1/*
   2 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
   3 *
   4 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
   5 *
   6 *  Interactivity improvements by Mike Galbraith
   7 *  (C) 2007 Mike Galbraith <efault@gmx.de>
   8 *
   9 *  Various enhancements by Dmitry Adamushko.
  10 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
  11 *
  12 *  Group scheduling enhancements by Srivatsa Vaddagiri
  13 *  Copyright IBM Corporation, 2007
  14 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
  15 *
  16 *  Scaled math optimizations by Thomas Gleixner
  17 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
  18 *
  19 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
  20 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
  21 */
  22
  23#include <linux/sched.h>
  24#include <linux/latencytop.h>
  25#include <linux/cpumask.h>
  26#include <linux/cpuidle.h>
  27#include <linux/slab.h>
  28#include <linux/profile.h>
  29#include <linux/interrupt.h>
  30#include <linux/mempolicy.h>
  31#include <linux/migrate.h>
  32#include <linux/task_work.h>
  33
  34#include <trace/events/sched.h>
  35
  36#include "sched.h"
  37
  38/*
  39 * Targeted preemption latency for CPU-bound tasks:
  40 *
  41 * NOTE: this latency value is not the same as the concept of
  42 * 'timeslice length' - timeslices in CFS are of variable length
  43 * and have no persistent notion like in traditional, time-slice
  44 * based scheduling concepts.
  45 *
  46 * (to see the precise effective timeslice length of your workload,
  47 *  run vmstat and monitor the context-switches (cs) field)
  48 *
  49 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
  50 */
  51unsigned int sysctl_sched_latency			= 6000000ULL;
  52unsigned int normalized_sysctl_sched_latency		= 6000000ULL;
  53
  54/*
  55 * The initial- and re-scaling of tunables is configurable
  56 *
  57 * Options are:
  58 *
  59 *   SCHED_TUNABLESCALING_NONE - unscaled, always *1
  60 *   SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
  61 *   SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
  62 *
  63 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
  64 */
  65enum sched_tunable_scaling sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
  66
  67/*
  68 * Minimal preemption granularity for CPU-bound tasks:
  69 *
  70 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
  71 */
  72unsigned int sysctl_sched_min_granularity		= 750000ULL;
  73unsigned int normalized_sysctl_sched_min_granularity	= 750000ULL;
  74
  75/*
  76 * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
  77 */
  78static unsigned int sched_nr_latency = 8;
  79
  80/*
  81 * After fork, child runs first. If set to 0 (default) then
  82 * parent will (try to) run first.
  83 */
  84unsigned int sysctl_sched_child_runs_first __read_mostly;
  85
  86/*
  87 * SCHED_OTHER wake-up granularity.
  88 *
  89 * This option delays the preemption effects of decoupled workloads
  90 * and reduces their over-scheduling. Synchronous workloads will still
  91 * have immediate wakeup/sleep latencies.
  92 *
  93 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
  94 */
  95unsigned int sysctl_sched_wakeup_granularity		= 1000000UL;
  96unsigned int normalized_sysctl_sched_wakeup_granularity	= 1000000UL;
  97
  98const_debug unsigned int sysctl_sched_migration_cost	= 500000UL;
  99
 
 
 
 
 
 
 
 
 
 
 
 
 
 100#ifdef CONFIG_SMP
 101/*
 102 * For asym packing, by default the lower numbered cpu has higher priority.
 103 */
 104int __weak arch_asym_cpu_priority(int cpu)
 105{
 106	return -cpu;
 107}
 
 
 
 
 
 
 
 
 108#endif
 109
 110#ifdef CONFIG_CFS_BANDWIDTH
 111/*
 112 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
 113 * each time a cfs_rq requests quota.
 114 *
 115 * Note: in the case that the slice exceeds the runtime remaining (either due
 116 * to consumption or the quota being specified to be smaller than the slice)
 117 * we will always only issue the remaining available time.
 118 *
 119 * (default: 5 msec, units: microseconds)
 120 */
 121unsigned int sysctl_sched_cfs_bandwidth_slice		= 5000UL;
 122#endif
 123
 124/*
 125 * The margin used when comparing utilization with CPU capacity:
 126 * util * margin < capacity * 1024
 127 *
 128 * (default: ~20%)
 129 */
 130unsigned int capacity_margin				= 1280;
 131
 132static inline void update_load_add(struct load_weight *lw, unsigned long inc)
 133{
 134	lw->weight += inc;
 135	lw->inv_weight = 0;
 136}
 137
 138static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
 139{
 140	lw->weight -= dec;
 141	lw->inv_weight = 0;
 142}
 143
 144static inline void update_load_set(struct load_weight *lw, unsigned long w)
 145{
 146	lw->weight = w;
 147	lw->inv_weight = 0;
 148}
 149
 150/*
 151 * Increase the granularity value when there are more CPUs,
 152 * because with more CPUs the 'effective latency' as visible
 153 * to users decreases. But the relationship is not linear,
 154 * so pick a second-best guess by going with the log2 of the
 155 * number of CPUs.
 156 *
 157 * This idea comes from the SD scheduler of Con Kolivas:
 158 */
 159static unsigned int get_update_sysctl_factor(void)
 160{
 161	unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
 162	unsigned int factor;
 163
 164	switch (sysctl_sched_tunable_scaling) {
 165	case SCHED_TUNABLESCALING_NONE:
 166		factor = 1;
 167		break;
 168	case SCHED_TUNABLESCALING_LINEAR:
 169		factor = cpus;
 170		break;
 171	case SCHED_TUNABLESCALING_LOG:
 172	default:
 173		factor = 1 + ilog2(cpus);
 174		break;
 175	}
 176
 177	return factor;
 178}
 179
 180static void update_sysctl(void)
 181{
 182	unsigned int factor = get_update_sysctl_factor();
 183
 184#define SET_SYSCTL(name) \
 185	(sysctl_##name = (factor) * normalized_sysctl_##name)
 186	SET_SYSCTL(sched_min_granularity);
 187	SET_SYSCTL(sched_latency);
 188	SET_SYSCTL(sched_wakeup_granularity);
 189#undef SET_SYSCTL
 190}
 191
 192void sched_init_granularity(void)
 193{
 194	update_sysctl();
 195}
 196
 197#define WMULT_CONST	(~0U)
 198#define WMULT_SHIFT	32
 199
 200static void __update_inv_weight(struct load_weight *lw)
 201{
 202	unsigned long w;
 203
 204	if (likely(lw->inv_weight))
 205		return;
 206
 207	w = scale_load_down(lw->weight);
 208
 209	if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
 210		lw->inv_weight = 1;
 211	else if (unlikely(!w))
 212		lw->inv_weight = WMULT_CONST;
 213	else
 214		lw->inv_weight = WMULT_CONST / w;
 215}
 216
 217/*
 218 * delta_exec * weight / lw.weight
 219 *   OR
 220 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
 221 *
 222 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
 223 * we're guaranteed shift stays positive because inv_weight is guaranteed to
 224 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
 225 *
 226 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
 227 * weight/lw.weight <= 1, and therefore our shift will also be positive.
 228 */
 229static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
 230{
 231	u64 fact = scale_load_down(weight);
 232	int shift = WMULT_SHIFT;
 233
 234	__update_inv_weight(lw);
 235
 236	if (unlikely(fact >> 32)) {
 237		while (fact >> 32) {
 238			fact >>= 1;
 239			shift--;
 240		}
 241	}
 242
 243	/* hint to use a 32x32->64 mul */
 244	fact = (u64)(u32)fact * lw->inv_weight;
 245
 246	while (fact >> 32) {
 247		fact >>= 1;
 248		shift--;
 249	}
 250
 251	return mul_u64_u32_shr(delta_exec, fact, shift);
 252}
 253
 254
 255const struct sched_class fair_sched_class;
 256
 257/**************************************************************
 258 * CFS operations on generic schedulable entities:
 259 */
 260
 261#ifdef CONFIG_FAIR_GROUP_SCHED
 262
 263/* cpu runqueue to which this cfs_rq is attached */
 264static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
 265{
 266	return cfs_rq->rq;
 267}
 268
 269/* An entity is a task if it doesn't "own" a runqueue */
 270#define entity_is_task(se)	(!se->my_q)
 271
 272static inline struct task_struct *task_of(struct sched_entity *se)
 273{
 274	SCHED_WARN_ON(!entity_is_task(se));
 275	return container_of(se, struct task_struct, se);
 276}
 277
 278/* Walk up scheduling entities hierarchy */
 279#define for_each_sched_entity(se) \
 280		for (; se; se = se->parent)
 281
 282static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
 283{
 284	return p->se.cfs_rq;
 285}
 286
 287/* runqueue on which this entity is (to be) queued */
 288static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
 289{
 290	return se->cfs_rq;
 291}
 292
 293/* runqueue "owned" by this group */
 294static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
 295{
 296	return grp->my_q;
 297}
 298
 299static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 300{
 301	if (!cfs_rq->on_list) {
 302		struct rq *rq = rq_of(cfs_rq);
 303		int cpu = cpu_of(rq);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 304		/*
 305		 * Ensure we either appear before our parent (if already
 306		 * enqueued) or force our parent to appear after us when it is
 307		 * enqueued. The fact that we always enqueue bottom-up
 308		 * reduces this to two cases and a special case for the root
 309		 * cfs_rq. Furthermore, it also means that we will always reset
 310		 * tmp_alone_branch either when the branch is connected
 311		 * to a tree or when we reach the beg of the tree
 312		 */
 313		if (cfs_rq->tg->parent &&
 314		    cfs_rq->tg->parent->cfs_rq[cpu]->on_list) {
 315			/*
 316			 * If parent is already on the list, we add the child
 317			 * just before. Thanks to circular linked property of
 318			 * the list, this means to put the child at the tail
 319			 * of the list that starts by parent.
 320			 */
 321			list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
 322				&(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list));
 323			/*
 324			 * The branch is now connected to its tree so we can
 325			 * reset tmp_alone_branch to the beginning of the
 326			 * list.
 327			 */
 328			rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
 329		} else if (!cfs_rq->tg->parent) {
 330			/*
 331			 * cfs rq without parent should be put
 332			 * at the tail of the list.
 333			 */
 334			list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
 335				&rq->leaf_cfs_rq_list);
 336			/*
 337			 * We have reach the beg of a tree so we can reset
 338			 * tmp_alone_branch to the beginning of the list.
 339			 */
 340			rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
 341		} else {
 342			/*
 343			 * The parent has not already been added so we want to
 344			 * make sure that it will be put after us.
 345			 * tmp_alone_branch points to the beg of the branch
 346			 * where we will add parent.
 347			 */
 348			list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
 349				rq->tmp_alone_branch);
 350			/*
 351			 * update tmp_alone_branch to points to the new beg
 352			 * of the branch
 353			 */
 354			rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list;
 355		}
 356
 357		cfs_rq->on_list = 1;
 
 
 
 
 
 
 
 
 
 
 
 
 358	}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 359}
 360
 361static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 362{
 363	if (cfs_rq->on_list) {
 
 
 
 
 
 
 
 
 
 
 
 
 364		list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
 365		cfs_rq->on_list = 0;
 366	}
 367}
 368
 
 
 
 
 
 369/* Iterate thr' all leaf cfs_rq's on a runqueue */
 370#define for_each_leaf_cfs_rq(rq, cfs_rq) \
 371	list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
 
 372
 373/* Do the two (enqueued) entities belong to the same group ? */
 374static inline struct cfs_rq *
 375is_same_group(struct sched_entity *se, struct sched_entity *pse)
 376{
 377	if (se->cfs_rq == pse->cfs_rq)
 378		return se->cfs_rq;
 379
 380	return NULL;
 381}
 382
 383static inline struct sched_entity *parent_entity(struct sched_entity *se)
 384{
 385	return se->parent;
 386}
 387
 388static void
 389find_matching_se(struct sched_entity **se, struct sched_entity **pse)
 390{
 391	int se_depth, pse_depth;
 392
 393	/*
 394	 * preemption test can be made between sibling entities who are in the
 395	 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
 396	 * both tasks until we find their ancestors who are siblings of common
 397	 * parent.
 398	 */
 399
 400	/* First walk up until both entities are at same depth */
 401	se_depth = (*se)->depth;
 402	pse_depth = (*pse)->depth;
 403
 404	while (se_depth > pse_depth) {
 405		se_depth--;
 406		*se = parent_entity(*se);
 407	}
 408
 409	while (pse_depth > se_depth) {
 410		pse_depth--;
 411		*pse = parent_entity(*pse);
 412	}
 413
 414	while (!is_same_group(*se, *pse)) {
 415		*se = parent_entity(*se);
 416		*pse = parent_entity(*pse);
 417	}
 418}
 419
 420#else	/* !CONFIG_FAIR_GROUP_SCHED */
 421
 422static inline struct task_struct *task_of(struct sched_entity *se)
 423{
 424	return container_of(se, struct task_struct, se);
 425}
 426
 427static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
 428{
 429	return container_of(cfs_rq, struct rq, cfs);
 430}
 431
 432#define entity_is_task(se)	1
 433
 434#define for_each_sched_entity(se) \
 435		for (; se; se = NULL)
 436
 437static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
 438{
 439	return &task_rq(p)->cfs;
 440}
 441
 442static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
 443{
 444	struct task_struct *p = task_of(se);
 445	struct rq *rq = task_rq(p);
 446
 447	return &rq->cfs;
 448}
 449
 450/* runqueue "owned" by this group */
 451static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
 452{
 453	return NULL;
 454}
 455
 456static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 
 
 
 
 
 
 457{
 
 458}
 459
 460static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 461{
 462}
 463
 464#define for_each_leaf_cfs_rq(rq, cfs_rq) \
 465		for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
 
 
 
 
 466
 467static inline struct sched_entity *parent_entity(struct sched_entity *se)
 468{
 469	return NULL;
 470}
 471
 472static inline void
 473find_matching_se(struct sched_entity **se, struct sched_entity **pse)
 474{
 475}
 476
 477#endif	/* CONFIG_FAIR_GROUP_SCHED */
 478
 479static __always_inline
 480void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
 481
 482/**************************************************************
 483 * Scheduling class tree data structure manipulation methods:
 484 */
 485
 486static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
 487{
 488	s64 delta = (s64)(vruntime - max_vruntime);
 489	if (delta > 0)
 490		max_vruntime = vruntime;
 491
 492	return max_vruntime;
 493}
 494
 495static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
 496{
 497	s64 delta = (s64)(vruntime - min_vruntime);
 498	if (delta < 0)
 499		min_vruntime = vruntime;
 500
 501	return min_vruntime;
 502}
 503
 504static inline int entity_before(struct sched_entity *a,
 505				struct sched_entity *b)
 506{
 507	return (s64)(a->vruntime - b->vruntime) < 0;
 508}
 509
 510static void update_min_vruntime(struct cfs_rq *cfs_rq)
 511{
 512	struct sched_entity *curr = cfs_rq->curr;
 
 513
 514	u64 vruntime = cfs_rq->min_vruntime;
 515
 516	if (curr) {
 517		if (curr->on_rq)
 518			vruntime = curr->vruntime;
 519		else
 520			curr = NULL;
 521	}
 522
 523	if (cfs_rq->rb_leftmost) {
 524		struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
 525						   struct sched_entity,
 526						   run_node);
 527
 528		if (!curr)
 529			vruntime = se->vruntime;
 530		else
 531			vruntime = min_vruntime(vruntime, se->vruntime);
 532	}
 533
 534	/* ensure we never gain time by being placed backwards. */
 535	cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
 536#ifndef CONFIG_64BIT
 537	smp_wmb();
 538	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
 539#endif
 540}
 541
 542/*
 543 * Enqueue an entity into the rb-tree:
 544 */
 545static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 546{
 547	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
 548	struct rb_node *parent = NULL;
 549	struct sched_entity *entry;
 550	int leftmost = 1;
 551
 552	/*
 553	 * Find the right place in the rbtree:
 554	 */
 555	while (*link) {
 556		parent = *link;
 557		entry = rb_entry(parent, struct sched_entity, run_node);
 558		/*
 559		 * We dont care about collisions. Nodes with
 560		 * the same key stay together.
 561		 */
 562		if (entity_before(se, entry)) {
 563			link = &parent->rb_left;
 564		} else {
 565			link = &parent->rb_right;
 566			leftmost = 0;
 567		}
 568	}
 569
 570	/*
 571	 * Maintain a cache of leftmost tree entries (it is frequently
 572	 * used):
 573	 */
 574	if (leftmost)
 575		cfs_rq->rb_leftmost = &se->run_node;
 576
 577	rb_link_node(&se->run_node, parent, link);
 578	rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
 
 579}
 580
 581static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 582{
 583	if (cfs_rq->rb_leftmost == &se->run_node) {
 584		struct rb_node *next_node;
 585
 586		next_node = rb_next(&se->run_node);
 587		cfs_rq->rb_leftmost = next_node;
 588	}
 589
 590	rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
 591}
 592
 593struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
 594{
 595	struct rb_node *left = cfs_rq->rb_leftmost;
 596
 597	if (!left)
 598		return NULL;
 599
 600	return rb_entry(left, struct sched_entity, run_node);
 601}
 602
 603static struct sched_entity *__pick_next_entity(struct sched_entity *se)
 604{
 605	struct rb_node *next = rb_next(&se->run_node);
 606
 607	if (!next)
 608		return NULL;
 609
 610	return rb_entry(next, struct sched_entity, run_node);
 611}
 612
 613#ifdef CONFIG_SCHED_DEBUG
 614struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
 615{
 616	struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
 617
 618	if (!last)
 619		return NULL;
 620
 621	return rb_entry(last, struct sched_entity, run_node);
 622}
 623
 624/**************************************************************
 625 * Scheduling class statistics methods:
 626 */
 627
 628int sched_proc_update_handler(struct ctl_table *table, int write,
 629		void __user *buffer, size_t *lenp,
 630		loff_t *ppos)
 631{
 632	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 633	unsigned int factor = get_update_sysctl_factor();
 634
 635	if (ret || !write)
 636		return ret;
 637
 638	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
 639					sysctl_sched_min_granularity);
 640
 641#define WRT_SYSCTL(name) \
 642	(normalized_sysctl_##name = sysctl_##name / (factor))
 643	WRT_SYSCTL(sched_min_granularity);
 644	WRT_SYSCTL(sched_latency);
 645	WRT_SYSCTL(sched_wakeup_granularity);
 646#undef WRT_SYSCTL
 647
 648	return 0;
 649}
 650#endif
 651
 652/*
 653 * delta /= w
 654 */
 655static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
 656{
 657	if (unlikely(se->load.weight != NICE_0_LOAD))
 658		delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
 659
 660	return delta;
 661}
 662
 663/*
 664 * The idea is to set a period in which each task runs once.
 665 *
 666 * When there are too many tasks (sched_nr_latency) we have to stretch
 667 * this period because otherwise the slices get too small.
 668 *
 669 * p = (nr <= nl) ? l : l*nr/nl
 670 */
 671static u64 __sched_period(unsigned long nr_running)
 672{
 673	if (unlikely(nr_running > sched_nr_latency))
 674		return nr_running * sysctl_sched_min_granularity;
 675	else
 676		return sysctl_sched_latency;
 677}
 678
 679/*
 680 * We calculate the wall-time slice from the period by taking a part
 681 * proportional to the weight.
 682 *
 683 * s = p*P[w/rw]
 684 */
 685static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
 686{
 687	u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
 688
 689	for_each_sched_entity(se) {
 690		struct load_weight *load;
 691		struct load_weight lw;
 692
 693		cfs_rq = cfs_rq_of(se);
 694		load = &cfs_rq->load;
 695
 696		if (unlikely(!se->on_rq)) {
 697			lw = cfs_rq->load;
 698
 699			update_load_add(&lw, se->load.weight);
 700			load = &lw;
 701		}
 702		slice = __calc_delta(slice, se->load.weight, load);
 703	}
 704	return slice;
 705}
 706
 707/*
 708 * We calculate the vruntime slice of a to-be-inserted task.
 709 *
 710 * vs = s/w
 711 */
 712static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
 713{
 714	return calc_delta_fair(sched_slice(cfs_rq, se), se);
 715}
 716
 
 717#ifdef CONFIG_SMP
 
 718static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
 719static unsigned long task_h_load(struct task_struct *p);
 720
 721/*
 722 * We choose a half-life close to 1 scheduling period.
 723 * Note: The tables runnable_avg_yN_inv and runnable_avg_yN_sum are
 724 * dependent on this value.
 725 */
 726#define LOAD_AVG_PERIOD 32
 727#define LOAD_AVG_MAX 47742 /* maximum possible load avg */
 728#define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_AVG_MAX */
 729
 730/* Give new sched_entity start runnable values to heavy its load in infant time */
 731void init_entity_runnable_average(struct sched_entity *se)
 732{
 733	struct sched_avg *sa = &se->avg;
 734
 735	sa->last_update_time = 0;
 736	/*
 737	 * sched_avg's period_contrib should be strictly less then 1024, so
 738	 * we give it 1023 to make sure it is almost a period (1024us), and
 739	 * will definitely be update (after enqueue).
 740	 */
 741	sa->period_contrib = 1023;
 742	/*
 743	 * Tasks are intialized with full load to be seen as heavy tasks until
 744	 * they get a chance to stabilize to their real load level.
 745	 * Group entities are intialized with zero load to reflect the fact that
 746	 * nothing has been attached to the task group yet.
 747	 */
 748	if (entity_is_task(se))
 749		sa->load_avg = scale_load_down(se->load.weight);
 750	sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
 751	/*
 752	 * At this point, util_avg won't be used in select_task_rq_fair anyway
 753	 */
 754	sa->util_avg = 0;
 755	sa->util_sum = 0;
 756	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
 757}
 758
 759static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
 760static void attach_entity_cfs_rq(struct sched_entity *se);
 761
 762/*
 763 * With new tasks being created, their initial util_avgs are extrapolated
 764 * based on the cfs_rq's current util_avg:
 765 *
 766 *   util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
 767 *
 768 * However, in many cases, the above util_avg does not give a desired
 769 * value. Moreover, the sum of the util_avgs may be divergent, such
 770 * as when the series is a harmonic series.
 771 *
 772 * To solve this problem, we also cap the util_avg of successive tasks to
 773 * only 1/2 of the left utilization budget:
 774 *
 775 *   util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n
 776 *
 777 * where n denotes the nth task.
 778 *
 779 * For example, a simplest series from the beginning would be like:
 
 780 *
 781 *  task  util_avg: 512, 256, 128,  64,  32,   16,    8, ...
 782 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
 783 *
 784 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
 785 * if util_avg > util_avg_cap.
 786 */
 787void post_init_entity_util_avg(struct sched_entity *se)
 788{
 
 789	struct cfs_rq *cfs_rq = cfs_rq_of(se);
 790	struct sched_avg *sa = &se->avg;
 791	long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2;
 
 792
 793	if (cap > 0) {
 794		if (cfs_rq->avg.util_avg != 0) {
 795			sa->util_avg  = cfs_rq->avg.util_avg * se->load.weight;
 796			sa->util_avg /= (cfs_rq->avg.load_avg + 1);
 797
 798			if (sa->util_avg > cap)
 799				sa->util_avg = cap;
 800		} else {
 801			sa->util_avg = cap;
 802		}
 803		sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
 804	}
 805
 806	if (entity_is_task(se)) {
 807		struct task_struct *p = task_of(se);
 808		if (p->sched_class != &fair_sched_class) {
 809			/*
 810			 * For !fair tasks do:
 811			 *
 812			update_cfs_rq_load_avg(now, cfs_rq, false);
 813			attach_entity_load_avg(cfs_rq, se);
 814			switched_from_fair(rq, p);
 815			 *
 816			 * such that the next switched_to_fair() has the
 817			 * expected state.
 818			 */
 819			se->avg.last_update_time = cfs_rq_clock_task(cfs_rq);
 820			return;
 821		}
 822	}
 823
 824	attach_entity_cfs_rq(se);
 825}
 826
 827#else /* !CONFIG_SMP */
 828void init_entity_runnable_average(struct sched_entity *se)
 829{
 830}
 831void post_init_entity_util_avg(struct sched_entity *se)
 832{
 833}
 834static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
 835{
 836}
 837#endif /* CONFIG_SMP */
 838
 839/*
 840 * Update the current task's runtime statistics.
 841 */
 842static void update_curr(struct cfs_rq *cfs_rq)
 843{
 844	struct sched_entity *curr = cfs_rq->curr;
 845	u64 now = rq_clock_task(rq_of(cfs_rq));
 846	u64 delta_exec;
 847
 848	if (unlikely(!curr))
 849		return;
 850
 851	delta_exec = now - curr->exec_start;
 852	if (unlikely((s64)delta_exec <= 0))
 853		return;
 854
 855	curr->exec_start = now;
 856
 857	schedstat_set(curr->statistics.exec_max,
 858		      max(delta_exec, curr->statistics.exec_max));
 859
 860	curr->sum_exec_runtime += delta_exec;
 861	schedstat_add(cfs_rq->exec_clock, delta_exec);
 862
 863	curr->vruntime += calc_delta_fair(delta_exec, curr);
 864	update_min_vruntime(cfs_rq);
 865
 866	if (entity_is_task(curr)) {
 867		struct task_struct *curtask = task_of(curr);
 868
 869		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
 870		cpuacct_charge(curtask, delta_exec);
 871		account_group_exec_runtime(curtask, delta_exec);
 872	}
 873
 874	account_cfs_rq_runtime(cfs_rq, delta_exec);
 875}
 876
 877static void update_curr_fair(struct rq *rq)
 878{
 879	update_curr(cfs_rq_of(&rq->curr->se));
 880}
 881
 882static inline void
 883update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
 884{
 885	u64 wait_start, prev_wait_start;
 886
 887	if (!schedstat_enabled())
 888		return;
 889
 890	wait_start = rq_clock(rq_of(cfs_rq));
 891	prev_wait_start = schedstat_val(se->statistics.wait_start);
 892
 893	if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
 894	    likely(wait_start > prev_wait_start))
 895		wait_start -= prev_wait_start;
 896
 897	schedstat_set(se->statistics.wait_start, wait_start);
 898}
 899
 900static inline void
 901update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
 902{
 903	struct task_struct *p;
 904	u64 delta;
 905
 906	if (!schedstat_enabled())
 907		return;
 908
 909	delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
 910
 911	if (entity_is_task(se)) {
 912		p = task_of(se);
 913		if (task_on_rq_migrating(p)) {
 914			/*
 915			 * Preserve migrating task's wait time so wait_start
 916			 * time stamp can be adjusted to accumulate wait time
 917			 * prior to migration.
 918			 */
 919			schedstat_set(se->statistics.wait_start, delta);
 920			return;
 921		}
 922		trace_sched_stat_wait(p, delta);
 923	}
 924
 925	schedstat_set(se->statistics.wait_max,
 926		      max(schedstat_val(se->statistics.wait_max), delta));
 927	schedstat_inc(se->statistics.wait_count);
 928	schedstat_add(se->statistics.wait_sum, delta);
 929	schedstat_set(se->statistics.wait_start, 0);
 930}
 931
 932static inline void
 933update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
 934{
 935	struct task_struct *tsk = NULL;
 936	u64 sleep_start, block_start;
 937
 938	if (!schedstat_enabled())
 939		return;
 940
 941	sleep_start = schedstat_val(se->statistics.sleep_start);
 942	block_start = schedstat_val(se->statistics.block_start);
 943
 944	if (entity_is_task(se))
 945		tsk = task_of(se);
 946
 947	if (sleep_start) {
 948		u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
 949
 950		if ((s64)delta < 0)
 951			delta = 0;
 952
 953		if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
 954			schedstat_set(se->statistics.sleep_max, delta);
 955
 956		schedstat_set(se->statistics.sleep_start, 0);
 957		schedstat_add(se->statistics.sum_sleep_runtime, delta);
 958
 959		if (tsk) {
 960			account_scheduler_latency(tsk, delta >> 10, 1);
 961			trace_sched_stat_sleep(tsk, delta);
 962		}
 963	}
 964	if (block_start) {
 965		u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
 966
 967		if ((s64)delta < 0)
 968			delta = 0;
 969
 970		if (unlikely(delta > schedstat_val(se->statistics.block_max)))
 971			schedstat_set(se->statistics.block_max, delta);
 972
 973		schedstat_set(se->statistics.block_start, 0);
 974		schedstat_add(se->statistics.sum_sleep_runtime, delta);
 975
 976		if (tsk) {
 977			if (tsk->in_iowait) {
 978				schedstat_add(se->statistics.iowait_sum, delta);
 979				schedstat_inc(se->statistics.iowait_count);
 980				trace_sched_stat_iowait(tsk, delta);
 981			}
 982
 983			trace_sched_stat_blocked(tsk, delta);
 984
 985			/*
 986			 * Blocking time is in units of nanosecs, so shift by
 987			 * 20 to get a milliseconds-range estimation of the
 988			 * amount of time that the task spent sleeping:
 989			 */
 990			if (unlikely(prof_on == SLEEP_PROFILING)) {
 991				profile_hits(SLEEP_PROFILING,
 992						(void *)get_wchan(tsk),
 993						delta >> 20);
 994			}
 995			account_scheduler_latency(tsk, delta >> 10, 0);
 996		}
 997	}
 998}
 999
1000/*
1001 * Task is being enqueued - update stats:
1002 */
1003static inline void
1004update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1005{
1006	if (!schedstat_enabled())
1007		return;
1008
1009	/*
1010	 * Are we enqueueing a waiting task? (for current tasks
1011	 * a dequeue/enqueue event is a NOP)
1012	 */
1013	if (se != cfs_rq->curr)
1014		update_stats_wait_start(cfs_rq, se);
1015
1016	if (flags & ENQUEUE_WAKEUP)
1017		update_stats_enqueue_sleeper(cfs_rq, se);
1018}
1019
1020static inline void
1021update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1022{
1023
1024	if (!schedstat_enabled())
1025		return;
1026
1027	/*
1028	 * Mark the end of the wait period if dequeueing a
1029	 * waiting task:
1030	 */
1031	if (se != cfs_rq->curr)
1032		update_stats_wait_end(cfs_rq, se);
1033
1034	if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
1035		struct task_struct *tsk = task_of(se);
1036
1037		if (tsk->state & TASK_INTERRUPTIBLE)
1038			schedstat_set(se->statistics.sleep_start,
1039				      rq_clock(rq_of(cfs_rq)));
1040		if (tsk->state & TASK_UNINTERRUPTIBLE)
1041			schedstat_set(se->statistics.block_start,
1042				      rq_clock(rq_of(cfs_rq)));
1043	}
1044}
1045
1046/*
1047 * We are picking a new current task - update its stats:
1048 */
1049static inline void
1050update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
1051{
1052	/*
1053	 * We are starting a new run period:
1054	 */
1055	se->exec_start = rq_clock_task(rq_of(cfs_rq));
1056}
1057
1058/**************************************************
1059 * Scheduling class queueing methods:
1060 */
1061
1062#ifdef CONFIG_NUMA_BALANCING
1063/*
1064 * Approximate time to scan a full NUMA task in ms. The task scan period is
1065 * calculated based on the tasks virtual memory size and
1066 * numa_balancing_scan_size.
1067 */
1068unsigned int sysctl_numa_balancing_scan_period_min = 1000;
1069unsigned int sysctl_numa_balancing_scan_period_max = 60000;
1070
1071/* Portion of address space to scan in MB */
1072unsigned int sysctl_numa_balancing_scan_size = 256;
1073
1074/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
1075unsigned int sysctl_numa_balancing_scan_delay = 1000;
1076
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1077static unsigned int task_nr_scan_windows(struct task_struct *p)
1078{
1079	unsigned long rss = 0;
1080	unsigned long nr_scan_pages;
1081
1082	/*
1083	 * Calculations based on RSS as non-present and empty pages are skipped
1084	 * by the PTE scanner and NUMA hinting faults should be trapped based
1085	 * on resident pages
1086	 */
1087	nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
1088	rss = get_mm_rss(p->mm);
1089	if (!rss)
1090		rss = nr_scan_pages;
1091
1092	rss = round_up(rss, nr_scan_pages);
1093	return rss / nr_scan_pages;
1094}
1095
1096/* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
1097#define MAX_SCAN_WINDOW 2560
1098
1099static unsigned int task_scan_min(struct task_struct *p)
1100{
1101	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
1102	unsigned int scan, floor;
1103	unsigned int windows = 1;
1104
1105	if (scan_size < MAX_SCAN_WINDOW)
1106		windows = MAX_SCAN_WINDOW / scan_size;
1107	floor = 1000 / windows;
1108
1109	scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
1110	return max_t(unsigned int, floor, scan);
1111}
1112
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1113static unsigned int task_scan_max(struct task_struct *p)
1114{
1115	unsigned int smin = task_scan_min(p);
1116	unsigned int smax;
 
1117
1118	/* Watch for min being lower than max due to floor calculations */
1119	smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1120	return max(smin, smax);
1121}
1122
1123static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
1124{
1125	rq->nr_numa_running += (p->numa_preferred_nid != -1);
1126	rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
1127}
1128
1129static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
1130{
1131	rq->nr_numa_running -= (p->numa_preferred_nid != -1);
1132	rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
1133}
1134
1135struct numa_group {
1136	atomic_t refcount;
1137
1138	spinlock_t lock; /* nr_tasks, tasks */
1139	int nr_tasks;
1140	pid_t gid;
1141	int active_nodes;
1142
1143	struct rcu_head rcu;
1144	unsigned long total_faults;
1145	unsigned long max_faults_cpu;
1146	/*
1147	 * Faults_cpu is used to decide whether memory should move
1148	 * towards the CPU. As a consequence, these stats are weighted
1149	 * more by CPU use than by memory faults.
1150	 */
1151	unsigned long *faults_cpu;
1152	unsigned long faults[0];
1153};
1154
1155/* Shared or private faults. */
1156#define NR_NUMA_HINT_FAULT_TYPES 2
1157
1158/* Memory and CPU locality */
1159#define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
1160
1161/* Averaged statistics, and temporary buffers. */
1162#define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
1163
1164pid_t task_numa_group_id(struct task_struct *p)
1165{
1166	return p->numa_group ? p->numa_group->gid : 0;
 
 
 
 
 
 
 
 
 
1167}
1168
1169/*
1170 * The averaged statistics, shared & private, memory & cpu,
1171 * occupy the first half of the array. The second half of the
1172 * array is for current counters, which are averaged into the
1173 * first set by task_numa_placement.
1174 */
1175static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
1176{
1177	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1178}
1179
1180static inline unsigned long task_faults(struct task_struct *p, int nid)
1181{
1182	if (!p->numa_faults)
1183		return 0;
1184
1185	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1186		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1187}
1188
1189static inline unsigned long group_faults(struct task_struct *p, int nid)
1190{
1191	if (!p->numa_group)
 
 
1192		return 0;
1193
1194	return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1195		p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1196}
1197
1198static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
1199{
1200	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
1201		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1202}
1203
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1204/*
1205 * A node triggering more than 1/3 as many NUMA faults as the maximum is
1206 * considered part of a numa group's pseudo-interleaving set. Migrations
1207 * between these nodes are slowed down, to allow things to settle down.
1208 */
1209#define ACTIVE_NODE_FRACTION 3
1210
1211static bool numa_is_active_node(int nid, struct numa_group *ng)
1212{
1213	return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
1214}
1215
1216/* Handle placement on systems where not all nodes are directly connected. */
1217static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
1218					int maxdist, bool task)
1219{
1220	unsigned long score = 0;
1221	int node;
1222
1223	/*
1224	 * All nodes are directly connected, and the same distance
1225	 * from each other. No need for fancy placement algorithms.
1226	 */
1227	if (sched_numa_topology_type == NUMA_DIRECT)
1228		return 0;
1229
1230	/*
1231	 * This code is called for each node, introducing N^2 complexity,
1232	 * which should be ok given the number of nodes rarely exceeds 8.
1233	 */
1234	for_each_online_node(node) {
1235		unsigned long faults;
1236		int dist = node_distance(nid, node);
1237
1238		/*
1239		 * The furthest away nodes in the system are not interesting
1240		 * for placement; nid was already counted.
1241		 */
1242		if (dist == sched_max_numa_distance || node == nid)
1243			continue;
1244
1245		/*
1246		 * On systems with a backplane NUMA topology, compare groups
1247		 * of nodes, and move tasks towards the group with the most
1248		 * memory accesses. When comparing two nodes at distance
1249		 * "hoplimit", only nodes closer by than "hoplimit" are part
1250		 * of each group. Skip other nodes.
1251		 */
1252		if (sched_numa_topology_type == NUMA_BACKPLANE &&
1253					dist > maxdist)
1254			continue;
1255
1256		/* Add up the faults from nearby nodes. */
1257		if (task)
1258			faults = task_faults(p, node);
1259		else
1260			faults = group_faults(p, node);
1261
1262		/*
1263		 * On systems with a glueless mesh NUMA topology, there are
1264		 * no fixed "groups of nodes". Instead, nodes that are not
1265		 * directly connected bounce traffic through intermediate
1266		 * nodes; a numa_group can occupy any set of nodes.
1267		 * The further away a node is, the less the faults count.
1268		 * This seems to result in good task placement.
1269		 */
1270		if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1271			faults *= (sched_max_numa_distance - dist);
1272			faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1273		}
1274
1275		score += faults;
1276	}
1277
1278	return score;
1279}
1280
1281/*
1282 * These return the fraction of accesses done by a particular task, or
1283 * task group, on a particular numa node.  The group weight is given a
1284 * larger multiplier, in order to group tasks together that are almost
1285 * evenly spread out between numa nodes.
1286 */
1287static inline unsigned long task_weight(struct task_struct *p, int nid,
1288					int dist)
1289{
1290	unsigned long faults, total_faults;
1291
1292	if (!p->numa_faults)
1293		return 0;
1294
1295	total_faults = p->total_numa_faults;
1296
1297	if (!total_faults)
1298		return 0;
1299
1300	faults = task_faults(p, nid);
1301	faults += score_nearby_nodes(p, nid, dist, true);
1302
1303	return 1000 * faults / total_faults;
1304}
1305
1306static inline unsigned long group_weight(struct task_struct *p, int nid,
1307					 int dist)
1308{
 
1309	unsigned long faults, total_faults;
1310
1311	if (!p->numa_group)
1312		return 0;
1313
1314	total_faults = p->numa_group->total_faults;
1315
1316	if (!total_faults)
1317		return 0;
1318
1319	faults = group_faults(p, nid);
1320	faults += score_nearby_nodes(p, nid, dist, false);
1321
1322	return 1000 * faults / total_faults;
1323}
1324
1325bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1326				int src_nid, int dst_cpu)
1327{
1328	struct numa_group *ng = p->numa_group;
1329	int dst_nid = cpu_to_node(dst_cpu);
1330	int last_cpupid, this_cpupid;
1331
1332	this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
 
 
 
 
 
 
 
 
 
 
 
1333
1334	/*
1335	 * Multi-stage node selection is used in conjunction with a periodic
1336	 * migration fault to build a temporal task<->page relation. By using
1337	 * a two-stage filter we remove short/unlikely relations.
1338	 *
1339	 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1340	 * a task's usage of a particular page (n_p) per total usage of this
1341	 * page (n_t) (in a given time-span) to a probability.
1342	 *
1343	 * Our periodic faults will sample this probability and getting the
1344	 * same result twice in a row, given these samples are fully
1345	 * independent, is then given by P(n)^2, provided our sample period
1346	 * is sufficiently short compared to the usage pattern.
1347	 *
1348	 * This quadric squishes small probabilities, making it less likely we
1349	 * act on an unlikely task<->page relation.
1350	 */
1351	last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1352	if (!cpupid_pid_unset(last_cpupid) &&
1353				cpupid_to_nid(last_cpupid) != dst_nid)
1354		return false;
1355
1356	/* Always allow migrate on private faults */
1357	if (cpupid_match_pid(p, last_cpupid))
1358		return true;
1359
1360	/* A shared fault, but p->numa_group has not been set up yet. */
1361	if (!ng)
1362		return true;
1363
1364	/*
1365	 * Destination node is much more heavily used than the source
1366	 * node? Allow migration.
1367	 */
1368	if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
1369					ACTIVE_NODE_FRACTION)
1370		return true;
1371
1372	/*
1373	 * Distribute memory according to CPU & memory use on each node,
1374	 * with 3/4 hysteresis to avoid unnecessary memory migrations:
1375	 *
1376	 * faults_cpu(dst)   3   faults_cpu(src)
1377	 * --------------- * - > ---------------
1378	 * faults_mem(dst)   4   faults_mem(src)
1379	 */
1380	return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
1381	       group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
1382}
1383
1384static unsigned long weighted_cpuload(const int cpu);
1385static unsigned long source_load(int cpu, int type);
1386static unsigned long target_load(int cpu, int type);
1387static unsigned long capacity_of(int cpu);
1388static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
 
 
 
 
 
 
 
 
 
 
 
 
1389
1390/* Cached statistics for all CPUs within a node */
1391struct numa_stats {
1392	unsigned long nr_running;
1393	unsigned long load;
1394
1395	/* Total compute capacity of CPUs on a node */
1396	unsigned long compute_capacity;
1397
1398	/* Approximate capacity in terms of runnable tasks on a node */
1399	unsigned long task_capacity;
1400	int has_free_capacity;
1401};
1402
1403/*
1404 * XXX borrowed from update_sg_lb_stats
1405 */
1406static void update_numa_stats(struct numa_stats *ns, int nid)
1407{
1408	int smt, cpu, cpus = 0;
1409	unsigned long capacity;
1410
1411	memset(ns, 0, sizeof(*ns));
1412	for_each_cpu(cpu, cpumask_of_node(nid)) {
1413		struct rq *rq = cpu_rq(cpu);
1414
1415		ns->nr_running += rq->nr_running;
1416		ns->load += weighted_cpuload(cpu);
1417		ns->compute_capacity += capacity_of(cpu);
1418
1419		cpus++;
 
1420	}
 
1421
1422	/*
1423	 * If we raced with hotplug and there are no CPUs left in our mask
1424	 * the @ns structure is NULL'ed and task_numa_compare() will
1425	 * not find this node attractive.
1426	 *
1427	 * We'll either bail at !has_free_capacity, or we'll detect a huge
1428	 * imbalance and bail there.
1429	 */
1430	if (!cpus)
1431		return;
1432
1433	/* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1434	smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1435	capacity = cpus / smt; /* cores */
1436
1437	ns->task_capacity = min_t(unsigned, capacity,
1438		DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1439	ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1440}
1441
1442struct task_numa_env {
1443	struct task_struct *p;
1444
1445	int src_cpu, src_nid;
1446	int dst_cpu, dst_nid;
1447
1448	struct numa_stats src_stats, dst_stats;
1449
1450	int imbalance_pct;
1451	int dist;
1452
1453	struct task_struct *best_task;
1454	long best_imp;
1455	int best_cpu;
1456};
1457
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1458static void task_numa_assign(struct task_numa_env *env,
1459			     struct task_struct *p, long imp)
1460{
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1461	if (env->best_task)
1462		put_task_struct(env->best_task);
1463	if (p)
1464		get_task_struct(p);
1465
1466	env->best_task = p;
1467	env->best_imp = imp;
1468	env->best_cpu = env->dst_cpu;
1469}
1470
1471static bool load_too_imbalanced(long src_load, long dst_load,
1472				struct task_numa_env *env)
1473{
1474	long imb, old_imb;
1475	long orig_src_load, orig_dst_load;
1476	long src_capacity, dst_capacity;
1477
1478	/*
1479	 * The load is corrected for the CPU capacity available on each node.
1480	 *
1481	 * src_load        dst_load
1482	 * ------------ vs ---------
1483	 * src_capacity    dst_capacity
1484	 */
1485	src_capacity = env->src_stats.compute_capacity;
1486	dst_capacity = env->dst_stats.compute_capacity;
1487
1488	/* We care about the slope of the imbalance, not the direction. */
1489	if (dst_load < src_load)
1490		swap(dst_load, src_load);
1491
1492	/* Is the difference below the threshold? */
1493	imb = dst_load * src_capacity * 100 -
1494	      src_load * dst_capacity * env->imbalance_pct;
1495	if (imb <= 0)
1496		return false;
1497
1498	/*
1499	 * The imbalance is above the allowed threshold.
1500	 * Compare it with the old imbalance.
1501	 */
1502	orig_src_load = env->src_stats.load;
1503	orig_dst_load = env->dst_stats.load;
1504
1505	if (orig_dst_load < orig_src_load)
1506		swap(orig_dst_load, orig_src_load);
1507
1508	old_imb = orig_dst_load * src_capacity * 100 -
1509		  orig_src_load * dst_capacity * env->imbalance_pct;
1510
1511	/* Would this change make things worse? */
1512	return (imb > old_imb);
1513}
1514
1515/*
 
 
 
 
 
 
 
1516 * This checks if the overall compute and NUMA accesses of the system would
1517 * be improved if the source tasks was migrated to the target dst_cpu taking
1518 * into account that it might be best if task running on the dst_cpu should
1519 * be exchanged with the source task
1520 */
1521static void task_numa_compare(struct task_numa_env *env,
1522			      long taskimp, long groupimp)
1523{
1524	struct rq *src_rq = cpu_rq(env->src_cpu);
1525	struct rq *dst_rq = cpu_rq(env->dst_cpu);
 
1526	struct task_struct *cur;
1527	long src_load, dst_load;
1528	long load;
1529	long imp = env->p->numa_group ? groupimp : taskimp;
1530	long moveimp = imp;
1531	int dist = env->dist;
 
 
 
 
 
 
1532
1533	rcu_read_lock();
1534	cur = task_rcu_dereference(&dst_rq->curr);
1535	if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1536		cur = NULL;
1537
1538	/*
1539	 * Because we have preemption enabled we can get migrated around and
1540	 * end try selecting ourselves (current == env->p) as a swap candidate.
1541	 */
1542	if (cur == env->p)
 
1543		goto unlock;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1544
1545	/*
1546	 * "imp" is the fault differential for the source task between the
1547	 * source and destination node. Calculate the total differential for
1548	 * the source task and potential destination task. The more negative
1549	 * the value is, the more rmeote accesses that would be expected to
1550	 * be incurred if the tasks were swapped.
 
 
 
1551	 */
1552	if (cur) {
1553		/* Skip this swap candidate if cannot move to the source cpu */
1554		if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1555			goto unlock;
1556
1557		/*
1558		 * If dst and source tasks are in the same NUMA group, or not
1559		 * in any group then look only at task weights.
1560		 */
1561		if (cur->numa_group == env->p->numa_group) {
1562			imp = taskimp + task_weight(cur, env->src_nid, dist) -
1563			      task_weight(cur, env->dst_nid, dist);
1564			/*
1565			 * Add some hysteresis to prevent swapping the
1566			 * tasks within a group over tiny differences.
1567			 */
1568			if (cur->numa_group)
1569				imp -= imp/16;
1570		} else {
1571			/*
1572			 * Compare the group weights. If a task is all by
1573			 * itself (not part of a group), use the task weight
1574			 * instead.
1575			 */
1576			if (cur->numa_group)
1577				imp += group_weight(cur, env->src_nid, dist) -
1578				       group_weight(cur, env->dst_nid, dist);
1579			else
1580				imp += task_weight(cur, env->src_nid, dist) -
1581				       task_weight(cur, env->dst_nid, dist);
1582		}
1583	}
1584
1585	if (imp <= env->best_imp && moveimp <= env->best_imp)
1586		goto unlock;
 
1587
1588	if (!cur) {
1589		/* Is there capacity at our destination? */
1590		if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1591		    !env->dst_stats.has_free_capacity)
1592			goto unlock;
 
 
 
1593
1594		goto balance;
 
 
 
1595	}
1596
1597	/* Balance doesn't matter much if we're running a task per cpu */
1598	if (imp > env->best_imp && src_rq->nr_running == 1 &&
1599			dst_rq->nr_running == 1)
 
 
 
1600		goto assign;
 
 
 
 
 
 
 
 
 
 
1601
1602	/*
1603	 * In the overloaded case, try and keep the load balanced.
1604	 */
1605balance:
1606	load = task_h_load(env->p);
 
 
1607	dst_load = env->dst_stats.load + load;
1608	src_load = env->src_stats.load - load;
1609
1610	if (moveimp > imp && moveimp > env->best_imp) {
1611		/*
1612		 * If the improvement from just moving env->p direction is
1613		 * better than swapping tasks around, check if a move is
1614		 * possible. Store a slightly smaller score than moveimp,
1615		 * so an actually idle CPU will win.
1616		 */
1617		if (!load_too_imbalanced(src_load, dst_load, env)) {
1618			imp = moveimp - 1;
1619			cur = NULL;
1620			goto assign;
1621		}
1622	}
1623
1624	if (imp <= env->best_imp)
1625		goto unlock;
1626
1627	if (cur) {
1628		load = task_h_load(cur);
1629		dst_load -= load;
1630		src_load += load;
1631	}
1632
1633	if (load_too_imbalanced(src_load, dst_load, env))
1634		goto unlock;
1635
1636	/*
1637	 * One idle CPU per node is evaluated for a task numa move.
1638	 * Call select_idle_sibling to maybe find a better one.
1639	 */
1640	if (!cur) {
 
 
 
 
 
 
1641		/*
1642		 * select_idle_siblings() uses an per-cpu cpumask that
1643		 * can be used from IRQ context.
1644		 */
1645		local_irq_disable();
1646		env->dst_cpu = select_idle_sibling(env->p, env->src_cpu,
1647						   env->dst_cpu);
1648		local_irq_enable();
 
 
1649	}
1650
1651assign:
1652	task_numa_assign(env, cur, imp);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1653unlock:
1654	rcu_read_unlock();
 
 
1655}
1656
1657static void task_numa_find_cpu(struct task_numa_env *env,
1658				long taskimp, long groupimp)
1659{
 
1660	int cpu;
1661
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1662	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1663		/* Skip this CPU if the source task cannot migrate */
1664		if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1665			continue;
1666
1667		env->dst_cpu = cpu;
1668		task_numa_compare(env, taskimp, groupimp);
 
1669	}
1670}
1671
1672/* Only move tasks to a NUMA node less busy than the current node. */
1673static bool numa_has_capacity(struct task_numa_env *env)
1674{
1675	struct numa_stats *src = &env->src_stats;
1676	struct numa_stats *dst = &env->dst_stats;
1677
1678	if (src->has_free_capacity && !dst->has_free_capacity)
1679		return false;
1680
1681	/*
1682	 * Only consider a task move if the source has a higher load
1683	 * than the destination, corrected for CPU capacity on each node.
1684	 *
1685	 *      src->load                dst->load
1686	 * --------------------- vs ---------------------
1687	 * src->compute_capacity    dst->compute_capacity
1688	 */
1689	if (src->load * dst->compute_capacity * env->imbalance_pct >
1690
1691	    dst->load * src->compute_capacity * 100)
1692		return true;
1693
1694	return false;
1695}
1696
1697static int task_numa_migrate(struct task_struct *p)
1698{
1699	struct task_numa_env env = {
1700		.p = p,
1701
1702		.src_cpu = task_cpu(p),
1703		.src_nid = task_node(p),
1704
1705		.imbalance_pct = 112,
1706
1707		.best_task = NULL,
1708		.best_imp = 0,
1709		.best_cpu = -1,
1710	};
1711	struct sched_domain *sd;
1712	unsigned long taskweight, groupweight;
1713	int nid, ret, dist;
1714	long taskimp, groupimp;
 
 
 
1715
1716	/*
1717	 * Pick the lowest SD_NUMA domain, as that would have the smallest
1718	 * imbalance and would be the first to start moving tasks about.
1719	 *
1720	 * And we want to avoid any moving of tasks about, as that would create
1721	 * random movement of tasks -- counter the numa conditions we're trying
1722	 * to satisfy here.
1723	 */
1724	rcu_read_lock();
1725	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1726	if (sd)
1727		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1728	rcu_read_unlock();
1729
1730	/*
1731	 * Cpusets can break the scheduler domain tree into smaller
1732	 * balance domains, some of which do not cross NUMA boundaries.
1733	 * Tasks that are "trapped" in such domains cannot be migrated
1734	 * elsewhere, so there is no point in (re)trying.
1735	 */
1736	if (unlikely(!sd)) {
1737		p->numa_preferred_nid = task_node(p);
1738		return -EINVAL;
1739	}
1740
1741	env.dst_nid = p->numa_preferred_nid;
1742	dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1743	taskweight = task_weight(p, env.src_nid, dist);
1744	groupweight = group_weight(p, env.src_nid, dist);
1745	update_numa_stats(&env.src_stats, env.src_nid);
1746	taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1747	groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1748	update_numa_stats(&env.dst_stats, env.dst_nid);
1749
1750	/* Try to find a spot on the preferred nid. */
1751	if (numa_has_capacity(&env))
1752		task_numa_find_cpu(&env, taskimp, groupimp);
1753
1754	/*
1755	 * Look at other nodes in these cases:
1756	 * - there is no space available on the preferred_nid
1757	 * - the task is part of a numa_group that is interleaved across
1758	 *   multiple NUMA nodes; in order to better consolidate the group,
1759	 *   we need to check other locations.
1760	 */
1761	if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
 
1762		for_each_online_node(nid) {
1763			if (nid == env.src_nid || nid == p->numa_preferred_nid)
1764				continue;
1765
1766			dist = node_distance(env.src_nid, env.dst_nid);
1767			if (sched_numa_topology_type == NUMA_BACKPLANE &&
1768						dist != env.dist) {
1769				taskweight = task_weight(p, env.src_nid, dist);
1770				groupweight = group_weight(p, env.src_nid, dist);
1771			}
1772
1773			/* Only consider nodes where both task and groups benefit */
1774			taskimp = task_weight(p, nid, dist) - taskweight;
1775			groupimp = group_weight(p, nid, dist) - groupweight;
1776			if (taskimp < 0 && groupimp < 0)
1777				continue;
1778
1779			env.dist = dist;
1780			env.dst_nid = nid;
1781			update_numa_stats(&env.dst_stats, env.dst_nid);
1782			if (numa_has_capacity(&env))
1783				task_numa_find_cpu(&env, taskimp, groupimp);
1784		}
1785	}
1786
1787	/*
1788	 * If the task is part of a workload that spans multiple NUMA nodes,
1789	 * and is migrating into one of the workload's active nodes, remember
1790	 * this node as the task's preferred numa node, so the workload can
1791	 * settle down.
1792	 * A task that migrated to a second choice node will be better off
1793	 * trying for a better one later. Do not set the preferred node here.
1794	 */
1795	if (p->numa_group) {
1796		struct numa_group *ng = p->numa_group;
1797
1798		if (env.best_cpu == -1)
1799			nid = env.src_nid;
1800		else
1801			nid = env.dst_nid;
1802
1803		if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng))
1804			sched_setnuma(p, env.dst_nid);
1805	}
1806
1807	/* No better CPU than the current one was found. */
1808	if (env.best_cpu == -1)
 
1809		return -EAGAIN;
 
1810
1811	/*
1812	 * Reset the scan period if the task is being rescheduled on an
1813	 * alternative node to recheck if the tasks is now properly placed.
1814	 */
1815	p->numa_scan_period = task_scan_min(p);
1816
1817	if (env.best_task == NULL) {
1818		ret = migrate_task_to(p, env.best_cpu);
 
1819		if (ret != 0)
1820			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1821		return ret;
1822	}
1823
1824	ret = migrate_swap(p, env.best_task);
 
 
1825	if (ret != 0)
1826		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1827	put_task_struct(env.best_task);
1828	return ret;
1829}
1830
1831/* Attempt to migrate a task to a CPU on the preferred node. */
1832static void numa_migrate_preferred(struct task_struct *p)
1833{
1834	unsigned long interval = HZ;
1835
1836	/* This task has no NUMA fault statistics yet */
1837	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1838		return;
1839
1840	/* Periodically retry migrating the task to the preferred node */
1841	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1842	p->numa_migrate_retry = jiffies + interval;
1843
1844	/* Success if task is already running on preferred CPU */
1845	if (task_node(p) == p->numa_preferred_nid)
1846		return;
1847
1848	/* Otherwise, try migrate to a CPU on the preferred node */
1849	task_numa_migrate(p);
1850}
1851
1852/*
1853 * Find out how many nodes on the workload is actively running on. Do this by
1854 * tracking the nodes from which NUMA hinting faults are triggered. This can
1855 * be different from the set of nodes where the workload's memory is currently
1856 * located.
1857 */
1858static void numa_group_count_active_nodes(struct numa_group *numa_group)
1859{
1860	unsigned long faults, max_faults = 0;
1861	int nid, active_nodes = 0;
1862
1863	for_each_online_node(nid) {
1864		faults = group_faults_cpu(numa_group, nid);
1865		if (faults > max_faults)
1866			max_faults = faults;
1867	}
1868
1869	for_each_online_node(nid) {
1870		faults = group_faults_cpu(numa_group, nid);
1871		if (faults * ACTIVE_NODE_FRACTION > max_faults)
1872			active_nodes++;
1873	}
1874
1875	numa_group->max_faults_cpu = max_faults;
1876	numa_group->active_nodes = active_nodes;
1877}
1878
1879/*
1880 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1881 * increments. The more local the fault statistics are, the higher the scan
1882 * period will be for the next scan window. If local/(local+remote) ratio is
1883 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1884 * the scan period will decrease. Aim for 70% local accesses.
1885 */
1886#define NUMA_PERIOD_SLOTS 10
1887#define NUMA_PERIOD_THRESHOLD 7
1888
1889/*
1890 * Increase the scan period (slow down scanning) if the majority of
1891 * our memory is already on our local node, or if the majority of
1892 * the page accesses are shared with other processes.
1893 * Otherwise, decrease the scan period.
1894 */
1895static void update_task_scan_period(struct task_struct *p,
1896			unsigned long shared, unsigned long private)
1897{
1898	unsigned int period_slot;
1899	int ratio;
1900	int diff;
1901
1902	unsigned long remote = p->numa_faults_locality[0];
1903	unsigned long local = p->numa_faults_locality[1];
1904
1905	/*
1906	 * If there were no record hinting faults then either the task is
1907	 * completely idle or all activity is areas that are not of interest
1908	 * to automatic numa balancing. Related to that, if there were failed
1909	 * migration then it implies we are migrating too quickly or the local
1910	 * node is overloaded. In either case, scan slower
1911	 */
1912	if (local + shared == 0 || p->numa_faults_locality[2]) {
1913		p->numa_scan_period = min(p->numa_scan_period_max,
1914			p->numa_scan_period << 1);
1915
1916		p->mm->numa_next_scan = jiffies +
1917			msecs_to_jiffies(p->numa_scan_period);
1918
1919		return;
1920	}
1921
1922	/*
1923	 * Prepare to scale scan period relative to the current period.
1924	 *	 == NUMA_PERIOD_THRESHOLD scan period stays the same
1925	 *       <  NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1926	 *	 >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1927	 */
1928	period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1929	ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1930	if (ratio >= NUMA_PERIOD_THRESHOLD) {
1931		int slot = ratio - NUMA_PERIOD_THRESHOLD;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1932		if (!slot)
1933			slot = 1;
1934		diff = slot * period_slot;
1935	} else {
1936		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1937
1938		/*
1939		 * Scale scan rate increases based on sharing. There is an
1940		 * inverse relationship between the degree of sharing and
1941		 * the adjustment made to the scanning period. Broadly
1942		 * speaking the intent is that there is little point
1943		 * scanning faster if shared accesses dominate as it may
1944		 * simply bounce migrations uselessly
1945		 */
1946		ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1947		diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1948	}
1949
1950	p->numa_scan_period = clamp(p->numa_scan_period + diff,
1951			task_scan_min(p), task_scan_max(p));
1952	memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1953}
1954
1955/*
1956 * Get the fraction of time the task has been running since the last
1957 * NUMA placement cycle. The scheduler keeps similar statistics, but
1958 * decays those on a 32ms period, which is orders of magnitude off
1959 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1960 * stats only if the task is so new there are no NUMA statistics yet.
1961 */
1962static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1963{
1964	u64 runtime, delta, now;
1965	/* Use the start of this time slice to avoid calculations. */
1966	now = p->se.exec_start;
1967	runtime = p->se.sum_exec_runtime;
1968
1969	if (p->last_task_numa_placement) {
1970		delta = runtime - p->last_sum_exec_runtime;
1971		*period = now - p->last_task_numa_placement;
 
 
 
 
1972	} else {
1973		delta = p->se.avg.load_sum / p->se.load.weight;
1974		*period = LOAD_AVG_MAX;
1975	}
1976
1977	p->last_sum_exec_runtime = runtime;
1978	p->last_task_numa_placement = now;
1979
1980	return delta;
1981}
1982
1983/*
1984 * Determine the preferred nid for a task in a numa_group. This needs to
1985 * be done in a way that produces consistent results with group_weight,
1986 * otherwise workloads might not converge.
1987 */
1988static int preferred_group_nid(struct task_struct *p, int nid)
1989{
1990	nodemask_t nodes;
1991	int dist;
1992
1993	/* Direct connections between all NUMA nodes. */
1994	if (sched_numa_topology_type == NUMA_DIRECT)
1995		return nid;
1996
1997	/*
1998	 * On a system with glueless mesh NUMA topology, group_weight
1999	 * scores nodes according to the number of NUMA hinting faults on
2000	 * both the node itself, and on nearby nodes.
2001	 */
2002	if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
2003		unsigned long score, max_score = 0;
2004		int node, max_node = nid;
2005
2006		dist = sched_max_numa_distance;
2007
2008		for_each_online_node(node) {
2009			score = group_weight(p, node, dist);
2010			if (score > max_score) {
2011				max_score = score;
2012				max_node = node;
2013			}
2014		}
2015		return max_node;
2016	}
2017
2018	/*
2019	 * Finding the preferred nid in a system with NUMA backplane
2020	 * interconnect topology is more involved. The goal is to locate
2021	 * tasks from numa_groups near each other in the system, and
2022	 * untangle workloads from different sides of the system. This requires
2023	 * searching down the hierarchy of node groups, recursively searching
2024	 * inside the highest scoring group of nodes. The nodemask tricks
2025	 * keep the complexity of the search down.
2026	 */
2027	nodes = node_online_map;
2028	for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
2029		unsigned long max_faults = 0;
2030		nodemask_t max_group = NODE_MASK_NONE;
2031		int a, b;
2032
2033		/* Are there nodes at this distance from each other? */
2034		if (!find_numa_distance(dist))
2035			continue;
2036
2037		for_each_node_mask(a, nodes) {
2038			unsigned long faults = 0;
2039			nodemask_t this_group;
2040			nodes_clear(this_group);
2041
2042			/* Sum group's NUMA faults; includes a==b case. */
2043			for_each_node_mask(b, nodes) {
2044				if (node_distance(a, b) < dist) {
2045					faults += group_faults(p, b);
2046					node_set(b, this_group);
2047					node_clear(b, nodes);
2048				}
2049			}
2050
2051			/* Remember the top group. */
2052			if (faults > max_faults) {
2053				max_faults = faults;
2054				max_group = this_group;
2055				/*
2056				 * subtle: at the smallest distance there is
2057				 * just one node left in each "group", the
2058				 * winner is the preferred nid.
2059				 */
2060				nid = a;
2061			}
2062		}
2063		/* Next round, evaluate the nodes within max_group. */
2064		if (!max_faults)
2065			break;
2066		nodes = max_group;
2067	}
2068	return nid;
2069}
2070
2071static void task_numa_placement(struct task_struct *p)
2072{
2073	int seq, nid, max_nid = -1, max_group_nid = -1;
2074	unsigned long max_faults = 0, max_group_faults = 0;
2075	unsigned long fault_types[2] = { 0, 0 };
2076	unsigned long total_faults;
2077	u64 runtime, period;
2078	spinlock_t *group_lock = NULL;
 
2079
2080	/*
2081	 * The p->mm->numa_scan_seq field gets updated without
2082	 * exclusive access. Use READ_ONCE() here to ensure
2083	 * that the field is read in a single access:
2084	 */
2085	seq = READ_ONCE(p->mm->numa_scan_seq);
2086	if (p->numa_scan_seq == seq)
2087		return;
2088	p->numa_scan_seq = seq;
2089	p->numa_scan_period_max = task_scan_max(p);
2090
2091	total_faults = p->numa_faults_locality[0] +
2092		       p->numa_faults_locality[1];
2093	runtime = numa_get_avg_runtime(p, &period);
2094
2095	/* If the task is part of a group prevent parallel updates to group stats */
2096	if (p->numa_group) {
2097		group_lock = &p->numa_group->lock;
 
2098		spin_lock_irq(group_lock);
2099	}
2100
2101	/* Find the node with the highest number of faults */
2102	for_each_online_node(nid) {
2103		/* Keep track of the offsets in numa_faults array */
2104		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
2105		unsigned long faults = 0, group_faults = 0;
2106		int priv;
2107
2108		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
2109			long diff, f_diff, f_weight;
2110
2111			mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
2112			membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
2113			cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
2114			cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
2115
2116			/* Decay existing window, copy faults since last scan */
2117			diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
2118			fault_types[priv] += p->numa_faults[membuf_idx];
2119			p->numa_faults[membuf_idx] = 0;
2120
2121			/*
2122			 * Normalize the faults_from, so all tasks in a group
2123			 * count according to CPU use, instead of by the raw
2124			 * number of faults. Tasks with little runtime have
2125			 * little over-all impact on throughput, and thus their
2126			 * faults are less important.
2127			 */
2128			f_weight = div64_u64(runtime << 16, period + 1);
2129			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
2130				   (total_faults + 1);
2131			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
2132			p->numa_faults[cpubuf_idx] = 0;
2133
2134			p->numa_faults[mem_idx] += diff;
2135			p->numa_faults[cpu_idx] += f_diff;
2136			faults += p->numa_faults[mem_idx];
2137			p->total_numa_faults += diff;
2138			if (p->numa_group) {
2139				/*
2140				 * safe because we can only change our own group
2141				 *
2142				 * mem_idx represents the offset for a given
2143				 * nid and priv in a specific region because it
2144				 * is at the beginning of the numa_faults array.
2145				 */
2146				p->numa_group->faults[mem_idx] += diff;
2147				p->numa_group->faults_cpu[mem_idx] += f_diff;
2148				p->numa_group->total_faults += diff;
2149				group_faults += p->numa_group->faults[mem_idx];
2150			}
2151		}
2152
2153		if (faults > max_faults) {
2154			max_faults = faults;
 
 
 
 
 
2155			max_nid = nid;
2156		}
2157
2158		if (group_faults > max_group_faults) {
2159			max_group_faults = group_faults;
2160			max_group_nid = nid;
2161		}
2162	}
2163
2164	update_task_scan_period(p, fault_types[0], fault_types[1]);
2165
2166	if (p->numa_group) {
2167		numa_group_count_active_nodes(p->numa_group);
2168		spin_unlock_irq(group_lock);
2169		max_nid = preferred_group_nid(p, max_group_nid);
2170	}
2171
2172	if (max_faults) {
2173		/* Set the new preferred node */
2174		if (max_nid != p->numa_preferred_nid)
2175			sched_setnuma(p, max_nid);
2176
2177		if (task_node(p) != p->numa_preferred_nid)
2178			numa_migrate_preferred(p);
2179	}
 
 
2180}
2181
2182static inline int get_numa_group(struct numa_group *grp)
2183{
2184	return atomic_inc_not_zero(&grp->refcount);
2185}
2186
2187static inline void put_numa_group(struct numa_group *grp)
2188{
2189	if (atomic_dec_and_test(&grp->refcount))
2190		kfree_rcu(grp, rcu);
2191}
2192
2193static void task_numa_group(struct task_struct *p, int cpupid, int flags,
2194			int *priv)
2195{
2196	struct numa_group *grp, *my_grp;
2197	struct task_struct *tsk;
2198	bool join = false;
2199	int cpu = cpupid_to_cpu(cpupid);
2200	int i;
2201
2202	if (unlikely(!p->numa_group)) {
2203		unsigned int size = sizeof(struct numa_group) +
2204				    4*nr_node_ids*sizeof(unsigned long);
2205
2206		grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
2207		if (!grp)
2208			return;
2209
2210		atomic_set(&grp->refcount, 1);
2211		grp->active_nodes = 1;
2212		grp->max_faults_cpu = 0;
2213		spin_lock_init(&grp->lock);
2214		grp->gid = p->pid;
2215		/* Second half of the array tracks nids where faults happen */
2216		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
2217						nr_node_ids;
2218
2219		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2220			grp->faults[i] = p->numa_faults[i];
2221
2222		grp->total_faults = p->total_numa_faults;
2223
2224		grp->nr_tasks++;
2225		rcu_assign_pointer(p->numa_group, grp);
2226	}
2227
2228	rcu_read_lock();
2229	tsk = READ_ONCE(cpu_rq(cpu)->curr);
2230
2231	if (!cpupid_match_pid(tsk, cpupid))
2232		goto no_join;
2233
2234	grp = rcu_dereference(tsk->numa_group);
2235	if (!grp)
2236		goto no_join;
2237
2238	my_grp = p->numa_group;
2239	if (grp == my_grp)
2240		goto no_join;
2241
2242	/*
2243	 * Only join the other group if its bigger; if we're the bigger group,
2244	 * the other task will join us.
2245	 */
2246	if (my_grp->nr_tasks > grp->nr_tasks)
2247		goto no_join;
2248
2249	/*
2250	 * Tie-break on the grp address.
2251	 */
2252	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2253		goto no_join;
2254
2255	/* Always join threads in the same process. */
2256	if (tsk->mm == current->mm)
2257		join = true;
2258
2259	/* Simple filter to avoid false positives due to PID collisions */
2260	if (flags & TNF_SHARED)
2261		join = true;
2262
2263	/* Update priv based on whether false sharing was detected */
2264	*priv = !join;
2265
2266	if (join && !get_numa_group(grp))
2267		goto no_join;
2268
2269	rcu_read_unlock();
2270
2271	if (!join)
2272		return;
2273
2274	BUG_ON(irqs_disabled());
2275	double_lock_irq(&my_grp->lock, &grp->lock);
2276
2277	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2278		my_grp->faults[i] -= p->numa_faults[i];
2279		grp->faults[i] += p->numa_faults[i];
2280	}
2281	my_grp->total_faults -= p->total_numa_faults;
2282	grp->total_faults += p->total_numa_faults;
2283
2284	my_grp->nr_tasks--;
2285	grp->nr_tasks++;
2286
2287	spin_unlock(&my_grp->lock);
2288	spin_unlock_irq(&grp->lock);
2289
2290	rcu_assign_pointer(p->numa_group, grp);
2291
2292	put_numa_group(my_grp);
2293	return;
2294
2295no_join:
2296	rcu_read_unlock();
2297	return;
2298}
2299
2300void task_numa_free(struct task_struct *p)
2301{
2302	struct numa_group *grp = p->numa_group;
2303	void *numa_faults = p->numa_faults;
 
 
 
 
 
 
 
 
2304	unsigned long flags;
2305	int i;
2306
 
 
 
2307	if (grp) {
2308		spin_lock_irqsave(&grp->lock, flags);
2309		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2310			grp->faults[i] -= p->numa_faults[i];
2311		grp->total_faults -= p->total_numa_faults;
2312
2313		grp->nr_tasks--;
2314		spin_unlock_irqrestore(&grp->lock, flags);
2315		RCU_INIT_POINTER(p->numa_group, NULL);
2316		put_numa_group(grp);
2317	}
2318
2319	p->numa_faults = NULL;
2320	kfree(numa_faults);
 
 
 
 
 
 
2321}
2322
2323/*
2324 * Got a PROT_NONE fault for a page on @node.
2325 */
2326void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2327{
2328	struct task_struct *p = current;
2329	bool migrated = flags & TNF_MIGRATED;
2330	int cpu_node = task_node(current);
2331	int local = !!(flags & TNF_FAULT_LOCAL);
2332	struct numa_group *ng;
2333	int priv;
2334
2335	if (!static_branch_likely(&sched_numa_balancing))
2336		return;
2337
2338	/* for example, ksmd faulting in a user's mm */
2339	if (!p->mm)
2340		return;
2341
2342	/* Allocate buffer to track faults on a per-node basis */
2343	if (unlikely(!p->numa_faults)) {
2344		int size = sizeof(*p->numa_faults) *
2345			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2346
2347		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2348		if (!p->numa_faults)
2349			return;
2350
2351		p->total_numa_faults = 0;
2352		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2353	}
2354
2355	/*
2356	 * First accesses are treated as private, otherwise consider accesses
2357	 * to be private if the accessing pid has not changed
2358	 */
2359	if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2360		priv = 1;
2361	} else {
2362		priv = cpupid_match_pid(p, last_cpupid);
2363		if (!priv && !(flags & TNF_NO_GROUP))
2364			task_numa_group(p, last_cpupid, flags, &priv);
2365	}
2366
2367	/*
2368	 * If a workload spans multiple NUMA nodes, a shared fault that
2369	 * occurs wholly within the set of nodes that the workload is
2370	 * actively using should be counted as local. This allows the
2371	 * scan rate to slow down when a workload has settled down.
2372	 */
2373	ng = p->numa_group;
2374	if (!priv && !local && ng && ng->active_nodes > 1 &&
2375				numa_is_active_node(cpu_node, ng) &&
2376				numa_is_active_node(mem_node, ng))
2377		local = 1;
2378
2379	task_numa_placement(p);
2380
2381	/*
2382	 * Retry task to preferred node migration periodically, in case it
2383	 * case it previously failed, or the scheduler moved us.
2384	 */
2385	if (time_after(jiffies, p->numa_migrate_retry))
 
2386		numa_migrate_preferred(p);
 
2387
2388	if (migrated)
2389		p->numa_pages_migrated += pages;
2390	if (flags & TNF_MIGRATE_FAIL)
2391		p->numa_faults_locality[2] += pages;
2392
2393	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2394	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2395	p->numa_faults_locality[local] += pages;
2396}
2397
2398static void reset_ptenuma_scan(struct task_struct *p)
2399{
2400	/*
2401	 * We only did a read acquisition of the mmap sem, so
2402	 * p->mm->numa_scan_seq is written to without exclusive access
2403	 * and the update is not guaranteed to be atomic. That's not
2404	 * much of an issue though, since this is just used for
2405	 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2406	 * expensive, to avoid any form of compiler optimizations:
2407	 */
2408	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2409	p->mm->numa_scan_offset = 0;
2410}
2411
2412/*
2413 * The expensive part of numa migration is done from task_work context.
2414 * Triggered from task_tick_numa().
2415 */
2416void task_numa_work(struct callback_head *work)
2417{
2418	unsigned long migrate, next_scan, now = jiffies;
2419	struct task_struct *p = current;
2420	struct mm_struct *mm = p->mm;
2421	u64 runtime = p->se.sum_exec_runtime;
2422	struct vm_area_struct *vma;
2423	unsigned long start, end;
2424	unsigned long nr_pte_updates = 0;
2425	long pages, virtpages;
2426
2427	SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
2428
2429	work->next = work; /* protect against double add */
2430	/*
2431	 * Who cares about NUMA placement when they're dying.
2432	 *
2433	 * NOTE: make sure not to dereference p->mm before this check,
2434	 * exit_task_work() happens _after_ exit_mm() so we could be called
2435	 * without p->mm even though we still had it when we enqueued this
2436	 * work.
2437	 */
2438	if (p->flags & PF_EXITING)
2439		return;
2440
2441	if (!mm->numa_next_scan) {
2442		mm->numa_next_scan = now +
2443			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2444	}
2445
2446	/*
2447	 * Enforce maximal scan/migration frequency..
2448	 */
2449	migrate = mm->numa_next_scan;
2450	if (time_before(now, migrate))
2451		return;
2452
2453	if (p->numa_scan_period == 0) {
2454		p->numa_scan_period_max = task_scan_max(p);
2455		p->numa_scan_period = task_scan_min(p);
2456	}
2457
2458	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2459	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2460		return;
2461
2462	/*
2463	 * Delay this task enough that another task of this mm will likely win
2464	 * the next time around.
2465	 */
2466	p->node_stamp += 2 * TICK_NSEC;
2467
2468	start = mm->numa_scan_offset;
2469	pages = sysctl_numa_balancing_scan_size;
2470	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2471	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2472	if (!pages)
2473		return;
2474
2475
2476	down_read(&mm->mmap_sem);
 
2477	vma = find_vma(mm, start);
2478	if (!vma) {
2479		reset_ptenuma_scan(p);
2480		start = 0;
2481		vma = mm->mmap;
2482	}
2483	for (; vma; vma = vma->vm_next) {
2484		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2485			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2486			continue;
2487		}
2488
2489		/*
2490		 * Shared library pages mapped by multiple processes are not
2491		 * migrated as it is expected they are cache replicated. Avoid
2492		 * hinting faults in read-only file-backed mappings or the vdso
2493		 * as migrating the pages will be of marginal benefit.
2494		 */
2495		if (!vma->vm_mm ||
2496		    (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2497			continue;
2498
2499		/*
2500		 * Skip inaccessible VMAs to avoid any confusion between
2501		 * PROT_NONE and NUMA hinting ptes
2502		 */
2503		if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2504			continue;
2505
2506		do {
2507			start = max(start, vma->vm_start);
2508			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2509			end = min(end, vma->vm_end);
2510			nr_pte_updates = change_prot_numa(vma, start, end);
2511
2512			/*
2513			 * Try to scan sysctl_numa_balancing_size worth of
2514			 * hpages that have at least one present PTE that
2515			 * is not already pte-numa. If the VMA contains
2516			 * areas that are unused or already full of prot_numa
2517			 * PTEs, scan up to virtpages, to skip through those
2518			 * areas faster.
2519			 */
2520			if (nr_pte_updates)
2521				pages -= (end - start) >> PAGE_SHIFT;
2522			virtpages -= (end - start) >> PAGE_SHIFT;
2523
2524			start = end;
2525			if (pages <= 0 || virtpages <= 0)
2526				goto out;
2527
2528			cond_resched();
2529		} while (end != vma->vm_end);
2530	}
2531
2532out:
2533	/*
2534	 * It is possible to reach the end of the VMA list but the last few
2535	 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2536	 * would find the !migratable VMA on the next scan but not reset the
2537	 * scanner to the start so check it now.
2538	 */
2539	if (vma)
2540		mm->numa_scan_offset = start;
2541	else
2542		reset_ptenuma_scan(p);
2543	up_read(&mm->mmap_sem);
2544
2545	/*
2546	 * Make sure tasks use at least 32x as much time to run other code
2547	 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2548	 * Usually update_task_scan_period slows down scanning enough; on an
2549	 * overloaded system we need to limit overhead on a per task basis.
2550	 */
2551	if (unlikely(p->se.sum_exec_runtime != runtime)) {
2552		u64 diff = p->se.sum_exec_runtime - runtime;
2553		p->node_stamp += 32 * diff;
2554	}
2555}
2556
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2557/*
2558 * Drive the periodic memory faults..
2559 */
2560void task_tick_numa(struct rq *rq, struct task_struct *curr)
2561{
2562	struct callback_head *work = &curr->numa_work;
2563	u64 period, now;
2564
2565	/*
2566	 * We don't care about NUMA placement if we don't have memory.
2567	 */
2568	if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2569		return;
2570
2571	/*
2572	 * Using runtime rather than walltime has the dual advantage that
2573	 * we (mostly) drive the selection from busy threads and that the
2574	 * task needs to have done some actual work before we bother with
2575	 * NUMA placement.
2576	 */
2577	now = curr->se.sum_exec_runtime;
2578	period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2579
2580	if (now > curr->node_stamp + period) {
2581		if (!curr->node_stamp)
2582			curr->numa_scan_period = task_scan_min(curr);
2583		curr->node_stamp += period;
2584
2585		if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2586			init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2587			task_work_add(curr, work, true);
2588		}
2589	}
2590}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2591#else
2592static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2593{
2594}
2595
2596static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2597{
2598}
2599
2600static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2601{
2602}
 
 
 
 
 
2603#endif /* CONFIG_NUMA_BALANCING */
2604
2605static void
2606account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2607{
2608	update_load_add(&cfs_rq->load, se->load.weight);
2609	if (!parent_entity(se))
2610		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2611#ifdef CONFIG_SMP
2612	if (entity_is_task(se)) {
2613		struct rq *rq = rq_of(cfs_rq);
2614
2615		account_numa_enqueue(rq, task_of(se));
2616		list_add(&se->group_node, &rq->cfs_tasks);
2617	}
2618#endif
2619	cfs_rq->nr_running++;
2620}
2621
2622static void
2623account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2624{
2625	update_load_sub(&cfs_rq->load, se->load.weight);
2626	if (!parent_entity(se))
2627		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2628#ifdef CONFIG_SMP
2629	if (entity_is_task(se)) {
2630		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2631		list_del_init(&se->group_node);
2632	}
2633#endif
2634	cfs_rq->nr_running--;
2635}
2636
2637#ifdef CONFIG_FAIR_GROUP_SCHED
2638# ifdef CONFIG_SMP
2639static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2640{
2641	long tg_weight, load, shares;
2642
2643	/*
2644	 * This really should be: cfs_rq->avg.load_avg, but instead we use
2645	 * cfs_rq->load.weight, which is its upper bound. This helps ramp up
2646	 * the shares for small weight interactive tasks.
2647	 */
2648	load = scale_load_down(cfs_rq->load.weight);
2649
2650	tg_weight = atomic_long_read(&tg->load_avg);
2651
2652	/* Ensure tg_weight >= load */
2653	tg_weight -= cfs_rq->tg_load_avg_contrib;
2654	tg_weight += load;
 
2655
2656	shares = (tg->shares * load);
2657	if (tg_weight)
2658		shares /= tg_weight;
 
 
 
 
 
 
 
 
 
 
 
 
 
2659
2660	if (shares < MIN_SHARES)
2661		shares = MIN_SHARES;
2662	if (shares > tg->shares)
2663		shares = tg->shares;
 
 
 
 
 
 
2664
2665	return shares;
 
 
 
 
 
2666}
2667# else /* CONFIG_SMP */
2668static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
 
2669{
2670	return tg->shares;
 
2671}
2672# endif /* CONFIG_SMP */
 
 
 
 
 
2673
2674static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2675			    unsigned long weight)
2676{
2677	if (se->on_rq) {
2678		/* commit outstanding execution time */
2679		if (cfs_rq->curr == se)
2680			update_curr(cfs_rq);
2681		account_entity_dequeue(cfs_rq, se);
2682	}
 
2683
2684	update_load_set(&se->load, weight);
2685
2686	if (se->on_rq)
2687		account_entity_enqueue(cfs_rq, se);
2688}
2689
2690static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2691
2692static void update_cfs_shares(struct cfs_rq *cfs_rq)
2693{
2694	struct task_group *tg;
2695	struct sched_entity *se;
2696	long shares;
2697
2698	tg = cfs_rq->tg;
2699	se = tg->se[cpu_of(rq_of(cfs_rq))];
2700	if (!se || throttled_hierarchy(cfs_rq))
2701		return;
2702#ifndef CONFIG_SMP
2703	if (likely(se->load.weight == tg->shares))
2704		return;
2705#endif
2706	shares = calc_cfs_shares(cfs_rq, tg);
2707
2708	reweight_entity(cfs_rq_of(se), se, shares);
2709}
2710#else /* CONFIG_FAIR_GROUP_SCHED */
2711static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2712{
2713}
2714#endif /* CONFIG_FAIR_GROUP_SCHED */
2715
2716#ifdef CONFIG_SMP
2717/* Precomputed fixed inverse multiplies for multiplication by y^n */
2718static const u32 runnable_avg_yN_inv[] = {
2719	0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2720	0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2721	0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2722	0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2723	0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2724	0x85aac367, 0x82cd8698,
2725};
2726
2727/*
2728 * Precomputed \Sum y^k { 1<=k<=n }.  These are floor(true_value) to prevent
2729 * over-estimates when re-combining.
2730 */
2731static const u32 runnable_avg_yN_sum[] = {
2732	    0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2733	 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2734	17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2735};
2736
2737/*
2738 * Precomputed \Sum y^k { 1<=k<=n, where n%32=0). Values are rolled down to
2739 * lower integers. See Documentation/scheduler/sched-avg.txt how these
2740 * were generated:
2741 */
2742static const u32 __accumulated_sum_N32[] = {
2743	    0, 23371, 35056, 40899, 43820, 45281,
2744	46011, 46376, 46559, 46650, 46696, 46719,
2745};
2746
2747/*
2748 * Approximate:
2749 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
2750 */
2751static __always_inline u64 decay_load(u64 val, u64 n)
2752{
2753	unsigned int local_n;
2754
2755	if (!n)
2756		return val;
2757	else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2758		return 0;
2759
2760	/* after bounds checking we can collapse to 32-bit */
2761	local_n = n;
 
2762
2763	/*
2764	 * As y^PERIOD = 1/2, we can combine
2765	 *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2766	 * With a look-up table which covers y^n (n<PERIOD)
2767	 *
2768	 * To achieve constant time decay_load.
2769	 */
2770	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2771		val >>= local_n / LOAD_AVG_PERIOD;
2772		local_n %= LOAD_AVG_PERIOD;
2773	}
2774
2775	val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
2776	return val;
2777}
2778
2779/*
2780 * For updates fully spanning n periods, the contribution to runnable
2781 * average will be: \Sum 1024*y^n
2782 *
2783 * We can compute this reasonably efficiently by combining:
2784 *   y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for  n <PERIOD}
2785 */
2786static u32 __compute_runnable_contrib(u64 n)
2787{
2788	u32 contrib = 0;
2789
2790	if (likely(n <= LOAD_AVG_PERIOD))
2791		return runnable_avg_yN_sum[n];
2792	else if (unlikely(n >= LOAD_AVG_MAX_N))
2793		return LOAD_AVG_MAX;
2794
2795	/* Since n < LOAD_AVG_MAX_N, n/LOAD_AVG_PERIOD < 11 */
2796	contrib = __accumulated_sum_N32[n/LOAD_AVG_PERIOD];
2797	n %= LOAD_AVG_PERIOD;
2798	contrib = decay_load(contrib, n);
2799	return contrib + runnable_avg_yN_sum[n];
2800}
2801
2802#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2803
2804/*
2805 * We can represent the historical contribution to runnable average as the
2806 * coefficients of a geometric series.  To do this we sub-divide our runnable
2807 * history into segments of approximately 1ms (1024us); label the segment that
2808 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2809 *
2810 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2811 *      p0            p1           p2
2812 *     (now)       (~1ms ago)  (~2ms ago)
2813 *
2814 * Let u_i denote the fraction of p_i that the entity was runnable.
 
2815 *
2816 * We then designate the fractions u_i as our co-efficients, yielding the
2817 * following representation of historical load:
2818 *   u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2819 *
2820 * We choose y based on the with of a reasonably scheduling period, fixing:
2821 *   y^32 = 0.5
 
2822 *
2823 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2824 * approximately half as much as the contribution to load within the last ms
2825 * (u_0).
2826 *
2827 * When a period "rolls over" and we have new u_0`, multiplying the previous
2828 * sum again by y is sufficient to update:
2829 *   load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2830 *            = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
 
 
 
 
 
 
 
 
 
 
 
 
 
2831 */
2832static __always_inline int
2833__update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2834		  unsigned long weight, int running, struct cfs_rq *cfs_rq)
2835{
2836	u64 delta, scaled_delta, periods;
2837	u32 contrib;
2838	unsigned int delta_w, scaled_delta_w, decayed = 0;
2839	unsigned long scale_freq, scale_cpu;
2840
2841	delta = now - sa->last_update_time;
2842	/*
2843	 * This should only happen when time goes backwards, which it
2844	 * unfortunately does during sched clock init when we swap over to TSC.
2845	 */
2846	if ((s64)delta < 0) {
2847		sa->last_update_time = now;
2848		return 0;
2849	}
2850
2851	/*
2852	 * Use 1024ns as the unit of measurement since it's a reasonable
2853	 * approximation of 1us and fast to compute.
2854	 */
2855	delta >>= 10;
2856	if (!delta)
2857		return 0;
2858	sa->last_update_time = now;
2859
2860	scale_freq = arch_scale_freq_capacity(NULL, cpu);
2861	scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
2862
2863	/* delta_w is the amount already accumulated against our next period */
2864	delta_w = sa->period_contrib;
2865	if (delta + delta_w >= 1024) {
2866		decayed = 1;
2867
2868		/* how much left for next period will start over, we don't know yet */
2869		sa->period_contrib = 0;
 
2870
2871		/*
2872		 * Now that we know we're crossing a period boundary, figure
2873		 * out how much from delta we need to complete the current
2874		 * period and accrue it.
2875		 */
2876		delta_w = 1024 - delta_w;
2877		scaled_delta_w = cap_scale(delta_w, scale_freq);
2878		if (weight) {
2879			sa->load_sum += weight * scaled_delta_w;
2880			if (cfs_rq) {
2881				cfs_rq->runnable_load_sum +=
2882						weight * scaled_delta_w;
2883			}
2884		}
2885		if (running)
2886			sa->util_sum += scaled_delta_w * scale_cpu;
2887
2888		delta -= delta_w;
2889
2890		/* Figure out how many additional periods this update spans */
2891		periods = delta / 1024;
2892		delta %= 1024;
 
 
 
 
 
2893
2894		sa->load_sum = decay_load(sa->load_sum, periods + 1);
2895		if (cfs_rq) {
2896			cfs_rq->runnable_load_sum =
2897				decay_load(cfs_rq->runnable_load_sum, periods + 1);
2898		}
2899		sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2900
2901		/* Efficiently calculate \sum (1..n_period) 1024*y^i */
2902		contrib = __compute_runnable_contrib(periods);
2903		contrib = cap_scale(contrib, scale_freq);
2904		if (weight) {
2905			sa->load_sum += weight * contrib;
2906			if (cfs_rq)
2907				cfs_rq->runnable_load_sum += weight * contrib;
2908		}
2909		if (running)
2910			sa->util_sum += contrib * scale_cpu;
2911	}
2912
2913	/* Remainder of delta accrued against u_0` */
2914	scaled_delta = cap_scale(delta, scale_freq);
2915	if (weight) {
2916		sa->load_sum += weight * scaled_delta;
2917		if (cfs_rq)
2918			cfs_rq->runnable_load_sum += weight * scaled_delta;
2919	}
2920	if (running)
2921		sa->util_sum += scaled_delta * scale_cpu;
2922
2923	sa->period_contrib += delta;
 
 
 
 
2924
2925	if (decayed) {
2926		sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2927		if (cfs_rq) {
2928			cfs_rq->runnable_load_avg =
2929				div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
2930		}
2931		sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2932	}
2933
2934	return decayed;
 
 
2935}
 
2936
2937/*
2938 * Signed add and clamp on underflow.
2939 *
2940 * Explicitly do a load-store to ensure the intermediate value never hits
2941 * memory. This allows lockless observations without ever seeing the negative
2942 * values.
2943 */
2944#define add_positive(_ptr, _val) do {                           \
2945	typeof(_ptr) ptr = (_ptr);                              \
2946	typeof(_val) val = (_val);                              \
2947	typeof(*ptr) res, var = READ_ONCE(*ptr);                \
2948								\
2949	res = var + val;                                        \
2950								\
2951	if (val < 0 && res > var)                               \
2952		res = 0;                                        \
2953								\
2954	WRITE_ONCE(*ptr, res);                                  \
2955} while (0)
2956
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2957#ifdef CONFIG_FAIR_GROUP_SCHED
2958/**
2959 * update_tg_load_avg - update the tg's load avg
2960 * @cfs_rq: the cfs_rq whose avg changed
2961 * @force: update regardless of how small the difference
2962 *
2963 * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
2964 * However, because tg->load_avg is a global value there are performance
2965 * considerations.
2966 *
2967 * In order to avoid having to look at the other cfs_rq's, we use a
2968 * differential update where we store the last value we propagated. This in
2969 * turn allows skipping updates if the differential is 'small'.
2970 *
2971 * Updating tg's load_avg is necessary before update_cfs_share() (which is
2972 * done) and effective_load() (which is not done because it is too costly).
2973 */
2974static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2975{
2976	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2977
2978	/*
2979	 * No need to update load_avg for root_task_group as it is not used.
2980	 */
2981	if (cfs_rq->tg == &root_task_group)
2982		return;
2983
2984	if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
2985		atomic_long_add(delta, &cfs_rq->tg->load_avg);
2986		cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2987	}
2988}
2989
2990/*
2991 * Called within set_task_rq() right before setting a task's cpu. The
2992 * caller only guarantees p->pi_lock is held; no other assumptions,
2993 * including the state of rq->lock, should be made.
2994 */
2995void set_task_rq_fair(struct sched_entity *se,
2996		      struct cfs_rq *prev, struct cfs_rq *next)
2997{
 
 
 
2998	if (!sched_feat(ATTACH_AGE_LOAD))
2999		return;
3000
3001	/*
3002	 * We are supposed to update the task to "current" time, then its up to
3003	 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
3004	 * getting what current time is, so simply throw away the out-of-date
3005	 * time. This will result in the wakee task is less decayed, but giving
3006	 * the wakee more load sounds not bad.
3007	 */
3008	if (se->avg.last_update_time && prev) {
3009		u64 p_last_update_time;
3010		u64 n_last_update_time;
3011
3012#ifndef CONFIG_64BIT
 
3013		u64 p_last_update_time_copy;
3014		u64 n_last_update_time_copy;
3015
3016		do {
3017			p_last_update_time_copy = prev->load_last_update_time_copy;
3018			n_last_update_time_copy = next->load_last_update_time_copy;
3019
3020			smp_rmb();
3021
3022			p_last_update_time = prev->avg.last_update_time;
3023			n_last_update_time = next->avg.last_update_time;
3024
3025		} while (p_last_update_time != p_last_update_time_copy ||
3026			 n_last_update_time != n_last_update_time_copy);
 
3027#else
3028		p_last_update_time = prev->avg.last_update_time;
3029		n_last_update_time = next->avg.last_update_time;
3030#endif
3031		__update_load_avg(p_last_update_time, cpu_of(rq_of(prev)),
3032				  &se->avg, 0, 0, NULL);
3033		se->avg.last_update_time = n_last_update_time;
3034	}
3035}
3036
3037/* Take into account change of utilization of a child task group */
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3038static inline void
3039update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se)
3040{
3041	struct cfs_rq *gcfs_rq = group_cfs_rq(se);
3042	long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;
 
3043
3044	/* Nothing to update */
3045	if (!delta)
3046		return;
3047
 
 
 
 
 
 
3048	/* Set new sched_entity's utilization */
3049	se->avg.util_avg = gcfs_rq->avg.util_avg;
3050	se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX;
3051
3052	/* Update parent cfs_rq utilization */
3053	add_positive(&cfs_rq->avg.util_avg, delta);
3054	cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX;
3055}
3056
3057/* Take into account change of load of a child task group */
3058static inline void
3059update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se)
3060{
3061	struct cfs_rq *gcfs_rq = group_cfs_rq(se);
3062	long delta, load = gcfs_rq->avg.load_avg;
 
 
 
 
3063
3064	/*
3065	 * If the load of group cfs_rq is null, the load of the
3066	 * sched_entity will also be null so we can skip the formula
3067	 */
3068	if (load) {
3069		long tg_load;
3070
3071		/* Get tg's load and ensure tg_load > 0 */
3072		tg_load = atomic_long_read(&gcfs_rq->tg->load_avg) + 1;
 
 
 
 
 
 
3073
3074		/* Ensure tg_load >= load and updated with current load*/
3075		tg_load -= gcfs_rq->tg_load_avg_contrib;
3076		tg_load += load;
 
 
 
 
 
3077
3078		/*
3079		 * We need to compute a correction term in the case that the
3080		 * task group is consuming more CPU than a task of equal
3081		 * weight. A task with a weight equals to tg->shares will have
3082		 * a load less or equal to scale_load_down(tg->shares).
3083		 * Similarly, the sched_entities that represent the task group
3084		 * at parent level, can't have a load higher than
3085		 * scale_load_down(tg->shares). And the Sum of sched_entities'
3086		 * load must be <= scale_load_down(tg->shares).
3087		 */
3088		if (tg_load > scale_load_down(gcfs_rq->tg->shares)) {
3089			/* scale gcfs_rq's load into tg's shares*/
3090			load *= scale_load_down(gcfs_rq->tg->shares);
3091			load /= tg_load;
3092		}
3093	}
3094
3095	delta = load - se->avg.load_avg;
3096
3097	/* Nothing to update */
3098	if (!delta)
3099		return;
 
 
3100
3101	/* Set new sched_entity's load */
3102	se->avg.load_avg = load;
3103	se->avg.load_sum = se->avg.load_avg * LOAD_AVG_MAX;
 
 
 
 
 
 
 
 
 
 
 
 
 
3104
3105	/* Update parent cfs_rq load */
3106	add_positive(&cfs_rq->avg.load_avg, delta);
3107	cfs_rq->avg.load_sum = cfs_rq->avg.load_avg * LOAD_AVG_MAX;
3108
3109	/*
3110	 * If the sched_entity is already enqueued, we also have to update the
3111	 * runnable load avg.
 
 
3112	 */
3113	if (se->on_rq) {
3114		/* Update parent cfs_rq runnable_load_avg */
3115		add_positive(&cfs_rq->runnable_load_avg, delta);
3116		cfs_rq->runnable_load_sum = cfs_rq->runnable_load_avg * LOAD_AVG_MAX;
3117	}
3118}
3119
3120static inline void set_tg_cfs_propagate(struct cfs_rq *cfs_rq)
3121{
3122	cfs_rq->propagate_avg = 1;
3123}
3124
3125static inline int test_and_clear_tg_cfs_propagate(struct sched_entity *se)
3126{
3127	struct cfs_rq *cfs_rq = group_cfs_rq(se);
3128
3129	if (!cfs_rq->propagate_avg)
3130		return 0;
 
 
 
3131
3132	cfs_rq->propagate_avg = 0;
3133	return 1;
 
 
3134}
3135
3136/* Update task and its cfs_rq load average */
3137static inline int propagate_entity_load_avg(struct sched_entity *se)
3138{
3139	struct cfs_rq *cfs_rq;
3140
3141	if (entity_is_task(se))
3142		return 0;
3143
3144	if (!test_and_clear_tg_cfs_propagate(se))
 
3145		return 0;
3146
 
 
3147	cfs_rq = cfs_rq_of(se);
3148
3149	set_tg_cfs_propagate(cfs_rq);
 
 
 
 
3150
3151	update_tg_cfs_util(cfs_rq, se);
3152	update_tg_cfs_load(cfs_rq, se);
3153
3154	return 1;
3155}
3156
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3157#else /* CONFIG_FAIR_GROUP_SCHED */
3158
3159static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
3160
3161static inline int propagate_entity_load_avg(struct sched_entity *se)
3162{
3163	return 0;
3164}
3165
3166static inline void set_tg_cfs_propagate(struct cfs_rq *cfs_rq) {}
3167
3168#endif /* CONFIG_FAIR_GROUP_SCHED */
3169
3170static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)
3171{
3172	if (&this_rq()->cfs == cfs_rq) {
3173		/*
3174		 * There are a few boundary cases this might miss but it should
3175		 * get called often enough that that should (hopefully) not be
3176		 * a real problem -- added to that it only calls on the local
3177		 * CPU, so if we enqueue remotely we'll miss an update, but
3178		 * the next tick/schedule should update.
3179		 *
3180		 * It will not get called when we go idle, because the idle
3181		 * thread is a different class (!fair), nor will the utilization
3182		 * number include things like RT tasks.
3183		 *
3184		 * As is, the util number is not freq-invariant (we'd have to
3185		 * implement arch_scale_freq_capacity() for that).
3186		 *
3187		 * See cpu_util().
3188		 */
3189		cpufreq_update_util(rq_of(cfs_rq), 0);
3190	}
3191}
3192
3193/*
3194 * Unsigned subtract and clamp on underflow.
3195 *
3196 * Explicitly do a load-store to ensure the intermediate value never hits
3197 * memory. This allows lockless observations without ever seeing the negative
3198 * values.
3199 */
3200#define sub_positive(_ptr, _val) do {				\
3201	typeof(_ptr) ptr = (_ptr);				\
3202	typeof(*ptr) val = (_val);				\
3203	typeof(*ptr) res, var = READ_ONCE(*ptr);		\
3204	res = var - val;					\
3205	if (res > var)						\
3206		res = 0;					\
3207	WRITE_ONCE(*ptr, res);					\
3208} while (0)
3209
3210/**
3211 * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
3212 * @now: current time, as per cfs_rq_clock_task()
3213 * @cfs_rq: cfs_rq to update
3214 * @update_freq: should we call cfs_rq_util_change() or will the call do so
3215 *
3216 * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
3217 * avg. The immediate corollary is that all (fair) tasks must be attached, see
3218 * post_init_entity_util_avg().
3219 *
3220 * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
3221 *
3222 * Returns true if the load decayed or we removed load.
3223 *
3224 * Since both these conditions indicate a changed cfs_rq->avg.load we should
3225 * call update_tg_load_avg() when this function returns true.
3226 */
3227static inline int
3228update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
3229{
 
3230	struct sched_avg *sa = &cfs_rq->avg;
3231	int decayed, removed_load = 0, removed_util = 0;
 
 
 
 
 
 
 
 
 
 
 
3232
3233	if (atomic_long_read(&cfs_rq->removed_load_avg)) {
3234		s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
3235		sub_positive(&sa->load_avg, r);
3236		sub_positive(&sa->load_sum, r * LOAD_AVG_MAX);
3237		removed_load = 1;
3238		set_tg_cfs_propagate(cfs_rq);
3239	}
3240
3241	if (atomic_long_read(&cfs_rq->removed_util_avg)) {
3242		long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
3243		sub_positive(&sa->util_avg, r);
3244		sub_positive(&sa->util_sum, r * LOAD_AVG_MAX);
3245		removed_util = 1;
3246		set_tg_cfs_propagate(cfs_rq);
 
 
 
 
 
 
 
 
 
 
 
3247	}
3248
3249	decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
3250		scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
3251
3252#ifndef CONFIG_64BIT
3253	smp_wmb();
3254	cfs_rq->load_last_update_time_copy = sa->last_update_time;
3255#endif
3256
3257	if (update_freq && (decayed || removed_util))
3258		cfs_rq_util_change(cfs_rq);
3259
3260	return decayed || removed_load;
3261}
3262
3263/*
3264 * Optional action to be done while updating the load average
3265 */
3266#define UPDATE_TG	0x1
3267#define SKIP_AGE_LOAD	0x2
3268
3269/* Update task and its cfs_rq load average */
3270static inline void update_load_avg(struct sched_entity *se, int flags)
3271{
3272	struct cfs_rq *cfs_rq = cfs_rq_of(se);
3273	u64 now = cfs_rq_clock_task(cfs_rq);
3274	struct rq *rq = rq_of(cfs_rq);
3275	int cpu = cpu_of(rq);
3276	int decayed;
3277
3278	/*
3279	 * Track task load average for carrying it to new CPU after migrated, and
3280	 * track group sched_entity load average for task_h_load calc in migration
3281	 */
3282	if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD)) {
3283		__update_load_avg(now, cpu, &se->avg,
3284			  se->on_rq * scale_load_down(se->load.weight),
3285			  cfs_rq->curr == se, NULL);
3286	}
3287
3288	decayed  = update_cfs_rq_load_avg(now, cfs_rq, true);
3289	decayed |= propagate_entity_load_avg(se);
3290
3291	if (decayed && (flags & UPDATE_TG))
3292		update_tg_load_avg(cfs_rq, 0);
3293}
3294
3295/**
3296 * attach_entity_load_avg - attach this entity to its cfs_rq load avg
3297 * @cfs_rq: cfs_rq to attach to
3298 * @se: sched_entity to attach
3299 *
3300 * Must call update_cfs_rq_load_avg() before this, since we rely on
3301 * cfs_rq->avg.last_update_time being current.
3302 */
3303static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3304{
 
 
 
 
 
 
 
 
 
 
 
 
 
3305	se->avg.last_update_time = cfs_rq->avg.last_update_time;
3306	cfs_rq->avg.load_avg += se->avg.load_avg;
3307	cfs_rq->avg.load_sum += se->avg.load_sum;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3308	cfs_rq->avg.util_avg += se->avg.util_avg;
3309	cfs_rq->avg.util_sum += se->avg.util_sum;
3310	set_tg_cfs_propagate(cfs_rq);
 
 
 
3311
3312	cfs_rq_util_change(cfs_rq);
 
 
3313}
3314
3315/**
3316 * detach_entity_load_avg - detach this entity from its cfs_rq load avg
3317 * @cfs_rq: cfs_rq to detach from
3318 * @se: sched_entity to detach
3319 *
3320 * Must call update_cfs_rq_load_avg() before this, since we rely on
3321 * cfs_rq->avg.last_update_time being current.
3322 */
3323static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3324{
3325
3326	sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
3327	sub_positive(&cfs_rq->avg.load_sum, se->avg.load_sum);
3328	sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
3329	sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
3330	set_tg_cfs_propagate(cfs_rq);
 
3331
3332	cfs_rq_util_change(cfs_rq);
 
 
 
 
3333}
3334
3335/* Add the load generated by se into cfs_rq's load average */
3336static inline void
3337enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 
 
 
 
 
 
3338{
3339	struct sched_avg *sa = &se->avg;
 
 
 
 
 
 
 
 
3340
3341	cfs_rq->runnable_load_avg += sa->load_avg;
3342	cfs_rq->runnable_load_sum += sa->load_sum;
 
 
3343
3344	if (!sa->last_update_time) {
 
 
 
 
 
 
3345		attach_entity_load_avg(cfs_rq, se);
3346		update_tg_load_avg(cfs_rq, 0);
3347	}
3348}
3349
3350/* Remove the runnable load generated by se from cfs_rq's runnable load average */
3351static inline void
3352dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3353{
3354	cfs_rq->runnable_load_avg =
3355		max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
3356	cfs_rq->runnable_load_sum =
3357		max_t(s64,  cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
3358}
3359
3360#ifndef CONFIG_64BIT
3361static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3362{
3363	u64 last_update_time_copy;
3364	u64 last_update_time;
3365
3366	do {
3367		last_update_time_copy = cfs_rq->load_last_update_time_copy;
3368		smp_rmb();
3369		last_update_time = cfs_rq->avg.last_update_time;
3370	} while (last_update_time != last_update_time_copy);
3371
3372	return last_update_time;
3373}
3374#else
3375static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3376{
3377	return cfs_rq->avg.last_update_time;
3378}
3379#endif
3380
3381/*
3382 * Synchronize entity load avg of dequeued entity without locking
3383 * the previous rq.
3384 */
3385void sync_entity_load_avg(struct sched_entity *se)
3386{
3387	struct cfs_rq *cfs_rq = cfs_rq_of(se);
3388	u64 last_update_time;
3389
3390	last_update_time = cfs_rq_last_update_time(cfs_rq);
3391	__update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
3392}
3393
3394/*
3395 * Task first catches up with cfs_rq, and then subtract
3396 * itself from the cfs_rq (task must be off the queue now).
3397 */
3398void remove_entity_load_avg(struct sched_entity *se)
3399{
3400	struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
3401
3402	/*
3403	 * tasks cannot exit without having gone through wake_up_new_task() ->
3404	 * post_init_entity_util_avg() which will have added things to the
3405	 * cfs_rq, so we can remove unconditionally.
3406	 *
3407	 * Similarly for groups, they will have passed through
3408	 * post_init_entity_util_avg() before unregister_sched_fair_group()
3409	 * calls this.
3410	 */
3411
3412	sync_entity_load_avg(se);
3413	atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
3414	atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
 
 
 
 
 
3415}
3416
3417static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
3418{
3419	return cfs_rq->runnable_load_avg;
3420}
3421
3422static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
3423{
3424	return cfs_rq->avg.load_avg;
3425}
3426
3427static int idle_balance(struct rq *this_rq);
3428
3429#else /* CONFIG_SMP */
 
 
 
3430
3431static inline int
3432update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
3433{
3434	return 0;
 
 
3435}
3436
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3437#define UPDATE_TG	0x0
3438#define SKIP_AGE_LOAD	0x0
 
3439
3440static inline void update_load_avg(struct sched_entity *se, int not_used1)
3441{
3442	cpufreq_update_util(rq_of(cfs_rq_of(se)), 0);
3443}
3444
3445static inline void
3446enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3447static inline void
3448dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3449static inline void remove_entity_load_avg(struct sched_entity *se) {}
3450
3451static inline void
3452attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3453static inline void
3454detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3455
3456static inline int idle_balance(struct rq *rq)
3457{
3458	return 0;
3459}
3460
 
 
 
 
 
 
 
 
3461#endif /* CONFIG_SMP */
3462
3463static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
3464{
3465#ifdef CONFIG_SCHED_DEBUG
3466	s64 d = se->vruntime - cfs_rq->min_vruntime;
3467
3468	if (d < 0)
3469		d = -d;
3470
3471	if (d > 3*sysctl_sched_latency)
3472		schedstat_inc(cfs_rq->nr_spread_over);
3473#endif
3474}
3475
3476static void
3477place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
3478{
3479	u64 vruntime = cfs_rq->min_vruntime;
3480
3481	/*
3482	 * The 'current' period is already promised to the current tasks,
3483	 * however the extra weight of the new task will slow them down a
3484	 * little, place the new task so that it fits in the slot that
3485	 * stays open at the end.
3486	 */
3487	if (initial && sched_feat(START_DEBIT))
3488		vruntime += sched_vslice(cfs_rq, se);
3489
3490	/* sleeps up to a single latency don't count. */
3491	if (!initial) {
3492		unsigned long thresh = sysctl_sched_latency;
3493
3494		/*
3495		 * Halve their sleep time's effect, to allow
3496		 * for a gentler effect of sleepers:
3497		 */
3498		if (sched_feat(GENTLE_FAIR_SLEEPERS))
3499			thresh >>= 1;
3500
3501		vruntime -= thresh;
3502	}
3503
3504	/* ensure we never gain time by being placed backwards. */
3505	se->vruntime = max_vruntime(se->vruntime, vruntime);
3506}
3507
3508static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
3509
3510static inline void check_schedstat_required(void)
3511{
3512#ifdef CONFIG_SCHEDSTATS
3513	if (schedstat_enabled())
3514		return;
3515
3516	/* Force schedstat enabled if a dependent tracepoint is active */
3517	if (trace_sched_stat_wait_enabled()    ||
3518			trace_sched_stat_sleep_enabled()   ||
3519			trace_sched_stat_iowait_enabled()  ||
3520			trace_sched_stat_blocked_enabled() ||
3521			trace_sched_stat_runtime_enabled())  {
3522		printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3523			     "stat_blocked and stat_runtime require the "
3524			     "kernel parameter schedstats=enabled or "
3525			     "kernel.sched_schedstats=1\n");
3526	}
3527#endif
3528}
3529
 
3530
3531/*
3532 * MIGRATION
3533 *
3534 *	dequeue
3535 *	  update_curr()
3536 *	    update_min_vruntime()
3537 *	  vruntime -= min_vruntime
3538 *
3539 *	enqueue
3540 *	  update_curr()
3541 *	    update_min_vruntime()
3542 *	  vruntime += min_vruntime
3543 *
3544 * this way the vruntime transition between RQs is done when both
3545 * min_vruntime are up-to-date.
3546 *
3547 * WAKEUP (remote)
3548 *
3549 *	->migrate_task_rq_fair() (p->state == TASK_WAKING)
3550 *	  vruntime -= min_vruntime
3551 *
3552 *	enqueue
3553 *	  update_curr()
3554 *	    update_min_vruntime()
3555 *	  vruntime += min_vruntime
3556 *
3557 * this way we don't have the most up-to-date min_vruntime on the originating
3558 * CPU and an up-to-date min_vruntime on the destination CPU.
3559 */
3560
3561static void
3562enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3563{
3564	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
3565	bool curr = cfs_rq->curr == se;
3566
3567	/*
3568	 * If we're the current task, we must renormalise before calling
3569	 * update_curr().
3570	 */
3571	if (renorm && curr)
3572		se->vruntime += cfs_rq->min_vruntime;
3573
3574	update_curr(cfs_rq);
3575
3576	/*
3577	 * Otherwise, renormalise after, such that we're placed at the current
3578	 * moment in time, instead of some random moment in the past. Being
3579	 * placed in the past could significantly boost this task to the
3580	 * fairness detriment of existing tasks.
3581	 */
3582	if (renorm && !curr)
3583		se->vruntime += cfs_rq->min_vruntime;
3584
3585	update_load_avg(se, UPDATE_TG);
3586	enqueue_entity_load_avg(cfs_rq, se);
 
 
 
 
 
 
 
 
 
3587	account_entity_enqueue(cfs_rq, se);
3588	update_cfs_shares(cfs_rq);
3589
3590	if (flags & ENQUEUE_WAKEUP)
3591		place_entity(cfs_rq, se, 0);
3592
3593	check_schedstat_required();
3594	update_stats_enqueue(cfs_rq, se, flags);
3595	check_spread(cfs_rq, se);
3596	if (!curr)
3597		__enqueue_entity(cfs_rq, se);
3598	se->on_rq = 1;
3599
3600	if (cfs_rq->nr_running == 1) {
 
 
 
 
 
3601		list_add_leaf_cfs_rq(cfs_rq);
 
 
3602		check_enqueue_throttle(cfs_rq);
3603	}
3604}
3605
3606static void __clear_buddies_last(struct sched_entity *se)
3607{
3608	for_each_sched_entity(se) {
3609		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3610		if (cfs_rq->last != se)
3611			break;
3612
3613		cfs_rq->last = NULL;
3614	}
3615}
3616
3617static void __clear_buddies_next(struct sched_entity *se)
3618{
3619	for_each_sched_entity(se) {
3620		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3621		if (cfs_rq->next != se)
3622			break;
3623
3624		cfs_rq->next = NULL;
3625	}
3626}
3627
3628static void __clear_buddies_skip(struct sched_entity *se)
3629{
3630	for_each_sched_entity(se) {
3631		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3632		if (cfs_rq->skip != se)
3633			break;
3634
3635		cfs_rq->skip = NULL;
3636	}
3637}
3638
3639static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3640{
3641	if (cfs_rq->last == se)
3642		__clear_buddies_last(se);
3643
3644	if (cfs_rq->next == se)
3645		__clear_buddies_next(se);
3646
3647	if (cfs_rq->skip == se)
3648		__clear_buddies_skip(se);
3649}
3650
3651static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3652
3653static void
3654dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3655{
3656	/*
3657	 * Update run-time statistics of the 'current'.
3658	 */
3659	update_curr(cfs_rq);
3660	update_load_avg(se, UPDATE_TG);
3661	dequeue_entity_load_avg(cfs_rq, se);
 
 
 
 
 
 
 
 
 
3662
3663	update_stats_dequeue(cfs_rq, se, flags);
3664
3665	clear_buddies(cfs_rq, se);
3666
3667	if (se != cfs_rq->curr)
3668		__dequeue_entity(cfs_rq, se);
3669	se->on_rq = 0;
3670	account_entity_dequeue(cfs_rq, se);
3671
3672	/*
3673	 * Normalize after update_curr(); which will also have moved
3674	 * min_vruntime if @se is the one holding it back. But before doing
3675	 * update_min_vruntime() again, which will discount @se's position and
3676	 * can move min_vruntime forward still more.
3677	 */
3678	if (!(flags & DEQUEUE_SLEEP))
3679		se->vruntime -= cfs_rq->min_vruntime;
3680
3681	/* return excess runtime on last dequeue */
3682	return_cfs_rq_runtime(cfs_rq);
3683
3684	update_cfs_shares(cfs_rq);
3685
3686	/*
3687	 * Now advance min_vruntime if @se was the entity holding it back,
3688	 * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
3689	 * put back on, and if we advance min_vruntime, we'll be placed back
3690	 * further than we started -- ie. we'll be penalized.
3691	 */
3692	if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE)
3693		update_min_vruntime(cfs_rq);
3694}
3695
3696/*
3697 * Preempt the current task with a newly woken task if needed:
3698 */
3699static void
3700check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3701{
3702	unsigned long ideal_runtime, delta_exec;
3703	struct sched_entity *se;
3704	s64 delta;
3705
3706	ideal_runtime = sched_slice(cfs_rq, curr);
3707	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3708	if (delta_exec > ideal_runtime) {
3709		resched_curr(rq_of(cfs_rq));
3710		/*
3711		 * The current task ran long enough, ensure it doesn't get
3712		 * re-elected due to buddy favours.
3713		 */
3714		clear_buddies(cfs_rq, curr);
3715		return;
3716	}
3717
3718	/*
3719	 * Ensure that a task that missed wakeup preemption by a
3720	 * narrow margin doesn't have to wait for a full slice.
3721	 * This also mitigates buddy induced latencies under load.
3722	 */
3723	if (delta_exec < sysctl_sched_min_granularity)
3724		return;
3725
3726	se = __pick_first_entity(cfs_rq);
3727	delta = curr->vruntime - se->vruntime;
3728
3729	if (delta < 0)
3730		return;
3731
3732	if (delta > ideal_runtime)
3733		resched_curr(rq_of(cfs_rq));
3734}
3735
3736static void
3737set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3738{
3739	/* 'current' is not kept within the tree. */
3740	if (se->on_rq) {
3741		/*
3742		 * Any task has to be enqueued before it get to execute on
3743		 * a CPU. So account for the time it spent waiting on the
3744		 * runqueue.
3745		 */
3746		update_stats_wait_end(cfs_rq, se);
3747		__dequeue_entity(cfs_rq, se);
3748		update_load_avg(se, UPDATE_TG);
3749	}
3750
3751	update_stats_curr_start(cfs_rq, se);
3752	cfs_rq->curr = se;
3753
3754	/*
3755	 * Track our maximum slice length, if the CPU's load is at
3756	 * least twice that of our own weight (i.e. dont track it
3757	 * when there are only lesser-weight tasks around):
3758	 */
3759	if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
 
3760		schedstat_set(se->statistics.slice_max,
3761			max((u64)schedstat_val(se->statistics.slice_max),
3762			    se->sum_exec_runtime - se->prev_sum_exec_runtime));
3763	}
3764
3765	se->prev_sum_exec_runtime = se->sum_exec_runtime;
3766}
3767
3768static int
3769wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3770
3771/*
3772 * Pick the next process, keeping these things in mind, in this order:
3773 * 1) keep things fair between processes/task groups
3774 * 2) pick the "next" process, since someone really wants that to run
3775 * 3) pick the "last" process, for cache locality
3776 * 4) do not run the "skip" process, if something else is available
3777 */
3778static struct sched_entity *
3779pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3780{
3781	struct sched_entity *left = __pick_first_entity(cfs_rq);
3782	struct sched_entity *se;
3783
3784	/*
3785	 * If curr is set we have to see if its left of the leftmost entity
3786	 * still in the tree, provided there was anything in the tree at all.
3787	 */
3788	if (!left || (curr && entity_before(curr, left)))
3789		left = curr;
3790
3791	se = left; /* ideally we run the leftmost entity */
3792
3793	/*
3794	 * Avoid running the skip buddy, if running something else can
3795	 * be done without getting too unfair.
3796	 */
3797	if (cfs_rq->skip == se) {
3798		struct sched_entity *second;
3799
3800		if (se == curr) {
3801			second = __pick_first_entity(cfs_rq);
3802		} else {
3803			second = __pick_next_entity(se);
3804			if (!second || (curr && entity_before(curr, second)))
3805				second = curr;
3806		}
3807
3808		if (second && wakeup_preempt_entity(second, left) < 1)
3809			se = second;
3810	}
3811
3812	/*
3813	 * Prefer last buddy, try to return the CPU to a preempted task.
3814	 */
3815	if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3816		se = cfs_rq->last;
3817
3818	/*
3819	 * Someone really wants this to run. If it's not unfair, run it.
3820	 */
3821	if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3822		se = cfs_rq->next;
3823
3824	clear_buddies(cfs_rq, se);
3825
3826	return se;
3827}
3828
3829static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3830
3831static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3832{
3833	/*
3834	 * If still on the runqueue then deactivate_task()
3835	 * was not called and update_curr() has to be done:
3836	 */
3837	if (prev->on_rq)
3838		update_curr(cfs_rq);
3839
3840	/* throttle cfs_rqs exceeding runtime */
3841	check_cfs_rq_runtime(cfs_rq);
3842
3843	check_spread(cfs_rq, prev);
3844
3845	if (prev->on_rq) {
3846		update_stats_wait_start(cfs_rq, prev);
3847		/* Put 'current' back into the tree. */
3848		__enqueue_entity(cfs_rq, prev);
3849		/* in !on_rq case, update occurred at dequeue */
3850		update_load_avg(prev, 0);
3851	}
3852	cfs_rq->curr = NULL;
3853}
3854
3855static void
3856entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3857{
3858	/*
3859	 * Update run-time statistics of the 'current'.
3860	 */
3861	update_curr(cfs_rq);
3862
3863	/*
3864	 * Ensure that runnable average is periodically updated.
3865	 */
3866	update_load_avg(curr, UPDATE_TG);
3867	update_cfs_shares(cfs_rq);
3868
3869#ifdef CONFIG_SCHED_HRTICK
3870	/*
3871	 * queued ticks are scheduled to match the slice, so don't bother
3872	 * validating it and just reschedule.
3873	 */
3874	if (queued) {
3875		resched_curr(rq_of(cfs_rq));
3876		return;
3877	}
3878	/*
3879	 * don't let the period tick interfere with the hrtick preemption
3880	 */
3881	if (!sched_feat(DOUBLE_TICK) &&
3882			hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3883		return;
3884#endif
3885
3886	if (cfs_rq->nr_running > 1)
3887		check_preempt_tick(cfs_rq, curr);
3888}
3889
3890
3891/**************************************************
3892 * CFS bandwidth control machinery
3893 */
3894
3895#ifdef CONFIG_CFS_BANDWIDTH
3896
3897#ifdef HAVE_JUMP_LABEL
3898static struct static_key __cfs_bandwidth_used;
3899
3900static inline bool cfs_bandwidth_used(void)
3901{
3902	return static_key_false(&__cfs_bandwidth_used);
3903}
3904
3905void cfs_bandwidth_usage_inc(void)
3906{
3907	static_key_slow_inc(&__cfs_bandwidth_used);
3908}
3909
3910void cfs_bandwidth_usage_dec(void)
3911{
3912	static_key_slow_dec(&__cfs_bandwidth_used);
3913}
3914#else /* HAVE_JUMP_LABEL */
3915static bool cfs_bandwidth_used(void)
3916{
3917	return true;
3918}
3919
3920void cfs_bandwidth_usage_inc(void) {}
3921void cfs_bandwidth_usage_dec(void) {}
3922#endif /* HAVE_JUMP_LABEL */
3923
3924/*
3925 * default period for cfs group bandwidth.
3926 * default: 0.1s, units: nanoseconds
3927 */
3928static inline u64 default_cfs_period(void)
3929{
3930	return 100000000ULL;
3931}
3932
3933static inline u64 sched_cfs_bandwidth_slice(void)
3934{
3935	return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3936}
3937
3938/*
3939 * Replenish runtime according to assigned quota and update expiration time.
3940 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3941 * additional synchronization around rq->lock.
3942 *
3943 * requires cfs_b->lock
3944 */
3945void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3946{
3947	u64 now;
3948
3949	if (cfs_b->quota == RUNTIME_INF)
3950		return;
3951
3952	now = sched_clock_cpu(smp_processor_id());
3953	cfs_b->runtime = cfs_b->quota;
3954	cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3955}
3956
3957static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3958{
3959	return &tg->cfs_bandwidth;
3960}
3961
3962/* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3963static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3964{
3965	if (unlikely(cfs_rq->throttle_count))
3966		return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
3967
3968	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3969}
3970
3971/* returns 0 on failure to allocate runtime */
3972static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
 
3973{
3974	struct task_group *tg = cfs_rq->tg;
3975	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3976	u64 amount = 0, min_amount, expires;
3977
3978	/* note: this is a positive sum as runtime_remaining <= 0 */
3979	min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3980
3981	raw_spin_lock(&cfs_b->lock);
3982	if (cfs_b->quota == RUNTIME_INF)
3983		amount = min_amount;
3984	else {
3985		start_cfs_bandwidth(cfs_b);
3986
3987		if (cfs_b->runtime > 0) {
3988			amount = min(cfs_b->runtime, min_amount);
3989			cfs_b->runtime -= amount;
3990			cfs_b->idle = 0;
3991		}
3992	}
3993	expires = cfs_b->runtime_expires;
3994	raw_spin_unlock(&cfs_b->lock);
3995
3996	cfs_rq->runtime_remaining += amount;
3997	/*
3998	 * we may have advanced our local expiration to account for allowed
3999	 * spread between our sched_clock and the one on which runtime was
4000	 * issued.
4001	 */
4002	if ((s64)(expires - cfs_rq->runtime_expires) > 0)
4003		cfs_rq->runtime_expires = expires;
4004
4005	return cfs_rq->runtime_remaining > 0;
4006}
4007
4008/*
4009 * Note: This depends on the synchronization provided by sched_clock and the
4010 * fact that rq->clock snapshots this value.
4011 */
4012static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4013{
4014	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
 
4015
4016	/* if the deadline is ahead of our clock, nothing to do */
4017	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
4018		return;
4019
4020	if (cfs_rq->runtime_remaining < 0)
4021		return;
4022
4023	/*
4024	 * If the local deadline has passed we have to consider the
4025	 * possibility that our sched_clock is 'fast' and the global deadline
4026	 * has not truly expired.
4027	 *
4028	 * Fortunately we can check determine whether this the case by checking
4029	 * whether the global deadline has advanced. It is valid to compare
4030	 * cfs_b->runtime_expires without any locks since we only care about
4031	 * exact equality, so a partial write will still work.
4032	 */
4033
4034	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
4035		/* extend local deadline, drift is bounded above by 2 ticks */
4036		cfs_rq->runtime_expires += TICK_NSEC;
4037	} else {
4038		/* global deadline is ahead, expiration has passed */
4039		cfs_rq->runtime_remaining = 0;
4040	}
4041}
4042
4043static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4044{
4045	/* dock delta_exec before expiring quota (as it could span periods) */
4046	cfs_rq->runtime_remaining -= delta_exec;
4047	expire_cfs_rq_runtime(cfs_rq);
4048
4049	if (likely(cfs_rq->runtime_remaining > 0))
4050		return;
4051
 
 
4052	/*
4053	 * if we're unable to extend our runtime we resched so that the active
4054	 * hierarchy can be throttled
4055	 */
4056	if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
4057		resched_curr(rq_of(cfs_rq));
4058}
4059
4060static __always_inline
4061void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4062{
4063	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
4064		return;
4065
4066	__account_cfs_rq_runtime(cfs_rq, delta_exec);
4067}
4068
4069static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4070{
4071	return cfs_bandwidth_used() && cfs_rq->throttled;
4072}
4073
4074/* check whether cfs_rq, or any parent, is throttled */
4075static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4076{
4077	return cfs_bandwidth_used() && cfs_rq->throttle_count;
4078}
4079
4080/*
4081 * Ensure that neither of the group entities corresponding to src_cpu or
4082 * dest_cpu are members of a throttled hierarchy when performing group
4083 * load-balance operations.
4084 */
4085static inline int throttled_lb_pair(struct task_group *tg,
4086				    int src_cpu, int dest_cpu)
4087{
4088	struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
4089
4090	src_cfs_rq = tg->cfs_rq[src_cpu];
4091	dest_cfs_rq = tg->cfs_rq[dest_cpu];
4092
4093	return throttled_hierarchy(src_cfs_rq) ||
4094	       throttled_hierarchy(dest_cfs_rq);
4095}
4096
4097/* updated child weight may affect parent so we have to do this bottom up */
4098static int tg_unthrottle_up(struct task_group *tg, void *data)
4099{
4100	struct rq *rq = data;
4101	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4102
4103	cfs_rq->throttle_count--;
4104	if (!cfs_rq->throttle_count) {
4105		/* adjust cfs_rq_clock_task() */
4106		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
4107					     cfs_rq->throttled_clock_task;
 
 
 
 
4108	}
4109
4110	return 0;
4111}
4112
4113static int tg_throttle_down(struct task_group *tg, void *data)
4114{
4115	struct rq *rq = data;
4116	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4117
4118	/* group is entering throttled state, stop time */
4119	if (!cfs_rq->throttle_count)
4120		cfs_rq->throttled_clock_task = rq_clock_task(rq);
 
 
4121	cfs_rq->throttle_count++;
4122
4123	return 0;
4124}
4125
4126static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
4127{
4128	struct rq *rq = rq_of(cfs_rq);
4129	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4130	struct sched_entity *se;
4131	long task_delta, dequeue = 1;
4132	bool empty;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4133
4134	se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
4135
4136	/* freeze hierarchy runnable averages while throttled */
4137	rcu_read_lock();
4138	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
4139	rcu_read_unlock();
4140
4141	task_delta = cfs_rq->h_nr_running;
 
4142	for_each_sched_entity(se) {
4143		struct cfs_rq *qcfs_rq = cfs_rq_of(se);
4144		/* throttled entity or throttle-on-deactivate */
4145		if (!se->on_rq)
4146			break;
4147
4148		if (dequeue)
4149			dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
 
 
 
 
 
4150		qcfs_rq->h_nr_running -= task_delta;
 
4151
4152		if (qcfs_rq->load.weight)
4153			dequeue = 0;
4154	}
4155
4156	if (!se)
4157		sub_nr_running(rq, task_delta);
4158
4159	cfs_rq->throttled = 1;
4160	cfs_rq->throttled_clock = rq_clock(rq);
4161	raw_spin_lock(&cfs_b->lock);
4162	empty = list_empty(&cfs_b->throttled_cfs_rq);
4163
4164	/*
4165	 * Add to the _head_ of the list, so that an already-started
4166	 * distribute_cfs_runtime will not see us
4167	 */
4168	list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
4169
4170	/*
4171	 * If we're the first throttled task, make sure the bandwidth
4172	 * timer is running.
4173	 */
4174	if (empty)
4175		start_cfs_bandwidth(cfs_b);
4176
4177	raw_spin_unlock(&cfs_b->lock);
4178}
4179
4180void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
4181{
4182	struct rq *rq = rq_of(cfs_rq);
4183	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4184	struct sched_entity *se;
4185	int enqueue = 1;
4186	long task_delta;
4187
4188	se = cfs_rq->tg->se[cpu_of(rq)];
4189
4190	cfs_rq->throttled = 0;
4191
4192	update_rq_clock(rq);
4193
4194	raw_spin_lock(&cfs_b->lock);
4195	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
4196	list_del_rcu(&cfs_rq->throttled_list);
4197	raw_spin_unlock(&cfs_b->lock);
4198
4199	/* update hierarchical throttle state */
4200	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
4201
4202	if (!cfs_rq->load.weight)
4203		return;
4204
4205	task_delta = cfs_rq->h_nr_running;
 
4206	for_each_sched_entity(se) {
4207		if (se->on_rq)
4208			enqueue = 0;
 
 
4209
 
 
 
 
 
 
 
 
 
4210		cfs_rq = cfs_rq_of(se);
4211		if (enqueue)
4212			enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
 
 
4213		cfs_rq->h_nr_running += task_delta;
 
4214
 
 
4215		if (cfs_rq_throttled(cfs_rq))
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4216			break;
4217	}
4218
4219	if (!se)
4220		add_nr_running(rq, task_delta);
4221
4222	/* determine whether we need to wake up potentially idle cpu */
4223	if (rq->curr == rq->idle && rq->cfs.nr_running)
4224		resched_curr(rq);
4225}
4226
4227static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
4228		u64 remaining, u64 expires)
4229{
4230	struct cfs_rq *cfs_rq;
4231	u64 runtime;
4232	u64 starting_runtime = remaining;
4233
4234	rcu_read_lock();
4235	list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
4236				throttled_list) {
4237		struct rq *rq = rq_of(cfs_rq);
 
4238
4239		raw_spin_lock(&rq->lock);
4240		if (!cfs_rq_throttled(cfs_rq))
4241			goto next;
4242
 
 
 
 
4243		runtime = -cfs_rq->runtime_remaining + 1;
4244		if (runtime > remaining)
4245			runtime = remaining;
4246		remaining -= runtime;
 
 
4247
4248		cfs_rq->runtime_remaining += runtime;
4249		cfs_rq->runtime_expires = expires;
4250
4251		/* we check whether we're throttled above */
4252		if (cfs_rq->runtime_remaining > 0)
4253			unthrottle_cfs_rq(cfs_rq);
4254
4255next:
4256		raw_spin_unlock(&rq->lock);
4257
4258		if (!remaining)
4259			break;
4260	}
4261	rcu_read_unlock();
4262
4263	return starting_runtime - remaining;
4264}
4265
4266/*
4267 * Responsible for refilling a task_group's bandwidth and unthrottling its
4268 * cfs_rqs as appropriate. If there has been no activity within the last
4269 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
4270 * used to track this state.
4271 */
4272static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
4273{
4274	u64 runtime, runtime_expires;
4275	int throttled;
4276
4277	/* no need to continue the timer with no bandwidth constraint */
4278	if (cfs_b->quota == RUNTIME_INF)
4279		goto out_deactivate;
4280
4281	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4282	cfs_b->nr_periods += overrun;
4283
4284	/*
4285	 * idle depends on !throttled (for the case of a large deficit), and if
4286	 * we're going inactive then everything else can be deferred
4287	 */
4288	if (cfs_b->idle && !throttled)
4289		goto out_deactivate;
4290
4291	__refill_cfs_bandwidth_runtime(cfs_b);
4292
4293	if (!throttled) {
4294		/* mark as potentially idle for the upcoming period */
4295		cfs_b->idle = 1;
4296		return 0;
4297	}
4298
4299	/* account preceding periods in which throttling occurred */
4300	cfs_b->nr_throttled += overrun;
4301
4302	runtime_expires = cfs_b->runtime_expires;
4303
4304	/*
4305	 * This check is repeated as we are holding onto the new bandwidth while
4306	 * we unthrottle. This can potentially race with an unthrottled group
4307	 * trying to acquire new bandwidth from the global pool. This can result
4308	 * in us over-using our runtime if it is all used during this loop, but
4309	 * only by limited amounts in that extreme case.
4310	 */
4311	while (throttled && cfs_b->runtime > 0) {
4312		runtime = cfs_b->runtime;
4313		raw_spin_unlock(&cfs_b->lock);
4314		/* we can't nest cfs_b->lock while distributing bandwidth */
4315		runtime = distribute_cfs_runtime(cfs_b, runtime,
4316						 runtime_expires);
4317		raw_spin_lock(&cfs_b->lock);
4318
4319		throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4320
4321		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4322	}
4323
4324	/*
4325	 * While we are ensured activity in the period following an
4326	 * unthrottle, this also covers the case in which the new bandwidth is
4327	 * insufficient to cover the existing bandwidth deficit.  (Forcing the
4328	 * timer to remain active while there are any throttled entities.)
4329	 */
4330	cfs_b->idle = 0;
4331
4332	return 0;
4333
4334out_deactivate:
4335	return 1;
4336}
4337
4338/* a cfs_rq won't donate quota below this amount */
4339static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
4340/* minimum remaining period time to redistribute slack quota */
4341static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
4342/* how long we wait to gather additional slack before distributing */
4343static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
4344
4345/*
4346 * Are we near the end of the current quota period?
4347 *
4348 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4349 * hrtimer base being cleared by hrtimer_start. In the case of
4350 * migrate_hrtimers, base is never cleared, so we are fine.
4351 */
4352static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
4353{
4354	struct hrtimer *refresh_timer = &cfs_b->period_timer;
4355	u64 remaining;
4356
4357	/* if the call-back is running a quota refresh is already occurring */
4358	if (hrtimer_callback_running(refresh_timer))
4359		return 1;
4360
4361	/* is a quota refresh about to occur? */
4362	remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
4363	if (remaining < min_expire)
4364		return 1;
4365
4366	return 0;
4367}
4368
4369static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
4370{
4371	u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
4372
4373	/* if there's a quota refresh soon don't bother with slack */
4374	if (runtime_refresh_within(cfs_b, min_left))
4375		return;
4376
 
 
 
 
 
4377	hrtimer_start(&cfs_b->slack_timer,
4378			ns_to_ktime(cfs_bandwidth_slack_period),
4379			HRTIMER_MODE_REL);
4380}
4381
4382/* we know any runtime found here is valid as update_curr() precedes return */
4383static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4384{
4385	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4386	s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
4387
4388	if (slack_runtime <= 0)
4389		return;
4390
4391	raw_spin_lock(&cfs_b->lock);
4392	if (cfs_b->quota != RUNTIME_INF &&
4393	    cfs_rq->runtime_expires == cfs_b->runtime_expires) {
4394		cfs_b->runtime += slack_runtime;
4395
4396		/* we are under rq->lock, defer unthrottling using a timer */
4397		if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
4398		    !list_empty(&cfs_b->throttled_cfs_rq))
4399			start_cfs_slack_bandwidth(cfs_b);
4400	}
4401	raw_spin_unlock(&cfs_b->lock);
4402
4403	/* even if it's not valid for return we don't want to try again */
4404	cfs_rq->runtime_remaining -= slack_runtime;
4405}
4406
4407static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4408{
4409	if (!cfs_bandwidth_used())
4410		return;
4411
4412	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4413		return;
4414
4415	__return_cfs_rq_runtime(cfs_rq);
4416}
4417
4418/*
4419 * This is done with a timer (instead of inline with bandwidth return) since
4420 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
4421 */
4422static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
4423{
4424	u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
4425	u64 expires;
4426
4427	/* confirm we're still not at a refresh boundary */
4428	raw_spin_lock(&cfs_b->lock);
 
 
4429	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
4430		raw_spin_unlock(&cfs_b->lock);
4431		return;
4432	}
4433
4434	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4435		runtime = cfs_b->runtime;
4436
4437	expires = cfs_b->runtime_expires;
4438	raw_spin_unlock(&cfs_b->lock);
4439
4440	if (!runtime)
4441		return;
4442
4443	runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
4444
4445	raw_spin_lock(&cfs_b->lock);
4446	if (expires == cfs_b->runtime_expires)
4447		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4448	raw_spin_unlock(&cfs_b->lock);
4449}
4450
4451/*
4452 * When a group wakes up we want to make sure that its quota is not already
4453 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
4454 * runtime as update_curr() throttling can not not trigger until it's on-rq.
4455 */
4456static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
4457{
4458	if (!cfs_bandwidth_used())
4459		return;
4460
4461	/* an active group must be handled by the update_curr()->put() path */
4462	if (!cfs_rq->runtime_enabled || cfs_rq->curr)
4463		return;
4464
4465	/* ensure the group is not already throttled */
4466	if (cfs_rq_throttled(cfs_rq))
4467		return;
4468
4469	/* update runtime allocation */
4470	account_cfs_rq_runtime(cfs_rq, 0);
4471	if (cfs_rq->runtime_remaining <= 0)
4472		throttle_cfs_rq(cfs_rq);
4473}
4474
4475static void sync_throttle(struct task_group *tg, int cpu)
4476{
4477	struct cfs_rq *pcfs_rq, *cfs_rq;
4478
4479	if (!cfs_bandwidth_used())
4480		return;
4481
4482	if (!tg->parent)
4483		return;
4484
4485	cfs_rq = tg->cfs_rq[cpu];
4486	pcfs_rq = tg->parent->cfs_rq[cpu];
4487
4488	cfs_rq->throttle_count = pcfs_rq->throttle_count;
4489	cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
4490}
4491
4492/* conditionally throttle active cfs_rq's from put_prev_entity() */
4493static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4494{
4495	if (!cfs_bandwidth_used())
4496		return false;
4497
4498	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4499		return false;
4500
4501	/*
4502	 * it's possible for a throttled entity to be forced into a running
4503	 * state (e.g. set_curr_task), in this case we're finished.
4504	 */
4505	if (cfs_rq_throttled(cfs_rq))
4506		return true;
4507
4508	throttle_cfs_rq(cfs_rq);
4509	return true;
4510}
4511
4512static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
4513{
4514	struct cfs_bandwidth *cfs_b =
4515		container_of(timer, struct cfs_bandwidth, slack_timer);
4516
4517	do_sched_cfs_slack_timer(cfs_b);
4518
4519	return HRTIMER_NORESTART;
4520}
4521
 
 
4522static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
4523{
4524	struct cfs_bandwidth *cfs_b =
4525		container_of(timer, struct cfs_bandwidth, period_timer);
 
4526	int overrun;
4527	int idle = 0;
 
4528
4529	raw_spin_lock(&cfs_b->lock);
4530	for (;;) {
4531		overrun = hrtimer_forward_now(timer, cfs_b->period);
4532		if (!overrun)
4533			break;
4534
4535		idle = do_sched_cfs_period_timer(cfs_b, overrun);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4536	}
4537	if (idle)
4538		cfs_b->period_active = 0;
4539	raw_spin_unlock(&cfs_b->lock);
4540
4541	return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
4542}
4543
4544void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4545{
4546	raw_spin_lock_init(&cfs_b->lock);
4547	cfs_b->runtime = 0;
4548	cfs_b->quota = RUNTIME_INF;
4549	cfs_b->period = ns_to_ktime(default_cfs_period());
4550
4551	INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
4552	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4553	cfs_b->period_timer.function = sched_cfs_period_timer;
4554	hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
4555	cfs_b->slack_timer.function = sched_cfs_slack_timer;
 
4556}
4557
4558static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4559{
4560	cfs_rq->runtime_enabled = 0;
4561	INIT_LIST_HEAD(&cfs_rq->throttled_list);
4562}
4563
4564void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4565{
4566	lockdep_assert_held(&cfs_b->lock);
4567
4568	if (!cfs_b->period_active) {
4569		cfs_b->period_active = 1;
4570		hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
4571		hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4572	}
 
4573}
4574
4575static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4576{
4577	/* init_cfs_bandwidth() was not called */
4578	if (!cfs_b->throttled_cfs_rq.next)
4579		return;
4580
4581	hrtimer_cancel(&cfs_b->period_timer);
4582	hrtimer_cancel(&cfs_b->slack_timer);
4583}
4584
 
 
 
 
 
 
 
 
4585static void __maybe_unused update_runtime_enabled(struct rq *rq)
4586{
4587	struct cfs_rq *cfs_rq;
 
 
4588
4589	for_each_leaf_cfs_rq(rq, cfs_rq) {
4590		struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
 
 
4591
4592		raw_spin_lock(&cfs_b->lock);
4593		cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
4594		raw_spin_unlock(&cfs_b->lock);
4595	}
 
4596}
4597
 
4598static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4599{
4600	struct cfs_rq *cfs_rq;
 
 
 
 
 
 
4601
4602	for_each_leaf_cfs_rq(rq, cfs_rq) {
4603		if (!cfs_rq->runtime_enabled)
4604			continue;
4605
4606		/*
4607		 * clock_task is not advancing so we just need to make sure
4608		 * there's some valid quota amount
4609		 */
4610		cfs_rq->runtime_remaining = 1;
4611		/*
4612		 * Offline rq is schedulable till cpu is completely disabled
4613		 * in take_cpu_down(), so we prevent new cfs throttling here.
4614		 */
4615		cfs_rq->runtime_enabled = 0;
4616
4617		if (cfs_rq_throttled(cfs_rq))
4618			unthrottle_cfs_rq(cfs_rq);
4619	}
 
4620}
4621
4622#else /* CONFIG_CFS_BANDWIDTH */
4623static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
 
4624{
4625	return rq_clock_task(rq_of(cfs_rq));
4626}
4627
4628static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4629static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4630static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4631static inline void sync_throttle(struct task_group *tg, int cpu) {}
4632static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4633
4634static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4635{
4636	return 0;
4637}
4638
4639static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4640{
4641	return 0;
4642}
4643
4644static inline int throttled_lb_pair(struct task_group *tg,
4645				    int src_cpu, int dest_cpu)
4646{
4647	return 0;
4648}
4649
4650void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4651
4652#ifdef CONFIG_FAIR_GROUP_SCHED
4653static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4654#endif
4655
4656static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4657{
4658	return NULL;
4659}
4660static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4661static inline void update_runtime_enabled(struct rq *rq) {}
4662static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4663
4664#endif /* CONFIG_CFS_BANDWIDTH */
4665
4666/**************************************************
4667 * CFS operations on tasks:
4668 */
4669
4670#ifdef CONFIG_SCHED_HRTICK
4671static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4672{
4673	struct sched_entity *se = &p->se;
4674	struct cfs_rq *cfs_rq = cfs_rq_of(se);
4675
4676	SCHED_WARN_ON(task_rq(p) != rq);
4677
4678	if (rq->cfs.h_nr_running > 1) {
4679		u64 slice = sched_slice(cfs_rq, se);
4680		u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4681		s64 delta = slice - ran;
4682
4683		if (delta < 0) {
4684			if (rq->curr == p)
4685				resched_curr(rq);
4686			return;
4687		}
4688		hrtick_start(rq, delta);
4689	}
4690}
4691
4692/*
4693 * called from enqueue/dequeue and updates the hrtick when the
4694 * current task is from our class and nr_running is low enough
4695 * to matter.
4696 */
4697static void hrtick_update(struct rq *rq)
4698{
4699	struct task_struct *curr = rq->curr;
4700
4701	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4702		return;
4703
4704	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4705		hrtick_start_fair(rq, curr);
4706}
4707#else /* !CONFIG_SCHED_HRTICK */
4708static inline void
4709hrtick_start_fair(struct rq *rq, struct task_struct *p)
4710{
4711}
4712
4713static inline void hrtick_update(struct rq *rq)
4714{
4715}
4716#endif
4717
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4718/*
4719 * The enqueue_task method is called before nr_running is
4720 * increased. Here we update the fair scheduling stats and
4721 * then put the task into the rbtree:
4722 */
4723static void
4724enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4725{
4726	struct cfs_rq *cfs_rq;
4727	struct sched_entity *se = &p->se;
 
 
 
 
 
 
 
 
 
4728
4729	/*
4730	 * If in_iowait is set, the code below may not trigger any cpufreq
4731	 * utilization updates, so do it here explicitly with the IOWAIT flag
4732	 * passed.
4733	 */
4734	if (p->in_iowait)
4735		cpufreq_update_this_cpu(rq, SCHED_CPUFREQ_IOWAIT);
4736
4737	for_each_sched_entity(se) {
4738		if (se->on_rq)
4739			break;
4740		cfs_rq = cfs_rq_of(se);
4741		enqueue_entity(cfs_rq, se, flags);
4742
4743		/*
4744		 * end evaluation on encountering a throttled cfs_rq
4745		 *
4746		 * note: in the case of encountering a throttled cfs_rq we will
4747		 * post the final h_nr_running increment below.
4748		 */
4749		if (cfs_rq_throttled(cfs_rq))
4750			break;
4751		cfs_rq->h_nr_running++;
 
 
 
 
 
4752
4753		flags = ENQUEUE_WAKEUP;
4754	}
4755
4756	for_each_sched_entity(se) {
4757		cfs_rq = cfs_rq_of(se);
 
 
 
 
 
4758		cfs_rq->h_nr_running++;
 
4759
 
4760		if (cfs_rq_throttled(cfs_rq))
4761			break;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4762
4763		update_load_avg(se, UPDATE_TG);
4764		update_cfs_shares(cfs_rq);
 
4765	}
4766
4767	if (!se)
4768		add_nr_running(rq, 1);
4769
4770	hrtick_update(rq);
4771}
4772
4773static void set_next_buddy(struct sched_entity *se);
4774
4775/*
4776 * The dequeue_task method is called before nr_running is
4777 * decreased. We remove the task from the rbtree and
4778 * update the fair scheduling stats:
4779 */
4780static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4781{
4782	struct cfs_rq *cfs_rq;
4783	struct sched_entity *se = &p->se;
4784	int task_sleep = flags & DEQUEUE_SLEEP;
 
 
4785
4786	for_each_sched_entity(se) {
4787		cfs_rq = cfs_rq_of(se);
4788		dequeue_entity(cfs_rq, se, flags);
4789
4790		/*
4791		 * end evaluation on encountering a throttled cfs_rq
4792		 *
4793		 * note: in the case of encountering a throttled cfs_rq we will
4794		 * post the final h_nr_running decrement below.
4795		*/
4796		if (cfs_rq_throttled(cfs_rq))
4797			break;
4798		cfs_rq->h_nr_running--;
 
 
 
 
 
4799
4800		/* Don't dequeue parent if it has other entities besides us */
4801		if (cfs_rq->load.weight) {
4802			/* Avoid re-evaluating load for this entity: */
4803			se = parent_entity(se);
4804			/*
4805			 * Bias pick_next to pick a task from this cfs_rq, as
4806			 * p is sleeping when it is within its sched_slice.
4807			 */
4808			if (task_sleep && se && !throttled_hierarchy(cfs_rq))
4809				set_next_buddy(se);
4810			break;
4811		}
4812		flags |= DEQUEUE_SLEEP;
4813	}
4814
4815	for_each_sched_entity(se) {
4816		cfs_rq = cfs_rq_of(se);
 
 
 
 
 
4817		cfs_rq->h_nr_running--;
 
4818
 
4819		if (cfs_rq_throttled(cfs_rq))
4820			break;
4821
4822		update_load_avg(se, UPDATE_TG);
4823		update_cfs_shares(cfs_rq);
4824	}
4825
4826	if (!se)
4827		sub_nr_running(rq, 1);
 
 
 
 
4828
 
 
4829	hrtick_update(rq);
4830}
4831
4832#ifdef CONFIG_SMP
4833
4834/* Working cpumask for: load_balance, load_balance_newidle. */
4835DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
4836DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
4837
4838#ifdef CONFIG_NO_HZ_COMMON
4839/*
4840 * per rq 'load' arrray crap; XXX kill this.
4841 */
4842
4843/*
4844 * The exact cpuload calculated at every tick would be:
4845 *
4846 *   load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
4847 *
4848 * If a cpu misses updates for n ticks (as it was idle) and update gets
4849 * called on the n+1-th tick when cpu may be busy, then we have:
4850 *
4851 *   load_n   = (1 - 1/2^i)^n * load_0
4852 *   load_n+1 = (1 - 1/2^i)   * load_n + (1/2^i) * cur_load
4853 *
4854 * decay_load_missed() below does efficient calculation of
4855 *
4856 *   load' = (1 - 1/2^i)^n * load
4857 *
4858 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
4859 * This allows us to precompute the above in said factors, thereby allowing the
4860 * reduction of an arbitrary n in O(log_2 n) steps. (See also
4861 * fixed_power_int())
4862 *
4863 * The calculation is approximated on a 128 point scale.
4864 */
4865#define DEGRADE_SHIFT		7
4866
4867static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4868static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4869	{   0,   0,  0,  0,  0,  0, 0, 0 },
4870	{  64,  32,  8,  0,  0,  0, 0, 0 },
4871	{  96,  72, 40, 12,  1,  0, 0, 0 },
4872	{ 112,  98, 75, 43, 15,  1, 0, 0 },
4873	{ 120, 112, 98, 76, 45, 16, 2, 0 }
4874};
4875
4876/*
4877 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4878 * would be when CPU is idle and so we just decay the old load without
4879 * adding any new load.
4880 */
4881static unsigned long
4882decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4883{
4884	int j = 0;
4885
4886	if (!missed_updates)
4887		return load;
4888
4889	if (missed_updates >= degrade_zero_ticks[idx])
4890		return 0;
4891
4892	if (idx == 1)
4893		return load >> missed_updates;
4894
4895	while (missed_updates) {
4896		if (missed_updates % 2)
4897			load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
 
4898
4899		missed_updates >>= 1;
4900		j++;
4901	}
4902	return load;
4903}
4904#endif /* CONFIG_NO_HZ_COMMON */
4905
4906/**
4907 * __cpu_load_update - update the rq->cpu_load[] statistics
4908 * @this_rq: The rq to update statistics for
4909 * @this_load: The current load
4910 * @pending_updates: The number of missed updates
4911 *
4912 * Update rq->cpu_load[] statistics. This function is usually called every
4913 * scheduler tick (TICK_NSEC).
4914 *
4915 * This function computes a decaying average:
4916 *
4917 *   load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
4918 *
4919 * Because of NOHZ it might not get called on every tick which gives need for
4920 * the @pending_updates argument.
4921 *
4922 *   load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
4923 *             = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
4924 *             = A * (A * load[i]_n-2 + B) + B
4925 *             = A * (A * (A * load[i]_n-3 + B) + B) + B
4926 *             = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
4927 *             = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
4928 *             = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
4929 *             = (1 - 1/2^i)^n * (load[i]_0 - load) + load
4930 *
4931 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
4932 * any change in load would have resulted in the tick being turned back on.
4933 *
4934 * For regular NOHZ, this reduces to:
4935 *
4936 *   load[i]_n = (1 - 1/2^i)^n * load[i]_0
4937 *
4938 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
4939 * term.
4940 */
4941static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
4942			    unsigned long pending_updates)
4943{
4944	unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
4945	int i, scale;
4946
4947	this_rq->nr_load_updates++;
4948
4949	/* Update our load: */
4950	this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4951	for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4952		unsigned long old_load, new_load;
4953
4954		/* scale is effectively 1 << i now, and >> i divides by scale */
4955
4956		old_load = this_rq->cpu_load[i];
4957#ifdef CONFIG_NO_HZ_COMMON
4958		old_load = decay_load_missed(old_load, pending_updates - 1, i);
4959		if (tickless_load) {
4960			old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
4961			/*
4962			 * old_load can never be a negative value because a
4963			 * decayed tickless_load cannot be greater than the
4964			 * original tickless_load.
4965			 */
4966			old_load += tickless_load;
4967		}
4968#endif
4969		new_load = this_load;
4970		/*
4971		 * Round up the averaging division if load is increasing. This
4972		 * prevents us from getting stuck on 9 if the load is 10, for
4973		 * example.
4974		 */
4975		if (new_load > old_load)
4976			new_load += scale - 1;
4977
4978		this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4979	}
4980
4981	sched_avg_update(this_rq);
4982}
4983
4984/* Used instead of source_load when we know the type == 0 */
4985static unsigned long weighted_cpuload(const int cpu)
4986{
4987	return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4988}
4989
4990#ifdef CONFIG_NO_HZ_COMMON
4991/*
4992 * There is no sane way to deal with nohz on smp when using jiffies because the
4993 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4994 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4995 *
4996 * Therefore we need to avoid the delta approach from the regular tick when
4997 * possible since that would seriously skew the load calculation. This is why we
4998 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
4999 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
5000 * loop exit, nohz_idle_balance, nohz full exit...)
5001 *
5002 * This means we might still be one tick off for nohz periods.
5003 */
5004
5005static void cpu_load_update_nohz(struct rq *this_rq,
5006				 unsigned long curr_jiffies,
5007				 unsigned long load)
5008{
5009	unsigned long pending_updates;
5010
5011	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
5012	if (pending_updates) {
5013		this_rq->last_load_update_tick = curr_jiffies;
5014		/*
5015		 * In the regular NOHZ case, we were idle, this means load 0.
5016		 * In the NOHZ_FULL case, we were non-idle, we should consider
5017		 * its weighted load.
5018		 */
5019		cpu_load_update(this_rq, load, pending_updates);
5020	}
5021}
5022
5023/*
5024 * Called from nohz_idle_balance() to update the load ratings before doing the
5025 * idle balance.
5026 */
5027static void cpu_load_update_idle(struct rq *this_rq)
5028{
5029	/*
5030	 * bail if there's load or we're actually up-to-date.
5031	 */
5032	if (weighted_cpuload(cpu_of(this_rq)))
5033		return;
5034
5035	cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
5036}
5037
5038/*
5039 * Record CPU load on nohz entry so we know the tickless load to account
5040 * on nohz exit. cpu_load[0] happens then to be updated more frequently
5041 * than other cpu_load[idx] but it should be fine as cpu_load readers
5042 * shouldn't rely into synchronized cpu_load[*] updates.
5043 */
5044void cpu_load_update_nohz_start(void)
5045{
5046	struct rq *this_rq = this_rq();
 
5047
5048	/*
5049	 * This is all lockless but should be fine. If weighted_cpuload changes
5050	 * concurrently we'll exit nohz. And cpu_load write can race with
5051	 * cpu_load_update_idle() but both updater would be writing the same.
5052	 */
5053	this_rq->cpu_load[0] = weighted_cpuload(cpu_of(this_rq));
5054}
5055
5056/*
5057 * Account the tickless load in the end of a nohz frame.
5058 */
5059void cpu_load_update_nohz_stop(void)
5060{
5061	unsigned long curr_jiffies = READ_ONCE(jiffies);
5062	struct rq *this_rq = this_rq();
5063	unsigned long load;
5064
5065	if (curr_jiffies == this_rq->last_load_update_tick)
5066		return;
5067
5068	load = weighted_cpuload(cpu_of(this_rq));
5069	raw_spin_lock(&this_rq->lock);
5070	update_rq_clock(this_rq);
5071	cpu_load_update_nohz(this_rq, curr_jiffies, load);
5072	raw_spin_unlock(&this_rq->lock);
5073}
5074#else /* !CONFIG_NO_HZ_COMMON */
5075static inline void cpu_load_update_nohz(struct rq *this_rq,
5076					unsigned long curr_jiffies,
5077					unsigned long load) { }
5078#endif /* CONFIG_NO_HZ_COMMON */
5079
5080static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load)
5081{
5082#ifdef CONFIG_NO_HZ_COMMON
5083	/* See the mess around cpu_load_update_nohz(). */
5084	this_rq->last_load_update_tick = READ_ONCE(jiffies);
5085#endif
5086	cpu_load_update(this_rq, load, 1);
5087}
5088
5089/*
5090 * Called from scheduler_tick()
5091 */
5092void cpu_load_update_active(struct rq *this_rq)
5093{
5094	unsigned long load = weighted_cpuload(cpu_of(this_rq));
5095
5096	if (tick_nohz_tick_stopped())
5097		cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
5098	else
5099		cpu_load_update_periodic(this_rq, load);
5100}
5101
5102/*
5103 * Return a low guess at the load of a migration-source cpu weighted
5104 * according to the scheduling class and "nice" value.
5105 *
5106 * We want to under-estimate the load of migration sources, to
5107 * balance conservatively.
5108 */
5109static unsigned long source_load(int cpu, int type)
5110{
5111	struct rq *rq = cpu_rq(cpu);
5112	unsigned long total = weighted_cpuload(cpu);
5113
5114	if (type == 0 || !sched_feat(LB_BIAS))
5115		return total;
5116
5117	return min(rq->cpu_load[type-1], total);
5118}
 
5119
5120/*
5121 * Return a high guess at the load of a migration-target cpu weighted
5122 * according to the scheduling class and "nice" value.
5123 */
5124static unsigned long target_load(int cpu, int type)
5125{
5126	struct rq *rq = cpu_rq(cpu);
5127	unsigned long total = weighted_cpuload(cpu);
5128
5129	if (type == 0 || !sched_feat(LB_BIAS))
5130		return total;
5131
5132	return max(rq->cpu_load[type-1], total);
5133}
5134
5135static unsigned long capacity_of(int cpu)
5136{
5137	return cpu_rq(cpu)->cpu_capacity;
5138}
5139
5140static unsigned long capacity_orig_of(int cpu)
5141{
5142	return cpu_rq(cpu)->cpu_capacity_orig;
5143}
5144
5145static unsigned long cpu_avg_load_per_task(int cpu)
5146{
5147	struct rq *rq = cpu_rq(cpu);
5148	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
5149	unsigned long load_avg = weighted_cpuload(cpu);
5150
5151	if (nr_running)
5152		return load_avg / nr_running;
5153
5154	return 0;
5155}
5156
5157#ifdef CONFIG_FAIR_GROUP_SCHED
5158/*
5159 * effective_load() calculates the load change as seen from the root_task_group
5160 *
5161 * Adding load to a group doesn't make a group heavier, but can cause movement
5162 * of group shares between cpus. Assuming the shares were perfectly aligned one
5163 * can calculate the shift in shares.
5164 *
5165 * Calculate the effective load difference if @wl is added (subtracted) to @tg
5166 * on this @cpu and results in a total addition (subtraction) of @wg to the
5167 * total group weight.
5168 *
5169 * Given a runqueue weight distribution (rw_i) we can compute a shares
5170 * distribution (s_i) using:
5171 *
5172 *   s_i = rw_i / \Sum rw_j						(1)
5173 *
5174 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
5175 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
5176 * shares distribution (s_i):
5177 *
5178 *   rw_i = {   2,   4,   1,   0 }
5179 *   s_i  = { 2/7, 4/7, 1/7,   0 }
5180 *
5181 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
5182 * task used to run on and the CPU the waker is running on), we need to
5183 * compute the effect of waking a task on either CPU and, in case of a sync
5184 * wakeup, compute the effect of the current task going to sleep.
5185 *
5186 * So for a change of @wl to the local @cpu with an overall group weight change
5187 * of @wl we can compute the new shares distribution (s'_i) using:
5188 *
5189 *   s'_i = (rw_i + @wl) / (@wg + \Sum rw_j)				(2)
5190 *
5191 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
5192 * differences in waking a task to CPU 0. The additional task changes the
5193 * weight and shares distributions like:
5194 *
5195 *   rw'_i = {   3,   4,   1,   0 }
5196 *   s'_i  = { 3/8, 4/8, 1/8,   0 }
5197 *
5198 * We can then compute the difference in effective weight by using:
5199 *
5200 *   dw_i = S * (s'_i - s_i)						(3)
5201 *
5202 * Where 'S' is the group weight as seen by its parent.
5203 *
5204 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
5205 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
5206 * 4/7) times the weight of the group.
5207 */
5208static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
5209{
5210	struct sched_entity *se = tg->se[cpu];
5211
5212	if (!tg->parent)	/* the trivial, non-cgroup case */
5213		return wl;
5214
5215	for_each_sched_entity(se) {
5216		struct cfs_rq *cfs_rq = se->my_q;
5217		long W, w = cfs_rq_load_avg(cfs_rq);
5218
5219		tg = cfs_rq->tg;
5220
5221		/*
5222		 * W = @wg + \Sum rw_j
5223		 */
5224		W = wg + atomic_long_read(&tg->load_avg);
5225
5226		/* Ensure \Sum rw_j >= rw_i */
5227		W -= cfs_rq->tg_load_avg_contrib;
5228		W += w;
5229
5230		/*
5231		 * w = rw_i + @wl
5232		 */
5233		w += wl;
5234
5235		/*
5236		 * wl = S * s'_i; see (2)
5237		 */
5238		if (W > 0 && w < W)
5239			wl = (w * (long)scale_load_down(tg->shares)) / W;
5240		else
5241			wl = scale_load_down(tg->shares);
5242
5243		/*
5244		 * Per the above, wl is the new se->load.weight value; since
5245		 * those are clipped to [MIN_SHARES, ...) do so now. See
5246		 * calc_cfs_shares().
5247		 */
5248		if (wl < MIN_SHARES)
5249			wl = MIN_SHARES;
5250
5251		/*
5252		 * wl = dw_i = S * (s'_i - s_i); see (3)
5253		 */
5254		wl -= se->avg.load_avg;
5255
5256		/*
5257		 * Recursively apply this logic to all parent groups to compute
5258		 * the final effective load change on the root group. Since
5259		 * only the @tg group gets extra weight, all parent groups can
5260		 * only redistribute existing shares. @wl is the shift in shares
5261		 * resulting from this level per the above.
5262		 */
5263		wg = 0;
5264	}
5265
5266	return wl;
5267}
5268#else
5269
5270static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
5271{
5272	return wl;
5273}
5274
5275#endif
5276
5277static void record_wakee(struct task_struct *p)
5278{
5279	/*
5280	 * Only decay a single time; tasks that have less then 1 wakeup per
5281	 * jiffy will not have built up many flips.
5282	 */
5283	if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
5284		current->wakee_flips >>= 1;
5285		current->wakee_flip_decay_ts = jiffies;
5286	}
5287
5288	if (current->last_wakee != p) {
5289		current->last_wakee = p;
5290		current->wakee_flips++;
5291	}
5292}
5293
5294/*
5295 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5296 *
5297 * A waker of many should wake a different task than the one last awakened
5298 * at a frequency roughly N times higher than one of its wakees.
5299 *
5300 * In order to determine whether we should let the load spread vs consolidating
5301 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
5302 * partner, and a factor of lls_size higher frequency in the other.
5303 *
5304 * With both conditions met, we can be relatively sure that the relationship is
5305 * non-monogamous, with partner count exceeding socket size.
5306 *
5307 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
5308 * whatever is irrelevant, spread criteria is apparent partner count exceeds
5309 * socket size.
5310 */
5311static int wake_wide(struct task_struct *p)
5312{
5313	unsigned int master = current->wakee_flips;
5314	unsigned int slave = p->wakee_flips;
5315	int factor = this_cpu_read(sd_llc_size);
5316
5317	if (master < slave)
5318		swap(master, slave);
5319	if (slave < factor || master < slave * factor)
5320		return 0;
5321	return 1;
5322}
5323
5324static int wake_affine(struct sched_domain *sd, struct task_struct *p,
5325		       int prev_cpu, int sync)
 
 
 
 
 
 
 
 
 
 
 
 
5326{
5327	s64 this_load, load;
5328	s64 this_eff_load, prev_eff_load;
5329	int idx, this_cpu;
5330	struct task_group *tg;
5331	unsigned long weight;
5332	int balanced;
5333
5334	idx	  = sd->wake_idx;
5335	this_cpu  = smp_processor_id();
5336	load	  = source_load(prev_cpu, idx);
5337	this_load = target_load(this_cpu, idx);
5338
5339	/*
5340	 * If sync wakeup then subtract the (maximum possible)
5341	 * effect of the currently running task from the load
5342	 * of the current CPU:
5343	 */
5344	if (sync) {
5345		tg = task_group(current);
5346		weight = current->se.avg.load_avg;
5347
5348		this_load += effective_load(tg, this_cpu, -weight, -weight);
5349		load += effective_load(tg, prev_cpu, 0, -weight);
5350	}
5351
5352	tg = task_group(p);
5353	weight = p->se.avg.load_avg;
5354
5355	/*
5356	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5357	 * due to the sync cause above having dropped this_load to 0, we'll
5358	 * always have an imbalance, but there's really nothing you can do
5359	 * about that, so that's good too.
5360	 *
5361	 * Otherwise check if either cpus are near enough in load to allow this
5362	 * task to be woken on this_cpu.
 
 
 
5363	 */
5364	this_eff_load = 100;
5365	this_eff_load *= capacity_of(prev_cpu);
5366
5367	prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
5368	prev_eff_load *= capacity_of(this_cpu);
5369
5370	if (this_load > 0) {
5371		this_eff_load *= this_load +
5372			effective_load(tg, this_cpu, weight, weight);
5373
5374		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
5375	}
5376
5377	balanced = this_eff_load <= prev_eff_load;
5378
5379	schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
5380
5381	if (!balanced)
5382		return 0;
5383
5384	schedstat_inc(sd->ttwu_move_affine);
5385	schedstat_inc(p->se.statistics.nr_wakeups_affine);
5386
5387	return 1;
5388}
5389
5390static inline int task_util(struct task_struct *p);
5391static int cpu_util_wake(int cpu, struct task_struct *p);
5392
5393static unsigned long capacity_spare_wake(int cpu, struct task_struct *p)
5394{
5395	return capacity_orig_of(cpu) - cpu_util_wake(cpu, p);
5396}
5397
5398/*
5399 * find_idlest_group finds and returns the least busy CPU group within the
5400 * domain.
5401 */
5402static struct sched_group *
5403find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5404		  int this_cpu, int sd_flag)
5405{
5406	struct sched_group *idlest = NULL, *group = sd->groups;
5407	struct sched_group *most_spare_sg = NULL;
5408	unsigned long min_runnable_load = ULONG_MAX, this_runnable_load = 0;
5409	unsigned long min_avg_load = ULONG_MAX, this_avg_load = 0;
5410	unsigned long most_spare = 0, this_spare = 0;
5411	int load_idx = sd->forkexec_idx;
5412	int imbalance_scale = 100 + (sd->imbalance_pct-100)/2;
5413	unsigned long imbalance = scale_load_down(NICE_0_LOAD) *
5414				(sd->imbalance_pct-100) / 100;
5415
5416	if (sd_flag & SD_BALANCE_WAKE)
5417		load_idx = sd->wake_idx;
5418
5419	do {
5420		unsigned long load, avg_load, runnable_load;
5421		unsigned long spare_cap, max_spare_cap;
5422		int local_group;
5423		int i;
5424
5425		/* Skip over this group if it has no CPUs allowed */
5426		if (!cpumask_intersects(sched_group_cpus(group),
5427					tsk_cpus_allowed(p)))
5428			continue;
5429
5430		local_group = cpumask_test_cpu(this_cpu,
5431					       sched_group_cpus(group));
5432
5433		/*
5434		 * Tally up the load of all CPUs in the group and find
5435		 * the group containing the CPU with most spare capacity.
5436		 */
5437		avg_load = 0;
5438		runnable_load = 0;
5439		max_spare_cap = 0;
5440
5441		for_each_cpu(i, sched_group_cpus(group)) {
5442			/* Bias balancing toward cpus of our domain */
5443			if (local_group)
5444				load = source_load(i, load_idx);
5445			else
5446				load = target_load(i, load_idx);
5447
5448			runnable_load += load;
5449
5450			avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs);
 
5451
5452			spare_cap = capacity_spare_wake(i, p);
 
5453
5454			if (spare_cap > max_spare_cap)
5455				max_spare_cap = spare_cap;
5456		}
5457
5458		/* Adjust by relative CPU capacity of the group */
5459		avg_load = (avg_load * SCHED_CAPACITY_SCALE) /
5460					group->sgc->capacity;
5461		runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) /
5462					group->sgc->capacity;
5463
5464		if (local_group) {
5465			this_runnable_load = runnable_load;
5466			this_avg_load = avg_load;
5467			this_spare = max_spare_cap;
5468		} else {
5469			if (min_runnable_load > (runnable_load + imbalance)) {
5470				/*
5471				 * The runnable load is significantly smaller
5472				 * so we can pick this new cpu
5473				 */
5474				min_runnable_load = runnable_load;
5475				min_avg_load = avg_load;
5476				idlest = group;
5477			} else if ((runnable_load < (min_runnable_load + imbalance)) &&
5478				   (100*min_avg_load > imbalance_scale*avg_load)) {
5479				/*
5480				 * The runnable loads are close so take the
5481				 * blocked load into account through avg_load.
5482				 */
5483				min_avg_load = avg_load;
5484				idlest = group;
5485			}
5486
5487			if (most_spare < max_spare_cap) {
5488				most_spare = max_spare_cap;
5489				most_spare_sg = group;
5490			}
5491		}
5492	} while (group = group->next, group != sd->groups);
5493
5494	/*
5495	 * The cross-over point between using spare capacity or least load
5496	 * is too conservative for high utilization tasks on partially
5497	 * utilized systems if we require spare_capacity > task_util(p),
5498	 * so we allow for some task stuffing by using
5499	 * spare_capacity > task_util(p)/2.
5500	 *
5501	 * Spare capacity can't be used for fork because the utilization has
5502	 * not been set yet, we must first select a rq to compute the initial
5503	 * utilization.
5504	 */
5505	if (sd_flag & SD_BALANCE_FORK)
5506		goto skip_spare;
5507
5508	if (this_spare > task_util(p) / 2 &&
5509	    imbalance_scale*this_spare > 100*most_spare)
5510		return NULL;
5511
5512	if (most_spare > task_util(p) / 2)
5513		return most_spare_sg;
 
 
5514
5515skip_spare:
5516	if (!idlest)
5517		return NULL;
5518
5519	if (min_runnable_load > (this_runnable_load + imbalance))
5520		return NULL;
5521
5522	if ((this_runnable_load < (min_runnable_load + imbalance)) &&
5523	     (100*this_avg_load < imbalance_scale*min_avg_load))
5524		return NULL;
5525
5526	return idlest;
 
 
5527}
5528
 
 
 
5529/*
5530 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5531 */
5532static int
5533find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5534{
5535	unsigned long load, min_load = ULONG_MAX;
5536	unsigned int min_exit_latency = UINT_MAX;
5537	u64 latest_idle_timestamp = 0;
5538	int least_loaded_cpu = this_cpu;
5539	int shallowest_idle_cpu = -1;
5540	int i;
5541
5542	/* Check if we have any choice: */
5543	if (group->group_weight == 1)
5544		return cpumask_first(sched_group_cpus(group));
5545
5546	/* Traverse only the allowed CPUs */
5547	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
5548		if (idle_cpu(i)) {
 
 
 
5549			struct rq *rq = cpu_rq(i);
5550			struct cpuidle_state *idle = idle_get_state(rq);
5551			if (idle && idle->exit_latency < min_exit_latency) {
5552				/*
5553				 * We give priority to a CPU whose idle state
5554				 * has the smallest exit latency irrespective
5555				 * of any idle timestamp.
5556				 */
5557				min_exit_latency = idle->exit_latency;
5558				latest_idle_timestamp = rq->idle_stamp;
5559				shallowest_idle_cpu = i;
5560			} else if ((!idle || idle->exit_latency == min_exit_latency) &&
5561				   rq->idle_stamp > latest_idle_timestamp) {
5562				/*
5563				 * If equal or no active idle state, then
5564				 * the most recently idled CPU might have
5565				 * a warmer cache.
5566				 */
5567				latest_idle_timestamp = rq->idle_stamp;
5568				shallowest_idle_cpu = i;
5569			}
5570		} else if (shallowest_idle_cpu == -1) {
5571			load = weighted_cpuload(i);
5572			if (load < min_load || (load == min_load && i == this_cpu)) {
5573				min_load = load;
5574				least_loaded_cpu = i;
5575			}
5576		}
5577	}
5578
5579	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5580}
5581
5582/*
5583 * Implement a for_each_cpu() variant that starts the scan at a given cpu
5584 * (@start), and wraps around.
5585 *
5586 * This is used to scan for idle CPUs; such that not all CPUs looking for an
5587 * idle CPU find the same CPU. The down-side is that tasks tend to cycle
5588 * through the LLC domain.
5589 *
5590 * Especially tbench is found sensitive to this.
5591 */
5592
5593static int cpumask_next_wrap(int n, const struct cpumask *mask, int start, int *wrapped)
5594{
5595	int next;
5596
5597again:
5598	next = find_next_bit(cpumask_bits(mask), nr_cpumask_bits, n+1);
5599
5600	if (*wrapped) {
5601		if (next >= start)
5602			return nr_cpumask_bits;
5603	} else {
5604		if (next >= nr_cpumask_bits) {
5605			*wrapped = 1;
5606			n = -1;
5607			goto again;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5608		}
5609	}
5610
5611	return next;
5612}
5613
5614#define for_each_cpu_wrap(cpu, mask, start, wrap)				\
5615	for ((wrap) = 0, (cpu) = (start)-1;					\
5616		(cpu) = cpumask_next_wrap((cpu), (mask), (start), &(wrap)),	\
5617		(cpu) < nr_cpumask_bits; )
5618
5619#ifdef CONFIG_SCHED_SMT
 
 
5620
5621static inline void set_idle_cores(int cpu, int val)
5622{
5623	struct sched_domain_shared *sds;
5624
5625	sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
5626	if (sds)
5627		WRITE_ONCE(sds->has_idle_cores, val);
5628}
5629
5630static inline bool test_idle_cores(int cpu, bool def)
5631{
5632	struct sched_domain_shared *sds;
5633
5634	sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
5635	if (sds)
5636		return READ_ONCE(sds->has_idle_cores);
5637
5638	return def;
5639}
5640
5641/*
5642 * Scans the local SMT mask to see if the entire core is idle, and records this
5643 * information in sd_llc_shared->has_idle_cores.
5644 *
5645 * Since SMT siblings share all cache levels, inspecting this limited remote
5646 * state should be fairly cheap.
5647 */
5648void __update_idle_core(struct rq *rq)
5649{
5650	int core = cpu_of(rq);
5651	int cpu;
5652
5653	rcu_read_lock();
5654	if (test_idle_cores(core, true))
5655		goto unlock;
5656
5657	for_each_cpu(cpu, cpu_smt_mask(core)) {
5658		if (cpu == core)
5659			continue;
5660
5661		if (!idle_cpu(cpu))
5662			goto unlock;
5663	}
5664
5665	set_idle_cores(core, 1);
5666unlock:
5667	rcu_read_unlock();
5668}
5669
5670/*
5671 * Scan the entire LLC domain for idle cores; this dynamically switches off if
5672 * there are no idle cores left in the system; tracked through
5673 * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
5674 */
5675static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
5676{
5677	struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
5678	int core, cpu, wrap;
5679
5680	if (!static_branch_likely(&sched_smt_present))
5681		return -1;
5682
5683	if (!test_idle_cores(target, false))
5684		return -1;
5685
5686	cpumask_and(cpus, sched_domain_span(sd), tsk_cpus_allowed(p));
5687
5688	for_each_cpu_wrap(core, cpus, target, wrap) {
5689		bool idle = true;
5690
5691		for_each_cpu(cpu, cpu_smt_mask(core)) {
5692			cpumask_clear_cpu(cpu, cpus);
5693			if (!idle_cpu(cpu))
5694				idle = false;
 
 
5695		}
 
5696
5697		if (idle)
5698			return core;
5699	}
5700
5701	/*
5702	 * Failed to find an idle core; stop looking for one.
5703	 */
5704	set_idle_cores(target, 0);
5705
5706	return -1;
5707}
5708
5709/*
5710 * Scan the local SMT mask for idle CPUs.
5711 */
5712static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
5713{
5714	int cpu;
5715
5716	if (!static_branch_likely(&sched_smt_present))
5717		return -1;
5718
5719	for_each_cpu(cpu, cpu_smt_mask(target)) {
5720		if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
5721			continue;
5722		if (idle_cpu(cpu))
5723			return cpu;
5724	}
5725
5726	return -1;
5727}
5728
5729#else /* CONFIG_SCHED_SMT */
5730
5731static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
5732{
5733	return -1;
5734}
5735
5736static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
5737{
5738	return -1;
5739}
5740
5741#endif /* CONFIG_SCHED_SMT */
5742
5743/*
5744 * Scan the LLC domain for idle CPUs; this is dynamically regulated by
5745 * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
5746 * average idle time for this rq (as found in rq->avg_idle).
5747 */
5748static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
5749{
 
5750	struct sched_domain *this_sd;
5751	u64 avg_cost, avg_idle = this_rq()->avg_idle;
5752	u64 time, cost;
5753	s64 delta;
5754	int cpu, wrap;
5755
5756	this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
5757	if (!this_sd)
5758		return -1;
5759
5760	avg_cost = this_sd->avg_scan_cost;
5761
5762	/*
5763	 * Due to large variance we need a large fuzz factor; hackbench in
5764	 * particularly is sensitive here.
5765	 */
5766	if ((avg_idle / 512) < avg_cost)
 
 
 
5767		return -1;
5768
5769	time = local_clock();
 
 
 
 
 
 
5770
5771	for_each_cpu_wrap(cpu, sched_domain_span(sd), target, wrap) {
5772		if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
5773			continue;
5774		if (idle_cpu(cpu))
 
 
 
 
5775			break;
5776	}
5777
5778	time = local_clock() - time;
5779	cost = this_sd->avg_scan_cost;
5780	delta = (s64)(time - cost) / 8;
5781	this_sd->avg_scan_cost += delta;
5782
5783	return cpu;
5784}
5785
5786/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5787 * Try and locate an idle core/thread in the LLC cache domain.
5788 */
5789static int select_idle_sibling(struct task_struct *p, int prev, int target)
5790{
5791	struct sched_domain *sd;
5792	int i;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5793
5794	if (idle_cpu(target))
 
5795		return target;
5796
5797	/*
5798	 * If the previous cpu is cache affine and idle, don't be stupid.
5799	 */
5800	if (prev != target && cpus_share_cache(prev, target) && idle_cpu(prev))
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5801		return prev;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5802
5803	sd = rcu_dereference(per_cpu(sd_llc, target));
5804	if (!sd)
5805		return target;
5806
5807	i = select_idle_core(p, sd, target);
5808	if ((unsigned)i < nr_cpumask_bits)
5809		return i;
5810
5811	i = select_idle_cpu(p, sd, target);
5812	if ((unsigned)i < nr_cpumask_bits)
5813		return i;
5814
5815	i = select_idle_smt(p, sd, target);
5816	if ((unsigned)i < nr_cpumask_bits)
5817		return i;
5818
5819	return target;
5820}
5821
5822/*
5823 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5824 * tasks. The unit of the return value must be the one of capacity so we can
5825 * compare the utilization with the capacity of the CPU that is available for
5826 * CFS task (ie cpu_capacity).
 
 
5827 *
5828 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
5829 * recent utilization of currently non-runnable tasks on a CPU. It represents
5830 * the amount of utilization of a CPU in the range [0..capacity_orig] where
5831 * capacity_orig is the cpu_capacity available at the highest frequency
5832 * (arch_scale_freq_capacity()).
5833 * The utilization of a CPU converges towards a sum equal to or less than the
5834 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
5835 * the running time on this CPU scaled by capacity_curr.
5836 *
 
 
 
 
 
 
 
 
5837 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
5838 * higher than capacity_orig because of unfortunate rounding in
5839 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
5840 * the average stabilizes with the new running time. We need to check that the
5841 * utilization stays within the range of [0..capacity_orig] and cap it if
5842 * necessary. Without utilization capping, a group could be seen as overloaded
5843 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
5844 * available capacity. We allow utilization to overshoot capacity_curr (but not
5845 * capacity_orig) as it useful for predicting the capacity required after task
5846 * migrations (scheduler-driven DVFS).
 
 
5847 */
5848static int cpu_util(int cpu)
5849{
5850	unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
5851	unsigned long capacity = capacity_orig_of(cpu);
5852
5853	return (util >= capacity) ? capacity : util;
5854}
5855
5856static inline int task_util(struct task_struct *p)
5857{
5858	return p->se.avg.util_avg;
 
5859}
5860
5861/*
5862 * cpu_util_wake: Compute cpu utilization with any contributions from
5863 * the waking task p removed.
 
 
 
 
 
 
 
 
 
5864 */
5865static int cpu_util_wake(int cpu, struct task_struct *p)
5866{
5867	unsigned long util, capacity;
 
5868
5869	/* Task has no contribution or is new */
5870	if (cpu != task_cpu(p) || !p->se.avg.last_update_time)
5871		return cpu_util(cpu);
5872
5873	capacity = capacity_orig_of(cpu);
5874	util = max_t(long, cpu_rq(cpu)->cfs.avg.util_avg - task_util(p), 0);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5875
5876	return (util >= capacity) ? capacity : util;
 
 
 
 
 
 
 
 
5877}
5878
5879/*
5880 * Disable WAKE_AFFINE in the case where task @p doesn't fit in the
5881 * capacity of either the waking CPU @cpu or the previous CPU @prev_cpu.
5882 *
5883 * In that case WAKE_AFFINE doesn't make sense and we'll let
5884 * BALANCE_WAKE sort things out.
5885 */
5886static int wake_cap(struct task_struct *p, int cpu, int prev_cpu)
5887{
5888	long min_cap, max_cap;
 
 
 
 
 
 
 
 
 
 
 
 
5889
5890	min_cap = min(capacity_orig_of(prev_cpu), capacity_orig_of(cpu));
5891	max_cap = cpu_rq(cpu)->rd->max_cpu_capacity;
5892
5893	/* Minimum capacity is close to max, no need to abort wake_affine */
5894	if (max_cap - min_cap < max_cap >> 3)
5895		return 0;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5896
5897	/* Bring task utilization in sync with prev_cpu */
5898	sync_entity_load_avg(&p->se);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5899
5900	return min_cap * 1024 < task_util(p) * capacity_margin;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5901}
5902
5903/*
5904 * select_task_rq_fair: Select target runqueue for the waking task in domains
5905 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5906 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5907 *
5908 * Balances load by selecting the idlest cpu in the idlest group, or under
5909 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5910 *
5911 * Returns the target cpu number.
5912 *
5913 * preempt must be disabled.
5914 */
5915static int
5916select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5917{
5918	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5919	int cpu = smp_processor_id();
5920	int new_cpu = prev_cpu;
5921	int want_affine = 0;
5922	int sync = wake_flags & WF_SYNC;
5923
5924	if (sd_flag & SD_BALANCE_WAKE) {
5925		record_wakee(p);
5926		want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu)
5927			      && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
 
 
 
 
 
 
 
5928	}
5929
5930	rcu_read_lock();
5931	for_each_domain(cpu, tmp) {
5932		if (!(tmp->flags & SD_LOAD_BALANCE))
5933			break;
5934
5935		/*
5936		 * If both cpu and prev_cpu are part of this domain,
5937		 * cpu is a valid SD_WAKE_AFFINE target.
5938		 */
5939		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
5940		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
5941			affine_sd = tmp;
 
 
 
5942			break;
5943		}
5944
5945		if (tmp->flags & sd_flag)
5946			sd = tmp;
5947		else if (!want_affine)
5948			break;
5949	}
5950
5951	if (affine_sd) {
5952		sd = NULL; /* Prefer wake_affine over balance flags */
5953		if (cpu != prev_cpu && wake_affine(affine_sd, p, prev_cpu, sync))
5954			new_cpu = cpu;
5955	}
5956
5957	if (!sd) {
5958		if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
5959			new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
5960
5961	} else while (sd) {
5962		struct sched_group *group;
5963		int weight;
5964
5965		if (!(sd->flags & sd_flag)) {
5966			sd = sd->child;
5967			continue;
5968		}
5969
5970		group = find_idlest_group(sd, p, cpu, sd_flag);
5971		if (!group) {
5972			sd = sd->child;
5973			continue;
5974		}
5975
5976		new_cpu = find_idlest_cpu(group, p, cpu);
5977		if (new_cpu == -1 || new_cpu == cpu) {
5978			/* Now try balancing at a lower domain level of cpu */
5979			sd = sd->child;
5980			continue;
5981		}
5982
5983		/* Now try balancing at a lower domain level of new_cpu */
5984		cpu = new_cpu;
5985		weight = sd->span_weight;
5986		sd = NULL;
5987		for_each_domain(cpu, tmp) {
5988			if (weight <= tmp->span_weight)
5989				break;
5990			if (tmp->flags & sd_flag)
5991				sd = tmp;
5992		}
5993		/* while loop will break here if sd == NULL */
5994	}
5995	rcu_read_unlock();
5996
5997	return new_cpu;
5998}
5999
 
 
6000/*
6001 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
6002 * cfs_rq_of(p) references at time of call are still valid and identify the
6003 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6004 */
6005static void migrate_task_rq_fair(struct task_struct *p)
6006{
6007	/*
6008	 * As blocked tasks retain absolute vruntime the migration needs to
6009	 * deal with this by subtracting the old and adding the new
6010	 * min_vruntime -- the latter is done by enqueue_entity() when placing
6011	 * the task on the new runqueue.
6012	 */
6013	if (p->state == TASK_WAKING) {
6014		struct sched_entity *se = &p->se;
6015		struct cfs_rq *cfs_rq = cfs_rq_of(se);
6016		u64 min_vruntime;
6017
6018#ifndef CONFIG_64BIT
6019		u64 min_vruntime_copy;
6020
6021		do {
6022			min_vruntime_copy = cfs_rq->min_vruntime_copy;
6023			smp_rmb();
6024			min_vruntime = cfs_rq->min_vruntime;
6025		} while (min_vruntime != min_vruntime_copy);
6026#else
6027		min_vruntime = cfs_rq->min_vruntime;
6028#endif
6029
6030		se->vruntime -= min_vruntime;
6031	}
6032
6033	/*
6034	 * We are supposed to update the task to "current" time, then its up to date
6035	 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
6036	 * what current time is, so simply throw away the out-of-date time. This
6037	 * will result in the wakee task is less decayed, but giving the wakee more
6038	 * load sounds not bad.
6039	 */
6040	remove_entity_load_avg(&p->se);
 
 
 
 
 
 
 
 
 
 
 
6041
6042	/* Tell new CPU we are migrated */
6043	p->se.avg.last_update_time = 0;
6044
6045	/* We have migrated, no longer consider this task hot */
6046	p->se.exec_start = 0;
 
 
6047}
6048
6049static void task_dead_fair(struct task_struct *p)
6050{
6051	remove_entity_load_avg(&p->se);
6052}
 
 
 
 
 
 
 
 
 
6053#endif /* CONFIG_SMP */
6054
6055static unsigned long
6056wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
6057{
6058	unsigned long gran = sysctl_sched_wakeup_granularity;
6059
6060	/*
6061	 * Since its curr running now, convert the gran from real-time
6062	 * to virtual-time in his units.
6063	 *
6064	 * By using 'se' instead of 'curr' we penalize light tasks, so
6065	 * they get preempted easier. That is, if 'se' < 'curr' then
6066	 * the resulting gran will be larger, therefore penalizing the
6067	 * lighter, if otoh 'se' > 'curr' then the resulting gran will
6068	 * be smaller, again penalizing the lighter task.
6069	 *
6070	 * This is especially important for buddies when the leftmost
6071	 * task is higher priority than the buddy.
6072	 */
6073	return calc_delta_fair(gran, se);
6074}
6075
6076/*
6077 * Should 'se' preempt 'curr'.
6078 *
6079 *             |s1
6080 *        |s2
6081 *   |s3
6082 *         g
6083 *      |<--->|c
6084 *
6085 *  w(c, s1) = -1
6086 *  w(c, s2) =  0
6087 *  w(c, s3) =  1
6088 *
6089 */
6090static int
6091wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
6092{
6093	s64 gran, vdiff = curr->vruntime - se->vruntime;
6094
6095	if (vdiff <= 0)
6096		return -1;
6097
6098	gran = wakeup_gran(curr, se);
6099	if (vdiff > gran)
6100		return 1;
6101
6102	return 0;
6103}
6104
6105static void set_last_buddy(struct sched_entity *se)
6106{
6107	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
6108		return;
6109
6110	for_each_sched_entity(se)
 
 
6111		cfs_rq_of(se)->last = se;
 
6112}
6113
6114static void set_next_buddy(struct sched_entity *se)
6115{
6116	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
6117		return;
6118
6119	for_each_sched_entity(se)
 
 
6120		cfs_rq_of(se)->next = se;
 
6121}
6122
6123static void set_skip_buddy(struct sched_entity *se)
6124{
6125	for_each_sched_entity(se)
6126		cfs_rq_of(se)->skip = se;
6127}
6128
6129/*
6130 * Preempt the current task with a newly woken task if needed:
6131 */
6132static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
6133{
6134	struct task_struct *curr = rq->curr;
6135	struct sched_entity *se = &curr->se, *pse = &p->se;
6136	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6137	int scale = cfs_rq->nr_running >= sched_nr_latency;
6138	int next_buddy_marked = 0;
6139
6140	if (unlikely(se == pse))
6141		return;
6142
6143	/*
6144	 * This is possible from callers such as attach_tasks(), in which we
6145	 * unconditionally check_prempt_curr() after an enqueue (which may have
6146	 * lead to a throttle).  This both saves work and prevents false
6147	 * next-buddy nomination below.
6148	 */
6149	if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
6150		return;
6151
6152	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
6153		set_next_buddy(pse);
6154		next_buddy_marked = 1;
6155	}
6156
6157	/*
6158	 * We can come here with TIF_NEED_RESCHED already set from new task
6159	 * wake up path.
6160	 *
6161	 * Note: this also catches the edge-case of curr being in a throttled
6162	 * group (e.g. via set_curr_task), since update_curr() (in the
6163	 * enqueue of curr) will have resulted in resched being set.  This
6164	 * prevents us from potentially nominating it as a false LAST_BUDDY
6165	 * below.
6166	 */
6167	if (test_tsk_need_resched(curr))
6168		return;
6169
6170	/* Idle tasks are by definition preempted by non-idle tasks. */
6171	if (unlikely(curr->policy == SCHED_IDLE) &&
6172	    likely(p->policy != SCHED_IDLE))
6173		goto preempt;
6174
6175	/*
6176	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
6177	 * is driven by the tick):
6178	 */
6179	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
6180		return;
6181
6182	find_matching_se(&se, &pse);
6183	update_curr(cfs_rq_of(se));
6184	BUG_ON(!pse);
6185	if (wakeup_preempt_entity(se, pse) == 1) {
6186		/*
6187		 * Bias pick_next to pick the sched entity that is
6188		 * triggering this preemption.
6189		 */
6190		if (!next_buddy_marked)
6191			set_next_buddy(pse);
6192		goto preempt;
6193	}
6194
6195	return;
6196
6197preempt:
6198	resched_curr(rq);
6199	/*
6200	 * Only set the backward buddy when the current task is still
6201	 * on the rq. This can happen when a wakeup gets interleaved
6202	 * with schedule on the ->pre_schedule() or idle_balance()
6203	 * point, either of which can * drop the rq lock.
6204	 *
6205	 * Also, during early boot the idle thread is in the fair class,
6206	 * for obvious reasons its a bad idea to schedule back to it.
6207	 */
6208	if (unlikely(!se->on_rq || curr == rq->idle))
6209		return;
6210
6211	if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
6212		set_last_buddy(se);
6213}
6214
6215static struct task_struct *
6216pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct pin_cookie cookie)
6217{
6218	struct cfs_rq *cfs_rq = &rq->cfs;
6219	struct sched_entity *se;
6220	struct task_struct *p;
6221	int new_tasks;
6222
6223again:
6224#ifdef CONFIG_FAIR_GROUP_SCHED
6225	if (!cfs_rq->nr_running)
6226		goto idle;
6227
6228	if (prev->sched_class != &fair_sched_class)
 
6229		goto simple;
6230
6231	/*
6232	 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
6233	 * likely that a next task is from the same cgroup as the current.
6234	 *
6235	 * Therefore attempt to avoid putting and setting the entire cgroup
6236	 * hierarchy, only change the part that actually changes.
6237	 */
6238
6239	do {
6240		struct sched_entity *curr = cfs_rq->curr;
6241
6242		/*
6243		 * Since we got here without doing put_prev_entity() we also
6244		 * have to consider cfs_rq->curr. If it is still a runnable
6245		 * entity, update_curr() will update its vruntime, otherwise
6246		 * forget we've ever seen it.
6247		 */
6248		if (curr) {
6249			if (curr->on_rq)
6250				update_curr(cfs_rq);
6251			else
6252				curr = NULL;
6253
6254			/*
6255			 * This call to check_cfs_rq_runtime() will do the
6256			 * throttle and dequeue its entity in the parent(s).
6257			 * Therefore the 'simple' nr_running test will indeed
6258			 * be correct.
6259			 */
6260			if (unlikely(check_cfs_rq_runtime(cfs_rq)))
 
 
 
 
 
6261				goto simple;
 
6262		}
6263
6264		se = pick_next_entity(cfs_rq, curr);
6265		cfs_rq = group_cfs_rq(se);
6266	} while (cfs_rq);
6267
6268	p = task_of(se);
6269
6270	/*
6271	 * Since we haven't yet done put_prev_entity and if the selected task
6272	 * is a different task than we started out with, try and touch the
6273	 * least amount of cfs_rqs.
6274	 */
6275	if (prev != p) {
6276		struct sched_entity *pse = &prev->se;
6277
6278		while (!(cfs_rq = is_same_group(se, pse))) {
6279			int se_depth = se->depth;
6280			int pse_depth = pse->depth;
6281
6282			if (se_depth <= pse_depth) {
6283				put_prev_entity(cfs_rq_of(pse), pse);
6284				pse = parent_entity(pse);
6285			}
6286			if (se_depth >= pse_depth) {
6287				set_next_entity(cfs_rq_of(se), se);
6288				se = parent_entity(se);
6289			}
6290		}
6291
6292		put_prev_entity(cfs_rq, pse);
6293		set_next_entity(cfs_rq, se);
6294	}
6295
6296	if (hrtick_enabled(rq))
6297		hrtick_start_fair(rq, p);
6298
6299	return p;
6300simple:
6301	cfs_rq = &rq->cfs;
6302#endif
6303
6304	if (!cfs_rq->nr_running)
6305		goto idle;
6306
6307	put_prev_task(rq, prev);
6308
6309	do {
6310		se = pick_next_entity(cfs_rq, NULL);
6311		set_next_entity(cfs_rq, se);
6312		cfs_rq = group_cfs_rq(se);
6313	} while (cfs_rq);
6314
6315	p = task_of(se);
6316
 
 
 
 
 
 
 
 
 
 
6317	if (hrtick_enabled(rq))
6318		hrtick_start_fair(rq, p);
6319
 
 
6320	return p;
6321
6322idle:
 
 
 
 
 
6323	/*
6324	 * This is OK, because current is on_cpu, which avoids it being picked
6325	 * for load-balance and preemption/IRQs are still disabled avoiding
6326	 * further scheduler activity on it and we're being very careful to
6327	 * re-start the picking loop.
6328	 */
6329	lockdep_unpin_lock(&rq->lock, cookie);
6330	new_tasks = idle_balance(rq);
6331	lockdep_repin_lock(&rq->lock, cookie);
6332	/*
6333	 * Because idle_balance() releases (and re-acquires) rq->lock, it is
6334	 * possible for any higher priority task to appear. In that case we
6335	 * must re-start the pick_next_entity() loop.
6336	 */
6337	if (new_tasks < 0)
6338		return RETRY_TASK;
6339
6340	if (new_tasks > 0)
6341		goto again;
6342
 
 
 
 
 
 
6343	return NULL;
6344}
6345
 
 
 
 
 
6346/*
6347 * Account for a descheduled task:
6348 */
6349static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
6350{
6351	struct sched_entity *se = &prev->se;
6352	struct cfs_rq *cfs_rq;
6353
6354	for_each_sched_entity(se) {
6355		cfs_rq = cfs_rq_of(se);
6356		put_prev_entity(cfs_rq, se);
6357	}
6358}
6359
6360/*
6361 * sched_yield() is very simple
6362 *
6363 * The magic of dealing with the ->skip buddy is in pick_next_entity.
6364 */
6365static void yield_task_fair(struct rq *rq)
6366{
6367	struct task_struct *curr = rq->curr;
6368	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6369	struct sched_entity *se = &curr->se;
6370
6371	/*
6372	 * Are we the only task in the tree?
6373	 */
6374	if (unlikely(rq->nr_running == 1))
6375		return;
6376
6377	clear_buddies(cfs_rq, se);
6378
6379	if (curr->policy != SCHED_BATCH) {
6380		update_rq_clock(rq);
6381		/*
6382		 * Update run-time statistics of the 'current'.
6383		 */
6384		update_curr(cfs_rq);
6385		/*
6386		 * Tell update_rq_clock() that we've just updated,
6387		 * so we don't do microscopic update in schedule()
6388		 * and double the fastpath cost.
6389		 */
6390		rq_clock_skip_update(rq, true);
6391	}
6392
6393	set_skip_buddy(se);
6394}
6395
6396static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
6397{
6398	struct sched_entity *se = &p->se;
6399
6400	/* throttled hierarchies are not runnable */
6401	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
6402		return false;
6403
6404	/* Tell the scheduler that we'd really like pse to run next. */
6405	set_next_buddy(se);
6406
6407	yield_task_fair(rq);
6408
6409	return true;
6410}
6411
6412#ifdef CONFIG_SMP
6413/**************************************************
6414 * Fair scheduling class load-balancing methods.
6415 *
6416 * BASICS
6417 *
6418 * The purpose of load-balancing is to achieve the same basic fairness the
6419 * per-cpu scheduler provides, namely provide a proportional amount of compute
6420 * time to each task. This is expressed in the following equation:
6421 *
6422 *   W_i,n/P_i == W_j,n/P_j for all i,j                               (1)
6423 *
6424 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
6425 * W_i,0 is defined as:
6426 *
6427 *   W_i,0 = \Sum_j w_i,j                                             (2)
6428 *
6429 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
6430 * is derived from the nice value as per sched_prio_to_weight[].
6431 *
6432 * The weight average is an exponential decay average of the instantaneous
6433 * weight:
6434 *
6435 *   W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0               (3)
6436 *
6437 * C_i is the compute capacity of cpu i, typically it is the
6438 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
6439 * can also include other factors [XXX].
6440 *
6441 * To achieve this balance we define a measure of imbalance which follows
6442 * directly from (1):
6443 *
6444 *   imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j }    (4)
6445 *
6446 * We them move tasks around to minimize the imbalance. In the continuous
6447 * function space it is obvious this converges, in the discrete case we get
6448 * a few fun cases generally called infeasible weight scenarios.
6449 *
6450 * [XXX expand on:
6451 *     - infeasible weights;
6452 *     - local vs global optima in the discrete case. ]
6453 *
6454 *
6455 * SCHED DOMAINS
6456 *
6457 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
6458 * for all i,j solution, we create a tree of cpus that follows the hardware
6459 * topology where each level pairs two lower groups (or better). This results
6460 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
6461 * tree to only the first of the previous level and we decrease the frequency
6462 * of load-balance at each level inv. proportional to the number of cpus in
6463 * the groups.
6464 *
6465 * This yields:
6466 *
6467 *     log_2 n     1     n
6468 *   \Sum       { --- * --- * 2^i } = O(n)                            (5)
6469 *     i = 0      2^i   2^i
6470 *                               `- size of each group
6471 *         |         |     `- number of cpus doing load-balance
6472 *         |         `- freq
6473 *         `- sum over all levels
6474 *
6475 * Coupled with a limit on how many tasks we can migrate every balance pass,
6476 * this makes (5) the runtime complexity of the balancer.
6477 *
6478 * An important property here is that each CPU is still (indirectly) connected
6479 * to every other cpu in at most O(log n) steps:
6480 *
6481 * The adjacency matrix of the resulting graph is given by:
6482 *
6483 *             log_2 n
6484 *   A_i,j = \Union     (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1)  (6)
6485 *             k = 0
6486 *
6487 * And you'll find that:
6488 *
6489 *   A^(log_2 n)_i,j != 0  for all i,j                                (7)
6490 *
6491 * Showing there's indeed a path between every cpu in at most O(log n) steps.
6492 * The task movement gives a factor of O(m), giving a convergence complexity
6493 * of:
6494 *
6495 *   O(nm log n),  n := nr_cpus, m := nr_tasks                        (8)
6496 *
6497 *
6498 * WORK CONSERVING
6499 *
6500 * In order to avoid CPUs going idle while there's still work to do, new idle
6501 * balancing is more aggressive and has the newly idle cpu iterate up the domain
6502 * tree itself instead of relying on other CPUs to bring it work.
6503 *
6504 * This adds some complexity to both (5) and (8) but it reduces the total idle
6505 * time.
6506 *
6507 * [XXX more?]
6508 *
6509 *
6510 * CGROUPS
6511 *
6512 * Cgroups make a horror show out of (2), instead of a simple sum we get:
6513 *
6514 *                                s_k,i
6515 *   W_i,0 = \Sum_j \Prod_k w_k * -----                               (9)
6516 *                                 S_k
6517 *
6518 * Where
6519 *
6520 *   s_k,i = \Sum_j w_i,j,k  and  S_k = \Sum_i s_k,i                 (10)
6521 *
6522 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
6523 *
6524 * The big problem is S_k, its a global sum needed to compute a local (W_i)
6525 * property.
6526 *
6527 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
6528 *      rewrite all of this once again.]
6529 */
6530
6531static unsigned long __read_mostly max_load_balance_interval = HZ/10;
6532
6533enum fbq_type { regular, remote, all };
6534
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6535#define LBF_ALL_PINNED	0x01
6536#define LBF_NEED_BREAK	0x02
6537#define LBF_DST_PINNED  0x04
6538#define LBF_SOME_PINNED	0x08
 
 
6539
6540struct lb_env {
6541	struct sched_domain	*sd;
6542
6543	struct rq		*src_rq;
6544	int			src_cpu;
6545
6546	int			dst_cpu;
6547	struct rq		*dst_rq;
6548
6549	struct cpumask		*dst_grpmask;
6550	int			new_dst_cpu;
6551	enum cpu_idle_type	idle;
6552	long			imbalance;
6553	/* The set of CPUs under consideration for load-balancing */
6554	struct cpumask		*cpus;
6555
6556	unsigned int		flags;
6557
6558	unsigned int		loop;
6559	unsigned int		loop_break;
6560	unsigned int		loop_max;
6561
6562	enum fbq_type		fbq_type;
 
6563	struct list_head	tasks;
6564};
6565
6566/*
6567 * Is this task likely cache-hot:
6568 */
6569static int task_hot(struct task_struct *p, struct lb_env *env)
6570{
6571	s64 delta;
6572
6573	lockdep_assert_held(&env->src_rq->lock);
6574
6575	if (p->sched_class != &fair_sched_class)
6576		return 0;
6577
6578	if (unlikely(p->policy == SCHED_IDLE))
6579		return 0;
6580
6581	/*
6582	 * Buddy candidates are cache hot:
6583	 */
6584	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6585			(&p->se == cfs_rq_of(&p->se)->next ||
6586			 &p->se == cfs_rq_of(&p->se)->last))
6587		return 1;
6588
6589	if (sysctl_sched_migration_cost == -1)
6590		return 1;
6591	if (sysctl_sched_migration_cost == 0)
6592		return 0;
6593
6594	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6595
6596	return delta < (s64)sysctl_sched_migration_cost;
6597}
6598
6599#ifdef CONFIG_NUMA_BALANCING
6600/*
6601 * Returns 1, if task migration degrades locality
6602 * Returns 0, if task migration improves locality i.e migration preferred.
6603 * Returns -1, if task migration is not affected by locality.
6604 */
6605static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6606{
6607	struct numa_group *numa_group = rcu_dereference(p->numa_group);
6608	unsigned long src_faults, dst_faults;
6609	int src_nid, dst_nid;
6610
6611	if (!static_branch_likely(&sched_numa_balancing))
6612		return -1;
6613
6614	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6615		return -1;
6616
6617	src_nid = cpu_to_node(env->src_cpu);
6618	dst_nid = cpu_to_node(env->dst_cpu);
6619
6620	if (src_nid == dst_nid)
6621		return -1;
6622
6623	/* Migrating away from the preferred node is always bad. */
6624	if (src_nid == p->numa_preferred_nid) {
6625		if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
6626			return 1;
6627		else
6628			return -1;
6629	}
6630
6631	/* Encourage migration to the preferred node. */
6632	if (dst_nid == p->numa_preferred_nid)
6633		return 0;
6634
 
 
 
 
 
6635	if (numa_group) {
6636		src_faults = group_faults(p, src_nid);
6637		dst_faults = group_faults(p, dst_nid);
6638	} else {
6639		src_faults = task_faults(p, src_nid);
6640		dst_faults = task_faults(p, dst_nid);
6641	}
6642
6643	return dst_faults < src_faults;
6644}
6645
6646#else
6647static inline int migrate_degrades_locality(struct task_struct *p,
6648					     struct lb_env *env)
6649{
6650	return -1;
6651}
6652#endif
6653
6654/*
6655 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
6656 */
6657static
6658int can_migrate_task(struct task_struct *p, struct lb_env *env)
6659{
6660	int tsk_cache_hot;
6661
6662	lockdep_assert_held(&env->src_rq->lock);
6663
6664	/*
6665	 * We do not migrate tasks that are:
6666	 * 1) throttled_lb_pair, or
6667	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6668	 * 3) running (obviously), or
6669	 * 4) are cache-hot on their current CPU.
6670	 */
6671	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
6672		return 0;
6673
6674	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
6675		int cpu;
6676
6677		schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
6678
6679		env->flags |= LBF_SOME_PINNED;
6680
6681		/*
6682		 * Remember if this task can be migrated to any other cpu in
6683		 * our sched_group. We may want to revisit it if we couldn't
6684		 * meet load balance goals by pulling other tasks on src_cpu.
6685		 *
6686		 * Also avoid computing new_dst_cpu if we have already computed
6687		 * one in current iteration.
6688		 */
6689		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
6690			return 0;
6691
6692		/* Prevent to re-select dst_cpu via env's cpus */
6693		for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
6694			if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
6695				env->flags |= LBF_DST_PINNED;
6696				env->new_dst_cpu = cpu;
6697				break;
6698			}
6699		}
6700
6701		return 0;
6702	}
6703
6704	/* Record that we found atleast one task that could run on dst_cpu */
6705	env->flags &= ~LBF_ALL_PINNED;
6706
6707	if (task_running(env->src_rq, p)) {
6708		schedstat_inc(p->se.statistics.nr_failed_migrations_running);
6709		return 0;
6710	}
6711
6712	/*
6713	 * Aggressive migration if:
6714	 * 1) destination numa is preferred
6715	 * 2) task is cache cold, or
6716	 * 3) too many balance attempts have failed.
6717	 */
6718	tsk_cache_hot = migrate_degrades_locality(p, env);
6719	if (tsk_cache_hot == -1)
6720		tsk_cache_hot = task_hot(p, env);
6721
6722	if (tsk_cache_hot <= 0 ||
6723	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6724		if (tsk_cache_hot == 1) {
6725			schedstat_inc(env->sd->lb_hot_gained[env->idle]);
6726			schedstat_inc(p->se.statistics.nr_forced_migrations);
6727		}
6728		return 1;
6729	}
6730
6731	schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
6732	return 0;
6733}
6734
6735/*
6736 * detach_task() -- detach the task for the migration specified in env
6737 */
6738static void detach_task(struct task_struct *p, struct lb_env *env)
6739{
6740	lockdep_assert_held(&env->src_rq->lock);
6741
6742	p->on_rq = TASK_ON_RQ_MIGRATING;
6743	deactivate_task(env->src_rq, p, 0);
6744	set_task_cpu(p, env->dst_cpu);
6745}
6746
6747/*
6748 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6749 * part of active balancing operations within "domain".
6750 *
6751 * Returns a task if successful and NULL otherwise.
6752 */
6753static struct task_struct *detach_one_task(struct lb_env *env)
6754{
6755	struct task_struct *p, *n;
6756
6757	lockdep_assert_held(&env->src_rq->lock);
6758
6759	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
 
6760		if (!can_migrate_task(p, env))
6761			continue;
6762
6763		detach_task(p, env);
6764
6765		/*
6766		 * Right now, this is only the second place where
6767		 * lb_gained[env->idle] is updated (other is detach_tasks)
6768		 * so we can safely collect stats here rather than
6769		 * inside detach_tasks().
6770		 */
6771		schedstat_inc(env->sd->lb_gained[env->idle]);
6772		return p;
6773	}
6774	return NULL;
6775}
6776
6777static const unsigned int sched_nr_migrate_break = 32;
6778
6779/*
6780 * detach_tasks() -- tries to detach up to imbalance weighted load from
6781 * busiest_rq, as part of a balancing operation within domain "sd".
6782 *
6783 * Returns number of detached tasks if successful and 0 otherwise.
6784 */
6785static int detach_tasks(struct lb_env *env)
6786{
6787	struct list_head *tasks = &env->src_rq->cfs_tasks;
 
6788	struct task_struct *p;
6789	unsigned long load;
6790	int detached = 0;
6791
6792	lockdep_assert_held(&env->src_rq->lock);
6793
6794	if (env->imbalance <= 0)
6795		return 0;
6796
6797	while (!list_empty(tasks)) {
6798		/*
6799		 * We don't want to steal all, otherwise we may be treated likewise,
6800		 * which could at worst lead to a livelock crash.
6801		 */
6802		if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
6803			break;
6804
6805		p = list_first_entry(tasks, struct task_struct, se.group_node);
6806
6807		env->loop++;
6808		/* We've more or less seen every task there is, call it quits */
6809		if (env->loop > env->loop_max)
6810			break;
6811
6812		/* take a breather every nr_migrate tasks */
6813		if (env->loop > env->loop_break) {
6814			env->loop_break += sched_nr_migrate_break;
6815			env->flags |= LBF_NEED_BREAK;
6816			break;
6817		}
6818
6819		if (!can_migrate_task(p, env))
6820			goto next;
6821
6822		load = task_h_load(p);
 
 
 
 
 
 
 
 
 
6823
6824		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6825			goto next;
 
6826
6827		if ((load / 2) > env->imbalance)
6828			goto next;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6829
6830		detach_task(p, env);
6831		list_add(&p->se.group_node, &env->tasks);
6832
6833		detached++;
6834		env->imbalance -= load;
6835
6836#ifdef CONFIG_PREEMPT
6837		/*
6838		 * NEWIDLE balancing is a source of latency, so preemptible
6839		 * kernels will stop after the first task is detached to minimize
6840		 * the critical section.
6841		 */
6842		if (env->idle == CPU_NEWLY_IDLE)
6843			break;
6844#endif
6845
6846		/*
6847		 * We only want to steal up to the prescribed amount of
6848		 * weighted load.
6849		 */
6850		if (env->imbalance <= 0)
6851			break;
6852
6853		continue;
6854next:
6855		list_move_tail(&p->se.group_node, tasks);
6856	}
6857
6858	/*
6859	 * Right now, this is one of only two places we collect this stat
6860	 * so we can safely collect detach_one_task() stats here rather
6861	 * than inside detach_one_task().
6862	 */
6863	schedstat_add(env->sd->lb_gained[env->idle], detached);
6864
6865	return detached;
6866}
6867
6868/*
6869 * attach_task() -- attach the task detached by detach_task() to its new rq.
6870 */
6871static void attach_task(struct rq *rq, struct task_struct *p)
6872{
6873	lockdep_assert_held(&rq->lock);
6874
6875	BUG_ON(task_rq(p) != rq);
6876	activate_task(rq, p, 0);
6877	p->on_rq = TASK_ON_RQ_QUEUED;
6878	check_preempt_curr(rq, p, 0);
6879}
6880
6881/*
6882 * attach_one_task() -- attaches the task returned from detach_one_task() to
6883 * its new rq.
6884 */
6885static void attach_one_task(struct rq *rq, struct task_struct *p)
6886{
6887	raw_spin_lock(&rq->lock);
 
 
 
6888	attach_task(rq, p);
6889	raw_spin_unlock(&rq->lock);
6890}
6891
6892/*
6893 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6894 * new rq.
6895 */
6896static void attach_tasks(struct lb_env *env)
6897{
6898	struct list_head *tasks = &env->tasks;
6899	struct task_struct *p;
 
6900
6901	raw_spin_lock(&env->dst_rq->lock);
 
6902
6903	while (!list_empty(tasks)) {
6904		p = list_first_entry(tasks, struct task_struct, se.group_node);
6905		list_del_init(&p->se.group_node);
6906
6907		attach_task(env->dst_rq, p);
6908	}
6909
6910	raw_spin_unlock(&env->dst_rq->lock);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6911}
6912
6913#ifdef CONFIG_FAIR_GROUP_SCHED
6914static void update_blocked_averages(int cpu)
 
6915{
6916	struct rq *rq = cpu_rq(cpu);
6917	struct cfs_rq *cfs_rq;
6918	unsigned long flags;
6919
6920	raw_spin_lock_irqsave(&rq->lock, flags);
6921	update_rq_clock(rq);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6922
6923	/*
6924	 * Iterates the task_group tree in a bottom up fashion, see
6925	 * list_add_leaf_cfs_rq() for details.
6926	 */
6927	for_each_leaf_cfs_rq(rq, cfs_rq) {
6928		/* throttled entities do not contribute to load */
6929		if (throttled_hierarchy(cfs_rq))
6930			continue;
6931
6932		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true))
6933			update_tg_load_avg(cfs_rq, 0);
6934
6935		/* Propagate pending load changes to the parent */
6936		if (cfs_rq->tg->se[cpu])
6937			update_load_avg(cfs_rq->tg->se[cpu], 0);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6938	}
6939	raw_spin_unlock_irqrestore(&rq->lock, flags);
 
6940}
6941
6942/*
6943 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6944 * This needs to be done in a top-down fashion because the load of a child
6945 * group is a fraction of its parents load.
6946 */
6947static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6948{
6949	struct rq *rq = rq_of(cfs_rq);
6950	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6951	unsigned long now = jiffies;
6952	unsigned long load;
6953
6954	if (cfs_rq->last_h_load_update == now)
6955		return;
6956
6957	cfs_rq->h_load_next = NULL;
6958	for_each_sched_entity(se) {
6959		cfs_rq = cfs_rq_of(se);
6960		cfs_rq->h_load_next = se;
6961		if (cfs_rq->last_h_load_update == now)
6962			break;
6963	}
6964
6965	if (!se) {
6966		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6967		cfs_rq->last_h_load_update = now;
6968	}
6969
6970	while ((se = cfs_rq->h_load_next) != NULL) {
6971		load = cfs_rq->h_load;
6972		load = div64_ul(load * se->avg.load_avg,
6973			cfs_rq_load_avg(cfs_rq) + 1);
6974		cfs_rq = group_cfs_rq(se);
6975		cfs_rq->h_load = load;
6976		cfs_rq->last_h_load_update = now;
6977	}
6978}
6979
6980static unsigned long task_h_load(struct task_struct *p)
6981{
6982	struct cfs_rq *cfs_rq = task_cfs_rq(p);
6983
6984	update_cfs_rq_h_load(cfs_rq);
6985	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6986			cfs_rq_load_avg(cfs_rq) + 1);
6987}
6988#else
6989static inline void update_blocked_averages(int cpu)
6990{
6991	struct rq *rq = cpu_rq(cpu);
6992	struct cfs_rq *cfs_rq = &rq->cfs;
6993	unsigned long flags;
6994
6995	raw_spin_lock_irqsave(&rq->lock, flags);
6996	update_rq_clock(rq);
6997	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true);
6998	raw_spin_unlock_irqrestore(&rq->lock, flags);
 
6999}
7000
7001static unsigned long task_h_load(struct task_struct *p)
7002{
7003	return p->se.avg.load_avg;
7004}
7005#endif
7006
7007/********** Helpers for find_busiest_group ************************/
 
 
 
 
7008
7009enum group_type {
7010	group_other = 0,
7011	group_imbalanced,
7012	group_overloaded,
7013};
 
 
 
 
 
 
 
 
7014
7015/*
7016 * sg_lb_stats - stats of a sched_group required for load_balancing
7017 */
7018struct sg_lb_stats {
7019	unsigned long avg_load; /*Avg load across the CPUs of the group */
7020	unsigned long group_load; /* Total load over the CPUs of the group */
7021	unsigned long sum_weighted_load; /* Weighted load of group's tasks */
7022	unsigned long load_per_task;
7023	unsigned long group_capacity;
7024	unsigned long group_util; /* Total utilization of the group */
7025	unsigned int sum_nr_running; /* Nr tasks running in the group */
 
 
7026	unsigned int idle_cpus;
7027	unsigned int group_weight;
7028	enum group_type group_type;
7029	int group_no_capacity;
 
7030#ifdef CONFIG_NUMA_BALANCING
7031	unsigned int nr_numa_running;
7032	unsigned int nr_preferred_running;
7033#endif
7034};
7035
7036/*
7037 * sd_lb_stats - Structure to store the statistics of a sched_domain
7038 *		 during load balancing.
7039 */
7040struct sd_lb_stats {
7041	struct sched_group *busiest;	/* Busiest group in this sd */
7042	struct sched_group *local;	/* Local group in this sd */
7043	unsigned long total_load;	/* Total load of all groups in sd */
7044	unsigned long total_capacity;	/* Total capacity of all groups in sd */
7045	unsigned long avg_load;	/* Average load across all groups in sd */
 
7046
7047	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
7048	struct sg_lb_stats local_stat;	/* Statistics of the local group */
7049};
7050
7051static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
7052{
7053	/*
7054	 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
7055	 * local_stat because update_sg_lb_stats() does a full clear/assignment.
7056	 * We must however clear busiest_stat::avg_load because
7057	 * update_sd_pick_busiest() reads this before assignment.
 
7058	 */
7059	*sds = (struct sd_lb_stats){
7060		.busiest = NULL,
7061		.local = NULL,
7062		.total_load = 0UL,
7063		.total_capacity = 0UL,
7064		.busiest_stat = {
7065			.avg_load = 0UL,
7066			.sum_nr_running = 0,
7067			.group_type = group_other,
7068		},
7069	};
7070}
7071
7072/**
7073 * get_sd_load_idx - Obtain the load index for a given sched domain.
7074 * @sd: The sched_domain whose load_idx is to be obtained.
7075 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
7076 *
7077 * Return: The load index.
7078 */
7079static inline int get_sd_load_idx(struct sched_domain *sd,
7080					enum cpu_idle_type idle)
7081{
7082	int load_idx;
7083
7084	switch (idle) {
7085	case CPU_NOT_IDLE:
7086		load_idx = sd->busy_idx;
7087		break;
7088
7089	case CPU_NEWLY_IDLE:
7090		load_idx = sd->newidle_idx;
7091		break;
7092	default:
7093		load_idx = sd->idle_idx;
7094		break;
7095	}
7096
7097	return load_idx;
7098}
7099
7100static unsigned long scale_rt_capacity(int cpu)
7101{
7102	struct rq *rq = cpu_rq(cpu);
7103	u64 total, used, age_stamp, avg;
7104	s64 delta;
 
7105
7106	/*
7107	 * Since we're reading these variables without serialization make sure
7108	 * we read them once before doing sanity checks on them.
7109	 */
7110	age_stamp = READ_ONCE(rq->age_stamp);
7111	avg = READ_ONCE(rq->rt_avg);
7112	delta = __rq_clock_broken(rq) - age_stamp;
7113
7114	if (unlikely(delta < 0))
7115		delta = 0;
7116
7117	total = sched_avg_period() + delta;
 
 
 
 
 
 
 
 
7118
7119	used = div_u64(avg, total);
 
7120
7121	if (likely(used < SCHED_CAPACITY_SCALE))
7122		return SCHED_CAPACITY_SCALE - used;
7123
7124	return 1;
7125}
7126
7127static void update_cpu_capacity(struct sched_domain *sd, int cpu)
7128{
7129	unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
7130	struct sched_group *sdg = sd->groups;
7131
7132	cpu_rq(cpu)->cpu_capacity_orig = capacity;
7133
7134	capacity *= scale_rt_capacity(cpu);
7135	capacity >>= SCHED_CAPACITY_SHIFT;
7136
7137	if (!capacity)
7138		capacity = 1;
7139
7140	cpu_rq(cpu)->cpu_capacity = capacity;
7141	sdg->sgc->capacity = capacity;
7142	sdg->sgc->min_capacity = capacity;
 
7143}
7144
7145void update_group_capacity(struct sched_domain *sd, int cpu)
7146{
7147	struct sched_domain *child = sd->child;
7148	struct sched_group *group, *sdg = sd->groups;
7149	unsigned long capacity, min_capacity;
7150	unsigned long interval;
7151
7152	interval = msecs_to_jiffies(sd->balance_interval);
7153	interval = clamp(interval, 1UL, max_load_balance_interval);
7154	sdg->sgc->next_update = jiffies + interval;
7155
7156	if (!child) {
7157		update_cpu_capacity(sd, cpu);
7158		return;
7159	}
7160
7161	capacity = 0;
7162	min_capacity = ULONG_MAX;
 
7163
7164	if (child->flags & SD_OVERLAP) {
7165		/*
7166		 * SD_OVERLAP domains cannot assume that child groups
7167		 * span the current group.
7168		 */
7169
7170		for_each_cpu(cpu, sched_group_cpus(sdg)) {
7171			struct sched_group_capacity *sgc;
7172			struct rq *rq = cpu_rq(cpu);
7173
7174			/*
7175			 * build_sched_domains() -> init_sched_groups_capacity()
7176			 * gets here before we've attached the domains to the
7177			 * runqueues.
7178			 *
7179			 * Use capacity_of(), which is set irrespective of domains
7180			 * in update_cpu_capacity().
7181			 *
7182			 * This avoids capacity from being 0 and
7183			 * causing divide-by-zero issues on boot.
7184			 */
7185			if (unlikely(!rq->sd)) {
7186				capacity += capacity_of(cpu);
7187			} else {
7188				sgc = rq->sd->groups->sgc;
7189				capacity += sgc->capacity;
7190			}
7191
7192			min_capacity = min(capacity, min_capacity);
 
 
7193		}
7194	} else  {
7195		/*
7196		 * !SD_OVERLAP domains can assume that child groups
7197		 * span the current group.
7198		 */
7199
7200		group = child->groups;
7201		do {
7202			struct sched_group_capacity *sgc = group->sgc;
7203
7204			capacity += sgc->capacity;
7205			min_capacity = min(sgc->min_capacity, min_capacity);
 
7206			group = group->next;
7207		} while (group != child->groups);
7208	}
7209
7210	sdg->sgc->capacity = capacity;
7211	sdg->sgc->min_capacity = min_capacity;
 
7212}
7213
7214/*
7215 * Check whether the capacity of the rq has been noticeably reduced by side
7216 * activity. The imbalance_pct is used for the threshold.
7217 * Return true is the capacity is reduced
7218 */
7219static inline int
7220check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
7221{
7222	return ((rq->cpu_capacity * sd->imbalance_pct) <
7223				(rq->cpu_capacity_orig * 100));
7224}
7225
7226/*
 
 
 
 
 
 
 
 
 
 
 
 
7227 * Group imbalance indicates (and tries to solve) the problem where balancing
7228 * groups is inadequate due to tsk_cpus_allowed() constraints.
7229 *
7230 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
7231 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
7232 * Something like:
7233 *
7234 *	{ 0 1 2 3 } { 4 5 6 7 }
7235 *	        *     * * *
7236 *
7237 * If we were to balance group-wise we'd place two tasks in the first group and
7238 * two tasks in the second group. Clearly this is undesired as it will overload
7239 * cpu 3 and leave one of the cpus in the second group unused.
7240 *
7241 * The current solution to this issue is detecting the skew in the first group
7242 * by noticing the lower domain failed to reach balance and had difficulty
7243 * moving tasks due to affinity constraints.
7244 *
7245 * When this is so detected; this group becomes a candidate for busiest; see
7246 * update_sd_pick_busiest(). And calculate_imbalance() and
7247 * find_busiest_group() avoid some of the usual balance conditions to allow it
7248 * to create an effective group imbalance.
7249 *
7250 * This is a somewhat tricky proposition since the next run might not find the
7251 * group imbalance and decide the groups need to be balanced again. A most
7252 * subtle and fragile situation.
7253 */
7254
7255static inline int sg_imbalanced(struct sched_group *group)
7256{
7257	return group->sgc->imbalance;
7258}
7259
7260/*
7261 * group_has_capacity returns true if the group has spare capacity that could
7262 * be used by some tasks.
7263 * We consider that a group has spare capacity if the  * number of task is
7264 * smaller than the number of CPUs or if the utilization is lower than the
7265 * available capacity for CFS tasks.
7266 * For the latter, we use a threshold to stabilize the state, to take into
7267 * account the variance of the tasks' load and to return true if the available
7268 * capacity in meaningful for the load balancer.
7269 * As an example, an available capacity of 1% can appear but it doesn't make
7270 * any benefit for the load balance.
7271 */
7272static inline bool
7273group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
7274{
7275	if (sgs->sum_nr_running < sgs->group_weight)
7276		return true;
7277
 
 
 
 
7278	if ((sgs->group_capacity * 100) >
7279			(sgs->group_util * env->sd->imbalance_pct))
7280		return true;
7281
7282	return false;
7283}
7284
7285/*
7286 *  group_is_overloaded returns true if the group has more tasks than it can
7287 *  handle.
7288 *  group_is_overloaded is not equals to !group_has_capacity because a group
7289 *  with the exact right number of tasks, has no more spare capacity but is not
7290 *  overloaded so both group_has_capacity and group_is_overloaded return
7291 *  false.
7292 */
7293static inline bool
7294group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
7295{
7296	if (sgs->sum_nr_running <= sgs->group_weight)
7297		return false;
7298
7299	if ((sgs->group_capacity * 100) <
7300			(sgs->group_util * env->sd->imbalance_pct))
 
 
 
 
7301		return true;
7302
7303	return false;
7304}
7305
7306/*
7307 * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller
7308 * per-CPU capacity than sched_group ref.
7309 */
7310static inline bool
7311group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
 
 
 
 
 
 
 
 
 
 
7312{
7313	return sg->sgc->min_capacity * capacity_margin <
7314						ref->sgc->min_capacity * 1024;
7315}
7316
7317static inline enum
7318group_type group_classify(struct sched_group *group,
 
7319			  struct sg_lb_stats *sgs)
7320{
7321	if (sgs->group_no_capacity)
7322		return group_overloaded;
7323
7324	if (sg_imbalanced(group))
7325		return group_imbalanced;
7326
7327	return group_other;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7328}
7329
7330/**
7331 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
7332 * @env: The load balancing environment.
7333 * @group: sched_group whose statistics are to be updated.
7334 * @load_idx: Load index of sched_domain of this_cpu for load calc.
7335 * @local_group: Does group contain this_cpu.
7336 * @sgs: variable to hold the statistics for this group.
7337 * @overload: Indicate more than one runnable task for any CPU.
7338 */
7339static inline void update_sg_lb_stats(struct lb_env *env,
7340			struct sched_group *group, int load_idx,
7341			int local_group, struct sg_lb_stats *sgs,
7342			bool *overload)
7343{
7344	unsigned long load;
7345	int i, nr_running;
7346
7347	memset(sgs, 0, sizeof(*sgs));
7348
7349	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
 
 
7350		struct rq *rq = cpu_rq(i);
7351
7352		/* Bias balancing toward cpus of our domain */
7353		if (local_group)
7354			load = target_load(i, load_idx);
7355		else
7356			load = source_load(i, load_idx);
7357
7358		sgs->group_load += load;
7359		sgs->group_util += cpu_util(i);
7360		sgs->sum_nr_running += rq->cfs.h_nr_running;
 
7361
7362		nr_running = rq->nr_running;
 
 
7363		if (nr_running > 1)
7364			*overload = true;
 
 
 
7365
7366#ifdef CONFIG_NUMA_BALANCING
7367		sgs->nr_numa_running += rq->nr_numa_running;
7368		sgs->nr_preferred_running += rq->nr_preferred_running;
7369#endif
7370		sgs->sum_weighted_load += weighted_cpuload(i);
7371		/*
7372		 * No need to call idle_cpu() if nr_running is not 0
7373		 */
7374		if (!nr_running && idle_cpu(i))
7375			sgs->idle_cpus++;
 
 
 
 
 
 
 
 
 
 
 
 
 
7376	}
7377
7378	/* Adjust by relative CPU capacity of the group */
7379	sgs->group_capacity = group->sgc->capacity;
7380	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
 
 
 
 
7381
7382	if (sgs->sum_nr_running)
7383		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
7384
7385	sgs->group_weight = group->group_weight;
7386
7387	sgs->group_no_capacity = group_is_overloaded(env, sgs);
7388	sgs->group_type = group_classify(group, sgs);
 
 
 
 
7389}
7390
7391/**
7392 * update_sd_pick_busiest - return 1 on busiest group
7393 * @env: The load balancing environment.
7394 * @sds: sched_domain statistics
7395 * @sg: sched_group candidate to be checked for being the busiest
7396 * @sgs: sched_group statistics
7397 *
7398 * Determine if @sg is a busier group than the previously selected
7399 * busiest group.
7400 *
7401 * Return: %true if @sg is a busier group than the previously selected
7402 * busiest group. %false otherwise.
7403 */
7404static bool update_sd_pick_busiest(struct lb_env *env,
7405				   struct sd_lb_stats *sds,
7406				   struct sched_group *sg,
7407				   struct sg_lb_stats *sgs)
7408{
7409	struct sg_lb_stats *busiest = &sds->busiest_stat;
7410
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7411	if (sgs->group_type > busiest->group_type)
7412		return true;
7413
7414	if (sgs->group_type < busiest->group_type)
7415		return false;
7416
7417	if (sgs->avg_load <= busiest->avg_load)
7418		return false;
7419
7420	if (!(env->sd->flags & SD_ASYM_CPUCAPACITY))
7421		goto asym_packing;
7422
7423	/*
7424	 * Candidate sg has no more than one task per CPU and
7425	 * has higher per-CPU capacity. Migrating tasks to less
7426	 * capable CPUs may harm throughput. Maximize throughput,
7427	 * power/energy consequences are not considered.
7428	 */
7429	if (sgs->sum_nr_running <= sgs->group_weight &&
7430	    group_smaller_cpu_capacity(sds->local, sg))
 
 
 
 
 
 
 
 
 
 
 
7431		return false;
7432
7433asym_packing:
7434	/* This is the busiest node in its class. */
7435	if (!(env->sd->flags & SD_ASYM_PACKING))
7436		return true;
 
7437
7438	/* No ASYM_PACKING if target cpu is already busy */
7439	if (env->idle == CPU_NOT_IDLE)
7440		return true;
7441	/*
7442	 * ASYM_PACKING needs to move all the work to the highest
7443	 * prority CPUs in the group, therefore mark all groups
7444	 * of lower priority than ourself as busy.
7445	 */
7446	if (sgs->sum_nr_running &&
7447	    sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) {
7448		if (!sds->busiest)
7449			return true;
7450
7451		/* Prefer to move from lowest priority cpu's work */
7452		if (sched_asym_prefer(sds->busiest->asym_prefer_cpu,
7453				      sg->asym_prefer_cpu))
7454			return true;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7455	}
7456
7457	return false;
 
 
 
 
 
 
 
 
 
 
 
7458}
7459
7460#ifdef CONFIG_NUMA_BALANCING
7461static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
7462{
7463	if (sgs->sum_nr_running > sgs->nr_numa_running)
7464		return regular;
7465	if (sgs->sum_nr_running > sgs->nr_preferred_running)
7466		return remote;
7467	return all;
7468}
7469
7470static inline enum fbq_type fbq_classify_rq(struct rq *rq)
7471{
7472	if (rq->nr_running > rq->nr_numa_running)
7473		return regular;
7474	if (rq->nr_running > rq->nr_preferred_running)
7475		return remote;
7476	return all;
7477}
7478#else
7479static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
7480{
7481	return all;
7482}
7483
7484static inline enum fbq_type fbq_classify_rq(struct rq *rq)
7485{
7486	return regular;
7487}
7488#endif /* CONFIG_NUMA_BALANCING */
7489
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7490/**
7491 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
7492 * @env: The load balancing environment.
7493 * @sds: variable to hold the statistics for this sched_domain.
7494 */
 
7495static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
7496{
7497	struct sched_domain *child = env->sd->child;
7498	struct sched_group *sg = env->sd->groups;
 
7499	struct sg_lb_stats tmp_sgs;
7500	int load_idx, prefer_sibling = 0;
7501	bool overload = false;
7502
7503	if (child && child->flags & SD_PREFER_SIBLING)
7504		prefer_sibling = 1;
7505
7506	load_idx = get_sd_load_idx(env->sd, env->idle);
 
 
 
7507
7508	do {
7509		struct sg_lb_stats *sgs = &tmp_sgs;
7510		int local_group;
7511
7512		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
7513		if (local_group) {
7514			sds->local = sg;
7515			sgs = &sds->local_stat;
7516
7517			if (env->idle != CPU_NEWLY_IDLE ||
7518			    time_after_eq(jiffies, sg->sgc->next_update))
7519				update_group_capacity(env->sd, env->dst_cpu);
7520		}
7521
7522		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
7523						&overload);
7524
7525		if (local_group)
7526			goto next_group;
7527
7528		/*
7529		 * In case the child domain prefers tasks go to siblings
7530		 * first, lower the sg capacity so that we'll try
7531		 * and move all the excess tasks away. We lower the capacity
7532		 * of a group only if the local group has the capacity to fit
7533		 * these excess tasks. The extra check prevents the case where
7534		 * you always pull from the heaviest group when it is already
7535		 * under-utilized (possible with a large weight task outweighs
7536		 * the tasks on the system).
7537		 */
7538		if (prefer_sibling && sds->local &&
7539		    group_has_capacity(env, &sds->local_stat) &&
7540		    (sgs->sum_nr_running > 1)) {
7541			sgs->group_no_capacity = 1;
7542			sgs->group_type = group_classify(sg, sgs);
7543		}
7544
7545		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
7546			sds->busiest = sg;
7547			sds->busiest_stat = *sgs;
7548		}
7549
7550next_group:
7551		/* Now, start updating sd_lb_stats */
7552		sds->total_load += sgs->group_load;
7553		sds->total_capacity += sgs->group_capacity;
7554
7555		sg = sg->next;
7556	} while (sg != env->sd->groups);
7557
7558	if (env->sd->flags & SD_NUMA)
7559		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
7560
7561	if (!env->sd->parent) {
7562		/* update overload indicator if we are at root domain */
7563		if (env->dst_rq->rd->overload != overload)
7564			env->dst_rq->rd->overload = overload;
7565	}
7566
7567}
7568
7569/**
7570 * check_asym_packing - Check to see if the group is packed into the
7571 *			sched doman.
7572 *
7573 * This is primarily intended to used at the sibling level.  Some
7574 * cores like POWER7 prefer to use lower numbered SMT threads.  In the
7575 * case of POWER7, it can move to lower SMT modes only when higher
7576 * threads are idle.  When in lower SMT modes, the threads will
7577 * perform better since they share less core resources.  Hence when we
7578 * have idle threads, we want them to be the higher ones.
7579 *
7580 * This packing function is run on idle threads.  It checks to see if
7581 * the busiest CPU in this domain (core in the P7 case) has a higher
7582 * CPU number than the packing function is being run on.  Here we are
7583 * assuming lower CPU number will be equivalent to lower a SMT thread
7584 * number.
7585 *
7586 * Return: 1 when packing is required and a task should be moved to
7587 * this CPU.  The amount of the imbalance is returned in *imbalance.
7588 *
7589 * @env: The load balancing environment.
7590 * @sds: Statistics of the sched_domain which is to be packed
7591 */
7592static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
7593{
7594	int busiest_cpu;
7595
7596	if (!(env->sd->flags & SD_ASYM_PACKING))
7597		return 0;
 
 
7598
7599	if (env->idle == CPU_NOT_IDLE)
7600		return 0;
7601
7602	if (!sds->busiest)
7603		return 0;
7604
7605	busiest_cpu = sds->busiest->asym_prefer_cpu;
7606	if (sched_asym_prefer(busiest_cpu, env->dst_cpu))
7607		return 0;
7608
7609	env->imbalance = DIV_ROUND_CLOSEST(
7610		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
7611		SCHED_CAPACITY_SCALE);
 
 
7612
7613	return 1;
 
 
7614}
7615
7616/**
7617 * fix_small_imbalance - Calculate the minor imbalance that exists
7618 *			amongst the groups of a sched_domain, during
7619 *			load balancing.
7620 * @env: The load balancing environment.
7621 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
7622 */
7623static inline
7624void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7625{
7626	unsigned long tmp, capa_now = 0, capa_move = 0;
7627	unsigned int imbn = 2;
7628	unsigned long scaled_busy_load_per_task;
7629	struct sg_lb_stats *local, *busiest;
7630
7631	local = &sds->local_stat;
7632	busiest = &sds->busiest_stat;
7633
7634	if (!local->sum_nr_running)
7635		local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
7636	else if (busiest->load_per_task > local->load_per_task)
7637		imbn = 1;
7638
7639	scaled_busy_load_per_task =
7640		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7641		busiest->group_capacity;
7642
7643	if (busiest->avg_load + scaled_busy_load_per_task >=
7644	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
7645		env->imbalance = busiest->load_per_task;
7646		return;
7647	}
7648
7649	/*
7650	 * OK, we don't have enough imbalance to justify moving tasks,
7651	 * however we may be able to increase total CPU capacity used by
7652	 * moving them.
7653	 */
 
 
 
7654
7655	capa_now += busiest->group_capacity *
7656			min(busiest->load_per_task, busiest->avg_load);
7657	capa_now += local->group_capacity *
7658			min(local->load_per_task, local->avg_load);
7659	capa_now /= SCHED_CAPACITY_SCALE;
7660
7661	/* Amount of load we'd subtract */
7662	if (busiest->avg_load > scaled_busy_load_per_task) {
7663		capa_move += busiest->group_capacity *
7664			    min(busiest->load_per_task,
7665				busiest->avg_load - scaled_busy_load_per_task);
7666	}
7667
7668	/* Amount of load we'd add */
7669	if (busiest->avg_load * busiest->group_capacity <
7670	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
7671		tmp = (busiest->avg_load * busiest->group_capacity) /
7672		      local->group_capacity;
7673	} else {
7674		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7675		      local->group_capacity;
7676	}
7677	capa_move += local->group_capacity *
7678		    min(local->load_per_task, local->avg_load + tmp);
7679	capa_move /= SCHED_CAPACITY_SCALE;
7680
7681	/* Move if we gain throughput */
7682	if (capa_move > capa_now)
7683		env->imbalance = busiest->load_per_task;
7684}
7685
7686/**
7687 * calculate_imbalance - Calculate the amount of imbalance present within the
7688 *			 groups of a given sched_domain during load balance.
7689 * @env: load balance environment
7690 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
7691 */
7692static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7693{
7694	unsigned long max_pull, load_above_capacity = ~0UL;
7695	struct sg_lb_stats *local, *busiest;
7696
7697	local = &sds->local_stat;
7698	busiest = &sds->busiest_stat;
7699
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7700	if (busiest->group_type == group_imbalanced) {
7701		/*
7702		 * In the group_imb case we cannot rely on group-wide averages
7703		 * to ensure cpu-load equilibrium, look at wider averages. XXX
 
 
7704		 */
7705		busiest->load_per_task =
7706			min(busiest->load_per_task, sds->avg_load);
 
7707	}
7708
7709	/*
7710	 * Avg load of busiest sg can be less and avg load of local sg can
7711	 * be greater than avg load across all sgs of sd because avg load
7712	 * factors in sg capacity and sgs with smaller group_type are
7713	 * skipped when updating the busiest sg:
7714	 */
7715	if (busiest->avg_load <= sds->avg_load ||
7716	    local->avg_load >= sds->avg_load) {
7717		env->imbalance = 0;
7718		return fix_small_imbalance(env, sds);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7719	}
7720
7721	/*
7722	 * If there aren't any idle cpus, avoid creating some.
 
7723	 */
7724	if (busiest->group_type == group_overloaded &&
7725	    local->group_type   == group_overloaded) {
7726		load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
7727		if (load_above_capacity > busiest->group_capacity) {
7728			load_above_capacity -= busiest->group_capacity;
7729			load_above_capacity *= scale_load_down(NICE_0_LOAD);
7730			load_above_capacity /= busiest->group_capacity;
7731		} else
7732			load_above_capacity = ~0UL;
 
 
 
 
 
 
 
 
 
 
7733	}
7734
7735	/*
7736	 * We're trying to get all the cpus to the average_load, so we don't
7737	 * want to push ourselves above the average load, nor do we wish to
7738	 * reduce the max loaded cpu below the average load. At the same time,
7739	 * we also don't want to reduce the group load below the group
7740	 * capacity. Thus we look for the minimum possible imbalance.
 
7741	 */
7742	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7743
7744	/* How much load to actually move to equalise the imbalance */
7745	env->imbalance = min(
7746		max_pull * busiest->group_capacity,
7747		(sds->avg_load - local->avg_load) * local->group_capacity
7748	) / SCHED_CAPACITY_SCALE;
7749
7750	/*
7751	 * if *imbalance is less than the average load per runnable task
7752	 * there is no guarantee that any tasks will be moved so we'll have
7753	 * a think about bumping its value to force at least one task to be
7754	 * moved
7755	 */
7756	if (env->imbalance < busiest->load_per_task)
7757		return fix_small_imbalance(env, sds);
7758}
7759
7760/******* find_busiest_group() helpers end here *********************/
7761
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7762/**
7763 * find_busiest_group - Returns the busiest group within the sched_domain
7764 * if there is an imbalance.
7765 *
7766 * Also calculates the amount of weighted load which should be moved
7767 * to restore balance.
7768 *
7769 * @env: The load balancing environment.
7770 *
7771 * Return:	- The busiest group if imbalance exists.
7772 */
7773static struct sched_group *find_busiest_group(struct lb_env *env)
7774{
7775	struct sg_lb_stats *local, *busiest;
7776	struct sd_lb_stats sds;
7777
7778	init_sd_lb_stats(&sds);
7779
7780	/*
7781	 * Compute the various statistics relavent for load balancing at
7782	 * this level.
7783	 */
7784	update_sd_lb_stats(env, &sds);
 
 
 
 
 
 
 
 
7785	local = &sds.local_stat;
7786	busiest = &sds.busiest_stat;
7787
7788	/* ASYM feature bypasses nice load balance check */
7789	if (check_asym_packing(env, &sds))
7790		return sds.busiest;
7791
7792	/* There is no busy sibling group to pull tasks from */
7793	if (!sds.busiest || busiest->sum_nr_running == 0)
7794		goto out_balanced;
7795
7796	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
7797						/ sds.total_capacity;
 
 
 
 
 
7798
7799	/*
7800	 * If the busiest group is imbalanced the below checks don't
7801	 * work because they assume all things are equal, which typically
7802	 * isn't true due to cpus_allowed constraints and the like.
7803	 */
7804	if (busiest->group_type == group_imbalanced)
7805		goto force_balance;
7806
7807	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7808	if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
7809	    busiest->group_no_capacity)
7810		goto force_balance;
7811
7812	/*
7813	 * If the local group is busier than the selected busiest group
7814	 * don't try and pull any tasks.
7815	 */
7816	if (local->avg_load >= busiest->avg_load)
7817		goto out_balanced;
7818
7819	/*
7820	 * Don't pull any tasks if this group is already above the domain
7821	 * average load.
7822	 */
7823	if (local->avg_load >= sds.avg_load)
7824		goto out_balanced;
 
 
 
 
 
 
 
 
 
7825
7826	if (env->idle == CPU_IDLE) {
7827		/*
7828		 * This cpu is idle. If the busiest group is not overloaded
7829		 * and there is no imbalance between this and busiest group
7830		 * wrt idle cpus, it is balanced. The imbalance becomes
7831		 * significant if the diff is greater than 1 otherwise we
7832		 * might end up to just move the imbalance on another group
7833		 */
7834		if ((busiest->group_type != group_overloaded) &&
7835				(local->idle_cpus <= (busiest->idle_cpus + 1)))
7836			goto out_balanced;
7837	} else {
7838		/*
7839		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7840		 * imbalance_pct to be conservative.
7841		 */
7842		if (100 * busiest->avg_load <=
7843				env->sd->imbalance_pct * local->avg_load)
7844			goto out_balanced;
7845	}
7846
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7847force_balance:
7848	/* Looks like there is an imbalance. Compute it */
7849	calculate_imbalance(env, &sds);
7850	return sds.busiest;
7851
7852out_balanced:
7853	env->imbalance = 0;
7854	return NULL;
7855}
7856
7857/*
7858 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7859 */
7860static struct rq *find_busiest_queue(struct lb_env *env,
7861				     struct sched_group *group)
7862{
7863	struct rq *busiest = NULL, *rq;
7864	unsigned long busiest_load = 0, busiest_capacity = 1;
 
7865	int i;
7866
7867	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7868		unsigned long capacity, wl;
 
7869		enum fbq_type rt;
7870
7871		rq = cpu_rq(i);
7872		rt = fbq_classify_rq(rq);
7873
7874		/*
7875		 * We classify groups/runqueues into three groups:
7876		 *  - regular: there are !numa tasks
7877		 *  - remote:  there are numa tasks that run on the 'wrong' node
7878		 *  - all:     there is no distinction
7879		 *
7880		 * In order to avoid migrating ideally placed numa tasks,
7881		 * ignore those when there's better options.
7882		 *
7883		 * If we ignore the actual busiest queue to migrate another
7884		 * task, the next balance pass can still reduce the busiest
7885		 * queue by moving tasks around inside the node.
7886		 *
7887		 * If we cannot move enough load due to this classification
7888		 * the next pass will adjust the group classification and
7889		 * allow migration of more tasks.
7890		 *
7891		 * Both cases only affect the total convergence complexity.
7892		 */
7893		if (rt > env->fbq_type)
7894			continue;
7895
7896		capacity = capacity_of(i);
7897
7898		wl = weighted_cpuload(i);
7899
7900		/*
7901		 * When comparing with imbalance, use weighted_cpuload()
7902		 * which is not scaled with the cpu capacity.
 
 
7903		 */
7904
7905		if (rq->nr_running == 1 && wl > env->imbalance &&
7906		    !check_cpu_capacity(rq, env->sd))
7907			continue;
7908
7909		/*
7910		 * For the load comparisons with the other cpu's, consider
7911		 * the weighted_cpuload() scaled with the cpu capacity, so
7912		 * that the load can be moved away from the cpu that is
7913		 * potentially running at a lower capacity.
7914		 *
7915		 * Thus we're looking for max(wl_i / capacity_i), crosswise
7916		 * multiplication to rid ourselves of the division works out
7917		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
7918		 * our previous maximum.
7919		 */
7920		if (wl * busiest_capacity > busiest_load * capacity) {
7921			busiest_load = wl;
7922			busiest_capacity = capacity;
7923			busiest = rq;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7924		}
7925	}
7926
7927	return busiest;
7928}
7929
7930/*
7931 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7932 * so long as it is large enough.
7933 */
7934#define MAX_PINNED_INTERVAL	512
7935
7936static int need_active_balance(struct lb_env *env)
 
7937{
7938	struct sched_domain *sd = env->sd;
 
 
 
 
 
 
 
7939
7940	if (env->idle == CPU_NEWLY_IDLE) {
 
 
 
7941
7942		/*
7943		 * ASYM_PACKING needs to force migrate tasks from busy but
7944		 * lower priority CPUs in order to pack all tasks in the
7945		 * highest priority CPUs.
7946		 */
7947		if ((sd->flags & SD_ASYM_PACKING) &&
7948		    sched_asym_prefer(env->dst_cpu, env->src_cpu))
7949			return 1;
7950	}
7951
7952	/*
7953	 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7954	 * It's worth migrating the task if the src_cpu's capacity is reduced
7955	 * because of other sched_class or IRQs if more capacity stays
7956	 * available on dst_cpu.
7957	 */
7958	if ((env->idle != CPU_NOT_IDLE) &&
7959	    (env->src_rq->cfs.h_nr_running == 1)) {
7960		if ((check_cpu_capacity(env->src_rq, sd)) &&
7961		    (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
7962			return 1;
7963	}
7964
 
 
 
 
 
 
 
 
 
 
 
 
 
7965	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
7966}
7967
7968static int active_load_balance_cpu_stop(void *data);
7969
7970static int should_we_balance(struct lb_env *env)
7971{
7972	struct sched_group *sg = env->sd->groups;
7973	struct cpumask *sg_cpus, *sg_mask;
7974	int cpu, balance_cpu = -1;
 
 
 
 
 
 
7975
7976	/*
7977	 * In the newly idle case, we will allow all the cpu's
7978	 * to do the newly idle load balance.
7979	 */
7980	if (env->idle == CPU_NEWLY_IDLE)
7981		return 1;
7982
7983	sg_cpus = sched_group_cpus(sg);
7984	sg_mask = sched_group_mask(sg);
7985	/* Try to find first idle cpu */
7986	for_each_cpu_and(cpu, sg_cpus, env->cpus) {
7987		if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
7988			continue;
7989
7990		balance_cpu = cpu;
7991		break;
7992	}
7993
7994	if (balance_cpu == -1)
7995		balance_cpu = group_balance_cpu(sg);
7996
7997	/*
7998	 * First idle cpu or the first cpu(busiest) in this sched group
7999	 * is eligible for doing load balancing at this and above domains.
8000	 */
8001	return balance_cpu == env->dst_cpu;
8002}
8003
8004/*
8005 * Check this_cpu to ensure it is balanced within domain. Attempt to move
8006 * tasks if there is an imbalance.
8007 */
8008static int load_balance(int this_cpu, struct rq *this_rq,
8009			struct sched_domain *sd, enum cpu_idle_type idle,
8010			int *continue_balancing)
8011{
8012	int ld_moved, cur_ld_moved, active_balance = 0;
8013	struct sched_domain *sd_parent = sd->parent;
8014	struct sched_group *group;
8015	struct rq *busiest;
8016	unsigned long flags;
8017	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
8018
8019	struct lb_env env = {
8020		.sd		= sd,
8021		.dst_cpu	= this_cpu,
8022		.dst_rq		= this_rq,
8023		.dst_grpmask    = sched_group_cpus(sd->groups),
8024		.idle		= idle,
8025		.loop_break	= sched_nr_migrate_break,
8026		.cpus		= cpus,
8027		.fbq_type	= all,
8028		.tasks		= LIST_HEAD_INIT(env.tasks),
8029	};
8030
8031	/*
8032	 * For NEWLY_IDLE load_balancing, we don't need to consider
8033	 * other cpus in our group
8034	 */
8035	if (idle == CPU_NEWLY_IDLE)
8036		env.dst_grpmask = NULL;
8037
8038	cpumask_copy(cpus, cpu_active_mask);
8039
8040	schedstat_inc(sd->lb_count[idle]);
8041
8042redo:
8043	if (!should_we_balance(&env)) {
8044		*continue_balancing = 0;
8045		goto out_balanced;
8046	}
8047
8048	group = find_busiest_group(&env);
8049	if (!group) {
8050		schedstat_inc(sd->lb_nobusyg[idle]);
8051		goto out_balanced;
8052	}
8053
8054	busiest = find_busiest_queue(&env, group);
8055	if (!busiest) {
8056		schedstat_inc(sd->lb_nobusyq[idle]);
8057		goto out_balanced;
8058	}
8059
8060	BUG_ON(busiest == env.dst_rq);
8061
8062	schedstat_add(sd->lb_imbalance[idle], env.imbalance);
8063
8064	env.src_cpu = busiest->cpu;
8065	env.src_rq = busiest;
8066
8067	ld_moved = 0;
8068	if (busiest->nr_running > 1) {
8069		/*
8070		 * Attempt to move tasks. If find_busiest_group has found
8071		 * an imbalance but busiest->nr_running <= 1, the group is
8072		 * still unbalanced. ld_moved simply stays zero, so it is
8073		 * correctly treated as an imbalance.
8074		 */
8075		env.flags |= LBF_ALL_PINNED;
8076		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
8077
8078more_balance:
8079		raw_spin_lock_irqsave(&busiest->lock, flags);
 
8080
8081		/*
8082		 * cur_ld_moved - load moved in current iteration
8083		 * ld_moved     - cumulative load moved across iterations
8084		 */
8085		cur_ld_moved = detach_tasks(&env);
8086
8087		/*
8088		 * We've detached some tasks from busiest_rq. Every
8089		 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
8090		 * unlock busiest->lock, and we are able to be sure
8091		 * that nobody can manipulate the tasks in parallel.
8092		 * See task_rq_lock() family for the details.
8093		 */
8094
8095		raw_spin_unlock(&busiest->lock);
8096
8097		if (cur_ld_moved) {
8098			attach_tasks(&env);
8099			ld_moved += cur_ld_moved;
8100		}
8101
8102		local_irq_restore(flags);
8103
8104		if (env.flags & LBF_NEED_BREAK) {
8105			env.flags &= ~LBF_NEED_BREAK;
8106			goto more_balance;
8107		}
8108
8109		/*
8110		 * Revisit (affine) tasks on src_cpu that couldn't be moved to
8111		 * us and move them to an alternate dst_cpu in our sched_group
8112		 * where they can run. The upper limit on how many times we
8113		 * iterate on same src_cpu is dependent on number of cpus in our
8114		 * sched_group.
8115		 *
8116		 * This changes load balance semantics a bit on who can move
8117		 * load to a given_cpu. In addition to the given_cpu itself
8118		 * (or a ilb_cpu acting on its behalf where given_cpu is
8119		 * nohz-idle), we now have balance_cpu in a position to move
8120		 * load to given_cpu. In rare situations, this may cause
8121		 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
8122		 * _independently_ and at _same_ time to move some load to
8123		 * given_cpu) causing exceess load to be moved to given_cpu.
8124		 * This however should not happen so much in practice and
8125		 * moreover subsequent load balance cycles should correct the
8126		 * excess load moved.
8127		 */
8128		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
8129
8130			/* Prevent to re-select dst_cpu via env's cpus */
8131			cpumask_clear_cpu(env.dst_cpu, env.cpus);
8132
8133			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
8134			env.dst_cpu	 = env.new_dst_cpu;
8135			env.flags	&= ~LBF_DST_PINNED;
8136			env.loop	 = 0;
8137			env.loop_break	 = sched_nr_migrate_break;
8138
8139			/*
8140			 * Go back to "more_balance" rather than "redo" since we
8141			 * need to continue with same src_cpu.
8142			 */
8143			goto more_balance;
8144		}
8145
8146		/*
8147		 * We failed to reach balance because of affinity.
8148		 */
8149		if (sd_parent) {
8150			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
8151
8152			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
8153				*group_imbalance = 1;
8154		}
8155
8156		/* All tasks on this runqueue were pinned by CPU affinity */
8157		if (unlikely(env.flags & LBF_ALL_PINNED)) {
8158			cpumask_clear_cpu(cpu_of(busiest), cpus);
8159			if (!cpumask_empty(cpus)) {
 
 
 
 
 
 
 
 
8160				env.loop = 0;
8161				env.loop_break = sched_nr_migrate_break;
8162				goto redo;
8163			}
8164			goto out_all_pinned;
8165		}
8166	}
8167
8168	if (!ld_moved) {
8169		schedstat_inc(sd->lb_failed[idle]);
8170		/*
8171		 * Increment the failure counter only on periodic balance.
8172		 * We do not want newidle balance, which can be very
8173		 * frequent, pollute the failure counter causing
8174		 * excessive cache_hot migrations and active balances.
8175		 */
8176		if (idle != CPU_NEWLY_IDLE)
8177			sd->nr_balance_failed++;
8178
8179		if (need_active_balance(&env)) {
 
 
8180			raw_spin_lock_irqsave(&busiest->lock, flags);
8181
8182			/* don't kick the active_load_balance_cpu_stop,
8183			 * if the curr task on busiest cpu can't be
8184			 * moved to this_cpu
 
8185			 */
8186			if (!cpumask_test_cpu(this_cpu,
8187					tsk_cpus_allowed(busiest->curr))) {
8188				raw_spin_unlock_irqrestore(&busiest->lock,
8189							    flags);
8190				env.flags |= LBF_ALL_PINNED;
8191				goto out_one_pinned;
8192			}
8193
8194			/*
8195			 * ->active_balance synchronizes accesses to
8196			 * ->active_balance_work.  Once set, it's cleared
8197			 * only after active load balance is finished.
8198			 */
8199			if (!busiest->active_balance) {
8200				busiest->active_balance = 1;
8201				busiest->push_cpu = this_cpu;
8202				active_balance = 1;
8203			}
8204			raw_spin_unlock_irqrestore(&busiest->lock, flags);
8205
8206			if (active_balance) {
8207				stop_one_cpu_nowait(cpu_of(busiest),
8208					active_load_balance_cpu_stop, busiest,
8209					&busiest->active_balance_work);
8210			}
8211
8212			/* We've kicked active balancing, force task migration. */
8213			sd->nr_balance_failed = sd->cache_nice_tries+1;
8214		}
8215	} else
8216		sd->nr_balance_failed = 0;
8217
8218	if (likely(!active_balance)) {
8219		/* We were unbalanced, so reset the balancing interval */
8220		sd->balance_interval = sd->min_interval;
8221	} else {
8222		/*
8223		 * If we've begun active balancing, start to back off. This
8224		 * case may not be covered by the all_pinned logic if there
8225		 * is only 1 task on the busy runqueue (because we don't call
8226		 * detach_tasks).
8227		 */
8228		if (sd->balance_interval < sd->max_interval)
8229			sd->balance_interval *= 2;
8230	}
8231
8232	goto out;
8233
8234out_balanced:
8235	/*
8236	 * We reach balance although we may have faced some affinity
8237	 * constraints. Clear the imbalance flag if it was set.
 
8238	 */
8239	if (sd_parent) {
8240		int *group_imbalance = &sd_parent->groups->sgc->imbalance;
8241
8242		if (*group_imbalance)
8243			*group_imbalance = 0;
8244	}
8245
8246out_all_pinned:
8247	/*
8248	 * We reach balance because all tasks are pinned at this level so
8249	 * we can't migrate them. Let the imbalance flag set so parent level
8250	 * can try to migrate them.
8251	 */
8252	schedstat_inc(sd->lb_balanced[idle]);
8253
8254	sd->nr_balance_failed = 0;
8255
8256out_one_pinned:
 
 
 
 
 
 
 
 
 
 
 
8257	/* tune up the balancing interval */
8258	if (((env.flags & LBF_ALL_PINNED) &&
8259			sd->balance_interval < MAX_PINNED_INTERVAL) ||
8260			(sd->balance_interval < sd->max_interval))
8261		sd->balance_interval *= 2;
8262
8263	ld_moved = 0;
8264out:
8265	return ld_moved;
8266}
8267
8268static inline unsigned long
8269get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
8270{
8271	unsigned long interval = sd->balance_interval;
8272
8273	if (cpu_busy)
8274		interval *= sd->busy_factor;
8275
8276	/* scale ms to jiffies */
8277	interval = msecs_to_jiffies(interval);
8278	interval = clamp(interval, 1UL, max_load_balance_interval);
8279
8280	return interval;
8281}
8282
8283static inline void
8284update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
8285{
8286	unsigned long interval, next;
8287
8288	/* used by idle balance, so cpu_busy = 0 */
8289	interval = get_sd_balance_interval(sd, 0);
8290	next = sd->last_balance + interval;
8291
8292	if (time_after(*next_balance, next))
8293		*next_balance = next;
8294}
8295
8296/*
8297 * idle_balance is called by schedule() if this_cpu is about to become
8298 * idle. Attempts to pull tasks from other CPUs.
8299 */
8300static int idle_balance(struct rq *this_rq)
8301{
8302	unsigned long next_balance = jiffies + HZ;
8303	int this_cpu = this_rq->cpu;
8304	struct sched_domain *sd;
8305	int pulled_task = 0;
8306	u64 curr_cost = 0;
8307
8308	/*
8309	 * We must set idle_stamp _before_ calling idle_balance(), such that we
8310	 * measure the duration of idle_balance() as idle time.
8311	 */
8312	this_rq->idle_stamp = rq_clock(this_rq);
8313
8314	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
8315	    !this_rq->rd->overload) {
8316		rcu_read_lock();
8317		sd = rcu_dereference_check_sched_domain(this_rq->sd);
8318		if (sd)
8319			update_next_balance(sd, &next_balance);
8320		rcu_read_unlock();
8321
8322		goto out;
8323	}
8324
8325	raw_spin_unlock(&this_rq->lock);
8326
8327	update_blocked_averages(this_cpu);
8328	rcu_read_lock();
8329	for_each_domain(this_cpu, sd) {
8330		int continue_balancing = 1;
8331		u64 t0, domain_cost;
8332
8333		if (!(sd->flags & SD_LOAD_BALANCE))
8334			continue;
8335
8336		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
8337			update_next_balance(sd, &next_balance);
8338			break;
8339		}
8340
8341		if (sd->flags & SD_BALANCE_NEWIDLE) {
8342			t0 = sched_clock_cpu(this_cpu);
8343
8344			pulled_task = load_balance(this_cpu, this_rq,
8345						   sd, CPU_NEWLY_IDLE,
8346						   &continue_balancing);
8347
8348			domain_cost = sched_clock_cpu(this_cpu) - t0;
8349			if (domain_cost > sd->max_newidle_lb_cost)
8350				sd->max_newidle_lb_cost = domain_cost;
8351
8352			curr_cost += domain_cost;
8353		}
8354
8355		update_next_balance(sd, &next_balance);
8356
8357		/*
8358		 * Stop searching for tasks to pull if there are
8359		 * now runnable tasks on this rq.
8360		 */
8361		if (pulled_task || this_rq->nr_running > 0)
8362			break;
8363	}
8364	rcu_read_unlock();
8365
8366	raw_spin_lock(&this_rq->lock);
8367
8368	if (curr_cost > this_rq->max_idle_balance_cost)
8369		this_rq->max_idle_balance_cost = curr_cost;
8370
8371	/*
8372	 * While browsing the domains, we released the rq lock, a task could
8373	 * have been enqueued in the meantime. Since we're not going idle,
8374	 * pretend we pulled a task.
8375	 */
8376	if (this_rq->cfs.h_nr_running && !pulled_task)
8377		pulled_task = 1;
8378
8379out:
8380	/* Move the next balance forward */
8381	if (time_after(this_rq->next_balance, next_balance))
8382		this_rq->next_balance = next_balance;
8383
8384	/* Is there a task of a high priority class? */
8385	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
8386		pulled_task = -1;
8387
8388	if (pulled_task)
8389		this_rq->idle_stamp = 0;
8390
8391	return pulled_task;
8392}
8393
8394/*
8395 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
8396 * running tasks off the busiest CPU onto idle CPUs. It requires at
8397 * least 1 task to be running on each physical CPU where possible, and
8398 * avoids physical / logical imbalances.
8399 */
8400static int active_load_balance_cpu_stop(void *data)
8401{
8402	struct rq *busiest_rq = data;
8403	int busiest_cpu = cpu_of(busiest_rq);
8404	int target_cpu = busiest_rq->push_cpu;
8405	struct rq *target_rq = cpu_rq(target_cpu);
8406	struct sched_domain *sd;
8407	struct task_struct *p = NULL;
 
8408
8409	raw_spin_lock_irq(&busiest_rq->lock);
 
 
 
 
 
 
 
8410
8411	/* make sure the requested cpu hasn't gone down in the meantime */
8412	if (unlikely(busiest_cpu != smp_processor_id() ||
8413		     !busiest_rq->active_balance))
8414		goto out_unlock;
8415
8416	/* Is there any task to move? */
8417	if (busiest_rq->nr_running <= 1)
8418		goto out_unlock;
8419
8420	/*
8421	 * This condition is "impossible", if it occurs
8422	 * we need to fix it. Originally reported by
8423	 * Bjorn Helgaas on a 128-cpu setup.
8424	 */
8425	BUG_ON(busiest_rq == target_rq);
8426
8427	/* Search for an sd spanning us and the target CPU. */
8428	rcu_read_lock();
8429	for_each_domain(target_cpu, sd) {
8430		if ((sd->flags & SD_LOAD_BALANCE) &&
8431		    cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
8432				break;
8433	}
8434
8435	if (likely(sd)) {
8436		struct lb_env env = {
8437			.sd		= sd,
8438			.dst_cpu	= target_cpu,
8439			.dst_rq		= target_rq,
8440			.src_cpu	= busiest_rq->cpu,
8441			.src_rq		= busiest_rq,
8442			.idle		= CPU_IDLE,
 
 
 
 
 
 
 
8443		};
8444
8445		schedstat_inc(sd->alb_count);
 
8446
8447		p = detach_one_task(&env);
8448		if (p) {
8449			schedstat_inc(sd->alb_pushed);
8450			/* Active balancing done, reset the failure counter. */
8451			sd->nr_balance_failed = 0;
8452		} else {
8453			schedstat_inc(sd->alb_failed);
8454		}
8455	}
8456	rcu_read_unlock();
8457out_unlock:
8458	busiest_rq->active_balance = 0;
8459	raw_spin_unlock(&busiest_rq->lock);
8460
8461	if (p)
8462		attach_one_task(target_rq, p);
8463
8464	local_irq_enable();
8465
8466	return 0;
8467}
8468
8469static inline int on_null_domain(struct rq *rq)
8470{
8471	return unlikely(!rcu_dereference_sched(rq->sd));
8472}
8473
8474#ifdef CONFIG_NO_HZ_COMMON
8475/*
8476 * idle load balancing details
8477 * - When one of the busy CPUs notice that there may be an idle rebalancing
8478 *   needed, they will kick the idle load balancer, which then does idle
8479 *   load balancing for all the idle CPUs.
8480 */
8481static struct {
8482	cpumask_var_t idle_cpus_mask;
8483	atomic_t nr_cpus;
8484	unsigned long next_balance;     /* in jiffy units */
8485} nohz ____cacheline_aligned;
8486
8487static inline int find_new_ilb(void)
8488{
8489	int ilb = cpumask_first(nohz.idle_cpus_mask);
8490
8491	if (ilb < nr_cpu_ids && idle_cpu(ilb))
8492		return ilb;
8493
8494	return nr_cpu_ids;
8495}
8496
8497/*
8498 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
8499 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
8500 * CPU (if there is one).
8501 */
8502static void nohz_balancer_kick(void)
8503{
8504	int ilb_cpu;
8505
8506	nohz.next_balance++;
8507
8508	ilb_cpu = find_new_ilb();
8509
8510	if (ilb_cpu >= nr_cpu_ids)
8511		return;
8512
8513	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
8514		return;
8515	/*
8516	 * Use smp_send_reschedule() instead of resched_cpu().
8517	 * This way we generate a sched IPI on the target cpu which
8518	 * is idle. And the softirq performing nohz idle load balance
8519	 * will be run before returning from the IPI.
8520	 */
8521	smp_send_reschedule(ilb_cpu);
8522	return;
8523}
8524
8525void nohz_balance_exit_idle(unsigned int cpu)
8526{
8527	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
8528		/*
8529		 * Completely isolated CPUs don't ever set, so we must test.
8530		 */
8531		if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
8532			cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
8533			atomic_dec(&nohz.nr_cpus);
8534		}
8535		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8536	}
8537}
8538
8539static inline void set_cpu_sd_state_busy(void)
8540{
8541	struct sched_domain *sd;
8542	int cpu = smp_processor_id();
8543
8544	rcu_read_lock();
8545	sd = rcu_dereference(per_cpu(sd_llc, cpu));
8546
8547	if (!sd || !sd->nohz_idle)
8548		goto unlock;
8549	sd->nohz_idle = 0;
8550
8551	atomic_inc(&sd->shared->nr_busy_cpus);
8552unlock:
8553	rcu_read_unlock();
8554}
8555
8556void set_cpu_sd_state_idle(void)
8557{
8558	struct sched_domain *sd;
8559	int cpu = smp_processor_id();
8560
8561	rcu_read_lock();
8562	sd = rcu_dereference(per_cpu(sd_llc, cpu));
8563
8564	if (!sd || sd->nohz_idle)
8565		goto unlock;
8566	sd->nohz_idle = 1;
8567
8568	atomic_dec(&sd->shared->nr_busy_cpus);
8569unlock:
8570	rcu_read_unlock();
8571}
8572
8573/*
8574 * This routine will record that the cpu is going idle with tick stopped.
8575 * This info will be used in performing idle load balancing in the future.
8576 */
8577void nohz_balance_enter_idle(int cpu)
8578{
8579	/*
8580	 * If this cpu is going down, then nothing needs to be done.
8581	 */
8582	if (!cpu_active(cpu))
8583		return;
8584
8585	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
8586		return;
8587
8588	/*
8589	 * If we're a completely isolated CPU, we don't play.
8590	 */
8591	if (on_null_domain(cpu_rq(cpu)))
8592		return;
8593
8594	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
8595	atomic_inc(&nohz.nr_cpus);
8596	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8597}
8598#endif
8599
8600static DEFINE_SPINLOCK(balancing);
8601
8602/*
8603 * Scale the max load_balance interval with the number of CPUs in the system.
8604 * This trades load-balance latency on larger machines for less cross talk.
8605 */
8606void update_max_interval(void)
8607{
8608	max_load_balance_interval = HZ*num_online_cpus()/10;
8609}
8610
8611/*
8612 * It checks each scheduling domain to see if it is due to be balanced,
8613 * and initiates a balancing operation if so.
8614 *
8615 * Balancing parameters are set up in init_sched_domains.
8616 */
8617static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
8618{
8619	int continue_balancing = 1;
8620	int cpu = rq->cpu;
 
8621	unsigned long interval;
8622	struct sched_domain *sd;
8623	/* Earliest time when we have to do rebalance again */
8624	unsigned long next_balance = jiffies + 60*HZ;
8625	int update_next_balance = 0;
8626	int need_serialize, need_decay = 0;
8627	u64 max_cost = 0;
8628
8629	update_blocked_averages(cpu);
8630
8631	rcu_read_lock();
8632	for_each_domain(cpu, sd) {
8633		/*
8634		 * Decay the newidle max times here because this is a regular
8635		 * visit to all the domains. Decay ~1% per second.
8636		 */
8637		if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
8638			sd->max_newidle_lb_cost =
8639				(sd->max_newidle_lb_cost * 253) / 256;
8640			sd->next_decay_max_lb_cost = jiffies + HZ;
8641			need_decay = 1;
8642		}
8643		max_cost += sd->max_newidle_lb_cost;
8644
8645		if (!(sd->flags & SD_LOAD_BALANCE))
8646			continue;
8647
8648		/*
8649		 * Stop the load balance at this level. There is another
8650		 * CPU in our sched group which is doing load balancing more
8651		 * actively.
8652		 */
8653		if (!continue_balancing) {
8654			if (need_decay)
8655				continue;
8656			break;
8657		}
8658
8659		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8660
8661		need_serialize = sd->flags & SD_SERIALIZE;
8662		if (need_serialize) {
8663			if (!spin_trylock(&balancing))
8664				goto out;
8665		}
8666
8667		if (time_after_eq(jiffies, sd->last_balance + interval)) {
8668			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
8669				/*
8670				 * The LBF_DST_PINNED logic could have changed
8671				 * env->dst_cpu, so we can't know our idle
8672				 * state even if we migrated tasks. Update it.
8673				 */
8674				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
 
8675			}
8676			sd->last_balance = jiffies;
8677			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8678		}
8679		if (need_serialize)
8680			spin_unlock(&balancing);
8681out:
8682		if (time_after(next_balance, sd->last_balance + interval)) {
8683			next_balance = sd->last_balance + interval;
8684			update_next_balance = 1;
8685		}
8686	}
8687	if (need_decay) {
8688		/*
8689		 * Ensure the rq-wide value also decays but keep it at a
8690		 * reasonable floor to avoid funnies with rq->avg_idle.
8691		 */
8692		rq->max_idle_balance_cost =
8693			max((u64)sysctl_sched_migration_cost, max_cost);
8694	}
8695	rcu_read_unlock();
8696
8697	/*
8698	 * next_balance will be updated only when there is a need.
8699	 * When the cpu is attached to null domain for ex, it will not be
8700	 * updated.
8701	 */
8702	if (likely(update_next_balance)) {
8703		rq->next_balance = next_balance;
8704
8705#ifdef CONFIG_NO_HZ_COMMON
8706		/*
8707		 * If this CPU has been elected to perform the nohz idle
8708		 * balance. Other idle CPUs have already rebalanced with
8709		 * nohz_idle_balance() and nohz.next_balance has been
8710		 * updated accordingly. This CPU is now running the idle load
8711		 * balance for itself and we need to update the
8712		 * nohz.next_balance accordingly.
8713		 */
8714		if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
8715			nohz.next_balance = rq->next_balance;
8716#endif
8717	}
8718}
8719
 
 
 
 
 
8720#ifdef CONFIG_NO_HZ_COMMON
8721/*
8722 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8723 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 
 
 
 
8724 */
8725static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
8726{
8727	int this_cpu = this_rq->cpu;
8728	struct rq *rq;
8729	int balance_cpu;
8730	/* Earliest time when we have to do rebalance again */
8731	unsigned long next_balance = jiffies + 60*HZ;
 
 
8732	int update_next_balance = 0;
 
 
 
 
 
 
8733
8734	if (idle != CPU_IDLE ||
8735	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
8736		goto end;
 
 
 
 
 
 
 
 
 
 
 
 
8737
8738	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8739		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8740			continue;
8741
8742		/*
8743		 * If this cpu gets work to do, stop the load balancing
8744		 * work being done for other cpus. Next load
8745		 * balancing owner will pick it up.
8746		 */
8747		if (need_resched())
8748			break;
 
 
8749
8750		rq = cpu_rq(balance_cpu);
8751
 
 
8752		/*
8753		 * If time for next balance is due,
8754		 * do the balance.
8755		 */
8756		if (time_after_eq(jiffies, rq->next_balance)) {
8757			raw_spin_lock_irq(&rq->lock);
 
 
8758			update_rq_clock(rq);
8759			cpu_load_update_idle(rq);
8760			raw_spin_unlock_irq(&rq->lock);
8761			rebalance_domains(rq, CPU_IDLE);
 
8762		}
8763
8764		if (time_after(next_balance, rq->next_balance)) {
8765			next_balance = rq->next_balance;
8766			update_next_balance = 1;
8767		}
8768	}
8769
8770	/*
8771	 * next_balance will be updated only when there is a need.
8772	 * When the CPU is attached to null domain for ex, it will not be
8773	 * updated.
8774	 */
8775	if (likely(update_next_balance))
8776		nohz.next_balance = next_balance;
8777end:
8778	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
8779}
8780
8781/*
8782 * Current heuristic for kicking the idle load balancer in the presence
8783 * of an idle cpu in the system.
8784 *   - This rq has more than one task.
8785 *   - This rq has at least one CFS task and the capacity of the CPU is
8786 *     significantly reduced because of RT tasks or IRQs.
8787 *   - At parent of LLC scheduler domain level, this cpu's scheduler group has
8788 *     multiple busy cpu.
8789 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
8790 *     domain span are idle.
8791 */
8792static inline bool nohz_kick_needed(struct rq *rq)
8793{
8794	unsigned long now = jiffies;
8795	struct sched_domain_shared *sds;
8796	struct sched_domain *sd;
8797	int nr_busy, i, cpu = rq->cpu;
8798	bool kick = false;
8799
8800	if (unlikely(rq->idle_balance))
 
 
 
 
 
8801		return false;
8802
8803       /*
8804	* We may be recently in ticked or tickless idle mode. At the first
8805	* busy tick after returning from idle, we will update the busy stats.
8806	*/
8807	set_cpu_sd_state_busy();
8808	nohz_balance_exit_idle(cpu);
 
 
8809
8810	/*
8811	 * None are in tickless mode and hence no need for NOHZ idle load
8812	 * balancing.
8813	 */
8814	if (likely(!atomic_read(&nohz.nr_cpus)))
8815		return false;
8816
8817	if (time_before(now, nohz.next_balance))
8818		return false;
 
8819
8820	if (rq->nr_running >= 2)
8821		return true;
 
 
8822
8823	rcu_read_lock();
8824	sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
8825	if (sds) {
8826		/*
8827		 * XXX: write a coherent comment on why we do this.
8828		 * See also: http://lkml.kernel.org/r/20111202010832.602203411@sbsiddha-desk.sc.intel.com
8829		 */
8830		nr_busy = atomic_read(&sds->nr_busy_cpus);
8831		if (nr_busy > 1) {
8832			kick = true;
8833			goto unlock;
8834		}
 
 
8835
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
8836	}
8837
8838	sd = rcu_dereference(rq->sd);
8839	if (sd) {
8840		if ((rq->cfs.h_nr_running >= 1) &&
8841				check_cpu_capacity(rq, sd)) {
8842			kick = true;
8843			goto unlock;
 
 
 
 
 
8844		}
8845	}
8846
8847	sd = rcu_dereference(per_cpu(sd_asym, cpu));
8848	if (sd) {
8849		for_each_cpu(i, sched_domain_span(sd)) {
8850			if (i == cpu ||
8851			    !cpumask_test_cpu(i, nohz.idle_cpus_mask))
8852				continue;
8853
8854			if (sched_asym_prefer(i, cpu)) {
8855				kick = true;
8856				goto unlock;
8857			}
 
 
 
 
 
8858		}
 
 
 
 
 
 
 
 
 
8859	}
8860unlock:
8861	rcu_read_unlock();
8862	return kick;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
8863}
8864#else
8865static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8866#endif
8867
8868/*
8869 * run_rebalance_domains is triggered when needed from the scheduler tick.
8870 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
8871 */
8872static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
8873{
8874	struct rq *this_rq = this_rq();
8875	enum cpu_idle_type idle = this_rq->idle_balance ?
8876						CPU_IDLE : CPU_NOT_IDLE;
8877
8878	/*
8879	 * If this cpu has a pending nohz_balance_kick, then do the
8880	 * balancing on behalf of the other idle cpus whose ticks are
8881	 * stopped. Do nohz_idle_balance *before* rebalance_domains to
8882	 * give the idle cpus a chance to load balance. Else we may
8883	 * load balance only within the local sched_domain hierarchy
8884	 * and abort nohz_idle_balance altogether if we pull some load.
8885	 */
8886	nohz_idle_balance(this_rq, idle);
 
 
 
 
8887	rebalance_domains(this_rq, idle);
8888}
8889
8890/*
8891 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
8892 */
8893void trigger_load_balance(struct rq *rq)
8894{
8895	/* Don't need to rebalance while attached to NULL domain */
8896	if (unlikely(on_null_domain(rq)))
8897		return;
8898
8899	if (time_after_eq(jiffies, rq->next_balance))
8900		raise_softirq(SCHED_SOFTIRQ);
8901#ifdef CONFIG_NO_HZ_COMMON
8902	if (nohz_kick_needed(rq))
8903		nohz_balancer_kick();
8904#endif
8905}
8906
8907static void rq_online_fair(struct rq *rq)
8908{
8909	update_sysctl();
8910
8911	update_runtime_enabled(rq);
8912}
8913
8914static void rq_offline_fair(struct rq *rq)
8915{
8916	update_sysctl();
8917
8918	/* Ensure any throttled groups are reachable by pick_next_task */
8919	unthrottle_offline_cfs_rqs(rq);
8920}
8921
8922#endif /* CONFIG_SMP */
8923
8924/*
8925 * scheduler tick hitting a task of our scheduling class:
 
 
 
 
 
8926 */
8927static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8928{
8929	struct cfs_rq *cfs_rq;
8930	struct sched_entity *se = &curr->se;
8931
8932	for_each_sched_entity(se) {
8933		cfs_rq = cfs_rq_of(se);
8934		entity_tick(cfs_rq, se, queued);
8935	}
8936
8937	if (static_branch_unlikely(&sched_numa_balancing))
8938		task_tick_numa(rq, curr);
 
 
 
8939}
8940
8941/*
8942 * called on fork with the child task as argument from the parent's context
8943 *  - child not yet on the tasklist
8944 *  - preemption disabled
8945 */
8946static void task_fork_fair(struct task_struct *p)
8947{
8948	struct cfs_rq *cfs_rq;
8949	struct sched_entity *se = &p->se, *curr;
8950	struct rq *rq = this_rq();
 
8951
8952	raw_spin_lock(&rq->lock);
8953	update_rq_clock(rq);
8954
8955	cfs_rq = task_cfs_rq(current);
8956	curr = cfs_rq->curr;
8957	if (curr) {
8958		update_curr(cfs_rq);
8959		se->vruntime = curr->vruntime;
8960	}
8961	place_entity(cfs_rq, se, 1);
8962
8963	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
8964		/*
8965		 * Upon rescheduling, sched_class::put_prev_task() will place
8966		 * 'current' within the tree based on its new key value.
8967		 */
8968		swap(curr->vruntime, se->vruntime);
8969		resched_curr(rq);
8970	}
8971
8972	se->vruntime -= cfs_rq->min_vruntime;
8973	raw_spin_unlock(&rq->lock);
8974}
8975
8976/*
8977 * Priority of the task has changed. Check to see if we preempt
8978 * the current task.
8979 */
8980static void
8981prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8982{
8983	if (!task_on_rq_queued(p))
8984		return;
8985
 
 
 
8986	/*
8987	 * Reschedule if we are currently running on this runqueue and
8988	 * our priority decreased, or if we are not currently running on
8989	 * this runqueue and our priority is higher than the current's
8990	 */
8991	if (rq->curr == p) {
8992		if (p->prio > oldprio)
8993			resched_curr(rq);
8994	} else
8995		check_preempt_curr(rq, p, 0);
8996}
8997
8998static inline bool vruntime_normalized(struct task_struct *p)
8999{
9000	struct sched_entity *se = &p->se;
9001
9002	/*
9003	 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
9004	 * the dequeue_entity(.flags=0) will already have normalized the
9005	 * vruntime.
9006	 */
9007	if (p->on_rq)
9008		return true;
9009
9010	/*
9011	 * When !on_rq, vruntime of the task has usually NOT been normalized.
9012	 * But there are some cases where it has already been normalized:
9013	 *
9014	 * - A forked child which is waiting for being woken up by
9015	 *   wake_up_new_task().
9016	 * - A task which has been woken up by try_to_wake_up() and
9017	 *   waiting for actually being woken up by sched_ttwu_pending().
9018	 */
9019	if (!se->sum_exec_runtime || p->state == TASK_WAKING)
 
9020		return true;
9021
9022	return false;
9023}
9024
9025#ifdef CONFIG_FAIR_GROUP_SCHED
9026/*
9027 * Propagate the changes of the sched_entity across the tg tree to make it
9028 * visible to the root
9029 */
9030static void propagate_entity_cfs_rq(struct sched_entity *se)
9031{
9032	struct cfs_rq *cfs_rq;
9033
9034	/* Start to propagate at parent */
9035	se = se->parent;
9036
9037	for_each_sched_entity(se) {
9038		cfs_rq = cfs_rq_of(se);
9039
9040		if (cfs_rq_throttled(cfs_rq))
9041			break;
9042
9043		update_load_avg(se, UPDATE_TG);
9044	}
9045}
9046#else
9047static void propagate_entity_cfs_rq(struct sched_entity *se) { }
9048#endif
9049
9050static void detach_entity_cfs_rq(struct sched_entity *se)
9051{
9052	struct cfs_rq *cfs_rq = cfs_rq_of(se);
9053
9054	/* Catch up with the cfs_rq and remove our load when we leave */
9055	update_load_avg(se, 0);
9056	detach_entity_load_avg(cfs_rq, se);
9057	update_tg_load_avg(cfs_rq, false);
9058	propagate_entity_cfs_rq(se);
9059}
9060
9061static void attach_entity_cfs_rq(struct sched_entity *se)
9062{
9063	struct cfs_rq *cfs_rq = cfs_rq_of(se);
9064
9065#ifdef CONFIG_FAIR_GROUP_SCHED
9066	/*
9067	 * Since the real-depth could have been changed (only FAIR
9068	 * class maintain depth value), reset depth properly.
9069	 */
9070	se->depth = se->parent ? se->parent->depth + 1 : 0;
9071#endif
9072
9073	/* Synchronize entity with its cfs_rq */
9074	update_load_avg(se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
9075	attach_entity_load_avg(cfs_rq, se);
9076	update_tg_load_avg(cfs_rq, false);
9077	propagate_entity_cfs_rq(se);
9078}
9079
9080static void detach_task_cfs_rq(struct task_struct *p)
9081{
9082	struct sched_entity *se = &p->se;
9083	struct cfs_rq *cfs_rq = cfs_rq_of(se);
9084
9085	if (!vruntime_normalized(p)) {
9086		/*
9087		 * Fix up our vruntime so that the current sleep doesn't
9088		 * cause 'unlimited' sleep bonus.
9089		 */
9090		place_entity(cfs_rq, se, 0);
9091		se->vruntime -= cfs_rq->min_vruntime;
9092	}
9093
9094	detach_entity_cfs_rq(se);
9095}
9096
9097static void attach_task_cfs_rq(struct task_struct *p)
9098{
9099	struct sched_entity *se = &p->se;
9100	struct cfs_rq *cfs_rq = cfs_rq_of(se);
9101
9102	attach_entity_cfs_rq(se);
9103
9104	if (!vruntime_normalized(p))
9105		se->vruntime += cfs_rq->min_vruntime;
9106}
9107
9108static void switched_from_fair(struct rq *rq, struct task_struct *p)
9109{
9110	detach_task_cfs_rq(p);
9111}
9112
9113static void switched_to_fair(struct rq *rq, struct task_struct *p)
9114{
9115	attach_task_cfs_rq(p);
9116
9117	if (task_on_rq_queued(p)) {
9118		/*
9119		 * We were most likely switched from sched_rt, so
9120		 * kick off the schedule if running, otherwise just see
9121		 * if we can still preempt the current task.
9122		 */
9123		if (rq->curr == p)
9124			resched_curr(rq);
9125		else
9126			check_preempt_curr(rq, p, 0);
9127	}
9128}
9129
9130/* Account for a task changing its policy or group.
9131 *
9132 * This routine is mostly called to set cfs_rq->curr field when a task
9133 * migrates between groups/classes.
9134 */
9135static void set_curr_task_fair(struct rq *rq)
9136{
9137	struct sched_entity *se = &rq->curr->se;
 
 
 
 
 
 
 
 
 
 
9138
9139	for_each_sched_entity(se) {
9140		struct cfs_rq *cfs_rq = cfs_rq_of(se);
9141
9142		set_next_entity(cfs_rq, se);
9143		/* ensure bandwidth has been allocated on our new cfs_rq */
9144		account_cfs_rq_runtime(cfs_rq, 0);
9145	}
9146}
9147
9148void init_cfs_rq(struct cfs_rq *cfs_rq)
9149{
9150	cfs_rq->tasks_timeline = RB_ROOT;
9151	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
9152#ifndef CONFIG_64BIT
9153	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
9154#endif
9155#ifdef CONFIG_SMP
9156#ifdef CONFIG_FAIR_GROUP_SCHED
9157	cfs_rq->propagate_avg = 0;
9158#endif
9159	atomic_long_set(&cfs_rq->removed_load_avg, 0);
9160	atomic_long_set(&cfs_rq->removed_util_avg, 0);
9161#endif
9162}
9163
9164#ifdef CONFIG_FAIR_GROUP_SCHED
9165static void task_set_group_fair(struct task_struct *p)
9166{
9167	struct sched_entity *se = &p->se;
9168
9169	set_task_rq(p, task_cpu(p));
9170	se->depth = se->parent ? se->parent->depth + 1 : 0;
9171}
9172
9173static void task_move_group_fair(struct task_struct *p)
9174{
9175	detach_task_cfs_rq(p);
9176	set_task_rq(p, task_cpu(p));
9177
9178#ifdef CONFIG_SMP
9179	/* Tell se's cfs_rq has been changed -- migrated */
9180	p->se.avg.last_update_time = 0;
9181#endif
9182	attach_task_cfs_rq(p);
9183}
9184
9185static void task_change_group_fair(struct task_struct *p, int type)
9186{
9187	switch (type) {
9188	case TASK_SET_GROUP:
9189		task_set_group_fair(p);
9190		break;
9191
9192	case TASK_MOVE_GROUP:
9193		task_move_group_fair(p);
9194		break;
9195	}
9196}
9197
9198void free_fair_sched_group(struct task_group *tg)
9199{
9200	int i;
9201
9202	destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
9203
9204	for_each_possible_cpu(i) {
9205		if (tg->cfs_rq)
9206			kfree(tg->cfs_rq[i]);
9207		if (tg->se)
9208			kfree(tg->se[i]);
9209	}
9210
9211	kfree(tg->cfs_rq);
9212	kfree(tg->se);
9213}
9214
9215int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
9216{
9217	struct sched_entity *se;
9218	struct cfs_rq *cfs_rq;
9219	int i;
9220
9221	tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
9222	if (!tg->cfs_rq)
9223		goto err;
9224	tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
9225	if (!tg->se)
9226		goto err;
9227
9228	tg->shares = NICE_0_LOAD;
9229
9230	init_cfs_bandwidth(tg_cfs_bandwidth(tg));
9231
9232	for_each_possible_cpu(i) {
9233		cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
9234				      GFP_KERNEL, cpu_to_node(i));
9235		if (!cfs_rq)
9236			goto err;
9237
9238		se = kzalloc_node(sizeof(struct sched_entity),
9239				  GFP_KERNEL, cpu_to_node(i));
9240		if (!se)
9241			goto err_free_rq;
9242
9243		init_cfs_rq(cfs_rq);
9244		init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
9245		init_entity_runnable_average(se);
9246	}
9247
9248	return 1;
9249
9250err_free_rq:
9251	kfree(cfs_rq);
9252err:
9253	return 0;
9254}
9255
9256void online_fair_sched_group(struct task_group *tg)
9257{
9258	struct sched_entity *se;
 
9259	struct rq *rq;
9260	int i;
9261
9262	for_each_possible_cpu(i) {
9263		rq = cpu_rq(i);
9264		se = tg->se[i];
9265
9266		raw_spin_lock_irq(&rq->lock);
9267		attach_entity_cfs_rq(se);
9268		sync_throttle(tg, i);
9269		raw_spin_unlock_irq(&rq->lock);
9270	}
9271}
9272
9273void unregister_fair_sched_group(struct task_group *tg)
9274{
9275	unsigned long flags;
9276	struct rq *rq;
9277	int cpu;
9278
9279	for_each_possible_cpu(cpu) {
9280		if (tg->se[cpu])
9281			remove_entity_load_avg(tg->se[cpu]);
9282
9283		/*
9284		 * Only empty task groups can be destroyed; so we can speculatively
9285		 * check on_list without danger of it being re-added.
9286		 */
9287		if (!tg->cfs_rq[cpu]->on_list)
9288			continue;
9289
9290		rq = cpu_rq(cpu);
9291
9292		raw_spin_lock_irqsave(&rq->lock, flags);
9293		list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
9294		raw_spin_unlock_irqrestore(&rq->lock, flags);
9295	}
9296}
9297
9298void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
9299			struct sched_entity *se, int cpu,
9300			struct sched_entity *parent)
9301{
9302	struct rq *rq = cpu_rq(cpu);
9303
9304	cfs_rq->tg = tg;
9305	cfs_rq->rq = rq;
9306	init_cfs_rq_runtime(cfs_rq);
9307
9308	tg->cfs_rq[cpu] = cfs_rq;
9309	tg->se[cpu] = se;
9310
9311	/* se could be NULL for root_task_group */
9312	if (!se)
9313		return;
9314
9315	if (!parent) {
9316		se->cfs_rq = &rq->cfs;
9317		se->depth = 0;
9318	} else {
9319		se->cfs_rq = parent->my_q;
9320		se->depth = parent->depth + 1;
9321	}
9322
9323	se->my_q = cfs_rq;
9324	/* guarantee group entities always have weight */
9325	update_load_set(&se->load, NICE_0_LOAD);
9326	se->parent = parent;
9327}
9328
9329static DEFINE_MUTEX(shares_mutex);
9330
9331int sched_group_set_shares(struct task_group *tg, unsigned long shares)
9332{
9333	int i;
9334	unsigned long flags;
9335
9336	/*
9337	 * We can't change the weight of the root cgroup.
9338	 */
9339	if (!tg->se[0])
9340		return -EINVAL;
9341
9342	shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
9343
9344	mutex_lock(&shares_mutex);
9345	if (tg->shares == shares)
9346		goto done;
9347
9348	tg->shares = shares;
9349	for_each_possible_cpu(i) {
9350		struct rq *rq = cpu_rq(i);
9351		struct sched_entity *se;
 
9352
9353		se = tg->se[i];
9354		/* Propagate contribution to hierarchy */
9355		raw_spin_lock_irqsave(&rq->lock, flags);
9356
9357		/* Possible calls to update_curr() need rq clock */
9358		update_rq_clock(rq);
9359		for_each_sched_entity(se)
9360			update_cfs_shares(group_cfs_rq(se));
9361		raw_spin_unlock_irqrestore(&rq->lock, flags);
 
 
9362	}
9363
9364done:
9365	mutex_unlock(&shares_mutex);
9366	return 0;
9367}
9368#else /* CONFIG_FAIR_GROUP_SCHED */
9369
9370void free_fair_sched_group(struct task_group *tg) { }
9371
9372int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
9373{
9374	return 1;
9375}
9376
9377void online_fair_sched_group(struct task_group *tg) { }
9378
9379void unregister_fair_sched_group(struct task_group *tg) { }
9380
9381#endif /* CONFIG_FAIR_GROUP_SCHED */
9382
9383
9384static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
9385{
9386	struct sched_entity *se = &task->se;
9387	unsigned int rr_interval = 0;
9388
9389	/*
9390	 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
9391	 * idle runqueue:
9392	 */
9393	if (rq->cfs.load.weight)
9394		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
9395
9396	return rr_interval;
9397}
9398
9399/*
9400 * All the scheduling class methods:
9401 */
9402const struct sched_class fair_sched_class = {
9403	.next			= &idle_sched_class,
9404	.enqueue_task		= enqueue_task_fair,
9405	.dequeue_task		= dequeue_task_fair,
9406	.yield_task		= yield_task_fair,
9407	.yield_to_task		= yield_to_task_fair,
9408
9409	.check_preempt_curr	= check_preempt_wakeup,
9410
9411	.pick_next_task		= pick_next_task_fair,
9412	.put_prev_task		= put_prev_task_fair,
 
9413
9414#ifdef CONFIG_SMP
 
9415	.select_task_rq		= select_task_rq_fair,
9416	.migrate_task_rq	= migrate_task_rq_fair,
9417
9418	.rq_online		= rq_online_fair,
9419	.rq_offline		= rq_offline_fair,
9420
9421	.task_dead		= task_dead_fair,
9422	.set_cpus_allowed	= set_cpus_allowed_common,
9423#endif
9424
9425	.set_curr_task          = set_curr_task_fair,
9426	.task_tick		= task_tick_fair,
9427	.task_fork		= task_fork_fair,
9428
9429	.prio_changed		= prio_changed_fair,
9430	.switched_from		= switched_from_fair,
9431	.switched_to		= switched_to_fair,
9432
9433	.get_rr_interval	= get_rr_interval_fair,
9434
9435	.update_curr		= update_curr_fair,
9436
9437#ifdef CONFIG_FAIR_GROUP_SCHED
9438	.task_change_group	= task_change_group_fair,
9439#endif
 
 
 
 
9440};
9441
9442#ifdef CONFIG_SCHED_DEBUG
9443void print_cfs_stats(struct seq_file *m, int cpu)
9444{
9445	struct cfs_rq *cfs_rq;
9446
9447	rcu_read_lock();
9448	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
9449		print_cfs_rq(m, cpu, cfs_rq);
9450	rcu_read_unlock();
9451}
9452
9453#ifdef CONFIG_NUMA_BALANCING
9454void show_numa_stats(struct task_struct *p, struct seq_file *m)
9455{
9456	int node;
9457	unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
 
9458
 
 
9459	for_each_online_node(node) {
9460		if (p->numa_faults) {
9461			tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
9462			tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
9463		}
9464		if (p->numa_group) {
9465			gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
9466			gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
9467		}
9468		print_numa_stats(m, node, tsf, tpf, gsf, gpf);
9469	}
 
9470}
9471#endif /* CONFIG_NUMA_BALANCING */
9472#endif /* CONFIG_SCHED_DEBUG */
9473
9474__init void init_sched_fair_class(void)
9475{
9476#ifdef CONFIG_SMP
9477	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
9478
9479#ifdef CONFIG_NO_HZ_COMMON
9480	nohz.next_balance = jiffies;
 
9481	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
9482#endif
9483#endif /* SMP */
9484
9485}