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
23 #include <linux/sched.h>
24 #include <linux/latencytop.h>
25 #include <linux/cpumask.h>
26 #include <linux/cpuidle.h>
27 #include <linux/slab.h>
28 #include <linux/profile.h>
29 #include <linux/interrupt.h>
30 #include <linux/mempolicy.h>
31 #include <linux/migrate.h>
32 #include <linux/task_work.h>
34 #include <trace/events/sched.h>
39 * Targeted preemption latency for CPU-bound tasks:
40 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
42 * NOTE: this latency value is not the same as the concept of
43 * 'timeslice length' - timeslices in CFS are of variable length
44 * and have no persistent notion like in traditional, time-slice
45 * based scheduling concepts.
47 * (to see the precise effective timeslice length of your workload,
48 * run vmstat and monitor the context-switches (cs) field)
50 unsigned int sysctl_sched_latency
= 6000000ULL;
51 unsigned int normalized_sysctl_sched_latency
= 6000000ULL;
54 * The initial- and re-scaling of tunables is configurable
55 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
58 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
59 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
60 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
62 enum sched_tunable_scaling sysctl_sched_tunable_scaling
63 = SCHED_TUNABLESCALING_LOG
;
66 * Minimal preemption granularity for CPU-bound tasks:
67 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
69 unsigned int sysctl_sched_min_granularity
= 750000ULL;
70 unsigned int normalized_sysctl_sched_min_granularity
= 750000ULL;
73 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
75 static unsigned int sched_nr_latency
= 8;
78 * After fork, child runs first. If set to 0 (default) then
79 * parent will (try to) run first.
81 unsigned int sysctl_sched_child_runs_first __read_mostly
;
84 * SCHED_OTHER wake-up granularity.
85 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
87 * This option delays the preemption effects of decoupled workloads
88 * and reduces their over-scheduling. Synchronous workloads will still
89 * have immediate wakeup/sleep latencies.
91 unsigned int sysctl_sched_wakeup_granularity
= 1000000UL;
92 unsigned int normalized_sysctl_sched_wakeup_granularity
= 1000000UL;
94 const_debug
unsigned int sysctl_sched_migration_cost
= 500000UL;
97 * The exponential sliding window over which load is averaged for shares
101 unsigned int __read_mostly sysctl_sched_shares_window
= 10000000UL;
103 #ifdef CONFIG_CFS_BANDWIDTH
105 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
106 * each time a cfs_rq requests quota.
108 * Note: in the case that the slice exceeds the runtime remaining (either due
109 * to consumption or the quota being specified to be smaller than the slice)
110 * we will always only issue the remaining available time.
112 * default: 5 msec, units: microseconds
114 unsigned int sysctl_sched_cfs_bandwidth_slice
= 5000UL;
117 static inline void update_load_add(struct load_weight
*lw
, unsigned long inc
)
123 static inline void update_load_sub(struct load_weight
*lw
, unsigned long dec
)
129 static inline void update_load_set(struct load_weight
*lw
, unsigned long w
)
136 * Increase the granularity value when there are more CPUs,
137 * because with more CPUs the 'effective latency' as visible
138 * to users decreases. But the relationship is not linear,
139 * so pick a second-best guess by going with the log2 of the
142 * This idea comes from the SD scheduler of Con Kolivas:
144 static unsigned int get_update_sysctl_factor(void)
146 unsigned int cpus
= min_t(unsigned int, num_online_cpus(), 8);
149 switch (sysctl_sched_tunable_scaling
) {
150 case SCHED_TUNABLESCALING_NONE
:
153 case SCHED_TUNABLESCALING_LINEAR
:
156 case SCHED_TUNABLESCALING_LOG
:
158 factor
= 1 + ilog2(cpus
);
165 static void update_sysctl(void)
167 unsigned int factor
= get_update_sysctl_factor();
169 #define SET_SYSCTL(name) \
170 (sysctl_##name = (factor) * normalized_sysctl_##name)
171 SET_SYSCTL(sched_min_granularity
);
172 SET_SYSCTL(sched_latency
);
173 SET_SYSCTL(sched_wakeup_granularity
);
177 void sched_init_granularity(void)
182 #define WMULT_CONST (~0U)
183 #define WMULT_SHIFT 32
185 static void __update_inv_weight(struct load_weight
*lw
)
189 if (likely(lw
->inv_weight
))
192 w
= scale_load_down(lw
->weight
);
194 if (BITS_PER_LONG
> 32 && unlikely(w
>= WMULT_CONST
))
196 else if (unlikely(!w
))
197 lw
->inv_weight
= WMULT_CONST
;
199 lw
->inv_weight
= WMULT_CONST
/ w
;
203 * delta_exec * weight / lw.weight
205 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
207 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
208 * we're guaranteed shift stays positive because inv_weight is guaranteed to
209 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
211 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
212 * weight/lw.weight <= 1, and therefore our shift will also be positive.
214 static u64
__calc_delta(u64 delta_exec
, unsigned long weight
, struct load_weight
*lw
)
216 u64 fact
= scale_load_down(weight
);
217 int shift
= WMULT_SHIFT
;
219 __update_inv_weight(lw
);
221 if (unlikely(fact
>> 32)) {
228 /* hint to use a 32x32->64 mul */
229 fact
= (u64
)(u32
)fact
* lw
->inv_weight
;
236 return mul_u64_u32_shr(delta_exec
, fact
, shift
);
240 const struct sched_class fair_sched_class
;
242 /**************************************************************
243 * CFS operations on generic schedulable entities:
246 #ifdef CONFIG_FAIR_GROUP_SCHED
248 /* cpu runqueue to which this cfs_rq is attached */
249 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
254 /* An entity is a task if it doesn't "own" a runqueue */
255 #define entity_is_task(se) (!se->my_q)
257 static inline struct task_struct
*task_of(struct sched_entity
*se
)
259 #ifdef CONFIG_SCHED_DEBUG
260 WARN_ON_ONCE(!entity_is_task(se
));
262 return container_of(se
, struct task_struct
, se
);
265 /* Walk up scheduling entities hierarchy */
266 #define for_each_sched_entity(se) \
267 for (; se; se = se->parent)
269 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
274 /* runqueue on which this entity is (to be) queued */
275 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
280 /* runqueue "owned" by this group */
281 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
286 static inline void list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
288 if (!cfs_rq
->on_list
) {
290 * Ensure we either appear before our parent (if already
291 * enqueued) or force our parent to appear after us when it is
292 * enqueued. The fact that we always enqueue bottom-up
293 * reduces this to two cases.
295 if (cfs_rq
->tg
->parent
&&
296 cfs_rq
->tg
->parent
->cfs_rq
[cpu_of(rq_of(cfs_rq
))]->on_list
) {
297 list_add_rcu(&cfs_rq
->leaf_cfs_rq_list
,
298 &rq_of(cfs_rq
)->leaf_cfs_rq_list
);
300 list_add_tail_rcu(&cfs_rq
->leaf_cfs_rq_list
,
301 &rq_of(cfs_rq
)->leaf_cfs_rq_list
);
308 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
310 if (cfs_rq
->on_list
) {
311 list_del_rcu(&cfs_rq
->leaf_cfs_rq_list
);
316 /* Iterate thr' all leaf cfs_rq's on a runqueue */
317 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
318 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
320 /* Do the two (enqueued) entities belong to the same group ? */
321 static inline struct cfs_rq
*
322 is_same_group(struct sched_entity
*se
, struct sched_entity
*pse
)
324 if (se
->cfs_rq
== pse
->cfs_rq
)
330 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
336 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
338 int se_depth
, pse_depth
;
341 * preemption test can be made between sibling entities who are in the
342 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
343 * both tasks until we find their ancestors who are siblings of common
347 /* First walk up until both entities are at same depth */
348 se_depth
= (*se
)->depth
;
349 pse_depth
= (*pse
)->depth
;
351 while (se_depth
> pse_depth
) {
353 *se
= parent_entity(*se
);
356 while (pse_depth
> se_depth
) {
358 *pse
= parent_entity(*pse
);
361 while (!is_same_group(*se
, *pse
)) {
362 *se
= parent_entity(*se
);
363 *pse
= parent_entity(*pse
);
367 #else /* !CONFIG_FAIR_GROUP_SCHED */
369 static inline struct task_struct
*task_of(struct sched_entity
*se
)
371 return container_of(se
, struct task_struct
, se
);
374 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
376 return container_of(cfs_rq
, struct rq
, cfs
);
379 #define entity_is_task(se) 1
381 #define for_each_sched_entity(se) \
382 for (; se; se = NULL)
384 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
386 return &task_rq(p
)->cfs
;
389 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
391 struct task_struct
*p
= task_of(se
);
392 struct rq
*rq
= task_rq(p
);
397 /* runqueue "owned" by this group */
398 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
403 static inline void list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
407 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
411 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
412 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
414 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
420 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
424 #endif /* CONFIG_FAIR_GROUP_SCHED */
426 static __always_inline
427 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
);
429 /**************************************************************
430 * Scheduling class tree data structure manipulation methods:
433 static inline u64
max_vruntime(u64 max_vruntime
, u64 vruntime
)
435 s64 delta
= (s64
)(vruntime
- max_vruntime
);
437 max_vruntime
= vruntime
;
442 static inline u64
min_vruntime(u64 min_vruntime
, u64 vruntime
)
444 s64 delta
= (s64
)(vruntime
- min_vruntime
);
446 min_vruntime
= vruntime
;
451 static inline int entity_before(struct sched_entity
*a
,
452 struct sched_entity
*b
)
454 return (s64
)(a
->vruntime
- b
->vruntime
) < 0;
457 static void update_min_vruntime(struct cfs_rq
*cfs_rq
)
459 u64 vruntime
= cfs_rq
->min_vruntime
;
462 vruntime
= cfs_rq
->curr
->vruntime
;
464 if (cfs_rq
->rb_leftmost
) {
465 struct sched_entity
*se
= rb_entry(cfs_rq
->rb_leftmost
,
470 vruntime
= se
->vruntime
;
472 vruntime
= min_vruntime(vruntime
, se
->vruntime
);
475 /* ensure we never gain time by being placed backwards. */
476 cfs_rq
->min_vruntime
= max_vruntime(cfs_rq
->min_vruntime
, vruntime
);
479 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
484 * Enqueue an entity into the rb-tree:
486 static void __enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
488 struct rb_node
**link
= &cfs_rq
->tasks_timeline
.rb_node
;
489 struct rb_node
*parent
= NULL
;
490 struct sched_entity
*entry
;
494 * Find the right place in the rbtree:
498 entry
= rb_entry(parent
, struct sched_entity
, run_node
);
500 * We dont care about collisions. Nodes with
501 * the same key stay together.
503 if (entity_before(se
, entry
)) {
504 link
= &parent
->rb_left
;
506 link
= &parent
->rb_right
;
512 * Maintain a cache of leftmost tree entries (it is frequently
516 cfs_rq
->rb_leftmost
= &se
->run_node
;
518 rb_link_node(&se
->run_node
, parent
, link
);
519 rb_insert_color(&se
->run_node
, &cfs_rq
->tasks_timeline
);
522 static void __dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
524 if (cfs_rq
->rb_leftmost
== &se
->run_node
) {
525 struct rb_node
*next_node
;
527 next_node
= rb_next(&se
->run_node
);
528 cfs_rq
->rb_leftmost
= next_node
;
531 rb_erase(&se
->run_node
, &cfs_rq
->tasks_timeline
);
534 struct sched_entity
*__pick_first_entity(struct cfs_rq
*cfs_rq
)
536 struct rb_node
*left
= cfs_rq
->rb_leftmost
;
541 return rb_entry(left
, struct sched_entity
, run_node
);
544 static struct sched_entity
*__pick_next_entity(struct sched_entity
*se
)
546 struct rb_node
*next
= rb_next(&se
->run_node
);
551 return rb_entry(next
, struct sched_entity
, run_node
);
554 #ifdef CONFIG_SCHED_DEBUG
555 struct sched_entity
*__pick_last_entity(struct cfs_rq
*cfs_rq
)
557 struct rb_node
*last
= rb_last(&cfs_rq
->tasks_timeline
);
562 return rb_entry(last
, struct sched_entity
, run_node
);
565 /**************************************************************
566 * Scheduling class statistics methods:
569 int sched_proc_update_handler(struct ctl_table
*table
, int write
,
570 void __user
*buffer
, size_t *lenp
,
573 int ret
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
574 unsigned int factor
= get_update_sysctl_factor();
579 sched_nr_latency
= DIV_ROUND_UP(sysctl_sched_latency
,
580 sysctl_sched_min_granularity
);
582 #define WRT_SYSCTL(name) \
583 (normalized_sysctl_##name = sysctl_##name / (factor))
584 WRT_SYSCTL(sched_min_granularity
);
585 WRT_SYSCTL(sched_latency
);
586 WRT_SYSCTL(sched_wakeup_granularity
);
596 static inline u64
calc_delta_fair(u64 delta
, struct sched_entity
*se
)
598 if (unlikely(se
->load
.weight
!= NICE_0_LOAD
))
599 delta
= __calc_delta(delta
, NICE_0_LOAD
, &se
->load
);
605 * The idea is to set a period in which each task runs once.
607 * When there are too many tasks (sched_nr_latency) we have to stretch
608 * this period because otherwise the slices get too small.
610 * p = (nr <= nl) ? l : l*nr/nl
612 static u64
__sched_period(unsigned long nr_running
)
614 if (unlikely(nr_running
> sched_nr_latency
))
615 return nr_running
* sysctl_sched_min_granularity
;
617 return sysctl_sched_latency
;
621 * We calculate the wall-time slice from the period by taking a part
622 * proportional to the weight.
626 static u64
sched_slice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
628 u64 slice
= __sched_period(cfs_rq
->nr_running
+ !se
->on_rq
);
630 for_each_sched_entity(se
) {
631 struct load_weight
*load
;
632 struct load_weight lw
;
634 cfs_rq
= cfs_rq_of(se
);
635 load
= &cfs_rq
->load
;
637 if (unlikely(!se
->on_rq
)) {
640 update_load_add(&lw
, se
->load
.weight
);
643 slice
= __calc_delta(slice
, se
->load
.weight
, load
);
649 * We calculate the vruntime slice of a to-be-inserted task.
653 static u64
sched_vslice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
655 return calc_delta_fair(sched_slice(cfs_rq
, se
), se
);
659 static int select_idle_sibling(struct task_struct
*p
, int cpu
);
660 static unsigned long task_h_load(struct task_struct
*p
);
663 * We choose a half-life close to 1 scheduling period.
664 * Note: The tables runnable_avg_yN_inv and runnable_avg_yN_sum are
665 * dependent on this value.
667 #define LOAD_AVG_PERIOD 32
668 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
669 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_AVG_MAX */
671 /* Give new sched_entity start runnable values to heavy its load in infant time */
672 void init_entity_runnable_average(struct sched_entity
*se
)
674 struct sched_avg
*sa
= &se
->avg
;
676 sa
->last_update_time
= 0;
678 * sched_avg's period_contrib should be strictly less then 1024, so
679 * we give it 1023 to make sure it is almost a period (1024us), and
680 * will definitely be update (after enqueue).
682 sa
->period_contrib
= 1023;
683 sa
->load_avg
= scale_load_down(se
->load
.weight
);
684 sa
->load_sum
= sa
->load_avg
* LOAD_AVG_MAX
;
686 * At this point, util_avg won't be used in select_task_rq_fair anyway
690 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
694 * With new tasks being created, their initial util_avgs are extrapolated
695 * based on the cfs_rq's current util_avg:
697 * util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
699 * However, in many cases, the above util_avg does not give a desired
700 * value. Moreover, the sum of the util_avgs may be divergent, such
701 * as when the series is a harmonic series.
703 * To solve this problem, we also cap the util_avg of successive tasks to
704 * only 1/2 of the left utilization budget:
706 * util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n
708 * where n denotes the nth task.
710 * For example, a simplest series from the beginning would be like:
712 * task util_avg: 512, 256, 128, 64, 32, 16, 8, ...
713 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
715 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
716 * if util_avg > util_avg_cap.
718 void post_init_entity_util_avg(struct sched_entity
*se
)
720 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
721 struct sched_avg
*sa
= &se
->avg
;
722 long cap
= (long)(SCHED_CAPACITY_SCALE
- cfs_rq
->avg
.util_avg
) / 2;
725 if (cfs_rq
->avg
.util_avg
!= 0) {
726 sa
->util_avg
= cfs_rq
->avg
.util_avg
* se
->load
.weight
;
727 sa
->util_avg
/= (cfs_rq
->avg
.load_avg
+ 1);
729 if (sa
->util_avg
> cap
)
734 sa
->util_sum
= sa
->util_avg
* LOAD_AVG_MAX
;
739 void init_entity_runnable_average(struct sched_entity
*se
)
742 void post_init_entity_util_avg(struct sched_entity
*se
)
748 * Update the current task's runtime statistics.
750 static void update_curr(struct cfs_rq
*cfs_rq
)
752 struct sched_entity
*curr
= cfs_rq
->curr
;
753 u64 now
= rq_clock_task(rq_of(cfs_rq
));
759 delta_exec
= now
- curr
->exec_start
;
760 if (unlikely((s64
)delta_exec
<= 0))
763 curr
->exec_start
= now
;
765 schedstat_set(curr
->statistics
.exec_max
,
766 max(delta_exec
, curr
->statistics
.exec_max
));
768 curr
->sum_exec_runtime
+= delta_exec
;
769 schedstat_add(cfs_rq
, exec_clock
, delta_exec
);
771 curr
->vruntime
+= calc_delta_fair(delta_exec
, curr
);
772 update_min_vruntime(cfs_rq
);
774 if (entity_is_task(curr
)) {
775 struct task_struct
*curtask
= task_of(curr
);
777 trace_sched_stat_runtime(curtask
, delta_exec
, curr
->vruntime
);
778 cpuacct_charge(curtask
, delta_exec
);
779 account_group_exec_runtime(curtask
, delta_exec
);
782 account_cfs_rq_runtime(cfs_rq
, delta_exec
);
785 static void update_curr_fair(struct rq
*rq
)
787 update_curr(cfs_rq_of(&rq
->curr
->se
));
790 #ifdef CONFIG_SCHEDSTATS
792 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
794 u64 wait_start
= rq_clock(rq_of(cfs_rq
));
796 if (entity_is_task(se
) && task_on_rq_migrating(task_of(se
)) &&
797 likely(wait_start
> se
->statistics
.wait_start
))
798 wait_start
-= se
->statistics
.wait_start
;
800 se
->statistics
.wait_start
= wait_start
;
804 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
806 struct task_struct
*p
;
809 delta
= rq_clock(rq_of(cfs_rq
)) - se
->statistics
.wait_start
;
811 if (entity_is_task(se
)) {
813 if (task_on_rq_migrating(p
)) {
815 * Preserve migrating task's wait time so wait_start
816 * time stamp can be adjusted to accumulate wait time
817 * prior to migration.
819 se
->statistics
.wait_start
= delta
;
822 trace_sched_stat_wait(p
, delta
);
825 se
->statistics
.wait_max
= max(se
->statistics
.wait_max
, delta
);
826 se
->statistics
.wait_count
++;
827 se
->statistics
.wait_sum
+= delta
;
828 se
->statistics
.wait_start
= 0;
832 * Task is being enqueued - update stats:
835 update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
838 * Are we enqueueing a waiting task? (for current tasks
839 * a dequeue/enqueue event is a NOP)
841 if (se
!= cfs_rq
->curr
)
842 update_stats_wait_start(cfs_rq
, se
);
846 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
849 * Mark the end of the wait period if dequeueing a
852 if (se
!= cfs_rq
->curr
)
853 update_stats_wait_end(cfs_rq
, se
);
855 if (flags
& DEQUEUE_SLEEP
) {
856 if (entity_is_task(se
)) {
857 struct task_struct
*tsk
= task_of(se
);
859 if (tsk
->state
& TASK_INTERRUPTIBLE
)
860 se
->statistics
.sleep_start
= rq_clock(rq_of(cfs_rq
));
861 if (tsk
->state
& TASK_UNINTERRUPTIBLE
)
862 se
->statistics
.block_start
= rq_clock(rq_of(cfs_rq
));
869 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
874 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
879 update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
884 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
890 * We are picking a new current task - update its stats:
893 update_stats_curr_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
896 * We are starting a new run period:
898 se
->exec_start
= rq_clock_task(rq_of(cfs_rq
));
901 /**************************************************
902 * Scheduling class queueing methods:
905 #ifdef CONFIG_NUMA_BALANCING
907 * Approximate time to scan a full NUMA task in ms. The task scan period is
908 * calculated based on the tasks virtual memory size and
909 * numa_balancing_scan_size.
911 unsigned int sysctl_numa_balancing_scan_period_min
= 1000;
912 unsigned int sysctl_numa_balancing_scan_period_max
= 60000;
914 /* Portion of address space to scan in MB */
915 unsigned int sysctl_numa_balancing_scan_size
= 256;
917 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
918 unsigned int sysctl_numa_balancing_scan_delay
= 1000;
920 static unsigned int task_nr_scan_windows(struct task_struct
*p
)
922 unsigned long rss
= 0;
923 unsigned long nr_scan_pages
;
926 * Calculations based on RSS as non-present and empty pages are skipped
927 * by the PTE scanner and NUMA hinting faults should be trapped based
930 nr_scan_pages
= sysctl_numa_balancing_scan_size
<< (20 - PAGE_SHIFT
);
931 rss
= get_mm_rss(p
->mm
);
935 rss
= round_up(rss
, nr_scan_pages
);
936 return rss
/ nr_scan_pages
;
939 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
940 #define MAX_SCAN_WINDOW 2560
942 static unsigned int task_scan_min(struct task_struct
*p
)
944 unsigned int scan_size
= READ_ONCE(sysctl_numa_balancing_scan_size
);
945 unsigned int scan
, floor
;
946 unsigned int windows
= 1;
948 if (scan_size
< MAX_SCAN_WINDOW
)
949 windows
= MAX_SCAN_WINDOW
/ scan_size
;
950 floor
= 1000 / windows
;
952 scan
= sysctl_numa_balancing_scan_period_min
/ task_nr_scan_windows(p
);
953 return max_t(unsigned int, floor
, scan
);
956 static unsigned int task_scan_max(struct task_struct
*p
)
958 unsigned int smin
= task_scan_min(p
);
961 /* Watch for min being lower than max due to floor calculations */
962 smax
= sysctl_numa_balancing_scan_period_max
/ task_nr_scan_windows(p
);
963 return max(smin
, smax
);
966 static void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
968 rq
->nr_numa_running
+= (p
->numa_preferred_nid
!= -1);
969 rq
->nr_preferred_running
+= (p
->numa_preferred_nid
== task_node(p
));
972 static void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
974 rq
->nr_numa_running
-= (p
->numa_preferred_nid
!= -1);
975 rq
->nr_preferred_running
-= (p
->numa_preferred_nid
== task_node(p
));
981 spinlock_t lock
; /* nr_tasks, tasks */
987 unsigned long total_faults
;
988 unsigned long max_faults_cpu
;
990 * Faults_cpu is used to decide whether memory should move
991 * towards the CPU. As a consequence, these stats are weighted
992 * more by CPU use than by memory faults.
994 unsigned long *faults_cpu
;
995 unsigned long faults
[0];
998 /* Shared or private faults. */
999 #define NR_NUMA_HINT_FAULT_TYPES 2
1001 /* Memory and CPU locality */
1002 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
1004 /* Averaged statistics, and temporary buffers. */
1005 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
1007 pid_t
task_numa_group_id(struct task_struct
*p
)
1009 return p
->numa_group
? p
->numa_group
->gid
: 0;
1013 * The averaged statistics, shared & private, memory & cpu,
1014 * occupy the first half of the array. The second half of the
1015 * array is for current counters, which are averaged into the
1016 * first set by task_numa_placement.
1018 static inline int task_faults_idx(enum numa_faults_stats s
, int nid
, int priv
)
1020 return NR_NUMA_HINT_FAULT_TYPES
* (s
* nr_node_ids
+ nid
) + priv
;
1023 static inline unsigned long task_faults(struct task_struct
*p
, int nid
)
1025 if (!p
->numa_faults
)
1028 return p
->numa_faults
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1029 p
->numa_faults
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1032 static inline unsigned long group_faults(struct task_struct
*p
, int nid
)
1037 return p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1038 p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1041 static inline unsigned long group_faults_cpu(struct numa_group
*group
, int nid
)
1043 return group
->faults_cpu
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1044 group
->faults_cpu
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1048 * A node triggering more than 1/3 as many NUMA faults as the maximum is
1049 * considered part of a numa group's pseudo-interleaving set. Migrations
1050 * between these nodes are slowed down, to allow things to settle down.
1052 #define ACTIVE_NODE_FRACTION 3
1054 static bool numa_is_active_node(int nid
, struct numa_group
*ng
)
1056 return group_faults_cpu(ng
, nid
) * ACTIVE_NODE_FRACTION
> ng
->max_faults_cpu
;
1059 /* Handle placement on systems where not all nodes are directly connected. */
1060 static unsigned long score_nearby_nodes(struct task_struct
*p
, int nid
,
1061 int maxdist
, bool task
)
1063 unsigned long score
= 0;
1067 * All nodes are directly connected, and the same distance
1068 * from each other. No need for fancy placement algorithms.
1070 if (sched_numa_topology_type
== NUMA_DIRECT
)
1074 * This code is called for each node, introducing N^2 complexity,
1075 * which should be ok given the number of nodes rarely exceeds 8.
1077 for_each_online_node(node
) {
1078 unsigned long faults
;
1079 int dist
= node_distance(nid
, node
);
1082 * The furthest away nodes in the system are not interesting
1083 * for placement; nid was already counted.
1085 if (dist
== sched_max_numa_distance
|| node
== nid
)
1089 * On systems with a backplane NUMA topology, compare groups
1090 * of nodes, and move tasks towards the group with the most
1091 * memory accesses. When comparing two nodes at distance
1092 * "hoplimit", only nodes closer by than "hoplimit" are part
1093 * of each group. Skip other nodes.
1095 if (sched_numa_topology_type
== NUMA_BACKPLANE
&&
1099 /* Add up the faults from nearby nodes. */
1101 faults
= task_faults(p
, node
);
1103 faults
= group_faults(p
, node
);
1106 * On systems with a glueless mesh NUMA topology, there are
1107 * no fixed "groups of nodes". Instead, nodes that are not
1108 * directly connected bounce traffic through intermediate
1109 * nodes; a numa_group can occupy any set of nodes.
1110 * The further away a node is, the less the faults count.
1111 * This seems to result in good task placement.
1113 if (sched_numa_topology_type
== NUMA_GLUELESS_MESH
) {
1114 faults
*= (sched_max_numa_distance
- dist
);
1115 faults
/= (sched_max_numa_distance
- LOCAL_DISTANCE
);
1125 * These return the fraction of accesses done by a particular task, or
1126 * task group, on a particular numa node. The group weight is given a
1127 * larger multiplier, in order to group tasks together that are almost
1128 * evenly spread out between numa nodes.
1130 static inline unsigned long task_weight(struct task_struct
*p
, int nid
,
1133 unsigned long faults
, total_faults
;
1135 if (!p
->numa_faults
)
1138 total_faults
= p
->total_numa_faults
;
1143 faults
= task_faults(p
, nid
);
1144 faults
+= score_nearby_nodes(p
, nid
, dist
, true);
1146 return 1000 * faults
/ total_faults
;
1149 static inline unsigned long group_weight(struct task_struct
*p
, int nid
,
1152 unsigned long faults
, total_faults
;
1157 total_faults
= p
->numa_group
->total_faults
;
1162 faults
= group_faults(p
, nid
);
1163 faults
+= score_nearby_nodes(p
, nid
, dist
, false);
1165 return 1000 * faults
/ total_faults
;
1168 bool should_numa_migrate_memory(struct task_struct
*p
, struct page
* page
,
1169 int src_nid
, int dst_cpu
)
1171 struct numa_group
*ng
= p
->numa_group
;
1172 int dst_nid
= cpu_to_node(dst_cpu
);
1173 int last_cpupid
, this_cpupid
;
1175 this_cpupid
= cpu_pid_to_cpupid(dst_cpu
, current
->pid
);
1178 * Multi-stage node selection is used in conjunction with a periodic
1179 * migration fault to build a temporal task<->page relation. By using
1180 * a two-stage filter we remove short/unlikely relations.
1182 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1183 * a task's usage of a particular page (n_p) per total usage of this
1184 * page (n_t) (in a given time-span) to a probability.
1186 * Our periodic faults will sample this probability and getting the
1187 * same result twice in a row, given these samples are fully
1188 * independent, is then given by P(n)^2, provided our sample period
1189 * is sufficiently short compared to the usage pattern.
1191 * This quadric squishes small probabilities, making it less likely we
1192 * act on an unlikely task<->page relation.
1194 last_cpupid
= page_cpupid_xchg_last(page
, this_cpupid
);
1195 if (!cpupid_pid_unset(last_cpupid
) &&
1196 cpupid_to_nid(last_cpupid
) != dst_nid
)
1199 /* Always allow migrate on private faults */
1200 if (cpupid_match_pid(p
, last_cpupid
))
1203 /* A shared fault, but p->numa_group has not been set up yet. */
1208 * Destination node is much more heavily used than the source
1209 * node? Allow migration.
1211 if (group_faults_cpu(ng
, dst_nid
) > group_faults_cpu(ng
, src_nid
) *
1212 ACTIVE_NODE_FRACTION
)
1216 * Distribute memory according to CPU & memory use on each node,
1217 * with 3/4 hysteresis to avoid unnecessary memory migrations:
1219 * faults_cpu(dst) 3 faults_cpu(src)
1220 * --------------- * - > ---------------
1221 * faults_mem(dst) 4 faults_mem(src)
1223 return group_faults_cpu(ng
, dst_nid
) * group_faults(p
, src_nid
) * 3 >
1224 group_faults_cpu(ng
, src_nid
) * group_faults(p
, dst_nid
) * 4;
1227 static unsigned long weighted_cpuload(const int cpu
);
1228 static unsigned long source_load(int cpu
, int type
);
1229 static unsigned long target_load(int cpu
, int type
);
1230 static unsigned long capacity_of(int cpu
);
1231 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
);
1233 /* Cached statistics for all CPUs within a node */
1235 unsigned long nr_running
;
1238 /* Total compute capacity of CPUs on a node */
1239 unsigned long compute_capacity
;
1241 /* Approximate capacity in terms of runnable tasks on a node */
1242 unsigned long task_capacity
;
1243 int has_free_capacity
;
1247 * XXX borrowed from update_sg_lb_stats
1249 static void update_numa_stats(struct numa_stats
*ns
, int nid
)
1251 int smt
, cpu
, cpus
= 0;
1252 unsigned long capacity
;
1254 memset(ns
, 0, sizeof(*ns
));
1255 for_each_cpu(cpu
, cpumask_of_node(nid
)) {
1256 struct rq
*rq
= cpu_rq(cpu
);
1258 ns
->nr_running
+= rq
->nr_running
;
1259 ns
->load
+= weighted_cpuload(cpu
);
1260 ns
->compute_capacity
+= capacity_of(cpu
);
1266 * If we raced with hotplug and there are no CPUs left in our mask
1267 * the @ns structure is NULL'ed and task_numa_compare() will
1268 * not find this node attractive.
1270 * We'll either bail at !has_free_capacity, or we'll detect a huge
1271 * imbalance and bail there.
1276 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1277 smt
= DIV_ROUND_UP(SCHED_CAPACITY_SCALE
* cpus
, ns
->compute_capacity
);
1278 capacity
= cpus
/ smt
; /* cores */
1280 ns
->task_capacity
= min_t(unsigned, capacity
,
1281 DIV_ROUND_CLOSEST(ns
->compute_capacity
, SCHED_CAPACITY_SCALE
));
1282 ns
->has_free_capacity
= (ns
->nr_running
< ns
->task_capacity
);
1285 struct task_numa_env
{
1286 struct task_struct
*p
;
1288 int src_cpu
, src_nid
;
1289 int dst_cpu
, dst_nid
;
1291 struct numa_stats src_stats
, dst_stats
;
1296 struct task_struct
*best_task
;
1301 static void task_numa_assign(struct task_numa_env
*env
,
1302 struct task_struct
*p
, long imp
)
1305 put_task_struct(env
->best_task
);
1310 env
->best_imp
= imp
;
1311 env
->best_cpu
= env
->dst_cpu
;
1314 static bool load_too_imbalanced(long src_load
, long dst_load
,
1315 struct task_numa_env
*env
)
1318 long orig_src_load
, orig_dst_load
;
1319 long src_capacity
, dst_capacity
;
1322 * The load is corrected for the CPU capacity available on each node.
1325 * ------------ vs ---------
1326 * src_capacity dst_capacity
1328 src_capacity
= env
->src_stats
.compute_capacity
;
1329 dst_capacity
= env
->dst_stats
.compute_capacity
;
1331 /* We care about the slope of the imbalance, not the direction. */
1332 if (dst_load
< src_load
)
1333 swap(dst_load
, src_load
);
1335 /* Is the difference below the threshold? */
1336 imb
= dst_load
* src_capacity
* 100 -
1337 src_load
* dst_capacity
* env
->imbalance_pct
;
1342 * The imbalance is above the allowed threshold.
1343 * Compare it with the old imbalance.
1345 orig_src_load
= env
->src_stats
.load
;
1346 orig_dst_load
= env
->dst_stats
.load
;
1348 if (orig_dst_load
< orig_src_load
)
1349 swap(orig_dst_load
, orig_src_load
);
1351 old_imb
= orig_dst_load
* src_capacity
* 100 -
1352 orig_src_load
* dst_capacity
* env
->imbalance_pct
;
1354 /* Would this change make things worse? */
1355 return (imb
> old_imb
);
1359 * This checks if the overall compute and NUMA accesses of the system would
1360 * be improved if the source tasks was migrated to the target dst_cpu taking
1361 * into account that it might be best if task running on the dst_cpu should
1362 * be exchanged with the source task
1364 static void task_numa_compare(struct task_numa_env
*env
,
1365 long taskimp
, long groupimp
)
1367 struct rq
*src_rq
= cpu_rq(env
->src_cpu
);
1368 struct rq
*dst_rq
= cpu_rq(env
->dst_cpu
);
1369 struct task_struct
*cur
;
1370 long src_load
, dst_load
;
1372 long imp
= env
->p
->numa_group
? groupimp
: taskimp
;
1374 int dist
= env
->dist
;
1377 cur
= task_rcu_dereference(&dst_rq
->curr
);
1378 if (cur
&& ((cur
->flags
& PF_EXITING
) || is_idle_task(cur
)))
1382 * Because we have preemption enabled we can get migrated around and
1383 * end try selecting ourselves (current == env->p) as a swap candidate.
1389 * "imp" is the fault differential for the source task between the
1390 * source and destination node. Calculate the total differential for
1391 * the source task and potential destination task. The more negative
1392 * the value is, the more rmeote accesses that would be expected to
1393 * be incurred if the tasks were swapped.
1396 /* Skip this swap candidate if cannot move to the source cpu */
1397 if (!cpumask_test_cpu(env
->src_cpu
, tsk_cpus_allowed(cur
)))
1401 * If dst and source tasks are in the same NUMA group, or not
1402 * in any group then look only at task weights.
1404 if (cur
->numa_group
== env
->p
->numa_group
) {
1405 imp
= taskimp
+ task_weight(cur
, env
->src_nid
, dist
) -
1406 task_weight(cur
, env
->dst_nid
, dist
);
1408 * Add some hysteresis to prevent swapping the
1409 * tasks within a group over tiny differences.
1411 if (cur
->numa_group
)
1415 * Compare the group weights. If a task is all by
1416 * itself (not part of a group), use the task weight
1419 if (cur
->numa_group
)
1420 imp
+= group_weight(cur
, env
->src_nid
, dist
) -
1421 group_weight(cur
, env
->dst_nid
, dist
);
1423 imp
+= task_weight(cur
, env
->src_nid
, dist
) -
1424 task_weight(cur
, env
->dst_nid
, dist
);
1428 if (imp
<= env
->best_imp
&& moveimp
<= env
->best_imp
)
1432 /* Is there capacity at our destination? */
1433 if (env
->src_stats
.nr_running
<= env
->src_stats
.task_capacity
&&
1434 !env
->dst_stats
.has_free_capacity
)
1440 /* Balance doesn't matter much if we're running a task per cpu */
1441 if (imp
> env
->best_imp
&& src_rq
->nr_running
== 1 &&
1442 dst_rq
->nr_running
== 1)
1446 * In the overloaded case, try and keep the load balanced.
1449 load
= task_h_load(env
->p
);
1450 dst_load
= env
->dst_stats
.load
+ load
;
1451 src_load
= env
->src_stats
.load
- load
;
1453 if (moveimp
> imp
&& moveimp
> env
->best_imp
) {
1455 * If the improvement from just moving env->p direction is
1456 * better than swapping tasks around, check if a move is
1457 * possible. Store a slightly smaller score than moveimp,
1458 * so an actually idle CPU will win.
1460 if (!load_too_imbalanced(src_load
, dst_load
, env
)) {
1467 if (imp
<= env
->best_imp
)
1471 load
= task_h_load(cur
);
1476 if (load_too_imbalanced(src_load
, dst_load
, env
))
1480 * One idle CPU per node is evaluated for a task numa move.
1481 * Call select_idle_sibling to maybe find a better one.
1484 env
->dst_cpu
= select_idle_sibling(env
->p
, env
->dst_cpu
);
1487 task_numa_assign(env
, cur
, imp
);
1492 static void task_numa_find_cpu(struct task_numa_env
*env
,
1493 long taskimp
, long groupimp
)
1497 for_each_cpu(cpu
, cpumask_of_node(env
->dst_nid
)) {
1498 /* Skip this CPU if the source task cannot migrate */
1499 if (!cpumask_test_cpu(cpu
, tsk_cpus_allowed(env
->p
)))
1503 task_numa_compare(env
, taskimp
, groupimp
);
1507 /* Only move tasks to a NUMA node less busy than the current node. */
1508 static bool numa_has_capacity(struct task_numa_env
*env
)
1510 struct numa_stats
*src
= &env
->src_stats
;
1511 struct numa_stats
*dst
= &env
->dst_stats
;
1513 if (src
->has_free_capacity
&& !dst
->has_free_capacity
)
1517 * Only consider a task move if the source has a higher load
1518 * than the destination, corrected for CPU capacity on each node.
1520 * src->load dst->load
1521 * --------------------- vs ---------------------
1522 * src->compute_capacity dst->compute_capacity
1524 if (src
->load
* dst
->compute_capacity
* env
->imbalance_pct
>
1526 dst
->load
* src
->compute_capacity
* 100)
1532 static int task_numa_migrate(struct task_struct
*p
)
1534 struct task_numa_env env
= {
1537 .src_cpu
= task_cpu(p
),
1538 .src_nid
= task_node(p
),
1540 .imbalance_pct
= 112,
1546 struct sched_domain
*sd
;
1547 unsigned long taskweight
, groupweight
;
1549 long taskimp
, groupimp
;
1552 * Pick the lowest SD_NUMA domain, as that would have the smallest
1553 * imbalance and would be the first to start moving tasks about.
1555 * And we want to avoid any moving of tasks about, as that would create
1556 * random movement of tasks -- counter the numa conditions we're trying
1560 sd
= rcu_dereference(per_cpu(sd_numa
, env
.src_cpu
));
1562 env
.imbalance_pct
= 100 + (sd
->imbalance_pct
- 100) / 2;
1566 * Cpusets can break the scheduler domain tree into smaller
1567 * balance domains, some of which do not cross NUMA boundaries.
1568 * Tasks that are "trapped" in such domains cannot be migrated
1569 * elsewhere, so there is no point in (re)trying.
1571 if (unlikely(!sd
)) {
1572 p
->numa_preferred_nid
= task_node(p
);
1576 env
.dst_nid
= p
->numa_preferred_nid
;
1577 dist
= env
.dist
= node_distance(env
.src_nid
, env
.dst_nid
);
1578 taskweight
= task_weight(p
, env
.src_nid
, dist
);
1579 groupweight
= group_weight(p
, env
.src_nid
, dist
);
1580 update_numa_stats(&env
.src_stats
, env
.src_nid
);
1581 taskimp
= task_weight(p
, env
.dst_nid
, dist
) - taskweight
;
1582 groupimp
= group_weight(p
, env
.dst_nid
, dist
) - groupweight
;
1583 update_numa_stats(&env
.dst_stats
, env
.dst_nid
);
1585 /* Try to find a spot on the preferred nid. */
1586 if (numa_has_capacity(&env
))
1587 task_numa_find_cpu(&env
, taskimp
, groupimp
);
1590 * Look at other nodes in these cases:
1591 * - there is no space available on the preferred_nid
1592 * - the task is part of a numa_group that is interleaved across
1593 * multiple NUMA nodes; in order to better consolidate the group,
1594 * we need to check other locations.
1596 if (env
.best_cpu
== -1 || (p
->numa_group
&& p
->numa_group
->active_nodes
> 1)) {
1597 for_each_online_node(nid
) {
1598 if (nid
== env
.src_nid
|| nid
== p
->numa_preferred_nid
)
1601 dist
= node_distance(env
.src_nid
, env
.dst_nid
);
1602 if (sched_numa_topology_type
== NUMA_BACKPLANE
&&
1604 taskweight
= task_weight(p
, env
.src_nid
, dist
);
1605 groupweight
= group_weight(p
, env
.src_nid
, dist
);
1608 /* Only consider nodes where both task and groups benefit */
1609 taskimp
= task_weight(p
, nid
, dist
) - taskweight
;
1610 groupimp
= group_weight(p
, nid
, dist
) - groupweight
;
1611 if (taskimp
< 0 && groupimp
< 0)
1616 update_numa_stats(&env
.dst_stats
, env
.dst_nid
);
1617 if (numa_has_capacity(&env
))
1618 task_numa_find_cpu(&env
, taskimp
, groupimp
);
1623 * If the task is part of a workload that spans multiple NUMA nodes,
1624 * and is migrating into one of the workload's active nodes, remember
1625 * this node as the task's preferred numa node, so the workload can
1627 * A task that migrated to a second choice node will be better off
1628 * trying for a better one later. Do not set the preferred node here.
1630 if (p
->numa_group
) {
1631 struct numa_group
*ng
= p
->numa_group
;
1633 if (env
.best_cpu
== -1)
1638 if (ng
->active_nodes
> 1 && numa_is_active_node(env
.dst_nid
, ng
))
1639 sched_setnuma(p
, env
.dst_nid
);
1642 /* No better CPU than the current one was found. */
1643 if (env
.best_cpu
== -1)
1647 * Reset the scan period if the task is being rescheduled on an
1648 * alternative node to recheck if the tasks is now properly placed.
1650 p
->numa_scan_period
= task_scan_min(p
);
1652 if (env
.best_task
== NULL
) {
1653 ret
= migrate_task_to(p
, env
.best_cpu
);
1655 trace_sched_stick_numa(p
, env
.src_cpu
, env
.best_cpu
);
1659 ret
= migrate_swap(p
, env
.best_task
);
1661 trace_sched_stick_numa(p
, env
.src_cpu
, task_cpu(env
.best_task
));
1662 put_task_struct(env
.best_task
);
1666 /* Attempt to migrate a task to a CPU on the preferred node. */
1667 static void numa_migrate_preferred(struct task_struct
*p
)
1669 unsigned long interval
= HZ
;
1671 /* This task has no NUMA fault statistics yet */
1672 if (unlikely(p
->numa_preferred_nid
== -1 || !p
->numa_faults
))
1675 /* Periodically retry migrating the task to the preferred node */
1676 interval
= min(interval
, msecs_to_jiffies(p
->numa_scan_period
) / 16);
1677 p
->numa_migrate_retry
= jiffies
+ interval
;
1679 /* Success if task is already running on preferred CPU */
1680 if (task_node(p
) == p
->numa_preferred_nid
)
1683 /* Otherwise, try migrate to a CPU on the preferred node */
1684 task_numa_migrate(p
);
1688 * Find out how many nodes on the workload is actively running on. Do this by
1689 * tracking the nodes from which NUMA hinting faults are triggered. This can
1690 * be different from the set of nodes where the workload's memory is currently
1693 static void numa_group_count_active_nodes(struct numa_group
*numa_group
)
1695 unsigned long faults
, max_faults
= 0;
1696 int nid
, active_nodes
= 0;
1698 for_each_online_node(nid
) {
1699 faults
= group_faults_cpu(numa_group
, nid
);
1700 if (faults
> max_faults
)
1701 max_faults
= faults
;
1704 for_each_online_node(nid
) {
1705 faults
= group_faults_cpu(numa_group
, nid
);
1706 if (faults
* ACTIVE_NODE_FRACTION
> max_faults
)
1710 numa_group
->max_faults_cpu
= max_faults
;
1711 numa_group
->active_nodes
= active_nodes
;
1715 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1716 * increments. The more local the fault statistics are, the higher the scan
1717 * period will be for the next scan window. If local/(local+remote) ratio is
1718 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1719 * the scan period will decrease. Aim for 70% local accesses.
1721 #define NUMA_PERIOD_SLOTS 10
1722 #define NUMA_PERIOD_THRESHOLD 7
1725 * Increase the scan period (slow down scanning) if the majority of
1726 * our memory is already on our local node, or if the majority of
1727 * the page accesses are shared with other processes.
1728 * Otherwise, decrease the scan period.
1730 static void update_task_scan_period(struct task_struct
*p
,
1731 unsigned long shared
, unsigned long private)
1733 unsigned int period_slot
;
1737 unsigned long remote
= p
->numa_faults_locality
[0];
1738 unsigned long local
= p
->numa_faults_locality
[1];
1741 * If there were no record hinting faults then either the task is
1742 * completely idle or all activity is areas that are not of interest
1743 * to automatic numa balancing. Related to that, if there were failed
1744 * migration then it implies we are migrating too quickly or the local
1745 * node is overloaded. In either case, scan slower
1747 if (local
+ shared
== 0 || p
->numa_faults_locality
[2]) {
1748 p
->numa_scan_period
= min(p
->numa_scan_period_max
,
1749 p
->numa_scan_period
<< 1);
1751 p
->mm
->numa_next_scan
= jiffies
+
1752 msecs_to_jiffies(p
->numa_scan_period
);
1758 * Prepare to scale scan period relative to the current period.
1759 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1760 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1761 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1763 period_slot
= DIV_ROUND_UP(p
->numa_scan_period
, NUMA_PERIOD_SLOTS
);
1764 ratio
= (local
* NUMA_PERIOD_SLOTS
) / (local
+ remote
);
1765 if (ratio
>= NUMA_PERIOD_THRESHOLD
) {
1766 int slot
= ratio
- NUMA_PERIOD_THRESHOLD
;
1769 diff
= slot
* period_slot
;
1771 diff
= -(NUMA_PERIOD_THRESHOLD
- ratio
) * period_slot
;
1774 * Scale scan rate increases based on sharing. There is an
1775 * inverse relationship between the degree of sharing and
1776 * the adjustment made to the scanning period. Broadly
1777 * speaking the intent is that there is little point
1778 * scanning faster if shared accesses dominate as it may
1779 * simply bounce migrations uselessly
1781 ratio
= DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS
, (private + shared
+ 1));
1782 diff
= (diff
* ratio
) / NUMA_PERIOD_SLOTS
;
1785 p
->numa_scan_period
= clamp(p
->numa_scan_period
+ diff
,
1786 task_scan_min(p
), task_scan_max(p
));
1787 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
1791 * Get the fraction of time the task has been running since the last
1792 * NUMA placement cycle. The scheduler keeps similar statistics, but
1793 * decays those on a 32ms period, which is orders of magnitude off
1794 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1795 * stats only if the task is so new there are no NUMA statistics yet.
1797 static u64
numa_get_avg_runtime(struct task_struct
*p
, u64
*period
)
1799 u64 runtime
, delta
, now
;
1800 /* Use the start of this time slice to avoid calculations. */
1801 now
= p
->se
.exec_start
;
1802 runtime
= p
->se
.sum_exec_runtime
;
1804 if (p
->last_task_numa_placement
) {
1805 delta
= runtime
- p
->last_sum_exec_runtime
;
1806 *period
= now
- p
->last_task_numa_placement
;
1808 delta
= p
->se
.avg
.load_sum
/ p
->se
.load
.weight
;
1809 *period
= LOAD_AVG_MAX
;
1812 p
->last_sum_exec_runtime
= runtime
;
1813 p
->last_task_numa_placement
= now
;
1819 * Determine the preferred nid for a task in a numa_group. This needs to
1820 * be done in a way that produces consistent results with group_weight,
1821 * otherwise workloads might not converge.
1823 static int preferred_group_nid(struct task_struct
*p
, int nid
)
1828 /* Direct connections between all NUMA nodes. */
1829 if (sched_numa_topology_type
== NUMA_DIRECT
)
1833 * On a system with glueless mesh NUMA topology, group_weight
1834 * scores nodes according to the number of NUMA hinting faults on
1835 * both the node itself, and on nearby nodes.
1837 if (sched_numa_topology_type
== NUMA_GLUELESS_MESH
) {
1838 unsigned long score
, max_score
= 0;
1839 int node
, max_node
= nid
;
1841 dist
= sched_max_numa_distance
;
1843 for_each_online_node(node
) {
1844 score
= group_weight(p
, node
, dist
);
1845 if (score
> max_score
) {
1854 * Finding the preferred nid in a system with NUMA backplane
1855 * interconnect topology is more involved. The goal is to locate
1856 * tasks from numa_groups near each other in the system, and
1857 * untangle workloads from different sides of the system. This requires
1858 * searching down the hierarchy of node groups, recursively searching
1859 * inside the highest scoring group of nodes. The nodemask tricks
1860 * keep the complexity of the search down.
1862 nodes
= node_online_map
;
1863 for (dist
= sched_max_numa_distance
; dist
> LOCAL_DISTANCE
; dist
--) {
1864 unsigned long max_faults
= 0;
1865 nodemask_t max_group
= NODE_MASK_NONE
;
1868 /* Are there nodes at this distance from each other? */
1869 if (!find_numa_distance(dist
))
1872 for_each_node_mask(a
, nodes
) {
1873 unsigned long faults
= 0;
1874 nodemask_t this_group
;
1875 nodes_clear(this_group
);
1877 /* Sum group's NUMA faults; includes a==b case. */
1878 for_each_node_mask(b
, nodes
) {
1879 if (node_distance(a
, b
) < dist
) {
1880 faults
+= group_faults(p
, b
);
1881 node_set(b
, this_group
);
1882 node_clear(b
, nodes
);
1886 /* Remember the top group. */
1887 if (faults
> max_faults
) {
1888 max_faults
= faults
;
1889 max_group
= this_group
;
1891 * subtle: at the smallest distance there is
1892 * just one node left in each "group", the
1893 * winner is the preferred nid.
1898 /* Next round, evaluate the nodes within max_group. */
1906 static void task_numa_placement(struct task_struct
*p
)
1908 int seq
, nid
, max_nid
= -1, max_group_nid
= -1;
1909 unsigned long max_faults
= 0, max_group_faults
= 0;
1910 unsigned long fault_types
[2] = { 0, 0 };
1911 unsigned long total_faults
;
1912 u64 runtime
, period
;
1913 spinlock_t
*group_lock
= NULL
;
1916 * The p->mm->numa_scan_seq field gets updated without
1917 * exclusive access. Use READ_ONCE() here to ensure
1918 * that the field is read in a single access:
1920 seq
= READ_ONCE(p
->mm
->numa_scan_seq
);
1921 if (p
->numa_scan_seq
== seq
)
1923 p
->numa_scan_seq
= seq
;
1924 p
->numa_scan_period_max
= task_scan_max(p
);
1926 total_faults
= p
->numa_faults_locality
[0] +
1927 p
->numa_faults_locality
[1];
1928 runtime
= numa_get_avg_runtime(p
, &period
);
1930 /* If the task is part of a group prevent parallel updates to group stats */
1931 if (p
->numa_group
) {
1932 group_lock
= &p
->numa_group
->lock
;
1933 spin_lock_irq(group_lock
);
1936 /* Find the node with the highest number of faults */
1937 for_each_online_node(nid
) {
1938 /* Keep track of the offsets in numa_faults array */
1939 int mem_idx
, membuf_idx
, cpu_idx
, cpubuf_idx
;
1940 unsigned long faults
= 0, group_faults
= 0;
1943 for (priv
= 0; priv
< NR_NUMA_HINT_FAULT_TYPES
; priv
++) {
1944 long diff
, f_diff
, f_weight
;
1946 mem_idx
= task_faults_idx(NUMA_MEM
, nid
, priv
);
1947 membuf_idx
= task_faults_idx(NUMA_MEMBUF
, nid
, priv
);
1948 cpu_idx
= task_faults_idx(NUMA_CPU
, nid
, priv
);
1949 cpubuf_idx
= task_faults_idx(NUMA_CPUBUF
, nid
, priv
);
1951 /* Decay existing window, copy faults since last scan */
1952 diff
= p
->numa_faults
[membuf_idx
] - p
->numa_faults
[mem_idx
] / 2;
1953 fault_types
[priv
] += p
->numa_faults
[membuf_idx
];
1954 p
->numa_faults
[membuf_idx
] = 0;
1957 * Normalize the faults_from, so all tasks in a group
1958 * count according to CPU use, instead of by the raw
1959 * number of faults. Tasks with little runtime have
1960 * little over-all impact on throughput, and thus their
1961 * faults are less important.
1963 f_weight
= div64_u64(runtime
<< 16, period
+ 1);
1964 f_weight
= (f_weight
* p
->numa_faults
[cpubuf_idx
]) /
1966 f_diff
= f_weight
- p
->numa_faults
[cpu_idx
] / 2;
1967 p
->numa_faults
[cpubuf_idx
] = 0;
1969 p
->numa_faults
[mem_idx
] += diff
;
1970 p
->numa_faults
[cpu_idx
] += f_diff
;
1971 faults
+= p
->numa_faults
[mem_idx
];
1972 p
->total_numa_faults
+= diff
;
1973 if (p
->numa_group
) {
1975 * safe because we can only change our own group
1977 * mem_idx represents the offset for a given
1978 * nid and priv in a specific region because it
1979 * is at the beginning of the numa_faults array.
1981 p
->numa_group
->faults
[mem_idx
] += diff
;
1982 p
->numa_group
->faults_cpu
[mem_idx
] += f_diff
;
1983 p
->numa_group
->total_faults
+= diff
;
1984 group_faults
+= p
->numa_group
->faults
[mem_idx
];
1988 if (faults
> max_faults
) {
1989 max_faults
= faults
;
1993 if (group_faults
> max_group_faults
) {
1994 max_group_faults
= group_faults
;
1995 max_group_nid
= nid
;
1999 update_task_scan_period(p
, fault_types
[0], fault_types
[1]);
2001 if (p
->numa_group
) {
2002 numa_group_count_active_nodes(p
->numa_group
);
2003 spin_unlock_irq(group_lock
);
2004 max_nid
= preferred_group_nid(p
, max_group_nid
);
2008 /* Set the new preferred node */
2009 if (max_nid
!= p
->numa_preferred_nid
)
2010 sched_setnuma(p
, max_nid
);
2012 if (task_node(p
) != p
->numa_preferred_nid
)
2013 numa_migrate_preferred(p
);
2017 static inline int get_numa_group(struct numa_group
*grp
)
2019 return atomic_inc_not_zero(&grp
->refcount
);
2022 static inline void put_numa_group(struct numa_group
*grp
)
2024 if (atomic_dec_and_test(&grp
->refcount
))
2025 kfree_rcu(grp
, rcu
);
2028 static void task_numa_group(struct task_struct
*p
, int cpupid
, int flags
,
2031 struct numa_group
*grp
, *my_grp
;
2032 struct task_struct
*tsk
;
2034 int cpu
= cpupid_to_cpu(cpupid
);
2037 if (unlikely(!p
->numa_group
)) {
2038 unsigned int size
= sizeof(struct numa_group
) +
2039 4*nr_node_ids
*sizeof(unsigned long);
2041 grp
= kzalloc(size
, GFP_KERNEL
| __GFP_NOWARN
);
2045 atomic_set(&grp
->refcount
, 1);
2046 grp
->active_nodes
= 1;
2047 grp
->max_faults_cpu
= 0;
2048 spin_lock_init(&grp
->lock
);
2050 /* Second half of the array tracks nids where faults happen */
2051 grp
->faults_cpu
= grp
->faults
+ NR_NUMA_HINT_FAULT_TYPES
*
2054 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
2055 grp
->faults
[i
] = p
->numa_faults
[i
];
2057 grp
->total_faults
= p
->total_numa_faults
;
2060 rcu_assign_pointer(p
->numa_group
, grp
);
2064 tsk
= READ_ONCE(cpu_rq(cpu
)->curr
);
2066 if (!cpupid_match_pid(tsk
, cpupid
))
2069 grp
= rcu_dereference(tsk
->numa_group
);
2073 my_grp
= p
->numa_group
;
2078 * Only join the other group if its bigger; if we're the bigger group,
2079 * the other task will join us.
2081 if (my_grp
->nr_tasks
> grp
->nr_tasks
)
2085 * Tie-break on the grp address.
2087 if (my_grp
->nr_tasks
== grp
->nr_tasks
&& my_grp
> grp
)
2090 /* Always join threads in the same process. */
2091 if (tsk
->mm
== current
->mm
)
2094 /* Simple filter to avoid false positives due to PID collisions */
2095 if (flags
& TNF_SHARED
)
2098 /* Update priv based on whether false sharing was detected */
2101 if (join
&& !get_numa_group(grp
))
2109 BUG_ON(irqs_disabled());
2110 double_lock_irq(&my_grp
->lock
, &grp
->lock
);
2112 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++) {
2113 my_grp
->faults
[i
] -= p
->numa_faults
[i
];
2114 grp
->faults
[i
] += p
->numa_faults
[i
];
2116 my_grp
->total_faults
-= p
->total_numa_faults
;
2117 grp
->total_faults
+= p
->total_numa_faults
;
2122 spin_unlock(&my_grp
->lock
);
2123 spin_unlock_irq(&grp
->lock
);
2125 rcu_assign_pointer(p
->numa_group
, grp
);
2127 put_numa_group(my_grp
);
2135 void task_numa_free(struct task_struct
*p
)
2137 struct numa_group
*grp
= p
->numa_group
;
2138 void *numa_faults
= p
->numa_faults
;
2139 unsigned long flags
;
2143 spin_lock_irqsave(&grp
->lock
, flags
);
2144 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
2145 grp
->faults
[i
] -= p
->numa_faults
[i
];
2146 grp
->total_faults
-= p
->total_numa_faults
;
2149 spin_unlock_irqrestore(&grp
->lock
, flags
);
2150 RCU_INIT_POINTER(p
->numa_group
, NULL
);
2151 put_numa_group(grp
);
2154 p
->numa_faults
= NULL
;
2159 * Got a PROT_NONE fault for a page on @node.
2161 void task_numa_fault(int last_cpupid
, int mem_node
, int pages
, int flags
)
2163 struct task_struct
*p
= current
;
2164 bool migrated
= flags
& TNF_MIGRATED
;
2165 int cpu_node
= task_node(current
);
2166 int local
= !!(flags
& TNF_FAULT_LOCAL
);
2167 struct numa_group
*ng
;
2170 if (!static_branch_likely(&sched_numa_balancing
))
2173 /* for example, ksmd faulting in a user's mm */
2177 /* Allocate buffer to track faults on a per-node basis */
2178 if (unlikely(!p
->numa_faults
)) {
2179 int size
= sizeof(*p
->numa_faults
) *
2180 NR_NUMA_HINT_FAULT_BUCKETS
* nr_node_ids
;
2182 p
->numa_faults
= kzalloc(size
, GFP_KERNEL
|__GFP_NOWARN
);
2183 if (!p
->numa_faults
)
2186 p
->total_numa_faults
= 0;
2187 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
2191 * First accesses are treated as private, otherwise consider accesses
2192 * to be private if the accessing pid has not changed
2194 if (unlikely(last_cpupid
== (-1 & LAST_CPUPID_MASK
))) {
2197 priv
= cpupid_match_pid(p
, last_cpupid
);
2198 if (!priv
&& !(flags
& TNF_NO_GROUP
))
2199 task_numa_group(p
, last_cpupid
, flags
, &priv
);
2203 * If a workload spans multiple NUMA nodes, a shared fault that
2204 * occurs wholly within the set of nodes that the workload is
2205 * actively using should be counted as local. This allows the
2206 * scan rate to slow down when a workload has settled down.
2209 if (!priv
&& !local
&& ng
&& ng
->active_nodes
> 1 &&
2210 numa_is_active_node(cpu_node
, ng
) &&
2211 numa_is_active_node(mem_node
, ng
))
2214 task_numa_placement(p
);
2217 * Retry task to preferred node migration periodically, in case it
2218 * case it previously failed, or the scheduler moved us.
2220 if (time_after(jiffies
, p
->numa_migrate_retry
))
2221 numa_migrate_preferred(p
);
2224 p
->numa_pages_migrated
+= pages
;
2225 if (flags
& TNF_MIGRATE_FAIL
)
2226 p
->numa_faults_locality
[2] += pages
;
2228 p
->numa_faults
[task_faults_idx(NUMA_MEMBUF
, mem_node
, priv
)] += pages
;
2229 p
->numa_faults
[task_faults_idx(NUMA_CPUBUF
, cpu_node
, priv
)] += pages
;
2230 p
->numa_faults_locality
[local
] += pages
;
2233 static void reset_ptenuma_scan(struct task_struct
*p
)
2236 * We only did a read acquisition of the mmap sem, so
2237 * p->mm->numa_scan_seq is written to without exclusive access
2238 * and the update is not guaranteed to be atomic. That's not
2239 * much of an issue though, since this is just used for
2240 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2241 * expensive, to avoid any form of compiler optimizations:
2243 WRITE_ONCE(p
->mm
->numa_scan_seq
, READ_ONCE(p
->mm
->numa_scan_seq
) + 1);
2244 p
->mm
->numa_scan_offset
= 0;
2248 * The expensive part of numa migration is done from task_work context.
2249 * Triggered from task_tick_numa().
2251 void task_numa_work(struct callback_head
*work
)
2253 unsigned long migrate
, next_scan
, now
= jiffies
;
2254 struct task_struct
*p
= current
;
2255 struct mm_struct
*mm
= p
->mm
;
2256 u64 runtime
= p
->se
.sum_exec_runtime
;
2257 struct vm_area_struct
*vma
;
2258 unsigned long start
, end
;
2259 unsigned long nr_pte_updates
= 0;
2260 long pages
, virtpages
;
2262 WARN_ON_ONCE(p
!= container_of(work
, struct task_struct
, numa_work
));
2264 work
->next
= work
; /* protect against double add */
2266 * Who cares about NUMA placement when they're dying.
2268 * NOTE: make sure not to dereference p->mm before this check,
2269 * exit_task_work() happens _after_ exit_mm() so we could be called
2270 * without p->mm even though we still had it when we enqueued this
2273 if (p
->flags
& PF_EXITING
)
2276 if (!mm
->numa_next_scan
) {
2277 mm
->numa_next_scan
= now
+
2278 msecs_to_jiffies(sysctl_numa_balancing_scan_delay
);
2282 * Enforce maximal scan/migration frequency..
2284 migrate
= mm
->numa_next_scan
;
2285 if (time_before(now
, migrate
))
2288 if (p
->numa_scan_period
== 0) {
2289 p
->numa_scan_period_max
= task_scan_max(p
);
2290 p
->numa_scan_period
= task_scan_min(p
);
2293 next_scan
= now
+ msecs_to_jiffies(p
->numa_scan_period
);
2294 if (cmpxchg(&mm
->numa_next_scan
, migrate
, next_scan
) != migrate
)
2298 * Delay this task enough that another task of this mm will likely win
2299 * the next time around.
2301 p
->node_stamp
+= 2 * TICK_NSEC
;
2303 start
= mm
->numa_scan_offset
;
2304 pages
= sysctl_numa_balancing_scan_size
;
2305 pages
<<= 20 - PAGE_SHIFT
; /* MB in pages */
2306 virtpages
= pages
* 8; /* Scan up to this much virtual space */
2311 down_read(&mm
->mmap_sem
);
2312 vma
= find_vma(mm
, start
);
2314 reset_ptenuma_scan(p
);
2318 for (; vma
; vma
= vma
->vm_next
) {
2319 if (!vma_migratable(vma
) || !vma_policy_mof(vma
) ||
2320 is_vm_hugetlb_page(vma
) || (vma
->vm_flags
& VM_MIXEDMAP
)) {
2325 * Shared library pages mapped by multiple processes are not
2326 * migrated as it is expected they are cache replicated. Avoid
2327 * hinting faults in read-only file-backed mappings or the vdso
2328 * as migrating the pages will be of marginal benefit.
2331 (vma
->vm_file
&& (vma
->vm_flags
& (VM_READ
|VM_WRITE
)) == (VM_READ
)))
2335 * Skip inaccessible VMAs to avoid any confusion between
2336 * PROT_NONE and NUMA hinting ptes
2338 if (!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
)))
2342 start
= max(start
, vma
->vm_start
);
2343 end
= ALIGN(start
+ (pages
<< PAGE_SHIFT
), HPAGE_SIZE
);
2344 end
= min(end
, vma
->vm_end
);
2345 nr_pte_updates
= change_prot_numa(vma
, start
, end
);
2348 * Try to scan sysctl_numa_balancing_size worth of
2349 * hpages that have at least one present PTE that
2350 * is not already pte-numa. If the VMA contains
2351 * areas that are unused or already full of prot_numa
2352 * PTEs, scan up to virtpages, to skip through those
2356 pages
-= (end
- start
) >> PAGE_SHIFT
;
2357 virtpages
-= (end
- start
) >> PAGE_SHIFT
;
2360 if (pages
<= 0 || virtpages
<= 0)
2364 } while (end
!= vma
->vm_end
);
2369 * It is possible to reach the end of the VMA list but the last few
2370 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2371 * would find the !migratable VMA on the next scan but not reset the
2372 * scanner to the start so check it now.
2375 mm
->numa_scan_offset
= start
;
2377 reset_ptenuma_scan(p
);
2378 up_read(&mm
->mmap_sem
);
2381 * Make sure tasks use at least 32x as much time to run other code
2382 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2383 * Usually update_task_scan_period slows down scanning enough; on an
2384 * overloaded system we need to limit overhead on a per task basis.
2386 if (unlikely(p
->se
.sum_exec_runtime
!= runtime
)) {
2387 u64 diff
= p
->se
.sum_exec_runtime
- runtime
;
2388 p
->node_stamp
+= 32 * diff
;
2393 * Drive the periodic memory faults..
2395 void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
2397 struct callback_head
*work
= &curr
->numa_work
;
2401 * We don't care about NUMA placement if we don't have memory.
2403 if (!curr
->mm
|| (curr
->flags
& PF_EXITING
) || work
->next
!= work
)
2407 * Using runtime rather than walltime has the dual advantage that
2408 * we (mostly) drive the selection from busy threads and that the
2409 * task needs to have done some actual work before we bother with
2412 now
= curr
->se
.sum_exec_runtime
;
2413 period
= (u64
)curr
->numa_scan_period
* NSEC_PER_MSEC
;
2415 if (now
> curr
->node_stamp
+ period
) {
2416 if (!curr
->node_stamp
)
2417 curr
->numa_scan_period
= task_scan_min(curr
);
2418 curr
->node_stamp
+= period
;
2420 if (!time_before(jiffies
, curr
->mm
->numa_next_scan
)) {
2421 init_task_work(work
, task_numa_work
); /* TODO: move this into sched_fork() */
2422 task_work_add(curr
, work
, true);
2427 static void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
2431 static inline void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
2435 static inline void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
2438 #endif /* CONFIG_NUMA_BALANCING */
2441 account_entity_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2443 update_load_add(&cfs_rq
->load
, se
->load
.weight
);
2444 if (!parent_entity(se
))
2445 update_load_add(&rq_of(cfs_rq
)->load
, se
->load
.weight
);
2447 if (entity_is_task(se
)) {
2448 struct rq
*rq
= rq_of(cfs_rq
);
2450 account_numa_enqueue(rq
, task_of(se
));
2451 list_add(&se
->group_node
, &rq
->cfs_tasks
);
2454 cfs_rq
->nr_running
++;
2458 account_entity_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2460 update_load_sub(&cfs_rq
->load
, se
->load
.weight
);
2461 if (!parent_entity(se
))
2462 update_load_sub(&rq_of(cfs_rq
)->load
, se
->load
.weight
);
2464 if (entity_is_task(se
)) {
2465 account_numa_dequeue(rq_of(cfs_rq
), task_of(se
));
2466 list_del_init(&se
->group_node
);
2469 cfs_rq
->nr_running
--;
2472 #ifdef CONFIG_FAIR_GROUP_SCHED
2474 static long calc_cfs_shares(struct cfs_rq
*cfs_rq
, struct task_group
*tg
)
2476 long tg_weight
, load
, shares
;
2479 * This really should be: cfs_rq->avg.load_avg, but instead we use
2480 * cfs_rq->load.weight, which is its upper bound. This helps ramp up
2481 * the shares for small weight interactive tasks.
2483 load
= scale_load_down(cfs_rq
->load
.weight
);
2485 tg_weight
= atomic_long_read(&tg
->load_avg
);
2487 /* Ensure tg_weight >= load */
2488 tg_weight
-= cfs_rq
->tg_load_avg_contrib
;
2491 shares
= (tg
->shares
* load
);
2493 shares
/= tg_weight
;
2495 if (shares
< MIN_SHARES
)
2496 shares
= MIN_SHARES
;
2497 if (shares
> tg
->shares
)
2498 shares
= tg
->shares
;
2502 # else /* CONFIG_SMP */
2503 static inline long calc_cfs_shares(struct cfs_rq
*cfs_rq
, struct task_group
*tg
)
2507 # endif /* CONFIG_SMP */
2509 static void reweight_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
,
2510 unsigned long weight
)
2513 /* commit outstanding execution time */
2514 if (cfs_rq
->curr
== se
)
2515 update_curr(cfs_rq
);
2516 account_entity_dequeue(cfs_rq
, se
);
2519 update_load_set(&se
->load
, weight
);
2522 account_entity_enqueue(cfs_rq
, se
);
2525 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
);
2527 static void update_cfs_shares(struct cfs_rq
*cfs_rq
)
2529 struct task_group
*tg
;
2530 struct sched_entity
*se
;
2534 se
= tg
->se
[cpu_of(rq_of(cfs_rq
))];
2535 if (!se
|| throttled_hierarchy(cfs_rq
))
2538 if (likely(se
->load
.weight
== tg
->shares
))
2541 shares
= calc_cfs_shares(cfs_rq
, tg
);
2543 reweight_entity(cfs_rq_of(se
), se
, shares
);
2545 #else /* CONFIG_FAIR_GROUP_SCHED */
2546 static inline void update_cfs_shares(struct cfs_rq
*cfs_rq
)
2549 #endif /* CONFIG_FAIR_GROUP_SCHED */
2552 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2553 static const u32 runnable_avg_yN_inv
[] = {
2554 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2555 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2556 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2557 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2558 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2559 0x85aac367, 0x82cd8698,
2563 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2564 * over-estimates when re-combining.
2566 static const u32 runnable_avg_yN_sum
[] = {
2567 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2568 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2569 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2573 * Precomputed \Sum y^k { 1<=k<=n, where n%32=0). Values are rolled down to
2574 * lower integers. See Documentation/scheduler/sched-avg.txt how these
2577 static const u32 __accumulated_sum_N32
[] = {
2578 0, 23371, 35056, 40899, 43820, 45281,
2579 46011, 46376, 46559, 46650, 46696, 46719,
2584 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2586 static __always_inline u64
decay_load(u64 val
, u64 n
)
2588 unsigned int local_n
;
2592 else if (unlikely(n
> LOAD_AVG_PERIOD
* 63))
2595 /* after bounds checking we can collapse to 32-bit */
2599 * As y^PERIOD = 1/2, we can combine
2600 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2601 * With a look-up table which covers y^n (n<PERIOD)
2603 * To achieve constant time decay_load.
2605 if (unlikely(local_n
>= LOAD_AVG_PERIOD
)) {
2606 val
>>= local_n
/ LOAD_AVG_PERIOD
;
2607 local_n
%= LOAD_AVG_PERIOD
;
2610 val
= mul_u64_u32_shr(val
, runnable_avg_yN_inv
[local_n
], 32);
2615 * For updates fully spanning n periods, the contribution to runnable
2616 * average will be: \Sum 1024*y^n
2618 * We can compute this reasonably efficiently by combining:
2619 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2621 static u32
__compute_runnable_contrib(u64 n
)
2625 if (likely(n
<= LOAD_AVG_PERIOD
))
2626 return runnable_avg_yN_sum
[n
];
2627 else if (unlikely(n
>= LOAD_AVG_MAX_N
))
2628 return LOAD_AVG_MAX
;
2630 /* Since n < LOAD_AVG_MAX_N, n/LOAD_AVG_PERIOD < 11 */
2631 contrib
= __accumulated_sum_N32
[n
/LOAD_AVG_PERIOD
];
2632 n
%= LOAD_AVG_PERIOD
;
2633 contrib
= decay_load(contrib
, n
);
2634 return contrib
+ runnable_avg_yN_sum
[n
];
2637 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2640 * We can represent the historical contribution to runnable average as the
2641 * coefficients of a geometric series. To do this we sub-divide our runnable
2642 * history into segments of approximately 1ms (1024us); label the segment that
2643 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2645 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2647 * (now) (~1ms ago) (~2ms ago)
2649 * Let u_i denote the fraction of p_i that the entity was runnable.
2651 * We then designate the fractions u_i as our co-efficients, yielding the
2652 * following representation of historical load:
2653 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2655 * We choose y based on the with of a reasonably scheduling period, fixing:
2658 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2659 * approximately half as much as the contribution to load within the last ms
2662 * When a period "rolls over" and we have new u_0`, multiplying the previous
2663 * sum again by y is sufficient to update:
2664 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2665 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2667 static __always_inline
int
2668 __update_load_avg(u64 now
, int cpu
, struct sched_avg
*sa
,
2669 unsigned long weight
, int running
, struct cfs_rq
*cfs_rq
)
2671 u64 delta
, scaled_delta
, periods
;
2673 unsigned int delta_w
, scaled_delta_w
, decayed
= 0;
2674 unsigned long scale_freq
, scale_cpu
;
2676 delta
= now
- sa
->last_update_time
;
2678 * This should only happen when time goes backwards, which it
2679 * unfortunately does during sched clock init when we swap over to TSC.
2681 if ((s64
)delta
< 0) {
2682 sa
->last_update_time
= now
;
2687 * Use 1024ns as the unit of measurement since it's a reasonable
2688 * approximation of 1us and fast to compute.
2693 sa
->last_update_time
= now
;
2695 scale_freq
= arch_scale_freq_capacity(NULL
, cpu
);
2696 scale_cpu
= arch_scale_cpu_capacity(NULL
, cpu
);
2698 /* delta_w is the amount already accumulated against our next period */
2699 delta_w
= sa
->period_contrib
;
2700 if (delta
+ delta_w
>= 1024) {
2703 /* how much left for next period will start over, we don't know yet */
2704 sa
->period_contrib
= 0;
2707 * Now that we know we're crossing a period boundary, figure
2708 * out how much from delta we need to complete the current
2709 * period and accrue it.
2711 delta_w
= 1024 - delta_w
;
2712 scaled_delta_w
= cap_scale(delta_w
, scale_freq
);
2714 sa
->load_sum
+= weight
* scaled_delta_w
;
2716 cfs_rq
->runnable_load_sum
+=
2717 weight
* scaled_delta_w
;
2721 sa
->util_sum
+= scaled_delta_w
* scale_cpu
;
2725 /* Figure out how many additional periods this update spans */
2726 periods
= delta
/ 1024;
2729 sa
->load_sum
= decay_load(sa
->load_sum
, periods
+ 1);
2731 cfs_rq
->runnable_load_sum
=
2732 decay_load(cfs_rq
->runnable_load_sum
, periods
+ 1);
2734 sa
->util_sum
= decay_load((u64
)(sa
->util_sum
), periods
+ 1);
2736 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2737 contrib
= __compute_runnable_contrib(periods
);
2738 contrib
= cap_scale(contrib
, scale_freq
);
2740 sa
->load_sum
+= weight
* contrib
;
2742 cfs_rq
->runnable_load_sum
+= weight
* contrib
;
2745 sa
->util_sum
+= contrib
* scale_cpu
;
2748 /* Remainder of delta accrued against u_0` */
2749 scaled_delta
= cap_scale(delta
, scale_freq
);
2751 sa
->load_sum
+= weight
* scaled_delta
;
2753 cfs_rq
->runnable_load_sum
+= weight
* scaled_delta
;
2756 sa
->util_sum
+= scaled_delta
* scale_cpu
;
2758 sa
->period_contrib
+= delta
;
2761 sa
->load_avg
= div_u64(sa
->load_sum
, LOAD_AVG_MAX
);
2763 cfs_rq
->runnable_load_avg
=
2764 div_u64(cfs_rq
->runnable_load_sum
, LOAD_AVG_MAX
);
2766 sa
->util_avg
= sa
->util_sum
/ LOAD_AVG_MAX
;
2772 #ifdef CONFIG_FAIR_GROUP_SCHED
2774 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2775 * and effective_load (which is not done because it is too costly).
2777 static inline void update_tg_load_avg(struct cfs_rq
*cfs_rq
, int force
)
2779 long delta
= cfs_rq
->avg
.load_avg
- cfs_rq
->tg_load_avg_contrib
;
2782 * No need to update load_avg for root_task_group as it is not used.
2784 if (cfs_rq
->tg
== &root_task_group
)
2787 if (force
|| abs(delta
) > cfs_rq
->tg_load_avg_contrib
/ 64) {
2788 atomic_long_add(delta
, &cfs_rq
->tg
->load_avg
);
2789 cfs_rq
->tg_load_avg_contrib
= cfs_rq
->avg
.load_avg
;
2794 * Called within set_task_rq() right before setting a task's cpu. The
2795 * caller only guarantees p->pi_lock is held; no other assumptions,
2796 * including the state of rq->lock, should be made.
2798 void set_task_rq_fair(struct sched_entity
*se
,
2799 struct cfs_rq
*prev
, struct cfs_rq
*next
)
2801 if (!sched_feat(ATTACH_AGE_LOAD
))
2805 * We are supposed to update the task to "current" time, then its up to
2806 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
2807 * getting what current time is, so simply throw away the out-of-date
2808 * time. This will result in the wakee task is less decayed, but giving
2809 * the wakee more load sounds not bad.
2811 if (se
->avg
.last_update_time
&& prev
) {
2812 u64 p_last_update_time
;
2813 u64 n_last_update_time
;
2815 #ifndef CONFIG_64BIT
2816 u64 p_last_update_time_copy
;
2817 u64 n_last_update_time_copy
;
2820 p_last_update_time_copy
= prev
->load_last_update_time_copy
;
2821 n_last_update_time_copy
= next
->load_last_update_time_copy
;
2825 p_last_update_time
= prev
->avg
.last_update_time
;
2826 n_last_update_time
= next
->avg
.last_update_time
;
2828 } while (p_last_update_time
!= p_last_update_time_copy
||
2829 n_last_update_time
!= n_last_update_time_copy
);
2831 p_last_update_time
= prev
->avg
.last_update_time
;
2832 n_last_update_time
= next
->avg
.last_update_time
;
2834 __update_load_avg(p_last_update_time
, cpu_of(rq_of(prev
)),
2835 &se
->avg
, 0, 0, NULL
);
2836 se
->avg
.last_update_time
= n_last_update_time
;
2839 #else /* CONFIG_FAIR_GROUP_SCHED */
2840 static inline void update_tg_load_avg(struct cfs_rq
*cfs_rq
, int force
) {}
2841 #endif /* CONFIG_FAIR_GROUP_SCHED */
2843 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
);
2845 static inline void cfs_rq_util_change(struct cfs_rq
*cfs_rq
)
2847 struct rq
*rq
= rq_of(cfs_rq
);
2848 int cpu
= cpu_of(rq
);
2850 if (cpu
== smp_processor_id() && &rq
->cfs
== cfs_rq
) {
2851 unsigned long max
= rq
->cpu_capacity_orig
;
2854 * There are a few boundary cases this might miss but it should
2855 * get called often enough that that should (hopefully) not be
2856 * a real problem -- added to that it only calls on the local
2857 * CPU, so if we enqueue remotely we'll miss an update, but
2858 * the next tick/schedule should update.
2860 * It will not get called when we go idle, because the idle
2861 * thread is a different class (!fair), nor will the utilization
2862 * number include things like RT tasks.
2864 * As is, the util number is not freq-invariant (we'd have to
2865 * implement arch_scale_freq_capacity() for that).
2869 cpufreq_update_util(rq_clock(rq
),
2870 min(cfs_rq
->avg
.util_avg
, max
), max
);
2875 * Unsigned subtract and clamp on underflow.
2877 * Explicitly do a load-store to ensure the intermediate value never hits
2878 * memory. This allows lockless observations without ever seeing the negative
2881 #define sub_positive(_ptr, _val) do { \
2882 typeof(_ptr) ptr = (_ptr); \
2883 typeof(*ptr) val = (_val); \
2884 typeof(*ptr) res, var = READ_ONCE(*ptr); \
2888 WRITE_ONCE(*ptr, res); \
2891 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2893 update_cfs_rq_load_avg(u64 now
, struct cfs_rq
*cfs_rq
, bool update_freq
)
2895 struct sched_avg
*sa
= &cfs_rq
->avg
;
2896 int decayed
, removed_load
= 0, removed_util
= 0;
2898 if (atomic_long_read(&cfs_rq
->removed_load_avg
)) {
2899 s64 r
= atomic_long_xchg(&cfs_rq
->removed_load_avg
, 0);
2900 sub_positive(&sa
->load_avg
, r
);
2901 sub_positive(&sa
->load_sum
, r
* LOAD_AVG_MAX
);
2905 if (atomic_long_read(&cfs_rq
->removed_util_avg
)) {
2906 long r
= atomic_long_xchg(&cfs_rq
->removed_util_avg
, 0);
2907 sub_positive(&sa
->util_avg
, r
);
2908 sub_positive(&sa
->util_sum
, r
* LOAD_AVG_MAX
);
2912 decayed
= __update_load_avg(now
, cpu_of(rq_of(cfs_rq
)), sa
,
2913 scale_load_down(cfs_rq
->load
.weight
), cfs_rq
->curr
!= NULL
, cfs_rq
);
2915 #ifndef CONFIG_64BIT
2917 cfs_rq
->load_last_update_time_copy
= sa
->last_update_time
;
2920 if (update_freq
&& (decayed
|| removed_util
))
2921 cfs_rq_util_change(cfs_rq
);
2923 return decayed
|| removed_load
;
2926 /* Update task and its cfs_rq load average */
2927 static inline void update_load_avg(struct sched_entity
*se
, int update_tg
)
2929 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
2930 u64 now
= cfs_rq_clock_task(cfs_rq
);
2931 struct rq
*rq
= rq_of(cfs_rq
);
2932 int cpu
= cpu_of(rq
);
2935 * Track task load average for carrying it to new CPU after migrated, and
2936 * track group sched_entity load average for task_h_load calc in migration
2938 __update_load_avg(now
, cpu
, &se
->avg
,
2939 se
->on_rq
* scale_load_down(se
->load
.weight
),
2940 cfs_rq
->curr
== se
, NULL
);
2942 if (update_cfs_rq_load_avg(now
, cfs_rq
, true) && update_tg
)
2943 update_tg_load_avg(cfs_rq
, 0);
2946 static void attach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2948 if (!sched_feat(ATTACH_AGE_LOAD
))
2952 * If we got migrated (either between CPUs or between cgroups) we'll
2953 * have aged the average right before clearing @last_update_time.
2955 if (se
->avg
.last_update_time
) {
2956 __update_load_avg(cfs_rq
->avg
.last_update_time
, cpu_of(rq_of(cfs_rq
)),
2957 &se
->avg
, 0, 0, NULL
);
2960 * XXX: we could have just aged the entire load away if we've been
2961 * absent from the fair class for too long.
2966 se
->avg
.last_update_time
= cfs_rq
->avg
.last_update_time
;
2967 cfs_rq
->avg
.load_avg
+= se
->avg
.load_avg
;
2968 cfs_rq
->avg
.load_sum
+= se
->avg
.load_sum
;
2969 cfs_rq
->avg
.util_avg
+= se
->avg
.util_avg
;
2970 cfs_rq
->avg
.util_sum
+= se
->avg
.util_sum
;
2972 cfs_rq_util_change(cfs_rq
);
2975 static void detach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2977 __update_load_avg(cfs_rq
->avg
.last_update_time
, cpu_of(rq_of(cfs_rq
)),
2978 &se
->avg
, se
->on_rq
* scale_load_down(se
->load
.weight
),
2979 cfs_rq
->curr
== se
, NULL
);
2981 sub_positive(&cfs_rq
->avg
.load_avg
, se
->avg
.load_avg
);
2982 sub_positive(&cfs_rq
->avg
.load_sum
, se
->avg
.load_sum
);
2983 sub_positive(&cfs_rq
->avg
.util_avg
, se
->avg
.util_avg
);
2984 sub_positive(&cfs_rq
->avg
.util_sum
, se
->avg
.util_sum
);
2986 cfs_rq_util_change(cfs_rq
);
2989 /* Add the load generated by se into cfs_rq's load average */
2991 enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2993 struct sched_avg
*sa
= &se
->avg
;
2994 u64 now
= cfs_rq_clock_task(cfs_rq
);
2995 int migrated
, decayed
;
2997 migrated
= !sa
->last_update_time
;
2999 __update_load_avg(now
, cpu_of(rq_of(cfs_rq
)), sa
,
3000 se
->on_rq
* scale_load_down(se
->load
.weight
),
3001 cfs_rq
->curr
== se
, NULL
);
3004 decayed
= update_cfs_rq_load_avg(now
, cfs_rq
, !migrated
);
3006 cfs_rq
->runnable_load_avg
+= sa
->load_avg
;
3007 cfs_rq
->runnable_load_sum
+= sa
->load_sum
;
3010 attach_entity_load_avg(cfs_rq
, se
);
3012 if (decayed
|| migrated
)
3013 update_tg_load_avg(cfs_rq
, 0);
3016 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
3018 dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3020 update_load_avg(se
, 1);
3022 cfs_rq
->runnable_load_avg
=
3023 max_t(long, cfs_rq
->runnable_load_avg
- se
->avg
.load_avg
, 0);
3024 cfs_rq
->runnable_load_sum
=
3025 max_t(s64
, cfs_rq
->runnable_load_sum
- se
->avg
.load_sum
, 0);
3028 #ifndef CONFIG_64BIT
3029 static inline u64
cfs_rq_last_update_time(struct cfs_rq
*cfs_rq
)
3031 u64 last_update_time_copy
;
3032 u64 last_update_time
;
3035 last_update_time_copy
= cfs_rq
->load_last_update_time_copy
;
3037 last_update_time
= cfs_rq
->avg
.last_update_time
;
3038 } while (last_update_time
!= last_update_time_copy
);
3040 return last_update_time
;
3043 static inline u64
cfs_rq_last_update_time(struct cfs_rq
*cfs_rq
)
3045 return cfs_rq
->avg
.last_update_time
;
3050 * Task first catches up with cfs_rq, and then subtract
3051 * itself from the cfs_rq (task must be off the queue now).
3053 void remove_entity_load_avg(struct sched_entity
*se
)
3055 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3056 u64 last_update_time
;
3059 * Newly created task or never used group entity should not be removed
3060 * from its (source) cfs_rq
3062 if (se
->avg
.last_update_time
== 0)
3065 last_update_time
= cfs_rq_last_update_time(cfs_rq
);
3067 __update_load_avg(last_update_time
, cpu_of(rq_of(cfs_rq
)), &se
->avg
, 0, 0, NULL
);
3068 atomic_long_add(se
->avg
.load_avg
, &cfs_rq
->removed_load_avg
);
3069 atomic_long_add(se
->avg
.util_avg
, &cfs_rq
->removed_util_avg
);
3072 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq
*cfs_rq
)
3074 return cfs_rq
->runnable_load_avg
;
3077 static inline unsigned long cfs_rq_load_avg(struct cfs_rq
*cfs_rq
)
3079 return cfs_rq
->avg
.load_avg
;
3082 static int idle_balance(struct rq
*this_rq
);
3084 #else /* CONFIG_SMP */
3087 update_cfs_rq_load_avg(u64 now
, struct cfs_rq
*cfs_rq
, bool update_freq
)
3092 static inline void update_load_avg(struct sched_entity
*se
, int not_used
)
3094 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3095 struct rq
*rq
= rq_of(cfs_rq
);
3097 cpufreq_trigger_update(rq_clock(rq
));
3101 enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3103 dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3104 static inline void remove_entity_load_avg(struct sched_entity
*se
) {}
3107 attach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3109 detach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3111 static inline int idle_balance(struct rq
*rq
)
3116 #endif /* CONFIG_SMP */
3118 static void enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3120 #ifdef CONFIG_SCHEDSTATS
3121 struct task_struct
*tsk
= NULL
;
3123 if (entity_is_task(se
))
3126 if (se
->statistics
.sleep_start
) {
3127 u64 delta
= rq_clock(rq_of(cfs_rq
)) - se
->statistics
.sleep_start
;
3132 if (unlikely(delta
> se
->statistics
.sleep_max
))
3133 se
->statistics
.sleep_max
= delta
;
3135 se
->statistics
.sleep_start
= 0;
3136 se
->statistics
.sum_sleep_runtime
+= delta
;
3139 account_scheduler_latency(tsk
, delta
>> 10, 1);
3140 trace_sched_stat_sleep(tsk
, delta
);
3143 if (se
->statistics
.block_start
) {
3144 u64 delta
= rq_clock(rq_of(cfs_rq
)) - se
->statistics
.block_start
;
3149 if (unlikely(delta
> se
->statistics
.block_max
))
3150 se
->statistics
.block_max
= delta
;
3152 se
->statistics
.block_start
= 0;
3153 se
->statistics
.sum_sleep_runtime
+= delta
;
3156 if (tsk
->in_iowait
) {
3157 se
->statistics
.iowait_sum
+= delta
;
3158 se
->statistics
.iowait_count
++;
3159 trace_sched_stat_iowait(tsk
, delta
);
3162 trace_sched_stat_blocked(tsk
, delta
);
3165 * Blocking time is in units of nanosecs, so shift by
3166 * 20 to get a milliseconds-range estimation of the
3167 * amount of time that the task spent sleeping:
3169 if (unlikely(prof_on
== SLEEP_PROFILING
)) {
3170 profile_hits(SLEEP_PROFILING
,
3171 (void *)get_wchan(tsk
),
3174 account_scheduler_latency(tsk
, delta
>> 10, 0);
3180 static void check_spread(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3182 #ifdef CONFIG_SCHED_DEBUG
3183 s64 d
= se
->vruntime
- cfs_rq
->min_vruntime
;
3188 if (d
> 3*sysctl_sched_latency
)
3189 schedstat_inc(cfs_rq
, nr_spread_over
);
3194 place_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int initial
)
3196 u64 vruntime
= cfs_rq
->min_vruntime
;
3199 * The 'current' period is already promised to the current tasks,
3200 * however the extra weight of the new task will slow them down a
3201 * little, place the new task so that it fits in the slot that
3202 * stays open at the end.
3204 if (initial
&& sched_feat(START_DEBIT
))
3205 vruntime
+= sched_vslice(cfs_rq
, se
);
3207 /* sleeps up to a single latency don't count. */
3209 unsigned long thresh
= sysctl_sched_latency
;
3212 * Halve their sleep time's effect, to allow
3213 * for a gentler effect of sleepers:
3215 if (sched_feat(GENTLE_FAIR_SLEEPERS
))
3221 /* ensure we never gain time by being placed backwards. */
3222 se
->vruntime
= max_vruntime(se
->vruntime
, vruntime
);
3225 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
);
3227 static inline void check_schedstat_required(void)
3229 #ifdef CONFIG_SCHEDSTATS
3230 if (schedstat_enabled())
3233 /* Force schedstat enabled if a dependent tracepoint is active */
3234 if (trace_sched_stat_wait_enabled() ||
3235 trace_sched_stat_sleep_enabled() ||
3236 trace_sched_stat_iowait_enabled() ||
3237 trace_sched_stat_blocked_enabled() ||
3238 trace_sched_stat_runtime_enabled()) {
3239 printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3240 "stat_blocked and stat_runtime require the "
3241 "kernel parameter schedstats=enabled or "
3242 "kernel.sched_schedstats=1\n");
3253 * update_min_vruntime()
3254 * vruntime -= min_vruntime
3258 * update_min_vruntime()
3259 * vruntime += min_vruntime
3261 * this way the vruntime transition between RQs is done when both
3262 * min_vruntime are up-to-date.
3266 * ->migrate_task_rq_fair() (p->state == TASK_WAKING)
3267 * vruntime -= min_vruntime
3271 * update_min_vruntime()
3272 * vruntime += min_vruntime
3274 * this way we don't have the most up-to-date min_vruntime on the originating
3275 * CPU and an up-to-date min_vruntime on the destination CPU.
3279 enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3281 bool renorm
= !(flags
& ENQUEUE_WAKEUP
) || (flags
& ENQUEUE_MIGRATED
);
3282 bool curr
= cfs_rq
->curr
== se
;
3285 * If we're the current task, we must renormalise before calling
3289 se
->vruntime
+= cfs_rq
->min_vruntime
;
3291 update_curr(cfs_rq
);
3294 * Otherwise, renormalise after, such that we're placed at the current
3295 * moment in time, instead of some random moment in the past. Being
3296 * placed in the past could significantly boost this task to the
3297 * fairness detriment of existing tasks.
3299 if (renorm
&& !curr
)
3300 se
->vruntime
+= cfs_rq
->min_vruntime
;
3302 enqueue_entity_load_avg(cfs_rq
, se
);
3303 account_entity_enqueue(cfs_rq
, se
);
3304 update_cfs_shares(cfs_rq
);
3306 if (flags
& ENQUEUE_WAKEUP
) {
3307 place_entity(cfs_rq
, se
, 0);
3308 if (schedstat_enabled())
3309 enqueue_sleeper(cfs_rq
, se
);
3312 check_schedstat_required();
3313 if (schedstat_enabled()) {
3314 update_stats_enqueue(cfs_rq
, se
);
3315 check_spread(cfs_rq
, se
);
3318 __enqueue_entity(cfs_rq
, se
);
3321 if (cfs_rq
->nr_running
== 1) {
3322 list_add_leaf_cfs_rq(cfs_rq
);
3323 check_enqueue_throttle(cfs_rq
);
3327 static void __clear_buddies_last(struct sched_entity
*se
)
3329 for_each_sched_entity(se
) {
3330 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3331 if (cfs_rq
->last
!= se
)
3334 cfs_rq
->last
= NULL
;
3338 static void __clear_buddies_next(struct sched_entity
*se
)
3340 for_each_sched_entity(se
) {
3341 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3342 if (cfs_rq
->next
!= se
)
3345 cfs_rq
->next
= NULL
;
3349 static void __clear_buddies_skip(struct sched_entity
*se
)
3351 for_each_sched_entity(se
) {
3352 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3353 if (cfs_rq
->skip
!= se
)
3356 cfs_rq
->skip
= NULL
;
3360 static void clear_buddies(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3362 if (cfs_rq
->last
== se
)
3363 __clear_buddies_last(se
);
3365 if (cfs_rq
->next
== se
)
3366 __clear_buddies_next(se
);
3368 if (cfs_rq
->skip
== se
)
3369 __clear_buddies_skip(se
);
3372 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
3375 dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3378 * Update run-time statistics of the 'current'.
3380 update_curr(cfs_rq
);
3381 dequeue_entity_load_avg(cfs_rq
, se
);
3383 if (schedstat_enabled())
3384 update_stats_dequeue(cfs_rq
, se
, flags
);
3386 clear_buddies(cfs_rq
, se
);
3388 if (se
!= cfs_rq
->curr
)
3389 __dequeue_entity(cfs_rq
, se
);
3391 account_entity_dequeue(cfs_rq
, se
);
3394 * Normalize the entity after updating the min_vruntime because the
3395 * update can refer to the ->curr item and we need to reflect this
3396 * movement in our normalized position.
3398 if (!(flags
& DEQUEUE_SLEEP
))
3399 se
->vruntime
-= cfs_rq
->min_vruntime
;
3401 /* return excess runtime on last dequeue */
3402 return_cfs_rq_runtime(cfs_rq
);
3404 update_min_vruntime(cfs_rq
);
3405 update_cfs_shares(cfs_rq
);
3409 * Preempt the current task with a newly woken task if needed:
3412 check_preempt_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
3414 unsigned long ideal_runtime
, delta_exec
;
3415 struct sched_entity
*se
;
3418 ideal_runtime
= sched_slice(cfs_rq
, curr
);
3419 delta_exec
= curr
->sum_exec_runtime
- curr
->prev_sum_exec_runtime
;
3420 if (delta_exec
> ideal_runtime
) {
3421 resched_curr(rq_of(cfs_rq
));
3423 * The current task ran long enough, ensure it doesn't get
3424 * re-elected due to buddy favours.
3426 clear_buddies(cfs_rq
, curr
);
3431 * Ensure that a task that missed wakeup preemption by a
3432 * narrow margin doesn't have to wait for a full slice.
3433 * This also mitigates buddy induced latencies under load.
3435 if (delta_exec
< sysctl_sched_min_granularity
)
3438 se
= __pick_first_entity(cfs_rq
);
3439 delta
= curr
->vruntime
- se
->vruntime
;
3444 if (delta
> ideal_runtime
)
3445 resched_curr(rq_of(cfs_rq
));
3449 set_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3451 /* 'current' is not kept within the tree. */
3454 * Any task has to be enqueued before it get to execute on
3455 * a CPU. So account for the time it spent waiting on the
3458 if (schedstat_enabled())
3459 update_stats_wait_end(cfs_rq
, se
);
3460 __dequeue_entity(cfs_rq
, se
);
3461 update_load_avg(se
, 1);
3464 update_stats_curr_start(cfs_rq
, se
);
3466 #ifdef CONFIG_SCHEDSTATS
3468 * Track our maximum slice length, if the CPU's load is at
3469 * least twice that of our own weight (i.e. dont track it
3470 * when there are only lesser-weight tasks around):
3472 if (schedstat_enabled() && rq_of(cfs_rq
)->load
.weight
>= 2*se
->load
.weight
) {
3473 se
->statistics
.slice_max
= max(se
->statistics
.slice_max
,
3474 se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
);
3477 se
->prev_sum_exec_runtime
= se
->sum_exec_runtime
;
3481 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
);
3484 * Pick the next process, keeping these things in mind, in this order:
3485 * 1) keep things fair between processes/task groups
3486 * 2) pick the "next" process, since someone really wants that to run
3487 * 3) pick the "last" process, for cache locality
3488 * 4) do not run the "skip" process, if something else is available
3490 static struct sched_entity
*
3491 pick_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
3493 struct sched_entity
*left
= __pick_first_entity(cfs_rq
);
3494 struct sched_entity
*se
;
3497 * If curr is set we have to see if its left of the leftmost entity
3498 * still in the tree, provided there was anything in the tree at all.
3500 if (!left
|| (curr
&& entity_before(curr
, left
)))
3503 se
= left
; /* ideally we run the leftmost entity */
3506 * Avoid running the skip buddy, if running something else can
3507 * be done without getting too unfair.
3509 if (cfs_rq
->skip
== se
) {
3510 struct sched_entity
*second
;
3513 second
= __pick_first_entity(cfs_rq
);
3515 second
= __pick_next_entity(se
);
3516 if (!second
|| (curr
&& entity_before(curr
, second
)))
3520 if (second
&& wakeup_preempt_entity(second
, left
) < 1)
3525 * Prefer last buddy, try to return the CPU to a preempted task.
3527 if (cfs_rq
->last
&& wakeup_preempt_entity(cfs_rq
->last
, left
) < 1)
3531 * Someone really wants this to run. If it's not unfair, run it.
3533 if (cfs_rq
->next
&& wakeup_preempt_entity(cfs_rq
->next
, left
) < 1)
3536 clear_buddies(cfs_rq
, se
);
3541 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
3543 static void put_prev_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*prev
)
3546 * If still on the runqueue then deactivate_task()
3547 * was not called and update_curr() has to be done:
3550 update_curr(cfs_rq
);
3552 /* throttle cfs_rqs exceeding runtime */
3553 check_cfs_rq_runtime(cfs_rq
);
3555 if (schedstat_enabled()) {
3556 check_spread(cfs_rq
, prev
);
3558 update_stats_wait_start(cfs_rq
, prev
);
3562 /* Put 'current' back into the tree. */
3563 __enqueue_entity(cfs_rq
, prev
);
3564 /* in !on_rq case, update occurred at dequeue */
3565 update_load_avg(prev
, 0);
3567 cfs_rq
->curr
= NULL
;
3571 entity_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
, int queued
)
3574 * Update run-time statistics of the 'current'.
3576 update_curr(cfs_rq
);
3579 * Ensure that runnable average is periodically updated.
3581 update_load_avg(curr
, 1);
3582 update_cfs_shares(cfs_rq
);
3584 #ifdef CONFIG_SCHED_HRTICK
3586 * queued ticks are scheduled to match the slice, so don't bother
3587 * validating it and just reschedule.
3590 resched_curr(rq_of(cfs_rq
));
3594 * don't let the period tick interfere with the hrtick preemption
3596 if (!sched_feat(DOUBLE_TICK
) &&
3597 hrtimer_active(&rq_of(cfs_rq
)->hrtick_timer
))
3601 if (cfs_rq
->nr_running
> 1)
3602 check_preempt_tick(cfs_rq
, curr
);
3606 /**************************************************
3607 * CFS bandwidth control machinery
3610 #ifdef CONFIG_CFS_BANDWIDTH
3612 #ifdef HAVE_JUMP_LABEL
3613 static struct static_key __cfs_bandwidth_used
;
3615 static inline bool cfs_bandwidth_used(void)
3617 return static_key_false(&__cfs_bandwidth_used
);
3620 void cfs_bandwidth_usage_inc(void)
3622 static_key_slow_inc(&__cfs_bandwidth_used
);
3625 void cfs_bandwidth_usage_dec(void)
3627 static_key_slow_dec(&__cfs_bandwidth_used
);
3629 #else /* HAVE_JUMP_LABEL */
3630 static bool cfs_bandwidth_used(void)
3635 void cfs_bandwidth_usage_inc(void) {}
3636 void cfs_bandwidth_usage_dec(void) {}
3637 #endif /* HAVE_JUMP_LABEL */
3640 * default period for cfs group bandwidth.
3641 * default: 0.1s, units: nanoseconds
3643 static inline u64
default_cfs_period(void)
3645 return 100000000ULL;
3648 static inline u64
sched_cfs_bandwidth_slice(void)
3650 return (u64
)sysctl_sched_cfs_bandwidth_slice
* NSEC_PER_USEC
;
3654 * Replenish runtime according to assigned quota and update expiration time.
3655 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3656 * additional synchronization around rq->lock.
3658 * requires cfs_b->lock
3660 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth
*cfs_b
)
3664 if (cfs_b
->quota
== RUNTIME_INF
)
3667 now
= sched_clock_cpu(smp_processor_id());
3668 cfs_b
->runtime
= cfs_b
->quota
;
3669 cfs_b
->runtime_expires
= now
+ ktime_to_ns(cfs_b
->period
);
3672 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
3674 return &tg
->cfs_bandwidth
;
3677 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3678 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
3680 if (unlikely(cfs_rq
->throttle_count
))
3681 return cfs_rq
->throttled_clock_task
- cfs_rq
->throttled_clock_task_time
;
3683 return rq_clock_task(rq_of(cfs_rq
)) - cfs_rq
->throttled_clock_task_time
;
3686 /* returns 0 on failure to allocate runtime */
3687 static int assign_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3689 struct task_group
*tg
= cfs_rq
->tg
;
3690 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(tg
);
3691 u64 amount
= 0, min_amount
, expires
;
3693 /* note: this is a positive sum as runtime_remaining <= 0 */
3694 min_amount
= sched_cfs_bandwidth_slice() - cfs_rq
->runtime_remaining
;
3696 raw_spin_lock(&cfs_b
->lock
);
3697 if (cfs_b
->quota
== RUNTIME_INF
)
3698 amount
= min_amount
;
3700 start_cfs_bandwidth(cfs_b
);
3702 if (cfs_b
->runtime
> 0) {
3703 amount
= min(cfs_b
->runtime
, min_amount
);
3704 cfs_b
->runtime
-= amount
;
3708 expires
= cfs_b
->runtime_expires
;
3709 raw_spin_unlock(&cfs_b
->lock
);
3711 cfs_rq
->runtime_remaining
+= amount
;
3713 * we may have advanced our local expiration to account for allowed
3714 * spread between our sched_clock and the one on which runtime was
3717 if ((s64
)(expires
- cfs_rq
->runtime_expires
) > 0)
3718 cfs_rq
->runtime_expires
= expires
;
3720 return cfs_rq
->runtime_remaining
> 0;
3724 * Note: This depends on the synchronization provided by sched_clock and the
3725 * fact that rq->clock snapshots this value.
3727 static void expire_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3729 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3731 /* if the deadline is ahead of our clock, nothing to do */
3732 if (likely((s64
)(rq_clock(rq_of(cfs_rq
)) - cfs_rq
->runtime_expires
) < 0))
3735 if (cfs_rq
->runtime_remaining
< 0)
3739 * If the local deadline has passed we have to consider the
3740 * possibility that our sched_clock is 'fast' and the global deadline
3741 * has not truly expired.
3743 * Fortunately we can check determine whether this the case by checking
3744 * whether the global deadline has advanced. It is valid to compare
3745 * cfs_b->runtime_expires without any locks since we only care about
3746 * exact equality, so a partial write will still work.
3749 if (cfs_rq
->runtime_expires
!= cfs_b
->runtime_expires
) {
3750 /* extend local deadline, drift is bounded above by 2 ticks */
3751 cfs_rq
->runtime_expires
+= TICK_NSEC
;
3753 /* global deadline is ahead, expiration has passed */
3754 cfs_rq
->runtime_remaining
= 0;
3758 static void __account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
3760 /* dock delta_exec before expiring quota (as it could span periods) */
3761 cfs_rq
->runtime_remaining
-= delta_exec
;
3762 expire_cfs_rq_runtime(cfs_rq
);
3764 if (likely(cfs_rq
->runtime_remaining
> 0))
3768 * if we're unable to extend our runtime we resched so that the active
3769 * hierarchy can be throttled
3771 if (!assign_cfs_rq_runtime(cfs_rq
) && likely(cfs_rq
->curr
))
3772 resched_curr(rq_of(cfs_rq
));
3775 static __always_inline
3776 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
3778 if (!cfs_bandwidth_used() || !cfs_rq
->runtime_enabled
)
3781 __account_cfs_rq_runtime(cfs_rq
, delta_exec
);
3784 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
3786 return cfs_bandwidth_used() && cfs_rq
->throttled
;
3789 /* check whether cfs_rq, or any parent, is throttled */
3790 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
3792 return cfs_bandwidth_used() && cfs_rq
->throttle_count
;
3796 * Ensure that neither of the group entities corresponding to src_cpu or
3797 * dest_cpu are members of a throttled hierarchy when performing group
3798 * load-balance operations.
3800 static inline int throttled_lb_pair(struct task_group
*tg
,
3801 int src_cpu
, int dest_cpu
)
3803 struct cfs_rq
*src_cfs_rq
, *dest_cfs_rq
;
3805 src_cfs_rq
= tg
->cfs_rq
[src_cpu
];
3806 dest_cfs_rq
= tg
->cfs_rq
[dest_cpu
];
3808 return throttled_hierarchy(src_cfs_rq
) ||
3809 throttled_hierarchy(dest_cfs_rq
);
3812 /* updated child weight may affect parent so we have to do this bottom up */
3813 static int tg_unthrottle_up(struct task_group
*tg
, void *data
)
3815 struct rq
*rq
= data
;
3816 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
3818 cfs_rq
->throttle_count
--;
3819 if (!cfs_rq
->throttle_count
) {
3820 /* adjust cfs_rq_clock_task() */
3821 cfs_rq
->throttled_clock_task_time
+= rq_clock_task(rq
) -
3822 cfs_rq
->throttled_clock_task
;
3828 static int tg_throttle_down(struct task_group
*tg
, void *data
)
3830 struct rq
*rq
= data
;
3831 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
3833 /* group is entering throttled state, stop time */
3834 if (!cfs_rq
->throttle_count
)
3835 cfs_rq
->throttled_clock_task
= rq_clock_task(rq
);
3836 cfs_rq
->throttle_count
++;
3841 static void throttle_cfs_rq(struct cfs_rq
*cfs_rq
)
3843 struct rq
*rq
= rq_of(cfs_rq
);
3844 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3845 struct sched_entity
*se
;
3846 long task_delta
, dequeue
= 1;
3849 se
= cfs_rq
->tg
->se
[cpu_of(rq_of(cfs_rq
))];
3851 /* freeze hierarchy runnable averages while throttled */
3853 walk_tg_tree_from(cfs_rq
->tg
, tg_throttle_down
, tg_nop
, (void *)rq
);
3856 task_delta
= cfs_rq
->h_nr_running
;
3857 for_each_sched_entity(se
) {
3858 struct cfs_rq
*qcfs_rq
= cfs_rq_of(se
);
3859 /* throttled entity or throttle-on-deactivate */
3864 dequeue_entity(qcfs_rq
, se
, DEQUEUE_SLEEP
);
3865 qcfs_rq
->h_nr_running
-= task_delta
;
3867 if (qcfs_rq
->load
.weight
)
3872 sub_nr_running(rq
, task_delta
);
3874 cfs_rq
->throttled
= 1;
3875 cfs_rq
->throttled_clock
= rq_clock(rq
);
3876 raw_spin_lock(&cfs_b
->lock
);
3877 empty
= list_empty(&cfs_b
->throttled_cfs_rq
);
3880 * Add to the _head_ of the list, so that an already-started
3881 * distribute_cfs_runtime will not see us
3883 list_add_rcu(&cfs_rq
->throttled_list
, &cfs_b
->throttled_cfs_rq
);
3886 * If we're the first throttled task, make sure the bandwidth
3890 start_cfs_bandwidth(cfs_b
);
3892 raw_spin_unlock(&cfs_b
->lock
);
3895 void unthrottle_cfs_rq(struct cfs_rq
*cfs_rq
)
3897 struct rq
*rq
= rq_of(cfs_rq
);
3898 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3899 struct sched_entity
*se
;
3903 se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
3905 cfs_rq
->throttled
= 0;
3907 update_rq_clock(rq
);
3909 raw_spin_lock(&cfs_b
->lock
);
3910 cfs_b
->throttled_time
+= rq_clock(rq
) - cfs_rq
->throttled_clock
;
3911 list_del_rcu(&cfs_rq
->throttled_list
);
3912 raw_spin_unlock(&cfs_b
->lock
);
3914 /* update hierarchical throttle state */
3915 walk_tg_tree_from(cfs_rq
->tg
, tg_nop
, tg_unthrottle_up
, (void *)rq
);
3917 if (!cfs_rq
->load
.weight
)
3920 task_delta
= cfs_rq
->h_nr_running
;
3921 for_each_sched_entity(se
) {
3925 cfs_rq
= cfs_rq_of(se
);
3927 enqueue_entity(cfs_rq
, se
, ENQUEUE_WAKEUP
);
3928 cfs_rq
->h_nr_running
+= task_delta
;
3930 if (cfs_rq_throttled(cfs_rq
))
3935 add_nr_running(rq
, task_delta
);
3937 /* determine whether we need to wake up potentially idle cpu */
3938 if (rq
->curr
== rq
->idle
&& rq
->cfs
.nr_running
)
3942 static u64
distribute_cfs_runtime(struct cfs_bandwidth
*cfs_b
,
3943 u64 remaining
, u64 expires
)
3945 struct cfs_rq
*cfs_rq
;
3947 u64 starting_runtime
= remaining
;
3950 list_for_each_entry_rcu(cfs_rq
, &cfs_b
->throttled_cfs_rq
,
3952 struct rq
*rq
= rq_of(cfs_rq
);
3954 raw_spin_lock(&rq
->lock
);
3955 if (!cfs_rq_throttled(cfs_rq
))
3958 runtime
= -cfs_rq
->runtime_remaining
+ 1;
3959 if (runtime
> remaining
)
3960 runtime
= remaining
;
3961 remaining
-= runtime
;
3963 cfs_rq
->runtime_remaining
+= runtime
;
3964 cfs_rq
->runtime_expires
= expires
;
3966 /* we check whether we're throttled above */
3967 if (cfs_rq
->runtime_remaining
> 0)
3968 unthrottle_cfs_rq(cfs_rq
);
3971 raw_spin_unlock(&rq
->lock
);
3978 return starting_runtime
- remaining
;
3982 * Responsible for refilling a task_group's bandwidth and unthrottling its
3983 * cfs_rqs as appropriate. If there has been no activity within the last
3984 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3985 * used to track this state.
3987 static int do_sched_cfs_period_timer(struct cfs_bandwidth
*cfs_b
, int overrun
)
3989 u64 runtime
, runtime_expires
;
3992 /* no need to continue the timer with no bandwidth constraint */
3993 if (cfs_b
->quota
== RUNTIME_INF
)
3994 goto out_deactivate
;
3996 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
3997 cfs_b
->nr_periods
+= overrun
;
4000 * idle depends on !throttled (for the case of a large deficit), and if
4001 * we're going inactive then everything else can be deferred
4003 if (cfs_b
->idle
&& !throttled
)
4004 goto out_deactivate
;
4006 __refill_cfs_bandwidth_runtime(cfs_b
);
4009 /* mark as potentially idle for the upcoming period */
4014 /* account preceding periods in which throttling occurred */
4015 cfs_b
->nr_throttled
+= overrun
;
4017 runtime_expires
= cfs_b
->runtime_expires
;
4020 * This check is repeated as we are holding onto the new bandwidth while
4021 * we unthrottle. This can potentially race with an unthrottled group
4022 * trying to acquire new bandwidth from the global pool. This can result
4023 * in us over-using our runtime if it is all used during this loop, but
4024 * only by limited amounts in that extreme case.
4026 while (throttled
&& cfs_b
->runtime
> 0) {
4027 runtime
= cfs_b
->runtime
;
4028 raw_spin_unlock(&cfs_b
->lock
);
4029 /* we can't nest cfs_b->lock while distributing bandwidth */
4030 runtime
= distribute_cfs_runtime(cfs_b
, runtime
,
4032 raw_spin_lock(&cfs_b
->lock
);
4034 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
4036 cfs_b
->runtime
-= min(runtime
, cfs_b
->runtime
);
4040 * While we are ensured activity in the period following an
4041 * unthrottle, this also covers the case in which the new bandwidth is
4042 * insufficient to cover the existing bandwidth deficit. (Forcing the
4043 * timer to remain active while there are any throttled entities.)
4053 /* a cfs_rq won't donate quota below this amount */
4054 static const u64 min_cfs_rq_runtime
= 1 * NSEC_PER_MSEC
;
4055 /* minimum remaining period time to redistribute slack quota */
4056 static const u64 min_bandwidth_expiration
= 2 * NSEC_PER_MSEC
;
4057 /* how long we wait to gather additional slack before distributing */
4058 static const u64 cfs_bandwidth_slack_period
= 5 * NSEC_PER_MSEC
;
4061 * Are we near the end of the current quota period?
4063 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4064 * hrtimer base being cleared by hrtimer_start. In the case of
4065 * migrate_hrtimers, base is never cleared, so we are fine.
4067 static int runtime_refresh_within(struct cfs_bandwidth
*cfs_b
, u64 min_expire
)
4069 struct hrtimer
*refresh_timer
= &cfs_b
->period_timer
;
4072 /* if the call-back is running a quota refresh is already occurring */
4073 if (hrtimer_callback_running(refresh_timer
))
4076 /* is a quota refresh about to occur? */
4077 remaining
= ktime_to_ns(hrtimer_expires_remaining(refresh_timer
));
4078 if (remaining
< min_expire
)
4084 static void start_cfs_slack_bandwidth(struct cfs_bandwidth
*cfs_b
)
4086 u64 min_left
= cfs_bandwidth_slack_period
+ min_bandwidth_expiration
;
4088 /* if there's a quota refresh soon don't bother with slack */
4089 if (runtime_refresh_within(cfs_b
, min_left
))
4092 hrtimer_start(&cfs_b
->slack_timer
,
4093 ns_to_ktime(cfs_bandwidth_slack_period
),
4097 /* we know any runtime found here is valid as update_curr() precedes return */
4098 static void __return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4100 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
4101 s64 slack_runtime
= cfs_rq
->runtime_remaining
- min_cfs_rq_runtime
;
4103 if (slack_runtime
<= 0)
4106 raw_spin_lock(&cfs_b
->lock
);
4107 if (cfs_b
->quota
!= RUNTIME_INF
&&
4108 cfs_rq
->runtime_expires
== cfs_b
->runtime_expires
) {
4109 cfs_b
->runtime
+= slack_runtime
;
4111 /* we are under rq->lock, defer unthrottling using a timer */
4112 if (cfs_b
->runtime
> sched_cfs_bandwidth_slice() &&
4113 !list_empty(&cfs_b
->throttled_cfs_rq
))
4114 start_cfs_slack_bandwidth(cfs_b
);
4116 raw_spin_unlock(&cfs_b
->lock
);
4118 /* even if it's not valid for return we don't want to try again */
4119 cfs_rq
->runtime_remaining
-= slack_runtime
;
4122 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4124 if (!cfs_bandwidth_used())
4127 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->nr_running
)
4130 __return_cfs_rq_runtime(cfs_rq
);
4134 * This is done with a timer (instead of inline with bandwidth return) since
4135 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
4137 static void do_sched_cfs_slack_timer(struct cfs_bandwidth
*cfs_b
)
4139 u64 runtime
= 0, slice
= sched_cfs_bandwidth_slice();
4142 /* confirm we're still not at a refresh boundary */
4143 raw_spin_lock(&cfs_b
->lock
);
4144 if (runtime_refresh_within(cfs_b
, min_bandwidth_expiration
)) {
4145 raw_spin_unlock(&cfs_b
->lock
);
4149 if (cfs_b
->quota
!= RUNTIME_INF
&& cfs_b
->runtime
> slice
)
4150 runtime
= cfs_b
->runtime
;
4152 expires
= cfs_b
->runtime_expires
;
4153 raw_spin_unlock(&cfs_b
->lock
);
4158 runtime
= distribute_cfs_runtime(cfs_b
, runtime
, expires
);
4160 raw_spin_lock(&cfs_b
->lock
);
4161 if (expires
== cfs_b
->runtime_expires
)
4162 cfs_b
->runtime
-= min(runtime
, cfs_b
->runtime
);
4163 raw_spin_unlock(&cfs_b
->lock
);
4167 * When a group wakes up we want to make sure that its quota is not already
4168 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
4169 * runtime as update_curr() throttling can not not trigger until it's on-rq.
4171 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
)
4173 if (!cfs_bandwidth_used())
4176 /* Synchronize hierarchical throttle counter: */
4177 if (unlikely(!cfs_rq
->throttle_uptodate
)) {
4178 struct rq
*rq
= rq_of(cfs_rq
);
4179 struct cfs_rq
*pcfs_rq
;
4180 struct task_group
*tg
;
4182 cfs_rq
->throttle_uptodate
= 1;
4184 /* Get closest up-to-date node, because leaves go first: */
4185 for (tg
= cfs_rq
->tg
->parent
; tg
; tg
= tg
->parent
) {
4186 pcfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
4187 if (pcfs_rq
->throttle_uptodate
)
4191 cfs_rq
->throttle_count
= pcfs_rq
->throttle_count
;
4192 cfs_rq
->throttled_clock_task
= rq_clock_task(rq
);
4196 /* an active group must be handled by the update_curr()->put() path */
4197 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->curr
)
4200 /* ensure the group is not already throttled */
4201 if (cfs_rq_throttled(cfs_rq
))
4204 /* update runtime allocation */
4205 account_cfs_rq_runtime(cfs_rq
, 0);
4206 if (cfs_rq
->runtime_remaining
<= 0)
4207 throttle_cfs_rq(cfs_rq
);
4210 /* conditionally throttle active cfs_rq's from put_prev_entity() */
4211 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4213 if (!cfs_bandwidth_used())
4216 if (likely(!cfs_rq
->runtime_enabled
|| cfs_rq
->runtime_remaining
> 0))
4220 * it's possible for a throttled entity to be forced into a running
4221 * state (e.g. set_curr_task), in this case we're finished.
4223 if (cfs_rq_throttled(cfs_rq
))
4226 throttle_cfs_rq(cfs_rq
);
4230 static enum hrtimer_restart
sched_cfs_slack_timer(struct hrtimer
*timer
)
4232 struct cfs_bandwidth
*cfs_b
=
4233 container_of(timer
, struct cfs_bandwidth
, slack_timer
);
4235 do_sched_cfs_slack_timer(cfs_b
);
4237 return HRTIMER_NORESTART
;
4240 static enum hrtimer_restart
sched_cfs_period_timer(struct hrtimer
*timer
)
4242 struct cfs_bandwidth
*cfs_b
=
4243 container_of(timer
, struct cfs_bandwidth
, period_timer
);
4247 raw_spin_lock(&cfs_b
->lock
);
4249 overrun
= hrtimer_forward_now(timer
, cfs_b
->period
);
4253 idle
= do_sched_cfs_period_timer(cfs_b
, overrun
);
4256 cfs_b
->period_active
= 0;
4257 raw_spin_unlock(&cfs_b
->lock
);
4259 return idle
? HRTIMER_NORESTART
: HRTIMER_RESTART
;
4262 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4264 raw_spin_lock_init(&cfs_b
->lock
);
4266 cfs_b
->quota
= RUNTIME_INF
;
4267 cfs_b
->period
= ns_to_ktime(default_cfs_period());
4269 INIT_LIST_HEAD(&cfs_b
->throttled_cfs_rq
);
4270 hrtimer_init(&cfs_b
->period_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_ABS_PINNED
);
4271 cfs_b
->period_timer
.function
= sched_cfs_period_timer
;
4272 hrtimer_init(&cfs_b
->slack_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
4273 cfs_b
->slack_timer
.function
= sched_cfs_slack_timer
;
4276 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4278 cfs_rq
->runtime_enabled
= 0;
4279 INIT_LIST_HEAD(&cfs_rq
->throttled_list
);
4282 void start_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4284 lockdep_assert_held(&cfs_b
->lock
);
4286 if (!cfs_b
->period_active
) {
4287 cfs_b
->period_active
= 1;
4288 hrtimer_forward_now(&cfs_b
->period_timer
, cfs_b
->period
);
4289 hrtimer_start_expires(&cfs_b
->period_timer
, HRTIMER_MODE_ABS_PINNED
);
4293 static void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4295 /* init_cfs_bandwidth() was not called */
4296 if (!cfs_b
->throttled_cfs_rq
.next
)
4299 hrtimer_cancel(&cfs_b
->period_timer
);
4300 hrtimer_cancel(&cfs_b
->slack_timer
);
4303 static void __maybe_unused
update_runtime_enabled(struct rq
*rq
)
4305 struct cfs_rq
*cfs_rq
;
4307 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
4308 struct cfs_bandwidth
*cfs_b
= &cfs_rq
->tg
->cfs_bandwidth
;
4310 raw_spin_lock(&cfs_b
->lock
);
4311 cfs_rq
->runtime_enabled
= cfs_b
->quota
!= RUNTIME_INF
;
4312 raw_spin_unlock(&cfs_b
->lock
);
4316 static void __maybe_unused
unthrottle_offline_cfs_rqs(struct rq
*rq
)
4318 struct cfs_rq
*cfs_rq
;
4320 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
4321 if (!cfs_rq
->runtime_enabled
)
4325 * clock_task is not advancing so we just need to make sure
4326 * there's some valid quota amount
4328 cfs_rq
->runtime_remaining
= 1;
4330 * Offline rq is schedulable till cpu is completely disabled
4331 * in take_cpu_down(), so we prevent new cfs throttling here.
4333 cfs_rq
->runtime_enabled
= 0;
4335 if (cfs_rq_throttled(cfs_rq
))
4336 unthrottle_cfs_rq(cfs_rq
);
4340 #else /* CONFIG_CFS_BANDWIDTH */
4341 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
4343 return rq_clock_task(rq_of(cfs_rq
));
4346 static void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
) {}
4347 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) { return false; }
4348 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
) {}
4349 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
4351 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
4356 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
4361 static inline int throttled_lb_pair(struct task_group
*tg
,
4362 int src_cpu
, int dest_cpu
)
4367 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
4369 #ifdef CONFIG_FAIR_GROUP_SCHED
4370 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
4373 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
4377 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
4378 static inline void update_runtime_enabled(struct rq
*rq
) {}
4379 static inline void unthrottle_offline_cfs_rqs(struct rq
*rq
) {}
4381 #endif /* CONFIG_CFS_BANDWIDTH */
4383 /**************************************************
4384 * CFS operations on tasks:
4387 #ifdef CONFIG_SCHED_HRTICK
4388 static void hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
4390 struct sched_entity
*se
= &p
->se
;
4391 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4393 WARN_ON(task_rq(p
) != rq
);
4395 if (cfs_rq
->nr_running
> 1) {
4396 u64 slice
= sched_slice(cfs_rq
, se
);
4397 u64 ran
= se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
;
4398 s64 delta
= slice
- ran
;
4405 hrtick_start(rq
, delta
);
4410 * called from enqueue/dequeue and updates the hrtick when the
4411 * current task is from our class and nr_running is low enough
4414 static void hrtick_update(struct rq
*rq
)
4416 struct task_struct
*curr
= rq
->curr
;
4418 if (!hrtick_enabled(rq
) || curr
->sched_class
!= &fair_sched_class
)
4421 if (cfs_rq_of(&curr
->se
)->nr_running
< sched_nr_latency
)
4422 hrtick_start_fair(rq
, curr
);
4424 #else /* !CONFIG_SCHED_HRTICK */
4426 hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
4430 static inline void hrtick_update(struct rq
*rq
)
4436 * The enqueue_task method is called before nr_running is
4437 * increased. Here we update the fair scheduling stats and
4438 * then put the task into the rbtree:
4441 enqueue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
4443 struct cfs_rq
*cfs_rq
;
4444 struct sched_entity
*se
= &p
->se
;
4446 for_each_sched_entity(se
) {
4449 cfs_rq
= cfs_rq_of(se
);
4450 enqueue_entity(cfs_rq
, se
, flags
);
4453 * end evaluation on encountering a throttled cfs_rq
4455 * note: in the case of encountering a throttled cfs_rq we will
4456 * post the final h_nr_running increment below.
4458 if (cfs_rq_throttled(cfs_rq
))
4460 cfs_rq
->h_nr_running
++;
4462 flags
= ENQUEUE_WAKEUP
;
4465 for_each_sched_entity(se
) {
4466 cfs_rq
= cfs_rq_of(se
);
4467 cfs_rq
->h_nr_running
++;
4469 if (cfs_rq_throttled(cfs_rq
))
4472 update_load_avg(se
, 1);
4473 update_cfs_shares(cfs_rq
);
4477 add_nr_running(rq
, 1);
4482 static void set_next_buddy(struct sched_entity
*se
);
4485 * The dequeue_task method is called before nr_running is
4486 * decreased. We remove the task from the rbtree and
4487 * update the fair scheduling stats:
4489 static void dequeue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
4491 struct cfs_rq
*cfs_rq
;
4492 struct sched_entity
*se
= &p
->se
;
4493 int task_sleep
= flags
& DEQUEUE_SLEEP
;
4495 for_each_sched_entity(se
) {
4496 cfs_rq
= cfs_rq_of(se
);
4497 dequeue_entity(cfs_rq
, se
, flags
);
4500 * end evaluation on encountering a throttled cfs_rq
4502 * note: in the case of encountering a throttled cfs_rq we will
4503 * post the final h_nr_running decrement below.
4505 if (cfs_rq_throttled(cfs_rq
))
4507 cfs_rq
->h_nr_running
--;
4509 /* Don't dequeue parent if it has other entities besides us */
4510 if (cfs_rq
->load
.weight
) {
4511 /* Avoid re-evaluating load for this entity: */
4512 se
= parent_entity(se
);
4514 * Bias pick_next to pick a task from this cfs_rq, as
4515 * p is sleeping when it is within its sched_slice.
4517 if (task_sleep
&& se
&& !throttled_hierarchy(cfs_rq
))
4521 flags
|= DEQUEUE_SLEEP
;
4524 for_each_sched_entity(se
) {
4525 cfs_rq
= cfs_rq_of(se
);
4526 cfs_rq
->h_nr_running
--;
4528 if (cfs_rq_throttled(cfs_rq
))
4531 update_load_avg(se
, 1);
4532 update_cfs_shares(cfs_rq
);
4536 sub_nr_running(rq
, 1);
4542 #ifdef CONFIG_NO_HZ_COMMON
4544 * per rq 'load' arrray crap; XXX kill this.
4548 * The exact cpuload calculated at every tick would be:
4550 * load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
4552 * If a cpu misses updates for n ticks (as it was idle) and update gets
4553 * called on the n+1-th tick when cpu may be busy, then we have:
4555 * load_n = (1 - 1/2^i)^n * load_0
4556 * load_n+1 = (1 - 1/2^i) * load_n + (1/2^i) * cur_load
4558 * decay_load_missed() below does efficient calculation of
4560 * load' = (1 - 1/2^i)^n * load
4562 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
4563 * This allows us to precompute the above in said factors, thereby allowing the
4564 * reduction of an arbitrary n in O(log_2 n) steps. (See also
4565 * fixed_power_int())
4567 * The calculation is approximated on a 128 point scale.
4569 #define DEGRADE_SHIFT 7
4571 static const u8 degrade_zero_ticks
[CPU_LOAD_IDX_MAX
] = {0, 8, 32, 64, 128};
4572 static const u8 degrade_factor
[CPU_LOAD_IDX_MAX
][DEGRADE_SHIFT
+ 1] = {
4573 { 0, 0, 0, 0, 0, 0, 0, 0 },
4574 { 64, 32, 8, 0, 0, 0, 0, 0 },
4575 { 96, 72, 40, 12, 1, 0, 0, 0 },
4576 { 112, 98, 75, 43, 15, 1, 0, 0 },
4577 { 120, 112, 98, 76, 45, 16, 2, 0 }
4581 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4582 * would be when CPU is idle and so we just decay the old load without
4583 * adding any new load.
4585 static unsigned long
4586 decay_load_missed(unsigned long load
, unsigned long missed_updates
, int idx
)
4590 if (!missed_updates
)
4593 if (missed_updates
>= degrade_zero_ticks
[idx
])
4597 return load
>> missed_updates
;
4599 while (missed_updates
) {
4600 if (missed_updates
% 2)
4601 load
= (load
* degrade_factor
[idx
][j
]) >> DEGRADE_SHIFT
;
4603 missed_updates
>>= 1;
4608 #endif /* CONFIG_NO_HZ_COMMON */
4611 * __cpu_load_update - update the rq->cpu_load[] statistics
4612 * @this_rq: The rq to update statistics for
4613 * @this_load: The current load
4614 * @pending_updates: The number of missed updates
4616 * Update rq->cpu_load[] statistics. This function is usually called every
4617 * scheduler tick (TICK_NSEC).
4619 * This function computes a decaying average:
4621 * load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
4623 * Because of NOHZ it might not get called on every tick which gives need for
4624 * the @pending_updates argument.
4626 * load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
4627 * = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
4628 * = A * (A * load[i]_n-2 + B) + B
4629 * = A * (A * (A * load[i]_n-3 + B) + B) + B
4630 * = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
4631 * = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
4632 * = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
4633 * = (1 - 1/2^i)^n * (load[i]_0 - load) + load
4635 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
4636 * any change in load would have resulted in the tick being turned back on.
4638 * For regular NOHZ, this reduces to:
4640 * load[i]_n = (1 - 1/2^i)^n * load[i]_0
4642 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
4645 static void cpu_load_update(struct rq
*this_rq
, unsigned long this_load
,
4646 unsigned long pending_updates
)
4648 unsigned long __maybe_unused tickless_load
= this_rq
->cpu_load
[0];
4651 this_rq
->nr_load_updates
++;
4653 /* Update our load: */
4654 this_rq
->cpu_load
[0] = this_load
; /* Fasttrack for idx 0 */
4655 for (i
= 1, scale
= 2; i
< CPU_LOAD_IDX_MAX
; i
++, scale
+= scale
) {
4656 unsigned long old_load
, new_load
;
4658 /* scale is effectively 1 << i now, and >> i divides by scale */
4660 old_load
= this_rq
->cpu_load
[i
];
4661 #ifdef CONFIG_NO_HZ_COMMON
4662 old_load
= decay_load_missed(old_load
, pending_updates
- 1, i
);
4663 if (tickless_load
) {
4664 old_load
-= decay_load_missed(tickless_load
, pending_updates
- 1, i
);
4666 * old_load can never be a negative value because a
4667 * decayed tickless_load cannot be greater than the
4668 * original tickless_load.
4670 old_load
+= tickless_load
;
4673 new_load
= this_load
;
4675 * Round up the averaging division if load is increasing. This
4676 * prevents us from getting stuck on 9 if the load is 10, for
4679 if (new_load
> old_load
)
4680 new_load
+= scale
- 1;
4682 this_rq
->cpu_load
[i
] = (old_load
* (scale
- 1) + new_load
) >> i
;
4685 sched_avg_update(this_rq
);
4688 /* Used instead of source_load when we know the type == 0 */
4689 static unsigned long weighted_cpuload(const int cpu
)
4691 return cfs_rq_runnable_load_avg(&cpu_rq(cpu
)->cfs
);
4694 #ifdef CONFIG_NO_HZ_COMMON
4696 * There is no sane way to deal with nohz on smp when using jiffies because the
4697 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4698 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4700 * Therefore we need to avoid the delta approach from the regular tick when
4701 * possible since that would seriously skew the load calculation. This is why we
4702 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
4703 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
4704 * loop exit, nohz_idle_balance, nohz full exit...)
4706 * This means we might still be one tick off for nohz periods.
4709 static void cpu_load_update_nohz(struct rq
*this_rq
,
4710 unsigned long curr_jiffies
,
4713 unsigned long pending_updates
;
4715 pending_updates
= curr_jiffies
- this_rq
->last_load_update_tick
;
4716 if (pending_updates
) {
4717 this_rq
->last_load_update_tick
= curr_jiffies
;
4719 * In the regular NOHZ case, we were idle, this means load 0.
4720 * In the NOHZ_FULL case, we were non-idle, we should consider
4721 * its weighted load.
4723 cpu_load_update(this_rq
, load
, pending_updates
);
4728 * Called from nohz_idle_balance() to update the load ratings before doing the
4731 static void cpu_load_update_idle(struct rq
*this_rq
)
4734 * bail if there's load or we're actually up-to-date.
4736 if (weighted_cpuload(cpu_of(this_rq
)))
4739 cpu_load_update_nohz(this_rq
, READ_ONCE(jiffies
), 0);
4743 * Record CPU load on nohz entry so we know the tickless load to account
4744 * on nohz exit. cpu_load[0] happens then to be updated more frequently
4745 * than other cpu_load[idx] but it should be fine as cpu_load readers
4746 * shouldn't rely into synchronized cpu_load[*] updates.
4748 void cpu_load_update_nohz_start(void)
4750 struct rq
*this_rq
= this_rq();
4753 * This is all lockless but should be fine. If weighted_cpuload changes
4754 * concurrently we'll exit nohz. And cpu_load write can race with
4755 * cpu_load_update_idle() but both updater would be writing the same.
4757 this_rq
->cpu_load
[0] = weighted_cpuload(cpu_of(this_rq
));
4761 * Account the tickless load in the end of a nohz frame.
4763 void cpu_load_update_nohz_stop(void)
4765 unsigned long curr_jiffies
= READ_ONCE(jiffies
);
4766 struct rq
*this_rq
= this_rq();
4769 if (curr_jiffies
== this_rq
->last_load_update_tick
)
4772 load
= weighted_cpuload(cpu_of(this_rq
));
4773 raw_spin_lock(&this_rq
->lock
);
4774 update_rq_clock(this_rq
);
4775 cpu_load_update_nohz(this_rq
, curr_jiffies
, load
);
4776 raw_spin_unlock(&this_rq
->lock
);
4778 #else /* !CONFIG_NO_HZ_COMMON */
4779 static inline void cpu_load_update_nohz(struct rq
*this_rq
,
4780 unsigned long curr_jiffies
,
4781 unsigned long load
) { }
4782 #endif /* CONFIG_NO_HZ_COMMON */
4784 static void cpu_load_update_periodic(struct rq
*this_rq
, unsigned long load
)
4786 #ifdef CONFIG_NO_HZ_COMMON
4787 /* See the mess around cpu_load_update_nohz(). */
4788 this_rq
->last_load_update_tick
= READ_ONCE(jiffies
);
4790 cpu_load_update(this_rq
, load
, 1);
4794 * Called from scheduler_tick()
4796 void cpu_load_update_active(struct rq
*this_rq
)
4798 unsigned long load
= weighted_cpuload(cpu_of(this_rq
));
4800 if (tick_nohz_tick_stopped())
4801 cpu_load_update_nohz(this_rq
, READ_ONCE(jiffies
), load
);
4803 cpu_load_update_periodic(this_rq
, load
);
4807 * Return a low guess at the load of a migration-source cpu weighted
4808 * according to the scheduling class and "nice" value.
4810 * We want to under-estimate the load of migration sources, to
4811 * balance conservatively.
4813 static unsigned long source_load(int cpu
, int type
)
4815 struct rq
*rq
= cpu_rq(cpu
);
4816 unsigned long total
= weighted_cpuload(cpu
);
4818 if (type
== 0 || !sched_feat(LB_BIAS
))
4821 return min(rq
->cpu_load
[type
-1], total
);
4825 * Return a high guess at the load of a migration-target cpu weighted
4826 * according to the scheduling class and "nice" value.
4828 static unsigned long target_load(int cpu
, int type
)
4830 struct rq
*rq
= cpu_rq(cpu
);
4831 unsigned long total
= weighted_cpuload(cpu
);
4833 if (type
== 0 || !sched_feat(LB_BIAS
))
4836 return max(rq
->cpu_load
[type
-1], total
);
4839 static unsigned long capacity_of(int cpu
)
4841 return cpu_rq(cpu
)->cpu_capacity
;
4844 static unsigned long capacity_orig_of(int cpu
)
4846 return cpu_rq(cpu
)->cpu_capacity_orig
;
4849 static unsigned long cpu_avg_load_per_task(int cpu
)
4851 struct rq
*rq
= cpu_rq(cpu
);
4852 unsigned long nr_running
= READ_ONCE(rq
->cfs
.h_nr_running
);
4853 unsigned long load_avg
= weighted_cpuload(cpu
);
4856 return load_avg
/ nr_running
;
4861 #ifdef CONFIG_FAIR_GROUP_SCHED
4863 * effective_load() calculates the load change as seen from the root_task_group
4865 * Adding load to a group doesn't make a group heavier, but can cause movement
4866 * of group shares between cpus. Assuming the shares were perfectly aligned one
4867 * can calculate the shift in shares.
4869 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4870 * on this @cpu and results in a total addition (subtraction) of @wg to the
4871 * total group weight.
4873 * Given a runqueue weight distribution (rw_i) we can compute a shares
4874 * distribution (s_i) using:
4876 * s_i = rw_i / \Sum rw_j (1)
4878 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4879 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4880 * shares distribution (s_i):
4882 * rw_i = { 2, 4, 1, 0 }
4883 * s_i = { 2/7, 4/7, 1/7, 0 }
4885 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4886 * task used to run on and the CPU the waker is running on), we need to
4887 * compute the effect of waking a task on either CPU and, in case of a sync
4888 * wakeup, compute the effect of the current task going to sleep.
4890 * So for a change of @wl to the local @cpu with an overall group weight change
4891 * of @wl we can compute the new shares distribution (s'_i) using:
4893 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4895 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4896 * differences in waking a task to CPU 0. The additional task changes the
4897 * weight and shares distributions like:
4899 * rw'_i = { 3, 4, 1, 0 }
4900 * s'_i = { 3/8, 4/8, 1/8, 0 }
4902 * We can then compute the difference in effective weight by using:
4904 * dw_i = S * (s'_i - s_i) (3)
4906 * Where 'S' is the group weight as seen by its parent.
4908 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4909 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4910 * 4/7) times the weight of the group.
4912 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
)
4914 struct sched_entity
*se
= tg
->se
[cpu
];
4916 if (!tg
->parent
) /* the trivial, non-cgroup case */
4919 for_each_sched_entity(se
) {
4920 struct cfs_rq
*cfs_rq
= se
->my_q
;
4921 long W
, w
= cfs_rq_load_avg(cfs_rq
);
4926 * W = @wg + \Sum rw_j
4928 W
= wg
+ atomic_long_read(&tg
->load_avg
);
4930 /* Ensure \Sum rw_j >= rw_i */
4931 W
-= cfs_rq
->tg_load_avg_contrib
;
4940 * wl = S * s'_i; see (2)
4943 wl
= (w
* (long)tg
->shares
) / W
;
4948 * Per the above, wl is the new se->load.weight value; since
4949 * those are clipped to [MIN_SHARES, ...) do so now. See
4950 * calc_cfs_shares().
4952 if (wl
< MIN_SHARES
)
4956 * wl = dw_i = S * (s'_i - s_i); see (3)
4958 wl
-= se
->avg
.load_avg
;
4961 * Recursively apply this logic to all parent groups to compute
4962 * the final effective load change on the root group. Since
4963 * only the @tg group gets extra weight, all parent groups can
4964 * only redistribute existing shares. @wl is the shift in shares
4965 * resulting from this level per the above.
4974 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
)
4981 static void record_wakee(struct task_struct
*p
)
4984 * Only decay a single time; tasks that have less then 1 wakeup per
4985 * jiffy will not have built up many flips.
4987 if (time_after(jiffies
, current
->wakee_flip_decay_ts
+ HZ
)) {
4988 current
->wakee_flips
>>= 1;
4989 current
->wakee_flip_decay_ts
= jiffies
;
4992 if (current
->last_wakee
!= p
) {
4993 current
->last_wakee
= p
;
4994 current
->wakee_flips
++;
4999 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5001 * A waker of many should wake a different task than the one last awakened
5002 * at a frequency roughly N times higher than one of its wakees.
5004 * In order to determine whether we should let the load spread vs consolidating
5005 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
5006 * partner, and a factor of lls_size higher frequency in the other.
5008 * With both conditions met, we can be relatively sure that the relationship is
5009 * non-monogamous, with partner count exceeding socket size.
5011 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
5012 * whatever is irrelevant, spread criteria is apparent partner count exceeds
5015 static int wake_wide(struct task_struct
*p
)
5017 unsigned int master
= current
->wakee_flips
;
5018 unsigned int slave
= p
->wakee_flips
;
5019 int factor
= this_cpu_read(sd_llc_size
);
5022 swap(master
, slave
);
5023 if (slave
< factor
|| master
< slave
* factor
)
5028 static int wake_affine(struct sched_domain
*sd
, struct task_struct
*p
, int sync
)
5030 s64 this_load
, load
;
5031 s64 this_eff_load
, prev_eff_load
;
5032 int idx
, this_cpu
, prev_cpu
;
5033 struct task_group
*tg
;
5034 unsigned long weight
;
5038 this_cpu
= smp_processor_id();
5039 prev_cpu
= task_cpu(p
);
5040 load
= source_load(prev_cpu
, idx
);
5041 this_load
= target_load(this_cpu
, idx
);
5044 * If sync wakeup then subtract the (maximum possible)
5045 * effect of the currently running task from the load
5046 * of the current CPU:
5049 tg
= task_group(current
);
5050 weight
= current
->se
.avg
.load_avg
;
5052 this_load
+= effective_load(tg
, this_cpu
, -weight
, -weight
);
5053 load
+= effective_load(tg
, prev_cpu
, 0, -weight
);
5057 weight
= p
->se
.avg
.load_avg
;
5060 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5061 * due to the sync cause above having dropped this_load to 0, we'll
5062 * always have an imbalance, but there's really nothing you can do
5063 * about that, so that's good too.
5065 * Otherwise check if either cpus are near enough in load to allow this
5066 * task to be woken on this_cpu.
5068 this_eff_load
= 100;
5069 this_eff_load
*= capacity_of(prev_cpu
);
5071 prev_eff_load
= 100 + (sd
->imbalance_pct
- 100) / 2;
5072 prev_eff_load
*= capacity_of(this_cpu
);
5074 if (this_load
> 0) {
5075 this_eff_load
*= this_load
+
5076 effective_load(tg
, this_cpu
, weight
, weight
);
5078 prev_eff_load
*= load
+ effective_load(tg
, prev_cpu
, 0, weight
);
5081 balanced
= this_eff_load
<= prev_eff_load
;
5083 schedstat_inc(p
, se
.statistics
.nr_wakeups_affine_attempts
);
5088 schedstat_inc(sd
, ttwu_move_affine
);
5089 schedstat_inc(p
, se
.statistics
.nr_wakeups_affine
);
5095 * find_idlest_group finds and returns the least busy CPU group within the
5098 static struct sched_group
*
5099 find_idlest_group(struct sched_domain
*sd
, struct task_struct
*p
,
5100 int this_cpu
, int sd_flag
)
5102 struct sched_group
*idlest
= NULL
, *group
= sd
->groups
;
5103 unsigned long min_load
= ULONG_MAX
, this_load
= 0;
5104 int load_idx
= sd
->forkexec_idx
;
5105 int imbalance
= 100 + (sd
->imbalance_pct
-100)/2;
5107 if (sd_flag
& SD_BALANCE_WAKE
)
5108 load_idx
= sd
->wake_idx
;
5111 unsigned long load
, avg_load
;
5115 /* Skip over this group if it has no CPUs allowed */
5116 if (!cpumask_intersects(sched_group_cpus(group
),
5117 tsk_cpus_allowed(p
)))
5120 local_group
= cpumask_test_cpu(this_cpu
,
5121 sched_group_cpus(group
));
5123 /* Tally up the load of all CPUs in the group */
5126 for_each_cpu(i
, sched_group_cpus(group
)) {
5127 /* Bias balancing toward cpus of our domain */
5129 load
= source_load(i
, load_idx
);
5131 load
= target_load(i
, load_idx
);
5136 /* Adjust by relative CPU capacity of the group */
5137 avg_load
= (avg_load
* SCHED_CAPACITY_SCALE
) / group
->sgc
->capacity
;
5140 this_load
= avg_load
;
5141 } else if (avg_load
< min_load
) {
5142 min_load
= avg_load
;
5145 } while (group
= group
->next
, group
!= sd
->groups
);
5147 if (!idlest
|| 100*this_load
< imbalance
*min_load
)
5153 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5156 find_idlest_cpu(struct sched_group
*group
, struct task_struct
*p
, int this_cpu
)
5158 unsigned long load
, min_load
= ULONG_MAX
;
5159 unsigned int min_exit_latency
= UINT_MAX
;
5160 u64 latest_idle_timestamp
= 0;
5161 int least_loaded_cpu
= this_cpu
;
5162 int shallowest_idle_cpu
= -1;
5165 /* Traverse only the allowed CPUs */
5166 for_each_cpu_and(i
, sched_group_cpus(group
), tsk_cpus_allowed(p
)) {
5168 struct rq
*rq
= cpu_rq(i
);
5169 struct cpuidle_state
*idle
= idle_get_state(rq
);
5170 if (idle
&& idle
->exit_latency
< min_exit_latency
) {
5172 * We give priority to a CPU whose idle state
5173 * has the smallest exit latency irrespective
5174 * of any idle timestamp.
5176 min_exit_latency
= idle
->exit_latency
;
5177 latest_idle_timestamp
= rq
->idle_stamp
;
5178 shallowest_idle_cpu
= i
;
5179 } else if ((!idle
|| idle
->exit_latency
== min_exit_latency
) &&
5180 rq
->idle_stamp
> latest_idle_timestamp
) {
5182 * If equal or no active idle state, then
5183 * the most recently idled CPU might have
5186 latest_idle_timestamp
= rq
->idle_stamp
;
5187 shallowest_idle_cpu
= i
;
5189 } else if (shallowest_idle_cpu
== -1) {
5190 load
= weighted_cpuload(i
);
5191 if (load
< min_load
|| (load
== min_load
&& i
== this_cpu
)) {
5193 least_loaded_cpu
= i
;
5198 return shallowest_idle_cpu
!= -1 ? shallowest_idle_cpu
: least_loaded_cpu
;
5202 * Try and locate an idle CPU in the sched_domain.
5204 static int select_idle_sibling(struct task_struct
*p
, int target
)
5206 struct sched_domain
*sd
;
5207 struct sched_group
*sg
;
5208 int i
= task_cpu(p
);
5210 if (idle_cpu(target
))
5214 * If the prevous cpu is cache affine and idle, don't be stupid.
5216 if (i
!= target
&& cpus_share_cache(i
, target
) && idle_cpu(i
))
5220 * Otherwise, iterate the domains and find an eligible idle cpu.
5222 * A completely idle sched group at higher domains is more
5223 * desirable than an idle group at a lower level, because lower
5224 * domains have smaller groups and usually share hardware
5225 * resources which causes tasks to contend on them, e.g. x86
5226 * hyperthread siblings in the lowest domain (SMT) can contend
5227 * on the shared cpu pipeline.
5229 * However, while we prefer idle groups at higher domains
5230 * finding an idle cpu at the lowest domain is still better than
5231 * returning 'target', which we've already established, isn't
5234 sd
= rcu_dereference(per_cpu(sd_llc
, target
));
5235 for_each_lower_domain(sd
) {
5238 if (!cpumask_intersects(sched_group_cpus(sg
),
5239 tsk_cpus_allowed(p
)))
5242 /* Ensure the entire group is idle */
5243 for_each_cpu(i
, sched_group_cpus(sg
)) {
5244 if (i
== target
|| !idle_cpu(i
))
5249 * It doesn't matter which cpu we pick, the
5250 * whole group is idle.
5252 target
= cpumask_first_and(sched_group_cpus(sg
),
5253 tsk_cpus_allowed(p
));
5257 } while (sg
!= sd
->groups
);
5264 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5265 * tasks. The unit of the return value must be the one of capacity so we can
5266 * compare the utilization with the capacity of the CPU that is available for
5267 * CFS task (ie cpu_capacity).
5269 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
5270 * recent utilization of currently non-runnable tasks on a CPU. It represents
5271 * the amount of utilization of a CPU in the range [0..capacity_orig] where
5272 * capacity_orig is the cpu_capacity available at the highest frequency
5273 * (arch_scale_freq_capacity()).
5274 * The utilization of a CPU converges towards a sum equal to or less than the
5275 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
5276 * the running time on this CPU scaled by capacity_curr.
5278 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
5279 * higher than capacity_orig because of unfortunate rounding in
5280 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
5281 * the average stabilizes with the new running time. We need to check that the
5282 * utilization stays within the range of [0..capacity_orig] and cap it if
5283 * necessary. Without utilization capping, a group could be seen as overloaded
5284 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
5285 * available capacity. We allow utilization to overshoot capacity_curr (but not
5286 * capacity_orig) as it useful for predicting the capacity required after task
5287 * migrations (scheduler-driven DVFS).
5289 static int cpu_util(int cpu
)
5291 unsigned long util
= cpu_rq(cpu
)->cfs
.avg
.util_avg
;
5292 unsigned long capacity
= capacity_orig_of(cpu
);
5294 return (util
>= capacity
) ? capacity
: util
;
5298 * select_task_rq_fair: Select target runqueue for the waking task in domains
5299 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5300 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5302 * Balances load by selecting the idlest cpu in the idlest group, or under
5303 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5305 * Returns the target cpu number.
5307 * preempt must be disabled.
5310 select_task_rq_fair(struct task_struct
*p
, int prev_cpu
, int sd_flag
, int wake_flags
)
5312 struct sched_domain
*tmp
, *affine_sd
= NULL
, *sd
= NULL
;
5313 int cpu
= smp_processor_id();
5314 int new_cpu
= prev_cpu
;
5315 int want_affine
= 0;
5316 int sync
= wake_flags
& WF_SYNC
;
5318 if (sd_flag
& SD_BALANCE_WAKE
) {
5320 want_affine
= !wake_wide(p
) && cpumask_test_cpu(cpu
, tsk_cpus_allowed(p
));
5324 for_each_domain(cpu
, tmp
) {
5325 if (!(tmp
->flags
& SD_LOAD_BALANCE
))
5329 * If both cpu and prev_cpu are part of this domain,
5330 * cpu is a valid SD_WAKE_AFFINE target.
5332 if (want_affine
&& (tmp
->flags
& SD_WAKE_AFFINE
) &&
5333 cpumask_test_cpu(prev_cpu
, sched_domain_span(tmp
))) {
5338 if (tmp
->flags
& sd_flag
)
5340 else if (!want_affine
)
5345 sd
= NULL
; /* Prefer wake_affine over balance flags */
5346 if (cpu
!= prev_cpu
&& wake_affine(affine_sd
, p
, sync
))
5351 if (sd_flag
& SD_BALANCE_WAKE
) /* XXX always ? */
5352 new_cpu
= select_idle_sibling(p
, new_cpu
);
5355 struct sched_group
*group
;
5358 if (!(sd
->flags
& sd_flag
)) {
5363 group
= find_idlest_group(sd
, p
, cpu
, sd_flag
);
5369 new_cpu
= find_idlest_cpu(group
, p
, cpu
);
5370 if (new_cpu
== -1 || new_cpu
== cpu
) {
5371 /* Now try balancing at a lower domain level of cpu */
5376 /* Now try balancing at a lower domain level of new_cpu */
5378 weight
= sd
->span_weight
;
5380 for_each_domain(cpu
, tmp
) {
5381 if (weight
<= tmp
->span_weight
)
5383 if (tmp
->flags
& sd_flag
)
5386 /* while loop will break here if sd == NULL */
5394 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5395 * cfs_rq_of(p) references at time of call are still valid and identify the
5396 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5398 static void migrate_task_rq_fair(struct task_struct
*p
)
5401 * As blocked tasks retain absolute vruntime the migration needs to
5402 * deal with this by subtracting the old and adding the new
5403 * min_vruntime -- the latter is done by enqueue_entity() when placing
5404 * the task on the new runqueue.
5406 if (p
->state
== TASK_WAKING
) {
5407 struct sched_entity
*se
= &p
->se
;
5408 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
5411 #ifndef CONFIG_64BIT
5412 u64 min_vruntime_copy
;
5415 min_vruntime_copy
= cfs_rq
->min_vruntime_copy
;
5417 min_vruntime
= cfs_rq
->min_vruntime
;
5418 } while (min_vruntime
!= min_vruntime_copy
);
5420 min_vruntime
= cfs_rq
->min_vruntime
;
5423 se
->vruntime
-= min_vruntime
;
5427 * We are supposed to update the task to "current" time, then its up to date
5428 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5429 * what current time is, so simply throw away the out-of-date time. This
5430 * will result in the wakee task is less decayed, but giving the wakee more
5431 * load sounds not bad.
5433 remove_entity_load_avg(&p
->se
);
5435 /* Tell new CPU we are migrated */
5436 p
->se
.avg
.last_update_time
= 0;
5438 /* We have migrated, no longer consider this task hot */
5439 p
->se
.exec_start
= 0;
5442 static void task_dead_fair(struct task_struct
*p
)
5444 remove_entity_load_avg(&p
->se
);
5446 #endif /* CONFIG_SMP */
5448 static unsigned long
5449 wakeup_gran(struct sched_entity
*curr
, struct sched_entity
*se
)
5451 unsigned long gran
= sysctl_sched_wakeup_granularity
;
5454 * Since its curr running now, convert the gran from real-time
5455 * to virtual-time in his units.
5457 * By using 'se' instead of 'curr' we penalize light tasks, so
5458 * they get preempted easier. That is, if 'se' < 'curr' then
5459 * the resulting gran will be larger, therefore penalizing the
5460 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5461 * be smaller, again penalizing the lighter task.
5463 * This is especially important for buddies when the leftmost
5464 * task is higher priority than the buddy.
5466 return calc_delta_fair(gran
, se
);
5470 * Should 'se' preempt 'curr'.
5484 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
)
5486 s64 gran
, vdiff
= curr
->vruntime
- se
->vruntime
;
5491 gran
= wakeup_gran(curr
, se
);
5498 static void set_last_buddy(struct sched_entity
*se
)
5500 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
5503 for_each_sched_entity(se
)
5504 cfs_rq_of(se
)->last
= se
;
5507 static void set_next_buddy(struct sched_entity
*se
)
5509 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
5512 for_each_sched_entity(se
)
5513 cfs_rq_of(se
)->next
= se
;
5516 static void set_skip_buddy(struct sched_entity
*se
)
5518 for_each_sched_entity(se
)
5519 cfs_rq_of(se
)->skip
= se
;
5523 * Preempt the current task with a newly woken task if needed:
5525 static void check_preempt_wakeup(struct rq
*rq
, struct task_struct
*p
, int wake_flags
)
5527 struct task_struct
*curr
= rq
->curr
;
5528 struct sched_entity
*se
= &curr
->se
, *pse
= &p
->se
;
5529 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
5530 int scale
= cfs_rq
->nr_running
>= sched_nr_latency
;
5531 int next_buddy_marked
= 0;
5533 if (unlikely(se
== pse
))
5537 * This is possible from callers such as attach_tasks(), in which we
5538 * unconditionally check_prempt_curr() after an enqueue (which may have
5539 * lead to a throttle). This both saves work and prevents false
5540 * next-buddy nomination below.
5542 if (unlikely(throttled_hierarchy(cfs_rq_of(pse
))))
5545 if (sched_feat(NEXT_BUDDY
) && scale
&& !(wake_flags
& WF_FORK
)) {
5546 set_next_buddy(pse
);
5547 next_buddy_marked
= 1;
5551 * We can come here with TIF_NEED_RESCHED already set from new task
5554 * Note: this also catches the edge-case of curr being in a throttled
5555 * group (e.g. via set_curr_task), since update_curr() (in the
5556 * enqueue of curr) will have resulted in resched being set. This
5557 * prevents us from potentially nominating it as a false LAST_BUDDY
5560 if (test_tsk_need_resched(curr
))
5563 /* Idle tasks are by definition preempted by non-idle tasks. */
5564 if (unlikely(curr
->policy
== SCHED_IDLE
) &&
5565 likely(p
->policy
!= SCHED_IDLE
))
5569 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5570 * is driven by the tick):
5572 if (unlikely(p
->policy
!= SCHED_NORMAL
) || !sched_feat(WAKEUP_PREEMPTION
))
5575 find_matching_se(&se
, &pse
);
5576 update_curr(cfs_rq_of(se
));
5578 if (wakeup_preempt_entity(se
, pse
) == 1) {
5580 * Bias pick_next to pick the sched entity that is
5581 * triggering this preemption.
5583 if (!next_buddy_marked
)
5584 set_next_buddy(pse
);
5593 * Only set the backward buddy when the current task is still
5594 * on the rq. This can happen when a wakeup gets interleaved
5595 * with schedule on the ->pre_schedule() or idle_balance()
5596 * point, either of which can * drop the rq lock.
5598 * Also, during early boot the idle thread is in the fair class,
5599 * for obvious reasons its a bad idea to schedule back to it.
5601 if (unlikely(!se
->on_rq
|| curr
== rq
->idle
))
5604 if (sched_feat(LAST_BUDDY
) && scale
&& entity_is_task(se
))
5608 static struct task_struct
*
5609 pick_next_task_fair(struct rq
*rq
, struct task_struct
*prev
, struct pin_cookie cookie
)
5611 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
5612 struct sched_entity
*se
;
5613 struct task_struct
*p
;
5617 #ifdef CONFIG_FAIR_GROUP_SCHED
5618 if (!cfs_rq
->nr_running
)
5621 if (prev
->sched_class
!= &fair_sched_class
)
5625 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5626 * likely that a next task is from the same cgroup as the current.
5628 * Therefore attempt to avoid putting and setting the entire cgroup
5629 * hierarchy, only change the part that actually changes.
5633 struct sched_entity
*curr
= cfs_rq
->curr
;
5636 * Since we got here without doing put_prev_entity() we also
5637 * have to consider cfs_rq->curr. If it is still a runnable
5638 * entity, update_curr() will update its vruntime, otherwise
5639 * forget we've ever seen it.
5643 update_curr(cfs_rq
);
5648 * This call to check_cfs_rq_runtime() will do the
5649 * throttle and dequeue its entity in the parent(s).
5650 * Therefore the 'simple' nr_running test will indeed
5653 if (unlikely(check_cfs_rq_runtime(cfs_rq
)))
5657 se
= pick_next_entity(cfs_rq
, curr
);
5658 cfs_rq
= group_cfs_rq(se
);
5664 * Since we haven't yet done put_prev_entity and if the selected task
5665 * is a different task than we started out with, try and touch the
5666 * least amount of cfs_rqs.
5669 struct sched_entity
*pse
= &prev
->se
;
5671 while (!(cfs_rq
= is_same_group(se
, pse
))) {
5672 int se_depth
= se
->depth
;
5673 int pse_depth
= pse
->depth
;
5675 if (se_depth
<= pse_depth
) {
5676 put_prev_entity(cfs_rq_of(pse
), pse
);
5677 pse
= parent_entity(pse
);
5679 if (se_depth
>= pse_depth
) {
5680 set_next_entity(cfs_rq_of(se
), se
);
5681 se
= parent_entity(se
);
5685 put_prev_entity(cfs_rq
, pse
);
5686 set_next_entity(cfs_rq
, se
);
5689 if (hrtick_enabled(rq
))
5690 hrtick_start_fair(rq
, p
);
5697 if (!cfs_rq
->nr_running
)
5700 put_prev_task(rq
, prev
);
5703 se
= pick_next_entity(cfs_rq
, NULL
);
5704 set_next_entity(cfs_rq
, se
);
5705 cfs_rq
= group_cfs_rq(se
);
5710 if (hrtick_enabled(rq
))
5711 hrtick_start_fair(rq
, p
);
5717 * This is OK, because current is on_cpu, which avoids it being picked
5718 * for load-balance and preemption/IRQs are still disabled avoiding
5719 * further scheduler activity on it and we're being very careful to
5720 * re-start the picking loop.
5722 lockdep_unpin_lock(&rq
->lock
, cookie
);
5723 new_tasks
= idle_balance(rq
);
5724 lockdep_repin_lock(&rq
->lock
, cookie
);
5726 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5727 * possible for any higher priority task to appear. In that case we
5728 * must re-start the pick_next_entity() loop.
5740 * Account for a descheduled task:
5742 static void put_prev_task_fair(struct rq
*rq
, struct task_struct
*prev
)
5744 struct sched_entity
*se
= &prev
->se
;
5745 struct cfs_rq
*cfs_rq
;
5747 for_each_sched_entity(se
) {
5748 cfs_rq
= cfs_rq_of(se
);
5749 put_prev_entity(cfs_rq
, se
);
5754 * sched_yield() is very simple
5756 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5758 static void yield_task_fair(struct rq
*rq
)
5760 struct task_struct
*curr
= rq
->curr
;
5761 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
5762 struct sched_entity
*se
= &curr
->se
;
5765 * Are we the only task in the tree?
5767 if (unlikely(rq
->nr_running
== 1))
5770 clear_buddies(cfs_rq
, se
);
5772 if (curr
->policy
!= SCHED_BATCH
) {
5773 update_rq_clock(rq
);
5775 * Update run-time statistics of the 'current'.
5777 update_curr(cfs_rq
);
5779 * Tell update_rq_clock() that we've just updated,
5780 * so we don't do microscopic update in schedule()
5781 * and double the fastpath cost.
5783 rq_clock_skip_update(rq
, true);
5789 static bool yield_to_task_fair(struct rq
*rq
, struct task_struct
*p
, bool preempt
)
5791 struct sched_entity
*se
= &p
->se
;
5793 /* throttled hierarchies are not runnable */
5794 if (!se
->on_rq
|| throttled_hierarchy(cfs_rq_of(se
)))
5797 /* Tell the scheduler that we'd really like pse to run next. */
5800 yield_task_fair(rq
);
5806 /**************************************************
5807 * Fair scheduling class load-balancing methods.
5811 * The purpose of load-balancing is to achieve the same basic fairness the
5812 * per-cpu scheduler provides, namely provide a proportional amount of compute
5813 * time to each task. This is expressed in the following equation:
5815 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5817 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5818 * W_i,0 is defined as:
5820 * W_i,0 = \Sum_j w_i,j (2)
5822 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5823 * is derived from the nice value as per sched_prio_to_weight[].
5825 * The weight average is an exponential decay average of the instantaneous
5828 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5830 * C_i is the compute capacity of cpu i, typically it is the
5831 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5832 * can also include other factors [XXX].
5834 * To achieve this balance we define a measure of imbalance which follows
5835 * directly from (1):
5837 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5839 * We them move tasks around to minimize the imbalance. In the continuous
5840 * function space it is obvious this converges, in the discrete case we get
5841 * a few fun cases generally called infeasible weight scenarios.
5844 * - infeasible weights;
5845 * - local vs global optima in the discrete case. ]
5850 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5851 * for all i,j solution, we create a tree of cpus that follows the hardware
5852 * topology where each level pairs two lower groups (or better). This results
5853 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5854 * tree to only the first of the previous level and we decrease the frequency
5855 * of load-balance at each level inv. proportional to the number of cpus in
5861 * \Sum { --- * --- * 2^i } = O(n) (5)
5863 * `- size of each group
5864 * | | `- number of cpus doing load-balance
5866 * `- sum over all levels
5868 * Coupled with a limit on how many tasks we can migrate every balance pass,
5869 * this makes (5) the runtime complexity of the balancer.
5871 * An important property here is that each CPU is still (indirectly) connected
5872 * to every other cpu in at most O(log n) steps:
5874 * The adjacency matrix of the resulting graph is given by:
5877 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5880 * And you'll find that:
5882 * A^(log_2 n)_i,j != 0 for all i,j (7)
5884 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5885 * The task movement gives a factor of O(m), giving a convergence complexity
5888 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5893 * In order to avoid CPUs going idle while there's still work to do, new idle
5894 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5895 * tree itself instead of relying on other CPUs to bring it work.
5897 * This adds some complexity to both (5) and (8) but it reduces the total idle
5905 * Cgroups make a horror show out of (2), instead of a simple sum we get:
5908 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
5913 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
5915 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5917 * The big problem is S_k, its a global sum needed to compute a local (W_i)
5920 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5921 * rewrite all of this once again.]
5924 static unsigned long __read_mostly max_load_balance_interval
= HZ
/10;
5926 enum fbq_type
{ regular
, remote
, all
};
5928 #define LBF_ALL_PINNED 0x01
5929 #define LBF_NEED_BREAK 0x02
5930 #define LBF_DST_PINNED 0x04
5931 #define LBF_SOME_PINNED 0x08
5934 struct sched_domain
*sd
;
5942 struct cpumask
*dst_grpmask
;
5944 enum cpu_idle_type idle
;
5946 /* The set of CPUs under consideration for load-balancing */
5947 struct cpumask
*cpus
;
5952 unsigned int loop_break
;
5953 unsigned int loop_max
;
5955 enum fbq_type fbq_type
;
5956 struct list_head tasks
;
5960 * Is this task likely cache-hot:
5962 static int task_hot(struct task_struct
*p
, struct lb_env
*env
)
5966 lockdep_assert_held(&env
->src_rq
->lock
);
5968 if (p
->sched_class
!= &fair_sched_class
)
5971 if (unlikely(p
->policy
== SCHED_IDLE
))
5975 * Buddy candidates are cache hot:
5977 if (sched_feat(CACHE_HOT_BUDDY
) && env
->dst_rq
->nr_running
&&
5978 (&p
->se
== cfs_rq_of(&p
->se
)->next
||
5979 &p
->se
== cfs_rq_of(&p
->se
)->last
))
5982 if (sysctl_sched_migration_cost
== -1)
5984 if (sysctl_sched_migration_cost
== 0)
5987 delta
= rq_clock_task(env
->src_rq
) - p
->se
.exec_start
;
5989 return delta
< (s64
)sysctl_sched_migration_cost
;
5992 #ifdef CONFIG_NUMA_BALANCING
5994 * Returns 1, if task migration degrades locality
5995 * Returns 0, if task migration improves locality i.e migration preferred.
5996 * Returns -1, if task migration is not affected by locality.
5998 static int migrate_degrades_locality(struct task_struct
*p
, struct lb_env
*env
)
6000 struct numa_group
*numa_group
= rcu_dereference(p
->numa_group
);
6001 unsigned long src_faults
, dst_faults
;
6002 int src_nid
, dst_nid
;
6004 if (!static_branch_likely(&sched_numa_balancing
))
6007 if (!p
->numa_faults
|| !(env
->sd
->flags
& SD_NUMA
))
6010 src_nid
= cpu_to_node(env
->src_cpu
);
6011 dst_nid
= cpu_to_node(env
->dst_cpu
);
6013 if (src_nid
== dst_nid
)
6016 /* Migrating away from the preferred node is always bad. */
6017 if (src_nid
== p
->numa_preferred_nid
) {
6018 if (env
->src_rq
->nr_running
> env
->src_rq
->nr_preferred_running
)
6024 /* Encourage migration to the preferred node. */
6025 if (dst_nid
== p
->numa_preferred_nid
)
6029 src_faults
= group_faults(p
, src_nid
);
6030 dst_faults
= group_faults(p
, dst_nid
);
6032 src_faults
= task_faults(p
, src_nid
);
6033 dst_faults
= task_faults(p
, dst_nid
);
6036 return dst_faults
< src_faults
;
6040 static inline int migrate_degrades_locality(struct task_struct
*p
,
6048 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
6051 int can_migrate_task(struct task_struct
*p
, struct lb_env
*env
)
6055 lockdep_assert_held(&env
->src_rq
->lock
);
6058 * We do not migrate tasks that are:
6059 * 1) throttled_lb_pair, or
6060 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6061 * 3) running (obviously), or
6062 * 4) are cache-hot on their current CPU.
6064 if (throttled_lb_pair(task_group(p
), env
->src_cpu
, env
->dst_cpu
))
6067 if (!cpumask_test_cpu(env
->dst_cpu
, tsk_cpus_allowed(p
))) {
6070 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_affine
);
6072 env
->flags
|= LBF_SOME_PINNED
;
6075 * Remember if this task can be migrated to any other cpu in
6076 * our sched_group. We may want to revisit it if we couldn't
6077 * meet load balance goals by pulling other tasks on src_cpu.
6079 * Also avoid computing new_dst_cpu if we have already computed
6080 * one in current iteration.
6082 if (!env
->dst_grpmask
|| (env
->flags
& LBF_DST_PINNED
))
6085 /* Prevent to re-select dst_cpu via env's cpus */
6086 for_each_cpu_and(cpu
, env
->dst_grpmask
, env
->cpus
) {
6087 if (cpumask_test_cpu(cpu
, tsk_cpus_allowed(p
))) {
6088 env
->flags
|= LBF_DST_PINNED
;
6089 env
->new_dst_cpu
= cpu
;
6097 /* Record that we found atleast one task that could run on dst_cpu */
6098 env
->flags
&= ~LBF_ALL_PINNED
;
6100 if (task_running(env
->src_rq
, p
)) {
6101 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_running
);
6106 * Aggressive migration if:
6107 * 1) destination numa is preferred
6108 * 2) task is cache cold, or
6109 * 3) too many balance attempts have failed.
6111 tsk_cache_hot
= migrate_degrades_locality(p
, env
);
6112 if (tsk_cache_hot
== -1)
6113 tsk_cache_hot
= task_hot(p
, env
);
6115 if (tsk_cache_hot
<= 0 ||
6116 env
->sd
->nr_balance_failed
> env
->sd
->cache_nice_tries
) {
6117 if (tsk_cache_hot
== 1) {
6118 schedstat_inc(env
->sd
, lb_hot_gained
[env
->idle
]);
6119 schedstat_inc(p
, se
.statistics
.nr_forced_migrations
);
6124 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_hot
);
6129 * detach_task() -- detach the task for the migration specified in env
6131 static void detach_task(struct task_struct
*p
, struct lb_env
*env
)
6133 lockdep_assert_held(&env
->src_rq
->lock
);
6135 p
->on_rq
= TASK_ON_RQ_MIGRATING
;
6136 deactivate_task(env
->src_rq
, p
, 0);
6137 set_task_cpu(p
, env
->dst_cpu
);
6141 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6142 * part of active balancing operations within "domain".
6144 * Returns a task if successful and NULL otherwise.
6146 static struct task_struct
*detach_one_task(struct lb_env
*env
)
6148 struct task_struct
*p
, *n
;
6150 lockdep_assert_held(&env
->src_rq
->lock
);
6152 list_for_each_entry_safe(p
, n
, &env
->src_rq
->cfs_tasks
, se
.group_node
) {
6153 if (!can_migrate_task(p
, env
))
6156 detach_task(p
, env
);
6159 * Right now, this is only the second place where
6160 * lb_gained[env->idle] is updated (other is detach_tasks)
6161 * so we can safely collect stats here rather than
6162 * inside detach_tasks().
6164 schedstat_inc(env
->sd
, lb_gained
[env
->idle
]);
6170 static const unsigned int sched_nr_migrate_break
= 32;
6173 * detach_tasks() -- tries to detach up to imbalance weighted load from
6174 * busiest_rq, as part of a balancing operation within domain "sd".
6176 * Returns number of detached tasks if successful and 0 otherwise.
6178 static int detach_tasks(struct lb_env
*env
)
6180 struct list_head
*tasks
= &env
->src_rq
->cfs_tasks
;
6181 struct task_struct
*p
;
6185 lockdep_assert_held(&env
->src_rq
->lock
);
6187 if (env
->imbalance
<= 0)
6190 while (!list_empty(tasks
)) {
6192 * We don't want to steal all, otherwise we may be treated likewise,
6193 * which could at worst lead to a livelock crash.
6195 if (env
->idle
!= CPU_NOT_IDLE
&& env
->src_rq
->nr_running
<= 1)
6198 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
6201 /* We've more or less seen every task there is, call it quits */
6202 if (env
->loop
> env
->loop_max
)
6205 /* take a breather every nr_migrate tasks */
6206 if (env
->loop
> env
->loop_break
) {
6207 env
->loop_break
+= sched_nr_migrate_break
;
6208 env
->flags
|= LBF_NEED_BREAK
;
6212 if (!can_migrate_task(p
, env
))
6215 load
= task_h_load(p
);
6217 if (sched_feat(LB_MIN
) && load
< 16 && !env
->sd
->nr_balance_failed
)
6220 if ((load
/ 2) > env
->imbalance
)
6223 detach_task(p
, env
);
6224 list_add(&p
->se
.group_node
, &env
->tasks
);
6227 env
->imbalance
-= load
;
6229 #ifdef CONFIG_PREEMPT
6231 * NEWIDLE balancing is a source of latency, so preemptible
6232 * kernels will stop after the first task is detached to minimize
6233 * the critical section.
6235 if (env
->idle
== CPU_NEWLY_IDLE
)
6240 * We only want to steal up to the prescribed amount of
6243 if (env
->imbalance
<= 0)
6248 list_move_tail(&p
->se
.group_node
, tasks
);
6252 * Right now, this is one of only two places we collect this stat
6253 * so we can safely collect detach_one_task() stats here rather
6254 * than inside detach_one_task().
6256 schedstat_add(env
->sd
, lb_gained
[env
->idle
], detached
);
6262 * attach_task() -- attach the task detached by detach_task() to its new rq.
6264 static void attach_task(struct rq
*rq
, struct task_struct
*p
)
6266 lockdep_assert_held(&rq
->lock
);
6268 BUG_ON(task_rq(p
) != rq
);
6269 activate_task(rq
, p
, 0);
6270 p
->on_rq
= TASK_ON_RQ_QUEUED
;
6271 check_preempt_curr(rq
, p
, 0);
6275 * attach_one_task() -- attaches the task returned from detach_one_task() to
6278 static void attach_one_task(struct rq
*rq
, struct task_struct
*p
)
6280 raw_spin_lock(&rq
->lock
);
6282 raw_spin_unlock(&rq
->lock
);
6286 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6289 static void attach_tasks(struct lb_env
*env
)
6291 struct list_head
*tasks
= &env
->tasks
;
6292 struct task_struct
*p
;
6294 raw_spin_lock(&env
->dst_rq
->lock
);
6296 while (!list_empty(tasks
)) {
6297 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
6298 list_del_init(&p
->se
.group_node
);
6300 attach_task(env
->dst_rq
, p
);
6303 raw_spin_unlock(&env
->dst_rq
->lock
);
6306 #ifdef CONFIG_FAIR_GROUP_SCHED
6307 static void update_blocked_averages(int cpu
)
6309 struct rq
*rq
= cpu_rq(cpu
);
6310 struct cfs_rq
*cfs_rq
;
6311 unsigned long flags
;
6313 raw_spin_lock_irqsave(&rq
->lock
, flags
);
6314 update_rq_clock(rq
);
6317 * Iterates the task_group tree in a bottom up fashion, see
6318 * list_add_leaf_cfs_rq() for details.
6320 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
6321 /* throttled entities do not contribute to load */
6322 if (throttled_hierarchy(cfs_rq
))
6325 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq
), cfs_rq
, true))
6326 update_tg_load_avg(cfs_rq
, 0);
6328 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
6332 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6333 * This needs to be done in a top-down fashion because the load of a child
6334 * group is a fraction of its parents load.
6336 static void update_cfs_rq_h_load(struct cfs_rq
*cfs_rq
)
6338 struct rq
*rq
= rq_of(cfs_rq
);
6339 struct sched_entity
*se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
6340 unsigned long now
= jiffies
;
6343 if (cfs_rq
->last_h_load_update
== now
)
6346 cfs_rq
->h_load_next
= NULL
;
6347 for_each_sched_entity(se
) {
6348 cfs_rq
= cfs_rq_of(se
);
6349 cfs_rq
->h_load_next
= se
;
6350 if (cfs_rq
->last_h_load_update
== now
)
6355 cfs_rq
->h_load
= cfs_rq_load_avg(cfs_rq
);
6356 cfs_rq
->last_h_load_update
= now
;
6359 while ((se
= cfs_rq
->h_load_next
) != NULL
) {
6360 load
= cfs_rq
->h_load
;
6361 load
= div64_ul(load
* se
->avg
.load_avg
,
6362 cfs_rq_load_avg(cfs_rq
) + 1);
6363 cfs_rq
= group_cfs_rq(se
);
6364 cfs_rq
->h_load
= load
;
6365 cfs_rq
->last_h_load_update
= now
;
6369 static unsigned long task_h_load(struct task_struct
*p
)
6371 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
6373 update_cfs_rq_h_load(cfs_rq
);
6374 return div64_ul(p
->se
.avg
.load_avg
* cfs_rq
->h_load
,
6375 cfs_rq_load_avg(cfs_rq
) + 1);
6378 static inline void update_blocked_averages(int cpu
)
6380 struct rq
*rq
= cpu_rq(cpu
);
6381 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
6382 unsigned long flags
;
6384 raw_spin_lock_irqsave(&rq
->lock
, flags
);
6385 update_rq_clock(rq
);
6386 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq
), cfs_rq
, true);
6387 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
6390 static unsigned long task_h_load(struct task_struct
*p
)
6392 return p
->se
.avg
.load_avg
;
6396 /********** Helpers for find_busiest_group ************************/
6405 * sg_lb_stats - stats of a sched_group required for load_balancing
6407 struct sg_lb_stats
{
6408 unsigned long avg_load
; /*Avg load across the CPUs of the group */
6409 unsigned long group_load
; /* Total load over the CPUs of the group */
6410 unsigned long sum_weighted_load
; /* Weighted load of group's tasks */
6411 unsigned long load_per_task
;
6412 unsigned long group_capacity
;
6413 unsigned long group_util
; /* Total utilization of the group */
6414 unsigned int sum_nr_running
; /* Nr tasks running in the group */
6415 unsigned int idle_cpus
;
6416 unsigned int group_weight
;
6417 enum group_type group_type
;
6418 int group_no_capacity
;
6419 #ifdef CONFIG_NUMA_BALANCING
6420 unsigned int nr_numa_running
;
6421 unsigned int nr_preferred_running
;
6426 * sd_lb_stats - Structure to store the statistics of a sched_domain
6427 * during load balancing.
6429 struct sd_lb_stats
{
6430 struct sched_group
*busiest
; /* Busiest group in this sd */
6431 struct sched_group
*local
; /* Local group in this sd */
6432 unsigned long total_load
; /* Total load of all groups in sd */
6433 unsigned long total_capacity
; /* Total capacity of all groups in sd */
6434 unsigned long avg_load
; /* Average load across all groups in sd */
6436 struct sg_lb_stats busiest_stat
;/* Statistics of the busiest group */
6437 struct sg_lb_stats local_stat
; /* Statistics of the local group */
6440 static inline void init_sd_lb_stats(struct sd_lb_stats
*sds
)
6443 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6444 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6445 * We must however clear busiest_stat::avg_load because
6446 * update_sd_pick_busiest() reads this before assignment.
6448 *sds
= (struct sd_lb_stats
){
6452 .total_capacity
= 0UL,
6455 .sum_nr_running
= 0,
6456 .group_type
= group_other
,
6462 * get_sd_load_idx - Obtain the load index for a given sched domain.
6463 * @sd: The sched_domain whose load_idx is to be obtained.
6464 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6466 * Return: The load index.
6468 static inline int get_sd_load_idx(struct sched_domain
*sd
,
6469 enum cpu_idle_type idle
)
6475 load_idx
= sd
->busy_idx
;
6478 case CPU_NEWLY_IDLE
:
6479 load_idx
= sd
->newidle_idx
;
6482 load_idx
= sd
->idle_idx
;
6489 static unsigned long scale_rt_capacity(int cpu
)
6491 struct rq
*rq
= cpu_rq(cpu
);
6492 u64 total
, used
, age_stamp
, avg
;
6496 * Since we're reading these variables without serialization make sure
6497 * we read them once before doing sanity checks on them.
6499 age_stamp
= READ_ONCE(rq
->age_stamp
);
6500 avg
= READ_ONCE(rq
->rt_avg
);
6501 delta
= __rq_clock_broken(rq
) - age_stamp
;
6503 if (unlikely(delta
< 0))
6506 total
= sched_avg_period() + delta
;
6508 used
= div_u64(avg
, total
);
6510 if (likely(used
< SCHED_CAPACITY_SCALE
))
6511 return SCHED_CAPACITY_SCALE
- used
;
6516 static void update_cpu_capacity(struct sched_domain
*sd
, int cpu
)
6518 unsigned long capacity
= arch_scale_cpu_capacity(sd
, cpu
);
6519 struct sched_group
*sdg
= sd
->groups
;
6521 cpu_rq(cpu
)->cpu_capacity_orig
= capacity
;
6523 capacity
*= scale_rt_capacity(cpu
);
6524 capacity
>>= SCHED_CAPACITY_SHIFT
;
6529 cpu_rq(cpu
)->cpu_capacity
= capacity
;
6530 sdg
->sgc
->capacity
= capacity
;
6533 void update_group_capacity(struct sched_domain
*sd
, int cpu
)
6535 struct sched_domain
*child
= sd
->child
;
6536 struct sched_group
*group
, *sdg
= sd
->groups
;
6537 unsigned long capacity
;
6538 unsigned long interval
;
6540 interval
= msecs_to_jiffies(sd
->balance_interval
);
6541 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
6542 sdg
->sgc
->next_update
= jiffies
+ interval
;
6545 update_cpu_capacity(sd
, cpu
);
6551 if (child
->flags
& SD_OVERLAP
) {
6553 * SD_OVERLAP domains cannot assume that child groups
6554 * span the current group.
6557 for_each_cpu(cpu
, sched_group_cpus(sdg
)) {
6558 struct sched_group_capacity
*sgc
;
6559 struct rq
*rq
= cpu_rq(cpu
);
6562 * build_sched_domains() -> init_sched_groups_capacity()
6563 * gets here before we've attached the domains to the
6566 * Use capacity_of(), which is set irrespective of domains
6567 * in update_cpu_capacity().
6569 * This avoids capacity from being 0 and
6570 * causing divide-by-zero issues on boot.
6572 if (unlikely(!rq
->sd
)) {
6573 capacity
+= capacity_of(cpu
);
6577 sgc
= rq
->sd
->groups
->sgc
;
6578 capacity
+= sgc
->capacity
;
6582 * !SD_OVERLAP domains can assume that child groups
6583 * span the current group.
6586 group
= child
->groups
;
6588 capacity
+= group
->sgc
->capacity
;
6589 group
= group
->next
;
6590 } while (group
!= child
->groups
);
6593 sdg
->sgc
->capacity
= capacity
;
6597 * Check whether the capacity of the rq has been noticeably reduced by side
6598 * activity. The imbalance_pct is used for the threshold.
6599 * Return true is the capacity is reduced
6602 check_cpu_capacity(struct rq
*rq
, struct sched_domain
*sd
)
6604 return ((rq
->cpu_capacity
* sd
->imbalance_pct
) <
6605 (rq
->cpu_capacity_orig
* 100));
6609 * Group imbalance indicates (and tries to solve) the problem where balancing
6610 * groups is inadequate due to tsk_cpus_allowed() constraints.
6612 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6613 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6616 * { 0 1 2 3 } { 4 5 6 7 }
6619 * If we were to balance group-wise we'd place two tasks in the first group and
6620 * two tasks in the second group. Clearly this is undesired as it will overload
6621 * cpu 3 and leave one of the cpus in the second group unused.
6623 * The current solution to this issue is detecting the skew in the first group
6624 * by noticing the lower domain failed to reach balance and had difficulty
6625 * moving tasks due to affinity constraints.
6627 * When this is so detected; this group becomes a candidate for busiest; see
6628 * update_sd_pick_busiest(). And calculate_imbalance() and
6629 * find_busiest_group() avoid some of the usual balance conditions to allow it
6630 * to create an effective group imbalance.
6632 * This is a somewhat tricky proposition since the next run might not find the
6633 * group imbalance and decide the groups need to be balanced again. A most
6634 * subtle and fragile situation.
6637 static inline int sg_imbalanced(struct sched_group
*group
)
6639 return group
->sgc
->imbalance
;
6643 * group_has_capacity returns true if the group has spare capacity that could
6644 * be used by some tasks.
6645 * We consider that a group has spare capacity if the * number of task is
6646 * smaller than the number of CPUs or if the utilization is lower than the
6647 * available capacity for CFS tasks.
6648 * For the latter, we use a threshold to stabilize the state, to take into
6649 * account the variance of the tasks' load and to return true if the available
6650 * capacity in meaningful for the load balancer.
6651 * As an example, an available capacity of 1% can appear but it doesn't make
6652 * any benefit for the load balance.
6655 group_has_capacity(struct lb_env
*env
, struct sg_lb_stats
*sgs
)
6657 if (sgs
->sum_nr_running
< sgs
->group_weight
)
6660 if ((sgs
->group_capacity
* 100) >
6661 (sgs
->group_util
* env
->sd
->imbalance_pct
))
6668 * group_is_overloaded returns true if the group has more tasks than it can
6670 * group_is_overloaded is not equals to !group_has_capacity because a group
6671 * with the exact right number of tasks, has no more spare capacity but is not
6672 * overloaded so both group_has_capacity and group_is_overloaded return
6676 group_is_overloaded(struct lb_env
*env
, struct sg_lb_stats
*sgs
)
6678 if (sgs
->sum_nr_running
<= sgs
->group_weight
)
6681 if ((sgs
->group_capacity
* 100) <
6682 (sgs
->group_util
* env
->sd
->imbalance_pct
))
6689 group_type
group_classify(struct sched_group
*group
,
6690 struct sg_lb_stats
*sgs
)
6692 if (sgs
->group_no_capacity
)
6693 return group_overloaded
;
6695 if (sg_imbalanced(group
))
6696 return group_imbalanced
;
6702 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6703 * @env: The load balancing environment.
6704 * @group: sched_group whose statistics are to be updated.
6705 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6706 * @local_group: Does group contain this_cpu.
6707 * @sgs: variable to hold the statistics for this group.
6708 * @overload: Indicate more than one runnable task for any CPU.
6710 static inline void update_sg_lb_stats(struct lb_env
*env
,
6711 struct sched_group
*group
, int load_idx
,
6712 int local_group
, struct sg_lb_stats
*sgs
,
6718 memset(sgs
, 0, sizeof(*sgs
));
6720 for_each_cpu_and(i
, sched_group_cpus(group
), env
->cpus
) {
6721 struct rq
*rq
= cpu_rq(i
);
6723 /* Bias balancing toward cpus of our domain */
6725 load
= target_load(i
, load_idx
);
6727 load
= source_load(i
, load_idx
);
6729 sgs
->group_load
+= load
;
6730 sgs
->group_util
+= cpu_util(i
);
6731 sgs
->sum_nr_running
+= rq
->cfs
.h_nr_running
;
6733 nr_running
= rq
->nr_running
;
6737 #ifdef CONFIG_NUMA_BALANCING
6738 sgs
->nr_numa_running
+= rq
->nr_numa_running
;
6739 sgs
->nr_preferred_running
+= rq
->nr_preferred_running
;
6741 sgs
->sum_weighted_load
+= weighted_cpuload(i
);
6743 * No need to call idle_cpu() if nr_running is not 0
6745 if (!nr_running
&& idle_cpu(i
))
6749 /* Adjust by relative CPU capacity of the group */
6750 sgs
->group_capacity
= group
->sgc
->capacity
;
6751 sgs
->avg_load
= (sgs
->group_load
*SCHED_CAPACITY_SCALE
) / sgs
->group_capacity
;
6753 if (sgs
->sum_nr_running
)
6754 sgs
->load_per_task
= sgs
->sum_weighted_load
/ sgs
->sum_nr_running
;
6756 sgs
->group_weight
= group
->group_weight
;
6758 sgs
->group_no_capacity
= group_is_overloaded(env
, sgs
);
6759 sgs
->group_type
= group_classify(group
, sgs
);
6763 * update_sd_pick_busiest - return 1 on busiest group
6764 * @env: The load balancing environment.
6765 * @sds: sched_domain statistics
6766 * @sg: sched_group candidate to be checked for being the busiest
6767 * @sgs: sched_group statistics
6769 * Determine if @sg is a busier group than the previously selected
6772 * Return: %true if @sg is a busier group than the previously selected
6773 * busiest group. %false otherwise.
6775 static bool update_sd_pick_busiest(struct lb_env
*env
,
6776 struct sd_lb_stats
*sds
,
6777 struct sched_group
*sg
,
6778 struct sg_lb_stats
*sgs
)
6780 struct sg_lb_stats
*busiest
= &sds
->busiest_stat
;
6782 if (sgs
->group_type
> busiest
->group_type
)
6785 if (sgs
->group_type
< busiest
->group_type
)
6788 if (sgs
->avg_load
<= busiest
->avg_load
)
6791 /* This is the busiest node in its class. */
6792 if (!(env
->sd
->flags
& SD_ASYM_PACKING
))
6795 /* No ASYM_PACKING if target cpu is already busy */
6796 if (env
->idle
== CPU_NOT_IDLE
)
6799 * ASYM_PACKING needs to move all the work to the lowest
6800 * numbered CPUs in the group, therefore mark all groups
6801 * higher than ourself as busy.
6803 if (sgs
->sum_nr_running
&& env
->dst_cpu
< group_first_cpu(sg
)) {
6807 /* Prefer to move from highest possible cpu's work */
6808 if (group_first_cpu(sds
->busiest
) < group_first_cpu(sg
))
6815 #ifdef CONFIG_NUMA_BALANCING
6816 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
6818 if (sgs
->sum_nr_running
> sgs
->nr_numa_running
)
6820 if (sgs
->sum_nr_running
> sgs
->nr_preferred_running
)
6825 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
6827 if (rq
->nr_running
> rq
->nr_numa_running
)
6829 if (rq
->nr_running
> rq
->nr_preferred_running
)
6834 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
6839 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
6843 #endif /* CONFIG_NUMA_BALANCING */
6846 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6847 * @env: The load balancing environment.
6848 * @sds: variable to hold the statistics for this sched_domain.
6850 static inline void update_sd_lb_stats(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6852 struct sched_domain
*child
= env
->sd
->child
;
6853 struct sched_group
*sg
= env
->sd
->groups
;
6854 struct sg_lb_stats tmp_sgs
;
6855 int load_idx
, prefer_sibling
= 0;
6856 bool overload
= false;
6858 if (child
&& child
->flags
& SD_PREFER_SIBLING
)
6861 load_idx
= get_sd_load_idx(env
->sd
, env
->idle
);
6864 struct sg_lb_stats
*sgs
= &tmp_sgs
;
6867 local_group
= cpumask_test_cpu(env
->dst_cpu
, sched_group_cpus(sg
));
6870 sgs
= &sds
->local_stat
;
6872 if (env
->idle
!= CPU_NEWLY_IDLE
||
6873 time_after_eq(jiffies
, sg
->sgc
->next_update
))
6874 update_group_capacity(env
->sd
, env
->dst_cpu
);
6877 update_sg_lb_stats(env
, sg
, load_idx
, local_group
, sgs
,
6884 * In case the child domain prefers tasks go to siblings
6885 * first, lower the sg capacity so that we'll try
6886 * and move all the excess tasks away. We lower the capacity
6887 * of a group only if the local group has the capacity to fit
6888 * these excess tasks. The extra check prevents the case where
6889 * you always pull from the heaviest group when it is already
6890 * under-utilized (possible with a large weight task outweighs
6891 * the tasks on the system).
6893 if (prefer_sibling
&& sds
->local
&&
6894 group_has_capacity(env
, &sds
->local_stat
) &&
6895 (sgs
->sum_nr_running
> 1)) {
6896 sgs
->group_no_capacity
= 1;
6897 sgs
->group_type
= group_classify(sg
, sgs
);
6900 if (update_sd_pick_busiest(env
, sds
, sg
, sgs
)) {
6902 sds
->busiest_stat
= *sgs
;
6906 /* Now, start updating sd_lb_stats */
6907 sds
->total_load
+= sgs
->group_load
;
6908 sds
->total_capacity
+= sgs
->group_capacity
;
6911 } while (sg
!= env
->sd
->groups
);
6913 if (env
->sd
->flags
& SD_NUMA
)
6914 env
->fbq_type
= fbq_classify_group(&sds
->busiest_stat
);
6916 if (!env
->sd
->parent
) {
6917 /* update overload indicator if we are at root domain */
6918 if (env
->dst_rq
->rd
->overload
!= overload
)
6919 env
->dst_rq
->rd
->overload
= overload
;
6925 * check_asym_packing - Check to see if the group is packed into the
6928 * This is primarily intended to used at the sibling level. Some
6929 * cores like POWER7 prefer to use lower numbered SMT threads. In the
6930 * case of POWER7, it can move to lower SMT modes only when higher
6931 * threads are idle. When in lower SMT modes, the threads will
6932 * perform better since they share less core resources. Hence when we
6933 * have idle threads, we want them to be the higher ones.
6935 * This packing function is run on idle threads. It checks to see if
6936 * the busiest CPU in this domain (core in the P7 case) has a higher
6937 * CPU number than the packing function is being run on. Here we are
6938 * assuming lower CPU number will be equivalent to lower a SMT thread
6941 * Return: 1 when packing is required and a task should be moved to
6942 * this CPU. The amount of the imbalance is returned in *imbalance.
6944 * @env: The load balancing environment.
6945 * @sds: Statistics of the sched_domain which is to be packed
6947 static int check_asym_packing(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6951 if (!(env
->sd
->flags
& SD_ASYM_PACKING
))
6954 if (env
->idle
== CPU_NOT_IDLE
)
6960 busiest_cpu
= group_first_cpu(sds
->busiest
);
6961 if (env
->dst_cpu
> busiest_cpu
)
6964 env
->imbalance
= DIV_ROUND_CLOSEST(
6965 sds
->busiest_stat
.avg_load
* sds
->busiest_stat
.group_capacity
,
6966 SCHED_CAPACITY_SCALE
);
6972 * fix_small_imbalance - Calculate the minor imbalance that exists
6973 * amongst the groups of a sched_domain, during
6975 * @env: The load balancing environment.
6976 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6979 void fix_small_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6981 unsigned long tmp
, capa_now
= 0, capa_move
= 0;
6982 unsigned int imbn
= 2;
6983 unsigned long scaled_busy_load_per_task
;
6984 struct sg_lb_stats
*local
, *busiest
;
6986 local
= &sds
->local_stat
;
6987 busiest
= &sds
->busiest_stat
;
6989 if (!local
->sum_nr_running
)
6990 local
->load_per_task
= cpu_avg_load_per_task(env
->dst_cpu
);
6991 else if (busiest
->load_per_task
> local
->load_per_task
)
6994 scaled_busy_load_per_task
=
6995 (busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) /
6996 busiest
->group_capacity
;
6998 if (busiest
->avg_load
+ scaled_busy_load_per_task
>=
6999 local
->avg_load
+ (scaled_busy_load_per_task
* imbn
)) {
7000 env
->imbalance
= busiest
->load_per_task
;
7005 * OK, we don't have enough imbalance to justify moving tasks,
7006 * however we may be able to increase total CPU capacity used by
7010 capa_now
+= busiest
->group_capacity
*
7011 min(busiest
->load_per_task
, busiest
->avg_load
);
7012 capa_now
+= local
->group_capacity
*
7013 min(local
->load_per_task
, local
->avg_load
);
7014 capa_now
/= SCHED_CAPACITY_SCALE
;
7016 /* Amount of load we'd subtract */
7017 if (busiest
->avg_load
> scaled_busy_load_per_task
) {
7018 capa_move
+= busiest
->group_capacity
*
7019 min(busiest
->load_per_task
,
7020 busiest
->avg_load
- scaled_busy_load_per_task
);
7023 /* Amount of load we'd add */
7024 if (busiest
->avg_load
* busiest
->group_capacity
<
7025 busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) {
7026 tmp
= (busiest
->avg_load
* busiest
->group_capacity
) /
7027 local
->group_capacity
;
7029 tmp
= (busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) /
7030 local
->group_capacity
;
7032 capa_move
+= local
->group_capacity
*
7033 min(local
->load_per_task
, local
->avg_load
+ tmp
);
7034 capa_move
/= SCHED_CAPACITY_SCALE
;
7036 /* Move if we gain throughput */
7037 if (capa_move
> capa_now
)
7038 env
->imbalance
= busiest
->load_per_task
;
7042 * calculate_imbalance - Calculate the amount of imbalance present within the
7043 * groups of a given sched_domain during load balance.
7044 * @env: load balance environment
7045 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
7047 static inline void calculate_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
7049 unsigned long max_pull
, load_above_capacity
= ~0UL;
7050 struct sg_lb_stats
*local
, *busiest
;
7052 local
= &sds
->local_stat
;
7053 busiest
= &sds
->busiest_stat
;
7055 if (busiest
->group_type
== group_imbalanced
) {
7057 * In the group_imb case we cannot rely on group-wide averages
7058 * to ensure cpu-load equilibrium, look at wider averages. XXX
7060 busiest
->load_per_task
=
7061 min(busiest
->load_per_task
, sds
->avg_load
);
7065 * Avg load of busiest sg can be less and avg load of local sg can
7066 * be greater than avg load across all sgs of sd because avg load
7067 * factors in sg capacity and sgs with smaller group_type are
7068 * skipped when updating the busiest sg:
7070 if (busiest
->avg_load
<= sds
->avg_load
||
7071 local
->avg_load
>= sds
->avg_load
) {
7073 return fix_small_imbalance(env
, sds
);
7077 * If there aren't any idle cpus, avoid creating some.
7079 if (busiest
->group_type
== group_overloaded
&&
7080 local
->group_type
== group_overloaded
) {
7081 load_above_capacity
= busiest
->sum_nr_running
* SCHED_CAPACITY_SCALE
;
7082 if (load_above_capacity
> busiest
->group_capacity
) {
7083 load_above_capacity
-= busiest
->group_capacity
;
7084 load_above_capacity
*= NICE_0_LOAD
;
7085 load_above_capacity
/= busiest
->group_capacity
;
7087 load_above_capacity
= ~0UL;
7091 * We're trying to get all the cpus to the average_load, so we don't
7092 * want to push ourselves above the average load, nor do we wish to
7093 * reduce the max loaded cpu below the average load. At the same time,
7094 * we also don't want to reduce the group load below the group
7095 * capacity. Thus we look for the minimum possible imbalance.
7097 max_pull
= min(busiest
->avg_load
- sds
->avg_load
, load_above_capacity
);
7099 /* How much load to actually move to equalise the imbalance */
7100 env
->imbalance
= min(
7101 max_pull
* busiest
->group_capacity
,
7102 (sds
->avg_load
- local
->avg_load
) * local
->group_capacity
7103 ) / SCHED_CAPACITY_SCALE
;
7106 * if *imbalance is less than the average load per runnable task
7107 * there is no guarantee that any tasks will be moved so we'll have
7108 * a think about bumping its value to force at least one task to be
7111 if (env
->imbalance
< busiest
->load_per_task
)
7112 return fix_small_imbalance(env
, sds
);
7115 /******* find_busiest_group() helpers end here *********************/
7118 * find_busiest_group - Returns the busiest group within the sched_domain
7119 * if there is an imbalance.
7121 * Also calculates the amount of weighted load which should be moved
7122 * to restore balance.
7124 * @env: The load balancing environment.
7126 * Return: - The busiest group if imbalance exists.
7128 static struct sched_group
*find_busiest_group(struct lb_env
*env
)
7130 struct sg_lb_stats
*local
, *busiest
;
7131 struct sd_lb_stats sds
;
7133 init_sd_lb_stats(&sds
);
7136 * Compute the various statistics relavent for load balancing at
7139 update_sd_lb_stats(env
, &sds
);
7140 local
= &sds
.local_stat
;
7141 busiest
= &sds
.busiest_stat
;
7143 /* ASYM feature bypasses nice load balance check */
7144 if (check_asym_packing(env
, &sds
))
7147 /* There is no busy sibling group to pull tasks from */
7148 if (!sds
.busiest
|| busiest
->sum_nr_running
== 0)
7151 sds
.avg_load
= (SCHED_CAPACITY_SCALE
* sds
.total_load
)
7152 / sds
.total_capacity
;
7155 * If the busiest group is imbalanced the below checks don't
7156 * work because they assume all things are equal, which typically
7157 * isn't true due to cpus_allowed constraints and the like.
7159 if (busiest
->group_type
== group_imbalanced
)
7162 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7163 if (env
->idle
== CPU_NEWLY_IDLE
&& group_has_capacity(env
, local
) &&
7164 busiest
->group_no_capacity
)
7168 * If the local group is busier than the selected busiest group
7169 * don't try and pull any tasks.
7171 if (local
->avg_load
>= busiest
->avg_load
)
7175 * Don't pull any tasks if this group is already above the domain
7178 if (local
->avg_load
>= sds
.avg_load
)
7181 if (env
->idle
== CPU_IDLE
) {
7183 * This cpu is idle. If the busiest group is not overloaded
7184 * and there is no imbalance between this and busiest group
7185 * wrt idle cpus, it is balanced. The imbalance becomes
7186 * significant if the diff is greater than 1 otherwise we
7187 * might end up to just move the imbalance on another group
7189 if ((busiest
->group_type
!= group_overloaded
) &&
7190 (local
->idle_cpus
<= (busiest
->idle_cpus
+ 1)))
7194 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7195 * imbalance_pct to be conservative.
7197 if (100 * busiest
->avg_load
<=
7198 env
->sd
->imbalance_pct
* local
->avg_load
)
7203 /* Looks like there is an imbalance. Compute it */
7204 calculate_imbalance(env
, &sds
);
7213 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7215 static struct rq
*find_busiest_queue(struct lb_env
*env
,
7216 struct sched_group
*group
)
7218 struct rq
*busiest
= NULL
, *rq
;
7219 unsigned long busiest_load
= 0, busiest_capacity
= 1;
7222 for_each_cpu_and(i
, sched_group_cpus(group
), env
->cpus
) {
7223 unsigned long capacity
, wl
;
7227 rt
= fbq_classify_rq(rq
);
7230 * We classify groups/runqueues into three groups:
7231 * - regular: there are !numa tasks
7232 * - remote: there are numa tasks that run on the 'wrong' node
7233 * - all: there is no distinction
7235 * In order to avoid migrating ideally placed numa tasks,
7236 * ignore those when there's better options.
7238 * If we ignore the actual busiest queue to migrate another
7239 * task, the next balance pass can still reduce the busiest
7240 * queue by moving tasks around inside the node.
7242 * If we cannot move enough load due to this classification
7243 * the next pass will adjust the group classification and
7244 * allow migration of more tasks.
7246 * Both cases only affect the total convergence complexity.
7248 if (rt
> env
->fbq_type
)
7251 capacity
= capacity_of(i
);
7253 wl
= weighted_cpuload(i
);
7256 * When comparing with imbalance, use weighted_cpuload()
7257 * which is not scaled with the cpu capacity.
7260 if (rq
->nr_running
== 1 && wl
> env
->imbalance
&&
7261 !check_cpu_capacity(rq
, env
->sd
))
7265 * For the load comparisons with the other cpu's, consider
7266 * the weighted_cpuload() scaled with the cpu capacity, so
7267 * that the load can be moved away from the cpu that is
7268 * potentially running at a lower capacity.
7270 * Thus we're looking for max(wl_i / capacity_i), crosswise
7271 * multiplication to rid ourselves of the division works out
7272 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
7273 * our previous maximum.
7275 if (wl
* busiest_capacity
> busiest_load
* capacity
) {
7277 busiest_capacity
= capacity
;
7286 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7287 * so long as it is large enough.
7289 #define MAX_PINNED_INTERVAL 512
7291 /* Working cpumask for load_balance and load_balance_newidle. */
7292 DEFINE_PER_CPU(cpumask_var_t
, load_balance_mask
);
7294 static int need_active_balance(struct lb_env
*env
)
7296 struct sched_domain
*sd
= env
->sd
;
7298 if (env
->idle
== CPU_NEWLY_IDLE
) {
7301 * ASYM_PACKING needs to force migrate tasks from busy but
7302 * higher numbered CPUs in order to pack all tasks in the
7303 * lowest numbered CPUs.
7305 if ((sd
->flags
& SD_ASYM_PACKING
) && env
->src_cpu
> env
->dst_cpu
)
7310 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7311 * It's worth migrating the task if the src_cpu's capacity is reduced
7312 * because of other sched_class or IRQs if more capacity stays
7313 * available on dst_cpu.
7315 if ((env
->idle
!= CPU_NOT_IDLE
) &&
7316 (env
->src_rq
->cfs
.h_nr_running
== 1)) {
7317 if ((check_cpu_capacity(env
->src_rq
, sd
)) &&
7318 (capacity_of(env
->src_cpu
)*sd
->imbalance_pct
< capacity_of(env
->dst_cpu
)*100))
7322 return unlikely(sd
->nr_balance_failed
> sd
->cache_nice_tries
+2);
7325 static int active_load_balance_cpu_stop(void *data
);
7327 static int should_we_balance(struct lb_env
*env
)
7329 struct sched_group
*sg
= env
->sd
->groups
;
7330 struct cpumask
*sg_cpus
, *sg_mask
;
7331 int cpu
, balance_cpu
= -1;
7334 * In the newly idle case, we will allow all the cpu's
7335 * to do the newly idle load balance.
7337 if (env
->idle
== CPU_NEWLY_IDLE
)
7340 sg_cpus
= sched_group_cpus(sg
);
7341 sg_mask
= sched_group_mask(sg
);
7342 /* Try to find first idle cpu */
7343 for_each_cpu_and(cpu
, sg_cpus
, env
->cpus
) {
7344 if (!cpumask_test_cpu(cpu
, sg_mask
) || !idle_cpu(cpu
))
7351 if (balance_cpu
== -1)
7352 balance_cpu
= group_balance_cpu(sg
);
7355 * First idle cpu or the first cpu(busiest) in this sched group
7356 * is eligible for doing load balancing at this and above domains.
7358 return balance_cpu
== env
->dst_cpu
;
7362 * Check this_cpu to ensure it is balanced within domain. Attempt to move
7363 * tasks if there is an imbalance.
7365 static int load_balance(int this_cpu
, struct rq
*this_rq
,
7366 struct sched_domain
*sd
, enum cpu_idle_type idle
,
7367 int *continue_balancing
)
7369 int ld_moved
, cur_ld_moved
, active_balance
= 0;
7370 struct sched_domain
*sd_parent
= sd
->parent
;
7371 struct sched_group
*group
;
7373 unsigned long flags
;
7374 struct cpumask
*cpus
= this_cpu_cpumask_var_ptr(load_balance_mask
);
7376 struct lb_env env
= {
7378 .dst_cpu
= this_cpu
,
7380 .dst_grpmask
= sched_group_cpus(sd
->groups
),
7382 .loop_break
= sched_nr_migrate_break
,
7385 .tasks
= LIST_HEAD_INIT(env
.tasks
),
7389 * For NEWLY_IDLE load_balancing, we don't need to consider
7390 * other cpus in our group
7392 if (idle
== CPU_NEWLY_IDLE
)
7393 env
.dst_grpmask
= NULL
;
7395 cpumask_copy(cpus
, cpu_active_mask
);
7397 schedstat_inc(sd
, lb_count
[idle
]);
7400 if (!should_we_balance(&env
)) {
7401 *continue_balancing
= 0;
7405 group
= find_busiest_group(&env
);
7407 schedstat_inc(sd
, lb_nobusyg
[idle
]);
7411 busiest
= find_busiest_queue(&env
, group
);
7413 schedstat_inc(sd
, lb_nobusyq
[idle
]);
7417 BUG_ON(busiest
== env
.dst_rq
);
7419 schedstat_add(sd
, lb_imbalance
[idle
], env
.imbalance
);
7421 env
.src_cpu
= busiest
->cpu
;
7422 env
.src_rq
= busiest
;
7425 if (busiest
->nr_running
> 1) {
7427 * Attempt to move tasks. If find_busiest_group has found
7428 * an imbalance but busiest->nr_running <= 1, the group is
7429 * still unbalanced. ld_moved simply stays zero, so it is
7430 * correctly treated as an imbalance.
7432 env
.flags
|= LBF_ALL_PINNED
;
7433 env
.loop_max
= min(sysctl_sched_nr_migrate
, busiest
->nr_running
);
7436 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
7439 * cur_ld_moved - load moved in current iteration
7440 * ld_moved - cumulative load moved across iterations
7442 cur_ld_moved
= detach_tasks(&env
);
7445 * We've detached some tasks from busiest_rq. Every
7446 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7447 * unlock busiest->lock, and we are able to be sure
7448 * that nobody can manipulate the tasks in parallel.
7449 * See task_rq_lock() family for the details.
7452 raw_spin_unlock(&busiest
->lock
);
7456 ld_moved
+= cur_ld_moved
;
7459 local_irq_restore(flags
);
7461 if (env
.flags
& LBF_NEED_BREAK
) {
7462 env
.flags
&= ~LBF_NEED_BREAK
;
7467 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7468 * us and move them to an alternate dst_cpu in our sched_group
7469 * where they can run. The upper limit on how many times we
7470 * iterate on same src_cpu is dependent on number of cpus in our
7473 * This changes load balance semantics a bit on who can move
7474 * load to a given_cpu. In addition to the given_cpu itself
7475 * (or a ilb_cpu acting on its behalf where given_cpu is
7476 * nohz-idle), we now have balance_cpu in a position to move
7477 * load to given_cpu. In rare situations, this may cause
7478 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7479 * _independently_ and at _same_ time to move some load to
7480 * given_cpu) causing exceess load to be moved to given_cpu.
7481 * This however should not happen so much in practice and
7482 * moreover subsequent load balance cycles should correct the
7483 * excess load moved.
7485 if ((env
.flags
& LBF_DST_PINNED
) && env
.imbalance
> 0) {
7487 /* Prevent to re-select dst_cpu via env's cpus */
7488 cpumask_clear_cpu(env
.dst_cpu
, env
.cpus
);
7490 env
.dst_rq
= cpu_rq(env
.new_dst_cpu
);
7491 env
.dst_cpu
= env
.new_dst_cpu
;
7492 env
.flags
&= ~LBF_DST_PINNED
;
7494 env
.loop_break
= sched_nr_migrate_break
;
7497 * Go back to "more_balance" rather than "redo" since we
7498 * need to continue with same src_cpu.
7504 * We failed to reach balance because of affinity.
7507 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
7509 if ((env
.flags
& LBF_SOME_PINNED
) && env
.imbalance
> 0)
7510 *group_imbalance
= 1;
7513 /* All tasks on this runqueue were pinned by CPU affinity */
7514 if (unlikely(env
.flags
& LBF_ALL_PINNED
)) {
7515 cpumask_clear_cpu(cpu_of(busiest
), cpus
);
7516 if (!cpumask_empty(cpus
)) {
7518 env
.loop_break
= sched_nr_migrate_break
;
7521 goto out_all_pinned
;
7526 schedstat_inc(sd
, lb_failed
[idle
]);
7528 * Increment the failure counter only on periodic balance.
7529 * We do not want newidle balance, which can be very
7530 * frequent, pollute the failure counter causing
7531 * excessive cache_hot migrations and active balances.
7533 if (idle
!= CPU_NEWLY_IDLE
)
7534 sd
->nr_balance_failed
++;
7536 if (need_active_balance(&env
)) {
7537 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
7539 /* don't kick the active_load_balance_cpu_stop,
7540 * if the curr task on busiest cpu can't be
7543 if (!cpumask_test_cpu(this_cpu
,
7544 tsk_cpus_allowed(busiest
->curr
))) {
7545 raw_spin_unlock_irqrestore(&busiest
->lock
,
7547 env
.flags
|= LBF_ALL_PINNED
;
7548 goto out_one_pinned
;
7552 * ->active_balance synchronizes accesses to
7553 * ->active_balance_work. Once set, it's cleared
7554 * only after active load balance is finished.
7556 if (!busiest
->active_balance
) {
7557 busiest
->active_balance
= 1;
7558 busiest
->push_cpu
= this_cpu
;
7561 raw_spin_unlock_irqrestore(&busiest
->lock
, flags
);
7563 if (active_balance
) {
7564 stop_one_cpu_nowait(cpu_of(busiest
),
7565 active_load_balance_cpu_stop
, busiest
,
7566 &busiest
->active_balance_work
);
7569 /* We've kicked active balancing, force task migration. */
7570 sd
->nr_balance_failed
= sd
->cache_nice_tries
+1;
7573 sd
->nr_balance_failed
= 0;
7575 if (likely(!active_balance
)) {
7576 /* We were unbalanced, so reset the balancing interval */
7577 sd
->balance_interval
= sd
->min_interval
;
7580 * If we've begun active balancing, start to back off. This
7581 * case may not be covered by the all_pinned logic if there
7582 * is only 1 task on the busy runqueue (because we don't call
7585 if (sd
->balance_interval
< sd
->max_interval
)
7586 sd
->balance_interval
*= 2;
7593 * We reach balance although we may have faced some affinity
7594 * constraints. Clear the imbalance flag if it was set.
7597 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
7599 if (*group_imbalance
)
7600 *group_imbalance
= 0;
7605 * We reach balance because all tasks are pinned at this level so
7606 * we can't migrate them. Let the imbalance flag set so parent level
7607 * can try to migrate them.
7609 schedstat_inc(sd
, lb_balanced
[idle
]);
7611 sd
->nr_balance_failed
= 0;
7614 /* tune up the balancing interval */
7615 if (((env
.flags
& LBF_ALL_PINNED
) &&
7616 sd
->balance_interval
< MAX_PINNED_INTERVAL
) ||
7617 (sd
->balance_interval
< sd
->max_interval
))
7618 sd
->balance_interval
*= 2;
7625 static inline unsigned long
7626 get_sd_balance_interval(struct sched_domain
*sd
, int cpu_busy
)
7628 unsigned long interval
= sd
->balance_interval
;
7631 interval
*= sd
->busy_factor
;
7633 /* scale ms to jiffies */
7634 interval
= msecs_to_jiffies(interval
);
7635 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
7641 update_next_balance(struct sched_domain
*sd
, int cpu_busy
, unsigned long *next_balance
)
7643 unsigned long interval
, next
;
7645 interval
= get_sd_balance_interval(sd
, cpu_busy
);
7646 next
= sd
->last_balance
+ interval
;
7648 if (time_after(*next_balance
, next
))
7649 *next_balance
= next
;
7653 * idle_balance is called by schedule() if this_cpu is about to become
7654 * idle. Attempts to pull tasks from other CPUs.
7656 static int idle_balance(struct rq
*this_rq
)
7658 unsigned long next_balance
= jiffies
+ HZ
;
7659 int this_cpu
= this_rq
->cpu
;
7660 struct sched_domain
*sd
;
7661 int pulled_task
= 0;
7665 * We must set idle_stamp _before_ calling idle_balance(), such that we
7666 * measure the duration of idle_balance() as idle time.
7668 this_rq
->idle_stamp
= rq_clock(this_rq
);
7670 if (this_rq
->avg_idle
< sysctl_sched_migration_cost
||
7671 !this_rq
->rd
->overload
) {
7673 sd
= rcu_dereference_check_sched_domain(this_rq
->sd
);
7675 update_next_balance(sd
, 0, &next_balance
);
7681 raw_spin_unlock(&this_rq
->lock
);
7683 update_blocked_averages(this_cpu
);
7685 for_each_domain(this_cpu
, sd
) {
7686 int continue_balancing
= 1;
7687 u64 t0
, domain_cost
;
7689 if (!(sd
->flags
& SD_LOAD_BALANCE
))
7692 if (this_rq
->avg_idle
< curr_cost
+ sd
->max_newidle_lb_cost
) {
7693 update_next_balance(sd
, 0, &next_balance
);
7697 if (sd
->flags
& SD_BALANCE_NEWIDLE
) {
7698 t0
= sched_clock_cpu(this_cpu
);
7700 pulled_task
= load_balance(this_cpu
, this_rq
,
7702 &continue_balancing
);
7704 domain_cost
= sched_clock_cpu(this_cpu
) - t0
;
7705 if (domain_cost
> sd
->max_newidle_lb_cost
)
7706 sd
->max_newidle_lb_cost
= domain_cost
;
7708 curr_cost
+= domain_cost
;
7711 update_next_balance(sd
, 0, &next_balance
);
7714 * Stop searching for tasks to pull if there are
7715 * now runnable tasks on this rq.
7717 if (pulled_task
|| this_rq
->nr_running
> 0)
7722 raw_spin_lock(&this_rq
->lock
);
7724 if (curr_cost
> this_rq
->max_idle_balance_cost
)
7725 this_rq
->max_idle_balance_cost
= curr_cost
;
7728 * While browsing the domains, we released the rq lock, a task could
7729 * have been enqueued in the meantime. Since we're not going idle,
7730 * pretend we pulled a task.
7732 if (this_rq
->cfs
.h_nr_running
&& !pulled_task
)
7736 /* Move the next balance forward */
7737 if (time_after(this_rq
->next_balance
, next_balance
))
7738 this_rq
->next_balance
= next_balance
;
7740 /* Is there a task of a high priority class? */
7741 if (this_rq
->nr_running
!= this_rq
->cfs
.h_nr_running
)
7745 this_rq
->idle_stamp
= 0;
7751 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7752 * running tasks off the busiest CPU onto idle CPUs. It requires at
7753 * least 1 task to be running on each physical CPU where possible, and
7754 * avoids physical / logical imbalances.
7756 static int active_load_balance_cpu_stop(void *data
)
7758 struct rq
*busiest_rq
= data
;
7759 int busiest_cpu
= cpu_of(busiest_rq
);
7760 int target_cpu
= busiest_rq
->push_cpu
;
7761 struct rq
*target_rq
= cpu_rq(target_cpu
);
7762 struct sched_domain
*sd
;
7763 struct task_struct
*p
= NULL
;
7765 raw_spin_lock_irq(&busiest_rq
->lock
);
7767 /* make sure the requested cpu hasn't gone down in the meantime */
7768 if (unlikely(busiest_cpu
!= smp_processor_id() ||
7769 !busiest_rq
->active_balance
))
7772 /* Is there any task to move? */
7773 if (busiest_rq
->nr_running
<= 1)
7777 * This condition is "impossible", if it occurs
7778 * we need to fix it. Originally reported by
7779 * Bjorn Helgaas on a 128-cpu setup.
7781 BUG_ON(busiest_rq
== target_rq
);
7783 /* Search for an sd spanning us and the target CPU. */
7785 for_each_domain(target_cpu
, sd
) {
7786 if ((sd
->flags
& SD_LOAD_BALANCE
) &&
7787 cpumask_test_cpu(busiest_cpu
, sched_domain_span(sd
)))
7792 struct lb_env env
= {
7794 .dst_cpu
= target_cpu
,
7795 .dst_rq
= target_rq
,
7796 .src_cpu
= busiest_rq
->cpu
,
7797 .src_rq
= busiest_rq
,
7801 schedstat_inc(sd
, alb_count
);
7803 p
= detach_one_task(&env
);
7805 schedstat_inc(sd
, alb_pushed
);
7806 /* Active balancing done, reset the failure counter. */
7807 sd
->nr_balance_failed
= 0;
7809 schedstat_inc(sd
, alb_failed
);
7814 busiest_rq
->active_balance
= 0;
7815 raw_spin_unlock(&busiest_rq
->lock
);
7818 attach_one_task(target_rq
, p
);
7825 static inline int on_null_domain(struct rq
*rq
)
7827 return unlikely(!rcu_dereference_sched(rq
->sd
));
7830 #ifdef CONFIG_NO_HZ_COMMON
7832 * idle load balancing details
7833 * - When one of the busy CPUs notice that there may be an idle rebalancing
7834 * needed, they will kick the idle load balancer, which then does idle
7835 * load balancing for all the idle CPUs.
7838 cpumask_var_t idle_cpus_mask
;
7840 unsigned long next_balance
; /* in jiffy units */
7841 } nohz ____cacheline_aligned
;
7843 static inline int find_new_ilb(void)
7845 int ilb
= cpumask_first(nohz
.idle_cpus_mask
);
7847 if (ilb
< nr_cpu_ids
&& idle_cpu(ilb
))
7854 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7855 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7856 * CPU (if there is one).
7858 static void nohz_balancer_kick(void)
7862 nohz
.next_balance
++;
7864 ilb_cpu
= find_new_ilb();
7866 if (ilb_cpu
>= nr_cpu_ids
)
7869 if (test_and_set_bit(NOHZ_BALANCE_KICK
, nohz_flags(ilb_cpu
)))
7872 * Use smp_send_reschedule() instead of resched_cpu().
7873 * This way we generate a sched IPI on the target cpu which
7874 * is idle. And the softirq performing nohz idle load balance
7875 * will be run before returning from the IPI.
7877 smp_send_reschedule(ilb_cpu
);
7881 void nohz_balance_exit_idle(unsigned int cpu
)
7883 if (unlikely(test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))) {
7885 * Completely isolated CPUs don't ever set, so we must test.
7887 if (likely(cpumask_test_cpu(cpu
, nohz
.idle_cpus_mask
))) {
7888 cpumask_clear_cpu(cpu
, nohz
.idle_cpus_mask
);
7889 atomic_dec(&nohz
.nr_cpus
);
7891 clear_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
7895 static inline void set_cpu_sd_state_busy(void)
7897 struct sched_domain
*sd
;
7898 int cpu
= smp_processor_id();
7901 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
7903 if (!sd
|| !sd
->nohz_idle
)
7907 atomic_inc(&sd
->groups
->sgc
->nr_busy_cpus
);
7912 void set_cpu_sd_state_idle(void)
7914 struct sched_domain
*sd
;
7915 int cpu
= smp_processor_id();
7918 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
7920 if (!sd
|| sd
->nohz_idle
)
7924 atomic_dec(&sd
->groups
->sgc
->nr_busy_cpus
);
7930 * This routine will record that the cpu is going idle with tick stopped.
7931 * This info will be used in performing idle load balancing in the future.
7933 void nohz_balance_enter_idle(int cpu
)
7936 * If this cpu is going down, then nothing needs to be done.
7938 if (!cpu_active(cpu
))
7941 if (test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))
7945 * If we're a completely isolated CPU, we don't play.
7947 if (on_null_domain(cpu_rq(cpu
)))
7950 cpumask_set_cpu(cpu
, nohz
.idle_cpus_mask
);
7951 atomic_inc(&nohz
.nr_cpus
);
7952 set_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
7956 static DEFINE_SPINLOCK(balancing
);
7959 * Scale the max load_balance interval with the number of CPUs in the system.
7960 * This trades load-balance latency on larger machines for less cross talk.
7962 void update_max_interval(void)
7964 max_load_balance_interval
= HZ
*num_online_cpus()/10;
7968 * It checks each scheduling domain to see if it is due to be balanced,
7969 * and initiates a balancing operation if so.
7971 * Balancing parameters are set up in init_sched_domains.
7973 static void rebalance_domains(struct rq
*rq
, enum cpu_idle_type idle
)
7975 int continue_balancing
= 1;
7977 unsigned long interval
;
7978 struct sched_domain
*sd
;
7979 /* Earliest time when we have to do rebalance again */
7980 unsigned long next_balance
= jiffies
+ 60*HZ
;
7981 int update_next_balance
= 0;
7982 int need_serialize
, need_decay
= 0;
7985 update_blocked_averages(cpu
);
7988 for_each_domain(cpu
, sd
) {
7990 * Decay the newidle max times here because this is a regular
7991 * visit to all the domains. Decay ~1% per second.
7993 if (time_after(jiffies
, sd
->next_decay_max_lb_cost
)) {
7994 sd
->max_newidle_lb_cost
=
7995 (sd
->max_newidle_lb_cost
* 253) / 256;
7996 sd
->next_decay_max_lb_cost
= jiffies
+ HZ
;
7999 max_cost
+= sd
->max_newidle_lb_cost
;
8001 if (!(sd
->flags
& SD_LOAD_BALANCE
))
8005 * Stop the load balance at this level. There is another
8006 * CPU in our sched group which is doing load balancing more
8009 if (!continue_balancing
) {
8015 interval
= get_sd_balance_interval(sd
, idle
!= CPU_IDLE
);
8017 need_serialize
= sd
->flags
& SD_SERIALIZE
;
8018 if (need_serialize
) {
8019 if (!spin_trylock(&balancing
))
8023 if (time_after_eq(jiffies
, sd
->last_balance
+ interval
)) {
8024 if (load_balance(cpu
, rq
, sd
, idle
, &continue_balancing
)) {
8026 * The LBF_DST_PINNED logic could have changed
8027 * env->dst_cpu, so we can't know our idle
8028 * state even if we migrated tasks. Update it.
8030 idle
= idle_cpu(cpu
) ? CPU_IDLE
: CPU_NOT_IDLE
;
8032 sd
->last_balance
= jiffies
;
8033 interval
= get_sd_balance_interval(sd
, idle
!= CPU_IDLE
);
8036 spin_unlock(&balancing
);
8038 if (time_after(next_balance
, sd
->last_balance
+ interval
)) {
8039 next_balance
= sd
->last_balance
+ interval
;
8040 update_next_balance
= 1;
8045 * Ensure the rq-wide value also decays but keep it at a
8046 * reasonable floor to avoid funnies with rq->avg_idle.
8048 rq
->max_idle_balance_cost
=
8049 max((u64
)sysctl_sched_migration_cost
, max_cost
);
8054 * next_balance will be updated only when there is a need.
8055 * When the cpu is attached to null domain for ex, it will not be
8058 if (likely(update_next_balance
)) {
8059 rq
->next_balance
= next_balance
;
8061 #ifdef CONFIG_NO_HZ_COMMON
8063 * If this CPU has been elected to perform the nohz idle
8064 * balance. Other idle CPUs have already rebalanced with
8065 * nohz_idle_balance() and nohz.next_balance has been
8066 * updated accordingly. This CPU is now running the idle load
8067 * balance for itself and we need to update the
8068 * nohz.next_balance accordingly.
8070 if ((idle
== CPU_IDLE
) && time_after(nohz
.next_balance
, rq
->next_balance
))
8071 nohz
.next_balance
= rq
->next_balance
;
8076 #ifdef CONFIG_NO_HZ_COMMON
8078 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8079 * rebalancing for all the cpus for whom scheduler ticks are stopped.
8081 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
)
8083 int this_cpu
= this_rq
->cpu
;
8086 /* Earliest time when we have to do rebalance again */
8087 unsigned long next_balance
= jiffies
+ 60*HZ
;
8088 int update_next_balance
= 0;
8090 if (idle
!= CPU_IDLE
||
8091 !test_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
)))
8094 for_each_cpu(balance_cpu
, nohz
.idle_cpus_mask
) {
8095 if (balance_cpu
== this_cpu
|| !idle_cpu(balance_cpu
))
8099 * If this cpu gets work to do, stop the load balancing
8100 * work being done for other cpus. Next load
8101 * balancing owner will pick it up.
8106 rq
= cpu_rq(balance_cpu
);
8109 * If time for next balance is due,
8112 if (time_after_eq(jiffies
, rq
->next_balance
)) {
8113 raw_spin_lock_irq(&rq
->lock
);
8114 update_rq_clock(rq
);
8115 cpu_load_update_idle(rq
);
8116 raw_spin_unlock_irq(&rq
->lock
);
8117 rebalance_domains(rq
, CPU_IDLE
);
8120 if (time_after(next_balance
, rq
->next_balance
)) {
8121 next_balance
= rq
->next_balance
;
8122 update_next_balance
= 1;
8127 * next_balance will be updated only when there is a need.
8128 * When the CPU is attached to null domain for ex, it will not be
8131 if (likely(update_next_balance
))
8132 nohz
.next_balance
= next_balance
;
8134 clear_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
));
8138 * Current heuristic for kicking the idle load balancer in the presence
8139 * of an idle cpu in the system.
8140 * - This rq has more than one task.
8141 * - This rq has at least one CFS task and the capacity of the CPU is
8142 * significantly reduced because of RT tasks or IRQs.
8143 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
8144 * multiple busy cpu.
8145 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
8146 * domain span are idle.
8148 static inline bool nohz_kick_needed(struct rq
*rq
)
8150 unsigned long now
= jiffies
;
8151 struct sched_domain
*sd
;
8152 struct sched_group_capacity
*sgc
;
8153 int nr_busy
, cpu
= rq
->cpu
;
8156 if (unlikely(rq
->idle_balance
))
8160 * We may be recently in ticked or tickless idle mode. At the first
8161 * busy tick after returning from idle, we will update the busy stats.
8163 set_cpu_sd_state_busy();
8164 nohz_balance_exit_idle(cpu
);
8167 * None are in tickless mode and hence no need for NOHZ idle load
8170 if (likely(!atomic_read(&nohz
.nr_cpus
)))
8173 if (time_before(now
, nohz
.next_balance
))
8176 if (rq
->nr_running
>= 2)
8180 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
8182 sgc
= sd
->groups
->sgc
;
8183 nr_busy
= atomic_read(&sgc
->nr_busy_cpus
);
8192 sd
= rcu_dereference(rq
->sd
);
8194 if ((rq
->cfs
.h_nr_running
>= 1) &&
8195 check_cpu_capacity(rq
, sd
)) {
8201 sd
= rcu_dereference(per_cpu(sd_asym
, cpu
));
8202 if (sd
&& (cpumask_first_and(nohz
.idle_cpus_mask
,
8203 sched_domain_span(sd
)) < cpu
)) {
8213 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
) { }
8217 * run_rebalance_domains is triggered when needed from the scheduler tick.
8218 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
8220 static void run_rebalance_domains(struct softirq_action
*h
)
8222 struct rq
*this_rq
= this_rq();
8223 enum cpu_idle_type idle
= this_rq
->idle_balance
?
8224 CPU_IDLE
: CPU_NOT_IDLE
;
8227 * If this cpu has a pending nohz_balance_kick, then do the
8228 * balancing on behalf of the other idle cpus whose ticks are
8229 * stopped. Do nohz_idle_balance *before* rebalance_domains to
8230 * give the idle cpus a chance to load balance. Else we may
8231 * load balance only within the local sched_domain hierarchy
8232 * and abort nohz_idle_balance altogether if we pull some load.
8234 nohz_idle_balance(this_rq
, idle
);
8235 rebalance_domains(this_rq
, idle
);
8239 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
8241 void trigger_load_balance(struct rq
*rq
)
8243 /* Don't need to rebalance while attached to NULL domain */
8244 if (unlikely(on_null_domain(rq
)))
8247 if (time_after_eq(jiffies
, rq
->next_balance
))
8248 raise_softirq(SCHED_SOFTIRQ
);
8249 #ifdef CONFIG_NO_HZ_COMMON
8250 if (nohz_kick_needed(rq
))
8251 nohz_balancer_kick();
8255 static void rq_online_fair(struct rq
*rq
)
8259 update_runtime_enabled(rq
);
8262 static void rq_offline_fair(struct rq
*rq
)
8266 /* Ensure any throttled groups are reachable by pick_next_task */
8267 unthrottle_offline_cfs_rqs(rq
);
8270 #endif /* CONFIG_SMP */
8273 * scheduler tick hitting a task of our scheduling class:
8275 static void task_tick_fair(struct rq
*rq
, struct task_struct
*curr
, int queued
)
8277 struct cfs_rq
*cfs_rq
;
8278 struct sched_entity
*se
= &curr
->se
;
8280 for_each_sched_entity(se
) {
8281 cfs_rq
= cfs_rq_of(se
);
8282 entity_tick(cfs_rq
, se
, queued
);
8285 if (static_branch_unlikely(&sched_numa_balancing
))
8286 task_tick_numa(rq
, curr
);
8290 * called on fork with the child task as argument from the parent's context
8291 * - child not yet on the tasklist
8292 * - preemption disabled
8294 static void task_fork_fair(struct task_struct
*p
)
8296 struct cfs_rq
*cfs_rq
;
8297 struct sched_entity
*se
= &p
->se
, *curr
;
8298 struct rq
*rq
= this_rq();
8300 raw_spin_lock(&rq
->lock
);
8301 update_rq_clock(rq
);
8303 cfs_rq
= task_cfs_rq(current
);
8304 curr
= cfs_rq
->curr
;
8306 update_curr(cfs_rq
);
8307 se
->vruntime
= curr
->vruntime
;
8309 place_entity(cfs_rq
, se
, 1);
8311 if (sysctl_sched_child_runs_first
&& curr
&& entity_before(curr
, se
)) {
8313 * Upon rescheduling, sched_class::put_prev_task() will place
8314 * 'current' within the tree based on its new key value.
8316 swap(curr
->vruntime
, se
->vruntime
);
8320 se
->vruntime
-= cfs_rq
->min_vruntime
;
8321 raw_spin_unlock(&rq
->lock
);
8325 * Priority of the task has changed. Check to see if we preempt
8329 prio_changed_fair(struct rq
*rq
, struct task_struct
*p
, int oldprio
)
8331 if (!task_on_rq_queued(p
))
8335 * Reschedule if we are currently running on this runqueue and
8336 * our priority decreased, or if we are not currently running on
8337 * this runqueue and our priority is higher than the current's
8339 if (rq
->curr
== p
) {
8340 if (p
->prio
> oldprio
)
8343 check_preempt_curr(rq
, p
, 0);
8346 static inline bool vruntime_normalized(struct task_struct
*p
)
8348 struct sched_entity
*se
= &p
->se
;
8351 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8352 * the dequeue_entity(.flags=0) will already have normalized the
8359 * When !on_rq, vruntime of the task has usually NOT been normalized.
8360 * But there are some cases where it has already been normalized:
8362 * - A forked child which is waiting for being woken up by
8363 * wake_up_new_task().
8364 * - A task which has been woken up by try_to_wake_up() and
8365 * waiting for actually being woken up by sched_ttwu_pending().
8367 if (!se
->sum_exec_runtime
|| p
->state
== TASK_WAKING
)
8373 static void detach_task_cfs_rq(struct task_struct
*p
)
8375 struct sched_entity
*se
= &p
->se
;
8376 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
8377 u64 now
= cfs_rq_clock_task(cfs_rq
);
8379 if (!vruntime_normalized(p
)) {
8381 * Fix up our vruntime so that the current sleep doesn't
8382 * cause 'unlimited' sleep bonus.
8384 place_entity(cfs_rq
, se
, 0);
8385 se
->vruntime
-= cfs_rq
->min_vruntime
;
8388 /* Catch up with the cfs_rq and remove our load when we leave */
8389 update_cfs_rq_load_avg(now
, cfs_rq
, false);
8390 detach_entity_load_avg(cfs_rq
, se
);
8393 static void attach_task_cfs_rq(struct task_struct
*p
)
8395 struct sched_entity
*se
= &p
->se
;
8396 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
8397 u64 now
= cfs_rq_clock_task(cfs_rq
);
8399 #ifdef CONFIG_FAIR_GROUP_SCHED
8401 * Since the real-depth could have been changed (only FAIR
8402 * class maintain depth value), reset depth properly.
8404 se
->depth
= se
->parent
? se
->parent
->depth
+ 1 : 0;
8407 /* Synchronize task with its cfs_rq */
8408 update_cfs_rq_load_avg(now
, cfs_rq
, false);
8409 attach_entity_load_avg(cfs_rq
, se
);
8411 if (!vruntime_normalized(p
))
8412 se
->vruntime
+= cfs_rq
->min_vruntime
;
8415 static void switched_from_fair(struct rq
*rq
, struct task_struct
*p
)
8417 detach_task_cfs_rq(p
);
8420 static void switched_to_fair(struct rq
*rq
, struct task_struct
*p
)
8422 attach_task_cfs_rq(p
);
8424 if (task_on_rq_queued(p
)) {
8426 * We were most likely switched from sched_rt, so
8427 * kick off the schedule if running, otherwise just see
8428 * if we can still preempt the current task.
8433 check_preempt_curr(rq
, p
, 0);
8437 /* Account for a task changing its policy or group.
8439 * This routine is mostly called to set cfs_rq->curr field when a task
8440 * migrates between groups/classes.
8442 static void set_curr_task_fair(struct rq
*rq
)
8444 struct sched_entity
*se
= &rq
->curr
->se
;
8446 for_each_sched_entity(se
) {
8447 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
8449 set_next_entity(cfs_rq
, se
);
8450 /* ensure bandwidth has been allocated on our new cfs_rq */
8451 account_cfs_rq_runtime(cfs_rq
, 0);
8455 void init_cfs_rq(struct cfs_rq
*cfs_rq
)
8457 cfs_rq
->tasks_timeline
= RB_ROOT
;
8458 cfs_rq
->min_vruntime
= (u64
)(-(1LL << 20));
8459 #ifndef CONFIG_64BIT
8460 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
8463 atomic_long_set(&cfs_rq
->removed_load_avg
, 0);
8464 atomic_long_set(&cfs_rq
->removed_util_avg
, 0);
8468 #ifdef CONFIG_FAIR_GROUP_SCHED
8469 static void task_set_group_fair(struct task_struct
*p
)
8471 struct sched_entity
*se
= &p
->se
;
8473 set_task_rq(p
, task_cpu(p
));
8474 se
->depth
= se
->parent
? se
->parent
->depth
+ 1 : 0;
8477 static void task_move_group_fair(struct task_struct
*p
)
8479 detach_task_cfs_rq(p
);
8480 set_task_rq(p
, task_cpu(p
));
8483 /* Tell se's cfs_rq has been changed -- migrated */
8484 p
->se
.avg
.last_update_time
= 0;
8486 attach_task_cfs_rq(p
);
8489 static void task_change_group_fair(struct task_struct
*p
, int type
)
8492 case TASK_SET_GROUP
:
8493 task_set_group_fair(p
);
8496 case TASK_MOVE_GROUP
:
8497 task_move_group_fair(p
);
8502 void free_fair_sched_group(struct task_group
*tg
)
8506 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg
));
8508 for_each_possible_cpu(i
) {
8510 kfree(tg
->cfs_rq
[i
]);
8519 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
8521 struct sched_entity
*se
;
8522 struct cfs_rq
*cfs_rq
;
8526 tg
->cfs_rq
= kzalloc(sizeof(cfs_rq
) * nr_cpu_ids
, GFP_KERNEL
);
8529 tg
->se
= kzalloc(sizeof(se
) * nr_cpu_ids
, GFP_KERNEL
);
8533 tg
->shares
= NICE_0_LOAD
;
8535 init_cfs_bandwidth(tg_cfs_bandwidth(tg
));
8537 for_each_possible_cpu(i
) {
8540 cfs_rq
= kzalloc_node(sizeof(struct cfs_rq
),
8541 GFP_KERNEL
, cpu_to_node(i
));
8545 se
= kzalloc_node(sizeof(struct sched_entity
),
8546 GFP_KERNEL
, cpu_to_node(i
));
8550 init_cfs_rq(cfs_rq
);
8551 init_tg_cfs_entry(tg
, cfs_rq
, se
, i
, parent
->se
[i
]);
8552 init_entity_runnable_average(se
);
8554 raw_spin_lock_irq(&rq
->lock
);
8555 post_init_entity_util_avg(se
);
8556 raw_spin_unlock_irq(&rq
->lock
);
8567 void unregister_fair_sched_group(struct task_group
*tg
)
8569 unsigned long flags
;
8573 for_each_possible_cpu(cpu
) {
8575 remove_entity_load_avg(tg
->se
[cpu
]);
8578 * Only empty task groups can be destroyed; so we can speculatively
8579 * check on_list without danger of it being re-added.
8581 if (!tg
->cfs_rq
[cpu
]->on_list
)
8586 raw_spin_lock_irqsave(&rq
->lock
, flags
);
8587 list_del_leaf_cfs_rq(tg
->cfs_rq
[cpu
]);
8588 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
8592 void init_tg_cfs_entry(struct task_group
*tg
, struct cfs_rq
*cfs_rq
,
8593 struct sched_entity
*se
, int cpu
,
8594 struct sched_entity
*parent
)
8596 struct rq
*rq
= cpu_rq(cpu
);
8600 init_cfs_rq_runtime(cfs_rq
);
8602 tg
->cfs_rq
[cpu
] = cfs_rq
;
8605 /* se could be NULL for root_task_group */
8610 se
->cfs_rq
= &rq
->cfs
;
8613 se
->cfs_rq
= parent
->my_q
;
8614 se
->depth
= parent
->depth
+ 1;
8618 /* guarantee group entities always have weight */
8619 update_load_set(&se
->load
, NICE_0_LOAD
);
8620 se
->parent
= parent
;
8623 static DEFINE_MUTEX(shares_mutex
);
8625 int sched_group_set_shares(struct task_group
*tg
, unsigned long shares
)
8628 unsigned long flags
;
8631 * We can't change the weight of the root cgroup.
8636 shares
= clamp(shares
, scale_load(MIN_SHARES
), scale_load(MAX_SHARES
));
8638 mutex_lock(&shares_mutex
);
8639 if (tg
->shares
== shares
)
8642 tg
->shares
= shares
;
8643 for_each_possible_cpu(i
) {
8644 struct rq
*rq
= cpu_rq(i
);
8645 struct sched_entity
*se
;
8648 /* Propagate contribution to hierarchy */
8649 raw_spin_lock_irqsave(&rq
->lock
, flags
);
8651 /* Possible calls to update_curr() need rq clock */
8652 update_rq_clock(rq
);
8653 for_each_sched_entity(se
)
8654 update_cfs_shares(group_cfs_rq(se
));
8655 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
8659 mutex_unlock(&shares_mutex
);
8662 #else /* CONFIG_FAIR_GROUP_SCHED */
8664 void free_fair_sched_group(struct task_group
*tg
) { }
8666 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
8671 void unregister_fair_sched_group(struct task_group
*tg
) { }
8673 #endif /* CONFIG_FAIR_GROUP_SCHED */
8676 static unsigned int get_rr_interval_fair(struct rq
*rq
, struct task_struct
*task
)
8678 struct sched_entity
*se
= &task
->se
;
8679 unsigned int rr_interval
= 0;
8682 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8685 if (rq
->cfs
.load
.weight
)
8686 rr_interval
= NS_TO_JIFFIES(sched_slice(cfs_rq_of(se
), se
));
8692 * All the scheduling class methods:
8694 const struct sched_class fair_sched_class
= {
8695 .next
= &idle_sched_class
,
8696 .enqueue_task
= enqueue_task_fair
,
8697 .dequeue_task
= dequeue_task_fair
,
8698 .yield_task
= yield_task_fair
,
8699 .yield_to_task
= yield_to_task_fair
,
8701 .check_preempt_curr
= check_preempt_wakeup
,
8703 .pick_next_task
= pick_next_task_fair
,
8704 .put_prev_task
= put_prev_task_fair
,
8707 .select_task_rq
= select_task_rq_fair
,
8708 .migrate_task_rq
= migrate_task_rq_fair
,
8710 .rq_online
= rq_online_fair
,
8711 .rq_offline
= rq_offline_fair
,
8713 .task_dead
= task_dead_fair
,
8714 .set_cpus_allowed
= set_cpus_allowed_common
,
8717 .set_curr_task
= set_curr_task_fair
,
8718 .task_tick
= task_tick_fair
,
8719 .task_fork
= task_fork_fair
,
8721 .prio_changed
= prio_changed_fair
,
8722 .switched_from
= switched_from_fair
,
8723 .switched_to
= switched_to_fair
,
8725 .get_rr_interval
= get_rr_interval_fair
,
8727 .update_curr
= update_curr_fair
,
8729 #ifdef CONFIG_FAIR_GROUP_SCHED
8730 .task_change_group
= task_change_group_fair
,
8734 #ifdef CONFIG_SCHED_DEBUG
8735 void print_cfs_stats(struct seq_file
*m
, int cpu
)
8737 struct cfs_rq
*cfs_rq
;
8740 for_each_leaf_cfs_rq(cpu_rq(cpu
), cfs_rq
)
8741 print_cfs_rq(m
, cpu
, cfs_rq
);
8745 #ifdef CONFIG_NUMA_BALANCING
8746 void show_numa_stats(struct task_struct
*p
, struct seq_file
*m
)
8749 unsigned long tsf
= 0, tpf
= 0, gsf
= 0, gpf
= 0;
8751 for_each_online_node(node
) {
8752 if (p
->numa_faults
) {
8753 tsf
= p
->numa_faults
[task_faults_idx(NUMA_MEM
, node
, 0)];
8754 tpf
= p
->numa_faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
8756 if (p
->numa_group
) {
8757 gsf
= p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, node
, 0)],
8758 gpf
= p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
8760 print_numa_stats(m
, node
, tsf
, tpf
, gsf
, gpf
);
8763 #endif /* CONFIG_NUMA_BALANCING */
8764 #endif /* CONFIG_SCHED_DEBUG */
8766 __init
void init_sched_fair_class(void)
8769 open_softirq(SCHED_SOFTIRQ
, run_rebalance_domains
);
8771 #ifdef CONFIG_NO_HZ_COMMON
8772 nohz
.next_balance
= jiffies
;
8773 zalloc_cpumask_var(&nohz
.idle_cpus_mask
, GFP_NOWAIT
);