2 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
4 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
6 * Interactivity improvements by Mike Galbraith
7 * (C) 2007 Mike Galbraith <efault@gmx.de>
9 * Various enhancements by Dmitry Adamushko.
10 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
12 * Group scheduling enhancements by Srivatsa Vaddagiri
13 * Copyright IBM Corporation, 2007
14 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
16 * Scaled math optimizations by Thomas Gleixner
17 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
19 * Adaptive scheduling granularity, math enhancements by Peter Zijlstra
20 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
23 #include <linux/latencytop.h>
24 #include <linux/sched.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>
34 #include <trace/events/sched.h>
39 * Targeted preemption latency for CPU-bound tasks:
40 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
42 * NOTE: this latency value is not the same as the concept of
43 * 'timeslice length' - timeslices in CFS are of variable length
44 * and have no persistent notion like in traditional, time-slice
45 * based scheduling concepts.
47 * (to see the precise effective timeslice length of your workload,
48 * run vmstat and monitor the context-switches (cs) field)
50 unsigned int sysctl_sched_latency = 6000000ULL;
51 unsigned int normalized_sysctl_sched_latency = 6000000ULL;
54 * The initial- and re-scaling of tunables is configurable
55 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
58 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
59 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
60 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
62 enum sched_tunable_scaling sysctl_sched_tunable_scaling
63 = SCHED_TUNABLESCALING_LOG;
66 * Minimal preemption granularity for CPU-bound tasks:
67 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
69 unsigned int sysctl_sched_min_granularity = 750000ULL;
70 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
73 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
75 static unsigned int sched_nr_latency = 8;
78 * After fork, child runs first. If set to 0 (default) then
79 * parent will (try to) run first.
81 unsigned int sysctl_sched_child_runs_first __read_mostly;
84 * SCHED_OTHER wake-up granularity.
85 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
87 * This option delays the preemption effects of decoupled workloads
88 * and reduces their over-scheduling. Synchronous workloads will still
89 * have immediate wakeup/sleep latencies.
91 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
92 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
94 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
97 * The exponential sliding window over which load is averaged for shares
101 unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
103 #ifdef CONFIG_CFS_BANDWIDTH
105 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
106 * each time a cfs_rq requests quota.
108 * Note: in the case that the slice exceeds the runtime remaining (either due
109 * to consumption or the quota being specified to be smaller than the slice)
110 * we will always only issue the remaining available time.
112 * default: 5 msec, units: microseconds
114 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
117 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
123 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
129 static inline void update_load_set(struct load_weight *lw, unsigned long w)
136 * Increase the granularity value when there are more CPUs,
137 * because with more CPUs the 'effective latency' as visible
138 * to users decreases. But the relationship is not linear,
139 * so pick a second-best guess by going with the log2 of the
142 * This idea comes from the SD scheduler of Con Kolivas:
144 static unsigned int get_update_sysctl_factor(void)
146 unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
149 switch (sysctl_sched_tunable_scaling) {
150 case SCHED_TUNABLESCALING_NONE:
153 case SCHED_TUNABLESCALING_LINEAR:
156 case SCHED_TUNABLESCALING_LOG:
158 factor = 1 + ilog2(cpus);
165 static void update_sysctl(void)
167 unsigned int factor = get_update_sysctl_factor();
169 #define SET_SYSCTL(name) \
170 (sysctl_##name = (factor) * normalized_sysctl_##name)
171 SET_SYSCTL(sched_min_granularity);
172 SET_SYSCTL(sched_latency);
173 SET_SYSCTL(sched_wakeup_granularity);
177 void sched_init_granularity(void)
182 #define WMULT_CONST (~0U)
183 #define WMULT_SHIFT 32
185 static void __update_inv_weight(struct load_weight *lw)
189 if (likely(lw->inv_weight))
192 w = scale_load_down(lw->weight);
194 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
196 else if (unlikely(!w))
197 lw->inv_weight = WMULT_CONST;
199 lw->inv_weight = WMULT_CONST / w;
203 * delta_exec * weight / lw.weight
205 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
207 * Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case
208 * we're guaranteed shift stays positive because inv_weight is guaranteed to
209 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
211 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
212 * weight/lw.weight <= 1, and therefore our shift will also be positive.
214 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
216 u64 fact = scale_load_down(weight);
217 int shift = WMULT_SHIFT;
219 __update_inv_weight(lw);
221 if (unlikely(fact >> 32)) {
228 /* hint to use a 32x32->64 mul */
229 fact = (u64)(u32)fact * lw->inv_weight;
236 return mul_u64_u32_shr(delta_exec, fact, shift);
240 const struct sched_class fair_sched_class;
242 /**************************************************************
243 * CFS operations on generic schedulable entities:
246 #ifdef CONFIG_FAIR_GROUP_SCHED
248 /* cpu runqueue to which this cfs_rq is attached */
249 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
254 /* An entity is a task if it doesn't "own" a runqueue */
255 #define entity_is_task(se) (!se->my_q)
257 static inline struct task_struct *task_of(struct sched_entity *se)
259 #ifdef CONFIG_SCHED_DEBUG
260 WARN_ON_ONCE(!entity_is_task(se));
262 return container_of(se, struct task_struct, se);
265 /* Walk up scheduling entities hierarchy */
266 #define for_each_sched_entity(se) \
267 for (; se; se = se->parent)
269 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
274 /* runqueue on which this entity is (to be) queued */
275 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
280 /* runqueue "owned" by this group */
281 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
286 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
288 if (!cfs_rq->on_list) {
290 * Ensure we either appear before our parent (if already
291 * enqueued) or force our parent to appear after us when it is
292 * enqueued. The fact that we always enqueue bottom-up
293 * reduces this to two cases.
295 if (cfs_rq->tg->parent &&
296 cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
297 list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
298 &rq_of(cfs_rq)->leaf_cfs_rq_list);
300 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
301 &rq_of(cfs_rq)->leaf_cfs_rq_list);
308 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
310 if (cfs_rq->on_list) {
311 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
316 /* Iterate thr' all leaf cfs_rq's on a runqueue */
317 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
318 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
320 /* Do the two (enqueued) entities belong to the same group ? */
321 static inline struct cfs_rq *
322 is_same_group(struct sched_entity *se, struct sched_entity *pse)
324 if (se->cfs_rq == pse->cfs_rq)
330 static inline struct sched_entity *parent_entity(struct sched_entity *se)
336 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
338 int se_depth, pse_depth;
341 * preemption test can be made between sibling entities who are in the
342 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
343 * both tasks until we find their ancestors who are siblings of common
347 /* First walk up until both entities are at same depth */
348 se_depth = (*se)->depth;
349 pse_depth = (*pse)->depth;
351 while (se_depth > pse_depth) {
353 *se = parent_entity(*se);
356 while (pse_depth > se_depth) {
358 *pse = parent_entity(*pse);
361 while (!is_same_group(*se, *pse)) {
362 *se = parent_entity(*se);
363 *pse = parent_entity(*pse);
367 #else /* !CONFIG_FAIR_GROUP_SCHED */
369 static inline struct task_struct *task_of(struct sched_entity *se)
371 return container_of(se, struct task_struct, se);
374 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
376 return container_of(cfs_rq, struct rq, cfs);
379 #define entity_is_task(se) 1
381 #define for_each_sched_entity(se) \
382 for (; se; se = NULL)
384 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
386 return &task_rq(p)->cfs;
389 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
391 struct task_struct *p = task_of(se);
392 struct rq *rq = task_rq(p);
397 /* runqueue "owned" by this group */
398 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
403 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
407 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
411 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
412 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
414 static inline struct sched_entity *parent_entity(struct sched_entity *se)
420 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
424 #endif /* CONFIG_FAIR_GROUP_SCHED */
426 static __always_inline
427 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
429 /**************************************************************
430 * Scheduling class tree data structure manipulation methods:
433 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
435 s64 delta = (s64)(vruntime - max_vruntime);
437 max_vruntime = vruntime;
442 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
444 s64 delta = (s64)(vruntime - min_vruntime);
446 min_vruntime = vruntime;
451 static inline int entity_before(struct sched_entity *a,
452 struct sched_entity *b)
454 return (s64)(a->vruntime - b->vruntime) < 0;
457 static void update_min_vruntime(struct cfs_rq *cfs_rq)
459 u64 vruntime = cfs_rq->min_vruntime;
462 vruntime = cfs_rq->curr->vruntime;
464 if (cfs_rq->rb_leftmost) {
465 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
470 vruntime = se->vruntime;
472 vruntime = min_vruntime(vruntime, se->vruntime);
475 /* ensure we never gain time by being placed backwards. */
476 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
479 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
484 * Enqueue an entity into the rb-tree:
486 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
488 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
489 struct rb_node *parent = NULL;
490 struct sched_entity *entry;
494 * Find the right place in the rbtree:
498 entry = rb_entry(parent, struct sched_entity, run_node);
500 * We dont care about collisions. Nodes with
501 * the same key stay together.
503 if (entity_before(se, entry)) {
504 link = &parent->rb_left;
506 link = &parent->rb_right;
512 * Maintain a cache of leftmost tree entries (it is frequently
516 cfs_rq->rb_leftmost = &se->run_node;
518 rb_link_node(&se->run_node, parent, link);
519 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
522 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
524 if (cfs_rq->rb_leftmost == &se->run_node) {
525 struct rb_node *next_node;
527 next_node = rb_next(&se->run_node);
528 cfs_rq->rb_leftmost = next_node;
531 rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
534 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
536 struct rb_node *left = cfs_rq->rb_leftmost;
541 return rb_entry(left, struct sched_entity, run_node);
544 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
546 struct rb_node *next = rb_next(&se->run_node);
551 return rb_entry(next, struct sched_entity, run_node);
554 #ifdef CONFIG_SCHED_DEBUG
555 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
557 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
562 return rb_entry(last, struct sched_entity, run_node);
565 /**************************************************************
566 * Scheduling class statistics methods:
569 int sched_proc_update_handler(struct ctl_table *table, int write,
570 void __user *buffer, size_t *lenp,
573 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
574 unsigned int factor = get_update_sysctl_factor();
579 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
580 sysctl_sched_min_granularity);
582 #define WRT_SYSCTL(name) \
583 (normalized_sysctl_##name = sysctl_##name / (factor))
584 WRT_SYSCTL(sched_min_granularity);
585 WRT_SYSCTL(sched_latency);
586 WRT_SYSCTL(sched_wakeup_granularity);
596 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
598 if (unlikely(se->load.weight != NICE_0_LOAD))
599 delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
605 * The idea is to set a period in which each task runs once.
607 * When there are too many tasks (sched_nr_latency) we have to stretch
608 * this period because otherwise the slices get too small.
610 * p = (nr <= nl) ? l : l*nr/nl
612 static u64 __sched_period(unsigned long nr_running)
614 if (unlikely(nr_running > sched_nr_latency))
615 return nr_running * sysctl_sched_min_granularity;
617 return sysctl_sched_latency;
621 * We calculate the wall-time slice from the period by taking a part
622 * proportional to the weight.
626 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
628 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
630 for_each_sched_entity(se) {
631 struct load_weight *load;
632 struct load_weight lw;
634 cfs_rq = cfs_rq_of(se);
635 load = &cfs_rq->load;
637 if (unlikely(!se->on_rq)) {
640 update_load_add(&lw, se->load.weight);
643 slice = __calc_delta(slice, se->load.weight, load);
649 * We calculate the vruntime slice of a to-be-inserted task.
653 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
655 return calc_delta_fair(sched_slice(cfs_rq, se), se);
659 static int select_idle_sibling(struct task_struct *p, int cpu);
660 static unsigned long task_h_load(struct task_struct *p);
663 * We choose a half-life close to 1 scheduling period.
664 * Note: The tables below are dependent on this value.
666 #define LOAD_AVG_PERIOD 32
667 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
668 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */
670 /* Give new sched_entity start runnable values to heavy its load in infant time */
671 void init_entity_runnable_average(struct sched_entity *se)
673 struct sched_avg *sa = &se->avg;
675 sa->last_update_time = 0;
677 * sched_avg's period_contrib should be strictly less then 1024, so
678 * we give it 1023 to make sure it is almost a period (1024us), and
679 * will definitely be update (after enqueue).
681 sa->period_contrib = 1023;
682 sa->load_avg = scale_load_down(se->load.weight);
683 sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
684 sa->util_avg = scale_load_down(SCHED_LOAD_SCALE);
685 sa->util_sum = LOAD_AVG_MAX;
686 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
689 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq);
690 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq);
692 void init_entity_runnable_average(struct sched_entity *se)
698 * Update the current task's runtime statistics.
700 static void update_curr(struct cfs_rq *cfs_rq)
702 struct sched_entity *curr = cfs_rq->curr;
703 u64 now = rq_clock_task(rq_of(cfs_rq));
709 delta_exec = now - curr->exec_start;
710 if (unlikely((s64)delta_exec <= 0))
713 curr->exec_start = now;
715 schedstat_set(curr->statistics.exec_max,
716 max(delta_exec, curr->statistics.exec_max));
718 curr->sum_exec_runtime += delta_exec;
719 schedstat_add(cfs_rq, exec_clock, delta_exec);
721 curr->vruntime += calc_delta_fair(delta_exec, curr);
722 update_min_vruntime(cfs_rq);
724 if (entity_is_task(curr)) {
725 struct task_struct *curtask = task_of(curr);
727 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
728 cpuacct_charge(curtask, delta_exec);
729 account_group_exec_runtime(curtask, delta_exec);
732 account_cfs_rq_runtime(cfs_rq, delta_exec);
735 static void update_curr_fair(struct rq *rq)
737 update_curr(cfs_rq_of(&rq->curr->se));
741 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
743 schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
747 * Task is being enqueued - update stats:
749 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
752 * Are we enqueueing a waiting task? (for current tasks
753 * a dequeue/enqueue event is a NOP)
755 if (se != cfs_rq->curr)
756 update_stats_wait_start(cfs_rq, se);
760 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
762 schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
763 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
764 schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
765 schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
766 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
767 #ifdef CONFIG_SCHEDSTATS
768 if (entity_is_task(se)) {
769 trace_sched_stat_wait(task_of(se),
770 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
773 schedstat_set(se->statistics.wait_start, 0);
777 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
780 * Mark the end of the wait period if dequeueing a
783 if (se != cfs_rq->curr)
784 update_stats_wait_end(cfs_rq, se);
788 * We are picking a new current task - update its stats:
791 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
794 * We are starting a new run period:
796 se->exec_start = rq_clock_task(rq_of(cfs_rq));
799 /**************************************************
800 * Scheduling class queueing methods:
803 #ifdef CONFIG_NUMA_BALANCING
805 * Approximate time to scan a full NUMA task in ms. The task scan period is
806 * calculated based on the tasks virtual memory size and
807 * numa_balancing_scan_size.
809 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
810 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
812 /* Portion of address space to scan in MB */
813 unsigned int sysctl_numa_balancing_scan_size = 256;
815 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
816 unsigned int sysctl_numa_balancing_scan_delay = 1000;
818 static unsigned int task_nr_scan_windows(struct task_struct *p)
820 unsigned long rss = 0;
821 unsigned long nr_scan_pages;
824 * Calculations based on RSS as non-present and empty pages are skipped
825 * by the PTE scanner and NUMA hinting faults should be trapped based
828 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
829 rss = get_mm_rss(p->mm);
833 rss = round_up(rss, nr_scan_pages);
834 return rss / nr_scan_pages;
837 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
838 #define MAX_SCAN_WINDOW 2560
840 static unsigned int task_scan_min(struct task_struct *p)
842 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
843 unsigned int scan, floor;
844 unsigned int windows = 1;
846 if (scan_size < MAX_SCAN_WINDOW)
847 windows = MAX_SCAN_WINDOW / scan_size;
848 floor = 1000 / windows;
850 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
851 return max_t(unsigned int, floor, scan);
854 static unsigned int task_scan_max(struct task_struct *p)
856 unsigned int smin = task_scan_min(p);
859 /* Watch for min being lower than max due to floor calculations */
860 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
861 return max(smin, smax);
864 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
866 rq->nr_numa_running += (p->numa_preferred_nid != -1);
867 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
870 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
872 rq->nr_numa_running -= (p->numa_preferred_nid != -1);
873 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
879 spinlock_t lock; /* nr_tasks, tasks */
884 nodemask_t active_nodes;
885 unsigned long total_faults;
887 * Faults_cpu is used to decide whether memory should move
888 * towards the CPU. As a consequence, these stats are weighted
889 * more by CPU use than by memory faults.
891 unsigned long *faults_cpu;
892 unsigned long faults[0];
895 /* Shared or private faults. */
896 #define NR_NUMA_HINT_FAULT_TYPES 2
898 /* Memory and CPU locality */
899 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
901 /* Averaged statistics, and temporary buffers. */
902 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
904 pid_t task_numa_group_id(struct task_struct *p)
906 return p->numa_group ? p->numa_group->gid : 0;
910 * The averaged statistics, shared & private, memory & cpu,
911 * occupy the first half of the array. The second half of the
912 * array is for current counters, which are averaged into the
913 * first set by task_numa_placement.
915 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
917 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
920 static inline unsigned long task_faults(struct task_struct *p, int nid)
925 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
926 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
929 static inline unsigned long group_faults(struct task_struct *p, int nid)
934 return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
935 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
938 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
940 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
941 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
944 /* Handle placement on systems where not all nodes are directly connected. */
945 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
946 int maxdist, bool task)
948 unsigned long score = 0;
952 * All nodes are directly connected, and the same distance
953 * from each other. No need for fancy placement algorithms.
955 if (sched_numa_topology_type == NUMA_DIRECT)
959 * This code is called for each node, introducing N^2 complexity,
960 * which should be ok given the number of nodes rarely exceeds 8.
962 for_each_online_node(node) {
963 unsigned long faults;
964 int dist = node_distance(nid, node);
967 * The furthest away nodes in the system are not interesting
968 * for placement; nid was already counted.
970 if (dist == sched_max_numa_distance || node == nid)
974 * On systems with a backplane NUMA topology, compare groups
975 * of nodes, and move tasks towards the group with the most
976 * memory accesses. When comparing two nodes at distance
977 * "hoplimit", only nodes closer by than "hoplimit" are part
978 * of each group. Skip other nodes.
980 if (sched_numa_topology_type == NUMA_BACKPLANE &&
984 /* Add up the faults from nearby nodes. */
986 faults = task_faults(p, node);
988 faults = group_faults(p, node);
991 * On systems with a glueless mesh NUMA topology, there are
992 * no fixed "groups of nodes". Instead, nodes that are not
993 * directly connected bounce traffic through intermediate
994 * nodes; a numa_group can occupy any set of nodes.
995 * The further away a node is, the less the faults count.
996 * This seems to result in good task placement.
998 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
999 faults *= (sched_max_numa_distance - dist);
1000 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1010 * These return the fraction of accesses done by a particular task, or
1011 * task group, on a particular numa node. The group weight is given a
1012 * larger multiplier, in order to group tasks together that are almost
1013 * evenly spread out between numa nodes.
1015 static inline unsigned long task_weight(struct task_struct *p, int nid,
1018 unsigned long faults, total_faults;
1020 if (!p->numa_faults)
1023 total_faults = p->total_numa_faults;
1028 faults = task_faults(p, nid);
1029 faults += score_nearby_nodes(p, nid, dist, true);
1031 return 1000 * faults / total_faults;
1034 static inline unsigned long group_weight(struct task_struct *p, int nid,
1037 unsigned long faults, total_faults;
1042 total_faults = p->numa_group->total_faults;
1047 faults = group_faults(p, nid);
1048 faults += score_nearby_nodes(p, nid, dist, false);
1050 return 1000 * faults / total_faults;
1053 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1054 int src_nid, int dst_cpu)
1056 struct numa_group *ng = p->numa_group;
1057 int dst_nid = cpu_to_node(dst_cpu);
1058 int last_cpupid, this_cpupid;
1060 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1063 * Multi-stage node selection is used in conjunction with a periodic
1064 * migration fault to build a temporal task<->page relation. By using
1065 * a two-stage filter we remove short/unlikely relations.
1067 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1068 * a task's usage of a particular page (n_p) per total usage of this
1069 * page (n_t) (in a given time-span) to a probability.
1071 * Our periodic faults will sample this probability and getting the
1072 * same result twice in a row, given these samples are fully
1073 * independent, is then given by P(n)^2, provided our sample period
1074 * is sufficiently short compared to the usage pattern.
1076 * This quadric squishes small probabilities, making it less likely we
1077 * act on an unlikely task<->page relation.
1079 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1080 if (!cpupid_pid_unset(last_cpupid) &&
1081 cpupid_to_nid(last_cpupid) != dst_nid)
1084 /* Always allow migrate on private faults */
1085 if (cpupid_match_pid(p, last_cpupid))
1088 /* A shared fault, but p->numa_group has not been set up yet. */
1093 * Do not migrate if the destination is not a node that
1094 * is actively used by this numa group.
1096 if (!node_isset(dst_nid, ng->active_nodes))
1100 * Source is a node that is not actively used by this
1101 * numa group, while the destination is. Migrate.
1103 if (!node_isset(src_nid, ng->active_nodes))
1107 * Both source and destination are nodes in active
1108 * use by this numa group. Maximize memory bandwidth
1109 * by migrating from more heavily used groups, to less
1110 * heavily used ones, spreading the load around.
1111 * Use a 1/4 hysteresis to avoid spurious page movement.
1113 return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4);
1116 static unsigned long weighted_cpuload(const int cpu);
1117 static unsigned long source_load(int cpu, int type);
1118 static unsigned long target_load(int cpu, int type);
1119 static unsigned long capacity_of(int cpu);
1120 static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1122 /* Cached statistics for all CPUs within a node */
1124 unsigned long nr_running;
1127 /* Total compute capacity of CPUs on a node */
1128 unsigned long compute_capacity;
1130 /* Approximate capacity in terms of runnable tasks on a node */
1131 unsigned long task_capacity;
1132 int has_free_capacity;
1136 * XXX borrowed from update_sg_lb_stats
1138 static void update_numa_stats(struct numa_stats *ns, int nid)
1140 int smt, cpu, cpus = 0;
1141 unsigned long capacity;
1143 memset(ns, 0, sizeof(*ns));
1144 for_each_cpu(cpu, cpumask_of_node(nid)) {
1145 struct rq *rq = cpu_rq(cpu);
1147 ns->nr_running += rq->nr_running;
1148 ns->load += weighted_cpuload(cpu);
1149 ns->compute_capacity += capacity_of(cpu);
1155 * If we raced with hotplug and there are no CPUs left in our mask
1156 * the @ns structure is NULL'ed and task_numa_compare() will
1157 * not find this node attractive.
1159 * We'll either bail at !has_free_capacity, or we'll detect a huge
1160 * imbalance and bail there.
1165 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1166 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1167 capacity = cpus / smt; /* cores */
1169 ns->task_capacity = min_t(unsigned, capacity,
1170 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1171 ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1174 struct task_numa_env {
1175 struct task_struct *p;
1177 int src_cpu, src_nid;
1178 int dst_cpu, dst_nid;
1180 struct numa_stats src_stats, dst_stats;
1185 struct task_struct *best_task;
1190 static void task_numa_assign(struct task_numa_env *env,
1191 struct task_struct *p, long imp)
1194 put_task_struct(env->best_task);
1199 env->best_imp = imp;
1200 env->best_cpu = env->dst_cpu;
1203 static bool load_too_imbalanced(long src_load, long dst_load,
1204 struct task_numa_env *env)
1207 long orig_src_load, orig_dst_load;
1208 long src_capacity, dst_capacity;
1211 * The load is corrected for the CPU capacity available on each node.
1214 * ------------ vs ---------
1215 * src_capacity dst_capacity
1217 src_capacity = env->src_stats.compute_capacity;
1218 dst_capacity = env->dst_stats.compute_capacity;
1220 /* We care about the slope of the imbalance, not the direction. */
1221 if (dst_load < src_load)
1222 swap(dst_load, src_load);
1224 /* Is the difference below the threshold? */
1225 imb = dst_load * src_capacity * 100 -
1226 src_load * dst_capacity * env->imbalance_pct;
1231 * The imbalance is above the allowed threshold.
1232 * Compare it with the old imbalance.
1234 orig_src_load = env->src_stats.load;
1235 orig_dst_load = env->dst_stats.load;
1237 if (orig_dst_load < orig_src_load)
1238 swap(orig_dst_load, orig_src_load);
1240 old_imb = orig_dst_load * src_capacity * 100 -
1241 orig_src_load * dst_capacity * env->imbalance_pct;
1243 /* Would this change make things worse? */
1244 return (imb > old_imb);
1248 * This checks if the overall compute and NUMA accesses of the system would
1249 * be improved if the source tasks was migrated to the target dst_cpu taking
1250 * into account that it might be best if task running on the dst_cpu should
1251 * be exchanged with the source task
1253 static void task_numa_compare(struct task_numa_env *env,
1254 long taskimp, long groupimp)
1256 struct rq *src_rq = cpu_rq(env->src_cpu);
1257 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1258 struct task_struct *cur;
1259 long src_load, dst_load;
1261 long imp = env->p->numa_group ? groupimp : taskimp;
1263 int dist = env->dist;
1267 raw_spin_lock_irq(&dst_rq->lock);
1270 * No need to move the exiting task, and this ensures that ->curr
1271 * wasn't reaped and thus get_task_struct() in task_numa_assign()
1272 * is safe under RCU read lock.
1273 * Note that rcu_read_lock() itself can't protect from the final
1274 * put_task_struct() after the last schedule().
1276 if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1278 raw_spin_unlock_irq(&dst_rq->lock);
1281 * Because we have preemption enabled we can get migrated around and
1282 * end try selecting ourselves (current == env->p) as a swap candidate.
1288 * "imp" is the fault differential for the source task between the
1289 * source and destination node. Calculate the total differential for
1290 * the source task and potential destination task. The more negative
1291 * the value is, the more rmeote accesses that would be expected to
1292 * be incurred if the tasks were swapped.
1295 /* Skip this swap candidate if cannot move to the source cpu */
1296 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1300 * If dst and source tasks are in the same NUMA group, or not
1301 * in any group then look only at task weights.
1303 if (cur->numa_group == env->p->numa_group) {
1304 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1305 task_weight(cur, env->dst_nid, dist);
1307 * Add some hysteresis to prevent swapping the
1308 * tasks within a group over tiny differences.
1310 if (cur->numa_group)
1314 * Compare the group weights. If a task is all by
1315 * itself (not part of a group), use the task weight
1318 if (cur->numa_group)
1319 imp += group_weight(cur, env->src_nid, dist) -
1320 group_weight(cur, env->dst_nid, dist);
1322 imp += task_weight(cur, env->src_nid, dist) -
1323 task_weight(cur, env->dst_nid, dist);
1327 if (imp <= env->best_imp && moveimp <= env->best_imp)
1331 /* Is there capacity at our destination? */
1332 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1333 !env->dst_stats.has_free_capacity)
1339 /* Balance doesn't matter much if we're running a task per cpu */
1340 if (imp > env->best_imp && src_rq->nr_running == 1 &&
1341 dst_rq->nr_running == 1)
1345 * In the overloaded case, try and keep the load balanced.
1348 load = task_h_load(env->p);
1349 dst_load = env->dst_stats.load + load;
1350 src_load = env->src_stats.load - load;
1352 if (moveimp > imp && moveimp > env->best_imp) {
1354 * If the improvement from just moving env->p direction is
1355 * better than swapping tasks around, check if a move is
1356 * possible. Store a slightly smaller score than moveimp,
1357 * so an actually idle CPU will win.
1359 if (!load_too_imbalanced(src_load, dst_load, env)) {
1366 if (imp <= env->best_imp)
1370 load = task_h_load(cur);
1375 if (load_too_imbalanced(src_load, dst_load, env))
1379 * One idle CPU per node is evaluated for a task numa move.
1380 * Call select_idle_sibling to maybe find a better one.
1383 env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);
1386 task_numa_assign(env, cur, imp);
1391 static void task_numa_find_cpu(struct task_numa_env *env,
1392 long taskimp, long groupimp)
1396 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1397 /* Skip this CPU if the source task cannot migrate */
1398 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1402 task_numa_compare(env, taskimp, groupimp);
1406 /* Only move tasks to a NUMA node less busy than the current node. */
1407 static bool numa_has_capacity(struct task_numa_env *env)
1409 struct numa_stats *src = &env->src_stats;
1410 struct numa_stats *dst = &env->dst_stats;
1412 if (src->has_free_capacity && !dst->has_free_capacity)
1416 * Only consider a task move if the source has a higher load
1417 * than the destination, corrected for CPU capacity on each node.
1419 * src->load dst->load
1420 * --------------------- vs ---------------------
1421 * src->compute_capacity dst->compute_capacity
1423 if (src->load * dst->compute_capacity * env->imbalance_pct >
1425 dst->load * src->compute_capacity * 100)
1431 static int task_numa_migrate(struct task_struct *p)
1433 struct task_numa_env env = {
1436 .src_cpu = task_cpu(p),
1437 .src_nid = task_node(p),
1439 .imbalance_pct = 112,
1445 struct sched_domain *sd;
1446 unsigned long taskweight, groupweight;
1448 long taskimp, groupimp;
1451 * Pick the lowest SD_NUMA domain, as that would have the smallest
1452 * imbalance and would be the first to start moving tasks about.
1454 * And we want to avoid any moving of tasks about, as that would create
1455 * random movement of tasks -- counter the numa conditions we're trying
1459 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1461 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1465 * Cpusets can break the scheduler domain tree into smaller
1466 * balance domains, some of which do not cross NUMA boundaries.
1467 * Tasks that are "trapped" in such domains cannot be migrated
1468 * elsewhere, so there is no point in (re)trying.
1470 if (unlikely(!sd)) {
1471 p->numa_preferred_nid = task_node(p);
1475 env.dst_nid = p->numa_preferred_nid;
1476 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1477 taskweight = task_weight(p, env.src_nid, dist);
1478 groupweight = group_weight(p, env.src_nid, dist);
1479 update_numa_stats(&env.src_stats, env.src_nid);
1480 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1481 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1482 update_numa_stats(&env.dst_stats, env.dst_nid);
1484 /* Try to find a spot on the preferred nid. */
1485 if (numa_has_capacity(&env))
1486 task_numa_find_cpu(&env, taskimp, groupimp);
1489 * Look at other nodes in these cases:
1490 * - there is no space available on the preferred_nid
1491 * - the task is part of a numa_group that is interleaved across
1492 * multiple NUMA nodes; in order to better consolidate the group,
1493 * we need to check other locations.
1495 if (env.best_cpu == -1 || (p->numa_group &&
1496 nodes_weight(p->numa_group->active_nodes) > 1)) {
1497 for_each_online_node(nid) {
1498 if (nid == env.src_nid || nid == p->numa_preferred_nid)
1501 dist = node_distance(env.src_nid, env.dst_nid);
1502 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1504 taskweight = task_weight(p, env.src_nid, dist);
1505 groupweight = group_weight(p, env.src_nid, dist);
1508 /* Only consider nodes where both task and groups benefit */
1509 taskimp = task_weight(p, nid, dist) - taskweight;
1510 groupimp = group_weight(p, nid, dist) - groupweight;
1511 if (taskimp < 0 && groupimp < 0)
1516 update_numa_stats(&env.dst_stats, env.dst_nid);
1517 if (numa_has_capacity(&env))
1518 task_numa_find_cpu(&env, taskimp, groupimp);
1523 * If the task is part of a workload that spans multiple NUMA nodes,
1524 * and is migrating into one of the workload's active nodes, remember
1525 * this node as the task's preferred numa node, so the workload can
1527 * A task that migrated to a second choice node will be better off
1528 * trying for a better one later. Do not set the preferred node here.
1530 if (p->numa_group) {
1531 if (env.best_cpu == -1)
1536 if (node_isset(nid, p->numa_group->active_nodes))
1537 sched_setnuma(p, env.dst_nid);
1540 /* No better CPU than the current one was found. */
1541 if (env.best_cpu == -1)
1545 * Reset the scan period if the task is being rescheduled on an
1546 * alternative node to recheck if the tasks is now properly placed.
1548 p->numa_scan_period = task_scan_min(p);
1550 if (env.best_task == NULL) {
1551 ret = migrate_task_to(p, env.best_cpu);
1553 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1557 ret = migrate_swap(p, env.best_task);
1559 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1560 put_task_struct(env.best_task);
1564 /* Attempt to migrate a task to a CPU on the preferred node. */
1565 static void numa_migrate_preferred(struct task_struct *p)
1567 unsigned long interval = HZ;
1569 /* This task has no NUMA fault statistics yet */
1570 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1573 /* Periodically retry migrating the task to the preferred node */
1574 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1575 p->numa_migrate_retry = jiffies + interval;
1577 /* Success if task is already running on preferred CPU */
1578 if (task_node(p) == p->numa_preferred_nid)
1581 /* Otherwise, try migrate to a CPU on the preferred node */
1582 task_numa_migrate(p);
1586 * Find the nodes on which the workload is actively running. We do this by
1587 * tracking the nodes from which NUMA hinting faults are triggered. This can
1588 * be different from the set of nodes where the workload's memory is currently
1591 * The bitmask is used to make smarter decisions on when to do NUMA page
1592 * migrations, To prevent flip-flopping, and excessive page migrations, nodes
1593 * are added when they cause over 6/16 of the maximum number of faults, but
1594 * only removed when they drop below 3/16.
1596 static void update_numa_active_node_mask(struct numa_group *numa_group)
1598 unsigned long faults, max_faults = 0;
1601 for_each_online_node(nid) {
1602 faults = group_faults_cpu(numa_group, nid);
1603 if (faults > max_faults)
1604 max_faults = faults;
1607 for_each_online_node(nid) {
1608 faults = group_faults_cpu(numa_group, nid);
1609 if (!node_isset(nid, numa_group->active_nodes)) {
1610 if (faults > max_faults * 6 / 16)
1611 node_set(nid, numa_group->active_nodes);
1612 } else if (faults < max_faults * 3 / 16)
1613 node_clear(nid, numa_group->active_nodes);
1618 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1619 * increments. The more local the fault statistics are, the higher the scan
1620 * period will be for the next scan window. If local/(local+remote) ratio is
1621 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1622 * the scan period will decrease. Aim for 70% local accesses.
1624 #define NUMA_PERIOD_SLOTS 10
1625 #define NUMA_PERIOD_THRESHOLD 7
1628 * Increase the scan period (slow down scanning) if the majority of
1629 * our memory is already on our local node, or if the majority of
1630 * the page accesses are shared with other processes.
1631 * Otherwise, decrease the scan period.
1633 static void update_task_scan_period(struct task_struct *p,
1634 unsigned long shared, unsigned long private)
1636 unsigned int period_slot;
1640 unsigned long remote = p->numa_faults_locality[0];
1641 unsigned long local = p->numa_faults_locality[1];
1644 * If there were no record hinting faults then either the task is
1645 * completely idle or all activity is areas that are not of interest
1646 * to automatic numa balancing. Related to that, if there were failed
1647 * migration then it implies we are migrating too quickly or the local
1648 * node is overloaded. In either case, scan slower
1650 if (local + shared == 0 || p->numa_faults_locality[2]) {
1651 p->numa_scan_period = min(p->numa_scan_period_max,
1652 p->numa_scan_period << 1);
1654 p->mm->numa_next_scan = jiffies +
1655 msecs_to_jiffies(p->numa_scan_period);
1661 * Prepare to scale scan period relative to the current period.
1662 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1663 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1664 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1666 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1667 ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1668 if (ratio >= NUMA_PERIOD_THRESHOLD) {
1669 int slot = ratio - NUMA_PERIOD_THRESHOLD;
1672 diff = slot * period_slot;
1674 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1677 * Scale scan rate increases based on sharing. There is an
1678 * inverse relationship between the degree of sharing and
1679 * the adjustment made to the scanning period. Broadly
1680 * speaking the intent is that there is little point
1681 * scanning faster if shared accesses dominate as it may
1682 * simply bounce migrations uselessly
1684 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1685 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1688 p->numa_scan_period = clamp(p->numa_scan_period + diff,
1689 task_scan_min(p), task_scan_max(p));
1690 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1694 * Get the fraction of time the task has been running since the last
1695 * NUMA placement cycle. The scheduler keeps similar statistics, but
1696 * decays those on a 32ms period, which is orders of magnitude off
1697 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1698 * stats only if the task is so new there are no NUMA statistics yet.
1700 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1702 u64 runtime, delta, now;
1703 /* Use the start of this time slice to avoid calculations. */
1704 now = p->se.exec_start;
1705 runtime = p->se.sum_exec_runtime;
1707 if (p->last_task_numa_placement) {
1708 delta = runtime - p->last_sum_exec_runtime;
1709 *period = now - p->last_task_numa_placement;
1711 delta = p->se.avg.load_sum / p->se.load.weight;
1712 *period = LOAD_AVG_MAX;
1715 p->last_sum_exec_runtime = runtime;
1716 p->last_task_numa_placement = now;
1722 * Determine the preferred nid for a task in a numa_group. This needs to
1723 * be done in a way that produces consistent results with group_weight,
1724 * otherwise workloads might not converge.
1726 static int preferred_group_nid(struct task_struct *p, int nid)
1731 /* Direct connections between all NUMA nodes. */
1732 if (sched_numa_topology_type == NUMA_DIRECT)
1736 * On a system with glueless mesh NUMA topology, group_weight
1737 * scores nodes according to the number of NUMA hinting faults on
1738 * both the node itself, and on nearby nodes.
1740 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1741 unsigned long score, max_score = 0;
1742 int node, max_node = nid;
1744 dist = sched_max_numa_distance;
1746 for_each_online_node(node) {
1747 score = group_weight(p, node, dist);
1748 if (score > max_score) {
1757 * Finding the preferred nid in a system with NUMA backplane
1758 * interconnect topology is more involved. The goal is to locate
1759 * tasks from numa_groups near each other in the system, and
1760 * untangle workloads from different sides of the system. This requires
1761 * searching down the hierarchy of node groups, recursively searching
1762 * inside the highest scoring group of nodes. The nodemask tricks
1763 * keep the complexity of the search down.
1765 nodes = node_online_map;
1766 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
1767 unsigned long max_faults = 0;
1768 nodemask_t max_group = NODE_MASK_NONE;
1771 /* Are there nodes at this distance from each other? */
1772 if (!find_numa_distance(dist))
1775 for_each_node_mask(a, nodes) {
1776 unsigned long faults = 0;
1777 nodemask_t this_group;
1778 nodes_clear(this_group);
1780 /* Sum group's NUMA faults; includes a==b case. */
1781 for_each_node_mask(b, nodes) {
1782 if (node_distance(a, b) < dist) {
1783 faults += group_faults(p, b);
1784 node_set(b, this_group);
1785 node_clear(b, nodes);
1789 /* Remember the top group. */
1790 if (faults > max_faults) {
1791 max_faults = faults;
1792 max_group = this_group;
1794 * subtle: at the smallest distance there is
1795 * just one node left in each "group", the
1796 * winner is the preferred nid.
1801 /* Next round, evaluate the nodes within max_group. */
1809 static void task_numa_placement(struct task_struct *p)
1811 int seq, nid, max_nid = -1, max_group_nid = -1;
1812 unsigned long max_faults = 0, max_group_faults = 0;
1813 unsigned long fault_types[2] = { 0, 0 };
1814 unsigned long total_faults;
1815 u64 runtime, period;
1816 spinlock_t *group_lock = NULL;
1819 * The p->mm->numa_scan_seq field gets updated without
1820 * exclusive access. Use READ_ONCE() here to ensure
1821 * that the field is read in a single access:
1823 seq = READ_ONCE(p->mm->numa_scan_seq);
1824 if (p->numa_scan_seq == seq)
1826 p->numa_scan_seq = seq;
1827 p->numa_scan_period_max = task_scan_max(p);
1829 total_faults = p->numa_faults_locality[0] +
1830 p->numa_faults_locality[1];
1831 runtime = numa_get_avg_runtime(p, &period);
1833 /* If the task is part of a group prevent parallel updates to group stats */
1834 if (p->numa_group) {
1835 group_lock = &p->numa_group->lock;
1836 spin_lock_irq(group_lock);
1839 /* Find the node with the highest number of faults */
1840 for_each_online_node(nid) {
1841 /* Keep track of the offsets in numa_faults array */
1842 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1843 unsigned long faults = 0, group_faults = 0;
1846 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1847 long diff, f_diff, f_weight;
1849 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
1850 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
1851 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
1852 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1854 /* Decay existing window, copy faults since last scan */
1855 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
1856 fault_types[priv] += p->numa_faults[membuf_idx];
1857 p->numa_faults[membuf_idx] = 0;
1860 * Normalize the faults_from, so all tasks in a group
1861 * count according to CPU use, instead of by the raw
1862 * number of faults. Tasks with little runtime have
1863 * little over-all impact on throughput, and thus their
1864 * faults are less important.
1866 f_weight = div64_u64(runtime << 16, period + 1);
1867 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1869 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
1870 p->numa_faults[cpubuf_idx] = 0;
1872 p->numa_faults[mem_idx] += diff;
1873 p->numa_faults[cpu_idx] += f_diff;
1874 faults += p->numa_faults[mem_idx];
1875 p->total_numa_faults += diff;
1876 if (p->numa_group) {
1878 * safe because we can only change our own group
1880 * mem_idx represents the offset for a given
1881 * nid and priv in a specific region because it
1882 * is at the beginning of the numa_faults array.
1884 p->numa_group->faults[mem_idx] += diff;
1885 p->numa_group->faults_cpu[mem_idx] += f_diff;
1886 p->numa_group->total_faults += diff;
1887 group_faults += p->numa_group->faults[mem_idx];
1891 if (faults > max_faults) {
1892 max_faults = faults;
1896 if (group_faults > max_group_faults) {
1897 max_group_faults = group_faults;
1898 max_group_nid = nid;
1902 update_task_scan_period(p, fault_types[0], fault_types[1]);
1904 if (p->numa_group) {
1905 update_numa_active_node_mask(p->numa_group);
1906 spin_unlock_irq(group_lock);
1907 max_nid = preferred_group_nid(p, max_group_nid);
1911 /* Set the new preferred node */
1912 if (max_nid != p->numa_preferred_nid)
1913 sched_setnuma(p, max_nid);
1915 if (task_node(p) != p->numa_preferred_nid)
1916 numa_migrate_preferred(p);
1920 static inline int get_numa_group(struct numa_group *grp)
1922 return atomic_inc_not_zero(&grp->refcount);
1925 static inline void put_numa_group(struct numa_group *grp)
1927 if (atomic_dec_and_test(&grp->refcount))
1928 kfree_rcu(grp, rcu);
1931 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
1934 struct numa_group *grp, *my_grp;
1935 struct task_struct *tsk;
1937 int cpu = cpupid_to_cpu(cpupid);
1940 if (unlikely(!p->numa_group)) {
1941 unsigned int size = sizeof(struct numa_group) +
1942 4*nr_node_ids*sizeof(unsigned long);
1944 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
1948 atomic_set(&grp->refcount, 1);
1949 spin_lock_init(&grp->lock);
1951 /* Second half of the array tracks nids where faults happen */
1952 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
1955 node_set(task_node(current), grp->active_nodes);
1957 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1958 grp->faults[i] = p->numa_faults[i];
1960 grp->total_faults = p->total_numa_faults;
1963 rcu_assign_pointer(p->numa_group, grp);
1967 tsk = READ_ONCE(cpu_rq(cpu)->curr);
1969 if (!cpupid_match_pid(tsk, cpupid))
1972 grp = rcu_dereference(tsk->numa_group);
1976 my_grp = p->numa_group;
1981 * Only join the other group if its bigger; if we're the bigger group,
1982 * the other task will join us.
1984 if (my_grp->nr_tasks > grp->nr_tasks)
1988 * Tie-break on the grp address.
1990 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1993 /* Always join threads in the same process. */
1994 if (tsk->mm == current->mm)
1997 /* Simple filter to avoid false positives due to PID collisions */
1998 if (flags & TNF_SHARED)
2001 /* Update priv based on whether false sharing was detected */
2004 if (join && !get_numa_group(grp))
2012 BUG_ON(irqs_disabled());
2013 double_lock_irq(&my_grp->lock, &grp->lock);
2015 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2016 my_grp->faults[i] -= p->numa_faults[i];
2017 grp->faults[i] += p->numa_faults[i];
2019 my_grp->total_faults -= p->total_numa_faults;
2020 grp->total_faults += p->total_numa_faults;
2025 spin_unlock(&my_grp->lock);
2026 spin_unlock_irq(&grp->lock);
2028 rcu_assign_pointer(p->numa_group, grp);
2030 put_numa_group(my_grp);
2038 void task_numa_free(struct task_struct *p)
2040 struct numa_group *grp = p->numa_group;
2041 void *numa_faults = p->numa_faults;
2042 unsigned long flags;
2046 spin_lock_irqsave(&grp->lock, flags);
2047 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2048 grp->faults[i] -= p->numa_faults[i];
2049 grp->total_faults -= p->total_numa_faults;
2052 spin_unlock_irqrestore(&grp->lock, flags);
2053 RCU_INIT_POINTER(p->numa_group, NULL);
2054 put_numa_group(grp);
2057 p->numa_faults = NULL;
2062 * Got a PROT_NONE fault for a page on @node.
2064 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2066 struct task_struct *p = current;
2067 bool migrated = flags & TNF_MIGRATED;
2068 int cpu_node = task_node(current);
2069 int local = !!(flags & TNF_FAULT_LOCAL);
2072 if (!numabalancing_enabled)
2075 /* for example, ksmd faulting in a user's mm */
2079 /* Allocate buffer to track faults on a per-node basis */
2080 if (unlikely(!p->numa_faults)) {
2081 int size = sizeof(*p->numa_faults) *
2082 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2084 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2085 if (!p->numa_faults)
2088 p->total_numa_faults = 0;
2089 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2093 * First accesses are treated as private, otherwise consider accesses
2094 * to be private if the accessing pid has not changed
2096 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2099 priv = cpupid_match_pid(p, last_cpupid);
2100 if (!priv && !(flags & TNF_NO_GROUP))
2101 task_numa_group(p, last_cpupid, flags, &priv);
2105 * If a workload spans multiple NUMA nodes, a shared fault that
2106 * occurs wholly within the set of nodes that the workload is
2107 * actively using should be counted as local. This allows the
2108 * scan rate to slow down when a workload has settled down.
2110 if (!priv && !local && p->numa_group &&
2111 node_isset(cpu_node, p->numa_group->active_nodes) &&
2112 node_isset(mem_node, p->numa_group->active_nodes))
2115 task_numa_placement(p);
2118 * Retry task to preferred node migration periodically, in case it
2119 * case it previously failed, or the scheduler moved us.
2121 if (time_after(jiffies, p->numa_migrate_retry))
2122 numa_migrate_preferred(p);
2125 p->numa_pages_migrated += pages;
2126 if (flags & TNF_MIGRATE_FAIL)
2127 p->numa_faults_locality[2] += pages;
2129 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2130 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2131 p->numa_faults_locality[local] += pages;
2134 static void reset_ptenuma_scan(struct task_struct *p)
2137 * We only did a read acquisition of the mmap sem, so
2138 * p->mm->numa_scan_seq is written to without exclusive access
2139 * and the update is not guaranteed to be atomic. That's not
2140 * much of an issue though, since this is just used for
2141 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2142 * expensive, to avoid any form of compiler optimizations:
2144 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2145 p->mm->numa_scan_offset = 0;
2149 * The expensive part of numa migration is done from task_work context.
2150 * Triggered from task_tick_numa().
2152 void task_numa_work(struct callback_head *work)
2154 unsigned long migrate, next_scan, now = jiffies;
2155 struct task_struct *p = current;
2156 struct mm_struct *mm = p->mm;
2157 struct vm_area_struct *vma;
2158 unsigned long start, end;
2159 unsigned long nr_pte_updates = 0;
2162 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
2164 work->next = work; /* protect against double add */
2166 * Who cares about NUMA placement when they're dying.
2168 * NOTE: make sure not to dereference p->mm before this check,
2169 * exit_task_work() happens _after_ exit_mm() so we could be called
2170 * without p->mm even though we still had it when we enqueued this
2173 if (p->flags & PF_EXITING)
2176 if (!mm->numa_next_scan) {
2177 mm->numa_next_scan = now +
2178 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2182 * Enforce maximal scan/migration frequency..
2184 migrate = mm->numa_next_scan;
2185 if (time_before(now, migrate))
2188 if (p->numa_scan_period == 0) {
2189 p->numa_scan_period_max = task_scan_max(p);
2190 p->numa_scan_period = task_scan_min(p);
2193 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2194 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2198 * Delay this task enough that another task of this mm will likely win
2199 * the next time around.
2201 p->node_stamp += 2 * TICK_NSEC;
2203 start = mm->numa_scan_offset;
2204 pages = sysctl_numa_balancing_scan_size;
2205 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2209 down_read(&mm->mmap_sem);
2210 vma = find_vma(mm, start);
2212 reset_ptenuma_scan(p);
2216 for (; vma; vma = vma->vm_next) {
2217 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2218 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2223 * Shared library pages mapped by multiple processes are not
2224 * migrated as it is expected they are cache replicated. Avoid
2225 * hinting faults in read-only file-backed mappings or the vdso
2226 * as migrating the pages will be of marginal benefit.
2229 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2233 * Skip inaccessible VMAs to avoid any confusion between
2234 * PROT_NONE and NUMA hinting ptes
2236 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2240 start = max(start, vma->vm_start);
2241 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2242 end = min(end, vma->vm_end);
2243 nr_pte_updates += change_prot_numa(vma, start, end);
2246 * Scan sysctl_numa_balancing_scan_size but ensure that
2247 * at least one PTE is updated so that unused virtual
2248 * address space is quickly skipped.
2251 pages -= (end - start) >> PAGE_SHIFT;
2258 } while (end != vma->vm_end);
2263 * It is possible to reach the end of the VMA list but the last few
2264 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2265 * would find the !migratable VMA on the next scan but not reset the
2266 * scanner to the start so check it now.
2269 mm->numa_scan_offset = start;
2271 reset_ptenuma_scan(p);
2272 up_read(&mm->mmap_sem);
2276 * Drive the periodic memory faults..
2278 void task_tick_numa(struct rq *rq, struct task_struct *curr)
2280 struct callback_head *work = &curr->numa_work;
2284 * We don't care about NUMA placement if we don't have memory.
2286 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2290 * Using runtime rather than walltime has the dual advantage that
2291 * we (mostly) drive the selection from busy threads and that the
2292 * task needs to have done some actual work before we bother with
2295 now = curr->se.sum_exec_runtime;
2296 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2298 if (now - curr->node_stamp > period) {
2299 if (!curr->node_stamp)
2300 curr->numa_scan_period = task_scan_min(curr);
2301 curr->node_stamp += period;
2303 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2304 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2305 task_work_add(curr, work, true);
2310 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2314 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2318 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2321 #endif /* CONFIG_NUMA_BALANCING */
2324 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2326 update_load_add(&cfs_rq->load, se->load.weight);
2327 if (!parent_entity(se))
2328 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2330 if (entity_is_task(se)) {
2331 struct rq *rq = rq_of(cfs_rq);
2333 account_numa_enqueue(rq, task_of(se));
2334 list_add(&se->group_node, &rq->cfs_tasks);
2337 cfs_rq->nr_running++;
2341 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2343 update_load_sub(&cfs_rq->load, se->load.weight);
2344 if (!parent_entity(se))
2345 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2346 if (entity_is_task(se)) {
2347 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2348 list_del_init(&se->group_node);
2350 cfs_rq->nr_running--;
2353 #ifdef CONFIG_FAIR_GROUP_SCHED
2355 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
2360 * Use this CPU's real-time load instead of the last load contribution
2361 * as the updating of the contribution is delayed, and we will use the
2362 * the real-time load to calc the share. See update_tg_load_avg().
2364 tg_weight = atomic_long_read(&tg->load_avg);
2365 tg_weight -= cfs_rq->tg_load_avg_contrib;
2366 tg_weight += cfs_rq_load_avg(cfs_rq);
2371 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2373 long tg_weight, load, shares;
2375 tg_weight = calc_tg_weight(tg, cfs_rq);
2376 load = cfs_rq_load_avg(cfs_rq);
2378 shares = (tg->shares * load);
2380 shares /= tg_weight;
2382 if (shares < MIN_SHARES)
2383 shares = MIN_SHARES;
2384 if (shares > tg->shares)
2385 shares = tg->shares;
2389 # else /* CONFIG_SMP */
2390 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2394 # endif /* CONFIG_SMP */
2395 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2396 unsigned long weight)
2399 /* commit outstanding execution time */
2400 if (cfs_rq->curr == se)
2401 update_curr(cfs_rq);
2402 account_entity_dequeue(cfs_rq, se);
2405 update_load_set(&se->load, weight);
2408 account_entity_enqueue(cfs_rq, se);
2411 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2413 static void update_cfs_shares(struct cfs_rq *cfs_rq)
2415 struct task_group *tg;
2416 struct sched_entity *se;
2420 se = tg->se[cpu_of(rq_of(cfs_rq))];
2421 if (!se || throttled_hierarchy(cfs_rq))
2424 if (likely(se->load.weight == tg->shares))
2427 shares = calc_cfs_shares(cfs_rq, tg);
2429 reweight_entity(cfs_rq_of(se), se, shares);
2431 #else /* CONFIG_FAIR_GROUP_SCHED */
2432 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2435 #endif /* CONFIG_FAIR_GROUP_SCHED */
2438 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2439 static const u32 runnable_avg_yN_inv[] = {
2440 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2441 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2442 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2443 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2444 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2445 0x85aac367, 0x82cd8698,
2449 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2450 * over-estimates when re-combining.
2452 static const u32 runnable_avg_yN_sum[] = {
2453 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2454 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2455 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2460 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2462 static __always_inline u64 decay_load(u64 val, u64 n)
2464 unsigned int local_n;
2468 else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2471 /* after bounds checking we can collapse to 32-bit */
2475 * As y^PERIOD = 1/2, we can combine
2476 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2477 * With a look-up table which covers y^n (n<PERIOD)
2479 * To achieve constant time decay_load.
2481 if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2482 val >>= local_n / LOAD_AVG_PERIOD;
2483 local_n %= LOAD_AVG_PERIOD;
2486 val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
2491 * For updates fully spanning n periods, the contribution to runnable
2492 * average will be: \Sum 1024*y^n
2494 * We can compute this reasonably efficiently by combining:
2495 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2497 static u32 __compute_runnable_contrib(u64 n)
2501 if (likely(n <= LOAD_AVG_PERIOD))
2502 return runnable_avg_yN_sum[n];
2503 else if (unlikely(n >= LOAD_AVG_MAX_N))
2504 return LOAD_AVG_MAX;
2506 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2508 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2509 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
2511 n -= LOAD_AVG_PERIOD;
2512 } while (n > LOAD_AVG_PERIOD);
2514 contrib = decay_load(contrib, n);
2515 return contrib + runnable_avg_yN_sum[n];
2519 * We can represent the historical contribution to runnable average as the
2520 * coefficients of a geometric series. To do this we sub-divide our runnable
2521 * history into segments of approximately 1ms (1024us); label the segment that
2522 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2524 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2526 * (now) (~1ms ago) (~2ms ago)
2528 * Let u_i denote the fraction of p_i that the entity was runnable.
2530 * We then designate the fractions u_i as our co-efficients, yielding the
2531 * following representation of historical load:
2532 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2534 * We choose y based on the with of a reasonably scheduling period, fixing:
2537 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2538 * approximately half as much as the contribution to load within the last ms
2541 * When a period "rolls over" and we have new u_0`, multiplying the previous
2542 * sum again by y is sufficient to update:
2543 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2544 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2546 static __always_inline int
2547 __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2548 unsigned long weight, int running, struct cfs_rq *cfs_rq)
2552 int delta_w, decayed = 0;
2553 unsigned long scale_freq = arch_scale_freq_capacity(NULL, cpu);
2555 delta = now - sa->last_update_time;
2557 * This should only happen when time goes backwards, which it
2558 * unfortunately does during sched clock init when we swap over to TSC.
2560 if ((s64)delta < 0) {
2561 sa->last_update_time = now;
2566 * Use 1024ns as the unit of measurement since it's a reasonable
2567 * approximation of 1us and fast to compute.
2572 sa->last_update_time = now;
2574 /* delta_w is the amount already accumulated against our next period */
2575 delta_w = sa->period_contrib;
2576 if (delta + delta_w >= 1024) {
2579 /* how much left for next period will start over, we don't know yet */
2580 sa->period_contrib = 0;
2583 * Now that we know we're crossing a period boundary, figure
2584 * out how much from delta we need to complete the current
2585 * period and accrue it.
2587 delta_w = 1024 - delta_w;
2589 sa->load_sum += weight * delta_w;
2591 cfs_rq->runnable_load_sum += weight * delta_w;
2594 sa->util_sum += delta_w * scale_freq >> SCHED_CAPACITY_SHIFT;
2598 /* Figure out how many additional periods this update spans */
2599 periods = delta / 1024;
2602 sa->load_sum = decay_load(sa->load_sum, periods + 1);
2604 cfs_rq->runnable_load_sum =
2605 decay_load(cfs_rq->runnable_load_sum, periods + 1);
2607 sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2609 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2610 contrib = __compute_runnable_contrib(periods);
2612 sa->load_sum += weight * contrib;
2614 cfs_rq->runnable_load_sum += weight * contrib;
2617 sa->util_sum += contrib * scale_freq >> SCHED_CAPACITY_SHIFT;
2620 /* Remainder of delta accrued against u_0` */
2622 sa->load_sum += weight * delta;
2624 cfs_rq->runnable_load_sum += weight * delta;
2627 sa->util_sum += delta * scale_freq >> SCHED_CAPACITY_SHIFT;
2629 sa->period_contrib += delta;
2632 sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2634 cfs_rq->runnable_load_avg =
2635 div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
2637 sa->util_avg = (sa->util_sum << SCHED_LOAD_SHIFT) / LOAD_AVG_MAX;
2643 #ifdef CONFIG_FAIR_GROUP_SCHED
2645 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2646 * and effective_load (which is not done because it is too costly).
2648 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2650 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2652 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
2653 atomic_long_add(delta, &cfs_rq->tg->load_avg);
2654 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2658 #else /* CONFIG_FAIR_GROUP_SCHED */
2659 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2660 #endif /* CONFIG_FAIR_GROUP_SCHED */
2662 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2664 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2665 static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
2668 struct sched_avg *sa = &cfs_rq->avg;
2670 if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2671 long r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2672 sa->load_avg = max_t(long, sa->load_avg - r, 0);
2673 sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
2676 if (atomic_long_read(&cfs_rq->removed_util_avg)) {
2677 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2678 sa->util_avg = max_t(long, sa->util_avg - r, 0);
2679 sa->util_sum = max_t(s32, sa->util_sum -
2680 ((r * LOAD_AVG_MAX) >> SCHED_LOAD_SHIFT), 0);
2683 decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2684 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2686 #ifndef CONFIG_64BIT
2688 cfs_rq->load_last_update_time_copy = sa->last_update_time;
2694 /* Update task and its cfs_rq load average */
2695 static inline void update_load_avg(struct sched_entity *se, int update_tg)
2697 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2698 int cpu = cpu_of(rq_of(cfs_rq));
2699 u64 now = cfs_rq_clock_task(cfs_rq);
2702 * Track task load average for carrying it to new CPU after migrated, and
2703 * track group sched_entity load average for task_h_load calc in migration
2705 __update_load_avg(now, cpu, &se->avg,
2706 se->on_rq * scale_load_down(se->load.weight), cfs_rq->curr == se, NULL);
2708 if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
2709 update_tg_load_avg(cfs_rq, 0);
2712 /* Add the load generated by se into cfs_rq's load average */
2714 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2716 struct sched_avg *sa = &se->avg;
2717 u64 now = cfs_rq_clock_task(cfs_rq);
2718 int migrated = 0, decayed;
2720 if (sa->last_update_time == 0) {
2721 sa->last_update_time = now;
2725 __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2726 se->on_rq * scale_load_down(se->load.weight),
2727 cfs_rq->curr == se, NULL);
2730 decayed = update_cfs_rq_load_avg(now, cfs_rq);
2732 cfs_rq->runnable_load_avg += sa->load_avg;
2733 cfs_rq->runnable_load_sum += sa->load_sum;
2736 cfs_rq->avg.load_avg += sa->load_avg;
2737 cfs_rq->avg.load_sum += sa->load_sum;
2738 cfs_rq->avg.util_avg += sa->util_avg;
2739 cfs_rq->avg.util_sum += sa->util_sum;
2742 if (decayed || migrated)
2743 update_tg_load_avg(cfs_rq, 0);
2746 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
2748 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2750 update_load_avg(se, 1);
2752 cfs_rq->runnable_load_avg =
2753 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
2754 cfs_rq->runnable_load_sum =
2755 max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2759 * Task first catches up with cfs_rq, and then subtract
2760 * itself from the cfs_rq (task must be off the queue now).
2762 void remove_entity_load_avg(struct sched_entity *se)
2764 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2765 u64 last_update_time;
2767 #ifndef CONFIG_64BIT
2768 u64 last_update_time_copy;
2771 last_update_time_copy = cfs_rq->load_last_update_time_copy;
2773 last_update_time = cfs_rq->avg.last_update_time;
2774 } while (last_update_time != last_update_time_copy);
2776 last_update_time = cfs_rq->avg.last_update_time;
2779 __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2780 atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
2781 atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2785 * Update the rq's load with the elapsed running time before entering
2786 * idle. if the last scheduled task is not a CFS task, idle_enter will
2787 * be the only way to update the runnable statistic.
2789 void idle_enter_fair(struct rq *this_rq)
2794 * Update the rq's load with the elapsed idle time before a task is
2795 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2796 * be the only way to update the runnable statistic.
2798 void idle_exit_fair(struct rq *this_rq)
2802 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
2804 return cfs_rq->runnable_load_avg;
2807 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
2809 return cfs_rq->avg.load_avg;
2812 static int idle_balance(struct rq *this_rq);
2814 #else /* CONFIG_SMP */
2816 static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
2818 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2820 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2821 static inline void remove_entity_load_avg(struct sched_entity *se) {}
2823 static inline int idle_balance(struct rq *rq)
2828 #endif /* CONFIG_SMP */
2830 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2832 #ifdef CONFIG_SCHEDSTATS
2833 struct task_struct *tsk = NULL;
2835 if (entity_is_task(se))
2838 if (se->statistics.sleep_start) {
2839 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2844 if (unlikely(delta > se->statistics.sleep_max))
2845 se->statistics.sleep_max = delta;
2847 se->statistics.sleep_start = 0;
2848 se->statistics.sum_sleep_runtime += delta;
2851 account_scheduler_latency(tsk, delta >> 10, 1);
2852 trace_sched_stat_sleep(tsk, delta);
2855 if (se->statistics.block_start) {
2856 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2861 if (unlikely(delta > se->statistics.block_max))
2862 se->statistics.block_max = delta;
2864 se->statistics.block_start = 0;
2865 se->statistics.sum_sleep_runtime += delta;
2868 if (tsk->in_iowait) {
2869 se->statistics.iowait_sum += delta;
2870 se->statistics.iowait_count++;
2871 trace_sched_stat_iowait(tsk, delta);
2874 trace_sched_stat_blocked(tsk, delta);
2877 * Blocking time is in units of nanosecs, so shift by
2878 * 20 to get a milliseconds-range estimation of the
2879 * amount of time that the task spent sleeping:
2881 if (unlikely(prof_on == SLEEP_PROFILING)) {
2882 profile_hits(SLEEP_PROFILING,
2883 (void *)get_wchan(tsk),
2886 account_scheduler_latency(tsk, delta >> 10, 0);
2892 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
2894 #ifdef CONFIG_SCHED_DEBUG
2895 s64 d = se->vruntime - cfs_rq->min_vruntime;
2900 if (d > 3*sysctl_sched_latency)
2901 schedstat_inc(cfs_rq, nr_spread_over);
2906 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
2908 u64 vruntime = cfs_rq->min_vruntime;
2911 * The 'current' period is already promised to the current tasks,
2912 * however the extra weight of the new task will slow them down a
2913 * little, place the new task so that it fits in the slot that
2914 * stays open at the end.
2916 if (initial && sched_feat(START_DEBIT))
2917 vruntime += sched_vslice(cfs_rq, se);
2919 /* sleeps up to a single latency don't count. */
2921 unsigned long thresh = sysctl_sched_latency;
2924 * Halve their sleep time's effect, to allow
2925 * for a gentler effect of sleepers:
2927 if (sched_feat(GENTLE_FAIR_SLEEPERS))
2933 /* ensure we never gain time by being placed backwards. */
2934 se->vruntime = max_vruntime(se->vruntime, vruntime);
2937 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
2940 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2943 * Update the normalized vruntime before updating min_vruntime
2944 * through calling update_curr().
2946 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
2947 se->vruntime += cfs_rq->min_vruntime;
2950 * Update run-time statistics of the 'current'.
2952 update_curr(cfs_rq);
2953 enqueue_entity_load_avg(cfs_rq, se);
2954 account_entity_enqueue(cfs_rq, se);
2955 update_cfs_shares(cfs_rq);
2957 if (flags & ENQUEUE_WAKEUP) {
2958 place_entity(cfs_rq, se, 0);
2959 enqueue_sleeper(cfs_rq, se);
2962 update_stats_enqueue(cfs_rq, se);
2963 check_spread(cfs_rq, se);
2964 if (se != cfs_rq->curr)
2965 __enqueue_entity(cfs_rq, se);
2968 if (cfs_rq->nr_running == 1) {
2969 list_add_leaf_cfs_rq(cfs_rq);
2970 check_enqueue_throttle(cfs_rq);
2974 static void __clear_buddies_last(struct sched_entity *se)
2976 for_each_sched_entity(se) {
2977 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2978 if (cfs_rq->last != se)
2981 cfs_rq->last = NULL;
2985 static void __clear_buddies_next(struct sched_entity *se)
2987 for_each_sched_entity(se) {
2988 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2989 if (cfs_rq->next != se)
2992 cfs_rq->next = NULL;
2996 static void __clear_buddies_skip(struct sched_entity *se)
2998 for_each_sched_entity(se) {
2999 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3000 if (cfs_rq->skip != se)
3003 cfs_rq->skip = NULL;
3007 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3009 if (cfs_rq->last == se)
3010 __clear_buddies_last(se);
3012 if (cfs_rq->next == se)
3013 __clear_buddies_next(se);
3015 if (cfs_rq->skip == se)
3016 __clear_buddies_skip(se);
3019 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3022 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3025 * Update run-time statistics of the 'current'.
3027 update_curr(cfs_rq);
3028 dequeue_entity_load_avg(cfs_rq, se);
3030 update_stats_dequeue(cfs_rq, se);
3031 if (flags & DEQUEUE_SLEEP) {
3032 #ifdef CONFIG_SCHEDSTATS
3033 if (entity_is_task(se)) {
3034 struct task_struct *tsk = task_of(se);
3036 if (tsk->state & TASK_INTERRUPTIBLE)
3037 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3038 if (tsk->state & TASK_UNINTERRUPTIBLE)
3039 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3044 clear_buddies(cfs_rq, se);
3046 if (se != cfs_rq->curr)
3047 __dequeue_entity(cfs_rq, se);
3049 account_entity_dequeue(cfs_rq, se);
3052 * Normalize the entity after updating the min_vruntime because the
3053 * update can refer to the ->curr item and we need to reflect this
3054 * movement in our normalized position.
3056 if (!(flags & DEQUEUE_SLEEP))
3057 se->vruntime -= cfs_rq->min_vruntime;
3059 /* return excess runtime on last dequeue */
3060 return_cfs_rq_runtime(cfs_rq);
3062 update_min_vruntime(cfs_rq);
3063 update_cfs_shares(cfs_rq);
3067 * Preempt the current task with a newly woken task if needed:
3070 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3072 unsigned long ideal_runtime, delta_exec;
3073 struct sched_entity *se;
3076 ideal_runtime = sched_slice(cfs_rq, curr);
3077 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3078 if (delta_exec > ideal_runtime) {
3079 resched_curr(rq_of(cfs_rq));
3081 * The current task ran long enough, ensure it doesn't get
3082 * re-elected due to buddy favours.
3084 clear_buddies(cfs_rq, curr);
3089 * Ensure that a task that missed wakeup preemption by a
3090 * narrow margin doesn't have to wait for a full slice.
3091 * This also mitigates buddy induced latencies under load.
3093 if (delta_exec < sysctl_sched_min_granularity)
3096 se = __pick_first_entity(cfs_rq);
3097 delta = curr->vruntime - se->vruntime;
3102 if (delta > ideal_runtime)
3103 resched_curr(rq_of(cfs_rq));
3107 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3109 /* 'current' is not kept within the tree. */
3112 * Any task has to be enqueued before it get to execute on
3113 * a CPU. So account for the time it spent waiting on the
3116 update_stats_wait_end(cfs_rq, se);
3117 __dequeue_entity(cfs_rq, se);
3118 update_load_avg(se, 1);
3121 update_stats_curr_start(cfs_rq, se);
3123 #ifdef CONFIG_SCHEDSTATS
3125 * Track our maximum slice length, if the CPU's load is at
3126 * least twice that of our own weight (i.e. dont track it
3127 * when there are only lesser-weight tasks around):
3129 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3130 se->statistics.slice_max = max(se->statistics.slice_max,
3131 se->sum_exec_runtime - se->prev_sum_exec_runtime);
3134 se->prev_sum_exec_runtime = se->sum_exec_runtime;
3138 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3141 * Pick the next process, keeping these things in mind, in this order:
3142 * 1) keep things fair between processes/task groups
3143 * 2) pick the "next" process, since someone really wants that to run
3144 * 3) pick the "last" process, for cache locality
3145 * 4) do not run the "skip" process, if something else is available
3147 static struct sched_entity *
3148 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3150 struct sched_entity *left = __pick_first_entity(cfs_rq);
3151 struct sched_entity *se;
3154 * If curr is set we have to see if its left of the leftmost entity
3155 * still in the tree, provided there was anything in the tree at all.
3157 if (!left || (curr && entity_before(curr, left)))
3160 se = left; /* ideally we run the leftmost entity */
3163 * Avoid running the skip buddy, if running something else can
3164 * be done without getting too unfair.
3166 if (cfs_rq->skip == se) {
3167 struct sched_entity *second;
3170 second = __pick_first_entity(cfs_rq);
3172 second = __pick_next_entity(se);
3173 if (!second || (curr && entity_before(curr, second)))
3177 if (second && wakeup_preempt_entity(second, left) < 1)
3182 * Prefer last buddy, try to return the CPU to a preempted task.
3184 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3188 * Someone really wants this to run. If it's not unfair, run it.
3190 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3193 clear_buddies(cfs_rq, se);
3198 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3200 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3203 * If still on the runqueue then deactivate_task()
3204 * was not called and update_curr() has to be done:
3207 update_curr(cfs_rq);
3209 /* throttle cfs_rqs exceeding runtime */
3210 check_cfs_rq_runtime(cfs_rq);
3212 check_spread(cfs_rq, prev);
3214 update_stats_wait_start(cfs_rq, prev);
3215 /* Put 'current' back into the tree. */
3216 __enqueue_entity(cfs_rq, prev);
3217 /* in !on_rq case, update occurred at dequeue */
3218 update_load_avg(prev, 0);
3220 cfs_rq->curr = NULL;
3224 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3227 * Update run-time statistics of the 'current'.
3229 update_curr(cfs_rq);
3232 * Ensure that runnable average is periodically updated.
3234 update_load_avg(curr, 1);
3235 update_cfs_shares(cfs_rq);
3237 #ifdef CONFIG_SCHED_HRTICK
3239 * queued ticks are scheduled to match the slice, so don't bother
3240 * validating it and just reschedule.
3243 resched_curr(rq_of(cfs_rq));
3247 * don't let the period tick interfere with the hrtick preemption
3249 if (!sched_feat(DOUBLE_TICK) &&
3250 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3254 if (cfs_rq->nr_running > 1)
3255 check_preempt_tick(cfs_rq, curr);
3259 /**************************************************
3260 * CFS bandwidth control machinery
3263 #ifdef CONFIG_CFS_BANDWIDTH
3265 #ifdef HAVE_JUMP_LABEL
3266 static struct static_key __cfs_bandwidth_used;
3268 static inline bool cfs_bandwidth_used(void)
3270 return static_key_false(&__cfs_bandwidth_used);
3273 void cfs_bandwidth_usage_inc(void)
3275 static_key_slow_inc(&__cfs_bandwidth_used);
3278 void cfs_bandwidth_usage_dec(void)
3280 static_key_slow_dec(&__cfs_bandwidth_used);
3282 #else /* HAVE_JUMP_LABEL */
3283 static bool cfs_bandwidth_used(void)
3288 void cfs_bandwidth_usage_inc(void) {}
3289 void cfs_bandwidth_usage_dec(void) {}
3290 #endif /* HAVE_JUMP_LABEL */
3293 * default period for cfs group bandwidth.
3294 * default: 0.1s, units: nanoseconds
3296 static inline u64 default_cfs_period(void)
3298 return 100000000ULL;
3301 static inline u64 sched_cfs_bandwidth_slice(void)
3303 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3307 * Replenish runtime according to assigned quota and update expiration time.
3308 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3309 * additional synchronization around rq->lock.
3311 * requires cfs_b->lock
3313 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3317 if (cfs_b->quota == RUNTIME_INF)
3320 now = sched_clock_cpu(smp_processor_id());
3321 cfs_b->runtime = cfs_b->quota;
3322 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3325 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3327 return &tg->cfs_bandwidth;
3330 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3331 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3333 if (unlikely(cfs_rq->throttle_count))
3334 return cfs_rq->throttled_clock_task;
3336 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3339 /* returns 0 on failure to allocate runtime */
3340 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3342 struct task_group *tg = cfs_rq->tg;
3343 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3344 u64 amount = 0, min_amount, expires;
3346 /* note: this is a positive sum as runtime_remaining <= 0 */
3347 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3349 raw_spin_lock(&cfs_b->lock);
3350 if (cfs_b->quota == RUNTIME_INF)
3351 amount = min_amount;
3353 start_cfs_bandwidth(cfs_b);
3355 if (cfs_b->runtime > 0) {
3356 amount = min(cfs_b->runtime, min_amount);
3357 cfs_b->runtime -= amount;
3361 expires = cfs_b->runtime_expires;
3362 raw_spin_unlock(&cfs_b->lock);
3364 cfs_rq->runtime_remaining += amount;
3366 * we may have advanced our local expiration to account for allowed
3367 * spread between our sched_clock and the one on which runtime was
3370 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3371 cfs_rq->runtime_expires = expires;
3373 return cfs_rq->runtime_remaining > 0;
3377 * Note: This depends on the synchronization provided by sched_clock and the
3378 * fact that rq->clock snapshots this value.
3380 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3382 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3384 /* if the deadline is ahead of our clock, nothing to do */
3385 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3388 if (cfs_rq->runtime_remaining < 0)
3392 * If the local deadline has passed we have to consider the
3393 * possibility that our sched_clock is 'fast' and the global deadline
3394 * has not truly expired.
3396 * Fortunately we can check determine whether this the case by checking
3397 * whether the global deadline has advanced. It is valid to compare
3398 * cfs_b->runtime_expires without any locks since we only care about
3399 * exact equality, so a partial write will still work.
3402 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3403 /* extend local deadline, drift is bounded above by 2 ticks */
3404 cfs_rq->runtime_expires += TICK_NSEC;
3406 /* global deadline is ahead, expiration has passed */
3407 cfs_rq->runtime_remaining = 0;
3411 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3413 /* dock delta_exec before expiring quota (as it could span periods) */
3414 cfs_rq->runtime_remaining -= delta_exec;
3415 expire_cfs_rq_runtime(cfs_rq);
3417 if (likely(cfs_rq->runtime_remaining > 0))
3421 * if we're unable to extend our runtime we resched so that the active
3422 * hierarchy can be throttled
3424 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3425 resched_curr(rq_of(cfs_rq));
3428 static __always_inline
3429 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3431 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3434 __account_cfs_rq_runtime(cfs_rq, delta_exec);
3437 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3439 return cfs_bandwidth_used() && cfs_rq->throttled;
3442 /* check whether cfs_rq, or any parent, is throttled */
3443 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3445 return cfs_bandwidth_used() && cfs_rq->throttle_count;
3449 * Ensure that neither of the group entities corresponding to src_cpu or
3450 * dest_cpu are members of a throttled hierarchy when performing group
3451 * load-balance operations.
3453 static inline int throttled_lb_pair(struct task_group *tg,
3454 int src_cpu, int dest_cpu)
3456 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3458 src_cfs_rq = tg->cfs_rq[src_cpu];
3459 dest_cfs_rq = tg->cfs_rq[dest_cpu];
3461 return throttled_hierarchy(src_cfs_rq) ||
3462 throttled_hierarchy(dest_cfs_rq);
3465 /* updated child weight may affect parent so we have to do this bottom up */
3466 static int tg_unthrottle_up(struct task_group *tg, void *data)
3468 struct rq *rq = data;
3469 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3471 cfs_rq->throttle_count--;
3473 if (!cfs_rq->throttle_count) {
3474 /* adjust cfs_rq_clock_task() */
3475 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3476 cfs_rq->throttled_clock_task;
3483 static int tg_throttle_down(struct task_group *tg, void *data)
3485 struct rq *rq = data;
3486 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3488 /* group is entering throttled state, stop time */
3489 if (!cfs_rq->throttle_count)
3490 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3491 cfs_rq->throttle_count++;
3496 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3498 struct rq *rq = rq_of(cfs_rq);
3499 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3500 struct sched_entity *se;
3501 long task_delta, dequeue = 1;
3504 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3506 /* freeze hierarchy runnable averages while throttled */
3508 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3511 task_delta = cfs_rq->h_nr_running;
3512 for_each_sched_entity(se) {
3513 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3514 /* throttled entity or throttle-on-deactivate */
3519 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3520 qcfs_rq->h_nr_running -= task_delta;
3522 if (qcfs_rq->load.weight)
3527 sub_nr_running(rq, task_delta);
3529 cfs_rq->throttled = 1;
3530 cfs_rq->throttled_clock = rq_clock(rq);
3531 raw_spin_lock(&cfs_b->lock);
3532 empty = list_empty(&cfs_b->throttled_cfs_rq);
3535 * Add to the _head_ of the list, so that an already-started
3536 * distribute_cfs_runtime will not see us
3538 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3541 * If we're the first throttled task, make sure the bandwidth
3545 start_cfs_bandwidth(cfs_b);
3547 raw_spin_unlock(&cfs_b->lock);
3550 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3552 struct rq *rq = rq_of(cfs_rq);
3553 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3554 struct sched_entity *se;
3558 se = cfs_rq->tg->se[cpu_of(rq)];
3560 cfs_rq->throttled = 0;
3562 update_rq_clock(rq);
3564 raw_spin_lock(&cfs_b->lock);
3565 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3566 list_del_rcu(&cfs_rq->throttled_list);
3567 raw_spin_unlock(&cfs_b->lock);
3569 /* update hierarchical throttle state */
3570 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3572 if (!cfs_rq->load.weight)
3575 task_delta = cfs_rq->h_nr_running;
3576 for_each_sched_entity(se) {
3580 cfs_rq = cfs_rq_of(se);
3582 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3583 cfs_rq->h_nr_running += task_delta;
3585 if (cfs_rq_throttled(cfs_rq))
3590 add_nr_running(rq, task_delta);
3592 /* determine whether we need to wake up potentially idle cpu */
3593 if (rq->curr == rq->idle && rq->cfs.nr_running)
3597 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3598 u64 remaining, u64 expires)
3600 struct cfs_rq *cfs_rq;
3602 u64 starting_runtime = remaining;
3605 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3607 struct rq *rq = rq_of(cfs_rq);
3609 raw_spin_lock(&rq->lock);
3610 if (!cfs_rq_throttled(cfs_rq))
3613 runtime = -cfs_rq->runtime_remaining + 1;
3614 if (runtime > remaining)
3615 runtime = remaining;
3616 remaining -= runtime;
3618 cfs_rq->runtime_remaining += runtime;
3619 cfs_rq->runtime_expires = expires;
3621 /* we check whether we're throttled above */
3622 if (cfs_rq->runtime_remaining > 0)
3623 unthrottle_cfs_rq(cfs_rq);
3626 raw_spin_unlock(&rq->lock);
3633 return starting_runtime - remaining;
3637 * Responsible for refilling a task_group's bandwidth and unthrottling its
3638 * cfs_rqs as appropriate. If there has been no activity within the last
3639 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3640 * used to track this state.
3642 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3644 u64 runtime, runtime_expires;
3647 /* no need to continue the timer with no bandwidth constraint */
3648 if (cfs_b->quota == RUNTIME_INF)
3649 goto out_deactivate;
3651 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3652 cfs_b->nr_periods += overrun;
3655 * idle depends on !throttled (for the case of a large deficit), and if
3656 * we're going inactive then everything else can be deferred
3658 if (cfs_b->idle && !throttled)
3659 goto out_deactivate;
3661 __refill_cfs_bandwidth_runtime(cfs_b);
3664 /* mark as potentially idle for the upcoming period */
3669 /* account preceding periods in which throttling occurred */
3670 cfs_b->nr_throttled += overrun;
3672 runtime_expires = cfs_b->runtime_expires;
3675 * This check is repeated as we are holding onto the new bandwidth while
3676 * we unthrottle. This can potentially race with an unthrottled group
3677 * trying to acquire new bandwidth from the global pool. This can result
3678 * in us over-using our runtime if it is all used during this loop, but
3679 * only by limited amounts in that extreme case.
3681 while (throttled && cfs_b->runtime > 0) {
3682 runtime = cfs_b->runtime;
3683 raw_spin_unlock(&cfs_b->lock);
3684 /* we can't nest cfs_b->lock while distributing bandwidth */
3685 runtime = distribute_cfs_runtime(cfs_b, runtime,
3687 raw_spin_lock(&cfs_b->lock);
3689 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3691 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3695 * While we are ensured activity in the period following an
3696 * unthrottle, this also covers the case in which the new bandwidth is
3697 * insufficient to cover the existing bandwidth deficit. (Forcing the
3698 * timer to remain active while there are any throttled entities.)
3708 /* a cfs_rq won't donate quota below this amount */
3709 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3710 /* minimum remaining period time to redistribute slack quota */
3711 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3712 /* how long we wait to gather additional slack before distributing */
3713 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3716 * Are we near the end of the current quota period?
3718 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3719 * hrtimer base being cleared by hrtimer_start. In the case of
3720 * migrate_hrtimers, base is never cleared, so we are fine.
3722 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3724 struct hrtimer *refresh_timer = &cfs_b->period_timer;
3727 /* if the call-back is running a quota refresh is already occurring */
3728 if (hrtimer_callback_running(refresh_timer))
3731 /* is a quota refresh about to occur? */
3732 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3733 if (remaining < min_expire)
3739 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3741 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3743 /* if there's a quota refresh soon don't bother with slack */
3744 if (runtime_refresh_within(cfs_b, min_left))
3747 hrtimer_start(&cfs_b->slack_timer,
3748 ns_to_ktime(cfs_bandwidth_slack_period),
3752 /* we know any runtime found here is valid as update_curr() precedes return */
3753 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3755 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3756 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3758 if (slack_runtime <= 0)
3761 raw_spin_lock(&cfs_b->lock);
3762 if (cfs_b->quota != RUNTIME_INF &&
3763 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3764 cfs_b->runtime += slack_runtime;
3766 /* we are under rq->lock, defer unthrottling using a timer */
3767 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3768 !list_empty(&cfs_b->throttled_cfs_rq))
3769 start_cfs_slack_bandwidth(cfs_b);
3771 raw_spin_unlock(&cfs_b->lock);
3773 /* even if it's not valid for return we don't want to try again */
3774 cfs_rq->runtime_remaining -= slack_runtime;
3777 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3779 if (!cfs_bandwidth_used())
3782 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3785 __return_cfs_rq_runtime(cfs_rq);
3789 * This is done with a timer (instead of inline with bandwidth return) since
3790 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3792 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
3794 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
3797 /* confirm we're still not at a refresh boundary */
3798 raw_spin_lock(&cfs_b->lock);
3799 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
3800 raw_spin_unlock(&cfs_b->lock);
3804 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3805 runtime = cfs_b->runtime;
3807 expires = cfs_b->runtime_expires;
3808 raw_spin_unlock(&cfs_b->lock);
3813 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
3815 raw_spin_lock(&cfs_b->lock);
3816 if (expires == cfs_b->runtime_expires)
3817 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3818 raw_spin_unlock(&cfs_b->lock);
3822 * When a group wakes up we want to make sure that its quota is not already
3823 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3824 * runtime as update_curr() throttling can not not trigger until it's on-rq.
3826 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
3828 if (!cfs_bandwidth_used())
3831 /* an active group must be handled by the update_curr()->put() path */
3832 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
3835 /* ensure the group is not already throttled */
3836 if (cfs_rq_throttled(cfs_rq))
3839 /* update runtime allocation */
3840 account_cfs_rq_runtime(cfs_rq, 0);
3841 if (cfs_rq->runtime_remaining <= 0)
3842 throttle_cfs_rq(cfs_rq);
3845 /* conditionally throttle active cfs_rq's from put_prev_entity() */
3846 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3848 if (!cfs_bandwidth_used())
3851 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3855 * it's possible for a throttled entity to be forced into a running
3856 * state (e.g. set_curr_task), in this case we're finished.
3858 if (cfs_rq_throttled(cfs_rq))
3861 throttle_cfs_rq(cfs_rq);
3865 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
3867 struct cfs_bandwidth *cfs_b =
3868 container_of(timer, struct cfs_bandwidth, slack_timer);
3870 do_sched_cfs_slack_timer(cfs_b);
3872 return HRTIMER_NORESTART;
3875 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
3877 struct cfs_bandwidth *cfs_b =
3878 container_of(timer, struct cfs_bandwidth, period_timer);
3882 raw_spin_lock(&cfs_b->lock);
3884 overrun = hrtimer_forward_now(timer, cfs_b->period);
3888 idle = do_sched_cfs_period_timer(cfs_b, overrun);
3891 cfs_b->period_active = 0;
3892 raw_spin_unlock(&cfs_b->lock);
3894 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
3897 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3899 raw_spin_lock_init(&cfs_b->lock);
3901 cfs_b->quota = RUNTIME_INF;
3902 cfs_b->period = ns_to_ktime(default_cfs_period());
3904 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
3905 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
3906 cfs_b->period_timer.function = sched_cfs_period_timer;
3907 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
3908 cfs_b->slack_timer.function = sched_cfs_slack_timer;
3911 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3913 cfs_rq->runtime_enabled = 0;
3914 INIT_LIST_HEAD(&cfs_rq->throttled_list);
3917 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3919 lockdep_assert_held(&cfs_b->lock);
3921 if (!cfs_b->period_active) {
3922 cfs_b->period_active = 1;
3923 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
3924 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
3928 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3930 /* init_cfs_bandwidth() was not called */
3931 if (!cfs_b->throttled_cfs_rq.next)
3934 hrtimer_cancel(&cfs_b->period_timer);
3935 hrtimer_cancel(&cfs_b->slack_timer);
3938 static void __maybe_unused update_runtime_enabled(struct rq *rq)
3940 struct cfs_rq *cfs_rq;
3942 for_each_leaf_cfs_rq(rq, cfs_rq) {
3943 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
3945 raw_spin_lock(&cfs_b->lock);
3946 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
3947 raw_spin_unlock(&cfs_b->lock);
3951 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
3953 struct cfs_rq *cfs_rq;
3955 for_each_leaf_cfs_rq(rq, cfs_rq) {
3956 if (!cfs_rq->runtime_enabled)
3960 * clock_task is not advancing so we just need to make sure
3961 * there's some valid quota amount
3963 cfs_rq->runtime_remaining = 1;
3965 * Offline rq is schedulable till cpu is completely disabled
3966 * in take_cpu_down(), so we prevent new cfs throttling here.
3968 cfs_rq->runtime_enabled = 0;
3970 if (cfs_rq_throttled(cfs_rq))
3971 unthrottle_cfs_rq(cfs_rq);
3975 #else /* CONFIG_CFS_BANDWIDTH */
3976 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3978 return rq_clock_task(rq_of(cfs_rq));
3981 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
3982 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
3983 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
3984 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
3986 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3991 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3996 static inline int throttled_lb_pair(struct task_group *tg,
3997 int src_cpu, int dest_cpu)
4002 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4004 #ifdef CONFIG_FAIR_GROUP_SCHED
4005 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4008 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4012 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4013 static inline void update_runtime_enabled(struct rq *rq) {}
4014 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4016 #endif /* CONFIG_CFS_BANDWIDTH */
4018 /**************************************************
4019 * CFS operations on tasks:
4022 #ifdef CONFIG_SCHED_HRTICK
4023 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4025 struct sched_entity *se = &p->se;
4026 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4028 WARN_ON(task_rq(p) != rq);
4030 if (cfs_rq->nr_running > 1) {
4031 u64 slice = sched_slice(cfs_rq, se);
4032 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4033 s64 delta = slice - ran;
4040 hrtick_start(rq, delta);
4045 * called from enqueue/dequeue and updates the hrtick when the
4046 * current task is from our class and nr_running is low enough
4049 static void hrtick_update(struct rq *rq)
4051 struct task_struct *curr = rq->curr;
4053 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4056 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4057 hrtick_start_fair(rq, curr);
4059 #else /* !CONFIG_SCHED_HRTICK */
4061 hrtick_start_fair(struct rq *rq, struct task_struct *p)
4065 static inline void hrtick_update(struct rq *rq)
4071 * The enqueue_task method is called before nr_running is
4072 * increased. Here we update the fair scheduling stats and
4073 * then put the task into the rbtree:
4076 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4078 struct cfs_rq *cfs_rq;
4079 struct sched_entity *se = &p->se;
4081 for_each_sched_entity(se) {
4084 cfs_rq = cfs_rq_of(se);
4085 enqueue_entity(cfs_rq, se, flags);
4088 * end evaluation on encountering a throttled cfs_rq
4090 * note: in the case of encountering a throttled cfs_rq we will
4091 * post the final h_nr_running increment below.
4093 if (cfs_rq_throttled(cfs_rq))
4095 cfs_rq->h_nr_running++;
4097 flags = ENQUEUE_WAKEUP;
4100 for_each_sched_entity(se) {
4101 cfs_rq = cfs_rq_of(se);
4102 cfs_rq->h_nr_running++;
4104 if (cfs_rq_throttled(cfs_rq))
4107 update_load_avg(se, 1);
4108 update_cfs_shares(cfs_rq);
4112 add_nr_running(rq, 1);
4117 static void set_next_buddy(struct sched_entity *se);
4120 * The dequeue_task method is called before nr_running is
4121 * decreased. We remove the task from the rbtree and
4122 * update the fair scheduling stats:
4124 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4126 struct cfs_rq *cfs_rq;
4127 struct sched_entity *se = &p->se;
4128 int task_sleep = flags & DEQUEUE_SLEEP;
4130 for_each_sched_entity(se) {
4131 cfs_rq = cfs_rq_of(se);
4132 dequeue_entity(cfs_rq, se, flags);
4135 * end evaluation on encountering a throttled cfs_rq
4137 * note: in the case of encountering a throttled cfs_rq we will
4138 * post the final h_nr_running decrement below.
4140 if (cfs_rq_throttled(cfs_rq))
4142 cfs_rq->h_nr_running--;
4144 /* Don't dequeue parent if it has other entities besides us */
4145 if (cfs_rq->load.weight) {
4147 * Bias pick_next to pick a task from this cfs_rq, as
4148 * p is sleeping when it is within its sched_slice.
4150 if (task_sleep && parent_entity(se))
4151 set_next_buddy(parent_entity(se));
4153 /* avoid re-evaluating load for this entity */
4154 se = parent_entity(se);
4157 flags |= DEQUEUE_SLEEP;
4160 for_each_sched_entity(se) {
4161 cfs_rq = cfs_rq_of(se);
4162 cfs_rq->h_nr_running--;
4164 if (cfs_rq_throttled(cfs_rq))
4167 update_load_avg(se, 1);
4168 update_cfs_shares(cfs_rq);
4172 sub_nr_running(rq, 1);
4180 * per rq 'load' arrray crap; XXX kill this.
4184 * The exact cpuload at various idx values, calculated at every tick would be
4185 * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
4187 * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
4188 * on nth tick when cpu may be busy, then we have:
4189 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4190 * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
4192 * decay_load_missed() below does efficient calculation of
4193 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4194 * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
4196 * The calculation is approximated on a 128 point scale.
4197 * degrade_zero_ticks is the number of ticks after which load at any
4198 * particular idx is approximated to be zero.
4199 * degrade_factor is a precomputed table, a row for each load idx.
4200 * Each column corresponds to degradation factor for a power of two ticks,
4201 * based on 128 point scale.
4203 * row 2, col 3 (=12) says that the degradation at load idx 2 after
4204 * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
4206 * With this power of 2 load factors, we can degrade the load n times
4207 * by looking at 1 bits in n and doing as many mult/shift instead of
4208 * n mult/shifts needed by the exact degradation.
4210 #define DEGRADE_SHIFT 7
4211 static const unsigned char
4212 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4213 static const unsigned char
4214 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4215 {0, 0, 0, 0, 0, 0, 0, 0},
4216 {64, 32, 8, 0, 0, 0, 0, 0},
4217 {96, 72, 40, 12, 1, 0, 0},
4218 {112, 98, 75, 43, 15, 1, 0},
4219 {120, 112, 98, 76, 45, 16, 2} };
4222 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4223 * would be when CPU is idle and so we just decay the old load without
4224 * adding any new load.
4226 static unsigned long
4227 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4231 if (!missed_updates)
4234 if (missed_updates >= degrade_zero_ticks[idx])
4238 return load >> missed_updates;
4240 while (missed_updates) {
4241 if (missed_updates % 2)
4242 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4244 missed_updates >>= 1;
4251 * Update rq->cpu_load[] statistics. This function is usually called every
4252 * scheduler tick (TICK_NSEC). With tickless idle this will not be called
4253 * every tick. We fix it up based on jiffies.
4255 static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4256 unsigned long pending_updates)
4260 this_rq->nr_load_updates++;
4262 /* Update our load: */
4263 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4264 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4265 unsigned long old_load, new_load;
4267 /* scale is effectively 1 << i now, and >> i divides by scale */
4269 old_load = this_rq->cpu_load[i];
4270 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4271 new_load = this_load;
4273 * Round up the averaging division if load is increasing. This
4274 * prevents us from getting stuck on 9 if the load is 10, for
4277 if (new_load > old_load)
4278 new_load += scale - 1;
4280 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4283 sched_avg_update(this_rq);
4286 /* Used instead of source_load when we know the type == 0 */
4287 static unsigned long weighted_cpuload(const int cpu)
4289 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4292 #ifdef CONFIG_NO_HZ_COMMON
4294 * There is no sane way to deal with nohz on smp when using jiffies because the
4295 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4296 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4298 * Therefore we cannot use the delta approach from the regular tick since that
4299 * would seriously skew the load calculation. However we'll make do for those
4300 * updates happening while idle (nohz_idle_balance) or coming out of idle
4301 * (tick_nohz_idle_exit).
4303 * This means we might still be one tick off for nohz periods.
4307 * Called from nohz_idle_balance() to update the load ratings before doing the
4310 static void update_idle_cpu_load(struct rq *this_rq)
4312 unsigned long curr_jiffies = READ_ONCE(jiffies);
4313 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4314 unsigned long pending_updates;
4317 * bail if there's load or we're actually up-to-date.
4319 if (load || curr_jiffies == this_rq->last_load_update_tick)
4322 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4323 this_rq->last_load_update_tick = curr_jiffies;
4325 __update_cpu_load(this_rq, load, pending_updates);
4329 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
4331 void update_cpu_load_nohz(void)
4333 struct rq *this_rq = this_rq();
4334 unsigned long curr_jiffies = READ_ONCE(jiffies);
4335 unsigned long pending_updates;
4337 if (curr_jiffies == this_rq->last_load_update_tick)
4340 raw_spin_lock(&this_rq->lock);
4341 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4342 if (pending_updates) {
4343 this_rq->last_load_update_tick = curr_jiffies;
4345 * We were idle, this means load 0, the current load might be
4346 * !0 due to remote wakeups and the sort.
4348 __update_cpu_load(this_rq, 0, pending_updates);
4350 raw_spin_unlock(&this_rq->lock);
4352 #endif /* CONFIG_NO_HZ */
4355 * Called from scheduler_tick()
4357 void update_cpu_load_active(struct rq *this_rq)
4359 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4361 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
4363 this_rq->last_load_update_tick = jiffies;
4364 __update_cpu_load(this_rq, load, 1);
4368 * Return a low guess at the load of a migration-source cpu weighted
4369 * according to the scheduling class and "nice" value.
4371 * We want to under-estimate the load of migration sources, to
4372 * balance conservatively.
4374 static unsigned long source_load(int cpu, int type)
4376 struct rq *rq = cpu_rq(cpu);
4377 unsigned long total = weighted_cpuload(cpu);
4379 if (type == 0 || !sched_feat(LB_BIAS))
4382 return min(rq->cpu_load[type-1], total);
4386 * Return a high guess at the load of a migration-target cpu weighted
4387 * according to the scheduling class and "nice" value.
4389 static unsigned long target_load(int cpu, int type)
4391 struct rq *rq = cpu_rq(cpu);
4392 unsigned long total = weighted_cpuload(cpu);
4394 if (type == 0 || !sched_feat(LB_BIAS))
4397 return max(rq->cpu_load[type-1], total);
4400 static unsigned long capacity_of(int cpu)
4402 return cpu_rq(cpu)->cpu_capacity;
4405 static unsigned long capacity_orig_of(int cpu)
4407 return cpu_rq(cpu)->cpu_capacity_orig;
4410 static unsigned long cpu_avg_load_per_task(int cpu)
4412 struct rq *rq = cpu_rq(cpu);
4413 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4414 unsigned long load_avg = weighted_cpuload(cpu);
4417 return load_avg / nr_running;
4422 static void record_wakee(struct task_struct *p)
4425 * Rough decay (wiping) for cost saving, don't worry
4426 * about the boundary, really active task won't care
4429 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4430 current->wakee_flips >>= 1;
4431 current->wakee_flip_decay_ts = jiffies;
4434 if (current->last_wakee != p) {
4435 current->last_wakee = p;
4436 current->wakee_flips++;
4440 static void task_waking_fair(struct task_struct *p)
4442 struct sched_entity *se = &p->se;
4443 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4446 #ifndef CONFIG_64BIT
4447 u64 min_vruntime_copy;
4450 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4452 min_vruntime = cfs_rq->min_vruntime;
4453 } while (min_vruntime != min_vruntime_copy);
4455 min_vruntime = cfs_rq->min_vruntime;
4458 se->vruntime -= min_vruntime;
4462 #ifdef CONFIG_FAIR_GROUP_SCHED
4464 * effective_load() calculates the load change as seen from the root_task_group
4466 * Adding load to a group doesn't make a group heavier, but can cause movement
4467 * of group shares between cpus. Assuming the shares were perfectly aligned one
4468 * can calculate the shift in shares.
4470 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4471 * on this @cpu and results in a total addition (subtraction) of @wg to the
4472 * total group weight.
4474 * Given a runqueue weight distribution (rw_i) we can compute a shares
4475 * distribution (s_i) using:
4477 * s_i = rw_i / \Sum rw_j (1)
4479 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4480 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4481 * shares distribution (s_i):
4483 * rw_i = { 2, 4, 1, 0 }
4484 * s_i = { 2/7, 4/7, 1/7, 0 }
4486 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4487 * task used to run on and the CPU the waker is running on), we need to
4488 * compute the effect of waking a task on either CPU and, in case of a sync
4489 * wakeup, compute the effect of the current task going to sleep.
4491 * So for a change of @wl to the local @cpu with an overall group weight change
4492 * of @wl we can compute the new shares distribution (s'_i) using:
4494 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4496 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4497 * differences in waking a task to CPU 0. The additional task changes the
4498 * weight and shares distributions like:
4500 * rw'_i = { 3, 4, 1, 0 }
4501 * s'_i = { 3/8, 4/8, 1/8, 0 }
4503 * We can then compute the difference in effective weight by using:
4505 * dw_i = S * (s'_i - s_i) (3)
4507 * Where 'S' is the group weight as seen by its parent.
4509 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4510 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4511 * 4/7) times the weight of the group.
4513 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4515 struct sched_entity *se = tg->se[cpu];
4517 if (!tg->parent) /* the trivial, non-cgroup case */
4520 for_each_sched_entity(se) {
4526 * W = @wg + \Sum rw_j
4528 W = wg + calc_tg_weight(tg, se->my_q);
4533 w = cfs_rq_load_avg(se->my_q) + wl;
4536 * wl = S * s'_i; see (2)
4539 wl = (w * (long)tg->shares) / W;
4544 * Per the above, wl is the new se->load.weight value; since
4545 * those are clipped to [MIN_SHARES, ...) do so now. See
4546 * calc_cfs_shares().
4548 if (wl < MIN_SHARES)
4552 * wl = dw_i = S * (s'_i - s_i); see (3)
4554 wl -= se->avg.load_avg;
4557 * Recursively apply this logic to all parent groups to compute
4558 * the final effective load change on the root group. Since
4559 * only the @tg group gets extra weight, all parent groups can
4560 * only redistribute existing shares. @wl is the shift in shares
4561 * resulting from this level per the above.
4570 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4578 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
4579 * A waker of many should wake a different task than the one last awakened
4580 * at a frequency roughly N times higher than one of its wakees. In order
4581 * to determine whether we should let the load spread vs consolodating to
4582 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
4583 * partner, and a factor of lls_size higher frequency in the other. With
4584 * both conditions met, we can be relatively sure that the relationship is
4585 * non-monogamous, with partner count exceeding socket size. Waker/wakee
4586 * being client/server, worker/dispatcher, interrupt source or whatever is
4587 * irrelevant, spread criteria is apparent partner count exceeds socket size.
4589 static int wake_wide(struct task_struct *p)
4591 unsigned int master = current->wakee_flips;
4592 unsigned int slave = p->wakee_flips;
4593 int factor = this_cpu_read(sd_llc_size);
4596 swap(master, slave);
4597 if (slave < factor || master < slave * factor)
4602 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4604 s64 this_load, load;
4605 s64 this_eff_load, prev_eff_load;
4606 int idx, this_cpu, prev_cpu;
4607 struct task_group *tg;
4608 unsigned long weight;
4612 this_cpu = smp_processor_id();
4613 prev_cpu = task_cpu(p);
4614 load = source_load(prev_cpu, idx);
4615 this_load = target_load(this_cpu, idx);
4618 * If sync wakeup then subtract the (maximum possible)
4619 * effect of the currently running task from the load
4620 * of the current CPU:
4623 tg = task_group(current);
4624 weight = current->se.avg.load_avg;
4626 this_load += effective_load(tg, this_cpu, -weight, -weight);
4627 load += effective_load(tg, prev_cpu, 0, -weight);
4631 weight = p->se.avg.load_avg;
4634 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4635 * due to the sync cause above having dropped this_load to 0, we'll
4636 * always have an imbalance, but there's really nothing you can do
4637 * about that, so that's good too.
4639 * Otherwise check if either cpus are near enough in load to allow this
4640 * task to be woken on this_cpu.
4642 this_eff_load = 100;
4643 this_eff_load *= capacity_of(prev_cpu);
4645 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
4646 prev_eff_load *= capacity_of(this_cpu);
4648 if (this_load > 0) {
4649 this_eff_load *= this_load +
4650 effective_load(tg, this_cpu, weight, weight);
4652 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4655 balanced = this_eff_load <= prev_eff_load;
4657 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4662 schedstat_inc(sd, ttwu_move_affine);
4663 schedstat_inc(p, se.statistics.nr_wakeups_affine);
4669 * find_idlest_group finds and returns the least busy CPU group within the
4672 static struct sched_group *
4673 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4674 int this_cpu, int sd_flag)
4676 struct sched_group *idlest = NULL, *group = sd->groups;
4677 unsigned long min_load = ULONG_MAX, this_load = 0;
4678 int load_idx = sd->forkexec_idx;
4679 int imbalance = 100 + (sd->imbalance_pct-100)/2;
4681 if (sd_flag & SD_BALANCE_WAKE)
4682 load_idx = sd->wake_idx;
4685 unsigned long load, avg_load;
4689 /* Skip over this group if it has no CPUs allowed */
4690 if (!cpumask_intersects(sched_group_cpus(group),
4691 tsk_cpus_allowed(p)))
4694 local_group = cpumask_test_cpu(this_cpu,
4695 sched_group_cpus(group));
4697 /* Tally up the load of all CPUs in the group */
4700 for_each_cpu(i, sched_group_cpus(group)) {
4701 /* Bias balancing toward cpus of our domain */
4703 load = source_load(i, load_idx);
4705 load = target_load(i, load_idx);
4710 /* Adjust by relative CPU capacity of the group */
4711 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
4714 this_load = avg_load;
4715 } else if (avg_load < min_load) {
4716 min_load = avg_load;
4719 } while (group = group->next, group != sd->groups);
4721 if (!idlest || 100*this_load < imbalance*min_load)
4727 * find_idlest_cpu - find the idlest cpu among the cpus in group.
4730 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
4732 unsigned long load, min_load = ULONG_MAX;
4733 unsigned int min_exit_latency = UINT_MAX;
4734 u64 latest_idle_timestamp = 0;
4735 int least_loaded_cpu = this_cpu;
4736 int shallowest_idle_cpu = -1;
4739 /* Traverse only the allowed CPUs */
4740 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4742 struct rq *rq = cpu_rq(i);
4743 struct cpuidle_state *idle = idle_get_state(rq);
4744 if (idle && idle->exit_latency < min_exit_latency) {
4746 * We give priority to a CPU whose idle state
4747 * has the smallest exit latency irrespective
4748 * of any idle timestamp.
4750 min_exit_latency = idle->exit_latency;
4751 latest_idle_timestamp = rq->idle_stamp;
4752 shallowest_idle_cpu = i;
4753 } else if ((!idle || idle->exit_latency == min_exit_latency) &&
4754 rq->idle_stamp > latest_idle_timestamp) {
4756 * If equal or no active idle state, then
4757 * the most recently idled CPU might have
4760 latest_idle_timestamp = rq->idle_stamp;
4761 shallowest_idle_cpu = i;
4763 } else if (shallowest_idle_cpu == -1) {
4764 load = weighted_cpuload(i);
4765 if (load < min_load || (load == min_load && i == this_cpu)) {
4767 least_loaded_cpu = i;
4772 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
4776 * Try and locate an idle CPU in the sched_domain.
4778 static int select_idle_sibling(struct task_struct *p, int target)
4780 struct sched_domain *sd;
4781 struct sched_group *sg;
4782 int i = task_cpu(p);
4784 if (idle_cpu(target))
4788 * If the prevous cpu is cache affine and idle, don't be stupid.
4790 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
4794 * Otherwise, iterate the domains and find an elegible idle cpu.
4796 sd = rcu_dereference(per_cpu(sd_llc, target));
4797 for_each_lower_domain(sd) {
4800 if (!cpumask_intersects(sched_group_cpus(sg),
4801 tsk_cpus_allowed(p)))
4804 for_each_cpu(i, sched_group_cpus(sg)) {
4805 if (i == target || !idle_cpu(i))
4809 target = cpumask_first_and(sched_group_cpus(sg),
4810 tsk_cpus_allowed(p));
4814 } while (sg != sd->groups);
4820 * get_cpu_usage returns the amount of capacity of a CPU that is used by CFS
4821 * tasks. The unit of the return value must be the one of capacity so we can
4822 * compare the usage with the capacity of the CPU that is available for CFS
4823 * task (ie cpu_capacity).
4824 * cfs.avg.util_avg is the sum of running time of runnable tasks on a
4825 * CPU. It represents the amount of utilization of a CPU in the range
4826 * [0..SCHED_LOAD_SCALE]. The usage of a CPU can't be higher than the full
4827 * capacity of the CPU because it's about the running time on this CPU.
4828 * Nevertheless, cfs.avg.util_avg can be higher than SCHED_LOAD_SCALE
4829 * because of unfortunate rounding in util_avg or just
4830 * after migrating tasks until the average stabilizes with the new running
4831 * time. So we need to check that the usage stays into the range
4832 * [0..cpu_capacity_orig] and cap if necessary.
4833 * Without capping the usage, a group could be seen as overloaded (CPU0 usage
4834 * at 121% + CPU1 usage at 80%) whereas CPU1 has 20% of available capacity
4836 static int get_cpu_usage(int cpu)
4838 unsigned long usage = cpu_rq(cpu)->cfs.avg.util_avg;
4839 unsigned long capacity = capacity_orig_of(cpu);
4841 if (usage >= SCHED_LOAD_SCALE)
4844 return (usage * capacity) >> SCHED_LOAD_SHIFT;
4848 * select_task_rq_fair: Select target runqueue for the waking task in domains
4849 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
4850 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
4852 * Balances load by selecting the idlest cpu in the idlest group, or under
4853 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
4855 * Returns the target cpu number.
4857 * preempt must be disabled.
4860 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
4862 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
4863 int cpu = smp_processor_id();
4864 int new_cpu = prev_cpu;
4865 int want_affine = 0;
4866 int sync = wake_flags & WF_SYNC;
4868 if (sd_flag & SD_BALANCE_WAKE)
4869 want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
4872 for_each_domain(cpu, tmp) {
4873 if (!(tmp->flags & SD_LOAD_BALANCE))
4877 * If both cpu and prev_cpu are part of this domain,
4878 * cpu is a valid SD_WAKE_AFFINE target.
4880 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
4881 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
4886 if (tmp->flags & sd_flag)
4888 else if (!want_affine)
4893 sd = NULL; /* Prefer wake_affine over balance flags */
4894 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
4899 if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
4900 new_cpu = select_idle_sibling(p, new_cpu);
4903 struct sched_group *group;
4906 if (!(sd->flags & sd_flag)) {
4911 group = find_idlest_group(sd, p, cpu, sd_flag);
4917 new_cpu = find_idlest_cpu(group, p, cpu);
4918 if (new_cpu == -1 || new_cpu == cpu) {
4919 /* Now try balancing at a lower domain level of cpu */
4924 /* Now try balancing at a lower domain level of new_cpu */
4926 weight = sd->span_weight;
4928 for_each_domain(cpu, tmp) {
4929 if (weight <= tmp->span_weight)
4931 if (tmp->flags & sd_flag)
4934 /* while loop will break here if sd == NULL */
4942 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
4943 * cfs_rq_of(p) references at time of call are still valid and identify the
4944 * previous cpu. However, the caller only guarantees p->pi_lock is held; no
4945 * other assumptions, including the state of rq->lock, should be made.
4947 static void migrate_task_rq_fair(struct task_struct *p, int next_cpu)
4950 * We are supposed to update the task to "current" time, then its up to date
4951 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
4952 * what current time is, so simply throw away the out-of-date time. This
4953 * will result in the wakee task is less decayed, but giving the wakee more
4954 * load sounds not bad.
4956 remove_entity_load_avg(&p->se);
4958 /* Tell new CPU we are migrated */
4959 p->se.avg.last_update_time = 0;
4961 /* We have migrated, no longer consider this task hot */
4962 p->se.exec_start = 0;
4965 static void task_dead_fair(struct task_struct *p)
4967 remove_entity_load_avg(&p->se);
4969 #endif /* CONFIG_SMP */
4971 static unsigned long
4972 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
4974 unsigned long gran = sysctl_sched_wakeup_granularity;
4977 * Since its curr running now, convert the gran from real-time
4978 * to virtual-time in his units.
4980 * By using 'se' instead of 'curr' we penalize light tasks, so
4981 * they get preempted easier. That is, if 'se' < 'curr' then
4982 * the resulting gran will be larger, therefore penalizing the
4983 * lighter, if otoh 'se' > 'curr' then the resulting gran will
4984 * be smaller, again penalizing the lighter task.
4986 * This is especially important for buddies when the leftmost
4987 * task is higher priority than the buddy.
4989 return calc_delta_fair(gran, se);
4993 * Should 'se' preempt 'curr'.
5007 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
5009 s64 gran, vdiff = curr->vruntime - se->vruntime;
5014 gran = wakeup_gran(curr, se);
5021 static void set_last_buddy(struct sched_entity *se)
5023 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5026 for_each_sched_entity(se)
5027 cfs_rq_of(se)->last = se;
5030 static void set_next_buddy(struct sched_entity *se)
5032 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5035 for_each_sched_entity(se)
5036 cfs_rq_of(se)->next = se;
5039 static void set_skip_buddy(struct sched_entity *se)
5041 for_each_sched_entity(se)
5042 cfs_rq_of(se)->skip = se;
5046 * Preempt the current task with a newly woken task if needed:
5048 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5050 struct task_struct *curr = rq->curr;
5051 struct sched_entity *se = &curr->se, *pse = &p->se;
5052 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5053 int scale = cfs_rq->nr_running >= sched_nr_latency;
5054 int next_buddy_marked = 0;
5056 if (unlikely(se == pse))
5060 * This is possible from callers such as attach_tasks(), in which we
5061 * unconditionally check_prempt_curr() after an enqueue (which may have
5062 * lead to a throttle). This both saves work and prevents false
5063 * next-buddy nomination below.
5065 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
5068 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
5069 set_next_buddy(pse);
5070 next_buddy_marked = 1;
5074 * We can come here with TIF_NEED_RESCHED already set from new task
5077 * Note: this also catches the edge-case of curr being in a throttled
5078 * group (e.g. via set_curr_task), since update_curr() (in the
5079 * enqueue of curr) will have resulted in resched being set. This
5080 * prevents us from potentially nominating it as a false LAST_BUDDY
5083 if (test_tsk_need_resched(curr))
5086 /* Idle tasks are by definition preempted by non-idle tasks. */
5087 if (unlikely(curr->policy == SCHED_IDLE) &&
5088 likely(p->policy != SCHED_IDLE))
5092 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5093 * is driven by the tick):
5095 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5098 find_matching_se(&se, &pse);
5099 update_curr(cfs_rq_of(se));
5101 if (wakeup_preempt_entity(se, pse) == 1) {
5103 * Bias pick_next to pick the sched entity that is
5104 * triggering this preemption.
5106 if (!next_buddy_marked)
5107 set_next_buddy(pse);
5116 * Only set the backward buddy when the current task is still
5117 * on the rq. This can happen when a wakeup gets interleaved
5118 * with schedule on the ->pre_schedule() or idle_balance()
5119 * point, either of which can * drop the rq lock.
5121 * Also, during early boot the idle thread is in the fair class,
5122 * for obvious reasons its a bad idea to schedule back to it.
5124 if (unlikely(!se->on_rq || curr == rq->idle))
5127 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
5131 static struct task_struct *
5132 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5134 struct cfs_rq *cfs_rq = &rq->cfs;
5135 struct sched_entity *se;
5136 struct task_struct *p;
5140 #ifdef CONFIG_FAIR_GROUP_SCHED
5141 if (!cfs_rq->nr_running)
5144 if (prev->sched_class != &fair_sched_class)
5148 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5149 * likely that a next task is from the same cgroup as the current.
5151 * Therefore attempt to avoid putting and setting the entire cgroup
5152 * hierarchy, only change the part that actually changes.
5156 struct sched_entity *curr = cfs_rq->curr;
5159 * Since we got here without doing put_prev_entity() we also
5160 * have to consider cfs_rq->curr. If it is still a runnable
5161 * entity, update_curr() will update its vruntime, otherwise
5162 * forget we've ever seen it.
5166 update_curr(cfs_rq);
5171 * This call to check_cfs_rq_runtime() will do the
5172 * throttle and dequeue its entity in the parent(s).
5173 * Therefore the 'simple' nr_running test will indeed
5176 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
5180 se = pick_next_entity(cfs_rq, curr);
5181 cfs_rq = group_cfs_rq(se);
5187 * Since we haven't yet done put_prev_entity and if the selected task
5188 * is a different task than we started out with, try and touch the
5189 * least amount of cfs_rqs.
5192 struct sched_entity *pse = &prev->se;
5194 while (!(cfs_rq = is_same_group(se, pse))) {
5195 int se_depth = se->depth;
5196 int pse_depth = pse->depth;
5198 if (se_depth <= pse_depth) {
5199 put_prev_entity(cfs_rq_of(pse), pse);
5200 pse = parent_entity(pse);
5202 if (se_depth >= pse_depth) {
5203 set_next_entity(cfs_rq_of(se), se);
5204 se = parent_entity(se);
5208 put_prev_entity(cfs_rq, pse);
5209 set_next_entity(cfs_rq, se);
5212 if (hrtick_enabled(rq))
5213 hrtick_start_fair(rq, p);
5220 if (!cfs_rq->nr_running)
5223 put_prev_task(rq, prev);
5226 se = pick_next_entity(cfs_rq, NULL);
5227 set_next_entity(cfs_rq, se);
5228 cfs_rq = group_cfs_rq(se);
5233 if (hrtick_enabled(rq))
5234 hrtick_start_fair(rq, p);
5240 * This is OK, because current is on_cpu, which avoids it being picked
5241 * for load-balance and preemption/IRQs are still disabled avoiding
5242 * further scheduler activity on it and we're being very careful to
5243 * re-start the picking loop.
5245 lockdep_unpin_lock(&rq->lock);
5246 new_tasks = idle_balance(rq);
5247 lockdep_pin_lock(&rq->lock);
5249 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5250 * possible for any higher priority task to appear. In that case we
5251 * must re-start the pick_next_entity() loop.
5263 * Account for a descheduled task:
5265 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5267 struct sched_entity *se = &prev->se;
5268 struct cfs_rq *cfs_rq;
5270 for_each_sched_entity(se) {
5271 cfs_rq = cfs_rq_of(se);
5272 put_prev_entity(cfs_rq, se);
5277 * sched_yield() is very simple
5279 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5281 static void yield_task_fair(struct rq *rq)
5283 struct task_struct *curr = rq->curr;
5284 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5285 struct sched_entity *se = &curr->se;
5288 * Are we the only task in the tree?
5290 if (unlikely(rq->nr_running == 1))
5293 clear_buddies(cfs_rq, se);
5295 if (curr->policy != SCHED_BATCH) {
5296 update_rq_clock(rq);
5298 * Update run-time statistics of the 'current'.
5300 update_curr(cfs_rq);
5302 * Tell update_rq_clock() that we've just updated,
5303 * so we don't do microscopic update in schedule()
5304 * and double the fastpath cost.
5306 rq_clock_skip_update(rq, true);
5312 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
5314 struct sched_entity *se = &p->se;
5316 /* throttled hierarchies are not runnable */
5317 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5320 /* Tell the scheduler that we'd really like pse to run next. */
5323 yield_task_fair(rq);
5329 /**************************************************
5330 * Fair scheduling class load-balancing methods.
5334 * The purpose of load-balancing is to achieve the same basic fairness the
5335 * per-cpu scheduler provides, namely provide a proportional amount of compute
5336 * time to each task. This is expressed in the following equation:
5338 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5340 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5341 * W_i,0 is defined as:
5343 * W_i,0 = \Sum_j w_i,j (2)
5345 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5346 * is derived from the nice value as per prio_to_weight[].
5348 * The weight average is an exponential decay average of the instantaneous
5351 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5353 * C_i is the compute capacity of cpu i, typically it is the
5354 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5355 * can also include other factors [XXX].
5357 * To achieve this balance we define a measure of imbalance which follows
5358 * directly from (1):
5360 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5362 * We them move tasks around to minimize the imbalance. In the continuous
5363 * function space it is obvious this converges, in the discrete case we get
5364 * a few fun cases generally called infeasible weight scenarios.
5367 * - infeasible weights;
5368 * - local vs global optima in the discrete case. ]
5373 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5374 * for all i,j solution, we create a tree of cpus that follows the hardware
5375 * topology where each level pairs two lower groups (or better). This results
5376 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5377 * tree to only the first of the previous level and we decrease the frequency
5378 * of load-balance at each level inv. proportional to the number of cpus in
5384 * \Sum { --- * --- * 2^i } = O(n) (5)
5386 * `- size of each group
5387 * | | `- number of cpus doing load-balance
5389 * `- sum over all levels
5391 * Coupled with a limit on how many tasks we can migrate every balance pass,
5392 * this makes (5) the runtime complexity of the balancer.
5394 * An important property here is that each CPU is still (indirectly) connected
5395 * to every other cpu in at most O(log n) steps:
5397 * The adjacency matrix of the resulting graph is given by:
5400 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5403 * And you'll find that:
5405 * A^(log_2 n)_i,j != 0 for all i,j (7)
5407 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5408 * The task movement gives a factor of O(m), giving a convergence complexity
5411 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5416 * In order to avoid CPUs going idle while there's still work to do, new idle
5417 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5418 * tree itself instead of relying on other CPUs to bring it work.
5420 * This adds some complexity to both (5) and (8) but it reduces the total idle
5428 * Cgroups make a horror show out of (2), instead of a simple sum we get:
5431 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
5436 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
5438 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5440 * The big problem is S_k, its a global sum needed to compute a local (W_i)
5443 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5444 * rewrite all of this once again.]
5447 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
5449 enum fbq_type { regular, remote, all };
5451 #define LBF_ALL_PINNED 0x01
5452 #define LBF_NEED_BREAK 0x02
5453 #define LBF_DST_PINNED 0x04
5454 #define LBF_SOME_PINNED 0x08
5457 struct sched_domain *sd;
5465 struct cpumask *dst_grpmask;
5467 enum cpu_idle_type idle;
5469 /* The set of CPUs under consideration for load-balancing */
5470 struct cpumask *cpus;
5475 unsigned int loop_break;
5476 unsigned int loop_max;
5478 enum fbq_type fbq_type;
5479 struct list_head tasks;
5483 * Is this task likely cache-hot:
5485 static int task_hot(struct task_struct *p, struct lb_env *env)
5489 lockdep_assert_held(&env->src_rq->lock);
5491 if (p->sched_class != &fair_sched_class)
5494 if (unlikely(p->policy == SCHED_IDLE))
5498 * Buddy candidates are cache hot:
5500 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5501 (&p->se == cfs_rq_of(&p->se)->next ||
5502 &p->se == cfs_rq_of(&p->se)->last))
5505 if (sysctl_sched_migration_cost == -1)
5507 if (sysctl_sched_migration_cost == 0)
5510 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5512 return delta < (s64)sysctl_sched_migration_cost;
5515 #ifdef CONFIG_NUMA_BALANCING
5517 * Returns 1, if task migration degrades locality
5518 * Returns 0, if task migration improves locality i.e migration preferred.
5519 * Returns -1, if task migration is not affected by locality.
5521 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5523 struct numa_group *numa_group = rcu_dereference(p->numa_group);
5524 unsigned long src_faults, dst_faults;
5525 int src_nid, dst_nid;
5527 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5530 if (!sched_feat(NUMA))
5533 src_nid = cpu_to_node(env->src_cpu);
5534 dst_nid = cpu_to_node(env->dst_cpu);
5536 if (src_nid == dst_nid)
5539 /* Migrating away from the preferred node is always bad. */
5540 if (src_nid == p->numa_preferred_nid) {
5541 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
5547 /* Encourage migration to the preferred node. */
5548 if (dst_nid == p->numa_preferred_nid)
5552 src_faults = group_faults(p, src_nid);
5553 dst_faults = group_faults(p, dst_nid);
5555 src_faults = task_faults(p, src_nid);
5556 dst_faults = task_faults(p, dst_nid);
5559 return dst_faults < src_faults;
5563 static inline int migrate_degrades_locality(struct task_struct *p,
5571 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
5574 int can_migrate_task(struct task_struct *p, struct lb_env *env)
5578 lockdep_assert_held(&env->src_rq->lock);
5581 * We do not migrate tasks that are:
5582 * 1) throttled_lb_pair, or
5583 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5584 * 3) running (obviously), or
5585 * 4) are cache-hot on their current CPU.
5587 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
5590 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5593 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5595 env->flags |= LBF_SOME_PINNED;
5598 * Remember if this task can be migrated to any other cpu in
5599 * our sched_group. We may want to revisit it if we couldn't
5600 * meet load balance goals by pulling other tasks on src_cpu.
5602 * Also avoid computing new_dst_cpu if we have already computed
5603 * one in current iteration.
5605 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5608 /* Prevent to re-select dst_cpu via env's cpus */
5609 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
5610 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
5611 env->flags |= LBF_DST_PINNED;
5612 env->new_dst_cpu = cpu;
5620 /* Record that we found atleast one task that could run on dst_cpu */
5621 env->flags &= ~LBF_ALL_PINNED;
5623 if (task_running(env->src_rq, p)) {
5624 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5629 * Aggressive migration if:
5630 * 1) destination numa is preferred
5631 * 2) task is cache cold, or
5632 * 3) too many balance attempts have failed.
5634 tsk_cache_hot = migrate_degrades_locality(p, env);
5635 if (tsk_cache_hot == -1)
5636 tsk_cache_hot = task_hot(p, env);
5638 if (tsk_cache_hot <= 0 ||
5639 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5640 if (tsk_cache_hot == 1) {
5641 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
5642 schedstat_inc(p, se.statistics.nr_forced_migrations);
5647 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
5652 * detach_task() -- detach the task for the migration specified in env
5654 static void detach_task(struct task_struct *p, struct lb_env *env)
5656 lockdep_assert_held(&env->src_rq->lock);
5658 deactivate_task(env->src_rq, p, 0);
5659 p->on_rq = TASK_ON_RQ_MIGRATING;
5660 set_task_cpu(p, env->dst_cpu);
5664 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
5665 * part of active balancing operations within "domain".
5667 * Returns a task if successful and NULL otherwise.
5669 static struct task_struct *detach_one_task(struct lb_env *env)
5671 struct task_struct *p, *n;
5673 lockdep_assert_held(&env->src_rq->lock);
5675 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
5676 if (!can_migrate_task(p, env))
5679 detach_task(p, env);
5682 * Right now, this is only the second place where
5683 * lb_gained[env->idle] is updated (other is detach_tasks)
5684 * so we can safely collect stats here rather than
5685 * inside detach_tasks().
5687 schedstat_inc(env->sd, lb_gained[env->idle]);
5693 static const unsigned int sched_nr_migrate_break = 32;
5696 * detach_tasks() -- tries to detach up to imbalance weighted load from
5697 * busiest_rq, as part of a balancing operation within domain "sd".
5699 * Returns number of detached tasks if successful and 0 otherwise.
5701 static int detach_tasks(struct lb_env *env)
5703 struct list_head *tasks = &env->src_rq->cfs_tasks;
5704 struct task_struct *p;
5708 lockdep_assert_held(&env->src_rq->lock);
5710 if (env->imbalance <= 0)
5713 while (!list_empty(tasks)) {
5715 * We don't want to steal all, otherwise we may be treated likewise,
5716 * which could at worst lead to a livelock crash.
5718 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
5721 p = list_first_entry(tasks, struct task_struct, se.group_node);
5724 /* We've more or less seen every task there is, call it quits */
5725 if (env->loop > env->loop_max)
5728 /* take a breather every nr_migrate tasks */
5729 if (env->loop > env->loop_break) {
5730 env->loop_break += sched_nr_migrate_break;
5731 env->flags |= LBF_NEED_BREAK;
5735 if (!can_migrate_task(p, env))
5738 load = task_h_load(p);
5740 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5743 if ((load / 2) > env->imbalance)
5746 detach_task(p, env);
5747 list_add(&p->se.group_node, &env->tasks);
5750 env->imbalance -= load;
5752 #ifdef CONFIG_PREEMPT
5754 * NEWIDLE balancing is a source of latency, so preemptible
5755 * kernels will stop after the first task is detached to minimize
5756 * the critical section.
5758 if (env->idle == CPU_NEWLY_IDLE)
5763 * We only want to steal up to the prescribed amount of
5766 if (env->imbalance <= 0)
5771 list_move_tail(&p->se.group_node, tasks);
5775 * Right now, this is one of only two places we collect this stat
5776 * so we can safely collect detach_one_task() stats here rather
5777 * than inside detach_one_task().
5779 schedstat_add(env->sd, lb_gained[env->idle], detached);
5785 * attach_task() -- attach the task detached by detach_task() to its new rq.
5787 static void attach_task(struct rq *rq, struct task_struct *p)
5789 lockdep_assert_held(&rq->lock);
5791 BUG_ON(task_rq(p) != rq);
5792 p->on_rq = TASK_ON_RQ_QUEUED;
5793 activate_task(rq, p, 0);
5794 check_preempt_curr(rq, p, 0);
5798 * attach_one_task() -- attaches the task returned from detach_one_task() to
5801 static void attach_one_task(struct rq *rq, struct task_struct *p)
5803 raw_spin_lock(&rq->lock);
5805 raw_spin_unlock(&rq->lock);
5809 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
5812 static void attach_tasks(struct lb_env *env)
5814 struct list_head *tasks = &env->tasks;
5815 struct task_struct *p;
5817 raw_spin_lock(&env->dst_rq->lock);
5819 while (!list_empty(tasks)) {
5820 p = list_first_entry(tasks, struct task_struct, se.group_node);
5821 list_del_init(&p->se.group_node);
5823 attach_task(env->dst_rq, p);
5826 raw_spin_unlock(&env->dst_rq->lock);
5829 #ifdef CONFIG_FAIR_GROUP_SCHED
5830 static void update_blocked_averages(int cpu)
5832 struct rq *rq = cpu_rq(cpu);
5833 struct cfs_rq *cfs_rq;
5834 unsigned long flags;
5836 raw_spin_lock_irqsave(&rq->lock, flags);
5837 update_rq_clock(rq);
5840 * Iterates the task_group tree in a bottom up fashion, see
5841 * list_add_leaf_cfs_rq() for details.
5843 for_each_leaf_cfs_rq(rq, cfs_rq) {
5844 /* throttled entities do not contribute to load */
5845 if (throttled_hierarchy(cfs_rq))
5848 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
5849 update_tg_load_avg(cfs_rq, 0);
5851 raw_spin_unlock_irqrestore(&rq->lock, flags);
5855 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5856 * This needs to be done in a top-down fashion because the load of a child
5857 * group is a fraction of its parents load.
5859 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
5861 struct rq *rq = rq_of(cfs_rq);
5862 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
5863 unsigned long now = jiffies;
5866 if (cfs_rq->last_h_load_update == now)
5869 cfs_rq->h_load_next = NULL;
5870 for_each_sched_entity(se) {
5871 cfs_rq = cfs_rq_of(se);
5872 cfs_rq->h_load_next = se;
5873 if (cfs_rq->last_h_load_update == now)
5878 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
5879 cfs_rq->last_h_load_update = now;
5882 while ((se = cfs_rq->h_load_next) != NULL) {
5883 load = cfs_rq->h_load;
5884 load = div64_ul(load * se->avg.load_avg,
5885 cfs_rq_load_avg(cfs_rq) + 1);
5886 cfs_rq = group_cfs_rq(se);
5887 cfs_rq->h_load = load;
5888 cfs_rq->last_h_load_update = now;
5892 static unsigned long task_h_load(struct task_struct *p)
5894 struct cfs_rq *cfs_rq = task_cfs_rq(p);
5896 update_cfs_rq_h_load(cfs_rq);
5897 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
5898 cfs_rq_load_avg(cfs_rq) + 1);
5901 static inline void update_blocked_averages(int cpu)
5903 struct rq *rq = cpu_rq(cpu);
5904 struct cfs_rq *cfs_rq = &rq->cfs;
5905 unsigned long flags;
5907 raw_spin_lock_irqsave(&rq->lock, flags);
5908 update_rq_clock(rq);
5909 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
5910 raw_spin_unlock_irqrestore(&rq->lock, flags);
5913 static unsigned long task_h_load(struct task_struct *p)
5915 return p->se.avg.load_avg;
5919 /********** Helpers for find_busiest_group ************************/
5928 * sg_lb_stats - stats of a sched_group required for load_balancing
5930 struct sg_lb_stats {
5931 unsigned long avg_load; /*Avg load across the CPUs of the group */
5932 unsigned long group_load; /* Total load over the CPUs of the group */
5933 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
5934 unsigned long load_per_task;
5935 unsigned long group_capacity;
5936 unsigned long group_usage; /* Total usage of the group */
5937 unsigned int sum_nr_running; /* Nr tasks running in the group */
5938 unsigned int idle_cpus;
5939 unsigned int group_weight;
5940 enum group_type group_type;
5941 int group_no_capacity;
5942 #ifdef CONFIG_NUMA_BALANCING
5943 unsigned int nr_numa_running;
5944 unsigned int nr_preferred_running;
5949 * sd_lb_stats - Structure to store the statistics of a sched_domain
5950 * during load balancing.
5952 struct sd_lb_stats {
5953 struct sched_group *busiest; /* Busiest group in this sd */
5954 struct sched_group *local; /* Local group in this sd */
5955 unsigned long total_load; /* Total load of all groups in sd */
5956 unsigned long total_capacity; /* Total capacity of all groups in sd */
5957 unsigned long avg_load; /* Average load across all groups in sd */
5959 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
5960 struct sg_lb_stats local_stat; /* Statistics of the local group */
5963 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
5966 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
5967 * local_stat because update_sg_lb_stats() does a full clear/assignment.
5968 * We must however clear busiest_stat::avg_load because
5969 * update_sd_pick_busiest() reads this before assignment.
5971 *sds = (struct sd_lb_stats){
5975 .total_capacity = 0UL,
5978 .sum_nr_running = 0,
5979 .group_type = group_other,
5985 * get_sd_load_idx - Obtain the load index for a given sched domain.
5986 * @sd: The sched_domain whose load_idx is to be obtained.
5987 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
5989 * Return: The load index.
5991 static inline int get_sd_load_idx(struct sched_domain *sd,
5992 enum cpu_idle_type idle)
5998 load_idx = sd->busy_idx;
6001 case CPU_NEWLY_IDLE:
6002 load_idx = sd->newidle_idx;
6005 load_idx = sd->idle_idx;
6012 static unsigned long default_scale_cpu_capacity(struct sched_domain *sd, int cpu)
6014 if ((sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1))
6015 return sd->smt_gain / sd->span_weight;
6017 return SCHED_CAPACITY_SCALE;
6020 unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
6022 return default_scale_cpu_capacity(sd, cpu);
6025 static unsigned long scale_rt_capacity(int cpu)
6027 struct rq *rq = cpu_rq(cpu);
6028 u64 total, used, age_stamp, avg;
6032 * Since we're reading these variables without serialization make sure
6033 * we read them once before doing sanity checks on them.
6035 age_stamp = READ_ONCE(rq->age_stamp);
6036 avg = READ_ONCE(rq->rt_avg);
6037 delta = __rq_clock_broken(rq) - age_stamp;
6039 if (unlikely(delta < 0))
6042 total = sched_avg_period() + delta;
6044 used = div_u64(avg, total);
6046 if (likely(used < SCHED_CAPACITY_SCALE))
6047 return SCHED_CAPACITY_SCALE - used;
6052 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6054 unsigned long capacity = SCHED_CAPACITY_SCALE;
6055 struct sched_group *sdg = sd->groups;
6057 if (sched_feat(ARCH_CAPACITY))
6058 capacity *= arch_scale_cpu_capacity(sd, cpu);
6060 capacity *= default_scale_cpu_capacity(sd, cpu);
6062 capacity >>= SCHED_CAPACITY_SHIFT;
6064 cpu_rq(cpu)->cpu_capacity_orig = capacity;
6066 capacity *= scale_rt_capacity(cpu);
6067 capacity >>= SCHED_CAPACITY_SHIFT;
6072 cpu_rq(cpu)->cpu_capacity = capacity;
6073 sdg->sgc->capacity = capacity;
6076 void update_group_capacity(struct sched_domain *sd, int cpu)
6078 struct sched_domain *child = sd->child;
6079 struct sched_group *group, *sdg = sd->groups;
6080 unsigned long capacity;
6081 unsigned long interval;
6083 interval = msecs_to_jiffies(sd->balance_interval);
6084 interval = clamp(interval, 1UL, max_load_balance_interval);
6085 sdg->sgc->next_update = jiffies + interval;
6088 update_cpu_capacity(sd, cpu);
6094 if (child->flags & SD_OVERLAP) {
6096 * SD_OVERLAP domains cannot assume that child groups
6097 * span the current group.
6100 for_each_cpu(cpu, sched_group_cpus(sdg)) {
6101 struct sched_group_capacity *sgc;
6102 struct rq *rq = cpu_rq(cpu);
6105 * build_sched_domains() -> init_sched_groups_capacity()
6106 * gets here before we've attached the domains to the
6109 * Use capacity_of(), which is set irrespective of domains
6110 * in update_cpu_capacity().
6112 * This avoids capacity from being 0 and
6113 * causing divide-by-zero issues on boot.
6115 if (unlikely(!rq->sd)) {
6116 capacity += capacity_of(cpu);
6120 sgc = rq->sd->groups->sgc;
6121 capacity += sgc->capacity;
6125 * !SD_OVERLAP domains can assume that child groups
6126 * span the current group.
6129 group = child->groups;
6131 capacity += group->sgc->capacity;
6132 group = group->next;
6133 } while (group != child->groups);
6136 sdg->sgc->capacity = capacity;
6140 * Check whether the capacity of the rq has been noticeably reduced by side
6141 * activity. The imbalance_pct is used for the threshold.
6142 * Return true is the capacity is reduced
6145 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6147 return ((rq->cpu_capacity * sd->imbalance_pct) <
6148 (rq->cpu_capacity_orig * 100));
6152 * Group imbalance indicates (and tries to solve) the problem where balancing
6153 * groups is inadequate due to tsk_cpus_allowed() constraints.
6155 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6156 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6159 * { 0 1 2 3 } { 4 5 6 7 }
6162 * If we were to balance group-wise we'd place two tasks in the first group and
6163 * two tasks in the second group. Clearly this is undesired as it will overload
6164 * cpu 3 and leave one of the cpus in the second group unused.
6166 * The current solution to this issue is detecting the skew in the first group
6167 * by noticing the lower domain failed to reach balance and had difficulty
6168 * moving tasks due to affinity constraints.
6170 * When this is so detected; this group becomes a candidate for busiest; see
6171 * update_sd_pick_busiest(). And calculate_imbalance() and
6172 * find_busiest_group() avoid some of the usual balance conditions to allow it
6173 * to create an effective group imbalance.
6175 * This is a somewhat tricky proposition since the next run might not find the
6176 * group imbalance and decide the groups need to be balanced again. A most
6177 * subtle and fragile situation.
6180 static inline int sg_imbalanced(struct sched_group *group)
6182 return group->sgc->imbalance;
6186 * group_has_capacity returns true if the group has spare capacity that could
6187 * be used by some tasks.
6188 * We consider that a group has spare capacity if the * number of task is
6189 * smaller than the number of CPUs or if the usage is lower than the available
6190 * capacity for CFS tasks.
6191 * For the latter, we use a threshold to stabilize the state, to take into
6192 * account the variance of the tasks' load and to return true if the available
6193 * capacity in meaningful for the load balancer.
6194 * As an example, an available capacity of 1% can appear but it doesn't make
6195 * any benefit for the load balance.
6198 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6200 if (sgs->sum_nr_running < sgs->group_weight)
6203 if ((sgs->group_capacity * 100) >
6204 (sgs->group_usage * env->sd->imbalance_pct))
6211 * group_is_overloaded returns true if the group has more tasks than it can
6213 * group_is_overloaded is not equals to !group_has_capacity because a group
6214 * with the exact right number of tasks, has no more spare capacity but is not
6215 * overloaded so both group_has_capacity and group_is_overloaded return
6219 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
6221 if (sgs->sum_nr_running <= sgs->group_weight)
6224 if ((sgs->group_capacity * 100) <
6225 (sgs->group_usage * env->sd->imbalance_pct))
6231 static enum group_type group_classify(struct lb_env *env,
6232 struct sched_group *group,
6233 struct sg_lb_stats *sgs)
6235 if (sgs->group_no_capacity)
6236 return group_overloaded;
6238 if (sg_imbalanced(group))
6239 return group_imbalanced;
6245 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6246 * @env: The load balancing environment.
6247 * @group: sched_group whose statistics are to be updated.
6248 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6249 * @local_group: Does group contain this_cpu.
6250 * @sgs: variable to hold the statistics for this group.
6251 * @overload: Indicate more than one runnable task for any CPU.
6253 static inline void update_sg_lb_stats(struct lb_env *env,
6254 struct sched_group *group, int load_idx,
6255 int local_group, struct sg_lb_stats *sgs,
6261 memset(sgs, 0, sizeof(*sgs));
6263 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6264 struct rq *rq = cpu_rq(i);
6266 /* Bias balancing toward cpus of our domain */
6268 load = target_load(i, load_idx);
6270 load = source_load(i, load_idx);
6272 sgs->group_load += load;
6273 sgs->group_usage += get_cpu_usage(i);
6274 sgs->sum_nr_running += rq->cfs.h_nr_running;
6276 if (rq->nr_running > 1)
6279 #ifdef CONFIG_NUMA_BALANCING
6280 sgs->nr_numa_running += rq->nr_numa_running;
6281 sgs->nr_preferred_running += rq->nr_preferred_running;
6283 sgs->sum_weighted_load += weighted_cpuload(i);
6288 /* Adjust by relative CPU capacity of the group */
6289 sgs->group_capacity = group->sgc->capacity;
6290 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6292 if (sgs->sum_nr_running)
6293 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6295 sgs->group_weight = group->group_weight;
6297 sgs->group_no_capacity = group_is_overloaded(env, sgs);
6298 sgs->group_type = group_classify(env, group, sgs);
6302 * update_sd_pick_busiest - return 1 on busiest group
6303 * @env: The load balancing environment.
6304 * @sds: sched_domain statistics
6305 * @sg: sched_group candidate to be checked for being the busiest
6306 * @sgs: sched_group statistics
6308 * Determine if @sg is a busier group than the previously selected
6311 * Return: %true if @sg is a busier group than the previously selected
6312 * busiest group. %false otherwise.
6314 static bool update_sd_pick_busiest(struct lb_env *env,
6315 struct sd_lb_stats *sds,
6316 struct sched_group *sg,
6317 struct sg_lb_stats *sgs)
6319 struct sg_lb_stats *busiest = &sds->busiest_stat;
6321 if (sgs->group_type > busiest->group_type)
6324 if (sgs->group_type < busiest->group_type)
6327 if (sgs->avg_load <= busiest->avg_load)
6330 /* This is the busiest node in its class. */
6331 if (!(env->sd->flags & SD_ASYM_PACKING))
6335 * ASYM_PACKING needs to move all the work to the lowest
6336 * numbered CPUs in the group, therefore mark all groups
6337 * higher than ourself as busy.
6339 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6343 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
6350 #ifdef CONFIG_NUMA_BALANCING
6351 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6353 if (sgs->sum_nr_running > sgs->nr_numa_running)
6355 if (sgs->sum_nr_running > sgs->nr_preferred_running)
6360 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6362 if (rq->nr_running > rq->nr_numa_running)
6364 if (rq->nr_running > rq->nr_preferred_running)
6369 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6374 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6378 #endif /* CONFIG_NUMA_BALANCING */
6381 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6382 * @env: The load balancing environment.
6383 * @sds: variable to hold the statistics for this sched_domain.
6385 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6387 struct sched_domain *child = env->sd->child;
6388 struct sched_group *sg = env->sd->groups;
6389 struct sg_lb_stats tmp_sgs;
6390 int load_idx, prefer_sibling = 0;
6391 bool overload = false;
6393 if (child && child->flags & SD_PREFER_SIBLING)
6396 load_idx = get_sd_load_idx(env->sd, env->idle);
6399 struct sg_lb_stats *sgs = &tmp_sgs;
6402 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
6405 sgs = &sds->local_stat;
6407 if (env->idle != CPU_NEWLY_IDLE ||
6408 time_after_eq(jiffies, sg->sgc->next_update))
6409 update_group_capacity(env->sd, env->dst_cpu);
6412 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
6419 * In case the child domain prefers tasks go to siblings
6420 * first, lower the sg capacity so that we'll try
6421 * and move all the excess tasks away. We lower the capacity
6422 * of a group only if the local group has the capacity to fit
6423 * these excess tasks. The extra check prevents the case where
6424 * you always pull from the heaviest group when it is already
6425 * under-utilized (possible with a large weight task outweighs
6426 * the tasks on the system).
6428 if (prefer_sibling && sds->local &&
6429 group_has_capacity(env, &sds->local_stat) &&
6430 (sgs->sum_nr_running > 1)) {
6431 sgs->group_no_capacity = 1;
6432 sgs->group_type = group_overloaded;
6435 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6437 sds->busiest_stat = *sgs;
6441 /* Now, start updating sd_lb_stats */
6442 sds->total_load += sgs->group_load;
6443 sds->total_capacity += sgs->group_capacity;
6446 } while (sg != env->sd->groups);
6448 if (env->sd->flags & SD_NUMA)
6449 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6451 if (!env->sd->parent) {
6452 /* update overload indicator if we are at root domain */
6453 if (env->dst_rq->rd->overload != overload)
6454 env->dst_rq->rd->overload = overload;
6460 * check_asym_packing - Check to see if the group is packed into the
6463 * This is primarily intended to used at the sibling level. Some
6464 * cores like POWER7 prefer to use lower numbered SMT threads. In the
6465 * case of POWER7, it can move to lower SMT modes only when higher
6466 * threads are idle. When in lower SMT modes, the threads will
6467 * perform better since they share less core resources. Hence when we
6468 * have idle threads, we want them to be the higher ones.
6470 * This packing function is run on idle threads. It checks to see if
6471 * the busiest CPU in this domain (core in the P7 case) has a higher
6472 * CPU number than the packing function is being run on. Here we are
6473 * assuming lower CPU number will be equivalent to lower a SMT thread
6476 * Return: 1 when packing is required and a task should be moved to
6477 * this CPU. The amount of the imbalance is returned in *imbalance.
6479 * @env: The load balancing environment.
6480 * @sds: Statistics of the sched_domain which is to be packed
6482 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6486 if (!(env->sd->flags & SD_ASYM_PACKING))
6492 busiest_cpu = group_first_cpu(sds->busiest);
6493 if (env->dst_cpu > busiest_cpu)
6496 env->imbalance = DIV_ROUND_CLOSEST(
6497 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6498 SCHED_CAPACITY_SCALE);
6504 * fix_small_imbalance - Calculate the minor imbalance that exists
6505 * amongst the groups of a sched_domain, during
6507 * @env: The load balancing environment.
6508 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6511 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6513 unsigned long tmp, capa_now = 0, capa_move = 0;
6514 unsigned int imbn = 2;
6515 unsigned long scaled_busy_load_per_task;
6516 struct sg_lb_stats *local, *busiest;
6518 local = &sds->local_stat;
6519 busiest = &sds->busiest_stat;
6521 if (!local->sum_nr_running)
6522 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
6523 else if (busiest->load_per_task > local->load_per_task)
6526 scaled_busy_load_per_task =
6527 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6528 busiest->group_capacity;
6530 if (busiest->avg_load + scaled_busy_load_per_task >=
6531 local->avg_load + (scaled_busy_load_per_task * imbn)) {
6532 env->imbalance = busiest->load_per_task;
6537 * OK, we don't have enough imbalance to justify moving tasks,
6538 * however we may be able to increase total CPU capacity used by
6542 capa_now += busiest->group_capacity *
6543 min(busiest->load_per_task, busiest->avg_load);
6544 capa_now += local->group_capacity *
6545 min(local->load_per_task, local->avg_load);
6546 capa_now /= SCHED_CAPACITY_SCALE;
6548 /* Amount of load we'd subtract */
6549 if (busiest->avg_load > scaled_busy_load_per_task) {
6550 capa_move += busiest->group_capacity *
6551 min(busiest->load_per_task,
6552 busiest->avg_load - scaled_busy_load_per_task);
6555 /* Amount of load we'd add */
6556 if (busiest->avg_load * busiest->group_capacity <
6557 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6558 tmp = (busiest->avg_load * busiest->group_capacity) /
6559 local->group_capacity;
6561 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6562 local->group_capacity;
6564 capa_move += local->group_capacity *
6565 min(local->load_per_task, local->avg_load + tmp);
6566 capa_move /= SCHED_CAPACITY_SCALE;
6568 /* Move if we gain throughput */
6569 if (capa_move > capa_now)
6570 env->imbalance = busiest->load_per_task;
6574 * calculate_imbalance - Calculate the amount of imbalance present within the
6575 * groups of a given sched_domain during load balance.
6576 * @env: load balance environment
6577 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
6579 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6581 unsigned long max_pull, load_above_capacity = ~0UL;
6582 struct sg_lb_stats *local, *busiest;
6584 local = &sds->local_stat;
6585 busiest = &sds->busiest_stat;
6587 if (busiest->group_type == group_imbalanced) {
6589 * In the group_imb case we cannot rely on group-wide averages
6590 * to ensure cpu-load equilibrium, look at wider averages. XXX
6592 busiest->load_per_task =
6593 min(busiest->load_per_task, sds->avg_load);
6597 * In the presence of smp nice balancing, certain scenarios can have
6598 * max load less than avg load(as we skip the groups at or below
6599 * its cpu_capacity, while calculating max_load..)
6601 if (busiest->avg_load <= sds->avg_load ||
6602 local->avg_load >= sds->avg_load) {
6604 return fix_small_imbalance(env, sds);
6608 * If there aren't any idle cpus, avoid creating some.
6610 if (busiest->group_type == group_overloaded &&
6611 local->group_type == group_overloaded) {
6612 load_above_capacity = busiest->sum_nr_running *
6614 if (load_above_capacity > busiest->group_capacity)
6615 load_above_capacity -= busiest->group_capacity;
6617 load_above_capacity = ~0UL;
6621 * We're trying to get all the cpus to the average_load, so we don't
6622 * want to push ourselves above the average load, nor do we wish to
6623 * reduce the max loaded cpu below the average load. At the same time,
6624 * we also don't want to reduce the group load below the group capacity
6625 * (so that we can implement power-savings policies etc). Thus we look
6626 * for the minimum possible imbalance.
6628 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6630 /* How much load to actually move to equalise the imbalance */
6631 env->imbalance = min(
6632 max_pull * busiest->group_capacity,
6633 (sds->avg_load - local->avg_load) * local->group_capacity
6634 ) / SCHED_CAPACITY_SCALE;
6637 * if *imbalance is less than the average load per runnable task
6638 * there is no guarantee that any tasks will be moved so we'll have
6639 * a think about bumping its value to force at least one task to be
6642 if (env->imbalance < busiest->load_per_task)
6643 return fix_small_imbalance(env, sds);
6646 /******* find_busiest_group() helpers end here *********************/
6649 * find_busiest_group - Returns the busiest group within the sched_domain
6650 * if there is an imbalance. If there isn't an imbalance, and
6651 * the user has opted for power-savings, it returns a group whose
6652 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
6653 * such a group exists.
6655 * Also calculates the amount of weighted load which should be moved
6656 * to restore balance.
6658 * @env: The load balancing environment.
6660 * Return: - The busiest group if imbalance exists.
6661 * - If no imbalance and user has opted for power-savings balance,
6662 * return the least loaded group whose CPUs can be
6663 * put to idle by rebalancing its tasks onto our group.
6665 static struct sched_group *find_busiest_group(struct lb_env *env)
6667 struct sg_lb_stats *local, *busiest;
6668 struct sd_lb_stats sds;
6670 init_sd_lb_stats(&sds);
6673 * Compute the various statistics relavent for load balancing at
6676 update_sd_lb_stats(env, &sds);
6677 local = &sds.local_stat;
6678 busiest = &sds.busiest_stat;
6680 /* ASYM feature bypasses nice load balance check */
6681 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
6682 check_asym_packing(env, &sds))
6685 /* There is no busy sibling group to pull tasks from */
6686 if (!sds.busiest || busiest->sum_nr_running == 0)
6689 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
6690 / sds.total_capacity;
6693 * If the busiest group is imbalanced the below checks don't
6694 * work because they assume all things are equal, which typically
6695 * isn't true due to cpus_allowed constraints and the like.
6697 if (busiest->group_type == group_imbalanced)
6700 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6701 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
6702 busiest->group_no_capacity)
6706 * If the local group is busier than the selected busiest group
6707 * don't try and pull any tasks.
6709 if (local->avg_load >= busiest->avg_load)
6713 * Don't pull any tasks if this group is already above the domain
6716 if (local->avg_load >= sds.avg_load)
6719 if (env->idle == CPU_IDLE) {
6721 * This cpu is idle. If the busiest group is not overloaded
6722 * and there is no imbalance between this and busiest group
6723 * wrt idle cpus, it is balanced. The imbalance becomes
6724 * significant if the diff is greater than 1 otherwise we
6725 * might end up to just move the imbalance on another group
6727 if ((busiest->group_type != group_overloaded) &&
6728 (local->idle_cpus <= (busiest->idle_cpus + 1)))
6732 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
6733 * imbalance_pct to be conservative.
6735 if (100 * busiest->avg_load <=
6736 env->sd->imbalance_pct * local->avg_load)
6741 /* Looks like there is an imbalance. Compute it */
6742 calculate_imbalance(env, &sds);
6751 * find_busiest_queue - find the busiest runqueue among the cpus in group.
6753 static struct rq *find_busiest_queue(struct lb_env *env,
6754 struct sched_group *group)
6756 struct rq *busiest = NULL, *rq;
6757 unsigned long busiest_load = 0, busiest_capacity = 1;
6760 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6761 unsigned long capacity, wl;
6765 rt = fbq_classify_rq(rq);
6768 * We classify groups/runqueues into three groups:
6769 * - regular: there are !numa tasks
6770 * - remote: there are numa tasks that run on the 'wrong' node
6771 * - all: there is no distinction
6773 * In order to avoid migrating ideally placed numa tasks,
6774 * ignore those when there's better options.
6776 * If we ignore the actual busiest queue to migrate another
6777 * task, the next balance pass can still reduce the busiest
6778 * queue by moving tasks around inside the node.
6780 * If we cannot move enough load due to this classification
6781 * the next pass will adjust the group classification and
6782 * allow migration of more tasks.
6784 * Both cases only affect the total convergence complexity.
6786 if (rt > env->fbq_type)
6789 capacity = capacity_of(i);
6791 wl = weighted_cpuload(i);
6794 * When comparing with imbalance, use weighted_cpuload()
6795 * which is not scaled with the cpu capacity.
6798 if (rq->nr_running == 1 && wl > env->imbalance &&
6799 !check_cpu_capacity(rq, env->sd))
6803 * For the load comparisons with the other cpu's, consider
6804 * the weighted_cpuload() scaled with the cpu capacity, so
6805 * that the load can be moved away from the cpu that is
6806 * potentially running at a lower capacity.
6808 * Thus we're looking for max(wl_i / capacity_i), crosswise
6809 * multiplication to rid ourselves of the division works out
6810 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
6811 * our previous maximum.
6813 if (wl * busiest_capacity > busiest_load * capacity) {
6815 busiest_capacity = capacity;
6824 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
6825 * so long as it is large enough.
6827 #define MAX_PINNED_INTERVAL 512
6829 /* Working cpumask for load_balance and load_balance_newidle. */
6830 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6832 static int need_active_balance(struct lb_env *env)
6834 struct sched_domain *sd = env->sd;
6836 if (env->idle == CPU_NEWLY_IDLE) {
6839 * ASYM_PACKING needs to force migrate tasks from busy but
6840 * higher numbered CPUs in order to pack all tasks in the
6841 * lowest numbered CPUs.
6843 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
6848 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
6849 * It's worth migrating the task if the src_cpu's capacity is reduced
6850 * because of other sched_class or IRQs if more capacity stays
6851 * available on dst_cpu.
6853 if ((env->idle != CPU_NOT_IDLE) &&
6854 (env->src_rq->cfs.h_nr_running == 1)) {
6855 if ((check_cpu_capacity(env->src_rq, sd)) &&
6856 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
6860 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
6863 static int active_load_balance_cpu_stop(void *data);
6865 static int should_we_balance(struct lb_env *env)
6867 struct sched_group *sg = env->sd->groups;
6868 struct cpumask *sg_cpus, *sg_mask;
6869 int cpu, balance_cpu = -1;
6872 * In the newly idle case, we will allow all the cpu's
6873 * to do the newly idle load balance.
6875 if (env->idle == CPU_NEWLY_IDLE)
6878 sg_cpus = sched_group_cpus(sg);
6879 sg_mask = sched_group_mask(sg);
6880 /* Try to find first idle cpu */
6881 for_each_cpu_and(cpu, sg_cpus, env->cpus) {
6882 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
6889 if (balance_cpu == -1)
6890 balance_cpu = group_balance_cpu(sg);
6893 * First idle cpu or the first cpu(busiest) in this sched group
6894 * is eligible for doing load balancing at this and above domains.
6896 return balance_cpu == env->dst_cpu;
6900 * Check this_cpu to ensure it is balanced within domain. Attempt to move
6901 * tasks if there is an imbalance.
6903 static int load_balance(int this_cpu, struct rq *this_rq,
6904 struct sched_domain *sd, enum cpu_idle_type idle,
6905 int *continue_balancing)
6907 int ld_moved, cur_ld_moved, active_balance = 0;
6908 struct sched_domain *sd_parent = sd->parent;
6909 struct sched_group *group;
6911 unsigned long flags;
6912 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
6914 struct lb_env env = {
6916 .dst_cpu = this_cpu,
6918 .dst_grpmask = sched_group_cpus(sd->groups),
6920 .loop_break = sched_nr_migrate_break,
6923 .tasks = LIST_HEAD_INIT(env.tasks),
6927 * For NEWLY_IDLE load_balancing, we don't need to consider
6928 * other cpus in our group
6930 if (idle == CPU_NEWLY_IDLE)
6931 env.dst_grpmask = NULL;
6933 cpumask_copy(cpus, cpu_active_mask);
6935 schedstat_inc(sd, lb_count[idle]);
6938 if (!should_we_balance(&env)) {
6939 *continue_balancing = 0;
6943 group = find_busiest_group(&env);
6945 schedstat_inc(sd, lb_nobusyg[idle]);
6949 busiest = find_busiest_queue(&env, group);
6951 schedstat_inc(sd, lb_nobusyq[idle]);
6955 BUG_ON(busiest == env.dst_rq);
6957 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
6959 env.src_cpu = busiest->cpu;
6960 env.src_rq = busiest;
6963 if (busiest->nr_running > 1) {
6965 * Attempt to move tasks. If find_busiest_group has found
6966 * an imbalance but busiest->nr_running <= 1, the group is
6967 * still unbalanced. ld_moved simply stays zero, so it is
6968 * correctly treated as an imbalance.
6970 env.flags |= LBF_ALL_PINNED;
6971 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
6974 raw_spin_lock_irqsave(&busiest->lock, flags);
6977 * cur_ld_moved - load moved in current iteration
6978 * ld_moved - cumulative load moved across iterations
6980 cur_ld_moved = detach_tasks(&env);
6983 * We've detached some tasks from busiest_rq. Every
6984 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
6985 * unlock busiest->lock, and we are able to be sure
6986 * that nobody can manipulate the tasks in parallel.
6987 * See task_rq_lock() family for the details.
6990 raw_spin_unlock(&busiest->lock);
6994 ld_moved += cur_ld_moved;
6997 local_irq_restore(flags);
6999 if (env.flags & LBF_NEED_BREAK) {
7000 env.flags &= ~LBF_NEED_BREAK;
7005 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7006 * us and move them to an alternate dst_cpu in our sched_group
7007 * where they can run. The upper limit on how many times we
7008 * iterate on same src_cpu is dependent on number of cpus in our
7011 * This changes load balance semantics a bit on who can move
7012 * load to a given_cpu. In addition to the given_cpu itself
7013 * (or a ilb_cpu acting on its behalf where given_cpu is
7014 * nohz-idle), we now have balance_cpu in a position to move
7015 * load to given_cpu. In rare situations, this may cause
7016 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7017 * _independently_ and at _same_ time to move some load to
7018 * given_cpu) causing exceess load to be moved to given_cpu.
7019 * This however should not happen so much in practice and
7020 * moreover subsequent load balance cycles should correct the
7021 * excess load moved.
7023 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7025 /* Prevent to re-select dst_cpu via env's cpus */
7026 cpumask_clear_cpu(env.dst_cpu, env.cpus);
7028 env.dst_rq = cpu_rq(env.new_dst_cpu);
7029 env.dst_cpu = env.new_dst_cpu;
7030 env.flags &= ~LBF_DST_PINNED;
7032 env.loop_break = sched_nr_migrate_break;
7035 * Go back to "more_balance" rather than "redo" since we
7036 * need to continue with same src_cpu.
7042 * We failed to reach balance because of affinity.
7045 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7047 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7048 *group_imbalance = 1;
7051 /* All tasks on this runqueue were pinned by CPU affinity */
7052 if (unlikely(env.flags & LBF_ALL_PINNED)) {
7053 cpumask_clear_cpu(cpu_of(busiest), cpus);
7054 if (!cpumask_empty(cpus)) {
7056 env.loop_break = sched_nr_migrate_break;
7059 goto out_all_pinned;
7064 schedstat_inc(sd, lb_failed[idle]);
7066 * Increment the failure counter only on periodic balance.
7067 * We do not want newidle balance, which can be very
7068 * frequent, pollute the failure counter causing
7069 * excessive cache_hot migrations and active balances.
7071 if (idle != CPU_NEWLY_IDLE)
7072 sd->nr_balance_failed++;
7074 if (need_active_balance(&env)) {
7075 raw_spin_lock_irqsave(&busiest->lock, flags);
7077 /* don't kick the active_load_balance_cpu_stop,
7078 * if the curr task on busiest cpu can't be
7081 if (!cpumask_test_cpu(this_cpu,
7082 tsk_cpus_allowed(busiest->curr))) {
7083 raw_spin_unlock_irqrestore(&busiest->lock,
7085 env.flags |= LBF_ALL_PINNED;
7086 goto out_one_pinned;
7090 * ->active_balance synchronizes accesses to
7091 * ->active_balance_work. Once set, it's cleared
7092 * only after active load balance is finished.
7094 if (!busiest->active_balance) {
7095 busiest->active_balance = 1;
7096 busiest->push_cpu = this_cpu;
7099 raw_spin_unlock_irqrestore(&busiest->lock, flags);
7101 if (active_balance) {
7102 stop_one_cpu_nowait(cpu_of(busiest),
7103 active_load_balance_cpu_stop, busiest,
7104 &busiest->active_balance_work);
7108 * We've kicked active balancing, reset the failure
7111 sd->nr_balance_failed = sd->cache_nice_tries+1;
7114 sd->nr_balance_failed = 0;
7116 if (likely(!active_balance)) {
7117 /* We were unbalanced, so reset the balancing interval */
7118 sd->balance_interval = sd->min_interval;
7121 * If we've begun active balancing, start to back off. This
7122 * case may not be covered by the all_pinned logic if there
7123 * is only 1 task on the busy runqueue (because we don't call
7126 if (sd->balance_interval < sd->max_interval)
7127 sd->balance_interval *= 2;
7134 * We reach balance although we may have faced some affinity
7135 * constraints. Clear the imbalance flag if it was set.
7138 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7140 if (*group_imbalance)
7141 *group_imbalance = 0;
7146 * We reach balance because all tasks are pinned at this level so
7147 * we can't migrate them. Let the imbalance flag set so parent level
7148 * can try to migrate them.
7150 schedstat_inc(sd, lb_balanced[idle]);
7152 sd->nr_balance_failed = 0;
7155 /* tune up the balancing interval */
7156 if (((env.flags & LBF_ALL_PINNED) &&
7157 sd->balance_interval < MAX_PINNED_INTERVAL) ||
7158 (sd->balance_interval < sd->max_interval))
7159 sd->balance_interval *= 2;
7166 static inline unsigned long
7167 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
7169 unsigned long interval = sd->balance_interval;
7172 interval *= sd->busy_factor;
7174 /* scale ms to jiffies */
7175 interval = msecs_to_jiffies(interval);
7176 interval = clamp(interval, 1UL, max_load_balance_interval);
7182 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
7184 unsigned long interval, next;
7186 interval = get_sd_balance_interval(sd, cpu_busy);
7187 next = sd->last_balance + interval;
7189 if (time_after(*next_balance, next))
7190 *next_balance = next;
7194 * idle_balance is called by schedule() if this_cpu is about to become
7195 * idle. Attempts to pull tasks from other CPUs.
7197 static int idle_balance(struct rq *this_rq)
7199 unsigned long next_balance = jiffies + HZ;
7200 int this_cpu = this_rq->cpu;
7201 struct sched_domain *sd;
7202 int pulled_task = 0;
7205 idle_enter_fair(this_rq);
7208 * We must set idle_stamp _before_ calling idle_balance(), such that we
7209 * measure the duration of idle_balance() as idle time.
7211 this_rq->idle_stamp = rq_clock(this_rq);
7213 if (this_rq->avg_idle < sysctl_sched_migration_cost ||
7214 !this_rq->rd->overload) {
7216 sd = rcu_dereference_check_sched_domain(this_rq->sd);
7218 update_next_balance(sd, 0, &next_balance);
7224 raw_spin_unlock(&this_rq->lock);
7226 update_blocked_averages(this_cpu);
7228 for_each_domain(this_cpu, sd) {
7229 int continue_balancing = 1;
7230 u64 t0, domain_cost;
7232 if (!(sd->flags & SD_LOAD_BALANCE))
7235 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
7236 update_next_balance(sd, 0, &next_balance);
7240 if (sd->flags & SD_BALANCE_NEWIDLE) {
7241 t0 = sched_clock_cpu(this_cpu);
7243 pulled_task = load_balance(this_cpu, this_rq,
7245 &continue_balancing);
7247 domain_cost = sched_clock_cpu(this_cpu) - t0;
7248 if (domain_cost > sd->max_newidle_lb_cost)
7249 sd->max_newidle_lb_cost = domain_cost;
7251 curr_cost += domain_cost;
7254 update_next_balance(sd, 0, &next_balance);
7257 * Stop searching for tasks to pull if there are
7258 * now runnable tasks on this rq.
7260 if (pulled_task || this_rq->nr_running > 0)
7265 raw_spin_lock(&this_rq->lock);
7267 if (curr_cost > this_rq->max_idle_balance_cost)
7268 this_rq->max_idle_balance_cost = curr_cost;
7271 * While browsing the domains, we released the rq lock, a task could
7272 * have been enqueued in the meantime. Since we're not going idle,
7273 * pretend we pulled a task.
7275 if (this_rq->cfs.h_nr_running && !pulled_task)
7279 /* Move the next balance forward */
7280 if (time_after(this_rq->next_balance, next_balance))
7281 this_rq->next_balance = next_balance;
7283 /* Is there a task of a high priority class? */
7284 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7288 idle_exit_fair(this_rq);
7289 this_rq->idle_stamp = 0;
7296 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7297 * running tasks off the busiest CPU onto idle CPUs. It requires at
7298 * least 1 task to be running on each physical CPU where possible, and
7299 * avoids physical / logical imbalances.
7301 static int active_load_balance_cpu_stop(void *data)
7303 struct rq *busiest_rq = data;
7304 int busiest_cpu = cpu_of(busiest_rq);
7305 int target_cpu = busiest_rq->push_cpu;
7306 struct rq *target_rq = cpu_rq(target_cpu);
7307 struct sched_domain *sd;
7308 struct task_struct *p = NULL;
7310 raw_spin_lock_irq(&busiest_rq->lock);
7312 /* make sure the requested cpu hasn't gone down in the meantime */
7313 if (unlikely(busiest_cpu != smp_processor_id() ||
7314 !busiest_rq->active_balance))
7317 /* Is there any task to move? */
7318 if (busiest_rq->nr_running <= 1)
7322 * This condition is "impossible", if it occurs
7323 * we need to fix it. Originally reported by
7324 * Bjorn Helgaas on a 128-cpu setup.
7326 BUG_ON(busiest_rq == target_rq);
7328 /* Search for an sd spanning us and the target CPU. */
7330 for_each_domain(target_cpu, sd) {
7331 if ((sd->flags & SD_LOAD_BALANCE) &&
7332 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
7337 struct lb_env env = {
7339 .dst_cpu = target_cpu,
7340 .dst_rq = target_rq,
7341 .src_cpu = busiest_rq->cpu,
7342 .src_rq = busiest_rq,
7346 schedstat_inc(sd, alb_count);
7348 p = detach_one_task(&env);
7350 schedstat_inc(sd, alb_pushed);
7352 schedstat_inc(sd, alb_failed);
7356 busiest_rq->active_balance = 0;
7357 raw_spin_unlock(&busiest_rq->lock);
7360 attach_one_task(target_rq, p);
7367 static inline int on_null_domain(struct rq *rq)
7369 return unlikely(!rcu_dereference_sched(rq->sd));
7372 #ifdef CONFIG_NO_HZ_COMMON
7374 * idle load balancing details
7375 * - When one of the busy CPUs notice that there may be an idle rebalancing
7376 * needed, they will kick the idle load balancer, which then does idle
7377 * load balancing for all the idle CPUs.
7380 cpumask_var_t idle_cpus_mask;
7382 unsigned long next_balance; /* in jiffy units */
7383 } nohz ____cacheline_aligned;
7385 static inline int find_new_ilb(void)
7387 int ilb = cpumask_first(nohz.idle_cpus_mask);
7389 if (ilb < nr_cpu_ids && idle_cpu(ilb))
7396 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7397 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7398 * CPU (if there is one).
7400 static void nohz_balancer_kick(void)
7404 nohz.next_balance++;
7406 ilb_cpu = find_new_ilb();
7408 if (ilb_cpu >= nr_cpu_ids)
7411 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7414 * Use smp_send_reschedule() instead of resched_cpu().
7415 * This way we generate a sched IPI on the target cpu which
7416 * is idle. And the softirq performing nohz idle load balance
7417 * will be run before returning from the IPI.
7419 smp_send_reschedule(ilb_cpu);
7423 static inline void nohz_balance_exit_idle(int cpu)
7425 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7427 * Completely isolated CPUs don't ever set, so we must test.
7429 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
7430 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
7431 atomic_dec(&nohz.nr_cpus);
7433 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7437 static inline void set_cpu_sd_state_busy(void)
7439 struct sched_domain *sd;
7440 int cpu = smp_processor_id();
7443 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7445 if (!sd || !sd->nohz_idle)
7449 atomic_inc(&sd->groups->sgc->nr_busy_cpus);
7454 void set_cpu_sd_state_idle(void)
7456 struct sched_domain *sd;
7457 int cpu = smp_processor_id();
7460 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7462 if (!sd || sd->nohz_idle)
7466 atomic_dec(&sd->groups->sgc->nr_busy_cpus);
7472 * This routine will record that the cpu is going idle with tick stopped.
7473 * This info will be used in performing idle load balancing in the future.
7475 void nohz_balance_enter_idle(int cpu)
7478 * If this cpu is going down, then nothing needs to be done.
7480 if (!cpu_active(cpu))
7483 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
7487 * If we're a completely isolated CPU, we don't play.
7489 if (on_null_domain(cpu_rq(cpu)))
7492 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
7493 atomic_inc(&nohz.nr_cpus);
7494 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7497 static int sched_ilb_notifier(struct notifier_block *nfb,
7498 unsigned long action, void *hcpu)
7500 switch (action & ~CPU_TASKS_FROZEN) {
7502 nohz_balance_exit_idle(smp_processor_id());
7510 static DEFINE_SPINLOCK(balancing);
7513 * Scale the max load_balance interval with the number of CPUs in the system.
7514 * This trades load-balance latency on larger machines for less cross talk.
7516 void update_max_interval(void)
7518 max_load_balance_interval = HZ*num_online_cpus()/10;
7522 * It checks each scheduling domain to see if it is due to be balanced,
7523 * and initiates a balancing operation if so.
7525 * Balancing parameters are set up in init_sched_domains.
7527 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7529 int continue_balancing = 1;
7531 unsigned long interval;
7532 struct sched_domain *sd;
7533 /* Earliest time when we have to do rebalance again */
7534 unsigned long next_balance = jiffies + 60*HZ;
7535 int update_next_balance = 0;
7536 int need_serialize, need_decay = 0;
7539 update_blocked_averages(cpu);
7542 for_each_domain(cpu, sd) {
7544 * Decay the newidle max times here because this is a regular
7545 * visit to all the domains. Decay ~1% per second.
7547 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
7548 sd->max_newidle_lb_cost =
7549 (sd->max_newidle_lb_cost * 253) / 256;
7550 sd->next_decay_max_lb_cost = jiffies + HZ;
7553 max_cost += sd->max_newidle_lb_cost;
7555 if (!(sd->flags & SD_LOAD_BALANCE))
7559 * Stop the load balance at this level. There is another
7560 * CPU in our sched group which is doing load balancing more
7563 if (!continue_balancing) {
7569 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7571 need_serialize = sd->flags & SD_SERIALIZE;
7572 if (need_serialize) {
7573 if (!spin_trylock(&balancing))
7577 if (time_after_eq(jiffies, sd->last_balance + interval)) {
7578 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7580 * The LBF_DST_PINNED logic could have changed
7581 * env->dst_cpu, so we can't know our idle
7582 * state even if we migrated tasks. Update it.
7584 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7586 sd->last_balance = jiffies;
7587 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7590 spin_unlock(&balancing);
7592 if (time_after(next_balance, sd->last_balance + interval)) {
7593 next_balance = sd->last_balance + interval;
7594 update_next_balance = 1;
7599 * Ensure the rq-wide value also decays but keep it at a
7600 * reasonable floor to avoid funnies with rq->avg_idle.
7602 rq->max_idle_balance_cost =
7603 max((u64)sysctl_sched_migration_cost, max_cost);
7608 * next_balance will be updated only when there is a need.
7609 * When the cpu is attached to null domain for ex, it will not be
7612 if (likely(update_next_balance))
7613 rq->next_balance = next_balance;
7616 #ifdef CONFIG_NO_HZ_COMMON
7618 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7619 * rebalancing for all the cpus for whom scheduler ticks are stopped.
7621 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7623 int this_cpu = this_rq->cpu;
7627 if (idle != CPU_IDLE ||
7628 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
7631 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7632 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7636 * If this cpu gets work to do, stop the load balancing
7637 * work being done for other cpus. Next load
7638 * balancing owner will pick it up.
7643 rq = cpu_rq(balance_cpu);
7646 * If time for next balance is due,
7649 if (time_after_eq(jiffies, rq->next_balance)) {
7650 raw_spin_lock_irq(&rq->lock);
7651 update_rq_clock(rq);
7652 update_idle_cpu_load(rq);
7653 raw_spin_unlock_irq(&rq->lock);
7654 rebalance_domains(rq, CPU_IDLE);
7657 if (time_after(this_rq->next_balance, rq->next_balance))
7658 this_rq->next_balance = rq->next_balance;
7660 nohz.next_balance = this_rq->next_balance;
7662 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7666 * Current heuristic for kicking the idle load balancer in the presence
7667 * of an idle cpu in the system.
7668 * - This rq has more than one task.
7669 * - This rq has at least one CFS task and the capacity of the CPU is
7670 * significantly reduced because of RT tasks or IRQs.
7671 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
7672 * multiple busy cpu.
7673 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
7674 * domain span are idle.
7676 static inline bool nohz_kick_needed(struct rq *rq)
7678 unsigned long now = jiffies;
7679 struct sched_domain *sd;
7680 struct sched_group_capacity *sgc;
7681 int nr_busy, cpu = rq->cpu;
7684 if (unlikely(rq->idle_balance))
7688 * We may be recently in ticked or tickless idle mode. At the first
7689 * busy tick after returning from idle, we will update the busy stats.
7691 set_cpu_sd_state_busy();
7692 nohz_balance_exit_idle(cpu);
7695 * None are in tickless mode and hence no need for NOHZ idle load
7698 if (likely(!atomic_read(&nohz.nr_cpus)))
7701 if (time_before(now, nohz.next_balance))
7704 if (rq->nr_running >= 2)
7708 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7710 sgc = sd->groups->sgc;
7711 nr_busy = atomic_read(&sgc->nr_busy_cpus);
7720 sd = rcu_dereference(rq->sd);
7722 if ((rq->cfs.h_nr_running >= 1) &&
7723 check_cpu_capacity(rq, sd)) {
7729 sd = rcu_dereference(per_cpu(sd_asym, cpu));
7730 if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
7731 sched_domain_span(sd)) < cpu)) {
7741 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7745 * run_rebalance_domains is triggered when needed from the scheduler tick.
7746 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
7748 static void run_rebalance_domains(struct softirq_action *h)
7750 struct rq *this_rq = this_rq();
7751 enum cpu_idle_type idle = this_rq->idle_balance ?
7752 CPU_IDLE : CPU_NOT_IDLE;
7755 * If this cpu has a pending nohz_balance_kick, then do the
7756 * balancing on behalf of the other idle cpus whose ticks are
7757 * stopped. Do nohz_idle_balance *before* rebalance_domains to
7758 * give the idle cpus a chance to load balance. Else we may
7759 * load balance only within the local sched_domain hierarchy
7760 * and abort nohz_idle_balance altogether if we pull some load.
7762 nohz_idle_balance(this_rq, idle);
7763 rebalance_domains(this_rq, idle);
7767 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
7769 void trigger_load_balance(struct rq *rq)
7771 /* Don't need to rebalance while attached to NULL domain */
7772 if (unlikely(on_null_domain(rq)))
7775 if (time_after_eq(jiffies, rq->next_balance))
7776 raise_softirq(SCHED_SOFTIRQ);
7777 #ifdef CONFIG_NO_HZ_COMMON
7778 if (nohz_kick_needed(rq))
7779 nohz_balancer_kick();
7783 static void rq_online_fair(struct rq *rq)
7787 update_runtime_enabled(rq);
7790 static void rq_offline_fair(struct rq *rq)
7794 /* Ensure any throttled groups are reachable by pick_next_task */
7795 unthrottle_offline_cfs_rqs(rq);
7798 #endif /* CONFIG_SMP */
7801 * scheduler tick hitting a task of our scheduling class:
7803 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
7805 struct cfs_rq *cfs_rq;
7806 struct sched_entity *se = &curr->se;
7808 for_each_sched_entity(se) {
7809 cfs_rq = cfs_rq_of(se);
7810 entity_tick(cfs_rq, se, queued);
7813 if (numabalancing_enabled)
7814 task_tick_numa(rq, curr);
7818 * called on fork with the child task as argument from the parent's context
7819 * - child not yet on the tasklist
7820 * - preemption disabled
7822 static void task_fork_fair(struct task_struct *p)
7824 struct cfs_rq *cfs_rq;
7825 struct sched_entity *se = &p->se, *curr;
7826 int this_cpu = smp_processor_id();
7827 struct rq *rq = this_rq();
7828 unsigned long flags;
7830 raw_spin_lock_irqsave(&rq->lock, flags);
7832 update_rq_clock(rq);
7834 cfs_rq = task_cfs_rq(current);
7835 curr = cfs_rq->curr;
7838 * Not only the cpu but also the task_group of the parent might have
7839 * been changed after parent->se.parent,cfs_rq were copied to
7840 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
7841 * of child point to valid ones.
7844 __set_task_cpu(p, this_cpu);
7847 update_curr(cfs_rq);
7850 se->vruntime = curr->vruntime;
7851 place_entity(cfs_rq, se, 1);
7853 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
7855 * Upon rescheduling, sched_class::put_prev_task() will place
7856 * 'current' within the tree based on its new key value.
7858 swap(curr->vruntime, se->vruntime);
7862 se->vruntime -= cfs_rq->min_vruntime;
7864 raw_spin_unlock_irqrestore(&rq->lock, flags);
7868 * Priority of the task has changed. Check to see if we preempt
7872 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
7874 if (!task_on_rq_queued(p))
7878 * Reschedule if we are currently running on this runqueue and
7879 * our priority decreased, or if we are not currently running on
7880 * this runqueue and our priority is higher than the current's
7882 if (rq->curr == p) {
7883 if (p->prio > oldprio)
7886 check_preempt_curr(rq, p, 0);
7889 static void switched_from_fair(struct rq *rq, struct task_struct *p)
7891 struct sched_entity *se = &p->se;
7892 struct cfs_rq *cfs_rq = cfs_rq_of(se);
7895 * Ensure the task's vruntime is normalized, so that when it's
7896 * switched back to the fair class the enqueue_entity(.flags=0) will
7897 * do the right thing.
7899 * If it's queued, then the dequeue_entity(.flags=0) will already
7900 * have normalized the vruntime, if it's !queued, then only when
7901 * the task is sleeping will it still have non-normalized vruntime.
7903 if (!task_on_rq_queued(p) && p->state != TASK_RUNNING) {
7905 * Fix up our vruntime so that the current sleep doesn't
7906 * cause 'unlimited' sleep bonus.
7908 place_entity(cfs_rq, se, 0);
7909 se->vruntime -= cfs_rq->min_vruntime;
7913 /* Catch up with the cfs_rq and remove our load when we leave */
7914 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq), &se->avg,
7915 se->on_rq * scale_load_down(se->load.weight), cfs_rq->curr == se, NULL);
7917 cfs_rq->avg.load_avg =
7918 max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
7919 cfs_rq->avg.load_sum =
7920 max_t(s64, cfs_rq->avg.load_sum - se->avg.load_sum, 0);
7921 cfs_rq->avg.util_avg =
7922 max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
7923 cfs_rq->avg.util_sum =
7924 max_t(s32, cfs_rq->avg.util_sum - se->avg.util_sum, 0);
7929 * We switched to the sched_fair class.
7931 static void switched_to_fair(struct rq *rq, struct task_struct *p)
7933 struct sched_entity *se = &p->se;
7935 #ifdef CONFIG_FAIR_GROUP_SCHED
7937 * Since the real-depth could have been changed (only FAIR
7938 * class maintain depth value), reset depth properly.
7940 se->depth = se->parent ? se->parent->depth + 1 : 0;
7943 if (!task_on_rq_queued(p)) {
7946 * Ensure the task has a non-normalized vruntime when it is switched
7947 * back to the fair class with !queued, so that enqueue_entity() at
7948 * wake-up time will do the right thing.
7950 * If it's queued, then the enqueue_entity(.flags=0) makes the task
7951 * has non-normalized vruntime, if it's !queued, then it still has
7952 * normalized vruntime.
7954 if (p->state != TASK_RUNNING)
7955 se->vruntime += cfs_rq_of(se)->min_vruntime;
7960 * We were most likely switched from sched_rt, so
7961 * kick off the schedule if running, otherwise just see
7962 * if we can still preempt the current task.
7967 check_preempt_curr(rq, p, 0);
7970 /* Account for a task changing its policy or group.
7972 * This routine is mostly called to set cfs_rq->curr field when a task
7973 * migrates between groups/classes.
7975 static void set_curr_task_fair(struct rq *rq)
7977 struct sched_entity *se = &rq->curr->se;
7979 for_each_sched_entity(se) {
7980 struct cfs_rq *cfs_rq = cfs_rq_of(se);
7982 set_next_entity(cfs_rq, se);
7983 /* ensure bandwidth has been allocated on our new cfs_rq */
7984 account_cfs_rq_runtime(cfs_rq, 0);
7988 void init_cfs_rq(struct cfs_rq *cfs_rq)
7990 cfs_rq->tasks_timeline = RB_ROOT;
7991 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
7992 #ifndef CONFIG_64BIT
7993 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
7996 atomic_long_set(&cfs_rq->removed_load_avg, 0);
7997 atomic_long_set(&cfs_rq->removed_util_avg, 0);
8001 #ifdef CONFIG_FAIR_GROUP_SCHED
8002 static void task_move_group_fair(struct task_struct *p, int queued)
8004 struct sched_entity *se = &p->se;
8005 struct cfs_rq *cfs_rq;
8008 * If the task was not on the rq at the time of this cgroup movement
8009 * it must have been asleep, sleeping tasks keep their ->vruntime
8010 * absolute on their old rq until wakeup (needed for the fair sleeper
8011 * bonus in place_entity()).
8013 * If it was on the rq, we've just 'preempted' it, which does convert
8014 * ->vruntime to a relative base.
8016 * Make sure both cases convert their relative position when migrating
8017 * to another cgroup's rq. This does somewhat interfere with the
8018 * fair sleeper stuff for the first placement, but who cares.
8021 * When !queued, vruntime of the task has usually NOT been normalized.
8022 * But there are some cases where it has already been normalized:
8024 * - Moving a forked child which is waiting for being woken up by
8025 * wake_up_new_task().
8026 * - Moving a task which has been woken up by try_to_wake_up() and
8027 * waiting for actually being woken up by sched_ttwu_pending().
8029 * To prevent boost or penalty in the new cfs_rq caused by delta
8030 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
8032 if (!queued && (!se->sum_exec_runtime || p->state == TASK_WAKING))
8036 se->vruntime -= cfs_rq_of(se)->min_vruntime;
8037 set_task_rq(p, task_cpu(p));
8038 se->depth = se->parent ? se->parent->depth + 1 : 0;
8040 cfs_rq = cfs_rq_of(se);
8041 se->vruntime += cfs_rq->min_vruntime;
8044 /* Virtually synchronize task with its new cfs_rq */
8045 p->se.avg.last_update_time = cfs_rq->avg.last_update_time;
8046 cfs_rq->avg.load_avg += p->se.avg.load_avg;
8047 cfs_rq->avg.load_sum += p->se.avg.load_sum;
8048 cfs_rq->avg.util_avg += p->se.avg.util_avg;
8049 cfs_rq->avg.util_sum += p->se.avg.util_sum;
8054 void free_fair_sched_group(struct task_group *tg)
8058 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
8060 for_each_possible_cpu(i) {
8062 kfree(tg->cfs_rq[i]);
8065 remove_entity_load_avg(tg->se[i]);
8074 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8076 struct cfs_rq *cfs_rq;
8077 struct sched_entity *se;
8080 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
8083 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
8087 tg->shares = NICE_0_LOAD;
8089 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
8091 for_each_possible_cpu(i) {
8092 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
8093 GFP_KERNEL, cpu_to_node(i));
8097 se = kzalloc_node(sizeof(struct sched_entity),
8098 GFP_KERNEL, cpu_to_node(i));
8102 init_cfs_rq(cfs_rq);
8103 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
8104 init_entity_runnable_average(se);
8115 void unregister_fair_sched_group(struct task_group *tg, int cpu)
8117 struct rq *rq = cpu_rq(cpu);
8118 unsigned long flags;
8121 * Only empty task groups can be destroyed; so we can speculatively
8122 * check on_list without danger of it being re-added.
8124 if (!tg->cfs_rq[cpu]->on_list)
8127 raw_spin_lock_irqsave(&rq->lock, flags);
8128 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
8129 raw_spin_unlock_irqrestore(&rq->lock, flags);
8132 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
8133 struct sched_entity *se, int cpu,
8134 struct sched_entity *parent)
8136 struct rq *rq = cpu_rq(cpu);
8140 init_cfs_rq_runtime(cfs_rq);
8142 tg->cfs_rq[cpu] = cfs_rq;
8145 /* se could be NULL for root_task_group */
8150 se->cfs_rq = &rq->cfs;
8153 se->cfs_rq = parent->my_q;
8154 se->depth = parent->depth + 1;
8158 /* guarantee group entities always have weight */
8159 update_load_set(&se->load, NICE_0_LOAD);
8160 se->parent = parent;
8163 static DEFINE_MUTEX(shares_mutex);
8165 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
8168 unsigned long flags;
8171 * We can't change the weight of the root cgroup.
8176 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
8178 mutex_lock(&shares_mutex);
8179 if (tg->shares == shares)
8182 tg->shares = shares;
8183 for_each_possible_cpu(i) {
8184 struct rq *rq = cpu_rq(i);
8185 struct sched_entity *se;
8188 /* Propagate contribution to hierarchy */
8189 raw_spin_lock_irqsave(&rq->lock, flags);
8191 /* Possible calls to update_curr() need rq clock */
8192 update_rq_clock(rq);
8193 for_each_sched_entity(se)
8194 update_cfs_shares(group_cfs_rq(se));
8195 raw_spin_unlock_irqrestore(&rq->lock, flags);
8199 mutex_unlock(&shares_mutex);
8202 #else /* CONFIG_FAIR_GROUP_SCHED */
8204 void free_fair_sched_group(struct task_group *tg) { }
8206 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8211 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
8213 #endif /* CONFIG_FAIR_GROUP_SCHED */
8216 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8218 struct sched_entity *se = &task->se;
8219 unsigned int rr_interval = 0;
8222 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8225 if (rq->cfs.load.weight)
8226 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8232 * All the scheduling class methods:
8234 const struct sched_class fair_sched_class = {
8235 .next = &idle_sched_class,
8236 .enqueue_task = enqueue_task_fair,
8237 .dequeue_task = dequeue_task_fair,
8238 .yield_task = yield_task_fair,
8239 .yield_to_task = yield_to_task_fair,
8241 .check_preempt_curr = check_preempt_wakeup,
8243 .pick_next_task = pick_next_task_fair,
8244 .put_prev_task = put_prev_task_fair,
8247 .select_task_rq = select_task_rq_fair,
8248 .migrate_task_rq = migrate_task_rq_fair,
8250 .rq_online = rq_online_fair,
8251 .rq_offline = rq_offline_fair,
8253 .task_waking = task_waking_fair,
8254 .task_dead = task_dead_fair,
8255 .set_cpus_allowed = set_cpus_allowed_common,
8258 .set_curr_task = set_curr_task_fair,
8259 .task_tick = task_tick_fair,
8260 .task_fork = task_fork_fair,
8262 .prio_changed = prio_changed_fair,
8263 .switched_from = switched_from_fair,
8264 .switched_to = switched_to_fair,
8266 .get_rr_interval = get_rr_interval_fair,
8268 .update_curr = update_curr_fair,
8270 #ifdef CONFIG_FAIR_GROUP_SCHED
8271 .task_move_group = task_move_group_fair,
8275 #ifdef CONFIG_SCHED_DEBUG
8276 void print_cfs_stats(struct seq_file *m, int cpu)
8278 struct cfs_rq *cfs_rq;
8281 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8282 print_cfs_rq(m, cpu, cfs_rq);
8286 #ifdef CONFIG_NUMA_BALANCING
8287 void show_numa_stats(struct task_struct *p, struct seq_file *m)
8290 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
8292 for_each_online_node(node) {
8293 if (p->numa_faults) {
8294 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
8295 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
8297 if (p->numa_group) {
8298 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
8299 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
8301 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
8304 #endif /* CONFIG_NUMA_BALANCING */
8305 #endif /* CONFIG_SCHED_DEBUG */
8307 __init void init_sched_fair_class(void)
8310 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
8312 #ifdef CONFIG_NO_HZ_COMMON
8313 nohz.next_balance = jiffies;
8314 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
8315 cpu_notifier(sched_ilb_notifier, 0);