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)(scale_load_down(SCHED_LOAD_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
;
738 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq
*cfs_rq
);
739 static inline unsigned long cfs_rq_load_avg(struct cfs_rq
*cfs_rq
);
741 void init_entity_runnable_average(struct sched_entity
*se
)
744 void post_init_entity_util_avg(struct sched_entity
*se
)
750 * Update the current task's runtime statistics.
752 static void update_curr(struct cfs_rq
*cfs_rq
)
754 struct sched_entity
*curr
= cfs_rq
->curr
;
755 u64 now
= rq_clock_task(rq_of(cfs_rq
));
761 delta_exec
= now
- curr
->exec_start
;
762 if (unlikely((s64
)delta_exec
<= 0))
765 curr
->exec_start
= now
;
767 schedstat_set(curr
->statistics
.exec_max
,
768 max(delta_exec
, curr
->statistics
.exec_max
));
770 curr
->sum_exec_runtime
+= delta_exec
;
771 schedstat_add(cfs_rq
, exec_clock
, delta_exec
);
773 curr
->vruntime
+= calc_delta_fair(delta_exec
, curr
);
774 update_min_vruntime(cfs_rq
);
776 if (entity_is_task(curr
)) {
777 struct task_struct
*curtask
= task_of(curr
);
779 trace_sched_stat_runtime(curtask
, delta_exec
, curr
->vruntime
);
780 cpuacct_charge(curtask
, delta_exec
);
781 account_group_exec_runtime(curtask
, delta_exec
);
784 account_cfs_rq_runtime(cfs_rq
, delta_exec
);
787 static void update_curr_fair(struct rq
*rq
)
789 update_curr(cfs_rq_of(&rq
->curr
->se
));
792 #ifdef CONFIG_SCHEDSTATS
794 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
796 u64 wait_start
= rq_clock(rq_of(cfs_rq
));
798 if (entity_is_task(se
) && task_on_rq_migrating(task_of(se
)) &&
799 likely(wait_start
> se
->statistics
.wait_start
))
800 wait_start
-= se
->statistics
.wait_start
;
802 se
->statistics
.wait_start
= wait_start
;
806 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
808 struct task_struct
*p
;
811 delta
= rq_clock(rq_of(cfs_rq
)) - se
->statistics
.wait_start
;
813 if (entity_is_task(se
)) {
815 if (task_on_rq_migrating(p
)) {
817 * Preserve migrating task's wait time so wait_start
818 * time stamp can be adjusted to accumulate wait time
819 * prior to migration.
821 se
->statistics
.wait_start
= delta
;
824 trace_sched_stat_wait(p
, delta
);
827 se
->statistics
.wait_max
= max(se
->statistics
.wait_max
, delta
);
828 se
->statistics
.wait_count
++;
829 se
->statistics
.wait_sum
+= delta
;
830 se
->statistics
.wait_start
= 0;
834 * Task is being enqueued - update stats:
837 update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
840 * Are we enqueueing a waiting task? (for current tasks
841 * a dequeue/enqueue event is a NOP)
843 if (se
!= cfs_rq
->curr
)
844 update_stats_wait_start(cfs_rq
, se
);
848 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
851 * Mark the end of the wait period if dequeueing a
854 if (se
!= cfs_rq
->curr
)
855 update_stats_wait_end(cfs_rq
, se
);
857 if (flags
& DEQUEUE_SLEEP
) {
858 if (entity_is_task(se
)) {
859 struct task_struct
*tsk
= task_of(se
);
861 if (tsk
->state
& TASK_INTERRUPTIBLE
)
862 se
->statistics
.sleep_start
= rq_clock(rq_of(cfs_rq
));
863 if (tsk
->state
& TASK_UNINTERRUPTIBLE
)
864 se
->statistics
.block_start
= rq_clock(rq_of(cfs_rq
));
871 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
876 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
881 update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
886 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
892 * We are picking a new current task - update its stats:
895 update_stats_curr_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
898 * We are starting a new run period:
900 se
->exec_start
= rq_clock_task(rq_of(cfs_rq
));
903 /**************************************************
904 * Scheduling class queueing methods:
907 #ifdef CONFIG_NUMA_BALANCING
909 * Approximate time to scan a full NUMA task in ms. The task scan period is
910 * calculated based on the tasks virtual memory size and
911 * numa_balancing_scan_size.
913 unsigned int sysctl_numa_balancing_scan_period_min
= 1000;
914 unsigned int sysctl_numa_balancing_scan_period_max
= 60000;
916 /* Portion of address space to scan in MB */
917 unsigned int sysctl_numa_balancing_scan_size
= 256;
919 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
920 unsigned int sysctl_numa_balancing_scan_delay
= 1000;
922 static unsigned int task_nr_scan_windows(struct task_struct
*p
)
924 unsigned long rss
= 0;
925 unsigned long nr_scan_pages
;
928 * Calculations based on RSS as non-present and empty pages are skipped
929 * by the PTE scanner and NUMA hinting faults should be trapped based
932 nr_scan_pages
= sysctl_numa_balancing_scan_size
<< (20 - PAGE_SHIFT
);
933 rss
= get_mm_rss(p
->mm
);
937 rss
= round_up(rss
, nr_scan_pages
);
938 return rss
/ nr_scan_pages
;
941 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
942 #define MAX_SCAN_WINDOW 2560
944 static unsigned int task_scan_min(struct task_struct
*p
)
946 unsigned int scan_size
= READ_ONCE(sysctl_numa_balancing_scan_size
);
947 unsigned int scan
, floor
;
948 unsigned int windows
= 1;
950 if (scan_size
< MAX_SCAN_WINDOW
)
951 windows
= MAX_SCAN_WINDOW
/ scan_size
;
952 floor
= 1000 / windows
;
954 scan
= sysctl_numa_balancing_scan_period_min
/ task_nr_scan_windows(p
);
955 return max_t(unsigned int, floor
, scan
);
958 static unsigned int task_scan_max(struct task_struct
*p
)
960 unsigned int smin
= task_scan_min(p
);
963 /* Watch for min being lower than max due to floor calculations */
964 smax
= sysctl_numa_balancing_scan_period_max
/ task_nr_scan_windows(p
);
965 return max(smin
, smax
);
968 static void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
970 rq
->nr_numa_running
+= (p
->numa_preferred_nid
!= -1);
971 rq
->nr_preferred_running
+= (p
->numa_preferred_nid
== task_node(p
));
974 static void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
976 rq
->nr_numa_running
-= (p
->numa_preferred_nid
!= -1);
977 rq
->nr_preferred_running
-= (p
->numa_preferred_nid
== task_node(p
));
983 spinlock_t lock
; /* nr_tasks, tasks */
989 unsigned long total_faults
;
990 unsigned long max_faults_cpu
;
992 * Faults_cpu is used to decide whether memory should move
993 * towards the CPU. As a consequence, these stats are weighted
994 * more by CPU use than by memory faults.
996 unsigned long *faults_cpu
;
997 unsigned long faults
[0];
1000 /* Shared or private faults. */
1001 #define NR_NUMA_HINT_FAULT_TYPES 2
1003 /* Memory and CPU locality */
1004 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
1006 /* Averaged statistics, and temporary buffers. */
1007 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
1009 pid_t
task_numa_group_id(struct task_struct
*p
)
1011 return p
->numa_group
? p
->numa_group
->gid
: 0;
1015 * The averaged statistics, shared & private, memory & cpu,
1016 * occupy the first half of the array. The second half of the
1017 * array is for current counters, which are averaged into the
1018 * first set by task_numa_placement.
1020 static inline int task_faults_idx(enum numa_faults_stats s
, int nid
, int priv
)
1022 return NR_NUMA_HINT_FAULT_TYPES
* (s
* nr_node_ids
+ nid
) + priv
;
1025 static inline unsigned long task_faults(struct task_struct
*p
, int nid
)
1027 if (!p
->numa_faults
)
1030 return p
->numa_faults
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1031 p
->numa_faults
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1034 static inline unsigned long group_faults(struct task_struct
*p
, int nid
)
1039 return p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1040 p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1043 static inline unsigned long group_faults_cpu(struct numa_group
*group
, int nid
)
1045 return group
->faults_cpu
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1046 group
->faults_cpu
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1050 * A node triggering more than 1/3 as many NUMA faults as the maximum is
1051 * considered part of a numa group's pseudo-interleaving set. Migrations
1052 * between these nodes are slowed down, to allow things to settle down.
1054 #define ACTIVE_NODE_FRACTION 3
1056 static bool numa_is_active_node(int nid
, struct numa_group
*ng
)
1058 return group_faults_cpu(ng
, nid
) * ACTIVE_NODE_FRACTION
> ng
->max_faults_cpu
;
1061 /* Handle placement on systems where not all nodes are directly connected. */
1062 static unsigned long score_nearby_nodes(struct task_struct
*p
, int nid
,
1063 int maxdist
, bool task
)
1065 unsigned long score
= 0;
1069 * All nodes are directly connected, and the same distance
1070 * from each other. No need for fancy placement algorithms.
1072 if (sched_numa_topology_type
== NUMA_DIRECT
)
1076 * This code is called for each node, introducing N^2 complexity,
1077 * which should be ok given the number of nodes rarely exceeds 8.
1079 for_each_online_node(node
) {
1080 unsigned long faults
;
1081 int dist
= node_distance(nid
, node
);
1084 * The furthest away nodes in the system are not interesting
1085 * for placement; nid was already counted.
1087 if (dist
== sched_max_numa_distance
|| node
== nid
)
1091 * On systems with a backplane NUMA topology, compare groups
1092 * of nodes, and move tasks towards the group with the most
1093 * memory accesses. When comparing two nodes at distance
1094 * "hoplimit", only nodes closer by than "hoplimit" are part
1095 * of each group. Skip other nodes.
1097 if (sched_numa_topology_type
== NUMA_BACKPLANE
&&
1101 /* Add up the faults from nearby nodes. */
1103 faults
= task_faults(p
, node
);
1105 faults
= group_faults(p
, node
);
1108 * On systems with a glueless mesh NUMA topology, there are
1109 * no fixed "groups of nodes". Instead, nodes that are not
1110 * directly connected bounce traffic through intermediate
1111 * nodes; a numa_group can occupy any set of nodes.
1112 * The further away a node is, the less the faults count.
1113 * This seems to result in good task placement.
1115 if (sched_numa_topology_type
== NUMA_GLUELESS_MESH
) {
1116 faults
*= (sched_max_numa_distance
- dist
);
1117 faults
/= (sched_max_numa_distance
- LOCAL_DISTANCE
);
1127 * These return the fraction of accesses done by a particular task, or
1128 * task group, on a particular numa node. The group weight is given a
1129 * larger multiplier, in order to group tasks together that are almost
1130 * evenly spread out between numa nodes.
1132 static inline unsigned long task_weight(struct task_struct
*p
, int nid
,
1135 unsigned long faults
, total_faults
;
1137 if (!p
->numa_faults
)
1140 total_faults
= p
->total_numa_faults
;
1145 faults
= task_faults(p
, nid
);
1146 faults
+= score_nearby_nodes(p
, nid
, dist
, true);
1148 return 1000 * faults
/ total_faults
;
1151 static inline unsigned long group_weight(struct task_struct
*p
, int nid
,
1154 unsigned long faults
, total_faults
;
1159 total_faults
= p
->numa_group
->total_faults
;
1164 faults
= group_faults(p
, nid
);
1165 faults
+= score_nearby_nodes(p
, nid
, dist
, false);
1167 return 1000 * faults
/ total_faults
;
1170 bool should_numa_migrate_memory(struct task_struct
*p
, struct page
* page
,
1171 int src_nid
, int dst_cpu
)
1173 struct numa_group
*ng
= p
->numa_group
;
1174 int dst_nid
= cpu_to_node(dst_cpu
);
1175 int last_cpupid
, this_cpupid
;
1177 this_cpupid
= cpu_pid_to_cpupid(dst_cpu
, current
->pid
);
1180 * Multi-stage node selection is used in conjunction with a periodic
1181 * migration fault to build a temporal task<->page relation. By using
1182 * a two-stage filter we remove short/unlikely relations.
1184 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1185 * a task's usage of a particular page (n_p) per total usage of this
1186 * page (n_t) (in a given time-span) to a probability.
1188 * Our periodic faults will sample this probability and getting the
1189 * same result twice in a row, given these samples are fully
1190 * independent, is then given by P(n)^2, provided our sample period
1191 * is sufficiently short compared to the usage pattern.
1193 * This quadric squishes small probabilities, making it less likely we
1194 * act on an unlikely task<->page relation.
1196 last_cpupid
= page_cpupid_xchg_last(page
, this_cpupid
);
1197 if (!cpupid_pid_unset(last_cpupid
) &&
1198 cpupid_to_nid(last_cpupid
) != dst_nid
)
1201 /* Always allow migrate on private faults */
1202 if (cpupid_match_pid(p
, last_cpupid
))
1205 /* A shared fault, but p->numa_group has not been set up yet. */
1210 * Destination node is much more heavily used than the source
1211 * node? Allow migration.
1213 if (group_faults_cpu(ng
, dst_nid
) > group_faults_cpu(ng
, src_nid
) *
1214 ACTIVE_NODE_FRACTION
)
1218 * Distribute memory according to CPU & memory use on each node,
1219 * with 3/4 hysteresis to avoid unnecessary memory migrations:
1221 * faults_cpu(dst) 3 faults_cpu(src)
1222 * --------------- * - > ---------------
1223 * faults_mem(dst) 4 faults_mem(src)
1225 return group_faults_cpu(ng
, dst_nid
) * group_faults(p
, src_nid
) * 3 >
1226 group_faults_cpu(ng
, src_nid
) * group_faults(p
, dst_nid
) * 4;
1229 static unsigned long weighted_cpuload(const int cpu
);
1230 static unsigned long source_load(int cpu
, int type
);
1231 static unsigned long target_load(int cpu
, int type
);
1232 static unsigned long capacity_of(int cpu
);
1233 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
);
1235 /* Cached statistics for all CPUs within a node */
1237 unsigned long nr_running
;
1240 /* Total compute capacity of CPUs on a node */
1241 unsigned long compute_capacity
;
1243 /* Approximate capacity in terms of runnable tasks on a node */
1244 unsigned long task_capacity
;
1245 int has_free_capacity
;
1249 * XXX borrowed from update_sg_lb_stats
1251 static void update_numa_stats(struct numa_stats
*ns
, int nid
)
1253 int smt
, cpu
, cpus
= 0;
1254 unsigned long capacity
;
1256 memset(ns
, 0, sizeof(*ns
));
1257 for_each_cpu(cpu
, cpumask_of_node(nid
)) {
1258 struct rq
*rq
= cpu_rq(cpu
);
1260 ns
->nr_running
+= rq
->nr_running
;
1261 ns
->load
+= weighted_cpuload(cpu
);
1262 ns
->compute_capacity
+= capacity_of(cpu
);
1268 * If we raced with hotplug and there are no CPUs left in our mask
1269 * the @ns structure is NULL'ed and task_numa_compare() will
1270 * not find this node attractive.
1272 * We'll either bail at !has_free_capacity, or we'll detect a huge
1273 * imbalance and bail there.
1278 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1279 smt
= DIV_ROUND_UP(SCHED_CAPACITY_SCALE
* cpus
, ns
->compute_capacity
);
1280 capacity
= cpus
/ smt
; /* cores */
1282 ns
->task_capacity
= min_t(unsigned, capacity
,
1283 DIV_ROUND_CLOSEST(ns
->compute_capacity
, SCHED_CAPACITY_SCALE
));
1284 ns
->has_free_capacity
= (ns
->nr_running
< ns
->task_capacity
);
1287 struct task_numa_env
{
1288 struct task_struct
*p
;
1290 int src_cpu
, src_nid
;
1291 int dst_cpu
, dst_nid
;
1293 struct numa_stats src_stats
, dst_stats
;
1298 struct task_struct
*best_task
;
1303 static void task_numa_assign(struct task_numa_env
*env
,
1304 struct task_struct
*p
, long imp
)
1307 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
;
1375 bool assigned
= false;
1379 raw_spin_lock_irq(&dst_rq
->lock
);
1382 * No need to move the exiting task or idle task.
1384 if ((cur
->flags
& PF_EXITING
) || is_idle_task(cur
))
1388 * The task_struct must be protected here to protect the
1389 * p->numa_faults access in the task_weight since the
1390 * numa_faults could already be freed in the following path:
1391 * finish_task_switch()
1392 * --> put_task_struct()
1393 * --> __put_task_struct()
1394 * --> task_numa_free()
1396 get_task_struct(cur
);
1399 raw_spin_unlock_irq(&dst_rq
->lock
);
1402 * Because we have preemption enabled we can get migrated around and
1403 * end try selecting ourselves (current == env->p) as a swap candidate.
1409 * "imp" is the fault differential for the source task between the
1410 * source and destination node. Calculate the total differential for
1411 * the source task and potential destination task. The more negative
1412 * the value is, the more rmeote accesses that would be expected to
1413 * be incurred if the tasks were swapped.
1416 /* Skip this swap candidate if cannot move to the source cpu */
1417 if (!cpumask_test_cpu(env
->src_cpu
, tsk_cpus_allowed(cur
)))
1421 * If dst and source tasks are in the same NUMA group, or not
1422 * in any group then look only at task weights.
1424 if (cur
->numa_group
== env
->p
->numa_group
) {
1425 imp
= taskimp
+ task_weight(cur
, env
->src_nid
, dist
) -
1426 task_weight(cur
, env
->dst_nid
, dist
);
1428 * Add some hysteresis to prevent swapping the
1429 * tasks within a group over tiny differences.
1431 if (cur
->numa_group
)
1435 * Compare the group weights. If a task is all by
1436 * itself (not part of a group), use the task weight
1439 if (cur
->numa_group
)
1440 imp
+= group_weight(cur
, env
->src_nid
, dist
) -
1441 group_weight(cur
, env
->dst_nid
, dist
);
1443 imp
+= task_weight(cur
, env
->src_nid
, dist
) -
1444 task_weight(cur
, env
->dst_nid
, dist
);
1448 if (imp
<= env
->best_imp
&& moveimp
<= env
->best_imp
)
1452 /* Is there capacity at our destination? */
1453 if (env
->src_stats
.nr_running
<= env
->src_stats
.task_capacity
&&
1454 !env
->dst_stats
.has_free_capacity
)
1460 /* Balance doesn't matter much if we're running a task per cpu */
1461 if (imp
> env
->best_imp
&& src_rq
->nr_running
== 1 &&
1462 dst_rq
->nr_running
== 1)
1466 * In the overloaded case, try and keep the load balanced.
1469 load
= task_h_load(env
->p
);
1470 dst_load
= env
->dst_stats
.load
+ load
;
1471 src_load
= env
->src_stats
.load
- load
;
1473 if (moveimp
> imp
&& moveimp
> env
->best_imp
) {
1475 * If the improvement from just moving env->p direction is
1476 * better than swapping tasks around, check if a move is
1477 * possible. Store a slightly smaller score than moveimp,
1478 * so an actually idle CPU will win.
1480 if (!load_too_imbalanced(src_load
, dst_load
, env
)) {
1482 put_task_struct(cur
);
1488 if (imp
<= env
->best_imp
)
1492 load
= task_h_load(cur
);
1497 if (load_too_imbalanced(src_load
, dst_load
, env
))
1501 * One idle CPU per node is evaluated for a task numa move.
1502 * Call select_idle_sibling to maybe find a better one.
1505 env
->dst_cpu
= select_idle_sibling(env
->p
, env
->dst_cpu
);
1509 task_numa_assign(env
, cur
, imp
);
1513 * The dst_rq->curr isn't assigned. The protection for task_struct is
1516 if (cur
&& !assigned
)
1517 put_task_struct(cur
);
1520 static void task_numa_find_cpu(struct task_numa_env
*env
,
1521 long taskimp
, long groupimp
)
1525 for_each_cpu(cpu
, cpumask_of_node(env
->dst_nid
)) {
1526 /* Skip this CPU if the source task cannot migrate */
1527 if (!cpumask_test_cpu(cpu
, tsk_cpus_allowed(env
->p
)))
1531 task_numa_compare(env
, taskimp
, groupimp
);
1535 /* Only move tasks to a NUMA node less busy than the current node. */
1536 static bool numa_has_capacity(struct task_numa_env
*env
)
1538 struct numa_stats
*src
= &env
->src_stats
;
1539 struct numa_stats
*dst
= &env
->dst_stats
;
1541 if (src
->has_free_capacity
&& !dst
->has_free_capacity
)
1545 * Only consider a task move if the source has a higher load
1546 * than the destination, corrected for CPU capacity on each node.
1548 * src->load dst->load
1549 * --------------------- vs ---------------------
1550 * src->compute_capacity dst->compute_capacity
1552 if (src
->load
* dst
->compute_capacity
* env
->imbalance_pct
>
1554 dst
->load
* src
->compute_capacity
* 100)
1560 static int task_numa_migrate(struct task_struct
*p
)
1562 struct task_numa_env env
= {
1565 .src_cpu
= task_cpu(p
),
1566 .src_nid
= task_node(p
),
1568 .imbalance_pct
= 112,
1574 struct sched_domain
*sd
;
1575 unsigned long taskweight
, groupweight
;
1577 long taskimp
, groupimp
;
1580 * Pick the lowest SD_NUMA domain, as that would have the smallest
1581 * imbalance and would be the first to start moving tasks about.
1583 * And we want to avoid any moving of tasks about, as that would create
1584 * random movement of tasks -- counter the numa conditions we're trying
1588 sd
= rcu_dereference(per_cpu(sd_numa
, env
.src_cpu
));
1590 env
.imbalance_pct
= 100 + (sd
->imbalance_pct
- 100) / 2;
1594 * Cpusets can break the scheduler domain tree into smaller
1595 * balance domains, some of which do not cross NUMA boundaries.
1596 * Tasks that are "trapped" in such domains cannot be migrated
1597 * elsewhere, so there is no point in (re)trying.
1599 if (unlikely(!sd
)) {
1600 p
->numa_preferred_nid
= task_node(p
);
1604 env
.dst_nid
= p
->numa_preferred_nid
;
1605 dist
= env
.dist
= node_distance(env
.src_nid
, env
.dst_nid
);
1606 taskweight
= task_weight(p
, env
.src_nid
, dist
);
1607 groupweight
= group_weight(p
, env
.src_nid
, dist
);
1608 update_numa_stats(&env
.src_stats
, env
.src_nid
);
1609 taskimp
= task_weight(p
, env
.dst_nid
, dist
) - taskweight
;
1610 groupimp
= group_weight(p
, env
.dst_nid
, dist
) - groupweight
;
1611 update_numa_stats(&env
.dst_stats
, env
.dst_nid
);
1613 /* Try to find a spot on the preferred nid. */
1614 if (numa_has_capacity(&env
))
1615 task_numa_find_cpu(&env
, taskimp
, groupimp
);
1618 * Look at other nodes in these cases:
1619 * - there is no space available on the preferred_nid
1620 * - the task is part of a numa_group that is interleaved across
1621 * multiple NUMA nodes; in order to better consolidate the group,
1622 * we need to check other locations.
1624 if (env
.best_cpu
== -1 || (p
->numa_group
&& p
->numa_group
->active_nodes
> 1)) {
1625 for_each_online_node(nid
) {
1626 if (nid
== env
.src_nid
|| nid
== p
->numa_preferred_nid
)
1629 dist
= node_distance(env
.src_nid
, env
.dst_nid
);
1630 if (sched_numa_topology_type
== NUMA_BACKPLANE
&&
1632 taskweight
= task_weight(p
, env
.src_nid
, dist
);
1633 groupweight
= group_weight(p
, env
.src_nid
, dist
);
1636 /* Only consider nodes where both task and groups benefit */
1637 taskimp
= task_weight(p
, nid
, dist
) - taskweight
;
1638 groupimp
= group_weight(p
, nid
, dist
) - groupweight
;
1639 if (taskimp
< 0 && groupimp
< 0)
1644 update_numa_stats(&env
.dst_stats
, env
.dst_nid
);
1645 if (numa_has_capacity(&env
))
1646 task_numa_find_cpu(&env
, taskimp
, groupimp
);
1651 * If the task is part of a workload that spans multiple NUMA nodes,
1652 * and is migrating into one of the workload's active nodes, remember
1653 * this node as the task's preferred numa node, so the workload can
1655 * A task that migrated to a second choice node will be better off
1656 * trying for a better one later. Do not set the preferred node here.
1658 if (p
->numa_group
) {
1659 struct numa_group
*ng
= p
->numa_group
;
1661 if (env
.best_cpu
== -1)
1666 if (ng
->active_nodes
> 1 && numa_is_active_node(env
.dst_nid
, ng
))
1667 sched_setnuma(p
, env
.dst_nid
);
1670 /* No better CPU than the current one was found. */
1671 if (env
.best_cpu
== -1)
1675 * Reset the scan period if the task is being rescheduled on an
1676 * alternative node to recheck if the tasks is now properly placed.
1678 p
->numa_scan_period
= task_scan_min(p
);
1680 if (env
.best_task
== NULL
) {
1681 ret
= migrate_task_to(p
, env
.best_cpu
);
1683 trace_sched_stick_numa(p
, env
.src_cpu
, env
.best_cpu
);
1687 ret
= migrate_swap(p
, env
.best_task
);
1689 trace_sched_stick_numa(p
, env
.src_cpu
, task_cpu(env
.best_task
));
1690 put_task_struct(env
.best_task
);
1694 /* Attempt to migrate a task to a CPU on the preferred node. */
1695 static void numa_migrate_preferred(struct task_struct
*p
)
1697 unsigned long interval
= HZ
;
1699 /* This task has no NUMA fault statistics yet */
1700 if (unlikely(p
->numa_preferred_nid
== -1 || !p
->numa_faults
))
1703 /* Periodically retry migrating the task to the preferred node */
1704 interval
= min(interval
, msecs_to_jiffies(p
->numa_scan_period
) / 16);
1705 p
->numa_migrate_retry
= jiffies
+ interval
;
1707 /* Success if task is already running on preferred CPU */
1708 if (task_node(p
) == p
->numa_preferred_nid
)
1711 /* Otherwise, try migrate to a CPU on the preferred node */
1712 task_numa_migrate(p
);
1716 * Find out how many nodes on the workload is actively running on. Do this by
1717 * tracking the nodes from which NUMA hinting faults are triggered. This can
1718 * be different from the set of nodes where the workload's memory is currently
1721 static void numa_group_count_active_nodes(struct numa_group
*numa_group
)
1723 unsigned long faults
, max_faults
= 0;
1724 int nid
, active_nodes
= 0;
1726 for_each_online_node(nid
) {
1727 faults
= group_faults_cpu(numa_group
, nid
);
1728 if (faults
> max_faults
)
1729 max_faults
= faults
;
1732 for_each_online_node(nid
) {
1733 faults
= group_faults_cpu(numa_group
, nid
);
1734 if (faults
* ACTIVE_NODE_FRACTION
> max_faults
)
1738 numa_group
->max_faults_cpu
= max_faults
;
1739 numa_group
->active_nodes
= active_nodes
;
1743 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1744 * increments. The more local the fault statistics are, the higher the scan
1745 * period will be for the next scan window. If local/(local+remote) ratio is
1746 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1747 * the scan period will decrease. Aim for 70% local accesses.
1749 #define NUMA_PERIOD_SLOTS 10
1750 #define NUMA_PERIOD_THRESHOLD 7
1753 * Increase the scan period (slow down scanning) if the majority of
1754 * our memory is already on our local node, or if the majority of
1755 * the page accesses are shared with other processes.
1756 * Otherwise, decrease the scan period.
1758 static void update_task_scan_period(struct task_struct
*p
,
1759 unsigned long shared
, unsigned long private)
1761 unsigned int period_slot
;
1765 unsigned long remote
= p
->numa_faults_locality
[0];
1766 unsigned long local
= p
->numa_faults_locality
[1];
1769 * If there were no record hinting faults then either the task is
1770 * completely idle or all activity is areas that are not of interest
1771 * to automatic numa balancing. Related to that, if there were failed
1772 * migration then it implies we are migrating too quickly or the local
1773 * node is overloaded. In either case, scan slower
1775 if (local
+ shared
== 0 || p
->numa_faults_locality
[2]) {
1776 p
->numa_scan_period
= min(p
->numa_scan_period_max
,
1777 p
->numa_scan_period
<< 1);
1779 p
->mm
->numa_next_scan
= jiffies
+
1780 msecs_to_jiffies(p
->numa_scan_period
);
1786 * Prepare to scale scan period relative to the current period.
1787 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1788 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1789 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1791 period_slot
= DIV_ROUND_UP(p
->numa_scan_period
, NUMA_PERIOD_SLOTS
);
1792 ratio
= (local
* NUMA_PERIOD_SLOTS
) / (local
+ remote
);
1793 if (ratio
>= NUMA_PERIOD_THRESHOLD
) {
1794 int slot
= ratio
- NUMA_PERIOD_THRESHOLD
;
1797 diff
= slot
* period_slot
;
1799 diff
= -(NUMA_PERIOD_THRESHOLD
- ratio
) * period_slot
;
1802 * Scale scan rate increases based on sharing. There is an
1803 * inverse relationship between the degree of sharing and
1804 * the adjustment made to the scanning period. Broadly
1805 * speaking the intent is that there is little point
1806 * scanning faster if shared accesses dominate as it may
1807 * simply bounce migrations uselessly
1809 ratio
= DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS
, (private + shared
+ 1));
1810 diff
= (diff
* ratio
) / NUMA_PERIOD_SLOTS
;
1813 p
->numa_scan_period
= clamp(p
->numa_scan_period
+ diff
,
1814 task_scan_min(p
), task_scan_max(p
));
1815 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
1819 * Get the fraction of time the task has been running since the last
1820 * NUMA placement cycle. The scheduler keeps similar statistics, but
1821 * decays those on a 32ms period, which is orders of magnitude off
1822 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1823 * stats only if the task is so new there are no NUMA statistics yet.
1825 static u64
numa_get_avg_runtime(struct task_struct
*p
, u64
*period
)
1827 u64 runtime
, delta
, now
;
1828 /* Use the start of this time slice to avoid calculations. */
1829 now
= p
->se
.exec_start
;
1830 runtime
= p
->se
.sum_exec_runtime
;
1832 if (p
->last_task_numa_placement
) {
1833 delta
= runtime
- p
->last_sum_exec_runtime
;
1834 *period
= now
- p
->last_task_numa_placement
;
1836 delta
= p
->se
.avg
.load_sum
/ p
->se
.load
.weight
;
1837 *period
= LOAD_AVG_MAX
;
1840 p
->last_sum_exec_runtime
= runtime
;
1841 p
->last_task_numa_placement
= now
;
1847 * Determine the preferred nid for a task in a numa_group. This needs to
1848 * be done in a way that produces consistent results with group_weight,
1849 * otherwise workloads might not converge.
1851 static int preferred_group_nid(struct task_struct
*p
, int nid
)
1856 /* Direct connections between all NUMA nodes. */
1857 if (sched_numa_topology_type
== NUMA_DIRECT
)
1861 * On a system with glueless mesh NUMA topology, group_weight
1862 * scores nodes according to the number of NUMA hinting faults on
1863 * both the node itself, and on nearby nodes.
1865 if (sched_numa_topology_type
== NUMA_GLUELESS_MESH
) {
1866 unsigned long score
, max_score
= 0;
1867 int node
, max_node
= nid
;
1869 dist
= sched_max_numa_distance
;
1871 for_each_online_node(node
) {
1872 score
= group_weight(p
, node
, dist
);
1873 if (score
> max_score
) {
1882 * Finding the preferred nid in a system with NUMA backplane
1883 * interconnect topology is more involved. The goal is to locate
1884 * tasks from numa_groups near each other in the system, and
1885 * untangle workloads from different sides of the system. This requires
1886 * searching down the hierarchy of node groups, recursively searching
1887 * inside the highest scoring group of nodes. The nodemask tricks
1888 * keep the complexity of the search down.
1890 nodes
= node_online_map
;
1891 for (dist
= sched_max_numa_distance
; dist
> LOCAL_DISTANCE
; dist
--) {
1892 unsigned long max_faults
= 0;
1893 nodemask_t max_group
= NODE_MASK_NONE
;
1896 /* Are there nodes at this distance from each other? */
1897 if (!find_numa_distance(dist
))
1900 for_each_node_mask(a
, nodes
) {
1901 unsigned long faults
= 0;
1902 nodemask_t this_group
;
1903 nodes_clear(this_group
);
1905 /* Sum group's NUMA faults; includes a==b case. */
1906 for_each_node_mask(b
, nodes
) {
1907 if (node_distance(a
, b
) < dist
) {
1908 faults
+= group_faults(p
, b
);
1909 node_set(b
, this_group
);
1910 node_clear(b
, nodes
);
1914 /* Remember the top group. */
1915 if (faults
> max_faults
) {
1916 max_faults
= faults
;
1917 max_group
= this_group
;
1919 * subtle: at the smallest distance there is
1920 * just one node left in each "group", the
1921 * winner is the preferred nid.
1926 /* Next round, evaluate the nodes within max_group. */
1934 static void task_numa_placement(struct task_struct
*p
)
1936 int seq
, nid
, max_nid
= -1, max_group_nid
= -1;
1937 unsigned long max_faults
= 0, max_group_faults
= 0;
1938 unsigned long fault_types
[2] = { 0, 0 };
1939 unsigned long total_faults
;
1940 u64 runtime
, period
;
1941 spinlock_t
*group_lock
= NULL
;
1944 * The p->mm->numa_scan_seq field gets updated without
1945 * exclusive access. Use READ_ONCE() here to ensure
1946 * that the field is read in a single access:
1948 seq
= READ_ONCE(p
->mm
->numa_scan_seq
);
1949 if (p
->numa_scan_seq
== seq
)
1951 p
->numa_scan_seq
= seq
;
1952 p
->numa_scan_period_max
= task_scan_max(p
);
1954 total_faults
= p
->numa_faults_locality
[0] +
1955 p
->numa_faults_locality
[1];
1956 runtime
= numa_get_avg_runtime(p
, &period
);
1958 /* If the task is part of a group prevent parallel updates to group stats */
1959 if (p
->numa_group
) {
1960 group_lock
= &p
->numa_group
->lock
;
1961 spin_lock_irq(group_lock
);
1964 /* Find the node with the highest number of faults */
1965 for_each_online_node(nid
) {
1966 /* Keep track of the offsets in numa_faults array */
1967 int mem_idx
, membuf_idx
, cpu_idx
, cpubuf_idx
;
1968 unsigned long faults
= 0, group_faults
= 0;
1971 for (priv
= 0; priv
< NR_NUMA_HINT_FAULT_TYPES
; priv
++) {
1972 long diff
, f_diff
, f_weight
;
1974 mem_idx
= task_faults_idx(NUMA_MEM
, nid
, priv
);
1975 membuf_idx
= task_faults_idx(NUMA_MEMBUF
, nid
, priv
);
1976 cpu_idx
= task_faults_idx(NUMA_CPU
, nid
, priv
);
1977 cpubuf_idx
= task_faults_idx(NUMA_CPUBUF
, nid
, priv
);
1979 /* Decay existing window, copy faults since last scan */
1980 diff
= p
->numa_faults
[membuf_idx
] - p
->numa_faults
[mem_idx
] / 2;
1981 fault_types
[priv
] += p
->numa_faults
[membuf_idx
];
1982 p
->numa_faults
[membuf_idx
] = 0;
1985 * Normalize the faults_from, so all tasks in a group
1986 * count according to CPU use, instead of by the raw
1987 * number of faults. Tasks with little runtime have
1988 * little over-all impact on throughput, and thus their
1989 * faults are less important.
1991 f_weight
= div64_u64(runtime
<< 16, period
+ 1);
1992 f_weight
= (f_weight
* p
->numa_faults
[cpubuf_idx
]) /
1994 f_diff
= f_weight
- p
->numa_faults
[cpu_idx
] / 2;
1995 p
->numa_faults
[cpubuf_idx
] = 0;
1997 p
->numa_faults
[mem_idx
] += diff
;
1998 p
->numa_faults
[cpu_idx
] += f_diff
;
1999 faults
+= p
->numa_faults
[mem_idx
];
2000 p
->total_numa_faults
+= diff
;
2001 if (p
->numa_group
) {
2003 * safe because we can only change our own group
2005 * mem_idx represents the offset for a given
2006 * nid and priv in a specific region because it
2007 * is at the beginning of the numa_faults array.
2009 p
->numa_group
->faults
[mem_idx
] += diff
;
2010 p
->numa_group
->faults_cpu
[mem_idx
] += f_diff
;
2011 p
->numa_group
->total_faults
+= diff
;
2012 group_faults
+= p
->numa_group
->faults
[mem_idx
];
2016 if (faults
> max_faults
) {
2017 max_faults
= faults
;
2021 if (group_faults
> max_group_faults
) {
2022 max_group_faults
= group_faults
;
2023 max_group_nid
= nid
;
2027 update_task_scan_period(p
, fault_types
[0], fault_types
[1]);
2029 if (p
->numa_group
) {
2030 numa_group_count_active_nodes(p
->numa_group
);
2031 spin_unlock_irq(group_lock
);
2032 max_nid
= preferred_group_nid(p
, max_group_nid
);
2036 /* Set the new preferred node */
2037 if (max_nid
!= p
->numa_preferred_nid
)
2038 sched_setnuma(p
, max_nid
);
2040 if (task_node(p
) != p
->numa_preferred_nid
)
2041 numa_migrate_preferred(p
);
2045 static inline int get_numa_group(struct numa_group
*grp
)
2047 return atomic_inc_not_zero(&grp
->refcount
);
2050 static inline void put_numa_group(struct numa_group
*grp
)
2052 if (atomic_dec_and_test(&grp
->refcount
))
2053 kfree_rcu(grp
, rcu
);
2056 static void task_numa_group(struct task_struct
*p
, int cpupid
, int flags
,
2059 struct numa_group
*grp
, *my_grp
;
2060 struct task_struct
*tsk
;
2062 int cpu
= cpupid_to_cpu(cpupid
);
2065 if (unlikely(!p
->numa_group
)) {
2066 unsigned int size
= sizeof(struct numa_group
) +
2067 4*nr_node_ids
*sizeof(unsigned long);
2069 grp
= kzalloc(size
, GFP_KERNEL
| __GFP_NOWARN
);
2073 atomic_set(&grp
->refcount
, 1);
2074 grp
->active_nodes
= 1;
2075 grp
->max_faults_cpu
= 0;
2076 spin_lock_init(&grp
->lock
);
2078 /* Second half of the array tracks nids where faults happen */
2079 grp
->faults_cpu
= grp
->faults
+ NR_NUMA_HINT_FAULT_TYPES
*
2082 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
2083 grp
->faults
[i
] = p
->numa_faults
[i
];
2085 grp
->total_faults
= p
->total_numa_faults
;
2088 rcu_assign_pointer(p
->numa_group
, grp
);
2092 tsk
= READ_ONCE(cpu_rq(cpu
)->curr
);
2094 if (!cpupid_match_pid(tsk
, cpupid
))
2097 grp
= rcu_dereference(tsk
->numa_group
);
2101 my_grp
= p
->numa_group
;
2106 * Only join the other group if its bigger; if we're the bigger group,
2107 * the other task will join us.
2109 if (my_grp
->nr_tasks
> grp
->nr_tasks
)
2113 * Tie-break on the grp address.
2115 if (my_grp
->nr_tasks
== grp
->nr_tasks
&& my_grp
> grp
)
2118 /* Always join threads in the same process. */
2119 if (tsk
->mm
== current
->mm
)
2122 /* Simple filter to avoid false positives due to PID collisions */
2123 if (flags
& TNF_SHARED
)
2126 /* Update priv based on whether false sharing was detected */
2129 if (join
&& !get_numa_group(grp
))
2137 BUG_ON(irqs_disabled());
2138 double_lock_irq(&my_grp
->lock
, &grp
->lock
);
2140 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++) {
2141 my_grp
->faults
[i
] -= p
->numa_faults
[i
];
2142 grp
->faults
[i
] += p
->numa_faults
[i
];
2144 my_grp
->total_faults
-= p
->total_numa_faults
;
2145 grp
->total_faults
+= p
->total_numa_faults
;
2150 spin_unlock(&my_grp
->lock
);
2151 spin_unlock_irq(&grp
->lock
);
2153 rcu_assign_pointer(p
->numa_group
, grp
);
2155 put_numa_group(my_grp
);
2163 void task_numa_free(struct task_struct
*p
)
2165 struct numa_group
*grp
= p
->numa_group
;
2166 void *numa_faults
= p
->numa_faults
;
2167 unsigned long flags
;
2171 spin_lock_irqsave(&grp
->lock
, flags
);
2172 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
2173 grp
->faults
[i
] -= p
->numa_faults
[i
];
2174 grp
->total_faults
-= p
->total_numa_faults
;
2177 spin_unlock_irqrestore(&grp
->lock
, flags
);
2178 RCU_INIT_POINTER(p
->numa_group
, NULL
);
2179 put_numa_group(grp
);
2182 p
->numa_faults
= NULL
;
2187 * Got a PROT_NONE fault for a page on @node.
2189 void task_numa_fault(int last_cpupid
, int mem_node
, int pages
, int flags
)
2191 struct task_struct
*p
= current
;
2192 bool migrated
= flags
& TNF_MIGRATED
;
2193 int cpu_node
= task_node(current
);
2194 int local
= !!(flags
& TNF_FAULT_LOCAL
);
2195 struct numa_group
*ng
;
2198 if (!static_branch_likely(&sched_numa_balancing
))
2201 /* for example, ksmd faulting in a user's mm */
2205 /* Allocate buffer to track faults on a per-node basis */
2206 if (unlikely(!p
->numa_faults
)) {
2207 int size
= sizeof(*p
->numa_faults
) *
2208 NR_NUMA_HINT_FAULT_BUCKETS
* nr_node_ids
;
2210 p
->numa_faults
= kzalloc(size
, GFP_KERNEL
|__GFP_NOWARN
);
2211 if (!p
->numa_faults
)
2214 p
->total_numa_faults
= 0;
2215 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
2219 * First accesses are treated as private, otherwise consider accesses
2220 * to be private if the accessing pid has not changed
2222 if (unlikely(last_cpupid
== (-1 & LAST_CPUPID_MASK
))) {
2225 priv
= cpupid_match_pid(p
, last_cpupid
);
2226 if (!priv
&& !(flags
& TNF_NO_GROUP
))
2227 task_numa_group(p
, last_cpupid
, flags
, &priv
);
2231 * If a workload spans multiple NUMA nodes, a shared fault that
2232 * occurs wholly within the set of nodes that the workload is
2233 * actively using should be counted as local. This allows the
2234 * scan rate to slow down when a workload has settled down.
2237 if (!priv
&& !local
&& ng
&& ng
->active_nodes
> 1 &&
2238 numa_is_active_node(cpu_node
, ng
) &&
2239 numa_is_active_node(mem_node
, ng
))
2242 task_numa_placement(p
);
2245 * Retry task to preferred node migration periodically, in case it
2246 * case it previously failed, or the scheduler moved us.
2248 if (time_after(jiffies
, p
->numa_migrate_retry
))
2249 numa_migrate_preferred(p
);
2252 p
->numa_pages_migrated
+= pages
;
2253 if (flags
& TNF_MIGRATE_FAIL
)
2254 p
->numa_faults_locality
[2] += pages
;
2256 p
->numa_faults
[task_faults_idx(NUMA_MEMBUF
, mem_node
, priv
)] += pages
;
2257 p
->numa_faults
[task_faults_idx(NUMA_CPUBUF
, cpu_node
, priv
)] += pages
;
2258 p
->numa_faults_locality
[local
] += pages
;
2261 static void reset_ptenuma_scan(struct task_struct
*p
)
2264 * We only did a read acquisition of the mmap sem, so
2265 * p->mm->numa_scan_seq is written to without exclusive access
2266 * and the update is not guaranteed to be atomic. That's not
2267 * much of an issue though, since this is just used for
2268 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2269 * expensive, to avoid any form of compiler optimizations:
2271 WRITE_ONCE(p
->mm
->numa_scan_seq
, READ_ONCE(p
->mm
->numa_scan_seq
) + 1);
2272 p
->mm
->numa_scan_offset
= 0;
2276 * The expensive part of numa migration is done from task_work context.
2277 * Triggered from task_tick_numa().
2279 void task_numa_work(struct callback_head
*work
)
2281 unsigned long migrate
, next_scan
, now
= jiffies
;
2282 struct task_struct
*p
= current
;
2283 struct mm_struct
*mm
= p
->mm
;
2284 u64 runtime
= p
->se
.sum_exec_runtime
;
2285 struct vm_area_struct
*vma
;
2286 unsigned long start
, end
;
2287 unsigned long nr_pte_updates
= 0;
2288 long pages
, virtpages
;
2290 WARN_ON_ONCE(p
!= container_of(work
, struct task_struct
, numa_work
));
2292 work
->next
= work
; /* protect against double add */
2294 * Who cares about NUMA placement when they're dying.
2296 * NOTE: make sure not to dereference p->mm before this check,
2297 * exit_task_work() happens _after_ exit_mm() so we could be called
2298 * without p->mm even though we still had it when we enqueued this
2301 if (p
->flags
& PF_EXITING
)
2304 if (!mm
->numa_next_scan
) {
2305 mm
->numa_next_scan
= now
+
2306 msecs_to_jiffies(sysctl_numa_balancing_scan_delay
);
2310 * Enforce maximal scan/migration frequency..
2312 migrate
= mm
->numa_next_scan
;
2313 if (time_before(now
, migrate
))
2316 if (p
->numa_scan_period
== 0) {
2317 p
->numa_scan_period_max
= task_scan_max(p
);
2318 p
->numa_scan_period
= task_scan_min(p
);
2321 next_scan
= now
+ msecs_to_jiffies(p
->numa_scan_period
);
2322 if (cmpxchg(&mm
->numa_next_scan
, migrate
, next_scan
) != migrate
)
2326 * Delay this task enough that another task of this mm will likely win
2327 * the next time around.
2329 p
->node_stamp
+= 2 * TICK_NSEC
;
2331 start
= mm
->numa_scan_offset
;
2332 pages
= sysctl_numa_balancing_scan_size
;
2333 pages
<<= 20 - PAGE_SHIFT
; /* MB in pages */
2334 virtpages
= pages
* 8; /* Scan up to this much virtual space */
2339 down_read(&mm
->mmap_sem
);
2340 vma
= find_vma(mm
, start
);
2342 reset_ptenuma_scan(p
);
2346 for (; vma
; vma
= vma
->vm_next
) {
2347 if (!vma_migratable(vma
) || !vma_policy_mof(vma
) ||
2348 is_vm_hugetlb_page(vma
) || (vma
->vm_flags
& VM_MIXEDMAP
)) {
2353 * Shared library pages mapped by multiple processes are not
2354 * migrated as it is expected they are cache replicated. Avoid
2355 * hinting faults in read-only file-backed mappings or the vdso
2356 * as migrating the pages will be of marginal benefit.
2359 (vma
->vm_file
&& (vma
->vm_flags
& (VM_READ
|VM_WRITE
)) == (VM_READ
)))
2363 * Skip inaccessible VMAs to avoid any confusion between
2364 * PROT_NONE and NUMA hinting ptes
2366 if (!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
)))
2370 start
= max(start
, vma
->vm_start
);
2371 end
= ALIGN(start
+ (pages
<< PAGE_SHIFT
), HPAGE_SIZE
);
2372 end
= min(end
, vma
->vm_end
);
2373 nr_pte_updates
= change_prot_numa(vma
, start
, end
);
2376 * Try to scan sysctl_numa_balancing_size worth of
2377 * hpages that have at least one present PTE that
2378 * is not already pte-numa. If the VMA contains
2379 * areas that are unused or already full of prot_numa
2380 * PTEs, scan up to virtpages, to skip through those
2384 pages
-= (end
- start
) >> PAGE_SHIFT
;
2385 virtpages
-= (end
- start
) >> PAGE_SHIFT
;
2388 if (pages
<= 0 || virtpages
<= 0)
2392 } while (end
!= vma
->vm_end
);
2397 * It is possible to reach the end of the VMA list but the last few
2398 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2399 * would find the !migratable VMA on the next scan but not reset the
2400 * scanner to the start so check it now.
2403 mm
->numa_scan_offset
= start
;
2405 reset_ptenuma_scan(p
);
2406 up_read(&mm
->mmap_sem
);
2409 * Make sure tasks use at least 32x as much time to run other code
2410 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2411 * Usually update_task_scan_period slows down scanning enough; on an
2412 * overloaded system we need to limit overhead on a per task basis.
2414 if (unlikely(p
->se
.sum_exec_runtime
!= runtime
)) {
2415 u64 diff
= p
->se
.sum_exec_runtime
- runtime
;
2416 p
->node_stamp
+= 32 * diff
;
2421 * Drive the periodic memory faults..
2423 void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
2425 struct callback_head
*work
= &curr
->numa_work
;
2429 * We don't care about NUMA placement if we don't have memory.
2431 if (!curr
->mm
|| (curr
->flags
& PF_EXITING
) || work
->next
!= work
)
2435 * Using runtime rather than walltime has the dual advantage that
2436 * we (mostly) drive the selection from busy threads and that the
2437 * task needs to have done some actual work before we bother with
2440 now
= curr
->se
.sum_exec_runtime
;
2441 period
= (u64
)curr
->numa_scan_period
* NSEC_PER_MSEC
;
2443 if (now
> curr
->node_stamp
+ period
) {
2444 if (!curr
->node_stamp
)
2445 curr
->numa_scan_period
= task_scan_min(curr
);
2446 curr
->node_stamp
+= period
;
2448 if (!time_before(jiffies
, curr
->mm
->numa_next_scan
)) {
2449 init_task_work(work
, task_numa_work
); /* TODO: move this into sched_fork() */
2450 task_work_add(curr
, work
, true);
2455 static void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
2459 static inline void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
2463 static inline void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
2466 #endif /* CONFIG_NUMA_BALANCING */
2469 account_entity_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2471 update_load_add(&cfs_rq
->load
, se
->load
.weight
);
2472 if (!parent_entity(se
))
2473 update_load_add(&rq_of(cfs_rq
)->load
, se
->load
.weight
);
2475 if (entity_is_task(se
)) {
2476 struct rq
*rq
= rq_of(cfs_rq
);
2478 account_numa_enqueue(rq
, task_of(se
));
2479 list_add(&se
->group_node
, &rq
->cfs_tasks
);
2482 cfs_rq
->nr_running
++;
2486 account_entity_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2488 update_load_sub(&cfs_rq
->load
, se
->load
.weight
);
2489 if (!parent_entity(se
))
2490 update_load_sub(&rq_of(cfs_rq
)->load
, se
->load
.weight
);
2492 if (entity_is_task(se
)) {
2493 account_numa_dequeue(rq_of(cfs_rq
), task_of(se
));
2494 list_del_init(&se
->group_node
);
2497 cfs_rq
->nr_running
--;
2500 #ifdef CONFIG_FAIR_GROUP_SCHED
2502 static inline long calc_tg_weight(struct task_group
*tg
, struct cfs_rq
*cfs_rq
)
2507 * Use this CPU's real-time load instead of the last load contribution
2508 * as the updating of the contribution is delayed, and we will use the
2509 * the real-time load to calc the share. See update_tg_load_avg().
2511 tg_weight
= atomic_long_read(&tg
->load_avg
);
2512 tg_weight
-= cfs_rq
->tg_load_avg_contrib
;
2513 tg_weight
+= cfs_rq
->load
.weight
;
2518 static long calc_cfs_shares(struct cfs_rq
*cfs_rq
, struct task_group
*tg
)
2520 long tg_weight
, load
, shares
;
2522 tg_weight
= calc_tg_weight(tg
, cfs_rq
);
2523 load
= cfs_rq
->load
.weight
;
2525 shares
= (tg
->shares
* load
);
2527 shares
/= tg_weight
;
2529 if (shares
< MIN_SHARES
)
2530 shares
= MIN_SHARES
;
2531 if (shares
> tg
->shares
)
2532 shares
= tg
->shares
;
2536 # else /* CONFIG_SMP */
2537 static inline long calc_cfs_shares(struct cfs_rq
*cfs_rq
, struct task_group
*tg
)
2541 # endif /* CONFIG_SMP */
2542 static void reweight_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
,
2543 unsigned long weight
)
2546 /* commit outstanding execution time */
2547 if (cfs_rq
->curr
== se
)
2548 update_curr(cfs_rq
);
2549 account_entity_dequeue(cfs_rq
, se
);
2552 update_load_set(&se
->load
, weight
);
2555 account_entity_enqueue(cfs_rq
, se
);
2558 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
);
2560 static void update_cfs_shares(struct cfs_rq
*cfs_rq
)
2562 struct task_group
*tg
;
2563 struct sched_entity
*se
;
2567 se
= tg
->se
[cpu_of(rq_of(cfs_rq
))];
2568 if (!se
|| throttled_hierarchy(cfs_rq
))
2571 if (likely(se
->load
.weight
== tg
->shares
))
2574 shares
= calc_cfs_shares(cfs_rq
, tg
);
2576 reweight_entity(cfs_rq_of(se
), se
, shares
);
2578 #else /* CONFIG_FAIR_GROUP_SCHED */
2579 static inline void update_cfs_shares(struct cfs_rq
*cfs_rq
)
2582 #endif /* CONFIG_FAIR_GROUP_SCHED */
2585 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2586 static const u32 runnable_avg_yN_inv
[] = {
2587 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2588 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2589 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2590 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2591 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2592 0x85aac367, 0x82cd8698,
2596 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2597 * over-estimates when re-combining.
2599 static const u32 runnable_avg_yN_sum
[] = {
2600 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2601 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2602 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2607 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2609 static __always_inline u64
decay_load(u64 val
, u64 n
)
2611 unsigned int local_n
;
2615 else if (unlikely(n
> LOAD_AVG_PERIOD
* 63))
2618 /* after bounds checking we can collapse to 32-bit */
2622 * As y^PERIOD = 1/2, we can combine
2623 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2624 * With a look-up table which covers y^n (n<PERIOD)
2626 * To achieve constant time decay_load.
2628 if (unlikely(local_n
>= LOAD_AVG_PERIOD
)) {
2629 val
>>= local_n
/ LOAD_AVG_PERIOD
;
2630 local_n
%= LOAD_AVG_PERIOD
;
2633 val
= mul_u64_u32_shr(val
, runnable_avg_yN_inv
[local_n
], 32);
2638 * For updates fully spanning n periods, the contribution to runnable
2639 * average will be: \Sum 1024*y^n
2641 * We can compute this reasonably efficiently by combining:
2642 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2644 static u32
__compute_runnable_contrib(u64 n
)
2648 if (likely(n
<= LOAD_AVG_PERIOD
))
2649 return runnable_avg_yN_sum
[n
];
2650 else if (unlikely(n
>= LOAD_AVG_MAX_N
))
2651 return LOAD_AVG_MAX
;
2653 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2655 contrib
/= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2656 contrib
+= runnable_avg_yN_sum
[LOAD_AVG_PERIOD
];
2658 n
-= LOAD_AVG_PERIOD
;
2659 } while (n
> LOAD_AVG_PERIOD
);
2661 contrib
= decay_load(contrib
, n
);
2662 return contrib
+ runnable_avg_yN_sum
[n
];
2665 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2668 * We can represent the historical contribution to runnable average as the
2669 * coefficients of a geometric series. To do this we sub-divide our runnable
2670 * history into segments of approximately 1ms (1024us); label the segment that
2671 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2673 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2675 * (now) (~1ms ago) (~2ms ago)
2677 * Let u_i denote the fraction of p_i that the entity was runnable.
2679 * We then designate the fractions u_i as our co-efficients, yielding the
2680 * following representation of historical load:
2681 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2683 * We choose y based on the with of a reasonably scheduling period, fixing:
2686 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2687 * approximately half as much as the contribution to load within the last ms
2690 * When a period "rolls over" and we have new u_0`, multiplying the previous
2691 * sum again by y is sufficient to update:
2692 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2693 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2695 static __always_inline
int
2696 __update_load_avg(u64 now
, int cpu
, struct sched_avg
*sa
,
2697 unsigned long weight
, int running
, struct cfs_rq
*cfs_rq
)
2699 u64 delta
, scaled_delta
, periods
;
2701 unsigned int delta_w
, scaled_delta_w
, decayed
= 0;
2702 unsigned long scale_freq
, scale_cpu
;
2704 delta
= now
- sa
->last_update_time
;
2706 * This should only happen when time goes backwards, which it
2707 * unfortunately does during sched clock init when we swap over to TSC.
2709 if ((s64
)delta
< 0) {
2710 sa
->last_update_time
= now
;
2715 * Use 1024ns as the unit of measurement since it's a reasonable
2716 * approximation of 1us and fast to compute.
2721 sa
->last_update_time
= now
;
2723 scale_freq
= arch_scale_freq_capacity(NULL
, cpu
);
2724 scale_cpu
= arch_scale_cpu_capacity(NULL
, cpu
);
2726 /* delta_w is the amount already accumulated against our next period */
2727 delta_w
= sa
->period_contrib
;
2728 if (delta
+ delta_w
>= 1024) {
2731 /* how much left for next period will start over, we don't know yet */
2732 sa
->period_contrib
= 0;
2735 * Now that we know we're crossing a period boundary, figure
2736 * out how much from delta we need to complete the current
2737 * period and accrue it.
2739 delta_w
= 1024 - delta_w
;
2740 scaled_delta_w
= cap_scale(delta_w
, scale_freq
);
2742 sa
->load_sum
+= weight
* scaled_delta_w
;
2744 cfs_rq
->runnable_load_sum
+=
2745 weight
* scaled_delta_w
;
2749 sa
->util_sum
+= scaled_delta_w
* scale_cpu
;
2753 /* Figure out how many additional periods this update spans */
2754 periods
= delta
/ 1024;
2757 sa
->load_sum
= decay_load(sa
->load_sum
, periods
+ 1);
2759 cfs_rq
->runnable_load_sum
=
2760 decay_load(cfs_rq
->runnable_load_sum
, periods
+ 1);
2762 sa
->util_sum
= decay_load((u64
)(sa
->util_sum
), periods
+ 1);
2764 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2765 contrib
= __compute_runnable_contrib(periods
);
2766 contrib
= cap_scale(contrib
, scale_freq
);
2768 sa
->load_sum
+= weight
* contrib
;
2770 cfs_rq
->runnable_load_sum
+= weight
* contrib
;
2773 sa
->util_sum
+= contrib
* scale_cpu
;
2776 /* Remainder of delta accrued against u_0` */
2777 scaled_delta
= cap_scale(delta
, scale_freq
);
2779 sa
->load_sum
+= weight
* scaled_delta
;
2781 cfs_rq
->runnable_load_sum
+= weight
* scaled_delta
;
2784 sa
->util_sum
+= scaled_delta
* scale_cpu
;
2786 sa
->period_contrib
+= delta
;
2789 sa
->load_avg
= div_u64(sa
->load_sum
, LOAD_AVG_MAX
);
2791 cfs_rq
->runnable_load_avg
=
2792 div_u64(cfs_rq
->runnable_load_sum
, LOAD_AVG_MAX
);
2794 sa
->util_avg
= sa
->util_sum
/ LOAD_AVG_MAX
;
2800 #ifdef CONFIG_FAIR_GROUP_SCHED
2802 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2803 * and effective_load (which is not done because it is too costly).
2805 static inline void update_tg_load_avg(struct cfs_rq
*cfs_rq
, int force
)
2807 long delta
= cfs_rq
->avg
.load_avg
- cfs_rq
->tg_load_avg_contrib
;
2810 * No need to update load_avg for root_task_group as it is not used.
2812 if (cfs_rq
->tg
== &root_task_group
)
2815 if (force
|| abs(delta
) > cfs_rq
->tg_load_avg_contrib
/ 64) {
2816 atomic_long_add(delta
, &cfs_rq
->tg
->load_avg
);
2817 cfs_rq
->tg_load_avg_contrib
= cfs_rq
->avg
.load_avg
;
2822 * Called within set_task_rq() right before setting a task's cpu. The
2823 * caller only guarantees p->pi_lock is held; no other assumptions,
2824 * including the state of rq->lock, should be made.
2826 void set_task_rq_fair(struct sched_entity
*se
,
2827 struct cfs_rq
*prev
, struct cfs_rq
*next
)
2829 if (!sched_feat(ATTACH_AGE_LOAD
))
2833 * We are supposed to update the task to "current" time, then its up to
2834 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
2835 * getting what current time is, so simply throw away the out-of-date
2836 * time. This will result in the wakee task is less decayed, but giving
2837 * the wakee more load sounds not bad.
2839 if (se
->avg
.last_update_time
&& prev
) {
2840 u64 p_last_update_time
;
2841 u64 n_last_update_time
;
2843 #ifndef CONFIG_64BIT
2844 u64 p_last_update_time_copy
;
2845 u64 n_last_update_time_copy
;
2848 p_last_update_time_copy
= prev
->load_last_update_time_copy
;
2849 n_last_update_time_copy
= next
->load_last_update_time_copy
;
2853 p_last_update_time
= prev
->avg
.last_update_time
;
2854 n_last_update_time
= next
->avg
.last_update_time
;
2856 } while (p_last_update_time
!= p_last_update_time_copy
||
2857 n_last_update_time
!= n_last_update_time_copy
);
2859 p_last_update_time
= prev
->avg
.last_update_time
;
2860 n_last_update_time
= next
->avg
.last_update_time
;
2862 __update_load_avg(p_last_update_time
, cpu_of(rq_of(prev
)),
2863 &se
->avg
, 0, 0, NULL
);
2864 se
->avg
.last_update_time
= n_last_update_time
;
2867 #else /* CONFIG_FAIR_GROUP_SCHED */
2868 static inline void update_tg_load_avg(struct cfs_rq
*cfs_rq
, int force
) {}
2869 #endif /* CONFIG_FAIR_GROUP_SCHED */
2871 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
);
2873 static inline void cfs_rq_util_change(struct cfs_rq
*cfs_rq
)
2875 struct rq
*rq
= rq_of(cfs_rq
);
2876 int cpu
= cpu_of(rq
);
2878 if (cpu
== smp_processor_id() && &rq
->cfs
== cfs_rq
) {
2879 unsigned long max
= rq
->cpu_capacity_orig
;
2882 * There are a few boundary cases this might miss but it should
2883 * get called often enough that that should (hopefully) not be
2884 * a real problem -- added to that it only calls on the local
2885 * CPU, so if we enqueue remotely we'll miss an update, but
2886 * the next tick/schedule should update.
2888 * It will not get called when we go idle, because the idle
2889 * thread is a different class (!fair), nor will the utilization
2890 * number include things like RT tasks.
2892 * As is, the util number is not freq-invariant (we'd have to
2893 * implement arch_scale_freq_capacity() for that).
2897 cpufreq_update_util(rq_clock(rq
),
2898 min(cfs_rq
->avg
.util_avg
, max
), max
);
2902 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2904 update_cfs_rq_load_avg(u64 now
, struct cfs_rq
*cfs_rq
, bool update_freq
)
2906 struct sched_avg
*sa
= &cfs_rq
->avg
;
2907 int decayed
, removed_load
= 0, removed_util
= 0;
2909 if (atomic_long_read(&cfs_rq
->removed_load_avg
)) {
2910 s64 r
= atomic_long_xchg(&cfs_rq
->removed_load_avg
, 0);
2911 sa
->load_avg
= max_t(long, sa
->load_avg
- r
, 0);
2912 sa
->load_sum
= max_t(s64
, sa
->load_sum
- r
* LOAD_AVG_MAX
, 0);
2916 if (atomic_long_read(&cfs_rq
->removed_util_avg
)) {
2917 long r
= atomic_long_xchg(&cfs_rq
->removed_util_avg
, 0);
2918 sa
->util_avg
= max_t(long, sa
->util_avg
- r
, 0);
2919 sa
->util_sum
= max_t(s32
, sa
->util_sum
- r
* LOAD_AVG_MAX
, 0);
2923 decayed
= __update_load_avg(now
, cpu_of(rq_of(cfs_rq
)), sa
,
2924 scale_load_down(cfs_rq
->load
.weight
), cfs_rq
->curr
!= NULL
, cfs_rq
);
2926 #ifndef CONFIG_64BIT
2928 cfs_rq
->load_last_update_time_copy
= sa
->last_update_time
;
2931 if (update_freq
&& (decayed
|| removed_util
))
2932 cfs_rq_util_change(cfs_rq
);
2934 return decayed
|| removed_load
;
2937 /* Update task and its cfs_rq load average */
2938 static inline void update_load_avg(struct sched_entity
*se
, int update_tg
)
2940 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
2941 u64 now
= cfs_rq_clock_task(cfs_rq
);
2942 struct rq
*rq
= rq_of(cfs_rq
);
2943 int cpu
= cpu_of(rq
);
2946 * Track task load average for carrying it to new CPU after migrated, and
2947 * track group sched_entity load average for task_h_load calc in migration
2949 __update_load_avg(now
, cpu
, &se
->avg
,
2950 se
->on_rq
* scale_load_down(se
->load
.weight
),
2951 cfs_rq
->curr
== se
, NULL
);
2953 if (update_cfs_rq_load_avg(now
, cfs_rq
, true) && update_tg
)
2954 update_tg_load_avg(cfs_rq
, 0);
2957 static void attach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2959 if (!sched_feat(ATTACH_AGE_LOAD
))
2963 * If we got migrated (either between CPUs or between cgroups) we'll
2964 * have aged the average right before clearing @last_update_time.
2966 if (se
->avg
.last_update_time
) {
2967 __update_load_avg(cfs_rq
->avg
.last_update_time
, cpu_of(rq_of(cfs_rq
)),
2968 &se
->avg
, 0, 0, NULL
);
2971 * XXX: we could have just aged the entire load away if we've been
2972 * absent from the fair class for too long.
2977 se
->avg
.last_update_time
= cfs_rq
->avg
.last_update_time
;
2978 cfs_rq
->avg
.load_avg
+= se
->avg
.load_avg
;
2979 cfs_rq
->avg
.load_sum
+= se
->avg
.load_sum
;
2980 cfs_rq
->avg
.util_avg
+= se
->avg
.util_avg
;
2981 cfs_rq
->avg
.util_sum
+= se
->avg
.util_sum
;
2983 cfs_rq_util_change(cfs_rq
);
2986 static void detach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2988 __update_load_avg(cfs_rq
->avg
.last_update_time
, cpu_of(rq_of(cfs_rq
)),
2989 &se
->avg
, se
->on_rq
* scale_load_down(se
->load
.weight
),
2990 cfs_rq
->curr
== se
, NULL
);
2992 cfs_rq
->avg
.load_avg
= max_t(long, cfs_rq
->avg
.load_avg
- se
->avg
.load_avg
, 0);
2993 cfs_rq
->avg
.load_sum
= max_t(s64
, cfs_rq
->avg
.load_sum
- se
->avg
.load_sum
, 0);
2994 cfs_rq
->avg
.util_avg
= max_t(long, cfs_rq
->avg
.util_avg
- se
->avg
.util_avg
, 0);
2995 cfs_rq
->avg
.util_sum
= max_t(s32
, cfs_rq
->avg
.util_sum
- se
->avg
.util_sum
, 0);
2997 cfs_rq_util_change(cfs_rq
);
3000 /* Add the load generated by se into cfs_rq's load average */
3002 enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3004 struct sched_avg
*sa
= &se
->avg
;
3005 u64 now
= cfs_rq_clock_task(cfs_rq
);
3006 int migrated
, decayed
;
3008 migrated
= !sa
->last_update_time
;
3010 __update_load_avg(now
, cpu_of(rq_of(cfs_rq
)), sa
,
3011 se
->on_rq
* scale_load_down(se
->load
.weight
),
3012 cfs_rq
->curr
== se
, NULL
);
3015 decayed
= update_cfs_rq_load_avg(now
, cfs_rq
, !migrated
);
3017 cfs_rq
->runnable_load_avg
+= sa
->load_avg
;
3018 cfs_rq
->runnable_load_sum
+= sa
->load_sum
;
3021 attach_entity_load_avg(cfs_rq
, se
);
3023 if (decayed
|| migrated
)
3024 update_tg_load_avg(cfs_rq
, 0);
3027 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
3029 dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3031 update_load_avg(se
, 1);
3033 cfs_rq
->runnable_load_avg
=
3034 max_t(long, cfs_rq
->runnable_load_avg
- se
->avg
.load_avg
, 0);
3035 cfs_rq
->runnable_load_sum
=
3036 max_t(s64
, cfs_rq
->runnable_load_sum
- se
->avg
.load_sum
, 0);
3039 #ifndef CONFIG_64BIT
3040 static inline u64
cfs_rq_last_update_time(struct cfs_rq
*cfs_rq
)
3042 u64 last_update_time_copy
;
3043 u64 last_update_time
;
3046 last_update_time_copy
= cfs_rq
->load_last_update_time_copy
;
3048 last_update_time
= cfs_rq
->avg
.last_update_time
;
3049 } while (last_update_time
!= last_update_time_copy
);
3051 return last_update_time
;
3054 static inline u64
cfs_rq_last_update_time(struct cfs_rq
*cfs_rq
)
3056 return cfs_rq
->avg
.last_update_time
;
3061 * Task first catches up with cfs_rq, and then subtract
3062 * itself from the cfs_rq (task must be off the queue now).
3064 void remove_entity_load_avg(struct sched_entity
*se
)
3066 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3067 u64 last_update_time
;
3070 * Newly created task or never used group entity should not be removed
3071 * from its (source) cfs_rq
3073 if (se
->avg
.last_update_time
== 0)
3076 last_update_time
= cfs_rq_last_update_time(cfs_rq
);
3078 __update_load_avg(last_update_time
, cpu_of(rq_of(cfs_rq
)), &se
->avg
, 0, 0, NULL
);
3079 atomic_long_add(se
->avg
.load_avg
, &cfs_rq
->removed_load_avg
);
3080 atomic_long_add(se
->avg
.util_avg
, &cfs_rq
->removed_util_avg
);
3083 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq
*cfs_rq
)
3085 return cfs_rq
->runnable_load_avg
;
3088 static inline unsigned long cfs_rq_load_avg(struct cfs_rq
*cfs_rq
)
3090 return cfs_rq
->avg
.load_avg
;
3093 static int idle_balance(struct rq
*this_rq
);
3095 #else /* CONFIG_SMP */
3097 static inline void update_load_avg(struct sched_entity
*se
, int update_tg
) {}
3099 enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3101 dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3102 static inline void remove_entity_load_avg(struct sched_entity
*se
) {}
3105 attach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3107 detach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3109 static inline int idle_balance(struct rq
*rq
)
3114 #endif /* CONFIG_SMP */
3116 static void enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3118 #ifdef CONFIG_SCHEDSTATS
3119 struct task_struct
*tsk
= NULL
;
3121 if (entity_is_task(se
))
3124 if (se
->statistics
.sleep_start
) {
3125 u64 delta
= rq_clock(rq_of(cfs_rq
)) - se
->statistics
.sleep_start
;
3130 if (unlikely(delta
> se
->statistics
.sleep_max
))
3131 se
->statistics
.sleep_max
= delta
;
3133 se
->statistics
.sleep_start
= 0;
3134 se
->statistics
.sum_sleep_runtime
+= delta
;
3137 account_scheduler_latency(tsk
, delta
>> 10, 1);
3138 trace_sched_stat_sleep(tsk
, delta
);
3141 if (se
->statistics
.block_start
) {
3142 u64 delta
= rq_clock(rq_of(cfs_rq
)) - se
->statistics
.block_start
;
3147 if (unlikely(delta
> se
->statistics
.block_max
))
3148 se
->statistics
.block_max
= delta
;
3150 se
->statistics
.block_start
= 0;
3151 se
->statistics
.sum_sleep_runtime
+= delta
;
3154 if (tsk
->in_iowait
) {
3155 se
->statistics
.iowait_sum
+= delta
;
3156 se
->statistics
.iowait_count
++;
3157 trace_sched_stat_iowait(tsk
, delta
);
3160 trace_sched_stat_blocked(tsk
, delta
);
3163 * Blocking time is in units of nanosecs, so shift by
3164 * 20 to get a milliseconds-range estimation of the
3165 * amount of time that the task spent sleeping:
3167 if (unlikely(prof_on
== SLEEP_PROFILING
)) {
3168 profile_hits(SLEEP_PROFILING
,
3169 (void *)get_wchan(tsk
),
3172 account_scheduler_latency(tsk
, delta
>> 10, 0);
3178 static void check_spread(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3180 #ifdef CONFIG_SCHED_DEBUG
3181 s64 d
= se
->vruntime
- cfs_rq
->min_vruntime
;
3186 if (d
> 3*sysctl_sched_latency
)
3187 schedstat_inc(cfs_rq
, nr_spread_over
);
3192 place_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int initial
)
3194 u64 vruntime
= cfs_rq
->min_vruntime
;
3197 * The 'current' period is already promised to the current tasks,
3198 * however the extra weight of the new task will slow them down a
3199 * little, place the new task so that it fits in the slot that
3200 * stays open at the end.
3202 if (initial
&& sched_feat(START_DEBIT
))
3203 vruntime
+= sched_vslice(cfs_rq
, se
);
3205 /* sleeps up to a single latency don't count. */
3207 unsigned long thresh
= sysctl_sched_latency
;
3210 * Halve their sleep time's effect, to allow
3211 * for a gentler effect of sleepers:
3213 if (sched_feat(GENTLE_FAIR_SLEEPERS
))
3219 /* ensure we never gain time by being placed backwards. */
3220 se
->vruntime
= max_vruntime(se
->vruntime
, vruntime
);
3223 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
);
3225 static inline void check_schedstat_required(void)
3227 #ifdef CONFIG_SCHEDSTATS
3228 if (schedstat_enabled())
3231 /* Force schedstat enabled if a dependent tracepoint is active */
3232 if (trace_sched_stat_wait_enabled() ||
3233 trace_sched_stat_sleep_enabled() ||
3234 trace_sched_stat_iowait_enabled() ||
3235 trace_sched_stat_blocked_enabled() ||
3236 trace_sched_stat_runtime_enabled()) {
3237 pr_warn_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3238 "stat_blocked and stat_runtime require the "
3239 "kernel parameter schedstats=enabled or "
3240 "kernel.sched_schedstats=1\n");
3246 enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3248 bool renorm
= !(flags
& ENQUEUE_WAKEUP
) || (flags
& ENQUEUE_WAKING
);
3249 bool curr
= cfs_rq
->curr
== se
;
3252 * If we're the current task, we must renormalise before calling
3256 se
->vruntime
+= cfs_rq
->min_vruntime
;
3258 update_curr(cfs_rq
);
3261 * Otherwise, renormalise after, such that we're placed at the current
3262 * moment in time, instead of some random moment in the past.
3264 if (renorm
&& !curr
)
3265 se
->vruntime
+= cfs_rq
->min_vruntime
;
3267 enqueue_entity_load_avg(cfs_rq
, se
);
3268 account_entity_enqueue(cfs_rq
, se
);
3269 update_cfs_shares(cfs_rq
);
3271 if (flags
& ENQUEUE_WAKEUP
) {
3272 place_entity(cfs_rq
, se
, 0);
3273 if (schedstat_enabled())
3274 enqueue_sleeper(cfs_rq
, se
);
3277 check_schedstat_required();
3278 if (schedstat_enabled()) {
3279 update_stats_enqueue(cfs_rq
, se
);
3280 check_spread(cfs_rq
, se
);
3283 __enqueue_entity(cfs_rq
, se
);
3286 if (cfs_rq
->nr_running
== 1) {
3287 list_add_leaf_cfs_rq(cfs_rq
);
3288 check_enqueue_throttle(cfs_rq
);
3292 static void __clear_buddies_last(struct sched_entity
*se
)
3294 for_each_sched_entity(se
) {
3295 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3296 if (cfs_rq
->last
!= se
)
3299 cfs_rq
->last
= NULL
;
3303 static void __clear_buddies_next(struct sched_entity
*se
)
3305 for_each_sched_entity(se
) {
3306 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3307 if (cfs_rq
->next
!= se
)
3310 cfs_rq
->next
= NULL
;
3314 static void __clear_buddies_skip(struct sched_entity
*se
)
3316 for_each_sched_entity(se
) {
3317 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3318 if (cfs_rq
->skip
!= se
)
3321 cfs_rq
->skip
= NULL
;
3325 static void clear_buddies(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3327 if (cfs_rq
->last
== se
)
3328 __clear_buddies_last(se
);
3330 if (cfs_rq
->next
== se
)
3331 __clear_buddies_next(se
);
3333 if (cfs_rq
->skip
== se
)
3334 __clear_buddies_skip(se
);
3337 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
3340 dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3343 * Update run-time statistics of the 'current'.
3345 update_curr(cfs_rq
);
3346 dequeue_entity_load_avg(cfs_rq
, se
);
3348 if (schedstat_enabled())
3349 update_stats_dequeue(cfs_rq
, se
, flags
);
3351 clear_buddies(cfs_rq
, se
);
3353 if (se
!= cfs_rq
->curr
)
3354 __dequeue_entity(cfs_rq
, se
);
3356 account_entity_dequeue(cfs_rq
, se
);
3359 * Normalize the entity after updating the min_vruntime because the
3360 * update can refer to the ->curr item and we need to reflect this
3361 * movement in our normalized position.
3363 if (!(flags
& DEQUEUE_SLEEP
))
3364 se
->vruntime
-= cfs_rq
->min_vruntime
;
3366 /* return excess runtime on last dequeue */
3367 return_cfs_rq_runtime(cfs_rq
);
3369 update_min_vruntime(cfs_rq
);
3370 update_cfs_shares(cfs_rq
);
3374 * Preempt the current task with a newly woken task if needed:
3377 check_preempt_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
3379 unsigned long ideal_runtime
, delta_exec
;
3380 struct sched_entity
*se
;
3383 ideal_runtime
= sched_slice(cfs_rq
, curr
);
3384 delta_exec
= curr
->sum_exec_runtime
- curr
->prev_sum_exec_runtime
;
3385 if (delta_exec
> ideal_runtime
) {
3386 resched_curr(rq_of(cfs_rq
));
3388 * The current task ran long enough, ensure it doesn't get
3389 * re-elected due to buddy favours.
3391 clear_buddies(cfs_rq
, curr
);
3396 * Ensure that a task that missed wakeup preemption by a
3397 * narrow margin doesn't have to wait for a full slice.
3398 * This also mitigates buddy induced latencies under load.
3400 if (delta_exec
< sysctl_sched_min_granularity
)
3403 se
= __pick_first_entity(cfs_rq
);
3404 delta
= curr
->vruntime
- se
->vruntime
;
3409 if (delta
> ideal_runtime
)
3410 resched_curr(rq_of(cfs_rq
));
3414 set_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3416 /* 'current' is not kept within the tree. */
3419 * Any task has to be enqueued before it get to execute on
3420 * a CPU. So account for the time it spent waiting on the
3423 if (schedstat_enabled())
3424 update_stats_wait_end(cfs_rq
, se
);
3425 __dequeue_entity(cfs_rq
, se
);
3426 update_load_avg(se
, 1);
3429 update_stats_curr_start(cfs_rq
, se
);
3431 #ifdef CONFIG_SCHEDSTATS
3433 * Track our maximum slice length, if the CPU's load is at
3434 * least twice that of our own weight (i.e. dont track it
3435 * when there are only lesser-weight tasks around):
3437 if (schedstat_enabled() && rq_of(cfs_rq
)->load
.weight
>= 2*se
->load
.weight
) {
3438 se
->statistics
.slice_max
= max(se
->statistics
.slice_max
,
3439 se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
);
3442 se
->prev_sum_exec_runtime
= se
->sum_exec_runtime
;
3446 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
);
3449 * Pick the next process, keeping these things in mind, in this order:
3450 * 1) keep things fair between processes/task groups
3451 * 2) pick the "next" process, since someone really wants that to run
3452 * 3) pick the "last" process, for cache locality
3453 * 4) do not run the "skip" process, if something else is available
3455 static struct sched_entity
*
3456 pick_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
3458 struct sched_entity
*left
= __pick_first_entity(cfs_rq
);
3459 struct sched_entity
*se
;
3462 * If curr is set we have to see if its left of the leftmost entity
3463 * still in the tree, provided there was anything in the tree at all.
3465 if (!left
|| (curr
&& entity_before(curr
, left
)))
3468 se
= left
; /* ideally we run the leftmost entity */
3471 * Avoid running the skip buddy, if running something else can
3472 * be done without getting too unfair.
3474 if (cfs_rq
->skip
== se
) {
3475 struct sched_entity
*second
;
3478 second
= __pick_first_entity(cfs_rq
);
3480 second
= __pick_next_entity(se
);
3481 if (!second
|| (curr
&& entity_before(curr
, second
)))
3485 if (second
&& wakeup_preempt_entity(second
, left
) < 1)
3490 * Prefer last buddy, try to return the CPU to a preempted task.
3492 if (cfs_rq
->last
&& wakeup_preempt_entity(cfs_rq
->last
, left
) < 1)
3496 * Someone really wants this to run. If it's not unfair, run it.
3498 if (cfs_rq
->next
&& wakeup_preempt_entity(cfs_rq
->next
, left
) < 1)
3501 clear_buddies(cfs_rq
, se
);
3506 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
3508 static void put_prev_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*prev
)
3511 * If still on the runqueue then deactivate_task()
3512 * was not called and update_curr() has to be done:
3515 update_curr(cfs_rq
);
3517 /* throttle cfs_rqs exceeding runtime */
3518 check_cfs_rq_runtime(cfs_rq
);
3520 if (schedstat_enabled()) {
3521 check_spread(cfs_rq
, prev
);
3523 update_stats_wait_start(cfs_rq
, prev
);
3527 /* Put 'current' back into the tree. */
3528 __enqueue_entity(cfs_rq
, prev
);
3529 /* in !on_rq case, update occurred at dequeue */
3530 update_load_avg(prev
, 0);
3532 cfs_rq
->curr
= NULL
;
3536 entity_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
, int queued
)
3539 * Update run-time statistics of the 'current'.
3541 update_curr(cfs_rq
);
3544 * Ensure that runnable average is periodically updated.
3546 update_load_avg(curr
, 1);
3547 update_cfs_shares(cfs_rq
);
3549 #ifdef CONFIG_SCHED_HRTICK
3551 * queued ticks are scheduled to match the slice, so don't bother
3552 * validating it and just reschedule.
3555 resched_curr(rq_of(cfs_rq
));
3559 * don't let the period tick interfere with the hrtick preemption
3561 if (!sched_feat(DOUBLE_TICK
) &&
3562 hrtimer_active(&rq_of(cfs_rq
)->hrtick_timer
))
3566 if (cfs_rq
->nr_running
> 1)
3567 check_preempt_tick(cfs_rq
, curr
);
3571 /**************************************************
3572 * CFS bandwidth control machinery
3575 #ifdef CONFIG_CFS_BANDWIDTH
3577 #ifdef HAVE_JUMP_LABEL
3578 static struct static_key __cfs_bandwidth_used
;
3580 static inline bool cfs_bandwidth_used(void)
3582 return static_key_false(&__cfs_bandwidth_used
);
3585 void cfs_bandwidth_usage_inc(void)
3587 static_key_slow_inc(&__cfs_bandwidth_used
);
3590 void cfs_bandwidth_usage_dec(void)
3592 static_key_slow_dec(&__cfs_bandwidth_used
);
3594 #else /* HAVE_JUMP_LABEL */
3595 static bool cfs_bandwidth_used(void)
3600 void cfs_bandwidth_usage_inc(void) {}
3601 void cfs_bandwidth_usage_dec(void) {}
3602 #endif /* HAVE_JUMP_LABEL */
3605 * default period for cfs group bandwidth.
3606 * default: 0.1s, units: nanoseconds
3608 static inline u64
default_cfs_period(void)
3610 return 100000000ULL;
3613 static inline u64
sched_cfs_bandwidth_slice(void)
3615 return (u64
)sysctl_sched_cfs_bandwidth_slice
* NSEC_PER_USEC
;
3619 * Replenish runtime according to assigned quota and update expiration time.
3620 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3621 * additional synchronization around rq->lock.
3623 * requires cfs_b->lock
3625 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth
*cfs_b
)
3629 if (cfs_b
->quota
== RUNTIME_INF
)
3632 now
= sched_clock_cpu(smp_processor_id());
3633 cfs_b
->runtime
= cfs_b
->quota
;
3634 cfs_b
->runtime_expires
= now
+ ktime_to_ns(cfs_b
->period
);
3637 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
3639 return &tg
->cfs_bandwidth
;
3642 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3643 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
3645 if (unlikely(cfs_rq
->throttle_count
))
3646 return cfs_rq
->throttled_clock_task
;
3648 return rq_clock_task(rq_of(cfs_rq
)) - cfs_rq
->throttled_clock_task_time
;
3651 /* returns 0 on failure to allocate runtime */
3652 static int assign_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3654 struct task_group
*tg
= cfs_rq
->tg
;
3655 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(tg
);
3656 u64 amount
= 0, min_amount
, expires
;
3658 /* note: this is a positive sum as runtime_remaining <= 0 */
3659 min_amount
= sched_cfs_bandwidth_slice() - cfs_rq
->runtime_remaining
;
3661 raw_spin_lock(&cfs_b
->lock
);
3662 if (cfs_b
->quota
== RUNTIME_INF
)
3663 amount
= min_amount
;
3665 start_cfs_bandwidth(cfs_b
);
3667 if (cfs_b
->runtime
> 0) {
3668 amount
= min(cfs_b
->runtime
, min_amount
);
3669 cfs_b
->runtime
-= amount
;
3673 expires
= cfs_b
->runtime_expires
;
3674 raw_spin_unlock(&cfs_b
->lock
);
3676 cfs_rq
->runtime_remaining
+= amount
;
3678 * we may have advanced our local expiration to account for allowed
3679 * spread between our sched_clock and the one on which runtime was
3682 if ((s64
)(expires
- cfs_rq
->runtime_expires
) > 0)
3683 cfs_rq
->runtime_expires
= expires
;
3685 return cfs_rq
->runtime_remaining
> 0;
3689 * Note: This depends on the synchronization provided by sched_clock and the
3690 * fact that rq->clock snapshots this value.
3692 static void expire_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3694 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3696 /* if the deadline is ahead of our clock, nothing to do */
3697 if (likely((s64
)(rq_clock(rq_of(cfs_rq
)) - cfs_rq
->runtime_expires
) < 0))
3700 if (cfs_rq
->runtime_remaining
< 0)
3704 * If the local deadline has passed we have to consider the
3705 * possibility that our sched_clock is 'fast' and the global deadline
3706 * has not truly expired.
3708 * Fortunately we can check determine whether this the case by checking
3709 * whether the global deadline has advanced. It is valid to compare
3710 * cfs_b->runtime_expires without any locks since we only care about
3711 * exact equality, so a partial write will still work.
3714 if (cfs_rq
->runtime_expires
!= cfs_b
->runtime_expires
) {
3715 /* extend local deadline, drift is bounded above by 2 ticks */
3716 cfs_rq
->runtime_expires
+= TICK_NSEC
;
3718 /* global deadline is ahead, expiration has passed */
3719 cfs_rq
->runtime_remaining
= 0;
3723 static void __account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
3725 /* dock delta_exec before expiring quota (as it could span periods) */
3726 cfs_rq
->runtime_remaining
-= delta_exec
;
3727 expire_cfs_rq_runtime(cfs_rq
);
3729 if (likely(cfs_rq
->runtime_remaining
> 0))
3733 * if we're unable to extend our runtime we resched so that the active
3734 * hierarchy can be throttled
3736 if (!assign_cfs_rq_runtime(cfs_rq
) && likely(cfs_rq
->curr
))
3737 resched_curr(rq_of(cfs_rq
));
3740 static __always_inline
3741 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
3743 if (!cfs_bandwidth_used() || !cfs_rq
->runtime_enabled
)
3746 __account_cfs_rq_runtime(cfs_rq
, delta_exec
);
3749 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
3751 return cfs_bandwidth_used() && cfs_rq
->throttled
;
3754 /* check whether cfs_rq, or any parent, is throttled */
3755 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
3757 return cfs_bandwidth_used() && cfs_rq
->throttle_count
;
3761 * Ensure that neither of the group entities corresponding to src_cpu or
3762 * dest_cpu are members of a throttled hierarchy when performing group
3763 * load-balance operations.
3765 static inline int throttled_lb_pair(struct task_group
*tg
,
3766 int src_cpu
, int dest_cpu
)
3768 struct cfs_rq
*src_cfs_rq
, *dest_cfs_rq
;
3770 src_cfs_rq
= tg
->cfs_rq
[src_cpu
];
3771 dest_cfs_rq
= tg
->cfs_rq
[dest_cpu
];
3773 return throttled_hierarchy(src_cfs_rq
) ||
3774 throttled_hierarchy(dest_cfs_rq
);
3777 /* updated child weight may affect parent so we have to do this bottom up */
3778 static int tg_unthrottle_up(struct task_group
*tg
, void *data
)
3780 struct rq
*rq
= data
;
3781 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
3783 cfs_rq
->throttle_count
--;
3785 if (!cfs_rq
->throttle_count
) {
3786 /* adjust cfs_rq_clock_task() */
3787 cfs_rq
->throttled_clock_task_time
+= rq_clock_task(rq
) -
3788 cfs_rq
->throttled_clock_task
;
3795 static int tg_throttle_down(struct task_group
*tg
, void *data
)
3797 struct rq
*rq
= data
;
3798 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
3800 /* group is entering throttled state, stop time */
3801 if (!cfs_rq
->throttle_count
)
3802 cfs_rq
->throttled_clock_task
= rq_clock_task(rq
);
3803 cfs_rq
->throttle_count
++;
3808 static void throttle_cfs_rq(struct cfs_rq
*cfs_rq
)
3810 struct rq
*rq
= rq_of(cfs_rq
);
3811 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3812 struct sched_entity
*se
;
3813 long task_delta
, dequeue
= 1;
3816 se
= cfs_rq
->tg
->se
[cpu_of(rq_of(cfs_rq
))];
3818 /* freeze hierarchy runnable averages while throttled */
3820 walk_tg_tree_from(cfs_rq
->tg
, tg_throttle_down
, tg_nop
, (void *)rq
);
3823 task_delta
= cfs_rq
->h_nr_running
;
3824 for_each_sched_entity(se
) {
3825 struct cfs_rq
*qcfs_rq
= cfs_rq_of(se
);
3826 /* throttled entity or throttle-on-deactivate */
3831 dequeue_entity(qcfs_rq
, se
, DEQUEUE_SLEEP
);
3832 qcfs_rq
->h_nr_running
-= task_delta
;
3834 if (qcfs_rq
->load
.weight
)
3839 sub_nr_running(rq
, task_delta
);
3841 cfs_rq
->throttled
= 1;
3842 cfs_rq
->throttled_clock
= rq_clock(rq
);
3843 raw_spin_lock(&cfs_b
->lock
);
3844 empty
= list_empty(&cfs_b
->throttled_cfs_rq
);
3847 * Add to the _head_ of the list, so that an already-started
3848 * distribute_cfs_runtime will not see us
3850 list_add_rcu(&cfs_rq
->throttled_list
, &cfs_b
->throttled_cfs_rq
);
3853 * If we're the first throttled task, make sure the bandwidth
3857 start_cfs_bandwidth(cfs_b
);
3859 raw_spin_unlock(&cfs_b
->lock
);
3862 void unthrottle_cfs_rq(struct cfs_rq
*cfs_rq
)
3864 struct rq
*rq
= rq_of(cfs_rq
);
3865 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3866 struct sched_entity
*se
;
3870 se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
3872 cfs_rq
->throttled
= 0;
3874 update_rq_clock(rq
);
3876 raw_spin_lock(&cfs_b
->lock
);
3877 cfs_b
->throttled_time
+= rq_clock(rq
) - cfs_rq
->throttled_clock
;
3878 list_del_rcu(&cfs_rq
->throttled_list
);
3879 raw_spin_unlock(&cfs_b
->lock
);
3881 /* update hierarchical throttle state */
3882 walk_tg_tree_from(cfs_rq
->tg
, tg_nop
, tg_unthrottle_up
, (void *)rq
);
3884 if (!cfs_rq
->load
.weight
)
3887 task_delta
= cfs_rq
->h_nr_running
;
3888 for_each_sched_entity(se
) {
3892 cfs_rq
= cfs_rq_of(se
);
3894 enqueue_entity(cfs_rq
, se
, ENQUEUE_WAKEUP
);
3895 cfs_rq
->h_nr_running
+= task_delta
;
3897 if (cfs_rq_throttled(cfs_rq
))
3902 add_nr_running(rq
, task_delta
);
3904 /* determine whether we need to wake up potentially idle cpu */
3905 if (rq
->curr
== rq
->idle
&& rq
->cfs
.nr_running
)
3909 static u64
distribute_cfs_runtime(struct cfs_bandwidth
*cfs_b
,
3910 u64 remaining
, u64 expires
)
3912 struct cfs_rq
*cfs_rq
;
3914 u64 starting_runtime
= remaining
;
3917 list_for_each_entry_rcu(cfs_rq
, &cfs_b
->throttled_cfs_rq
,
3919 struct rq
*rq
= rq_of(cfs_rq
);
3921 raw_spin_lock(&rq
->lock
);
3922 if (!cfs_rq_throttled(cfs_rq
))
3925 runtime
= -cfs_rq
->runtime_remaining
+ 1;
3926 if (runtime
> remaining
)
3927 runtime
= remaining
;
3928 remaining
-= runtime
;
3930 cfs_rq
->runtime_remaining
+= runtime
;
3931 cfs_rq
->runtime_expires
= expires
;
3933 /* we check whether we're throttled above */
3934 if (cfs_rq
->runtime_remaining
> 0)
3935 unthrottle_cfs_rq(cfs_rq
);
3938 raw_spin_unlock(&rq
->lock
);
3945 return starting_runtime
- remaining
;
3949 * Responsible for refilling a task_group's bandwidth and unthrottling its
3950 * cfs_rqs as appropriate. If there has been no activity within the last
3951 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3952 * used to track this state.
3954 static int do_sched_cfs_period_timer(struct cfs_bandwidth
*cfs_b
, int overrun
)
3956 u64 runtime
, runtime_expires
;
3959 /* no need to continue the timer with no bandwidth constraint */
3960 if (cfs_b
->quota
== RUNTIME_INF
)
3961 goto out_deactivate
;
3963 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
3964 cfs_b
->nr_periods
+= overrun
;
3967 * idle depends on !throttled (for the case of a large deficit), and if
3968 * we're going inactive then everything else can be deferred
3970 if (cfs_b
->idle
&& !throttled
)
3971 goto out_deactivate
;
3973 __refill_cfs_bandwidth_runtime(cfs_b
);
3976 /* mark as potentially idle for the upcoming period */
3981 /* account preceding periods in which throttling occurred */
3982 cfs_b
->nr_throttled
+= overrun
;
3984 runtime_expires
= cfs_b
->runtime_expires
;
3987 * This check is repeated as we are holding onto the new bandwidth while
3988 * we unthrottle. This can potentially race with an unthrottled group
3989 * trying to acquire new bandwidth from the global pool. This can result
3990 * in us over-using our runtime if it is all used during this loop, but
3991 * only by limited amounts in that extreme case.
3993 while (throttled
&& cfs_b
->runtime
> 0) {
3994 runtime
= cfs_b
->runtime
;
3995 raw_spin_unlock(&cfs_b
->lock
);
3996 /* we can't nest cfs_b->lock while distributing bandwidth */
3997 runtime
= distribute_cfs_runtime(cfs_b
, runtime
,
3999 raw_spin_lock(&cfs_b
->lock
);
4001 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
4003 cfs_b
->runtime
-= min(runtime
, cfs_b
->runtime
);
4007 * While we are ensured activity in the period following an
4008 * unthrottle, this also covers the case in which the new bandwidth is
4009 * insufficient to cover the existing bandwidth deficit. (Forcing the
4010 * timer to remain active while there are any throttled entities.)
4020 /* a cfs_rq won't donate quota below this amount */
4021 static const u64 min_cfs_rq_runtime
= 1 * NSEC_PER_MSEC
;
4022 /* minimum remaining period time to redistribute slack quota */
4023 static const u64 min_bandwidth_expiration
= 2 * NSEC_PER_MSEC
;
4024 /* how long we wait to gather additional slack before distributing */
4025 static const u64 cfs_bandwidth_slack_period
= 5 * NSEC_PER_MSEC
;
4028 * Are we near the end of the current quota period?
4030 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4031 * hrtimer base being cleared by hrtimer_start. In the case of
4032 * migrate_hrtimers, base is never cleared, so we are fine.
4034 static int runtime_refresh_within(struct cfs_bandwidth
*cfs_b
, u64 min_expire
)
4036 struct hrtimer
*refresh_timer
= &cfs_b
->period_timer
;
4039 /* if the call-back is running a quota refresh is already occurring */
4040 if (hrtimer_callback_running(refresh_timer
))
4043 /* is a quota refresh about to occur? */
4044 remaining
= ktime_to_ns(hrtimer_expires_remaining(refresh_timer
));
4045 if (remaining
< min_expire
)
4051 static void start_cfs_slack_bandwidth(struct cfs_bandwidth
*cfs_b
)
4053 u64 min_left
= cfs_bandwidth_slack_period
+ min_bandwidth_expiration
;
4055 /* if there's a quota refresh soon don't bother with slack */
4056 if (runtime_refresh_within(cfs_b
, min_left
))
4059 hrtimer_start(&cfs_b
->slack_timer
,
4060 ns_to_ktime(cfs_bandwidth_slack_period
),
4064 /* we know any runtime found here is valid as update_curr() precedes return */
4065 static void __return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4067 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
4068 s64 slack_runtime
= cfs_rq
->runtime_remaining
- min_cfs_rq_runtime
;
4070 if (slack_runtime
<= 0)
4073 raw_spin_lock(&cfs_b
->lock
);
4074 if (cfs_b
->quota
!= RUNTIME_INF
&&
4075 cfs_rq
->runtime_expires
== cfs_b
->runtime_expires
) {
4076 cfs_b
->runtime
+= slack_runtime
;
4078 /* we are under rq->lock, defer unthrottling using a timer */
4079 if (cfs_b
->runtime
> sched_cfs_bandwidth_slice() &&
4080 !list_empty(&cfs_b
->throttled_cfs_rq
))
4081 start_cfs_slack_bandwidth(cfs_b
);
4083 raw_spin_unlock(&cfs_b
->lock
);
4085 /* even if it's not valid for return we don't want to try again */
4086 cfs_rq
->runtime_remaining
-= slack_runtime
;
4089 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4091 if (!cfs_bandwidth_used())
4094 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->nr_running
)
4097 __return_cfs_rq_runtime(cfs_rq
);
4101 * This is done with a timer (instead of inline with bandwidth return) since
4102 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
4104 static void do_sched_cfs_slack_timer(struct cfs_bandwidth
*cfs_b
)
4106 u64 runtime
= 0, slice
= sched_cfs_bandwidth_slice();
4109 /* confirm we're still not at a refresh boundary */
4110 raw_spin_lock(&cfs_b
->lock
);
4111 if (runtime_refresh_within(cfs_b
, min_bandwidth_expiration
)) {
4112 raw_spin_unlock(&cfs_b
->lock
);
4116 if (cfs_b
->quota
!= RUNTIME_INF
&& cfs_b
->runtime
> slice
)
4117 runtime
= cfs_b
->runtime
;
4119 expires
= cfs_b
->runtime_expires
;
4120 raw_spin_unlock(&cfs_b
->lock
);
4125 runtime
= distribute_cfs_runtime(cfs_b
, runtime
, expires
);
4127 raw_spin_lock(&cfs_b
->lock
);
4128 if (expires
== cfs_b
->runtime_expires
)
4129 cfs_b
->runtime
-= min(runtime
, cfs_b
->runtime
);
4130 raw_spin_unlock(&cfs_b
->lock
);
4134 * When a group wakes up we want to make sure that its quota is not already
4135 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
4136 * runtime as update_curr() throttling can not not trigger until it's on-rq.
4138 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
)
4140 if (!cfs_bandwidth_used())
4143 /* an active group must be handled by the update_curr()->put() path */
4144 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->curr
)
4147 /* ensure the group is not already throttled */
4148 if (cfs_rq_throttled(cfs_rq
))
4151 /* update runtime allocation */
4152 account_cfs_rq_runtime(cfs_rq
, 0);
4153 if (cfs_rq
->runtime_remaining
<= 0)
4154 throttle_cfs_rq(cfs_rq
);
4157 /* conditionally throttle active cfs_rq's from put_prev_entity() */
4158 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4160 if (!cfs_bandwidth_used())
4163 if (likely(!cfs_rq
->runtime_enabled
|| cfs_rq
->runtime_remaining
> 0))
4167 * it's possible for a throttled entity to be forced into a running
4168 * state (e.g. set_curr_task), in this case we're finished.
4170 if (cfs_rq_throttled(cfs_rq
))
4173 throttle_cfs_rq(cfs_rq
);
4177 static enum hrtimer_restart
sched_cfs_slack_timer(struct hrtimer
*timer
)
4179 struct cfs_bandwidth
*cfs_b
=
4180 container_of(timer
, struct cfs_bandwidth
, slack_timer
);
4182 do_sched_cfs_slack_timer(cfs_b
);
4184 return HRTIMER_NORESTART
;
4187 static enum hrtimer_restart
sched_cfs_period_timer(struct hrtimer
*timer
)
4189 struct cfs_bandwidth
*cfs_b
=
4190 container_of(timer
, struct cfs_bandwidth
, period_timer
);
4194 raw_spin_lock(&cfs_b
->lock
);
4196 overrun
= hrtimer_forward_now(timer
, cfs_b
->period
);
4200 idle
= do_sched_cfs_period_timer(cfs_b
, overrun
);
4203 cfs_b
->period_active
= 0;
4204 raw_spin_unlock(&cfs_b
->lock
);
4206 return idle
? HRTIMER_NORESTART
: HRTIMER_RESTART
;
4209 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4211 raw_spin_lock_init(&cfs_b
->lock
);
4213 cfs_b
->quota
= RUNTIME_INF
;
4214 cfs_b
->period
= ns_to_ktime(default_cfs_period());
4216 INIT_LIST_HEAD(&cfs_b
->throttled_cfs_rq
);
4217 hrtimer_init(&cfs_b
->period_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_ABS_PINNED
);
4218 cfs_b
->period_timer
.function
= sched_cfs_period_timer
;
4219 hrtimer_init(&cfs_b
->slack_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
4220 cfs_b
->slack_timer
.function
= sched_cfs_slack_timer
;
4223 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4225 cfs_rq
->runtime_enabled
= 0;
4226 INIT_LIST_HEAD(&cfs_rq
->throttled_list
);
4229 void start_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4231 lockdep_assert_held(&cfs_b
->lock
);
4233 if (!cfs_b
->period_active
) {
4234 cfs_b
->period_active
= 1;
4235 hrtimer_forward_now(&cfs_b
->period_timer
, cfs_b
->period
);
4236 hrtimer_start_expires(&cfs_b
->period_timer
, HRTIMER_MODE_ABS_PINNED
);
4240 static void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4242 /* init_cfs_bandwidth() was not called */
4243 if (!cfs_b
->throttled_cfs_rq
.next
)
4246 hrtimer_cancel(&cfs_b
->period_timer
);
4247 hrtimer_cancel(&cfs_b
->slack_timer
);
4250 static void __maybe_unused
update_runtime_enabled(struct rq
*rq
)
4252 struct cfs_rq
*cfs_rq
;
4254 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
4255 struct cfs_bandwidth
*cfs_b
= &cfs_rq
->tg
->cfs_bandwidth
;
4257 raw_spin_lock(&cfs_b
->lock
);
4258 cfs_rq
->runtime_enabled
= cfs_b
->quota
!= RUNTIME_INF
;
4259 raw_spin_unlock(&cfs_b
->lock
);
4263 static void __maybe_unused
unthrottle_offline_cfs_rqs(struct rq
*rq
)
4265 struct cfs_rq
*cfs_rq
;
4267 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
4268 if (!cfs_rq
->runtime_enabled
)
4272 * clock_task is not advancing so we just need to make sure
4273 * there's some valid quota amount
4275 cfs_rq
->runtime_remaining
= 1;
4277 * Offline rq is schedulable till cpu is completely disabled
4278 * in take_cpu_down(), so we prevent new cfs throttling here.
4280 cfs_rq
->runtime_enabled
= 0;
4282 if (cfs_rq_throttled(cfs_rq
))
4283 unthrottle_cfs_rq(cfs_rq
);
4287 #else /* CONFIG_CFS_BANDWIDTH */
4288 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
4290 return rq_clock_task(rq_of(cfs_rq
));
4293 static void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
) {}
4294 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) { return false; }
4295 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
) {}
4296 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
4298 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
4303 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
4308 static inline int throttled_lb_pair(struct task_group
*tg
,
4309 int src_cpu
, int dest_cpu
)
4314 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
4316 #ifdef CONFIG_FAIR_GROUP_SCHED
4317 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
4320 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
4324 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
4325 static inline void update_runtime_enabled(struct rq
*rq
) {}
4326 static inline void unthrottle_offline_cfs_rqs(struct rq
*rq
) {}
4328 #endif /* CONFIG_CFS_BANDWIDTH */
4330 /**************************************************
4331 * CFS operations on tasks:
4334 #ifdef CONFIG_SCHED_HRTICK
4335 static void hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
4337 struct sched_entity
*se
= &p
->se
;
4338 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4340 WARN_ON(task_rq(p
) != rq
);
4342 if (cfs_rq
->nr_running
> 1) {
4343 u64 slice
= sched_slice(cfs_rq
, se
);
4344 u64 ran
= se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
;
4345 s64 delta
= slice
- ran
;
4352 hrtick_start(rq
, delta
);
4357 * called from enqueue/dequeue and updates the hrtick when the
4358 * current task is from our class and nr_running is low enough
4361 static void hrtick_update(struct rq
*rq
)
4363 struct task_struct
*curr
= rq
->curr
;
4365 if (!hrtick_enabled(rq
) || curr
->sched_class
!= &fair_sched_class
)
4368 if (cfs_rq_of(&curr
->se
)->nr_running
< sched_nr_latency
)
4369 hrtick_start_fair(rq
, curr
);
4371 #else /* !CONFIG_SCHED_HRTICK */
4373 hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
4377 static inline void hrtick_update(struct rq
*rq
)
4383 * The enqueue_task method is called before nr_running is
4384 * increased. Here we update the fair scheduling stats and
4385 * then put the task into the rbtree:
4388 enqueue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
4390 struct cfs_rq
*cfs_rq
;
4391 struct sched_entity
*se
= &p
->se
;
4393 for_each_sched_entity(se
) {
4396 cfs_rq
= cfs_rq_of(se
);
4397 enqueue_entity(cfs_rq
, se
, flags
);
4400 * end evaluation on encountering a throttled cfs_rq
4402 * note: in the case of encountering a throttled cfs_rq we will
4403 * post the final h_nr_running increment below.
4405 if (cfs_rq_throttled(cfs_rq
))
4407 cfs_rq
->h_nr_running
++;
4409 flags
= ENQUEUE_WAKEUP
;
4412 for_each_sched_entity(se
) {
4413 cfs_rq
= cfs_rq_of(se
);
4414 cfs_rq
->h_nr_running
++;
4416 if (cfs_rq_throttled(cfs_rq
))
4419 update_load_avg(se
, 1);
4420 update_cfs_shares(cfs_rq
);
4424 add_nr_running(rq
, 1);
4429 static void set_next_buddy(struct sched_entity
*se
);
4432 * The dequeue_task method is called before nr_running is
4433 * decreased. We remove the task from the rbtree and
4434 * update the fair scheduling stats:
4436 static void dequeue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
4438 struct cfs_rq
*cfs_rq
;
4439 struct sched_entity
*se
= &p
->se
;
4440 int task_sleep
= flags
& DEQUEUE_SLEEP
;
4442 for_each_sched_entity(se
) {
4443 cfs_rq
= cfs_rq_of(se
);
4444 dequeue_entity(cfs_rq
, se
, flags
);
4447 * end evaluation on encountering a throttled cfs_rq
4449 * note: in the case of encountering a throttled cfs_rq we will
4450 * post the final h_nr_running decrement below.
4452 if (cfs_rq_throttled(cfs_rq
))
4454 cfs_rq
->h_nr_running
--;
4456 /* Don't dequeue parent if it has other entities besides us */
4457 if (cfs_rq
->load
.weight
) {
4459 * Bias pick_next to pick a task from this cfs_rq, as
4460 * p is sleeping when it is within its sched_slice.
4462 if (task_sleep
&& parent_entity(se
))
4463 set_next_buddy(parent_entity(se
));
4465 /* avoid re-evaluating load for this entity */
4466 se
= parent_entity(se
);
4469 flags
|= DEQUEUE_SLEEP
;
4472 for_each_sched_entity(se
) {
4473 cfs_rq
= cfs_rq_of(se
);
4474 cfs_rq
->h_nr_running
--;
4476 if (cfs_rq_throttled(cfs_rq
))
4479 update_load_avg(se
, 1);
4480 update_cfs_shares(cfs_rq
);
4484 sub_nr_running(rq
, 1);
4490 #ifdef CONFIG_NO_HZ_COMMON
4492 * per rq 'load' arrray crap; XXX kill this.
4496 * The exact cpuload calculated at every tick would be:
4498 * load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
4500 * If a cpu misses updates for n ticks (as it was idle) and update gets
4501 * called on the n+1-th tick when cpu may be busy, then we have:
4503 * load_n = (1 - 1/2^i)^n * load_0
4504 * load_n+1 = (1 - 1/2^i) * load_n + (1/2^i) * cur_load
4506 * decay_load_missed() below does efficient calculation of
4508 * load' = (1 - 1/2^i)^n * load
4510 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
4511 * This allows us to precompute the above in said factors, thereby allowing the
4512 * reduction of an arbitrary n in O(log_2 n) steps. (See also
4513 * fixed_power_int())
4515 * The calculation is approximated on a 128 point scale.
4517 #define DEGRADE_SHIFT 7
4519 static const u8 degrade_zero_ticks
[CPU_LOAD_IDX_MAX
] = {0, 8, 32, 64, 128};
4520 static const u8 degrade_factor
[CPU_LOAD_IDX_MAX
][DEGRADE_SHIFT
+ 1] = {
4521 { 0, 0, 0, 0, 0, 0, 0, 0 },
4522 { 64, 32, 8, 0, 0, 0, 0, 0 },
4523 { 96, 72, 40, 12, 1, 0, 0, 0 },
4524 { 112, 98, 75, 43, 15, 1, 0, 0 },
4525 { 120, 112, 98, 76, 45, 16, 2, 0 }
4529 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4530 * would be when CPU is idle and so we just decay the old load without
4531 * adding any new load.
4533 static unsigned long
4534 decay_load_missed(unsigned long load
, unsigned long missed_updates
, int idx
)
4538 if (!missed_updates
)
4541 if (missed_updates
>= degrade_zero_ticks
[idx
])
4545 return load
>> missed_updates
;
4547 while (missed_updates
) {
4548 if (missed_updates
% 2)
4549 load
= (load
* degrade_factor
[idx
][j
]) >> DEGRADE_SHIFT
;
4551 missed_updates
>>= 1;
4556 #endif /* CONFIG_NO_HZ_COMMON */
4559 * __cpu_load_update - update the rq->cpu_load[] statistics
4560 * @this_rq: The rq to update statistics for
4561 * @this_load: The current load
4562 * @pending_updates: The number of missed updates
4564 * Update rq->cpu_load[] statistics. This function is usually called every
4565 * scheduler tick (TICK_NSEC).
4567 * This function computes a decaying average:
4569 * load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
4571 * Because of NOHZ it might not get called on every tick which gives need for
4572 * the @pending_updates argument.
4574 * load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
4575 * = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
4576 * = A * (A * load[i]_n-2 + B) + B
4577 * = A * (A * (A * load[i]_n-3 + B) + B) + B
4578 * = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
4579 * = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
4580 * = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
4581 * = (1 - 1/2^i)^n * (load[i]_0 - load) + load
4583 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
4584 * any change in load would have resulted in the tick being turned back on.
4586 * For regular NOHZ, this reduces to:
4588 * load[i]_n = (1 - 1/2^i)^n * load[i]_0
4590 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
4593 static void cpu_load_update(struct rq
*this_rq
, unsigned long this_load
,
4594 unsigned long pending_updates
)
4596 unsigned long __maybe_unused tickless_load
= this_rq
->cpu_load
[0];
4599 this_rq
->nr_load_updates
++;
4601 /* Update our load: */
4602 this_rq
->cpu_load
[0] = this_load
; /* Fasttrack for idx 0 */
4603 for (i
= 1, scale
= 2; i
< CPU_LOAD_IDX_MAX
; i
++, scale
+= scale
) {
4604 unsigned long old_load
, new_load
;
4606 /* scale is effectively 1 << i now, and >> i divides by scale */
4608 old_load
= this_rq
->cpu_load
[i
];
4609 #ifdef CONFIG_NO_HZ_COMMON
4610 old_load
= decay_load_missed(old_load
, pending_updates
- 1, i
);
4611 if (tickless_load
) {
4612 old_load
-= decay_load_missed(tickless_load
, pending_updates
- 1, i
);
4614 * old_load can never be a negative value because a
4615 * decayed tickless_load cannot be greater than the
4616 * original tickless_load.
4618 old_load
+= tickless_load
;
4621 new_load
= this_load
;
4623 * Round up the averaging division if load is increasing. This
4624 * prevents us from getting stuck on 9 if the load is 10, for
4627 if (new_load
> old_load
)
4628 new_load
+= scale
- 1;
4630 this_rq
->cpu_load
[i
] = (old_load
* (scale
- 1) + new_load
) >> i
;
4633 sched_avg_update(this_rq
);
4636 /* Used instead of source_load when we know the type == 0 */
4637 static unsigned long weighted_cpuload(const int cpu
)
4639 return cfs_rq_runnable_load_avg(&cpu_rq(cpu
)->cfs
);
4642 #ifdef CONFIG_NO_HZ_COMMON
4644 * There is no sane way to deal with nohz on smp when using jiffies because the
4645 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4646 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4648 * Therefore we need to avoid the delta approach from the regular tick when
4649 * possible since that would seriously skew the load calculation. This is why we
4650 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
4651 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
4652 * loop exit, nohz_idle_balance, nohz full exit...)
4654 * This means we might still be one tick off for nohz periods.
4657 static void cpu_load_update_nohz(struct rq
*this_rq
,
4658 unsigned long curr_jiffies
,
4661 unsigned long pending_updates
;
4663 pending_updates
= curr_jiffies
- this_rq
->last_load_update_tick
;
4664 if (pending_updates
) {
4665 this_rq
->last_load_update_tick
= curr_jiffies
;
4667 * In the regular NOHZ case, we were idle, this means load 0.
4668 * In the NOHZ_FULL case, we were non-idle, we should consider
4669 * its weighted load.
4671 cpu_load_update(this_rq
, load
, pending_updates
);
4676 * Called from nohz_idle_balance() to update the load ratings before doing the
4679 static void cpu_load_update_idle(struct rq
*this_rq
)
4682 * bail if there's load or we're actually up-to-date.
4684 if (weighted_cpuload(cpu_of(this_rq
)))
4687 cpu_load_update_nohz(this_rq
, READ_ONCE(jiffies
), 0);
4691 * Record CPU load on nohz entry so we know the tickless load to account
4692 * on nohz exit. cpu_load[0] happens then to be updated more frequently
4693 * than other cpu_load[idx] but it should be fine as cpu_load readers
4694 * shouldn't rely into synchronized cpu_load[*] updates.
4696 void cpu_load_update_nohz_start(void)
4698 struct rq
*this_rq
= this_rq();
4701 * This is all lockless but should be fine. If weighted_cpuload changes
4702 * concurrently we'll exit nohz. And cpu_load write can race with
4703 * cpu_load_update_idle() but both updater would be writing the same.
4705 this_rq
->cpu_load
[0] = weighted_cpuload(cpu_of(this_rq
));
4709 * Account the tickless load in the end of a nohz frame.
4711 void cpu_load_update_nohz_stop(void)
4713 unsigned long curr_jiffies
= READ_ONCE(jiffies
);
4714 struct rq
*this_rq
= this_rq();
4717 if (curr_jiffies
== this_rq
->last_load_update_tick
)
4720 load
= weighted_cpuload(cpu_of(this_rq
));
4721 raw_spin_lock(&this_rq
->lock
);
4722 cpu_load_update_nohz(this_rq
, curr_jiffies
, load
);
4723 raw_spin_unlock(&this_rq
->lock
);
4725 #else /* !CONFIG_NO_HZ_COMMON */
4726 static inline void cpu_load_update_nohz(struct rq
*this_rq
,
4727 unsigned long curr_jiffies
,
4728 unsigned long load
) { }
4729 #endif /* CONFIG_NO_HZ_COMMON */
4731 static void cpu_load_update_periodic(struct rq
*this_rq
, unsigned long load
)
4733 #ifdef CONFIG_NO_HZ_COMMON
4734 /* See the mess around cpu_load_update_nohz(). */
4735 this_rq
->last_load_update_tick
= READ_ONCE(jiffies
);
4737 cpu_load_update(this_rq
, load
, 1);
4741 * Called from scheduler_tick()
4743 void cpu_load_update_active(struct rq
*this_rq
)
4745 unsigned long load
= weighted_cpuload(cpu_of(this_rq
));
4747 if (tick_nohz_tick_stopped())
4748 cpu_load_update_nohz(this_rq
, READ_ONCE(jiffies
), load
);
4750 cpu_load_update_periodic(this_rq
, load
);
4754 * Return a low guess at the load of a migration-source cpu weighted
4755 * according to the scheduling class and "nice" value.
4757 * We want to under-estimate the load of migration sources, to
4758 * balance conservatively.
4760 static unsigned long source_load(int cpu
, int type
)
4762 struct rq
*rq
= cpu_rq(cpu
);
4763 unsigned long total
= weighted_cpuload(cpu
);
4765 if (type
== 0 || !sched_feat(LB_BIAS
))
4768 return min(rq
->cpu_load
[type
-1], total
);
4772 * Return a high guess at the load of a migration-target cpu weighted
4773 * according to the scheduling class and "nice" value.
4775 static unsigned long target_load(int cpu
, int type
)
4777 struct rq
*rq
= cpu_rq(cpu
);
4778 unsigned long total
= weighted_cpuload(cpu
);
4780 if (type
== 0 || !sched_feat(LB_BIAS
))
4783 return max(rq
->cpu_load
[type
-1], total
);
4786 static unsigned long capacity_of(int cpu
)
4788 return cpu_rq(cpu
)->cpu_capacity
;
4791 static unsigned long capacity_orig_of(int cpu
)
4793 return cpu_rq(cpu
)->cpu_capacity_orig
;
4796 static unsigned long cpu_avg_load_per_task(int cpu
)
4798 struct rq
*rq
= cpu_rq(cpu
);
4799 unsigned long nr_running
= READ_ONCE(rq
->cfs
.h_nr_running
);
4800 unsigned long load_avg
= weighted_cpuload(cpu
);
4803 return load_avg
/ nr_running
;
4808 static void record_wakee(struct task_struct
*p
)
4811 * Rough decay (wiping) for cost saving, don't worry
4812 * about the boundary, really active task won't care
4815 if (time_after(jiffies
, current
->wakee_flip_decay_ts
+ HZ
)) {
4816 current
->wakee_flips
>>= 1;
4817 current
->wakee_flip_decay_ts
= jiffies
;
4820 if (current
->last_wakee
!= p
) {
4821 current
->last_wakee
= p
;
4822 current
->wakee_flips
++;
4826 static void task_waking_fair(struct task_struct
*p
)
4828 struct sched_entity
*se
= &p
->se
;
4829 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4832 #ifndef CONFIG_64BIT
4833 u64 min_vruntime_copy
;
4836 min_vruntime_copy
= cfs_rq
->min_vruntime_copy
;
4838 min_vruntime
= cfs_rq
->min_vruntime
;
4839 } while (min_vruntime
!= min_vruntime_copy
);
4841 min_vruntime
= cfs_rq
->min_vruntime
;
4844 se
->vruntime
-= min_vruntime
;
4848 #ifdef CONFIG_FAIR_GROUP_SCHED
4850 * effective_load() calculates the load change as seen from the root_task_group
4852 * Adding load to a group doesn't make a group heavier, but can cause movement
4853 * of group shares between cpus. Assuming the shares were perfectly aligned one
4854 * can calculate the shift in shares.
4856 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4857 * on this @cpu and results in a total addition (subtraction) of @wg to the
4858 * total group weight.
4860 * Given a runqueue weight distribution (rw_i) we can compute a shares
4861 * distribution (s_i) using:
4863 * s_i = rw_i / \Sum rw_j (1)
4865 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4866 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4867 * shares distribution (s_i):
4869 * rw_i = { 2, 4, 1, 0 }
4870 * s_i = { 2/7, 4/7, 1/7, 0 }
4872 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4873 * task used to run on and the CPU the waker is running on), we need to
4874 * compute the effect of waking a task on either CPU and, in case of a sync
4875 * wakeup, compute the effect of the current task going to sleep.
4877 * So for a change of @wl to the local @cpu with an overall group weight change
4878 * of @wl we can compute the new shares distribution (s'_i) using:
4880 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4882 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4883 * differences in waking a task to CPU 0. The additional task changes the
4884 * weight and shares distributions like:
4886 * rw'_i = { 3, 4, 1, 0 }
4887 * s'_i = { 3/8, 4/8, 1/8, 0 }
4889 * We can then compute the difference in effective weight by using:
4891 * dw_i = S * (s'_i - s_i) (3)
4893 * Where 'S' is the group weight as seen by its parent.
4895 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4896 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4897 * 4/7) times the weight of the group.
4899 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
)
4901 struct sched_entity
*se
= tg
->se
[cpu
];
4903 if (!tg
->parent
) /* the trivial, non-cgroup case */
4906 for_each_sched_entity(se
) {
4912 * W = @wg + \Sum rw_j
4914 W
= wg
+ calc_tg_weight(tg
, se
->my_q
);
4919 w
= cfs_rq_load_avg(se
->my_q
) + wl
;
4922 * wl = S * s'_i; see (2)
4925 wl
= (w
* (long)tg
->shares
) / W
;
4930 * Per the above, wl is the new se->load.weight value; since
4931 * those are clipped to [MIN_SHARES, ...) do so now. See
4932 * calc_cfs_shares().
4934 if (wl
< MIN_SHARES
)
4938 * wl = dw_i = S * (s'_i - s_i); see (3)
4940 wl
-= se
->avg
.load_avg
;
4943 * Recursively apply this logic to all parent groups to compute
4944 * the final effective load change on the root group. Since
4945 * only the @tg group gets extra weight, all parent groups can
4946 * only redistribute existing shares. @wl is the shift in shares
4947 * resulting from this level per the above.
4956 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
)
4964 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
4965 * A waker of many should wake a different task than the one last awakened
4966 * at a frequency roughly N times higher than one of its wakees. In order
4967 * to determine whether we should let the load spread vs consolodating to
4968 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
4969 * partner, and a factor of lls_size higher frequency in the other. With
4970 * both conditions met, we can be relatively sure that the relationship is
4971 * non-monogamous, with partner count exceeding socket size. Waker/wakee
4972 * being client/server, worker/dispatcher, interrupt source or whatever is
4973 * irrelevant, spread criteria is apparent partner count exceeds socket size.
4975 static int wake_wide(struct task_struct
*p
)
4977 unsigned int master
= current
->wakee_flips
;
4978 unsigned int slave
= p
->wakee_flips
;
4979 int factor
= this_cpu_read(sd_llc_size
);
4982 swap(master
, slave
);
4983 if (slave
< factor
|| master
< slave
* factor
)
4988 static int wake_affine(struct sched_domain
*sd
, struct task_struct
*p
, int sync
)
4990 s64 this_load
, load
;
4991 s64 this_eff_load
, prev_eff_load
;
4992 int idx
, this_cpu
, prev_cpu
;
4993 struct task_group
*tg
;
4994 unsigned long weight
;
4998 this_cpu
= smp_processor_id();
4999 prev_cpu
= task_cpu(p
);
5000 load
= source_load(prev_cpu
, idx
);
5001 this_load
= target_load(this_cpu
, idx
);
5004 * If sync wakeup then subtract the (maximum possible)
5005 * effect of the currently running task from the load
5006 * of the current CPU:
5009 tg
= task_group(current
);
5010 weight
= current
->se
.avg
.load_avg
;
5012 this_load
+= effective_load(tg
, this_cpu
, -weight
, -weight
);
5013 load
+= effective_load(tg
, prev_cpu
, 0, -weight
);
5017 weight
= p
->se
.avg
.load_avg
;
5020 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5021 * due to the sync cause above having dropped this_load to 0, we'll
5022 * always have an imbalance, but there's really nothing you can do
5023 * about that, so that's good too.
5025 * Otherwise check if either cpus are near enough in load to allow this
5026 * task to be woken on this_cpu.
5028 this_eff_load
= 100;
5029 this_eff_load
*= capacity_of(prev_cpu
);
5031 prev_eff_load
= 100 + (sd
->imbalance_pct
- 100) / 2;
5032 prev_eff_load
*= capacity_of(this_cpu
);
5034 if (this_load
> 0) {
5035 this_eff_load
*= this_load
+
5036 effective_load(tg
, this_cpu
, weight
, weight
);
5038 prev_eff_load
*= load
+ effective_load(tg
, prev_cpu
, 0, weight
);
5041 balanced
= this_eff_load
<= prev_eff_load
;
5043 schedstat_inc(p
, se
.statistics
.nr_wakeups_affine_attempts
);
5048 schedstat_inc(sd
, ttwu_move_affine
);
5049 schedstat_inc(p
, se
.statistics
.nr_wakeups_affine
);
5055 * find_idlest_group finds and returns the least busy CPU group within the
5058 static struct sched_group
*
5059 find_idlest_group(struct sched_domain
*sd
, struct task_struct
*p
,
5060 int this_cpu
, int sd_flag
)
5062 struct sched_group
*idlest
= NULL
, *group
= sd
->groups
;
5063 unsigned long min_load
= ULONG_MAX
, this_load
= 0;
5064 int load_idx
= sd
->forkexec_idx
;
5065 int imbalance
= 100 + (sd
->imbalance_pct
-100)/2;
5067 if (sd_flag
& SD_BALANCE_WAKE
)
5068 load_idx
= sd
->wake_idx
;
5071 unsigned long load
, avg_load
;
5075 /* Skip over this group if it has no CPUs allowed */
5076 if (!cpumask_intersects(sched_group_cpus(group
),
5077 tsk_cpus_allowed(p
)))
5080 local_group
= cpumask_test_cpu(this_cpu
,
5081 sched_group_cpus(group
));
5083 /* Tally up the load of all CPUs in the group */
5086 for_each_cpu(i
, sched_group_cpus(group
)) {
5087 /* Bias balancing toward cpus of our domain */
5089 load
= source_load(i
, load_idx
);
5091 load
= target_load(i
, load_idx
);
5096 /* Adjust by relative CPU capacity of the group */
5097 avg_load
= (avg_load
* SCHED_CAPACITY_SCALE
) / group
->sgc
->capacity
;
5100 this_load
= avg_load
;
5101 } else if (avg_load
< min_load
) {
5102 min_load
= avg_load
;
5105 } while (group
= group
->next
, group
!= sd
->groups
);
5107 if (!idlest
|| 100*this_load
< imbalance
*min_load
)
5113 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5116 find_idlest_cpu(struct sched_group
*group
, struct task_struct
*p
, int this_cpu
)
5118 unsigned long load
, min_load
= ULONG_MAX
;
5119 unsigned int min_exit_latency
= UINT_MAX
;
5120 u64 latest_idle_timestamp
= 0;
5121 int least_loaded_cpu
= this_cpu
;
5122 int shallowest_idle_cpu
= -1;
5125 /* Traverse only the allowed CPUs */
5126 for_each_cpu_and(i
, sched_group_cpus(group
), tsk_cpus_allowed(p
)) {
5128 struct rq
*rq
= cpu_rq(i
);
5129 struct cpuidle_state
*idle
= idle_get_state(rq
);
5130 if (idle
&& idle
->exit_latency
< min_exit_latency
) {
5132 * We give priority to a CPU whose idle state
5133 * has the smallest exit latency irrespective
5134 * of any idle timestamp.
5136 min_exit_latency
= idle
->exit_latency
;
5137 latest_idle_timestamp
= rq
->idle_stamp
;
5138 shallowest_idle_cpu
= i
;
5139 } else if ((!idle
|| idle
->exit_latency
== min_exit_latency
) &&
5140 rq
->idle_stamp
> latest_idle_timestamp
) {
5142 * If equal or no active idle state, then
5143 * the most recently idled CPU might have
5146 latest_idle_timestamp
= rq
->idle_stamp
;
5147 shallowest_idle_cpu
= i
;
5149 } else if (shallowest_idle_cpu
== -1) {
5150 load
= weighted_cpuload(i
);
5151 if (load
< min_load
|| (load
== min_load
&& i
== this_cpu
)) {
5153 least_loaded_cpu
= i
;
5158 return shallowest_idle_cpu
!= -1 ? shallowest_idle_cpu
: least_loaded_cpu
;
5162 * Try and locate an idle CPU in the sched_domain.
5164 static int select_idle_sibling(struct task_struct
*p
, int target
)
5166 struct sched_domain
*sd
;
5167 struct sched_group
*sg
;
5168 int i
= task_cpu(p
);
5170 if (idle_cpu(target
))
5174 * If the prevous cpu is cache affine and idle, don't be stupid.
5176 if (i
!= target
&& cpus_share_cache(i
, target
) && idle_cpu(i
))
5180 * Otherwise, iterate the domains and find an eligible idle cpu.
5182 * A completely idle sched group at higher domains is more
5183 * desirable than an idle group at a lower level, because lower
5184 * domains have smaller groups and usually share hardware
5185 * resources which causes tasks to contend on them, e.g. x86
5186 * hyperthread siblings in the lowest domain (SMT) can contend
5187 * on the shared cpu pipeline.
5189 * However, while we prefer idle groups at higher domains
5190 * finding an idle cpu at the lowest domain is still better than
5191 * returning 'target', which we've already established, isn't
5194 sd
= rcu_dereference(per_cpu(sd_llc
, target
));
5195 for_each_lower_domain(sd
) {
5198 if (!cpumask_intersects(sched_group_cpus(sg
),
5199 tsk_cpus_allowed(p
)))
5202 /* Ensure the entire group is idle */
5203 for_each_cpu(i
, sched_group_cpus(sg
)) {
5204 if (i
== target
|| !idle_cpu(i
))
5209 * It doesn't matter which cpu we pick, the
5210 * whole group is idle.
5212 target
= cpumask_first_and(sched_group_cpus(sg
),
5213 tsk_cpus_allowed(p
));
5217 } while (sg
!= sd
->groups
);
5224 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5225 * tasks. The unit of the return value must be the one of capacity so we can
5226 * compare the utilization with the capacity of the CPU that is available for
5227 * CFS task (ie cpu_capacity).
5229 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
5230 * recent utilization of currently non-runnable tasks on a CPU. It represents
5231 * the amount of utilization of a CPU in the range [0..capacity_orig] where
5232 * capacity_orig is the cpu_capacity available at the highest frequency
5233 * (arch_scale_freq_capacity()).
5234 * The utilization of a CPU converges towards a sum equal to or less than the
5235 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
5236 * the running time on this CPU scaled by capacity_curr.
5238 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
5239 * higher than capacity_orig because of unfortunate rounding in
5240 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
5241 * the average stabilizes with the new running time. We need to check that the
5242 * utilization stays within the range of [0..capacity_orig] and cap it if
5243 * necessary. Without utilization capping, a group could be seen as overloaded
5244 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
5245 * available capacity. We allow utilization to overshoot capacity_curr (but not
5246 * capacity_orig) as it useful for predicting the capacity required after task
5247 * migrations (scheduler-driven DVFS).
5249 static int cpu_util(int cpu
)
5251 unsigned long util
= cpu_rq(cpu
)->cfs
.avg
.util_avg
;
5252 unsigned long capacity
= capacity_orig_of(cpu
);
5254 return (util
>= capacity
) ? capacity
: util
;
5258 * select_task_rq_fair: Select target runqueue for the waking task in domains
5259 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5260 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5262 * Balances load by selecting the idlest cpu in the idlest group, or under
5263 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5265 * Returns the target cpu number.
5267 * preempt must be disabled.
5270 select_task_rq_fair(struct task_struct
*p
, int prev_cpu
, int sd_flag
, int wake_flags
)
5272 struct sched_domain
*tmp
, *affine_sd
= NULL
, *sd
= NULL
;
5273 int cpu
= smp_processor_id();
5274 int new_cpu
= prev_cpu
;
5275 int want_affine
= 0;
5276 int sync
= wake_flags
& WF_SYNC
;
5278 if (sd_flag
& SD_BALANCE_WAKE
)
5279 want_affine
= !wake_wide(p
) && cpumask_test_cpu(cpu
, tsk_cpus_allowed(p
));
5282 for_each_domain(cpu
, tmp
) {
5283 if (!(tmp
->flags
& SD_LOAD_BALANCE
))
5287 * If both cpu and prev_cpu are part of this domain,
5288 * cpu is a valid SD_WAKE_AFFINE target.
5290 if (want_affine
&& (tmp
->flags
& SD_WAKE_AFFINE
) &&
5291 cpumask_test_cpu(prev_cpu
, sched_domain_span(tmp
))) {
5296 if (tmp
->flags
& sd_flag
)
5298 else if (!want_affine
)
5303 sd
= NULL
; /* Prefer wake_affine over balance flags */
5304 if (cpu
!= prev_cpu
&& wake_affine(affine_sd
, p
, sync
))
5309 if (sd_flag
& SD_BALANCE_WAKE
) /* XXX always ? */
5310 new_cpu
= select_idle_sibling(p
, new_cpu
);
5313 struct sched_group
*group
;
5316 if (!(sd
->flags
& sd_flag
)) {
5321 group
= find_idlest_group(sd
, p
, cpu
, sd_flag
);
5327 new_cpu
= find_idlest_cpu(group
, p
, cpu
);
5328 if (new_cpu
== -1 || new_cpu
== cpu
) {
5329 /* Now try balancing at a lower domain level of cpu */
5334 /* Now try balancing at a lower domain level of new_cpu */
5336 weight
= sd
->span_weight
;
5338 for_each_domain(cpu
, tmp
) {
5339 if (weight
<= tmp
->span_weight
)
5341 if (tmp
->flags
& sd_flag
)
5344 /* while loop will break here if sd == NULL */
5352 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5353 * cfs_rq_of(p) references at time of call are still valid and identify the
5354 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5356 static void migrate_task_rq_fair(struct task_struct
*p
)
5359 * We are supposed to update the task to "current" time, then its up to date
5360 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5361 * what current time is, so simply throw away the out-of-date time. This
5362 * will result in the wakee task is less decayed, but giving the wakee more
5363 * load sounds not bad.
5365 remove_entity_load_avg(&p
->se
);
5367 /* Tell new CPU we are migrated */
5368 p
->se
.avg
.last_update_time
= 0;
5370 /* We have migrated, no longer consider this task hot */
5371 p
->se
.exec_start
= 0;
5374 static void task_dead_fair(struct task_struct
*p
)
5376 remove_entity_load_avg(&p
->se
);
5378 #endif /* CONFIG_SMP */
5380 static unsigned long
5381 wakeup_gran(struct sched_entity
*curr
, struct sched_entity
*se
)
5383 unsigned long gran
= sysctl_sched_wakeup_granularity
;
5386 * Since its curr running now, convert the gran from real-time
5387 * to virtual-time in his units.
5389 * By using 'se' instead of 'curr' we penalize light tasks, so
5390 * they get preempted easier. That is, if 'se' < 'curr' then
5391 * the resulting gran will be larger, therefore penalizing the
5392 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5393 * be smaller, again penalizing the lighter task.
5395 * This is especially important for buddies when the leftmost
5396 * task is higher priority than the buddy.
5398 return calc_delta_fair(gran
, se
);
5402 * Should 'se' preempt 'curr'.
5416 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
)
5418 s64 gran
, vdiff
= curr
->vruntime
- se
->vruntime
;
5423 gran
= wakeup_gran(curr
, se
);
5430 static void set_last_buddy(struct sched_entity
*se
)
5432 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
5435 for_each_sched_entity(se
)
5436 cfs_rq_of(se
)->last
= se
;
5439 static void set_next_buddy(struct sched_entity
*se
)
5441 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
5444 for_each_sched_entity(se
)
5445 cfs_rq_of(se
)->next
= se
;
5448 static void set_skip_buddy(struct sched_entity
*se
)
5450 for_each_sched_entity(se
)
5451 cfs_rq_of(se
)->skip
= se
;
5455 * Preempt the current task with a newly woken task if needed:
5457 static void check_preempt_wakeup(struct rq
*rq
, struct task_struct
*p
, int wake_flags
)
5459 struct task_struct
*curr
= rq
->curr
;
5460 struct sched_entity
*se
= &curr
->se
, *pse
= &p
->se
;
5461 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
5462 int scale
= cfs_rq
->nr_running
>= sched_nr_latency
;
5463 int next_buddy_marked
= 0;
5465 if (unlikely(se
== pse
))
5469 * This is possible from callers such as attach_tasks(), in which we
5470 * unconditionally check_prempt_curr() after an enqueue (which may have
5471 * lead to a throttle). This both saves work and prevents false
5472 * next-buddy nomination below.
5474 if (unlikely(throttled_hierarchy(cfs_rq_of(pse
))))
5477 if (sched_feat(NEXT_BUDDY
) && scale
&& !(wake_flags
& WF_FORK
)) {
5478 set_next_buddy(pse
);
5479 next_buddy_marked
= 1;
5483 * We can come here with TIF_NEED_RESCHED already set from new task
5486 * Note: this also catches the edge-case of curr being in a throttled
5487 * group (e.g. via set_curr_task), since update_curr() (in the
5488 * enqueue of curr) will have resulted in resched being set. This
5489 * prevents us from potentially nominating it as a false LAST_BUDDY
5492 if (test_tsk_need_resched(curr
))
5495 /* Idle tasks are by definition preempted by non-idle tasks. */
5496 if (unlikely(curr
->policy
== SCHED_IDLE
) &&
5497 likely(p
->policy
!= SCHED_IDLE
))
5501 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5502 * is driven by the tick):
5504 if (unlikely(p
->policy
!= SCHED_NORMAL
) || !sched_feat(WAKEUP_PREEMPTION
))
5507 find_matching_se(&se
, &pse
);
5508 update_curr(cfs_rq_of(se
));
5510 if (wakeup_preempt_entity(se
, pse
) == 1) {
5512 * Bias pick_next to pick the sched entity that is
5513 * triggering this preemption.
5515 if (!next_buddy_marked
)
5516 set_next_buddy(pse
);
5525 * Only set the backward buddy when the current task is still
5526 * on the rq. This can happen when a wakeup gets interleaved
5527 * with schedule on the ->pre_schedule() or idle_balance()
5528 * point, either of which can * drop the rq lock.
5530 * Also, during early boot the idle thread is in the fair class,
5531 * for obvious reasons its a bad idea to schedule back to it.
5533 if (unlikely(!se
->on_rq
|| curr
== rq
->idle
))
5536 if (sched_feat(LAST_BUDDY
) && scale
&& entity_is_task(se
))
5540 static struct task_struct
*
5541 pick_next_task_fair(struct rq
*rq
, struct task_struct
*prev
, struct pin_cookie cookie
)
5543 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
5544 struct sched_entity
*se
;
5545 struct task_struct
*p
;
5549 #ifdef CONFIG_FAIR_GROUP_SCHED
5550 if (!cfs_rq
->nr_running
)
5553 if (prev
->sched_class
!= &fair_sched_class
)
5557 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5558 * likely that a next task is from the same cgroup as the current.
5560 * Therefore attempt to avoid putting and setting the entire cgroup
5561 * hierarchy, only change the part that actually changes.
5565 struct sched_entity
*curr
= cfs_rq
->curr
;
5568 * Since we got here without doing put_prev_entity() we also
5569 * have to consider cfs_rq->curr. If it is still a runnable
5570 * entity, update_curr() will update its vruntime, otherwise
5571 * forget we've ever seen it.
5575 update_curr(cfs_rq
);
5580 * This call to check_cfs_rq_runtime() will do the
5581 * throttle and dequeue its entity in the parent(s).
5582 * Therefore the 'simple' nr_running test will indeed
5585 if (unlikely(check_cfs_rq_runtime(cfs_rq
)))
5589 se
= pick_next_entity(cfs_rq
, curr
);
5590 cfs_rq
= group_cfs_rq(se
);
5596 * Since we haven't yet done put_prev_entity and if the selected task
5597 * is a different task than we started out with, try and touch the
5598 * least amount of cfs_rqs.
5601 struct sched_entity
*pse
= &prev
->se
;
5603 while (!(cfs_rq
= is_same_group(se
, pse
))) {
5604 int se_depth
= se
->depth
;
5605 int pse_depth
= pse
->depth
;
5607 if (se_depth
<= pse_depth
) {
5608 put_prev_entity(cfs_rq_of(pse
), pse
);
5609 pse
= parent_entity(pse
);
5611 if (se_depth
>= pse_depth
) {
5612 set_next_entity(cfs_rq_of(se
), se
);
5613 se
= parent_entity(se
);
5617 put_prev_entity(cfs_rq
, pse
);
5618 set_next_entity(cfs_rq
, se
);
5621 if (hrtick_enabled(rq
))
5622 hrtick_start_fair(rq
, p
);
5629 if (!cfs_rq
->nr_running
)
5632 put_prev_task(rq
, prev
);
5635 se
= pick_next_entity(cfs_rq
, NULL
);
5636 set_next_entity(cfs_rq
, se
);
5637 cfs_rq
= group_cfs_rq(se
);
5642 if (hrtick_enabled(rq
))
5643 hrtick_start_fair(rq
, p
);
5649 * This is OK, because current is on_cpu, which avoids it being picked
5650 * for load-balance and preemption/IRQs are still disabled avoiding
5651 * further scheduler activity on it and we're being very careful to
5652 * re-start the picking loop.
5654 lockdep_unpin_lock(&rq
->lock
, cookie
);
5655 new_tasks
= idle_balance(rq
);
5656 lockdep_repin_lock(&rq
->lock
, cookie
);
5658 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5659 * possible for any higher priority task to appear. In that case we
5660 * must re-start the pick_next_entity() loop.
5672 * Account for a descheduled task:
5674 static void put_prev_task_fair(struct rq
*rq
, struct task_struct
*prev
)
5676 struct sched_entity
*se
= &prev
->se
;
5677 struct cfs_rq
*cfs_rq
;
5679 for_each_sched_entity(se
) {
5680 cfs_rq
= cfs_rq_of(se
);
5681 put_prev_entity(cfs_rq
, se
);
5686 * sched_yield() is very simple
5688 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5690 static void yield_task_fair(struct rq
*rq
)
5692 struct task_struct
*curr
= rq
->curr
;
5693 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
5694 struct sched_entity
*se
= &curr
->se
;
5697 * Are we the only task in the tree?
5699 if (unlikely(rq
->nr_running
== 1))
5702 clear_buddies(cfs_rq
, se
);
5704 if (curr
->policy
!= SCHED_BATCH
) {
5705 update_rq_clock(rq
);
5707 * Update run-time statistics of the 'current'.
5709 update_curr(cfs_rq
);
5711 * Tell update_rq_clock() that we've just updated,
5712 * so we don't do microscopic update in schedule()
5713 * and double the fastpath cost.
5715 rq_clock_skip_update(rq
, true);
5721 static bool yield_to_task_fair(struct rq
*rq
, struct task_struct
*p
, bool preempt
)
5723 struct sched_entity
*se
= &p
->se
;
5725 /* throttled hierarchies are not runnable */
5726 if (!se
->on_rq
|| throttled_hierarchy(cfs_rq_of(se
)))
5729 /* Tell the scheduler that we'd really like pse to run next. */
5732 yield_task_fair(rq
);
5738 /**************************************************
5739 * Fair scheduling class load-balancing methods.
5743 * The purpose of load-balancing is to achieve the same basic fairness the
5744 * per-cpu scheduler provides, namely provide a proportional amount of compute
5745 * time to each task. This is expressed in the following equation:
5747 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5749 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5750 * W_i,0 is defined as:
5752 * W_i,0 = \Sum_j w_i,j (2)
5754 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5755 * is derived from the nice value as per sched_prio_to_weight[].
5757 * The weight average is an exponential decay average of the instantaneous
5760 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5762 * C_i is the compute capacity of cpu i, typically it is the
5763 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5764 * can also include other factors [XXX].
5766 * To achieve this balance we define a measure of imbalance which follows
5767 * directly from (1):
5769 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5771 * We them move tasks around to minimize the imbalance. In the continuous
5772 * function space it is obvious this converges, in the discrete case we get
5773 * a few fun cases generally called infeasible weight scenarios.
5776 * - infeasible weights;
5777 * - local vs global optima in the discrete case. ]
5782 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5783 * for all i,j solution, we create a tree of cpus that follows the hardware
5784 * topology where each level pairs two lower groups (or better). This results
5785 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5786 * tree to only the first of the previous level and we decrease the frequency
5787 * of load-balance at each level inv. proportional to the number of cpus in
5793 * \Sum { --- * --- * 2^i } = O(n) (5)
5795 * `- size of each group
5796 * | | `- number of cpus doing load-balance
5798 * `- sum over all levels
5800 * Coupled with a limit on how many tasks we can migrate every balance pass,
5801 * this makes (5) the runtime complexity of the balancer.
5803 * An important property here is that each CPU is still (indirectly) connected
5804 * to every other cpu in at most O(log n) steps:
5806 * The adjacency matrix of the resulting graph is given by:
5809 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5812 * And you'll find that:
5814 * A^(log_2 n)_i,j != 0 for all i,j (7)
5816 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5817 * The task movement gives a factor of O(m), giving a convergence complexity
5820 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5825 * In order to avoid CPUs going idle while there's still work to do, new idle
5826 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5827 * tree itself instead of relying on other CPUs to bring it work.
5829 * This adds some complexity to both (5) and (8) but it reduces the total idle
5837 * Cgroups make a horror show out of (2), instead of a simple sum we get:
5840 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
5845 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
5847 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5849 * The big problem is S_k, its a global sum needed to compute a local (W_i)
5852 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5853 * rewrite all of this once again.]
5856 static unsigned long __read_mostly max_load_balance_interval
= HZ
/10;
5858 enum fbq_type
{ regular
, remote
, all
};
5860 #define LBF_ALL_PINNED 0x01
5861 #define LBF_NEED_BREAK 0x02
5862 #define LBF_DST_PINNED 0x04
5863 #define LBF_SOME_PINNED 0x08
5866 struct sched_domain
*sd
;
5874 struct cpumask
*dst_grpmask
;
5876 enum cpu_idle_type idle
;
5878 /* The set of CPUs under consideration for load-balancing */
5879 struct cpumask
*cpus
;
5884 unsigned int loop_break
;
5885 unsigned int loop_max
;
5887 enum fbq_type fbq_type
;
5888 struct list_head tasks
;
5892 * Is this task likely cache-hot:
5894 static int task_hot(struct task_struct
*p
, struct lb_env
*env
)
5898 lockdep_assert_held(&env
->src_rq
->lock
);
5900 if (p
->sched_class
!= &fair_sched_class
)
5903 if (unlikely(p
->policy
== SCHED_IDLE
))
5907 * Buddy candidates are cache hot:
5909 if (sched_feat(CACHE_HOT_BUDDY
) && env
->dst_rq
->nr_running
&&
5910 (&p
->se
== cfs_rq_of(&p
->se
)->next
||
5911 &p
->se
== cfs_rq_of(&p
->se
)->last
))
5914 if (sysctl_sched_migration_cost
== -1)
5916 if (sysctl_sched_migration_cost
== 0)
5919 delta
= rq_clock_task(env
->src_rq
) - p
->se
.exec_start
;
5921 return delta
< (s64
)sysctl_sched_migration_cost
;
5924 #ifdef CONFIG_NUMA_BALANCING
5926 * Returns 1, if task migration degrades locality
5927 * Returns 0, if task migration improves locality i.e migration preferred.
5928 * Returns -1, if task migration is not affected by locality.
5930 static int migrate_degrades_locality(struct task_struct
*p
, struct lb_env
*env
)
5932 struct numa_group
*numa_group
= rcu_dereference(p
->numa_group
);
5933 unsigned long src_faults
, dst_faults
;
5934 int src_nid
, dst_nid
;
5936 if (!static_branch_likely(&sched_numa_balancing
))
5939 if (!p
->numa_faults
|| !(env
->sd
->flags
& SD_NUMA
))
5942 src_nid
= cpu_to_node(env
->src_cpu
);
5943 dst_nid
= cpu_to_node(env
->dst_cpu
);
5945 if (src_nid
== dst_nid
)
5948 /* Migrating away from the preferred node is always bad. */
5949 if (src_nid
== p
->numa_preferred_nid
) {
5950 if (env
->src_rq
->nr_running
> env
->src_rq
->nr_preferred_running
)
5956 /* Encourage migration to the preferred node. */
5957 if (dst_nid
== p
->numa_preferred_nid
)
5961 src_faults
= group_faults(p
, src_nid
);
5962 dst_faults
= group_faults(p
, dst_nid
);
5964 src_faults
= task_faults(p
, src_nid
);
5965 dst_faults
= task_faults(p
, dst_nid
);
5968 return dst_faults
< src_faults
;
5972 static inline int migrate_degrades_locality(struct task_struct
*p
,
5980 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
5983 int can_migrate_task(struct task_struct
*p
, struct lb_env
*env
)
5987 lockdep_assert_held(&env
->src_rq
->lock
);
5990 * We do not migrate tasks that are:
5991 * 1) throttled_lb_pair, or
5992 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5993 * 3) running (obviously), or
5994 * 4) are cache-hot on their current CPU.
5996 if (throttled_lb_pair(task_group(p
), env
->src_cpu
, env
->dst_cpu
))
5999 if (!cpumask_test_cpu(env
->dst_cpu
, tsk_cpus_allowed(p
))) {
6002 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_affine
);
6004 env
->flags
|= LBF_SOME_PINNED
;
6007 * Remember if this task can be migrated to any other cpu in
6008 * our sched_group. We may want to revisit it if we couldn't
6009 * meet load balance goals by pulling other tasks on src_cpu.
6011 * Also avoid computing new_dst_cpu if we have already computed
6012 * one in current iteration.
6014 if (!env
->dst_grpmask
|| (env
->flags
& LBF_DST_PINNED
))
6017 /* Prevent to re-select dst_cpu via env's cpus */
6018 for_each_cpu_and(cpu
, env
->dst_grpmask
, env
->cpus
) {
6019 if (cpumask_test_cpu(cpu
, tsk_cpus_allowed(p
))) {
6020 env
->flags
|= LBF_DST_PINNED
;
6021 env
->new_dst_cpu
= cpu
;
6029 /* Record that we found atleast one task that could run on dst_cpu */
6030 env
->flags
&= ~LBF_ALL_PINNED
;
6032 if (task_running(env
->src_rq
, p
)) {
6033 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_running
);
6038 * Aggressive migration if:
6039 * 1) destination numa is preferred
6040 * 2) task is cache cold, or
6041 * 3) too many balance attempts have failed.
6043 tsk_cache_hot
= migrate_degrades_locality(p
, env
);
6044 if (tsk_cache_hot
== -1)
6045 tsk_cache_hot
= task_hot(p
, env
);
6047 if (tsk_cache_hot
<= 0 ||
6048 env
->sd
->nr_balance_failed
> env
->sd
->cache_nice_tries
) {
6049 if (tsk_cache_hot
== 1) {
6050 schedstat_inc(env
->sd
, lb_hot_gained
[env
->idle
]);
6051 schedstat_inc(p
, se
.statistics
.nr_forced_migrations
);
6056 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_hot
);
6061 * detach_task() -- detach the task for the migration specified in env
6063 static void detach_task(struct task_struct
*p
, struct lb_env
*env
)
6065 lockdep_assert_held(&env
->src_rq
->lock
);
6067 p
->on_rq
= TASK_ON_RQ_MIGRATING
;
6068 deactivate_task(env
->src_rq
, p
, 0);
6069 set_task_cpu(p
, env
->dst_cpu
);
6073 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6074 * part of active balancing operations within "domain".
6076 * Returns a task if successful and NULL otherwise.
6078 static struct task_struct
*detach_one_task(struct lb_env
*env
)
6080 struct task_struct
*p
, *n
;
6082 lockdep_assert_held(&env
->src_rq
->lock
);
6084 list_for_each_entry_safe(p
, n
, &env
->src_rq
->cfs_tasks
, se
.group_node
) {
6085 if (!can_migrate_task(p
, env
))
6088 detach_task(p
, env
);
6091 * Right now, this is only the second place where
6092 * lb_gained[env->idle] is updated (other is detach_tasks)
6093 * so we can safely collect stats here rather than
6094 * inside detach_tasks().
6096 schedstat_inc(env
->sd
, lb_gained
[env
->idle
]);
6102 static const unsigned int sched_nr_migrate_break
= 32;
6105 * detach_tasks() -- tries to detach up to imbalance weighted load from
6106 * busiest_rq, as part of a balancing operation within domain "sd".
6108 * Returns number of detached tasks if successful and 0 otherwise.
6110 static int detach_tasks(struct lb_env
*env
)
6112 struct list_head
*tasks
= &env
->src_rq
->cfs_tasks
;
6113 struct task_struct
*p
;
6117 lockdep_assert_held(&env
->src_rq
->lock
);
6119 if (env
->imbalance
<= 0)
6122 while (!list_empty(tasks
)) {
6124 * We don't want to steal all, otherwise we may be treated likewise,
6125 * which could at worst lead to a livelock crash.
6127 if (env
->idle
!= CPU_NOT_IDLE
&& env
->src_rq
->nr_running
<= 1)
6130 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
6133 /* We've more or less seen every task there is, call it quits */
6134 if (env
->loop
> env
->loop_max
)
6137 /* take a breather every nr_migrate tasks */
6138 if (env
->loop
> env
->loop_break
) {
6139 env
->loop_break
+= sched_nr_migrate_break
;
6140 env
->flags
|= LBF_NEED_BREAK
;
6144 if (!can_migrate_task(p
, env
))
6147 load
= task_h_load(p
);
6149 if (sched_feat(LB_MIN
) && load
< 16 && !env
->sd
->nr_balance_failed
)
6152 if ((load
/ 2) > env
->imbalance
)
6155 detach_task(p
, env
);
6156 list_add(&p
->se
.group_node
, &env
->tasks
);
6159 env
->imbalance
-= load
;
6161 #ifdef CONFIG_PREEMPT
6163 * NEWIDLE balancing is a source of latency, so preemptible
6164 * kernels will stop after the first task is detached to minimize
6165 * the critical section.
6167 if (env
->idle
== CPU_NEWLY_IDLE
)
6172 * We only want to steal up to the prescribed amount of
6175 if (env
->imbalance
<= 0)
6180 list_move_tail(&p
->se
.group_node
, tasks
);
6184 * Right now, this is one of only two places we collect this stat
6185 * so we can safely collect detach_one_task() stats here rather
6186 * than inside detach_one_task().
6188 schedstat_add(env
->sd
, lb_gained
[env
->idle
], detached
);
6194 * attach_task() -- attach the task detached by detach_task() to its new rq.
6196 static void attach_task(struct rq
*rq
, struct task_struct
*p
)
6198 lockdep_assert_held(&rq
->lock
);
6200 BUG_ON(task_rq(p
) != rq
);
6201 activate_task(rq
, p
, 0);
6202 p
->on_rq
= TASK_ON_RQ_QUEUED
;
6203 check_preempt_curr(rq
, p
, 0);
6207 * attach_one_task() -- attaches the task returned from detach_one_task() to
6210 static void attach_one_task(struct rq
*rq
, struct task_struct
*p
)
6212 raw_spin_lock(&rq
->lock
);
6214 raw_spin_unlock(&rq
->lock
);
6218 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6221 static void attach_tasks(struct lb_env
*env
)
6223 struct list_head
*tasks
= &env
->tasks
;
6224 struct task_struct
*p
;
6226 raw_spin_lock(&env
->dst_rq
->lock
);
6228 while (!list_empty(tasks
)) {
6229 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
6230 list_del_init(&p
->se
.group_node
);
6232 attach_task(env
->dst_rq
, p
);
6235 raw_spin_unlock(&env
->dst_rq
->lock
);
6238 #ifdef CONFIG_FAIR_GROUP_SCHED
6239 static void update_blocked_averages(int cpu
)
6241 struct rq
*rq
= cpu_rq(cpu
);
6242 struct cfs_rq
*cfs_rq
;
6243 unsigned long flags
;
6245 raw_spin_lock_irqsave(&rq
->lock
, flags
);
6246 update_rq_clock(rq
);
6249 * Iterates the task_group tree in a bottom up fashion, see
6250 * list_add_leaf_cfs_rq() for details.
6252 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
6253 /* throttled entities do not contribute to load */
6254 if (throttled_hierarchy(cfs_rq
))
6257 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq
), cfs_rq
, true))
6258 update_tg_load_avg(cfs_rq
, 0);
6260 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
6264 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6265 * This needs to be done in a top-down fashion because the load of a child
6266 * group is a fraction of its parents load.
6268 static void update_cfs_rq_h_load(struct cfs_rq
*cfs_rq
)
6270 struct rq
*rq
= rq_of(cfs_rq
);
6271 struct sched_entity
*se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
6272 unsigned long now
= jiffies
;
6275 if (cfs_rq
->last_h_load_update
== now
)
6278 cfs_rq
->h_load_next
= NULL
;
6279 for_each_sched_entity(se
) {
6280 cfs_rq
= cfs_rq_of(se
);
6281 cfs_rq
->h_load_next
= se
;
6282 if (cfs_rq
->last_h_load_update
== now
)
6287 cfs_rq
->h_load
= cfs_rq_load_avg(cfs_rq
);
6288 cfs_rq
->last_h_load_update
= now
;
6291 while ((se
= cfs_rq
->h_load_next
) != NULL
) {
6292 load
= cfs_rq
->h_load
;
6293 load
= div64_ul(load
* se
->avg
.load_avg
,
6294 cfs_rq_load_avg(cfs_rq
) + 1);
6295 cfs_rq
= group_cfs_rq(se
);
6296 cfs_rq
->h_load
= load
;
6297 cfs_rq
->last_h_load_update
= now
;
6301 static unsigned long task_h_load(struct task_struct
*p
)
6303 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
6305 update_cfs_rq_h_load(cfs_rq
);
6306 return div64_ul(p
->se
.avg
.load_avg
* cfs_rq
->h_load
,
6307 cfs_rq_load_avg(cfs_rq
) + 1);
6310 static inline void update_blocked_averages(int cpu
)
6312 struct rq
*rq
= cpu_rq(cpu
);
6313 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
6314 unsigned long flags
;
6316 raw_spin_lock_irqsave(&rq
->lock
, flags
);
6317 update_rq_clock(rq
);
6318 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq
), cfs_rq
, true);
6319 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
6322 static unsigned long task_h_load(struct task_struct
*p
)
6324 return p
->se
.avg
.load_avg
;
6328 /********** Helpers for find_busiest_group ************************/
6337 * sg_lb_stats - stats of a sched_group required for load_balancing
6339 struct sg_lb_stats
{
6340 unsigned long avg_load
; /*Avg load across the CPUs of the group */
6341 unsigned long group_load
; /* Total load over the CPUs of the group */
6342 unsigned long sum_weighted_load
; /* Weighted load of group's tasks */
6343 unsigned long load_per_task
;
6344 unsigned long group_capacity
;
6345 unsigned long group_util
; /* Total utilization of the group */
6346 unsigned int sum_nr_running
; /* Nr tasks running in the group */
6347 unsigned int idle_cpus
;
6348 unsigned int group_weight
;
6349 enum group_type group_type
;
6350 int group_no_capacity
;
6351 #ifdef CONFIG_NUMA_BALANCING
6352 unsigned int nr_numa_running
;
6353 unsigned int nr_preferred_running
;
6358 * sd_lb_stats - Structure to store the statistics of a sched_domain
6359 * during load balancing.
6361 struct sd_lb_stats
{
6362 struct sched_group
*busiest
; /* Busiest group in this sd */
6363 struct sched_group
*local
; /* Local group in this sd */
6364 unsigned long total_load
; /* Total load of all groups in sd */
6365 unsigned long total_capacity
; /* Total capacity of all groups in sd */
6366 unsigned long avg_load
; /* Average load across all groups in sd */
6368 struct sg_lb_stats busiest_stat
;/* Statistics of the busiest group */
6369 struct sg_lb_stats local_stat
; /* Statistics of the local group */
6372 static inline void init_sd_lb_stats(struct sd_lb_stats
*sds
)
6375 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6376 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6377 * We must however clear busiest_stat::avg_load because
6378 * update_sd_pick_busiest() reads this before assignment.
6380 *sds
= (struct sd_lb_stats
){
6384 .total_capacity
= 0UL,
6387 .sum_nr_running
= 0,
6388 .group_type
= group_other
,
6394 * get_sd_load_idx - Obtain the load index for a given sched domain.
6395 * @sd: The sched_domain whose load_idx is to be obtained.
6396 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6398 * Return: The load index.
6400 static inline int get_sd_load_idx(struct sched_domain
*sd
,
6401 enum cpu_idle_type idle
)
6407 load_idx
= sd
->busy_idx
;
6410 case CPU_NEWLY_IDLE
:
6411 load_idx
= sd
->newidle_idx
;
6414 load_idx
= sd
->idle_idx
;
6421 static unsigned long scale_rt_capacity(int cpu
)
6423 struct rq
*rq
= cpu_rq(cpu
);
6424 u64 total
, used
, age_stamp
, avg
;
6428 * Since we're reading these variables without serialization make sure
6429 * we read them once before doing sanity checks on them.
6431 age_stamp
= READ_ONCE(rq
->age_stamp
);
6432 avg
= READ_ONCE(rq
->rt_avg
);
6433 delta
= __rq_clock_broken(rq
) - age_stamp
;
6435 if (unlikely(delta
< 0))
6438 total
= sched_avg_period() + delta
;
6440 used
= div_u64(avg
, total
);
6442 if (likely(used
< SCHED_CAPACITY_SCALE
))
6443 return SCHED_CAPACITY_SCALE
- used
;
6448 static void update_cpu_capacity(struct sched_domain
*sd
, int cpu
)
6450 unsigned long capacity
= arch_scale_cpu_capacity(sd
, cpu
);
6451 struct sched_group
*sdg
= sd
->groups
;
6453 cpu_rq(cpu
)->cpu_capacity_orig
= capacity
;
6455 capacity
*= scale_rt_capacity(cpu
);
6456 capacity
>>= SCHED_CAPACITY_SHIFT
;
6461 cpu_rq(cpu
)->cpu_capacity
= capacity
;
6462 sdg
->sgc
->capacity
= capacity
;
6465 void update_group_capacity(struct sched_domain
*sd
, int cpu
)
6467 struct sched_domain
*child
= sd
->child
;
6468 struct sched_group
*group
, *sdg
= sd
->groups
;
6469 unsigned long capacity
;
6470 unsigned long interval
;
6472 interval
= msecs_to_jiffies(sd
->balance_interval
);
6473 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
6474 sdg
->sgc
->next_update
= jiffies
+ interval
;
6477 update_cpu_capacity(sd
, cpu
);
6483 if (child
->flags
& SD_OVERLAP
) {
6485 * SD_OVERLAP domains cannot assume that child groups
6486 * span the current group.
6489 for_each_cpu(cpu
, sched_group_cpus(sdg
)) {
6490 struct sched_group_capacity
*sgc
;
6491 struct rq
*rq
= cpu_rq(cpu
);
6494 * build_sched_domains() -> init_sched_groups_capacity()
6495 * gets here before we've attached the domains to the
6498 * Use capacity_of(), which is set irrespective of domains
6499 * in update_cpu_capacity().
6501 * This avoids capacity from being 0 and
6502 * causing divide-by-zero issues on boot.
6504 if (unlikely(!rq
->sd
)) {
6505 capacity
+= capacity_of(cpu
);
6509 sgc
= rq
->sd
->groups
->sgc
;
6510 capacity
+= sgc
->capacity
;
6514 * !SD_OVERLAP domains can assume that child groups
6515 * span the current group.
6518 group
= child
->groups
;
6520 capacity
+= group
->sgc
->capacity
;
6521 group
= group
->next
;
6522 } while (group
!= child
->groups
);
6525 sdg
->sgc
->capacity
= capacity
;
6529 * Check whether the capacity of the rq has been noticeably reduced by side
6530 * activity. The imbalance_pct is used for the threshold.
6531 * Return true is the capacity is reduced
6534 check_cpu_capacity(struct rq
*rq
, struct sched_domain
*sd
)
6536 return ((rq
->cpu_capacity
* sd
->imbalance_pct
) <
6537 (rq
->cpu_capacity_orig
* 100));
6541 * Group imbalance indicates (and tries to solve) the problem where balancing
6542 * groups is inadequate due to tsk_cpus_allowed() constraints.
6544 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6545 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6548 * { 0 1 2 3 } { 4 5 6 7 }
6551 * If we were to balance group-wise we'd place two tasks in the first group and
6552 * two tasks in the second group. Clearly this is undesired as it will overload
6553 * cpu 3 and leave one of the cpus in the second group unused.
6555 * The current solution to this issue is detecting the skew in the first group
6556 * by noticing the lower domain failed to reach balance and had difficulty
6557 * moving tasks due to affinity constraints.
6559 * When this is so detected; this group becomes a candidate for busiest; see
6560 * update_sd_pick_busiest(). And calculate_imbalance() and
6561 * find_busiest_group() avoid some of the usual balance conditions to allow it
6562 * to create an effective group imbalance.
6564 * This is a somewhat tricky proposition since the next run might not find the
6565 * group imbalance and decide the groups need to be balanced again. A most
6566 * subtle and fragile situation.
6569 static inline int sg_imbalanced(struct sched_group
*group
)
6571 return group
->sgc
->imbalance
;
6575 * group_has_capacity returns true if the group has spare capacity that could
6576 * be used by some tasks.
6577 * We consider that a group has spare capacity if the * number of task is
6578 * smaller than the number of CPUs or if the utilization is lower than the
6579 * available capacity for CFS tasks.
6580 * For the latter, we use a threshold to stabilize the state, to take into
6581 * account the variance of the tasks' load and to return true if the available
6582 * capacity in meaningful for the load balancer.
6583 * As an example, an available capacity of 1% can appear but it doesn't make
6584 * any benefit for the load balance.
6587 group_has_capacity(struct lb_env
*env
, struct sg_lb_stats
*sgs
)
6589 if (sgs
->sum_nr_running
< sgs
->group_weight
)
6592 if ((sgs
->group_capacity
* 100) >
6593 (sgs
->group_util
* env
->sd
->imbalance_pct
))
6600 * group_is_overloaded returns true if the group has more tasks than it can
6602 * group_is_overloaded is not equals to !group_has_capacity because a group
6603 * with the exact right number of tasks, has no more spare capacity but is not
6604 * overloaded so both group_has_capacity and group_is_overloaded return
6608 group_is_overloaded(struct lb_env
*env
, struct sg_lb_stats
*sgs
)
6610 if (sgs
->sum_nr_running
<= sgs
->group_weight
)
6613 if ((sgs
->group_capacity
* 100) <
6614 (sgs
->group_util
* env
->sd
->imbalance_pct
))
6621 group_type
group_classify(struct sched_group
*group
,
6622 struct sg_lb_stats
*sgs
)
6624 if (sgs
->group_no_capacity
)
6625 return group_overloaded
;
6627 if (sg_imbalanced(group
))
6628 return group_imbalanced
;
6634 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6635 * @env: The load balancing environment.
6636 * @group: sched_group whose statistics are to be updated.
6637 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6638 * @local_group: Does group contain this_cpu.
6639 * @sgs: variable to hold the statistics for this group.
6640 * @overload: Indicate more than one runnable task for any CPU.
6642 static inline void update_sg_lb_stats(struct lb_env
*env
,
6643 struct sched_group
*group
, int load_idx
,
6644 int local_group
, struct sg_lb_stats
*sgs
,
6650 memset(sgs
, 0, sizeof(*sgs
));
6652 for_each_cpu_and(i
, sched_group_cpus(group
), env
->cpus
) {
6653 struct rq
*rq
= cpu_rq(i
);
6655 /* Bias balancing toward cpus of our domain */
6657 load
= target_load(i
, load_idx
);
6659 load
= source_load(i
, load_idx
);
6661 sgs
->group_load
+= load
;
6662 sgs
->group_util
+= cpu_util(i
);
6663 sgs
->sum_nr_running
+= rq
->cfs
.h_nr_running
;
6665 nr_running
= rq
->nr_running
;
6669 #ifdef CONFIG_NUMA_BALANCING
6670 sgs
->nr_numa_running
+= rq
->nr_numa_running
;
6671 sgs
->nr_preferred_running
+= rq
->nr_preferred_running
;
6673 sgs
->sum_weighted_load
+= weighted_cpuload(i
);
6675 * No need to call idle_cpu() if nr_running is not 0
6677 if (!nr_running
&& idle_cpu(i
))
6681 /* Adjust by relative CPU capacity of the group */
6682 sgs
->group_capacity
= group
->sgc
->capacity
;
6683 sgs
->avg_load
= (sgs
->group_load
*SCHED_CAPACITY_SCALE
) / sgs
->group_capacity
;
6685 if (sgs
->sum_nr_running
)
6686 sgs
->load_per_task
= sgs
->sum_weighted_load
/ sgs
->sum_nr_running
;
6688 sgs
->group_weight
= group
->group_weight
;
6690 sgs
->group_no_capacity
= group_is_overloaded(env
, sgs
);
6691 sgs
->group_type
= group_classify(group
, sgs
);
6695 * update_sd_pick_busiest - return 1 on busiest group
6696 * @env: The load balancing environment.
6697 * @sds: sched_domain statistics
6698 * @sg: sched_group candidate to be checked for being the busiest
6699 * @sgs: sched_group statistics
6701 * Determine if @sg is a busier group than the previously selected
6704 * Return: %true if @sg is a busier group than the previously selected
6705 * busiest group. %false otherwise.
6707 static bool update_sd_pick_busiest(struct lb_env
*env
,
6708 struct sd_lb_stats
*sds
,
6709 struct sched_group
*sg
,
6710 struct sg_lb_stats
*sgs
)
6712 struct sg_lb_stats
*busiest
= &sds
->busiest_stat
;
6714 if (sgs
->group_type
> busiest
->group_type
)
6717 if (sgs
->group_type
< busiest
->group_type
)
6720 if (sgs
->avg_load
<= busiest
->avg_load
)
6723 /* This is the busiest node in its class. */
6724 if (!(env
->sd
->flags
& SD_ASYM_PACKING
))
6727 /* No ASYM_PACKING if target cpu is already busy */
6728 if (env
->idle
== CPU_NOT_IDLE
)
6731 * ASYM_PACKING needs to move all the work to the lowest
6732 * numbered CPUs in the group, therefore mark all groups
6733 * higher than ourself as busy.
6735 if (sgs
->sum_nr_running
&& env
->dst_cpu
< group_first_cpu(sg
)) {
6739 /* Prefer to move from highest possible cpu's work */
6740 if (group_first_cpu(sds
->busiest
) < group_first_cpu(sg
))
6747 #ifdef CONFIG_NUMA_BALANCING
6748 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
6750 if (sgs
->sum_nr_running
> sgs
->nr_numa_running
)
6752 if (sgs
->sum_nr_running
> sgs
->nr_preferred_running
)
6757 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
6759 if (rq
->nr_running
> rq
->nr_numa_running
)
6761 if (rq
->nr_running
> rq
->nr_preferred_running
)
6766 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
6771 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
6775 #endif /* CONFIG_NUMA_BALANCING */
6778 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6779 * @env: The load balancing environment.
6780 * @sds: variable to hold the statistics for this sched_domain.
6782 static inline void update_sd_lb_stats(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6784 struct sched_domain
*child
= env
->sd
->child
;
6785 struct sched_group
*sg
= env
->sd
->groups
;
6786 struct sg_lb_stats tmp_sgs
;
6787 int load_idx
, prefer_sibling
= 0;
6788 bool overload
= false;
6790 if (child
&& child
->flags
& SD_PREFER_SIBLING
)
6793 load_idx
= get_sd_load_idx(env
->sd
, env
->idle
);
6796 struct sg_lb_stats
*sgs
= &tmp_sgs
;
6799 local_group
= cpumask_test_cpu(env
->dst_cpu
, sched_group_cpus(sg
));
6802 sgs
= &sds
->local_stat
;
6804 if (env
->idle
!= CPU_NEWLY_IDLE
||
6805 time_after_eq(jiffies
, sg
->sgc
->next_update
))
6806 update_group_capacity(env
->sd
, env
->dst_cpu
);
6809 update_sg_lb_stats(env
, sg
, load_idx
, local_group
, sgs
,
6816 * In case the child domain prefers tasks go to siblings
6817 * first, lower the sg capacity so that we'll try
6818 * and move all the excess tasks away. We lower the capacity
6819 * of a group only if the local group has the capacity to fit
6820 * these excess tasks. The extra check prevents the case where
6821 * you always pull from the heaviest group when it is already
6822 * under-utilized (possible with a large weight task outweighs
6823 * the tasks on the system).
6825 if (prefer_sibling
&& sds
->local
&&
6826 group_has_capacity(env
, &sds
->local_stat
) &&
6827 (sgs
->sum_nr_running
> 1)) {
6828 sgs
->group_no_capacity
= 1;
6829 sgs
->group_type
= group_classify(sg
, sgs
);
6832 if (update_sd_pick_busiest(env
, sds
, sg
, sgs
)) {
6834 sds
->busiest_stat
= *sgs
;
6838 /* Now, start updating sd_lb_stats */
6839 sds
->total_load
+= sgs
->group_load
;
6840 sds
->total_capacity
+= sgs
->group_capacity
;
6843 } while (sg
!= env
->sd
->groups
);
6845 if (env
->sd
->flags
& SD_NUMA
)
6846 env
->fbq_type
= fbq_classify_group(&sds
->busiest_stat
);
6848 if (!env
->sd
->parent
) {
6849 /* update overload indicator if we are at root domain */
6850 if (env
->dst_rq
->rd
->overload
!= overload
)
6851 env
->dst_rq
->rd
->overload
= overload
;
6857 * check_asym_packing - Check to see if the group is packed into the
6860 * This is primarily intended to used at the sibling level. Some
6861 * cores like POWER7 prefer to use lower numbered SMT threads. In the
6862 * case of POWER7, it can move to lower SMT modes only when higher
6863 * threads are idle. When in lower SMT modes, the threads will
6864 * perform better since they share less core resources. Hence when we
6865 * have idle threads, we want them to be the higher ones.
6867 * This packing function is run on idle threads. It checks to see if
6868 * the busiest CPU in this domain (core in the P7 case) has a higher
6869 * CPU number than the packing function is being run on. Here we are
6870 * assuming lower CPU number will be equivalent to lower a SMT thread
6873 * Return: 1 when packing is required and a task should be moved to
6874 * this CPU. The amount of the imbalance is returned in *imbalance.
6876 * @env: The load balancing environment.
6877 * @sds: Statistics of the sched_domain which is to be packed
6879 static int check_asym_packing(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6883 if (!(env
->sd
->flags
& SD_ASYM_PACKING
))
6886 if (env
->idle
== CPU_NOT_IDLE
)
6892 busiest_cpu
= group_first_cpu(sds
->busiest
);
6893 if (env
->dst_cpu
> busiest_cpu
)
6896 env
->imbalance
= DIV_ROUND_CLOSEST(
6897 sds
->busiest_stat
.avg_load
* sds
->busiest_stat
.group_capacity
,
6898 SCHED_CAPACITY_SCALE
);
6904 * fix_small_imbalance - Calculate the minor imbalance that exists
6905 * amongst the groups of a sched_domain, during
6907 * @env: The load balancing environment.
6908 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6911 void fix_small_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6913 unsigned long tmp
, capa_now
= 0, capa_move
= 0;
6914 unsigned int imbn
= 2;
6915 unsigned long scaled_busy_load_per_task
;
6916 struct sg_lb_stats
*local
, *busiest
;
6918 local
= &sds
->local_stat
;
6919 busiest
= &sds
->busiest_stat
;
6921 if (!local
->sum_nr_running
)
6922 local
->load_per_task
= cpu_avg_load_per_task(env
->dst_cpu
);
6923 else if (busiest
->load_per_task
> local
->load_per_task
)
6926 scaled_busy_load_per_task
=
6927 (busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) /
6928 busiest
->group_capacity
;
6930 if (busiest
->avg_load
+ scaled_busy_load_per_task
>=
6931 local
->avg_load
+ (scaled_busy_load_per_task
* imbn
)) {
6932 env
->imbalance
= busiest
->load_per_task
;
6937 * OK, we don't have enough imbalance to justify moving tasks,
6938 * however we may be able to increase total CPU capacity used by
6942 capa_now
+= busiest
->group_capacity
*
6943 min(busiest
->load_per_task
, busiest
->avg_load
);
6944 capa_now
+= local
->group_capacity
*
6945 min(local
->load_per_task
, local
->avg_load
);
6946 capa_now
/= SCHED_CAPACITY_SCALE
;
6948 /* Amount of load we'd subtract */
6949 if (busiest
->avg_load
> scaled_busy_load_per_task
) {
6950 capa_move
+= busiest
->group_capacity
*
6951 min(busiest
->load_per_task
,
6952 busiest
->avg_load
- scaled_busy_load_per_task
);
6955 /* Amount of load we'd add */
6956 if (busiest
->avg_load
* busiest
->group_capacity
<
6957 busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) {
6958 tmp
= (busiest
->avg_load
* busiest
->group_capacity
) /
6959 local
->group_capacity
;
6961 tmp
= (busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) /
6962 local
->group_capacity
;
6964 capa_move
+= local
->group_capacity
*
6965 min(local
->load_per_task
, local
->avg_load
+ tmp
);
6966 capa_move
/= SCHED_CAPACITY_SCALE
;
6968 /* Move if we gain throughput */
6969 if (capa_move
> capa_now
)
6970 env
->imbalance
= busiest
->load_per_task
;
6974 * calculate_imbalance - Calculate the amount of imbalance present within the
6975 * groups of a given sched_domain during load balance.
6976 * @env: load balance environment
6977 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
6979 static inline void calculate_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6981 unsigned long max_pull
, load_above_capacity
= ~0UL;
6982 struct sg_lb_stats
*local
, *busiest
;
6984 local
= &sds
->local_stat
;
6985 busiest
= &sds
->busiest_stat
;
6987 if (busiest
->group_type
== group_imbalanced
) {
6989 * In the group_imb case we cannot rely on group-wide averages
6990 * to ensure cpu-load equilibrium, look at wider averages. XXX
6992 busiest
->load_per_task
=
6993 min(busiest
->load_per_task
, sds
->avg_load
);
6997 * In the presence of smp nice balancing, certain scenarios can have
6998 * max load less than avg load(as we skip the groups at or below
6999 * its cpu_capacity, while calculating max_load..)
7001 if (busiest
->avg_load
<= sds
->avg_load
||
7002 local
->avg_load
>= sds
->avg_load
) {
7004 return fix_small_imbalance(env
, sds
);
7008 * If there aren't any idle cpus, avoid creating some.
7010 if (busiest
->group_type
== group_overloaded
&&
7011 local
->group_type
== group_overloaded
) {
7012 load_above_capacity
= busiest
->sum_nr_running
*
7014 if (load_above_capacity
> busiest
->group_capacity
)
7015 load_above_capacity
-= busiest
->group_capacity
;
7017 load_above_capacity
= ~0UL;
7021 * We're trying to get all the cpus to the average_load, so we don't
7022 * want to push ourselves above the average load, nor do we wish to
7023 * reduce the max loaded cpu below the average load. At the same time,
7024 * we also don't want to reduce the group load below the group capacity
7025 * (so that we can implement power-savings policies etc). Thus we look
7026 * for the minimum possible imbalance.
7028 max_pull
= min(busiest
->avg_load
- sds
->avg_load
, load_above_capacity
);
7030 /* How much load to actually move to equalise the imbalance */
7031 env
->imbalance
= min(
7032 max_pull
* busiest
->group_capacity
,
7033 (sds
->avg_load
- local
->avg_load
) * local
->group_capacity
7034 ) / SCHED_CAPACITY_SCALE
;
7037 * if *imbalance is less than the average load per runnable task
7038 * there is no guarantee that any tasks will be moved so we'll have
7039 * a think about bumping its value to force at least one task to be
7042 if (env
->imbalance
< busiest
->load_per_task
)
7043 return fix_small_imbalance(env
, sds
);
7046 /******* find_busiest_group() helpers end here *********************/
7049 * find_busiest_group - Returns the busiest group within the sched_domain
7050 * if there is an imbalance. If there isn't an imbalance, and
7051 * the user has opted for power-savings, it returns a group whose
7052 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
7053 * such a group exists.
7055 * Also calculates the amount of weighted load which should be moved
7056 * to restore balance.
7058 * @env: The load balancing environment.
7060 * Return: - The busiest group if imbalance exists.
7061 * - If no imbalance and user has opted for power-savings balance,
7062 * return the least loaded group whose CPUs can be
7063 * put to idle by rebalancing its tasks onto our group.
7065 static struct sched_group
*find_busiest_group(struct lb_env
*env
)
7067 struct sg_lb_stats
*local
, *busiest
;
7068 struct sd_lb_stats sds
;
7070 init_sd_lb_stats(&sds
);
7073 * Compute the various statistics relavent for load balancing at
7076 update_sd_lb_stats(env
, &sds
);
7077 local
= &sds
.local_stat
;
7078 busiest
= &sds
.busiest_stat
;
7080 /* ASYM feature bypasses nice load balance check */
7081 if (check_asym_packing(env
, &sds
))
7084 /* There is no busy sibling group to pull tasks from */
7085 if (!sds
.busiest
|| busiest
->sum_nr_running
== 0)
7088 sds
.avg_load
= (SCHED_CAPACITY_SCALE
* sds
.total_load
)
7089 / sds
.total_capacity
;
7092 * If the busiest group is imbalanced the below checks don't
7093 * work because they assume all things are equal, which typically
7094 * isn't true due to cpus_allowed constraints and the like.
7096 if (busiest
->group_type
== group_imbalanced
)
7099 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7100 if (env
->idle
== CPU_NEWLY_IDLE
&& group_has_capacity(env
, local
) &&
7101 busiest
->group_no_capacity
)
7105 * If the local group is busier than the selected busiest group
7106 * don't try and pull any tasks.
7108 if (local
->avg_load
>= busiest
->avg_load
)
7112 * Don't pull any tasks if this group is already above the domain
7115 if (local
->avg_load
>= sds
.avg_load
)
7118 if (env
->idle
== CPU_IDLE
) {
7120 * This cpu is idle. If the busiest group is not overloaded
7121 * and there is no imbalance between this and busiest group
7122 * wrt idle cpus, it is balanced. The imbalance becomes
7123 * significant if the diff is greater than 1 otherwise we
7124 * might end up to just move the imbalance on another group
7126 if ((busiest
->group_type
!= group_overloaded
) &&
7127 (local
->idle_cpus
<= (busiest
->idle_cpus
+ 1)))
7131 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7132 * imbalance_pct to be conservative.
7134 if (100 * busiest
->avg_load
<=
7135 env
->sd
->imbalance_pct
* local
->avg_load
)
7140 /* Looks like there is an imbalance. Compute it */
7141 calculate_imbalance(env
, &sds
);
7150 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7152 static struct rq
*find_busiest_queue(struct lb_env
*env
,
7153 struct sched_group
*group
)
7155 struct rq
*busiest
= NULL
, *rq
;
7156 unsigned long busiest_load
= 0, busiest_capacity
= 1;
7159 for_each_cpu_and(i
, sched_group_cpus(group
), env
->cpus
) {
7160 unsigned long capacity
, wl
;
7164 rt
= fbq_classify_rq(rq
);
7167 * We classify groups/runqueues into three groups:
7168 * - regular: there are !numa tasks
7169 * - remote: there are numa tasks that run on the 'wrong' node
7170 * - all: there is no distinction
7172 * In order to avoid migrating ideally placed numa tasks,
7173 * ignore those when there's better options.
7175 * If we ignore the actual busiest queue to migrate another
7176 * task, the next balance pass can still reduce the busiest
7177 * queue by moving tasks around inside the node.
7179 * If we cannot move enough load due to this classification
7180 * the next pass will adjust the group classification and
7181 * allow migration of more tasks.
7183 * Both cases only affect the total convergence complexity.
7185 if (rt
> env
->fbq_type
)
7188 capacity
= capacity_of(i
);
7190 wl
= weighted_cpuload(i
);
7193 * When comparing with imbalance, use weighted_cpuload()
7194 * which is not scaled with the cpu capacity.
7197 if (rq
->nr_running
== 1 && wl
> env
->imbalance
&&
7198 !check_cpu_capacity(rq
, env
->sd
))
7202 * For the load comparisons with the other cpu's, consider
7203 * the weighted_cpuload() scaled with the cpu capacity, so
7204 * that the load can be moved away from the cpu that is
7205 * potentially running at a lower capacity.
7207 * Thus we're looking for max(wl_i / capacity_i), crosswise
7208 * multiplication to rid ourselves of the division works out
7209 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
7210 * our previous maximum.
7212 if (wl
* busiest_capacity
> busiest_load
* capacity
) {
7214 busiest_capacity
= capacity
;
7223 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7224 * so long as it is large enough.
7226 #define MAX_PINNED_INTERVAL 512
7228 /* Working cpumask for load_balance and load_balance_newidle. */
7229 DEFINE_PER_CPU(cpumask_var_t
, load_balance_mask
);
7231 static int need_active_balance(struct lb_env
*env
)
7233 struct sched_domain
*sd
= env
->sd
;
7235 if (env
->idle
== CPU_NEWLY_IDLE
) {
7238 * ASYM_PACKING needs to force migrate tasks from busy but
7239 * higher numbered CPUs in order to pack all tasks in the
7240 * lowest numbered CPUs.
7242 if ((sd
->flags
& SD_ASYM_PACKING
) && env
->src_cpu
> env
->dst_cpu
)
7247 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7248 * It's worth migrating the task if the src_cpu's capacity is reduced
7249 * because of other sched_class or IRQs if more capacity stays
7250 * available on dst_cpu.
7252 if ((env
->idle
!= CPU_NOT_IDLE
) &&
7253 (env
->src_rq
->cfs
.h_nr_running
== 1)) {
7254 if ((check_cpu_capacity(env
->src_rq
, sd
)) &&
7255 (capacity_of(env
->src_cpu
)*sd
->imbalance_pct
< capacity_of(env
->dst_cpu
)*100))
7259 return unlikely(sd
->nr_balance_failed
> sd
->cache_nice_tries
+2);
7262 static int active_load_balance_cpu_stop(void *data
);
7264 static int should_we_balance(struct lb_env
*env
)
7266 struct sched_group
*sg
= env
->sd
->groups
;
7267 struct cpumask
*sg_cpus
, *sg_mask
;
7268 int cpu
, balance_cpu
= -1;
7271 * In the newly idle case, we will allow all the cpu's
7272 * to do the newly idle load balance.
7274 if (env
->idle
== CPU_NEWLY_IDLE
)
7277 sg_cpus
= sched_group_cpus(sg
);
7278 sg_mask
= sched_group_mask(sg
);
7279 /* Try to find first idle cpu */
7280 for_each_cpu_and(cpu
, sg_cpus
, env
->cpus
) {
7281 if (!cpumask_test_cpu(cpu
, sg_mask
) || !idle_cpu(cpu
))
7288 if (balance_cpu
== -1)
7289 balance_cpu
= group_balance_cpu(sg
);
7292 * First idle cpu or the first cpu(busiest) in this sched group
7293 * is eligible for doing load balancing at this and above domains.
7295 return balance_cpu
== env
->dst_cpu
;
7299 * Check this_cpu to ensure it is balanced within domain. Attempt to move
7300 * tasks if there is an imbalance.
7302 static int load_balance(int this_cpu
, struct rq
*this_rq
,
7303 struct sched_domain
*sd
, enum cpu_idle_type idle
,
7304 int *continue_balancing
)
7306 int ld_moved
, cur_ld_moved
, active_balance
= 0;
7307 struct sched_domain
*sd_parent
= sd
->parent
;
7308 struct sched_group
*group
;
7310 unsigned long flags
;
7311 struct cpumask
*cpus
= this_cpu_cpumask_var_ptr(load_balance_mask
);
7313 struct lb_env env
= {
7315 .dst_cpu
= this_cpu
,
7317 .dst_grpmask
= sched_group_cpus(sd
->groups
),
7319 .loop_break
= sched_nr_migrate_break
,
7322 .tasks
= LIST_HEAD_INIT(env
.tasks
),
7326 * For NEWLY_IDLE load_balancing, we don't need to consider
7327 * other cpus in our group
7329 if (idle
== CPU_NEWLY_IDLE
)
7330 env
.dst_grpmask
= NULL
;
7332 cpumask_copy(cpus
, cpu_active_mask
);
7334 schedstat_inc(sd
, lb_count
[idle
]);
7337 if (!should_we_balance(&env
)) {
7338 *continue_balancing
= 0;
7342 group
= find_busiest_group(&env
);
7344 schedstat_inc(sd
, lb_nobusyg
[idle
]);
7348 busiest
= find_busiest_queue(&env
, group
);
7350 schedstat_inc(sd
, lb_nobusyq
[idle
]);
7354 BUG_ON(busiest
== env
.dst_rq
);
7356 schedstat_add(sd
, lb_imbalance
[idle
], env
.imbalance
);
7358 env
.src_cpu
= busiest
->cpu
;
7359 env
.src_rq
= busiest
;
7362 if (busiest
->nr_running
> 1) {
7364 * Attempt to move tasks. If find_busiest_group has found
7365 * an imbalance but busiest->nr_running <= 1, the group is
7366 * still unbalanced. ld_moved simply stays zero, so it is
7367 * correctly treated as an imbalance.
7369 env
.flags
|= LBF_ALL_PINNED
;
7370 env
.loop_max
= min(sysctl_sched_nr_migrate
, busiest
->nr_running
);
7373 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
7376 * cur_ld_moved - load moved in current iteration
7377 * ld_moved - cumulative load moved across iterations
7379 cur_ld_moved
= detach_tasks(&env
);
7382 * We've detached some tasks from busiest_rq. Every
7383 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7384 * unlock busiest->lock, and we are able to be sure
7385 * that nobody can manipulate the tasks in parallel.
7386 * See task_rq_lock() family for the details.
7389 raw_spin_unlock(&busiest
->lock
);
7393 ld_moved
+= cur_ld_moved
;
7396 local_irq_restore(flags
);
7398 if (env
.flags
& LBF_NEED_BREAK
) {
7399 env
.flags
&= ~LBF_NEED_BREAK
;
7404 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7405 * us and move them to an alternate dst_cpu in our sched_group
7406 * where they can run. The upper limit on how many times we
7407 * iterate on same src_cpu is dependent on number of cpus in our
7410 * This changes load balance semantics a bit on who can move
7411 * load to a given_cpu. In addition to the given_cpu itself
7412 * (or a ilb_cpu acting on its behalf where given_cpu is
7413 * nohz-idle), we now have balance_cpu in a position to move
7414 * load to given_cpu. In rare situations, this may cause
7415 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7416 * _independently_ and at _same_ time to move some load to
7417 * given_cpu) causing exceess load to be moved to given_cpu.
7418 * This however should not happen so much in practice and
7419 * moreover subsequent load balance cycles should correct the
7420 * excess load moved.
7422 if ((env
.flags
& LBF_DST_PINNED
) && env
.imbalance
> 0) {
7424 /* Prevent to re-select dst_cpu via env's cpus */
7425 cpumask_clear_cpu(env
.dst_cpu
, env
.cpus
);
7427 env
.dst_rq
= cpu_rq(env
.new_dst_cpu
);
7428 env
.dst_cpu
= env
.new_dst_cpu
;
7429 env
.flags
&= ~LBF_DST_PINNED
;
7431 env
.loop_break
= sched_nr_migrate_break
;
7434 * Go back to "more_balance" rather than "redo" since we
7435 * need to continue with same src_cpu.
7441 * We failed to reach balance because of affinity.
7444 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
7446 if ((env
.flags
& LBF_SOME_PINNED
) && env
.imbalance
> 0)
7447 *group_imbalance
= 1;
7450 /* All tasks on this runqueue were pinned by CPU affinity */
7451 if (unlikely(env
.flags
& LBF_ALL_PINNED
)) {
7452 cpumask_clear_cpu(cpu_of(busiest
), cpus
);
7453 if (!cpumask_empty(cpus
)) {
7455 env
.loop_break
= sched_nr_migrate_break
;
7458 goto out_all_pinned
;
7463 schedstat_inc(sd
, lb_failed
[idle
]);
7465 * Increment the failure counter only on periodic balance.
7466 * We do not want newidle balance, which can be very
7467 * frequent, pollute the failure counter causing
7468 * excessive cache_hot migrations and active balances.
7470 if (idle
!= CPU_NEWLY_IDLE
)
7471 sd
->nr_balance_failed
++;
7473 if (need_active_balance(&env
)) {
7474 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
7476 /* don't kick the active_load_balance_cpu_stop,
7477 * if the curr task on busiest cpu can't be
7480 if (!cpumask_test_cpu(this_cpu
,
7481 tsk_cpus_allowed(busiest
->curr
))) {
7482 raw_spin_unlock_irqrestore(&busiest
->lock
,
7484 env
.flags
|= LBF_ALL_PINNED
;
7485 goto out_one_pinned
;
7489 * ->active_balance synchronizes accesses to
7490 * ->active_balance_work. Once set, it's cleared
7491 * only after active load balance is finished.
7493 if (!busiest
->active_balance
) {
7494 busiest
->active_balance
= 1;
7495 busiest
->push_cpu
= this_cpu
;
7498 raw_spin_unlock_irqrestore(&busiest
->lock
, flags
);
7500 if (active_balance
) {
7501 stop_one_cpu_nowait(cpu_of(busiest
),
7502 active_load_balance_cpu_stop
, busiest
,
7503 &busiest
->active_balance_work
);
7506 /* We've kicked active balancing, force task migration. */
7507 sd
->nr_balance_failed
= sd
->cache_nice_tries
+1;
7510 sd
->nr_balance_failed
= 0;
7512 if (likely(!active_balance
)) {
7513 /* We were unbalanced, so reset the balancing interval */
7514 sd
->balance_interval
= sd
->min_interval
;
7517 * If we've begun active balancing, start to back off. This
7518 * case may not be covered by the all_pinned logic if there
7519 * is only 1 task on the busy runqueue (because we don't call
7522 if (sd
->balance_interval
< sd
->max_interval
)
7523 sd
->balance_interval
*= 2;
7530 * We reach balance although we may have faced some affinity
7531 * constraints. Clear the imbalance flag if it was set.
7534 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
7536 if (*group_imbalance
)
7537 *group_imbalance
= 0;
7542 * We reach balance because all tasks are pinned at this level so
7543 * we can't migrate them. Let the imbalance flag set so parent level
7544 * can try to migrate them.
7546 schedstat_inc(sd
, lb_balanced
[idle
]);
7548 sd
->nr_balance_failed
= 0;
7551 /* tune up the balancing interval */
7552 if (((env
.flags
& LBF_ALL_PINNED
) &&
7553 sd
->balance_interval
< MAX_PINNED_INTERVAL
) ||
7554 (sd
->balance_interval
< sd
->max_interval
))
7555 sd
->balance_interval
*= 2;
7562 static inline unsigned long
7563 get_sd_balance_interval(struct sched_domain
*sd
, int cpu_busy
)
7565 unsigned long interval
= sd
->balance_interval
;
7568 interval
*= sd
->busy_factor
;
7570 /* scale ms to jiffies */
7571 interval
= msecs_to_jiffies(interval
);
7572 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
7578 update_next_balance(struct sched_domain
*sd
, int cpu_busy
, unsigned long *next_balance
)
7580 unsigned long interval
, next
;
7582 interval
= get_sd_balance_interval(sd
, cpu_busy
);
7583 next
= sd
->last_balance
+ interval
;
7585 if (time_after(*next_balance
, next
))
7586 *next_balance
= next
;
7590 * idle_balance is called by schedule() if this_cpu is about to become
7591 * idle. Attempts to pull tasks from other CPUs.
7593 static int idle_balance(struct rq
*this_rq
)
7595 unsigned long next_balance
= jiffies
+ HZ
;
7596 int this_cpu
= this_rq
->cpu
;
7597 struct sched_domain
*sd
;
7598 int pulled_task
= 0;
7602 * We must set idle_stamp _before_ calling idle_balance(), such that we
7603 * measure the duration of idle_balance() as idle time.
7605 this_rq
->idle_stamp
= rq_clock(this_rq
);
7607 if (this_rq
->avg_idle
< sysctl_sched_migration_cost
||
7608 !this_rq
->rd
->overload
) {
7610 sd
= rcu_dereference_check_sched_domain(this_rq
->sd
);
7612 update_next_balance(sd
, 0, &next_balance
);
7618 raw_spin_unlock(&this_rq
->lock
);
7620 update_blocked_averages(this_cpu
);
7622 for_each_domain(this_cpu
, sd
) {
7623 int continue_balancing
= 1;
7624 u64 t0
, domain_cost
;
7626 if (!(sd
->flags
& SD_LOAD_BALANCE
))
7629 if (this_rq
->avg_idle
< curr_cost
+ sd
->max_newidle_lb_cost
) {
7630 update_next_balance(sd
, 0, &next_balance
);
7634 if (sd
->flags
& SD_BALANCE_NEWIDLE
) {
7635 t0
= sched_clock_cpu(this_cpu
);
7637 pulled_task
= load_balance(this_cpu
, this_rq
,
7639 &continue_balancing
);
7641 domain_cost
= sched_clock_cpu(this_cpu
) - t0
;
7642 if (domain_cost
> sd
->max_newidle_lb_cost
)
7643 sd
->max_newidle_lb_cost
= domain_cost
;
7645 curr_cost
+= domain_cost
;
7648 update_next_balance(sd
, 0, &next_balance
);
7651 * Stop searching for tasks to pull if there are
7652 * now runnable tasks on this rq.
7654 if (pulled_task
|| this_rq
->nr_running
> 0)
7659 raw_spin_lock(&this_rq
->lock
);
7661 if (curr_cost
> this_rq
->max_idle_balance_cost
)
7662 this_rq
->max_idle_balance_cost
= curr_cost
;
7665 * While browsing the domains, we released the rq lock, a task could
7666 * have been enqueued in the meantime. Since we're not going idle,
7667 * pretend we pulled a task.
7669 if (this_rq
->cfs
.h_nr_running
&& !pulled_task
)
7673 /* Move the next balance forward */
7674 if (time_after(this_rq
->next_balance
, next_balance
))
7675 this_rq
->next_balance
= next_balance
;
7677 /* Is there a task of a high priority class? */
7678 if (this_rq
->nr_running
!= this_rq
->cfs
.h_nr_running
)
7682 this_rq
->idle_stamp
= 0;
7688 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7689 * running tasks off the busiest CPU onto idle CPUs. It requires at
7690 * least 1 task to be running on each physical CPU where possible, and
7691 * avoids physical / logical imbalances.
7693 static int active_load_balance_cpu_stop(void *data
)
7695 struct rq
*busiest_rq
= data
;
7696 int busiest_cpu
= cpu_of(busiest_rq
);
7697 int target_cpu
= busiest_rq
->push_cpu
;
7698 struct rq
*target_rq
= cpu_rq(target_cpu
);
7699 struct sched_domain
*sd
;
7700 struct task_struct
*p
= NULL
;
7702 raw_spin_lock_irq(&busiest_rq
->lock
);
7704 /* make sure the requested cpu hasn't gone down in the meantime */
7705 if (unlikely(busiest_cpu
!= smp_processor_id() ||
7706 !busiest_rq
->active_balance
))
7709 /* Is there any task to move? */
7710 if (busiest_rq
->nr_running
<= 1)
7714 * This condition is "impossible", if it occurs
7715 * we need to fix it. Originally reported by
7716 * Bjorn Helgaas on a 128-cpu setup.
7718 BUG_ON(busiest_rq
== target_rq
);
7720 /* Search for an sd spanning us and the target CPU. */
7722 for_each_domain(target_cpu
, sd
) {
7723 if ((sd
->flags
& SD_LOAD_BALANCE
) &&
7724 cpumask_test_cpu(busiest_cpu
, sched_domain_span(sd
)))
7729 struct lb_env env
= {
7731 .dst_cpu
= target_cpu
,
7732 .dst_rq
= target_rq
,
7733 .src_cpu
= busiest_rq
->cpu
,
7734 .src_rq
= busiest_rq
,
7738 schedstat_inc(sd
, alb_count
);
7740 p
= detach_one_task(&env
);
7742 schedstat_inc(sd
, alb_pushed
);
7743 /* Active balancing done, reset the failure counter. */
7744 sd
->nr_balance_failed
= 0;
7746 schedstat_inc(sd
, alb_failed
);
7751 busiest_rq
->active_balance
= 0;
7752 raw_spin_unlock(&busiest_rq
->lock
);
7755 attach_one_task(target_rq
, p
);
7762 static inline int on_null_domain(struct rq
*rq
)
7764 return unlikely(!rcu_dereference_sched(rq
->sd
));
7767 #ifdef CONFIG_NO_HZ_COMMON
7769 * idle load balancing details
7770 * - When one of the busy CPUs notice that there may be an idle rebalancing
7771 * needed, they will kick the idle load balancer, which then does idle
7772 * load balancing for all the idle CPUs.
7775 cpumask_var_t idle_cpus_mask
;
7777 unsigned long next_balance
; /* in jiffy units */
7778 } nohz ____cacheline_aligned
;
7780 static inline int find_new_ilb(void)
7782 int ilb
= cpumask_first(nohz
.idle_cpus_mask
);
7784 if (ilb
< nr_cpu_ids
&& idle_cpu(ilb
))
7791 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7792 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7793 * CPU (if there is one).
7795 static void nohz_balancer_kick(void)
7799 nohz
.next_balance
++;
7801 ilb_cpu
= find_new_ilb();
7803 if (ilb_cpu
>= nr_cpu_ids
)
7806 if (test_and_set_bit(NOHZ_BALANCE_KICK
, nohz_flags(ilb_cpu
)))
7809 * Use smp_send_reschedule() instead of resched_cpu().
7810 * This way we generate a sched IPI on the target cpu which
7811 * is idle. And the softirq performing nohz idle load balance
7812 * will be run before returning from the IPI.
7814 smp_send_reschedule(ilb_cpu
);
7818 static inline void nohz_balance_exit_idle(int cpu
)
7820 if (unlikely(test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))) {
7822 * Completely isolated CPUs don't ever set, so we must test.
7824 if (likely(cpumask_test_cpu(cpu
, nohz
.idle_cpus_mask
))) {
7825 cpumask_clear_cpu(cpu
, nohz
.idle_cpus_mask
);
7826 atomic_dec(&nohz
.nr_cpus
);
7828 clear_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
7832 static inline void set_cpu_sd_state_busy(void)
7834 struct sched_domain
*sd
;
7835 int cpu
= smp_processor_id();
7838 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
7840 if (!sd
|| !sd
->nohz_idle
)
7844 atomic_inc(&sd
->groups
->sgc
->nr_busy_cpus
);
7849 void set_cpu_sd_state_idle(void)
7851 struct sched_domain
*sd
;
7852 int cpu
= smp_processor_id();
7855 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
7857 if (!sd
|| sd
->nohz_idle
)
7861 atomic_dec(&sd
->groups
->sgc
->nr_busy_cpus
);
7867 * This routine will record that the cpu is going idle with tick stopped.
7868 * This info will be used in performing idle load balancing in the future.
7870 void nohz_balance_enter_idle(int cpu
)
7873 * If this cpu is going down, then nothing needs to be done.
7875 if (!cpu_active(cpu
))
7878 if (test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))
7882 * If we're a completely isolated CPU, we don't play.
7884 if (on_null_domain(cpu_rq(cpu
)))
7887 cpumask_set_cpu(cpu
, nohz
.idle_cpus_mask
);
7888 atomic_inc(&nohz
.nr_cpus
);
7889 set_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
7892 static int sched_ilb_notifier(struct notifier_block
*nfb
,
7893 unsigned long action
, void *hcpu
)
7895 switch (action
& ~CPU_TASKS_FROZEN
) {
7897 nohz_balance_exit_idle(smp_processor_id());
7905 static DEFINE_SPINLOCK(balancing
);
7908 * Scale the max load_balance interval with the number of CPUs in the system.
7909 * This trades load-balance latency on larger machines for less cross talk.
7911 void update_max_interval(void)
7913 max_load_balance_interval
= HZ
*num_online_cpus()/10;
7917 * It checks each scheduling domain to see if it is due to be balanced,
7918 * and initiates a balancing operation if so.
7920 * Balancing parameters are set up in init_sched_domains.
7922 static void rebalance_domains(struct rq
*rq
, enum cpu_idle_type idle
)
7924 int continue_balancing
= 1;
7926 unsigned long interval
;
7927 struct sched_domain
*sd
;
7928 /* Earliest time when we have to do rebalance again */
7929 unsigned long next_balance
= jiffies
+ 60*HZ
;
7930 int update_next_balance
= 0;
7931 int need_serialize
, need_decay
= 0;
7934 update_blocked_averages(cpu
);
7937 for_each_domain(cpu
, sd
) {
7939 * Decay the newidle max times here because this is a regular
7940 * visit to all the domains. Decay ~1% per second.
7942 if (time_after(jiffies
, sd
->next_decay_max_lb_cost
)) {
7943 sd
->max_newidle_lb_cost
=
7944 (sd
->max_newidle_lb_cost
* 253) / 256;
7945 sd
->next_decay_max_lb_cost
= jiffies
+ HZ
;
7948 max_cost
+= sd
->max_newidle_lb_cost
;
7950 if (!(sd
->flags
& SD_LOAD_BALANCE
))
7954 * Stop the load balance at this level. There is another
7955 * CPU in our sched group which is doing load balancing more
7958 if (!continue_balancing
) {
7964 interval
= get_sd_balance_interval(sd
, idle
!= CPU_IDLE
);
7966 need_serialize
= sd
->flags
& SD_SERIALIZE
;
7967 if (need_serialize
) {
7968 if (!spin_trylock(&balancing
))
7972 if (time_after_eq(jiffies
, sd
->last_balance
+ interval
)) {
7973 if (load_balance(cpu
, rq
, sd
, idle
, &continue_balancing
)) {
7975 * The LBF_DST_PINNED logic could have changed
7976 * env->dst_cpu, so we can't know our idle
7977 * state even if we migrated tasks. Update it.
7979 idle
= idle_cpu(cpu
) ? CPU_IDLE
: CPU_NOT_IDLE
;
7981 sd
->last_balance
= jiffies
;
7982 interval
= get_sd_balance_interval(sd
, idle
!= CPU_IDLE
);
7985 spin_unlock(&balancing
);
7987 if (time_after(next_balance
, sd
->last_balance
+ interval
)) {
7988 next_balance
= sd
->last_balance
+ interval
;
7989 update_next_balance
= 1;
7994 * Ensure the rq-wide value also decays but keep it at a
7995 * reasonable floor to avoid funnies with rq->avg_idle.
7997 rq
->max_idle_balance_cost
=
7998 max((u64
)sysctl_sched_migration_cost
, max_cost
);
8003 * next_balance will be updated only when there is a need.
8004 * When the cpu is attached to null domain for ex, it will not be
8007 if (likely(update_next_balance
)) {
8008 rq
->next_balance
= next_balance
;
8010 #ifdef CONFIG_NO_HZ_COMMON
8012 * If this CPU has been elected to perform the nohz idle
8013 * balance. Other idle CPUs have already rebalanced with
8014 * nohz_idle_balance() and nohz.next_balance has been
8015 * updated accordingly. This CPU is now running the idle load
8016 * balance for itself and we need to update the
8017 * nohz.next_balance accordingly.
8019 if ((idle
== CPU_IDLE
) && time_after(nohz
.next_balance
, rq
->next_balance
))
8020 nohz
.next_balance
= rq
->next_balance
;
8025 #ifdef CONFIG_NO_HZ_COMMON
8027 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8028 * rebalancing for all the cpus for whom scheduler ticks are stopped.
8030 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
)
8032 int this_cpu
= this_rq
->cpu
;
8035 /* Earliest time when we have to do rebalance again */
8036 unsigned long next_balance
= jiffies
+ 60*HZ
;
8037 int update_next_balance
= 0;
8039 if (idle
!= CPU_IDLE
||
8040 !test_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
)))
8043 for_each_cpu(balance_cpu
, nohz
.idle_cpus_mask
) {
8044 if (balance_cpu
== this_cpu
|| !idle_cpu(balance_cpu
))
8048 * If this cpu gets work to do, stop the load balancing
8049 * work being done for other cpus. Next load
8050 * balancing owner will pick it up.
8055 rq
= cpu_rq(balance_cpu
);
8058 * If time for next balance is due,
8061 if (time_after_eq(jiffies
, rq
->next_balance
)) {
8062 raw_spin_lock_irq(&rq
->lock
);
8063 update_rq_clock(rq
);
8064 cpu_load_update_idle(rq
);
8065 raw_spin_unlock_irq(&rq
->lock
);
8066 rebalance_domains(rq
, CPU_IDLE
);
8069 if (time_after(next_balance
, rq
->next_balance
)) {
8070 next_balance
= rq
->next_balance
;
8071 update_next_balance
= 1;
8076 * next_balance will be updated only when there is a need.
8077 * When the CPU is attached to null domain for ex, it will not be
8080 if (likely(update_next_balance
))
8081 nohz
.next_balance
= next_balance
;
8083 clear_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
));
8087 * Current heuristic for kicking the idle load balancer in the presence
8088 * of an idle cpu in the system.
8089 * - This rq has more than one task.
8090 * - This rq has at least one CFS task and the capacity of the CPU is
8091 * significantly reduced because of RT tasks or IRQs.
8092 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
8093 * multiple busy cpu.
8094 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
8095 * domain span are idle.
8097 static inline bool nohz_kick_needed(struct rq
*rq
)
8099 unsigned long now
= jiffies
;
8100 struct sched_domain
*sd
;
8101 struct sched_group_capacity
*sgc
;
8102 int nr_busy
, cpu
= rq
->cpu
;
8105 if (unlikely(rq
->idle_balance
))
8109 * We may be recently in ticked or tickless idle mode. At the first
8110 * busy tick after returning from idle, we will update the busy stats.
8112 set_cpu_sd_state_busy();
8113 nohz_balance_exit_idle(cpu
);
8116 * None are in tickless mode and hence no need for NOHZ idle load
8119 if (likely(!atomic_read(&nohz
.nr_cpus
)))
8122 if (time_before(now
, nohz
.next_balance
))
8125 if (rq
->nr_running
>= 2)
8129 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
8131 sgc
= sd
->groups
->sgc
;
8132 nr_busy
= atomic_read(&sgc
->nr_busy_cpus
);
8141 sd
= rcu_dereference(rq
->sd
);
8143 if ((rq
->cfs
.h_nr_running
>= 1) &&
8144 check_cpu_capacity(rq
, sd
)) {
8150 sd
= rcu_dereference(per_cpu(sd_asym
, cpu
));
8151 if (sd
&& (cpumask_first_and(nohz
.idle_cpus_mask
,
8152 sched_domain_span(sd
)) < cpu
)) {
8162 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
) { }
8166 * run_rebalance_domains is triggered when needed from the scheduler tick.
8167 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
8169 static void run_rebalance_domains(struct softirq_action
*h
)
8171 struct rq
*this_rq
= this_rq();
8172 enum cpu_idle_type idle
= this_rq
->idle_balance
?
8173 CPU_IDLE
: CPU_NOT_IDLE
;
8176 * If this cpu has a pending nohz_balance_kick, then do the
8177 * balancing on behalf of the other idle cpus whose ticks are
8178 * stopped. Do nohz_idle_balance *before* rebalance_domains to
8179 * give the idle cpus a chance to load balance. Else we may
8180 * load balance only within the local sched_domain hierarchy
8181 * and abort nohz_idle_balance altogether if we pull some load.
8183 nohz_idle_balance(this_rq
, idle
);
8184 rebalance_domains(this_rq
, idle
);
8188 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
8190 void trigger_load_balance(struct rq
*rq
)
8192 /* Don't need to rebalance while attached to NULL domain */
8193 if (unlikely(on_null_domain(rq
)))
8196 if (time_after_eq(jiffies
, rq
->next_balance
))
8197 raise_softirq(SCHED_SOFTIRQ
);
8198 #ifdef CONFIG_NO_HZ_COMMON
8199 if (nohz_kick_needed(rq
))
8200 nohz_balancer_kick();
8204 static void rq_online_fair(struct rq
*rq
)
8208 update_runtime_enabled(rq
);
8211 static void rq_offline_fair(struct rq
*rq
)
8215 /* Ensure any throttled groups are reachable by pick_next_task */
8216 unthrottle_offline_cfs_rqs(rq
);
8219 #endif /* CONFIG_SMP */
8222 * scheduler tick hitting a task of our scheduling class:
8224 static void task_tick_fair(struct rq
*rq
, struct task_struct
*curr
, int queued
)
8226 struct cfs_rq
*cfs_rq
;
8227 struct sched_entity
*se
= &curr
->se
;
8229 for_each_sched_entity(se
) {
8230 cfs_rq
= cfs_rq_of(se
);
8231 entity_tick(cfs_rq
, se
, queued
);
8234 if (static_branch_unlikely(&sched_numa_balancing
))
8235 task_tick_numa(rq
, curr
);
8239 * called on fork with the child task as argument from the parent's context
8240 * - child not yet on the tasklist
8241 * - preemption disabled
8243 static void task_fork_fair(struct task_struct
*p
)
8245 struct cfs_rq
*cfs_rq
;
8246 struct sched_entity
*se
= &p
->se
, *curr
;
8247 int this_cpu
= smp_processor_id();
8248 struct rq
*rq
= this_rq();
8249 unsigned long flags
;
8251 raw_spin_lock_irqsave(&rq
->lock
, flags
);
8253 update_rq_clock(rq
);
8255 cfs_rq
= task_cfs_rq(current
);
8256 curr
= cfs_rq
->curr
;
8259 * Not only the cpu but also the task_group of the parent might have
8260 * been changed after parent->se.parent,cfs_rq were copied to
8261 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
8262 * of child point to valid ones.
8265 __set_task_cpu(p
, this_cpu
);
8268 update_curr(cfs_rq
);
8271 se
->vruntime
= curr
->vruntime
;
8272 place_entity(cfs_rq
, se
, 1);
8274 if (sysctl_sched_child_runs_first
&& curr
&& entity_before(curr
, se
)) {
8276 * Upon rescheduling, sched_class::put_prev_task() will place
8277 * 'current' within the tree based on its new key value.
8279 swap(curr
->vruntime
, se
->vruntime
);
8283 se
->vruntime
-= cfs_rq
->min_vruntime
;
8285 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
8289 * Priority of the task has changed. Check to see if we preempt
8293 prio_changed_fair(struct rq
*rq
, struct task_struct
*p
, int oldprio
)
8295 if (!task_on_rq_queued(p
))
8299 * Reschedule if we are currently running on this runqueue and
8300 * our priority decreased, or if we are not currently running on
8301 * this runqueue and our priority is higher than the current's
8303 if (rq
->curr
== p
) {
8304 if (p
->prio
> oldprio
)
8307 check_preempt_curr(rq
, p
, 0);
8310 static inline bool vruntime_normalized(struct task_struct
*p
)
8312 struct sched_entity
*se
= &p
->se
;
8315 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8316 * the dequeue_entity(.flags=0) will already have normalized the
8323 * When !on_rq, vruntime of the task has usually NOT been normalized.
8324 * But there are some cases where it has already been normalized:
8326 * - A forked child which is waiting for being woken up by
8327 * wake_up_new_task().
8328 * - A task which has been woken up by try_to_wake_up() and
8329 * waiting for actually being woken up by sched_ttwu_pending().
8331 if (!se
->sum_exec_runtime
|| p
->state
== TASK_WAKING
)
8337 static void detach_task_cfs_rq(struct task_struct
*p
)
8339 struct sched_entity
*se
= &p
->se
;
8340 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
8342 if (!vruntime_normalized(p
)) {
8344 * Fix up our vruntime so that the current sleep doesn't
8345 * cause 'unlimited' sleep bonus.
8347 place_entity(cfs_rq
, se
, 0);
8348 se
->vruntime
-= cfs_rq
->min_vruntime
;
8351 /* Catch up with the cfs_rq and remove our load when we leave */
8352 detach_entity_load_avg(cfs_rq
, se
);
8355 static void attach_task_cfs_rq(struct task_struct
*p
)
8357 struct sched_entity
*se
= &p
->se
;
8358 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
8360 #ifdef CONFIG_FAIR_GROUP_SCHED
8362 * Since the real-depth could have been changed (only FAIR
8363 * class maintain depth value), reset depth properly.
8365 se
->depth
= se
->parent
? se
->parent
->depth
+ 1 : 0;
8368 /* Synchronize task with its cfs_rq */
8369 attach_entity_load_avg(cfs_rq
, se
);
8371 if (!vruntime_normalized(p
))
8372 se
->vruntime
+= cfs_rq
->min_vruntime
;
8375 static void switched_from_fair(struct rq
*rq
, struct task_struct
*p
)
8377 detach_task_cfs_rq(p
);
8380 static void switched_to_fair(struct rq
*rq
, struct task_struct
*p
)
8382 attach_task_cfs_rq(p
);
8384 if (task_on_rq_queued(p
)) {
8386 * We were most likely switched from sched_rt, so
8387 * kick off the schedule if running, otherwise just see
8388 * if we can still preempt the current task.
8393 check_preempt_curr(rq
, p
, 0);
8397 /* Account for a task changing its policy or group.
8399 * This routine is mostly called to set cfs_rq->curr field when a task
8400 * migrates between groups/classes.
8402 static void set_curr_task_fair(struct rq
*rq
)
8404 struct sched_entity
*se
= &rq
->curr
->se
;
8406 for_each_sched_entity(se
) {
8407 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
8409 set_next_entity(cfs_rq
, se
);
8410 /* ensure bandwidth has been allocated on our new cfs_rq */
8411 account_cfs_rq_runtime(cfs_rq
, 0);
8415 void init_cfs_rq(struct cfs_rq
*cfs_rq
)
8417 cfs_rq
->tasks_timeline
= RB_ROOT
;
8418 cfs_rq
->min_vruntime
= (u64
)(-(1LL << 20));
8419 #ifndef CONFIG_64BIT
8420 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
8423 atomic_long_set(&cfs_rq
->removed_load_avg
, 0);
8424 atomic_long_set(&cfs_rq
->removed_util_avg
, 0);
8428 #ifdef CONFIG_FAIR_GROUP_SCHED
8429 static void task_move_group_fair(struct task_struct
*p
)
8431 detach_task_cfs_rq(p
);
8432 set_task_rq(p
, task_cpu(p
));
8435 /* Tell se's cfs_rq has been changed -- migrated */
8436 p
->se
.avg
.last_update_time
= 0;
8438 attach_task_cfs_rq(p
);
8441 void free_fair_sched_group(struct task_group
*tg
)
8445 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg
));
8447 for_each_possible_cpu(i
) {
8449 kfree(tg
->cfs_rq
[i
]);
8458 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
8460 struct cfs_rq
*cfs_rq
;
8461 struct sched_entity
*se
;
8464 tg
->cfs_rq
= kzalloc(sizeof(cfs_rq
) * nr_cpu_ids
, GFP_KERNEL
);
8467 tg
->se
= kzalloc(sizeof(se
) * nr_cpu_ids
, GFP_KERNEL
);
8471 tg
->shares
= NICE_0_LOAD
;
8473 init_cfs_bandwidth(tg_cfs_bandwidth(tg
));
8475 for_each_possible_cpu(i
) {
8476 cfs_rq
= kzalloc_node(sizeof(struct cfs_rq
),
8477 GFP_KERNEL
, cpu_to_node(i
));
8481 se
= kzalloc_node(sizeof(struct sched_entity
),
8482 GFP_KERNEL
, cpu_to_node(i
));
8486 init_cfs_rq(cfs_rq
);
8487 init_tg_cfs_entry(tg
, cfs_rq
, se
, i
, parent
->se
[i
]);
8488 init_entity_runnable_average(se
);
8489 post_init_entity_util_avg(se
);
8500 void unregister_fair_sched_group(struct task_group
*tg
)
8502 unsigned long flags
;
8506 for_each_possible_cpu(cpu
) {
8508 remove_entity_load_avg(tg
->se
[cpu
]);
8511 * Only empty task groups can be destroyed; so we can speculatively
8512 * check on_list without danger of it being re-added.
8514 if (!tg
->cfs_rq
[cpu
]->on_list
)
8519 raw_spin_lock_irqsave(&rq
->lock
, flags
);
8520 list_del_leaf_cfs_rq(tg
->cfs_rq
[cpu
]);
8521 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
8525 void init_tg_cfs_entry(struct task_group
*tg
, struct cfs_rq
*cfs_rq
,
8526 struct sched_entity
*se
, int cpu
,
8527 struct sched_entity
*parent
)
8529 struct rq
*rq
= cpu_rq(cpu
);
8533 init_cfs_rq_runtime(cfs_rq
);
8535 tg
->cfs_rq
[cpu
] = cfs_rq
;
8538 /* se could be NULL for root_task_group */
8543 se
->cfs_rq
= &rq
->cfs
;
8546 se
->cfs_rq
= parent
->my_q
;
8547 se
->depth
= parent
->depth
+ 1;
8551 /* guarantee group entities always have weight */
8552 update_load_set(&se
->load
, NICE_0_LOAD
);
8553 se
->parent
= parent
;
8556 static DEFINE_MUTEX(shares_mutex
);
8558 int sched_group_set_shares(struct task_group
*tg
, unsigned long shares
)
8561 unsigned long flags
;
8564 * We can't change the weight of the root cgroup.
8569 shares
= clamp(shares
, scale_load(MIN_SHARES
), scale_load(MAX_SHARES
));
8571 mutex_lock(&shares_mutex
);
8572 if (tg
->shares
== shares
)
8575 tg
->shares
= shares
;
8576 for_each_possible_cpu(i
) {
8577 struct rq
*rq
= cpu_rq(i
);
8578 struct sched_entity
*se
;
8581 /* Propagate contribution to hierarchy */
8582 raw_spin_lock_irqsave(&rq
->lock
, flags
);
8584 /* Possible calls to update_curr() need rq clock */
8585 update_rq_clock(rq
);
8586 for_each_sched_entity(se
)
8587 update_cfs_shares(group_cfs_rq(se
));
8588 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
8592 mutex_unlock(&shares_mutex
);
8595 #else /* CONFIG_FAIR_GROUP_SCHED */
8597 void free_fair_sched_group(struct task_group
*tg
) { }
8599 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
8604 void unregister_fair_sched_group(struct task_group
*tg
) { }
8606 #endif /* CONFIG_FAIR_GROUP_SCHED */
8609 static unsigned int get_rr_interval_fair(struct rq
*rq
, struct task_struct
*task
)
8611 struct sched_entity
*se
= &task
->se
;
8612 unsigned int rr_interval
= 0;
8615 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8618 if (rq
->cfs
.load
.weight
)
8619 rr_interval
= NS_TO_JIFFIES(sched_slice(cfs_rq_of(se
), se
));
8625 * All the scheduling class methods:
8627 const struct sched_class fair_sched_class
= {
8628 .next
= &idle_sched_class
,
8629 .enqueue_task
= enqueue_task_fair
,
8630 .dequeue_task
= dequeue_task_fair
,
8631 .yield_task
= yield_task_fair
,
8632 .yield_to_task
= yield_to_task_fair
,
8634 .check_preempt_curr
= check_preempt_wakeup
,
8636 .pick_next_task
= pick_next_task_fair
,
8637 .put_prev_task
= put_prev_task_fair
,
8640 .select_task_rq
= select_task_rq_fair
,
8641 .migrate_task_rq
= migrate_task_rq_fair
,
8643 .rq_online
= rq_online_fair
,
8644 .rq_offline
= rq_offline_fair
,
8646 .task_waking
= task_waking_fair
,
8647 .task_dead
= task_dead_fair
,
8648 .set_cpus_allowed
= set_cpus_allowed_common
,
8651 .set_curr_task
= set_curr_task_fair
,
8652 .task_tick
= task_tick_fair
,
8653 .task_fork
= task_fork_fair
,
8655 .prio_changed
= prio_changed_fair
,
8656 .switched_from
= switched_from_fair
,
8657 .switched_to
= switched_to_fair
,
8659 .get_rr_interval
= get_rr_interval_fair
,
8661 .update_curr
= update_curr_fair
,
8663 #ifdef CONFIG_FAIR_GROUP_SCHED
8664 .task_move_group
= task_move_group_fair
,
8668 #ifdef CONFIG_SCHED_DEBUG
8669 void print_cfs_stats(struct seq_file
*m
, int cpu
)
8671 struct cfs_rq
*cfs_rq
;
8674 for_each_leaf_cfs_rq(cpu_rq(cpu
), cfs_rq
)
8675 print_cfs_rq(m
, cpu
, cfs_rq
);
8679 #ifdef CONFIG_NUMA_BALANCING
8680 void show_numa_stats(struct task_struct
*p
, struct seq_file
*m
)
8683 unsigned long tsf
= 0, tpf
= 0, gsf
= 0, gpf
= 0;
8685 for_each_online_node(node
) {
8686 if (p
->numa_faults
) {
8687 tsf
= p
->numa_faults
[task_faults_idx(NUMA_MEM
, node
, 0)];
8688 tpf
= p
->numa_faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
8690 if (p
->numa_group
) {
8691 gsf
= p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, node
, 0)],
8692 gpf
= p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
8694 print_numa_stats(m
, node
, tsf
, tpf
, gsf
, gpf
);
8697 #endif /* CONFIG_NUMA_BALANCING */
8698 #endif /* CONFIG_SCHED_DEBUG */
8700 __init
void init_sched_fair_class(void)
8703 open_softirq(SCHED_SOFTIRQ
, run_rebalance_domains
);
8705 #ifdef CONFIG_NO_HZ_COMMON
8706 nohz
.next_balance
= jiffies
;
8707 zalloc_cpumask_var(&nohz
.idle_cpus_mask
, GFP_NOWAIT
);
8708 cpu_notifier(sched_ilb_notifier
, 0);