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/slab.h>
27 #include <linux/profile.h>
28 #include <linux/interrupt.h>
29 #include <linux/random.h>
30 #include <linux/mempolicy.h>
31 #include <linux/task_work.h>
33 #include <trace/events/sched.h>
38 * Targeted preemption latency for CPU-bound tasks:
39 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
41 * NOTE: this latency value is not the same as the concept of
42 * 'timeslice length' - timeslices in CFS are of variable length
43 * and have no persistent notion like in traditional, time-slice
44 * based scheduling concepts.
46 * (to see the precise effective timeslice length of your workload,
47 * run vmstat and monitor the context-switches (cs) field)
49 unsigned int sysctl_sched_latency = 6000000ULL;
50 unsigned int normalized_sysctl_sched_latency = 6000000ULL;
53 * The initial- and re-scaling of tunables is configurable
54 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
57 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
58 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
59 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
61 enum sched_tunable_scaling sysctl_sched_tunable_scaling
62 = SCHED_TUNABLESCALING_LOG;
65 * Minimal preemption granularity for CPU-bound tasks:
66 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
68 unsigned int sysctl_sched_min_granularity = 750000ULL;
69 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
72 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
74 static unsigned int sched_nr_latency = 8;
77 * After fork, child runs first. If set to 0 (default) then
78 * parent will (try to) run first.
80 unsigned int sysctl_sched_child_runs_first __read_mostly;
83 * SCHED_OTHER wake-up granularity.
84 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
86 * This option delays the preemption effects of decoupled workloads
87 * and reduces their over-scheduling. Synchronous workloads will still
88 * have immediate wakeup/sleep latencies.
90 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
91 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
93 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
96 * The exponential sliding window over which load is averaged for shares
100 unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
102 #ifdef CONFIG_CFS_BANDWIDTH
104 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
105 * each time a cfs_rq requests quota.
107 * Note: in the case that the slice exceeds the runtime remaining (either due
108 * to consumption or the quota being specified to be smaller than the slice)
109 * we will always only issue the remaining available time.
111 * default: 5 msec, units: microseconds
113 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
117 * Increase the granularity value when there are more CPUs,
118 * because with more CPUs the 'effective latency' as visible
119 * to users decreases. But the relationship is not linear,
120 * so pick a second-best guess by going with the log2 of the
123 * This idea comes from the SD scheduler of Con Kolivas:
125 static int get_update_sysctl_factor(void)
127 unsigned int cpus = min_t(int, num_online_cpus(), 8);
130 switch (sysctl_sched_tunable_scaling) {
131 case SCHED_TUNABLESCALING_NONE:
134 case SCHED_TUNABLESCALING_LINEAR:
137 case SCHED_TUNABLESCALING_LOG:
139 factor = 1 + ilog2(cpus);
146 static void update_sysctl(void)
148 unsigned int factor = get_update_sysctl_factor();
150 #define SET_SYSCTL(name) \
151 (sysctl_##name = (factor) * normalized_sysctl_##name)
152 SET_SYSCTL(sched_min_granularity);
153 SET_SYSCTL(sched_latency);
154 SET_SYSCTL(sched_wakeup_granularity);
158 void sched_init_granularity(void)
163 #if BITS_PER_LONG == 32
164 # define WMULT_CONST (~0UL)
166 # define WMULT_CONST (1UL << 32)
169 #define WMULT_SHIFT 32
172 * Shift right and round:
174 #define SRR(x, y) (((x) + (1UL << ((y) - 1))) >> (y))
177 * delta *= weight / lw
180 calc_delta_mine(unsigned long delta_exec, unsigned long weight,
181 struct load_weight *lw)
186 * weight can be less than 2^SCHED_LOAD_RESOLUTION for task group sched
187 * entities since MIN_SHARES = 2. Treat weight as 1 if less than
188 * 2^SCHED_LOAD_RESOLUTION.
190 if (likely(weight > (1UL << SCHED_LOAD_RESOLUTION)))
191 tmp = (u64)delta_exec * scale_load_down(weight);
193 tmp = (u64)delta_exec;
195 if (!lw->inv_weight) {
196 unsigned long w = scale_load_down(lw->weight);
198 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
200 else if (unlikely(!w))
201 lw->inv_weight = WMULT_CONST;
203 lw->inv_weight = WMULT_CONST / w;
207 * Check whether we'd overflow the 64-bit multiplication:
209 if (unlikely(tmp > WMULT_CONST))
210 tmp = SRR(SRR(tmp, WMULT_SHIFT/2) * lw->inv_weight,
213 tmp = SRR(tmp * lw->inv_weight, WMULT_SHIFT);
215 return (unsigned long)min(tmp, (u64)(unsigned long)LONG_MAX);
219 const struct sched_class fair_sched_class;
221 /**************************************************************
222 * CFS operations on generic schedulable entities:
225 #ifdef CONFIG_FAIR_GROUP_SCHED
227 /* cpu runqueue to which this cfs_rq is attached */
228 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
233 /* An entity is a task if it doesn't "own" a runqueue */
234 #define entity_is_task(se) (!se->my_q)
236 static inline struct task_struct *task_of(struct sched_entity *se)
238 #ifdef CONFIG_SCHED_DEBUG
239 WARN_ON_ONCE(!entity_is_task(se));
241 return container_of(se, struct task_struct, se);
244 /* Walk up scheduling entities hierarchy */
245 #define for_each_sched_entity(se) \
246 for (; se; se = se->parent)
248 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
253 /* runqueue on which this entity is (to be) queued */
254 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
259 /* runqueue "owned" by this group */
260 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
265 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
267 if (!cfs_rq->on_list) {
269 * Ensure we either appear before our parent (if already
270 * enqueued) or force our parent to appear after us when it is
271 * enqueued. The fact that we always enqueue bottom-up
272 * reduces this to two cases.
274 if (cfs_rq->tg->parent &&
275 cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
276 list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
277 &rq_of(cfs_rq)->leaf_cfs_rq_list);
279 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
280 &rq_of(cfs_rq)->leaf_cfs_rq_list);
287 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
289 if (cfs_rq->on_list) {
290 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
295 /* Iterate thr' all leaf cfs_rq's on a runqueue */
296 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
297 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
299 /* Do the two (enqueued) entities belong to the same group ? */
301 is_same_group(struct sched_entity *se, struct sched_entity *pse)
303 if (se->cfs_rq == pse->cfs_rq)
309 static inline struct sched_entity *parent_entity(struct sched_entity *se)
314 /* return depth at which a sched entity is present in the hierarchy */
315 static inline int depth_se(struct sched_entity *se)
319 for_each_sched_entity(se)
326 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
328 int se_depth, pse_depth;
331 * preemption test can be made between sibling entities who are in the
332 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
333 * both tasks until we find their ancestors who are siblings of common
337 /* First walk up until both entities are at same depth */
338 se_depth = depth_se(*se);
339 pse_depth = depth_se(*pse);
341 while (se_depth > pse_depth) {
343 *se = parent_entity(*se);
346 while (pse_depth > se_depth) {
348 *pse = parent_entity(*pse);
351 while (!is_same_group(*se, *pse)) {
352 *se = parent_entity(*se);
353 *pse = parent_entity(*pse);
357 #else /* !CONFIG_FAIR_GROUP_SCHED */
359 static inline struct task_struct *task_of(struct sched_entity *se)
361 return container_of(se, struct task_struct, se);
364 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
366 return container_of(cfs_rq, struct rq, cfs);
369 #define entity_is_task(se) 1
371 #define for_each_sched_entity(se) \
372 for (; se; se = NULL)
374 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
376 return &task_rq(p)->cfs;
379 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
381 struct task_struct *p = task_of(se);
382 struct rq *rq = task_rq(p);
387 /* runqueue "owned" by this group */
388 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
393 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
397 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
401 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
402 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
405 is_same_group(struct sched_entity *se, struct sched_entity *pse)
410 static inline struct sched_entity *parent_entity(struct sched_entity *se)
416 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
420 #endif /* CONFIG_FAIR_GROUP_SCHED */
422 static __always_inline
423 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec);
425 /**************************************************************
426 * Scheduling class tree data structure manipulation methods:
429 static inline u64 max_vruntime(u64 min_vruntime, u64 vruntime)
431 s64 delta = (s64)(vruntime - min_vruntime);
433 min_vruntime = vruntime;
438 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
440 s64 delta = (s64)(vruntime - min_vruntime);
442 min_vruntime = vruntime;
447 static inline int entity_before(struct sched_entity *a,
448 struct sched_entity *b)
450 return (s64)(a->vruntime - b->vruntime) < 0;
453 static void update_min_vruntime(struct cfs_rq *cfs_rq)
455 u64 vruntime = cfs_rq->min_vruntime;
458 vruntime = cfs_rq->curr->vruntime;
460 if (cfs_rq->rb_leftmost) {
461 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
466 vruntime = se->vruntime;
468 vruntime = min_vruntime(vruntime, se->vruntime);
471 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
474 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
479 * Enqueue an entity into the rb-tree:
481 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
483 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
484 struct rb_node *parent = NULL;
485 struct sched_entity *entry;
489 * Find the right place in the rbtree:
493 entry = rb_entry(parent, struct sched_entity, run_node);
495 * We dont care about collisions. Nodes with
496 * the same key stay together.
498 if (entity_before(se, entry)) {
499 link = &parent->rb_left;
501 link = &parent->rb_right;
507 * Maintain a cache of leftmost tree entries (it is frequently
511 cfs_rq->rb_leftmost = &se->run_node;
513 rb_link_node(&se->run_node, parent, link);
514 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
517 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
519 if (cfs_rq->rb_leftmost == &se->run_node) {
520 struct rb_node *next_node;
522 next_node = rb_next(&se->run_node);
523 cfs_rq->rb_leftmost = next_node;
526 rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
529 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
531 struct rb_node *left = cfs_rq->rb_leftmost;
536 return rb_entry(left, struct sched_entity, run_node);
539 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
541 struct rb_node *next = rb_next(&se->run_node);
546 return rb_entry(next, struct sched_entity, run_node);
549 #ifdef CONFIG_SCHED_DEBUG
550 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
552 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
557 return rb_entry(last, struct sched_entity, run_node);
560 /**************************************************************
561 * Scheduling class statistics methods:
564 int sched_proc_update_handler(struct ctl_table *table, int write,
565 void __user *buffer, size_t *lenp,
568 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
569 int factor = get_update_sysctl_factor();
574 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
575 sysctl_sched_min_granularity);
577 #define WRT_SYSCTL(name) \
578 (normalized_sysctl_##name = sysctl_##name / (factor))
579 WRT_SYSCTL(sched_min_granularity);
580 WRT_SYSCTL(sched_latency);
581 WRT_SYSCTL(sched_wakeup_granularity);
591 static inline unsigned long
592 calc_delta_fair(unsigned long delta, struct sched_entity *se)
594 if (unlikely(se->load.weight != NICE_0_LOAD))
595 delta = calc_delta_mine(delta, NICE_0_LOAD, &se->load);
601 * The idea is to set a period in which each task runs once.
603 * When there are too many tasks (sched_nr_latency) we have to stretch
604 * this period because otherwise the slices get too small.
606 * p = (nr <= nl) ? l : l*nr/nl
608 static u64 __sched_period(unsigned long nr_running)
610 u64 period = sysctl_sched_latency;
611 unsigned long nr_latency = sched_nr_latency;
613 if (unlikely(nr_running > nr_latency)) {
614 period = sysctl_sched_min_granularity;
615 period *= nr_running;
622 * We calculate the wall-time slice from the period by taking a part
623 * proportional to the weight.
627 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
629 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
631 for_each_sched_entity(se) {
632 struct load_weight *load;
633 struct load_weight lw;
635 cfs_rq = cfs_rq_of(se);
636 load = &cfs_rq->load;
638 if (unlikely(!se->on_rq)) {
641 update_load_add(&lw, se->load.weight);
644 slice = calc_delta_mine(slice, se->load.weight, load);
650 * We calculate the vruntime slice of a to be inserted task
654 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
656 return calc_delta_fair(sched_slice(cfs_rq, se), se);
659 static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update);
660 static void update_cfs_shares(struct cfs_rq *cfs_rq);
663 * Update the current task's runtime statistics. Skip current tasks that
664 * are not in our scheduling class.
667 __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
668 unsigned long delta_exec)
670 unsigned long delta_exec_weighted;
672 schedstat_set(curr->statistics.exec_max,
673 max((u64)delta_exec, curr->statistics.exec_max));
675 curr->sum_exec_runtime += delta_exec;
676 schedstat_add(cfs_rq, exec_clock, delta_exec);
677 delta_exec_weighted = calc_delta_fair(delta_exec, curr);
679 curr->vruntime += delta_exec_weighted;
680 update_min_vruntime(cfs_rq);
682 #if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
683 cfs_rq->load_unacc_exec_time += delta_exec;
687 static void update_curr(struct cfs_rq *cfs_rq)
689 struct sched_entity *curr = cfs_rq->curr;
690 u64 now = rq_of(cfs_rq)->clock_task;
691 unsigned long delta_exec;
697 * Get the amount of time the current task was running
698 * since the last time we changed load (this cannot
699 * overflow on 32 bits):
701 delta_exec = (unsigned long)(now - curr->exec_start);
705 __update_curr(cfs_rq, curr, delta_exec);
706 curr->exec_start = now;
708 if (entity_is_task(curr)) {
709 struct task_struct *curtask = task_of(curr);
711 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
712 cpuacct_charge(curtask, delta_exec);
713 account_group_exec_runtime(curtask, delta_exec);
716 account_cfs_rq_runtime(cfs_rq, delta_exec);
720 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
722 schedstat_set(se->statistics.wait_start, rq_of(cfs_rq)->clock);
726 * Task is being enqueued - update stats:
728 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
731 * Are we enqueueing a waiting task? (for current tasks
732 * a dequeue/enqueue event is a NOP)
734 if (se != cfs_rq->curr)
735 update_stats_wait_start(cfs_rq, se);
739 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
741 schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
742 rq_of(cfs_rq)->clock - se->statistics.wait_start));
743 schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
744 schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
745 rq_of(cfs_rq)->clock - se->statistics.wait_start);
746 #ifdef CONFIG_SCHEDSTATS
747 if (entity_is_task(se)) {
748 trace_sched_stat_wait(task_of(se),
749 rq_of(cfs_rq)->clock - se->statistics.wait_start);
752 schedstat_set(se->statistics.wait_start, 0);
756 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
759 * Mark the end of the wait period if dequeueing a
762 if (se != cfs_rq->curr)
763 update_stats_wait_end(cfs_rq, se);
767 * We are picking a new current task - update its stats:
770 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
773 * We are starting a new run period:
775 se->exec_start = rq_of(cfs_rq)->clock_task;
778 /**************************************************
779 * Scheduling class numa methods.
781 * The purpose of the NUMA bits are to maintain compute (task) and data
782 * (memory) locality. We try and achieve this by making tasks stick to
783 * a particular node (their home node) but if fairness mandates they run
784 * elsewhere for long enough, we let the memory follow them.
786 * Tasks start out with their home-node unset (-1) this effectively means
787 * they act !NUMA until we've established the task is busy enough to bother
790 * Once we start doing NUMA placement there's two modes, 'small' process-wide
791 * and 'big' per-task. For the small mode we have a process-wide home node
792 * and lazily mirgrate all memory only when this home-node changes.
794 * For big mode we keep a home-node per task and use periodic fault scans
795 * to try and estalish a task<->page relation. This assumes the task<->page
796 * relation is a compute<->data relation, this is false for things like virt.
797 * and n:m threading solutions but its the best we can do given the
798 * information we have.
801 static unsigned long task_h_load(struct task_struct *p);
803 #ifdef CONFIG_SCHED_NUMA
804 static void account_offnode_enqueue(struct rq *rq, struct task_struct *p)
806 p->numa_contrib = task_h_load(p);
807 rq->offnode_weight += p->numa_contrib;
808 rq->offnode_running++;
811 static void account_offnode_dequeue(struct rq *rq, struct task_struct *p)
813 rq->offnode_weight -= p->numa_contrib;
814 rq->offnode_running--;
818 * numa task sample period in ms: 2.5s
820 unsigned int sysctl_sched_numa_task_period = 2500;
823 * Determine if a process is 'big'.
825 * Currently only looks at CPU-time used, maybe we should also add an RSS
828 static bool task_numa_big(struct task_struct *p)
830 struct sched_domain *sd;
831 struct task_struct *t;
832 u64 walltime = local_clock();
836 if (sched_feat(NUMA_FORCE_BIG))
842 if (t->sched_class == &fair_sched_class)
843 runtime += t->se.sum_exec_runtime;
844 } while ((t = next_thread(t)) != p);
846 sd = rcu_dereference(__raw_get_cpu_var(sd_node));
848 weight = sd->span_weight;
851 runtime -= p->numa_runtime_stamp;
852 walltime -= p->numa_walltime_stamp;
854 p->numa_runtime_stamp += runtime;
855 p->numa_walltime_stamp += walltime;
858 * We're 'big' when we burn more than half a node's worth
861 return runtime > walltime * max(1, weight / 2);
864 static bool had_many_migrate_failures(struct task_struct *p)
866 /* More than 1/4 of the attempted NUMA page migrations failed. */
867 return p->mm->numa_migrate_failed * 3 > p->mm->numa_migrate_success;
870 static inline bool need_numa_migration(struct task_struct *p)
873 * We need to change our home-node, its been different for 2 samples.
874 * See the whole P(n)^2 story in task_tick_numa().
876 return p->node_curr == p->node_last && p->node != p->node_curr;
879 static void sched_setnode_process(struct task_struct *p, int node)
881 struct task_struct *t = p;
885 sched_setnode(t, node);
886 } while ((t = next_thread(t)) != p);
891 * The expensive part of numa migration is done from task_work context.
892 * Triggered from task_tick_numa().
894 void task_numa_work(struct callback_head *work)
896 unsigned long migrate, next_scan, now = jiffies;
897 struct task_struct *p = current;
901 WARN_ON_ONCE(p != container_of(work, struct task_struct, rcu));
904 * Who cares about NUMA placement when they're dying.
906 * NOTE: make sure not to dereference p->mm before this check,
907 * exit_task_work() happens _after_ exit_mm() so we could be called
908 * without p->mm even though we still had it when we enqueued this
911 if (p->flags & PF_EXITING)
914 big = p->mm->numa_big;
915 need_migration = need_numa_migration(p);
918 * Change per-task state before the process wide freq. throttle,
919 * otherwise it might be a long while ere this task wins the
920 * lottery and gets its home-node set.
922 if (big && need_migration)
923 sched_setnode(p, p->node_curr);
926 * Enforce maximal scan/migration frequency..
928 migrate = p->mm->numa_next_scan;
929 if (time_before(now, migrate))
932 next_scan = now + 2*msecs_to_jiffies(sysctl_sched_numa_task_period);
933 if (cmpxchg(&p->mm->numa_next_scan, migrate, next_scan) != migrate)
937 /* Age the numa migrate statistics. */
938 p->mm->numa_migrate_failed /= 2;
939 p->mm->numa_migrate_success /= 2;
941 big = p->mm->numa_big = task_numa_big(p);
944 if (need_migration) {
946 sched_setnode(p, p->node_curr);
948 sched_setnode_process(p, p->node_curr);
951 if (big || need_migration || had_many_migrate_failures(p))
952 lazy_migrate_process(p->mm);
956 * Sample task location from hardirq context (tick), this has minimal bias with
957 * obvious exceptions of frequency interference and tick avoidance techniques.
958 * If this were to become a problem we could move this sampling into the
959 * sleep/wakeup path -- but we'd prefer to avoid that for obvious reasons.
961 void task_tick_numa(struct rq *rq, struct task_struct *curr)
966 * We don't care about NUMA placement if we don't have memory.
972 * Sample our node location every @sysctl_sched_numa_task_period
973 * runtime ms. We use a two stage selection in order to filter
974 * unlikely locations.
976 * If P(n) is the probability we're on node 'n', then the probability
977 * we sample the same node twice is P(n)^2. This quadric squishes small
978 * values and makes it more likely we end up on nodes where we have
979 * significant presence.
981 * Using runtime rather than walltime has the dual advantage that
982 * we (mostly) drive the selection from busy threads and that the
983 * task needs to have done some actual work before we bother with
986 now = curr->se.sum_exec_runtime;
987 period = (u64)sysctl_sched_numa_task_period * NSEC_PER_MSEC;
989 if (now - curr->node_stamp > period) {
990 curr->node_stamp = now;
992 curr->node_last = curr->node_curr;
993 curr->node_curr = numa_node_id();
996 * We need to do expensive work to either migrate or
997 * drive priodic state update or scanning for 'big' processes.
999 if (need_numa_migration(curr) ||
1000 !time_before(jiffies, curr->mm->numa_next_scan)) {
1002 * We can re-use curr->rcu because we checked curr->mm
1003 * != NULL so release_task()->call_rcu() was not called
1004 * yet and exit_task_work() is called before
1007 init_task_work(&curr->rcu, task_numa_work);
1008 task_work_add(curr, &curr->rcu, true);
1013 static void account_offnode_enqueue(struct rq *rq, struct task_struct *p)
1017 static void account_offnode_dequeue(struct rq *rq, struct task_struct *p)
1021 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
1024 #endif /* CONFIG_SCHED_NUMA */
1026 /**************************************************
1027 * Scheduling class queueing methods:
1031 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
1033 update_load_add(&cfs_rq->load, se->load.weight);
1034 if (!parent_entity(se))
1035 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
1037 if (entity_is_task(se)) {
1038 struct rq *rq = rq_of(cfs_rq);
1039 struct task_struct *p = task_of(se);
1040 struct list_head *tasks = &rq->cfs_tasks;
1042 if (offnode_task(p)) {
1043 account_offnode_enqueue(rq, p);
1044 tasks = offnode_tasks(rq);
1047 list_add(&se->group_node, tasks);
1049 #endif /* CONFIG_SMP */
1050 cfs_rq->nr_running++;
1054 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
1056 update_load_sub(&cfs_rq->load, se->load.weight);
1057 if (!parent_entity(se))
1058 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
1059 if (entity_is_task(se)) {
1060 struct task_struct *p = task_of(se);
1062 list_del_init(&se->group_node);
1064 if (offnode_task(p))
1065 account_offnode_dequeue(rq_of(cfs_rq), p);
1067 cfs_rq->nr_running--;
1070 #ifdef CONFIG_FAIR_GROUP_SCHED
1071 /* we need this in update_cfs_load and load-balance functions below */
1072 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
1074 static void update_cfs_rq_load_contribution(struct cfs_rq *cfs_rq,
1077 struct task_group *tg = cfs_rq->tg;
1080 load_avg = div64_u64(cfs_rq->load_avg, cfs_rq->load_period+1);
1081 load_avg -= cfs_rq->load_contribution;
1083 if (global_update || abs(load_avg) > cfs_rq->load_contribution / 8) {
1084 atomic_add(load_avg, &tg->load_weight);
1085 cfs_rq->load_contribution += load_avg;
1089 static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
1091 u64 period = sysctl_sched_shares_window;
1093 unsigned long load = cfs_rq->load.weight;
1095 if (cfs_rq->tg == &root_task_group || throttled_hierarchy(cfs_rq))
1098 now = rq_of(cfs_rq)->clock_task;
1099 delta = now - cfs_rq->load_stamp;
1101 /* truncate load history at 4 idle periods */
1102 if (cfs_rq->load_stamp > cfs_rq->load_last &&
1103 now - cfs_rq->load_last > 4 * period) {
1104 cfs_rq->load_period = 0;
1105 cfs_rq->load_avg = 0;
1109 cfs_rq->load_stamp = now;
1110 cfs_rq->load_unacc_exec_time = 0;
1111 cfs_rq->load_period += delta;
1113 cfs_rq->load_last = now;
1114 cfs_rq->load_avg += delta * load;
1117 /* consider updating load contribution on each fold or truncate */
1118 if (global_update || cfs_rq->load_period > period
1119 || !cfs_rq->load_period)
1120 update_cfs_rq_load_contribution(cfs_rq, global_update);
1122 while (cfs_rq->load_period > period) {
1124 * Inline assembly required to prevent the compiler
1125 * optimising this loop into a divmod call.
1126 * See __iter_div_u64_rem() for another example of this.
1128 asm("" : "+rm" (cfs_rq->load_period));
1129 cfs_rq->load_period /= 2;
1130 cfs_rq->load_avg /= 2;
1133 if (!cfs_rq->curr && !cfs_rq->nr_running && !cfs_rq->load_avg)
1134 list_del_leaf_cfs_rq(cfs_rq);
1137 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
1142 * Use this CPU's actual weight instead of the last load_contribution
1143 * to gain a more accurate current total weight. See
1144 * update_cfs_rq_load_contribution().
1146 tg_weight = atomic_read(&tg->load_weight);
1147 tg_weight -= cfs_rq->load_contribution;
1148 tg_weight += cfs_rq->load.weight;
1153 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1155 long tg_weight, load, shares;
1157 tg_weight = calc_tg_weight(tg, cfs_rq);
1158 load = cfs_rq->load.weight;
1160 shares = (tg->shares * load);
1162 shares /= tg_weight;
1164 if (shares < MIN_SHARES)
1165 shares = MIN_SHARES;
1166 if (shares > tg->shares)
1167 shares = tg->shares;
1172 static void update_entity_shares_tick(struct cfs_rq *cfs_rq)
1174 if (cfs_rq->load_unacc_exec_time > sysctl_sched_shares_window) {
1175 update_cfs_load(cfs_rq, 0);
1176 update_cfs_shares(cfs_rq);
1179 # else /* CONFIG_SMP */
1180 static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
1184 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1189 static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
1192 # endif /* CONFIG_SMP */
1193 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
1194 unsigned long weight)
1197 /* commit outstanding execution time */
1198 if (cfs_rq->curr == se)
1199 update_curr(cfs_rq);
1200 account_entity_dequeue(cfs_rq, se);
1203 update_load_set(&se->load, weight);
1206 account_entity_enqueue(cfs_rq, se);
1209 static void update_cfs_shares(struct cfs_rq *cfs_rq)
1211 struct task_group *tg;
1212 struct sched_entity *se;
1216 se = tg->se[cpu_of(rq_of(cfs_rq))];
1217 if (!se || throttled_hierarchy(cfs_rq))
1220 if (likely(se->load.weight == tg->shares))
1223 shares = calc_cfs_shares(cfs_rq, tg);
1225 reweight_entity(cfs_rq_of(se), se, shares);
1227 #else /* CONFIG_FAIR_GROUP_SCHED */
1228 static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
1232 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
1236 static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
1239 #endif /* CONFIG_FAIR_GROUP_SCHED */
1241 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
1243 #ifdef CONFIG_SCHEDSTATS
1244 struct task_struct *tsk = NULL;
1246 if (entity_is_task(se))
1249 if (se->statistics.sleep_start) {
1250 u64 delta = rq_of(cfs_rq)->clock - se->statistics.sleep_start;
1255 if (unlikely(delta > se->statistics.sleep_max))
1256 se->statistics.sleep_max = delta;
1258 se->statistics.sleep_start = 0;
1259 se->statistics.sum_sleep_runtime += delta;
1262 account_scheduler_latency(tsk, delta >> 10, 1);
1263 trace_sched_stat_sleep(tsk, delta);
1266 if (se->statistics.block_start) {
1267 u64 delta = rq_of(cfs_rq)->clock - se->statistics.block_start;
1272 if (unlikely(delta > se->statistics.block_max))
1273 se->statistics.block_max = delta;
1275 se->statistics.block_start = 0;
1276 se->statistics.sum_sleep_runtime += delta;
1279 if (tsk->in_iowait) {
1280 se->statistics.iowait_sum += delta;
1281 se->statistics.iowait_count++;
1282 trace_sched_stat_iowait(tsk, delta);
1285 trace_sched_stat_blocked(tsk, delta);
1288 * Blocking time is in units of nanosecs, so shift by
1289 * 20 to get a milliseconds-range estimation of the
1290 * amount of time that the task spent sleeping:
1292 if (unlikely(prof_on == SLEEP_PROFILING)) {
1293 profile_hits(SLEEP_PROFILING,
1294 (void *)get_wchan(tsk),
1297 account_scheduler_latency(tsk, delta >> 10, 0);
1303 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
1305 #ifdef CONFIG_SCHED_DEBUG
1306 s64 d = se->vruntime - cfs_rq->min_vruntime;
1311 if (d > 3*sysctl_sched_latency)
1312 schedstat_inc(cfs_rq, nr_spread_over);
1317 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
1319 u64 vruntime = cfs_rq->min_vruntime;
1322 * The 'current' period is already promised to the current tasks,
1323 * however the extra weight of the new task will slow them down a
1324 * little, place the new task so that it fits in the slot that
1325 * stays open at the end.
1327 if (initial && sched_feat(START_DEBIT))
1328 vruntime += sched_vslice(cfs_rq, se);
1330 /* sleeps up to a single latency don't count. */
1332 unsigned long thresh = sysctl_sched_latency;
1335 * Halve their sleep time's effect, to allow
1336 * for a gentler effect of sleepers:
1338 if (sched_feat(GENTLE_FAIR_SLEEPERS))
1344 /* ensure we never gain time by being placed backwards. */
1345 vruntime = max_vruntime(se->vruntime, vruntime);
1347 se->vruntime = vruntime;
1350 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
1353 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1356 * Update the normalized vruntime before updating min_vruntime
1357 * through callig update_curr().
1359 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
1360 se->vruntime += cfs_rq->min_vruntime;
1363 * Update run-time statistics of the 'current'.
1365 update_curr(cfs_rq);
1366 update_cfs_load(cfs_rq, 0);
1367 account_entity_enqueue(cfs_rq, se);
1368 update_cfs_shares(cfs_rq);
1370 if (flags & ENQUEUE_WAKEUP) {
1371 place_entity(cfs_rq, se, 0);
1372 enqueue_sleeper(cfs_rq, se);
1375 update_stats_enqueue(cfs_rq, se);
1376 check_spread(cfs_rq, se);
1377 if (se != cfs_rq->curr)
1378 __enqueue_entity(cfs_rq, se);
1381 if (cfs_rq->nr_running == 1) {
1382 list_add_leaf_cfs_rq(cfs_rq);
1383 check_enqueue_throttle(cfs_rq);
1387 static void __clear_buddies_last(struct sched_entity *se)
1389 for_each_sched_entity(se) {
1390 struct cfs_rq *cfs_rq = cfs_rq_of(se);
1391 if (cfs_rq->last == se)
1392 cfs_rq->last = NULL;
1398 static void __clear_buddies_next(struct sched_entity *se)
1400 for_each_sched_entity(se) {
1401 struct cfs_rq *cfs_rq = cfs_rq_of(se);
1402 if (cfs_rq->next == se)
1403 cfs_rq->next = NULL;
1409 static void __clear_buddies_skip(struct sched_entity *se)
1411 for_each_sched_entity(se) {
1412 struct cfs_rq *cfs_rq = cfs_rq_of(se);
1413 if (cfs_rq->skip == se)
1414 cfs_rq->skip = NULL;
1420 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
1422 if (cfs_rq->last == se)
1423 __clear_buddies_last(se);
1425 if (cfs_rq->next == se)
1426 __clear_buddies_next(se);
1428 if (cfs_rq->skip == se)
1429 __clear_buddies_skip(se);
1432 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
1435 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1438 * Update run-time statistics of the 'current'.
1440 update_curr(cfs_rq);
1442 update_stats_dequeue(cfs_rq, se);
1443 if (flags & DEQUEUE_SLEEP) {
1444 #ifdef CONFIG_SCHEDSTATS
1445 if (entity_is_task(se)) {
1446 struct task_struct *tsk = task_of(se);
1448 if (tsk->state & TASK_INTERRUPTIBLE)
1449 se->statistics.sleep_start = rq_of(cfs_rq)->clock;
1450 if (tsk->state & TASK_UNINTERRUPTIBLE)
1451 se->statistics.block_start = rq_of(cfs_rq)->clock;
1456 clear_buddies(cfs_rq, se);
1458 if (se != cfs_rq->curr)
1459 __dequeue_entity(cfs_rq, se);
1461 update_cfs_load(cfs_rq, 0);
1462 account_entity_dequeue(cfs_rq, se);
1465 * Normalize the entity after updating the min_vruntime because the
1466 * update can refer to the ->curr item and we need to reflect this
1467 * movement in our normalized position.
1469 if (!(flags & DEQUEUE_SLEEP))
1470 se->vruntime -= cfs_rq->min_vruntime;
1472 /* return excess runtime on last dequeue */
1473 return_cfs_rq_runtime(cfs_rq);
1475 update_min_vruntime(cfs_rq);
1476 update_cfs_shares(cfs_rq);
1480 * Preempt the current task with a newly woken task if needed:
1483 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
1485 unsigned long ideal_runtime, delta_exec;
1486 struct sched_entity *se;
1489 ideal_runtime = sched_slice(cfs_rq, curr);
1490 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
1491 if (delta_exec > ideal_runtime) {
1492 resched_task(rq_of(cfs_rq)->curr);
1494 * The current task ran long enough, ensure it doesn't get
1495 * re-elected due to buddy favours.
1497 clear_buddies(cfs_rq, curr);
1502 * Ensure that a task that missed wakeup preemption by a
1503 * narrow margin doesn't have to wait for a full slice.
1504 * This also mitigates buddy induced latencies under load.
1506 if (delta_exec < sysctl_sched_min_granularity)
1509 se = __pick_first_entity(cfs_rq);
1510 delta = curr->vruntime - se->vruntime;
1515 if (delta > ideal_runtime)
1516 resched_task(rq_of(cfs_rq)->curr);
1520 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
1522 /* 'current' is not kept within the tree. */
1525 * Any task has to be enqueued before it get to execute on
1526 * a CPU. So account for the time it spent waiting on the
1529 update_stats_wait_end(cfs_rq, se);
1530 __dequeue_entity(cfs_rq, se);
1533 update_stats_curr_start(cfs_rq, se);
1535 #ifdef CONFIG_SCHEDSTATS
1537 * Track our maximum slice length, if the CPU's load is at
1538 * least twice that of our own weight (i.e. dont track it
1539 * when there are only lesser-weight tasks around):
1541 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
1542 se->statistics.slice_max = max(se->statistics.slice_max,
1543 se->sum_exec_runtime - se->prev_sum_exec_runtime);
1546 se->prev_sum_exec_runtime = se->sum_exec_runtime;
1550 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
1553 * Pick the next process, keeping these things in mind, in this order:
1554 * 1) keep things fair between processes/task groups
1555 * 2) pick the "next" process, since someone really wants that to run
1556 * 3) pick the "last" process, for cache locality
1557 * 4) do not run the "skip" process, if something else is available
1559 static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
1561 struct sched_entity *se = __pick_first_entity(cfs_rq);
1562 struct sched_entity *left = se;
1565 * Avoid running the skip buddy, if running something else can
1566 * be done without getting too unfair.
1568 if (cfs_rq->skip == se) {
1569 struct sched_entity *second = __pick_next_entity(se);
1570 if (second && wakeup_preempt_entity(second, left) < 1)
1575 * Prefer last buddy, try to return the CPU to a preempted task.
1577 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
1581 * Someone really wants this to run. If it's not unfair, run it.
1583 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
1586 clear_buddies(cfs_rq, se);
1591 static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
1593 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
1596 * If still on the runqueue then deactivate_task()
1597 * was not called and update_curr() has to be done:
1600 update_curr(cfs_rq);
1602 /* throttle cfs_rqs exceeding runtime */
1603 check_cfs_rq_runtime(cfs_rq);
1605 check_spread(cfs_rq, prev);
1607 update_stats_wait_start(cfs_rq, prev);
1608 /* Put 'current' back into the tree. */
1609 __enqueue_entity(cfs_rq, prev);
1611 cfs_rq->curr = NULL;
1615 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
1618 * Update run-time statistics of the 'current'.
1620 update_curr(cfs_rq);
1623 * Update share accounting for long-running entities.
1625 update_entity_shares_tick(cfs_rq);
1627 #ifdef CONFIG_SCHED_HRTICK
1629 * queued ticks are scheduled to match the slice, so don't bother
1630 * validating it and just reschedule.
1633 resched_task(rq_of(cfs_rq)->curr);
1637 * don't let the period tick interfere with the hrtick preemption
1639 if (!sched_feat(DOUBLE_TICK) &&
1640 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
1644 if (cfs_rq->nr_running > 1)
1645 check_preempt_tick(cfs_rq, curr);
1649 /**************************************************
1650 * CFS bandwidth control machinery
1653 #ifdef CONFIG_CFS_BANDWIDTH
1655 #ifdef HAVE_JUMP_LABEL
1656 static struct static_key __cfs_bandwidth_used;
1658 static inline bool cfs_bandwidth_used(void)
1660 return static_key_false(&__cfs_bandwidth_used);
1663 void account_cfs_bandwidth_used(int enabled, int was_enabled)
1665 /* only need to count groups transitioning between enabled/!enabled */
1666 if (enabled && !was_enabled)
1667 static_key_slow_inc(&__cfs_bandwidth_used);
1668 else if (!enabled && was_enabled)
1669 static_key_slow_dec(&__cfs_bandwidth_used);
1671 #else /* HAVE_JUMP_LABEL */
1672 static bool cfs_bandwidth_used(void)
1677 void account_cfs_bandwidth_used(int enabled, int was_enabled) {}
1678 #endif /* HAVE_JUMP_LABEL */
1681 * default period for cfs group bandwidth.
1682 * default: 0.1s, units: nanoseconds
1684 static inline u64 default_cfs_period(void)
1686 return 100000000ULL;
1689 static inline u64 sched_cfs_bandwidth_slice(void)
1691 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
1695 * Replenish runtime according to assigned quota and update expiration time.
1696 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
1697 * additional synchronization around rq->lock.
1699 * requires cfs_b->lock
1701 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
1705 if (cfs_b->quota == RUNTIME_INF)
1708 now = sched_clock_cpu(smp_processor_id());
1709 cfs_b->runtime = cfs_b->quota;
1710 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
1713 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
1715 return &tg->cfs_bandwidth;
1718 /* returns 0 on failure to allocate runtime */
1719 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
1721 struct task_group *tg = cfs_rq->tg;
1722 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
1723 u64 amount = 0, min_amount, expires;
1725 /* note: this is a positive sum as runtime_remaining <= 0 */
1726 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
1728 raw_spin_lock(&cfs_b->lock);
1729 if (cfs_b->quota == RUNTIME_INF)
1730 amount = min_amount;
1733 * If the bandwidth pool has become inactive, then at least one
1734 * period must have elapsed since the last consumption.
1735 * Refresh the global state and ensure bandwidth timer becomes
1738 if (!cfs_b->timer_active) {
1739 __refill_cfs_bandwidth_runtime(cfs_b);
1740 __start_cfs_bandwidth(cfs_b);
1743 if (cfs_b->runtime > 0) {
1744 amount = min(cfs_b->runtime, min_amount);
1745 cfs_b->runtime -= amount;
1749 expires = cfs_b->runtime_expires;
1750 raw_spin_unlock(&cfs_b->lock);
1752 cfs_rq->runtime_remaining += amount;
1754 * we may have advanced our local expiration to account for allowed
1755 * spread between our sched_clock and the one on which runtime was
1758 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
1759 cfs_rq->runtime_expires = expires;
1761 return cfs_rq->runtime_remaining > 0;
1765 * Note: This depends on the synchronization provided by sched_clock and the
1766 * fact that rq->clock snapshots this value.
1768 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
1770 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
1771 struct rq *rq = rq_of(cfs_rq);
1773 /* if the deadline is ahead of our clock, nothing to do */
1774 if (likely((s64)(rq->clock - cfs_rq->runtime_expires) < 0))
1777 if (cfs_rq->runtime_remaining < 0)
1781 * If the local deadline has passed we have to consider the
1782 * possibility that our sched_clock is 'fast' and the global deadline
1783 * has not truly expired.
1785 * Fortunately we can check determine whether this the case by checking
1786 * whether the global deadline has advanced.
1789 if ((s64)(cfs_rq->runtime_expires - cfs_b->runtime_expires) >= 0) {
1790 /* extend local deadline, drift is bounded above by 2 ticks */
1791 cfs_rq->runtime_expires += TICK_NSEC;
1793 /* global deadline is ahead, expiration has passed */
1794 cfs_rq->runtime_remaining = 0;
1798 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
1799 unsigned long delta_exec)
1801 /* dock delta_exec before expiring quota (as it could span periods) */
1802 cfs_rq->runtime_remaining -= delta_exec;
1803 expire_cfs_rq_runtime(cfs_rq);
1805 if (likely(cfs_rq->runtime_remaining > 0))
1809 * if we're unable to extend our runtime we resched so that the active
1810 * hierarchy can be throttled
1812 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
1813 resched_task(rq_of(cfs_rq)->curr);
1816 static __always_inline
1817 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec)
1819 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
1822 __account_cfs_rq_runtime(cfs_rq, delta_exec);
1825 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
1827 return cfs_bandwidth_used() && cfs_rq->throttled;
1830 /* check whether cfs_rq, or any parent, is throttled */
1831 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
1833 return cfs_bandwidth_used() && cfs_rq->throttle_count;
1837 * Ensure that neither of the group entities corresponding to src_cpu or
1838 * dest_cpu are members of a throttled hierarchy when performing group
1839 * load-balance operations.
1841 static inline int throttled_lb_pair(struct task_group *tg,
1842 int src_cpu, int dest_cpu)
1844 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
1846 src_cfs_rq = tg->cfs_rq[src_cpu];
1847 dest_cfs_rq = tg->cfs_rq[dest_cpu];
1849 return throttled_hierarchy(src_cfs_rq) ||
1850 throttled_hierarchy(dest_cfs_rq);
1853 /* updated child weight may affect parent so we have to do this bottom up */
1854 static int tg_unthrottle_up(struct task_group *tg, void *data)
1856 struct rq *rq = data;
1857 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
1859 cfs_rq->throttle_count--;
1861 if (!cfs_rq->throttle_count) {
1862 u64 delta = rq->clock_task - cfs_rq->load_stamp;
1864 /* leaving throttled state, advance shares averaging windows */
1865 cfs_rq->load_stamp += delta;
1866 cfs_rq->load_last += delta;
1868 /* update entity weight now that we are on_rq again */
1869 update_cfs_shares(cfs_rq);
1876 static int tg_throttle_down(struct task_group *tg, void *data)
1878 struct rq *rq = data;
1879 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
1881 /* group is entering throttled state, record last load */
1882 if (!cfs_rq->throttle_count)
1883 update_cfs_load(cfs_rq, 0);
1884 cfs_rq->throttle_count++;
1889 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
1891 struct rq *rq = rq_of(cfs_rq);
1892 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
1893 struct sched_entity *se;
1894 long task_delta, dequeue = 1;
1896 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
1898 /* account load preceding throttle */
1900 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
1903 task_delta = cfs_rq->h_nr_running;
1904 for_each_sched_entity(se) {
1905 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
1906 /* throttled entity or throttle-on-deactivate */
1911 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
1912 qcfs_rq->h_nr_running -= task_delta;
1914 if (qcfs_rq->load.weight)
1919 rq->nr_running -= task_delta;
1921 cfs_rq->throttled = 1;
1922 cfs_rq->throttled_timestamp = rq->clock;
1923 raw_spin_lock(&cfs_b->lock);
1924 list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
1925 raw_spin_unlock(&cfs_b->lock);
1928 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
1930 struct rq *rq = rq_of(cfs_rq);
1931 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
1932 struct sched_entity *se;
1936 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
1938 cfs_rq->throttled = 0;
1939 raw_spin_lock(&cfs_b->lock);
1940 cfs_b->throttled_time += rq->clock - cfs_rq->throttled_timestamp;
1941 list_del_rcu(&cfs_rq->throttled_list);
1942 raw_spin_unlock(&cfs_b->lock);
1943 cfs_rq->throttled_timestamp = 0;
1945 update_rq_clock(rq);
1946 /* update hierarchical throttle state */
1947 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
1949 if (!cfs_rq->load.weight)
1952 task_delta = cfs_rq->h_nr_running;
1953 for_each_sched_entity(se) {
1957 cfs_rq = cfs_rq_of(se);
1959 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
1960 cfs_rq->h_nr_running += task_delta;
1962 if (cfs_rq_throttled(cfs_rq))
1967 rq->nr_running += task_delta;
1969 /* determine whether we need to wake up potentially idle cpu */
1970 if (rq->curr == rq->idle && rq->cfs.nr_running)
1971 resched_task(rq->curr);
1974 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
1975 u64 remaining, u64 expires)
1977 struct cfs_rq *cfs_rq;
1978 u64 runtime = remaining;
1981 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
1983 struct rq *rq = rq_of(cfs_rq);
1985 raw_spin_lock(&rq->lock);
1986 if (!cfs_rq_throttled(cfs_rq))
1989 runtime = -cfs_rq->runtime_remaining + 1;
1990 if (runtime > remaining)
1991 runtime = remaining;
1992 remaining -= runtime;
1994 cfs_rq->runtime_remaining += runtime;
1995 cfs_rq->runtime_expires = expires;
1997 /* we check whether we're throttled above */
1998 if (cfs_rq->runtime_remaining > 0)
1999 unthrottle_cfs_rq(cfs_rq);
2002 raw_spin_unlock(&rq->lock);
2013 * Responsible for refilling a task_group's bandwidth and unthrottling its
2014 * cfs_rqs as appropriate. If there has been no activity within the last
2015 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
2016 * used to track this state.
2018 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
2020 u64 runtime, runtime_expires;
2021 int idle = 1, throttled;
2023 raw_spin_lock(&cfs_b->lock);
2024 /* no need to continue the timer with no bandwidth constraint */
2025 if (cfs_b->quota == RUNTIME_INF)
2028 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
2029 /* idle depends on !throttled (for the case of a large deficit) */
2030 idle = cfs_b->idle && !throttled;
2031 cfs_b->nr_periods += overrun;
2033 /* if we're going inactive then everything else can be deferred */
2037 __refill_cfs_bandwidth_runtime(cfs_b);
2040 /* mark as potentially idle for the upcoming period */
2045 /* account preceding periods in which throttling occurred */
2046 cfs_b->nr_throttled += overrun;
2049 * There are throttled entities so we must first use the new bandwidth
2050 * to unthrottle them before making it generally available. This
2051 * ensures that all existing debts will be paid before a new cfs_rq is
2054 runtime = cfs_b->runtime;
2055 runtime_expires = cfs_b->runtime_expires;
2059 * This check is repeated as we are holding onto the new bandwidth
2060 * while we unthrottle. This can potentially race with an unthrottled
2061 * group trying to acquire new bandwidth from the global pool.
2063 while (throttled && runtime > 0) {
2064 raw_spin_unlock(&cfs_b->lock);
2065 /* we can't nest cfs_b->lock while distributing bandwidth */
2066 runtime = distribute_cfs_runtime(cfs_b, runtime,
2068 raw_spin_lock(&cfs_b->lock);
2070 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
2073 /* return (any) remaining runtime */
2074 cfs_b->runtime = runtime;
2076 * While we are ensured activity in the period following an
2077 * unthrottle, this also covers the case in which the new bandwidth is
2078 * insufficient to cover the existing bandwidth deficit. (Forcing the
2079 * timer to remain active while there are any throttled entities.)
2084 cfs_b->timer_active = 0;
2085 raw_spin_unlock(&cfs_b->lock);
2090 /* a cfs_rq won't donate quota below this amount */
2091 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
2092 /* minimum remaining period time to redistribute slack quota */
2093 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
2094 /* how long we wait to gather additional slack before distributing */
2095 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
2097 /* are we near the end of the current quota period? */
2098 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
2100 struct hrtimer *refresh_timer = &cfs_b->period_timer;
2103 /* if the call-back is running a quota refresh is already occurring */
2104 if (hrtimer_callback_running(refresh_timer))
2107 /* is a quota refresh about to occur? */
2108 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
2109 if (remaining < min_expire)
2115 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
2117 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
2119 /* if there's a quota refresh soon don't bother with slack */
2120 if (runtime_refresh_within(cfs_b, min_left))
2123 start_bandwidth_timer(&cfs_b->slack_timer,
2124 ns_to_ktime(cfs_bandwidth_slack_period));
2127 /* we know any runtime found here is valid as update_curr() precedes return */
2128 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2130 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
2131 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
2133 if (slack_runtime <= 0)
2136 raw_spin_lock(&cfs_b->lock);
2137 if (cfs_b->quota != RUNTIME_INF &&
2138 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
2139 cfs_b->runtime += slack_runtime;
2141 /* we are under rq->lock, defer unthrottling using a timer */
2142 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
2143 !list_empty(&cfs_b->throttled_cfs_rq))
2144 start_cfs_slack_bandwidth(cfs_b);
2146 raw_spin_unlock(&cfs_b->lock);
2148 /* even if it's not valid for return we don't want to try again */
2149 cfs_rq->runtime_remaining -= slack_runtime;
2152 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2154 if (!cfs_bandwidth_used())
2157 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
2160 __return_cfs_rq_runtime(cfs_rq);
2164 * This is done with a timer (instead of inline with bandwidth return) since
2165 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
2167 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
2169 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
2172 /* confirm we're still not at a refresh boundary */
2173 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration))
2176 raw_spin_lock(&cfs_b->lock);
2177 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
2178 runtime = cfs_b->runtime;
2181 expires = cfs_b->runtime_expires;
2182 raw_spin_unlock(&cfs_b->lock);
2187 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
2189 raw_spin_lock(&cfs_b->lock);
2190 if (expires == cfs_b->runtime_expires)
2191 cfs_b->runtime = runtime;
2192 raw_spin_unlock(&cfs_b->lock);
2196 * When a group wakes up we want to make sure that its quota is not already
2197 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
2198 * runtime as update_curr() throttling can not not trigger until it's on-rq.
2200 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
2202 if (!cfs_bandwidth_used())
2205 /* an active group must be handled by the update_curr()->put() path */
2206 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
2209 /* ensure the group is not already throttled */
2210 if (cfs_rq_throttled(cfs_rq))
2213 /* update runtime allocation */
2214 account_cfs_rq_runtime(cfs_rq, 0);
2215 if (cfs_rq->runtime_remaining <= 0)
2216 throttle_cfs_rq(cfs_rq);
2219 /* conditionally throttle active cfs_rq's from put_prev_entity() */
2220 static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2222 if (!cfs_bandwidth_used())
2225 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
2229 * it's possible for a throttled entity to be forced into a running
2230 * state (e.g. set_curr_task), in this case we're finished.
2232 if (cfs_rq_throttled(cfs_rq))
2235 throttle_cfs_rq(cfs_rq);
2238 static inline u64 default_cfs_period(void);
2239 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun);
2240 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b);
2242 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
2244 struct cfs_bandwidth *cfs_b =
2245 container_of(timer, struct cfs_bandwidth, slack_timer);
2246 do_sched_cfs_slack_timer(cfs_b);
2248 return HRTIMER_NORESTART;
2251 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
2253 struct cfs_bandwidth *cfs_b =
2254 container_of(timer, struct cfs_bandwidth, period_timer);
2260 now = hrtimer_cb_get_time(timer);
2261 overrun = hrtimer_forward(timer, now, cfs_b->period);
2266 idle = do_sched_cfs_period_timer(cfs_b, overrun);
2269 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
2272 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
2274 raw_spin_lock_init(&cfs_b->lock);
2276 cfs_b->quota = RUNTIME_INF;
2277 cfs_b->period = ns_to_ktime(default_cfs_period());
2279 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
2280 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
2281 cfs_b->period_timer.function = sched_cfs_period_timer;
2282 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
2283 cfs_b->slack_timer.function = sched_cfs_slack_timer;
2286 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2288 cfs_rq->runtime_enabled = 0;
2289 INIT_LIST_HEAD(&cfs_rq->throttled_list);
2292 /* requires cfs_b->lock, may release to reprogram timer */
2293 void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
2296 * The timer may be active because we're trying to set a new bandwidth
2297 * period or because we're racing with the tear-down path
2298 * (timer_active==0 becomes visible before the hrtimer call-back
2299 * terminates). In either case we ensure that it's re-programmed
2301 while (unlikely(hrtimer_active(&cfs_b->period_timer))) {
2302 raw_spin_unlock(&cfs_b->lock);
2303 /* ensure cfs_b->lock is available while we wait */
2304 hrtimer_cancel(&cfs_b->period_timer);
2306 raw_spin_lock(&cfs_b->lock);
2307 /* if someone else restarted the timer then we're done */
2308 if (cfs_b->timer_active)
2312 cfs_b->timer_active = 1;
2313 start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period);
2316 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
2318 hrtimer_cancel(&cfs_b->period_timer);
2319 hrtimer_cancel(&cfs_b->slack_timer);
2322 static void unthrottle_offline_cfs_rqs(struct rq *rq)
2324 struct cfs_rq *cfs_rq;
2326 for_each_leaf_cfs_rq(rq, cfs_rq) {
2327 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
2329 if (!cfs_rq->runtime_enabled)
2333 * clock_task is not advancing so we just need to make sure
2334 * there's some valid quota amount
2336 cfs_rq->runtime_remaining = cfs_b->quota;
2337 if (cfs_rq_throttled(cfs_rq))
2338 unthrottle_cfs_rq(cfs_rq);
2342 #else /* CONFIG_CFS_BANDWIDTH */
2343 static __always_inline
2344 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec) {}
2345 static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
2346 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
2347 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
2349 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
2354 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
2359 static inline int throttled_lb_pair(struct task_group *tg,
2360 int src_cpu, int dest_cpu)
2365 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
2367 #ifdef CONFIG_FAIR_GROUP_SCHED
2368 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
2371 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
2375 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
2376 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
2378 #endif /* CONFIG_CFS_BANDWIDTH */
2380 /**************************************************
2381 * CFS operations on tasks:
2384 #ifdef CONFIG_SCHED_HRTICK
2385 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
2387 struct sched_entity *se = &p->se;
2388 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2390 WARN_ON(task_rq(p) != rq);
2392 if (cfs_rq->nr_running > 1) {
2393 u64 slice = sched_slice(cfs_rq, se);
2394 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
2395 s64 delta = slice - ran;
2404 * Don't schedule slices shorter than 10000ns, that just
2405 * doesn't make sense. Rely on vruntime for fairness.
2408 delta = max_t(s64, 10000LL, delta);
2410 hrtick_start(rq, delta);
2415 * called from enqueue/dequeue and updates the hrtick when the
2416 * current task is from our class and nr_running is low enough
2419 static void hrtick_update(struct rq *rq)
2421 struct task_struct *curr = rq->curr;
2423 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
2426 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
2427 hrtick_start_fair(rq, curr);
2429 #else /* !CONFIG_SCHED_HRTICK */
2431 hrtick_start_fair(struct rq *rq, struct task_struct *p)
2435 static inline void hrtick_update(struct rq *rq)
2441 * The enqueue_task method is called before nr_running is
2442 * increased. Here we update the fair scheduling stats and
2443 * then put the task into the rbtree:
2446 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
2448 struct cfs_rq *cfs_rq;
2449 struct sched_entity *se = &p->se;
2451 for_each_sched_entity(se) {
2454 cfs_rq = cfs_rq_of(se);
2455 enqueue_entity(cfs_rq, se, flags);
2458 * end evaluation on encountering a throttled cfs_rq
2460 * note: in the case of encountering a throttled cfs_rq we will
2461 * post the final h_nr_running increment below.
2463 if (cfs_rq_throttled(cfs_rq))
2465 cfs_rq->h_nr_running++;
2467 flags = ENQUEUE_WAKEUP;
2470 for_each_sched_entity(se) {
2471 cfs_rq = cfs_rq_of(se);
2472 cfs_rq->h_nr_running++;
2474 if (cfs_rq_throttled(cfs_rq))
2477 update_cfs_load(cfs_rq, 0);
2478 update_cfs_shares(cfs_rq);
2486 static void set_next_buddy(struct sched_entity *se);
2489 * The dequeue_task method is called before nr_running is
2490 * decreased. We remove the task from the rbtree and
2491 * update the fair scheduling stats:
2493 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
2495 struct cfs_rq *cfs_rq;
2496 struct sched_entity *se = &p->se;
2497 int task_sleep = flags & DEQUEUE_SLEEP;
2499 for_each_sched_entity(se) {
2500 cfs_rq = cfs_rq_of(se);
2501 dequeue_entity(cfs_rq, se, flags);
2504 * end evaluation on encountering a throttled cfs_rq
2506 * note: in the case of encountering a throttled cfs_rq we will
2507 * post the final h_nr_running decrement below.
2509 if (cfs_rq_throttled(cfs_rq))
2511 cfs_rq->h_nr_running--;
2513 /* Don't dequeue parent if it has other entities besides us */
2514 if (cfs_rq->load.weight) {
2516 * Bias pick_next to pick a task from this cfs_rq, as
2517 * p is sleeping when it is within its sched_slice.
2519 if (task_sleep && parent_entity(se))
2520 set_next_buddy(parent_entity(se));
2522 /* avoid re-evaluating load for this entity */
2523 se = parent_entity(se);
2526 flags |= DEQUEUE_SLEEP;
2529 for_each_sched_entity(se) {
2530 cfs_rq = cfs_rq_of(se);
2531 cfs_rq->h_nr_running--;
2533 if (cfs_rq_throttled(cfs_rq))
2536 update_cfs_load(cfs_rq, 0);
2537 update_cfs_shares(cfs_rq);
2546 /* Used instead of source_load when we know the type == 0 */
2547 static unsigned long weighted_cpuload(const int cpu)
2549 return cpu_rq(cpu)->load.weight;
2553 * Return a low guess at the load of a migration-source cpu weighted
2554 * according to the scheduling class and "nice" value.
2556 * We want to under-estimate the load of migration sources, to
2557 * balance conservatively.
2559 static unsigned long source_load(int cpu, int type)
2561 struct rq *rq = cpu_rq(cpu);
2562 unsigned long total = weighted_cpuload(cpu);
2564 if (type == 0 || !sched_feat(LB_BIAS))
2567 return min(rq->cpu_load[type-1], total);
2571 * Return a high guess at the load of a migration-target cpu weighted
2572 * according to the scheduling class and "nice" value.
2574 static unsigned long target_load(int cpu, int type)
2576 struct rq *rq = cpu_rq(cpu);
2577 unsigned long total = weighted_cpuload(cpu);
2579 if (type == 0 || !sched_feat(LB_BIAS))
2582 return max(rq->cpu_load[type-1], total);
2585 static unsigned long power_of(int cpu)
2587 return cpu_rq(cpu)->cpu_power;
2590 static unsigned long cpu_avg_load_per_task(int cpu)
2592 struct rq *rq = cpu_rq(cpu);
2593 unsigned long nr_running = ACCESS_ONCE(rq->nr_running);
2596 return rq->load.weight / nr_running;
2602 static void task_waking_fair(struct task_struct *p)
2604 struct sched_entity *se = &p->se;
2605 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2608 #ifndef CONFIG_64BIT
2609 u64 min_vruntime_copy;
2612 min_vruntime_copy = cfs_rq->min_vruntime_copy;
2614 min_vruntime = cfs_rq->min_vruntime;
2615 } while (min_vruntime != min_vruntime_copy);
2617 min_vruntime = cfs_rq->min_vruntime;
2620 se->vruntime -= min_vruntime;
2623 #ifdef CONFIG_FAIR_GROUP_SCHED
2625 * effective_load() calculates the load change as seen from the root_task_group
2627 * Adding load to a group doesn't make a group heavier, but can cause movement
2628 * of group shares between cpus. Assuming the shares were perfectly aligned one
2629 * can calculate the shift in shares.
2631 * Calculate the effective load difference if @wl is added (subtracted) to @tg
2632 * on this @cpu and results in a total addition (subtraction) of @wg to the
2633 * total group weight.
2635 * Given a runqueue weight distribution (rw_i) we can compute a shares
2636 * distribution (s_i) using:
2638 * s_i = rw_i / \Sum rw_j (1)
2640 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
2641 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
2642 * shares distribution (s_i):
2644 * rw_i = { 2, 4, 1, 0 }
2645 * s_i = { 2/7, 4/7, 1/7, 0 }
2647 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
2648 * task used to run on and the CPU the waker is running on), we need to
2649 * compute the effect of waking a task on either CPU and, in case of a sync
2650 * wakeup, compute the effect of the current task going to sleep.
2652 * So for a change of @wl to the local @cpu with an overall group weight change
2653 * of @wl we can compute the new shares distribution (s'_i) using:
2655 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
2657 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
2658 * differences in waking a task to CPU 0. The additional task changes the
2659 * weight and shares distributions like:
2661 * rw'_i = { 3, 4, 1, 0 }
2662 * s'_i = { 3/8, 4/8, 1/8, 0 }
2664 * We can then compute the difference in effective weight by using:
2666 * dw_i = S * (s'_i - s_i) (3)
2668 * Where 'S' is the group weight as seen by its parent.
2670 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
2671 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
2672 * 4/7) times the weight of the group.
2674 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
2676 struct sched_entity *se = tg->se[cpu];
2678 if (!tg->parent) /* the trivial, non-cgroup case */
2681 for_each_sched_entity(se) {
2687 * W = @wg + \Sum rw_j
2689 W = wg + calc_tg_weight(tg, se->my_q);
2694 w = se->my_q->load.weight + wl;
2697 * wl = S * s'_i; see (2)
2700 wl = (w * tg->shares) / W;
2705 * Per the above, wl is the new se->load.weight value; since
2706 * those are clipped to [MIN_SHARES, ...) do so now. See
2707 * calc_cfs_shares().
2709 if (wl < MIN_SHARES)
2713 * wl = dw_i = S * (s'_i - s_i); see (3)
2715 wl -= se->load.weight;
2718 * Recursively apply this logic to all parent groups to compute
2719 * the final effective load change on the root group. Since
2720 * only the @tg group gets extra weight, all parent groups can
2721 * only redistribute existing shares. @wl is the shift in shares
2722 * resulting from this level per the above.
2731 static inline unsigned long effective_load(struct task_group *tg, int cpu,
2732 unsigned long wl, unsigned long wg)
2739 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
2741 s64 this_load, load;
2742 int idx, this_cpu, prev_cpu;
2743 unsigned long tl_per_task;
2744 struct task_group *tg;
2745 unsigned long weight;
2749 this_cpu = smp_processor_id();
2750 prev_cpu = task_cpu(p);
2751 load = source_load(prev_cpu, idx);
2752 this_load = target_load(this_cpu, idx);
2755 * If sync wakeup then subtract the (maximum possible)
2756 * effect of the currently running task from the load
2757 * of the current CPU:
2760 tg = task_group(current);
2761 weight = current->se.load.weight;
2763 this_load += effective_load(tg, this_cpu, -weight, -weight);
2764 load += effective_load(tg, prev_cpu, 0, -weight);
2768 weight = p->se.load.weight;
2771 * In low-load situations, where prev_cpu is idle and this_cpu is idle
2772 * due to the sync cause above having dropped this_load to 0, we'll
2773 * always have an imbalance, but there's really nothing you can do
2774 * about that, so that's good too.
2776 * Otherwise check if either cpus are near enough in load to allow this
2777 * task to be woken on this_cpu.
2779 if (this_load > 0) {
2780 s64 this_eff_load, prev_eff_load;
2782 this_eff_load = 100;
2783 this_eff_load *= power_of(prev_cpu);
2784 this_eff_load *= this_load +
2785 effective_load(tg, this_cpu, weight, weight);
2787 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
2788 prev_eff_load *= power_of(this_cpu);
2789 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
2791 balanced = this_eff_load <= prev_eff_load;
2796 * If the currently running task will sleep within
2797 * a reasonable amount of time then attract this newly
2800 if (sync && balanced)
2803 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
2804 tl_per_task = cpu_avg_load_per_task(this_cpu);
2807 (this_load <= load &&
2808 this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
2810 * This domain has SD_WAKE_AFFINE and
2811 * p is cache cold in this domain, and
2812 * there is no bad imbalance.
2814 schedstat_inc(sd, ttwu_move_affine);
2815 schedstat_inc(p, se.statistics.nr_wakeups_affine);
2823 * find_idlest_group finds and returns the least busy CPU group within the
2826 static struct sched_group *
2827 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
2828 int this_cpu, int load_idx)
2830 struct sched_group *idlest = NULL, *group = sd->groups;
2831 unsigned long min_load = ULONG_MAX, this_load = 0;
2832 int imbalance = 100 + (sd->imbalance_pct-100)/2;
2835 unsigned long load, avg_load;
2839 /* Skip over this group if it has no CPUs allowed */
2840 if (!cpumask_intersects(sched_group_cpus(group),
2841 tsk_cpus_allowed(p)))
2844 local_group = cpumask_test_cpu(this_cpu,
2845 sched_group_cpus(group));
2847 /* Tally up the load of all CPUs in the group */
2850 for_each_cpu(i, sched_group_cpus(group)) {
2851 /* Bias balancing toward cpus of our domain */
2853 load = source_load(i, load_idx);
2855 load = target_load(i, load_idx);
2860 /* Adjust by relative CPU power of the group */
2861 avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power;
2864 this_load = avg_load;
2865 } else if (avg_load < min_load) {
2866 min_load = avg_load;
2869 } while (group = group->next, group != sd->groups);
2871 if (!idlest || 100*this_load < imbalance*min_load)
2877 * find_idlest_cpu - find the idlest cpu among the cpus in group.
2880 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
2882 unsigned long load, min_load = ULONG_MAX;
2886 /* Traverse only the allowed CPUs */
2887 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
2888 load = weighted_cpuload(i);
2890 if (load < min_load || (load == min_load && i == this_cpu)) {
2900 * Try and locate an idle CPU in the sched_domain.
2902 static int select_idle_sibling(struct task_struct *p, int target)
2904 int cpu = smp_processor_id();
2905 int prev_cpu = task_cpu(p);
2906 struct sched_domain *sd;
2907 struct sched_group *sg;
2911 * If the task is going to be woken-up on this cpu and if it is
2912 * already idle, then it is the right target.
2914 if (target == cpu && idle_cpu(cpu))
2918 * If the task is going to be woken-up on the cpu where it previously
2919 * ran and if it is currently idle, then it the right target.
2921 if (target == prev_cpu && idle_cpu(prev_cpu))
2925 * Otherwise, iterate the domains and find an elegible idle cpu.
2927 sd = rcu_dereference(per_cpu(sd_llc, target));
2928 for_each_lower_domain(sd) {
2931 if (!cpumask_intersects(sched_group_cpus(sg),
2932 tsk_cpus_allowed(p)))
2935 for_each_cpu(i, sched_group_cpus(sg)) {
2940 target = cpumask_first_and(sched_group_cpus(sg),
2941 tsk_cpus_allowed(p));
2945 } while (sg != sd->groups);
2951 #ifdef CONFIG_SCHED_NUMA
2952 static inline bool pick_numa_rand(int n)
2954 return !(get_random_int() % n);
2958 * Pick a random elegible CPU in the target node, hopefully faster
2959 * than doing a least-loaded scan.
2961 static int numa_select_node_cpu(struct task_struct *p, int node)
2963 int weight = cpumask_weight(cpumask_of_node(node));
2966 for_each_cpu_and(i, cpumask_of_node(node), tsk_cpus_allowed(p)) {
2967 if (cpu < 0 || pick_numa_rand(weight))
2974 static int numa_select_node_cpu(struct task_struct *p, int node)
2978 #endif /* CONFIG_SCHED_NUMA */
2981 * sched_balance_self: balance the current task (running on cpu) in domains
2982 * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
2985 * Balance, ie. select the least loaded group.
2987 * Returns the target CPU number, or the same CPU if no balancing is needed.
2989 * preempt must be disabled.
2992 select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
2994 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
2995 int cpu = smp_processor_id();
2996 int prev_cpu = task_cpu(p);
2998 int want_affine = 0;
2999 int sync = wake_flags & WF_SYNC;
3000 int node = tsk_home_node(p);
3002 if (p->nr_cpus_allowed == 1)
3005 if (sd_flag & SD_BALANCE_WAKE) {
3006 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
3012 if (sched_feat_numa(NUMA_BIAS) && node != -1) {
3014 * For fork,exec find the idlest cpu in the home-node.
3016 if (sd_flag & (SD_BALANCE_FORK|SD_BALANCE_EXEC)) {
3017 int node_cpu = numa_select_node_cpu(p, node);
3021 new_cpu = cpu = node_cpu;
3022 sd = per_cpu(sd_node, cpu);
3027 * For wake, pretend we were running in the home-node.
3029 if (cpu_to_node(prev_cpu) != node) {
3030 int node_cpu = numa_select_node_cpu(p, node);
3034 prev_cpu = node_cpu;
3039 for_each_domain(cpu, tmp) {
3040 if (!(tmp->flags & SD_LOAD_BALANCE))
3044 * If both cpu and prev_cpu are part of this domain,
3045 * cpu is a valid SD_WAKE_AFFINE target.
3047 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
3048 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
3053 if (tmp->flags & sd_flag)
3058 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
3061 new_cpu = select_idle_sibling(p, prev_cpu);
3067 int load_idx = sd->forkexec_idx;
3068 struct sched_group *group;
3071 if (!(sd->flags & sd_flag)) {
3076 if (sd_flag & SD_BALANCE_WAKE)
3077 load_idx = sd->wake_idx;
3079 group = find_idlest_group(sd, p, cpu, load_idx);
3085 new_cpu = find_idlest_cpu(group, p, cpu);
3086 if (new_cpu == -1 || new_cpu == cpu) {
3087 /* Now try balancing at a lower domain level of cpu */
3092 /* Now try balancing at a lower domain level of new_cpu */
3094 weight = sd->span_weight;
3096 for_each_domain(cpu, tmp) {
3097 if (weight <= tmp->span_weight)
3099 if (tmp->flags & sd_flag)
3102 /* while loop will break here if sd == NULL */
3109 #endif /* CONFIG_SMP */
3111 static unsigned long
3112 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
3114 unsigned long gran = sysctl_sched_wakeup_granularity;
3117 * Since its curr running now, convert the gran from real-time
3118 * to virtual-time in his units.
3120 * By using 'se' instead of 'curr' we penalize light tasks, so
3121 * they get preempted easier. That is, if 'se' < 'curr' then
3122 * the resulting gran will be larger, therefore penalizing the
3123 * lighter, if otoh 'se' > 'curr' then the resulting gran will
3124 * be smaller, again penalizing the lighter task.
3126 * This is especially important for buddies when the leftmost
3127 * task is higher priority than the buddy.
3129 return calc_delta_fair(gran, se);
3133 * Should 'se' preempt 'curr'.
3147 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
3149 s64 gran, vdiff = curr->vruntime - se->vruntime;
3154 gran = wakeup_gran(curr, se);
3161 static void set_last_buddy(struct sched_entity *se)
3163 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
3166 for_each_sched_entity(se)
3167 cfs_rq_of(se)->last = se;
3170 static void set_next_buddy(struct sched_entity *se)
3172 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
3175 for_each_sched_entity(se)
3176 cfs_rq_of(se)->next = se;
3179 static void set_skip_buddy(struct sched_entity *se)
3181 for_each_sched_entity(se)
3182 cfs_rq_of(se)->skip = se;
3186 * Preempt the current task with a newly woken task if needed:
3188 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
3190 struct task_struct *curr = rq->curr;
3191 struct sched_entity *se = &curr->se, *pse = &p->se;
3192 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
3193 int scale = cfs_rq->nr_running >= sched_nr_latency;
3194 int next_buddy_marked = 0;
3196 if (unlikely(se == pse))
3200 * This is possible from callers such as move_task(), in which we
3201 * unconditionally check_prempt_curr() after an enqueue (which may have
3202 * lead to a throttle). This both saves work and prevents false
3203 * next-buddy nomination below.
3205 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
3208 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
3209 set_next_buddy(pse);
3210 next_buddy_marked = 1;
3214 * We can come here with TIF_NEED_RESCHED already set from new task
3217 * Note: this also catches the edge-case of curr being in a throttled
3218 * group (e.g. via set_curr_task), since update_curr() (in the
3219 * enqueue of curr) will have resulted in resched being set. This
3220 * prevents us from potentially nominating it as a false LAST_BUDDY
3223 if (test_tsk_need_resched(curr))
3226 /* Idle tasks are by definition preempted by non-idle tasks. */
3227 if (unlikely(curr->policy == SCHED_IDLE) &&
3228 likely(p->policy != SCHED_IDLE))
3232 * Batch and idle tasks do not preempt non-idle tasks (their preemption
3233 * is driven by the tick):
3235 if (unlikely(p->policy != SCHED_NORMAL))
3238 find_matching_se(&se, &pse);
3239 update_curr(cfs_rq_of(se));
3241 if (wakeup_preempt_entity(se, pse) == 1) {
3243 * Bias pick_next to pick the sched entity that is
3244 * triggering this preemption.
3246 if (!next_buddy_marked)
3247 set_next_buddy(pse);
3256 * Only set the backward buddy when the current task is still
3257 * on the rq. This can happen when a wakeup gets interleaved
3258 * with schedule on the ->pre_schedule() or idle_balance()
3259 * point, either of which can * drop the rq lock.
3261 * Also, during early boot the idle thread is in the fair class,
3262 * for obvious reasons its a bad idea to schedule back to it.
3264 if (unlikely(!se->on_rq || curr == rq->idle))
3267 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
3271 static struct task_struct *pick_next_task_fair(struct rq *rq)
3273 struct task_struct *p;
3274 struct cfs_rq *cfs_rq = &rq->cfs;
3275 struct sched_entity *se;
3277 if (!cfs_rq->nr_running)
3281 se = pick_next_entity(cfs_rq);
3282 set_next_entity(cfs_rq, se);
3283 cfs_rq = group_cfs_rq(se);
3287 if (hrtick_enabled(rq))
3288 hrtick_start_fair(rq, p);
3294 * Account for a descheduled task:
3296 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
3298 struct sched_entity *se = &prev->se;
3299 struct cfs_rq *cfs_rq;
3301 for_each_sched_entity(se) {
3302 cfs_rq = cfs_rq_of(se);
3303 put_prev_entity(cfs_rq, se);
3308 * sched_yield() is very simple
3310 * The magic of dealing with the ->skip buddy is in pick_next_entity.
3312 static void yield_task_fair(struct rq *rq)
3314 struct task_struct *curr = rq->curr;
3315 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
3316 struct sched_entity *se = &curr->se;
3319 * Are we the only task in the tree?
3321 if (unlikely(rq->nr_running == 1))
3324 clear_buddies(cfs_rq, se);
3326 if (curr->policy != SCHED_BATCH) {
3327 update_rq_clock(rq);
3329 * Update run-time statistics of the 'current'.
3331 update_curr(cfs_rq);
3333 * Tell update_rq_clock() that we've just updated,
3334 * so we don't do microscopic update in schedule()
3335 * and double the fastpath cost.
3337 rq->skip_clock_update = 1;
3343 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
3345 struct sched_entity *se = &p->se;
3347 /* throttled hierarchies are not runnable */
3348 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
3351 /* Tell the scheduler that we'd really like pse to run next. */
3354 yield_task_fair(rq);
3360 /**************************************************
3361 * Fair scheduling class load-balancing methods:
3364 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
3366 #define LBF_ALL_PINNED 0x01
3367 #define LBF_NEED_BREAK 0x02
3368 #define LBF_SOME_PINNED 0x04
3371 struct sched_domain *sd;
3379 struct cpumask *dst_grpmask;
3381 enum cpu_idle_type idle;
3383 /* The set of CPUs under consideration for load-balancing */
3384 struct cpumask *cpus;
3388 struct list_head *tasks;
3391 unsigned int loop_break;
3392 unsigned int loop_max;
3394 struct rq * (*find_busiest_queue)(struct lb_env *,
3395 struct sched_group *);
3399 * move_task - move a task from one runqueue to another runqueue.
3400 * Both runqueues must be locked.
3402 static void move_task(struct task_struct *p, struct lb_env *env)
3404 deactivate_task(env->src_rq, p, 0);
3405 set_task_cpu(p, env->dst_cpu);
3406 activate_task(env->dst_rq, p, 0);
3407 check_preempt_curr(env->dst_rq, p, 0);
3410 static int task_numa_hot(struct task_struct *p, int from_cpu, int to_cpu)
3412 int from_dist, to_dist;
3413 int node = tsk_home_node(p);
3415 if (!sched_feat_numa(NUMA_HOT) || node == -1)
3416 return 0; /* no node preference */
3418 from_dist = node_distance(cpu_to_node(from_cpu), node);
3419 to_dist = node_distance(cpu_to_node(to_cpu), node);
3421 if (to_dist < from_dist)
3422 return 0; /* getting closer is ok */
3424 return 1; /* stick to where we are */
3428 * Is this task likely cache-hot:
3431 task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
3435 if (p->sched_class != &fair_sched_class)
3438 if (unlikely(p->policy == SCHED_IDLE))
3442 * Buddy candidates are cache hot:
3444 if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running &&
3445 (&p->se == cfs_rq_of(&p->se)->next ||
3446 &p->se == cfs_rq_of(&p->se)->last))
3449 if (sysctl_sched_migration_cost == -1)
3451 if (sysctl_sched_migration_cost == 0)
3454 delta = now - p->se.exec_start;
3456 return delta < (s64)sysctl_sched_migration_cost;
3460 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
3463 int can_migrate_task(struct task_struct *p, struct lb_env *env)
3465 int tsk_cache_hot = 0;
3467 * We do not migrate tasks that are:
3468 * 1) running (obviously), or
3469 * 2) cannot be migrated to this CPU due to cpus_allowed, or
3470 * 3) are cache-hot on their current CPU.
3472 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
3475 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
3478 * Remember if this task can be migrated to any other cpu in
3479 * our sched_group. We may want to revisit it if we couldn't
3480 * meet load balance goals by pulling other tasks on src_cpu.
3482 * Also avoid computing new_dst_cpu if we have already computed
3483 * one in current iteration.
3485 if (!env->dst_grpmask || (env->flags & LBF_SOME_PINNED))
3488 new_dst_cpu = cpumask_first_and(env->dst_grpmask,
3489 tsk_cpus_allowed(p));
3490 if (new_dst_cpu < nr_cpu_ids) {
3491 env->flags |= LBF_SOME_PINNED;
3492 env->new_dst_cpu = new_dst_cpu;
3497 /* Record that we found atleast one task that could run on dst_cpu */
3498 env->flags &= ~LBF_ALL_PINNED;
3500 if (task_running(env->src_rq, p)) {
3501 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
3506 * Aggressive migration if:
3507 * 1) task is cache cold, or
3508 * 2) too many balance attempts have failed.
3511 tsk_cache_hot = task_hot(p, env->src_rq->clock_task, env->sd);
3512 tsk_cache_hot |= task_numa_hot(p, env->src_cpu, env->dst_cpu);
3513 if (!tsk_cache_hot ||
3514 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
3515 #ifdef CONFIG_SCHEDSTATS
3516 if (tsk_cache_hot) {
3517 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
3518 schedstat_inc(p, se.statistics.nr_forced_migrations);
3524 if (tsk_cache_hot) {
3525 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
3532 * move_one_task tries to move exactly one task from busiest to this_rq, as
3533 * part of active balancing operations within "domain".
3534 * Returns 1 if successful and 0 otherwise.
3536 * Called with both runqueues locked.
3538 static int __move_one_task(struct lb_env *env)
3540 struct task_struct *p, *n;
3542 list_for_each_entry_safe(p, n, env->tasks, se.group_node) {
3543 if (throttled_lb_pair(task_group(p), env->src_rq->cpu, env->dst_cpu))
3546 if (!can_migrate_task(p, env))
3551 * Right now, this is only the second place move_task()
3552 * is called, so we can safely collect move_task()
3553 * stats here rather than inside move_task().
3555 schedstat_inc(env->sd, lb_gained[env->idle]);
3561 static int move_one_task(struct lb_env *env)
3563 if (sched_feat_numa(NUMA_PULL)) {
3564 env->tasks = offnode_tasks(env->src_rq);
3565 if (__move_one_task(env))
3569 env->tasks = &env->src_rq->cfs_tasks;
3570 if (__move_one_task(env))
3576 static const unsigned int sched_nr_migrate_break = 32;
3579 * move_tasks tries to move up to imbalance weighted load from busiest to
3580 * this_rq, as part of a balancing operation within domain "sd".
3581 * Returns 1 if successful and 0 otherwise.
3583 * Called with both runqueues locked.
3585 static int move_tasks(struct lb_env *env)
3587 struct task_struct *p;
3591 if (env->imbalance <= 0)
3595 while (!list_empty(env->tasks)) {
3596 p = list_first_entry(env->tasks, struct task_struct, se.group_node);
3599 /* We've more or less seen every task there is, call it quits */
3600 if (env->loop > env->loop_max)
3603 /* take a breather every nr_migrate tasks */
3604 if (env->loop > env->loop_break) {
3605 env->loop_break += sched_nr_migrate_break;
3606 env->flags |= LBF_NEED_BREAK;
3610 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
3613 load = task_h_load(p);
3615 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
3618 if ((load / 2) > env->imbalance)
3621 if (!can_migrate_task(p, env))
3626 env->imbalance -= load;
3628 #ifdef CONFIG_PREEMPT
3630 * NEWIDLE balancing is a source of latency, so preemptible
3631 * kernels will stop after the first task is pulled to minimize
3632 * the critical section.
3634 if (env->idle == CPU_NEWLY_IDLE)
3639 * We only want to steal up to the prescribed amount of
3642 if (env->imbalance <= 0)
3647 list_move_tail(&p->se.group_node, env->tasks);
3650 if (env->tasks == offnode_tasks(env->src_rq)) {
3651 env->tasks = &env->src_rq->cfs_tasks;
3658 * Right now, this is one of only two places move_task() is called,
3659 * so we can safely collect move_task() stats here rather than
3660 * inside move_task().
3662 schedstat_add(env->sd, lb_gained[env->idle], pulled);
3667 #ifdef CONFIG_FAIR_GROUP_SCHED
3669 * update tg->load_weight by folding this cpu's load_avg
3671 static int update_shares_cpu(struct task_group *tg, int cpu)
3673 struct cfs_rq *cfs_rq;
3674 unsigned long flags;
3681 cfs_rq = tg->cfs_rq[cpu];
3683 raw_spin_lock_irqsave(&rq->lock, flags);
3685 update_rq_clock(rq);
3686 update_cfs_load(cfs_rq, 1);
3689 * We need to update shares after updating tg->load_weight in
3690 * order to adjust the weight of groups with long running tasks.
3692 update_cfs_shares(cfs_rq);
3694 raw_spin_unlock_irqrestore(&rq->lock, flags);
3699 static void update_shares(int cpu)
3701 struct cfs_rq *cfs_rq;
3702 struct rq *rq = cpu_rq(cpu);
3706 * Iterates the task_group tree in a bottom up fashion, see
3707 * list_add_leaf_cfs_rq() for details.
3709 for_each_leaf_cfs_rq(rq, cfs_rq) {
3710 /* throttled entities do not contribute to load */
3711 if (throttled_hierarchy(cfs_rq))
3714 update_shares_cpu(cfs_rq->tg, cpu);
3720 * Compute the cpu's hierarchical load factor for each task group.
3721 * This needs to be done in a top-down fashion because the load of a child
3722 * group is a fraction of its parents load.
3724 static int tg_load_down(struct task_group *tg, void *data)
3727 long cpu = (long)data;
3730 load = cpu_rq(cpu)->load.weight;
3732 load = tg->parent->cfs_rq[cpu]->h_load;
3733 load *= tg->se[cpu]->load.weight;
3734 load /= tg->parent->cfs_rq[cpu]->load.weight + 1;
3737 tg->cfs_rq[cpu]->h_load = load;
3742 static void update_h_load(long cpu)
3744 struct rq *rq = cpu_rq(cpu);
3745 unsigned long now = jiffies;
3747 if (rq->h_load_throttle == now)
3750 rq->h_load_throttle = now;
3753 walk_tg_tree(tg_load_down, tg_nop, (void *)cpu);
3757 static unsigned long task_h_load(struct task_struct *p)
3759 struct cfs_rq *cfs_rq = task_cfs_rq(p);
3762 load = p->se.load.weight;
3763 load = div_u64(load * cfs_rq->h_load, cfs_rq->load.weight + 1);
3768 static inline void update_shares(int cpu)
3772 static inline void update_h_load(long cpu)
3776 static unsigned long task_h_load(struct task_struct *p)
3778 return p->se.load.weight;
3782 /********** Helpers for find_busiest_group ************************/
3784 * sd_lb_stats - Structure to store the statistics of a sched_domain
3785 * during load balancing.
3787 struct sd_lb_stats {
3788 struct sched_group *busiest; /* Busiest group in this sd */
3789 struct sched_group *this; /* Local group in this sd */
3790 unsigned long total_load; /* Total load of all groups in sd */
3791 unsigned long total_pwr; /* Total power of all groups in sd */
3792 unsigned long avg_load; /* Average load across all groups in sd */
3794 /** Statistics of this group */
3795 unsigned long this_load;
3796 unsigned long this_load_per_task;
3797 unsigned long this_nr_running;
3798 unsigned long this_has_capacity;
3799 unsigned int this_idle_cpus;
3801 /* Statistics of the busiest group */
3802 unsigned int busiest_idle_cpus;
3803 unsigned long max_load;
3804 unsigned long busiest_load_per_task;
3805 unsigned long busiest_nr_running;
3806 unsigned long busiest_group_capacity;
3807 unsigned long busiest_has_capacity;
3808 unsigned int busiest_group_weight;
3810 int group_imb; /* Is there imbalance in this sd */
3811 #ifdef CONFIG_SCHED_NUMA
3812 struct sched_group *numa_group; /* group which has offnode_tasks */
3813 unsigned long numa_group_weight;
3814 unsigned long numa_group_running;
3819 * sg_lb_stats - stats of a sched_group required for load_balancing
3821 struct sg_lb_stats {
3822 unsigned long avg_load; /*Avg load across the CPUs of the group */
3823 unsigned long group_load; /* Total load over the CPUs of the group */
3824 unsigned long sum_nr_running; /* Nr tasks running in the group */
3825 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
3826 unsigned long group_capacity;
3827 unsigned long idle_cpus;
3828 unsigned long group_weight;
3829 int group_imb; /* Is there an imbalance in the group ? */
3830 int group_has_capacity; /* Is there extra capacity in the group? */
3831 #ifdef CONFIG_SCHED_NUMA
3832 unsigned long numa_weight;
3833 unsigned long numa_running;
3838 * get_sd_load_idx - Obtain the load index for a given sched domain.
3839 * @sd: The sched_domain whose load_idx is to be obtained.
3840 * @idle: The Idle status of the CPU for whose sd load_icx is obtained.
3842 static inline int get_sd_load_idx(struct sched_domain *sd,
3843 enum cpu_idle_type idle)
3849 load_idx = sd->busy_idx;
3852 case CPU_NEWLY_IDLE:
3853 load_idx = sd->newidle_idx;
3856 load_idx = sd->idle_idx;
3863 #ifdef CONFIG_SCHED_NUMA
3864 static inline void update_sg_numa_stats(struct sg_lb_stats *sgs, struct rq *rq)
3866 sgs->numa_weight += rq->offnode_weight;
3867 sgs->numa_running += rq->offnode_running;
3871 * Since the offnode lists are indiscriminate (they contain tasks for all other
3872 * nodes) it is impossible to say if there's any task on there that wants to
3873 * move towards the pulling cpu. Therefore select a random offnode list to pull
3874 * from such that eventually we'll try them all.
3876 * Select a random group that has offnode tasks as sds->numa_group
3878 static inline void update_sd_numa_stats(struct sched_domain *sd,
3879 struct sched_group *group, struct sd_lb_stats *sds,
3880 int local_group, struct sg_lb_stats *sgs)
3882 if (!(sd->flags & SD_NUMA))
3888 if (!sgs->numa_running)
3891 if (!sds->numa_group || pick_numa_rand(sd->span_weight / group->group_weight)) {
3892 sds->numa_group = group;
3893 sds->numa_group_weight = sgs->numa_weight;
3894 sds->numa_group_running = sgs->numa_running;
3899 * Pick a random queue from the group that has offnode tasks.
3901 static struct rq *find_busiest_numa_queue(struct lb_env *env,
3902 struct sched_group *group)
3904 struct rq *busiest = NULL, *rq;
3907 for_each_cpu_and(cpu, sched_group_cpus(group), env->cpus) {
3909 if (!rq->offnode_running)
3911 if (!busiest || pick_numa_rand(group->group_weight))
3919 * Called in case of no other imbalance, if there is a queue running offnode
3920 * tasksk we'll say we're imbalanced anyway to nudge these tasks towards their
3923 static inline int check_numa_busiest_group(struct lb_env *env, struct sd_lb_stats *sds)
3925 if (!sched_feat(NUMA_PULL_BIAS))
3928 if (!sds->numa_group)
3931 env->imbalance = sds->numa_group_weight / sds->numa_group_running;
3932 sds->busiest = sds->numa_group;
3933 env->find_busiest_queue = find_busiest_numa_queue;
3937 static inline bool need_active_numa_balance(struct lb_env *env)
3939 return env->find_busiest_queue == find_busiest_numa_queue &&
3940 env->src_rq->offnode_running == 1 &&
3941 env->src_rq->nr_running == 1;
3944 #else /* CONFIG_SCHED_NUMA */
3946 static inline void update_sg_numa_stats(struct sg_lb_stats *sgs, struct rq *rq)
3950 static inline void update_sd_numa_stats(struct sched_domain *sd,
3951 struct sched_group *group, struct sd_lb_stats *sds,
3952 int local_group, struct sg_lb_stats *sgs)
3956 static inline int check_numa_busiest_group(struct lb_env *env, struct sd_lb_stats *sds)
3961 static inline bool need_active_numa_balance(struct lb_env *env)
3965 #endif /* CONFIG_SCHED_NUMA */
3967 unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
3969 return SCHED_POWER_SCALE;
3972 unsigned long __weak arch_scale_freq_power(struct sched_domain *sd, int cpu)
3974 return default_scale_freq_power(sd, cpu);
3977 unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
3979 unsigned long weight = sd->span_weight;
3980 unsigned long smt_gain = sd->smt_gain;
3987 unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu)
3989 return default_scale_smt_power(sd, cpu);
3992 unsigned long scale_rt_power(int cpu)
3994 struct rq *rq = cpu_rq(cpu);
3995 u64 total, available, age_stamp, avg;
3998 * Since we're reading these variables without serialization make sure
3999 * we read them once before doing sanity checks on them.
4001 age_stamp = ACCESS_ONCE(rq->age_stamp);
4002 avg = ACCESS_ONCE(rq->rt_avg);
4004 total = sched_avg_period() + (rq->clock - age_stamp);
4006 if (unlikely(total < avg)) {
4007 /* Ensures that power won't end up being negative */
4010 available = total - avg;
4013 if (unlikely((s64)total < SCHED_POWER_SCALE))
4014 total = SCHED_POWER_SCALE;
4016 total >>= SCHED_POWER_SHIFT;
4018 return div_u64(available, total);
4021 static void update_cpu_power(struct sched_domain *sd, int cpu)
4023 unsigned long weight = sd->span_weight;
4024 unsigned long power = SCHED_POWER_SCALE;
4025 struct sched_group *sdg = sd->groups;
4027 if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
4028 if (sched_feat(ARCH_POWER))
4029 power *= arch_scale_smt_power(sd, cpu);
4031 power *= default_scale_smt_power(sd, cpu);
4033 power >>= SCHED_POWER_SHIFT;
4036 sdg->sgp->power_orig = power;
4038 if (sched_feat(ARCH_POWER))
4039 power *= arch_scale_freq_power(sd, cpu);
4041 power *= default_scale_freq_power(sd, cpu);
4043 power >>= SCHED_POWER_SHIFT;
4045 power *= scale_rt_power(cpu);
4046 power >>= SCHED_POWER_SHIFT;
4051 cpu_rq(cpu)->cpu_power = power;
4052 sdg->sgp->power = power;
4055 void update_group_power(struct sched_domain *sd, int cpu)
4057 struct sched_domain *child = sd->child;
4058 struct sched_group *group, *sdg = sd->groups;
4059 unsigned long power;
4060 unsigned long interval;
4062 interval = msecs_to_jiffies(sd->balance_interval);
4063 interval = clamp(interval, 1UL, max_load_balance_interval);
4064 sdg->sgp->next_update = jiffies + interval;
4067 update_cpu_power(sd, cpu);
4073 if (child->flags & SD_OVERLAP) {
4075 * SD_OVERLAP domains cannot assume that child groups
4076 * span the current group.
4079 for_each_cpu(cpu, sched_group_cpus(sdg))
4080 power += power_of(cpu);
4083 * !SD_OVERLAP domains can assume that child groups
4084 * span the current group.
4087 group = child->groups;
4089 power += group->sgp->power;
4090 group = group->next;
4091 } while (group != child->groups);
4094 sdg->sgp->power_orig = sdg->sgp->power = power;
4098 * Try and fix up capacity for tiny siblings, this is needed when
4099 * things like SD_ASYM_PACKING need f_b_g to select another sibling
4100 * which on its own isn't powerful enough.
4102 * See update_sd_pick_busiest() and check_asym_packing().
4105 fix_small_capacity(struct sched_domain *sd, struct sched_group *group)
4108 * Only siblings can have significantly less than SCHED_POWER_SCALE
4110 if (!(sd->flags & SD_SHARE_CPUPOWER))
4114 * If ~90% of the cpu_power is still there, we're good.
4116 if (group->sgp->power * 32 > group->sgp->power_orig * 29)
4123 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
4124 * @env: The load balancing environment.
4125 * @group: sched_group whose statistics are to be updated.
4126 * @load_idx: Load index of sched_domain of this_cpu for load calc.
4127 * @local_group: Does group contain this_cpu.
4128 * @balance: Should we balance.
4129 * @sgs: variable to hold the statistics for this group.
4131 static inline void update_sg_lb_stats(struct lb_env *env,
4132 struct sched_group *group, int load_idx,
4133 int local_group, int *balance, struct sg_lb_stats *sgs)
4135 unsigned long nr_running, max_nr_running, min_nr_running;
4136 unsigned long load, max_cpu_load, min_cpu_load;
4137 unsigned int balance_cpu = -1, first_idle_cpu = 0;
4138 unsigned long avg_load_per_task = 0;
4142 balance_cpu = group_balance_cpu(group);
4144 /* Tally up the load of all CPUs in the group */
4146 min_cpu_load = ~0UL;
4148 min_nr_running = ~0UL;
4150 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
4151 struct rq *rq = cpu_rq(i);
4153 nr_running = rq->nr_running;
4155 /* Bias balancing toward cpus of our domain */
4157 if (idle_cpu(i) && !first_idle_cpu &&
4158 cpumask_test_cpu(i, sched_group_mask(group))) {
4163 load = target_load(i, load_idx);
4165 load = source_load(i, load_idx);
4166 if (load > max_cpu_load)
4167 max_cpu_load = load;
4168 if (min_cpu_load > load)
4169 min_cpu_load = load;
4171 if (nr_running > max_nr_running)
4172 max_nr_running = nr_running;
4173 if (min_nr_running > nr_running)
4174 min_nr_running = nr_running;
4177 sgs->group_load += load;
4178 sgs->sum_nr_running += nr_running;
4179 sgs->sum_weighted_load += weighted_cpuload(i);
4183 update_sg_numa_stats(sgs, rq);
4187 * First idle cpu or the first cpu(busiest) in this sched group
4188 * is eligible for doing load balancing at this and above
4189 * domains. In the newly idle case, we will allow all the cpu's
4190 * to do the newly idle load balance.
4193 if (env->idle != CPU_NEWLY_IDLE) {
4194 if (balance_cpu != env->dst_cpu) {
4198 update_group_power(env->sd, env->dst_cpu);
4199 } else if (time_after_eq(jiffies, group->sgp->next_update))
4200 update_group_power(env->sd, env->dst_cpu);
4203 /* Adjust by relative CPU power of the group */
4204 sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / group->sgp->power;
4207 * Consider the group unbalanced when the imbalance is larger
4208 * than the average weight of a task.
4210 * APZ: with cgroup the avg task weight can vary wildly and
4211 * might not be a suitable number - should we keep a
4212 * normalized nr_running number somewhere that negates
4215 if (sgs->sum_nr_running)
4216 avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
4218 if ((max_cpu_load - min_cpu_load) >= avg_load_per_task &&
4219 (max_nr_running - min_nr_running) > 1)
4222 sgs->group_capacity = DIV_ROUND_CLOSEST(group->sgp->power,
4224 if (!sgs->group_capacity)
4225 sgs->group_capacity = fix_small_capacity(env->sd, group);
4226 sgs->group_weight = group->group_weight;
4228 if (sgs->group_capacity > sgs->sum_nr_running)
4229 sgs->group_has_capacity = 1;
4233 * update_sd_pick_busiest - return 1 on busiest group
4234 * @env: The load balancing environment.
4235 * @sds: sched_domain statistics
4236 * @sg: sched_group candidate to be checked for being the busiest
4237 * @sgs: sched_group statistics
4239 * Determine if @sg is a busier group than the previously selected
4242 static bool update_sd_pick_busiest(struct lb_env *env,
4243 struct sd_lb_stats *sds,
4244 struct sched_group *sg,
4245 struct sg_lb_stats *sgs)
4247 if (sgs->avg_load <= sds->max_load)
4250 if (sgs->sum_nr_running > sgs->group_capacity)
4257 * ASYM_PACKING needs to move all the work to the lowest
4258 * numbered CPUs in the group, therefore mark all groups
4259 * higher than ourself as busy.
4261 if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
4262 env->dst_cpu < group_first_cpu(sg)) {
4266 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
4274 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
4275 * @env: The load balancing environment.
4276 * @balance: Should we balance.
4277 * @sds: variable to hold the statistics for this sched_domain.
4279 static inline void update_sd_lb_stats(struct lb_env *env,
4280 int *balance, struct sd_lb_stats *sds)
4282 struct sched_domain *child = env->sd->child;
4283 struct sched_group *sg = env->sd->groups;
4284 struct sg_lb_stats sgs;
4285 int load_idx, prefer_sibling = 0;
4287 if (child && child->flags & SD_PREFER_SIBLING)
4290 load_idx = get_sd_load_idx(env->sd, env->idle);
4295 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
4296 memset(&sgs, 0, sizeof(sgs));
4297 update_sg_lb_stats(env, sg, load_idx, local_group, balance, &sgs);
4299 if (local_group && !(*balance))
4302 sds->total_load += sgs.group_load;
4303 sds->total_pwr += sg->sgp->power;
4306 * In case the child domain prefers tasks go to siblings
4307 * first, lower the sg capacity to one so that we'll try
4308 * and move all the excess tasks away. We lower the capacity
4309 * of a group only if the local group has the capacity to fit
4310 * these excess tasks, i.e. nr_running < group_capacity. The
4311 * extra check prevents the case where you always pull from the
4312 * heaviest group when it is already under-utilized (possible
4313 * with a large weight task outweighs the tasks on the system).
4315 if (prefer_sibling && !local_group && sds->this_has_capacity)
4316 sgs.group_capacity = min(sgs.group_capacity, 1UL);
4319 sds->this_load = sgs.avg_load;
4321 sds->this_nr_running = sgs.sum_nr_running;
4322 sds->this_load_per_task = sgs.sum_weighted_load;
4323 sds->this_has_capacity = sgs.group_has_capacity;
4324 sds->this_idle_cpus = sgs.idle_cpus;
4325 } else if (update_sd_pick_busiest(env, sds, sg, &sgs)) {
4326 sds->max_load = sgs.avg_load;
4328 sds->busiest_nr_running = sgs.sum_nr_running;
4329 sds->busiest_idle_cpus = sgs.idle_cpus;
4330 sds->busiest_group_capacity = sgs.group_capacity;
4331 sds->busiest_load_per_task = sgs.sum_weighted_load;
4332 sds->busiest_has_capacity = sgs.group_has_capacity;
4333 sds->busiest_group_weight = sgs.group_weight;
4334 sds->group_imb = sgs.group_imb;
4337 update_sd_numa_stats(env->sd, sg, sds, local_group, &sgs);
4340 } while (sg != env->sd->groups);
4344 * check_asym_packing - Check to see if the group is packed into the
4347 * This is primarily intended to used at the sibling level. Some
4348 * cores like POWER7 prefer to use lower numbered SMT threads. In the
4349 * case of POWER7, it can move to lower SMT modes only when higher
4350 * threads are idle. When in lower SMT modes, the threads will
4351 * perform better since they share less core resources. Hence when we
4352 * have idle threads, we want them to be the higher ones.
4354 * This packing function is run on idle threads. It checks to see if
4355 * the busiest CPU in this domain (core in the P7 case) has a higher
4356 * CPU number than the packing function is being run on. Here we are
4357 * assuming lower CPU number will be equivalent to lower a SMT thread
4360 * Returns 1 when packing is required and a task should be moved to
4361 * this CPU. The amount of the imbalance is returned in *imbalance.
4363 * @env: The load balancing environment.
4364 * @sds: Statistics of the sched_domain which is to be packed
4366 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
4370 if (!(env->sd->flags & SD_ASYM_PACKING))
4376 busiest_cpu = group_first_cpu(sds->busiest);
4377 if (env->dst_cpu > busiest_cpu)
4380 env->imbalance = DIV_ROUND_CLOSEST(
4381 sds->max_load * sds->busiest->sgp->power, SCHED_POWER_SCALE);
4387 * fix_small_imbalance - Calculate the minor imbalance that exists
4388 * amongst the groups of a sched_domain, during
4390 * @env: The load balancing environment.
4391 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
4394 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
4396 unsigned long tmp, pwr_now = 0, pwr_move = 0;
4397 unsigned int imbn = 2;
4398 unsigned long scaled_busy_load_per_task;
4400 if (sds->this_nr_running) {
4401 sds->this_load_per_task /= sds->this_nr_running;
4402 if (sds->busiest_load_per_task >
4403 sds->this_load_per_task)
4406 sds->this_load_per_task =
4407 cpu_avg_load_per_task(env->dst_cpu);
4410 scaled_busy_load_per_task = sds->busiest_load_per_task
4411 * SCHED_POWER_SCALE;
4412 scaled_busy_load_per_task /= sds->busiest->sgp->power;
4414 if (sds->max_load - sds->this_load + scaled_busy_load_per_task >=
4415 (scaled_busy_load_per_task * imbn)) {
4416 env->imbalance = sds->busiest_load_per_task;
4421 * OK, we don't have enough imbalance to justify moving tasks,
4422 * however we may be able to increase total CPU power used by
4426 pwr_now += sds->busiest->sgp->power *
4427 min(sds->busiest_load_per_task, sds->max_load);
4428 pwr_now += sds->this->sgp->power *
4429 min(sds->this_load_per_task, sds->this_load);
4430 pwr_now /= SCHED_POWER_SCALE;
4432 /* Amount of load we'd subtract */
4433 tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
4434 sds->busiest->sgp->power;
4435 if (sds->max_load > tmp)
4436 pwr_move += sds->busiest->sgp->power *
4437 min(sds->busiest_load_per_task, sds->max_load - tmp);
4439 /* Amount of load we'd add */
4440 if (sds->max_load * sds->busiest->sgp->power <
4441 sds->busiest_load_per_task * SCHED_POWER_SCALE)
4442 tmp = (sds->max_load * sds->busiest->sgp->power) /
4443 sds->this->sgp->power;
4445 tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
4446 sds->this->sgp->power;
4447 pwr_move += sds->this->sgp->power *
4448 min(sds->this_load_per_task, sds->this_load + tmp);
4449 pwr_move /= SCHED_POWER_SCALE;
4451 /* Move if we gain throughput */
4452 if (pwr_move > pwr_now)
4453 env->imbalance = sds->busiest_load_per_task;
4457 * calculate_imbalance - Calculate the amount of imbalance present within the
4458 * groups of a given sched_domain during load balance.
4459 * @env: load balance environment
4460 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
4462 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
4464 unsigned long max_pull, load_above_capacity = ~0UL;
4466 sds->busiest_load_per_task /= sds->busiest_nr_running;
4467 if (sds->group_imb) {
4468 sds->busiest_load_per_task =
4469 min(sds->busiest_load_per_task, sds->avg_load);
4473 * In the presence of smp nice balancing, certain scenarios can have
4474 * max load less than avg load(as we skip the groups at or below
4475 * its cpu_power, while calculating max_load..)
4477 if (sds->max_load < sds->avg_load) {
4479 return fix_small_imbalance(env, sds);
4482 if (!sds->group_imb) {
4484 * Don't want to pull so many tasks that a group would go idle.
4486 load_above_capacity = (sds->busiest_nr_running -
4487 sds->busiest_group_capacity);
4489 load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
4491 load_above_capacity /= sds->busiest->sgp->power;
4495 * We're trying to get all the cpus to the average_load, so we don't
4496 * want to push ourselves above the average load, nor do we wish to
4497 * reduce the max loaded cpu below the average load. At the same time,
4498 * we also don't want to reduce the group load below the group capacity
4499 * (so that we can implement power-savings policies etc). Thus we look
4500 * for the minimum possible imbalance.
4501 * Be careful of negative numbers as they'll appear as very large values
4502 * with unsigned longs.
4504 max_pull = min(sds->max_load - sds->avg_load, load_above_capacity);
4506 /* How much load to actually move to equalise the imbalance */
4507 env->imbalance = min(max_pull * sds->busiest->sgp->power,
4508 (sds->avg_load - sds->this_load) * sds->this->sgp->power)
4509 / SCHED_POWER_SCALE;
4512 * if *imbalance is less than the average load per runnable task
4513 * there is no guarantee that any tasks will be moved so we'll have
4514 * a think about bumping its value to force at least one task to be
4517 if (env->imbalance < sds->busiest_load_per_task)
4518 return fix_small_imbalance(env, sds);
4522 /******* find_busiest_group() helpers end here *********************/
4525 * find_busiest_group - Returns the busiest group within the sched_domain
4526 * if there is an imbalance. If there isn't an imbalance, and
4527 * the user has opted for power-savings, it returns a group whose
4528 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
4529 * such a group exists.
4531 * Also calculates the amount of weighted load which should be moved
4532 * to restore balance.
4534 * @env: The load balancing environment.
4535 * @balance: Pointer to a variable indicating if this_cpu
4536 * is the appropriate cpu to perform load balancing at this_level.
4538 * Returns: - the busiest group if imbalance exists.
4539 * - If no imbalance and user has opted for power-savings balance,
4540 * return the least loaded group whose CPUs can be
4541 * put to idle by rebalancing its tasks onto our group.
4543 static struct sched_group *
4544 find_busiest_group(struct lb_env *env, int *balance)
4546 struct sd_lb_stats sds;
4548 memset(&sds, 0, sizeof(sds));
4551 * Compute the various statistics relavent for load balancing at
4554 update_sd_lb_stats(env, balance, &sds);
4557 * this_cpu is not the appropriate cpu to perform load balancing at
4563 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
4564 check_asym_packing(env, &sds))
4567 /* There is no busy sibling group to pull tasks from */
4568 if (!sds.busiest || sds.busiest_nr_running == 0)
4571 sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
4574 * If the busiest group is imbalanced the below checks don't
4575 * work because they assumes all things are equal, which typically
4576 * isn't true due to cpus_allowed constraints and the like.
4581 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
4582 if (env->idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
4583 !sds.busiest_has_capacity)
4587 * If the local group is more busy than the selected busiest group
4588 * don't try and pull any tasks.
4590 if (sds.this_load >= sds.max_load)
4594 * Don't pull any tasks if this group is already above the domain
4597 if (sds.this_load >= sds.avg_load)
4600 if (env->idle == CPU_IDLE) {
4602 * This cpu is idle. If the busiest group load doesn't
4603 * have more tasks than the number of available cpu's and
4604 * there is no imbalance between this and busiest group
4605 * wrt to idle cpu's, it is balanced.
4607 if ((sds.this_idle_cpus <= sds.busiest_idle_cpus + 1) &&
4608 sds.busiest_nr_running <= sds.busiest_group_weight)
4612 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
4613 * imbalance_pct to be conservative.
4615 if (100 * sds.max_load <= env->sd->imbalance_pct * sds.this_load)
4620 /* Looks like there is an imbalance. Compute it */
4621 calculate_imbalance(env, &sds);
4625 if (check_numa_busiest_group(env, &sds))
4634 * find_busiest_queue - find the busiest runqueue among the cpus in group.
4636 static struct rq *find_busiest_queue(struct lb_env *env,
4637 struct sched_group *group)
4639 struct rq *busiest = NULL, *rq;
4640 unsigned long max_load = 0;
4643 for_each_cpu(i, sched_group_cpus(group)) {
4644 unsigned long power = power_of(i);
4645 unsigned long capacity = DIV_ROUND_CLOSEST(power,
4650 capacity = fix_small_capacity(env->sd, group);
4652 if (!cpumask_test_cpu(i, env->cpus))
4656 wl = weighted_cpuload(i);
4659 * When comparing with imbalance, use weighted_cpuload()
4660 * which is not scaled with the cpu power.
4662 if (capacity && rq->nr_running == 1 && wl > env->imbalance)
4666 * For the load comparisons with the other cpu's, consider
4667 * the weighted_cpuload() scaled with the cpu power, so that
4668 * the load can be moved away from the cpu that is potentially
4669 * running at a lower capacity.
4671 wl = (wl * SCHED_POWER_SCALE) / power;
4673 if (wl > max_load) {
4683 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
4684 * so long as it is large enough.
4686 #define MAX_PINNED_INTERVAL 512
4688 /* Working cpumask for load_balance and load_balance_newidle. */
4689 DEFINE_PER_CPU(cpumask_var_t, load_balance_tmpmask);
4691 static int need_active_balance(struct lb_env *env)
4693 struct sched_domain *sd = env->sd;
4695 if (env->idle == CPU_NEWLY_IDLE) {
4698 * ASYM_PACKING needs to force migrate tasks from busy but
4699 * higher numbered CPUs in order to pack all tasks in the
4700 * lowest numbered CPUs.
4702 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
4706 if (need_active_numa_balance(env))
4709 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
4712 static int active_load_balance_cpu_stop(void *data);
4715 * Check this_cpu to ensure it is balanced within domain. Attempt to move
4716 * tasks if there is an imbalance.
4718 static int load_balance(int this_cpu, struct rq *this_rq,
4719 struct sched_domain *sd, enum cpu_idle_type idle,
4722 int ld_moved, cur_ld_moved, active_balance = 0;
4723 int lb_iterations, max_lb_iterations;
4724 struct sched_group *group;
4726 unsigned long flags;
4727 struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);
4729 struct lb_env env = {
4731 .dst_cpu = this_cpu,
4733 .dst_grpmask = sched_group_cpus(sd->groups),
4735 .loop_break = sched_nr_migrate_break,
4737 .find_busiest_queue = find_busiest_queue,
4740 cpumask_copy(cpus, cpu_active_mask);
4741 max_lb_iterations = cpumask_weight(env.dst_grpmask);
4743 schedstat_inc(sd, lb_count[idle]);
4746 group = find_busiest_group(&env, balance);
4752 schedstat_inc(sd, lb_nobusyg[idle]);
4756 busiest = env.find_busiest_queue(&env, group);
4758 schedstat_inc(sd, lb_nobusyq[idle]);
4761 env.src_rq = busiest;
4762 env.src_cpu = busiest->cpu;
4764 BUG_ON(busiest == env.dst_rq);
4766 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
4770 if (busiest->nr_running > 1) {
4772 * Attempt to move tasks. If find_busiest_group has found
4773 * an imbalance but busiest->nr_running <= 1, the group is
4774 * still unbalanced. ld_moved simply stays zero, so it is
4775 * correctly treated as an imbalance.
4777 env.flags |= LBF_ALL_PINNED;
4778 env.src_cpu = busiest->cpu;
4779 env.src_rq = busiest;
4780 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
4781 if (sched_feat_numa(NUMA_PULL))
4782 env.tasks = offnode_tasks(busiest);
4784 env.tasks = &busiest->cfs_tasks;
4786 update_h_load(env.src_cpu);
4788 local_irq_save(flags);
4789 double_rq_lock(env.dst_rq, busiest);
4792 * cur_ld_moved - load moved in current iteration
4793 * ld_moved - cumulative load moved across iterations
4795 cur_ld_moved = move_tasks(&env);
4796 ld_moved += cur_ld_moved;
4797 double_rq_unlock(env.dst_rq, busiest);
4798 local_irq_restore(flags);
4800 if (env.flags & LBF_NEED_BREAK) {
4801 env.flags &= ~LBF_NEED_BREAK;
4806 * some other cpu did the load balance for us.
4808 if (cur_ld_moved && env.dst_cpu != smp_processor_id())
4809 resched_cpu(env.dst_cpu);
4812 * Revisit (affine) tasks on src_cpu that couldn't be moved to
4813 * us and move them to an alternate dst_cpu in our sched_group
4814 * where they can run. The upper limit on how many times we
4815 * iterate on same src_cpu is dependent on number of cpus in our
4818 * This changes load balance semantics a bit on who can move
4819 * load to a given_cpu. In addition to the given_cpu itself
4820 * (or a ilb_cpu acting on its behalf where given_cpu is
4821 * nohz-idle), we now have balance_cpu in a position to move
4822 * load to given_cpu. In rare situations, this may cause
4823 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
4824 * _independently_ and at _same_ time to move some load to
4825 * given_cpu) causing exceess load to be moved to given_cpu.
4826 * This however should not happen so much in practice and
4827 * moreover subsequent load balance cycles should correct the
4828 * excess load moved.
4830 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0 &&
4831 lb_iterations++ < max_lb_iterations) {
4833 env.dst_rq = cpu_rq(env.new_dst_cpu);
4834 env.dst_cpu = env.new_dst_cpu;
4835 env.flags &= ~LBF_SOME_PINNED;
4837 env.loop_break = sched_nr_migrate_break;
4839 * Go back to "more_balance" rather than "redo" since we
4840 * need to continue with same src_cpu.
4845 /* All tasks on this runqueue were pinned by CPU affinity */
4846 if (unlikely(env.flags & LBF_ALL_PINNED)) {
4847 cpumask_clear_cpu(cpu_of(busiest), cpus);
4848 if (!cpumask_empty(cpus)) {
4850 env.loop_break = sched_nr_migrate_break;
4858 schedstat_inc(sd, lb_failed[idle]);
4860 * Increment the failure counter only on periodic balance.
4861 * We do not want newidle balance, which can be very
4862 * frequent, pollute the failure counter causing
4863 * excessive cache_hot migrations and active balances.
4865 if (idle != CPU_NEWLY_IDLE)
4866 sd->nr_balance_failed++;
4868 if (need_active_balance(&env)) {
4869 raw_spin_lock_irqsave(&busiest->lock, flags);
4871 /* don't kick the active_load_balance_cpu_stop,
4872 * if the curr task on busiest cpu can't be
4875 if (!cpumask_test_cpu(this_cpu,
4876 tsk_cpus_allowed(busiest->curr))) {
4877 raw_spin_unlock_irqrestore(&busiest->lock,
4879 env.flags |= LBF_ALL_PINNED;
4880 goto out_one_pinned;
4884 * ->active_balance synchronizes accesses to
4885 * ->active_balance_work. Once set, it's cleared
4886 * only after active load balance is finished.
4888 if (!busiest->active_balance) {
4889 busiest->active_balance = 1;
4890 busiest->push_cpu = this_cpu;
4893 raw_spin_unlock_irqrestore(&busiest->lock, flags);
4895 if (active_balance) {
4896 stop_one_cpu_nowait(cpu_of(busiest),
4897 active_load_balance_cpu_stop, busiest,
4898 &busiest->active_balance_work);
4902 * We've kicked active balancing, reset the failure
4905 sd->nr_balance_failed = sd->cache_nice_tries+1;
4908 sd->nr_balance_failed = 0;
4910 if (likely(!active_balance)) {
4911 /* We were unbalanced, so reset the balancing interval */
4912 sd->balance_interval = sd->min_interval;
4915 * If we've begun active balancing, start to back off. This
4916 * case may not be covered by the all_pinned logic if there
4917 * is only 1 task on the busy runqueue (because we don't call
4920 if (sd->balance_interval < sd->max_interval)
4921 sd->balance_interval *= 2;
4927 schedstat_inc(sd, lb_balanced[idle]);
4929 sd->nr_balance_failed = 0;
4932 /* tune up the balancing interval */
4933 if (((env.flags & LBF_ALL_PINNED) &&
4934 sd->balance_interval < MAX_PINNED_INTERVAL) ||
4935 (sd->balance_interval < sd->max_interval))
4936 sd->balance_interval *= 2;
4944 * idle_balance is called by schedule() if this_cpu is about to become
4945 * idle. Attempts to pull tasks from other CPUs.
4947 void idle_balance(int this_cpu, struct rq *this_rq)
4949 struct sched_domain *sd;
4950 int pulled_task = 0;
4951 unsigned long next_balance = jiffies + HZ;
4953 this_rq->idle_stamp = this_rq->clock;
4955 if (this_rq->avg_idle < sysctl_sched_migration_cost)
4959 * Drop the rq->lock, but keep IRQ/preempt disabled.
4961 raw_spin_unlock(&this_rq->lock);
4963 update_shares(this_cpu);
4965 for_each_domain(this_cpu, sd) {
4966 unsigned long interval;
4969 if (!(sd->flags & SD_LOAD_BALANCE))
4972 if (sd->flags & SD_BALANCE_NEWIDLE) {
4973 /* If we've pulled tasks over stop searching: */
4974 pulled_task = load_balance(this_cpu, this_rq,
4975 sd, CPU_NEWLY_IDLE, &balance);
4978 interval = msecs_to_jiffies(sd->balance_interval);
4979 if (time_after(next_balance, sd->last_balance + interval))
4980 next_balance = sd->last_balance + interval;
4982 this_rq->idle_stamp = 0;
4988 raw_spin_lock(&this_rq->lock);
4990 if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
4992 * We are going idle. next_balance may be set based on
4993 * a busy processor. So reset next_balance.
4995 this_rq->next_balance = next_balance;
5000 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
5001 * running tasks off the busiest CPU onto idle CPUs. It requires at
5002 * least 1 task to be running on each physical CPU where possible, and
5003 * avoids physical / logical imbalances.
5005 static int active_load_balance_cpu_stop(void *data)
5007 struct rq *busiest_rq = data;
5008 int busiest_cpu = cpu_of(busiest_rq);
5009 int target_cpu = busiest_rq->push_cpu;
5010 struct rq *target_rq = cpu_rq(target_cpu);
5011 struct sched_domain *sd;
5013 raw_spin_lock_irq(&busiest_rq->lock);
5015 /* make sure the requested cpu hasn't gone down in the meantime */
5016 if (unlikely(busiest_cpu != smp_processor_id() ||
5017 !busiest_rq->active_balance))
5020 /* Is there any task to move? */
5021 if (busiest_rq->nr_running <= 1)
5025 * This condition is "impossible", if it occurs
5026 * we need to fix it. Originally reported by
5027 * Bjorn Helgaas on a 128-cpu setup.
5029 BUG_ON(busiest_rq == target_rq);
5031 /* move a task from busiest_rq to target_rq */
5032 double_lock_balance(busiest_rq, target_rq);
5034 /* Search for an sd spanning us and the target CPU. */
5036 for_each_domain(target_cpu, sd) {
5037 if ((sd->flags & SD_LOAD_BALANCE) &&
5038 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
5043 struct lb_env env = {
5045 .dst_cpu = target_cpu,
5046 .dst_rq = target_rq,
5047 .src_cpu = busiest_rq->cpu,
5048 .src_rq = busiest_rq,
5052 schedstat_inc(sd, alb_count);
5054 if (move_one_task(&env))
5055 schedstat_inc(sd, alb_pushed);
5057 schedstat_inc(sd, alb_failed);
5060 double_unlock_balance(busiest_rq, target_rq);
5062 busiest_rq->active_balance = 0;
5063 raw_spin_unlock_irq(&busiest_rq->lock);
5069 * idle load balancing details
5070 * - When one of the busy CPUs notice that there may be an idle rebalancing
5071 * needed, they will kick the idle load balancer, which then does idle
5072 * load balancing for all the idle CPUs.
5075 cpumask_var_t idle_cpus_mask;
5077 unsigned long next_balance; /* in jiffy units */
5078 } nohz ____cacheline_aligned;
5080 static inline int find_new_ilb(int call_cpu)
5082 int ilb = cpumask_first(nohz.idle_cpus_mask);
5084 if (ilb < nr_cpu_ids && idle_cpu(ilb))
5091 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
5092 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
5093 * CPU (if there is one).
5095 static void nohz_balancer_kick(int cpu)
5099 nohz.next_balance++;
5101 ilb_cpu = find_new_ilb(cpu);
5103 if (ilb_cpu >= nr_cpu_ids)
5106 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
5109 * Use smp_send_reschedule() instead of resched_cpu().
5110 * This way we generate a sched IPI on the target cpu which
5111 * is idle. And the softirq performing nohz idle load balance
5112 * will be run before returning from the IPI.
5114 smp_send_reschedule(ilb_cpu);
5118 static inline void nohz_balance_exit_idle(int cpu)
5120 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
5121 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
5122 atomic_dec(&nohz.nr_cpus);
5123 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
5127 static inline void set_cpu_sd_state_busy(void)
5129 struct sched_domain *sd;
5130 int cpu = smp_processor_id();
5132 if (!test_bit(NOHZ_IDLE, nohz_flags(cpu)))
5134 clear_bit(NOHZ_IDLE, nohz_flags(cpu));
5137 for_each_domain(cpu, sd)
5138 atomic_inc(&sd->groups->sgp->nr_busy_cpus);
5142 void set_cpu_sd_state_idle(void)
5144 struct sched_domain *sd;
5145 int cpu = smp_processor_id();
5147 if (test_bit(NOHZ_IDLE, nohz_flags(cpu)))
5149 set_bit(NOHZ_IDLE, nohz_flags(cpu));
5152 for_each_domain(cpu, sd)
5153 atomic_dec(&sd->groups->sgp->nr_busy_cpus);
5158 * This routine will record that the cpu is going idle with tick stopped.
5159 * This info will be used in performing idle load balancing in the future.
5161 void nohz_balance_enter_idle(int cpu)
5164 * If this cpu is going down, then nothing needs to be done.
5166 if (!cpu_active(cpu))
5169 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
5172 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
5173 atomic_inc(&nohz.nr_cpus);
5174 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
5177 static int __cpuinit sched_ilb_notifier(struct notifier_block *nfb,
5178 unsigned long action, void *hcpu)
5180 switch (action & ~CPU_TASKS_FROZEN) {
5182 nohz_balance_exit_idle(smp_processor_id());
5190 static DEFINE_SPINLOCK(balancing);
5193 * Scale the max load_balance interval with the number of CPUs in the system.
5194 * This trades load-balance latency on larger machines for less cross talk.
5196 void update_max_interval(void)
5198 max_load_balance_interval = HZ*num_online_cpus()/10;
5202 * It checks each scheduling domain to see if it is due to be balanced,
5203 * and initiates a balancing operation if so.
5205 * Balancing parameters are set up in arch_init_sched_domains.
5207 static void rebalance_domains(int cpu, enum cpu_idle_type idle)
5210 struct rq *rq = cpu_rq(cpu);
5211 unsigned long interval;
5212 struct sched_domain *sd;
5213 /* Earliest time when we have to do rebalance again */
5214 unsigned long next_balance = jiffies + 60*HZ;
5215 int update_next_balance = 0;
5221 for_each_domain(cpu, sd) {
5222 if (!(sd->flags & SD_LOAD_BALANCE))
5225 interval = sd->balance_interval;
5226 if (idle != CPU_IDLE)
5227 interval *= sd->busy_factor;
5229 /* scale ms to jiffies */
5230 interval = msecs_to_jiffies(interval);
5231 interval = clamp(interval, 1UL, max_load_balance_interval);
5233 need_serialize = sd->flags & SD_SERIALIZE;
5235 if (need_serialize) {
5236 if (!spin_trylock(&balancing))
5240 if (time_after_eq(jiffies, sd->last_balance + interval)) {
5241 if (load_balance(cpu, rq, sd, idle, &balance)) {
5243 * We've pulled tasks over so either we're no
5246 idle = CPU_NOT_IDLE;
5248 sd->last_balance = jiffies;
5251 spin_unlock(&balancing);
5253 if (time_after(next_balance, sd->last_balance + interval)) {
5254 next_balance = sd->last_balance + interval;
5255 update_next_balance = 1;
5259 * Stop the load balance at this level. There is another
5260 * CPU in our sched group which is doing load balancing more
5269 * next_balance will be updated only when there is a need.
5270 * When the cpu is attached to null domain for ex, it will not be
5273 if (likely(update_next_balance))
5274 rq->next_balance = next_balance;
5279 * In CONFIG_NO_HZ case, the idle balance kickee will do the
5280 * rebalancing for all the cpus for whom scheduler ticks are stopped.
5282 static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle)
5284 struct rq *this_rq = cpu_rq(this_cpu);
5288 if (idle != CPU_IDLE ||
5289 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
5292 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
5293 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
5297 * If this cpu gets work to do, stop the load balancing
5298 * work being done for other cpus. Next load
5299 * balancing owner will pick it up.
5304 rq = cpu_rq(balance_cpu);
5306 raw_spin_lock_irq(&rq->lock);
5307 update_rq_clock(rq);
5308 update_idle_cpu_load(rq);
5309 raw_spin_unlock_irq(&rq->lock);
5311 rebalance_domains(balance_cpu, CPU_IDLE);
5313 if (time_after(this_rq->next_balance, rq->next_balance))
5314 this_rq->next_balance = rq->next_balance;
5316 nohz.next_balance = this_rq->next_balance;
5318 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
5322 * Current heuristic for kicking the idle load balancer in the presence
5323 * of an idle cpu is the system.
5324 * - This rq has more than one task.
5325 * - At any scheduler domain level, this cpu's scheduler group has multiple
5326 * busy cpu's exceeding the group's power.
5327 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
5328 * domain span are idle.
5330 static inline int nohz_kick_needed(struct rq *rq, int cpu)
5332 unsigned long now = jiffies;
5333 struct sched_domain *sd;
5335 if (unlikely(idle_cpu(cpu)))
5339 * We may be recently in ticked or tickless idle mode. At the first
5340 * busy tick after returning from idle, we will update the busy stats.
5342 set_cpu_sd_state_busy();
5343 nohz_balance_exit_idle(cpu);
5346 * None are in tickless mode and hence no need for NOHZ idle load
5349 if (likely(!atomic_read(&nohz.nr_cpus)))
5352 if (time_before(now, nohz.next_balance))
5355 if (rq->nr_running >= 2)
5359 for_each_domain(cpu, sd) {
5360 struct sched_group *sg = sd->groups;
5361 struct sched_group_power *sgp = sg->sgp;
5362 int nr_busy = atomic_read(&sgp->nr_busy_cpus);
5364 if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1)
5365 goto need_kick_unlock;
5367 if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight
5368 && (cpumask_first_and(nohz.idle_cpus_mask,
5369 sched_domain_span(sd)) < cpu))
5370 goto need_kick_unlock;
5372 if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING)))
5384 static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle) { }
5388 * run_rebalance_domains is triggered when needed from the scheduler tick.
5389 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
5391 static void run_rebalance_domains(struct softirq_action *h)
5393 int this_cpu = smp_processor_id();
5394 struct rq *this_rq = cpu_rq(this_cpu);
5395 enum cpu_idle_type idle = this_rq->idle_balance ?
5396 CPU_IDLE : CPU_NOT_IDLE;
5398 rebalance_domains(this_cpu, idle);
5401 * If this cpu has a pending nohz_balance_kick, then do the
5402 * balancing on behalf of the other idle cpus whose ticks are
5405 nohz_idle_balance(this_cpu, idle);
5408 static inline int on_null_domain(int cpu)
5410 return !rcu_dereference_sched(cpu_rq(cpu)->sd);
5414 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
5416 void trigger_load_balance(struct rq *rq, int cpu)
5418 /* Don't need to rebalance while attached to NULL domain */
5419 if (time_after_eq(jiffies, rq->next_balance) &&
5420 likely(!on_null_domain(cpu)))
5421 raise_softirq(SCHED_SOFTIRQ);
5423 if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
5424 nohz_balancer_kick(cpu);
5428 static void rq_online_fair(struct rq *rq)
5433 static void rq_offline_fair(struct rq *rq)
5437 /* Ensure any throttled groups are reachable by pick_next_task */
5438 unthrottle_offline_cfs_rqs(rq);
5441 #endif /* CONFIG_SMP */
5444 * scheduler tick hitting a task of our scheduling class:
5446 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
5448 struct cfs_rq *cfs_rq;
5449 struct sched_entity *se = &curr->se;
5451 for_each_sched_entity(se) {
5452 cfs_rq = cfs_rq_of(se);
5453 entity_tick(cfs_rq, se, queued);
5456 if (sched_feat_numa(NUMA))
5457 task_tick_numa(rq, curr);
5461 * called on fork with the child task as argument from the parent's context
5462 * - child not yet on the tasklist
5463 * - preemption disabled
5465 static void task_fork_fair(struct task_struct *p)
5467 struct cfs_rq *cfs_rq;
5468 struct sched_entity *se = &p->se, *curr;
5469 int this_cpu = smp_processor_id();
5470 struct rq *rq = this_rq();
5471 unsigned long flags;
5473 raw_spin_lock_irqsave(&rq->lock, flags);
5475 update_rq_clock(rq);
5477 cfs_rq = task_cfs_rq(current);
5478 curr = cfs_rq->curr;
5480 if (unlikely(task_cpu(p) != this_cpu)) {
5482 __set_task_cpu(p, this_cpu);
5486 update_curr(cfs_rq);
5489 se->vruntime = curr->vruntime;
5490 place_entity(cfs_rq, se, 1);
5492 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
5494 * Upon rescheduling, sched_class::put_prev_task() will place
5495 * 'current' within the tree based on its new key value.
5497 swap(curr->vruntime, se->vruntime);
5498 resched_task(rq->curr);
5501 se->vruntime -= cfs_rq->min_vruntime;
5503 raw_spin_unlock_irqrestore(&rq->lock, flags);
5507 * Priority of the task has changed. Check to see if we preempt
5511 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
5517 * Reschedule if we are currently running on this runqueue and
5518 * our priority decreased, or if we are not currently running on
5519 * this runqueue and our priority is higher than the current's
5521 if (rq->curr == p) {
5522 if (p->prio > oldprio)
5523 resched_task(rq->curr);
5525 check_preempt_curr(rq, p, 0);
5528 static void switched_from_fair(struct rq *rq, struct task_struct *p)
5530 struct sched_entity *se = &p->se;
5531 struct cfs_rq *cfs_rq = cfs_rq_of(se);
5534 * Ensure the task's vruntime is normalized, so that when its
5535 * switched back to the fair class the enqueue_entity(.flags=0) will
5536 * do the right thing.
5538 * If it was on_rq, then the dequeue_entity(.flags=0) will already
5539 * have normalized the vruntime, if it was !on_rq, then only when
5540 * the task is sleeping will it still have non-normalized vruntime.
5542 if (!se->on_rq && p->state != TASK_RUNNING) {
5544 * Fix up our vruntime so that the current sleep doesn't
5545 * cause 'unlimited' sleep bonus.
5547 place_entity(cfs_rq, se, 0);
5548 se->vruntime -= cfs_rq->min_vruntime;
5553 * We switched to the sched_fair class.
5555 static void switched_to_fair(struct rq *rq, struct task_struct *p)
5561 * We were most likely switched from sched_rt, so
5562 * kick off the schedule if running, otherwise just see
5563 * if we can still preempt the current task.
5566 resched_task(rq->curr);
5568 check_preempt_curr(rq, p, 0);
5571 /* Account for a task changing its policy or group.
5573 * This routine is mostly called to set cfs_rq->curr field when a task
5574 * migrates between groups/classes.
5576 static void set_curr_task_fair(struct rq *rq)
5578 struct sched_entity *se = &rq->curr->se;
5580 for_each_sched_entity(se) {
5581 struct cfs_rq *cfs_rq = cfs_rq_of(se);
5583 set_next_entity(cfs_rq, se);
5584 /* ensure bandwidth has been allocated on our new cfs_rq */
5585 account_cfs_rq_runtime(cfs_rq, 0);
5589 void init_cfs_rq(struct cfs_rq *cfs_rq)
5591 cfs_rq->tasks_timeline = RB_ROOT;
5592 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
5593 #ifndef CONFIG_64BIT
5594 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
5598 #ifdef CONFIG_FAIR_GROUP_SCHED
5599 static void task_move_group_fair(struct task_struct *p, int on_rq)
5602 * If the task was not on the rq at the time of this cgroup movement
5603 * it must have been asleep, sleeping tasks keep their ->vruntime
5604 * absolute on their old rq until wakeup (needed for the fair sleeper
5605 * bonus in place_entity()).
5607 * If it was on the rq, we've just 'preempted' it, which does convert
5608 * ->vruntime to a relative base.
5610 * Make sure both cases convert their relative position when migrating
5611 * to another cgroup's rq. This does somewhat interfere with the
5612 * fair sleeper stuff for the first placement, but who cares.
5615 * When !on_rq, vruntime of the task has usually NOT been normalized.
5616 * But there are some cases where it has already been normalized:
5618 * - Moving a forked child which is waiting for being woken up by
5619 * wake_up_new_task().
5620 * - Moving a task which has been woken up by try_to_wake_up() and
5621 * waiting for actually being woken up by sched_ttwu_pending().
5623 * To prevent boost or penalty in the new cfs_rq caused by delta
5624 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
5626 if (!on_rq && (!p->se.sum_exec_runtime || p->state == TASK_WAKING))
5630 p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime;
5631 set_task_rq(p, task_cpu(p));
5633 p->se.vruntime += cfs_rq_of(&p->se)->min_vruntime;
5636 void free_fair_sched_group(struct task_group *tg)
5640 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
5642 for_each_possible_cpu(i) {
5644 kfree(tg->cfs_rq[i]);
5653 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
5655 struct cfs_rq *cfs_rq;
5656 struct sched_entity *se;
5659 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
5662 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
5666 tg->shares = NICE_0_LOAD;
5668 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
5670 for_each_possible_cpu(i) {
5671 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
5672 GFP_KERNEL, cpu_to_node(i));
5676 se = kzalloc_node(sizeof(struct sched_entity),
5677 GFP_KERNEL, cpu_to_node(i));
5681 init_cfs_rq(cfs_rq);
5682 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
5693 void unregister_fair_sched_group(struct task_group *tg, int cpu)
5695 struct rq *rq = cpu_rq(cpu);
5696 unsigned long flags;
5699 * Only empty task groups can be destroyed; so we can speculatively
5700 * check on_list without danger of it being re-added.
5702 if (!tg->cfs_rq[cpu]->on_list)
5705 raw_spin_lock_irqsave(&rq->lock, flags);
5706 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
5707 raw_spin_unlock_irqrestore(&rq->lock, flags);
5710 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
5711 struct sched_entity *se, int cpu,
5712 struct sched_entity *parent)
5714 struct rq *rq = cpu_rq(cpu);
5719 /* allow initial update_cfs_load() to truncate */
5720 cfs_rq->load_stamp = 1;
5722 init_cfs_rq_runtime(cfs_rq);
5724 tg->cfs_rq[cpu] = cfs_rq;
5727 /* se could be NULL for root_task_group */
5732 se->cfs_rq = &rq->cfs;
5734 se->cfs_rq = parent->my_q;
5737 update_load_set(&se->load, 0);
5738 se->parent = parent;
5741 static DEFINE_MUTEX(shares_mutex);
5743 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
5746 unsigned long flags;
5749 * We can't change the weight of the root cgroup.
5754 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
5756 mutex_lock(&shares_mutex);
5757 if (tg->shares == shares)
5760 tg->shares = shares;
5761 for_each_possible_cpu(i) {
5762 struct rq *rq = cpu_rq(i);
5763 struct sched_entity *se;
5766 /* Propagate contribution to hierarchy */
5767 raw_spin_lock_irqsave(&rq->lock, flags);
5768 for_each_sched_entity(se)
5769 update_cfs_shares(group_cfs_rq(se));
5770 raw_spin_unlock_irqrestore(&rq->lock, flags);
5774 mutex_unlock(&shares_mutex);
5777 #else /* CONFIG_FAIR_GROUP_SCHED */
5779 void free_fair_sched_group(struct task_group *tg) { }
5781 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
5786 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
5788 #endif /* CONFIG_FAIR_GROUP_SCHED */
5791 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
5793 struct sched_entity *se = &task->se;
5794 unsigned int rr_interval = 0;
5797 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
5800 if (rq->cfs.load.weight)
5801 rr_interval = NS_TO_JIFFIES(sched_slice(&rq->cfs, se));
5807 * All the scheduling class methods:
5809 const struct sched_class fair_sched_class = {
5810 .next = &idle_sched_class,
5811 .enqueue_task = enqueue_task_fair,
5812 .dequeue_task = dequeue_task_fair,
5813 .yield_task = yield_task_fair,
5814 .yield_to_task = yield_to_task_fair,
5816 .check_preempt_curr = check_preempt_wakeup,
5818 .pick_next_task = pick_next_task_fair,
5819 .put_prev_task = put_prev_task_fair,
5822 .select_task_rq = select_task_rq_fair,
5824 .rq_online = rq_online_fair,
5825 .rq_offline = rq_offline_fair,
5827 .task_waking = task_waking_fair,
5830 .set_curr_task = set_curr_task_fair,
5831 .task_tick = task_tick_fair,
5832 .task_fork = task_fork_fair,
5834 .prio_changed = prio_changed_fair,
5835 .switched_from = switched_from_fair,
5836 .switched_to = switched_to_fair,
5838 .get_rr_interval = get_rr_interval_fair,
5840 #ifdef CONFIG_FAIR_GROUP_SCHED
5841 .task_move_group = task_move_group_fair,
5845 #ifdef CONFIG_SCHED_DEBUG
5846 void print_cfs_stats(struct seq_file *m, int cpu)
5848 struct cfs_rq *cfs_rq;
5851 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
5852 print_cfs_rq(m, cpu, cfs_rq);
5857 __init void init_sched_fair_class(void)
5860 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
5863 nohz.next_balance = jiffies;
5864 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
5865 cpu_notifier(sched_ilb_notifier, 0);