147
	for_each_sched_entity(se) {
5148
		cfs_rq = cfs_rq_of(se);
5149
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
5150

5151 5152 5153
		if (cfs_rq_throttled(cfs_rq))
			break;

5154
		update_load_avg(cfs_rq, se, UPDATE_TG);
5155
		update_cfs_group(se);
P
Peter Zijlstra 已提交
5156 5157
	}

Y
Yuyang Du 已提交
5158
	if (!se)
5159
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
5160

5161
	hrtick_update(rq);
5162 5163
}

5164 5165
static void set_next_buddy(struct sched_entity *se);

5166 5167 5168 5169 5170
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
5171
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5172 5173
{
	struct cfs_rq *cfs_rq;
5174
	struct sched_entity *se = &p->se;
5175
	int task_sleep = flags & DEQUEUE_SLEEP;
5176 5177 5178

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5179
		dequeue_entity(cfs_rq, se, flags);
5180 5181 5182 5183 5184 5185 5186 5187 5188

		/*
		 * 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;
5189
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
5190

5191
		/* Don't dequeue parent if it has other entities besides us */
5192
		if (cfs_rq->load.weight) {
5193 5194
			/* Avoid re-evaluating load for this entity: */
			se = parent_entity(se);
5195 5196 5197 5198
			/*
			 * Bias pick_next to pick a task from this cfs_rq, as
			 * p is sleeping when it is within its sched_slice.
			 */
5199 5200
			if (task_sleep && se && !throttled_hierarchy(cfs_rq))
				set_next_buddy(se);
5201
			break;
5202
		}
5203
		flags |= DEQUEUE_SLEEP;
5204
	}
P
Peter Zijlstra 已提交
5205

P
Peter Zijlstra 已提交
5206
	for_each_sched_entity(se) {
5207
		cfs_rq = cfs_rq_of(se);
5208
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
5209

5210 5211 5212
		if (cfs_rq_throttled(cfs_rq))
			break;

5213
		update_load_avg(cfs_rq, se, UPDATE_TG);
5214
		update_cfs_group(se);
P
Peter Zijlstra 已提交
5215 5216
	}

Y
Yuyang Du 已提交
5217
	if (!se)
5218
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
5219

5220
	util_est_dequeue(&rq->cfs, p, task_sleep);
5221
	hrtick_update(rq);
5222 5223
}

5224
#ifdef CONFIG_SMP
5225 5226 5227 5228 5229

/* Working cpumask for: load_balance, load_balance_newidle. */
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);

5230
#ifdef CONFIG_NO_HZ_COMMON
5231 5232 5233 5234 5235
/*
 * per rq 'load' arrray crap; XXX kill this.
 */

/*
5236
 * The exact cpuload calculated at every tick would be:
5237
 *
5238 5239
 *   load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
 *
5240 5241
 * 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:
5242 5243 5244
 *
 *   load_n   = (1 - 1/2^i)^n * load_0
 *   load_n+1 = (1 - 1/2^i)   * load_n + (1/2^i) * cur_load
5245 5246 5247
 *
 * decay_load_missed() below does efficient calculation of
 *
5248 5249 5250 5251 5252 5253
 *   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())
5254
 *
5255
 * The calculation is approximated on a 128 point scale.
5256 5257
 */
#define DEGRADE_SHIFT		7
5258 5259 5260 5261 5262 5263 5264 5265 5266

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 }
};
5267 5268 5269 5270 5271 5272 5273 5274 5275 5276 5277 5278 5279 5280 5281 5282 5283 5284 5285 5286 5287 5288 5289 5290 5291 5292 5293 5294 5295

/*
 * 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;
}
5296 5297 5298 5299

static struct {
	cpumask_var_t idle_cpus_mask;
	atomic_t nr_cpus;
5300
	int has_blocked;		/* Idle CPUS has blocked load */
5301
	unsigned long next_balance;     /* in jiffy units */
5302
	unsigned long next_blocked;	/* Next update of blocked load in jiffies */
5303 5304
} nohz ____cacheline_aligned;

5305
#endif /* CONFIG_NO_HZ_COMMON */
5306

5307
/**
5308
 * __cpu_load_update - update the rq->cpu_load[] statistics
5309 5310 5311 5312
 * @this_rq: The rq to update statistics for
 * @this_load: The current load
 * @pending_updates: The number of missed updates
 *
5313
 * Update rq->cpu_load[] statistics. This function is usually called every
5314 5315 5316 5317 5318 5319 5320 5321 5322 5323 5324 5325 5326 5327 5328 5329 5330 5331 5332 5333 5334 5335 5336 5337 5338 5339
 * 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
5340
 * term.
5341
 */
5342 5343
static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
			    unsigned long pending_updates)
5344
{
5345
	unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
5346 5347 5348 5349 5350 5351 5352 5353 5354 5355 5356
	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 */

5357
		old_load = this_rq->cpu_load[i];
5358
#ifdef CONFIG_NO_HZ_COMMON
5359
		old_load = decay_load_missed(old_load, pending_updates - 1, i);
5360 5361 5362 5363 5364 5365 5366 5367 5368
		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;
		}
5369
#endif
5370 5371 5372 5373 5374 5375 5376 5377 5378 5379 5380 5381 5382
		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;
	}
}

5383
/* Used instead of source_load when we know the type == 0 */
5384
static unsigned long weighted_cpuload(struct rq *rq)
5385
{
5386
	return cfs_rq_runnable_load_avg(&rq->cfs);
5387 5388
}

5389
#ifdef CONFIG_NO_HZ_COMMON
5390 5391
/*
 * There is no sane way to deal with nohz on smp when using jiffies because the
5392
 * CPU doing the jiffies update might drift wrt the CPU doing the jiffy reading
5393 5394 5395 5396 5397 5398 5399 5400 5401 5402 5403 5404 5405 5406
 * 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)
5407 5408 5409 5410 5411 5412 5413 5414 5415 5416 5417
{
	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.
		 */
5418
		cpu_load_update(this_rq, load, pending_updates);
5419 5420 5421
	}
}

5422 5423 5424 5425
/*
 * Called from nohz_idle_balance() to update the load ratings before doing the
 * idle balance.
 */
5426
static void cpu_load_update_idle(struct rq *this_rq)
5427 5428 5429 5430
{
	/*
	 * bail if there's load or we're actually up-to-date.
	 */
5431
	if (weighted_cpuload(this_rq))
5432 5433
		return;

5434
	cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
5435 5436 5437
}

/*
5438 5439 5440 5441
 * 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.
5442
 */
5443
void cpu_load_update_nohz_start(void)
5444 5445
{
	struct rq *this_rq = this_rq();
5446 5447 5448 5449 5450 5451

	/*
	 * 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.
	 */
5452
	this_rq->cpu_load[0] = weighted_cpuload(this_rq);
5453 5454 5455 5456 5457 5458 5459
}

/*
 * Account the tickless load in the end of a nohz frame.
 */
void cpu_load_update_nohz_stop(void)
{
5460
	unsigned long curr_jiffies = READ_ONCE(jiffies);
5461 5462
	struct rq *this_rq = this_rq();
	unsigned long load;
5463
	struct rq_flags rf;
5464 5465 5466 5467

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

5468
	load = weighted_cpuload(this_rq);
5469
	rq_lock(this_rq, &rf);
5470
	update_rq_clock(this_rq);
5471
	cpu_load_update_nohz(this_rq, curr_jiffies, load);
5472
	rq_unlock(this_rq, &rf);
5473
}
5474 5475 5476 5477 5478 5479 5480 5481
#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)
{
5482
#ifdef CONFIG_NO_HZ_COMMON
5483 5484
	/* See the mess around cpu_load_update_nohz(). */
	this_rq->last_load_update_tick = READ_ONCE(jiffies);
5485
#endif
5486 5487
	cpu_load_update(this_rq, load, 1);
}
5488 5489 5490 5491

/*
 * Called from scheduler_tick()
 */
5492
void cpu_load_update_active(struct rq *this_rq)
5493
{
5494
	unsigned long load = weighted_cpuload(this_rq);
5495 5496 5497 5498 5499

	if (tick_nohz_tick_stopped())
		cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
	else
		cpu_load_update_periodic(this_rq, load);
5500 5501
}

5502
/*
5503
 * Return a low guess at the load of a migration-source CPU weighted
5504 5505 5506 5507 5508 5509 5510 5511
 * 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);
5512
	unsigned long total = weighted_cpuload(rq);
5513 5514 5515 5516 5517 5518 5519 5520

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

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

/*
5521
 * Return a high guess at the load of a migration-target CPU weighted
5522 5523 5524 5525 5526
 * according to the scheduling class and "nice" value.
 */
static unsigned long target_load(int cpu, int type)
{
	struct rq *rq = cpu_rq(cpu);
5527
	unsigned long total = weighted_cpuload(rq);
5528 5529 5530 5531 5532 5533 5534

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

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

5535
static unsigned long capacity_of(int cpu)
5536
{
5537
	return cpu_rq(cpu)->cpu_capacity;
5538 5539
}

5540 5541 5542 5543 5544
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

5545 5546 5547
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
5548
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
5549
	unsigned long load_avg = weighted_cpuload(rq);
5550 5551

	if (nr_running)
5552
		return load_avg / nr_running;
5553 5554 5555 5556

	return 0;
}

P
Peter Zijlstra 已提交
5557 5558 5559 5560 5561 5562 5563 5564 5565 5566 5567 5568 5569 5570 5571 5572 5573
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
5574 5575
/*
 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
P
Peter Zijlstra 已提交
5576
 *
M
Mike Galbraith 已提交
5577
 * A waker of many should wake a different task than the one last awakened
P
Peter Zijlstra 已提交
5578 5579 5580 5581 5582 5583 5584 5585 5586 5587 5588 5589
 * 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
5590
 */
5591 5592
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
5593 5594
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
5595
	int factor = this_cpu_read(sd_llc_size);
5596

M
Mike Galbraith 已提交
5597 5598 5599 5600 5601
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
5602 5603
}

5604
/*
5605 5606 5607
 * The purpose of wake_affine() is to quickly determine on which CPU we can run
 * soonest. For the purpose of speed we only consider the waking and previous
 * CPU.
5608
 *
5609 5610
 * wake_affine_idle() - only considers 'now', it check if the waking CPU is
 *			cache-affine and is (or	will be) idle.
5611 5612 5613 5614
 *
 * wake_affine_weight() - considers the weight to reflect the average
 *			  scheduling latency of the CPUs. This seems to work
 *			  for the overloaded case.
5615
 */
5616
static int
5617
wake_affine_idle(int this_cpu, int prev_cpu, int sync)
5618
{
5619 5620 5621 5622 5623
	/*
	 * If this_cpu is idle, it implies the wakeup is from interrupt
	 * context. Only allow the move if cache is shared. Otherwise an
	 * interrupt intensive workload could force all tasks onto one
	 * node depending on the IO topology or IRQ affinity settings.
5624 5625 5626 5627 5628 5629
	 *
	 * If the prev_cpu is idle and cache affine then avoid a migration.
	 * There is no guarantee that the cache hot data from an interrupt
	 * is more important than cache hot data on the prev_cpu and from
	 * a cpufreq perspective, it's better to have higher utilisation
	 * on one CPU.
5630
	 */
5631 5632
	if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
		return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
5633

5634
	if (sync && cpu_rq(this_cpu)->nr_running == 1)
5635
		return this_cpu;
5636

5637
	return nr_cpumask_bits;
5638 5639
}

5640
static int
5641 5642
wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
		   int this_cpu, int prev_cpu, int sync)
5643 5644 5645 5646
{
	s64 this_eff_load, prev_eff_load;
	unsigned long task_load;

5647
	this_eff_load = target_load(this_cpu, sd->wake_idx);
5648 5649 5650 5651

	if (sync) {
		unsigned long current_load = task_h_load(current);

5652
		if (current_load > this_eff_load)
5653
			return this_cpu;
5654

5655
		this_eff_load -= current_load;
5656 5657 5658 5659
	}

	task_load = task_h_load(p);

5660 5661 5662 5663
	this_eff_load += task_load;
	if (sched_feat(WA_BIAS))
		this_eff_load *= 100;
	this_eff_load *= capacity_of(prev_cpu);
5664

5665
	prev_eff_load = source_load(prev_cpu, sd->wake_idx);
5666 5667 5668 5669
	prev_eff_load -= task_load;
	if (sched_feat(WA_BIAS))
		prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2;
	prev_eff_load *= capacity_of(this_cpu);
5670

5671 5672 5673 5674 5675 5676 5677 5678 5679 5680
	/*
	 * If sync, adjust the weight of prev_eff_load such that if
	 * prev_eff == this_eff that select_idle_sibling() will consider
	 * stacking the wakee on top of the waker if no other CPU is
	 * idle.
	 */
	if (sync)
		prev_eff_load += 1;

	return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
5681 5682
}

5683
static int wake_affine(struct sched_domain *sd, struct task_struct *p,
5684
		       int this_cpu, int prev_cpu, int sync)
5685
{
5686
	int target = nr_cpumask_bits;
5687

5688
	if (sched_feat(WA_IDLE))
5689
		target = wake_affine_idle(this_cpu, prev_cpu, sync);
5690

5691 5692
	if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
		target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
5693

5694
	schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
5695 5696
	if (target == nr_cpumask_bits)
		return prev_cpu;
5697

5698 5699 5700
	schedstat_inc(sd->ttwu_move_affine);
	schedstat_inc(p->se.statistics.nr_wakeups_affine);
	return target;
5701 5702
}

5703
static unsigned long cpu_util_without(int cpu, struct task_struct *p);
5704

5705
static unsigned long capacity_spare_without(int cpu, struct task_struct *p)
5706
{
5707
	return max_t(long, capacity_of(cpu) - cpu_util_without(cpu, p), 0);
5708 5709
}

5710 5711 5712
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
5713 5714
 *
 * Assumes p is allowed on at least one CPU in sd.
5715 5716
 */
static struct sched_group *
P
Peter Zijlstra 已提交
5717
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5718
		  int this_cpu, int sd_flag)
5719
{
5720
	struct sched_group *idlest = NULL, *group = sd->groups;
5721
	struct sched_group *most_spare_sg = NULL;
5722 5723 5724
	unsigned long min_runnable_load = ULONG_MAX;
	unsigned long this_runnable_load = ULONG_MAX;
	unsigned long min_avg_load = ULONG_MAX, this_avg_load = ULONG_MAX;
5725
	unsigned long most_spare = 0, this_spare = 0;
5726
	int load_idx = sd->forkexec_idx;
5727 5728 5729
	int imbalance_scale = 100 + (sd->imbalance_pct-100)/2;
	unsigned long imbalance = scale_load_down(NICE_0_LOAD) *
				(sd->imbalance_pct-100) / 100;
5730

5731 5732 5733
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

5734
	do {
5735 5736
		unsigned long load, avg_load, runnable_load;
		unsigned long spare_cap, max_spare_cap;
5737 5738
		int local_group;
		int i;
5739

5740
		/* Skip over this group if it has no CPUs allowed */
5741
		if (!cpumask_intersects(sched_group_span(group),
5742
					&p->cpus_allowed))
5743 5744 5745
			continue;

		local_group = cpumask_test_cpu(this_cpu,
5746
					       sched_group_span(group));
5747

5748 5749 5750 5751
		/*
		 * Tally up the load of all CPUs in the group and find
		 * the group containing the CPU with most spare capacity.
		 */
5752
		avg_load = 0;
5753
		runnable_load = 0;
5754
		max_spare_cap = 0;
5755

5756
		for_each_cpu(i, sched_group_span(group)) {
5757
			/* Bias balancing toward CPUs of our domain */
5758 5759 5760 5761 5762
			if (local_group)
				load = source_load(i, load_idx);
			else
				load = target_load(i, load_idx);

5763 5764 5765
			runnable_load += load;

			avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs);
5766

5767
			spare_cap = capacity_spare_without(i, p);
5768 5769 5770

			if (spare_cap > max_spare_cap)
				max_spare_cap = spare_cap;
5771 5772
		}

5773
		/* Adjust by relative CPU capacity of the group */
5774 5775 5776 5777
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
		runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
5778 5779

		if (local_group) {
5780 5781
			this_runnable_load = runnable_load;
			this_avg_load = avg_load;
5782 5783
			this_spare = max_spare_cap;
		} else {
5784 5785 5786
			if (min_runnable_load > (runnable_load + imbalance)) {
				/*
				 * The runnable load is significantly smaller
5787
				 * so we can pick this new CPU:
5788 5789 5790 5791 5792 5793 5794 5795
				 */
				min_runnable_load = runnable_load;
				min_avg_load = avg_load;
				idlest = group;
			} else if ((runnable_load < (min_runnable_load + imbalance)) &&
				   (100*min_avg_load > imbalance_scale*avg_load)) {
				/*
				 * The runnable loads are close so take the
5796
				 * blocked load into account through avg_load:
5797 5798
				 */
				min_avg_load = avg_load;
5799 5800 5801 5802 5803 5804 5805
				idlest = group;
			}

			if (most_spare < max_spare_cap) {
				most_spare = max_spare_cap;
				most_spare_sg = group;
			}
5806 5807 5808
		}
	} while (group = group->next, group != sd->groups);

5809 5810 5811 5812 5813 5814
	/*
	 * The cross-over point between using spare capacity or least load
	 * is too conservative for high utilization tasks on partially
	 * utilized systems if we require spare_capacity > task_util(p),
	 * so we allow for some task stuffing by using
	 * spare_capacity > task_util(p)/2.
5815 5816 5817 5818
	 *
	 * Spare capacity can't be used for fork because the utilization has
	 * not been set yet, we must first select a rq to compute the initial
	 * utilization.
5819
	 */
5820 5821 5822
	if (sd_flag & SD_BALANCE_FORK)
		goto skip_spare;

5823
	if (this_spare > task_util(p) / 2 &&
5824
	    imbalance_scale*this_spare > 100*most_spare)
5825
		return NULL;
5826 5827

	if (most_spare > task_util(p) / 2)
5828 5829
		return most_spare_sg;

5830
skip_spare:
5831 5832 5833
	if (!idlest)
		return NULL;

5834 5835 5836 5837 5838 5839 5840 5841 5842 5843 5844 5845
	/*
	 * When comparing groups across NUMA domains, it's possible for the
	 * local domain to be very lightly loaded relative to the remote
	 * domains but "imbalance" skews the comparison making remote CPUs
	 * look much more favourable. When considering cross-domain, add
	 * imbalance to the runnable load on the remote node and consider
	 * staying local.
	 */
	if ((sd->flags & SD_NUMA) &&
	    min_runnable_load + imbalance >= this_runnable_load)
		return NULL;

5846
	if (min_runnable_load > (this_runnable_load + imbalance))
5847
		return NULL;
5848 5849 5850 5851 5852

	if ((this_runnable_load < (min_runnable_load + imbalance)) &&
	     (100*this_avg_load < imbalance_scale*min_avg_load))
		return NULL;

5853 5854 5855 5856
	return idlest;
}

/*
5857
 * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
5858 5859
 */
static int
5860
find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5861 5862
{
	unsigned long load, min_load = ULONG_MAX;
5863 5864 5865 5866
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
5867 5868
	int i;

5869 5870
	/* Check if we have any choice: */
	if (group->group_weight == 1)
5871
		return cpumask_first(sched_group_span(group));
5872

5873
	/* Traverse only the allowed CPUs */
5874
	for_each_cpu_and(i, sched_group_span(group), &p->cpus_allowed) {
5875
		if (available_idle_cpu(i)) {
5876 5877 5878 5879 5880 5881 5882 5883 5884 5885 5886 5887 5888 5889 5890 5891 5892 5893 5894 5895 5896
			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;
			}
5897
		} else if (shallowest_idle_cpu == -1) {
5898
			load = weighted_cpuload(cpu_rq(i));
5899
			if (load < min_load) {
5900 5901 5902
				min_load = load;
				least_loaded_cpu = i;
			}
5903 5904 5905
		}
	}

5906
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5907
}
5908

5909 5910 5911
static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
				  int cpu, int prev_cpu, int sd_flag)
{
5912
	int new_cpu = cpu;
5913

5914 5915 5916
	if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed))
		return prev_cpu;

5917
	/*
5918 5919
	 * We need task's util for capacity_spare_without, sync it up to
	 * prev_cpu's last_update_time.
5920 5921 5922 5923
	 */
	if (!(sd_flag & SD_BALANCE_FORK))
		sync_entity_load_avg(&p->se);

5924 5925 5926 5927 5928 5929 5930 5931 5932 5933 5934 5935 5936 5937 5938 5939 5940
	while (sd) {
		struct sched_group *group;
		struct sched_domain *tmp;
		int weight;

		if (!(sd->flags & sd_flag)) {
			sd = sd->child;
			continue;
		}

		group = find_idlest_group(sd, p, cpu, sd_flag);
		if (!group) {
			sd = sd->child;
			continue;
		}

		new_cpu = find_idlest_group_cpu(group, p, cpu);
5941
		if (new_cpu == cpu) {
5942
			/* Now try balancing at a lower domain level of 'cpu': */
5943 5944 5945 5946
			sd = sd->child;
			continue;
		}

5947
		/* Now try balancing at a lower domain level of 'new_cpu': */
5948 5949 5950 5951 5952 5953 5954 5955 5956 5957 5958 5959 5960 5961
		cpu = new_cpu;
		weight = sd->span_weight;
		sd = NULL;
		for_each_domain(cpu, tmp) {
			if (weight <= tmp->span_weight)
				break;
			if (tmp->flags & sd_flag)
				sd = tmp;
		}
	}

	return new_cpu;
}

5962
#ifdef CONFIG_SCHED_SMT
5963
DEFINE_STATIC_KEY_FALSE(sched_smt_present);
5964
EXPORT_SYMBOL_GPL(sched_smt_present);
5965 5966 5967 5968 5969 5970 5971 5972 5973 5974 5975 5976 5977 5978 5979 5980 5981 5982 5983 5984 5985 5986 5987 5988 5989 5990 5991 5992

static inline void set_idle_cores(int cpu, int val)
{
	struct sched_domain_shared *sds;

	sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
	if (sds)
		WRITE_ONCE(sds->has_idle_cores, val);
}

static inline bool test_idle_cores(int cpu, bool def)
{
	struct sched_domain_shared *sds;

	sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
	if (sds)
		return READ_ONCE(sds->has_idle_cores);

	return def;
}

/*
 * Scans the local SMT mask to see if the entire core is idle, and records this
 * information in sd_llc_shared->has_idle_cores.
 *
 * Since SMT siblings share all cache levels, inspecting this limited remote
 * state should be fairly cheap.
 */
P
Peter Zijlstra 已提交
5993
void __update_idle_core(struct rq *rq)
5994 5995 5996 5997 5998 5999 6000 6001 6002 6003 6004 6005
{
	int core = cpu_of(rq);
	int cpu;

	rcu_read_lock();
	if (test_idle_cores(core, true))
		goto unlock;

	for_each_cpu(cpu, cpu_smt_mask(core)) {
		if (cpu == core)
			continue;

6006
		if (!available_idle_cpu(cpu))
6007 6008 6009 6010 6011 6012 6013 6014 6015 6016 6017 6018 6019 6020 6021 6022
			goto unlock;
	}

	set_idle_cores(core, 1);
unlock:
	rcu_read_unlock();
}

/*
 * Scan the entire LLC domain for idle cores; this dynamically switches off if
 * there are no idle cores left in the system; tracked through
 * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
 */
static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
{
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
6023
	int core, cpu;
6024

P
Peter Zijlstra 已提交
6025 6026 6027
	if (!static_branch_likely(&sched_smt_present))
		return -1;

6028 6029 6030
	if (!test_idle_cores(target, false))
		return -1;

6031
	cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed);
6032

6033
	for_each_cpu_wrap(core, cpus, target) {
6034 6035 6036 6037
		bool idle = true;

		for_each_cpu(cpu, cpu_smt_mask(core)) {
			cpumask_clear_cpu(cpu, cpus);
6038
			if (!available_idle_cpu(cpu))
6039 6040 6041 6042 6043 6044 6045 6046 6047 6048 6049 6050 6051 6052 6053 6054 6055 6056 6057 6058 6059 6060
				idle = false;
		}

		if (idle)
			return core;
	}

	/*
	 * Failed to find an idle core; stop looking for one.
	 */
	set_idle_cores(target, 0);

	return -1;
}

/*
 * Scan the local SMT mask for idle CPUs.
 */
static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
{
	int cpu;

P
Peter Zijlstra 已提交
6061 6062 6063
	if (!static_branch_likely(&sched_smt_present))
		return -1;

6064
	for_each_cpu(cpu, cpu_smt_mask(target)) {
6065
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
6066
			continue;
6067
		if (available_idle_cpu(cpu))
6068 6069 6070 6071 6072 6073 6074 6075 6076 6077 6078 6079 6080 6081 6082 6083 6084 6085 6086 6087 6088 6089 6090 6091
			return cpu;
	}

	return -1;
}

#else /* CONFIG_SCHED_SMT */

static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
{
	return -1;
}

static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
{
	return -1;
}

#endif /* CONFIG_SCHED_SMT */

/*
 * Scan the LLC domain for idle CPUs; this is dynamically regulated by
 * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
 * average idle time for this rq (as found in rq->avg_idle).
6092
 */
6093 6094
static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
{
6095
	struct sched_domain *this_sd;
6096
	u64 avg_cost, avg_idle;
6097 6098
	u64 time, cost;
	s64 delta;
6099
	int cpu, nr = INT_MAX;
6100

6101 6102 6103 6104
	this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
	if (!this_sd)
		return -1;

6105 6106 6107 6108
	/*
	 * Due to large variance we need a large fuzz factor; hackbench in
	 * particularly is sensitive here.
	 */
6109 6110 6111 6112
	avg_idle = this_rq()->avg_idle / 512;
	avg_cost = this_sd->avg_scan_cost + 1;

	if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost)
6113 6114
		return -1;

6115 6116 6117 6118 6119 6120 6121 6122
	if (sched_feat(SIS_PROP)) {
		u64 span_avg = sd->span_weight * avg_idle;
		if (span_avg > 4*avg_cost)
			nr = div_u64(span_avg, avg_cost);
		else
			nr = 4;
	}

6123 6124
	time = local_clock();

6125
	for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
6126 6127
		if (!--nr)
			return -1;
6128
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
6129
			continue;
6130
		if (available_idle_cpu(cpu))
6131 6132 6133 6134 6135 6136 6137 6138 6139 6140 6141 6142 6143
			break;
	}

	time = local_clock() - time;
	cost = this_sd->avg_scan_cost;
	delta = (s64)(time - cost) / 8;
	this_sd->avg_scan_cost += delta;

	return cpu;
}

/*
 * Try and locate an idle core/thread in the LLC cache domain.
6144
 */
6145
static int select_idle_sibling(struct task_struct *p, int prev, int target)
6146
{
6147
	struct sched_domain *sd;
6148
	int i, recent_used_cpu;
6149

6150
	if (available_idle_cpu(target))
6151
		return target;
6152 6153

	/*
6154
	 * If the previous CPU is cache affine and idle, don't be stupid:
6155
	 */
6156
	if (prev != target && cpus_share_cache(prev, target) && available_idle_cpu(prev))
6157
		return prev;
6158

6159
	/* Check a recently used CPU as a potential idle candidate: */
6160 6161 6162 6163
	recent_used_cpu = p->recent_used_cpu;
	if (recent_used_cpu != prev &&
	    recent_used_cpu != target &&
	    cpus_share_cache(recent_used_cpu, target) &&
6164
	    available_idle_cpu(recent_used_cpu) &&
6165 6166 6167
	    cpumask_test_cpu(p->recent_used_cpu, &p->cpus_allowed)) {
		/*
		 * Replace recent_used_cpu with prev as it is a potential
6168
		 * candidate for the next wake:
6169 6170 6171 6172 6173
		 */
		p->recent_used_cpu = prev;
		return recent_used_cpu;
	}

6174
	sd = rcu_dereference(per_cpu(sd_llc, target));
6175 6176
	if (!sd)
		return target;
6177

6178 6179 6180
	i = select_idle_core(p, sd, target);
	if ((unsigned)i < nr_cpumask_bits)
		return i;
6181

6182 6183 6184 6185 6186 6187 6188
	i = select_idle_cpu(p, sd, target);
	if ((unsigned)i < nr_cpumask_bits)
		return i;

	i = select_idle_smt(p, sd, target);
	if ((unsigned)i < nr_cpumask_bits)
		return i;
6189

6190 6191
	return target;
}
6192

6193 6194 6195 6196 6197 6198 6199
/**
 * Amount of capacity of a CPU that is (estimated to be) used by CFS tasks
 * @cpu: the CPU to get the utilization of
 *
 * The unit of the return value must be the one of capacity so we can compare
 * the utilization with the capacity of the CPU that is available for CFS task
 * (ie cpu_capacity).
6200 6201 6202 6203 6204 6205 6206 6207 6208 6209
 *
 * 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.
 *
6210 6211 6212 6213 6214 6215 6216 6217
 * The estimated utilization of a CPU is defined to be the maximum between its
 * cfs_rq.avg.util_avg and the sum of the estimated utilization of the tasks
 * currently RUNNABLE on that CPU.
 * This allows to properly represent the expected utilization of a CPU which
 * has just got a big task running since a long sleep period. At the same time
 * however it preserves the benefits of the "blocked utilization" in
 * describing the potential for other tasks waking up on the same CPU.
 *
6218 6219 6220 6221 6222 6223 6224 6225 6226 6227
 * 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).
6228 6229
 *
 * Return: the (estimated) utilization for the specified CPU
6230
 */
6231
static inline unsigned long cpu_util(int cpu)
6232
{
6233 6234 6235 6236 6237 6238 6239 6240
	struct cfs_rq *cfs_rq;
	unsigned int util;

	cfs_rq = &cpu_rq(cpu)->cfs;
	util = READ_ONCE(cfs_rq->avg.util_avg);

	if (sched_feat(UTIL_EST))
		util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued));
6241

6242
	return min_t(unsigned long, util, capacity_orig_of(cpu));
6243
}
6244

6245
/*
6246 6247 6248 6249 6250 6251 6252 6253 6254 6255 6256
 * cpu_util_without: compute cpu utilization without any contributions from *p
 * @cpu: the CPU which utilization is requested
 * @p: the task which utilization should be discounted
 *
 * The utilization of a CPU is defined by the utilization of tasks currently
 * enqueued on that CPU as well as tasks which are currently sleeping after an
 * execution on that CPU.
 *
 * This method returns the utilization of the specified CPU by discounting the
 * utilization of the specified task, whenever the task is currently
 * contributing to the CPU utilization.
6257
 */
6258
static unsigned long cpu_util_without(int cpu, struct task_struct *p)
6259
{
6260 6261
	struct cfs_rq *cfs_rq;
	unsigned int util;
6262 6263

	/* Task has no contribution or is new */
6264
	if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
6265 6266
		return cpu_util(cpu);

6267 6268 6269
	cfs_rq = &cpu_rq(cpu)->cfs;
	util = READ_ONCE(cfs_rq->avg.util_avg);

6270
	/* Discount task's util from CPU's util */
6271
	util -= min_t(unsigned int, util, task_util(p));
6272

6273 6274 6275 6276 6277 6278
	/*
	 * Covered cases:
	 *
	 * a) if *p is the only task sleeping on this CPU, then:
	 *      cpu_util (== task_util) > util_est (== 0)
	 *    and thus we return:
6279
	 *      cpu_util_without = (cpu_util - task_util) = 0
6280 6281 6282 6283 6284 6285
	 *
	 * b) if other tasks are SLEEPING on this CPU, which is now exiting
	 *    IDLE, then:
	 *      cpu_util >= task_util
	 *      cpu_util > util_est (== 0)
	 *    and thus we discount *p's blocked utilization to return:
6286
	 *      cpu_util_without = (cpu_util - task_util) >= 0
6287 6288 6289 6290 6291 6292 6293 6294 6295 6296 6297 6298
	 *
	 * c) if other tasks are RUNNABLE on that CPU and
	 *      util_est > cpu_util
	 *    then we use util_est since it returns a more restrictive
	 *    estimation of the spare capacity on that CPU, by just
	 *    considering the expected utilization of tasks already
	 *    runnable on that CPU.
	 *
	 * Cases a) and b) are covered by the above code, while case c) is
	 * covered by the following code when estimated utilization is
	 * enabled.
	 */
6299 6300 6301 6302 6303 6304 6305 6306 6307 6308 6309 6310 6311 6312 6313 6314 6315 6316 6317 6318 6319 6320 6321 6322 6323 6324 6325
	if (sched_feat(UTIL_EST)) {
		unsigned int estimated =
			READ_ONCE(cfs_rq->avg.util_est.enqueued);

		/*
		 * Despite the following checks we still have a small window
		 * for a possible race, when an execl's select_task_rq_fair()
		 * races with LB's detach_task():
		 *
		 *   detach_task()
		 *     p->on_rq = TASK_ON_RQ_MIGRATING;
		 *     ---------------------------------- A
		 *     deactivate_task()                   \
		 *       dequeue_task()                     + RaceTime
		 *         util_est_dequeue()              /
		 *     ---------------------------------- B
		 *
		 * The additional check on "current == p" it's required to
		 * properly fix the execl regression and it helps in further
		 * reducing the chances for the above race.
		 */
		if (unlikely(task_on_rq_queued(p) || current == p)) {
			estimated -= min_t(unsigned int, estimated,
					   (_task_util_est(p) | UTIL_AVG_UNCHANGED));
		}
		util = max(util, estimated);
	}
6326 6327 6328 6329 6330 6331 6332

	/*
	 * Utilization (estimated) can exceed the CPU capacity, thus let's
	 * clamp to the maximum CPU capacity to ensure consistency with
	 * the cpu_util call.
	 */
	return min_t(unsigned long, util, capacity_orig_of(cpu));
6333 6334
}

6335 6336 6337 6338 6339 6340 6341 6342 6343 6344 6345 6346 6347 6348 6349 6350 6351 6352
/*
 * Disable WAKE_AFFINE in the case where task @p doesn't fit in the
 * capacity of either the waking CPU @cpu or the previous CPU @prev_cpu.
 *
 * In that case WAKE_AFFINE doesn't make sense and we'll let
 * BALANCE_WAKE sort things out.
 */
static int wake_cap(struct task_struct *p, int cpu, int prev_cpu)
{
	long min_cap, max_cap;

	min_cap = min(capacity_orig_of(prev_cpu), capacity_orig_of(cpu));
	max_cap = cpu_rq(cpu)->rd->max_cpu_capacity;

	/* Minimum capacity is close to max, no need to abort wake_affine */
	if (max_cap - min_cap < max_cap >> 3)
		return 0;

6353 6354 6355
	/* Bring task utilization in sync with prev_cpu */
	sync_entity_load_avg(&p->se);

6356 6357 6358
	return min_cap * 1024 < task_util(p) * capacity_margin;
}

6359
/*
6360 6361 6362
 * 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.
6363
 *
6364 6365
 * 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.
6366
 *
6367
 * Returns the target CPU number.
6368 6369 6370
 *
 * preempt must be disabled.
 */
6371
static int
6372
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
6373
{
6374
	struct sched_domain *tmp, *sd = NULL;
6375
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
6376
	int new_cpu = prev_cpu;
6377
	int want_affine = 0;
6378
	int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
6379

P
Peter Zijlstra 已提交
6380 6381
	if (sd_flag & SD_BALANCE_WAKE) {
		record_wakee(p);
6382
		want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu)
6383
			      && cpumask_test_cpu(cpu, &p->cpus_allowed);
P
Peter Zijlstra 已提交
6384
	}
6385

6386
	rcu_read_lock();
6387
	for_each_domain(cpu, tmp) {
6388
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
6389
			break;
6390

6391
		/*
6392
		 * If both 'cpu' and 'prev_cpu' are part of this domain,
6393
		 * cpu is a valid SD_WAKE_AFFINE target.
6394
		 */
6395 6396
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
6397 6398 6399 6400
			if (cpu != prev_cpu)
				new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync);

			sd = NULL; /* Prefer wake_affine over balance flags */
6401
			break;
6402
		}
6403

6404
		if (tmp->flags & sd_flag)
6405
			sd = tmp;
M
Mike Galbraith 已提交
6406 6407
		else if (!want_affine)
			break;
6408 6409
	}

6410 6411
	if (unlikely(sd)) {
		/* Slow path */
6412
		new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
6413 6414 6415 6416 6417 6418 6419
	} else if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */
		/* Fast path */

		new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);

		if (want_affine)
			current->recent_used_cpu = cpu;
6420
	}
6421
	rcu_read_unlock();
6422

6423
	return new_cpu;
6424
}
6425

6426 6427
static void detach_entity_cfs_rq(struct sched_entity *se);

6428
/*
6429
 * Called immediately before a task is migrated to a new CPU; task_cpu(p) and
6430
 * cfs_rq_of(p) references at time of call are still valid and identify the
6431
 * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6432
 */
6433
static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
6434
{
6435 6436 6437 6438 6439 6440 6441 6442 6443 6444 6445 6446 6447 6448 6449 6450 6451 6452 6453 6454 6455 6456 6457 6458 6459 6460
	/*
	 * 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;
	}

6461 6462 6463 6464 6465 6466 6467 6468 6469 6470 6471 6472 6473 6474 6475 6476 6477 6478 6479
	if (p->on_rq == TASK_ON_RQ_MIGRATING) {
		/*
		 * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old'
		 * rq->lock and can modify state directly.
		 */
		lockdep_assert_held(&task_rq(p)->lock);
		detach_entity_cfs_rq(&p->se);

	} else {
		/*
		 * 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.
		 */
		remove_entity_load_avg(&p->se);
	}
6480 6481 6482

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
6483 6484

	/* We have migrated, no longer consider this task hot */
6485
	p->se.exec_start = 0;
6486 6487

	update_scan_period(p, new_cpu);
6488
}
6489 6490 6491 6492 6493

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
6494 6495
#endif /* CONFIG_SMP */

6496
static unsigned long wakeup_gran(struct sched_entity *se)
6497 6498 6499 6500
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
6501 6502
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
6503 6504 6505 6506 6507 6508 6509 6510 6511
	 *
	 * 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.
6512
	 */
6513
	return calc_delta_fair(gran, se);
6514 6515
}

6516 6517 6518 6519 6520 6521 6522 6523 6524 6525 6526 6527 6528 6529 6530 6531 6532 6533 6534 6535 6536 6537
/*
 * 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;

6538
	gran = wakeup_gran(se);
6539 6540 6541 6542 6543 6544
	if (vdiff > gran)
		return 1;

	return 0;
}

6545 6546
static void set_last_buddy(struct sched_entity *se)
{
6547 6548 6549
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6550 6551 6552
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6553
		cfs_rq_of(se)->last = se;
6554
	}
6555 6556 6557 6558
}

static void set_next_buddy(struct sched_entity *se)
{
6559 6560 6561
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6562 6563 6564
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6565
		cfs_rq_of(se)->next = se;
6566
	}
6567 6568
}

6569 6570
static void set_skip_buddy(struct sched_entity *se)
{
6571 6572
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
6573 6574
}

6575 6576 6577
/*
 * Preempt the current task with a newly woken task if needed:
 */
6578
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
6579 6580
{
	struct task_struct *curr = rq->curr;
6581
	struct sched_entity *se = &curr->se, *pse = &p->se;
6582
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6583
	int scale = cfs_rq->nr_running >= sched_nr_latency;
6584
	int next_buddy_marked = 0;
6585

I
Ingo Molnar 已提交
6586 6587 6588
	if (unlikely(se == pse))
		return;

6589
	/*
6590
	 * This is possible from callers such as attach_tasks(), in which we
6591 6592 6593 6594 6595 6596 6597
	 * 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;

6598
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
6599
		set_next_buddy(pse);
6600 6601
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
6602

6603 6604 6605
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
6606 6607 6608 6609 6610 6611
	 *
	 * 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.
6612 6613 6614 6615
	 */
	if (test_tsk_need_resched(curr))
		return;

6616 6617 6618 6619 6620
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

6621
	/*
6622 6623
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
6624
	 */
6625
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
6626
		return;
6627

6628
	find_matching_se(&se, &pse);
6629
	update_curr(cfs_rq_of(se));
6630
	BUG_ON(!pse);
6631 6632 6633 6634 6635 6636 6637
	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);
6638
		goto preempt;
6639
	}
6640

6641
	return;
6642

6643
preempt:
6644
	resched_curr(rq);
6645 6646 6647 6648 6649 6650 6651 6652 6653 6654 6655 6656 6657 6658
	/*
	 * 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);
6659 6660
}

6661
static struct task_struct *
6662
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6663 6664 6665
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
6666
	struct task_struct *p;
6667
	int new_tasks;
6668

6669
again:
6670
	if (!cfs_rq->nr_running)
6671
		goto idle;
6672

6673
#ifdef CONFIG_FAIR_GROUP_SCHED
6674
	if (prev->sched_class != &fair_sched_class)
6675 6676 6677 6678 6679 6680 6681 6682 6683 6684 6685 6686 6687 6688 6689 6690 6691 6692 6693
		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.
		 */
6694 6695 6696 6697 6698
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
6699

6700 6701 6702
			/*
			 * This call to check_cfs_rq_runtime() will do the
			 * throttle and dequeue its entity in the parent(s).
6703
			 * Therefore the nr_running test will indeed
6704 6705
			 * be correct.
			 */
6706 6707 6708 6709 6710 6711
			if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
				cfs_rq = &rq->cfs;

				if (!cfs_rq->nr_running)
					goto idle;

6712
				goto simple;
6713
			}
6714
		}
6715 6716 6717 6718 6719 6720 6721 6722 6723 6724 6725 6726 6727 6728 6729 6730 6731 6732 6733 6734 6735 6736 6737 6738 6739 6740 6741 6742 6743 6744 6745 6746 6747

		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);
	}

6748
	goto done;
6749 6750
simple:
#endif
6751

6752
	put_prev_task(rq, prev);
6753

6754
	do {
6755
		se = pick_next_entity(cfs_rq, NULL);
6756
		set_next_entity(cfs_rq, se);
6757 6758 6759
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
6760
	p = task_of(se);
6761

6762
done: __maybe_unused;
6763 6764 6765 6766 6767 6768 6769 6770 6771
#ifdef CONFIG_SMP
	/*
	 * Move the next running task to the front of
	 * the list, so our cfs_tasks list becomes MRU
	 * one.
	 */
	list_move(&p->se.group_node, &rq->cfs_tasks);
#endif

6772 6773
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
6774 6775

	return p;
6776 6777

idle:
6778 6779
	new_tasks = idle_balance(rq, rf);

6780 6781 6782 6783 6784
	/*
	 * 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.
	 */
6785
	if (new_tasks < 0)
6786 6787
		return RETRY_TASK;

6788
	if (new_tasks > 0)
6789 6790 6791
		goto again;

	return NULL;
6792 6793 6794 6795 6796
}

/*
 * Account for a descheduled task:
 */
6797
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
6798 6799 6800 6801 6802 6803
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
6804
		put_prev_entity(cfs_rq, se);
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
/*
 * 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);
6833 6834 6835 6836 6837
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
6838
		rq_clock_skip_update(rq);
6839 6840 6841 6842 6843
	}

	set_skip_buddy(se);
}

6844 6845 6846 6847
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

6848 6849
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
6850 6851 6852 6853 6854 6855 6856 6857 6858 6859
		return false;

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

	yield_task_fair(rq);

	return true;
}

6860
#ifdef CONFIG_SMP
6861
/**************************************************
P
Peter Zijlstra 已提交
6862 6863 6864 6865 6866
 * Fair scheduling class load-balancing methods.
 *
 * BASICS
 *
 * The purpose of load-balancing is to achieve the same basic fairness the
6867
 * per-CPU scheduler provides, namely provide a proportional amount of compute
P
Peter Zijlstra 已提交
6868 6869 6870 6871
 * 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)
 *
6872
 * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
P
Peter Zijlstra 已提交
6873 6874 6875 6876
 * W_i,0 is defined as:
 *
 *   W_i,0 = \Sum_j w_i,j                                             (2)
 *
6877
 * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
6878
 * is derived from the nice value as per sched_prio_to_weight[].
P
Peter Zijlstra 已提交
6879 6880 6881 6882 6883 6884
 *
 * 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)
 *
6885
 * C_i is the compute capacity of CPU i, typically it is the
P
Peter Zijlstra 已提交
6886 6887 6888 6889 6890 6891
 * 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):
 *
6892
 *   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
6893 6894 6895 6896 6897 6898 6899 6900 6901 6902 6903 6904 6905
 *
 * 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)
6906
 * for all i,j solution, we create a tree of CPUs that follows the hardware
P
Peter Zijlstra 已提交
6907
 * topology where each level pairs two lower groups (or better). This results
6908
 * in O(log n) layers. Furthermore we reduce the number of CPUs going up the
P
Peter Zijlstra 已提交
6909
 * tree to only the first of the previous level and we decrease the frequency
6910
 * of load-balance at each level inv. proportional to the number of CPUs in
P
Peter Zijlstra 已提交
6911 6912 6913 6914 6915 6916 6917 6918
 * 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
6919
 *         |         |     `- number of CPUs doing load-balance
P
Peter Zijlstra 已提交
6920 6921 6922 6923 6924 6925 6926
 *         |         `- 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
6927
 * to every other CPU in at most O(log n) steps:
P
Peter Zijlstra 已提交
6928 6929 6930
 *
 * The adjacency matrix of the resulting graph is given by:
 *
6931
 *             log_2 n
P
Peter Zijlstra 已提交
6932 6933 6934 6935 6936 6937 6938
 *   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)
 *
6939
 * Showing there's indeed a path between every CPU in at most O(log n) steps.
P
Peter Zijlstra 已提交
6940 6941 6942 6943 6944 6945 6946 6947 6948
 * 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
6949
 * balancing is more aggressive and has the newly idle CPU iterate up the domain
P
Peter Zijlstra 已提交
6950 6951 6952 6953 6954 6955 6956 6957 6958 6959 6960 6961 6962 6963 6964 6965 6966 6967 6968 6969
 * 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)
 *
6970
 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i.
P
Peter Zijlstra 已提交
6971 6972 6973 6974 6975 6976
 *
 * 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.]
6977
 */
6978

6979 6980
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

6981 6982
enum fbq_type { regular, remote, all };

6983
#define LBF_ALL_PINNED	0x01
6984
#define LBF_NEED_BREAK	0x02
6985 6986
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
6987
#define LBF_NOHZ_STATS	0x10
6988
#define LBF_NOHZ_AGAIN	0x20
6989 6990 6991 6992 6993

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
6994
	int			src_cpu;
6995 6996 6997 6998

	int			dst_cpu;
	struct rq		*dst_rq;

6999 7000
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
7001
	enum cpu_idle_type	idle;
7002
	long			imbalance;
7003 7004 7005
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

7006
	unsigned int		flags;
7007 7008 7009 7010

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
7011 7012

	enum fbq_type		fbq_type;
7013
	struct list_head	tasks;
7014 7015
};

7016 7017 7018
/*
 * Is this task likely cache-hot:
 */
7019
static int task_hot(struct task_struct *p, struct lb_env *env)
7020 7021 7022
{
	s64 delta;

7023 7024
	lockdep_assert_held(&env->src_rq->lock);

7025 7026 7027 7028 7029 7030 7031 7032 7033
	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
7034
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
7035 7036 7037 7038 7039 7040 7041 7042 7043
			(&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;

7044
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
7045 7046 7047 7048

	return delta < (s64)sysctl_sched_migration_cost;
}

7049
#ifdef CONFIG_NUMA_BALANCING
7050
/*
7051 7052 7053
 * 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.
7054
 */
7055
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
7056
{
7057
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
7058 7059
	unsigned long src_weight, dst_weight;
	int src_nid, dst_nid, dist;
7060

7061
	if (!static_branch_likely(&sched_numa_balancing))
7062 7063
		return -1;

7064
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
7065
		return -1;
7066 7067 7068 7069

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

7070
	if (src_nid == dst_nid)
7071
		return -1;
7072

7073 7074 7075 7076 7077 7078 7079
	/* 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;
	}
7080

7081 7082
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
7083
		return 0;
7084

7085
	/* Leaving a core idle is often worse than degrading locality. */
7086
	if (env->idle == CPU_IDLE)
7087 7088
		return -1;

7089
	dist = node_distance(src_nid, dst_nid);
7090
	if (numa_group) {
7091 7092
		src_weight = group_weight(p, src_nid, dist);
		dst_weight = group_weight(p, dst_nid, dist);
7093
	} else {
7094 7095
		src_weight = task_weight(p, src_nid, dist);
		dst_weight = task_weight(p, dst_nid, dist);
7096 7097
	}

7098
	return dst_weight < src_weight;
7099 7100
}

7101
#else
7102
static inline int migrate_degrades_locality(struct task_struct *p,
7103 7104
					     struct lb_env *env)
{
7105
	return -1;
7106
}
7107 7108
#endif

7109 7110 7111 7112
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
7113
int can_migrate_task(struct task_struct *p, struct lb_env *env)
7114
{
7115
	int tsk_cache_hot;
7116 7117 7118

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

7119 7120
	/*
	 * We do not migrate tasks that are:
7121
	 * 1) throttled_lb_pair, or
7122
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
7123 7124
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
7125
	 */
7126 7127 7128
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

7129
	if (!cpumask_test_cpu(env->dst_cpu, &p->cpus_allowed)) {
7130
		int cpu;
7131

7132
		schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
7133

7134 7135
		env->flags |= LBF_SOME_PINNED;

7136
		/*
7137
		 * Remember if this task can be migrated to any other CPU in
7138 7139 7140
		 * our sched_group. We may want to revisit it if we couldn't
		 * meet load balance goals by pulling other tasks on src_cpu.
		 *
7141 7142
		 * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have
		 * already computed one in current iteration.
7143
		 */
7144
		if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED))
7145 7146
			return 0;

7147
		/* Prevent to re-select dst_cpu via env's CPUs: */
7148
		for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
7149
			if (cpumask_test_cpu(cpu, &p->cpus_allowed)) {
7150
				env->flags |= LBF_DST_PINNED;
7151 7152 7153
				env->new_dst_cpu = cpu;
				break;
			}
7154
		}
7155

7156 7157
		return 0;
	}
7158 7159

	/* Record that we found atleast one task that could run on dst_cpu */
7160
	env->flags &= ~LBF_ALL_PINNED;
7161

7162
	if (task_running(env->src_rq, p)) {
7163
		schedstat_inc(p->se.statistics.nr_failed_migrations_running);
7164 7165 7166 7167 7168
		return 0;
	}

	/*
	 * Aggressive migration if:
7169 7170 7171
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
7172
	 */
7173 7174 7175
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
7176

7177
	if (tsk_cache_hot <= 0 ||
7178
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
7179
		if (tsk_cache_hot == 1) {
7180 7181
			schedstat_inc(env->sd->lb_hot_gained[env->idle]);
			schedstat_inc(p->se.statistics.nr_forced_migrations);
7182
		}
7183 7184 7185
		return 1;
	}

7186
	schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
Z
Zhang Hang 已提交
7187
	return 0;
7188 7189
}

7190
/*
7191 7192 7193 7194 7195 7196 7197
 * 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;
7198
	deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
7199 7200 7201
	set_task_cpu(p, env->dst_cpu);
}

7202
/*
7203
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
7204 7205
 * part of active balancing operations within "domain".
 *
7206
 * Returns a task if successful and NULL otherwise.
7207
 */
7208
static struct task_struct *detach_one_task(struct lb_env *env)
7209
{
7210
	struct task_struct *p;
7211

7212 7213
	lockdep_assert_held(&env->src_rq->lock);

7214 7215
	list_for_each_entry_reverse(p,
			&env->src_rq->cfs_tasks, se.group_node) {
7216 7217
		if (!can_migrate_task(p, env))
			continue;
7218

7219
		detach_task(p, env);
7220

7221
		/*
7222
		 * Right now, this is only the second place where
7223
		 * lb_gained[env->idle] is updated (other is detach_tasks)
7224
		 * so we can safely collect stats here rather than
7225
		 * inside detach_tasks().
7226
		 */
7227
		schedstat_inc(env->sd->lb_gained[env->idle]);
7228
		return p;
7229
	}
7230
	return NULL;
7231 7232
}

7233 7234
static const unsigned int sched_nr_migrate_break = 32;

7235
/*
7236 7237
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
7238
 *
7239
 * Returns number of detached tasks if successful and 0 otherwise.
7240
 */
7241
static int detach_tasks(struct lb_env *env)
7242
{
7243 7244
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
7245
	unsigned long load;
7246 7247 7248
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
7249

7250
	if (env->imbalance <= 0)
7251
		return 0;
7252

7253
	while (!list_empty(tasks)) {
7254 7255 7256 7257 7258 7259 7260
		/*
		 * 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;

7261
		p = list_last_entry(tasks, struct task_struct, se.group_node);
7262

7263 7264
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
7265
		if (env->loop > env->loop_max)
7266
			break;
7267 7268

		/* take a breather every nr_migrate tasks */
7269
		if (env->loop > env->loop_break) {
7270
			env->loop_break += sched_nr_migrate_break;
7271
			env->flags |= LBF_NEED_BREAK;
7272
			break;
7273
		}
7274

7275
		if (!can_migrate_task(p, env))
7276 7277 7278
			goto next;

		load = task_h_load(p);
7279

7280
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
7281 7282
			goto next;

7283
		if ((load / 2) > env->imbalance)
7284
			goto next;
7285

7286 7287 7288 7289
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
7290
		env->imbalance -= load;
7291 7292

#ifdef CONFIG_PREEMPT
7293 7294
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
7295
		 * kernels will stop after the first task is detached to minimize
7296 7297
		 * the critical section.
		 */
7298
		if (env->idle == CPU_NEWLY_IDLE)
7299
			break;
7300 7301
#endif

7302 7303 7304 7305
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
7306
		if (env->imbalance <= 0)
7307
			break;
7308 7309 7310

		continue;
next:
7311
		list_move(&p->se.group_node, tasks);
7312
	}
7313

7314
	/*
7315 7316 7317
	 * 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().
7318
	 */
7319
	schedstat_add(env->sd->lb_gained[env->idle], detached);
7320

7321 7322 7323 7324 7325 7326 7327 7328 7329 7330 7331
	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);
7332
	activate_task(rq, p, ENQUEUE_NOCLOCK);
7333
	p->on_rq = TASK_ON_RQ_QUEUED;
7334 7335 7336 7337 7338 7339 7340 7341 7342
	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)
{
7343 7344 7345
	struct rq_flags rf;

	rq_lock(rq, &rf);
7346
	update_rq_clock(rq);
7347
	attach_task(rq, p);
7348
	rq_unlock(rq, &rf);
7349 7350 7351 7352 7353 7354 7355 7356 7357 7358
}

/*
 * 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;
7359
	struct rq_flags rf;
7360

7361
	rq_lock(env->dst_rq, &rf);
7362
	update_rq_clock(env->dst_rq);
7363 7364 7365 7366

	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
		list_del_init(&p->se.group_node);
7367

7368 7369 7370
		attach_task(env->dst_rq, p);
	}

7371
	rq_unlock(env->dst_rq, &rf);
7372 7373
}

7374 7375 7376 7377 7378 7379 7380 7381 7382 7383 7384
static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
{
	if (cfs_rq->avg.load_avg)
		return true;

	if (cfs_rq->avg.util_avg)
		return true;

	return false;
}

7385
static inline bool others_have_blocked(struct rq *rq)
7386 7387 7388 7389
{
	if (READ_ONCE(rq->avg_rt.util_avg))
		return true;

7390 7391 7392
	if (READ_ONCE(rq->avg_dl.util_avg))
		return true;

7393
#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
7394 7395 7396 7397
	if (READ_ONCE(rq->avg_irq.util_avg))
		return true;
#endif

7398 7399 7400
	return false;
}

7401 7402
#ifdef CONFIG_FAIR_GROUP_SCHED

7403
static void update_blocked_averages(int cpu)
7404 7405
{
	struct rq *rq = cpu_rq(cpu);
7406
	struct cfs_rq *cfs_rq;
7407
	const struct sched_class *curr_class;
7408
	struct rq_flags rf;
7409
	bool done = true;
7410

7411
	rq_lock_irqsave(rq, &rf);
7412
	update_rq_clock(rq);
7413

7414 7415 7416 7417
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
7418
	for_each_leaf_cfs_rq(rq, cfs_rq) {
7419 7420
		struct sched_entity *se;

7421 7422 7423
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
7424

7425
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
7426
			update_tg_load_avg(cfs_rq, 0);
7427

7428 7429 7430
		/* Propagate pending load changes to the parent, if any: */
		se = cfs_rq->tg->se[cpu];
		if (se && !skip_blocked_update(se))
7431
			update_load_avg(cfs_rq_of(se), se, 0);
7432

7433 7434
		/* Don't need periodic decay once load/util_avg are null */
		if (cfs_rq_has_blocked(cfs_rq))
7435
			done = false;
7436
	}
7437 7438 7439 7440

	curr_class = rq->curr->sched_class;
	update_rt_rq_load_avg(rq_clock_task(rq), rq, curr_class == &rt_sched_class);
	update_dl_rq_load_avg(rq_clock_task(rq), rq, curr_class == &dl_sched_class);
7441
	update_irq_load_avg(rq, 0);
7442
	/* Don't need periodic decay once load/util_avg are null */
7443
	if (others_have_blocked(rq))
7444
		done = false;
7445 7446 7447

#ifdef CONFIG_NO_HZ_COMMON
	rq->last_blocked_load_update_tick = jiffies;
7448 7449
	if (done)
		rq->has_blocked_load = 0;
7450
#endif
7451
	rq_unlock_irqrestore(rq, &rf);
7452 7453
}

7454
/*
7455
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
7456 7457 7458
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
7459
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
7460
{
7461 7462
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
7463
	unsigned long now = jiffies;
7464
	unsigned long load;
7465

7466
	if (cfs_rq->last_h_load_update == now)
7467 7468
		return;

7469
	WRITE_ONCE(cfs_rq->h_load_next, NULL);
7470 7471
	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
7472
		WRITE_ONCE(cfs_rq->h_load_next, se);
7473 7474 7475
		if (cfs_rq->last_h_load_update == now)
			break;
	}
7476

7477
	if (!se) {
7478
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
7479 7480 7481
		cfs_rq->last_h_load_update = now;
	}

7482
	while ((se = READ_ONCE(cfs_rq->h_load_next)) != NULL) {
7483
		load = cfs_rq->h_load;
7484 7485
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
7486 7487 7488 7489
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
7490 7491
}

7492
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
7493
{
7494
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
7495

7496
	update_cfs_rq_h_load(cfs_rq);
7497
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
7498
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
7499 7500
}
#else
7501
static inline void update_blocked_averages(int cpu)
7502
{
7503 7504
	struct rq *rq = cpu_rq(cpu);
	struct cfs_rq *cfs_rq = &rq->cfs;
7505
	const struct sched_class *curr_class;
7506
	struct rq_flags rf;
7507

7508
	rq_lock_irqsave(rq, &rf);
7509
	update_rq_clock(rq);
7510
	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
7511 7512 7513 7514

	curr_class = rq->curr->sched_class;
	update_rt_rq_load_avg(rq_clock_task(rq), rq, curr_class == &rt_sched_class);
	update_dl_rq_load_avg(rq_clock_task(rq), rq, curr_class == &dl_sched_class);
7515
	update_irq_load_avg(rq, 0);
7516 7517
#ifdef CONFIG_NO_HZ_COMMON
	rq->last_blocked_load_update_tick = jiffies;
7518
	if (!cfs_rq_has_blocked(cfs_rq) && !others_have_blocked(rq))
7519
		rq->has_blocked_load = 0;
7520
#endif
7521
	rq_unlock_irqrestore(rq, &rf);
7522 7523
}

7524
static unsigned long task_h_load(struct task_struct *p)
7525
{
7526
	return p->se.avg.load_avg;
7527
}
P
Peter Zijlstra 已提交
7528
#endif
7529 7530

/********** Helpers for find_busiest_group ************************/
7531 7532 7533 7534 7535 7536 7537

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

7538 7539 7540 7541 7542 7543 7544
/*
 * 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
7545
	unsigned long load_per_task;
7546
	unsigned long group_capacity;
7547
	unsigned long group_util; /* Total utilization of the group */
7548 7549 7550
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
7551
	enum group_type group_type;
7552
	int group_no_capacity;
7553 7554 7555 7556
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
7557 7558
};

J
Joonsoo Kim 已提交
7559 7560 7561 7562 7563 7564 7565
/*
 * 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 */
7566
	unsigned long total_running;
J
Joonsoo Kim 已提交
7567
	unsigned long total_load;	/* Total load of all groups in sd */
7568
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
7569 7570 7571
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
7572
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
7573 7574
};

7575 7576 7577 7578 7579 7580 7581 7582 7583 7584 7585
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,
7586
		.total_running = 0UL,
7587
		.total_load = 0UL,
7588
		.total_capacity = 0UL,
7589 7590
		.busiest_stat = {
			.avg_load = 0UL,
7591 7592
			.sum_nr_running = 0,
			.group_type = group_other,
7593 7594 7595 7596
		},
	};
}

7597 7598 7599
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
7600
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
7601 7602
 *
 * Return: The load index.
7603 7604 7605 7606 7607 7608 7609 7610 7611 7612 7613 7614 7615 7616 7617 7618 7619 7620 7621 7622 7623 7624
 */
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;
}

7625
static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu)
7626 7627
{
	struct rq *rq = cpu_rq(cpu);
7628
	unsigned long max = arch_scale_cpu_capacity(sd, cpu);
7629 7630
	unsigned long used, free;
	unsigned long irq;
7631

7632
	irq = cpu_util_irq(rq);
7633

7634 7635
	if (unlikely(irq >= max))
		return 1;
7636

7637 7638
	used = READ_ONCE(rq->avg_rt.util_avg);
	used += READ_ONCE(rq->avg_dl.util_avg);
7639

7640 7641
	if (unlikely(used >= max))
		return 1;
7642

7643
	free = max - used;
7644 7645

	return scale_irq_capacity(free, irq, max);
7646 7647
}

7648
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
7649
{
7650
	unsigned long capacity = scale_rt_capacity(sd, cpu);
7651 7652
	struct sched_group *sdg = sd->groups;

7653
	cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(sd, cpu);
7654

7655 7656
	if (!capacity)
		capacity = 1;
7657

7658 7659
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
7660
	sdg->sgc->min_capacity = capacity;
7661 7662
}

7663
void update_group_capacity(struct sched_domain *sd, int cpu)
7664 7665 7666
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
7667
	unsigned long capacity, min_capacity;
7668 7669 7670 7671
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
7672
	sdg->sgc->next_update = jiffies + interval;
7673 7674

	if (!child) {
7675
		update_cpu_capacity(sd, cpu);
7676 7677 7678
		return;
	}

7679
	capacity = 0;
7680
	min_capacity = ULONG_MAX;
7681

P
Peter Zijlstra 已提交
7682 7683 7684 7685 7686 7687
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

7688
		for_each_cpu(cpu, sched_group_span(sdg)) {
7689
			struct sched_group_capacity *sgc;
7690
			struct rq *rq = cpu_rq(cpu);
7691

7692
			/*
7693
			 * build_sched_domains() -> init_sched_groups_capacity()
7694 7695 7696
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
7697 7698
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
7699
			 *
7700
			 * This avoids capacity from being 0 and
7701 7702 7703
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
7704
				capacity += capacity_of(cpu);
7705 7706 7707
			} else {
				sgc = rq->sd->groups->sgc;
				capacity += sgc->capacity;
7708
			}
7709

7710
			min_capacity = min(capacity, min_capacity);
7711
		}
P
Peter Zijlstra 已提交
7712 7713 7714 7715
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
7716
		 */
P
Peter Zijlstra 已提交
7717 7718 7719

		group = child->groups;
		do {
7720 7721 7722 7723
			struct sched_group_capacity *sgc = group->sgc;

			capacity += sgc->capacity;
			min_capacity = min(sgc->min_capacity, min_capacity);
P
Peter Zijlstra 已提交
7724 7725 7726
			group = group->next;
		} while (group != child->groups);
	}
7727

7728
	sdg->sgc->capacity = capacity;
7729
	sdg->sgc->min_capacity = min_capacity;
7730 7731
}

7732
/*
7733 7734 7735
 * 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
7736 7737
 */
static inline int
7738
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
7739
{
7740 7741
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
7742 7743
}

7744 7745
/*
 * Group imbalance indicates (and tries to solve) the problem where balancing
7746
 * groups is inadequate due to ->cpus_allowed constraints.
7747
 *
7748 7749
 * 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.
7750 7751
 * Something like:
 *
7752 7753
 *	{ 0 1 2 3 } { 4 5 6 7 }
 *	        *     * * *
7754 7755 7756
 *
 * 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
7757
 * cpu 3 and leave one of the CPUs in the second group unused.
7758 7759
 *
 * The current solution to this issue is detecting the skew in the first group
7760 7761
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
7762 7763
 *
 * When this is so detected; this group becomes a candidate for busiest; see
7764
 * update_sd_pick_busiest(). And calculate_imbalance() and
7765
 * find_busiest_group() avoid some of the usual balance conditions to allow it
7766 7767 7768 7769 7770 7771 7772
 * 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.
 */

7773
static inline int sg_imbalanced(struct sched_group *group)
7774
{
7775
	return group->sgc->imbalance;
7776 7777
}

7778
/*
7779 7780 7781
 * 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
7782 7783
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
7784 7785 7786 7787 7788
 * 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.
7789
 */
7790 7791
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
7792
{
7793 7794
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
7795

7796
	if ((sgs->group_capacity * 100) >
7797
			(sgs->group_util * env->sd->imbalance_pct))
7798
		return true;
7799

7800 7801 7802 7803 7804 7805 7806 7807 7808 7809 7810 7811 7812 7813 7814 7815
	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;
7816

7817
	if ((sgs->group_capacity * 100) <
7818
			(sgs->group_util * env->sd->imbalance_pct))
7819
		return true;
7820

7821
	return false;
7822 7823
}

7824 7825 7826 7827 7828 7829 7830 7831 7832 7833 7834
/*
 * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller
 * per-CPU capacity than sched_group ref.
 */
static inline bool
group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
{
	return sg->sgc->min_capacity * capacity_margin <
						ref->sgc->min_capacity * 1024;
}

7835 7836 7837
static inline enum
group_type group_classify(struct sched_group *group,
			  struct sg_lb_stats *sgs)
7838
{
7839
	if (sgs->group_no_capacity)
7840 7841 7842 7843 7844 7845 7846 7847
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

7848
static bool update_nohz_stats(struct rq *rq, bool force)
7849 7850 7851 7852
{
#ifdef CONFIG_NO_HZ_COMMON
	unsigned int cpu = rq->cpu;

7853 7854 7855
	if (!rq->has_blocked_load)
		return false;

7856
	if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
7857
		return false;
7858

7859
	if (!force && !time_after(jiffies, rq->last_blocked_load_update_tick))
7860
		return true;
7861 7862

	update_blocked_averages(cpu);
7863 7864 7865 7866

	return rq->has_blocked_load;
#else
	return false;
7867 7868 7869
#endif
}

7870 7871
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
7872
 * @env: The load balancing environment.
7873 7874 7875 7876
 * @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.
7877
 * @overload: Indicate more than one runnable task for any CPU.
7878
 */
7879 7880
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
7881 7882
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
7883
{
7884
	unsigned long load;
7885
	int i, nr_running;
7886

7887 7888
	memset(sgs, 0, sizeof(*sgs));

7889
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
7890 7891
		struct rq *rq = cpu_rq(i);

7892
		if ((env->flags & LBF_NOHZ_STATS) && update_nohz_stats(rq, false))
7893
			env->flags |= LBF_NOHZ_AGAIN;
7894

7895
		/* Bias balancing toward CPUs of our domain: */
7896
		if (local_group)
7897
			load = target_load(i, load_idx);
7898
		else
7899 7900 7901
			load = source_load(i, load_idx);

		sgs->group_load += load;
7902
		sgs->group_util += cpu_util(i);
7903
		sgs->sum_nr_running += rq->cfs.h_nr_running;
7904

7905 7906
		nr_running = rq->nr_running;
		if (nr_running > 1)
7907 7908
			*overload = true;

7909 7910 7911 7912
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
7913
		sgs->sum_weighted_load += weighted_cpuload(rq);
7914 7915 7916 7917
		/*
		 * No need to call idle_cpu() if nr_running is not 0
		 */
		if (!nr_running && idle_cpu(i))
7918
			sgs->idle_cpus++;
7919 7920
	}

7921 7922
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
7923
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
7924

7925
	if (sgs->sum_nr_running)
7926
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
7927

7928
	sgs->group_weight = group->group_weight;
7929

7930
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
7931
	sgs->group_type = group_classify(group, sgs);
7932 7933
}

7934 7935
/**
 * update_sd_pick_busiest - return 1 on busiest group
7936
 * @env: The load balancing environment.
7937 7938
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
7939
 * @sgs: sched_group statistics
7940 7941 7942
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
7943 7944 7945
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
7946
 */
7947
static bool update_sd_pick_busiest(struct lb_env *env,
7948 7949
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
7950
				   struct sg_lb_stats *sgs)
7951
{
7952
	struct sg_lb_stats *busiest = &sds->busiest_stat;
7953

7954
	if (sgs->group_type > busiest->group_type)
7955 7956
		return true;

7957 7958 7959 7960 7961 7962
	if (sgs->group_type < busiest->group_type)
		return false;

	if (sgs->avg_load <= busiest->avg_load)
		return false;

7963 7964 7965 7966 7967 7968 7969 7970 7971 7972 7973 7974 7975 7976
	if (!(env->sd->flags & SD_ASYM_CPUCAPACITY))
		goto asym_packing;

	/*
	 * Candidate sg has no more than one task per CPU and
	 * has higher per-CPU capacity. Migrating tasks to less
	 * capable CPUs may harm throughput. Maximize throughput,
	 * power/energy consequences are not considered.
	 */
	if (sgs->sum_nr_running <= sgs->group_weight &&
	    group_smaller_cpu_capacity(sds->local, sg))
		return false;

asym_packing:
7977 7978
	/* This is the busiest node in its class. */
	if (!(env->sd->flags & SD_ASYM_PACKING))
7979 7980
		return true;

7981
	/* No ASYM_PACKING if target CPU is already busy */
7982 7983
	if (env->idle == CPU_NOT_IDLE)
		return true;
7984
	/*
T
Tim Chen 已提交
7985 7986 7987
	 * ASYM_PACKING needs to move all the work to the highest
	 * prority CPUs in the group, therefore mark all groups
	 * of lower priority than ourself as busy.
7988
	 */
T
Tim Chen 已提交
7989 7990
	if (sgs->sum_nr_running &&
	    sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) {
7991 7992 7993
		if (!sds->busiest)
			return true;

7994
		/* Prefer to move from lowest priority CPU's work */
T
Tim Chen 已提交
7995 7996
		if (sched_asym_prefer(sds->busiest->asym_prefer_cpu,
				      sg->asym_prefer_cpu))
7997 7998 7999 8000 8001 8002
			return true;
	}

	return false;
}

8003 8004 8005 8006 8007 8008 8009 8010 8011 8012 8013 8014 8015 8016 8017 8018 8019 8020 8021 8022 8023 8024 8025 8026 8027 8028 8029 8030 8031 8032
#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 */

8033
/**
8034
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
8035
 * @env: The load balancing environment.
8036 8037
 * @sds: variable to hold the statistics for this sched_domain.
 */
8038
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
8039
{
8040 8041
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
8042
	struct sg_lb_stats *local = &sds->local_stat;
J
Joonsoo Kim 已提交
8043
	struct sg_lb_stats tmp_sgs;
8044
	int load_idx, prefer_sibling = 0;
8045
	bool overload = false;
8046 8047 8048 8049

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

8050
#ifdef CONFIG_NO_HZ_COMMON
8051
	if (env->idle == CPU_NEWLY_IDLE && READ_ONCE(nohz.has_blocked))
8052 8053 8054
		env->flags |= LBF_NOHZ_STATS;
#endif

8055
	load_idx = get_sd_load_idx(env->sd, env->idle);
8056 8057

	do {
J
Joonsoo Kim 已提交
8058
		struct sg_lb_stats *sgs = &tmp_sgs;
8059 8060
		int local_group;

8061
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
J
Joonsoo Kim 已提交
8062 8063
		if (local_group) {
			sds->local = sg;
8064
			sgs = local;
8065 8066

			if (env->idle != CPU_NEWLY_IDLE ||
8067 8068
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
8069
		}
8070

8071 8072
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
8073

8074 8075 8076
		if (local_group)
			goto next_group;

8077 8078
		/*
		 * In case the child domain prefers tasks go to siblings
8079
		 * first, lower the sg capacity so that we'll try
8080 8081
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
8082 8083 8084 8085
		 * 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).
8086
		 */
8087
		if (prefer_sibling && sds->local &&
8088 8089
		    group_has_capacity(env, local) &&
		    (sgs->sum_nr_running > local->sum_nr_running + 1)) {
8090
			sgs->group_no_capacity = 1;
8091
			sgs->group_type = group_classify(sg, sgs);
8092
		}
8093

8094
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
8095
			sds->busiest = sg;
J
Joonsoo Kim 已提交
8096
			sds->busiest_stat = *sgs;
8097 8098
		}

8099 8100
next_group:
		/* Now, start updating sd_lb_stats */
8101
		sds->total_running += sgs->sum_nr_running;
8102
		sds->total_load += sgs->group_load;
8103
		sds->total_capacity += sgs->group_capacity;
8104

8105
		sg = sg->next;
8106
	} while (sg != env->sd->groups);
8107

8108 8109 8110 8111 8112 8113 8114 8115 8116
#ifdef CONFIG_NO_HZ_COMMON
	if ((env->flags & LBF_NOHZ_AGAIN) &&
	    cpumask_subset(nohz.idle_cpus_mask, sched_domain_span(env->sd))) {

		WRITE_ONCE(nohz.next_blocked,
			   jiffies + msecs_to_jiffies(LOAD_AVG_PERIOD));
	}
#endif

8117 8118
	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
8119 8120 8121 8122 8123 8124

	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;
	}
8125 8126 8127 8128
}

/**
 * check_asym_packing - Check to see if the group is packed into the
8129
 *			sched domain.
8130 8131 8132 8133 8134 8135 8136 8137 8138 8139 8140 8141 8142 8143
 *
 * 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.
 *
8144
 * Return: 1 when packing is required and a task should be moved to
8145
 * this CPU.  The amount of the imbalance is returned in env->imbalance.
8146
 *
8147
 * @env: The load balancing environment.
8148 8149
 * @sds: Statistics of the sched_domain which is to be packed
 */
8150
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
8151 8152 8153
{
	int busiest_cpu;

8154
	if (!(env->sd->flags & SD_ASYM_PACKING))
8155 8156
		return 0;

8157 8158 8159
	if (env->idle == CPU_NOT_IDLE)
		return 0;

8160 8161 8162
	if (!sds->busiest)
		return 0;

T
Tim Chen 已提交
8163 8164
	busiest_cpu = sds->busiest->asym_prefer_cpu;
	if (sched_asym_prefer(busiest_cpu, env->dst_cpu))
8165 8166
		return 0;

8167
	env->imbalance = DIV_ROUND_CLOSEST(
8168
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
8169
		SCHED_CAPACITY_SCALE);
8170

8171
	return 1;
8172 8173 8174 8175 8176 8177
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
8178
 * @env: The load balancing environment.
8179 8180
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
8181 8182
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8183
{
8184
	unsigned long tmp, capa_now = 0, capa_move = 0;
8185
	unsigned int imbn = 2;
8186
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
8187
	struct sg_lb_stats *local, *busiest;
8188

J
Joonsoo Kim 已提交
8189 8190
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
8191

J
Joonsoo Kim 已提交
8192 8193 8194 8195
	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;
8196

J
Joonsoo Kim 已提交
8197
	scaled_busy_load_per_task =
8198
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
8199
		busiest->group_capacity;
J
Joonsoo Kim 已提交
8200

8201 8202
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
8203
		env->imbalance = busiest->load_per_task;
8204 8205 8206 8207 8208
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
8209
	 * however we may be able to increase total CPU capacity used by
8210 8211 8212
	 * moving them.
	 */

8213
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
8214
			min(busiest->load_per_task, busiest->avg_load);
8215
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
8216
			min(local->load_per_task, local->avg_load);
8217
	capa_now /= SCHED_CAPACITY_SCALE;
8218 8219

	/* Amount of load we'd subtract */
8220
	if (busiest->avg_load > scaled_busy_load_per_task) {
8221
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
8222
			    min(busiest->load_per_task,
8223
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
8224
	}
8225 8226

	/* Amount of load we'd add */
8227
	if (busiest->avg_load * busiest->group_capacity <
8228
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
8229 8230
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
8231
	} else {
8232
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
8233
		      local->group_capacity;
J
Joonsoo Kim 已提交
8234
	}
8235
	capa_move += local->group_capacity *
8236
		    min(local->load_per_task, local->avg_load + tmp);
8237
	capa_move /= SCHED_CAPACITY_SCALE;
8238 8239

	/* Move if we gain throughput */
8240
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
8241
		env->imbalance = busiest->load_per_task;
8242 8243 8244 8245 8246
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
8247
 * @env: load balance environment
8248 8249
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
8250
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8251
{
8252
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
8253 8254 8255 8256
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
8257

8258
	if (busiest->group_type == group_imbalanced) {
8259 8260
		/*
		 * In the group_imb case we cannot rely on group-wide averages
8261
		 * to ensure CPU-load equilibrium, look at wider averages. XXX
8262
		 */
J
Joonsoo Kim 已提交
8263 8264
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
8265 8266
	}

8267
	/*
8268 8269 8270 8271
	 * 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:
8272
	 */
8273 8274
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
8275 8276
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
8277 8278
	}

8279
	/*
8280
	 * If there aren't any idle CPUs, avoid creating some.
8281 8282 8283
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
8284
		load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
8285
		if (load_above_capacity > busiest->group_capacity) {
8286
			load_above_capacity -= busiest->group_capacity;
8287
			load_above_capacity *= scale_load_down(NICE_0_LOAD);
8288 8289
			load_above_capacity /= busiest->group_capacity;
		} else
8290
			load_above_capacity = ~0UL;
8291 8292 8293
	}

	/*
8294
	 * We're trying to get all the CPUs to the average_load, so we don't
8295
	 * want to push ourselves above the average load, nor do we wish to
8296
	 * reduce the max loaded CPU below the average load. At the same time,
8297 8298
	 * we also don't want to reduce the group load below the group
	 * capacity. Thus we look for the minimum possible imbalance.
8299
	 */
8300
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
8301 8302

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
8303
	env->imbalance = min(
8304 8305
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
8306
	) / SCHED_CAPACITY_SCALE;
8307 8308 8309

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
8310
	 * there is no guarantee that any tasks will be moved so we'll have
8311 8312 8313
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
8314
	if (env->imbalance < busiest->load_per_task)
8315
		return fix_small_imbalance(env, sds);
8316
}
8317

8318 8319 8320 8321
/******* find_busiest_group() helpers end here *********************/

/**
 * find_busiest_group - Returns the busiest group within the sched_domain
8322
 * if there is an imbalance.
8323 8324 8325 8326
 *
 * Also calculates the amount of weighted load which should be moved
 * to restore balance.
 *
8327
 * @env: The load balancing environment.
8328
 *
8329
 * Return:	- The busiest group if imbalance exists.
8330
 */
J
Joonsoo Kim 已提交
8331
static struct sched_group *find_busiest_group(struct lb_env *env)
8332
{
J
Joonsoo Kim 已提交
8333
	struct sg_lb_stats *local, *busiest;
8334 8335
	struct sd_lb_stats sds;

8336
	init_sd_lb_stats(&sds);
8337 8338 8339 8340 8341

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
8342
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
8343 8344
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
8345

8346
	/* ASYM feature bypasses nice load balance check */
8347
	if (check_asym_packing(env, &sds))
8348 8349
		return sds.busiest;

8350
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
8351
	if (!sds.busiest || busiest->sum_nr_running == 0)
8352 8353
		goto out_balanced;

8354
	/* XXX broken for overlapping NUMA groups */
8355 8356
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
8357

P
Peter Zijlstra 已提交
8358 8359
	/*
	 * If the busiest group is imbalanced the below checks don't
8360
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
8361 8362
	 * isn't true due to cpus_allowed constraints and the like.
	 */
8363
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
8364 8365
		goto force_balance;

8366 8367 8368 8369 8370
	/*
	 * When dst_cpu is idle, prevent SMP nice and/or asymmetric group
	 * capacities from resulting in underutilization due to avg_load.
	 */
	if (env->idle != CPU_NOT_IDLE && group_has_capacity(env, local) &&
8371
	    busiest->group_no_capacity)
8372 8373
		goto force_balance;

8374
	/*
8375
	 * If the local group is busier than the selected busiest group
8376 8377
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
8378
	if (local->avg_load >= busiest->avg_load)
8379 8380
		goto out_balanced;

8381 8382 8383 8384
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
8385
	if (local->avg_load >= sds.avg_load)
8386 8387
		goto out_balanced;

8388
	if (env->idle == CPU_IDLE) {
8389
		/*
8390
		 * This CPU is idle. If the busiest group is not overloaded
8391
		 * and there is no imbalance between this and busiest group
8392
		 * wrt idle CPUs, it is balanced. The imbalance becomes
8393 8394
		 * significant if the diff is greater than 1 otherwise we
		 * might end up to just move the imbalance on another group
8395
		 */
8396 8397
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
8398
			goto out_balanced;
8399 8400 8401 8402 8403
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
8404 8405
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
8406
			goto out_balanced;
8407
	}
8408

8409
force_balance:
8410
	/* Looks like there is an imbalance. Compute it */
8411
	calculate_imbalance(env, &sds);
8412
	return env->imbalance ? sds.busiest : NULL;
8413 8414

out_balanced:
8415
	env->imbalance = 0;
8416 8417 8418 8419
	return NULL;
}

/*
8420
 * find_busiest_queue - find the busiest runqueue among the CPUs in the group.
8421
 */
8422
static struct rq *find_busiest_queue(struct lb_env *env,
8423
				     struct sched_group *group)
8424 8425
{
	struct rq *busiest = NULL, *rq;
8426
	unsigned long busiest_load = 0, busiest_capacity = 1;
8427 8428
	int i;

8429
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
8430
		unsigned long capacity, wl;
8431 8432 8433 8434
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
8435

8436 8437 8438 8439 8440 8441 8442 8443 8444 8445 8446 8447 8448 8449 8450 8451 8452 8453 8454 8455 8456 8457
		/*
		 * 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;

8458
		capacity = capacity_of(i);
8459

8460
		wl = weighted_cpuload(rq);
8461

8462 8463
		/*
		 * When comparing with imbalance, use weighted_cpuload()
8464
		 * which is not scaled with the CPU capacity.
8465
		 */
8466 8467 8468

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
8469 8470
			continue;

8471
		/*
8472 8473 8474
		 * For the load comparisons with the other CPU's, consider
		 * the weighted_cpuload() scaled with the CPU capacity, so
		 * that the load can be moved away from the CPU that is
8475
		 * potentially running at a lower capacity.
8476
		 *
8477
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
8478
		 * multiplication to rid ourselves of the division works out
8479 8480
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
8481
		 */
8482
		if (wl * busiest_capacity > busiest_load * capacity) {
8483
			busiest_load = wl;
8484
			busiest_capacity = capacity;
8485 8486 8487 8488 8489 8490 8491 8492 8493 8494 8495 8496 8497
			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

8498
static int need_active_balance(struct lb_env *env)
8499
{
8500 8501 8502
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
8503 8504 8505

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
T
Tim Chen 已提交
8506 8507
		 * lower priority CPUs in order to pack all tasks in the
		 * highest priority CPUs.
8508
		 */
T
Tim Chen 已提交
8509 8510
		if ((sd->flags & SD_ASYM_PACKING) &&
		    sched_asym_prefer(env->dst_cpu, env->src_cpu))
8511
			return 1;
8512 8513
	}

8514 8515 8516 8517 8518 8519 8520 8521 8522 8523 8524 8525 8526
	/*
	 * 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;
	}

8527 8528 8529
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

8530 8531
static int active_load_balance_cpu_stop(void *data);

8532 8533 8534 8535 8536
static int should_we_balance(struct lb_env *env)
{
	struct sched_group *sg = env->sd->groups;
	int cpu, balance_cpu = -1;

8537 8538 8539 8540 8541 8542 8543
	/*
	 * Ensure the balancing environment is consistent; can happen
	 * when the softirq triggers 'during' hotplug.
	 */
	if (!cpumask_test_cpu(env->dst_cpu, env->cpus))
		return 0;

8544
	/*
8545
	 * In the newly idle case, we will allow all the CPUs
8546 8547 8548 8549 8550
	 * to do the newly idle load balance.
	 */
	if (env->idle == CPU_NEWLY_IDLE)
		return 1;

8551
	/* Try to find first idle CPU */
8552
	for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
8553
		if (!idle_cpu(cpu))
8554 8555 8556 8557 8558 8559 8560 8561 8562 8563
			continue;

		balance_cpu = cpu;
		break;
	}

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

	/*
8564
	 * First idle CPU or the first CPU(busiest) in this sched group
8565 8566
	 * is eligible for doing load balancing at this and above domains.
	 */
8567
	return balance_cpu == env->dst_cpu;
8568 8569
}

8570 8571 8572 8573 8574 8575
/*
 * 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,
8576
			int *continue_balancing)
8577
{
8578
	int ld_moved, cur_ld_moved, active_balance = 0;
8579
	struct sched_domain *sd_parent = sd->parent;
8580 8581
	struct sched_group *group;
	struct rq *busiest;
8582
	struct rq_flags rf;
8583
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
8584

8585 8586
	struct lb_env env = {
		.sd		= sd,
8587 8588
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
8589
		.dst_grpmask    = sched_group_span(sd->groups),
8590
		.idle		= idle,
8591
		.loop_break	= sched_nr_migrate_break,
8592
		.cpus		= cpus,
8593
		.fbq_type	= all,
8594
		.tasks		= LIST_HEAD_INIT(env.tasks),
8595 8596
	};

8597
	cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
8598

8599
	schedstat_inc(sd->lb_count[idle]);
8600 8601

redo:
8602 8603
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
8604
		goto out_balanced;
8605
	}
8606

8607
	group = find_busiest_group(&env);
8608
	if (!group) {
8609
		schedstat_inc(sd->lb_nobusyg[idle]);
8610 8611 8612
		goto out_balanced;
	}

8613
	busiest = find_busiest_queue(&env, group);
8614
	if (!busiest) {
8615
		schedstat_inc(sd->lb_nobusyq[idle]);
8616 8617 8618
		goto out_balanced;
	}

8619
	BUG_ON(busiest == env.dst_rq);
8620

8621
	schedstat_add(sd->lb_imbalance[idle], env.imbalance);
8622

8623 8624 8625
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

8626 8627 8628 8629 8630 8631 8632 8633
	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.
		 */
8634
		env.flags |= LBF_ALL_PINNED;
8635
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
8636

8637
more_balance:
8638
		rq_lock_irqsave(busiest, &rf);
8639
		update_rq_clock(busiest);
8640 8641 8642 8643 8644

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
8645
		cur_ld_moved = detach_tasks(&env);
8646 8647

		/*
8648 8649 8650 8651 8652
		 * 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.
8653
		 */
8654

8655
		rq_unlock(busiest, &rf);
8656 8657 8658 8659 8660 8661

		if (cur_ld_moved) {
			attach_tasks(&env);
			ld_moved += cur_ld_moved;
		}

8662
		local_irq_restore(rf.flags);
8663

8664 8665 8666 8667 8668
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

8669 8670 8671 8672
		/*
		 * 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
8673
		 * iterate on same src_cpu is dependent on number of CPUs in our
8674 8675 8676 8677 8678 8679 8680 8681 8682 8683 8684 8685 8686 8687
		 * 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.
		 */
8688
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
8689

8690
			/* Prevent to re-select dst_cpu via env's CPUs */
8691 8692
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

8693
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
8694
			env.dst_cpu	 = env.new_dst_cpu;
8695
			env.flags	&= ~LBF_DST_PINNED;
8696 8697
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
8698

8699 8700 8701 8702 8703 8704
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
8705

8706 8707 8708 8709
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
8710
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
8711

8712
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
8713 8714 8715
				*group_imbalance = 1;
		}

8716
		/* All tasks on this runqueue were pinned by CPU affinity */
8717
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
8718
			cpumask_clear_cpu(cpu_of(busiest), cpus);
8719 8720 8721 8722 8723 8724 8725 8726 8727
			/*
			 * Attempting to continue load balancing at the current
			 * sched_domain level only makes sense if there are
			 * active CPUs remaining as possible busiest CPUs to
			 * pull load from which are not contained within the
			 * destination group that is receiving any migrated
			 * load.
			 */
			if (!cpumask_subset(cpus, env.dst_grpmask)) {
8728 8729
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
8730
				goto redo;
8731
			}
8732
			goto out_all_pinned;
8733 8734 8735 8736
		}
	}

	if (!ld_moved) {
8737
		schedstat_inc(sd->lb_failed[idle]);
8738 8739 8740 8741 8742 8743 8744 8745
		/*
		 * 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++;
8746

8747
		if (need_active_balance(&env)) {
8748 8749
			unsigned long flags;

8750 8751
			raw_spin_lock_irqsave(&busiest->lock, flags);

8752 8753 8754 8755
			/*
			 * Don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest CPU can't be
			 * moved to this_cpu:
8756
			 */
8757
			if (!cpumask_test_cpu(this_cpu, &busiest->curr->cpus_allowed)) {
8758 8759
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
8760
				env.flags |= LBF_ALL_PINNED;
8761 8762 8763
				goto out_one_pinned;
			}

8764 8765 8766 8767 8768
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
8769 8770 8771 8772 8773 8774
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
8775

8776
			if (active_balance) {
8777 8778 8779
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
8780
			}
8781

8782
			/* We've kicked active balancing, force task migration. */
8783 8784 8785 8786 8787 8788 8789 8790 8791 8792 8793 8794 8795
			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
8796
		 * detach_tasks).
8797 8798 8799 8800 8801 8802 8803 8804
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
8805 8806 8807 8808 8809 8810 8811 8812 8813 8814 8815 8816 8817 8818 8819 8820 8821
	/*
	 * 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.
	 */
8822
	schedstat_inc(sd->lb_balanced[idle]);
8823 8824 8825 8826 8827

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
8828
	if (((env.flags & LBF_ALL_PINNED) &&
8829
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
8830 8831 8832
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

8833
	ld_moved = 0;
8834 8835 8836 8837
out:
	return ld_moved;
}

8838 8839 8840 8841 8842 8843 8844 8845 8846 8847 8848 8849 8850 8851 8852 8853
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
8854
update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
8855 8856 8857
{
	unsigned long interval, next;

8858 8859
	/* used by idle balance, so cpu_busy = 0 */
	interval = get_sd_balance_interval(sd, 0);
8860 8861 8862 8863 8864 8865
	next = sd->last_balance + interval;

	if (time_after(*next_balance, next))
		*next_balance = next;
}

8866
/*
8867
 * active_load_balance_cpu_stop is run by the CPU stopper. It pushes
8868 8869 8870
 * 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.
8871
 */
8872
static int active_load_balance_cpu_stop(void *data)
8873
{
8874 8875
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
8876
	int target_cpu = busiest_rq->push_cpu;
8877
	struct rq *target_rq = cpu_rq(target_cpu);
8878
	struct sched_domain *sd;
8879
	struct task_struct *p = NULL;
8880
	struct rq_flags rf;
8881

8882
	rq_lock_irq(busiest_rq, &rf);
8883 8884 8885 8886 8887 8888 8889
	/*
	 * Between queueing the stop-work and running it is a hole in which
	 * CPUs can become inactive. We should not move tasks from or to
	 * inactive CPUs.
	 */
	if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu))
		goto out_unlock;
8890

8891
	/* Make sure the requested CPU hasn't gone down in the meantime: */
8892 8893 8894
	if (unlikely(busiest_cpu != smp_processor_id() ||
		     !busiest_rq->active_balance))
		goto out_unlock;
8895 8896 8897

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
8898
		goto out_unlock;
8899 8900 8901 8902

	/*
	 * This condition is "impossible", if it occurs
	 * we need to fix it. Originally reported by
8903
	 * Bjorn Helgaas on a 128-CPU setup.
8904 8905 8906 8907
	 */
	BUG_ON(busiest_rq == target_rq);

	/* Search for an sd spanning us and the target CPU. */
8908
	rcu_read_lock();
8909 8910 8911 8912 8913 8914 8915
	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)) {
8916 8917
		struct lb_env env = {
			.sd		= sd,
8918 8919 8920 8921
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
8922
			.idle		= CPU_IDLE,
8923 8924 8925 8926 8927 8928 8929
			/*
			 * can_migrate_task() doesn't need to compute new_dst_cpu
			 * for active balancing. Since we have CPU_IDLE, but no
			 * @dst_grpmask we need to make that test go away with lying
			 * about DST_PINNED.
			 */
			.flags		= LBF_DST_PINNED,
8930 8931
		};

8932
		schedstat_inc(sd->alb_count);
8933
		update_rq_clock(busiest_rq);
8934

8935
		p = detach_one_task(&env);
8936
		if (p) {
8937
			schedstat_inc(sd->alb_pushed);
8938 8939 8940
			/* Active balancing done, reset the failure counter. */
			sd->nr_balance_failed = 0;
		} else {
8941
			schedstat_inc(sd->alb_failed);
8942
		}
8943
	}
8944
	rcu_read_unlock();
8945 8946
out_unlock:
	busiest_rq->active_balance = 0;
8947
	rq_unlock(busiest_rq, &rf);
8948 8949 8950 8951 8952 8953

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

8954
	return 0;
8955 8956
}

8957 8958 8959 8960 8961 8962 8963 8964 8965 8966 8967 8968 8969 8970 8971 8972 8973 8974 8975 8976 8977 8978 8979 8980 8981 8982 8983 8984 8985 8986 8987 8988 8989 8990 8991 8992 8993 8994 8995 8996 8997 8998 8999 9000 9001 9002 9003 9004 9005 9006 9007 9008 9009 9010 9011 9012 9013 9014 9015 9016 9017 9018 9019 9020 9021 9022 9023 9024 9025 9026 9027 9028 9029 9030 9031 9032 9033 9034 9035 9036 9037 9038 9039 9040 9041 9042 9043 9044 9045 9046 9047 9048 9049 9050 9051 9052 9053 9054 9055 9056 9057 9058 9059 9060 9061 9062 9063 9064 9065 9066 9067 9068 9069 9070 9071 9072 9073 9074
static DEFINE_SPINLOCK(balancing);

/*
 * 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.
 */
void update_max_interval(void)
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
 * Balancing parameters are set up in init_sched_domains.
 */
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
{
	int continue_balancing = 1;
	int cpu = rq->cpu;
	unsigned long interval;
	struct sched_domain *sd;
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;

	rcu_read_lock();
	for_each_domain(cpu, sd) {
		/*
		 * 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;

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

		/*
		 * 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;
		}

		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);

		need_serialize = sd->flags & SD_SERIALIZE;
		if (need_serialize) {
			if (!spin_trylock(&balancing))
				goto out;
		}

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
				/*
				 * The LBF_DST_PINNED logic could have changed
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
				 */
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
			}
			sd->last_balance = jiffies;
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
		}
		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;
		}
	}
	if (need_decay) {
		/*
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
		 */
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
	}
	rcu_read_unlock();

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

#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
	}
}

9075 9076 9077 9078 9079
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

9080
#ifdef CONFIG_NO_HZ_COMMON
9081 9082 9083 9084 9085
/*
 * 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.
9086 9087
 * - HK_FLAG_MISC CPUs are used for this task, because HK_FLAG_SCHED not set
 *   anywhere yet.
9088
 */
9089

9090
static inline int find_new_ilb(void)
9091
{
9092
	int ilb;
9093

9094 9095 9096 9097 9098
	for_each_cpu_and(ilb, nohz.idle_cpus_mask,
			      housekeeping_cpumask(HK_FLAG_MISC)) {
		if (idle_cpu(ilb))
			return ilb;
	}
9099 9100

	return nr_cpu_ids;
9101 9102
}

9103
/*
9104 9105
 * Kick a CPU to do the nohz balancing, if it is time for it. We pick any
 * idle CPU in the HK_FLAG_MISC housekeeping set (if there is one).
9106
 */
9107
static void kick_ilb(unsigned int flags)
9108 9109 9110 9111 9112
{
	int ilb_cpu;

	nohz.next_balance++;

9113
	ilb_cpu = find_new_ilb();
9114

9115 9116
	if (ilb_cpu >= nr_cpu_ids)
		return;
9117

9118
	flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
P
Peter Zijlstra 已提交
9119
	if (flags & NOHZ_KICK_MASK)
9120
		return;
9121

9122 9123
	/*
	 * Use smp_send_reschedule() instead of resched_cpu().
9124
	 * This way we generate a sched IPI on the target CPU which
9125 9126 9127 9128
	 * is idle. And the softirq performing nohz idle load balance
	 * will be run before returning from the IPI.
	 */
	smp_send_reschedule(ilb_cpu);
9129 9130 9131 9132 9133 9134 9135 9136 9137 9138 9139 9140 9141 9142 9143 9144 9145 9146 9147
}

/*
 * Current heuristic for kicking the idle load balancer in the presence
 * of an idle cpu in the system.
 *   - This rq has more than one task.
 *   - 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.
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
 */
static void nohz_balancer_kick(struct rq *rq)
{
	unsigned long now = jiffies;
	struct sched_domain_shared *sds;
	struct sched_domain *sd;
	int nr_busy, i, cpu = rq->cpu;
9148
	unsigned int flags = 0;
9149 9150 9151 9152 9153 9154 9155 9156

	if (unlikely(rq->idle_balance))
		return;

	/*
	 * 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.
	 */
9157
	nohz_balance_exit_idle(rq);
9158 9159 9160 9161 9162 9163 9164 9165

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

9166 9167
	if (READ_ONCE(nohz.has_blocked) &&
	    time_after(now, READ_ONCE(nohz.next_blocked)))
9168 9169
		flags = NOHZ_STATS_KICK;

9170
	if (time_before(now, nohz.next_balance))
9171
		goto out;
9172 9173

	if (rq->nr_running >= 2) {
9174
		flags = NOHZ_KICK_MASK;
9175 9176 9177 9178 9179 9180 9181 9182 9183 9184 9185 9186
		goto out;
	}

	rcu_read_lock();
	sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
	if (sds) {
		/*
		 * XXX: write a coherent comment on why we do this.
		 * See also: http://lkml.kernel.org/r/20111202010832.602203411@sbsiddha-desk.sc.intel.com
		 */
		nr_busy = atomic_read(&sds->nr_busy_cpus);
		if (nr_busy > 1) {
9187
			flags = NOHZ_KICK_MASK;
9188 9189 9190 9191 9192 9193 9194 9195 9196
			goto unlock;
		}

	}

	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
9197
			flags = NOHZ_KICK_MASK;
9198 9199 9200 9201 9202 9203 9204 9205 9206 9207 9208 9209
			goto unlock;
		}
	}

	sd = rcu_dereference(per_cpu(sd_asym, cpu));
	if (sd) {
		for_each_cpu(i, sched_domain_span(sd)) {
			if (i == cpu ||
			    !cpumask_test_cpu(i, nohz.idle_cpus_mask))
				continue;

			if (sched_asym_prefer(i, cpu)) {
9210
				flags = NOHZ_KICK_MASK;
9211 9212 9213 9214 9215 9216 9217
				goto unlock;
			}
		}
	}
unlock:
	rcu_read_unlock();
out:
9218 9219
	if (flags)
		kick_ilb(flags);
9220 9221
}

9222
static void set_cpu_sd_state_busy(int cpu)
9223
{
9224
	struct sched_domain *sd;
9225

9226 9227
	rcu_read_lock();
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
9228

9229 9230 9231 9232 9233 9234 9235
	if (!sd || !sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 0;

	atomic_inc(&sd->shared->nr_busy_cpus);
unlock:
	rcu_read_unlock();
9236 9237
}

9238 9239 9240 9241 9242 9243 9244 9245 9246 9247 9248 9249 9250 9251 9252
void nohz_balance_exit_idle(struct rq *rq)
{
	SCHED_WARN_ON(rq != this_rq());

	if (likely(!rq->nohz_tick_stopped))
		return;

	rq->nohz_tick_stopped = 0;
	cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask);
	atomic_dec(&nohz.nr_cpus);

	set_cpu_sd_state_busy(rq->cpu);
}

static void set_cpu_sd_state_idle(int cpu)
9253 9254 9255 9256
{
	struct sched_domain *sd;

	rcu_read_lock();
9257
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
V
Vincent Guittot 已提交
9258 9259 9260 9261 9262

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

9263
	atomic_dec(&sd->shared->nr_busy_cpus);
V
Vincent Guittot 已提交
9264
unlock:
9265 9266 9267
	rcu_read_unlock();
}

9268
/*
9269
 * This routine will record that the CPU is going idle with tick stopped.
9270
 * This info will be used in performing idle load balancing in the future.
9271
 */
9272
void nohz_balance_enter_idle(int cpu)
9273
{
9274 9275 9276 9277
	struct rq *rq = cpu_rq(cpu);

	SCHED_WARN_ON(cpu != smp_processor_id());

9278
	/* If this CPU is going down, then nothing needs to be done: */
9279 9280 9281
	if (!cpu_active(cpu))
		return;

9282
	/* Spare idle load balancing on CPUs that don't want to be disturbed: */
9283
	if (!housekeeping_cpu(cpu, HK_FLAG_SCHED))
9284 9285
		return;

9286 9287 9288 9289 9290 9291 9292 9293 9294 9295 9296 9297 9298
	/*
	 * Can be set safely without rq->lock held
	 * If a clear happens, it will have evaluated last additions because
	 * rq->lock is held during the check and the clear
	 */
	rq->has_blocked_load = 1;

	/*
	 * The tick is still stopped but load could have been added in the
	 * meantime. We set the nohz.has_blocked flag to trig a check of the
	 * *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear
	 * of nohz.has_blocked can only happen after checking the new load
	 */
9299
	if (rq->nohz_tick_stopped)
9300
		goto out;
9301

9302
	/* If we're a completely isolated CPU, we don't play: */
9303
	if (on_null_domain(rq))
9304 9305
		return;

9306 9307
	rq->nohz_tick_stopped = 1;

9308 9309
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
9310

9311 9312 9313 9314 9315 9316 9317
	/*
	 * Ensures that if nohz_idle_balance() fails to observe our
	 * @idle_cpus_mask store, it must observe the @has_blocked
	 * store.
	 */
	smp_mb__after_atomic();

9318
	set_cpu_sd_state_idle(cpu);
9319 9320 9321 9322 9323 9324 9325

out:
	/*
	 * Each time a cpu enter idle, we assume that it has blocked load and
	 * enable the periodic update of the load of idle cpus
	 */
	WRITE_ONCE(nohz.has_blocked, 1);
9326 9327 9328
}

/*
9329 9330 9331 9332 9333
 * Internal function that runs load balance for all idle cpus. The load balance
 * can be a simple update of blocked load or a complete load balance with
 * tasks movement depending of flags.
 * The function returns false if the loop has stopped before running
 * through all idle CPUs.
9334
 */
9335 9336
static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags,
			       enum cpu_idle_type idle)
9337
{
9338
	/* Earliest time when we have to do rebalance again */
9339 9340
	unsigned long now = jiffies;
	unsigned long next_balance = now + 60*HZ;
9341
	bool has_blocked_load = false;
9342
	int update_next_balance = 0;
P
Peter Zijlstra 已提交
9343 9344
	int this_cpu = this_rq->cpu;
	int balance_cpu;
9345
	int ret = false;
P
Peter Zijlstra 已提交
9346
	struct rq *rq;
9347

P
Peter Zijlstra 已提交
9348
	SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);
9349

9350 9351 9352 9353 9354 9355 9356 9357 9358 9359 9360 9361 9362 9363 9364 9365
	/*
	 * We assume there will be no idle load after this update and clear
	 * the has_blocked flag. If a cpu enters idle in the mean time, it will
	 * set the has_blocked flag and trig another update of idle load.
	 * Because a cpu that becomes idle, is added to idle_cpus_mask before
	 * setting the flag, we are sure to not clear the state and not
	 * check the load of an idle cpu.
	 */
	WRITE_ONCE(nohz.has_blocked, 0);

	/*
	 * Ensures that if we miss the CPU, we must see the has_blocked
	 * store from nohz_balance_enter_idle().
	 */
	smp_mb();

9366
	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
9367
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
9368 9369 9370
			continue;

		/*
9371 9372
		 * If this CPU gets work to do, stop the load balancing
		 * work being done for other CPUs. Next load
9373 9374
		 * balancing owner will pick it up.
		 */
9375 9376 9377 9378
		if (need_resched()) {
			has_blocked_load = true;
			goto abort;
		}
9379

V
Vincent Guittot 已提交
9380 9381
		rq = cpu_rq(balance_cpu);

9382
		has_blocked_load |= update_nohz_stats(rq, true);
9383

9384 9385 9386 9387 9388
		/*
		 * If time for next balance is due,
		 * do the balance.
		 */
		if (time_after_eq(jiffies, rq->next_balance)) {
9389 9390
			struct rq_flags rf;

9391
			rq_lock_irqsave(rq, &rf);
9392
			update_rq_clock(rq);
9393
			cpu_load_update_idle(rq);
9394
			rq_unlock_irqrestore(rq, &rf);
9395

P
Peter Zijlstra 已提交
9396 9397
			if (flags & NOHZ_BALANCE_KICK)
				rebalance_domains(rq, CPU_IDLE);
9398
		}
9399

9400 9401 9402 9403
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
9404
	}
9405

9406 9407 9408 9409 9410 9411
	/* Newly idle CPU doesn't need an update */
	if (idle != CPU_NEWLY_IDLE) {
		update_blocked_averages(this_cpu);
		has_blocked_load |= this_rq->has_blocked_load;
	}

P
Peter Zijlstra 已提交
9412 9413 9414
	if (flags & NOHZ_BALANCE_KICK)
		rebalance_domains(this_rq, CPU_IDLE);

9415 9416 9417
	WRITE_ONCE(nohz.next_blocked,
		now + msecs_to_jiffies(LOAD_AVG_PERIOD));

9418 9419 9420
	/* The full idle balance loop has been done */
	ret = true;

9421 9422 9423 9424
abort:
	/* There is still blocked load, enable periodic update */
	if (has_blocked_load)
		WRITE_ONCE(nohz.has_blocked, 1);
9425

9426 9427 9428 9429 9430 9431 9432
	/*
	 * 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;
P
Peter Zijlstra 已提交
9433

9434 9435 9436 9437 9438 9439 9440 9441 9442 9443 9444 9445 9446 9447 9448 9449 9450 9451 9452 9453 9454 9455 9456 9457 9458 9459 9460 9461 9462
	return ret;
}

/*
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
{
	int this_cpu = this_rq->cpu;
	unsigned int flags;

	if (!(atomic_read(nohz_flags(this_cpu)) & NOHZ_KICK_MASK))
		return false;

	if (idle != CPU_IDLE) {
		atomic_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));
		return false;
	}

	/*
	 * barrier, pairs with nohz_balance_enter_idle(), ensures ...
	 */
	flags = atomic_fetch_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));
	if (!(flags & NOHZ_KICK_MASK))
		return false;

	_nohz_idle_balance(this_rq, flags, idle);

P
Peter Zijlstra 已提交
9463
	return true;
9464
}
9465 9466 9467 9468 9469 9470 9471 9472 9473 9474 9475 9476 9477 9478 9479 9480 9481 9482 9483 9484 9485 9486 9487 9488 9489 9490 9491 9492 9493 9494 9495 9496 9497

static void nohz_newidle_balance(struct rq *this_rq)
{
	int this_cpu = this_rq->cpu;

	/*
	 * This CPU doesn't want to be disturbed by scheduler
	 * housekeeping
	 */
	if (!housekeeping_cpu(this_cpu, HK_FLAG_SCHED))
		return;

	/* Will wake up very soon. No time for doing anything else*/
	if (this_rq->avg_idle < sysctl_sched_migration_cost)
		return;

	/* Don't need to update blocked load of idle CPUs*/
	if (!READ_ONCE(nohz.has_blocked) ||
	    time_before(jiffies, READ_ONCE(nohz.next_blocked)))
		return;

	raw_spin_unlock(&this_rq->lock);
	/*
	 * This CPU is going to be idle and blocked load of idle CPUs
	 * need to be updated. Run the ilb locally as it is a good
	 * candidate for ilb instead of waking up another idle CPU.
	 * Kick an normal ilb if we failed to do the update.
	 */
	if (!_nohz_idle_balance(this_rq, NOHZ_STATS_KICK, CPU_NEWLY_IDLE))
		kick_ilb(NOHZ_STATS_KICK);
	raw_spin_lock(&this_rq->lock);
}

9498 9499 9500
#else /* !CONFIG_NO_HZ_COMMON */
static inline void nohz_balancer_kick(struct rq *rq) { }

9501
static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
P
Peter Zijlstra 已提交
9502 9503 9504
{
	return false;
}
9505 9506

static inline void nohz_newidle_balance(struct rq *this_rq) { }
9507
#endif /* CONFIG_NO_HZ_COMMON */
9508

P
Peter Zijlstra 已提交
9509 9510 9511 9512 9513 9514 9515 9516 9517 9518 9519 9520 9521 9522 9523 9524 9525 9526 9527 9528 9529 9530 9531 9532 9533 9534 9535 9536 9537 9538 9539 9540 9541 9542
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
{
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
	struct sched_domain *sd;
	int pulled_task = 0;
	u64 curr_cost = 0;

	/*
	 * 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);

	/*
	 * Do not pull tasks towards !active CPUs...
	 */
	if (!cpu_active(this_cpu))
		return 0;

	/*
	 * 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.
	 */
	rq_unpin_lock(this_rq, rf);

	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
9543

P
Peter Zijlstra 已提交
9544 9545 9546 9547 9548 9549
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
			update_next_balance(sd, &next_balance);
		rcu_read_unlock();

9550 9551
		nohz_newidle_balance(this_rq);

P
Peter Zijlstra 已提交
9552 9553 9554 9555 9556 9557 9558 9559 9560 9561 9562 9563 9564 9565 9566 9567 9568 9569 9570 9571 9572 9573 9574 9575 9576 9577 9578 9579 9580 9581 9582 9583 9584 9585 9586 9587 9588 9589 9590 9591 9592 9593 9594 9595 9596 9597 9598 9599 9600
		goto out;
	}

	raw_spin_unlock(&this_rq->lock);

	update_blocked_averages(this_cpu);
	rcu_read_lock();
	for_each_domain(this_cpu, sd) {
		int continue_balancing = 1;
		u64 t0, domain_cost;

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

		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
			update_next_balance(sd, &next_balance);
			break;
		}

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

			pulled_task = load_balance(this_cpu, this_rq,
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);

			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;
		}

		update_next_balance(sd, &next_balance);

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
			break;
	}
	rcu_read_unlock();

	raw_spin_lock(&this_rq->lock);

	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

9601
out:
P
Peter Zijlstra 已提交
9602 9603 9604 9605 9606 9607 9608 9609 9610 9611 9612 9613 9614 9615 9616 9617 9618 9619 9620 9621 9622 9623 9624 9625
	/*
	 * 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.
	 */
	if (this_rq->cfs.h_nr_running && !pulled_task)
		pulled_task = 1;

	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
		this_rq->next_balance = next_balance;

	/* Is there a task of a high priority class? */
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
		pulled_task = -1;

	if (pulled_task)
		this_rq->idle_stamp = 0;

	rq_repin_lock(this_rq, rf);

	return pulled_task;
}

9626 9627 9628 9629
/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
9630
static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
9631
{
9632
	struct rq *this_rq = this_rq();
9633
	enum cpu_idle_type idle = this_rq->idle_balance ?
9634 9635 9636
						CPU_IDLE : CPU_NOT_IDLE;

	/*
9637 9638
	 * If this CPU has a pending nohz_balance_kick, then do the
	 * balancing on behalf of the other idle CPUs whose ticks are
9639
	 * stopped. Do nohz_idle_balance *before* rebalance_domains to
9640
	 * give the idle CPUs a chance to load balance. Else we may
9641 9642
	 * load balance only within the local sched_domain hierarchy
	 * and abort nohz_idle_balance altogether if we pull some load.
9643
	 */
P
Peter Zijlstra 已提交
9644 9645 9646 9647 9648
	if (nohz_idle_balance(this_rq, idle))
		return;

	/* normal load balance */
	update_blocked_averages(this_rq->cpu);
9649
	rebalance_domains(this_rq, idle);
9650 9651 9652 9653 9654
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
9655
void trigger_load_balance(struct rq *rq)
9656 9657
{
	/* Don't need to rebalance while attached to NULL domain */
9658 9659 9660 9661
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
9662
		raise_softirq(SCHED_SOFTIRQ);
9663 9664

	nohz_balancer_kick(rq);
9665 9666
}

9667 9668 9669
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
9670 9671

	update_runtime_enabled(rq);
9672 9673 9674 9675 9676
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
9677 9678 9679

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
9680 9681
}

9682
#endif /* CONFIG_SMP */
9683

9684
/*
9685 9686 9687 9688 9689 9690
 * scheduler tick hitting a task of our scheduling class.
 *
 * NOTE: This function can be called remotely by the tick offload that
 * goes along full dynticks. Therefore no local assumption can be made
 * and everything must be accessed through the @rq and @curr passed in
 * parameters.
9691
 */
P
Peter Zijlstra 已提交
9692
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
9693 9694 9695 9696 9697 9698
{
	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
9699
		entity_tick(cfs_rq, se, queued);
9700
	}
9701

9702
	if (static_branch_unlikely(&sched_numa_balancing))
9703
		task_tick_numa(rq, curr);
9704 9705 9706
}

/*
P
Peter Zijlstra 已提交
9707 9708 9709
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
9710
 */
P
Peter Zijlstra 已提交
9711
static void task_fork_fair(struct task_struct *p)
9712
{
9713 9714
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
P
Peter Zijlstra 已提交
9715
	struct rq *rq = this_rq();
9716
	struct rq_flags rf;
9717

9718
	rq_lock(rq, &rf);
9719 9720
	update_rq_clock(rq);

9721 9722
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;
9723 9724
	if (curr) {
		update_curr(cfs_rq);
9725
		se->vruntime = curr->vruntime;
9726
	}
9727
	place_entity(cfs_rq, se, 1);
9728

P
Peter Zijlstra 已提交
9729
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
9730
		/*
9731 9732 9733
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
9734
		swap(curr->vruntime, se->vruntime);
9735
		resched_curr(rq);
9736
	}
9737

9738
	se->vruntime -= cfs_rq->min_vruntime;
9739
	rq_unlock(rq, &rf);
9740 9741
}

9742 9743 9744 9745
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
9746 9747
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
9748
{
9749
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
9750 9751
		return;

9752 9753 9754 9755 9756
	/*
	 * 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
9757
	if (rq->curr == p) {
9758
		if (p->prio > oldprio)
9759
			resched_curr(rq);
9760
	} else
9761
		check_preempt_curr(rq, p, 0);
9762 9763
}

9764
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
9765 9766 9767 9768
{
	struct sched_entity *se = &p->se;

	/*
9769 9770 9771 9772 9773 9774 9775 9776 9777 9778
	 * 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
9779
	 *
9780 9781 9782 9783
	 * - 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
9784
	 */
9785 9786
	if (!se->sum_exec_runtime ||
	    (p->state == TASK_WAKING && p->sched_remote_wakeup))
9787 9788 9789 9790 9791
		return true;

	return false;
}

9792 9793 9794 9795 9796 9797 9798 9799 9800 9801 9802 9803 9804 9805 9806 9807 9808 9809
#ifdef CONFIG_FAIR_GROUP_SCHED
/*
 * Propagate the changes of the sched_entity across the tg tree to make it
 * visible to the root
 */
static void propagate_entity_cfs_rq(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq;

	/* Start to propagate at parent */
	se = se->parent;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);

		if (cfs_rq_throttled(cfs_rq))
			break;

9810
		update_load_avg(cfs_rq, se, UPDATE_TG);
9811 9812 9813 9814 9815 9816
	}
}
#else
static void propagate_entity_cfs_rq(struct sched_entity *se) { }
#endif

9817
static void detach_entity_cfs_rq(struct sched_entity *se)
9818 9819 9820
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

9821
	/* Catch up with the cfs_rq and remove our load when we leave */
9822
	update_load_avg(cfs_rq, se, 0);
9823
	detach_entity_load_avg(cfs_rq, se);
9824
	update_tg_load_avg(cfs_rq, false);
9825
	propagate_entity_cfs_rq(se);
P
Peter Zijlstra 已提交
9826 9827
}

9828
static void attach_entity_cfs_rq(struct sched_entity *se)
9829
{
9830
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
9831 9832

#ifdef CONFIG_FAIR_GROUP_SCHED
9833 9834 9835 9836 9837 9838
	/*
	 * 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
9839

9840
	/* Synchronize entity with its cfs_rq */
9841
	update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
9842
	attach_entity_load_avg(cfs_rq, se, 0);
9843
	update_tg_load_avg(cfs_rq, false);
9844
	propagate_entity_cfs_rq(se);
9845 9846 9847 9848 9849 9850 9851 9852 9853 9854 9855 9856 9857 9858 9859 9860 9861 9862 9863 9864 9865 9866 9867 9868 9869
}

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)) {
		/*
		 * 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;
	}

	detach_entity_cfs_rq(se);
}

static void attach_task_cfs_rq(struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	attach_entity_cfs_rq(se);
9870 9871 9872 9873

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
9874

9875 9876 9877 9878 9879 9880 9881 9882
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);
9883

9884
	if (task_on_rq_queued(p)) {
9885
		/*
9886 9887 9888
		 * 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.
9889
		 */
9890 9891 9892 9893
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
9894
	}
9895 9896
}

9897 9898 9899 9900 9901 9902 9903 9904 9905
/* 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;

9906 9907 9908 9909 9910 9911 9912
	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);
	}
9913 9914
}

9915 9916
void init_cfs_rq(struct cfs_rq *cfs_rq)
{
9917
	cfs_rq->tasks_timeline = RB_ROOT_CACHED;
9918 9919 9920 9921
	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
#ifndef CONFIG_64BIT
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
9922
#ifdef CONFIG_SMP
9923
	raw_spin_lock_init(&cfs_rq->removed.lock);
9924
#endif
9925 9926
}

P
Peter Zijlstra 已提交
9927
#ifdef CONFIG_FAIR_GROUP_SCHED
9928 9929 9930 9931 9932 9933 9934 9935
static void task_set_group_fair(struct task_struct *p)
{
	struct sched_entity *se = &p->se;

	set_task_rq(p, task_cpu(p));
	se->depth = se->parent ? se->parent->depth + 1 : 0;
}

9936
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
9937
{
9938
	detach_task_cfs_rq(p);
9939
	set_task_rq(p, task_cpu(p));
9940 9941 9942 9943 9944

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
9945
	attach_task_cfs_rq(p);
P
Peter Zijlstra 已提交
9946
}
9947

9948 9949 9950 9951 9952 9953 9954 9955 9956 9957 9958 9959 9960
static void task_change_group_fair(struct task_struct *p, int type)
{
	switch (type) {
	case TASK_SET_GROUP:
		task_set_group_fair(p);
		break;

	case TASK_MOVE_GROUP:
		task_move_group_fair(p);
		break;
	}
}

9961 9962 9963 9964 9965 9966 9967 9968 9969
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]);
9970
		if (tg->se)
9971 9972 9973 9974 9975 9976 9977 9978 9979 9980
			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 sched_entity *se;
9981
	struct cfs_rq *cfs_rq;
9982 9983
	int i;

K
Kees Cook 已提交
9984
	tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL);
9985 9986
	if (!tg->cfs_rq)
		goto err;
K
Kees Cook 已提交
9987
	tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL);
9988 9989 9990 9991 9992 9993 9994 9995 9996 9997 9998 9999 10000 10001 10002 10003 10004 10005 10006 10007
	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]);
10008
		init_entity_runnable_average(se);
10009 10010 10011 10012 10013 10014 10015 10016 10017 10018
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

10019 10020 10021 10022 10023 10024 10025 10026 10027 10028 10029
void online_fair_sched_group(struct task_group *tg)
{
	struct sched_entity *se;
	struct rq *rq;
	int i;

	for_each_possible_cpu(i) {
		rq = cpu_rq(i);
		se = tg->se[i];

		raw_spin_lock_irq(&rq->lock);
10030
		update_rq_clock(rq);
10031
		attach_entity_cfs_rq(se);
10032
		sync_throttle(tg, i);
10033 10034 10035 10036
		raw_spin_unlock_irq(&rq->lock);
	}
}

10037
void unregister_fair_sched_group(struct task_group *tg)
10038 10039
{
	unsigned long flags;
10040 10041
	struct rq *rq;
	int cpu;
10042

10043 10044 10045
	for_each_possible_cpu(cpu) {
		if (tg->se[cpu])
			remove_entity_load_avg(tg->se[cpu]);
10046

10047 10048 10049 10050 10051 10052 10053 10054 10055 10056 10057 10058 10059
		/*
		 * 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);
	}
10060 10061 10062 10063 10064 10065 10066 10067 10068 10069 10070 10071 10072 10073 10074 10075 10076 10077 10078
}

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
10079
	if (!parent) {
10080
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
10081 10082
		se->depth = 0;
	} else {
10083
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
10084 10085
		se->depth = parent->depth + 1;
	}
10086 10087

	se->my_q = cfs_rq;
10088 10089
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
10090 10091 10092 10093 10094 10095 10096 10097 10098 10099 10100 10101 10102 10103 10104 10105 10106 10107 10108 10109 10110 10111 10112 10113
	se->parent = parent;
}

static DEFINE_MUTEX(shares_mutex);

int sched_group_set_shares(struct task_group *tg, unsigned long shares)
{
	int i;

	/*
	 * 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);
10114 10115
		struct sched_entity *se = tg->se[i];
		struct rq_flags rf;
10116 10117

		/* Propagate contribution to hierarchy */
10118
		rq_lock_irqsave(rq, &rf);
10119
		update_rq_clock(rq);
10120
		for_each_sched_entity(se) {
10121
			update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
10122
			update_cfs_group(se);
10123
		}
10124
		rq_unlock_irqrestore(rq, &rf);
10125 10126 10127 10128 10129 10130 10131 10132 10133 10134 10135 10136 10137 10138 10139
	}

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;
}

10140 10141
void online_fair_sched_group(struct task_group *tg) { }

10142
void unregister_fair_sched_group(struct task_group *tg) { }
10143 10144 10145

#endif /* CONFIG_FAIR_GROUP_SCHED */

P
Peter Zijlstra 已提交
10146

10147
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
10148 10149 10150 10151 10152 10153 10154 10155 10156
{
	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)
10157
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
10158 10159 10160 10161

	return rr_interval;
}

10162 10163 10164
/*
 * All the scheduling class methods:
 */
10165
const struct sched_class fair_sched_class = {
10166
	.next			= &idle_sched_class,
10167 10168 10169
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
10170
	.yield_to_task		= yield_to_task_fair,
10171

I
Ingo Molnar 已提交
10172
	.check_preempt_curr	= check_preempt_wakeup,
10173 10174 10175 10176

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

10177
#ifdef CONFIG_SMP
L
Li Zefan 已提交
10178
	.select_task_rq		= select_task_rq_fair,
10179
	.migrate_task_rq	= migrate_task_rq_fair,
10180

10181 10182
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
10183

10184
	.task_dead		= task_dead_fair,
10185
	.set_cpus_allowed	= set_cpus_allowed_common,
10186
#endif
10187

10188
	.set_curr_task          = set_curr_task_fair,
10189
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
10190
	.task_fork		= task_fork_fair,
10191 10192

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
10193
	.switched_from		= switched_from_fair,
10194
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
10195

10196 10197
	.get_rr_interval	= get_rr_interval_fair,

10198 10199
	.update_curr		= update_curr_fair,

P
Peter Zijlstra 已提交
10200
#ifdef CONFIG_FAIR_GROUP_SCHED
10201
	.task_change_group	= task_change_group_fair,
P
Peter Zijlstra 已提交
10202
#endif
10203 10204 10205
};

#ifdef CONFIG_SCHED_DEBUG
10206
void print_cfs_stats(struct seq_file *m, int cpu)
10207
{
10208
	struct cfs_rq *cfs_rq;
10209

10210
	rcu_read_lock();
10211
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
10212
		print_cfs_rq(m, cpu, cfs_rq);
10213
	rcu_read_unlock();
10214
}
10215 10216 10217 10218 10219 10220 10221 10222 10223 10224 10225 10226 10227 10228 10229 10230 10231 10232 10233 10234 10235

#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 */
10236 10237 10238 10239 10240 10241

__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

10242
#ifdef CONFIG_NO_HZ_COMMON
10243
	nohz.next_balance = jiffies;
10244
	nohz.next_blocked = jiffies;
10245 10246 10247 10248 10249
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
#endif
#endif /* SMP */

}