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/mm.h>
24 #include <linux/sched/topology.h>
26 #include <linux/latencytop.h>
27 #include <linux/cpumask.h>
28 #include <linux/cpuidle.h>
29 #include <linux/slab.h>
30 #include <linux/profile.h>
31 #include <linux/interrupt.h>
32 #include <linux/mempolicy.h>
33 #include <linux/migrate.h>
34 #include <linux/task_work.h>
36 #include <trace/events/sched.h>
41 * Targeted preemption latency for CPU-bound tasks:
43 * NOTE: this latency value is not the same as the concept of
44 * 'timeslice length' - timeslices in CFS are of variable length
45 * and have no persistent notion like in traditional, time-slice
46 * based scheduling concepts.
48 * (to see the precise effective timeslice length of your workload,
49 * run vmstat and monitor the context-switches (cs) field)
51 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
53 unsigned int sysctl_sched_latency
= 6000000ULL;
54 unsigned int normalized_sysctl_sched_latency
= 6000000ULL;
57 * The initial- and re-scaling of tunables is configurable
61 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
62 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
63 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
65 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
67 enum sched_tunable_scaling sysctl_sched_tunable_scaling
= SCHED_TUNABLESCALING_LOG
;
70 * Minimal preemption granularity for CPU-bound tasks:
72 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
74 unsigned int sysctl_sched_min_granularity
= 750000ULL;
75 unsigned int normalized_sysctl_sched_min_granularity
= 750000ULL;
78 * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
80 static unsigned int sched_nr_latency
= 8;
83 * After fork, child runs first. If set to 0 (default) then
84 * parent will (try to) run first.
86 unsigned int sysctl_sched_child_runs_first __read_mostly
;
89 * SCHED_OTHER wake-up granularity.
91 * This option delays the preemption effects of decoupled workloads
92 * and reduces their over-scheduling. Synchronous workloads will still
93 * have immediate wakeup/sleep latencies.
95 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
97 unsigned int sysctl_sched_wakeup_granularity
= 1000000UL;
98 unsigned int normalized_sysctl_sched_wakeup_granularity
= 1000000UL;
100 const_debug
unsigned int sysctl_sched_migration_cost
= 500000UL;
104 * For asym packing, by default the lower numbered cpu has higher priority.
106 int __weak
arch_asym_cpu_priority(int cpu
)
112 #ifdef CONFIG_CFS_BANDWIDTH
114 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
115 * each time a cfs_rq requests quota.
117 * Note: in the case that the slice exceeds the runtime remaining (either due
118 * to consumption or the quota being specified to be smaller than the slice)
119 * we will always only issue the remaining available time.
121 * (default: 5 msec, units: microseconds)
123 unsigned int sysctl_sched_cfs_bandwidth_slice
= 5000UL;
127 * The margin used when comparing utilization with CPU capacity:
128 * util * margin < capacity * 1024
132 unsigned int capacity_margin
= 1280;
134 static inline void update_load_add(struct load_weight
*lw
, unsigned long inc
)
140 static inline void update_load_sub(struct load_weight
*lw
, unsigned long dec
)
146 static inline void update_load_set(struct load_weight
*lw
, unsigned long w
)
153 * Increase the granularity value when there are more CPUs,
154 * because with more CPUs the 'effective latency' as visible
155 * to users decreases. But the relationship is not linear,
156 * so pick a second-best guess by going with the log2 of the
159 * This idea comes from the SD scheduler of Con Kolivas:
161 static unsigned int get_update_sysctl_factor(void)
163 unsigned int cpus
= min_t(unsigned int, num_online_cpus(), 8);
166 switch (sysctl_sched_tunable_scaling
) {
167 case SCHED_TUNABLESCALING_NONE
:
170 case SCHED_TUNABLESCALING_LINEAR
:
173 case SCHED_TUNABLESCALING_LOG
:
175 factor
= 1 + ilog2(cpus
);
182 static void update_sysctl(void)
184 unsigned int factor
= get_update_sysctl_factor();
186 #define SET_SYSCTL(name) \
187 (sysctl_##name = (factor) * normalized_sysctl_##name)
188 SET_SYSCTL(sched_min_granularity
);
189 SET_SYSCTL(sched_latency
);
190 SET_SYSCTL(sched_wakeup_granularity
);
194 void sched_init_granularity(void)
199 #define WMULT_CONST (~0U)
200 #define WMULT_SHIFT 32
202 static void __update_inv_weight(struct load_weight
*lw
)
206 if (likely(lw
->inv_weight
))
209 w
= scale_load_down(lw
->weight
);
211 if (BITS_PER_LONG
> 32 && unlikely(w
>= WMULT_CONST
))
213 else if (unlikely(!w
))
214 lw
->inv_weight
= WMULT_CONST
;
216 lw
->inv_weight
= WMULT_CONST
/ w
;
220 * delta_exec * weight / lw.weight
222 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
224 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
225 * we're guaranteed shift stays positive because inv_weight is guaranteed to
226 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
228 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
229 * weight/lw.weight <= 1, and therefore our shift will also be positive.
231 static u64
__calc_delta(u64 delta_exec
, unsigned long weight
, struct load_weight
*lw
)
233 u64 fact
= scale_load_down(weight
);
234 int shift
= WMULT_SHIFT
;
236 __update_inv_weight(lw
);
238 if (unlikely(fact
>> 32)) {
245 /* hint to use a 32x32->64 mul */
246 fact
= (u64
)(u32
)fact
* lw
->inv_weight
;
253 return mul_u64_u32_shr(delta_exec
, fact
, shift
);
257 const struct sched_class fair_sched_class
;
259 /**************************************************************
260 * CFS operations on generic schedulable entities:
263 #ifdef CONFIG_FAIR_GROUP_SCHED
265 /* cpu runqueue to which this cfs_rq is attached */
266 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
271 /* An entity is a task if it doesn't "own" a runqueue */
272 #define entity_is_task(se) (!se->my_q)
274 static inline struct task_struct
*task_of(struct sched_entity
*se
)
276 SCHED_WARN_ON(!entity_is_task(se
));
277 return container_of(se
, struct task_struct
, se
);
280 /* Walk up scheduling entities hierarchy */
281 #define for_each_sched_entity(se) \
282 for (; se; se = se->parent)
284 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
289 /* runqueue on which this entity is (to be) queued */
290 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
295 /* runqueue "owned" by this group */
296 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
301 static inline void list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
303 if (!cfs_rq
->on_list
) {
304 struct rq
*rq
= rq_of(cfs_rq
);
305 int cpu
= cpu_of(rq
);
307 * Ensure we either appear before our parent (if already
308 * enqueued) or force our parent to appear after us when it is
309 * enqueued. The fact that we always enqueue bottom-up
310 * reduces this to two cases and a special case for the root
311 * cfs_rq. Furthermore, it also means that we will always reset
312 * tmp_alone_branch either when the branch is connected
313 * to a tree or when we reach the beg of the tree
315 if (cfs_rq
->tg
->parent
&&
316 cfs_rq
->tg
->parent
->cfs_rq
[cpu
]->on_list
) {
318 * If parent is already on the list, we add the child
319 * just before. Thanks to circular linked property of
320 * the list, this means to put the child at the tail
321 * of the list that starts by parent.
323 list_add_tail_rcu(&cfs_rq
->leaf_cfs_rq_list
,
324 &(cfs_rq
->tg
->parent
->cfs_rq
[cpu
]->leaf_cfs_rq_list
));
326 * The branch is now connected to its tree so we can
327 * reset tmp_alone_branch to the beginning of the
330 rq
->tmp_alone_branch
= &rq
->leaf_cfs_rq_list
;
331 } else if (!cfs_rq
->tg
->parent
) {
333 * cfs rq without parent should be put
334 * at the tail of the list.
336 list_add_tail_rcu(&cfs_rq
->leaf_cfs_rq_list
,
337 &rq
->leaf_cfs_rq_list
);
339 * We have reach the beg of a tree so we can reset
340 * tmp_alone_branch to the beginning of the list.
342 rq
->tmp_alone_branch
= &rq
->leaf_cfs_rq_list
;
345 * The parent has not already been added so we want to
346 * make sure that it will be put after us.
347 * tmp_alone_branch points to the beg of the branch
348 * where we will add parent.
350 list_add_rcu(&cfs_rq
->leaf_cfs_rq_list
,
351 rq
->tmp_alone_branch
);
353 * update tmp_alone_branch to points to the new beg
356 rq
->tmp_alone_branch
= &cfs_rq
->leaf_cfs_rq_list
;
363 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
365 if (cfs_rq
->on_list
) {
366 list_del_rcu(&cfs_rq
->leaf_cfs_rq_list
);
371 /* Iterate thr' all leaf cfs_rq's on a runqueue */
372 #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
373 list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list, \
376 /* Do the two (enqueued) entities belong to the same group ? */
377 static inline struct cfs_rq
*
378 is_same_group(struct sched_entity
*se
, struct sched_entity
*pse
)
380 if (se
->cfs_rq
== pse
->cfs_rq
)
386 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
392 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
394 int se_depth
, pse_depth
;
397 * preemption test can be made between sibling entities who are in the
398 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
399 * both tasks until we find their ancestors who are siblings of common
403 /* First walk up until both entities are at same depth */
404 se_depth
= (*se
)->depth
;
405 pse_depth
= (*pse
)->depth
;
407 while (se_depth
> pse_depth
) {
409 *se
= parent_entity(*se
);
412 while (pse_depth
> se_depth
) {
414 *pse
= parent_entity(*pse
);
417 while (!is_same_group(*se
, *pse
)) {
418 *se
= parent_entity(*se
);
419 *pse
= parent_entity(*pse
);
423 #else /* !CONFIG_FAIR_GROUP_SCHED */
425 static inline struct task_struct
*task_of(struct sched_entity
*se
)
427 return container_of(se
, struct task_struct
, se
);
430 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
432 return container_of(cfs_rq
, struct rq
, cfs
);
435 #define entity_is_task(se) 1
437 #define for_each_sched_entity(se) \
438 for (; se; se = NULL)
440 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
442 return &task_rq(p
)->cfs
;
445 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
447 struct task_struct
*p
= task_of(se
);
448 struct rq
*rq
= task_rq(p
);
453 /* runqueue "owned" by this group */
454 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
459 static inline void list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
463 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
467 #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
468 for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
470 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
476 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
480 #endif /* CONFIG_FAIR_GROUP_SCHED */
482 static __always_inline
483 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
);
485 /**************************************************************
486 * Scheduling class tree data structure manipulation methods:
489 static inline u64
max_vruntime(u64 max_vruntime
, u64 vruntime
)
491 s64 delta
= (s64
)(vruntime
- max_vruntime
);
493 max_vruntime
= vruntime
;
498 static inline u64
min_vruntime(u64 min_vruntime
, u64 vruntime
)
500 s64 delta
= (s64
)(vruntime
- min_vruntime
);
502 min_vruntime
= vruntime
;
507 static inline int entity_before(struct sched_entity
*a
,
508 struct sched_entity
*b
)
510 return (s64
)(a
->vruntime
- b
->vruntime
) < 0;
513 static void update_min_vruntime(struct cfs_rq
*cfs_rq
)
515 struct sched_entity
*curr
= cfs_rq
->curr
;
516 struct rb_node
*leftmost
= rb_first_cached(&cfs_rq
->tasks_timeline
);
518 u64 vruntime
= cfs_rq
->min_vruntime
;
522 vruntime
= curr
->vruntime
;
527 if (leftmost
) { /* non-empty tree */
528 struct sched_entity
*se
;
529 se
= rb_entry(leftmost
, struct sched_entity
, run_node
);
532 vruntime
= se
->vruntime
;
534 vruntime
= min_vruntime(vruntime
, se
->vruntime
);
537 /* ensure we never gain time by being placed backwards. */
538 cfs_rq
->min_vruntime
= max_vruntime(cfs_rq
->min_vruntime
, vruntime
);
541 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
546 * Enqueue an entity into the rb-tree:
548 static void __enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
550 struct rb_node
**link
= &cfs_rq
->tasks_timeline
.rb_root
.rb_node
;
551 struct rb_node
*parent
= NULL
;
552 struct sched_entity
*entry
;
553 bool leftmost
= true;
556 * Find the right place in the rbtree:
560 entry
= rb_entry(parent
, struct sched_entity
, run_node
);
562 * We dont care about collisions. Nodes with
563 * the same key stay together.
565 if (entity_before(se
, entry
)) {
566 link
= &parent
->rb_left
;
568 link
= &parent
->rb_right
;
573 rb_link_node(&se
->run_node
, parent
, link
);
574 rb_insert_color_cached(&se
->run_node
,
575 &cfs_rq
->tasks_timeline
, leftmost
);
578 static void __dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
580 rb_erase_cached(&se
->run_node
, &cfs_rq
->tasks_timeline
);
583 struct sched_entity
*__pick_first_entity(struct cfs_rq
*cfs_rq
)
585 struct rb_node
*left
= rb_first_cached(&cfs_rq
->tasks_timeline
);
590 return rb_entry(left
, struct sched_entity
, run_node
);
593 static struct sched_entity
*__pick_next_entity(struct sched_entity
*se
)
595 struct rb_node
*next
= rb_next(&se
->run_node
);
600 return rb_entry(next
, struct sched_entity
, run_node
);
603 #ifdef CONFIG_SCHED_DEBUG
604 struct sched_entity
*__pick_last_entity(struct cfs_rq
*cfs_rq
)
606 struct rb_node
*last
= rb_last(&cfs_rq
->tasks_timeline
.rb_root
);
611 return rb_entry(last
, struct sched_entity
, run_node
);
614 /**************************************************************
615 * Scheduling class statistics methods:
618 int sched_proc_update_handler(struct ctl_table
*table
, int write
,
619 void __user
*buffer
, size_t *lenp
,
622 int ret
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
623 unsigned int factor
= get_update_sysctl_factor();
628 sched_nr_latency
= DIV_ROUND_UP(sysctl_sched_latency
,
629 sysctl_sched_min_granularity
);
631 #define WRT_SYSCTL(name) \
632 (normalized_sysctl_##name = sysctl_##name / (factor))
633 WRT_SYSCTL(sched_min_granularity
);
634 WRT_SYSCTL(sched_latency
);
635 WRT_SYSCTL(sched_wakeup_granularity
);
645 static inline u64
calc_delta_fair(u64 delta
, struct sched_entity
*se
)
647 if (unlikely(se
->load
.weight
!= NICE_0_LOAD
))
648 delta
= __calc_delta(delta
, NICE_0_LOAD
, &se
->load
);
654 * The idea is to set a period in which each task runs once.
656 * When there are too many tasks (sched_nr_latency) we have to stretch
657 * this period because otherwise the slices get too small.
659 * p = (nr <= nl) ? l : l*nr/nl
661 static u64
__sched_period(unsigned long nr_running
)
663 if (unlikely(nr_running
> sched_nr_latency
))
664 return nr_running
* sysctl_sched_min_granularity
;
666 return sysctl_sched_latency
;
670 * We calculate the wall-time slice from the period by taking a part
671 * proportional to the weight.
675 static u64
sched_slice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
677 u64 slice
= __sched_period(cfs_rq
->nr_running
+ !se
->on_rq
);
679 for_each_sched_entity(se
) {
680 struct load_weight
*load
;
681 struct load_weight lw
;
683 cfs_rq
= cfs_rq_of(se
);
684 load
= &cfs_rq
->load
;
686 if (unlikely(!se
->on_rq
)) {
689 update_load_add(&lw
, se
->load
.weight
);
692 slice
= __calc_delta(slice
, se
->load
.weight
, load
);
698 * We calculate the vruntime slice of a to-be-inserted task.
702 static u64
sched_vslice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
704 return calc_delta_fair(sched_slice(cfs_rq
, se
), se
);
709 #include "sched-pelt.h"
711 static int select_idle_sibling(struct task_struct
*p
, int prev_cpu
, int cpu
);
712 static unsigned long task_h_load(struct task_struct
*p
);
714 /* Give new sched_entity start runnable values to heavy its load in infant time */
715 void init_entity_runnable_average(struct sched_entity
*se
)
717 struct sched_avg
*sa
= &se
->avg
;
719 sa
->last_update_time
= 0;
721 * sched_avg's period_contrib should be strictly less then 1024, so
722 * we give it 1023 to make sure it is almost a period (1024us), and
723 * will definitely be update (after enqueue).
725 sa
->period_contrib
= 1023;
727 * Tasks are intialized with full load to be seen as heavy tasks until
728 * they get a chance to stabilize to their real load level.
729 * Group entities are intialized with zero load to reflect the fact that
730 * nothing has been attached to the task group yet.
732 if (entity_is_task(se
))
733 sa
->load_avg
= scale_load_down(se
->load
.weight
);
734 sa
->load_sum
= LOAD_AVG_MAX
;
736 * At this point, util_avg won't be used in select_task_rq_fair anyway
740 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
743 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
);
744 static void attach_entity_cfs_rq(struct sched_entity
*se
);
747 * With new tasks being created, their initial util_avgs are extrapolated
748 * based on the cfs_rq's current util_avg:
750 * util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
752 * However, in many cases, the above util_avg does not give a desired
753 * value. Moreover, the sum of the util_avgs may be divergent, such
754 * as when the series is a harmonic series.
756 * To solve this problem, we also cap the util_avg of successive tasks to
757 * only 1/2 of the left utilization budget:
759 * util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n
761 * where n denotes the nth task.
763 * For example, a simplest series from the beginning would be like:
765 * task util_avg: 512, 256, 128, 64, 32, 16, 8, ...
766 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
768 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
769 * if util_avg > util_avg_cap.
771 void post_init_entity_util_avg(struct sched_entity
*se
)
773 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
774 struct sched_avg
*sa
= &se
->avg
;
775 long cap
= (long)(SCHED_CAPACITY_SCALE
- cfs_rq
->avg
.util_avg
) / 2;
778 if (cfs_rq
->avg
.util_avg
!= 0) {
779 sa
->util_avg
= cfs_rq
->avg
.util_avg
* se
->load
.weight
;
780 sa
->util_avg
/= (cfs_rq
->avg
.load_avg
+ 1);
782 if (sa
->util_avg
> cap
)
787 sa
->util_sum
= sa
->util_avg
* LOAD_AVG_MAX
;
790 if (entity_is_task(se
)) {
791 struct task_struct
*p
= task_of(se
);
792 if (p
->sched_class
!= &fair_sched_class
) {
794 * For !fair tasks do:
796 update_cfs_rq_load_avg(now, cfs_rq);
797 attach_entity_load_avg(cfs_rq, se);
798 switched_from_fair(rq, p);
800 * such that the next switched_to_fair() has the
803 se
->avg
.last_update_time
= cfs_rq_clock_task(cfs_rq
);
808 attach_entity_cfs_rq(se
);
811 #else /* !CONFIG_SMP */
812 void init_entity_runnable_average(struct sched_entity
*se
)
815 void post_init_entity_util_avg(struct sched_entity
*se
)
818 static void update_tg_load_avg(struct cfs_rq
*cfs_rq
, int force
)
821 #endif /* CONFIG_SMP */
824 * Update the current task's runtime statistics.
826 static void update_curr(struct cfs_rq
*cfs_rq
)
828 struct sched_entity
*curr
= cfs_rq
->curr
;
829 u64 now
= rq_clock_task(rq_of(cfs_rq
));
835 delta_exec
= now
- curr
->exec_start
;
836 if (unlikely((s64
)delta_exec
<= 0))
839 curr
->exec_start
= now
;
841 schedstat_set(curr
->statistics
.exec_max
,
842 max(delta_exec
, curr
->statistics
.exec_max
));
844 curr
->sum_exec_runtime
+= delta_exec
;
845 schedstat_add(cfs_rq
->exec_clock
, delta_exec
);
847 curr
->vruntime
+= calc_delta_fair(delta_exec
, curr
);
848 update_min_vruntime(cfs_rq
);
850 if (entity_is_task(curr
)) {
851 struct task_struct
*curtask
= task_of(curr
);
853 trace_sched_stat_runtime(curtask
, delta_exec
, curr
->vruntime
);
854 cpuacct_charge(curtask
, delta_exec
);
855 account_group_exec_runtime(curtask
, delta_exec
);
858 account_cfs_rq_runtime(cfs_rq
, delta_exec
);
861 static void update_curr_fair(struct rq
*rq
)
863 update_curr(cfs_rq_of(&rq
->curr
->se
));
867 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
869 u64 wait_start
, prev_wait_start
;
871 if (!schedstat_enabled())
874 wait_start
= rq_clock(rq_of(cfs_rq
));
875 prev_wait_start
= schedstat_val(se
->statistics
.wait_start
);
877 if (entity_is_task(se
) && task_on_rq_migrating(task_of(se
)) &&
878 likely(wait_start
> prev_wait_start
))
879 wait_start
-= prev_wait_start
;
881 schedstat_set(se
->statistics
.wait_start
, wait_start
);
885 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
887 struct task_struct
*p
;
890 if (!schedstat_enabled())
893 delta
= rq_clock(rq_of(cfs_rq
)) - schedstat_val(se
->statistics
.wait_start
);
895 if (entity_is_task(se
)) {
897 if (task_on_rq_migrating(p
)) {
899 * Preserve migrating task's wait time so wait_start
900 * time stamp can be adjusted to accumulate wait time
901 * prior to migration.
903 schedstat_set(se
->statistics
.wait_start
, delta
);
906 trace_sched_stat_wait(p
, delta
);
909 schedstat_set(se
->statistics
.wait_max
,
910 max(schedstat_val(se
->statistics
.wait_max
), delta
));
911 schedstat_inc(se
->statistics
.wait_count
);
912 schedstat_add(se
->statistics
.wait_sum
, delta
);
913 schedstat_set(se
->statistics
.wait_start
, 0);
917 update_stats_enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
919 struct task_struct
*tsk
= NULL
;
920 u64 sleep_start
, block_start
;
922 if (!schedstat_enabled())
925 sleep_start
= schedstat_val(se
->statistics
.sleep_start
);
926 block_start
= schedstat_val(se
->statistics
.block_start
);
928 if (entity_is_task(se
))
932 u64 delta
= rq_clock(rq_of(cfs_rq
)) - sleep_start
;
937 if (unlikely(delta
> schedstat_val(se
->statistics
.sleep_max
)))
938 schedstat_set(se
->statistics
.sleep_max
, delta
);
940 schedstat_set(se
->statistics
.sleep_start
, 0);
941 schedstat_add(se
->statistics
.sum_sleep_runtime
, delta
);
944 account_scheduler_latency(tsk
, delta
>> 10, 1);
945 trace_sched_stat_sleep(tsk
, delta
);
949 u64 delta
= rq_clock(rq_of(cfs_rq
)) - block_start
;
954 if (unlikely(delta
> schedstat_val(se
->statistics
.block_max
)))
955 schedstat_set(se
->statistics
.block_max
, delta
);
957 schedstat_set(se
->statistics
.block_start
, 0);
958 schedstat_add(se
->statistics
.sum_sleep_runtime
, delta
);
961 if (tsk
->in_iowait
) {
962 schedstat_add(se
->statistics
.iowait_sum
, delta
);
963 schedstat_inc(se
->statistics
.iowait_count
);
964 trace_sched_stat_iowait(tsk
, delta
);
967 trace_sched_stat_blocked(tsk
, delta
);
970 * Blocking time is in units of nanosecs, so shift by
971 * 20 to get a milliseconds-range estimation of the
972 * amount of time that the task spent sleeping:
974 if (unlikely(prof_on
== SLEEP_PROFILING
)) {
975 profile_hits(SLEEP_PROFILING
,
976 (void *)get_wchan(tsk
),
979 account_scheduler_latency(tsk
, delta
>> 10, 0);
985 * Task is being enqueued - update stats:
988 update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
990 if (!schedstat_enabled())
994 * Are we enqueueing a waiting task? (for current tasks
995 * a dequeue/enqueue event is a NOP)
997 if (se
!= cfs_rq
->curr
)
998 update_stats_wait_start(cfs_rq
, se
);
1000 if (flags
& ENQUEUE_WAKEUP
)
1001 update_stats_enqueue_sleeper(cfs_rq
, se
);
1005 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
1008 if (!schedstat_enabled())
1012 * Mark the end of the wait period if dequeueing a
1015 if (se
!= cfs_rq
->curr
)
1016 update_stats_wait_end(cfs_rq
, se
);
1018 if ((flags
& DEQUEUE_SLEEP
) && entity_is_task(se
)) {
1019 struct task_struct
*tsk
= task_of(se
);
1021 if (tsk
->state
& TASK_INTERRUPTIBLE
)
1022 schedstat_set(se
->statistics
.sleep_start
,
1023 rq_clock(rq_of(cfs_rq
)));
1024 if (tsk
->state
& TASK_UNINTERRUPTIBLE
)
1025 schedstat_set(se
->statistics
.block_start
,
1026 rq_clock(rq_of(cfs_rq
)));
1031 * We are picking a new current task - update its stats:
1034 update_stats_curr_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
1037 * We are starting a new run period:
1039 se
->exec_start
= rq_clock_task(rq_of(cfs_rq
));
1042 /**************************************************
1043 * Scheduling class queueing methods:
1046 #ifdef CONFIG_NUMA_BALANCING
1048 * Approximate time to scan a full NUMA task in ms. The task scan period is
1049 * calculated based on the tasks virtual memory size and
1050 * numa_balancing_scan_size.
1052 unsigned int sysctl_numa_balancing_scan_period_min
= 1000;
1053 unsigned int sysctl_numa_balancing_scan_period_max
= 60000;
1055 /* Portion of address space to scan in MB */
1056 unsigned int sysctl_numa_balancing_scan_size
= 256;
1058 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
1059 unsigned int sysctl_numa_balancing_scan_delay
= 1000;
1064 spinlock_t lock
; /* nr_tasks, tasks */
1069 struct rcu_head rcu
;
1070 unsigned long total_faults
;
1071 unsigned long max_faults_cpu
;
1073 * Faults_cpu is used to decide whether memory should move
1074 * towards the CPU. As a consequence, these stats are weighted
1075 * more by CPU use than by memory faults.
1077 unsigned long *faults_cpu
;
1078 unsigned long faults
[0];
1081 static inline unsigned long group_faults_priv(struct numa_group
*ng
);
1082 static inline unsigned long group_faults_shared(struct numa_group
*ng
);
1084 static unsigned int task_nr_scan_windows(struct task_struct
*p
)
1086 unsigned long rss
= 0;
1087 unsigned long nr_scan_pages
;
1090 * Calculations based on RSS as non-present and empty pages are skipped
1091 * by the PTE scanner and NUMA hinting faults should be trapped based
1094 nr_scan_pages
= sysctl_numa_balancing_scan_size
<< (20 - PAGE_SHIFT
);
1095 rss
= get_mm_rss(p
->mm
);
1097 rss
= nr_scan_pages
;
1099 rss
= round_up(rss
, nr_scan_pages
);
1100 return rss
/ nr_scan_pages
;
1103 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
1104 #define MAX_SCAN_WINDOW 2560
1106 static unsigned int task_scan_min(struct task_struct
*p
)
1108 unsigned int scan_size
= READ_ONCE(sysctl_numa_balancing_scan_size
);
1109 unsigned int scan
, floor
;
1110 unsigned int windows
= 1;
1112 if (scan_size
< MAX_SCAN_WINDOW
)
1113 windows
= MAX_SCAN_WINDOW
/ scan_size
;
1114 floor
= 1000 / windows
;
1116 scan
= sysctl_numa_balancing_scan_period_min
/ task_nr_scan_windows(p
);
1117 return max_t(unsigned int, floor
, scan
);
1120 static unsigned int task_scan_start(struct task_struct
*p
)
1122 unsigned long smin
= task_scan_min(p
);
1123 unsigned long period
= smin
;
1125 /* Scale the maximum scan period with the amount of shared memory. */
1126 if (p
->numa_group
) {
1127 struct numa_group
*ng
= p
->numa_group
;
1128 unsigned long shared
= group_faults_shared(ng
);
1129 unsigned long private = group_faults_priv(ng
);
1131 period
*= atomic_read(&ng
->refcount
);
1132 period
*= shared
+ 1;
1133 period
/= private + shared
+ 1;
1136 return max(smin
, period
);
1139 static unsigned int task_scan_max(struct task_struct
*p
)
1141 unsigned long smin
= task_scan_min(p
);
1144 /* Watch for min being lower than max due to floor calculations */
1145 smax
= sysctl_numa_balancing_scan_period_max
/ task_nr_scan_windows(p
);
1147 /* Scale the maximum scan period with the amount of shared memory. */
1148 if (p
->numa_group
) {
1149 struct numa_group
*ng
= p
->numa_group
;
1150 unsigned long shared
= group_faults_shared(ng
);
1151 unsigned long private = group_faults_priv(ng
);
1152 unsigned long period
= smax
;
1154 period
*= atomic_read(&ng
->refcount
);
1155 period
*= shared
+ 1;
1156 period
/= private + shared
+ 1;
1158 smax
= max(smax
, period
);
1161 return max(smin
, smax
);
1164 static void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
1166 rq
->nr_numa_running
+= (p
->numa_preferred_nid
!= -1);
1167 rq
->nr_preferred_running
+= (p
->numa_preferred_nid
== task_node(p
));
1170 static void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
1172 rq
->nr_numa_running
-= (p
->numa_preferred_nid
!= -1);
1173 rq
->nr_preferred_running
-= (p
->numa_preferred_nid
== task_node(p
));
1176 /* Shared or private faults. */
1177 #define NR_NUMA_HINT_FAULT_TYPES 2
1179 /* Memory and CPU locality */
1180 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
1182 /* Averaged statistics, and temporary buffers. */
1183 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
1185 pid_t
task_numa_group_id(struct task_struct
*p
)
1187 return p
->numa_group
? p
->numa_group
->gid
: 0;
1191 * The averaged statistics, shared & private, memory & cpu,
1192 * occupy the first half of the array. The second half of the
1193 * array is for current counters, which are averaged into the
1194 * first set by task_numa_placement.
1196 static inline int task_faults_idx(enum numa_faults_stats s
, int nid
, int priv
)
1198 return NR_NUMA_HINT_FAULT_TYPES
* (s
* nr_node_ids
+ nid
) + priv
;
1201 static inline unsigned long task_faults(struct task_struct
*p
, int nid
)
1203 if (!p
->numa_faults
)
1206 return p
->numa_faults
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1207 p
->numa_faults
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1210 static inline unsigned long group_faults(struct task_struct
*p
, int nid
)
1215 return p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1216 p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1219 static inline unsigned long group_faults_cpu(struct numa_group
*group
, int nid
)
1221 return group
->faults_cpu
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1222 group
->faults_cpu
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1225 static inline unsigned long group_faults_priv(struct numa_group
*ng
)
1227 unsigned long faults
= 0;
1230 for_each_online_node(node
) {
1231 faults
+= ng
->faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
1237 static inline unsigned long group_faults_shared(struct numa_group
*ng
)
1239 unsigned long faults
= 0;
1242 for_each_online_node(node
) {
1243 faults
+= ng
->faults
[task_faults_idx(NUMA_MEM
, node
, 0)];
1250 * A node triggering more than 1/3 as many NUMA faults as the maximum is
1251 * considered part of a numa group's pseudo-interleaving set. Migrations
1252 * between these nodes are slowed down, to allow things to settle down.
1254 #define ACTIVE_NODE_FRACTION 3
1256 static bool numa_is_active_node(int nid
, struct numa_group
*ng
)
1258 return group_faults_cpu(ng
, nid
) * ACTIVE_NODE_FRACTION
> ng
->max_faults_cpu
;
1261 /* Handle placement on systems where not all nodes are directly connected. */
1262 static unsigned long score_nearby_nodes(struct task_struct
*p
, int nid
,
1263 int maxdist
, bool task
)
1265 unsigned long score
= 0;
1269 * All nodes are directly connected, and the same distance
1270 * from each other. No need for fancy placement algorithms.
1272 if (sched_numa_topology_type
== NUMA_DIRECT
)
1276 * This code is called for each node, introducing N^2 complexity,
1277 * which should be ok given the number of nodes rarely exceeds 8.
1279 for_each_online_node(node
) {
1280 unsigned long faults
;
1281 int dist
= node_distance(nid
, node
);
1284 * The furthest away nodes in the system are not interesting
1285 * for placement; nid was already counted.
1287 if (dist
== sched_max_numa_distance
|| node
== nid
)
1291 * On systems with a backplane NUMA topology, compare groups
1292 * of nodes, and move tasks towards the group with the most
1293 * memory accesses. When comparing two nodes at distance
1294 * "hoplimit", only nodes closer by than "hoplimit" are part
1295 * of each group. Skip other nodes.
1297 if (sched_numa_topology_type
== NUMA_BACKPLANE
&&
1301 /* Add up the faults from nearby nodes. */
1303 faults
= task_faults(p
, node
);
1305 faults
= group_faults(p
, node
);
1308 * On systems with a glueless mesh NUMA topology, there are
1309 * no fixed "groups of nodes". Instead, nodes that are not
1310 * directly connected bounce traffic through intermediate
1311 * nodes; a numa_group can occupy any set of nodes.
1312 * The further away a node is, the less the faults count.
1313 * This seems to result in good task placement.
1315 if (sched_numa_topology_type
== NUMA_GLUELESS_MESH
) {
1316 faults
*= (sched_max_numa_distance
- dist
);
1317 faults
/= (sched_max_numa_distance
- LOCAL_DISTANCE
);
1327 * These return the fraction of accesses done by a particular task, or
1328 * task group, on a particular numa node. The group weight is given a
1329 * larger multiplier, in order to group tasks together that are almost
1330 * evenly spread out between numa nodes.
1332 static inline unsigned long task_weight(struct task_struct
*p
, int nid
,
1335 unsigned long faults
, total_faults
;
1337 if (!p
->numa_faults
)
1340 total_faults
= p
->total_numa_faults
;
1345 faults
= task_faults(p
, nid
);
1346 faults
+= score_nearby_nodes(p
, nid
, dist
, true);
1348 return 1000 * faults
/ total_faults
;
1351 static inline unsigned long group_weight(struct task_struct
*p
, int nid
,
1354 unsigned long faults
, total_faults
;
1359 total_faults
= p
->numa_group
->total_faults
;
1364 faults
= group_faults(p
, nid
);
1365 faults
+= score_nearby_nodes(p
, nid
, dist
, false);
1367 return 1000 * faults
/ total_faults
;
1370 bool should_numa_migrate_memory(struct task_struct
*p
, struct page
* page
,
1371 int src_nid
, int dst_cpu
)
1373 struct numa_group
*ng
= p
->numa_group
;
1374 int dst_nid
= cpu_to_node(dst_cpu
);
1375 int last_cpupid
, this_cpupid
;
1377 this_cpupid
= cpu_pid_to_cpupid(dst_cpu
, current
->pid
);
1380 * Multi-stage node selection is used in conjunction with a periodic
1381 * migration fault to build a temporal task<->page relation. By using
1382 * a two-stage filter we remove short/unlikely relations.
1384 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1385 * a task's usage of a particular page (n_p) per total usage of this
1386 * page (n_t) (in a given time-span) to a probability.
1388 * Our periodic faults will sample this probability and getting the
1389 * same result twice in a row, given these samples are fully
1390 * independent, is then given by P(n)^2, provided our sample period
1391 * is sufficiently short compared to the usage pattern.
1393 * This quadric squishes small probabilities, making it less likely we
1394 * act on an unlikely task<->page relation.
1396 last_cpupid
= page_cpupid_xchg_last(page
, this_cpupid
);
1397 if (!cpupid_pid_unset(last_cpupid
) &&
1398 cpupid_to_nid(last_cpupid
) != dst_nid
)
1401 /* Always allow migrate on private faults */
1402 if (cpupid_match_pid(p
, last_cpupid
))
1405 /* A shared fault, but p->numa_group has not been set up yet. */
1410 * Destination node is much more heavily used than the source
1411 * node? Allow migration.
1413 if (group_faults_cpu(ng
, dst_nid
) > group_faults_cpu(ng
, src_nid
) *
1414 ACTIVE_NODE_FRACTION
)
1418 * Distribute memory according to CPU & memory use on each node,
1419 * with 3/4 hysteresis to avoid unnecessary memory migrations:
1421 * faults_cpu(dst) 3 faults_cpu(src)
1422 * --------------- * - > ---------------
1423 * faults_mem(dst) 4 faults_mem(src)
1425 return group_faults_cpu(ng
, dst_nid
) * group_faults(p
, src_nid
) * 3 >
1426 group_faults_cpu(ng
, src_nid
) * group_faults(p
, dst_nid
) * 4;
1429 static unsigned long weighted_cpuload(struct rq
*rq
);
1430 static unsigned long source_load(int cpu
, int type
);
1431 static unsigned long target_load(int cpu
, int type
);
1432 static unsigned long capacity_of(int cpu
);
1434 /* Cached statistics for all CPUs within a node */
1436 unsigned long nr_running
;
1439 /* Total compute capacity of CPUs on a node */
1440 unsigned long compute_capacity
;
1442 /* Approximate capacity in terms of runnable tasks on a node */
1443 unsigned long task_capacity
;
1444 int has_free_capacity
;
1448 * XXX borrowed from update_sg_lb_stats
1450 static void update_numa_stats(struct numa_stats
*ns
, int nid
)
1452 int smt
, cpu
, cpus
= 0;
1453 unsigned long capacity
;
1455 memset(ns
, 0, sizeof(*ns
));
1456 for_each_cpu(cpu
, cpumask_of_node(nid
)) {
1457 struct rq
*rq
= cpu_rq(cpu
);
1459 ns
->nr_running
+= rq
->nr_running
;
1460 ns
->load
+= weighted_cpuload(rq
);
1461 ns
->compute_capacity
+= capacity_of(cpu
);
1467 * If we raced with hotplug and there are no CPUs left in our mask
1468 * the @ns structure is NULL'ed and task_numa_compare() will
1469 * not find this node attractive.
1471 * We'll either bail at !has_free_capacity, or we'll detect a huge
1472 * imbalance and bail there.
1477 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1478 smt
= DIV_ROUND_UP(SCHED_CAPACITY_SCALE
* cpus
, ns
->compute_capacity
);
1479 capacity
= cpus
/ smt
; /* cores */
1481 ns
->task_capacity
= min_t(unsigned, capacity
,
1482 DIV_ROUND_CLOSEST(ns
->compute_capacity
, SCHED_CAPACITY_SCALE
));
1483 ns
->has_free_capacity
= (ns
->nr_running
< ns
->task_capacity
);
1486 struct task_numa_env
{
1487 struct task_struct
*p
;
1489 int src_cpu
, src_nid
;
1490 int dst_cpu
, dst_nid
;
1492 struct numa_stats src_stats
, dst_stats
;
1497 struct task_struct
*best_task
;
1502 static void task_numa_assign(struct task_numa_env
*env
,
1503 struct task_struct
*p
, long imp
)
1506 put_task_struct(env
->best_task
);
1511 env
->best_imp
= imp
;
1512 env
->best_cpu
= env
->dst_cpu
;
1515 static bool load_too_imbalanced(long src_load
, long dst_load
,
1516 struct task_numa_env
*env
)
1519 long orig_src_load
, orig_dst_load
;
1520 long src_capacity
, dst_capacity
;
1523 * The load is corrected for the CPU capacity available on each node.
1526 * ------------ vs ---------
1527 * src_capacity dst_capacity
1529 src_capacity
= env
->src_stats
.compute_capacity
;
1530 dst_capacity
= env
->dst_stats
.compute_capacity
;
1532 /* We care about the slope of the imbalance, not the direction. */
1533 if (dst_load
< src_load
)
1534 swap(dst_load
, src_load
);
1536 /* Is the difference below the threshold? */
1537 imb
= dst_load
* src_capacity
* 100 -
1538 src_load
* dst_capacity
* env
->imbalance_pct
;
1543 * The imbalance is above the allowed threshold.
1544 * Compare it with the old imbalance.
1546 orig_src_load
= env
->src_stats
.load
;
1547 orig_dst_load
= env
->dst_stats
.load
;
1549 if (orig_dst_load
< orig_src_load
)
1550 swap(orig_dst_load
, orig_src_load
);
1552 old_imb
= orig_dst_load
* src_capacity
* 100 -
1553 orig_src_load
* dst_capacity
* env
->imbalance_pct
;
1555 /* Would this change make things worse? */
1556 return (imb
> old_imb
);
1560 * This checks if the overall compute and NUMA accesses of the system would
1561 * be improved if the source tasks was migrated to the target dst_cpu taking
1562 * into account that it might be best if task running on the dst_cpu should
1563 * be exchanged with the source task
1565 static void task_numa_compare(struct task_numa_env
*env
,
1566 long taskimp
, long groupimp
)
1568 struct rq
*src_rq
= cpu_rq(env
->src_cpu
);
1569 struct rq
*dst_rq
= cpu_rq(env
->dst_cpu
);
1570 struct task_struct
*cur
;
1571 long src_load
, dst_load
;
1573 long imp
= env
->p
->numa_group
? groupimp
: taskimp
;
1575 int dist
= env
->dist
;
1578 cur
= task_rcu_dereference(&dst_rq
->curr
);
1579 if (cur
&& ((cur
->flags
& PF_EXITING
) || is_idle_task(cur
)))
1583 * Because we have preemption enabled we can get migrated around and
1584 * end try selecting ourselves (current == env->p) as a swap candidate.
1590 * "imp" is the fault differential for the source task between the
1591 * source and destination node. Calculate the total differential for
1592 * the source task and potential destination task. The more negative
1593 * the value is, the more rmeote accesses that would be expected to
1594 * be incurred if the tasks were swapped.
1597 /* Skip this swap candidate if cannot move to the source cpu */
1598 if (!cpumask_test_cpu(env
->src_cpu
, &cur
->cpus_allowed
))
1602 * If dst and source tasks are in the same NUMA group, or not
1603 * in any group then look only at task weights.
1605 if (cur
->numa_group
== env
->p
->numa_group
) {
1606 imp
= taskimp
+ task_weight(cur
, env
->src_nid
, dist
) -
1607 task_weight(cur
, env
->dst_nid
, dist
);
1609 * Add some hysteresis to prevent swapping the
1610 * tasks within a group over tiny differences.
1612 if (cur
->numa_group
)
1616 * Compare the group weights. If a task is all by
1617 * itself (not part of a group), use the task weight
1620 if (cur
->numa_group
)
1621 imp
+= group_weight(cur
, env
->src_nid
, dist
) -
1622 group_weight(cur
, env
->dst_nid
, dist
);
1624 imp
+= task_weight(cur
, env
->src_nid
, dist
) -
1625 task_weight(cur
, env
->dst_nid
, dist
);
1629 if (imp
<= env
->best_imp
&& moveimp
<= env
->best_imp
)
1633 /* Is there capacity at our destination? */
1634 if (env
->src_stats
.nr_running
<= env
->src_stats
.task_capacity
&&
1635 !env
->dst_stats
.has_free_capacity
)
1641 /* Balance doesn't matter much if we're running a task per cpu */
1642 if (imp
> env
->best_imp
&& src_rq
->nr_running
== 1 &&
1643 dst_rq
->nr_running
== 1)
1647 * In the overloaded case, try and keep the load balanced.
1650 load
= task_h_load(env
->p
);
1651 dst_load
= env
->dst_stats
.load
+ load
;
1652 src_load
= env
->src_stats
.load
- load
;
1654 if (moveimp
> imp
&& moveimp
> env
->best_imp
) {
1656 * If the improvement from just moving env->p direction is
1657 * better than swapping tasks around, check if a move is
1658 * possible. Store a slightly smaller score than moveimp,
1659 * so an actually idle CPU will win.
1661 if (!load_too_imbalanced(src_load
, dst_load
, env
)) {
1668 if (imp
<= env
->best_imp
)
1672 load
= task_h_load(cur
);
1677 if (load_too_imbalanced(src_load
, dst_load
, env
))
1681 * One idle CPU per node is evaluated for a task numa move.
1682 * Call select_idle_sibling to maybe find a better one.
1686 * select_idle_siblings() uses an per-cpu cpumask that
1687 * can be used from IRQ context.
1689 local_irq_disable();
1690 env
->dst_cpu
= select_idle_sibling(env
->p
, env
->src_cpu
,
1696 task_numa_assign(env
, cur
, imp
);
1701 static void task_numa_find_cpu(struct task_numa_env
*env
,
1702 long taskimp
, long groupimp
)
1706 for_each_cpu(cpu
, cpumask_of_node(env
->dst_nid
)) {
1707 /* Skip this CPU if the source task cannot migrate */
1708 if (!cpumask_test_cpu(cpu
, &env
->p
->cpus_allowed
))
1712 task_numa_compare(env
, taskimp
, groupimp
);
1716 /* Only move tasks to a NUMA node less busy than the current node. */
1717 static bool numa_has_capacity(struct task_numa_env
*env
)
1719 struct numa_stats
*src
= &env
->src_stats
;
1720 struct numa_stats
*dst
= &env
->dst_stats
;
1722 if (src
->has_free_capacity
&& !dst
->has_free_capacity
)
1726 * Only consider a task move if the source has a higher load
1727 * than the destination, corrected for CPU capacity on each node.
1729 * src->load dst->load
1730 * --------------------- vs ---------------------
1731 * src->compute_capacity dst->compute_capacity
1733 if (src
->load
* dst
->compute_capacity
* env
->imbalance_pct
>
1735 dst
->load
* src
->compute_capacity
* 100)
1741 static int task_numa_migrate(struct task_struct
*p
)
1743 struct task_numa_env env
= {
1746 .src_cpu
= task_cpu(p
),
1747 .src_nid
= task_node(p
),
1749 .imbalance_pct
= 112,
1755 struct sched_domain
*sd
;
1756 unsigned long taskweight
, groupweight
;
1758 long taskimp
, groupimp
;
1761 * Pick the lowest SD_NUMA domain, as that would have the smallest
1762 * imbalance and would be the first to start moving tasks about.
1764 * And we want to avoid any moving of tasks about, as that would create
1765 * random movement of tasks -- counter the numa conditions we're trying
1769 sd
= rcu_dereference(per_cpu(sd_numa
, env
.src_cpu
));
1771 env
.imbalance_pct
= 100 + (sd
->imbalance_pct
- 100) / 2;
1775 * Cpusets can break the scheduler domain tree into smaller
1776 * balance domains, some of which do not cross NUMA boundaries.
1777 * Tasks that are "trapped" in such domains cannot be migrated
1778 * elsewhere, so there is no point in (re)trying.
1780 if (unlikely(!sd
)) {
1781 p
->numa_preferred_nid
= task_node(p
);
1785 env
.dst_nid
= p
->numa_preferred_nid
;
1786 dist
= env
.dist
= node_distance(env
.src_nid
, env
.dst_nid
);
1787 taskweight
= task_weight(p
, env
.src_nid
, dist
);
1788 groupweight
= group_weight(p
, env
.src_nid
, dist
);
1789 update_numa_stats(&env
.src_stats
, env
.src_nid
);
1790 taskimp
= task_weight(p
, env
.dst_nid
, dist
) - taskweight
;
1791 groupimp
= group_weight(p
, env
.dst_nid
, dist
) - groupweight
;
1792 update_numa_stats(&env
.dst_stats
, env
.dst_nid
);
1794 /* Try to find a spot on the preferred nid. */
1795 if (numa_has_capacity(&env
))
1796 task_numa_find_cpu(&env
, taskimp
, groupimp
);
1799 * Look at other nodes in these cases:
1800 * - there is no space available on the preferred_nid
1801 * - the task is part of a numa_group that is interleaved across
1802 * multiple NUMA nodes; in order to better consolidate the group,
1803 * we need to check other locations.
1805 if (env
.best_cpu
== -1 || (p
->numa_group
&& p
->numa_group
->active_nodes
> 1)) {
1806 for_each_online_node(nid
) {
1807 if (nid
== env
.src_nid
|| nid
== p
->numa_preferred_nid
)
1810 dist
= node_distance(env
.src_nid
, env
.dst_nid
);
1811 if (sched_numa_topology_type
== NUMA_BACKPLANE
&&
1813 taskweight
= task_weight(p
, env
.src_nid
, dist
);
1814 groupweight
= group_weight(p
, env
.src_nid
, dist
);
1817 /* Only consider nodes where both task and groups benefit */
1818 taskimp
= task_weight(p
, nid
, dist
) - taskweight
;
1819 groupimp
= group_weight(p
, nid
, dist
) - groupweight
;
1820 if (taskimp
< 0 && groupimp
< 0)
1825 update_numa_stats(&env
.dst_stats
, env
.dst_nid
);
1826 if (numa_has_capacity(&env
))
1827 task_numa_find_cpu(&env
, taskimp
, groupimp
);
1832 * If the task is part of a workload that spans multiple NUMA nodes,
1833 * and is migrating into one of the workload's active nodes, remember
1834 * this node as the task's preferred numa node, so the workload can
1836 * A task that migrated to a second choice node will be better off
1837 * trying for a better one later. Do not set the preferred node here.
1839 if (p
->numa_group
) {
1840 struct numa_group
*ng
= p
->numa_group
;
1842 if (env
.best_cpu
== -1)
1847 if (ng
->active_nodes
> 1 && numa_is_active_node(env
.dst_nid
, ng
))
1848 sched_setnuma(p
, env
.dst_nid
);
1851 /* No better CPU than the current one was found. */
1852 if (env
.best_cpu
== -1)
1856 * Reset the scan period if the task is being rescheduled on an
1857 * alternative node to recheck if the tasks is now properly placed.
1859 p
->numa_scan_period
= task_scan_start(p
);
1861 if (env
.best_task
== NULL
) {
1862 ret
= migrate_task_to(p
, env
.best_cpu
);
1864 trace_sched_stick_numa(p
, env
.src_cpu
, env
.best_cpu
);
1868 ret
= migrate_swap(p
, env
.best_task
);
1870 trace_sched_stick_numa(p
, env
.src_cpu
, task_cpu(env
.best_task
));
1871 put_task_struct(env
.best_task
);
1875 /* Attempt to migrate a task to a CPU on the preferred node. */
1876 static void numa_migrate_preferred(struct task_struct
*p
)
1878 unsigned long interval
= HZ
;
1880 /* This task has no NUMA fault statistics yet */
1881 if (unlikely(p
->numa_preferred_nid
== -1 || !p
->numa_faults
))
1884 /* Periodically retry migrating the task to the preferred node */
1885 interval
= min(interval
, msecs_to_jiffies(p
->numa_scan_period
) / 16);
1886 p
->numa_migrate_retry
= jiffies
+ interval
;
1888 /* Success if task is already running on preferred CPU */
1889 if (task_node(p
) == p
->numa_preferred_nid
)
1892 /* Otherwise, try migrate to a CPU on the preferred node */
1893 task_numa_migrate(p
);
1897 * Find out how many nodes on the workload is actively running on. Do this by
1898 * tracking the nodes from which NUMA hinting faults are triggered. This can
1899 * be different from the set of nodes where the workload's memory is currently
1902 static void numa_group_count_active_nodes(struct numa_group
*numa_group
)
1904 unsigned long faults
, max_faults
= 0;
1905 int nid
, active_nodes
= 0;
1907 for_each_online_node(nid
) {
1908 faults
= group_faults_cpu(numa_group
, nid
);
1909 if (faults
> max_faults
)
1910 max_faults
= faults
;
1913 for_each_online_node(nid
) {
1914 faults
= group_faults_cpu(numa_group
, nid
);
1915 if (faults
* ACTIVE_NODE_FRACTION
> max_faults
)
1919 numa_group
->max_faults_cpu
= max_faults
;
1920 numa_group
->active_nodes
= active_nodes
;
1924 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1925 * increments. The more local the fault statistics are, the higher the scan
1926 * period will be for the next scan window. If local/(local+remote) ratio is
1927 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1928 * the scan period will decrease. Aim for 70% local accesses.
1930 #define NUMA_PERIOD_SLOTS 10
1931 #define NUMA_PERIOD_THRESHOLD 7
1934 * Increase the scan period (slow down scanning) if the majority of
1935 * our memory is already on our local node, or if the majority of
1936 * the page accesses are shared with other processes.
1937 * Otherwise, decrease the scan period.
1939 static void update_task_scan_period(struct task_struct
*p
,
1940 unsigned long shared
, unsigned long private)
1942 unsigned int period_slot
;
1943 int lr_ratio
, ps_ratio
;
1946 unsigned long remote
= p
->numa_faults_locality
[0];
1947 unsigned long local
= p
->numa_faults_locality
[1];
1950 * If there were no record hinting faults then either the task is
1951 * completely idle or all activity is areas that are not of interest
1952 * to automatic numa balancing. Related to that, if there were failed
1953 * migration then it implies we are migrating too quickly or the local
1954 * node is overloaded. In either case, scan slower
1956 if (local
+ shared
== 0 || p
->numa_faults_locality
[2]) {
1957 p
->numa_scan_period
= min(p
->numa_scan_period_max
,
1958 p
->numa_scan_period
<< 1);
1960 p
->mm
->numa_next_scan
= jiffies
+
1961 msecs_to_jiffies(p
->numa_scan_period
);
1967 * Prepare to scale scan period relative to the current period.
1968 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1969 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1970 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1972 period_slot
= DIV_ROUND_UP(p
->numa_scan_period
, NUMA_PERIOD_SLOTS
);
1973 lr_ratio
= (local
* NUMA_PERIOD_SLOTS
) / (local
+ remote
);
1974 ps_ratio
= (private * NUMA_PERIOD_SLOTS
) / (private + shared
);
1976 if (ps_ratio
>= NUMA_PERIOD_THRESHOLD
) {
1978 * Most memory accesses are local. There is no need to
1979 * do fast NUMA scanning, since memory is already local.
1981 int slot
= ps_ratio
- NUMA_PERIOD_THRESHOLD
;
1984 diff
= slot
* period_slot
;
1985 } else if (lr_ratio
>= NUMA_PERIOD_THRESHOLD
) {
1987 * Most memory accesses are shared with other tasks.
1988 * There is no point in continuing fast NUMA scanning,
1989 * since other tasks may just move the memory elsewhere.
1991 int slot
= lr_ratio
- NUMA_PERIOD_THRESHOLD
;
1994 diff
= slot
* period_slot
;
1997 * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
1998 * yet they are not on the local NUMA node. Speed up
1999 * NUMA scanning to get the memory moved over.
2001 int ratio
= max(lr_ratio
, ps_ratio
);
2002 diff
= -(NUMA_PERIOD_THRESHOLD
- ratio
) * period_slot
;
2005 p
->numa_scan_period
= clamp(p
->numa_scan_period
+ diff
,
2006 task_scan_min(p
), task_scan_max(p
));
2007 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
2011 * Get the fraction of time the task has been running since the last
2012 * NUMA placement cycle. The scheduler keeps similar statistics, but
2013 * decays those on a 32ms period, which is orders of magnitude off
2014 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
2015 * stats only if the task is so new there are no NUMA statistics yet.
2017 static u64
numa_get_avg_runtime(struct task_struct
*p
, u64
*period
)
2019 u64 runtime
, delta
, now
;
2020 /* Use the start of this time slice to avoid calculations. */
2021 now
= p
->se
.exec_start
;
2022 runtime
= p
->se
.sum_exec_runtime
;
2024 if (p
->last_task_numa_placement
) {
2025 delta
= runtime
- p
->last_sum_exec_runtime
;
2026 *period
= now
- p
->last_task_numa_placement
;
2028 delta
= p
->se
.avg
.load_sum
;
2029 *period
= LOAD_AVG_MAX
;
2032 p
->last_sum_exec_runtime
= runtime
;
2033 p
->last_task_numa_placement
= now
;
2039 * Determine the preferred nid for a task in a numa_group. This needs to
2040 * be done in a way that produces consistent results with group_weight,
2041 * otherwise workloads might not converge.
2043 static int preferred_group_nid(struct task_struct
*p
, int nid
)
2048 /* Direct connections between all NUMA nodes. */
2049 if (sched_numa_topology_type
== NUMA_DIRECT
)
2053 * On a system with glueless mesh NUMA topology, group_weight
2054 * scores nodes according to the number of NUMA hinting faults on
2055 * both the node itself, and on nearby nodes.
2057 if (sched_numa_topology_type
== NUMA_GLUELESS_MESH
) {
2058 unsigned long score
, max_score
= 0;
2059 int node
, max_node
= nid
;
2061 dist
= sched_max_numa_distance
;
2063 for_each_online_node(node
) {
2064 score
= group_weight(p
, node
, dist
);
2065 if (score
> max_score
) {
2074 * Finding the preferred nid in a system with NUMA backplane
2075 * interconnect topology is more involved. The goal is to locate
2076 * tasks from numa_groups near each other in the system, and
2077 * untangle workloads from different sides of the system. This requires
2078 * searching down the hierarchy of node groups, recursively searching
2079 * inside the highest scoring group of nodes. The nodemask tricks
2080 * keep the complexity of the search down.
2082 nodes
= node_online_map
;
2083 for (dist
= sched_max_numa_distance
; dist
> LOCAL_DISTANCE
; dist
--) {
2084 unsigned long max_faults
= 0;
2085 nodemask_t max_group
= NODE_MASK_NONE
;
2088 /* Are there nodes at this distance from each other? */
2089 if (!find_numa_distance(dist
))
2092 for_each_node_mask(a
, nodes
) {
2093 unsigned long faults
= 0;
2094 nodemask_t this_group
;
2095 nodes_clear(this_group
);
2097 /* Sum group's NUMA faults; includes a==b case. */
2098 for_each_node_mask(b
, nodes
) {
2099 if (node_distance(a
, b
) < dist
) {
2100 faults
+= group_faults(p
, b
);
2101 node_set(b
, this_group
);
2102 node_clear(b
, nodes
);
2106 /* Remember the top group. */
2107 if (faults
> max_faults
) {
2108 max_faults
= faults
;
2109 max_group
= this_group
;
2111 * subtle: at the smallest distance there is
2112 * just one node left in each "group", the
2113 * winner is the preferred nid.
2118 /* Next round, evaluate the nodes within max_group. */
2126 static void task_numa_placement(struct task_struct
*p
)
2128 int seq
, nid
, max_nid
= -1, max_group_nid
= -1;
2129 unsigned long max_faults
= 0, max_group_faults
= 0;
2130 unsigned long fault_types
[2] = { 0, 0 };
2131 unsigned long total_faults
;
2132 u64 runtime
, period
;
2133 spinlock_t
*group_lock
= NULL
;
2136 * The p->mm->numa_scan_seq field gets updated without
2137 * exclusive access. Use READ_ONCE() here to ensure
2138 * that the field is read in a single access:
2140 seq
= READ_ONCE(p
->mm
->numa_scan_seq
);
2141 if (p
->numa_scan_seq
== seq
)
2143 p
->numa_scan_seq
= seq
;
2144 p
->numa_scan_period_max
= task_scan_max(p
);
2146 total_faults
= p
->numa_faults_locality
[0] +
2147 p
->numa_faults_locality
[1];
2148 runtime
= numa_get_avg_runtime(p
, &period
);
2150 /* If the task is part of a group prevent parallel updates to group stats */
2151 if (p
->numa_group
) {
2152 group_lock
= &p
->numa_group
->lock
;
2153 spin_lock_irq(group_lock
);
2156 /* Find the node with the highest number of faults */
2157 for_each_online_node(nid
) {
2158 /* Keep track of the offsets in numa_faults array */
2159 int mem_idx
, membuf_idx
, cpu_idx
, cpubuf_idx
;
2160 unsigned long faults
= 0, group_faults
= 0;
2163 for (priv
= 0; priv
< NR_NUMA_HINT_FAULT_TYPES
; priv
++) {
2164 long diff
, f_diff
, f_weight
;
2166 mem_idx
= task_faults_idx(NUMA_MEM
, nid
, priv
);
2167 membuf_idx
= task_faults_idx(NUMA_MEMBUF
, nid
, priv
);
2168 cpu_idx
= task_faults_idx(NUMA_CPU
, nid
, priv
);
2169 cpubuf_idx
= task_faults_idx(NUMA_CPUBUF
, nid
, priv
);
2171 /* Decay existing window, copy faults since last scan */
2172 diff
= p
->numa_faults
[membuf_idx
] - p
->numa_faults
[mem_idx
] / 2;
2173 fault_types
[priv
] += p
->numa_faults
[membuf_idx
];
2174 p
->numa_faults
[membuf_idx
] = 0;
2177 * Normalize the faults_from, so all tasks in a group
2178 * count according to CPU use, instead of by the raw
2179 * number of faults. Tasks with little runtime have
2180 * little over-all impact on throughput, and thus their
2181 * faults are less important.
2183 f_weight
= div64_u64(runtime
<< 16, period
+ 1);
2184 f_weight
= (f_weight
* p
->numa_faults
[cpubuf_idx
]) /
2186 f_diff
= f_weight
- p
->numa_faults
[cpu_idx
] / 2;
2187 p
->numa_faults
[cpubuf_idx
] = 0;
2189 p
->numa_faults
[mem_idx
] += diff
;
2190 p
->numa_faults
[cpu_idx
] += f_diff
;
2191 faults
+= p
->numa_faults
[mem_idx
];
2192 p
->total_numa_faults
+= diff
;
2193 if (p
->numa_group
) {
2195 * safe because we can only change our own group
2197 * mem_idx represents the offset for a given
2198 * nid and priv in a specific region because it
2199 * is at the beginning of the numa_faults array.
2201 p
->numa_group
->faults
[mem_idx
] += diff
;
2202 p
->numa_group
->faults_cpu
[mem_idx
] += f_diff
;
2203 p
->numa_group
->total_faults
+= diff
;
2204 group_faults
+= p
->numa_group
->faults
[mem_idx
];
2208 if (faults
> max_faults
) {
2209 max_faults
= faults
;
2213 if (group_faults
> max_group_faults
) {
2214 max_group_faults
= group_faults
;
2215 max_group_nid
= nid
;
2219 update_task_scan_period(p
, fault_types
[0], fault_types
[1]);
2221 if (p
->numa_group
) {
2222 numa_group_count_active_nodes(p
->numa_group
);
2223 spin_unlock_irq(group_lock
);
2224 max_nid
= preferred_group_nid(p
, max_group_nid
);
2228 /* Set the new preferred node */
2229 if (max_nid
!= p
->numa_preferred_nid
)
2230 sched_setnuma(p
, max_nid
);
2232 if (task_node(p
) != p
->numa_preferred_nid
)
2233 numa_migrate_preferred(p
);
2237 static inline int get_numa_group(struct numa_group
*grp
)
2239 return atomic_inc_not_zero(&grp
->refcount
);
2242 static inline void put_numa_group(struct numa_group
*grp
)
2244 if (atomic_dec_and_test(&grp
->refcount
))
2245 kfree_rcu(grp
, rcu
);
2248 static void task_numa_group(struct task_struct
*p
, int cpupid
, int flags
,
2251 struct numa_group
*grp
, *my_grp
;
2252 struct task_struct
*tsk
;
2254 int cpu
= cpupid_to_cpu(cpupid
);
2257 if (unlikely(!p
->numa_group
)) {
2258 unsigned int size
= sizeof(struct numa_group
) +
2259 4*nr_node_ids
*sizeof(unsigned long);
2261 grp
= kzalloc(size
, GFP_KERNEL
| __GFP_NOWARN
);
2265 atomic_set(&grp
->refcount
, 1);
2266 grp
->active_nodes
= 1;
2267 grp
->max_faults_cpu
= 0;
2268 spin_lock_init(&grp
->lock
);
2270 /* Second half of the array tracks nids where faults happen */
2271 grp
->faults_cpu
= grp
->faults
+ NR_NUMA_HINT_FAULT_TYPES
*
2274 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
2275 grp
->faults
[i
] = p
->numa_faults
[i
];
2277 grp
->total_faults
= p
->total_numa_faults
;
2280 rcu_assign_pointer(p
->numa_group
, grp
);
2284 tsk
= READ_ONCE(cpu_rq(cpu
)->curr
);
2286 if (!cpupid_match_pid(tsk
, cpupid
))
2289 grp
= rcu_dereference(tsk
->numa_group
);
2293 my_grp
= p
->numa_group
;
2298 * Only join the other group if its bigger; if we're the bigger group,
2299 * the other task will join us.
2301 if (my_grp
->nr_tasks
> grp
->nr_tasks
)
2305 * Tie-break on the grp address.
2307 if (my_grp
->nr_tasks
== grp
->nr_tasks
&& my_grp
> grp
)
2310 /* Always join threads in the same process. */
2311 if (tsk
->mm
== current
->mm
)
2314 /* Simple filter to avoid false positives due to PID collisions */
2315 if (flags
& TNF_SHARED
)
2318 /* Update priv based on whether false sharing was detected */
2321 if (join
&& !get_numa_group(grp
))
2329 BUG_ON(irqs_disabled());
2330 double_lock_irq(&my_grp
->lock
, &grp
->lock
);
2332 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++) {
2333 my_grp
->faults
[i
] -= p
->numa_faults
[i
];
2334 grp
->faults
[i
] += p
->numa_faults
[i
];
2336 my_grp
->total_faults
-= p
->total_numa_faults
;
2337 grp
->total_faults
+= p
->total_numa_faults
;
2342 spin_unlock(&my_grp
->lock
);
2343 spin_unlock_irq(&grp
->lock
);
2345 rcu_assign_pointer(p
->numa_group
, grp
);
2347 put_numa_group(my_grp
);
2355 void task_numa_free(struct task_struct
*p
)
2357 struct numa_group
*grp
= p
->numa_group
;
2358 void *numa_faults
= p
->numa_faults
;
2359 unsigned long flags
;
2363 spin_lock_irqsave(&grp
->lock
, flags
);
2364 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
2365 grp
->faults
[i
] -= p
->numa_faults
[i
];
2366 grp
->total_faults
-= p
->total_numa_faults
;
2369 spin_unlock_irqrestore(&grp
->lock
, flags
);
2370 RCU_INIT_POINTER(p
->numa_group
, NULL
);
2371 put_numa_group(grp
);
2374 p
->numa_faults
= NULL
;
2379 * Got a PROT_NONE fault for a page on @node.
2381 void task_numa_fault(int last_cpupid
, int mem_node
, int pages
, int flags
)
2383 struct task_struct
*p
= current
;
2384 bool migrated
= flags
& TNF_MIGRATED
;
2385 int cpu_node
= task_node(current
);
2386 int local
= !!(flags
& TNF_FAULT_LOCAL
);
2387 struct numa_group
*ng
;
2390 if (!static_branch_likely(&sched_numa_balancing
))
2393 /* for example, ksmd faulting in a user's mm */
2397 /* Allocate buffer to track faults on a per-node basis */
2398 if (unlikely(!p
->numa_faults
)) {
2399 int size
= sizeof(*p
->numa_faults
) *
2400 NR_NUMA_HINT_FAULT_BUCKETS
* nr_node_ids
;
2402 p
->numa_faults
= kzalloc(size
, GFP_KERNEL
|__GFP_NOWARN
);
2403 if (!p
->numa_faults
)
2406 p
->total_numa_faults
= 0;
2407 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
2411 * First accesses are treated as private, otherwise consider accesses
2412 * to be private if the accessing pid has not changed
2414 if (unlikely(last_cpupid
== (-1 & LAST_CPUPID_MASK
))) {
2417 priv
= cpupid_match_pid(p
, last_cpupid
);
2418 if (!priv
&& !(flags
& TNF_NO_GROUP
))
2419 task_numa_group(p
, last_cpupid
, flags
, &priv
);
2423 * If a workload spans multiple NUMA nodes, a shared fault that
2424 * occurs wholly within the set of nodes that the workload is
2425 * actively using should be counted as local. This allows the
2426 * scan rate to slow down when a workload has settled down.
2429 if (!priv
&& !local
&& ng
&& ng
->active_nodes
> 1 &&
2430 numa_is_active_node(cpu_node
, ng
) &&
2431 numa_is_active_node(mem_node
, ng
))
2434 task_numa_placement(p
);
2437 * Retry task to preferred node migration periodically, in case it
2438 * case it previously failed, or the scheduler moved us.
2440 if (time_after(jiffies
, p
->numa_migrate_retry
))
2441 numa_migrate_preferred(p
);
2444 p
->numa_pages_migrated
+= pages
;
2445 if (flags
& TNF_MIGRATE_FAIL
)
2446 p
->numa_faults_locality
[2] += pages
;
2448 p
->numa_faults
[task_faults_idx(NUMA_MEMBUF
, mem_node
, priv
)] += pages
;
2449 p
->numa_faults
[task_faults_idx(NUMA_CPUBUF
, cpu_node
, priv
)] += pages
;
2450 p
->numa_faults_locality
[local
] += pages
;
2453 static void reset_ptenuma_scan(struct task_struct
*p
)
2456 * We only did a read acquisition of the mmap sem, so
2457 * p->mm->numa_scan_seq is written to without exclusive access
2458 * and the update is not guaranteed to be atomic. That's not
2459 * much of an issue though, since this is just used for
2460 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2461 * expensive, to avoid any form of compiler optimizations:
2463 WRITE_ONCE(p
->mm
->numa_scan_seq
, READ_ONCE(p
->mm
->numa_scan_seq
) + 1);
2464 p
->mm
->numa_scan_offset
= 0;
2468 * The expensive part of numa migration is done from task_work context.
2469 * Triggered from task_tick_numa().
2471 void task_numa_work(struct callback_head
*work
)
2473 unsigned long migrate
, next_scan
, now
= jiffies
;
2474 struct task_struct
*p
= current
;
2475 struct mm_struct
*mm
= p
->mm
;
2476 u64 runtime
= p
->se
.sum_exec_runtime
;
2477 struct vm_area_struct
*vma
;
2478 unsigned long start
, end
;
2479 unsigned long nr_pte_updates
= 0;
2480 long pages
, virtpages
;
2482 SCHED_WARN_ON(p
!= container_of(work
, struct task_struct
, numa_work
));
2484 work
->next
= work
; /* protect against double add */
2486 * Who cares about NUMA placement when they're dying.
2488 * NOTE: make sure not to dereference p->mm before this check,
2489 * exit_task_work() happens _after_ exit_mm() so we could be called
2490 * without p->mm even though we still had it when we enqueued this
2493 if (p
->flags
& PF_EXITING
)
2496 if (!mm
->numa_next_scan
) {
2497 mm
->numa_next_scan
= now
+
2498 msecs_to_jiffies(sysctl_numa_balancing_scan_delay
);
2502 * Enforce maximal scan/migration frequency..
2504 migrate
= mm
->numa_next_scan
;
2505 if (time_before(now
, migrate
))
2508 if (p
->numa_scan_period
== 0) {
2509 p
->numa_scan_period_max
= task_scan_max(p
);
2510 p
->numa_scan_period
= task_scan_start(p
);
2513 next_scan
= now
+ msecs_to_jiffies(p
->numa_scan_period
);
2514 if (cmpxchg(&mm
->numa_next_scan
, migrate
, next_scan
) != migrate
)
2518 * Delay this task enough that another task of this mm will likely win
2519 * the next time around.
2521 p
->node_stamp
+= 2 * TICK_NSEC
;
2523 start
= mm
->numa_scan_offset
;
2524 pages
= sysctl_numa_balancing_scan_size
;
2525 pages
<<= 20 - PAGE_SHIFT
; /* MB in pages */
2526 virtpages
= pages
* 8; /* Scan up to this much virtual space */
2531 if (!down_read_trylock(&mm
->mmap_sem
))
2533 vma
= find_vma(mm
, start
);
2535 reset_ptenuma_scan(p
);
2539 for (; vma
; vma
= vma
->vm_next
) {
2540 if (!vma_migratable(vma
) || !vma_policy_mof(vma
) ||
2541 is_vm_hugetlb_page(vma
) || (vma
->vm_flags
& VM_MIXEDMAP
)) {
2546 * Shared library pages mapped by multiple processes are not
2547 * migrated as it is expected they are cache replicated. Avoid
2548 * hinting faults in read-only file-backed mappings or the vdso
2549 * as migrating the pages will be of marginal benefit.
2552 (vma
->vm_file
&& (vma
->vm_flags
& (VM_READ
|VM_WRITE
)) == (VM_READ
)))
2556 * Skip inaccessible VMAs to avoid any confusion between
2557 * PROT_NONE and NUMA hinting ptes
2559 if (!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
)))
2563 start
= max(start
, vma
->vm_start
);
2564 end
= ALIGN(start
+ (pages
<< PAGE_SHIFT
), HPAGE_SIZE
);
2565 end
= min(end
, vma
->vm_end
);
2566 nr_pte_updates
= change_prot_numa(vma
, start
, end
);
2569 * Try to scan sysctl_numa_balancing_size worth of
2570 * hpages that have at least one present PTE that
2571 * is not already pte-numa. If the VMA contains
2572 * areas that are unused or already full of prot_numa
2573 * PTEs, scan up to virtpages, to skip through those
2577 pages
-= (end
- start
) >> PAGE_SHIFT
;
2578 virtpages
-= (end
- start
) >> PAGE_SHIFT
;
2581 if (pages
<= 0 || virtpages
<= 0)
2585 } while (end
!= vma
->vm_end
);
2590 * It is possible to reach the end of the VMA list but the last few
2591 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2592 * would find the !migratable VMA on the next scan but not reset the
2593 * scanner to the start so check it now.
2596 mm
->numa_scan_offset
= start
;
2598 reset_ptenuma_scan(p
);
2599 up_read(&mm
->mmap_sem
);
2602 * Make sure tasks use at least 32x as much time to run other code
2603 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2604 * Usually update_task_scan_period slows down scanning enough; on an
2605 * overloaded system we need to limit overhead on a per task basis.
2607 if (unlikely(p
->se
.sum_exec_runtime
!= runtime
)) {
2608 u64 diff
= p
->se
.sum_exec_runtime
- runtime
;
2609 p
->node_stamp
+= 32 * diff
;
2614 * Drive the periodic memory faults..
2616 void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
2618 struct callback_head
*work
= &curr
->numa_work
;
2622 * We don't care about NUMA placement if we don't have memory.
2624 if (!curr
->mm
|| (curr
->flags
& PF_EXITING
) || work
->next
!= work
)
2628 * Using runtime rather than walltime has the dual advantage that
2629 * we (mostly) drive the selection from busy threads and that the
2630 * task needs to have done some actual work before we bother with
2633 now
= curr
->se
.sum_exec_runtime
;
2634 period
= (u64
)curr
->numa_scan_period
* NSEC_PER_MSEC
;
2636 if (now
> curr
->node_stamp
+ period
) {
2637 if (!curr
->node_stamp
)
2638 curr
->numa_scan_period
= task_scan_start(curr
);
2639 curr
->node_stamp
+= period
;
2641 if (!time_before(jiffies
, curr
->mm
->numa_next_scan
)) {
2642 init_task_work(work
, task_numa_work
); /* TODO: move this into sched_fork() */
2643 task_work_add(curr
, work
, true);
2649 static void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
2653 static inline void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
2657 static inline void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
2661 #endif /* CONFIG_NUMA_BALANCING */
2664 account_entity_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2666 update_load_add(&cfs_rq
->load
, se
->load
.weight
);
2667 if (!parent_entity(se
))
2668 update_load_add(&rq_of(cfs_rq
)->load
, se
->load
.weight
);
2670 if (entity_is_task(se
)) {
2671 struct rq
*rq
= rq_of(cfs_rq
);
2673 account_numa_enqueue(rq
, task_of(se
));
2674 list_add(&se
->group_node
, &rq
->cfs_tasks
);
2677 cfs_rq
->nr_running
++;
2681 account_entity_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2683 update_load_sub(&cfs_rq
->load
, se
->load
.weight
);
2684 if (!parent_entity(se
))
2685 update_load_sub(&rq_of(cfs_rq
)->load
, se
->load
.weight
);
2687 if (entity_is_task(se
)) {
2688 account_numa_dequeue(rq_of(cfs_rq
), task_of(se
));
2689 list_del_init(&se
->group_node
);
2692 cfs_rq
->nr_running
--;
2695 #ifdef CONFIG_FAIR_GROUP_SCHED
2698 * All this does is approximate the hierarchical proportion which includes that
2699 * global sum we all love to hate.
2701 * That is, the weight of a group entity, is the proportional share of the
2702 * group weight based on the group runqueue weights. That is:
2704 * tg->weight * grq->load.weight
2705 * ge->load.weight = ----------------------------- (1)
2706 * \Sum grq->load.weight
2708 * Now, because computing that sum is prohibitively expensive to compute (been
2709 * there, done that) we approximate it with this average stuff. The average
2710 * moves slower and therefore the approximation is cheaper and more stable.
2712 * So instead of the above, we substitute:
2714 * grq->load.weight -> grq->avg.load_avg (2)
2716 * which yields the following:
2718 * tg->weight * grq->avg.load_avg
2719 * ge->load.weight = ------------------------------ (3)
2722 * Where: tg->load_avg ~= \Sum grq->avg.load_avg
2724 * That is shares_avg, and it is right (given the approximation (2)).
2726 * The problem with it is that because the average is slow -- it was designed
2727 * to be exactly that of course -- this leads to transients in boundary
2728 * conditions. In specific, the case where the group was idle and we start the
2729 * one task. It takes time for our CPU's grq->avg.load_avg to build up,
2730 * yielding bad latency etc..
2732 * Now, in that special case (1) reduces to:
2734 * tg->weight * grq->load.weight
2735 * ge->load.weight = ----------------------------- = tg>weight (4)
2738 * That is, the sum collapses because all other CPUs are idle; the UP scenario.
2740 * So what we do is modify our approximation (3) to approach (4) in the (near)
2745 * tg->weight * grq->load.weight
2746 * --------------------------------------------------- (5)
2747 * tg->load_avg - grq->avg.load_avg + grq->load.weight
2750 * And that is shares_weight and is icky. In the (near) UP case it approaches
2751 * (4) while in the normal case it approaches (3). It consistently
2752 * overestimates the ge->load.weight and therefore:
2754 * \Sum ge->load.weight >= tg->weight
2758 static long calc_cfs_shares(struct cfs_rq
*cfs_rq
)
2760 long tg_weight
, tg_shares
, load
, shares
;
2761 struct task_group
*tg
= cfs_rq
->tg
;
2763 tg_shares
= READ_ONCE(tg
->shares
);
2766 * Because (5) drops to 0 when the cfs_rq is idle, we need to use (3)
2769 load
= max(scale_load_down(cfs_rq
->load
.weight
), cfs_rq
->avg
.load_avg
);
2771 tg_weight
= atomic_long_read(&tg
->load_avg
);
2773 /* Ensure tg_weight >= load */
2774 tg_weight
-= cfs_rq
->tg_load_avg_contrib
;
2777 shares
= (tg_shares
* load
);
2779 shares
/= tg_weight
;
2782 * MIN_SHARES has to be unscaled here to support per-CPU partitioning
2783 * of a group with small tg->shares value. It is a floor value which is
2784 * assigned as a minimum load.weight to the sched_entity representing
2785 * the group on a CPU.
2787 * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024
2788 * on an 8-core system with 8 tasks each runnable on one CPU shares has
2789 * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In
2790 * case no task is runnable on a CPU MIN_SHARES=2 should be returned
2793 return clamp_t(long, shares
, MIN_SHARES
, tg_shares
);
2795 # endif /* CONFIG_SMP */
2797 static void reweight_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
,
2798 unsigned long weight
)
2801 /* commit outstanding execution time */
2802 if (cfs_rq
->curr
== se
)
2803 update_curr(cfs_rq
);
2804 account_entity_dequeue(cfs_rq
, se
);
2807 update_load_set(&se
->load
, weight
);
2810 account_entity_enqueue(cfs_rq
, se
);
2813 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
);
2815 static void update_cfs_shares(struct sched_entity
*se
)
2817 struct cfs_rq
*cfs_rq
= group_cfs_rq(se
);
2823 if (throttled_hierarchy(cfs_rq
))
2827 shares
= READ_ONCE(cfs_rq
->tg
->shares
);
2829 if (likely(se
->load
.weight
== shares
))
2832 shares
= calc_cfs_shares(cfs_rq
);
2835 reweight_entity(cfs_rq_of(se
), se
, shares
);
2838 #else /* CONFIG_FAIR_GROUP_SCHED */
2839 static inline void update_cfs_shares(struct sched_entity
*se
)
2842 #endif /* CONFIG_FAIR_GROUP_SCHED */
2844 static inline void cfs_rq_util_change(struct cfs_rq
*cfs_rq
)
2846 struct rq
*rq
= rq_of(cfs_rq
);
2848 if (&rq
->cfs
== cfs_rq
) {
2850 * There are a few boundary cases this might miss but it should
2851 * get called often enough that that should (hopefully) not be
2852 * a real problem -- added to that it only calls on the local
2853 * CPU, so if we enqueue remotely we'll miss an update, but
2854 * the next tick/schedule should update.
2856 * It will not get called when we go idle, because the idle
2857 * thread is a different class (!fair), nor will the utilization
2858 * number include things like RT tasks.
2860 * As is, the util number is not freq-invariant (we'd have to
2861 * implement arch_scale_freq_capacity() for that).
2865 cpufreq_update_util(rq
, 0);
2872 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2874 static u64
decay_load(u64 val
, u64 n
)
2876 unsigned int local_n
;
2878 if (unlikely(n
> LOAD_AVG_PERIOD
* 63))
2881 /* after bounds checking we can collapse to 32-bit */
2885 * As y^PERIOD = 1/2, we can combine
2886 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2887 * With a look-up table which covers y^n (n<PERIOD)
2889 * To achieve constant time decay_load.
2891 if (unlikely(local_n
>= LOAD_AVG_PERIOD
)) {
2892 val
>>= local_n
/ LOAD_AVG_PERIOD
;
2893 local_n
%= LOAD_AVG_PERIOD
;
2896 val
= mul_u64_u32_shr(val
, runnable_avg_yN_inv
[local_n
], 32);
2900 static u32
__accumulate_pelt_segments(u64 periods
, u32 d1
, u32 d3
)
2902 u32 c1
, c2
, c3
= d3
; /* y^0 == 1 */
2907 c1
= decay_load((u64
)d1
, periods
);
2911 * c2 = 1024 \Sum y^n
2915 * = 1024 ( \Sum y^n - \Sum y^n - y^0 )
2918 c2
= LOAD_AVG_MAX
- decay_load(LOAD_AVG_MAX
, periods
) - 1024;
2920 return c1
+ c2
+ c3
;
2923 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2926 * Accumulate the three separate parts of the sum; d1 the remainder
2927 * of the last (incomplete) period, d2 the span of full periods and d3
2928 * the remainder of the (incomplete) current period.
2933 * |<->|<----------------->|<--->|
2934 * ... |---x---|------| ... |------|-----x (now)
2937 * u' = (u + d1) y^p + 1024 \Sum y^n + d3 y^0
2940 * = u y^p + (Step 1)
2943 * d1 y^p + 1024 \Sum y^n + d3 y^0 (Step 2)
2946 static __always_inline u32
2947 accumulate_sum(u64 delta
, int cpu
, struct sched_avg
*sa
,
2948 unsigned long weight
, int running
, struct cfs_rq
*cfs_rq
)
2950 unsigned long scale_freq
, scale_cpu
;
2951 u32 contrib
= (u32
)delta
; /* p == 0 -> delta < 1024 */
2954 scale_freq
= arch_scale_freq_capacity(NULL
, cpu
);
2955 scale_cpu
= arch_scale_cpu_capacity(NULL
, cpu
);
2957 delta
+= sa
->period_contrib
;
2958 periods
= delta
/ 1024; /* A period is 1024us (~1ms) */
2961 * Step 1: decay old *_sum if we crossed period boundaries.
2964 sa
->load_sum
= decay_load(sa
->load_sum
, periods
);
2966 cfs_rq
->runnable_load_sum
=
2967 decay_load(cfs_rq
->runnable_load_sum
, periods
);
2969 sa
->util_sum
= decay_load((u64
)(sa
->util_sum
), periods
);
2975 contrib
= __accumulate_pelt_segments(periods
,
2976 1024 - sa
->period_contrib
, delta
);
2978 sa
->period_contrib
= delta
;
2980 contrib
= cap_scale(contrib
, scale_freq
);
2982 sa
->load_sum
+= weight
* contrib
;
2984 cfs_rq
->runnable_load_sum
+= weight
* contrib
;
2987 sa
->util_sum
+= contrib
* scale_cpu
;
2993 * We can represent the historical contribution to runnable average as the
2994 * coefficients of a geometric series. To do this we sub-divide our runnable
2995 * history into segments of approximately 1ms (1024us); label the segment that
2996 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2998 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
3000 * (now) (~1ms ago) (~2ms ago)
3002 * Let u_i denote the fraction of p_i that the entity was runnable.
3004 * We then designate the fractions u_i as our co-efficients, yielding the
3005 * following representation of historical load:
3006 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
3008 * We choose y based on the with of a reasonably scheduling period, fixing:
3011 * This means that the contribution to load ~32ms ago (u_32) will be weighted
3012 * approximately half as much as the contribution to load within the last ms
3015 * When a period "rolls over" and we have new u_0`, multiplying the previous
3016 * sum again by y is sufficient to update:
3017 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
3018 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
3020 static __always_inline
int
3021 ___update_load_sum(u64 now
, int cpu
, struct sched_avg
*sa
,
3022 unsigned long weight
, int running
, struct cfs_rq
*cfs_rq
)
3026 delta
= now
- sa
->last_update_time
;
3028 * This should only happen when time goes backwards, which it
3029 * unfortunately does during sched clock init when we swap over to TSC.
3031 if ((s64
)delta
< 0) {
3032 sa
->last_update_time
= now
;
3037 * Use 1024ns as the unit of measurement since it's a reasonable
3038 * approximation of 1us and fast to compute.
3044 sa
->last_update_time
+= delta
<< 10;
3047 * running is a subset of runnable (weight) so running can't be set if
3048 * runnable is clear. But there are some corner cases where the current
3049 * se has been already dequeued but cfs_rq->curr still points to it.
3050 * This means that weight will be 0 but not running for a sched_entity
3051 * but also for a cfs_rq if the latter becomes idle. As an example,
3052 * this happens during idle_balance() which calls
3053 * update_blocked_averages()
3059 * Now we know we crossed measurement unit boundaries. The *_avg
3060 * accrues by two steps:
3062 * Step 1: accumulate *_sum since last_update_time. If we haven't
3063 * crossed period boundaries, finish.
3065 if (!accumulate_sum(delta
, cpu
, sa
, weight
, running
, cfs_rq
))
3071 static __always_inline
void
3072 ___update_load_avg(struct sched_avg
*sa
, unsigned long weight
, struct cfs_rq
*cfs_rq
)
3074 u32 divider
= LOAD_AVG_MAX
- 1024 + sa
->period_contrib
;
3077 * Step 2: update *_avg.
3079 sa
->load_avg
= div_u64(weight
* sa
->load_sum
, divider
);
3081 cfs_rq
->runnable_load_avg
=
3082 div_u64(cfs_rq
->runnable_load_sum
, divider
);
3084 sa
->util_avg
= sa
->util_sum
/ divider
;
3088 * XXX we want to get rid of this helper and use the full load resolution.
3090 static inline long se_weight(struct sched_entity
*se
)
3092 return scale_load_down(se
->load
.weight
);
3098 * load_sum := runnable_sum
3099 * load_avg = se_weight(se) * runnable_avg
3103 * load_sum = \Sum se_weight(se) * se->avg.load_sum
3104 * load_avg = \Sum se->avg.load_avg
3108 __update_load_avg_blocked_se(u64 now
, int cpu
, struct sched_entity
*se
)
3110 if (___update_load_sum(now
, cpu
, &se
->avg
, 0, 0, NULL
)) {
3111 ___update_load_avg(&se
->avg
, se_weight(se
), NULL
);
3119 __update_load_avg_se(u64 now
, int cpu
, struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3121 if (___update_load_sum(now
, cpu
, &se
->avg
, !!se
->on_rq
,
3122 cfs_rq
->curr
== se
, NULL
)) {
3124 ___update_load_avg(&se
->avg
, se_weight(se
), NULL
);
3132 __update_load_avg_cfs_rq(u64 now
, int cpu
, struct cfs_rq
*cfs_rq
)
3134 if (___update_load_sum(now
, cpu
, &cfs_rq
->avg
,
3135 scale_load_down(cfs_rq
->load
.weight
),
3136 cfs_rq
->curr
!= NULL
, cfs_rq
)) {
3137 ___update_load_avg(&cfs_rq
->avg
, 1, cfs_rq
);
3145 * Signed add and clamp on underflow.
3147 * Explicitly do a load-store to ensure the intermediate value never hits
3148 * memory. This allows lockless observations without ever seeing the negative
3151 #define add_positive(_ptr, _val) do { \
3152 typeof(_ptr) ptr = (_ptr); \
3153 typeof(_val) val = (_val); \
3154 typeof(*ptr) res, var = READ_ONCE(*ptr); \
3158 if (val < 0 && res > var) \
3161 WRITE_ONCE(*ptr, res); \
3164 #ifdef CONFIG_FAIR_GROUP_SCHED
3166 * update_tg_load_avg - update the tg's load avg
3167 * @cfs_rq: the cfs_rq whose avg changed
3168 * @force: update regardless of how small the difference
3170 * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
3171 * However, because tg->load_avg is a global value there are performance
3174 * In order to avoid having to look at the other cfs_rq's, we use a
3175 * differential update where we store the last value we propagated. This in
3176 * turn allows skipping updates if the differential is 'small'.
3178 * Updating tg's load_avg is necessary before update_cfs_share().
3180 static inline void update_tg_load_avg(struct cfs_rq
*cfs_rq
, int force
)
3182 long delta
= cfs_rq
->avg
.load_avg
- cfs_rq
->tg_load_avg_contrib
;
3185 * No need to update load_avg for root_task_group as it is not used.
3187 if (cfs_rq
->tg
== &root_task_group
)
3190 if (force
|| abs(delta
) > cfs_rq
->tg_load_avg_contrib
/ 64) {
3191 atomic_long_add(delta
, &cfs_rq
->tg
->load_avg
);
3192 cfs_rq
->tg_load_avg_contrib
= cfs_rq
->avg
.load_avg
;
3197 * Called within set_task_rq() right before setting a task's cpu. The
3198 * caller only guarantees p->pi_lock is held; no other assumptions,
3199 * including the state of rq->lock, should be made.
3201 void set_task_rq_fair(struct sched_entity
*se
,
3202 struct cfs_rq
*prev
, struct cfs_rq
*next
)
3204 u64 p_last_update_time
;
3205 u64 n_last_update_time
;
3207 if (!sched_feat(ATTACH_AGE_LOAD
))
3211 * We are supposed to update the task to "current" time, then its up to
3212 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
3213 * getting what current time is, so simply throw away the out-of-date
3214 * time. This will result in the wakee task is less decayed, but giving
3215 * the wakee more load sounds not bad.
3217 if (!(se
->avg
.last_update_time
&& prev
))
3220 #ifndef CONFIG_64BIT
3222 u64 p_last_update_time_copy
;
3223 u64 n_last_update_time_copy
;
3226 p_last_update_time_copy
= prev
->load_last_update_time_copy
;
3227 n_last_update_time_copy
= next
->load_last_update_time_copy
;
3231 p_last_update_time
= prev
->avg
.last_update_time
;
3232 n_last_update_time
= next
->avg
.last_update_time
;
3234 } while (p_last_update_time
!= p_last_update_time_copy
||
3235 n_last_update_time
!= n_last_update_time_copy
);
3238 p_last_update_time
= prev
->avg
.last_update_time
;
3239 n_last_update_time
= next
->avg
.last_update_time
;
3241 __update_load_avg_blocked_se(p_last_update_time
, cpu_of(rq_of(prev
)), se
);
3242 se
->avg
.last_update_time
= n_last_update_time
;
3245 /* Take into account change of utilization of a child task group */
3247 update_tg_cfs_util(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3249 struct cfs_rq
*gcfs_rq
= group_cfs_rq(se
);
3250 long delta
= gcfs_rq
->avg
.util_avg
- se
->avg
.util_avg
;
3252 /* Nothing to update */
3256 /* Set new sched_entity's utilization */
3257 se
->avg
.util_avg
= gcfs_rq
->avg
.util_avg
;
3258 se
->avg
.util_sum
= se
->avg
.util_avg
* LOAD_AVG_MAX
;
3260 /* Update parent cfs_rq utilization */
3261 add_positive(&cfs_rq
->avg
.util_avg
, delta
);
3262 cfs_rq
->avg
.util_sum
= cfs_rq
->avg
.util_avg
* LOAD_AVG_MAX
;
3265 /* Take into account change of load of a child task group */
3267 update_tg_cfs_load(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3269 struct cfs_rq
*gcfs_rq
= group_cfs_rq(se
);
3270 long delta
, load
= gcfs_rq
->avg
.load_avg
;
3273 * If the load of group cfs_rq is null, the load of the
3274 * sched_entity will also be null so we can skip the formula
3279 /* Get tg's load and ensure tg_load > 0 */
3280 tg_load
= atomic_long_read(&gcfs_rq
->tg
->load_avg
) + 1;
3282 /* Ensure tg_load >= load and updated with current load*/
3283 tg_load
-= gcfs_rq
->tg_load_avg_contrib
;
3287 * We need to compute a correction term in the case that the
3288 * task group is consuming more CPU than a task of equal
3289 * weight. A task with a weight equals to tg->shares will have
3290 * a load less or equal to scale_load_down(tg->shares).
3291 * Similarly, the sched_entities that represent the task group
3292 * at parent level, can't have a load higher than
3293 * scale_load_down(tg->shares). And the Sum of sched_entities'
3294 * load must be <= scale_load_down(tg->shares).
3296 if (tg_load
> scale_load_down(gcfs_rq
->tg
->shares
)) {
3297 /* scale gcfs_rq's load into tg's shares*/
3298 load
*= scale_load_down(gcfs_rq
->tg
->shares
);
3303 delta
= load
- se
->avg
.load_avg
;
3305 /* Nothing to update */
3309 /* Set new sched_entity's load */
3310 se
->avg
.load_avg
= load
;
3311 se
->avg
.load_sum
= LOAD_AVG_MAX
;
3313 /* Update parent cfs_rq load */
3314 add_positive(&cfs_rq
->avg
.load_avg
, delta
);
3315 cfs_rq
->avg
.load_sum
= cfs_rq
->avg
.load_avg
* LOAD_AVG_MAX
;
3318 * If the sched_entity is already enqueued, we also have to update the
3319 * runnable load avg.
3322 /* Update parent cfs_rq runnable_load_avg */
3323 add_positive(&cfs_rq
->runnable_load_avg
, delta
);
3324 cfs_rq
->runnable_load_sum
= cfs_rq
->runnable_load_avg
* LOAD_AVG_MAX
;
3328 static inline void set_tg_cfs_propagate(struct cfs_rq
*cfs_rq
)
3330 cfs_rq
->propagate_avg
= 1;
3333 static inline int test_and_clear_tg_cfs_propagate(struct sched_entity
*se
)
3335 struct cfs_rq
*cfs_rq
= group_cfs_rq(se
);
3337 if (!cfs_rq
->propagate_avg
)
3340 cfs_rq
->propagate_avg
= 0;
3344 /* Update task and its cfs_rq load average */
3345 static inline int propagate_entity_load_avg(struct sched_entity
*se
)
3347 struct cfs_rq
*cfs_rq
;
3349 if (entity_is_task(se
))
3352 if (!test_and_clear_tg_cfs_propagate(se
))
3355 cfs_rq
= cfs_rq_of(se
);
3357 set_tg_cfs_propagate(cfs_rq
);
3359 update_tg_cfs_util(cfs_rq
, se
);
3360 update_tg_cfs_load(cfs_rq
, se
);
3366 * Check if we need to update the load and the utilization of a blocked
3369 static inline bool skip_blocked_update(struct sched_entity
*se
)
3371 struct cfs_rq
*gcfs_rq
= group_cfs_rq(se
);
3374 * If sched_entity still have not zero load or utilization, we have to
3377 if (se
->avg
.load_avg
|| se
->avg
.util_avg
)
3381 * If there is a pending propagation, we have to update the load and
3382 * the utilization of the sched_entity:
3384 if (gcfs_rq
->propagate_avg
)
3388 * Otherwise, the load and the utilization of the sched_entity is
3389 * already zero and there is no pending propagation, so it will be a
3390 * waste of time to try to decay it:
3395 #else /* CONFIG_FAIR_GROUP_SCHED */
3397 static inline void update_tg_load_avg(struct cfs_rq
*cfs_rq
, int force
) {}
3399 static inline int propagate_entity_load_avg(struct sched_entity
*se
)
3404 static inline void set_tg_cfs_propagate(struct cfs_rq
*cfs_rq
) {}
3406 #endif /* CONFIG_FAIR_GROUP_SCHED */
3409 * Unsigned subtract and clamp on underflow.
3411 * Explicitly do a load-store to ensure the intermediate value never hits
3412 * memory. This allows lockless observations without ever seeing the negative
3415 #define sub_positive(_ptr, _val) do { \
3416 typeof(_ptr) ptr = (_ptr); \
3417 typeof(*ptr) val = (_val); \
3418 typeof(*ptr) res, var = READ_ONCE(*ptr); \
3422 WRITE_ONCE(*ptr, res); \
3426 * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
3427 * @now: current time, as per cfs_rq_clock_task()
3428 * @cfs_rq: cfs_rq to update
3430 * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
3431 * avg. The immediate corollary is that all (fair) tasks must be attached, see
3432 * post_init_entity_util_avg().
3434 * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
3436 * Returns true if the load decayed or we removed load.
3438 * Since both these conditions indicate a changed cfs_rq->avg.load we should
3439 * call update_tg_load_avg() when this function returns true.
3442 update_cfs_rq_load_avg(u64 now
, struct cfs_rq
*cfs_rq
)
3444 struct sched_avg
*sa
= &cfs_rq
->avg
;
3445 int decayed
, removed_load
= 0, removed_util
= 0;
3447 if (atomic_long_read(&cfs_rq
->removed_load_avg
)) {
3448 s64 r
= atomic_long_xchg(&cfs_rq
->removed_load_avg
, 0);
3449 sub_positive(&sa
->load_avg
, r
);
3450 sub_positive(&sa
->load_sum
, r
* LOAD_AVG_MAX
);
3452 set_tg_cfs_propagate(cfs_rq
);
3455 if (atomic_long_read(&cfs_rq
->removed_util_avg
)) {
3456 long r
= atomic_long_xchg(&cfs_rq
->removed_util_avg
, 0);
3457 sub_positive(&sa
->util_avg
, r
);
3458 sub_positive(&sa
->util_sum
, r
* LOAD_AVG_MAX
);
3460 set_tg_cfs_propagate(cfs_rq
);
3463 decayed
= __update_load_avg_cfs_rq(now
, cpu_of(rq_of(cfs_rq
)), cfs_rq
);
3465 #ifndef CONFIG_64BIT
3467 cfs_rq
->load_last_update_time_copy
= sa
->last_update_time
;
3470 if (decayed
|| removed_util
)
3471 cfs_rq_util_change(cfs_rq
);
3473 return decayed
|| removed_load
;
3477 * Optional action to be done while updating the load average
3479 #define UPDATE_TG 0x1
3480 #define SKIP_AGE_LOAD 0x2
3482 /* Update task and its cfs_rq load average */
3483 static inline void update_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3485 u64 now
= cfs_rq_clock_task(cfs_rq
);
3486 struct rq
*rq
= rq_of(cfs_rq
);
3487 int cpu
= cpu_of(rq
);
3491 * Track task load average for carrying it to new CPU after migrated, and
3492 * track group sched_entity load average for task_h_load calc in migration
3494 if (se
->avg
.last_update_time
&& !(flags
& SKIP_AGE_LOAD
))
3495 __update_load_avg_se(now
, cpu
, cfs_rq
, se
);
3497 decayed
= update_cfs_rq_load_avg(now
, cfs_rq
);
3498 decayed
|= propagate_entity_load_avg(se
);
3500 if (decayed
&& (flags
& UPDATE_TG
))
3501 update_tg_load_avg(cfs_rq
, 0);
3505 * attach_entity_load_avg - attach this entity to its cfs_rq load avg
3506 * @cfs_rq: cfs_rq to attach to
3507 * @se: sched_entity to attach
3509 * Must call update_cfs_rq_load_avg() before this, since we rely on
3510 * cfs_rq->avg.last_update_time being current.
3512 static void attach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3514 se
->avg
.last_update_time
= cfs_rq
->avg
.last_update_time
;
3515 cfs_rq
->avg
.load_avg
+= se
->avg
.load_avg
;
3516 cfs_rq
->avg
.load_sum
+= se_weight(se
) * se
->avg
.load_sum
;
3517 cfs_rq
->avg
.util_avg
+= se
->avg
.util_avg
;
3518 cfs_rq
->avg
.util_sum
+= se
->avg
.util_sum
;
3519 set_tg_cfs_propagate(cfs_rq
);
3521 cfs_rq_util_change(cfs_rq
);
3525 * detach_entity_load_avg - detach this entity from its cfs_rq load avg
3526 * @cfs_rq: cfs_rq to detach from
3527 * @se: sched_entity to detach
3529 * Must call update_cfs_rq_load_avg() before this, since we rely on
3530 * cfs_rq->avg.last_update_time being current.
3532 static void detach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3535 sub_positive(&cfs_rq
->avg
.load_avg
, se
->avg
.load_avg
);
3536 sub_positive(&cfs_rq
->avg
.load_sum
, se_weight(se
) * se
->avg
.load_sum
);
3537 sub_positive(&cfs_rq
->avg
.util_avg
, se
->avg
.util_avg
);
3538 sub_positive(&cfs_rq
->avg
.util_sum
, se
->avg
.util_sum
);
3539 set_tg_cfs_propagate(cfs_rq
);
3541 cfs_rq_util_change(cfs_rq
);
3544 /* Add the load generated by se into cfs_rq's load average */
3546 enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3548 cfs_rq
->runnable_load_avg
+= se
->avg
.load_avg
;
3549 cfs_rq
->runnable_load_sum
+= se_weight(se
) * se
->avg
.load_sum
;
3551 if (!se
->avg
.last_update_time
) {
3552 attach_entity_load_avg(cfs_rq
, se
);
3553 update_tg_load_avg(cfs_rq
, 0);
3557 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
3559 dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3561 sub_positive(&cfs_rq
->runnable_load_avg
, se
->avg
.load_avg
);
3562 sub_positive(&cfs_rq
->runnable_load_sum
, se_weight(se
) * se
->avg
.load_sum
);
3565 #ifndef CONFIG_64BIT
3566 static inline u64
cfs_rq_last_update_time(struct cfs_rq
*cfs_rq
)
3568 u64 last_update_time_copy
;
3569 u64 last_update_time
;
3572 last_update_time_copy
= cfs_rq
->load_last_update_time_copy
;
3574 last_update_time
= cfs_rq
->avg
.last_update_time
;
3575 } while (last_update_time
!= last_update_time_copy
);
3577 return last_update_time
;
3580 static inline u64
cfs_rq_last_update_time(struct cfs_rq
*cfs_rq
)
3582 return cfs_rq
->avg
.last_update_time
;
3587 * Synchronize entity load avg of dequeued entity without locking
3590 void sync_entity_load_avg(struct sched_entity
*se
)
3592 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3593 u64 last_update_time
;
3595 last_update_time
= cfs_rq_last_update_time(cfs_rq
);
3596 __update_load_avg_blocked_se(last_update_time
, cpu_of(rq_of(cfs_rq
)), se
);
3600 * Task first catches up with cfs_rq, and then subtract
3601 * itself from the cfs_rq (task must be off the queue now).
3603 void remove_entity_load_avg(struct sched_entity
*se
)
3605 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3608 * tasks cannot exit without having gone through wake_up_new_task() ->
3609 * post_init_entity_util_avg() which will have added things to the
3610 * cfs_rq, so we can remove unconditionally.
3612 * Similarly for groups, they will have passed through
3613 * post_init_entity_util_avg() before unregister_sched_fair_group()
3617 sync_entity_load_avg(se
);
3618 atomic_long_add(se
->avg
.load_avg
, &cfs_rq
->removed_load_avg
);
3619 atomic_long_add(se
->avg
.util_avg
, &cfs_rq
->removed_util_avg
);
3622 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq
*cfs_rq
)
3624 return cfs_rq
->runnable_load_avg
;
3627 static inline unsigned long cfs_rq_load_avg(struct cfs_rq
*cfs_rq
)
3629 return cfs_rq
->avg
.load_avg
;
3632 static int idle_balance(struct rq
*this_rq
, struct rq_flags
*rf
);
3634 #else /* CONFIG_SMP */
3637 update_cfs_rq_load_avg(u64 now
, struct cfs_rq
*cfs_rq
)
3642 #define UPDATE_TG 0x0
3643 #define SKIP_AGE_LOAD 0x0
3645 static inline void update_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int not_used1
)
3647 cfs_rq_util_change(cfs_rq
);
3651 enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3653 dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3654 static inline void remove_entity_load_avg(struct sched_entity
*se
) {}
3657 attach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3659 detach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3661 static inline int idle_balance(struct rq
*rq
, struct rq_flags
*rf
)
3666 #endif /* CONFIG_SMP */
3668 static void check_spread(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3670 #ifdef CONFIG_SCHED_DEBUG
3671 s64 d
= se
->vruntime
- cfs_rq
->min_vruntime
;
3676 if (d
> 3*sysctl_sched_latency
)
3677 schedstat_inc(cfs_rq
->nr_spread_over
);
3682 place_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int initial
)
3684 u64 vruntime
= cfs_rq
->min_vruntime
;
3687 * The 'current' period is already promised to the current tasks,
3688 * however the extra weight of the new task will slow them down a
3689 * little, place the new task so that it fits in the slot that
3690 * stays open at the end.
3692 if (initial
&& sched_feat(START_DEBIT
))
3693 vruntime
+= sched_vslice(cfs_rq
, se
);
3695 /* sleeps up to a single latency don't count. */
3697 unsigned long thresh
= sysctl_sched_latency
;
3700 * Halve their sleep time's effect, to allow
3701 * for a gentler effect of sleepers:
3703 if (sched_feat(GENTLE_FAIR_SLEEPERS
))
3709 /* ensure we never gain time by being placed backwards. */
3710 se
->vruntime
= max_vruntime(se
->vruntime
, vruntime
);
3713 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
);
3715 static inline void check_schedstat_required(void)
3717 #ifdef CONFIG_SCHEDSTATS
3718 if (schedstat_enabled())
3721 /* Force schedstat enabled if a dependent tracepoint is active */
3722 if (trace_sched_stat_wait_enabled() ||
3723 trace_sched_stat_sleep_enabled() ||
3724 trace_sched_stat_iowait_enabled() ||
3725 trace_sched_stat_blocked_enabled() ||
3726 trace_sched_stat_runtime_enabled()) {
3727 printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3728 "stat_blocked and stat_runtime require the "
3729 "kernel parameter schedstats=enable or "
3730 "kernel.sched_schedstats=1\n");
3741 * update_min_vruntime()
3742 * vruntime -= min_vruntime
3746 * update_min_vruntime()
3747 * vruntime += min_vruntime
3749 * this way the vruntime transition between RQs is done when both
3750 * min_vruntime are up-to-date.
3754 * ->migrate_task_rq_fair() (p->state == TASK_WAKING)
3755 * vruntime -= min_vruntime
3759 * update_min_vruntime()
3760 * vruntime += min_vruntime
3762 * this way we don't have the most up-to-date min_vruntime on the originating
3763 * CPU and an up-to-date min_vruntime on the destination CPU.
3767 enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3769 bool renorm
= !(flags
& ENQUEUE_WAKEUP
) || (flags
& ENQUEUE_MIGRATED
);
3770 bool curr
= cfs_rq
->curr
== se
;
3773 * If we're the current task, we must renormalise before calling
3777 se
->vruntime
+= cfs_rq
->min_vruntime
;
3779 update_curr(cfs_rq
);
3782 * Otherwise, renormalise after, such that we're placed at the current
3783 * moment in time, instead of some random moment in the past. Being
3784 * placed in the past could significantly boost this task to the
3785 * fairness detriment of existing tasks.
3787 if (renorm
&& !curr
)
3788 se
->vruntime
+= cfs_rq
->min_vruntime
;
3791 * When enqueuing a sched_entity, we must:
3792 * - Update loads to have both entity and cfs_rq synced with now.
3793 * - Add its load to cfs_rq->runnable_avg
3794 * - For group_entity, update its weight to reflect the new share of
3796 * - Add its new weight to cfs_rq->load.weight
3798 update_load_avg(cfs_rq
, se
, UPDATE_TG
);
3799 enqueue_entity_load_avg(cfs_rq
, se
);
3800 update_cfs_shares(se
);
3801 account_entity_enqueue(cfs_rq
, se
);
3803 if (flags
& ENQUEUE_WAKEUP
)
3804 place_entity(cfs_rq
, se
, 0);
3806 check_schedstat_required();
3807 update_stats_enqueue(cfs_rq
, se
, flags
);
3808 check_spread(cfs_rq
, se
);
3810 __enqueue_entity(cfs_rq
, se
);
3813 if (cfs_rq
->nr_running
== 1) {
3814 list_add_leaf_cfs_rq(cfs_rq
);
3815 check_enqueue_throttle(cfs_rq
);
3819 static void __clear_buddies_last(struct sched_entity
*se
)
3821 for_each_sched_entity(se
) {
3822 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3823 if (cfs_rq
->last
!= se
)
3826 cfs_rq
->last
= NULL
;
3830 static void __clear_buddies_next(struct sched_entity
*se
)
3832 for_each_sched_entity(se
) {
3833 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3834 if (cfs_rq
->next
!= se
)
3837 cfs_rq
->next
= NULL
;
3841 static void __clear_buddies_skip(struct sched_entity
*se
)
3843 for_each_sched_entity(se
) {
3844 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3845 if (cfs_rq
->skip
!= se
)
3848 cfs_rq
->skip
= NULL
;
3852 static void clear_buddies(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3854 if (cfs_rq
->last
== se
)
3855 __clear_buddies_last(se
);
3857 if (cfs_rq
->next
== se
)
3858 __clear_buddies_next(se
);
3860 if (cfs_rq
->skip
== se
)
3861 __clear_buddies_skip(se
);
3864 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
3867 dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3870 * Update run-time statistics of the 'current'.
3872 update_curr(cfs_rq
);
3875 * When dequeuing a sched_entity, we must:
3876 * - Update loads to have both entity and cfs_rq synced with now.
3877 * - Substract its load from the cfs_rq->runnable_avg.
3878 * - Substract its previous weight from cfs_rq->load.weight.
3879 * - For group entity, update its weight to reflect the new share
3880 * of its group cfs_rq.
3882 update_load_avg(cfs_rq
, se
, UPDATE_TG
);
3883 dequeue_entity_load_avg(cfs_rq
, se
);
3885 update_stats_dequeue(cfs_rq
, se
, flags
);
3887 clear_buddies(cfs_rq
, se
);
3889 if (se
!= cfs_rq
->curr
)
3890 __dequeue_entity(cfs_rq
, se
);
3892 account_entity_dequeue(cfs_rq
, se
);
3895 * Normalize after update_curr(); which will also have moved
3896 * min_vruntime if @se is the one holding it back. But before doing
3897 * update_min_vruntime() again, which will discount @se's position and
3898 * can move min_vruntime forward still more.
3900 if (!(flags
& DEQUEUE_SLEEP
))
3901 se
->vruntime
-= cfs_rq
->min_vruntime
;
3903 /* return excess runtime on last dequeue */
3904 return_cfs_rq_runtime(cfs_rq
);
3906 update_cfs_shares(se
);
3909 * Now advance min_vruntime if @se was the entity holding it back,
3910 * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
3911 * put back on, and if we advance min_vruntime, we'll be placed back
3912 * further than we started -- ie. we'll be penalized.
3914 if ((flags
& (DEQUEUE_SAVE
| DEQUEUE_MOVE
)) == DEQUEUE_SAVE
)
3915 update_min_vruntime(cfs_rq
);
3919 * Preempt the current task with a newly woken task if needed:
3922 check_preempt_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
3924 unsigned long ideal_runtime
, delta_exec
;
3925 struct sched_entity
*se
;
3928 ideal_runtime
= sched_slice(cfs_rq
, curr
);
3929 delta_exec
= curr
->sum_exec_runtime
- curr
->prev_sum_exec_runtime
;
3930 if (delta_exec
> ideal_runtime
) {
3931 resched_curr(rq_of(cfs_rq
));
3933 * The current task ran long enough, ensure it doesn't get
3934 * re-elected due to buddy favours.
3936 clear_buddies(cfs_rq
, curr
);
3941 * Ensure that a task that missed wakeup preemption by a
3942 * narrow margin doesn't have to wait for a full slice.
3943 * This also mitigates buddy induced latencies under load.
3945 if (delta_exec
< sysctl_sched_min_granularity
)
3948 se
= __pick_first_entity(cfs_rq
);
3949 delta
= curr
->vruntime
- se
->vruntime
;
3954 if (delta
> ideal_runtime
)
3955 resched_curr(rq_of(cfs_rq
));
3959 set_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3961 /* 'current' is not kept within the tree. */
3964 * Any task has to be enqueued before it get to execute on
3965 * a CPU. So account for the time it spent waiting on the
3968 update_stats_wait_end(cfs_rq
, se
);
3969 __dequeue_entity(cfs_rq
, se
);
3970 update_load_avg(cfs_rq
, se
, UPDATE_TG
);
3973 update_stats_curr_start(cfs_rq
, se
);
3977 * Track our maximum slice length, if the CPU's load is at
3978 * least twice that of our own weight (i.e. dont track it
3979 * when there are only lesser-weight tasks around):
3981 if (schedstat_enabled() && rq_of(cfs_rq
)->load
.weight
>= 2*se
->load
.weight
) {
3982 schedstat_set(se
->statistics
.slice_max
,
3983 max((u64
)schedstat_val(se
->statistics
.slice_max
),
3984 se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
));
3987 se
->prev_sum_exec_runtime
= se
->sum_exec_runtime
;
3991 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
);
3994 * Pick the next process, keeping these things in mind, in this order:
3995 * 1) keep things fair between processes/task groups
3996 * 2) pick the "next" process, since someone really wants that to run
3997 * 3) pick the "last" process, for cache locality
3998 * 4) do not run the "skip" process, if something else is available
4000 static struct sched_entity
*
4001 pick_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
4003 struct sched_entity
*left
= __pick_first_entity(cfs_rq
);
4004 struct sched_entity
*se
;
4007 * If curr is set we have to see if its left of the leftmost entity
4008 * still in the tree, provided there was anything in the tree at all.
4010 if (!left
|| (curr
&& entity_before(curr
, left
)))
4013 se
= left
; /* ideally we run the leftmost entity */
4016 * Avoid running the skip buddy, if running something else can
4017 * be done without getting too unfair.
4019 if (cfs_rq
->skip
== se
) {
4020 struct sched_entity
*second
;
4023 second
= __pick_first_entity(cfs_rq
);
4025 second
= __pick_next_entity(se
);
4026 if (!second
|| (curr
&& entity_before(curr
, second
)))
4030 if (second
&& wakeup_preempt_entity(second
, left
) < 1)
4035 * Prefer last buddy, try to return the CPU to a preempted task.
4037 if (cfs_rq
->last
&& wakeup_preempt_entity(cfs_rq
->last
, left
) < 1)
4041 * Someone really wants this to run. If it's not unfair, run it.
4043 if (cfs_rq
->next
&& wakeup_preempt_entity(cfs_rq
->next
, left
) < 1)
4046 clear_buddies(cfs_rq
, se
);
4051 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
4053 static void put_prev_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*prev
)
4056 * If still on the runqueue then deactivate_task()
4057 * was not called and update_curr() has to be done:
4060 update_curr(cfs_rq
);
4062 /* throttle cfs_rqs exceeding runtime */
4063 check_cfs_rq_runtime(cfs_rq
);
4065 check_spread(cfs_rq
, prev
);
4068 update_stats_wait_start(cfs_rq
, prev
);
4069 /* Put 'current' back into the tree. */
4070 __enqueue_entity(cfs_rq
, prev
);
4071 /* in !on_rq case, update occurred at dequeue */
4072 update_load_avg(cfs_rq
, prev
, 0);
4074 cfs_rq
->curr
= NULL
;
4078 entity_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
, int queued
)
4081 * Update run-time statistics of the 'current'.
4083 update_curr(cfs_rq
);
4086 * Ensure that runnable average is periodically updated.
4088 update_load_avg(cfs_rq
, curr
, UPDATE_TG
);
4089 update_cfs_shares(curr
);
4091 #ifdef CONFIG_SCHED_HRTICK
4093 * queued ticks are scheduled to match the slice, so don't bother
4094 * validating it and just reschedule.
4097 resched_curr(rq_of(cfs_rq
));
4101 * don't let the period tick interfere with the hrtick preemption
4103 if (!sched_feat(DOUBLE_TICK
) &&
4104 hrtimer_active(&rq_of(cfs_rq
)->hrtick_timer
))
4108 if (cfs_rq
->nr_running
> 1)
4109 check_preempt_tick(cfs_rq
, curr
);
4113 /**************************************************
4114 * CFS bandwidth control machinery
4117 #ifdef CONFIG_CFS_BANDWIDTH
4119 #ifdef HAVE_JUMP_LABEL
4120 static struct static_key __cfs_bandwidth_used
;
4122 static inline bool cfs_bandwidth_used(void)
4124 return static_key_false(&__cfs_bandwidth_used
);
4127 void cfs_bandwidth_usage_inc(void)
4129 static_key_slow_inc(&__cfs_bandwidth_used
);
4132 void cfs_bandwidth_usage_dec(void)
4134 static_key_slow_dec(&__cfs_bandwidth_used
);
4136 #else /* HAVE_JUMP_LABEL */
4137 static bool cfs_bandwidth_used(void)
4142 void cfs_bandwidth_usage_inc(void) {}
4143 void cfs_bandwidth_usage_dec(void) {}
4144 #endif /* HAVE_JUMP_LABEL */
4147 * default period for cfs group bandwidth.
4148 * default: 0.1s, units: nanoseconds
4150 static inline u64
default_cfs_period(void)
4152 return 100000000ULL;
4155 static inline u64
sched_cfs_bandwidth_slice(void)
4157 return (u64
)sysctl_sched_cfs_bandwidth_slice
* NSEC_PER_USEC
;
4161 * Replenish runtime according to assigned quota and update expiration time.
4162 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
4163 * additional synchronization around rq->lock.
4165 * requires cfs_b->lock
4167 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth
*cfs_b
)
4171 if (cfs_b
->quota
== RUNTIME_INF
)
4174 now
= sched_clock_cpu(smp_processor_id());
4175 cfs_b
->runtime
= cfs_b
->quota
;
4176 cfs_b
->runtime_expires
= now
+ ktime_to_ns(cfs_b
->period
);
4179 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
4181 return &tg
->cfs_bandwidth
;
4184 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
4185 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
4187 if (unlikely(cfs_rq
->throttle_count
))
4188 return cfs_rq
->throttled_clock_task
- cfs_rq
->throttled_clock_task_time
;
4190 return rq_clock_task(rq_of(cfs_rq
)) - cfs_rq
->throttled_clock_task_time
;
4193 /* returns 0 on failure to allocate runtime */
4194 static int assign_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4196 struct task_group
*tg
= cfs_rq
->tg
;
4197 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(tg
);
4198 u64 amount
= 0, min_amount
, expires
;
4200 /* note: this is a positive sum as runtime_remaining <= 0 */
4201 min_amount
= sched_cfs_bandwidth_slice() - cfs_rq
->runtime_remaining
;
4203 raw_spin_lock(&cfs_b
->lock
);
4204 if (cfs_b
->quota
== RUNTIME_INF
)
4205 amount
= min_amount
;
4207 start_cfs_bandwidth(cfs_b
);
4209 if (cfs_b
->runtime
> 0) {
4210 amount
= min(cfs_b
->runtime
, min_amount
);
4211 cfs_b
->runtime
-= amount
;
4215 expires
= cfs_b
->runtime_expires
;
4216 raw_spin_unlock(&cfs_b
->lock
);
4218 cfs_rq
->runtime_remaining
+= amount
;
4220 * we may have advanced our local expiration to account for allowed
4221 * spread between our sched_clock and the one on which runtime was
4224 if ((s64
)(expires
- cfs_rq
->runtime_expires
) > 0)
4225 cfs_rq
->runtime_expires
= expires
;
4227 return cfs_rq
->runtime_remaining
> 0;
4231 * Note: This depends on the synchronization provided by sched_clock and the
4232 * fact that rq->clock snapshots this value.
4234 static void expire_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4236 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
4238 /* if the deadline is ahead of our clock, nothing to do */
4239 if (likely((s64
)(rq_clock(rq_of(cfs_rq
)) - cfs_rq
->runtime_expires
) < 0))
4242 if (cfs_rq
->runtime_remaining
< 0)
4246 * If the local deadline has passed we have to consider the
4247 * possibility that our sched_clock is 'fast' and the global deadline
4248 * has not truly expired.
4250 * Fortunately we can check determine whether this the case by checking
4251 * whether the global deadline has advanced. It is valid to compare
4252 * cfs_b->runtime_expires without any locks since we only care about
4253 * exact equality, so a partial write will still work.
4256 if (cfs_rq
->runtime_expires
!= cfs_b
->runtime_expires
) {
4257 /* extend local deadline, drift is bounded above by 2 ticks */
4258 cfs_rq
->runtime_expires
+= TICK_NSEC
;
4260 /* global deadline is ahead, expiration has passed */
4261 cfs_rq
->runtime_remaining
= 0;
4265 static void __account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
4267 /* dock delta_exec before expiring quota (as it could span periods) */
4268 cfs_rq
->runtime_remaining
-= delta_exec
;
4269 expire_cfs_rq_runtime(cfs_rq
);
4271 if (likely(cfs_rq
->runtime_remaining
> 0))
4275 * if we're unable to extend our runtime we resched so that the active
4276 * hierarchy can be throttled
4278 if (!assign_cfs_rq_runtime(cfs_rq
) && likely(cfs_rq
->curr
))
4279 resched_curr(rq_of(cfs_rq
));
4282 static __always_inline
4283 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
4285 if (!cfs_bandwidth_used() || !cfs_rq
->runtime_enabled
)
4288 __account_cfs_rq_runtime(cfs_rq
, delta_exec
);
4291 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
4293 return cfs_bandwidth_used() && cfs_rq
->throttled
;
4296 /* check whether cfs_rq, or any parent, is throttled */
4297 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
4299 return cfs_bandwidth_used() && cfs_rq
->throttle_count
;
4303 * Ensure that neither of the group entities corresponding to src_cpu or
4304 * dest_cpu are members of a throttled hierarchy when performing group
4305 * load-balance operations.
4307 static inline int throttled_lb_pair(struct task_group
*tg
,
4308 int src_cpu
, int dest_cpu
)
4310 struct cfs_rq
*src_cfs_rq
, *dest_cfs_rq
;
4312 src_cfs_rq
= tg
->cfs_rq
[src_cpu
];
4313 dest_cfs_rq
= tg
->cfs_rq
[dest_cpu
];
4315 return throttled_hierarchy(src_cfs_rq
) ||
4316 throttled_hierarchy(dest_cfs_rq
);
4319 /* updated child weight may affect parent so we have to do this bottom up */
4320 static int tg_unthrottle_up(struct task_group
*tg
, void *data
)
4322 struct rq
*rq
= data
;
4323 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
4325 cfs_rq
->throttle_count
--;
4326 if (!cfs_rq
->throttle_count
) {
4327 /* adjust cfs_rq_clock_task() */
4328 cfs_rq
->throttled_clock_task_time
+= rq_clock_task(rq
) -
4329 cfs_rq
->throttled_clock_task
;
4335 static int tg_throttle_down(struct task_group
*tg
, void *data
)
4337 struct rq
*rq
= data
;
4338 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
4340 /* group is entering throttled state, stop time */
4341 if (!cfs_rq
->throttle_count
)
4342 cfs_rq
->throttled_clock_task
= rq_clock_task(rq
);
4343 cfs_rq
->throttle_count
++;
4348 static void throttle_cfs_rq(struct cfs_rq
*cfs_rq
)
4350 struct rq
*rq
= rq_of(cfs_rq
);
4351 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
4352 struct sched_entity
*se
;
4353 long task_delta
, dequeue
= 1;
4356 se
= cfs_rq
->tg
->se
[cpu_of(rq_of(cfs_rq
))];
4358 /* freeze hierarchy runnable averages while throttled */
4360 walk_tg_tree_from(cfs_rq
->tg
, tg_throttle_down
, tg_nop
, (void *)rq
);
4363 task_delta
= cfs_rq
->h_nr_running
;
4364 for_each_sched_entity(se
) {
4365 struct cfs_rq
*qcfs_rq
= cfs_rq_of(se
);
4366 /* throttled entity or throttle-on-deactivate */
4371 dequeue_entity(qcfs_rq
, se
, DEQUEUE_SLEEP
);
4372 qcfs_rq
->h_nr_running
-= task_delta
;
4374 if (qcfs_rq
->load
.weight
)
4379 sub_nr_running(rq
, task_delta
);
4381 cfs_rq
->throttled
= 1;
4382 cfs_rq
->throttled_clock
= rq_clock(rq
);
4383 raw_spin_lock(&cfs_b
->lock
);
4384 empty
= list_empty(&cfs_b
->throttled_cfs_rq
);
4387 * Add to the _head_ of the list, so that an already-started
4388 * distribute_cfs_runtime will not see us
4390 list_add_rcu(&cfs_rq
->throttled_list
, &cfs_b
->throttled_cfs_rq
);
4393 * If we're the first throttled task, make sure the bandwidth
4397 start_cfs_bandwidth(cfs_b
);
4399 raw_spin_unlock(&cfs_b
->lock
);
4402 void unthrottle_cfs_rq(struct cfs_rq
*cfs_rq
)
4404 struct rq
*rq
= rq_of(cfs_rq
);
4405 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
4406 struct sched_entity
*se
;
4410 se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
4412 cfs_rq
->throttled
= 0;
4414 update_rq_clock(rq
);
4416 raw_spin_lock(&cfs_b
->lock
);
4417 cfs_b
->throttled_time
+= rq_clock(rq
) - cfs_rq
->throttled_clock
;
4418 list_del_rcu(&cfs_rq
->throttled_list
);
4419 raw_spin_unlock(&cfs_b
->lock
);
4421 /* update hierarchical throttle state */
4422 walk_tg_tree_from(cfs_rq
->tg
, tg_nop
, tg_unthrottle_up
, (void *)rq
);
4424 if (!cfs_rq
->load
.weight
)
4427 task_delta
= cfs_rq
->h_nr_running
;
4428 for_each_sched_entity(se
) {
4432 cfs_rq
= cfs_rq_of(se
);
4434 enqueue_entity(cfs_rq
, se
, ENQUEUE_WAKEUP
);
4435 cfs_rq
->h_nr_running
+= task_delta
;
4437 if (cfs_rq_throttled(cfs_rq
))
4442 add_nr_running(rq
, task_delta
);
4444 /* determine whether we need to wake up potentially idle cpu */
4445 if (rq
->curr
== rq
->idle
&& rq
->cfs
.nr_running
)
4449 static u64
distribute_cfs_runtime(struct cfs_bandwidth
*cfs_b
,
4450 u64 remaining
, u64 expires
)
4452 struct cfs_rq
*cfs_rq
;
4454 u64 starting_runtime
= remaining
;
4457 list_for_each_entry_rcu(cfs_rq
, &cfs_b
->throttled_cfs_rq
,
4459 struct rq
*rq
= rq_of(cfs_rq
);
4463 if (!cfs_rq_throttled(cfs_rq
))
4466 runtime
= -cfs_rq
->runtime_remaining
+ 1;
4467 if (runtime
> remaining
)
4468 runtime
= remaining
;
4469 remaining
-= runtime
;
4471 cfs_rq
->runtime_remaining
+= runtime
;
4472 cfs_rq
->runtime_expires
= expires
;
4474 /* we check whether we're throttled above */
4475 if (cfs_rq
->runtime_remaining
> 0)
4476 unthrottle_cfs_rq(cfs_rq
);
4486 return starting_runtime
- remaining
;
4490 * Responsible for refilling a task_group's bandwidth and unthrottling its
4491 * cfs_rqs as appropriate. If there has been no activity within the last
4492 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
4493 * used to track this state.
4495 static int do_sched_cfs_period_timer(struct cfs_bandwidth
*cfs_b
, int overrun
)
4497 u64 runtime
, runtime_expires
;
4500 /* no need to continue the timer with no bandwidth constraint */
4501 if (cfs_b
->quota
== RUNTIME_INF
)
4502 goto out_deactivate
;
4504 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
4505 cfs_b
->nr_periods
+= overrun
;
4508 * idle depends on !throttled (for the case of a large deficit), and if
4509 * we're going inactive then everything else can be deferred
4511 if (cfs_b
->idle
&& !throttled
)
4512 goto out_deactivate
;
4514 __refill_cfs_bandwidth_runtime(cfs_b
);
4517 /* mark as potentially idle for the upcoming period */
4522 /* account preceding periods in which throttling occurred */
4523 cfs_b
->nr_throttled
+= overrun
;
4525 runtime_expires
= cfs_b
->runtime_expires
;
4528 * This check is repeated as we are holding onto the new bandwidth while
4529 * we unthrottle. This can potentially race with an unthrottled group
4530 * trying to acquire new bandwidth from the global pool. This can result
4531 * in us over-using our runtime if it is all used during this loop, but
4532 * only by limited amounts in that extreme case.
4534 while (throttled
&& cfs_b
->runtime
> 0) {
4535 runtime
= cfs_b
->runtime
;
4536 raw_spin_unlock(&cfs_b
->lock
);
4537 /* we can't nest cfs_b->lock while distributing bandwidth */
4538 runtime
= distribute_cfs_runtime(cfs_b
, runtime
,
4540 raw_spin_lock(&cfs_b
->lock
);
4542 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
4544 cfs_b
->runtime
-= min(runtime
, cfs_b
->runtime
);
4548 * While we are ensured activity in the period following an
4549 * unthrottle, this also covers the case in which the new bandwidth is
4550 * insufficient to cover the existing bandwidth deficit. (Forcing the
4551 * timer to remain active while there are any throttled entities.)
4561 /* a cfs_rq won't donate quota below this amount */
4562 static const u64 min_cfs_rq_runtime
= 1 * NSEC_PER_MSEC
;
4563 /* minimum remaining period time to redistribute slack quota */
4564 static const u64 min_bandwidth_expiration
= 2 * NSEC_PER_MSEC
;
4565 /* how long we wait to gather additional slack before distributing */
4566 static const u64 cfs_bandwidth_slack_period
= 5 * NSEC_PER_MSEC
;
4569 * Are we near the end of the current quota period?
4571 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4572 * hrtimer base being cleared by hrtimer_start. In the case of
4573 * migrate_hrtimers, base is never cleared, so we are fine.
4575 static int runtime_refresh_within(struct cfs_bandwidth
*cfs_b
, u64 min_expire
)
4577 struct hrtimer
*refresh_timer
= &cfs_b
->period_timer
;
4580 /* if the call-back is running a quota refresh is already occurring */
4581 if (hrtimer_callback_running(refresh_timer
))
4584 /* is a quota refresh about to occur? */
4585 remaining
= ktime_to_ns(hrtimer_expires_remaining(refresh_timer
));
4586 if (remaining
< min_expire
)
4592 static void start_cfs_slack_bandwidth(struct cfs_bandwidth
*cfs_b
)
4594 u64 min_left
= cfs_bandwidth_slack_period
+ min_bandwidth_expiration
;
4596 /* if there's a quota refresh soon don't bother with slack */
4597 if (runtime_refresh_within(cfs_b
, min_left
))
4600 hrtimer_start(&cfs_b
->slack_timer
,
4601 ns_to_ktime(cfs_bandwidth_slack_period
),
4605 /* we know any runtime found here is valid as update_curr() precedes return */
4606 static void __return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4608 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
4609 s64 slack_runtime
= cfs_rq
->runtime_remaining
- min_cfs_rq_runtime
;
4611 if (slack_runtime
<= 0)
4614 raw_spin_lock(&cfs_b
->lock
);
4615 if (cfs_b
->quota
!= RUNTIME_INF
&&
4616 cfs_rq
->runtime_expires
== cfs_b
->runtime_expires
) {
4617 cfs_b
->runtime
+= slack_runtime
;
4619 /* we are under rq->lock, defer unthrottling using a timer */
4620 if (cfs_b
->runtime
> sched_cfs_bandwidth_slice() &&
4621 !list_empty(&cfs_b
->throttled_cfs_rq
))
4622 start_cfs_slack_bandwidth(cfs_b
);
4624 raw_spin_unlock(&cfs_b
->lock
);
4626 /* even if it's not valid for return we don't want to try again */
4627 cfs_rq
->runtime_remaining
-= slack_runtime
;
4630 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4632 if (!cfs_bandwidth_used())
4635 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->nr_running
)
4638 __return_cfs_rq_runtime(cfs_rq
);
4642 * This is done with a timer (instead of inline with bandwidth return) since
4643 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
4645 static void do_sched_cfs_slack_timer(struct cfs_bandwidth
*cfs_b
)
4647 u64 runtime
= 0, slice
= sched_cfs_bandwidth_slice();
4650 /* confirm we're still not at a refresh boundary */
4651 raw_spin_lock(&cfs_b
->lock
);
4652 if (runtime_refresh_within(cfs_b
, min_bandwidth_expiration
)) {
4653 raw_spin_unlock(&cfs_b
->lock
);
4657 if (cfs_b
->quota
!= RUNTIME_INF
&& cfs_b
->runtime
> slice
)
4658 runtime
= cfs_b
->runtime
;
4660 expires
= cfs_b
->runtime_expires
;
4661 raw_spin_unlock(&cfs_b
->lock
);
4666 runtime
= distribute_cfs_runtime(cfs_b
, runtime
, expires
);
4668 raw_spin_lock(&cfs_b
->lock
);
4669 if (expires
== cfs_b
->runtime_expires
)
4670 cfs_b
->runtime
-= min(runtime
, cfs_b
->runtime
);
4671 raw_spin_unlock(&cfs_b
->lock
);
4675 * When a group wakes up we want to make sure that its quota is not already
4676 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
4677 * runtime as update_curr() throttling can not not trigger until it's on-rq.
4679 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
)
4681 if (!cfs_bandwidth_used())
4684 /* an active group must be handled by the update_curr()->put() path */
4685 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->curr
)
4688 /* ensure the group is not already throttled */
4689 if (cfs_rq_throttled(cfs_rq
))
4692 /* update runtime allocation */
4693 account_cfs_rq_runtime(cfs_rq
, 0);
4694 if (cfs_rq
->runtime_remaining
<= 0)
4695 throttle_cfs_rq(cfs_rq
);
4698 static void sync_throttle(struct task_group
*tg
, int cpu
)
4700 struct cfs_rq
*pcfs_rq
, *cfs_rq
;
4702 if (!cfs_bandwidth_used())
4708 cfs_rq
= tg
->cfs_rq
[cpu
];
4709 pcfs_rq
= tg
->parent
->cfs_rq
[cpu
];
4711 cfs_rq
->throttle_count
= pcfs_rq
->throttle_count
;
4712 cfs_rq
->throttled_clock_task
= rq_clock_task(cpu_rq(cpu
));
4715 /* conditionally throttle active cfs_rq's from put_prev_entity() */
4716 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4718 if (!cfs_bandwidth_used())
4721 if (likely(!cfs_rq
->runtime_enabled
|| cfs_rq
->runtime_remaining
> 0))
4725 * it's possible for a throttled entity to be forced into a running
4726 * state (e.g. set_curr_task), in this case we're finished.
4728 if (cfs_rq_throttled(cfs_rq
))
4731 throttle_cfs_rq(cfs_rq
);
4735 static enum hrtimer_restart
sched_cfs_slack_timer(struct hrtimer
*timer
)
4737 struct cfs_bandwidth
*cfs_b
=
4738 container_of(timer
, struct cfs_bandwidth
, slack_timer
);
4740 do_sched_cfs_slack_timer(cfs_b
);
4742 return HRTIMER_NORESTART
;
4745 static enum hrtimer_restart
sched_cfs_period_timer(struct hrtimer
*timer
)
4747 struct cfs_bandwidth
*cfs_b
=
4748 container_of(timer
, struct cfs_bandwidth
, period_timer
);
4752 raw_spin_lock(&cfs_b
->lock
);
4754 overrun
= hrtimer_forward_now(timer
, cfs_b
->period
);
4758 idle
= do_sched_cfs_period_timer(cfs_b
, overrun
);
4761 cfs_b
->period_active
= 0;
4762 raw_spin_unlock(&cfs_b
->lock
);
4764 return idle
? HRTIMER_NORESTART
: HRTIMER_RESTART
;
4767 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4769 raw_spin_lock_init(&cfs_b
->lock
);
4771 cfs_b
->quota
= RUNTIME_INF
;
4772 cfs_b
->period
= ns_to_ktime(default_cfs_period());
4774 INIT_LIST_HEAD(&cfs_b
->throttled_cfs_rq
);
4775 hrtimer_init(&cfs_b
->period_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_ABS_PINNED
);
4776 cfs_b
->period_timer
.function
= sched_cfs_period_timer
;
4777 hrtimer_init(&cfs_b
->slack_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
4778 cfs_b
->slack_timer
.function
= sched_cfs_slack_timer
;
4781 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4783 cfs_rq
->runtime_enabled
= 0;
4784 INIT_LIST_HEAD(&cfs_rq
->throttled_list
);
4787 void start_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4789 lockdep_assert_held(&cfs_b
->lock
);
4791 if (!cfs_b
->period_active
) {
4792 cfs_b
->period_active
= 1;
4793 hrtimer_forward_now(&cfs_b
->period_timer
, cfs_b
->period
);
4794 hrtimer_start_expires(&cfs_b
->period_timer
, HRTIMER_MODE_ABS_PINNED
);
4798 static void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4800 /* init_cfs_bandwidth() was not called */
4801 if (!cfs_b
->throttled_cfs_rq
.next
)
4804 hrtimer_cancel(&cfs_b
->period_timer
);
4805 hrtimer_cancel(&cfs_b
->slack_timer
);
4809 * Both these cpu hotplug callbacks race against unregister_fair_sched_group()
4811 * The race is harmless, since modifying bandwidth settings of unhooked group
4812 * bits doesn't do much.
4815 /* cpu online calback */
4816 static void __maybe_unused
update_runtime_enabled(struct rq
*rq
)
4818 struct task_group
*tg
;
4820 lockdep_assert_held(&rq
->lock
);
4823 list_for_each_entry_rcu(tg
, &task_groups
, list
) {
4824 struct cfs_bandwidth
*cfs_b
= &tg
->cfs_bandwidth
;
4825 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
4827 raw_spin_lock(&cfs_b
->lock
);
4828 cfs_rq
->runtime_enabled
= cfs_b
->quota
!= RUNTIME_INF
;
4829 raw_spin_unlock(&cfs_b
->lock
);
4834 /* cpu offline callback */
4835 static void __maybe_unused
unthrottle_offline_cfs_rqs(struct rq
*rq
)
4837 struct task_group
*tg
;
4839 lockdep_assert_held(&rq
->lock
);
4842 list_for_each_entry_rcu(tg
, &task_groups
, list
) {
4843 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
4845 if (!cfs_rq
->runtime_enabled
)
4849 * clock_task is not advancing so we just need to make sure
4850 * there's some valid quota amount
4852 cfs_rq
->runtime_remaining
= 1;
4854 * Offline rq is schedulable till cpu is completely disabled
4855 * in take_cpu_down(), so we prevent new cfs throttling here.
4857 cfs_rq
->runtime_enabled
= 0;
4859 if (cfs_rq_throttled(cfs_rq
))
4860 unthrottle_cfs_rq(cfs_rq
);
4865 #else /* CONFIG_CFS_BANDWIDTH */
4866 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
4868 return rq_clock_task(rq_of(cfs_rq
));
4871 static void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
) {}
4872 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) { return false; }
4873 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
) {}
4874 static inline void sync_throttle(struct task_group
*tg
, int cpu
) {}
4875 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
4877 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
4882 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
4887 static inline int throttled_lb_pair(struct task_group
*tg
,
4888 int src_cpu
, int dest_cpu
)
4893 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
4895 #ifdef CONFIG_FAIR_GROUP_SCHED
4896 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
4899 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
4903 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
4904 static inline void update_runtime_enabled(struct rq
*rq
) {}
4905 static inline void unthrottle_offline_cfs_rqs(struct rq
*rq
) {}
4907 #endif /* CONFIG_CFS_BANDWIDTH */
4909 /**************************************************
4910 * CFS operations on tasks:
4913 #ifdef CONFIG_SCHED_HRTICK
4914 static void hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
4916 struct sched_entity
*se
= &p
->se
;
4917 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4919 SCHED_WARN_ON(task_rq(p
) != rq
);
4921 if (rq
->cfs
.h_nr_running
> 1) {
4922 u64 slice
= sched_slice(cfs_rq
, se
);
4923 u64 ran
= se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
;
4924 s64 delta
= slice
- ran
;
4931 hrtick_start(rq
, delta
);
4936 * called from enqueue/dequeue and updates the hrtick when the
4937 * current task is from our class and nr_running is low enough
4940 static void hrtick_update(struct rq
*rq
)
4942 struct task_struct
*curr
= rq
->curr
;
4944 if (!hrtick_enabled(rq
) || curr
->sched_class
!= &fair_sched_class
)
4947 if (cfs_rq_of(&curr
->se
)->nr_running
< sched_nr_latency
)
4948 hrtick_start_fair(rq
, curr
);
4950 #else /* !CONFIG_SCHED_HRTICK */
4952 hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
4956 static inline void hrtick_update(struct rq
*rq
)
4962 * The enqueue_task method is called before nr_running is
4963 * increased. Here we update the fair scheduling stats and
4964 * then put the task into the rbtree:
4967 enqueue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
4969 struct cfs_rq
*cfs_rq
;
4970 struct sched_entity
*se
= &p
->se
;
4973 * If in_iowait is set, the code below may not trigger any cpufreq
4974 * utilization updates, so do it here explicitly with the IOWAIT flag
4978 cpufreq_update_util(rq
, SCHED_CPUFREQ_IOWAIT
);
4980 for_each_sched_entity(se
) {
4983 cfs_rq
= cfs_rq_of(se
);
4984 enqueue_entity(cfs_rq
, se
, flags
);
4987 * end evaluation on encountering a throttled cfs_rq
4989 * note: in the case of encountering a throttled cfs_rq we will
4990 * post the final h_nr_running increment below.
4992 if (cfs_rq_throttled(cfs_rq
))
4994 cfs_rq
->h_nr_running
++;
4996 flags
= ENQUEUE_WAKEUP
;
4999 for_each_sched_entity(se
) {
5000 cfs_rq
= cfs_rq_of(se
);
5001 cfs_rq
->h_nr_running
++;
5003 if (cfs_rq_throttled(cfs_rq
))
5006 update_load_avg(cfs_rq
, se
, UPDATE_TG
);
5007 update_cfs_shares(se
);
5011 add_nr_running(rq
, 1);
5016 static void set_next_buddy(struct sched_entity
*se
);
5019 * The dequeue_task method is called before nr_running is
5020 * decreased. We remove the task from the rbtree and
5021 * update the fair scheduling stats:
5023 static void dequeue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
5025 struct cfs_rq
*cfs_rq
;
5026 struct sched_entity
*se
= &p
->se
;
5027 int task_sleep
= flags
& DEQUEUE_SLEEP
;
5029 for_each_sched_entity(se
) {
5030 cfs_rq
= cfs_rq_of(se
);
5031 dequeue_entity(cfs_rq
, se
, flags
);
5034 * end evaluation on encountering a throttled cfs_rq
5036 * note: in the case of encountering a throttled cfs_rq we will
5037 * post the final h_nr_running decrement below.
5039 if (cfs_rq_throttled(cfs_rq
))
5041 cfs_rq
->h_nr_running
--;
5043 /* Don't dequeue parent if it has other entities besides us */
5044 if (cfs_rq
->load
.weight
) {
5045 /* Avoid re-evaluating load for this entity: */
5046 se
= parent_entity(se
);
5048 * Bias pick_next to pick a task from this cfs_rq, as
5049 * p is sleeping when it is within its sched_slice.
5051 if (task_sleep
&& se
&& !throttled_hierarchy(cfs_rq
))
5055 flags
|= DEQUEUE_SLEEP
;
5058 for_each_sched_entity(se
) {
5059 cfs_rq
= cfs_rq_of(se
);
5060 cfs_rq
->h_nr_running
--;
5062 if (cfs_rq_throttled(cfs_rq
))
5065 update_load_avg(cfs_rq
, se
, UPDATE_TG
);
5066 update_cfs_shares(se
);
5070 sub_nr_running(rq
, 1);
5077 /* Working cpumask for: load_balance, load_balance_newidle. */
5078 DEFINE_PER_CPU(cpumask_var_t
, load_balance_mask
);
5079 DEFINE_PER_CPU(cpumask_var_t
, select_idle_mask
);
5081 #ifdef CONFIG_NO_HZ_COMMON
5083 * per rq 'load' arrray crap; XXX kill this.
5087 * The exact cpuload calculated at every tick would be:
5089 * load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
5091 * If a cpu misses updates for n ticks (as it was idle) and update gets
5092 * called on the n+1-th tick when cpu may be busy, then we have:
5094 * load_n = (1 - 1/2^i)^n * load_0
5095 * load_n+1 = (1 - 1/2^i) * load_n + (1/2^i) * cur_load
5097 * decay_load_missed() below does efficient calculation of
5099 * load' = (1 - 1/2^i)^n * load
5101 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
5102 * This allows us to precompute the above in said factors, thereby allowing the
5103 * reduction of an arbitrary n in O(log_2 n) steps. (See also
5104 * fixed_power_int())
5106 * The calculation is approximated on a 128 point scale.
5108 #define DEGRADE_SHIFT 7
5110 static const u8 degrade_zero_ticks
[CPU_LOAD_IDX_MAX
] = {0, 8, 32, 64, 128};
5111 static const u8 degrade_factor
[CPU_LOAD_IDX_MAX
][DEGRADE_SHIFT
+ 1] = {
5112 { 0, 0, 0, 0, 0, 0, 0, 0 },
5113 { 64, 32, 8, 0, 0, 0, 0, 0 },
5114 { 96, 72, 40, 12, 1, 0, 0, 0 },
5115 { 112, 98, 75, 43, 15, 1, 0, 0 },
5116 { 120, 112, 98, 76, 45, 16, 2, 0 }
5120 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
5121 * would be when CPU is idle and so we just decay the old load without
5122 * adding any new load.
5124 static unsigned long
5125 decay_load_missed(unsigned long load
, unsigned long missed_updates
, int idx
)
5129 if (!missed_updates
)
5132 if (missed_updates
>= degrade_zero_ticks
[idx
])
5136 return load
>> missed_updates
;
5138 while (missed_updates
) {
5139 if (missed_updates
% 2)
5140 load
= (load
* degrade_factor
[idx
][j
]) >> DEGRADE_SHIFT
;
5142 missed_updates
>>= 1;
5147 #endif /* CONFIG_NO_HZ_COMMON */
5150 * __cpu_load_update - update the rq->cpu_load[] statistics
5151 * @this_rq: The rq to update statistics for
5152 * @this_load: The current load
5153 * @pending_updates: The number of missed updates
5155 * Update rq->cpu_load[] statistics. This function is usually called every
5156 * scheduler tick (TICK_NSEC).
5158 * This function computes a decaying average:
5160 * load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
5162 * Because of NOHZ it might not get called on every tick which gives need for
5163 * the @pending_updates argument.
5165 * load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
5166 * = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
5167 * = A * (A * load[i]_n-2 + B) + B
5168 * = A * (A * (A * load[i]_n-3 + B) + B) + B
5169 * = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
5170 * = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
5171 * = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
5172 * = (1 - 1/2^i)^n * (load[i]_0 - load) + load
5174 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
5175 * any change in load would have resulted in the tick being turned back on.
5177 * For regular NOHZ, this reduces to:
5179 * load[i]_n = (1 - 1/2^i)^n * load[i]_0
5181 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
5184 static void cpu_load_update(struct rq
*this_rq
, unsigned long this_load
,
5185 unsigned long pending_updates
)
5187 unsigned long __maybe_unused tickless_load
= this_rq
->cpu_load
[0];
5190 this_rq
->nr_load_updates
++;
5192 /* Update our load: */
5193 this_rq
->cpu_load
[0] = this_load
; /* Fasttrack for idx 0 */
5194 for (i
= 1, scale
= 2; i
< CPU_LOAD_IDX_MAX
; i
++, scale
+= scale
) {
5195 unsigned long old_load
, new_load
;
5197 /* scale is effectively 1 << i now, and >> i divides by scale */
5199 old_load
= this_rq
->cpu_load
[i
];
5200 #ifdef CONFIG_NO_HZ_COMMON
5201 old_load
= decay_load_missed(old_load
, pending_updates
- 1, i
);
5202 if (tickless_load
) {
5203 old_load
-= decay_load_missed(tickless_load
, pending_updates
- 1, i
);
5205 * old_load can never be a negative value because a
5206 * decayed tickless_load cannot be greater than the
5207 * original tickless_load.
5209 old_load
+= tickless_load
;
5212 new_load
= this_load
;
5214 * Round up the averaging division if load is increasing. This
5215 * prevents us from getting stuck on 9 if the load is 10, for
5218 if (new_load
> old_load
)
5219 new_load
+= scale
- 1;
5221 this_rq
->cpu_load
[i
] = (old_load
* (scale
- 1) + new_load
) >> i
;
5224 sched_avg_update(this_rq
);
5227 /* Used instead of source_load when we know the type == 0 */
5228 static unsigned long weighted_cpuload(struct rq
*rq
)
5230 return cfs_rq_runnable_load_avg(&rq
->cfs
);
5233 #ifdef CONFIG_NO_HZ_COMMON
5235 * There is no sane way to deal with nohz on smp when using jiffies because the
5236 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
5237 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
5239 * Therefore we need to avoid the delta approach from the regular tick when
5240 * possible since that would seriously skew the load calculation. This is why we
5241 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
5242 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
5243 * loop exit, nohz_idle_balance, nohz full exit...)
5245 * This means we might still be one tick off for nohz periods.
5248 static void cpu_load_update_nohz(struct rq
*this_rq
,
5249 unsigned long curr_jiffies
,
5252 unsigned long pending_updates
;
5254 pending_updates
= curr_jiffies
- this_rq
->last_load_update_tick
;
5255 if (pending_updates
) {
5256 this_rq
->last_load_update_tick
= curr_jiffies
;
5258 * In the regular NOHZ case, we were idle, this means load 0.
5259 * In the NOHZ_FULL case, we were non-idle, we should consider
5260 * its weighted load.
5262 cpu_load_update(this_rq
, load
, pending_updates
);
5267 * Called from nohz_idle_balance() to update the load ratings before doing the
5270 static void cpu_load_update_idle(struct rq
*this_rq
)
5273 * bail if there's load or we're actually up-to-date.
5275 if (weighted_cpuload(this_rq
))
5278 cpu_load_update_nohz(this_rq
, READ_ONCE(jiffies
), 0);
5282 * Record CPU load on nohz entry so we know the tickless load to account
5283 * on nohz exit. cpu_load[0] happens then to be updated more frequently
5284 * than other cpu_load[idx] but it should be fine as cpu_load readers
5285 * shouldn't rely into synchronized cpu_load[*] updates.
5287 void cpu_load_update_nohz_start(void)
5289 struct rq
*this_rq
= this_rq();
5292 * This is all lockless but should be fine. If weighted_cpuload changes
5293 * concurrently we'll exit nohz. And cpu_load write can race with
5294 * cpu_load_update_idle() but both updater would be writing the same.
5296 this_rq
->cpu_load
[0] = weighted_cpuload(this_rq
);
5300 * Account the tickless load in the end of a nohz frame.
5302 void cpu_load_update_nohz_stop(void)
5304 unsigned long curr_jiffies
= READ_ONCE(jiffies
);
5305 struct rq
*this_rq
= this_rq();
5309 if (curr_jiffies
== this_rq
->last_load_update_tick
)
5312 load
= weighted_cpuload(this_rq
);
5313 rq_lock(this_rq
, &rf
);
5314 update_rq_clock(this_rq
);
5315 cpu_load_update_nohz(this_rq
, curr_jiffies
, load
);
5316 rq_unlock(this_rq
, &rf
);
5318 #else /* !CONFIG_NO_HZ_COMMON */
5319 static inline void cpu_load_update_nohz(struct rq
*this_rq
,
5320 unsigned long curr_jiffies
,
5321 unsigned long load
) { }
5322 #endif /* CONFIG_NO_HZ_COMMON */
5324 static void cpu_load_update_periodic(struct rq
*this_rq
, unsigned long load
)
5326 #ifdef CONFIG_NO_HZ_COMMON
5327 /* See the mess around cpu_load_update_nohz(). */
5328 this_rq
->last_load_update_tick
= READ_ONCE(jiffies
);
5330 cpu_load_update(this_rq
, load
, 1);
5334 * Called from scheduler_tick()
5336 void cpu_load_update_active(struct rq
*this_rq
)
5338 unsigned long load
= weighted_cpuload(this_rq
);
5340 if (tick_nohz_tick_stopped())
5341 cpu_load_update_nohz(this_rq
, READ_ONCE(jiffies
), load
);
5343 cpu_load_update_periodic(this_rq
, load
);
5347 * Return a low guess at the load of a migration-source cpu weighted
5348 * according to the scheduling class and "nice" value.
5350 * We want to under-estimate the load of migration sources, to
5351 * balance conservatively.
5353 static unsigned long source_load(int cpu
, int type
)
5355 struct rq
*rq
= cpu_rq(cpu
);
5356 unsigned long total
= weighted_cpuload(rq
);
5358 if (type
== 0 || !sched_feat(LB_BIAS
))
5361 return min(rq
->cpu_load
[type
-1], total
);
5365 * Return a high guess at the load of a migration-target cpu weighted
5366 * according to the scheduling class and "nice" value.
5368 static unsigned long target_load(int cpu
, int type
)
5370 struct rq
*rq
= cpu_rq(cpu
);
5371 unsigned long total
= weighted_cpuload(rq
);
5373 if (type
== 0 || !sched_feat(LB_BIAS
))
5376 return max(rq
->cpu_load
[type
-1], total
);
5379 static unsigned long capacity_of(int cpu
)
5381 return cpu_rq(cpu
)->cpu_capacity
;
5384 static unsigned long capacity_orig_of(int cpu
)
5386 return cpu_rq(cpu
)->cpu_capacity_orig
;
5389 static unsigned long cpu_avg_load_per_task(int cpu
)
5391 struct rq
*rq
= cpu_rq(cpu
);
5392 unsigned long nr_running
= READ_ONCE(rq
->cfs
.h_nr_running
);
5393 unsigned long load_avg
= weighted_cpuload(rq
);
5396 return load_avg
/ nr_running
;
5401 static void record_wakee(struct task_struct
*p
)
5404 * Only decay a single time; tasks that have less then 1 wakeup per
5405 * jiffy will not have built up many flips.
5407 if (time_after(jiffies
, current
->wakee_flip_decay_ts
+ HZ
)) {
5408 current
->wakee_flips
>>= 1;
5409 current
->wakee_flip_decay_ts
= jiffies
;
5412 if (current
->last_wakee
!= p
) {
5413 current
->last_wakee
= p
;
5414 current
->wakee_flips
++;
5419 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5421 * A waker of many should wake a different task than the one last awakened
5422 * at a frequency roughly N times higher than one of its wakees.
5424 * In order to determine whether we should let the load spread vs consolidating
5425 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
5426 * partner, and a factor of lls_size higher frequency in the other.
5428 * With both conditions met, we can be relatively sure that the relationship is
5429 * non-monogamous, with partner count exceeding socket size.
5431 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
5432 * whatever is irrelevant, spread criteria is apparent partner count exceeds
5435 static int wake_wide(struct task_struct
*p
)
5437 unsigned int master
= current
->wakee_flips
;
5438 unsigned int slave
= p
->wakee_flips
;
5439 int factor
= this_cpu_read(sd_llc_size
);
5442 swap(master
, slave
);
5443 if (slave
< factor
|| master
< slave
* factor
)
5449 unsigned long nr_running
;
5451 unsigned long capacity
;
5455 static bool get_llc_stats(struct llc_stats
*stats
, int cpu
)
5457 struct sched_domain_shared
*sds
= rcu_dereference(per_cpu(sd_llc_shared
, cpu
));
5462 stats
->nr_running
= READ_ONCE(sds
->nr_running
);
5463 stats
->load
= READ_ONCE(sds
->load
);
5464 stats
->capacity
= READ_ONCE(sds
->capacity
);
5465 stats
->has_capacity
= stats
->nr_running
< per_cpu(sd_llc_size
, cpu
);
5471 * Can a task be moved from prev_cpu to this_cpu without causing a load
5472 * imbalance that would trigger the load balancer?
5474 * Since we're running on 'stale' values, we might in fact create an imbalance
5475 * but recomputing these values is expensive, as that'd mean iteration 2 cache
5476 * domains worth of CPUs.
5479 wake_affine_llc(struct sched_domain
*sd
, struct task_struct
*p
,
5480 int this_cpu
, int prev_cpu
, int sync
)
5482 struct llc_stats prev_stats
, this_stats
;
5483 s64 this_eff_load
, prev_eff_load
;
5484 unsigned long task_load
;
5486 if (!get_llc_stats(&prev_stats
, prev_cpu
) ||
5487 !get_llc_stats(&this_stats
, this_cpu
))
5491 * If sync wakeup then subtract the (maximum possible)
5492 * effect of the currently running task from the load
5493 * of the current LLC.
5496 unsigned long current_load
= task_h_load(current
);
5498 /* in this case load hits 0 and this LLC is considered 'idle' */
5499 if (current_load
> this_stats
.load
)
5502 this_stats
.load
-= current_load
;
5506 * The has_capacity stuff is not SMT aware, but by trying to balance
5507 * the nr_running on both ends we try and fill the domain at equal
5508 * rates, thereby first consuming cores before siblings.
5511 /* if the old cache has capacity, stay there */
5512 if (prev_stats
.has_capacity
&& prev_stats
.nr_running
< this_stats
.nr_running
+1)
5515 /* if this cache has capacity, come here */
5516 if (this_stats
.has_capacity
&& this_stats
.nr_running
+1 < prev_stats
.nr_running
)
5520 * Check to see if we can move the load without causing too much
5523 task_load
= task_h_load(p
);
5525 this_eff_load
= 100;
5526 this_eff_load
*= prev_stats
.capacity
;
5528 prev_eff_load
= 100 + (sd
->imbalance_pct
- 100) / 2;
5529 prev_eff_load
*= this_stats
.capacity
;
5531 this_eff_load
*= this_stats
.load
+ task_load
;
5532 prev_eff_load
*= prev_stats
.load
- task_load
;
5534 return this_eff_load
<= prev_eff_load
;
5537 static int wake_affine(struct sched_domain
*sd
, struct task_struct
*p
,
5538 int prev_cpu
, int sync
)
5540 int this_cpu
= smp_processor_id();
5544 * Default to no affine wakeups; wake_affine() should not effect a task
5545 * placement the load-balancer feels inclined to undo. The conservative
5546 * option is therefore to not move tasks when they wake up.
5551 * If the wakeup is across cache domains, try to evaluate if movement
5552 * makes sense, otherwise rely on select_idle_siblings() to do
5553 * placement inside the cache domain.
5555 if (!cpus_share_cache(prev_cpu
, this_cpu
))
5556 affine
= wake_affine_llc(sd
, p
, this_cpu
, prev_cpu
, sync
);
5558 schedstat_inc(p
->se
.statistics
.nr_wakeups_affine_attempts
);
5560 schedstat_inc(sd
->ttwu_move_affine
);
5561 schedstat_inc(p
->se
.statistics
.nr_wakeups_affine
);
5567 static inline int task_util(struct task_struct
*p
);
5568 static int cpu_util_wake(int cpu
, struct task_struct
*p
);
5570 static unsigned long capacity_spare_wake(int cpu
, struct task_struct
*p
)
5572 return capacity_orig_of(cpu
) - cpu_util_wake(cpu
, p
);
5576 * find_idlest_group finds and returns the least busy CPU group within the
5579 static struct sched_group
*
5580 find_idlest_group(struct sched_domain
*sd
, struct task_struct
*p
,
5581 int this_cpu
, int sd_flag
)
5583 struct sched_group
*idlest
= NULL
, *group
= sd
->groups
;
5584 struct sched_group
*most_spare_sg
= NULL
;
5585 unsigned long min_runnable_load
= ULONG_MAX
, this_runnable_load
= 0;
5586 unsigned long min_avg_load
= ULONG_MAX
, this_avg_load
= 0;
5587 unsigned long most_spare
= 0, this_spare
= 0;
5588 int load_idx
= sd
->forkexec_idx
;
5589 int imbalance_scale
= 100 + (sd
->imbalance_pct
-100)/2;
5590 unsigned long imbalance
= scale_load_down(NICE_0_LOAD
) *
5591 (sd
->imbalance_pct
-100) / 100;
5593 if (sd_flag
& SD_BALANCE_WAKE
)
5594 load_idx
= sd
->wake_idx
;
5597 unsigned long load
, avg_load
, runnable_load
;
5598 unsigned long spare_cap
, max_spare_cap
;
5602 /* Skip over this group if it has no CPUs allowed */
5603 if (!cpumask_intersects(sched_group_span(group
),
5607 local_group
= cpumask_test_cpu(this_cpu
,
5608 sched_group_span(group
));
5611 * Tally up the load of all CPUs in the group and find
5612 * the group containing the CPU with most spare capacity.
5618 for_each_cpu(i
, sched_group_span(group
)) {
5619 /* Bias balancing toward cpus of our domain */
5621 load
= source_load(i
, load_idx
);
5623 load
= target_load(i
, load_idx
);
5625 runnable_load
+= load
;
5627 avg_load
+= cfs_rq_load_avg(&cpu_rq(i
)->cfs
);
5629 spare_cap
= capacity_spare_wake(i
, p
);
5631 if (spare_cap
> max_spare_cap
)
5632 max_spare_cap
= spare_cap
;
5635 /* Adjust by relative CPU capacity of the group */
5636 avg_load
= (avg_load
* SCHED_CAPACITY_SCALE
) /
5637 group
->sgc
->capacity
;
5638 runnable_load
= (runnable_load
* SCHED_CAPACITY_SCALE
) /
5639 group
->sgc
->capacity
;
5642 this_runnable_load
= runnable_load
;
5643 this_avg_load
= avg_load
;
5644 this_spare
= max_spare_cap
;
5646 if (min_runnable_load
> (runnable_load
+ imbalance
)) {
5648 * The runnable load is significantly smaller
5649 * so we can pick this new cpu
5651 min_runnable_load
= runnable_load
;
5652 min_avg_load
= avg_load
;
5654 } else if ((runnable_load
< (min_runnable_load
+ imbalance
)) &&
5655 (100*min_avg_load
> imbalance_scale
*avg_load
)) {
5657 * The runnable loads are close so take the
5658 * blocked load into account through avg_load.
5660 min_avg_load
= avg_load
;
5664 if (most_spare
< max_spare_cap
) {
5665 most_spare
= max_spare_cap
;
5666 most_spare_sg
= group
;
5669 } while (group
= group
->next
, group
!= sd
->groups
);
5672 * The cross-over point between using spare capacity or least load
5673 * is too conservative for high utilization tasks on partially
5674 * utilized systems if we require spare_capacity > task_util(p),
5675 * so we allow for some task stuffing by using
5676 * spare_capacity > task_util(p)/2.
5678 * Spare capacity can't be used for fork because the utilization has
5679 * not been set yet, we must first select a rq to compute the initial
5682 if (sd_flag
& SD_BALANCE_FORK
)
5685 if (this_spare
> task_util(p
) / 2 &&
5686 imbalance_scale
*this_spare
> 100*most_spare
)
5689 if (most_spare
> task_util(p
) / 2)
5690 return most_spare_sg
;
5696 if (min_runnable_load
> (this_runnable_load
+ imbalance
))
5699 if ((this_runnable_load
< (min_runnable_load
+ imbalance
)) &&
5700 (100*this_avg_load
< imbalance_scale
*min_avg_load
))
5707 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5710 find_idlest_cpu(struct sched_group
*group
, struct task_struct
*p
, int this_cpu
)
5712 unsigned long load
, min_load
= ULONG_MAX
;
5713 unsigned int min_exit_latency
= UINT_MAX
;
5714 u64 latest_idle_timestamp
= 0;
5715 int least_loaded_cpu
= this_cpu
;
5716 int shallowest_idle_cpu
= -1;
5719 /* Check if we have any choice: */
5720 if (group
->group_weight
== 1)
5721 return cpumask_first(sched_group_span(group
));
5723 /* Traverse only the allowed CPUs */
5724 for_each_cpu_and(i
, sched_group_span(group
), &p
->cpus_allowed
) {
5726 struct rq
*rq
= cpu_rq(i
);
5727 struct cpuidle_state
*idle
= idle_get_state(rq
);
5728 if (idle
&& idle
->exit_latency
< min_exit_latency
) {
5730 * We give priority to a CPU whose idle state
5731 * has the smallest exit latency irrespective
5732 * of any idle timestamp.
5734 min_exit_latency
= idle
->exit_latency
;
5735 latest_idle_timestamp
= rq
->idle_stamp
;
5736 shallowest_idle_cpu
= i
;
5737 } else if ((!idle
|| idle
->exit_latency
== min_exit_latency
) &&
5738 rq
->idle_stamp
> latest_idle_timestamp
) {
5740 * If equal or no active idle state, then
5741 * the most recently idled CPU might have
5744 latest_idle_timestamp
= rq
->idle_stamp
;
5745 shallowest_idle_cpu
= i
;
5747 } else if (shallowest_idle_cpu
== -1) {
5748 load
= weighted_cpuload(cpu_rq(i
));
5749 if (load
< min_load
|| (load
== min_load
&& i
== this_cpu
)) {
5751 least_loaded_cpu
= i
;
5756 return shallowest_idle_cpu
!= -1 ? shallowest_idle_cpu
: least_loaded_cpu
;
5759 #ifdef CONFIG_SCHED_SMT
5761 static inline void set_idle_cores(int cpu
, int val
)
5763 struct sched_domain_shared
*sds
;
5765 sds
= rcu_dereference(per_cpu(sd_llc_shared
, cpu
));
5767 WRITE_ONCE(sds
->has_idle_cores
, val
);
5770 static inline bool test_idle_cores(int cpu
, bool def
)
5772 struct sched_domain_shared
*sds
;
5774 sds
= rcu_dereference(per_cpu(sd_llc_shared
, cpu
));
5776 return READ_ONCE(sds
->has_idle_cores
);
5782 * Scans the local SMT mask to see if the entire core is idle, and records this
5783 * information in sd_llc_shared->has_idle_cores.
5785 * Since SMT siblings share all cache levels, inspecting this limited remote
5786 * state should be fairly cheap.
5788 void __update_idle_core(struct rq
*rq
)
5790 int core
= cpu_of(rq
);
5794 if (test_idle_cores(core
, true))
5797 for_each_cpu(cpu
, cpu_smt_mask(core
)) {
5805 set_idle_cores(core
, 1);
5811 * Scan the entire LLC domain for idle cores; this dynamically switches off if
5812 * there are no idle cores left in the system; tracked through
5813 * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
5815 static int select_idle_core(struct task_struct
*p
, struct sched_domain
*sd
, int target
)
5817 struct cpumask
*cpus
= this_cpu_cpumask_var_ptr(select_idle_mask
);
5820 if (!static_branch_likely(&sched_smt_present
))
5823 if (!test_idle_cores(target
, false))
5826 cpumask_and(cpus
, sched_domain_span(sd
), &p
->cpus_allowed
);
5828 for_each_cpu_wrap(core
, cpus
, target
) {
5831 for_each_cpu(cpu
, cpu_smt_mask(core
)) {
5832 cpumask_clear_cpu(cpu
, cpus
);
5842 * Failed to find an idle core; stop looking for one.
5844 set_idle_cores(target
, 0);
5850 * Scan the local SMT mask for idle CPUs.
5852 static int select_idle_smt(struct task_struct
*p
, struct sched_domain
*sd
, int target
)
5856 if (!static_branch_likely(&sched_smt_present
))
5859 for_each_cpu(cpu
, cpu_smt_mask(target
)) {
5860 if (!cpumask_test_cpu(cpu
, &p
->cpus_allowed
))
5869 #else /* CONFIG_SCHED_SMT */
5871 static inline int select_idle_core(struct task_struct
*p
, struct sched_domain
*sd
, int target
)
5876 static inline int select_idle_smt(struct task_struct
*p
, struct sched_domain
*sd
, int target
)
5881 #endif /* CONFIG_SCHED_SMT */
5884 * Scan the LLC domain for idle CPUs; this is dynamically regulated by
5885 * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
5886 * average idle time for this rq (as found in rq->avg_idle).
5888 static int select_idle_cpu(struct task_struct
*p
, struct sched_domain
*sd
, int target
)
5890 struct sched_domain
*this_sd
;
5891 u64 avg_cost
, avg_idle
;
5894 int cpu
, nr
= INT_MAX
;
5896 this_sd
= rcu_dereference(*this_cpu_ptr(&sd_llc
));
5901 * Due to large variance we need a large fuzz factor; hackbench in
5902 * particularly is sensitive here.
5904 avg_idle
= this_rq()->avg_idle
/ 512;
5905 avg_cost
= this_sd
->avg_scan_cost
+ 1;
5907 if (sched_feat(SIS_AVG_CPU
) && avg_idle
< avg_cost
)
5910 if (sched_feat(SIS_PROP
)) {
5911 u64 span_avg
= sd
->span_weight
* avg_idle
;
5912 if (span_avg
> 4*avg_cost
)
5913 nr
= div_u64(span_avg
, avg_cost
);
5918 time
= local_clock();
5920 for_each_cpu_wrap(cpu
, sched_domain_span(sd
), target
) {
5923 if (!cpumask_test_cpu(cpu
, &p
->cpus_allowed
))
5929 time
= local_clock() - time
;
5930 cost
= this_sd
->avg_scan_cost
;
5931 delta
= (s64
)(time
- cost
) / 8;
5932 this_sd
->avg_scan_cost
+= delta
;
5938 * Try and locate an idle core/thread in the LLC cache domain.
5940 static int select_idle_sibling(struct task_struct
*p
, int prev
, int target
)
5942 struct sched_domain
*sd
;
5945 if (idle_cpu(target
))
5949 * If the previous cpu is cache affine and idle, don't be stupid.
5951 if (prev
!= target
&& cpus_share_cache(prev
, target
) && idle_cpu(prev
))
5954 sd
= rcu_dereference(per_cpu(sd_llc
, target
));
5958 i
= select_idle_core(p
, sd
, target
);
5959 if ((unsigned)i
< nr_cpumask_bits
)
5962 i
= select_idle_cpu(p
, sd
, target
);
5963 if ((unsigned)i
< nr_cpumask_bits
)
5966 i
= select_idle_smt(p
, sd
, target
);
5967 if ((unsigned)i
< nr_cpumask_bits
)
5974 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5975 * tasks. The unit of the return value must be the one of capacity so we can
5976 * compare the utilization with the capacity of the CPU that is available for
5977 * CFS task (ie cpu_capacity).
5979 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
5980 * recent utilization of currently non-runnable tasks on a CPU. It represents
5981 * the amount of utilization of a CPU in the range [0..capacity_orig] where
5982 * capacity_orig is the cpu_capacity available at the highest frequency
5983 * (arch_scale_freq_capacity()).
5984 * The utilization of a CPU converges towards a sum equal to or less than the
5985 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
5986 * the running time on this CPU scaled by capacity_curr.
5988 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
5989 * higher than capacity_orig because of unfortunate rounding in
5990 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
5991 * the average stabilizes with the new running time. We need to check that the
5992 * utilization stays within the range of [0..capacity_orig] and cap it if
5993 * necessary. Without utilization capping, a group could be seen as overloaded
5994 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
5995 * available capacity. We allow utilization to overshoot capacity_curr (but not
5996 * capacity_orig) as it useful for predicting the capacity required after task
5997 * migrations (scheduler-driven DVFS).
5999 static int cpu_util(int cpu
)
6001 unsigned long util
= cpu_rq(cpu
)->cfs
.avg
.util_avg
;
6002 unsigned long capacity
= capacity_orig_of(cpu
);
6004 return (util
>= capacity
) ? capacity
: util
;
6007 static inline int task_util(struct task_struct
*p
)
6009 return p
->se
.avg
.util_avg
;
6013 * cpu_util_wake: Compute cpu utilization with any contributions from
6014 * the waking task p removed.
6016 static int cpu_util_wake(int cpu
, struct task_struct
*p
)
6018 unsigned long util
, capacity
;
6020 /* Task has no contribution or is new */
6021 if (cpu
!= task_cpu(p
) || !p
->se
.avg
.last_update_time
)
6022 return cpu_util(cpu
);
6024 capacity
= capacity_orig_of(cpu
);
6025 util
= max_t(long, cpu_rq(cpu
)->cfs
.avg
.util_avg
- task_util(p
), 0);
6027 return (util
>= capacity
) ? capacity
: util
;
6031 * Disable WAKE_AFFINE in the case where task @p doesn't fit in the
6032 * capacity of either the waking CPU @cpu or the previous CPU @prev_cpu.
6034 * In that case WAKE_AFFINE doesn't make sense and we'll let
6035 * BALANCE_WAKE sort things out.
6037 static int wake_cap(struct task_struct
*p
, int cpu
, int prev_cpu
)
6039 long min_cap
, max_cap
;
6041 min_cap
= min(capacity_orig_of(prev_cpu
), capacity_orig_of(cpu
));
6042 max_cap
= cpu_rq(cpu
)->rd
->max_cpu_capacity
;
6044 /* Minimum capacity is close to max, no need to abort wake_affine */
6045 if (max_cap
- min_cap
< max_cap
>> 3)
6048 /* Bring task utilization in sync with prev_cpu */
6049 sync_entity_load_avg(&p
->se
);
6051 return min_cap
* 1024 < task_util(p
) * capacity_margin
;
6055 * select_task_rq_fair: Select target runqueue for the waking task in domains
6056 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
6057 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
6059 * Balances load by selecting the idlest cpu in the idlest group, or under
6060 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
6062 * Returns the target cpu number.
6064 * preempt must be disabled.
6067 select_task_rq_fair(struct task_struct
*p
, int prev_cpu
, int sd_flag
, int wake_flags
)
6069 struct sched_domain
*tmp
, *affine_sd
= NULL
, *sd
= NULL
;
6070 int cpu
= smp_processor_id();
6071 int new_cpu
= prev_cpu
;
6072 int want_affine
= 0;
6073 int sync
= wake_flags
& WF_SYNC
;
6075 if (sd_flag
& SD_BALANCE_WAKE
) {
6077 want_affine
= !wake_wide(p
) && !wake_cap(p
, cpu
, prev_cpu
)
6078 && cpumask_test_cpu(cpu
, &p
->cpus_allowed
);
6082 for_each_domain(cpu
, tmp
) {
6083 if (!(tmp
->flags
& SD_LOAD_BALANCE
))
6087 * If both cpu and prev_cpu are part of this domain,
6088 * cpu is a valid SD_WAKE_AFFINE target.
6090 if (want_affine
&& (tmp
->flags
& SD_WAKE_AFFINE
) &&
6091 cpumask_test_cpu(prev_cpu
, sched_domain_span(tmp
))) {
6096 if (tmp
->flags
& sd_flag
)
6098 else if (!want_affine
)
6103 sd
= NULL
; /* Prefer wake_affine over balance flags */
6104 if (cpu
== prev_cpu
)
6107 if (wake_affine(affine_sd
, p
, prev_cpu
, sync
))
6113 if (sd_flag
& SD_BALANCE_WAKE
) /* XXX always ? */
6114 new_cpu
= select_idle_sibling(p
, prev_cpu
, new_cpu
);
6117 struct sched_group
*group
;
6120 if (!(sd
->flags
& sd_flag
)) {
6125 group
= find_idlest_group(sd
, p
, cpu
, sd_flag
);
6131 new_cpu
= find_idlest_cpu(group
, p
, cpu
);
6132 if (new_cpu
== -1 || new_cpu
== cpu
) {
6133 /* Now try balancing at a lower domain level of cpu */
6138 /* Now try balancing at a lower domain level of new_cpu */
6140 weight
= sd
->span_weight
;
6142 for_each_domain(cpu
, tmp
) {
6143 if (weight
<= tmp
->span_weight
)
6145 if (tmp
->flags
& sd_flag
)
6148 /* while loop will break here if sd == NULL */
6156 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
6157 * cfs_rq_of(p) references at time of call are still valid and identify the
6158 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6160 static void migrate_task_rq_fair(struct task_struct
*p
)
6163 * As blocked tasks retain absolute vruntime the migration needs to
6164 * deal with this by subtracting the old and adding the new
6165 * min_vruntime -- the latter is done by enqueue_entity() when placing
6166 * the task on the new runqueue.
6168 if (p
->state
== TASK_WAKING
) {
6169 struct sched_entity
*se
= &p
->se
;
6170 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
6173 #ifndef CONFIG_64BIT
6174 u64 min_vruntime_copy
;
6177 min_vruntime_copy
= cfs_rq
->min_vruntime_copy
;
6179 min_vruntime
= cfs_rq
->min_vruntime
;
6180 } while (min_vruntime
!= min_vruntime_copy
);
6182 min_vruntime
= cfs_rq
->min_vruntime
;
6185 se
->vruntime
-= min_vruntime
;
6189 * We are supposed to update the task to "current" time, then its up to date
6190 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
6191 * what current time is, so simply throw away the out-of-date time. This
6192 * will result in the wakee task is less decayed, but giving the wakee more
6193 * load sounds not bad.
6195 remove_entity_load_avg(&p
->se
);
6197 /* Tell new CPU we are migrated */
6198 p
->se
.avg
.last_update_time
= 0;
6200 /* We have migrated, no longer consider this task hot */
6201 p
->se
.exec_start
= 0;
6204 static void task_dead_fair(struct task_struct
*p
)
6206 remove_entity_load_avg(&p
->se
);
6208 #endif /* CONFIG_SMP */
6210 static unsigned long
6211 wakeup_gran(struct sched_entity
*curr
, struct sched_entity
*se
)
6213 unsigned long gran
= sysctl_sched_wakeup_granularity
;
6216 * Since its curr running now, convert the gran from real-time
6217 * to virtual-time in his units.
6219 * By using 'se' instead of 'curr' we penalize light tasks, so
6220 * they get preempted easier. That is, if 'se' < 'curr' then
6221 * the resulting gran will be larger, therefore penalizing the
6222 * lighter, if otoh 'se' > 'curr' then the resulting gran will
6223 * be smaller, again penalizing the lighter task.
6225 * This is especially important for buddies when the leftmost
6226 * task is higher priority than the buddy.
6228 return calc_delta_fair(gran
, se
);
6232 * Should 'se' preempt 'curr'.
6246 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
)
6248 s64 gran
, vdiff
= curr
->vruntime
- se
->vruntime
;
6253 gran
= wakeup_gran(curr
, se
);
6260 static void set_last_buddy(struct sched_entity
*se
)
6262 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
6265 for_each_sched_entity(se
) {
6266 if (SCHED_WARN_ON(!se
->on_rq
))
6268 cfs_rq_of(se
)->last
= se
;
6272 static void set_next_buddy(struct sched_entity
*se
)
6274 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
6277 for_each_sched_entity(se
) {
6278 if (SCHED_WARN_ON(!se
->on_rq
))
6280 cfs_rq_of(se
)->next
= se
;
6284 static void set_skip_buddy(struct sched_entity
*se
)
6286 for_each_sched_entity(se
)
6287 cfs_rq_of(se
)->skip
= se
;
6291 * Preempt the current task with a newly woken task if needed:
6293 static void check_preempt_wakeup(struct rq
*rq
, struct task_struct
*p
, int wake_flags
)
6295 struct task_struct
*curr
= rq
->curr
;
6296 struct sched_entity
*se
= &curr
->se
, *pse
= &p
->se
;
6297 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
6298 int scale
= cfs_rq
->nr_running
>= sched_nr_latency
;
6299 int next_buddy_marked
= 0;
6301 if (unlikely(se
== pse
))
6305 * This is possible from callers such as attach_tasks(), in which we
6306 * unconditionally check_prempt_curr() after an enqueue (which may have
6307 * lead to a throttle). This both saves work and prevents false
6308 * next-buddy nomination below.
6310 if (unlikely(throttled_hierarchy(cfs_rq_of(pse
))))
6313 if (sched_feat(NEXT_BUDDY
) && scale
&& !(wake_flags
& WF_FORK
)) {
6314 set_next_buddy(pse
);
6315 next_buddy_marked
= 1;
6319 * We can come here with TIF_NEED_RESCHED already set from new task
6322 * Note: this also catches the edge-case of curr being in a throttled
6323 * group (e.g. via set_curr_task), since update_curr() (in the
6324 * enqueue of curr) will have resulted in resched being set. This
6325 * prevents us from potentially nominating it as a false LAST_BUDDY
6328 if (test_tsk_need_resched(curr
))
6331 /* Idle tasks are by definition preempted by non-idle tasks. */
6332 if (unlikely(curr
->policy
== SCHED_IDLE
) &&
6333 likely(p
->policy
!= SCHED_IDLE
))
6337 * Batch and idle tasks do not preempt non-idle tasks (their preemption
6338 * is driven by the tick):
6340 if (unlikely(p
->policy
!= SCHED_NORMAL
) || !sched_feat(WAKEUP_PREEMPTION
))
6343 find_matching_se(&se
, &pse
);
6344 update_curr(cfs_rq_of(se
));
6346 if (wakeup_preempt_entity(se
, pse
) == 1) {
6348 * Bias pick_next to pick the sched entity that is
6349 * triggering this preemption.
6351 if (!next_buddy_marked
)
6352 set_next_buddy(pse
);
6361 * Only set the backward buddy when the current task is still
6362 * on the rq. This can happen when a wakeup gets interleaved
6363 * with schedule on the ->pre_schedule() or idle_balance()
6364 * point, either of which can * drop the rq lock.
6366 * Also, during early boot the idle thread is in the fair class,
6367 * for obvious reasons its a bad idea to schedule back to it.
6369 if (unlikely(!se
->on_rq
|| curr
== rq
->idle
))
6372 if (sched_feat(LAST_BUDDY
) && scale
&& entity_is_task(se
))
6376 static struct task_struct
*
6377 pick_next_task_fair(struct rq
*rq
, struct task_struct
*prev
, struct rq_flags
*rf
)
6379 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
6380 struct sched_entity
*se
;
6381 struct task_struct
*p
;
6385 if (!cfs_rq
->nr_running
)
6388 #ifdef CONFIG_FAIR_GROUP_SCHED
6389 if (prev
->sched_class
!= &fair_sched_class
)
6393 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
6394 * likely that a next task is from the same cgroup as the current.
6396 * Therefore attempt to avoid putting and setting the entire cgroup
6397 * hierarchy, only change the part that actually changes.
6401 struct sched_entity
*curr
= cfs_rq
->curr
;
6404 * Since we got here without doing put_prev_entity() we also
6405 * have to consider cfs_rq->curr. If it is still a runnable
6406 * entity, update_curr() will update its vruntime, otherwise
6407 * forget we've ever seen it.
6411 update_curr(cfs_rq
);
6416 * This call to check_cfs_rq_runtime() will do the
6417 * throttle and dequeue its entity in the parent(s).
6418 * Therefore the nr_running test will indeed
6421 if (unlikely(check_cfs_rq_runtime(cfs_rq
))) {
6424 if (!cfs_rq
->nr_running
)
6431 se
= pick_next_entity(cfs_rq
, curr
);
6432 cfs_rq
= group_cfs_rq(se
);
6438 * Since we haven't yet done put_prev_entity and if the selected task
6439 * is a different task than we started out with, try and touch the
6440 * least amount of cfs_rqs.
6443 struct sched_entity
*pse
= &prev
->se
;
6445 while (!(cfs_rq
= is_same_group(se
, pse
))) {
6446 int se_depth
= se
->depth
;
6447 int pse_depth
= pse
->depth
;
6449 if (se_depth
<= pse_depth
) {
6450 put_prev_entity(cfs_rq_of(pse
), pse
);
6451 pse
= parent_entity(pse
);
6453 if (se_depth
>= pse_depth
) {
6454 set_next_entity(cfs_rq_of(se
), se
);
6455 se
= parent_entity(se
);
6459 put_prev_entity(cfs_rq
, pse
);
6460 set_next_entity(cfs_rq
, se
);
6463 if (hrtick_enabled(rq
))
6464 hrtick_start_fair(rq
, p
);
6470 put_prev_task(rq
, prev
);
6473 se
= pick_next_entity(cfs_rq
, NULL
);
6474 set_next_entity(cfs_rq
, se
);
6475 cfs_rq
= group_cfs_rq(se
);
6480 if (hrtick_enabled(rq
))
6481 hrtick_start_fair(rq
, p
);
6486 new_tasks
= idle_balance(rq
, rf
);
6489 * Because idle_balance() releases (and re-acquires) rq->lock, it is
6490 * possible for any higher priority task to appear. In that case we
6491 * must re-start the pick_next_entity() loop.
6503 * Account for a descheduled task:
6505 static void put_prev_task_fair(struct rq
*rq
, struct task_struct
*prev
)
6507 struct sched_entity
*se
= &prev
->se
;
6508 struct cfs_rq
*cfs_rq
;
6510 for_each_sched_entity(se
) {
6511 cfs_rq
= cfs_rq_of(se
);
6512 put_prev_entity(cfs_rq
, se
);
6517 * sched_yield() is very simple
6519 * The magic of dealing with the ->skip buddy is in pick_next_entity.
6521 static void yield_task_fair(struct rq
*rq
)
6523 struct task_struct
*curr
= rq
->curr
;
6524 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
6525 struct sched_entity
*se
= &curr
->se
;
6528 * Are we the only task in the tree?
6530 if (unlikely(rq
->nr_running
== 1))
6533 clear_buddies(cfs_rq
, se
);
6535 if (curr
->policy
!= SCHED_BATCH
) {
6536 update_rq_clock(rq
);
6538 * Update run-time statistics of the 'current'.
6540 update_curr(cfs_rq
);
6542 * Tell update_rq_clock() that we've just updated,
6543 * so we don't do microscopic update in schedule()
6544 * and double the fastpath cost.
6546 rq_clock_skip_update(rq
, true);
6552 static bool yield_to_task_fair(struct rq
*rq
, struct task_struct
*p
, bool preempt
)
6554 struct sched_entity
*se
= &p
->se
;
6556 /* throttled hierarchies are not runnable */
6557 if (!se
->on_rq
|| throttled_hierarchy(cfs_rq_of(se
)))
6560 /* Tell the scheduler that we'd really like pse to run next. */
6563 yield_task_fair(rq
);
6569 /**************************************************
6570 * Fair scheduling class load-balancing methods.
6574 * The purpose of load-balancing is to achieve the same basic fairness the
6575 * per-cpu scheduler provides, namely provide a proportional amount of compute
6576 * time to each task. This is expressed in the following equation:
6578 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
6580 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
6581 * W_i,0 is defined as:
6583 * W_i,0 = \Sum_j w_i,j (2)
6585 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
6586 * is derived from the nice value as per sched_prio_to_weight[].
6588 * The weight average is an exponential decay average of the instantaneous
6591 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
6593 * C_i is the compute capacity of cpu i, typically it is the
6594 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
6595 * can also include other factors [XXX].
6597 * To achieve this balance we define a measure of imbalance which follows
6598 * directly from (1):
6600 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
6602 * We them move tasks around to minimize the imbalance. In the continuous
6603 * function space it is obvious this converges, in the discrete case we get
6604 * a few fun cases generally called infeasible weight scenarios.
6607 * - infeasible weights;
6608 * - local vs global optima in the discrete case. ]
6613 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
6614 * for all i,j solution, we create a tree of cpus that follows the hardware
6615 * topology where each level pairs two lower groups (or better). This results
6616 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
6617 * tree to only the first of the previous level and we decrease the frequency
6618 * of load-balance at each level inv. proportional to the number of cpus in
6624 * \Sum { --- * --- * 2^i } = O(n) (5)
6626 * `- size of each group
6627 * | | `- number of cpus doing load-balance
6629 * `- sum over all levels
6631 * Coupled with a limit on how many tasks we can migrate every balance pass,
6632 * this makes (5) the runtime complexity of the balancer.
6634 * An important property here is that each CPU is still (indirectly) connected
6635 * to every other cpu in at most O(log n) steps:
6637 * The adjacency matrix of the resulting graph is given by:
6640 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
6643 * And you'll find that:
6645 * A^(log_2 n)_i,j != 0 for all i,j (7)
6647 * Showing there's indeed a path between every cpu in at most O(log n) steps.
6648 * The task movement gives a factor of O(m), giving a convergence complexity
6651 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
6656 * In order to avoid CPUs going idle while there's still work to do, new idle
6657 * balancing is more aggressive and has the newly idle cpu iterate up the domain
6658 * tree itself instead of relying on other CPUs to bring it work.
6660 * This adds some complexity to both (5) and (8) but it reduces the total idle
6668 * Cgroups make a horror show out of (2), instead of a simple sum we get:
6671 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
6676 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
6678 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
6680 * The big problem is S_k, its a global sum needed to compute a local (W_i)
6683 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
6684 * rewrite all of this once again.]
6687 static unsigned long __read_mostly max_load_balance_interval
= HZ
/10;
6689 enum fbq_type
{ regular
, remote
, all
};
6691 #define LBF_ALL_PINNED 0x01
6692 #define LBF_NEED_BREAK 0x02
6693 #define LBF_DST_PINNED 0x04
6694 #define LBF_SOME_PINNED 0x08
6697 struct sched_domain
*sd
;
6705 struct cpumask
*dst_grpmask
;
6707 enum cpu_idle_type idle
;
6709 /* The set of CPUs under consideration for load-balancing */
6710 struct cpumask
*cpus
;
6715 unsigned int loop_break
;
6716 unsigned int loop_max
;
6718 enum fbq_type fbq_type
;
6719 struct list_head tasks
;
6723 * Is this task likely cache-hot:
6725 static int task_hot(struct task_struct
*p
, struct lb_env
*env
)
6729 lockdep_assert_held(&env
->src_rq
->lock
);
6731 if (p
->sched_class
!= &fair_sched_class
)
6734 if (unlikely(p
->policy
== SCHED_IDLE
))
6738 * Buddy candidates are cache hot:
6740 if (sched_feat(CACHE_HOT_BUDDY
) && env
->dst_rq
->nr_running
&&
6741 (&p
->se
== cfs_rq_of(&p
->se
)->next
||
6742 &p
->se
== cfs_rq_of(&p
->se
)->last
))
6745 if (sysctl_sched_migration_cost
== -1)
6747 if (sysctl_sched_migration_cost
== 0)
6750 delta
= rq_clock_task(env
->src_rq
) - p
->se
.exec_start
;
6752 return delta
< (s64
)sysctl_sched_migration_cost
;
6755 #ifdef CONFIG_NUMA_BALANCING
6757 * Returns 1, if task migration degrades locality
6758 * Returns 0, if task migration improves locality i.e migration preferred.
6759 * Returns -1, if task migration is not affected by locality.
6761 static int migrate_degrades_locality(struct task_struct
*p
, struct lb_env
*env
)
6763 struct numa_group
*numa_group
= rcu_dereference(p
->numa_group
);
6764 unsigned long src_faults
, dst_faults
;
6765 int src_nid
, dst_nid
;
6767 if (!static_branch_likely(&sched_numa_balancing
))
6770 if (!p
->numa_faults
|| !(env
->sd
->flags
& SD_NUMA
))
6773 src_nid
= cpu_to_node(env
->src_cpu
);
6774 dst_nid
= cpu_to_node(env
->dst_cpu
);
6776 if (src_nid
== dst_nid
)
6779 /* Migrating away from the preferred node is always bad. */
6780 if (src_nid
== p
->numa_preferred_nid
) {
6781 if (env
->src_rq
->nr_running
> env
->src_rq
->nr_preferred_running
)
6787 /* Encourage migration to the preferred node. */
6788 if (dst_nid
== p
->numa_preferred_nid
)
6791 /* Leaving a core idle is often worse than degrading locality. */
6792 if (env
->idle
!= CPU_NOT_IDLE
)
6796 src_faults
= group_faults(p
, src_nid
);
6797 dst_faults
= group_faults(p
, dst_nid
);
6799 src_faults
= task_faults(p
, src_nid
);
6800 dst_faults
= task_faults(p
, dst_nid
);
6803 return dst_faults
< src_faults
;
6807 static inline int migrate_degrades_locality(struct task_struct
*p
,
6815 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
6818 int can_migrate_task(struct task_struct
*p
, struct lb_env
*env
)
6822 lockdep_assert_held(&env
->src_rq
->lock
);
6825 * We do not migrate tasks that are:
6826 * 1) throttled_lb_pair, or
6827 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6828 * 3) running (obviously), or
6829 * 4) are cache-hot on their current CPU.
6831 if (throttled_lb_pair(task_group(p
), env
->src_cpu
, env
->dst_cpu
))
6834 if (!cpumask_test_cpu(env
->dst_cpu
, &p
->cpus_allowed
)) {
6837 schedstat_inc(p
->se
.statistics
.nr_failed_migrations_affine
);
6839 env
->flags
|= LBF_SOME_PINNED
;
6842 * Remember if this task can be migrated to any other cpu in
6843 * our sched_group. We may want to revisit it if we couldn't
6844 * meet load balance goals by pulling other tasks on src_cpu.
6846 * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have
6847 * already computed one in current iteration.
6849 if (env
->idle
== CPU_NEWLY_IDLE
|| (env
->flags
& LBF_DST_PINNED
))
6852 /* Prevent to re-select dst_cpu via env's cpus */
6853 for_each_cpu_and(cpu
, env
->dst_grpmask
, env
->cpus
) {
6854 if (cpumask_test_cpu(cpu
, &p
->cpus_allowed
)) {
6855 env
->flags
|= LBF_DST_PINNED
;
6856 env
->new_dst_cpu
= cpu
;
6864 /* Record that we found atleast one task that could run on dst_cpu */
6865 env
->flags
&= ~LBF_ALL_PINNED
;
6867 if (task_running(env
->src_rq
, p
)) {
6868 schedstat_inc(p
->se
.statistics
.nr_failed_migrations_running
);
6873 * Aggressive migration if:
6874 * 1) destination numa is preferred
6875 * 2) task is cache cold, or
6876 * 3) too many balance attempts have failed.
6878 tsk_cache_hot
= migrate_degrades_locality(p
, env
);
6879 if (tsk_cache_hot
== -1)
6880 tsk_cache_hot
= task_hot(p
, env
);
6882 if (tsk_cache_hot
<= 0 ||
6883 env
->sd
->nr_balance_failed
> env
->sd
->cache_nice_tries
) {
6884 if (tsk_cache_hot
== 1) {
6885 schedstat_inc(env
->sd
->lb_hot_gained
[env
->idle
]);
6886 schedstat_inc(p
->se
.statistics
.nr_forced_migrations
);
6891 schedstat_inc(p
->se
.statistics
.nr_failed_migrations_hot
);
6896 * detach_task() -- detach the task for the migration specified in env
6898 static void detach_task(struct task_struct
*p
, struct lb_env
*env
)
6900 lockdep_assert_held(&env
->src_rq
->lock
);
6902 p
->on_rq
= TASK_ON_RQ_MIGRATING
;
6903 deactivate_task(env
->src_rq
, p
, DEQUEUE_NOCLOCK
);
6904 set_task_cpu(p
, env
->dst_cpu
);
6908 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6909 * part of active balancing operations within "domain".
6911 * Returns a task if successful and NULL otherwise.
6913 static struct task_struct
*detach_one_task(struct lb_env
*env
)
6915 struct task_struct
*p
, *n
;
6917 lockdep_assert_held(&env
->src_rq
->lock
);
6919 list_for_each_entry_safe(p
, n
, &env
->src_rq
->cfs_tasks
, se
.group_node
) {
6920 if (!can_migrate_task(p
, env
))
6923 detach_task(p
, env
);
6926 * Right now, this is only the second place where
6927 * lb_gained[env->idle] is updated (other is detach_tasks)
6928 * so we can safely collect stats here rather than
6929 * inside detach_tasks().
6931 schedstat_inc(env
->sd
->lb_gained
[env
->idle
]);
6937 static const unsigned int sched_nr_migrate_break
= 32;
6940 * detach_tasks() -- tries to detach up to imbalance weighted load from
6941 * busiest_rq, as part of a balancing operation within domain "sd".
6943 * Returns number of detached tasks if successful and 0 otherwise.
6945 static int detach_tasks(struct lb_env
*env
)
6947 struct list_head
*tasks
= &env
->src_rq
->cfs_tasks
;
6948 struct task_struct
*p
;
6952 lockdep_assert_held(&env
->src_rq
->lock
);
6954 if (env
->imbalance
<= 0)
6957 while (!list_empty(tasks
)) {
6959 * We don't want to steal all, otherwise we may be treated likewise,
6960 * which could at worst lead to a livelock crash.
6962 if (env
->idle
!= CPU_NOT_IDLE
&& env
->src_rq
->nr_running
<= 1)
6965 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
6968 /* We've more or less seen every task there is, call it quits */
6969 if (env
->loop
> env
->loop_max
)
6972 /* take a breather every nr_migrate tasks */
6973 if (env
->loop
> env
->loop_break
) {
6974 env
->loop_break
+= sched_nr_migrate_break
;
6975 env
->flags
|= LBF_NEED_BREAK
;
6979 if (!can_migrate_task(p
, env
))
6982 load
= task_h_load(p
);
6984 if (sched_feat(LB_MIN
) && load
< 16 && !env
->sd
->nr_balance_failed
)
6987 if ((load
/ 2) > env
->imbalance
)
6990 detach_task(p
, env
);
6991 list_add(&p
->se
.group_node
, &env
->tasks
);
6994 env
->imbalance
-= load
;
6996 #ifdef CONFIG_PREEMPT
6998 * NEWIDLE balancing is a source of latency, so preemptible
6999 * kernels will stop after the first task is detached to minimize
7000 * the critical section.
7002 if (env
->idle
== CPU_NEWLY_IDLE
)
7007 * We only want to steal up to the prescribed amount of
7010 if (env
->imbalance
<= 0)
7015 list_move_tail(&p
->se
.group_node
, tasks
);
7019 * Right now, this is one of only two places we collect this stat
7020 * so we can safely collect detach_one_task() stats here rather
7021 * than inside detach_one_task().
7023 schedstat_add(env
->sd
->lb_gained
[env
->idle
], detached
);
7029 * attach_task() -- attach the task detached by detach_task() to its new rq.
7031 static void attach_task(struct rq
*rq
, struct task_struct
*p
)
7033 lockdep_assert_held(&rq
->lock
);
7035 BUG_ON(task_rq(p
) != rq
);
7036 activate_task(rq
, p
, ENQUEUE_NOCLOCK
);
7037 p
->on_rq
= TASK_ON_RQ_QUEUED
;
7038 check_preempt_curr(rq
, p
, 0);
7042 * attach_one_task() -- attaches the task returned from detach_one_task() to
7045 static void attach_one_task(struct rq
*rq
, struct task_struct
*p
)
7050 update_rq_clock(rq
);
7056 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
7059 static void attach_tasks(struct lb_env
*env
)
7061 struct list_head
*tasks
= &env
->tasks
;
7062 struct task_struct
*p
;
7065 rq_lock(env
->dst_rq
, &rf
);
7066 update_rq_clock(env
->dst_rq
);
7068 while (!list_empty(tasks
)) {
7069 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
7070 list_del_init(&p
->se
.group_node
);
7072 attach_task(env
->dst_rq
, p
);
7075 rq_unlock(env
->dst_rq
, &rf
);
7078 #ifdef CONFIG_FAIR_GROUP_SCHED
7080 static inline bool cfs_rq_is_decayed(struct cfs_rq
*cfs_rq
)
7082 if (cfs_rq
->load
.weight
)
7085 if (cfs_rq
->avg
.load_sum
)
7088 if (cfs_rq
->avg
.util_sum
)
7091 if (cfs_rq
->runnable_load_sum
)
7097 static void update_blocked_averages(int cpu
)
7099 struct rq
*rq
= cpu_rq(cpu
);
7100 struct cfs_rq
*cfs_rq
, *pos
;
7103 rq_lock_irqsave(rq
, &rf
);
7104 update_rq_clock(rq
);
7107 * Iterates the task_group tree in a bottom up fashion, see
7108 * list_add_leaf_cfs_rq() for details.
7110 for_each_leaf_cfs_rq_safe(rq
, cfs_rq
, pos
) {
7111 struct sched_entity
*se
;
7113 /* throttled entities do not contribute to load */
7114 if (throttled_hierarchy(cfs_rq
))
7117 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq
), cfs_rq
))
7118 update_tg_load_avg(cfs_rq
, 0);
7120 /* Propagate pending load changes to the parent, if any: */
7121 se
= cfs_rq
->tg
->se
[cpu
];
7122 if (se
&& !skip_blocked_update(se
))
7123 update_load_avg(cfs_rq_of(se
), se
, 0);
7126 * There can be a lot of idle CPU cgroups. Don't let fully
7127 * decayed cfs_rqs linger on the list.
7129 if (cfs_rq_is_decayed(cfs_rq
))
7130 list_del_leaf_cfs_rq(cfs_rq
);
7132 rq_unlock_irqrestore(rq
, &rf
);
7136 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
7137 * This needs to be done in a top-down fashion because the load of a child
7138 * group is a fraction of its parents load.
7140 static void update_cfs_rq_h_load(struct cfs_rq
*cfs_rq
)
7142 struct rq
*rq
= rq_of(cfs_rq
);
7143 struct sched_entity
*se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
7144 unsigned long now
= jiffies
;
7147 if (cfs_rq
->last_h_load_update
== now
)
7150 cfs_rq
->h_load_next
= NULL
;
7151 for_each_sched_entity(se
) {
7152 cfs_rq
= cfs_rq_of(se
);
7153 cfs_rq
->h_load_next
= se
;
7154 if (cfs_rq
->last_h_load_update
== now
)
7159 cfs_rq
->h_load
= cfs_rq_load_avg(cfs_rq
);
7160 cfs_rq
->last_h_load_update
= now
;
7163 while ((se
= cfs_rq
->h_load_next
) != NULL
) {
7164 load
= cfs_rq
->h_load
;
7165 load
= div64_ul(load
* se
->avg
.load_avg
,
7166 cfs_rq_load_avg(cfs_rq
) + 1);
7167 cfs_rq
= group_cfs_rq(se
);
7168 cfs_rq
->h_load
= load
;
7169 cfs_rq
->last_h_load_update
= now
;
7173 static unsigned long task_h_load(struct task_struct
*p
)
7175 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
7177 update_cfs_rq_h_load(cfs_rq
);
7178 return div64_ul(p
->se
.avg
.load_avg
* cfs_rq
->h_load
,
7179 cfs_rq_load_avg(cfs_rq
) + 1);
7182 static inline void update_blocked_averages(int cpu
)
7184 struct rq
*rq
= cpu_rq(cpu
);
7185 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
7188 rq_lock_irqsave(rq
, &rf
);
7189 update_rq_clock(rq
);
7190 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq
), cfs_rq
);
7191 rq_unlock_irqrestore(rq
, &rf
);
7194 static unsigned long task_h_load(struct task_struct
*p
)
7196 return p
->se
.avg
.load_avg
;
7200 /********** Helpers for find_busiest_group ************************/
7209 * sg_lb_stats - stats of a sched_group required for load_balancing
7211 struct sg_lb_stats
{
7212 unsigned long avg_load
; /*Avg load across the CPUs of the group */
7213 unsigned long group_load
; /* Total load over the CPUs of the group */
7214 unsigned long sum_weighted_load
; /* Weighted load of group's tasks */
7215 unsigned long load_per_task
;
7216 unsigned long group_capacity
;
7217 unsigned long group_util
; /* Total utilization of the group */
7218 unsigned int sum_nr_running
; /* Nr tasks running in the group */
7219 unsigned int idle_cpus
;
7220 unsigned int group_weight
;
7221 enum group_type group_type
;
7222 int group_no_capacity
;
7223 #ifdef CONFIG_NUMA_BALANCING
7224 unsigned int nr_numa_running
;
7225 unsigned int nr_preferred_running
;
7230 * sd_lb_stats - Structure to store the statistics of a sched_domain
7231 * during load balancing.
7233 struct sd_lb_stats
{
7234 struct sched_group
*busiest
; /* Busiest group in this sd */
7235 struct sched_group
*local
; /* Local group in this sd */
7236 unsigned long total_running
;
7237 unsigned long total_load
; /* Total load of all groups in sd */
7238 unsigned long total_capacity
; /* Total capacity of all groups in sd */
7239 unsigned long avg_load
; /* Average load across all groups in sd */
7241 struct sg_lb_stats busiest_stat
;/* Statistics of the busiest group */
7242 struct sg_lb_stats local_stat
; /* Statistics of the local group */
7245 static inline void init_sd_lb_stats(struct sd_lb_stats
*sds
)
7248 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
7249 * local_stat because update_sg_lb_stats() does a full clear/assignment.
7250 * We must however clear busiest_stat::avg_load because
7251 * update_sd_pick_busiest() reads this before assignment.
7253 *sds
= (struct sd_lb_stats
){
7256 .total_running
= 0UL,
7258 .total_capacity
= 0UL,
7261 .sum_nr_running
= 0,
7262 .group_type
= group_other
,
7268 * get_sd_load_idx - Obtain the load index for a given sched domain.
7269 * @sd: The sched_domain whose load_idx is to be obtained.
7270 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
7272 * Return: The load index.
7274 static inline int get_sd_load_idx(struct sched_domain
*sd
,
7275 enum cpu_idle_type idle
)
7281 load_idx
= sd
->busy_idx
;
7284 case CPU_NEWLY_IDLE
:
7285 load_idx
= sd
->newidle_idx
;
7288 load_idx
= sd
->idle_idx
;
7295 static unsigned long scale_rt_capacity(int cpu
)
7297 struct rq
*rq
= cpu_rq(cpu
);
7298 u64 total
, used
, age_stamp
, avg
;
7302 * Since we're reading these variables without serialization make sure
7303 * we read them once before doing sanity checks on them.
7305 age_stamp
= READ_ONCE(rq
->age_stamp
);
7306 avg
= READ_ONCE(rq
->rt_avg
);
7307 delta
= __rq_clock_broken(rq
) - age_stamp
;
7309 if (unlikely(delta
< 0))
7312 total
= sched_avg_period() + delta
;
7314 used
= div_u64(avg
, total
);
7316 if (likely(used
< SCHED_CAPACITY_SCALE
))
7317 return SCHED_CAPACITY_SCALE
- used
;
7322 static void update_cpu_capacity(struct sched_domain
*sd
, int cpu
)
7324 unsigned long capacity
= arch_scale_cpu_capacity(sd
, cpu
);
7325 struct sched_group
*sdg
= sd
->groups
;
7327 cpu_rq(cpu
)->cpu_capacity_orig
= capacity
;
7329 capacity
*= scale_rt_capacity(cpu
);
7330 capacity
>>= SCHED_CAPACITY_SHIFT
;
7335 cpu_rq(cpu
)->cpu_capacity
= capacity
;
7336 sdg
->sgc
->capacity
= capacity
;
7337 sdg
->sgc
->min_capacity
= capacity
;
7340 void update_group_capacity(struct sched_domain
*sd
, int cpu
)
7342 struct sched_domain
*child
= sd
->child
;
7343 struct sched_group
*group
, *sdg
= sd
->groups
;
7344 unsigned long capacity
, min_capacity
;
7345 unsigned long interval
;
7347 interval
= msecs_to_jiffies(sd
->balance_interval
);
7348 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
7349 sdg
->sgc
->next_update
= jiffies
+ interval
;
7352 update_cpu_capacity(sd
, cpu
);
7357 min_capacity
= ULONG_MAX
;
7359 if (child
->flags
& SD_OVERLAP
) {
7361 * SD_OVERLAP domains cannot assume that child groups
7362 * span the current group.
7365 for_each_cpu(cpu
, sched_group_span(sdg
)) {
7366 struct sched_group_capacity
*sgc
;
7367 struct rq
*rq
= cpu_rq(cpu
);
7370 * build_sched_domains() -> init_sched_groups_capacity()
7371 * gets here before we've attached the domains to the
7374 * Use capacity_of(), which is set irrespective of domains
7375 * in update_cpu_capacity().
7377 * This avoids capacity from being 0 and
7378 * causing divide-by-zero issues on boot.
7380 if (unlikely(!rq
->sd
)) {
7381 capacity
+= capacity_of(cpu
);
7383 sgc
= rq
->sd
->groups
->sgc
;
7384 capacity
+= sgc
->capacity
;
7387 min_capacity
= min(capacity
, min_capacity
);
7391 * !SD_OVERLAP domains can assume that child groups
7392 * span the current group.
7395 group
= child
->groups
;
7397 struct sched_group_capacity
*sgc
= group
->sgc
;
7399 capacity
+= sgc
->capacity
;
7400 min_capacity
= min(sgc
->min_capacity
, min_capacity
);
7401 group
= group
->next
;
7402 } while (group
!= child
->groups
);
7405 sdg
->sgc
->capacity
= capacity
;
7406 sdg
->sgc
->min_capacity
= min_capacity
;
7410 * Check whether the capacity of the rq has been noticeably reduced by side
7411 * activity. The imbalance_pct is used for the threshold.
7412 * Return true is the capacity is reduced
7415 check_cpu_capacity(struct rq
*rq
, struct sched_domain
*sd
)
7417 return ((rq
->cpu_capacity
* sd
->imbalance_pct
) <
7418 (rq
->cpu_capacity_orig
* 100));
7422 * Group imbalance indicates (and tries to solve) the problem where balancing
7423 * groups is inadequate due to ->cpus_allowed constraints.
7425 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
7426 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
7429 * { 0 1 2 3 } { 4 5 6 7 }
7432 * If we were to balance group-wise we'd place two tasks in the first group and
7433 * two tasks in the second group. Clearly this is undesired as it will overload
7434 * cpu 3 and leave one of the cpus in the second group unused.
7436 * The current solution to this issue is detecting the skew in the first group
7437 * by noticing the lower domain failed to reach balance and had difficulty
7438 * moving tasks due to affinity constraints.
7440 * When this is so detected; this group becomes a candidate for busiest; see
7441 * update_sd_pick_busiest(). And calculate_imbalance() and
7442 * find_busiest_group() avoid some of the usual balance conditions to allow it
7443 * to create an effective group imbalance.
7445 * This is a somewhat tricky proposition since the next run might not find the
7446 * group imbalance and decide the groups need to be balanced again. A most
7447 * subtle and fragile situation.
7450 static inline int sg_imbalanced(struct sched_group
*group
)
7452 return group
->sgc
->imbalance
;
7456 * group_has_capacity returns true if the group has spare capacity that could
7457 * be used by some tasks.
7458 * We consider that a group has spare capacity if the * number of task is
7459 * smaller than the number of CPUs or if the utilization is lower than the
7460 * available capacity for CFS tasks.
7461 * For the latter, we use a threshold to stabilize the state, to take into
7462 * account the variance of the tasks' load and to return true if the available
7463 * capacity in meaningful for the load balancer.
7464 * As an example, an available capacity of 1% can appear but it doesn't make
7465 * any benefit for the load balance.
7468 group_has_capacity(struct lb_env
*env
, struct sg_lb_stats
*sgs
)
7470 if (sgs
->sum_nr_running
< sgs
->group_weight
)
7473 if ((sgs
->group_capacity
* 100) >
7474 (sgs
->group_util
* env
->sd
->imbalance_pct
))
7481 * group_is_overloaded returns true if the group has more tasks than it can
7483 * group_is_overloaded is not equals to !group_has_capacity because a group
7484 * with the exact right number of tasks, has no more spare capacity but is not
7485 * overloaded so both group_has_capacity and group_is_overloaded return
7489 group_is_overloaded(struct lb_env
*env
, struct sg_lb_stats
*sgs
)
7491 if (sgs
->sum_nr_running
<= sgs
->group_weight
)
7494 if ((sgs
->group_capacity
* 100) <
7495 (sgs
->group_util
* env
->sd
->imbalance_pct
))
7502 * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller
7503 * per-CPU capacity than sched_group ref.
7506 group_smaller_cpu_capacity(struct sched_group
*sg
, struct sched_group
*ref
)
7508 return sg
->sgc
->min_capacity
* capacity_margin
<
7509 ref
->sgc
->min_capacity
* 1024;
7513 group_type
group_classify(struct sched_group
*group
,
7514 struct sg_lb_stats
*sgs
)
7516 if (sgs
->group_no_capacity
)
7517 return group_overloaded
;
7519 if (sg_imbalanced(group
))
7520 return group_imbalanced
;
7526 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
7527 * @env: The load balancing environment.
7528 * @group: sched_group whose statistics are to be updated.
7529 * @load_idx: Load index of sched_domain of this_cpu for load calc.
7530 * @local_group: Does group contain this_cpu.
7531 * @sgs: variable to hold the statistics for this group.
7532 * @overload: Indicate more than one runnable task for any CPU.
7534 static inline void update_sg_lb_stats(struct lb_env
*env
,
7535 struct sched_group
*group
, int load_idx
,
7536 int local_group
, struct sg_lb_stats
*sgs
,
7542 memset(sgs
, 0, sizeof(*sgs
));
7544 for_each_cpu_and(i
, sched_group_span(group
), env
->cpus
) {
7545 struct rq
*rq
= cpu_rq(i
);
7547 /* Bias balancing toward cpus of our domain */
7549 load
= target_load(i
, load_idx
);
7551 load
= source_load(i
, load_idx
);
7553 sgs
->group_load
+= load
;
7554 sgs
->group_util
+= cpu_util(i
);
7555 sgs
->sum_nr_running
+= rq
->cfs
.h_nr_running
;
7557 nr_running
= rq
->nr_running
;
7561 #ifdef CONFIG_NUMA_BALANCING
7562 sgs
->nr_numa_running
+= rq
->nr_numa_running
;
7563 sgs
->nr_preferred_running
+= rq
->nr_preferred_running
;
7565 sgs
->sum_weighted_load
+= weighted_cpuload(rq
);
7567 * No need to call idle_cpu() if nr_running is not 0
7569 if (!nr_running
&& idle_cpu(i
))
7573 /* Adjust by relative CPU capacity of the group */
7574 sgs
->group_capacity
= group
->sgc
->capacity
;
7575 sgs
->avg_load
= (sgs
->group_load
*SCHED_CAPACITY_SCALE
) / sgs
->group_capacity
;
7577 if (sgs
->sum_nr_running
)
7578 sgs
->load_per_task
= sgs
->sum_weighted_load
/ sgs
->sum_nr_running
;
7580 sgs
->group_weight
= group
->group_weight
;
7582 sgs
->group_no_capacity
= group_is_overloaded(env
, sgs
);
7583 sgs
->group_type
= group_classify(group
, sgs
);
7587 * update_sd_pick_busiest - return 1 on busiest group
7588 * @env: The load balancing environment.
7589 * @sds: sched_domain statistics
7590 * @sg: sched_group candidate to be checked for being the busiest
7591 * @sgs: sched_group statistics
7593 * Determine if @sg is a busier group than the previously selected
7596 * Return: %true if @sg is a busier group than the previously selected
7597 * busiest group. %false otherwise.
7599 static bool update_sd_pick_busiest(struct lb_env
*env
,
7600 struct sd_lb_stats
*sds
,
7601 struct sched_group
*sg
,
7602 struct sg_lb_stats
*sgs
)
7604 struct sg_lb_stats
*busiest
= &sds
->busiest_stat
;
7606 if (sgs
->group_type
> busiest
->group_type
)
7609 if (sgs
->group_type
< busiest
->group_type
)
7612 if (sgs
->avg_load
<= busiest
->avg_load
)
7615 if (!(env
->sd
->flags
& SD_ASYM_CPUCAPACITY
))
7619 * Candidate sg has no more than one task per CPU and
7620 * has higher per-CPU capacity. Migrating tasks to less
7621 * capable CPUs may harm throughput. Maximize throughput,
7622 * power/energy consequences are not considered.
7624 if (sgs
->sum_nr_running
<= sgs
->group_weight
&&
7625 group_smaller_cpu_capacity(sds
->local
, sg
))
7629 /* This is the busiest node in its class. */
7630 if (!(env
->sd
->flags
& SD_ASYM_PACKING
))
7633 /* No ASYM_PACKING if target cpu is already busy */
7634 if (env
->idle
== CPU_NOT_IDLE
)
7637 * ASYM_PACKING needs to move all the work to the highest
7638 * prority CPUs in the group, therefore mark all groups
7639 * of lower priority than ourself as busy.
7641 if (sgs
->sum_nr_running
&&
7642 sched_asym_prefer(env
->dst_cpu
, sg
->asym_prefer_cpu
)) {
7646 /* Prefer to move from lowest priority cpu's work */
7647 if (sched_asym_prefer(sds
->busiest
->asym_prefer_cpu
,
7648 sg
->asym_prefer_cpu
))
7655 #ifdef CONFIG_NUMA_BALANCING
7656 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
7658 if (sgs
->sum_nr_running
> sgs
->nr_numa_running
)
7660 if (sgs
->sum_nr_running
> sgs
->nr_preferred_running
)
7665 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
7667 if (rq
->nr_running
> rq
->nr_numa_running
)
7669 if (rq
->nr_running
> rq
->nr_preferred_running
)
7674 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
7679 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
7683 #endif /* CONFIG_NUMA_BALANCING */
7686 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
7687 * @env: The load balancing environment.
7688 * @sds: variable to hold the statistics for this sched_domain.
7690 static inline void update_sd_lb_stats(struct lb_env
*env
, struct sd_lb_stats
*sds
)
7692 struct sched_domain_shared
*shared
= env
->sd
->shared
;
7693 struct sched_domain
*child
= env
->sd
->child
;
7694 struct sched_group
*sg
= env
->sd
->groups
;
7695 struct sg_lb_stats
*local
= &sds
->local_stat
;
7696 struct sg_lb_stats tmp_sgs
;
7697 int load_idx
, prefer_sibling
= 0;
7698 bool overload
= false;
7700 if (child
&& child
->flags
& SD_PREFER_SIBLING
)
7703 load_idx
= get_sd_load_idx(env
->sd
, env
->idle
);
7706 struct sg_lb_stats
*sgs
= &tmp_sgs
;
7709 local_group
= cpumask_test_cpu(env
->dst_cpu
, sched_group_span(sg
));
7714 if (env
->idle
!= CPU_NEWLY_IDLE
||
7715 time_after_eq(jiffies
, sg
->sgc
->next_update
))
7716 update_group_capacity(env
->sd
, env
->dst_cpu
);
7719 update_sg_lb_stats(env
, sg
, load_idx
, local_group
, sgs
,
7726 * In case the child domain prefers tasks go to siblings
7727 * first, lower the sg capacity so that we'll try
7728 * and move all the excess tasks away. We lower the capacity
7729 * of a group only if the local group has the capacity to fit
7730 * these excess tasks. The extra check prevents the case where
7731 * you always pull from the heaviest group when it is already
7732 * under-utilized (possible with a large weight task outweighs
7733 * the tasks on the system).
7735 if (prefer_sibling
&& sds
->local
&&
7736 group_has_capacity(env
, local
) &&
7737 (sgs
->sum_nr_running
> local
->sum_nr_running
+ 1)) {
7738 sgs
->group_no_capacity
= 1;
7739 sgs
->group_type
= group_classify(sg
, sgs
);
7742 if (update_sd_pick_busiest(env
, sds
, sg
, sgs
)) {
7744 sds
->busiest_stat
= *sgs
;
7748 /* Now, start updating sd_lb_stats */
7749 sds
->total_running
+= sgs
->sum_nr_running
;
7750 sds
->total_load
+= sgs
->group_load
;
7751 sds
->total_capacity
+= sgs
->group_capacity
;
7754 } while (sg
!= env
->sd
->groups
);
7756 if (env
->sd
->flags
& SD_NUMA
)
7757 env
->fbq_type
= fbq_classify_group(&sds
->busiest_stat
);
7759 if (!env
->sd
->parent
) {
7760 /* update overload indicator if we are at root domain */
7761 if (env
->dst_rq
->rd
->overload
!= overload
)
7762 env
->dst_rq
->rd
->overload
= overload
;
7769 * Since these are sums over groups they can contain some CPUs
7770 * multiple times for the NUMA domains.
7772 * Currently only wake_affine_llc() and find_busiest_group()
7773 * uses these numbers, only the last is affected by this problem.
7777 WRITE_ONCE(shared
->nr_running
, sds
->total_running
);
7778 WRITE_ONCE(shared
->load
, sds
->total_load
);
7779 WRITE_ONCE(shared
->capacity
, sds
->total_capacity
);
7783 * check_asym_packing - Check to see if the group is packed into the
7786 * This is primarily intended to used at the sibling level. Some
7787 * cores like POWER7 prefer to use lower numbered SMT threads. In the
7788 * case of POWER7, it can move to lower SMT modes only when higher
7789 * threads are idle. When in lower SMT modes, the threads will
7790 * perform better since they share less core resources. Hence when we
7791 * have idle threads, we want them to be the higher ones.
7793 * This packing function is run on idle threads. It checks to see if
7794 * the busiest CPU in this domain (core in the P7 case) has a higher
7795 * CPU number than the packing function is being run on. Here we are
7796 * assuming lower CPU number will be equivalent to lower a SMT thread
7799 * Return: 1 when packing is required and a task should be moved to
7800 * this CPU. The amount of the imbalance is returned in env->imbalance.
7802 * @env: The load balancing environment.
7803 * @sds: Statistics of the sched_domain which is to be packed
7805 static int check_asym_packing(struct lb_env
*env
, struct sd_lb_stats
*sds
)
7809 if (!(env
->sd
->flags
& SD_ASYM_PACKING
))
7812 if (env
->idle
== CPU_NOT_IDLE
)
7818 busiest_cpu
= sds
->busiest
->asym_prefer_cpu
;
7819 if (sched_asym_prefer(busiest_cpu
, env
->dst_cpu
))
7822 env
->imbalance
= DIV_ROUND_CLOSEST(
7823 sds
->busiest_stat
.avg_load
* sds
->busiest_stat
.group_capacity
,
7824 SCHED_CAPACITY_SCALE
);
7830 * fix_small_imbalance - Calculate the minor imbalance that exists
7831 * amongst the groups of a sched_domain, during
7833 * @env: The load balancing environment.
7834 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
7837 void fix_small_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
7839 unsigned long tmp
, capa_now
= 0, capa_move
= 0;
7840 unsigned int imbn
= 2;
7841 unsigned long scaled_busy_load_per_task
;
7842 struct sg_lb_stats
*local
, *busiest
;
7844 local
= &sds
->local_stat
;
7845 busiest
= &sds
->busiest_stat
;
7847 if (!local
->sum_nr_running
)
7848 local
->load_per_task
= cpu_avg_load_per_task(env
->dst_cpu
);
7849 else if (busiest
->load_per_task
> local
->load_per_task
)
7852 scaled_busy_load_per_task
=
7853 (busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) /
7854 busiest
->group_capacity
;
7856 if (busiest
->avg_load
+ scaled_busy_load_per_task
>=
7857 local
->avg_load
+ (scaled_busy_load_per_task
* imbn
)) {
7858 env
->imbalance
= busiest
->load_per_task
;
7863 * OK, we don't have enough imbalance to justify moving tasks,
7864 * however we may be able to increase total CPU capacity used by
7868 capa_now
+= busiest
->group_capacity
*
7869 min(busiest
->load_per_task
, busiest
->avg_load
);
7870 capa_now
+= local
->group_capacity
*
7871 min(local
->load_per_task
, local
->avg_load
);
7872 capa_now
/= SCHED_CAPACITY_SCALE
;
7874 /* Amount of load we'd subtract */
7875 if (busiest
->avg_load
> scaled_busy_load_per_task
) {
7876 capa_move
+= busiest
->group_capacity
*
7877 min(busiest
->load_per_task
,
7878 busiest
->avg_load
- scaled_busy_load_per_task
);
7881 /* Amount of load we'd add */
7882 if (busiest
->avg_load
* busiest
->group_capacity
<
7883 busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) {
7884 tmp
= (busiest
->avg_load
* busiest
->group_capacity
) /
7885 local
->group_capacity
;
7887 tmp
= (busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) /
7888 local
->group_capacity
;
7890 capa_move
+= local
->group_capacity
*
7891 min(local
->load_per_task
, local
->avg_load
+ tmp
);
7892 capa_move
/= SCHED_CAPACITY_SCALE
;
7894 /* Move if we gain throughput */
7895 if (capa_move
> capa_now
)
7896 env
->imbalance
= busiest
->load_per_task
;
7900 * calculate_imbalance - Calculate the amount of imbalance present within the
7901 * groups of a given sched_domain during load balance.
7902 * @env: load balance environment
7903 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
7905 static inline void calculate_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
7907 unsigned long max_pull
, load_above_capacity
= ~0UL;
7908 struct sg_lb_stats
*local
, *busiest
;
7910 local
= &sds
->local_stat
;
7911 busiest
= &sds
->busiest_stat
;
7913 if (busiest
->group_type
== group_imbalanced
) {
7915 * In the group_imb case we cannot rely on group-wide averages
7916 * to ensure cpu-load equilibrium, look at wider averages. XXX
7918 busiest
->load_per_task
=
7919 min(busiest
->load_per_task
, sds
->avg_load
);
7923 * Avg load of busiest sg can be less and avg load of local sg can
7924 * be greater than avg load across all sgs of sd because avg load
7925 * factors in sg capacity and sgs with smaller group_type are
7926 * skipped when updating the busiest sg:
7928 if (busiest
->avg_load
<= sds
->avg_load
||
7929 local
->avg_load
>= sds
->avg_load
) {
7931 return fix_small_imbalance(env
, sds
);
7935 * If there aren't any idle cpus, avoid creating some.
7937 if (busiest
->group_type
== group_overloaded
&&
7938 local
->group_type
== group_overloaded
) {
7939 load_above_capacity
= busiest
->sum_nr_running
* SCHED_CAPACITY_SCALE
;
7940 if (load_above_capacity
> busiest
->group_capacity
) {
7941 load_above_capacity
-= busiest
->group_capacity
;
7942 load_above_capacity
*= scale_load_down(NICE_0_LOAD
);
7943 load_above_capacity
/= busiest
->group_capacity
;
7945 load_above_capacity
= ~0UL;
7949 * We're trying to get all the cpus to the average_load, so we don't
7950 * want to push ourselves above the average load, nor do we wish to
7951 * reduce the max loaded cpu below the average load. At the same time,
7952 * we also don't want to reduce the group load below the group
7953 * capacity. Thus we look for the minimum possible imbalance.
7955 max_pull
= min(busiest
->avg_load
- sds
->avg_load
, load_above_capacity
);
7957 /* How much load to actually move to equalise the imbalance */
7958 env
->imbalance
= min(
7959 max_pull
* busiest
->group_capacity
,
7960 (sds
->avg_load
- local
->avg_load
) * local
->group_capacity
7961 ) / SCHED_CAPACITY_SCALE
;
7964 * if *imbalance is less than the average load per runnable task
7965 * there is no guarantee that any tasks will be moved so we'll have
7966 * a think about bumping its value to force at least one task to be
7969 if (env
->imbalance
< busiest
->load_per_task
)
7970 return fix_small_imbalance(env
, sds
);
7973 /******* find_busiest_group() helpers end here *********************/
7976 * find_busiest_group - Returns the busiest group within the sched_domain
7977 * if there is an imbalance.
7979 * Also calculates the amount of weighted load which should be moved
7980 * to restore balance.
7982 * @env: The load balancing environment.
7984 * Return: - The busiest group if imbalance exists.
7986 static struct sched_group
*find_busiest_group(struct lb_env
*env
)
7988 struct sg_lb_stats
*local
, *busiest
;
7989 struct sd_lb_stats sds
;
7991 init_sd_lb_stats(&sds
);
7994 * Compute the various statistics relavent for load balancing at
7997 update_sd_lb_stats(env
, &sds
);
7998 local
= &sds
.local_stat
;
7999 busiest
= &sds
.busiest_stat
;
8001 /* ASYM feature bypasses nice load balance check */
8002 if (check_asym_packing(env
, &sds
))
8005 /* There is no busy sibling group to pull tasks from */
8006 if (!sds
.busiest
|| busiest
->sum_nr_running
== 0)
8009 /* XXX broken for overlapping NUMA groups */
8010 sds
.avg_load
= (SCHED_CAPACITY_SCALE
* sds
.total_load
)
8011 / sds
.total_capacity
;
8014 * If the busiest group is imbalanced the below checks don't
8015 * work because they assume all things are equal, which typically
8016 * isn't true due to cpus_allowed constraints and the like.
8018 if (busiest
->group_type
== group_imbalanced
)
8021 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
8022 if (env
->idle
== CPU_NEWLY_IDLE
&& group_has_capacity(env
, local
) &&
8023 busiest
->group_no_capacity
)
8027 * If the local group is busier than the selected busiest group
8028 * don't try and pull any tasks.
8030 if (local
->avg_load
>= busiest
->avg_load
)
8034 * Don't pull any tasks if this group is already above the domain
8037 if (local
->avg_load
>= sds
.avg_load
)
8040 if (env
->idle
== CPU_IDLE
) {
8042 * This cpu is idle. If the busiest group is not overloaded
8043 * and there is no imbalance between this and busiest group
8044 * wrt idle cpus, it is balanced. The imbalance becomes
8045 * significant if the diff is greater than 1 otherwise we
8046 * might end up to just move the imbalance on another group
8048 if ((busiest
->group_type
!= group_overloaded
) &&
8049 (local
->idle_cpus
<= (busiest
->idle_cpus
+ 1)))
8053 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
8054 * imbalance_pct to be conservative.
8056 if (100 * busiest
->avg_load
<=
8057 env
->sd
->imbalance_pct
* local
->avg_load
)
8062 /* Looks like there is an imbalance. Compute it */
8063 calculate_imbalance(env
, &sds
);
8072 * find_busiest_queue - find the busiest runqueue among the cpus in group.
8074 static struct rq
*find_busiest_queue(struct lb_env
*env
,
8075 struct sched_group
*group
)
8077 struct rq
*busiest
= NULL
, *rq
;
8078 unsigned long busiest_load
= 0, busiest_capacity
= 1;
8081 for_each_cpu_and(i
, sched_group_span(group
), env
->cpus
) {
8082 unsigned long capacity
, wl
;
8086 rt
= fbq_classify_rq(rq
);
8089 * We classify groups/runqueues into three groups:
8090 * - regular: there are !numa tasks
8091 * - remote: there are numa tasks that run on the 'wrong' node
8092 * - all: there is no distinction
8094 * In order to avoid migrating ideally placed numa tasks,
8095 * ignore those when there's better options.
8097 * If we ignore the actual busiest queue to migrate another
8098 * task, the next balance pass can still reduce the busiest
8099 * queue by moving tasks around inside the node.
8101 * If we cannot move enough load due to this classification
8102 * the next pass will adjust the group classification and
8103 * allow migration of more tasks.
8105 * Both cases only affect the total convergence complexity.
8107 if (rt
> env
->fbq_type
)
8110 capacity
= capacity_of(i
);
8112 wl
= weighted_cpuload(rq
);
8115 * When comparing with imbalance, use weighted_cpuload()
8116 * which is not scaled with the cpu capacity.
8119 if (rq
->nr_running
== 1 && wl
> env
->imbalance
&&
8120 !check_cpu_capacity(rq
, env
->sd
))
8124 * For the load comparisons with the other cpu's, consider
8125 * the weighted_cpuload() scaled with the cpu capacity, so
8126 * that the load can be moved away from the cpu that is
8127 * potentially running at a lower capacity.
8129 * Thus we're looking for max(wl_i / capacity_i), crosswise
8130 * multiplication to rid ourselves of the division works out
8131 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
8132 * our previous maximum.
8134 if (wl
* busiest_capacity
> busiest_load
* capacity
) {
8136 busiest_capacity
= capacity
;
8145 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
8146 * so long as it is large enough.
8148 #define MAX_PINNED_INTERVAL 512
8150 static int need_active_balance(struct lb_env
*env
)
8152 struct sched_domain
*sd
= env
->sd
;
8154 if (env
->idle
== CPU_NEWLY_IDLE
) {
8157 * ASYM_PACKING needs to force migrate tasks from busy but
8158 * lower priority CPUs in order to pack all tasks in the
8159 * highest priority CPUs.
8161 if ((sd
->flags
& SD_ASYM_PACKING
) &&
8162 sched_asym_prefer(env
->dst_cpu
, env
->src_cpu
))
8167 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
8168 * It's worth migrating the task if the src_cpu's capacity is reduced
8169 * because of other sched_class or IRQs if more capacity stays
8170 * available on dst_cpu.
8172 if ((env
->idle
!= CPU_NOT_IDLE
) &&
8173 (env
->src_rq
->cfs
.h_nr_running
== 1)) {
8174 if ((check_cpu_capacity(env
->src_rq
, sd
)) &&
8175 (capacity_of(env
->src_cpu
)*sd
->imbalance_pct
< capacity_of(env
->dst_cpu
)*100))
8179 return unlikely(sd
->nr_balance_failed
> sd
->cache_nice_tries
+2);
8182 static int active_load_balance_cpu_stop(void *data
);
8184 static int should_we_balance(struct lb_env
*env
)
8186 struct sched_group
*sg
= env
->sd
->groups
;
8187 int cpu
, balance_cpu
= -1;
8190 * In the newly idle case, we will allow all the cpu's
8191 * to do the newly idle load balance.
8193 if (env
->idle
== CPU_NEWLY_IDLE
)
8196 /* Try to find first idle cpu */
8197 for_each_cpu_and(cpu
, group_balance_mask(sg
), env
->cpus
) {
8205 if (balance_cpu
== -1)
8206 balance_cpu
= group_balance_cpu(sg
);
8209 * First idle cpu or the first cpu(busiest) in this sched group
8210 * is eligible for doing load balancing at this and above domains.
8212 return balance_cpu
== env
->dst_cpu
;
8216 * Check this_cpu to ensure it is balanced within domain. Attempt to move
8217 * tasks if there is an imbalance.
8219 static int load_balance(int this_cpu
, struct rq
*this_rq
,
8220 struct sched_domain
*sd
, enum cpu_idle_type idle
,
8221 int *continue_balancing
)
8223 int ld_moved
, cur_ld_moved
, active_balance
= 0;
8224 struct sched_domain
*sd_parent
= sd
->parent
;
8225 struct sched_group
*group
;
8228 struct cpumask
*cpus
= this_cpu_cpumask_var_ptr(load_balance_mask
);
8230 struct lb_env env
= {
8232 .dst_cpu
= this_cpu
,
8234 .dst_grpmask
= sched_group_span(sd
->groups
),
8236 .loop_break
= sched_nr_migrate_break
,
8239 .tasks
= LIST_HEAD_INIT(env
.tasks
),
8242 cpumask_and(cpus
, sched_domain_span(sd
), cpu_active_mask
);
8244 schedstat_inc(sd
->lb_count
[idle
]);
8247 if (!should_we_balance(&env
)) {
8248 *continue_balancing
= 0;
8252 group
= find_busiest_group(&env
);
8254 schedstat_inc(sd
->lb_nobusyg
[idle
]);
8258 busiest
= find_busiest_queue(&env
, group
);
8260 schedstat_inc(sd
->lb_nobusyq
[idle
]);
8264 BUG_ON(busiest
== env
.dst_rq
);
8266 schedstat_add(sd
->lb_imbalance
[idle
], env
.imbalance
);
8268 env
.src_cpu
= busiest
->cpu
;
8269 env
.src_rq
= busiest
;
8272 if (busiest
->nr_running
> 1) {
8274 * Attempt to move tasks. If find_busiest_group has found
8275 * an imbalance but busiest->nr_running <= 1, the group is
8276 * still unbalanced. ld_moved simply stays zero, so it is
8277 * correctly treated as an imbalance.
8279 env
.flags
|= LBF_ALL_PINNED
;
8280 env
.loop_max
= min(sysctl_sched_nr_migrate
, busiest
->nr_running
);
8283 rq_lock_irqsave(busiest
, &rf
);
8284 update_rq_clock(busiest
);
8287 * cur_ld_moved - load moved in current iteration
8288 * ld_moved - cumulative load moved across iterations
8290 cur_ld_moved
= detach_tasks(&env
);
8293 * We've detached some tasks from busiest_rq. Every
8294 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
8295 * unlock busiest->lock, and we are able to be sure
8296 * that nobody can manipulate the tasks in parallel.
8297 * See task_rq_lock() family for the details.
8300 rq_unlock(busiest
, &rf
);
8304 ld_moved
+= cur_ld_moved
;
8307 local_irq_restore(rf
.flags
);
8309 if (env
.flags
& LBF_NEED_BREAK
) {
8310 env
.flags
&= ~LBF_NEED_BREAK
;
8315 * Revisit (affine) tasks on src_cpu that couldn't be moved to
8316 * us and move them to an alternate dst_cpu in our sched_group
8317 * where they can run. The upper limit on how many times we
8318 * iterate on same src_cpu is dependent on number of cpus in our
8321 * This changes load balance semantics a bit on who can move
8322 * load to a given_cpu. In addition to the given_cpu itself
8323 * (or a ilb_cpu acting on its behalf where given_cpu is
8324 * nohz-idle), we now have balance_cpu in a position to move
8325 * load to given_cpu. In rare situations, this may cause
8326 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
8327 * _independently_ and at _same_ time to move some load to
8328 * given_cpu) causing exceess load to be moved to given_cpu.
8329 * This however should not happen so much in practice and
8330 * moreover subsequent load balance cycles should correct the
8331 * excess load moved.
8333 if ((env
.flags
& LBF_DST_PINNED
) && env
.imbalance
> 0) {
8335 /* Prevent to re-select dst_cpu via env's cpus */
8336 cpumask_clear_cpu(env
.dst_cpu
, env
.cpus
);
8338 env
.dst_rq
= cpu_rq(env
.new_dst_cpu
);
8339 env
.dst_cpu
= env
.new_dst_cpu
;
8340 env
.flags
&= ~LBF_DST_PINNED
;
8342 env
.loop_break
= sched_nr_migrate_break
;
8345 * Go back to "more_balance" rather than "redo" since we
8346 * need to continue with same src_cpu.
8352 * We failed to reach balance because of affinity.
8355 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
8357 if ((env
.flags
& LBF_SOME_PINNED
) && env
.imbalance
> 0)
8358 *group_imbalance
= 1;
8361 /* All tasks on this runqueue were pinned by CPU affinity */
8362 if (unlikely(env
.flags
& LBF_ALL_PINNED
)) {
8363 cpumask_clear_cpu(cpu_of(busiest
), cpus
);
8365 * Attempting to continue load balancing at the current
8366 * sched_domain level only makes sense if there are
8367 * active CPUs remaining as possible busiest CPUs to
8368 * pull load from which are not contained within the
8369 * destination group that is receiving any migrated
8372 if (!cpumask_subset(cpus
, env
.dst_grpmask
)) {
8374 env
.loop_break
= sched_nr_migrate_break
;
8377 goto out_all_pinned
;
8382 schedstat_inc(sd
->lb_failed
[idle
]);
8384 * Increment the failure counter only on periodic balance.
8385 * We do not want newidle balance, which can be very
8386 * frequent, pollute the failure counter causing
8387 * excessive cache_hot migrations and active balances.
8389 if (idle
!= CPU_NEWLY_IDLE
)
8390 sd
->nr_balance_failed
++;
8392 if (need_active_balance(&env
)) {
8393 unsigned long flags
;
8395 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
8397 /* don't kick the active_load_balance_cpu_stop,
8398 * if the curr task on busiest cpu can't be
8401 if (!cpumask_test_cpu(this_cpu
, &busiest
->curr
->cpus_allowed
)) {
8402 raw_spin_unlock_irqrestore(&busiest
->lock
,
8404 env
.flags
|= LBF_ALL_PINNED
;
8405 goto out_one_pinned
;
8409 * ->active_balance synchronizes accesses to
8410 * ->active_balance_work. Once set, it's cleared
8411 * only after active load balance is finished.
8413 if (!busiest
->active_balance
) {
8414 busiest
->active_balance
= 1;
8415 busiest
->push_cpu
= this_cpu
;
8418 raw_spin_unlock_irqrestore(&busiest
->lock
, flags
);
8420 if (active_balance
) {
8421 stop_one_cpu_nowait(cpu_of(busiest
),
8422 active_load_balance_cpu_stop
, busiest
,
8423 &busiest
->active_balance_work
);
8426 /* We've kicked active balancing, force task migration. */
8427 sd
->nr_balance_failed
= sd
->cache_nice_tries
+1;
8430 sd
->nr_balance_failed
= 0;
8432 if (likely(!active_balance
)) {
8433 /* We were unbalanced, so reset the balancing interval */
8434 sd
->balance_interval
= sd
->min_interval
;
8437 * If we've begun active balancing, start to back off. This
8438 * case may not be covered by the all_pinned logic if there
8439 * is only 1 task on the busy runqueue (because we don't call
8442 if (sd
->balance_interval
< sd
->max_interval
)
8443 sd
->balance_interval
*= 2;
8450 * We reach balance although we may have faced some affinity
8451 * constraints. Clear the imbalance flag if it was set.
8454 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
8456 if (*group_imbalance
)
8457 *group_imbalance
= 0;
8462 * We reach balance because all tasks are pinned at this level so
8463 * we can't migrate them. Let the imbalance flag set so parent level
8464 * can try to migrate them.
8466 schedstat_inc(sd
->lb_balanced
[idle
]);
8468 sd
->nr_balance_failed
= 0;
8471 /* tune up the balancing interval */
8472 if (((env
.flags
& LBF_ALL_PINNED
) &&
8473 sd
->balance_interval
< MAX_PINNED_INTERVAL
) ||
8474 (sd
->balance_interval
< sd
->max_interval
))
8475 sd
->balance_interval
*= 2;
8482 static inline unsigned long
8483 get_sd_balance_interval(struct sched_domain
*sd
, int cpu_busy
)
8485 unsigned long interval
= sd
->balance_interval
;
8488 interval
*= sd
->busy_factor
;
8490 /* scale ms to jiffies */
8491 interval
= msecs_to_jiffies(interval
);
8492 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
8498 update_next_balance(struct sched_domain
*sd
, unsigned long *next_balance
)
8500 unsigned long interval
, next
;
8502 /* used by idle balance, so cpu_busy = 0 */
8503 interval
= get_sd_balance_interval(sd
, 0);
8504 next
= sd
->last_balance
+ interval
;
8506 if (time_after(*next_balance
, next
))
8507 *next_balance
= next
;
8511 * idle_balance is called by schedule() if this_cpu is about to become
8512 * idle. Attempts to pull tasks from other CPUs.
8514 static int idle_balance(struct rq
*this_rq
, struct rq_flags
*rf
)
8516 unsigned long next_balance
= jiffies
+ HZ
;
8517 int this_cpu
= this_rq
->cpu
;
8518 struct sched_domain
*sd
;
8519 int pulled_task
= 0;
8523 * We must set idle_stamp _before_ calling idle_balance(), such that we
8524 * measure the duration of idle_balance() as idle time.
8526 this_rq
->idle_stamp
= rq_clock(this_rq
);
8529 * Do not pull tasks towards !active CPUs...
8531 if (!cpu_active(this_cpu
))
8535 * This is OK, because current is on_cpu, which avoids it being picked
8536 * for load-balance and preemption/IRQs are still disabled avoiding
8537 * further scheduler activity on it and we're being very careful to
8538 * re-start the picking loop.
8540 rq_unpin_lock(this_rq
, rf
);
8542 if (this_rq
->avg_idle
< sysctl_sched_migration_cost
||
8543 !this_rq
->rd
->overload
) {
8545 sd
= rcu_dereference_check_sched_domain(this_rq
->sd
);
8547 update_next_balance(sd
, &next_balance
);
8553 raw_spin_unlock(&this_rq
->lock
);
8555 update_blocked_averages(this_cpu
);
8557 for_each_domain(this_cpu
, sd
) {
8558 int continue_balancing
= 1;
8559 u64 t0
, domain_cost
;
8561 if (!(sd
->flags
& SD_LOAD_BALANCE
))
8564 if (this_rq
->avg_idle
< curr_cost
+ sd
->max_newidle_lb_cost
) {
8565 update_next_balance(sd
, &next_balance
);
8569 if (sd
->flags
& SD_BALANCE_NEWIDLE
) {
8570 t0
= sched_clock_cpu(this_cpu
);
8572 pulled_task
= load_balance(this_cpu
, this_rq
,
8574 &continue_balancing
);
8576 domain_cost
= sched_clock_cpu(this_cpu
) - t0
;
8577 if (domain_cost
> sd
->max_newidle_lb_cost
)
8578 sd
->max_newidle_lb_cost
= domain_cost
;
8580 curr_cost
+= domain_cost
;
8583 update_next_balance(sd
, &next_balance
);
8586 * Stop searching for tasks to pull if there are
8587 * now runnable tasks on this rq.
8589 if (pulled_task
|| this_rq
->nr_running
> 0)
8594 raw_spin_lock(&this_rq
->lock
);
8596 if (curr_cost
> this_rq
->max_idle_balance_cost
)
8597 this_rq
->max_idle_balance_cost
= curr_cost
;
8600 * While browsing the domains, we released the rq lock, a task could
8601 * have been enqueued in the meantime. Since we're not going idle,
8602 * pretend we pulled a task.
8604 if (this_rq
->cfs
.h_nr_running
&& !pulled_task
)
8608 /* Move the next balance forward */
8609 if (time_after(this_rq
->next_balance
, next_balance
))
8610 this_rq
->next_balance
= next_balance
;
8612 /* Is there a task of a high priority class? */
8613 if (this_rq
->nr_running
!= this_rq
->cfs
.h_nr_running
)
8617 this_rq
->idle_stamp
= 0;
8619 rq_repin_lock(this_rq
, rf
);
8625 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
8626 * running tasks off the busiest CPU onto idle CPUs. It requires at
8627 * least 1 task to be running on each physical CPU where possible, and
8628 * avoids physical / logical imbalances.
8630 static int active_load_balance_cpu_stop(void *data
)
8632 struct rq
*busiest_rq
= data
;
8633 int busiest_cpu
= cpu_of(busiest_rq
);
8634 int target_cpu
= busiest_rq
->push_cpu
;
8635 struct rq
*target_rq
= cpu_rq(target_cpu
);
8636 struct sched_domain
*sd
;
8637 struct task_struct
*p
= NULL
;
8640 rq_lock_irq(busiest_rq
, &rf
);
8642 * Between queueing the stop-work and running it is a hole in which
8643 * CPUs can become inactive. We should not move tasks from or to
8646 if (!cpu_active(busiest_cpu
) || !cpu_active(target_cpu
))
8649 /* make sure the requested cpu hasn't gone down in the meantime */
8650 if (unlikely(busiest_cpu
!= smp_processor_id() ||
8651 !busiest_rq
->active_balance
))
8654 /* Is there any task to move? */
8655 if (busiest_rq
->nr_running
<= 1)
8659 * This condition is "impossible", if it occurs
8660 * we need to fix it. Originally reported by
8661 * Bjorn Helgaas on a 128-cpu setup.
8663 BUG_ON(busiest_rq
== target_rq
);
8665 /* Search for an sd spanning us and the target CPU. */
8667 for_each_domain(target_cpu
, sd
) {
8668 if ((sd
->flags
& SD_LOAD_BALANCE
) &&
8669 cpumask_test_cpu(busiest_cpu
, sched_domain_span(sd
)))
8674 struct lb_env env
= {
8676 .dst_cpu
= target_cpu
,
8677 .dst_rq
= target_rq
,
8678 .src_cpu
= busiest_rq
->cpu
,
8679 .src_rq
= busiest_rq
,
8682 * can_migrate_task() doesn't need to compute new_dst_cpu
8683 * for active balancing. Since we have CPU_IDLE, but no
8684 * @dst_grpmask we need to make that test go away with lying
8687 .flags
= LBF_DST_PINNED
,
8690 schedstat_inc(sd
->alb_count
);
8691 update_rq_clock(busiest_rq
);
8693 p
= detach_one_task(&env
);
8695 schedstat_inc(sd
->alb_pushed
);
8696 /* Active balancing done, reset the failure counter. */
8697 sd
->nr_balance_failed
= 0;
8699 schedstat_inc(sd
->alb_failed
);
8704 busiest_rq
->active_balance
= 0;
8705 rq_unlock(busiest_rq
, &rf
);
8708 attach_one_task(target_rq
, p
);
8715 static inline int on_null_domain(struct rq
*rq
)
8717 return unlikely(!rcu_dereference_sched(rq
->sd
));
8720 #ifdef CONFIG_NO_HZ_COMMON
8722 * idle load balancing details
8723 * - When one of the busy CPUs notice that there may be an idle rebalancing
8724 * needed, they will kick the idle load balancer, which then does idle
8725 * load balancing for all the idle CPUs.
8728 cpumask_var_t idle_cpus_mask
;
8730 unsigned long next_balance
; /* in jiffy units */
8731 } nohz ____cacheline_aligned
;
8733 static inline int find_new_ilb(void)
8735 int ilb
= cpumask_first(nohz
.idle_cpus_mask
);
8737 if (ilb
< nr_cpu_ids
&& idle_cpu(ilb
))
8744 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
8745 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
8746 * CPU (if there is one).
8748 static void nohz_balancer_kick(void)
8752 nohz
.next_balance
++;
8754 ilb_cpu
= find_new_ilb();
8756 if (ilb_cpu
>= nr_cpu_ids
)
8759 if (test_and_set_bit(NOHZ_BALANCE_KICK
, nohz_flags(ilb_cpu
)))
8762 * Use smp_send_reschedule() instead of resched_cpu().
8763 * This way we generate a sched IPI on the target cpu which
8764 * is idle. And the softirq performing nohz idle load balance
8765 * will be run before returning from the IPI.
8767 smp_send_reschedule(ilb_cpu
);
8771 void nohz_balance_exit_idle(unsigned int cpu
)
8773 if (unlikely(test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))) {
8775 * Completely isolated CPUs don't ever set, so we must test.
8777 if (likely(cpumask_test_cpu(cpu
, nohz
.idle_cpus_mask
))) {
8778 cpumask_clear_cpu(cpu
, nohz
.idle_cpus_mask
);
8779 atomic_dec(&nohz
.nr_cpus
);
8781 clear_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
8785 static inline void set_cpu_sd_state_busy(void)
8787 struct sched_domain
*sd
;
8788 int cpu
= smp_processor_id();
8791 sd
= rcu_dereference(per_cpu(sd_llc
, cpu
));
8793 if (!sd
|| !sd
->nohz_idle
)
8797 atomic_inc(&sd
->shared
->nr_busy_cpus
);
8802 void set_cpu_sd_state_idle(void)
8804 struct sched_domain
*sd
;
8805 int cpu
= smp_processor_id();
8808 sd
= rcu_dereference(per_cpu(sd_llc
, cpu
));
8810 if (!sd
|| sd
->nohz_idle
)
8814 atomic_dec(&sd
->shared
->nr_busy_cpus
);
8820 * This routine will record that the cpu is going idle with tick stopped.
8821 * This info will be used in performing idle load balancing in the future.
8823 void nohz_balance_enter_idle(int cpu
)
8826 * If this cpu is going down, then nothing needs to be done.
8828 if (!cpu_active(cpu
))
8831 /* Spare idle load balancing on CPUs that don't want to be disturbed: */
8832 if (!is_housekeeping_cpu(cpu
))
8835 if (test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))
8839 * If we're a completely isolated CPU, we don't play.
8841 if (on_null_domain(cpu_rq(cpu
)))
8844 cpumask_set_cpu(cpu
, nohz
.idle_cpus_mask
);
8845 atomic_inc(&nohz
.nr_cpus
);
8846 set_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
8850 static DEFINE_SPINLOCK(balancing
);
8853 * Scale the max load_balance interval with the number of CPUs in the system.
8854 * This trades load-balance latency on larger machines for less cross talk.
8856 void update_max_interval(void)
8858 max_load_balance_interval
= HZ
*num_online_cpus()/10;
8862 * It checks each scheduling domain to see if it is due to be balanced,
8863 * and initiates a balancing operation if so.
8865 * Balancing parameters are set up in init_sched_domains.
8867 static void rebalance_domains(struct rq
*rq
, enum cpu_idle_type idle
)
8869 int continue_balancing
= 1;
8871 unsigned long interval
;
8872 struct sched_domain
*sd
;
8873 /* Earliest time when we have to do rebalance again */
8874 unsigned long next_balance
= jiffies
+ 60*HZ
;
8875 int update_next_balance
= 0;
8876 int need_serialize
, need_decay
= 0;
8879 update_blocked_averages(cpu
);
8882 for_each_domain(cpu
, sd
) {
8884 * Decay the newidle max times here because this is a regular
8885 * visit to all the domains. Decay ~1% per second.
8887 if (time_after(jiffies
, sd
->next_decay_max_lb_cost
)) {
8888 sd
->max_newidle_lb_cost
=
8889 (sd
->max_newidle_lb_cost
* 253) / 256;
8890 sd
->next_decay_max_lb_cost
= jiffies
+ HZ
;
8893 max_cost
+= sd
->max_newidle_lb_cost
;
8895 if (!(sd
->flags
& SD_LOAD_BALANCE
))
8899 * Stop the load balance at this level. There is another
8900 * CPU in our sched group which is doing load balancing more
8903 if (!continue_balancing
) {
8909 interval
= get_sd_balance_interval(sd
, idle
!= CPU_IDLE
);
8911 need_serialize
= sd
->flags
& SD_SERIALIZE
;
8912 if (need_serialize
) {
8913 if (!spin_trylock(&balancing
))
8917 if (time_after_eq(jiffies
, sd
->last_balance
+ interval
)) {
8918 if (load_balance(cpu
, rq
, sd
, idle
, &continue_balancing
)) {
8920 * The LBF_DST_PINNED logic could have changed
8921 * env->dst_cpu, so we can't know our idle
8922 * state even if we migrated tasks. Update it.
8924 idle
= idle_cpu(cpu
) ? CPU_IDLE
: CPU_NOT_IDLE
;
8926 sd
->last_balance
= jiffies
;
8927 interval
= get_sd_balance_interval(sd
, idle
!= CPU_IDLE
);
8930 spin_unlock(&balancing
);
8932 if (time_after(next_balance
, sd
->last_balance
+ interval
)) {
8933 next_balance
= sd
->last_balance
+ interval
;
8934 update_next_balance
= 1;
8939 * Ensure the rq-wide value also decays but keep it at a
8940 * reasonable floor to avoid funnies with rq->avg_idle.
8942 rq
->max_idle_balance_cost
=
8943 max((u64
)sysctl_sched_migration_cost
, max_cost
);
8948 * next_balance will be updated only when there is a need.
8949 * When the cpu is attached to null domain for ex, it will not be
8952 if (likely(update_next_balance
)) {
8953 rq
->next_balance
= next_balance
;
8955 #ifdef CONFIG_NO_HZ_COMMON
8957 * If this CPU has been elected to perform the nohz idle
8958 * balance. Other idle CPUs have already rebalanced with
8959 * nohz_idle_balance() and nohz.next_balance has been
8960 * updated accordingly. This CPU is now running the idle load
8961 * balance for itself and we need to update the
8962 * nohz.next_balance accordingly.
8964 if ((idle
== CPU_IDLE
) && time_after(nohz
.next_balance
, rq
->next_balance
))
8965 nohz
.next_balance
= rq
->next_balance
;
8970 #ifdef CONFIG_NO_HZ_COMMON
8972 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8973 * rebalancing for all the cpus for whom scheduler ticks are stopped.
8975 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
)
8977 int this_cpu
= this_rq
->cpu
;
8980 /* Earliest time when we have to do rebalance again */
8981 unsigned long next_balance
= jiffies
+ 60*HZ
;
8982 int update_next_balance
= 0;
8984 if (idle
!= CPU_IDLE
||
8985 !test_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
)))
8988 for_each_cpu(balance_cpu
, nohz
.idle_cpus_mask
) {
8989 if (balance_cpu
== this_cpu
|| !idle_cpu(balance_cpu
))
8993 * If this cpu gets work to do, stop the load balancing
8994 * work being done for other cpus. Next load
8995 * balancing owner will pick it up.
9000 rq
= cpu_rq(balance_cpu
);
9003 * If time for next balance is due,
9006 if (time_after_eq(jiffies
, rq
->next_balance
)) {
9009 rq_lock_irq(rq
, &rf
);
9010 update_rq_clock(rq
);
9011 cpu_load_update_idle(rq
);
9012 rq_unlock_irq(rq
, &rf
);
9014 rebalance_domains(rq
, CPU_IDLE
);
9017 if (time_after(next_balance
, rq
->next_balance
)) {
9018 next_balance
= rq
->next_balance
;
9019 update_next_balance
= 1;
9024 * next_balance will be updated only when there is a need.
9025 * When the CPU is attached to null domain for ex, it will not be
9028 if (likely(update_next_balance
))
9029 nohz
.next_balance
= next_balance
;
9031 clear_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
));
9035 * Current heuristic for kicking the idle load balancer in the presence
9036 * of an idle cpu in the system.
9037 * - This rq has more than one task.
9038 * - This rq has at least one CFS task and the capacity of the CPU is
9039 * significantly reduced because of RT tasks or IRQs.
9040 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
9041 * multiple busy cpu.
9042 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
9043 * domain span are idle.
9045 static inline bool nohz_kick_needed(struct rq
*rq
)
9047 unsigned long now
= jiffies
;
9048 struct sched_domain_shared
*sds
;
9049 struct sched_domain
*sd
;
9050 int nr_busy
, i
, cpu
= rq
->cpu
;
9053 if (unlikely(rq
->idle_balance
))
9057 * We may be recently in ticked or tickless idle mode. At the first
9058 * busy tick after returning from idle, we will update the busy stats.
9060 set_cpu_sd_state_busy();
9061 nohz_balance_exit_idle(cpu
);
9064 * None are in tickless mode and hence no need for NOHZ idle load
9067 if (likely(!atomic_read(&nohz
.nr_cpus
)))
9070 if (time_before(now
, nohz
.next_balance
))
9073 if (rq
->nr_running
>= 2)
9077 sds
= rcu_dereference(per_cpu(sd_llc_shared
, cpu
));
9080 * XXX: write a coherent comment on why we do this.
9081 * See also: http://lkml.kernel.org/r/20111202010832.602203411@sbsiddha-desk.sc.intel.com
9083 nr_busy
= atomic_read(&sds
->nr_busy_cpus
);
9091 sd
= rcu_dereference(rq
->sd
);
9093 if ((rq
->cfs
.h_nr_running
>= 1) &&
9094 check_cpu_capacity(rq
, sd
)) {
9100 sd
= rcu_dereference(per_cpu(sd_asym
, cpu
));
9102 for_each_cpu(i
, sched_domain_span(sd
)) {
9104 !cpumask_test_cpu(i
, nohz
.idle_cpus_mask
))
9107 if (sched_asym_prefer(i
, cpu
)) {
9118 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
) { }
9122 * run_rebalance_domains is triggered when needed from the scheduler tick.
9123 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
9125 static __latent_entropy
void run_rebalance_domains(struct softirq_action
*h
)
9127 struct rq
*this_rq
= this_rq();
9128 enum cpu_idle_type idle
= this_rq
->idle_balance
?
9129 CPU_IDLE
: CPU_NOT_IDLE
;
9132 * If this cpu has a pending nohz_balance_kick, then do the
9133 * balancing on behalf of the other idle cpus whose ticks are
9134 * stopped. Do nohz_idle_balance *before* rebalance_domains to
9135 * give the idle cpus a chance to load balance. Else we may
9136 * load balance only within the local sched_domain hierarchy
9137 * and abort nohz_idle_balance altogether if we pull some load.
9139 nohz_idle_balance(this_rq
, idle
);
9140 rebalance_domains(this_rq
, idle
);
9144 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
9146 void trigger_load_balance(struct rq
*rq
)
9148 /* Don't need to rebalance while attached to NULL domain */
9149 if (unlikely(on_null_domain(rq
)))
9152 if (time_after_eq(jiffies
, rq
->next_balance
))
9153 raise_softirq(SCHED_SOFTIRQ
);
9154 #ifdef CONFIG_NO_HZ_COMMON
9155 if (nohz_kick_needed(rq
))
9156 nohz_balancer_kick();
9160 static void rq_online_fair(struct rq
*rq
)
9164 update_runtime_enabled(rq
);
9167 static void rq_offline_fair(struct rq
*rq
)
9171 /* Ensure any throttled groups are reachable by pick_next_task */
9172 unthrottle_offline_cfs_rqs(rq
);
9175 #endif /* CONFIG_SMP */
9178 * scheduler tick hitting a task of our scheduling class:
9180 static void task_tick_fair(struct rq
*rq
, struct task_struct
*curr
, int queued
)
9182 struct cfs_rq
*cfs_rq
;
9183 struct sched_entity
*se
= &curr
->se
;
9185 for_each_sched_entity(se
) {
9186 cfs_rq
= cfs_rq_of(se
);
9187 entity_tick(cfs_rq
, se
, queued
);
9190 if (static_branch_unlikely(&sched_numa_balancing
))
9191 task_tick_numa(rq
, curr
);
9195 * called on fork with the child task as argument from the parent's context
9196 * - child not yet on the tasklist
9197 * - preemption disabled
9199 static void task_fork_fair(struct task_struct
*p
)
9201 struct cfs_rq
*cfs_rq
;
9202 struct sched_entity
*se
= &p
->se
, *curr
;
9203 struct rq
*rq
= this_rq();
9207 update_rq_clock(rq
);
9209 cfs_rq
= task_cfs_rq(current
);
9210 curr
= cfs_rq
->curr
;
9212 update_curr(cfs_rq
);
9213 se
->vruntime
= curr
->vruntime
;
9215 place_entity(cfs_rq
, se
, 1);
9217 if (sysctl_sched_child_runs_first
&& curr
&& entity_before(curr
, se
)) {
9219 * Upon rescheduling, sched_class::put_prev_task() will place
9220 * 'current' within the tree based on its new key value.
9222 swap(curr
->vruntime
, se
->vruntime
);
9226 se
->vruntime
-= cfs_rq
->min_vruntime
;
9231 * Priority of the task has changed. Check to see if we preempt
9235 prio_changed_fair(struct rq
*rq
, struct task_struct
*p
, int oldprio
)
9237 if (!task_on_rq_queued(p
))
9241 * Reschedule if we are currently running on this runqueue and
9242 * our priority decreased, or if we are not currently running on
9243 * this runqueue and our priority is higher than the current's
9245 if (rq
->curr
== p
) {
9246 if (p
->prio
> oldprio
)
9249 check_preempt_curr(rq
, p
, 0);
9252 static inline bool vruntime_normalized(struct task_struct
*p
)
9254 struct sched_entity
*se
= &p
->se
;
9257 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
9258 * the dequeue_entity(.flags=0) will already have normalized the
9265 * When !on_rq, vruntime of the task has usually NOT been normalized.
9266 * But there are some cases where it has already been normalized:
9268 * - A forked child which is waiting for being woken up by
9269 * wake_up_new_task().
9270 * - A task which has been woken up by try_to_wake_up() and
9271 * waiting for actually being woken up by sched_ttwu_pending().
9273 if (!se
->sum_exec_runtime
|| p
->state
== TASK_WAKING
)
9279 #ifdef CONFIG_FAIR_GROUP_SCHED
9281 * Propagate the changes of the sched_entity across the tg tree to make it
9282 * visible to the root
9284 static void propagate_entity_cfs_rq(struct sched_entity
*se
)
9286 struct cfs_rq
*cfs_rq
;
9288 /* Start to propagate at parent */
9291 for_each_sched_entity(se
) {
9292 cfs_rq
= cfs_rq_of(se
);
9294 if (cfs_rq_throttled(cfs_rq
))
9297 update_load_avg(cfs_rq
, se
, UPDATE_TG
);
9301 static void propagate_entity_cfs_rq(struct sched_entity
*se
) { }
9304 static void detach_entity_cfs_rq(struct sched_entity
*se
)
9306 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
9308 /* Catch up with the cfs_rq and remove our load when we leave */
9309 update_load_avg(cfs_rq
, se
, 0);
9310 detach_entity_load_avg(cfs_rq
, se
);
9311 update_tg_load_avg(cfs_rq
, false);
9312 propagate_entity_cfs_rq(se
);
9315 static void attach_entity_cfs_rq(struct sched_entity
*se
)
9317 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
9319 #ifdef CONFIG_FAIR_GROUP_SCHED
9321 * Since the real-depth could have been changed (only FAIR
9322 * class maintain depth value), reset depth properly.
9324 se
->depth
= se
->parent
? se
->parent
->depth
+ 1 : 0;
9327 /* Synchronize entity with its cfs_rq */
9328 update_load_avg(cfs_rq
, se
, sched_feat(ATTACH_AGE_LOAD
) ? 0 : SKIP_AGE_LOAD
);
9329 attach_entity_load_avg(cfs_rq
, se
);
9330 update_tg_load_avg(cfs_rq
, false);
9331 propagate_entity_cfs_rq(se
);
9334 static void detach_task_cfs_rq(struct task_struct
*p
)
9336 struct sched_entity
*se
= &p
->se
;
9337 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
9339 if (!vruntime_normalized(p
)) {
9341 * Fix up our vruntime so that the current sleep doesn't
9342 * cause 'unlimited' sleep bonus.
9344 place_entity(cfs_rq
, se
, 0);
9345 se
->vruntime
-= cfs_rq
->min_vruntime
;
9348 detach_entity_cfs_rq(se
);
9351 static void attach_task_cfs_rq(struct task_struct
*p
)
9353 struct sched_entity
*se
= &p
->se
;
9354 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
9356 attach_entity_cfs_rq(se
);
9358 if (!vruntime_normalized(p
))
9359 se
->vruntime
+= cfs_rq
->min_vruntime
;
9362 static void switched_from_fair(struct rq
*rq
, struct task_struct
*p
)
9364 detach_task_cfs_rq(p
);
9367 static void switched_to_fair(struct rq
*rq
, struct task_struct
*p
)
9369 attach_task_cfs_rq(p
);
9371 if (task_on_rq_queued(p
)) {
9373 * We were most likely switched from sched_rt, so
9374 * kick off the schedule if running, otherwise just see
9375 * if we can still preempt the current task.
9380 check_preempt_curr(rq
, p
, 0);
9384 /* Account for a task changing its policy or group.
9386 * This routine is mostly called to set cfs_rq->curr field when a task
9387 * migrates between groups/classes.
9389 static void set_curr_task_fair(struct rq
*rq
)
9391 struct sched_entity
*se
= &rq
->curr
->se
;
9393 for_each_sched_entity(se
) {
9394 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
9396 set_next_entity(cfs_rq
, se
);
9397 /* ensure bandwidth has been allocated on our new cfs_rq */
9398 account_cfs_rq_runtime(cfs_rq
, 0);
9402 void init_cfs_rq(struct cfs_rq
*cfs_rq
)
9404 cfs_rq
->tasks_timeline
= RB_ROOT_CACHED
;
9405 cfs_rq
->min_vruntime
= (u64
)(-(1LL << 20));
9406 #ifndef CONFIG_64BIT
9407 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
9410 #ifdef CONFIG_FAIR_GROUP_SCHED
9411 cfs_rq
->propagate_avg
= 0;
9413 atomic_long_set(&cfs_rq
->removed_load_avg
, 0);
9414 atomic_long_set(&cfs_rq
->removed_util_avg
, 0);
9418 #ifdef CONFIG_FAIR_GROUP_SCHED
9419 static void task_set_group_fair(struct task_struct
*p
)
9421 struct sched_entity
*se
= &p
->se
;
9423 set_task_rq(p
, task_cpu(p
));
9424 se
->depth
= se
->parent
? se
->parent
->depth
+ 1 : 0;
9427 static void task_move_group_fair(struct task_struct
*p
)
9429 detach_task_cfs_rq(p
);
9430 set_task_rq(p
, task_cpu(p
));
9433 /* Tell se's cfs_rq has been changed -- migrated */
9434 p
->se
.avg
.last_update_time
= 0;
9436 attach_task_cfs_rq(p
);
9439 static void task_change_group_fair(struct task_struct
*p
, int type
)
9442 case TASK_SET_GROUP
:
9443 task_set_group_fair(p
);
9446 case TASK_MOVE_GROUP
:
9447 task_move_group_fair(p
);
9452 void free_fair_sched_group(struct task_group
*tg
)
9456 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg
));
9458 for_each_possible_cpu(i
) {
9460 kfree(tg
->cfs_rq
[i
]);
9469 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
9471 struct sched_entity
*se
;
9472 struct cfs_rq
*cfs_rq
;
9475 tg
->cfs_rq
= kzalloc(sizeof(cfs_rq
) * nr_cpu_ids
, GFP_KERNEL
);
9478 tg
->se
= kzalloc(sizeof(se
) * nr_cpu_ids
, GFP_KERNEL
);
9482 tg
->shares
= NICE_0_LOAD
;
9484 init_cfs_bandwidth(tg_cfs_bandwidth(tg
));
9486 for_each_possible_cpu(i
) {
9487 cfs_rq
= kzalloc_node(sizeof(struct cfs_rq
),
9488 GFP_KERNEL
, cpu_to_node(i
));
9492 se
= kzalloc_node(sizeof(struct sched_entity
),
9493 GFP_KERNEL
, cpu_to_node(i
));
9497 init_cfs_rq(cfs_rq
);
9498 init_tg_cfs_entry(tg
, cfs_rq
, se
, i
, parent
->se
[i
]);
9499 init_entity_runnable_average(se
);
9510 void online_fair_sched_group(struct task_group
*tg
)
9512 struct sched_entity
*se
;
9516 for_each_possible_cpu(i
) {
9520 raw_spin_lock_irq(&rq
->lock
);
9521 update_rq_clock(rq
);
9522 attach_entity_cfs_rq(se
);
9523 sync_throttle(tg
, i
);
9524 raw_spin_unlock_irq(&rq
->lock
);
9528 void unregister_fair_sched_group(struct task_group
*tg
)
9530 unsigned long flags
;
9534 for_each_possible_cpu(cpu
) {
9536 remove_entity_load_avg(tg
->se
[cpu
]);
9539 * Only empty task groups can be destroyed; so we can speculatively
9540 * check on_list without danger of it being re-added.
9542 if (!tg
->cfs_rq
[cpu
]->on_list
)
9547 raw_spin_lock_irqsave(&rq
->lock
, flags
);
9548 list_del_leaf_cfs_rq(tg
->cfs_rq
[cpu
]);
9549 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
9553 void init_tg_cfs_entry(struct task_group
*tg
, struct cfs_rq
*cfs_rq
,
9554 struct sched_entity
*se
, int cpu
,
9555 struct sched_entity
*parent
)
9557 struct rq
*rq
= cpu_rq(cpu
);
9561 init_cfs_rq_runtime(cfs_rq
);
9563 tg
->cfs_rq
[cpu
] = cfs_rq
;
9566 /* se could be NULL for root_task_group */
9571 se
->cfs_rq
= &rq
->cfs
;
9574 se
->cfs_rq
= parent
->my_q
;
9575 se
->depth
= parent
->depth
+ 1;
9579 /* guarantee group entities always have weight */
9580 update_load_set(&se
->load
, NICE_0_LOAD
);
9581 se
->parent
= parent
;
9584 static DEFINE_MUTEX(shares_mutex
);
9586 int sched_group_set_shares(struct task_group
*tg
, unsigned long shares
)
9591 * We can't change the weight of the root cgroup.
9596 shares
= clamp(shares
, scale_load(MIN_SHARES
), scale_load(MAX_SHARES
));
9598 mutex_lock(&shares_mutex
);
9599 if (tg
->shares
== shares
)
9602 tg
->shares
= shares
;
9603 for_each_possible_cpu(i
) {
9604 struct rq
*rq
= cpu_rq(i
);
9605 struct sched_entity
*se
= tg
->se
[i
];
9608 /* Propagate contribution to hierarchy */
9609 rq_lock_irqsave(rq
, &rf
);
9610 update_rq_clock(rq
);
9611 for_each_sched_entity(se
) {
9612 update_load_avg(cfs_rq_of(se
), se
, UPDATE_TG
);
9613 update_cfs_shares(se
);
9615 rq_unlock_irqrestore(rq
, &rf
);
9619 mutex_unlock(&shares_mutex
);
9622 #else /* CONFIG_FAIR_GROUP_SCHED */
9624 void free_fair_sched_group(struct task_group
*tg
) { }
9626 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
9631 void online_fair_sched_group(struct task_group
*tg
) { }
9633 void unregister_fair_sched_group(struct task_group
*tg
) { }
9635 #endif /* CONFIG_FAIR_GROUP_SCHED */
9638 static unsigned int get_rr_interval_fair(struct rq
*rq
, struct task_struct
*task
)
9640 struct sched_entity
*se
= &task
->se
;
9641 unsigned int rr_interval
= 0;
9644 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
9647 if (rq
->cfs
.load
.weight
)
9648 rr_interval
= NS_TO_JIFFIES(sched_slice(cfs_rq_of(se
), se
));
9654 * All the scheduling class methods:
9656 const struct sched_class fair_sched_class
= {
9657 .next
= &idle_sched_class
,
9658 .enqueue_task
= enqueue_task_fair
,
9659 .dequeue_task
= dequeue_task_fair
,
9660 .yield_task
= yield_task_fair
,
9661 .yield_to_task
= yield_to_task_fair
,
9663 .check_preempt_curr
= check_preempt_wakeup
,
9665 .pick_next_task
= pick_next_task_fair
,
9666 .put_prev_task
= put_prev_task_fair
,
9669 .select_task_rq
= select_task_rq_fair
,
9670 .migrate_task_rq
= migrate_task_rq_fair
,
9672 .rq_online
= rq_online_fair
,
9673 .rq_offline
= rq_offline_fair
,
9675 .task_dead
= task_dead_fair
,
9676 .set_cpus_allowed
= set_cpus_allowed_common
,
9679 .set_curr_task
= set_curr_task_fair
,
9680 .task_tick
= task_tick_fair
,
9681 .task_fork
= task_fork_fair
,
9683 .prio_changed
= prio_changed_fair
,
9684 .switched_from
= switched_from_fair
,
9685 .switched_to
= switched_to_fair
,
9687 .get_rr_interval
= get_rr_interval_fair
,
9689 .update_curr
= update_curr_fair
,
9691 #ifdef CONFIG_FAIR_GROUP_SCHED
9692 .task_change_group
= task_change_group_fair
,
9696 #ifdef CONFIG_SCHED_DEBUG
9697 void print_cfs_stats(struct seq_file
*m
, int cpu
)
9699 struct cfs_rq
*cfs_rq
, *pos
;
9702 for_each_leaf_cfs_rq_safe(cpu_rq(cpu
), cfs_rq
, pos
)
9703 print_cfs_rq(m
, cpu
, cfs_rq
);
9707 #ifdef CONFIG_NUMA_BALANCING
9708 void show_numa_stats(struct task_struct
*p
, struct seq_file
*m
)
9711 unsigned long tsf
= 0, tpf
= 0, gsf
= 0, gpf
= 0;
9713 for_each_online_node(node
) {
9714 if (p
->numa_faults
) {
9715 tsf
= p
->numa_faults
[task_faults_idx(NUMA_MEM
, node
, 0)];
9716 tpf
= p
->numa_faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
9718 if (p
->numa_group
) {
9719 gsf
= p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, node
, 0)],
9720 gpf
= p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
9722 print_numa_stats(m
, node
, tsf
, tpf
, gsf
, gpf
);
9725 #endif /* CONFIG_NUMA_BALANCING */
9726 #endif /* CONFIG_SCHED_DEBUG */
9728 __init
void init_sched_fair_class(void)
9731 open_softirq(SCHED_SOFTIRQ
, run_rebalance_domains
);
9733 #ifdef CONFIG_NO_HZ_COMMON
9734 nohz
.next_balance
= jiffies
;
9735 zalloc_cpumask_var(&nohz
.idle_cpus_mask
, GFP_NOWAIT
);