2 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
4 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
6 * Interactivity improvements by Mike Galbraith
7 * (C) 2007 Mike Galbraith <efault@gmx.de>
9 * Various enhancements by Dmitry Adamushko.
10 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
12 * Group scheduling enhancements by Srivatsa Vaddagiri
13 * Copyright IBM Corporation, 2007
14 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
16 * Scaled math optimizations by Thomas Gleixner
17 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
19 * Adaptive scheduling granularity, math enhancements by Peter Zijlstra
20 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
23 #include <linux/latencytop.h>
24 #include <linux/sched.h>
25 #include <linux/cpumask.h>
26 #include <linux/cpuidle.h>
27 #include <linux/slab.h>
28 #include <linux/profile.h>
29 #include <linux/interrupt.h>
30 #include <linux/mempolicy.h>
31 #include <linux/migrate.h>
32 #include <linux/task_work.h>
34 #include <trace/events/sched.h>
39 * Targeted preemption latency for CPU-bound tasks:
40 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
42 * NOTE: this latency value is not the same as the concept of
43 * 'timeslice length' - timeslices in CFS are of variable length
44 * and have no persistent notion like in traditional, time-slice
45 * based scheduling concepts.
47 * (to see the precise effective timeslice length of your workload,
48 * run vmstat and monitor the context-switches (cs) field)
50 unsigned int sysctl_sched_latency
= 6000000ULL;
51 unsigned int normalized_sysctl_sched_latency
= 6000000ULL;
54 * The initial- and re-scaling of tunables is configurable
55 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
58 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
59 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
60 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
62 enum sched_tunable_scaling sysctl_sched_tunable_scaling
63 = SCHED_TUNABLESCALING_LOG
;
66 * Minimal preemption granularity for CPU-bound tasks:
67 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
69 unsigned int sysctl_sched_min_granularity
= 750000ULL;
70 unsigned int normalized_sysctl_sched_min_granularity
= 750000ULL;
73 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
75 static unsigned int sched_nr_latency
= 8;
78 * After fork, child runs first. If set to 0 (default) then
79 * parent will (try to) run first.
81 unsigned int sysctl_sched_child_runs_first __read_mostly
;
84 * SCHED_OTHER wake-up granularity.
85 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
87 * This option delays the preemption effects of decoupled workloads
88 * and reduces their over-scheduling. Synchronous workloads will still
89 * have immediate wakeup/sleep latencies.
91 unsigned int sysctl_sched_wakeup_granularity
= 1000000UL;
92 unsigned int normalized_sysctl_sched_wakeup_granularity
= 1000000UL;
94 const_debug
unsigned int sysctl_sched_migration_cost
= 500000UL;
97 * The exponential sliding window over which load is averaged for shares
101 unsigned int __read_mostly sysctl_sched_shares_window
= 10000000UL;
103 #ifdef CONFIG_CFS_BANDWIDTH
105 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
106 * each time a cfs_rq requests quota.
108 * Note: in the case that the slice exceeds the runtime remaining (either due
109 * to consumption or the quota being specified to be smaller than the slice)
110 * we will always only issue the remaining available time.
112 * default: 5 msec, units: microseconds
114 unsigned int sysctl_sched_cfs_bandwidth_slice
= 5000UL;
117 static inline void update_load_add(struct load_weight
*lw
, unsigned long inc
)
123 static inline void update_load_sub(struct load_weight
*lw
, unsigned long dec
)
129 static inline void update_load_set(struct load_weight
*lw
, unsigned long w
)
136 * Increase the granularity value when there are more CPUs,
137 * because with more CPUs the 'effective latency' as visible
138 * to users decreases. But the relationship is not linear,
139 * so pick a second-best guess by going with the log2 of the
142 * This idea comes from the SD scheduler of Con Kolivas:
144 static int get_update_sysctl_factor(void)
146 unsigned int cpus
= min_t(int, num_online_cpus(), 8);
149 switch (sysctl_sched_tunable_scaling
) {
150 case SCHED_TUNABLESCALING_NONE
:
153 case SCHED_TUNABLESCALING_LINEAR
:
156 case SCHED_TUNABLESCALING_LOG
:
158 factor
= 1 + ilog2(cpus
);
165 static void update_sysctl(void)
167 unsigned int factor
= get_update_sysctl_factor();
169 #define SET_SYSCTL(name) \
170 (sysctl_##name = (factor) * normalized_sysctl_##name)
171 SET_SYSCTL(sched_min_granularity
);
172 SET_SYSCTL(sched_latency
);
173 SET_SYSCTL(sched_wakeup_granularity
);
177 void sched_init_granularity(void)
182 #define WMULT_CONST (~0U)
183 #define WMULT_SHIFT 32
185 static void __update_inv_weight(struct load_weight
*lw
)
189 if (likely(lw
->inv_weight
))
192 w
= scale_load_down(lw
->weight
);
194 if (BITS_PER_LONG
> 32 && unlikely(w
>= WMULT_CONST
))
196 else if (unlikely(!w
))
197 lw
->inv_weight
= WMULT_CONST
;
199 lw
->inv_weight
= WMULT_CONST
/ w
;
203 * delta_exec * weight / lw.weight
205 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
207 * Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case
208 * we're guaranteed shift stays positive because inv_weight is guaranteed to
209 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
211 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
212 * weight/lw.weight <= 1, and therefore our shift will also be positive.
214 static u64
__calc_delta(u64 delta_exec
, unsigned long weight
, struct load_weight
*lw
)
216 u64 fact
= scale_load_down(weight
);
217 int shift
= WMULT_SHIFT
;
219 __update_inv_weight(lw
);
221 if (unlikely(fact
>> 32)) {
228 /* hint to use a 32x32->64 mul */
229 fact
= (u64
)(u32
)fact
* lw
->inv_weight
;
236 return mul_u64_u32_shr(delta_exec
, fact
, shift
);
240 const struct sched_class fair_sched_class
;
242 /**************************************************************
243 * CFS operations on generic schedulable entities:
246 #ifdef CONFIG_FAIR_GROUP_SCHED
248 /* cpu runqueue to which this cfs_rq is attached */
249 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
254 /* An entity is a task if it doesn't "own" a runqueue */
255 #define entity_is_task(se) (!se->my_q)
257 static inline struct task_struct
*task_of(struct sched_entity
*se
)
259 #ifdef CONFIG_SCHED_DEBUG
260 WARN_ON_ONCE(!entity_is_task(se
));
262 return container_of(se
, struct task_struct
, se
);
265 /* Walk up scheduling entities hierarchy */
266 #define for_each_sched_entity(se) \
267 for (; se; se = se->parent)
269 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
274 /* runqueue on which this entity is (to be) queued */
275 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
280 /* runqueue "owned" by this group */
281 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
286 static void update_cfs_rq_blocked_load(struct cfs_rq
*cfs_rq
,
289 static inline void list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
291 if (!cfs_rq
->on_list
) {
293 * Ensure we either appear before our parent (if already
294 * enqueued) or force our parent to appear after us when it is
295 * enqueued. The fact that we always enqueue bottom-up
296 * reduces this to two cases.
298 if (cfs_rq
->tg
->parent
&&
299 cfs_rq
->tg
->parent
->cfs_rq
[cpu_of(rq_of(cfs_rq
))]->on_list
) {
300 list_add_rcu(&cfs_rq
->leaf_cfs_rq_list
,
301 &rq_of(cfs_rq
)->leaf_cfs_rq_list
);
303 list_add_tail_rcu(&cfs_rq
->leaf_cfs_rq_list
,
304 &rq_of(cfs_rq
)->leaf_cfs_rq_list
);
308 /* We should have no load, but we need to update last_decay. */
309 update_cfs_rq_blocked_load(cfs_rq
, 0);
313 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
315 if (cfs_rq
->on_list
) {
316 list_del_rcu(&cfs_rq
->leaf_cfs_rq_list
);
321 /* Iterate thr' all leaf cfs_rq's on a runqueue */
322 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
323 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
325 /* Do the two (enqueued) entities belong to the same group ? */
326 static inline struct cfs_rq
*
327 is_same_group(struct sched_entity
*se
, struct sched_entity
*pse
)
329 if (se
->cfs_rq
== pse
->cfs_rq
)
335 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
341 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
343 int se_depth
, pse_depth
;
346 * preemption test can be made between sibling entities who are in the
347 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
348 * both tasks until we find their ancestors who are siblings of common
352 /* First walk up until both entities are at same depth */
353 se_depth
= (*se
)->depth
;
354 pse_depth
= (*pse
)->depth
;
356 while (se_depth
> pse_depth
) {
358 *se
= parent_entity(*se
);
361 while (pse_depth
> se_depth
) {
363 *pse
= parent_entity(*pse
);
366 while (!is_same_group(*se
, *pse
)) {
367 *se
= parent_entity(*se
);
368 *pse
= parent_entity(*pse
);
372 #else /* !CONFIG_FAIR_GROUP_SCHED */
374 static inline struct task_struct
*task_of(struct sched_entity
*se
)
376 return container_of(se
, struct task_struct
, se
);
379 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
381 return container_of(cfs_rq
, struct rq
, cfs
);
384 #define entity_is_task(se) 1
386 #define for_each_sched_entity(se) \
387 for (; se; se = NULL)
389 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
391 return &task_rq(p
)->cfs
;
394 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
396 struct task_struct
*p
= task_of(se
);
397 struct rq
*rq
= task_rq(p
);
402 /* runqueue "owned" by this group */
403 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
408 static inline void list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
412 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
416 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
417 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
419 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
425 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
429 #endif /* CONFIG_FAIR_GROUP_SCHED */
431 static __always_inline
432 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
);
434 /**************************************************************
435 * Scheduling class tree data structure manipulation methods:
438 static inline u64
max_vruntime(u64 max_vruntime
, u64 vruntime
)
440 s64 delta
= (s64
)(vruntime
- max_vruntime
);
442 max_vruntime
= vruntime
;
447 static inline u64
min_vruntime(u64 min_vruntime
, u64 vruntime
)
449 s64 delta
= (s64
)(vruntime
- min_vruntime
);
451 min_vruntime
= vruntime
;
456 static inline int entity_before(struct sched_entity
*a
,
457 struct sched_entity
*b
)
459 return (s64
)(a
->vruntime
- b
->vruntime
) < 0;
462 static void update_min_vruntime(struct cfs_rq
*cfs_rq
)
464 u64 vruntime
= cfs_rq
->min_vruntime
;
467 vruntime
= cfs_rq
->curr
->vruntime
;
469 if (cfs_rq
->rb_leftmost
) {
470 struct sched_entity
*se
= rb_entry(cfs_rq
->rb_leftmost
,
475 vruntime
= se
->vruntime
;
477 vruntime
= min_vruntime(vruntime
, se
->vruntime
);
480 /* ensure we never gain time by being placed backwards. */
481 cfs_rq
->min_vruntime
= max_vruntime(cfs_rq
->min_vruntime
, vruntime
);
484 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
489 * Enqueue an entity into the rb-tree:
491 static void __enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
493 struct rb_node
**link
= &cfs_rq
->tasks_timeline
.rb_node
;
494 struct rb_node
*parent
= NULL
;
495 struct sched_entity
*entry
;
499 * Find the right place in the rbtree:
503 entry
= rb_entry(parent
, struct sched_entity
, run_node
);
505 * We dont care about collisions. Nodes with
506 * the same key stay together.
508 if (entity_before(se
, entry
)) {
509 link
= &parent
->rb_left
;
511 link
= &parent
->rb_right
;
517 * Maintain a cache of leftmost tree entries (it is frequently
521 cfs_rq
->rb_leftmost
= &se
->run_node
;
523 rb_link_node(&se
->run_node
, parent
, link
);
524 rb_insert_color(&se
->run_node
, &cfs_rq
->tasks_timeline
);
527 static void __dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
529 if (cfs_rq
->rb_leftmost
== &se
->run_node
) {
530 struct rb_node
*next_node
;
532 next_node
= rb_next(&se
->run_node
);
533 cfs_rq
->rb_leftmost
= next_node
;
536 rb_erase(&se
->run_node
, &cfs_rq
->tasks_timeline
);
539 struct sched_entity
*__pick_first_entity(struct cfs_rq
*cfs_rq
)
541 struct rb_node
*left
= cfs_rq
->rb_leftmost
;
546 return rb_entry(left
, struct sched_entity
, run_node
);
549 static struct sched_entity
*__pick_next_entity(struct sched_entity
*se
)
551 struct rb_node
*next
= rb_next(&se
->run_node
);
556 return rb_entry(next
, struct sched_entity
, run_node
);
559 #ifdef CONFIG_SCHED_DEBUG
560 struct sched_entity
*__pick_last_entity(struct cfs_rq
*cfs_rq
)
562 struct rb_node
*last
= rb_last(&cfs_rq
->tasks_timeline
);
567 return rb_entry(last
, struct sched_entity
, run_node
);
570 /**************************************************************
571 * Scheduling class statistics methods:
574 int sched_proc_update_handler(struct ctl_table
*table
, int write
,
575 void __user
*buffer
, size_t *lenp
,
578 int ret
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
579 int factor
= get_update_sysctl_factor();
584 sched_nr_latency
= DIV_ROUND_UP(sysctl_sched_latency
,
585 sysctl_sched_min_granularity
);
587 #define WRT_SYSCTL(name) \
588 (normalized_sysctl_##name = sysctl_##name / (factor))
589 WRT_SYSCTL(sched_min_granularity
);
590 WRT_SYSCTL(sched_latency
);
591 WRT_SYSCTL(sched_wakeup_granularity
);
601 static inline u64
calc_delta_fair(u64 delta
, struct sched_entity
*se
)
603 if (unlikely(se
->load
.weight
!= NICE_0_LOAD
))
604 delta
= __calc_delta(delta
, NICE_0_LOAD
, &se
->load
);
610 * The idea is to set a period in which each task runs once.
612 * When there are too many tasks (sched_nr_latency) we have to stretch
613 * this period because otherwise the slices get too small.
615 * p = (nr <= nl) ? l : l*nr/nl
617 static u64
__sched_period(unsigned long nr_running
)
619 u64 period
= sysctl_sched_latency
;
620 unsigned long nr_latency
= sched_nr_latency
;
622 if (unlikely(nr_running
> nr_latency
)) {
623 period
= sysctl_sched_min_granularity
;
624 period
*= nr_running
;
631 * We calculate the wall-time slice from the period by taking a part
632 * proportional to the weight.
636 static u64
sched_slice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
638 u64 slice
= __sched_period(cfs_rq
->nr_running
+ !se
->on_rq
);
640 for_each_sched_entity(se
) {
641 struct load_weight
*load
;
642 struct load_weight lw
;
644 cfs_rq
= cfs_rq_of(se
);
645 load
= &cfs_rq
->load
;
647 if (unlikely(!se
->on_rq
)) {
650 update_load_add(&lw
, se
->load
.weight
);
653 slice
= __calc_delta(slice
, se
->load
.weight
, load
);
659 * We calculate the vruntime slice of a to-be-inserted task.
663 static u64
sched_vslice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
665 return calc_delta_fair(sched_slice(cfs_rq
, se
), se
);
669 static int select_idle_sibling(struct task_struct
*p
, int cpu
);
670 static unsigned long task_h_load(struct task_struct
*p
);
672 static inline void __update_task_entity_contrib(struct sched_entity
*se
);
673 static inline void __update_task_entity_utilization(struct sched_entity
*se
);
675 /* Give new task start runnable values to heavy its load in infant time */
676 void init_task_runnable_average(struct task_struct
*p
)
680 slice
= sched_slice(task_cfs_rq(p
), &p
->se
) >> 10;
681 p
->se
.avg
.runnable_avg_sum
= p
->se
.avg
.running_avg_sum
= slice
;
682 p
->se
.avg
.avg_period
= slice
;
683 __update_task_entity_contrib(&p
->se
);
684 __update_task_entity_utilization(&p
->se
);
687 void init_task_runnable_average(struct task_struct
*p
)
693 * Update the current task's runtime statistics.
695 static void update_curr(struct cfs_rq
*cfs_rq
)
697 struct sched_entity
*curr
= cfs_rq
->curr
;
698 u64 now
= rq_clock_task(rq_of(cfs_rq
));
704 delta_exec
= now
- curr
->exec_start
;
705 if (unlikely((s64
)delta_exec
<= 0))
708 curr
->exec_start
= now
;
710 schedstat_set(curr
->statistics
.exec_max
,
711 max(delta_exec
, curr
->statistics
.exec_max
));
713 curr
->sum_exec_runtime
+= delta_exec
;
714 schedstat_add(cfs_rq
, exec_clock
, delta_exec
);
716 curr
->vruntime
+= calc_delta_fair(delta_exec
, curr
);
717 update_min_vruntime(cfs_rq
);
719 if (entity_is_task(curr
)) {
720 struct task_struct
*curtask
= task_of(curr
);
722 trace_sched_stat_runtime(curtask
, delta_exec
, curr
->vruntime
);
723 cpuacct_charge(curtask
, delta_exec
);
724 account_group_exec_runtime(curtask
, delta_exec
);
727 account_cfs_rq_runtime(cfs_rq
, delta_exec
);
730 static void update_curr_fair(struct rq
*rq
)
732 update_curr(cfs_rq_of(&rq
->curr
->se
));
736 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
738 schedstat_set(se
->statistics
.wait_start
, rq_clock(rq_of(cfs_rq
)));
742 * Task is being enqueued - update stats:
744 static void update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
747 * Are we enqueueing a waiting task? (for current tasks
748 * a dequeue/enqueue event is a NOP)
750 if (se
!= cfs_rq
->curr
)
751 update_stats_wait_start(cfs_rq
, se
);
755 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
757 schedstat_set(se
->statistics
.wait_max
, max(se
->statistics
.wait_max
,
758 rq_clock(rq_of(cfs_rq
)) - se
->statistics
.wait_start
));
759 schedstat_set(se
->statistics
.wait_count
, se
->statistics
.wait_count
+ 1);
760 schedstat_set(se
->statistics
.wait_sum
, se
->statistics
.wait_sum
+
761 rq_clock(rq_of(cfs_rq
)) - se
->statistics
.wait_start
);
762 #ifdef CONFIG_SCHEDSTATS
763 if (entity_is_task(se
)) {
764 trace_sched_stat_wait(task_of(se
),
765 rq_clock(rq_of(cfs_rq
)) - se
->statistics
.wait_start
);
768 schedstat_set(se
->statistics
.wait_start
, 0);
772 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
775 * Mark the end of the wait period if dequeueing a
778 if (se
!= cfs_rq
->curr
)
779 update_stats_wait_end(cfs_rq
, se
);
783 * We are picking a new current task - update its stats:
786 update_stats_curr_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
789 * We are starting a new run period:
791 se
->exec_start
= rq_clock_task(rq_of(cfs_rq
));
794 /**************************************************
795 * Scheduling class queueing methods:
798 #ifdef CONFIG_NUMA_BALANCING
800 * Approximate time to scan a full NUMA task in ms. The task scan period is
801 * calculated based on the tasks virtual memory size and
802 * numa_balancing_scan_size.
804 unsigned int sysctl_numa_balancing_scan_period_min
= 1000;
805 unsigned int sysctl_numa_balancing_scan_period_max
= 60000;
807 /* Portion of address space to scan in MB */
808 unsigned int sysctl_numa_balancing_scan_size
= 256;
810 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
811 unsigned int sysctl_numa_balancing_scan_delay
= 1000;
813 static unsigned int task_nr_scan_windows(struct task_struct
*p
)
815 unsigned long rss
= 0;
816 unsigned long nr_scan_pages
;
819 * Calculations based on RSS as non-present and empty pages are skipped
820 * by the PTE scanner and NUMA hinting faults should be trapped based
823 nr_scan_pages
= sysctl_numa_balancing_scan_size
<< (20 - PAGE_SHIFT
);
824 rss
= get_mm_rss(p
->mm
);
828 rss
= round_up(rss
, nr_scan_pages
);
829 return rss
/ nr_scan_pages
;
832 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
833 #define MAX_SCAN_WINDOW 2560
835 static unsigned int task_scan_min(struct task_struct
*p
)
837 unsigned int scan_size
= ACCESS_ONCE(sysctl_numa_balancing_scan_size
);
838 unsigned int scan
, floor
;
839 unsigned int windows
= 1;
841 if (scan_size
< MAX_SCAN_WINDOW
)
842 windows
= MAX_SCAN_WINDOW
/ scan_size
;
843 floor
= 1000 / windows
;
845 scan
= sysctl_numa_balancing_scan_period_min
/ task_nr_scan_windows(p
);
846 return max_t(unsigned int, floor
, scan
);
849 static unsigned int task_scan_max(struct task_struct
*p
)
851 unsigned int smin
= task_scan_min(p
);
854 /* Watch for min being lower than max due to floor calculations */
855 smax
= sysctl_numa_balancing_scan_period_max
/ task_nr_scan_windows(p
);
856 return max(smin
, smax
);
859 static void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
861 rq
->nr_numa_running
+= (p
->numa_preferred_nid
!= -1);
862 rq
->nr_preferred_running
+= (p
->numa_preferred_nid
== task_node(p
));
865 static void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
867 rq
->nr_numa_running
-= (p
->numa_preferred_nid
!= -1);
868 rq
->nr_preferred_running
-= (p
->numa_preferred_nid
== task_node(p
));
874 spinlock_t lock
; /* nr_tasks, tasks */
879 nodemask_t active_nodes
;
880 unsigned long total_faults
;
882 * Faults_cpu is used to decide whether memory should move
883 * towards the CPU. As a consequence, these stats are weighted
884 * more by CPU use than by memory faults.
886 unsigned long *faults_cpu
;
887 unsigned long faults
[0];
890 /* Shared or private faults. */
891 #define NR_NUMA_HINT_FAULT_TYPES 2
893 /* Memory and CPU locality */
894 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
896 /* Averaged statistics, and temporary buffers. */
897 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
899 pid_t
task_numa_group_id(struct task_struct
*p
)
901 return p
->numa_group
? p
->numa_group
->gid
: 0;
905 * The averaged statistics, shared & private, memory & cpu,
906 * occupy the first half of the array. The second half of the
907 * array is for current counters, which are averaged into the
908 * first set by task_numa_placement.
910 static inline int task_faults_idx(enum numa_faults_stats s
, int nid
, int priv
)
912 return NR_NUMA_HINT_FAULT_TYPES
* (s
* nr_node_ids
+ nid
) + priv
;
915 static inline unsigned long task_faults(struct task_struct
*p
, int nid
)
920 return p
->numa_faults
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
921 p
->numa_faults
[task_faults_idx(NUMA_MEM
, nid
, 1)];
924 static inline unsigned long group_faults(struct task_struct
*p
, int nid
)
929 return p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
930 p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, nid
, 1)];
933 static inline unsigned long group_faults_cpu(struct numa_group
*group
, int nid
)
935 return group
->faults_cpu
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
936 group
->faults_cpu
[task_faults_idx(NUMA_MEM
, nid
, 1)];
939 /* Handle placement on systems where not all nodes are directly connected. */
940 static unsigned long score_nearby_nodes(struct task_struct
*p
, int nid
,
941 int maxdist
, bool task
)
943 unsigned long score
= 0;
947 * All nodes are directly connected, and the same distance
948 * from each other. No need for fancy placement algorithms.
950 if (sched_numa_topology_type
== NUMA_DIRECT
)
954 * This code is called for each node, introducing N^2 complexity,
955 * which should be ok given the number of nodes rarely exceeds 8.
957 for_each_online_node(node
) {
958 unsigned long faults
;
959 int dist
= node_distance(nid
, node
);
962 * The furthest away nodes in the system are not interesting
963 * for placement; nid was already counted.
965 if (dist
== sched_max_numa_distance
|| node
== nid
)
969 * On systems with a backplane NUMA topology, compare groups
970 * of nodes, and move tasks towards the group with the most
971 * memory accesses. When comparing two nodes at distance
972 * "hoplimit", only nodes closer by than "hoplimit" are part
973 * of each group. Skip other nodes.
975 if (sched_numa_topology_type
== NUMA_BACKPLANE
&&
979 /* Add up the faults from nearby nodes. */
981 faults
= task_faults(p
, node
);
983 faults
= group_faults(p
, node
);
986 * On systems with a glueless mesh NUMA topology, there are
987 * no fixed "groups of nodes". Instead, nodes that are not
988 * directly connected bounce traffic through intermediate
989 * nodes; a numa_group can occupy any set of nodes.
990 * The further away a node is, the less the faults count.
991 * This seems to result in good task placement.
993 if (sched_numa_topology_type
== NUMA_GLUELESS_MESH
) {
994 faults
*= (sched_max_numa_distance
- dist
);
995 faults
/= (sched_max_numa_distance
- LOCAL_DISTANCE
);
1005 * These return the fraction of accesses done by a particular task, or
1006 * task group, on a particular numa node. The group weight is given a
1007 * larger multiplier, in order to group tasks together that are almost
1008 * evenly spread out between numa nodes.
1010 static inline unsigned long task_weight(struct task_struct
*p
, int nid
,
1013 unsigned long faults
, total_faults
;
1015 if (!p
->numa_faults
)
1018 total_faults
= p
->total_numa_faults
;
1023 faults
= task_faults(p
, nid
);
1024 faults
+= score_nearby_nodes(p
, nid
, dist
, true);
1026 return 1000 * faults
/ total_faults
;
1029 static inline unsigned long group_weight(struct task_struct
*p
, int nid
,
1032 unsigned long faults
, total_faults
;
1037 total_faults
= p
->numa_group
->total_faults
;
1042 faults
= group_faults(p
, nid
);
1043 faults
+= score_nearby_nodes(p
, nid
, dist
, false);
1045 return 1000 * faults
/ total_faults
;
1048 bool should_numa_migrate_memory(struct task_struct
*p
, struct page
* page
,
1049 int src_nid
, int dst_cpu
)
1051 struct numa_group
*ng
= p
->numa_group
;
1052 int dst_nid
= cpu_to_node(dst_cpu
);
1053 int last_cpupid
, this_cpupid
;
1055 this_cpupid
= cpu_pid_to_cpupid(dst_cpu
, current
->pid
);
1058 * Multi-stage node selection is used in conjunction with a periodic
1059 * migration fault to build a temporal task<->page relation. By using
1060 * a two-stage filter we remove short/unlikely relations.
1062 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1063 * a task's usage of a particular page (n_p) per total usage of this
1064 * page (n_t) (in a given time-span) to a probability.
1066 * Our periodic faults will sample this probability and getting the
1067 * same result twice in a row, given these samples are fully
1068 * independent, is then given by P(n)^2, provided our sample period
1069 * is sufficiently short compared to the usage pattern.
1071 * This quadric squishes small probabilities, making it less likely we
1072 * act on an unlikely task<->page relation.
1074 last_cpupid
= page_cpupid_xchg_last(page
, this_cpupid
);
1075 if (!cpupid_pid_unset(last_cpupid
) &&
1076 cpupid_to_nid(last_cpupid
) != dst_nid
)
1079 /* Always allow migrate on private faults */
1080 if (cpupid_match_pid(p
, last_cpupid
))
1083 /* A shared fault, but p->numa_group has not been set up yet. */
1088 * Do not migrate if the destination is not a node that
1089 * is actively used by this numa group.
1091 if (!node_isset(dst_nid
, ng
->active_nodes
))
1095 * Source is a node that is not actively used by this
1096 * numa group, while the destination is. Migrate.
1098 if (!node_isset(src_nid
, ng
->active_nodes
))
1102 * Both source and destination are nodes in active
1103 * use by this numa group. Maximize memory bandwidth
1104 * by migrating from more heavily used groups, to less
1105 * heavily used ones, spreading the load around.
1106 * Use a 1/4 hysteresis to avoid spurious page movement.
1108 return group_faults(p
, dst_nid
) < (group_faults(p
, src_nid
) * 3 / 4);
1111 static unsigned long weighted_cpuload(const int cpu
);
1112 static unsigned long source_load(int cpu
, int type
);
1113 static unsigned long target_load(int cpu
, int type
);
1114 static unsigned long capacity_of(int cpu
);
1115 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
);
1117 /* Cached statistics for all CPUs within a node */
1119 unsigned long nr_running
;
1122 /* Total compute capacity of CPUs on a node */
1123 unsigned long compute_capacity
;
1125 /* Approximate capacity in terms of runnable tasks on a node */
1126 unsigned long task_capacity
;
1127 int has_free_capacity
;
1131 * XXX borrowed from update_sg_lb_stats
1133 static void update_numa_stats(struct numa_stats
*ns
, int nid
)
1135 int smt
, cpu
, cpus
= 0;
1136 unsigned long capacity
;
1138 memset(ns
, 0, sizeof(*ns
));
1139 for_each_cpu(cpu
, cpumask_of_node(nid
)) {
1140 struct rq
*rq
= cpu_rq(cpu
);
1142 ns
->nr_running
+= rq
->nr_running
;
1143 ns
->load
+= weighted_cpuload(cpu
);
1144 ns
->compute_capacity
+= capacity_of(cpu
);
1150 * If we raced with hotplug and there are no CPUs left in our mask
1151 * the @ns structure is NULL'ed and task_numa_compare() will
1152 * not find this node attractive.
1154 * We'll either bail at !has_free_capacity, or we'll detect a huge
1155 * imbalance and bail there.
1160 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1161 smt
= DIV_ROUND_UP(SCHED_CAPACITY_SCALE
* cpus
, ns
->compute_capacity
);
1162 capacity
= cpus
/ smt
; /* cores */
1164 ns
->task_capacity
= min_t(unsigned, capacity
,
1165 DIV_ROUND_CLOSEST(ns
->compute_capacity
, SCHED_CAPACITY_SCALE
));
1166 ns
->has_free_capacity
= (ns
->nr_running
< ns
->task_capacity
);
1169 struct task_numa_env
{
1170 struct task_struct
*p
;
1172 int src_cpu
, src_nid
;
1173 int dst_cpu
, dst_nid
;
1175 struct numa_stats src_stats
, dst_stats
;
1180 struct task_struct
*best_task
;
1185 static void task_numa_assign(struct task_numa_env
*env
,
1186 struct task_struct
*p
, long imp
)
1189 put_task_struct(env
->best_task
);
1194 env
->best_imp
= imp
;
1195 env
->best_cpu
= env
->dst_cpu
;
1198 static bool load_too_imbalanced(long src_load
, long dst_load
,
1199 struct task_numa_env
*env
)
1201 long src_capacity
, dst_capacity
;
1203 long load_a
, load_b
;
1208 * The load is corrected for the CPU capacity available on each node.
1211 * ------------ vs ---------
1212 * src_capacity dst_capacity
1214 src_capacity
= env
->src_stats
.compute_capacity
;
1215 dst_capacity
= env
->dst_stats
.compute_capacity
;
1217 /* We care about the slope of the imbalance, not the direction. */
1220 if (load_a
< load_b
)
1221 swap(load_a
, load_b
);
1223 /* Is the difference below the threshold? */
1224 imb
= load_a
* src_capacity
* 100 -
1225 load_b
* dst_capacity
* env
->imbalance_pct
;
1230 * The imbalance is above the allowed threshold.
1231 * Allow a move that brings us closer to a balanced situation,
1232 * without moving things past the point of balance.
1234 orig_src_load
= env
->src_stats
.load
;
1237 * In a task swap, there will be one load moving from src to dst,
1238 * and another moving back. This is the net sum of both moves.
1239 * A simple task move will always have a positive value.
1240 * Allow the move if it brings the system closer to a balanced
1241 * situation, without crossing over the balance point.
1243 moved_load
= orig_src_load
- src_load
;
1246 /* Moving src -> dst. Did we overshoot balance? */
1247 return src_load
* dst_capacity
< dst_load
* src_capacity
;
1249 /* Moving dst -> src. Did we overshoot balance? */
1250 return dst_load
* src_capacity
< src_load
* dst_capacity
;
1254 * This checks if the overall compute and NUMA accesses of the system would
1255 * be improved if the source tasks was migrated to the target dst_cpu taking
1256 * into account that it might be best if task running on the dst_cpu should
1257 * be exchanged with the source task
1259 static void task_numa_compare(struct task_numa_env
*env
,
1260 long taskimp
, long groupimp
)
1262 struct rq
*src_rq
= cpu_rq(env
->src_cpu
);
1263 struct rq
*dst_rq
= cpu_rq(env
->dst_cpu
);
1264 struct task_struct
*cur
;
1265 long src_load
, dst_load
;
1267 long imp
= env
->p
->numa_group
? groupimp
: taskimp
;
1269 int dist
= env
->dist
;
1273 raw_spin_lock_irq(&dst_rq
->lock
);
1276 * No need to move the exiting task, and this ensures that ->curr
1277 * wasn't reaped and thus get_task_struct() in task_numa_assign()
1278 * is safe under RCU read lock.
1279 * Note that rcu_read_lock() itself can't protect from the final
1280 * put_task_struct() after the last schedule().
1282 if ((cur
->flags
& PF_EXITING
) || is_idle_task(cur
))
1284 raw_spin_unlock_irq(&dst_rq
->lock
);
1287 * Because we have preemption enabled we can get migrated around and
1288 * end try selecting ourselves (current == env->p) as a swap candidate.
1294 * "imp" is the fault differential for the source task between the
1295 * source and destination node. Calculate the total differential for
1296 * the source task and potential destination task. The more negative
1297 * the value is, the more rmeote accesses that would be expected to
1298 * be incurred if the tasks were swapped.
1301 /* Skip this swap candidate if cannot move to the source cpu */
1302 if (!cpumask_test_cpu(env
->src_cpu
, tsk_cpus_allowed(cur
)))
1306 * If dst and source tasks are in the same NUMA group, or not
1307 * in any group then look only at task weights.
1309 if (cur
->numa_group
== env
->p
->numa_group
) {
1310 imp
= taskimp
+ task_weight(cur
, env
->src_nid
, dist
) -
1311 task_weight(cur
, env
->dst_nid
, dist
);
1313 * Add some hysteresis to prevent swapping the
1314 * tasks within a group over tiny differences.
1316 if (cur
->numa_group
)
1320 * Compare the group weights. If a task is all by
1321 * itself (not part of a group), use the task weight
1324 if (cur
->numa_group
)
1325 imp
+= group_weight(cur
, env
->src_nid
, dist
) -
1326 group_weight(cur
, env
->dst_nid
, dist
);
1328 imp
+= task_weight(cur
, env
->src_nid
, dist
) -
1329 task_weight(cur
, env
->dst_nid
, dist
);
1333 if (imp
<= env
->best_imp
&& moveimp
<= env
->best_imp
)
1337 /* Is there capacity at our destination? */
1338 if (env
->src_stats
.nr_running
<= env
->src_stats
.task_capacity
&&
1339 !env
->dst_stats
.has_free_capacity
)
1345 /* Balance doesn't matter much if we're running a task per cpu */
1346 if (imp
> env
->best_imp
&& src_rq
->nr_running
== 1 &&
1347 dst_rq
->nr_running
== 1)
1351 * In the overloaded case, try and keep the load balanced.
1354 load
= task_h_load(env
->p
);
1355 dst_load
= env
->dst_stats
.load
+ load
;
1356 src_load
= env
->src_stats
.load
- load
;
1358 if (moveimp
> imp
&& moveimp
> env
->best_imp
) {
1360 * If the improvement from just moving env->p direction is
1361 * better than swapping tasks around, check if a move is
1362 * possible. Store a slightly smaller score than moveimp,
1363 * so an actually idle CPU will win.
1365 if (!load_too_imbalanced(src_load
, dst_load
, env
)) {
1372 if (imp
<= env
->best_imp
)
1376 load
= task_h_load(cur
);
1381 if (load_too_imbalanced(src_load
, dst_load
, env
))
1385 * One idle CPU per node is evaluated for a task numa move.
1386 * Call select_idle_sibling to maybe find a better one.
1389 env
->dst_cpu
= select_idle_sibling(env
->p
, env
->dst_cpu
);
1392 task_numa_assign(env
, cur
, imp
);
1397 static void task_numa_find_cpu(struct task_numa_env
*env
,
1398 long taskimp
, long groupimp
)
1402 for_each_cpu(cpu
, cpumask_of_node(env
->dst_nid
)) {
1403 /* Skip this CPU if the source task cannot migrate */
1404 if (!cpumask_test_cpu(cpu
, tsk_cpus_allowed(env
->p
)))
1408 task_numa_compare(env
, taskimp
, groupimp
);
1412 static int task_numa_migrate(struct task_struct
*p
)
1414 struct task_numa_env env
= {
1417 .src_cpu
= task_cpu(p
),
1418 .src_nid
= task_node(p
),
1420 .imbalance_pct
= 112,
1426 struct sched_domain
*sd
;
1427 unsigned long taskweight
, groupweight
;
1429 long taskimp
, groupimp
;
1432 * Pick the lowest SD_NUMA domain, as that would have the smallest
1433 * imbalance and would be the first to start moving tasks about.
1435 * And we want to avoid any moving of tasks about, as that would create
1436 * random movement of tasks -- counter the numa conditions we're trying
1440 sd
= rcu_dereference(per_cpu(sd_numa
, env
.src_cpu
));
1442 env
.imbalance_pct
= 100 + (sd
->imbalance_pct
- 100) / 2;
1446 * Cpusets can break the scheduler domain tree into smaller
1447 * balance domains, some of which do not cross NUMA boundaries.
1448 * Tasks that are "trapped" in such domains cannot be migrated
1449 * elsewhere, so there is no point in (re)trying.
1451 if (unlikely(!sd
)) {
1452 p
->numa_preferred_nid
= task_node(p
);
1456 env
.dst_nid
= p
->numa_preferred_nid
;
1457 dist
= env
.dist
= node_distance(env
.src_nid
, env
.dst_nid
);
1458 taskweight
= task_weight(p
, env
.src_nid
, dist
);
1459 groupweight
= group_weight(p
, env
.src_nid
, dist
);
1460 update_numa_stats(&env
.src_stats
, env
.src_nid
);
1461 taskimp
= task_weight(p
, env
.dst_nid
, dist
) - taskweight
;
1462 groupimp
= group_weight(p
, env
.dst_nid
, dist
) - groupweight
;
1463 update_numa_stats(&env
.dst_stats
, env
.dst_nid
);
1465 /* Try to find a spot on the preferred nid. */
1466 task_numa_find_cpu(&env
, taskimp
, groupimp
);
1469 * Look at other nodes in these cases:
1470 * - there is no space available on the preferred_nid
1471 * - the task is part of a numa_group that is interleaved across
1472 * multiple NUMA nodes; in order to better consolidate the group,
1473 * we need to check other locations.
1475 if (env
.best_cpu
== -1 || (p
->numa_group
&&
1476 nodes_weight(p
->numa_group
->active_nodes
) > 1)) {
1477 for_each_online_node(nid
) {
1478 if (nid
== env
.src_nid
|| nid
== p
->numa_preferred_nid
)
1481 dist
= node_distance(env
.src_nid
, env
.dst_nid
);
1482 if (sched_numa_topology_type
== NUMA_BACKPLANE
&&
1484 taskweight
= task_weight(p
, env
.src_nid
, dist
);
1485 groupweight
= group_weight(p
, env
.src_nid
, dist
);
1488 /* Only consider nodes where both task and groups benefit */
1489 taskimp
= task_weight(p
, nid
, dist
) - taskweight
;
1490 groupimp
= group_weight(p
, nid
, dist
) - groupweight
;
1491 if (taskimp
< 0 && groupimp
< 0)
1496 update_numa_stats(&env
.dst_stats
, env
.dst_nid
);
1497 task_numa_find_cpu(&env
, taskimp
, groupimp
);
1502 * If the task is part of a workload that spans multiple NUMA nodes,
1503 * and is migrating into one of the workload's active nodes, remember
1504 * this node as the task's preferred numa node, so the workload can
1506 * A task that migrated to a second choice node will be better off
1507 * trying for a better one later. Do not set the preferred node here.
1509 if (p
->numa_group
) {
1510 if (env
.best_cpu
== -1)
1515 if (node_isset(nid
, p
->numa_group
->active_nodes
))
1516 sched_setnuma(p
, env
.dst_nid
);
1519 /* No better CPU than the current one was found. */
1520 if (env
.best_cpu
== -1)
1524 * Reset the scan period if the task is being rescheduled on an
1525 * alternative node to recheck if the tasks is now properly placed.
1527 p
->numa_scan_period
= task_scan_min(p
);
1529 if (env
.best_task
== NULL
) {
1530 ret
= migrate_task_to(p
, env
.best_cpu
);
1532 trace_sched_stick_numa(p
, env
.src_cpu
, env
.best_cpu
);
1536 ret
= migrate_swap(p
, env
.best_task
);
1538 trace_sched_stick_numa(p
, env
.src_cpu
, task_cpu(env
.best_task
));
1539 put_task_struct(env
.best_task
);
1543 /* Attempt to migrate a task to a CPU on the preferred node. */
1544 static void numa_migrate_preferred(struct task_struct
*p
)
1546 unsigned long interval
= HZ
;
1548 /* This task has no NUMA fault statistics yet */
1549 if (unlikely(p
->numa_preferred_nid
== -1 || !p
->numa_faults
))
1552 /* Periodically retry migrating the task to the preferred node */
1553 interval
= min(interval
, msecs_to_jiffies(p
->numa_scan_period
) / 16);
1554 p
->numa_migrate_retry
= jiffies
+ interval
;
1556 /* Success if task is already running on preferred CPU */
1557 if (task_node(p
) == p
->numa_preferred_nid
)
1560 /* Otherwise, try migrate to a CPU on the preferred node */
1561 task_numa_migrate(p
);
1565 * Find the nodes on which the workload is actively running. We do this by
1566 * tracking the nodes from which NUMA hinting faults are triggered. This can
1567 * be different from the set of nodes where the workload's memory is currently
1570 * The bitmask is used to make smarter decisions on when to do NUMA page
1571 * migrations, To prevent flip-flopping, and excessive page migrations, nodes
1572 * are added when they cause over 6/16 of the maximum number of faults, but
1573 * only removed when they drop below 3/16.
1575 static void update_numa_active_node_mask(struct numa_group
*numa_group
)
1577 unsigned long faults
, max_faults
= 0;
1580 for_each_online_node(nid
) {
1581 faults
= group_faults_cpu(numa_group
, nid
);
1582 if (faults
> max_faults
)
1583 max_faults
= faults
;
1586 for_each_online_node(nid
) {
1587 faults
= group_faults_cpu(numa_group
, nid
);
1588 if (!node_isset(nid
, numa_group
->active_nodes
)) {
1589 if (faults
> max_faults
* 6 / 16)
1590 node_set(nid
, numa_group
->active_nodes
);
1591 } else if (faults
< max_faults
* 3 / 16)
1592 node_clear(nid
, numa_group
->active_nodes
);
1597 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1598 * increments. The more local the fault statistics are, the higher the scan
1599 * period will be for the next scan window. If local/(local+remote) ratio is
1600 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1601 * the scan period will decrease. Aim for 70% local accesses.
1603 #define NUMA_PERIOD_SLOTS 10
1604 #define NUMA_PERIOD_THRESHOLD 7
1607 * Increase the scan period (slow down scanning) if the majority of
1608 * our memory is already on our local node, or if the majority of
1609 * the page accesses are shared with other processes.
1610 * Otherwise, decrease the scan period.
1612 static void update_task_scan_period(struct task_struct
*p
,
1613 unsigned long shared
, unsigned long private)
1615 unsigned int period_slot
;
1619 unsigned long remote
= p
->numa_faults_locality
[0];
1620 unsigned long local
= p
->numa_faults_locality
[1];
1623 * If there were no record hinting faults then either the task is
1624 * completely idle or all activity is areas that are not of interest
1625 * to automatic numa balancing. Scan slower
1627 if (local
+ shared
== 0) {
1628 p
->numa_scan_period
= min(p
->numa_scan_period_max
,
1629 p
->numa_scan_period
<< 1);
1631 p
->mm
->numa_next_scan
= jiffies
+
1632 msecs_to_jiffies(p
->numa_scan_period
);
1638 * Prepare to scale scan period relative to the current period.
1639 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1640 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1641 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1643 period_slot
= DIV_ROUND_UP(p
->numa_scan_period
, NUMA_PERIOD_SLOTS
);
1644 ratio
= (local
* NUMA_PERIOD_SLOTS
) / (local
+ remote
);
1645 if (ratio
>= NUMA_PERIOD_THRESHOLD
) {
1646 int slot
= ratio
- NUMA_PERIOD_THRESHOLD
;
1649 diff
= slot
* period_slot
;
1651 diff
= -(NUMA_PERIOD_THRESHOLD
- ratio
) * period_slot
;
1654 * Scale scan rate increases based on sharing. There is an
1655 * inverse relationship between the degree of sharing and
1656 * the adjustment made to the scanning period. Broadly
1657 * speaking the intent is that there is little point
1658 * scanning faster if shared accesses dominate as it may
1659 * simply bounce migrations uselessly
1661 ratio
= DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS
, (private + shared
+ 1));
1662 diff
= (diff
* ratio
) / NUMA_PERIOD_SLOTS
;
1665 p
->numa_scan_period
= clamp(p
->numa_scan_period
+ diff
,
1666 task_scan_min(p
), task_scan_max(p
));
1667 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
1671 * Get the fraction of time the task has been running since the last
1672 * NUMA placement cycle. The scheduler keeps similar statistics, but
1673 * decays those on a 32ms period, which is orders of magnitude off
1674 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1675 * stats only if the task is so new there are no NUMA statistics yet.
1677 static u64
numa_get_avg_runtime(struct task_struct
*p
, u64
*period
)
1679 u64 runtime
, delta
, now
;
1680 /* Use the start of this time slice to avoid calculations. */
1681 now
= p
->se
.exec_start
;
1682 runtime
= p
->se
.sum_exec_runtime
;
1684 if (p
->last_task_numa_placement
) {
1685 delta
= runtime
- p
->last_sum_exec_runtime
;
1686 *period
= now
- p
->last_task_numa_placement
;
1688 delta
= p
->se
.avg
.runnable_avg_sum
;
1689 *period
= p
->se
.avg
.avg_period
;
1692 p
->last_sum_exec_runtime
= runtime
;
1693 p
->last_task_numa_placement
= now
;
1699 * Determine the preferred nid for a task in a numa_group. This needs to
1700 * be done in a way that produces consistent results with group_weight,
1701 * otherwise workloads might not converge.
1703 static int preferred_group_nid(struct task_struct
*p
, int nid
)
1708 /* Direct connections between all NUMA nodes. */
1709 if (sched_numa_topology_type
== NUMA_DIRECT
)
1713 * On a system with glueless mesh NUMA topology, group_weight
1714 * scores nodes according to the number of NUMA hinting faults on
1715 * both the node itself, and on nearby nodes.
1717 if (sched_numa_topology_type
== NUMA_GLUELESS_MESH
) {
1718 unsigned long score
, max_score
= 0;
1719 int node
, max_node
= nid
;
1721 dist
= sched_max_numa_distance
;
1723 for_each_online_node(node
) {
1724 score
= group_weight(p
, node
, dist
);
1725 if (score
> max_score
) {
1734 * Finding the preferred nid in a system with NUMA backplane
1735 * interconnect topology is more involved. The goal is to locate
1736 * tasks from numa_groups near each other in the system, and
1737 * untangle workloads from different sides of the system. This requires
1738 * searching down the hierarchy of node groups, recursively searching
1739 * inside the highest scoring group of nodes. The nodemask tricks
1740 * keep the complexity of the search down.
1742 nodes
= node_online_map
;
1743 for (dist
= sched_max_numa_distance
; dist
> LOCAL_DISTANCE
; dist
--) {
1744 unsigned long max_faults
= 0;
1745 nodemask_t max_group
= NODE_MASK_NONE
;
1748 /* Are there nodes at this distance from each other? */
1749 if (!find_numa_distance(dist
))
1752 for_each_node_mask(a
, nodes
) {
1753 unsigned long faults
= 0;
1754 nodemask_t this_group
;
1755 nodes_clear(this_group
);
1757 /* Sum group's NUMA faults; includes a==b case. */
1758 for_each_node_mask(b
, nodes
) {
1759 if (node_distance(a
, b
) < dist
) {
1760 faults
+= group_faults(p
, b
);
1761 node_set(b
, this_group
);
1762 node_clear(b
, nodes
);
1766 /* Remember the top group. */
1767 if (faults
> max_faults
) {
1768 max_faults
= faults
;
1769 max_group
= this_group
;
1771 * subtle: at the smallest distance there is
1772 * just one node left in each "group", the
1773 * winner is the preferred nid.
1778 /* Next round, evaluate the nodes within max_group. */
1786 static void task_numa_placement(struct task_struct
*p
)
1788 int seq
, nid
, max_nid
= -1, max_group_nid
= -1;
1789 unsigned long max_faults
= 0, max_group_faults
= 0;
1790 unsigned long fault_types
[2] = { 0, 0 };
1791 unsigned long total_faults
;
1792 u64 runtime
, period
;
1793 spinlock_t
*group_lock
= NULL
;
1795 seq
= ACCESS_ONCE(p
->mm
->numa_scan_seq
);
1796 if (p
->numa_scan_seq
== seq
)
1798 p
->numa_scan_seq
= seq
;
1799 p
->numa_scan_period_max
= task_scan_max(p
);
1801 total_faults
= p
->numa_faults_locality
[0] +
1802 p
->numa_faults_locality
[1];
1803 runtime
= numa_get_avg_runtime(p
, &period
);
1805 /* If the task is part of a group prevent parallel updates to group stats */
1806 if (p
->numa_group
) {
1807 group_lock
= &p
->numa_group
->lock
;
1808 spin_lock_irq(group_lock
);
1811 /* Find the node with the highest number of faults */
1812 for_each_online_node(nid
) {
1813 /* Keep track of the offsets in numa_faults array */
1814 int mem_idx
, membuf_idx
, cpu_idx
, cpubuf_idx
;
1815 unsigned long faults
= 0, group_faults
= 0;
1818 for (priv
= 0; priv
< NR_NUMA_HINT_FAULT_TYPES
; priv
++) {
1819 long diff
, f_diff
, f_weight
;
1821 mem_idx
= task_faults_idx(NUMA_MEM
, nid
, priv
);
1822 membuf_idx
= task_faults_idx(NUMA_MEMBUF
, nid
, priv
);
1823 cpu_idx
= task_faults_idx(NUMA_CPU
, nid
, priv
);
1824 cpubuf_idx
= task_faults_idx(NUMA_CPUBUF
, nid
, priv
);
1826 /* Decay existing window, copy faults since last scan */
1827 diff
= p
->numa_faults
[membuf_idx
] - p
->numa_faults
[mem_idx
] / 2;
1828 fault_types
[priv
] += p
->numa_faults
[membuf_idx
];
1829 p
->numa_faults
[membuf_idx
] = 0;
1832 * Normalize the faults_from, so all tasks in a group
1833 * count according to CPU use, instead of by the raw
1834 * number of faults. Tasks with little runtime have
1835 * little over-all impact on throughput, and thus their
1836 * faults are less important.
1838 f_weight
= div64_u64(runtime
<< 16, period
+ 1);
1839 f_weight
= (f_weight
* p
->numa_faults
[cpubuf_idx
]) /
1841 f_diff
= f_weight
- p
->numa_faults
[cpu_idx
] / 2;
1842 p
->numa_faults
[cpubuf_idx
] = 0;
1844 p
->numa_faults
[mem_idx
] += diff
;
1845 p
->numa_faults
[cpu_idx
] += f_diff
;
1846 faults
+= p
->numa_faults
[mem_idx
];
1847 p
->total_numa_faults
+= diff
;
1848 if (p
->numa_group
) {
1850 * safe because we can only change our own group
1852 * mem_idx represents the offset for a given
1853 * nid and priv in a specific region because it
1854 * is at the beginning of the numa_faults array.
1856 p
->numa_group
->faults
[mem_idx
] += diff
;
1857 p
->numa_group
->faults_cpu
[mem_idx
] += f_diff
;
1858 p
->numa_group
->total_faults
+= diff
;
1859 group_faults
+= p
->numa_group
->faults
[mem_idx
];
1863 if (faults
> max_faults
) {
1864 max_faults
= faults
;
1868 if (group_faults
> max_group_faults
) {
1869 max_group_faults
= group_faults
;
1870 max_group_nid
= nid
;
1874 update_task_scan_period(p
, fault_types
[0], fault_types
[1]);
1876 if (p
->numa_group
) {
1877 update_numa_active_node_mask(p
->numa_group
);
1878 spin_unlock_irq(group_lock
);
1879 max_nid
= preferred_group_nid(p
, max_group_nid
);
1883 /* Set the new preferred node */
1884 if (max_nid
!= p
->numa_preferred_nid
)
1885 sched_setnuma(p
, max_nid
);
1887 if (task_node(p
) != p
->numa_preferred_nid
)
1888 numa_migrate_preferred(p
);
1892 static inline int get_numa_group(struct numa_group
*grp
)
1894 return atomic_inc_not_zero(&grp
->refcount
);
1897 static inline void put_numa_group(struct numa_group
*grp
)
1899 if (atomic_dec_and_test(&grp
->refcount
))
1900 kfree_rcu(grp
, rcu
);
1903 static void task_numa_group(struct task_struct
*p
, int cpupid
, int flags
,
1906 struct numa_group
*grp
, *my_grp
;
1907 struct task_struct
*tsk
;
1909 int cpu
= cpupid_to_cpu(cpupid
);
1912 if (unlikely(!p
->numa_group
)) {
1913 unsigned int size
= sizeof(struct numa_group
) +
1914 4*nr_node_ids
*sizeof(unsigned long);
1916 grp
= kzalloc(size
, GFP_KERNEL
| __GFP_NOWARN
);
1920 atomic_set(&grp
->refcount
, 1);
1921 spin_lock_init(&grp
->lock
);
1923 /* Second half of the array tracks nids where faults happen */
1924 grp
->faults_cpu
= grp
->faults
+ NR_NUMA_HINT_FAULT_TYPES
*
1927 node_set(task_node(current
), grp
->active_nodes
);
1929 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
1930 grp
->faults
[i
] = p
->numa_faults
[i
];
1932 grp
->total_faults
= p
->total_numa_faults
;
1935 rcu_assign_pointer(p
->numa_group
, grp
);
1939 tsk
= ACCESS_ONCE(cpu_rq(cpu
)->curr
);
1941 if (!cpupid_match_pid(tsk
, cpupid
))
1944 grp
= rcu_dereference(tsk
->numa_group
);
1948 my_grp
= p
->numa_group
;
1953 * Only join the other group if its bigger; if we're the bigger group,
1954 * the other task will join us.
1956 if (my_grp
->nr_tasks
> grp
->nr_tasks
)
1960 * Tie-break on the grp address.
1962 if (my_grp
->nr_tasks
== grp
->nr_tasks
&& my_grp
> grp
)
1965 /* Always join threads in the same process. */
1966 if (tsk
->mm
== current
->mm
)
1969 /* Simple filter to avoid false positives due to PID collisions */
1970 if (flags
& TNF_SHARED
)
1973 /* Update priv based on whether false sharing was detected */
1976 if (join
&& !get_numa_group(grp
))
1984 BUG_ON(irqs_disabled());
1985 double_lock_irq(&my_grp
->lock
, &grp
->lock
);
1987 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++) {
1988 my_grp
->faults
[i
] -= p
->numa_faults
[i
];
1989 grp
->faults
[i
] += p
->numa_faults
[i
];
1991 my_grp
->total_faults
-= p
->total_numa_faults
;
1992 grp
->total_faults
+= p
->total_numa_faults
;
1997 spin_unlock(&my_grp
->lock
);
1998 spin_unlock_irq(&grp
->lock
);
2000 rcu_assign_pointer(p
->numa_group
, grp
);
2002 put_numa_group(my_grp
);
2010 void task_numa_free(struct task_struct
*p
)
2012 struct numa_group
*grp
= p
->numa_group
;
2013 void *numa_faults
= p
->numa_faults
;
2014 unsigned long flags
;
2018 spin_lock_irqsave(&grp
->lock
, flags
);
2019 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
2020 grp
->faults
[i
] -= p
->numa_faults
[i
];
2021 grp
->total_faults
-= p
->total_numa_faults
;
2024 spin_unlock_irqrestore(&grp
->lock
, flags
);
2025 RCU_INIT_POINTER(p
->numa_group
, NULL
);
2026 put_numa_group(grp
);
2029 p
->numa_faults
= NULL
;
2034 * Got a PROT_NONE fault for a page on @node.
2036 void task_numa_fault(int last_cpupid
, int mem_node
, int pages
, int flags
)
2038 struct task_struct
*p
= current
;
2039 bool migrated
= flags
& TNF_MIGRATED
;
2040 int cpu_node
= task_node(current
);
2041 int local
= !!(flags
& TNF_FAULT_LOCAL
);
2044 if (!numabalancing_enabled
)
2047 /* for example, ksmd faulting in a user's mm */
2051 /* Allocate buffer to track faults on a per-node basis */
2052 if (unlikely(!p
->numa_faults
)) {
2053 int size
= sizeof(*p
->numa_faults
) *
2054 NR_NUMA_HINT_FAULT_BUCKETS
* nr_node_ids
;
2056 p
->numa_faults
= kzalloc(size
, GFP_KERNEL
|__GFP_NOWARN
);
2057 if (!p
->numa_faults
)
2060 p
->total_numa_faults
= 0;
2061 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
2065 * First accesses are treated as private, otherwise consider accesses
2066 * to be private if the accessing pid has not changed
2068 if (unlikely(last_cpupid
== (-1 & LAST_CPUPID_MASK
))) {
2071 priv
= cpupid_match_pid(p
, last_cpupid
);
2072 if (!priv
&& !(flags
& TNF_NO_GROUP
))
2073 task_numa_group(p
, last_cpupid
, flags
, &priv
);
2077 * If a workload spans multiple NUMA nodes, a shared fault that
2078 * occurs wholly within the set of nodes that the workload is
2079 * actively using should be counted as local. This allows the
2080 * scan rate to slow down when a workload has settled down.
2082 if (!priv
&& !local
&& p
->numa_group
&&
2083 node_isset(cpu_node
, p
->numa_group
->active_nodes
) &&
2084 node_isset(mem_node
, p
->numa_group
->active_nodes
))
2087 task_numa_placement(p
);
2090 * Retry task to preferred node migration periodically, in case it
2091 * case it previously failed, or the scheduler moved us.
2093 if (time_after(jiffies
, p
->numa_migrate_retry
))
2094 numa_migrate_preferred(p
);
2097 p
->numa_pages_migrated
+= pages
;
2099 p
->numa_faults
[task_faults_idx(NUMA_MEMBUF
, mem_node
, priv
)] += pages
;
2100 p
->numa_faults
[task_faults_idx(NUMA_CPUBUF
, cpu_node
, priv
)] += pages
;
2101 p
->numa_faults_locality
[local
] += pages
;
2104 static void reset_ptenuma_scan(struct task_struct
*p
)
2106 ACCESS_ONCE(p
->mm
->numa_scan_seq
)++;
2107 p
->mm
->numa_scan_offset
= 0;
2111 * The expensive part of numa migration is done from task_work context.
2112 * Triggered from task_tick_numa().
2114 void task_numa_work(struct callback_head
*work
)
2116 unsigned long migrate
, next_scan
, now
= jiffies
;
2117 struct task_struct
*p
= current
;
2118 struct mm_struct
*mm
= p
->mm
;
2119 struct vm_area_struct
*vma
;
2120 unsigned long start
, end
;
2121 unsigned long nr_pte_updates
= 0;
2124 WARN_ON_ONCE(p
!= container_of(work
, struct task_struct
, numa_work
));
2126 work
->next
= work
; /* protect against double add */
2128 * Who cares about NUMA placement when they're dying.
2130 * NOTE: make sure not to dereference p->mm before this check,
2131 * exit_task_work() happens _after_ exit_mm() so we could be called
2132 * without p->mm even though we still had it when we enqueued this
2135 if (p
->flags
& PF_EXITING
)
2138 if (!mm
->numa_next_scan
) {
2139 mm
->numa_next_scan
= now
+
2140 msecs_to_jiffies(sysctl_numa_balancing_scan_delay
);
2144 * Enforce maximal scan/migration frequency..
2146 migrate
= mm
->numa_next_scan
;
2147 if (time_before(now
, migrate
))
2150 if (p
->numa_scan_period
== 0) {
2151 p
->numa_scan_period_max
= task_scan_max(p
);
2152 p
->numa_scan_period
= task_scan_min(p
);
2155 next_scan
= now
+ msecs_to_jiffies(p
->numa_scan_period
);
2156 if (cmpxchg(&mm
->numa_next_scan
, migrate
, next_scan
) != migrate
)
2160 * Delay this task enough that another task of this mm will likely win
2161 * the next time around.
2163 p
->node_stamp
+= 2 * TICK_NSEC
;
2165 start
= mm
->numa_scan_offset
;
2166 pages
= sysctl_numa_balancing_scan_size
;
2167 pages
<<= 20 - PAGE_SHIFT
; /* MB in pages */
2171 down_read(&mm
->mmap_sem
);
2172 vma
= find_vma(mm
, start
);
2174 reset_ptenuma_scan(p
);
2178 for (; vma
; vma
= vma
->vm_next
) {
2179 if (!vma_migratable(vma
) || !vma_policy_mof(vma
))
2183 * Shared library pages mapped by multiple processes are not
2184 * migrated as it is expected they are cache replicated. Avoid
2185 * hinting faults in read-only file-backed mappings or the vdso
2186 * as migrating the pages will be of marginal benefit.
2189 (vma
->vm_file
&& (vma
->vm_flags
& (VM_READ
|VM_WRITE
)) == (VM_READ
)))
2193 * Skip inaccessible VMAs to avoid any confusion between
2194 * PROT_NONE and NUMA hinting ptes
2196 if (!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
)))
2200 start
= max(start
, vma
->vm_start
);
2201 end
= ALIGN(start
+ (pages
<< PAGE_SHIFT
), HPAGE_SIZE
);
2202 end
= min(end
, vma
->vm_end
);
2203 nr_pte_updates
+= change_prot_numa(vma
, start
, end
);
2206 * Scan sysctl_numa_balancing_scan_size but ensure that
2207 * at least one PTE is updated so that unused virtual
2208 * address space is quickly skipped.
2211 pages
-= (end
- start
) >> PAGE_SHIFT
;
2218 } while (end
!= vma
->vm_end
);
2223 * It is possible to reach the end of the VMA list but the last few
2224 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2225 * would find the !migratable VMA on the next scan but not reset the
2226 * scanner to the start so check it now.
2229 mm
->numa_scan_offset
= start
;
2231 reset_ptenuma_scan(p
);
2232 up_read(&mm
->mmap_sem
);
2236 * Drive the periodic memory faults..
2238 void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
2240 struct callback_head
*work
= &curr
->numa_work
;
2244 * We don't care about NUMA placement if we don't have memory.
2246 if (!curr
->mm
|| (curr
->flags
& PF_EXITING
) || work
->next
!= work
)
2250 * Using runtime rather than walltime has the dual advantage that
2251 * we (mostly) drive the selection from busy threads and that the
2252 * task needs to have done some actual work before we bother with
2255 now
= curr
->se
.sum_exec_runtime
;
2256 period
= (u64
)curr
->numa_scan_period
* NSEC_PER_MSEC
;
2258 if (now
- curr
->node_stamp
> period
) {
2259 if (!curr
->node_stamp
)
2260 curr
->numa_scan_period
= task_scan_min(curr
);
2261 curr
->node_stamp
+= period
;
2263 if (!time_before(jiffies
, curr
->mm
->numa_next_scan
)) {
2264 init_task_work(work
, task_numa_work
); /* TODO: move this into sched_fork() */
2265 task_work_add(curr
, work
, true);
2270 static void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
2274 static inline void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
2278 static inline void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
2281 #endif /* CONFIG_NUMA_BALANCING */
2284 account_entity_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2286 update_load_add(&cfs_rq
->load
, se
->load
.weight
);
2287 if (!parent_entity(se
))
2288 update_load_add(&rq_of(cfs_rq
)->load
, se
->load
.weight
);
2290 if (entity_is_task(se
)) {
2291 struct rq
*rq
= rq_of(cfs_rq
);
2293 account_numa_enqueue(rq
, task_of(se
));
2294 list_add(&se
->group_node
, &rq
->cfs_tasks
);
2297 cfs_rq
->nr_running
++;
2301 account_entity_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2303 update_load_sub(&cfs_rq
->load
, se
->load
.weight
);
2304 if (!parent_entity(se
))
2305 update_load_sub(&rq_of(cfs_rq
)->load
, se
->load
.weight
);
2306 if (entity_is_task(se
)) {
2307 account_numa_dequeue(rq_of(cfs_rq
), task_of(se
));
2308 list_del_init(&se
->group_node
);
2310 cfs_rq
->nr_running
--;
2313 #ifdef CONFIG_FAIR_GROUP_SCHED
2315 static inline long calc_tg_weight(struct task_group
*tg
, struct cfs_rq
*cfs_rq
)
2320 * Use this CPU's actual weight instead of the last load_contribution
2321 * to gain a more accurate current total weight. See
2322 * update_cfs_rq_load_contribution().
2324 tg_weight
= atomic_long_read(&tg
->load_avg
);
2325 tg_weight
-= cfs_rq
->tg_load_contrib
;
2326 tg_weight
+= cfs_rq
->load
.weight
;
2331 static long calc_cfs_shares(struct cfs_rq
*cfs_rq
, struct task_group
*tg
)
2333 long tg_weight
, load
, shares
;
2335 tg_weight
= calc_tg_weight(tg
, cfs_rq
);
2336 load
= cfs_rq
->load
.weight
;
2338 shares
= (tg
->shares
* load
);
2340 shares
/= tg_weight
;
2342 if (shares
< MIN_SHARES
)
2343 shares
= MIN_SHARES
;
2344 if (shares
> tg
->shares
)
2345 shares
= tg
->shares
;
2349 # else /* CONFIG_SMP */
2350 static inline long calc_cfs_shares(struct cfs_rq
*cfs_rq
, struct task_group
*tg
)
2354 # endif /* CONFIG_SMP */
2355 static void reweight_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
,
2356 unsigned long weight
)
2359 /* commit outstanding execution time */
2360 if (cfs_rq
->curr
== se
)
2361 update_curr(cfs_rq
);
2362 account_entity_dequeue(cfs_rq
, se
);
2365 update_load_set(&se
->load
, weight
);
2368 account_entity_enqueue(cfs_rq
, se
);
2371 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
);
2373 static void update_cfs_shares(struct cfs_rq
*cfs_rq
)
2375 struct task_group
*tg
;
2376 struct sched_entity
*se
;
2380 se
= tg
->se
[cpu_of(rq_of(cfs_rq
))];
2381 if (!se
|| throttled_hierarchy(cfs_rq
))
2384 if (likely(se
->load
.weight
== tg
->shares
))
2387 shares
= calc_cfs_shares(cfs_rq
, tg
);
2389 reweight_entity(cfs_rq_of(se
), se
, shares
);
2391 #else /* CONFIG_FAIR_GROUP_SCHED */
2392 static inline void update_cfs_shares(struct cfs_rq
*cfs_rq
)
2395 #endif /* CONFIG_FAIR_GROUP_SCHED */
2399 * We choose a half-life close to 1 scheduling period.
2400 * Note: The tables below are dependent on this value.
2402 #define LOAD_AVG_PERIOD 32
2403 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
2404 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */
2406 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2407 static const u32 runnable_avg_yN_inv
[] = {
2408 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2409 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2410 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2411 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2412 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2413 0x85aac367, 0x82cd8698,
2417 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2418 * over-estimates when re-combining.
2420 static const u32 runnable_avg_yN_sum
[] = {
2421 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2422 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2423 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2428 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2430 static __always_inline u64
decay_load(u64 val
, u64 n
)
2432 unsigned int local_n
;
2436 else if (unlikely(n
> LOAD_AVG_PERIOD
* 63))
2439 /* after bounds checking we can collapse to 32-bit */
2443 * As y^PERIOD = 1/2, we can combine
2444 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2445 * With a look-up table which covers y^n (n<PERIOD)
2447 * To achieve constant time decay_load.
2449 if (unlikely(local_n
>= LOAD_AVG_PERIOD
)) {
2450 val
>>= local_n
/ LOAD_AVG_PERIOD
;
2451 local_n
%= LOAD_AVG_PERIOD
;
2454 val
*= runnable_avg_yN_inv
[local_n
];
2455 /* We don't use SRR here since we always want to round down. */
2460 * For updates fully spanning n periods, the contribution to runnable
2461 * average will be: \Sum 1024*y^n
2463 * We can compute this reasonably efficiently by combining:
2464 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2466 static u32
__compute_runnable_contrib(u64 n
)
2470 if (likely(n
<= LOAD_AVG_PERIOD
))
2471 return runnable_avg_yN_sum
[n
];
2472 else if (unlikely(n
>= LOAD_AVG_MAX_N
))
2473 return LOAD_AVG_MAX
;
2475 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2477 contrib
/= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2478 contrib
+= runnable_avg_yN_sum
[LOAD_AVG_PERIOD
];
2480 n
-= LOAD_AVG_PERIOD
;
2481 } while (n
> LOAD_AVG_PERIOD
);
2483 contrib
= decay_load(contrib
, n
);
2484 return contrib
+ runnable_avg_yN_sum
[n
];
2488 * We can represent the historical contribution to runnable average as the
2489 * coefficients of a geometric series. To do this we sub-divide our runnable
2490 * history into segments of approximately 1ms (1024us); label the segment that
2491 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2493 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2495 * (now) (~1ms ago) (~2ms ago)
2497 * Let u_i denote the fraction of p_i that the entity was runnable.
2499 * We then designate the fractions u_i as our co-efficients, yielding the
2500 * following representation of historical load:
2501 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2503 * We choose y based on the with of a reasonably scheduling period, fixing:
2506 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2507 * approximately half as much as the contribution to load within the last ms
2510 * When a period "rolls over" and we have new u_0`, multiplying the previous
2511 * sum again by y is sufficient to update:
2512 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2513 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2515 static __always_inline
int __update_entity_runnable_avg(u64 now
,
2516 struct sched_avg
*sa
,
2521 u32 runnable_contrib
;
2522 int delta_w
, decayed
= 0;
2524 delta
= now
- sa
->last_runnable_update
;
2526 * This should only happen when time goes backwards, which it
2527 * unfortunately does during sched clock init when we swap over to TSC.
2529 if ((s64
)delta
< 0) {
2530 sa
->last_runnable_update
= now
;
2535 * Use 1024ns as the unit of measurement since it's a reasonable
2536 * approximation of 1us and fast to compute.
2541 sa
->last_runnable_update
= now
;
2543 /* delta_w is the amount already accumulated against our next period */
2544 delta_w
= sa
->avg_period
% 1024;
2545 if (delta
+ delta_w
>= 1024) {
2546 /* period roll-over */
2550 * Now that we know we're crossing a period boundary, figure
2551 * out how much from delta we need to complete the current
2552 * period and accrue it.
2554 delta_w
= 1024 - delta_w
;
2556 sa
->runnable_avg_sum
+= delta_w
;
2558 sa
->running_avg_sum
+= delta_w
;
2559 sa
->avg_period
+= delta_w
;
2563 /* Figure out how many additional periods this update spans */
2564 periods
= delta
/ 1024;
2567 sa
->runnable_avg_sum
= decay_load(sa
->runnable_avg_sum
,
2569 sa
->running_avg_sum
= decay_load(sa
->running_avg_sum
,
2571 sa
->avg_period
= decay_load(sa
->avg_period
,
2574 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2575 runnable_contrib
= __compute_runnable_contrib(periods
);
2577 sa
->runnable_avg_sum
+= runnable_contrib
;
2579 sa
->running_avg_sum
+= runnable_contrib
;
2580 sa
->avg_period
+= runnable_contrib
;
2583 /* Remainder of delta accrued against u_0` */
2585 sa
->runnable_avg_sum
+= delta
;
2587 sa
->running_avg_sum
+= delta
;
2588 sa
->avg_period
+= delta
;
2593 /* Synchronize an entity's decay with its parenting cfs_rq.*/
2594 static inline u64
__synchronize_entity_decay(struct sched_entity
*se
)
2596 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
2597 u64 decays
= atomic64_read(&cfs_rq
->decay_counter
);
2599 decays
-= se
->avg
.decay_count
;
2600 se
->avg
.decay_count
= 0;
2604 se
->avg
.load_avg_contrib
= decay_load(se
->avg
.load_avg_contrib
, decays
);
2605 se
->avg
.utilization_avg_contrib
=
2606 decay_load(se
->avg
.utilization_avg_contrib
, decays
);
2611 #ifdef CONFIG_FAIR_GROUP_SCHED
2612 static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq
*cfs_rq
,
2615 struct task_group
*tg
= cfs_rq
->tg
;
2618 tg_contrib
= cfs_rq
->runnable_load_avg
+ cfs_rq
->blocked_load_avg
;
2619 tg_contrib
-= cfs_rq
->tg_load_contrib
;
2624 if (force_update
|| abs(tg_contrib
) > cfs_rq
->tg_load_contrib
/ 8) {
2625 atomic_long_add(tg_contrib
, &tg
->load_avg
);
2626 cfs_rq
->tg_load_contrib
+= tg_contrib
;
2631 * Aggregate cfs_rq runnable averages into an equivalent task_group
2632 * representation for computing load contributions.
2634 static inline void __update_tg_runnable_avg(struct sched_avg
*sa
,
2635 struct cfs_rq
*cfs_rq
)
2637 struct task_group
*tg
= cfs_rq
->tg
;
2640 /* The fraction of a cpu used by this cfs_rq */
2641 contrib
= div_u64((u64
)sa
->runnable_avg_sum
<< NICE_0_SHIFT
,
2642 sa
->avg_period
+ 1);
2643 contrib
-= cfs_rq
->tg_runnable_contrib
;
2645 if (abs(contrib
) > cfs_rq
->tg_runnable_contrib
/ 64) {
2646 atomic_add(contrib
, &tg
->runnable_avg
);
2647 cfs_rq
->tg_runnable_contrib
+= contrib
;
2651 static inline void __update_group_entity_contrib(struct sched_entity
*se
)
2653 struct cfs_rq
*cfs_rq
= group_cfs_rq(se
);
2654 struct task_group
*tg
= cfs_rq
->tg
;
2659 contrib
= cfs_rq
->tg_load_contrib
* tg
->shares
;
2660 se
->avg
.load_avg_contrib
= div_u64(contrib
,
2661 atomic_long_read(&tg
->load_avg
) + 1);
2664 * For group entities we need to compute a correction term in the case
2665 * that they are consuming <1 cpu so that we would contribute the same
2666 * load as a task of equal weight.
2668 * Explicitly co-ordinating this measurement would be expensive, but
2669 * fortunately the sum of each cpus contribution forms a usable
2670 * lower-bound on the true value.
2672 * Consider the aggregate of 2 contributions. Either they are disjoint
2673 * (and the sum represents true value) or they are disjoint and we are
2674 * understating by the aggregate of their overlap.
2676 * Extending this to N cpus, for a given overlap, the maximum amount we
2677 * understand is then n_i(n_i+1)/2 * w_i where n_i is the number of
2678 * cpus that overlap for this interval and w_i is the interval width.
2680 * On a small machine; the first term is well-bounded which bounds the
2681 * total error since w_i is a subset of the period. Whereas on a
2682 * larger machine, while this first term can be larger, if w_i is the
2683 * of consequential size guaranteed to see n_i*w_i quickly converge to
2684 * our upper bound of 1-cpu.
2686 runnable_avg
= atomic_read(&tg
->runnable_avg
);
2687 if (runnable_avg
< NICE_0_LOAD
) {
2688 se
->avg
.load_avg_contrib
*= runnable_avg
;
2689 se
->avg
.load_avg_contrib
>>= NICE_0_SHIFT
;
2693 static inline void update_rq_runnable_avg(struct rq
*rq
, int runnable
)
2695 __update_entity_runnable_avg(rq_clock_task(rq
), &rq
->avg
, runnable
,
2697 __update_tg_runnable_avg(&rq
->avg
, &rq
->cfs
);
2699 #else /* CONFIG_FAIR_GROUP_SCHED */
2700 static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq
*cfs_rq
,
2701 int force_update
) {}
2702 static inline void __update_tg_runnable_avg(struct sched_avg
*sa
,
2703 struct cfs_rq
*cfs_rq
) {}
2704 static inline void __update_group_entity_contrib(struct sched_entity
*se
) {}
2705 static inline void update_rq_runnable_avg(struct rq
*rq
, int runnable
) {}
2706 #endif /* CONFIG_FAIR_GROUP_SCHED */
2708 static inline void __update_task_entity_contrib(struct sched_entity
*se
)
2712 /* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
2713 contrib
= se
->avg
.runnable_avg_sum
* scale_load_down(se
->load
.weight
);
2714 contrib
/= (se
->avg
.avg_period
+ 1);
2715 se
->avg
.load_avg_contrib
= scale_load(contrib
);
2718 /* Compute the current contribution to load_avg by se, return any delta */
2719 static long __update_entity_load_avg_contrib(struct sched_entity
*se
)
2721 long old_contrib
= se
->avg
.load_avg_contrib
;
2723 if (entity_is_task(se
)) {
2724 __update_task_entity_contrib(se
);
2726 __update_tg_runnable_avg(&se
->avg
, group_cfs_rq(se
));
2727 __update_group_entity_contrib(se
);
2730 return se
->avg
.load_avg_contrib
- old_contrib
;
2734 static inline void __update_task_entity_utilization(struct sched_entity
*se
)
2738 /* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
2739 contrib
= se
->avg
.running_avg_sum
* scale_load_down(SCHED_LOAD_SCALE
);
2740 contrib
/= (se
->avg
.avg_period
+ 1);
2741 se
->avg
.utilization_avg_contrib
= scale_load(contrib
);
2744 static long __update_entity_utilization_avg_contrib(struct sched_entity
*se
)
2746 long old_contrib
= se
->avg
.utilization_avg_contrib
;
2748 if (entity_is_task(se
))
2749 __update_task_entity_utilization(se
);
2751 return se
->avg
.utilization_avg_contrib
- old_contrib
;
2754 static inline void subtract_blocked_load_contrib(struct cfs_rq
*cfs_rq
,
2757 if (likely(load_contrib
< cfs_rq
->blocked_load_avg
))
2758 cfs_rq
->blocked_load_avg
-= load_contrib
;
2760 cfs_rq
->blocked_load_avg
= 0;
2763 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
);
2765 /* Update a sched_entity's runnable average */
2766 static inline void update_entity_load_avg(struct sched_entity
*se
,
2769 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
2770 long contrib_delta
, utilization_delta
;
2774 * For a group entity we need to use their owned cfs_rq_clock_task() in
2775 * case they are the parent of a throttled hierarchy.
2777 if (entity_is_task(se
))
2778 now
= cfs_rq_clock_task(cfs_rq
);
2780 now
= cfs_rq_clock_task(group_cfs_rq(se
));
2782 if (!__update_entity_runnable_avg(now
, &se
->avg
, se
->on_rq
,
2783 cfs_rq
->curr
== se
))
2786 contrib_delta
= __update_entity_load_avg_contrib(se
);
2787 utilization_delta
= __update_entity_utilization_avg_contrib(se
);
2793 cfs_rq
->runnable_load_avg
+= contrib_delta
;
2794 cfs_rq
->utilization_load_avg
+= utilization_delta
;
2796 subtract_blocked_load_contrib(cfs_rq
, -contrib_delta
);
2801 * Decay the load contributed by all blocked children and account this so that
2802 * their contribution may appropriately discounted when they wake up.
2804 static void update_cfs_rq_blocked_load(struct cfs_rq
*cfs_rq
, int force_update
)
2806 u64 now
= cfs_rq_clock_task(cfs_rq
) >> 20;
2809 decays
= now
- cfs_rq
->last_decay
;
2810 if (!decays
&& !force_update
)
2813 if (atomic_long_read(&cfs_rq
->removed_load
)) {
2814 unsigned long removed_load
;
2815 removed_load
= atomic_long_xchg(&cfs_rq
->removed_load
, 0);
2816 subtract_blocked_load_contrib(cfs_rq
, removed_load
);
2820 cfs_rq
->blocked_load_avg
= decay_load(cfs_rq
->blocked_load_avg
,
2822 atomic64_add(decays
, &cfs_rq
->decay_counter
);
2823 cfs_rq
->last_decay
= now
;
2826 __update_cfs_rq_tg_load_contrib(cfs_rq
, force_update
);
2829 /* Add the load generated by se into cfs_rq's child load-average */
2830 static inline void enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
,
2831 struct sched_entity
*se
,
2835 * We track migrations using entity decay_count <= 0, on a wake-up
2836 * migration we use a negative decay count to track the remote decays
2837 * accumulated while sleeping.
2839 * Newly forked tasks are enqueued with se->avg.decay_count == 0, they
2840 * are seen by enqueue_entity_load_avg() as a migration with an already
2841 * constructed load_avg_contrib.
2843 if (unlikely(se
->avg
.decay_count
<= 0)) {
2844 se
->avg
.last_runnable_update
= rq_clock_task(rq_of(cfs_rq
));
2845 if (se
->avg
.decay_count
) {
2847 * In a wake-up migration we have to approximate the
2848 * time sleeping. This is because we can't synchronize
2849 * clock_task between the two cpus, and it is not
2850 * guaranteed to be read-safe. Instead, we can
2851 * approximate this using our carried decays, which are
2852 * explicitly atomically readable.
2854 se
->avg
.last_runnable_update
-= (-se
->avg
.decay_count
)
2856 update_entity_load_avg(se
, 0);
2857 /* Indicate that we're now synchronized and on-rq */
2858 se
->avg
.decay_count
= 0;
2862 __synchronize_entity_decay(se
);
2865 /* migrated tasks did not contribute to our blocked load */
2867 subtract_blocked_load_contrib(cfs_rq
, se
->avg
.load_avg_contrib
);
2868 update_entity_load_avg(se
, 0);
2871 cfs_rq
->runnable_load_avg
+= se
->avg
.load_avg_contrib
;
2872 cfs_rq
->utilization_load_avg
+= se
->avg
.utilization_avg_contrib
;
2873 /* we force update consideration on load-balancer moves */
2874 update_cfs_rq_blocked_load(cfs_rq
, !wakeup
);
2878 * Remove se's load from this cfs_rq child load-average, if the entity is
2879 * transitioning to a blocked state we track its projected decay using
2882 static inline void dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
,
2883 struct sched_entity
*se
,
2886 update_entity_load_avg(se
, 1);
2887 /* we force update consideration on load-balancer moves */
2888 update_cfs_rq_blocked_load(cfs_rq
, !sleep
);
2890 cfs_rq
->runnable_load_avg
-= se
->avg
.load_avg_contrib
;
2891 cfs_rq
->utilization_load_avg
-= se
->avg
.utilization_avg_contrib
;
2893 cfs_rq
->blocked_load_avg
+= se
->avg
.load_avg_contrib
;
2894 se
->avg
.decay_count
= atomic64_read(&cfs_rq
->decay_counter
);
2895 } /* migrations, e.g. sleep=0 leave decay_count == 0 */
2899 * Update the rq's load with the elapsed running time before entering
2900 * idle. if the last scheduled task is not a CFS task, idle_enter will
2901 * be the only way to update the runnable statistic.
2903 void idle_enter_fair(struct rq
*this_rq
)
2905 update_rq_runnable_avg(this_rq
, 1);
2909 * Update the rq's load with the elapsed idle time before a task is
2910 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2911 * be the only way to update the runnable statistic.
2913 void idle_exit_fair(struct rq
*this_rq
)
2915 update_rq_runnable_avg(this_rq
, 0);
2918 static int idle_balance(struct rq
*this_rq
);
2920 #else /* CONFIG_SMP */
2922 static inline void update_entity_load_avg(struct sched_entity
*se
,
2923 int update_cfs_rq
) {}
2924 static inline void update_rq_runnable_avg(struct rq
*rq
, int runnable
) {}
2925 static inline void enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
,
2926 struct sched_entity
*se
,
2928 static inline void dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
,
2929 struct sched_entity
*se
,
2931 static inline void update_cfs_rq_blocked_load(struct cfs_rq
*cfs_rq
,
2932 int force_update
) {}
2934 static inline int idle_balance(struct rq
*rq
)
2939 #endif /* CONFIG_SMP */
2941 static void enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2943 #ifdef CONFIG_SCHEDSTATS
2944 struct task_struct
*tsk
= NULL
;
2946 if (entity_is_task(se
))
2949 if (se
->statistics
.sleep_start
) {
2950 u64 delta
= rq_clock(rq_of(cfs_rq
)) - se
->statistics
.sleep_start
;
2955 if (unlikely(delta
> se
->statistics
.sleep_max
))
2956 se
->statistics
.sleep_max
= delta
;
2958 se
->statistics
.sleep_start
= 0;
2959 se
->statistics
.sum_sleep_runtime
+= delta
;
2962 account_scheduler_latency(tsk
, delta
>> 10, 1);
2963 trace_sched_stat_sleep(tsk
, delta
);
2966 if (se
->statistics
.block_start
) {
2967 u64 delta
= rq_clock(rq_of(cfs_rq
)) - se
->statistics
.block_start
;
2972 if (unlikely(delta
> se
->statistics
.block_max
))
2973 se
->statistics
.block_max
= delta
;
2975 se
->statistics
.block_start
= 0;
2976 se
->statistics
.sum_sleep_runtime
+= delta
;
2979 if (tsk
->in_iowait
) {
2980 se
->statistics
.iowait_sum
+= delta
;
2981 se
->statistics
.iowait_count
++;
2982 trace_sched_stat_iowait(tsk
, delta
);
2985 trace_sched_stat_blocked(tsk
, delta
);
2988 * Blocking time is in units of nanosecs, so shift by
2989 * 20 to get a milliseconds-range estimation of the
2990 * amount of time that the task spent sleeping:
2992 if (unlikely(prof_on
== SLEEP_PROFILING
)) {
2993 profile_hits(SLEEP_PROFILING
,
2994 (void *)get_wchan(tsk
),
2997 account_scheduler_latency(tsk
, delta
>> 10, 0);
3003 static void check_spread(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3005 #ifdef CONFIG_SCHED_DEBUG
3006 s64 d
= se
->vruntime
- cfs_rq
->min_vruntime
;
3011 if (d
> 3*sysctl_sched_latency
)
3012 schedstat_inc(cfs_rq
, nr_spread_over
);
3017 place_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int initial
)
3019 u64 vruntime
= cfs_rq
->min_vruntime
;
3022 * The 'current' period is already promised to the current tasks,
3023 * however the extra weight of the new task will slow them down a
3024 * little, place the new task so that it fits in the slot that
3025 * stays open at the end.
3027 if (initial
&& sched_feat(START_DEBIT
))
3028 vruntime
+= sched_vslice(cfs_rq
, se
);
3030 /* sleeps up to a single latency don't count. */
3032 unsigned long thresh
= sysctl_sched_latency
;
3035 * Halve their sleep time's effect, to allow
3036 * for a gentler effect of sleepers:
3038 if (sched_feat(GENTLE_FAIR_SLEEPERS
))
3044 /* ensure we never gain time by being placed backwards. */
3045 se
->vruntime
= max_vruntime(se
->vruntime
, vruntime
);
3048 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
);
3051 enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3054 * Update the normalized vruntime before updating min_vruntime
3055 * through calling update_curr().
3057 if (!(flags
& ENQUEUE_WAKEUP
) || (flags
& ENQUEUE_WAKING
))
3058 se
->vruntime
+= cfs_rq
->min_vruntime
;
3061 * Update run-time statistics of the 'current'.
3063 update_curr(cfs_rq
);
3064 enqueue_entity_load_avg(cfs_rq
, se
, flags
& ENQUEUE_WAKEUP
);
3065 account_entity_enqueue(cfs_rq
, se
);
3066 update_cfs_shares(cfs_rq
);
3068 if (flags
& ENQUEUE_WAKEUP
) {
3069 place_entity(cfs_rq
, se
, 0);
3070 enqueue_sleeper(cfs_rq
, se
);
3073 update_stats_enqueue(cfs_rq
, se
);
3074 check_spread(cfs_rq
, se
);
3075 if (se
!= cfs_rq
->curr
)
3076 __enqueue_entity(cfs_rq
, se
);
3079 if (cfs_rq
->nr_running
== 1) {
3080 list_add_leaf_cfs_rq(cfs_rq
);
3081 check_enqueue_throttle(cfs_rq
);
3085 static void __clear_buddies_last(struct sched_entity
*se
)
3087 for_each_sched_entity(se
) {
3088 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3089 if (cfs_rq
->last
!= se
)
3092 cfs_rq
->last
= NULL
;
3096 static void __clear_buddies_next(struct sched_entity
*se
)
3098 for_each_sched_entity(se
) {
3099 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3100 if (cfs_rq
->next
!= se
)
3103 cfs_rq
->next
= NULL
;
3107 static void __clear_buddies_skip(struct sched_entity
*se
)
3109 for_each_sched_entity(se
) {
3110 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3111 if (cfs_rq
->skip
!= se
)
3114 cfs_rq
->skip
= NULL
;
3118 static void clear_buddies(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3120 if (cfs_rq
->last
== se
)
3121 __clear_buddies_last(se
);
3123 if (cfs_rq
->next
== se
)
3124 __clear_buddies_next(se
);
3126 if (cfs_rq
->skip
== se
)
3127 __clear_buddies_skip(se
);
3130 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
3133 dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3136 * Update run-time statistics of the 'current'.
3138 update_curr(cfs_rq
);
3139 dequeue_entity_load_avg(cfs_rq
, se
, flags
& DEQUEUE_SLEEP
);
3141 update_stats_dequeue(cfs_rq
, se
);
3142 if (flags
& DEQUEUE_SLEEP
) {
3143 #ifdef CONFIG_SCHEDSTATS
3144 if (entity_is_task(se
)) {
3145 struct task_struct
*tsk
= task_of(se
);
3147 if (tsk
->state
& TASK_INTERRUPTIBLE
)
3148 se
->statistics
.sleep_start
= rq_clock(rq_of(cfs_rq
));
3149 if (tsk
->state
& TASK_UNINTERRUPTIBLE
)
3150 se
->statistics
.block_start
= rq_clock(rq_of(cfs_rq
));
3155 clear_buddies(cfs_rq
, se
);
3157 if (se
!= cfs_rq
->curr
)
3158 __dequeue_entity(cfs_rq
, se
);
3160 account_entity_dequeue(cfs_rq
, se
);
3163 * Normalize the entity after updating the min_vruntime because the
3164 * update can refer to the ->curr item and we need to reflect this
3165 * movement in our normalized position.
3167 if (!(flags
& DEQUEUE_SLEEP
))
3168 se
->vruntime
-= cfs_rq
->min_vruntime
;
3170 /* return excess runtime on last dequeue */
3171 return_cfs_rq_runtime(cfs_rq
);
3173 update_min_vruntime(cfs_rq
);
3174 update_cfs_shares(cfs_rq
);
3178 * Preempt the current task with a newly woken task if needed:
3181 check_preempt_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
3183 unsigned long ideal_runtime
, delta_exec
;
3184 struct sched_entity
*se
;
3187 ideal_runtime
= sched_slice(cfs_rq
, curr
);
3188 delta_exec
= curr
->sum_exec_runtime
- curr
->prev_sum_exec_runtime
;
3189 if (delta_exec
> ideal_runtime
) {
3190 resched_curr(rq_of(cfs_rq
));
3192 * The current task ran long enough, ensure it doesn't get
3193 * re-elected due to buddy favours.
3195 clear_buddies(cfs_rq
, curr
);
3200 * Ensure that a task that missed wakeup preemption by a
3201 * narrow margin doesn't have to wait for a full slice.
3202 * This also mitigates buddy induced latencies under load.
3204 if (delta_exec
< sysctl_sched_min_granularity
)
3207 se
= __pick_first_entity(cfs_rq
);
3208 delta
= curr
->vruntime
- se
->vruntime
;
3213 if (delta
> ideal_runtime
)
3214 resched_curr(rq_of(cfs_rq
));
3218 set_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3220 /* 'current' is not kept within the tree. */
3223 * Any task has to be enqueued before it get to execute on
3224 * a CPU. So account for the time it spent waiting on the
3227 update_stats_wait_end(cfs_rq
, se
);
3228 __dequeue_entity(cfs_rq
, se
);
3229 update_entity_load_avg(se
, 1);
3232 update_stats_curr_start(cfs_rq
, se
);
3234 #ifdef CONFIG_SCHEDSTATS
3236 * Track our maximum slice length, if the CPU's load is at
3237 * least twice that of our own weight (i.e. dont track it
3238 * when there are only lesser-weight tasks around):
3240 if (rq_of(cfs_rq
)->load
.weight
>= 2*se
->load
.weight
) {
3241 se
->statistics
.slice_max
= max(se
->statistics
.slice_max
,
3242 se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
);
3245 se
->prev_sum_exec_runtime
= se
->sum_exec_runtime
;
3249 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
);
3252 * Pick the next process, keeping these things in mind, in this order:
3253 * 1) keep things fair between processes/task groups
3254 * 2) pick the "next" process, since someone really wants that to run
3255 * 3) pick the "last" process, for cache locality
3256 * 4) do not run the "skip" process, if something else is available
3258 static struct sched_entity
*
3259 pick_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
3261 struct sched_entity
*left
= __pick_first_entity(cfs_rq
);
3262 struct sched_entity
*se
;
3265 * If curr is set we have to see if its left of the leftmost entity
3266 * still in the tree, provided there was anything in the tree at all.
3268 if (!left
|| (curr
&& entity_before(curr
, left
)))
3271 se
= left
; /* ideally we run the leftmost entity */
3274 * Avoid running the skip buddy, if running something else can
3275 * be done without getting too unfair.
3277 if (cfs_rq
->skip
== se
) {
3278 struct sched_entity
*second
;
3281 second
= __pick_first_entity(cfs_rq
);
3283 second
= __pick_next_entity(se
);
3284 if (!second
|| (curr
&& entity_before(curr
, second
)))
3288 if (second
&& wakeup_preempt_entity(second
, left
) < 1)
3293 * Prefer last buddy, try to return the CPU to a preempted task.
3295 if (cfs_rq
->last
&& wakeup_preempt_entity(cfs_rq
->last
, left
) < 1)
3299 * Someone really wants this to run. If it's not unfair, run it.
3301 if (cfs_rq
->next
&& wakeup_preempt_entity(cfs_rq
->next
, left
) < 1)
3304 clear_buddies(cfs_rq
, se
);
3309 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
3311 static void put_prev_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*prev
)
3314 * If still on the runqueue then deactivate_task()
3315 * was not called and update_curr() has to be done:
3318 update_curr(cfs_rq
);
3320 /* throttle cfs_rqs exceeding runtime */
3321 check_cfs_rq_runtime(cfs_rq
);
3323 check_spread(cfs_rq
, prev
);
3325 update_stats_wait_start(cfs_rq
, prev
);
3326 /* Put 'current' back into the tree. */
3327 __enqueue_entity(cfs_rq
, prev
);
3328 /* in !on_rq case, update occurred at dequeue */
3329 update_entity_load_avg(prev
, 1);
3331 cfs_rq
->curr
= NULL
;
3335 entity_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
, int queued
)
3338 * Update run-time statistics of the 'current'.
3340 update_curr(cfs_rq
);
3343 * Ensure that runnable average is periodically updated.
3345 update_entity_load_avg(curr
, 1);
3346 update_cfs_rq_blocked_load(cfs_rq
, 1);
3347 update_cfs_shares(cfs_rq
);
3349 #ifdef CONFIG_SCHED_HRTICK
3351 * queued ticks are scheduled to match the slice, so don't bother
3352 * validating it and just reschedule.
3355 resched_curr(rq_of(cfs_rq
));
3359 * don't let the period tick interfere with the hrtick preemption
3361 if (!sched_feat(DOUBLE_TICK
) &&
3362 hrtimer_active(&rq_of(cfs_rq
)->hrtick_timer
))
3366 if (cfs_rq
->nr_running
> 1)
3367 check_preempt_tick(cfs_rq
, curr
);
3371 /**************************************************
3372 * CFS bandwidth control machinery
3375 #ifdef CONFIG_CFS_BANDWIDTH
3377 #ifdef HAVE_JUMP_LABEL
3378 static struct static_key __cfs_bandwidth_used
;
3380 static inline bool cfs_bandwidth_used(void)
3382 return static_key_false(&__cfs_bandwidth_used
);
3385 void cfs_bandwidth_usage_inc(void)
3387 static_key_slow_inc(&__cfs_bandwidth_used
);
3390 void cfs_bandwidth_usage_dec(void)
3392 static_key_slow_dec(&__cfs_bandwidth_used
);
3394 #else /* HAVE_JUMP_LABEL */
3395 static bool cfs_bandwidth_used(void)
3400 void cfs_bandwidth_usage_inc(void) {}
3401 void cfs_bandwidth_usage_dec(void) {}
3402 #endif /* HAVE_JUMP_LABEL */
3405 * default period for cfs group bandwidth.
3406 * default: 0.1s, units: nanoseconds
3408 static inline u64
default_cfs_period(void)
3410 return 100000000ULL;
3413 static inline u64
sched_cfs_bandwidth_slice(void)
3415 return (u64
)sysctl_sched_cfs_bandwidth_slice
* NSEC_PER_USEC
;
3419 * Replenish runtime according to assigned quota and update expiration time.
3420 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3421 * additional synchronization around rq->lock.
3423 * requires cfs_b->lock
3425 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth
*cfs_b
)
3429 if (cfs_b
->quota
== RUNTIME_INF
)
3432 now
= sched_clock_cpu(smp_processor_id());
3433 cfs_b
->runtime
= cfs_b
->quota
;
3434 cfs_b
->runtime_expires
= now
+ ktime_to_ns(cfs_b
->period
);
3437 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
3439 return &tg
->cfs_bandwidth
;
3442 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3443 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
3445 if (unlikely(cfs_rq
->throttle_count
))
3446 return cfs_rq
->throttled_clock_task
;
3448 return rq_clock_task(rq_of(cfs_rq
)) - cfs_rq
->throttled_clock_task_time
;
3451 /* returns 0 on failure to allocate runtime */
3452 static int assign_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3454 struct task_group
*tg
= cfs_rq
->tg
;
3455 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(tg
);
3456 u64 amount
= 0, min_amount
, expires
;
3458 /* note: this is a positive sum as runtime_remaining <= 0 */
3459 min_amount
= sched_cfs_bandwidth_slice() - cfs_rq
->runtime_remaining
;
3461 raw_spin_lock(&cfs_b
->lock
);
3462 if (cfs_b
->quota
== RUNTIME_INF
)
3463 amount
= min_amount
;
3466 * If the bandwidth pool has become inactive, then at least one
3467 * period must have elapsed since the last consumption.
3468 * Refresh the global state and ensure bandwidth timer becomes
3471 if (!cfs_b
->timer_active
) {
3472 __refill_cfs_bandwidth_runtime(cfs_b
);
3473 __start_cfs_bandwidth(cfs_b
, false);
3476 if (cfs_b
->runtime
> 0) {
3477 amount
= min(cfs_b
->runtime
, min_amount
);
3478 cfs_b
->runtime
-= amount
;
3482 expires
= cfs_b
->runtime_expires
;
3483 raw_spin_unlock(&cfs_b
->lock
);
3485 cfs_rq
->runtime_remaining
+= amount
;
3487 * we may have advanced our local expiration to account for allowed
3488 * spread between our sched_clock and the one on which runtime was
3491 if ((s64
)(expires
- cfs_rq
->runtime_expires
) > 0)
3492 cfs_rq
->runtime_expires
= expires
;
3494 return cfs_rq
->runtime_remaining
> 0;
3498 * Note: This depends on the synchronization provided by sched_clock and the
3499 * fact that rq->clock snapshots this value.
3501 static void expire_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3503 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3505 /* if the deadline is ahead of our clock, nothing to do */
3506 if (likely((s64
)(rq_clock(rq_of(cfs_rq
)) - cfs_rq
->runtime_expires
) < 0))
3509 if (cfs_rq
->runtime_remaining
< 0)
3513 * If the local deadline has passed we have to consider the
3514 * possibility that our sched_clock is 'fast' and the global deadline
3515 * has not truly expired.
3517 * Fortunately we can check determine whether this the case by checking
3518 * whether the global deadline has advanced. It is valid to compare
3519 * cfs_b->runtime_expires without any locks since we only care about
3520 * exact equality, so a partial write will still work.
3523 if (cfs_rq
->runtime_expires
!= cfs_b
->runtime_expires
) {
3524 /* extend local deadline, drift is bounded above by 2 ticks */
3525 cfs_rq
->runtime_expires
+= TICK_NSEC
;
3527 /* global deadline is ahead, expiration has passed */
3528 cfs_rq
->runtime_remaining
= 0;
3532 static void __account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
3534 /* dock delta_exec before expiring quota (as it could span periods) */
3535 cfs_rq
->runtime_remaining
-= delta_exec
;
3536 expire_cfs_rq_runtime(cfs_rq
);
3538 if (likely(cfs_rq
->runtime_remaining
> 0))
3542 * if we're unable to extend our runtime we resched so that the active
3543 * hierarchy can be throttled
3545 if (!assign_cfs_rq_runtime(cfs_rq
) && likely(cfs_rq
->curr
))
3546 resched_curr(rq_of(cfs_rq
));
3549 static __always_inline
3550 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
3552 if (!cfs_bandwidth_used() || !cfs_rq
->runtime_enabled
)
3555 __account_cfs_rq_runtime(cfs_rq
, delta_exec
);
3558 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
3560 return cfs_bandwidth_used() && cfs_rq
->throttled
;
3563 /* check whether cfs_rq, or any parent, is throttled */
3564 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
3566 return cfs_bandwidth_used() && cfs_rq
->throttle_count
;
3570 * Ensure that neither of the group entities corresponding to src_cpu or
3571 * dest_cpu are members of a throttled hierarchy when performing group
3572 * load-balance operations.
3574 static inline int throttled_lb_pair(struct task_group
*tg
,
3575 int src_cpu
, int dest_cpu
)
3577 struct cfs_rq
*src_cfs_rq
, *dest_cfs_rq
;
3579 src_cfs_rq
= tg
->cfs_rq
[src_cpu
];
3580 dest_cfs_rq
= tg
->cfs_rq
[dest_cpu
];
3582 return throttled_hierarchy(src_cfs_rq
) ||
3583 throttled_hierarchy(dest_cfs_rq
);
3586 /* updated child weight may affect parent so we have to do this bottom up */
3587 static int tg_unthrottle_up(struct task_group
*tg
, void *data
)
3589 struct rq
*rq
= data
;
3590 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
3592 cfs_rq
->throttle_count
--;
3594 if (!cfs_rq
->throttle_count
) {
3595 /* adjust cfs_rq_clock_task() */
3596 cfs_rq
->throttled_clock_task_time
+= rq_clock_task(rq
) -
3597 cfs_rq
->throttled_clock_task
;
3604 static int tg_throttle_down(struct task_group
*tg
, void *data
)
3606 struct rq
*rq
= data
;
3607 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
3609 /* group is entering throttled state, stop time */
3610 if (!cfs_rq
->throttle_count
)
3611 cfs_rq
->throttled_clock_task
= rq_clock_task(rq
);
3612 cfs_rq
->throttle_count
++;
3617 static void throttle_cfs_rq(struct cfs_rq
*cfs_rq
)
3619 struct rq
*rq
= rq_of(cfs_rq
);
3620 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3621 struct sched_entity
*se
;
3622 long task_delta
, dequeue
= 1;
3624 se
= cfs_rq
->tg
->se
[cpu_of(rq_of(cfs_rq
))];
3626 /* freeze hierarchy runnable averages while throttled */
3628 walk_tg_tree_from(cfs_rq
->tg
, tg_throttle_down
, tg_nop
, (void *)rq
);
3631 task_delta
= cfs_rq
->h_nr_running
;
3632 for_each_sched_entity(se
) {
3633 struct cfs_rq
*qcfs_rq
= cfs_rq_of(se
);
3634 /* throttled entity or throttle-on-deactivate */
3639 dequeue_entity(qcfs_rq
, se
, DEQUEUE_SLEEP
);
3640 qcfs_rq
->h_nr_running
-= task_delta
;
3642 if (qcfs_rq
->load
.weight
)
3647 sub_nr_running(rq
, task_delta
);
3649 cfs_rq
->throttled
= 1;
3650 cfs_rq
->throttled_clock
= rq_clock(rq
);
3651 raw_spin_lock(&cfs_b
->lock
);
3653 * Add to the _head_ of the list, so that an already-started
3654 * distribute_cfs_runtime will not see us
3656 list_add_rcu(&cfs_rq
->throttled_list
, &cfs_b
->throttled_cfs_rq
);
3657 if (!cfs_b
->timer_active
)
3658 __start_cfs_bandwidth(cfs_b
, false);
3659 raw_spin_unlock(&cfs_b
->lock
);
3662 void unthrottle_cfs_rq(struct cfs_rq
*cfs_rq
)
3664 struct rq
*rq
= rq_of(cfs_rq
);
3665 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3666 struct sched_entity
*se
;
3670 se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
3672 cfs_rq
->throttled
= 0;
3674 update_rq_clock(rq
);
3676 raw_spin_lock(&cfs_b
->lock
);
3677 cfs_b
->throttled_time
+= rq_clock(rq
) - cfs_rq
->throttled_clock
;
3678 list_del_rcu(&cfs_rq
->throttled_list
);
3679 raw_spin_unlock(&cfs_b
->lock
);
3681 /* update hierarchical throttle state */
3682 walk_tg_tree_from(cfs_rq
->tg
, tg_nop
, tg_unthrottle_up
, (void *)rq
);
3684 if (!cfs_rq
->load
.weight
)
3687 task_delta
= cfs_rq
->h_nr_running
;
3688 for_each_sched_entity(se
) {
3692 cfs_rq
= cfs_rq_of(se
);
3694 enqueue_entity(cfs_rq
, se
, ENQUEUE_WAKEUP
);
3695 cfs_rq
->h_nr_running
+= task_delta
;
3697 if (cfs_rq_throttled(cfs_rq
))
3702 add_nr_running(rq
, task_delta
);
3704 /* determine whether we need to wake up potentially idle cpu */
3705 if (rq
->curr
== rq
->idle
&& rq
->cfs
.nr_running
)
3709 static u64
distribute_cfs_runtime(struct cfs_bandwidth
*cfs_b
,
3710 u64 remaining
, u64 expires
)
3712 struct cfs_rq
*cfs_rq
;
3714 u64 starting_runtime
= remaining
;
3717 list_for_each_entry_rcu(cfs_rq
, &cfs_b
->throttled_cfs_rq
,
3719 struct rq
*rq
= rq_of(cfs_rq
);
3721 raw_spin_lock(&rq
->lock
);
3722 if (!cfs_rq_throttled(cfs_rq
))
3725 runtime
= -cfs_rq
->runtime_remaining
+ 1;
3726 if (runtime
> remaining
)
3727 runtime
= remaining
;
3728 remaining
-= runtime
;
3730 cfs_rq
->runtime_remaining
+= runtime
;
3731 cfs_rq
->runtime_expires
= expires
;
3733 /* we check whether we're throttled above */
3734 if (cfs_rq
->runtime_remaining
> 0)
3735 unthrottle_cfs_rq(cfs_rq
);
3738 raw_spin_unlock(&rq
->lock
);
3745 return starting_runtime
- remaining
;
3749 * Responsible for refilling a task_group's bandwidth and unthrottling its
3750 * cfs_rqs as appropriate. If there has been no activity within the last
3751 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3752 * used to track this state.
3754 static int do_sched_cfs_period_timer(struct cfs_bandwidth
*cfs_b
, int overrun
)
3756 u64 runtime
, runtime_expires
;
3759 /* no need to continue the timer with no bandwidth constraint */
3760 if (cfs_b
->quota
== RUNTIME_INF
)
3761 goto out_deactivate
;
3763 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
3764 cfs_b
->nr_periods
+= overrun
;
3767 * idle depends on !throttled (for the case of a large deficit), and if
3768 * we're going inactive then everything else can be deferred
3770 if (cfs_b
->idle
&& !throttled
)
3771 goto out_deactivate
;
3774 * if we have relooped after returning idle once, we need to update our
3775 * status as actually running, so that other cpus doing
3776 * __start_cfs_bandwidth will stop trying to cancel us.
3778 cfs_b
->timer_active
= 1;
3780 __refill_cfs_bandwidth_runtime(cfs_b
);
3783 /* mark as potentially idle for the upcoming period */
3788 /* account preceding periods in which throttling occurred */
3789 cfs_b
->nr_throttled
+= overrun
;
3791 runtime_expires
= cfs_b
->runtime_expires
;
3794 * This check is repeated as we are holding onto the new bandwidth while
3795 * we unthrottle. This can potentially race with an unthrottled group
3796 * trying to acquire new bandwidth from the global pool. This can result
3797 * in us over-using our runtime if it is all used during this loop, but
3798 * only by limited amounts in that extreme case.
3800 while (throttled
&& cfs_b
->runtime
> 0) {
3801 runtime
= cfs_b
->runtime
;
3802 raw_spin_unlock(&cfs_b
->lock
);
3803 /* we can't nest cfs_b->lock while distributing bandwidth */
3804 runtime
= distribute_cfs_runtime(cfs_b
, runtime
,
3806 raw_spin_lock(&cfs_b
->lock
);
3808 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
3810 cfs_b
->runtime
-= min(runtime
, cfs_b
->runtime
);
3814 * While we are ensured activity in the period following an
3815 * unthrottle, this also covers the case in which the new bandwidth is
3816 * insufficient to cover the existing bandwidth deficit. (Forcing the
3817 * timer to remain active while there are any throttled entities.)
3824 cfs_b
->timer_active
= 0;
3828 /* a cfs_rq won't donate quota below this amount */
3829 static const u64 min_cfs_rq_runtime
= 1 * NSEC_PER_MSEC
;
3830 /* minimum remaining period time to redistribute slack quota */
3831 static const u64 min_bandwidth_expiration
= 2 * NSEC_PER_MSEC
;
3832 /* how long we wait to gather additional slack before distributing */
3833 static const u64 cfs_bandwidth_slack_period
= 5 * NSEC_PER_MSEC
;
3836 * Are we near the end of the current quota period?
3838 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3839 * hrtimer base being cleared by __hrtimer_start_range_ns. In the case of
3840 * migrate_hrtimers, base is never cleared, so we are fine.
3842 static int runtime_refresh_within(struct cfs_bandwidth
*cfs_b
, u64 min_expire
)
3844 struct hrtimer
*refresh_timer
= &cfs_b
->period_timer
;
3847 /* if the call-back is running a quota refresh is already occurring */
3848 if (hrtimer_callback_running(refresh_timer
))
3851 /* is a quota refresh about to occur? */
3852 remaining
= ktime_to_ns(hrtimer_expires_remaining(refresh_timer
));
3853 if (remaining
< min_expire
)
3859 static void start_cfs_slack_bandwidth(struct cfs_bandwidth
*cfs_b
)
3861 u64 min_left
= cfs_bandwidth_slack_period
+ min_bandwidth_expiration
;
3863 /* if there's a quota refresh soon don't bother with slack */
3864 if (runtime_refresh_within(cfs_b
, min_left
))
3867 start_bandwidth_timer(&cfs_b
->slack_timer
,
3868 ns_to_ktime(cfs_bandwidth_slack_period
));
3871 /* we know any runtime found here is valid as update_curr() precedes return */
3872 static void __return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3874 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3875 s64 slack_runtime
= cfs_rq
->runtime_remaining
- min_cfs_rq_runtime
;
3877 if (slack_runtime
<= 0)
3880 raw_spin_lock(&cfs_b
->lock
);
3881 if (cfs_b
->quota
!= RUNTIME_INF
&&
3882 cfs_rq
->runtime_expires
== cfs_b
->runtime_expires
) {
3883 cfs_b
->runtime
+= slack_runtime
;
3885 /* we are under rq->lock, defer unthrottling using a timer */
3886 if (cfs_b
->runtime
> sched_cfs_bandwidth_slice() &&
3887 !list_empty(&cfs_b
->throttled_cfs_rq
))
3888 start_cfs_slack_bandwidth(cfs_b
);
3890 raw_spin_unlock(&cfs_b
->lock
);
3892 /* even if it's not valid for return we don't want to try again */
3893 cfs_rq
->runtime_remaining
-= slack_runtime
;
3896 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3898 if (!cfs_bandwidth_used())
3901 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->nr_running
)
3904 __return_cfs_rq_runtime(cfs_rq
);
3908 * This is done with a timer (instead of inline with bandwidth return) since
3909 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3911 static void do_sched_cfs_slack_timer(struct cfs_bandwidth
*cfs_b
)
3913 u64 runtime
= 0, slice
= sched_cfs_bandwidth_slice();
3916 /* confirm we're still not at a refresh boundary */
3917 raw_spin_lock(&cfs_b
->lock
);
3918 if (runtime_refresh_within(cfs_b
, min_bandwidth_expiration
)) {
3919 raw_spin_unlock(&cfs_b
->lock
);
3923 if (cfs_b
->quota
!= RUNTIME_INF
&& cfs_b
->runtime
> slice
)
3924 runtime
= cfs_b
->runtime
;
3926 expires
= cfs_b
->runtime_expires
;
3927 raw_spin_unlock(&cfs_b
->lock
);
3932 runtime
= distribute_cfs_runtime(cfs_b
, runtime
, expires
);
3934 raw_spin_lock(&cfs_b
->lock
);
3935 if (expires
== cfs_b
->runtime_expires
)
3936 cfs_b
->runtime
-= min(runtime
, cfs_b
->runtime
);
3937 raw_spin_unlock(&cfs_b
->lock
);
3941 * When a group wakes up we want to make sure that its quota is not already
3942 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3943 * runtime as update_curr() throttling can not not trigger until it's on-rq.
3945 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
)
3947 if (!cfs_bandwidth_used())
3950 /* an active group must be handled by the update_curr()->put() path */
3951 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->curr
)
3954 /* ensure the group is not already throttled */
3955 if (cfs_rq_throttled(cfs_rq
))
3958 /* update runtime allocation */
3959 account_cfs_rq_runtime(cfs_rq
, 0);
3960 if (cfs_rq
->runtime_remaining
<= 0)
3961 throttle_cfs_rq(cfs_rq
);
3964 /* conditionally throttle active cfs_rq's from put_prev_entity() */
3965 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3967 if (!cfs_bandwidth_used())
3970 if (likely(!cfs_rq
->runtime_enabled
|| cfs_rq
->runtime_remaining
> 0))
3974 * it's possible for a throttled entity to be forced into a running
3975 * state (e.g. set_curr_task), in this case we're finished.
3977 if (cfs_rq_throttled(cfs_rq
))
3980 throttle_cfs_rq(cfs_rq
);
3984 static enum hrtimer_restart
sched_cfs_slack_timer(struct hrtimer
*timer
)
3986 struct cfs_bandwidth
*cfs_b
=
3987 container_of(timer
, struct cfs_bandwidth
, slack_timer
);
3988 do_sched_cfs_slack_timer(cfs_b
);
3990 return HRTIMER_NORESTART
;
3993 static enum hrtimer_restart
sched_cfs_period_timer(struct hrtimer
*timer
)
3995 struct cfs_bandwidth
*cfs_b
=
3996 container_of(timer
, struct cfs_bandwidth
, period_timer
);
4001 raw_spin_lock(&cfs_b
->lock
);
4003 now
= hrtimer_cb_get_time(timer
);
4004 overrun
= hrtimer_forward(timer
, now
, cfs_b
->period
);
4009 idle
= do_sched_cfs_period_timer(cfs_b
, overrun
);
4011 raw_spin_unlock(&cfs_b
->lock
);
4013 return idle
? HRTIMER_NORESTART
: HRTIMER_RESTART
;
4016 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4018 raw_spin_lock_init(&cfs_b
->lock
);
4020 cfs_b
->quota
= RUNTIME_INF
;
4021 cfs_b
->period
= ns_to_ktime(default_cfs_period());
4023 INIT_LIST_HEAD(&cfs_b
->throttled_cfs_rq
);
4024 hrtimer_init(&cfs_b
->period_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
4025 cfs_b
->period_timer
.function
= sched_cfs_period_timer
;
4026 hrtimer_init(&cfs_b
->slack_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
4027 cfs_b
->slack_timer
.function
= sched_cfs_slack_timer
;
4030 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4032 cfs_rq
->runtime_enabled
= 0;
4033 INIT_LIST_HEAD(&cfs_rq
->throttled_list
);
4036 /* requires cfs_b->lock, may release to reprogram timer */
4037 void __start_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
, bool force
)
4040 * The timer may be active because we're trying to set a new bandwidth
4041 * period or because we're racing with the tear-down path
4042 * (timer_active==0 becomes visible before the hrtimer call-back
4043 * terminates). In either case we ensure that it's re-programmed
4045 while (unlikely(hrtimer_active(&cfs_b
->period_timer
)) &&
4046 hrtimer_try_to_cancel(&cfs_b
->period_timer
) < 0) {
4047 /* bounce the lock to allow do_sched_cfs_period_timer to run */
4048 raw_spin_unlock(&cfs_b
->lock
);
4050 raw_spin_lock(&cfs_b
->lock
);
4051 /* if someone else restarted the timer then we're done */
4052 if (!force
&& cfs_b
->timer_active
)
4056 cfs_b
->timer_active
= 1;
4057 start_bandwidth_timer(&cfs_b
->period_timer
, cfs_b
->period
);
4060 static void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4062 /* init_cfs_bandwidth() was not called */
4063 if (!cfs_b
->throttled_cfs_rq
.next
)
4066 hrtimer_cancel(&cfs_b
->period_timer
);
4067 hrtimer_cancel(&cfs_b
->slack_timer
);
4070 static void __maybe_unused
update_runtime_enabled(struct rq
*rq
)
4072 struct cfs_rq
*cfs_rq
;
4074 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
4075 struct cfs_bandwidth
*cfs_b
= &cfs_rq
->tg
->cfs_bandwidth
;
4077 raw_spin_lock(&cfs_b
->lock
);
4078 cfs_rq
->runtime_enabled
= cfs_b
->quota
!= RUNTIME_INF
;
4079 raw_spin_unlock(&cfs_b
->lock
);
4083 static void __maybe_unused
unthrottle_offline_cfs_rqs(struct rq
*rq
)
4085 struct cfs_rq
*cfs_rq
;
4087 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
4088 if (!cfs_rq
->runtime_enabled
)
4092 * clock_task is not advancing so we just need to make sure
4093 * there's some valid quota amount
4095 cfs_rq
->runtime_remaining
= 1;
4097 * Offline rq is schedulable till cpu is completely disabled
4098 * in take_cpu_down(), so we prevent new cfs throttling here.
4100 cfs_rq
->runtime_enabled
= 0;
4102 if (cfs_rq_throttled(cfs_rq
))
4103 unthrottle_cfs_rq(cfs_rq
);
4107 #else /* CONFIG_CFS_BANDWIDTH */
4108 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
4110 return rq_clock_task(rq_of(cfs_rq
));
4113 static void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
) {}
4114 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) { return false; }
4115 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
) {}
4116 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
4118 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
4123 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
4128 static inline int throttled_lb_pair(struct task_group
*tg
,
4129 int src_cpu
, int dest_cpu
)
4134 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
4136 #ifdef CONFIG_FAIR_GROUP_SCHED
4137 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
4140 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
4144 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
4145 static inline void update_runtime_enabled(struct rq
*rq
) {}
4146 static inline void unthrottle_offline_cfs_rqs(struct rq
*rq
) {}
4148 #endif /* CONFIG_CFS_BANDWIDTH */
4150 /**************************************************
4151 * CFS operations on tasks:
4154 #ifdef CONFIG_SCHED_HRTICK
4155 static void hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
4157 struct sched_entity
*se
= &p
->se
;
4158 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4160 WARN_ON(task_rq(p
) != rq
);
4162 if (cfs_rq
->nr_running
> 1) {
4163 u64 slice
= sched_slice(cfs_rq
, se
);
4164 u64 ran
= se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
;
4165 s64 delta
= slice
- ran
;
4172 hrtick_start(rq
, delta
);
4177 * called from enqueue/dequeue and updates the hrtick when the
4178 * current task is from our class and nr_running is low enough
4181 static void hrtick_update(struct rq
*rq
)
4183 struct task_struct
*curr
= rq
->curr
;
4185 if (!hrtick_enabled(rq
) || curr
->sched_class
!= &fair_sched_class
)
4188 if (cfs_rq_of(&curr
->se
)->nr_running
< sched_nr_latency
)
4189 hrtick_start_fair(rq
, curr
);
4191 #else /* !CONFIG_SCHED_HRTICK */
4193 hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
4197 static inline void hrtick_update(struct rq
*rq
)
4203 * The enqueue_task method is called before nr_running is
4204 * increased. Here we update the fair scheduling stats and
4205 * then put the task into the rbtree:
4208 enqueue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
4210 struct cfs_rq
*cfs_rq
;
4211 struct sched_entity
*se
= &p
->se
;
4213 for_each_sched_entity(se
) {
4216 cfs_rq
= cfs_rq_of(se
);
4217 enqueue_entity(cfs_rq
, se
, flags
);
4220 * end evaluation on encountering a throttled cfs_rq
4222 * note: in the case of encountering a throttled cfs_rq we will
4223 * post the final h_nr_running increment below.
4225 if (cfs_rq_throttled(cfs_rq
))
4227 cfs_rq
->h_nr_running
++;
4229 flags
= ENQUEUE_WAKEUP
;
4232 for_each_sched_entity(se
) {
4233 cfs_rq
= cfs_rq_of(se
);
4234 cfs_rq
->h_nr_running
++;
4236 if (cfs_rq_throttled(cfs_rq
))
4239 update_cfs_shares(cfs_rq
);
4240 update_entity_load_avg(se
, 1);
4244 update_rq_runnable_avg(rq
, rq
->nr_running
);
4245 add_nr_running(rq
, 1);
4250 static void set_next_buddy(struct sched_entity
*se
);
4253 * The dequeue_task method is called before nr_running is
4254 * decreased. We remove the task from the rbtree and
4255 * update the fair scheduling stats:
4257 static void dequeue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
4259 struct cfs_rq
*cfs_rq
;
4260 struct sched_entity
*se
= &p
->se
;
4261 int task_sleep
= flags
& DEQUEUE_SLEEP
;
4263 for_each_sched_entity(se
) {
4264 cfs_rq
= cfs_rq_of(se
);
4265 dequeue_entity(cfs_rq
, se
, flags
);
4268 * end evaluation on encountering a throttled cfs_rq
4270 * note: in the case of encountering a throttled cfs_rq we will
4271 * post the final h_nr_running decrement below.
4273 if (cfs_rq_throttled(cfs_rq
))
4275 cfs_rq
->h_nr_running
--;
4277 /* Don't dequeue parent if it has other entities besides us */
4278 if (cfs_rq
->load
.weight
) {
4280 * Bias pick_next to pick a task from this cfs_rq, as
4281 * p is sleeping when it is within its sched_slice.
4283 if (task_sleep
&& parent_entity(se
))
4284 set_next_buddy(parent_entity(se
));
4286 /* avoid re-evaluating load for this entity */
4287 se
= parent_entity(se
);
4290 flags
|= DEQUEUE_SLEEP
;
4293 for_each_sched_entity(se
) {
4294 cfs_rq
= cfs_rq_of(se
);
4295 cfs_rq
->h_nr_running
--;
4297 if (cfs_rq_throttled(cfs_rq
))
4300 update_cfs_shares(cfs_rq
);
4301 update_entity_load_avg(se
, 1);
4305 sub_nr_running(rq
, 1);
4306 update_rq_runnable_avg(rq
, 1);
4312 /* Used instead of source_load when we know the type == 0 */
4313 static unsigned long weighted_cpuload(const int cpu
)
4315 return cpu_rq(cpu
)->cfs
.runnable_load_avg
;
4319 * Return a low guess at the load of a migration-source cpu weighted
4320 * according to the scheduling class and "nice" value.
4322 * We want to under-estimate the load of migration sources, to
4323 * balance conservatively.
4325 static unsigned long source_load(int cpu
, int type
)
4327 struct rq
*rq
= cpu_rq(cpu
);
4328 unsigned long total
= weighted_cpuload(cpu
);
4330 if (type
== 0 || !sched_feat(LB_BIAS
))
4333 return min(rq
->cpu_load
[type
-1], total
);
4337 * Return a high guess at the load of a migration-target cpu weighted
4338 * according to the scheduling class and "nice" value.
4340 static unsigned long target_load(int cpu
, int type
)
4342 struct rq
*rq
= cpu_rq(cpu
);
4343 unsigned long total
= weighted_cpuload(cpu
);
4345 if (type
== 0 || !sched_feat(LB_BIAS
))
4348 return max(rq
->cpu_load
[type
-1], total
);
4351 static unsigned long capacity_of(int cpu
)
4353 return cpu_rq(cpu
)->cpu_capacity
;
4356 static unsigned long cpu_avg_load_per_task(int cpu
)
4358 struct rq
*rq
= cpu_rq(cpu
);
4359 unsigned long nr_running
= ACCESS_ONCE(rq
->cfs
.h_nr_running
);
4360 unsigned long load_avg
= rq
->cfs
.runnable_load_avg
;
4363 return load_avg
/ nr_running
;
4368 static void record_wakee(struct task_struct
*p
)
4371 * Rough decay (wiping) for cost saving, don't worry
4372 * about the boundary, really active task won't care
4375 if (time_after(jiffies
, current
->wakee_flip_decay_ts
+ HZ
)) {
4376 current
->wakee_flips
>>= 1;
4377 current
->wakee_flip_decay_ts
= jiffies
;
4380 if (current
->last_wakee
!= p
) {
4381 current
->last_wakee
= p
;
4382 current
->wakee_flips
++;
4386 static void task_waking_fair(struct task_struct
*p
)
4388 struct sched_entity
*se
= &p
->se
;
4389 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4392 #ifndef CONFIG_64BIT
4393 u64 min_vruntime_copy
;
4396 min_vruntime_copy
= cfs_rq
->min_vruntime_copy
;
4398 min_vruntime
= cfs_rq
->min_vruntime
;
4399 } while (min_vruntime
!= min_vruntime_copy
);
4401 min_vruntime
= cfs_rq
->min_vruntime
;
4404 se
->vruntime
-= min_vruntime
;
4408 #ifdef CONFIG_FAIR_GROUP_SCHED
4410 * effective_load() calculates the load change as seen from the root_task_group
4412 * Adding load to a group doesn't make a group heavier, but can cause movement
4413 * of group shares between cpus. Assuming the shares were perfectly aligned one
4414 * can calculate the shift in shares.
4416 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4417 * on this @cpu and results in a total addition (subtraction) of @wg to the
4418 * total group weight.
4420 * Given a runqueue weight distribution (rw_i) we can compute a shares
4421 * distribution (s_i) using:
4423 * s_i = rw_i / \Sum rw_j (1)
4425 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4426 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4427 * shares distribution (s_i):
4429 * rw_i = { 2, 4, 1, 0 }
4430 * s_i = { 2/7, 4/7, 1/7, 0 }
4432 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4433 * task used to run on and the CPU the waker is running on), we need to
4434 * compute the effect of waking a task on either CPU and, in case of a sync
4435 * wakeup, compute the effect of the current task going to sleep.
4437 * So for a change of @wl to the local @cpu with an overall group weight change
4438 * of @wl we can compute the new shares distribution (s'_i) using:
4440 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4442 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4443 * differences in waking a task to CPU 0. The additional task changes the
4444 * weight and shares distributions like:
4446 * rw'_i = { 3, 4, 1, 0 }
4447 * s'_i = { 3/8, 4/8, 1/8, 0 }
4449 * We can then compute the difference in effective weight by using:
4451 * dw_i = S * (s'_i - s_i) (3)
4453 * Where 'S' is the group weight as seen by its parent.
4455 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4456 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4457 * 4/7) times the weight of the group.
4459 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
)
4461 struct sched_entity
*se
= tg
->se
[cpu
];
4463 if (!tg
->parent
) /* the trivial, non-cgroup case */
4466 for_each_sched_entity(se
) {
4472 * W = @wg + \Sum rw_j
4474 W
= wg
+ calc_tg_weight(tg
, se
->my_q
);
4479 w
= se
->my_q
->load
.weight
+ wl
;
4482 * wl = S * s'_i; see (2)
4485 wl
= (w
* (long)tg
->shares
) / W
;
4490 * Per the above, wl is the new se->load.weight value; since
4491 * those are clipped to [MIN_SHARES, ...) do so now. See
4492 * calc_cfs_shares().
4494 if (wl
< MIN_SHARES
)
4498 * wl = dw_i = S * (s'_i - s_i); see (3)
4500 wl
-= se
->load
.weight
;
4503 * Recursively apply this logic to all parent groups to compute
4504 * the final effective load change on the root group. Since
4505 * only the @tg group gets extra weight, all parent groups can
4506 * only redistribute existing shares. @wl is the shift in shares
4507 * resulting from this level per the above.
4516 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
)
4523 static int wake_wide(struct task_struct
*p
)
4525 int factor
= this_cpu_read(sd_llc_size
);
4528 * Yeah, it's the switching-frequency, could means many wakee or
4529 * rapidly switch, use factor here will just help to automatically
4530 * adjust the loose-degree, so bigger node will lead to more pull.
4532 if (p
->wakee_flips
> factor
) {
4534 * wakee is somewhat hot, it needs certain amount of cpu
4535 * resource, so if waker is far more hot, prefer to leave
4538 if (current
->wakee_flips
> (factor
* p
->wakee_flips
))
4545 static int wake_affine(struct sched_domain
*sd
, struct task_struct
*p
, int sync
)
4547 s64 this_load
, load
;
4548 s64 this_eff_load
, prev_eff_load
;
4549 int idx
, this_cpu
, prev_cpu
;
4550 struct task_group
*tg
;
4551 unsigned long weight
;
4555 * If we wake multiple tasks be careful to not bounce
4556 * ourselves around too much.
4562 this_cpu
= smp_processor_id();
4563 prev_cpu
= task_cpu(p
);
4564 load
= source_load(prev_cpu
, idx
);
4565 this_load
= target_load(this_cpu
, idx
);
4568 * If sync wakeup then subtract the (maximum possible)
4569 * effect of the currently running task from the load
4570 * of the current CPU:
4573 tg
= task_group(current
);
4574 weight
= current
->se
.load
.weight
;
4576 this_load
+= effective_load(tg
, this_cpu
, -weight
, -weight
);
4577 load
+= effective_load(tg
, prev_cpu
, 0, -weight
);
4581 weight
= p
->se
.load
.weight
;
4584 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4585 * due to the sync cause above having dropped this_load to 0, we'll
4586 * always have an imbalance, but there's really nothing you can do
4587 * about that, so that's good too.
4589 * Otherwise check if either cpus are near enough in load to allow this
4590 * task to be woken on this_cpu.
4592 this_eff_load
= 100;
4593 this_eff_load
*= capacity_of(prev_cpu
);
4595 prev_eff_load
= 100 + (sd
->imbalance_pct
- 100) / 2;
4596 prev_eff_load
*= capacity_of(this_cpu
);
4598 if (this_load
> 0) {
4599 this_eff_load
*= this_load
+
4600 effective_load(tg
, this_cpu
, weight
, weight
);
4602 prev_eff_load
*= load
+ effective_load(tg
, prev_cpu
, 0, weight
);
4605 balanced
= this_eff_load
<= prev_eff_load
;
4607 schedstat_inc(p
, se
.statistics
.nr_wakeups_affine_attempts
);
4612 schedstat_inc(sd
, ttwu_move_affine
);
4613 schedstat_inc(p
, se
.statistics
.nr_wakeups_affine
);
4619 * find_idlest_group finds and returns the least busy CPU group within the
4622 static struct sched_group
*
4623 find_idlest_group(struct sched_domain
*sd
, struct task_struct
*p
,
4624 int this_cpu
, int sd_flag
)
4626 struct sched_group
*idlest
= NULL
, *group
= sd
->groups
;
4627 unsigned long min_load
= ULONG_MAX
, this_load
= 0;
4628 int load_idx
= sd
->forkexec_idx
;
4629 int imbalance
= 100 + (sd
->imbalance_pct
-100)/2;
4631 if (sd_flag
& SD_BALANCE_WAKE
)
4632 load_idx
= sd
->wake_idx
;
4635 unsigned long load
, avg_load
;
4639 /* Skip over this group if it has no CPUs allowed */
4640 if (!cpumask_intersects(sched_group_cpus(group
),
4641 tsk_cpus_allowed(p
)))
4644 local_group
= cpumask_test_cpu(this_cpu
,
4645 sched_group_cpus(group
));
4647 /* Tally up the load of all CPUs in the group */
4650 for_each_cpu(i
, sched_group_cpus(group
)) {
4651 /* Bias balancing toward cpus of our domain */
4653 load
= source_load(i
, load_idx
);
4655 load
= target_load(i
, load_idx
);
4660 /* Adjust by relative CPU capacity of the group */
4661 avg_load
= (avg_load
* SCHED_CAPACITY_SCALE
) / group
->sgc
->capacity
;
4664 this_load
= avg_load
;
4665 } else if (avg_load
< min_load
) {
4666 min_load
= avg_load
;
4669 } while (group
= group
->next
, group
!= sd
->groups
);
4671 if (!idlest
|| 100*this_load
< imbalance
*min_load
)
4677 * find_idlest_cpu - find the idlest cpu among the cpus in group.
4680 find_idlest_cpu(struct sched_group
*group
, struct task_struct
*p
, int this_cpu
)
4682 unsigned long load
, min_load
= ULONG_MAX
;
4683 unsigned int min_exit_latency
= UINT_MAX
;
4684 u64 latest_idle_timestamp
= 0;
4685 int least_loaded_cpu
= this_cpu
;
4686 int shallowest_idle_cpu
= -1;
4689 /* Traverse only the allowed CPUs */
4690 for_each_cpu_and(i
, sched_group_cpus(group
), tsk_cpus_allowed(p
)) {
4692 struct rq
*rq
= cpu_rq(i
);
4693 struct cpuidle_state
*idle
= idle_get_state(rq
);
4694 if (idle
&& idle
->exit_latency
< min_exit_latency
) {
4696 * We give priority to a CPU whose idle state
4697 * has the smallest exit latency irrespective
4698 * of any idle timestamp.
4700 min_exit_latency
= idle
->exit_latency
;
4701 latest_idle_timestamp
= rq
->idle_stamp
;
4702 shallowest_idle_cpu
= i
;
4703 } else if ((!idle
|| idle
->exit_latency
== min_exit_latency
) &&
4704 rq
->idle_stamp
> latest_idle_timestamp
) {
4706 * If equal or no active idle state, then
4707 * the most recently idled CPU might have
4710 latest_idle_timestamp
= rq
->idle_stamp
;
4711 shallowest_idle_cpu
= i
;
4713 } else if (shallowest_idle_cpu
== -1) {
4714 load
= weighted_cpuload(i
);
4715 if (load
< min_load
|| (load
== min_load
&& i
== this_cpu
)) {
4717 least_loaded_cpu
= i
;
4722 return shallowest_idle_cpu
!= -1 ? shallowest_idle_cpu
: least_loaded_cpu
;
4726 * Try and locate an idle CPU in the sched_domain.
4728 static int select_idle_sibling(struct task_struct
*p
, int target
)
4730 struct sched_domain
*sd
;
4731 struct sched_group
*sg
;
4732 int i
= task_cpu(p
);
4734 if (idle_cpu(target
))
4738 * If the prevous cpu is cache affine and idle, don't be stupid.
4740 if (i
!= target
&& cpus_share_cache(i
, target
) && idle_cpu(i
))
4744 * Otherwise, iterate the domains and find an elegible idle cpu.
4746 sd
= rcu_dereference(per_cpu(sd_llc
, target
));
4747 for_each_lower_domain(sd
) {
4750 if (!cpumask_intersects(sched_group_cpus(sg
),
4751 tsk_cpus_allowed(p
)))
4754 for_each_cpu(i
, sched_group_cpus(sg
)) {
4755 if (i
== target
|| !idle_cpu(i
))
4759 target
= cpumask_first_and(sched_group_cpus(sg
),
4760 tsk_cpus_allowed(p
));
4764 } while (sg
!= sd
->groups
);
4771 * select_task_rq_fair: Select target runqueue for the waking task in domains
4772 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
4773 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
4775 * Balances load by selecting the idlest cpu in the idlest group, or under
4776 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
4778 * Returns the target cpu number.
4780 * preempt must be disabled.
4783 select_task_rq_fair(struct task_struct
*p
, int prev_cpu
, int sd_flag
, int wake_flags
)
4785 struct sched_domain
*tmp
, *affine_sd
= NULL
, *sd
= NULL
;
4786 int cpu
= smp_processor_id();
4788 int want_affine
= 0;
4789 int sync
= wake_flags
& WF_SYNC
;
4791 if (sd_flag
& SD_BALANCE_WAKE
)
4792 want_affine
= cpumask_test_cpu(cpu
, tsk_cpus_allowed(p
));
4795 for_each_domain(cpu
, tmp
) {
4796 if (!(tmp
->flags
& SD_LOAD_BALANCE
))
4800 * If both cpu and prev_cpu are part of this domain,
4801 * cpu is a valid SD_WAKE_AFFINE target.
4803 if (want_affine
&& (tmp
->flags
& SD_WAKE_AFFINE
) &&
4804 cpumask_test_cpu(prev_cpu
, sched_domain_span(tmp
))) {
4809 if (tmp
->flags
& sd_flag
)
4813 if (affine_sd
&& cpu
!= prev_cpu
&& wake_affine(affine_sd
, p
, sync
))
4816 if (sd_flag
& SD_BALANCE_WAKE
) {
4817 new_cpu
= select_idle_sibling(p
, prev_cpu
);
4822 struct sched_group
*group
;
4825 if (!(sd
->flags
& sd_flag
)) {
4830 group
= find_idlest_group(sd
, p
, cpu
, sd_flag
);
4836 new_cpu
= find_idlest_cpu(group
, p
, cpu
);
4837 if (new_cpu
== -1 || new_cpu
== cpu
) {
4838 /* Now try balancing at a lower domain level of cpu */
4843 /* Now try balancing at a lower domain level of new_cpu */
4845 weight
= sd
->span_weight
;
4847 for_each_domain(cpu
, tmp
) {
4848 if (weight
<= tmp
->span_weight
)
4850 if (tmp
->flags
& sd_flag
)
4853 /* while loop will break here if sd == NULL */
4862 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
4863 * cfs_rq_of(p) references at time of call are still valid and identify the
4864 * previous cpu. However, the caller only guarantees p->pi_lock is held; no
4865 * other assumptions, including the state of rq->lock, should be made.
4868 migrate_task_rq_fair(struct task_struct
*p
, int next_cpu
)
4870 struct sched_entity
*se
= &p
->se
;
4871 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4874 * Load tracking: accumulate removed load so that it can be processed
4875 * when we next update owning cfs_rq under rq->lock. Tasks contribute
4876 * to blocked load iff they have a positive decay-count. It can never
4877 * be negative here since on-rq tasks have decay-count == 0.
4879 if (se
->avg
.decay_count
) {
4880 se
->avg
.decay_count
= -__synchronize_entity_decay(se
);
4881 atomic_long_add(se
->avg
.load_avg_contrib
,
4882 &cfs_rq
->removed_load
);
4885 /* We have migrated, no longer consider this task hot */
4888 #endif /* CONFIG_SMP */
4890 static unsigned long
4891 wakeup_gran(struct sched_entity
*curr
, struct sched_entity
*se
)
4893 unsigned long gran
= sysctl_sched_wakeup_granularity
;
4896 * Since its curr running now, convert the gran from real-time
4897 * to virtual-time in his units.
4899 * By using 'se' instead of 'curr' we penalize light tasks, so
4900 * they get preempted easier. That is, if 'se' < 'curr' then
4901 * the resulting gran will be larger, therefore penalizing the
4902 * lighter, if otoh 'se' > 'curr' then the resulting gran will
4903 * be smaller, again penalizing the lighter task.
4905 * This is especially important for buddies when the leftmost
4906 * task is higher priority than the buddy.
4908 return calc_delta_fair(gran
, se
);
4912 * Should 'se' preempt 'curr'.
4926 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
)
4928 s64 gran
, vdiff
= curr
->vruntime
- se
->vruntime
;
4933 gran
= wakeup_gran(curr
, se
);
4940 static void set_last_buddy(struct sched_entity
*se
)
4942 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
4945 for_each_sched_entity(se
)
4946 cfs_rq_of(se
)->last
= se
;
4949 static void set_next_buddy(struct sched_entity
*se
)
4951 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
4954 for_each_sched_entity(se
)
4955 cfs_rq_of(se
)->next
= se
;
4958 static void set_skip_buddy(struct sched_entity
*se
)
4960 for_each_sched_entity(se
)
4961 cfs_rq_of(se
)->skip
= se
;
4965 * Preempt the current task with a newly woken task if needed:
4967 static void check_preempt_wakeup(struct rq
*rq
, struct task_struct
*p
, int wake_flags
)
4969 struct task_struct
*curr
= rq
->curr
;
4970 struct sched_entity
*se
= &curr
->se
, *pse
= &p
->se
;
4971 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
4972 int scale
= cfs_rq
->nr_running
>= sched_nr_latency
;
4973 int next_buddy_marked
= 0;
4975 if (unlikely(se
== pse
))
4979 * This is possible from callers such as attach_tasks(), in which we
4980 * unconditionally check_prempt_curr() after an enqueue (which may have
4981 * lead to a throttle). This both saves work and prevents false
4982 * next-buddy nomination below.
4984 if (unlikely(throttled_hierarchy(cfs_rq_of(pse
))))
4987 if (sched_feat(NEXT_BUDDY
) && scale
&& !(wake_flags
& WF_FORK
)) {
4988 set_next_buddy(pse
);
4989 next_buddy_marked
= 1;
4993 * We can come here with TIF_NEED_RESCHED already set from new task
4996 * Note: this also catches the edge-case of curr being in a throttled
4997 * group (e.g. via set_curr_task), since update_curr() (in the
4998 * enqueue of curr) will have resulted in resched being set. This
4999 * prevents us from potentially nominating it as a false LAST_BUDDY
5002 if (test_tsk_need_resched(curr
))
5005 /* Idle tasks are by definition preempted by non-idle tasks. */
5006 if (unlikely(curr
->policy
== SCHED_IDLE
) &&
5007 likely(p
->policy
!= SCHED_IDLE
))
5011 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5012 * is driven by the tick):
5014 if (unlikely(p
->policy
!= SCHED_NORMAL
) || !sched_feat(WAKEUP_PREEMPTION
))
5017 find_matching_se(&se
, &pse
);
5018 update_curr(cfs_rq_of(se
));
5020 if (wakeup_preempt_entity(se
, pse
) == 1) {
5022 * Bias pick_next to pick the sched entity that is
5023 * triggering this preemption.
5025 if (!next_buddy_marked
)
5026 set_next_buddy(pse
);
5035 * Only set the backward buddy when the current task is still
5036 * on the rq. This can happen when a wakeup gets interleaved
5037 * with schedule on the ->pre_schedule() or idle_balance()
5038 * point, either of which can * drop the rq lock.
5040 * Also, during early boot the idle thread is in the fair class,
5041 * for obvious reasons its a bad idea to schedule back to it.
5043 if (unlikely(!se
->on_rq
|| curr
== rq
->idle
))
5046 if (sched_feat(LAST_BUDDY
) && scale
&& entity_is_task(se
))
5050 static struct task_struct
*
5051 pick_next_task_fair(struct rq
*rq
, struct task_struct
*prev
)
5053 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
5054 struct sched_entity
*se
;
5055 struct task_struct
*p
;
5059 #ifdef CONFIG_FAIR_GROUP_SCHED
5060 if (!cfs_rq
->nr_running
)
5063 if (prev
->sched_class
!= &fair_sched_class
)
5067 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5068 * likely that a next task is from the same cgroup as the current.
5070 * Therefore attempt to avoid putting and setting the entire cgroup
5071 * hierarchy, only change the part that actually changes.
5075 struct sched_entity
*curr
= cfs_rq
->curr
;
5078 * Since we got here without doing put_prev_entity() we also
5079 * have to consider cfs_rq->curr. If it is still a runnable
5080 * entity, update_curr() will update its vruntime, otherwise
5081 * forget we've ever seen it.
5083 if (curr
&& curr
->on_rq
)
5084 update_curr(cfs_rq
);
5089 * This call to check_cfs_rq_runtime() will do the throttle and
5090 * dequeue its entity in the parent(s). Therefore the 'simple'
5091 * nr_running test will indeed be correct.
5093 if (unlikely(check_cfs_rq_runtime(cfs_rq
)))
5096 se
= pick_next_entity(cfs_rq
, curr
);
5097 cfs_rq
= group_cfs_rq(se
);
5103 * Since we haven't yet done put_prev_entity and if the selected task
5104 * is a different task than we started out with, try and touch the
5105 * least amount of cfs_rqs.
5108 struct sched_entity
*pse
= &prev
->se
;
5110 while (!(cfs_rq
= is_same_group(se
, pse
))) {
5111 int se_depth
= se
->depth
;
5112 int pse_depth
= pse
->depth
;
5114 if (se_depth
<= pse_depth
) {
5115 put_prev_entity(cfs_rq_of(pse
), pse
);
5116 pse
= parent_entity(pse
);
5118 if (se_depth
>= pse_depth
) {
5119 set_next_entity(cfs_rq_of(se
), se
);
5120 se
= parent_entity(se
);
5124 put_prev_entity(cfs_rq
, pse
);
5125 set_next_entity(cfs_rq
, se
);
5128 if (hrtick_enabled(rq
))
5129 hrtick_start_fair(rq
, p
);
5136 if (!cfs_rq
->nr_running
)
5139 put_prev_task(rq
, prev
);
5142 se
= pick_next_entity(cfs_rq
, NULL
);
5143 set_next_entity(cfs_rq
, se
);
5144 cfs_rq
= group_cfs_rq(se
);
5149 if (hrtick_enabled(rq
))
5150 hrtick_start_fair(rq
, p
);
5155 new_tasks
= idle_balance(rq
);
5157 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5158 * possible for any higher priority task to appear. In that case we
5159 * must re-start the pick_next_entity() loop.
5171 * Account for a descheduled task:
5173 static void put_prev_task_fair(struct rq
*rq
, struct task_struct
*prev
)
5175 struct sched_entity
*se
= &prev
->se
;
5176 struct cfs_rq
*cfs_rq
;
5178 for_each_sched_entity(se
) {
5179 cfs_rq
= cfs_rq_of(se
);
5180 put_prev_entity(cfs_rq
, se
);
5185 * sched_yield() is very simple
5187 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5189 static void yield_task_fair(struct rq
*rq
)
5191 struct task_struct
*curr
= rq
->curr
;
5192 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
5193 struct sched_entity
*se
= &curr
->se
;
5196 * Are we the only task in the tree?
5198 if (unlikely(rq
->nr_running
== 1))
5201 clear_buddies(cfs_rq
, se
);
5203 if (curr
->policy
!= SCHED_BATCH
) {
5204 update_rq_clock(rq
);
5206 * Update run-time statistics of the 'current'.
5208 update_curr(cfs_rq
);
5210 * Tell update_rq_clock() that we've just updated,
5211 * so we don't do microscopic update in schedule()
5212 * and double the fastpath cost.
5214 rq_clock_skip_update(rq
, true);
5220 static bool yield_to_task_fair(struct rq
*rq
, struct task_struct
*p
, bool preempt
)
5222 struct sched_entity
*se
= &p
->se
;
5224 /* throttled hierarchies are not runnable */
5225 if (!se
->on_rq
|| throttled_hierarchy(cfs_rq_of(se
)))
5228 /* Tell the scheduler that we'd really like pse to run next. */
5231 yield_task_fair(rq
);
5237 /**************************************************
5238 * Fair scheduling class load-balancing methods.
5242 * The purpose of load-balancing is to achieve the same basic fairness the
5243 * per-cpu scheduler provides, namely provide a proportional amount of compute
5244 * time to each task. This is expressed in the following equation:
5246 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5248 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5249 * W_i,0 is defined as:
5251 * W_i,0 = \Sum_j w_i,j (2)
5253 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5254 * is derived from the nice value as per prio_to_weight[].
5256 * The weight average is an exponential decay average of the instantaneous
5259 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5261 * C_i is the compute capacity of cpu i, typically it is the
5262 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5263 * can also include other factors [XXX].
5265 * To achieve this balance we define a measure of imbalance which follows
5266 * directly from (1):
5268 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5270 * We them move tasks around to minimize the imbalance. In the continuous
5271 * function space it is obvious this converges, in the discrete case we get
5272 * a few fun cases generally called infeasible weight scenarios.
5275 * - infeasible weights;
5276 * - local vs global optima in the discrete case. ]
5281 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5282 * for all i,j solution, we create a tree of cpus that follows the hardware
5283 * topology where each level pairs two lower groups (or better). This results
5284 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5285 * tree to only the first of the previous level and we decrease the frequency
5286 * of load-balance at each level inv. proportional to the number of cpus in
5292 * \Sum { --- * --- * 2^i } = O(n) (5)
5294 * `- size of each group
5295 * | | `- number of cpus doing load-balance
5297 * `- sum over all levels
5299 * Coupled with a limit on how many tasks we can migrate every balance pass,
5300 * this makes (5) the runtime complexity of the balancer.
5302 * An important property here is that each CPU is still (indirectly) connected
5303 * to every other cpu in at most O(log n) steps:
5305 * The adjacency matrix of the resulting graph is given by:
5308 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5311 * And you'll find that:
5313 * A^(log_2 n)_i,j != 0 for all i,j (7)
5315 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5316 * The task movement gives a factor of O(m), giving a convergence complexity
5319 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5324 * In order to avoid CPUs going idle while there's still work to do, new idle
5325 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5326 * tree itself instead of relying on other CPUs to bring it work.
5328 * This adds some complexity to both (5) and (8) but it reduces the total idle
5336 * Cgroups make a horror show out of (2), instead of a simple sum we get:
5339 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
5344 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
5346 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5348 * The big problem is S_k, its a global sum needed to compute a local (W_i)
5351 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5352 * rewrite all of this once again.]
5355 static unsigned long __read_mostly max_load_balance_interval
= HZ
/10;
5357 enum fbq_type
{ regular
, remote
, all
};
5359 #define LBF_ALL_PINNED 0x01
5360 #define LBF_NEED_BREAK 0x02
5361 #define LBF_DST_PINNED 0x04
5362 #define LBF_SOME_PINNED 0x08
5365 struct sched_domain
*sd
;
5373 struct cpumask
*dst_grpmask
;
5375 enum cpu_idle_type idle
;
5377 /* The set of CPUs under consideration for load-balancing */
5378 struct cpumask
*cpus
;
5383 unsigned int loop_break
;
5384 unsigned int loop_max
;
5386 enum fbq_type fbq_type
;
5387 struct list_head tasks
;
5391 * Is this task likely cache-hot:
5393 static int task_hot(struct task_struct
*p
, struct lb_env
*env
)
5397 lockdep_assert_held(&env
->src_rq
->lock
);
5399 if (p
->sched_class
!= &fair_sched_class
)
5402 if (unlikely(p
->policy
== SCHED_IDLE
))
5406 * Buddy candidates are cache hot:
5408 if (sched_feat(CACHE_HOT_BUDDY
) && env
->dst_rq
->nr_running
&&
5409 (&p
->se
== cfs_rq_of(&p
->se
)->next
||
5410 &p
->se
== cfs_rq_of(&p
->se
)->last
))
5413 if (sysctl_sched_migration_cost
== -1)
5415 if (sysctl_sched_migration_cost
== 0)
5418 delta
= rq_clock_task(env
->src_rq
) - p
->se
.exec_start
;
5420 return delta
< (s64
)sysctl_sched_migration_cost
;
5423 #ifdef CONFIG_NUMA_BALANCING
5424 /* Returns true if the destination node has incurred more faults */
5425 static bool migrate_improves_locality(struct task_struct
*p
, struct lb_env
*env
)
5427 struct numa_group
*numa_group
= rcu_dereference(p
->numa_group
);
5428 int src_nid
, dst_nid
;
5430 if (!sched_feat(NUMA_FAVOUR_HIGHER
) || !p
->numa_faults
||
5431 !(env
->sd
->flags
& SD_NUMA
)) {
5435 src_nid
= cpu_to_node(env
->src_cpu
);
5436 dst_nid
= cpu_to_node(env
->dst_cpu
);
5438 if (src_nid
== dst_nid
)
5442 /* Task is already in the group's interleave set. */
5443 if (node_isset(src_nid
, numa_group
->active_nodes
))
5446 /* Task is moving into the group's interleave set. */
5447 if (node_isset(dst_nid
, numa_group
->active_nodes
))
5450 return group_faults(p
, dst_nid
) > group_faults(p
, src_nid
);
5453 /* Encourage migration to the preferred node. */
5454 if (dst_nid
== p
->numa_preferred_nid
)
5457 return task_faults(p
, dst_nid
) > task_faults(p
, src_nid
);
5461 static bool migrate_degrades_locality(struct task_struct
*p
, struct lb_env
*env
)
5463 struct numa_group
*numa_group
= rcu_dereference(p
->numa_group
);
5464 int src_nid
, dst_nid
;
5466 if (!sched_feat(NUMA
) || !sched_feat(NUMA_RESIST_LOWER
))
5469 if (!p
->numa_faults
|| !(env
->sd
->flags
& SD_NUMA
))
5472 src_nid
= cpu_to_node(env
->src_cpu
);
5473 dst_nid
= cpu_to_node(env
->dst_cpu
);
5475 if (src_nid
== dst_nid
)
5479 /* Task is moving within/into the group's interleave set. */
5480 if (node_isset(dst_nid
, numa_group
->active_nodes
))
5483 /* Task is moving out of the group's interleave set. */
5484 if (node_isset(src_nid
, numa_group
->active_nodes
))
5487 return group_faults(p
, dst_nid
) < group_faults(p
, src_nid
);
5490 /* Migrating away from the preferred node is always bad. */
5491 if (src_nid
== p
->numa_preferred_nid
)
5494 return task_faults(p
, dst_nid
) < task_faults(p
, src_nid
);
5498 static inline bool migrate_improves_locality(struct task_struct
*p
,
5504 static inline bool migrate_degrades_locality(struct task_struct
*p
,
5512 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
5515 int can_migrate_task(struct task_struct
*p
, struct lb_env
*env
)
5517 int tsk_cache_hot
= 0;
5519 lockdep_assert_held(&env
->src_rq
->lock
);
5522 * We do not migrate tasks that are:
5523 * 1) throttled_lb_pair, or
5524 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5525 * 3) running (obviously), or
5526 * 4) are cache-hot on their current CPU.
5528 if (throttled_lb_pair(task_group(p
), env
->src_cpu
, env
->dst_cpu
))
5531 if (!cpumask_test_cpu(env
->dst_cpu
, tsk_cpus_allowed(p
))) {
5534 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_affine
);
5536 env
->flags
|= LBF_SOME_PINNED
;
5539 * Remember if this task can be migrated to any other cpu in
5540 * our sched_group. We may want to revisit it if we couldn't
5541 * meet load balance goals by pulling other tasks on src_cpu.
5543 * Also avoid computing new_dst_cpu if we have already computed
5544 * one in current iteration.
5546 if (!env
->dst_grpmask
|| (env
->flags
& LBF_DST_PINNED
))
5549 /* Prevent to re-select dst_cpu via env's cpus */
5550 for_each_cpu_and(cpu
, env
->dst_grpmask
, env
->cpus
) {
5551 if (cpumask_test_cpu(cpu
, tsk_cpus_allowed(p
))) {
5552 env
->flags
|= LBF_DST_PINNED
;
5553 env
->new_dst_cpu
= cpu
;
5561 /* Record that we found atleast one task that could run on dst_cpu */
5562 env
->flags
&= ~LBF_ALL_PINNED
;
5564 if (task_running(env
->src_rq
, p
)) {
5565 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_running
);
5570 * Aggressive migration if:
5571 * 1) destination numa is preferred
5572 * 2) task is cache cold, or
5573 * 3) too many balance attempts have failed.
5575 tsk_cache_hot
= task_hot(p
, env
);
5577 tsk_cache_hot
= migrate_degrades_locality(p
, env
);
5579 if (migrate_improves_locality(p
, env
) || !tsk_cache_hot
||
5580 env
->sd
->nr_balance_failed
> env
->sd
->cache_nice_tries
) {
5581 if (tsk_cache_hot
) {
5582 schedstat_inc(env
->sd
, lb_hot_gained
[env
->idle
]);
5583 schedstat_inc(p
, se
.statistics
.nr_forced_migrations
);
5588 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_hot
);
5593 * detach_task() -- detach the task for the migration specified in env
5595 static void detach_task(struct task_struct
*p
, struct lb_env
*env
)
5597 lockdep_assert_held(&env
->src_rq
->lock
);
5599 deactivate_task(env
->src_rq
, p
, 0);
5600 p
->on_rq
= TASK_ON_RQ_MIGRATING
;
5601 set_task_cpu(p
, env
->dst_cpu
);
5605 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
5606 * part of active balancing operations within "domain".
5608 * Returns a task if successful and NULL otherwise.
5610 static struct task_struct
*detach_one_task(struct lb_env
*env
)
5612 struct task_struct
*p
, *n
;
5614 lockdep_assert_held(&env
->src_rq
->lock
);
5616 list_for_each_entry_safe(p
, n
, &env
->src_rq
->cfs_tasks
, se
.group_node
) {
5617 if (!can_migrate_task(p
, env
))
5620 detach_task(p
, env
);
5623 * Right now, this is only the second place where
5624 * lb_gained[env->idle] is updated (other is detach_tasks)
5625 * so we can safely collect stats here rather than
5626 * inside detach_tasks().
5628 schedstat_inc(env
->sd
, lb_gained
[env
->idle
]);
5634 static const unsigned int sched_nr_migrate_break
= 32;
5637 * detach_tasks() -- tries to detach up to imbalance weighted load from
5638 * busiest_rq, as part of a balancing operation within domain "sd".
5640 * Returns number of detached tasks if successful and 0 otherwise.
5642 static int detach_tasks(struct lb_env
*env
)
5644 struct list_head
*tasks
= &env
->src_rq
->cfs_tasks
;
5645 struct task_struct
*p
;
5649 lockdep_assert_held(&env
->src_rq
->lock
);
5651 if (env
->imbalance
<= 0)
5654 while (!list_empty(tasks
)) {
5655 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
5658 /* We've more or less seen every task there is, call it quits */
5659 if (env
->loop
> env
->loop_max
)
5662 /* take a breather every nr_migrate tasks */
5663 if (env
->loop
> env
->loop_break
) {
5664 env
->loop_break
+= sched_nr_migrate_break
;
5665 env
->flags
|= LBF_NEED_BREAK
;
5669 if (!can_migrate_task(p
, env
))
5672 load
= task_h_load(p
);
5674 if (sched_feat(LB_MIN
) && load
< 16 && !env
->sd
->nr_balance_failed
)
5677 if ((load
/ 2) > env
->imbalance
)
5680 detach_task(p
, env
);
5681 list_add(&p
->se
.group_node
, &env
->tasks
);
5684 env
->imbalance
-= load
;
5686 #ifdef CONFIG_PREEMPT
5688 * NEWIDLE balancing is a source of latency, so preemptible
5689 * kernels will stop after the first task is detached to minimize
5690 * the critical section.
5692 if (env
->idle
== CPU_NEWLY_IDLE
)
5697 * We only want to steal up to the prescribed amount of
5700 if (env
->imbalance
<= 0)
5705 list_move_tail(&p
->se
.group_node
, tasks
);
5709 * Right now, this is one of only two places we collect this stat
5710 * so we can safely collect detach_one_task() stats here rather
5711 * than inside detach_one_task().
5713 schedstat_add(env
->sd
, lb_gained
[env
->idle
], detached
);
5719 * attach_task() -- attach the task detached by detach_task() to its new rq.
5721 static void attach_task(struct rq
*rq
, struct task_struct
*p
)
5723 lockdep_assert_held(&rq
->lock
);
5725 BUG_ON(task_rq(p
) != rq
);
5726 p
->on_rq
= TASK_ON_RQ_QUEUED
;
5727 activate_task(rq
, p
, 0);
5728 check_preempt_curr(rq
, p
, 0);
5732 * attach_one_task() -- attaches the task returned from detach_one_task() to
5735 static void attach_one_task(struct rq
*rq
, struct task_struct
*p
)
5737 raw_spin_lock(&rq
->lock
);
5739 raw_spin_unlock(&rq
->lock
);
5743 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
5746 static void attach_tasks(struct lb_env
*env
)
5748 struct list_head
*tasks
= &env
->tasks
;
5749 struct task_struct
*p
;
5751 raw_spin_lock(&env
->dst_rq
->lock
);
5753 while (!list_empty(tasks
)) {
5754 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
5755 list_del_init(&p
->se
.group_node
);
5757 attach_task(env
->dst_rq
, p
);
5760 raw_spin_unlock(&env
->dst_rq
->lock
);
5763 #ifdef CONFIG_FAIR_GROUP_SCHED
5765 * update tg->load_weight by folding this cpu's load_avg
5767 static void __update_blocked_averages_cpu(struct task_group
*tg
, int cpu
)
5769 struct sched_entity
*se
= tg
->se
[cpu
];
5770 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu
];
5772 /* throttled entities do not contribute to load */
5773 if (throttled_hierarchy(cfs_rq
))
5776 update_cfs_rq_blocked_load(cfs_rq
, 1);
5779 update_entity_load_avg(se
, 1);
5781 * We pivot on our runnable average having decayed to zero for
5782 * list removal. This generally implies that all our children
5783 * have also been removed (modulo rounding error or bandwidth
5784 * control); however, such cases are rare and we can fix these
5787 * TODO: fix up out-of-order children on enqueue.
5789 if (!se
->avg
.runnable_avg_sum
&& !cfs_rq
->nr_running
)
5790 list_del_leaf_cfs_rq(cfs_rq
);
5792 struct rq
*rq
= rq_of(cfs_rq
);
5793 update_rq_runnable_avg(rq
, rq
->nr_running
);
5797 static void update_blocked_averages(int cpu
)
5799 struct rq
*rq
= cpu_rq(cpu
);
5800 struct cfs_rq
*cfs_rq
;
5801 unsigned long flags
;
5803 raw_spin_lock_irqsave(&rq
->lock
, flags
);
5804 update_rq_clock(rq
);
5806 * Iterates the task_group tree in a bottom up fashion, see
5807 * list_add_leaf_cfs_rq() for details.
5809 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
5811 * Note: We may want to consider periodically releasing
5812 * rq->lock about these updates so that creating many task
5813 * groups does not result in continually extending hold time.
5815 __update_blocked_averages_cpu(cfs_rq
->tg
, rq
->cpu
);
5818 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
5822 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5823 * This needs to be done in a top-down fashion because the load of a child
5824 * group is a fraction of its parents load.
5826 static void update_cfs_rq_h_load(struct cfs_rq
*cfs_rq
)
5828 struct rq
*rq
= rq_of(cfs_rq
);
5829 struct sched_entity
*se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
5830 unsigned long now
= jiffies
;
5833 if (cfs_rq
->last_h_load_update
== now
)
5836 cfs_rq
->h_load_next
= NULL
;
5837 for_each_sched_entity(se
) {
5838 cfs_rq
= cfs_rq_of(se
);
5839 cfs_rq
->h_load_next
= se
;
5840 if (cfs_rq
->last_h_load_update
== now
)
5845 cfs_rq
->h_load
= cfs_rq
->runnable_load_avg
;
5846 cfs_rq
->last_h_load_update
= now
;
5849 while ((se
= cfs_rq
->h_load_next
) != NULL
) {
5850 load
= cfs_rq
->h_load
;
5851 load
= div64_ul(load
* se
->avg
.load_avg_contrib
,
5852 cfs_rq
->runnable_load_avg
+ 1);
5853 cfs_rq
= group_cfs_rq(se
);
5854 cfs_rq
->h_load
= load
;
5855 cfs_rq
->last_h_load_update
= now
;
5859 static unsigned long task_h_load(struct task_struct
*p
)
5861 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
5863 update_cfs_rq_h_load(cfs_rq
);
5864 return div64_ul(p
->se
.avg
.load_avg_contrib
* cfs_rq
->h_load
,
5865 cfs_rq
->runnable_load_avg
+ 1);
5868 static inline void update_blocked_averages(int cpu
)
5872 static unsigned long task_h_load(struct task_struct
*p
)
5874 return p
->se
.avg
.load_avg_contrib
;
5878 /********** Helpers for find_busiest_group ************************/
5887 * sg_lb_stats - stats of a sched_group required for load_balancing
5889 struct sg_lb_stats
{
5890 unsigned long avg_load
; /*Avg load across the CPUs of the group */
5891 unsigned long group_load
; /* Total load over the CPUs of the group */
5892 unsigned long sum_weighted_load
; /* Weighted load of group's tasks */
5893 unsigned long load_per_task
;
5894 unsigned long group_capacity
;
5895 unsigned int sum_nr_running
; /* Nr tasks running in the group */
5896 unsigned int group_capacity_factor
;
5897 unsigned int idle_cpus
;
5898 unsigned int group_weight
;
5899 enum group_type group_type
;
5900 int group_has_free_capacity
;
5901 #ifdef CONFIG_NUMA_BALANCING
5902 unsigned int nr_numa_running
;
5903 unsigned int nr_preferred_running
;
5908 * sd_lb_stats - Structure to store the statistics of a sched_domain
5909 * during load balancing.
5911 struct sd_lb_stats
{
5912 struct sched_group
*busiest
; /* Busiest group in this sd */
5913 struct sched_group
*local
; /* Local group in this sd */
5914 unsigned long total_load
; /* Total load of all groups in sd */
5915 unsigned long total_capacity
; /* Total capacity of all groups in sd */
5916 unsigned long avg_load
; /* Average load across all groups in sd */
5918 struct sg_lb_stats busiest_stat
;/* Statistics of the busiest group */
5919 struct sg_lb_stats local_stat
; /* Statistics of the local group */
5922 static inline void init_sd_lb_stats(struct sd_lb_stats
*sds
)
5925 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
5926 * local_stat because update_sg_lb_stats() does a full clear/assignment.
5927 * We must however clear busiest_stat::avg_load because
5928 * update_sd_pick_busiest() reads this before assignment.
5930 *sds
= (struct sd_lb_stats
){
5934 .total_capacity
= 0UL,
5937 .sum_nr_running
= 0,
5938 .group_type
= group_other
,
5944 * get_sd_load_idx - Obtain the load index for a given sched domain.
5945 * @sd: The sched_domain whose load_idx is to be obtained.
5946 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
5948 * Return: The load index.
5950 static inline int get_sd_load_idx(struct sched_domain
*sd
,
5951 enum cpu_idle_type idle
)
5957 load_idx
= sd
->busy_idx
;
5960 case CPU_NEWLY_IDLE
:
5961 load_idx
= sd
->newidle_idx
;
5964 load_idx
= sd
->idle_idx
;
5971 static unsigned long default_scale_capacity(struct sched_domain
*sd
, int cpu
)
5973 return SCHED_CAPACITY_SCALE
;
5976 unsigned long __weak
arch_scale_freq_capacity(struct sched_domain
*sd
, int cpu
)
5978 return default_scale_capacity(sd
, cpu
);
5981 static unsigned long default_scale_cpu_capacity(struct sched_domain
*sd
, int cpu
)
5983 if ((sd
->flags
& SD_SHARE_CPUCAPACITY
) && (sd
->span_weight
> 1))
5984 return sd
->smt_gain
/ sd
->span_weight
;
5986 return SCHED_CAPACITY_SCALE
;
5989 unsigned long __weak
arch_scale_cpu_capacity(struct sched_domain
*sd
, int cpu
)
5991 return default_scale_cpu_capacity(sd
, cpu
);
5994 static unsigned long scale_rt_capacity(int cpu
)
5996 struct rq
*rq
= cpu_rq(cpu
);
5997 u64 total
, available
, age_stamp
, avg
;
6001 * Since we're reading these variables without serialization make sure
6002 * we read them once before doing sanity checks on them.
6004 age_stamp
= ACCESS_ONCE(rq
->age_stamp
);
6005 avg
= ACCESS_ONCE(rq
->rt_avg
);
6006 delta
= __rq_clock_broken(rq
) - age_stamp
;
6008 if (unlikely(delta
< 0))
6011 total
= sched_avg_period() + delta
;
6013 if (unlikely(total
< avg
)) {
6014 /* Ensures that capacity won't end up being negative */
6017 available
= total
- avg
;
6020 if (unlikely((s64
)total
< SCHED_CAPACITY_SCALE
))
6021 total
= SCHED_CAPACITY_SCALE
;
6023 total
>>= SCHED_CAPACITY_SHIFT
;
6025 return div_u64(available
, total
);
6028 static void update_cpu_capacity(struct sched_domain
*sd
, int cpu
)
6030 unsigned long capacity
= SCHED_CAPACITY_SCALE
;
6031 struct sched_group
*sdg
= sd
->groups
;
6033 if (sched_feat(ARCH_CAPACITY
))
6034 capacity
*= arch_scale_cpu_capacity(sd
, cpu
);
6036 capacity
*= default_scale_cpu_capacity(sd
, cpu
);
6038 capacity
>>= SCHED_CAPACITY_SHIFT
;
6040 sdg
->sgc
->capacity_orig
= capacity
;
6042 if (sched_feat(ARCH_CAPACITY
))
6043 capacity
*= arch_scale_freq_capacity(sd
, cpu
);
6045 capacity
*= default_scale_capacity(sd
, cpu
);
6047 capacity
>>= SCHED_CAPACITY_SHIFT
;
6049 capacity
*= scale_rt_capacity(cpu
);
6050 capacity
>>= SCHED_CAPACITY_SHIFT
;
6055 cpu_rq(cpu
)->cpu_capacity
= capacity
;
6056 sdg
->sgc
->capacity
= capacity
;
6059 void update_group_capacity(struct sched_domain
*sd
, int cpu
)
6061 struct sched_domain
*child
= sd
->child
;
6062 struct sched_group
*group
, *sdg
= sd
->groups
;
6063 unsigned long capacity
, capacity_orig
;
6064 unsigned long interval
;
6066 interval
= msecs_to_jiffies(sd
->balance_interval
);
6067 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
6068 sdg
->sgc
->next_update
= jiffies
+ interval
;
6071 update_cpu_capacity(sd
, cpu
);
6075 capacity_orig
= capacity
= 0;
6077 if (child
->flags
& SD_OVERLAP
) {
6079 * SD_OVERLAP domains cannot assume that child groups
6080 * span the current group.
6083 for_each_cpu(cpu
, sched_group_cpus(sdg
)) {
6084 struct sched_group_capacity
*sgc
;
6085 struct rq
*rq
= cpu_rq(cpu
);
6088 * build_sched_domains() -> init_sched_groups_capacity()
6089 * gets here before we've attached the domains to the
6092 * Use capacity_of(), which is set irrespective of domains
6093 * in update_cpu_capacity().
6095 * This avoids capacity/capacity_orig from being 0 and
6096 * causing divide-by-zero issues on boot.
6098 * Runtime updates will correct capacity_orig.
6100 if (unlikely(!rq
->sd
)) {
6101 capacity_orig
+= capacity_of(cpu
);
6102 capacity
+= capacity_of(cpu
);
6106 sgc
= rq
->sd
->groups
->sgc
;
6107 capacity_orig
+= sgc
->capacity_orig
;
6108 capacity
+= sgc
->capacity
;
6112 * !SD_OVERLAP domains can assume that child groups
6113 * span the current group.
6116 group
= child
->groups
;
6118 capacity_orig
+= group
->sgc
->capacity_orig
;
6119 capacity
+= group
->sgc
->capacity
;
6120 group
= group
->next
;
6121 } while (group
!= child
->groups
);
6124 sdg
->sgc
->capacity_orig
= capacity_orig
;
6125 sdg
->sgc
->capacity
= capacity
;
6129 * Try and fix up capacity for tiny siblings, this is needed when
6130 * things like SD_ASYM_PACKING need f_b_g to select another sibling
6131 * which on its own isn't powerful enough.
6133 * See update_sd_pick_busiest() and check_asym_packing().
6136 fix_small_capacity(struct sched_domain
*sd
, struct sched_group
*group
)
6139 * Only siblings can have significantly less than SCHED_CAPACITY_SCALE
6141 if (!(sd
->flags
& SD_SHARE_CPUCAPACITY
))
6145 * If ~90% of the cpu_capacity is still there, we're good.
6147 if (group
->sgc
->capacity
* 32 > group
->sgc
->capacity_orig
* 29)
6154 * Group imbalance indicates (and tries to solve) the problem where balancing
6155 * groups is inadequate due to tsk_cpus_allowed() constraints.
6157 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6158 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6161 * { 0 1 2 3 } { 4 5 6 7 }
6164 * If we were to balance group-wise we'd place two tasks in the first group and
6165 * two tasks in the second group. Clearly this is undesired as it will overload
6166 * cpu 3 and leave one of the cpus in the second group unused.
6168 * The current solution to this issue is detecting the skew in the first group
6169 * by noticing the lower domain failed to reach balance and had difficulty
6170 * moving tasks due to affinity constraints.
6172 * When this is so detected; this group becomes a candidate for busiest; see
6173 * update_sd_pick_busiest(). And calculate_imbalance() and
6174 * find_busiest_group() avoid some of the usual balance conditions to allow it
6175 * to create an effective group imbalance.
6177 * This is a somewhat tricky proposition since the next run might not find the
6178 * group imbalance and decide the groups need to be balanced again. A most
6179 * subtle and fragile situation.
6182 static inline int sg_imbalanced(struct sched_group
*group
)
6184 return group
->sgc
->imbalance
;
6188 * Compute the group capacity factor.
6190 * Avoid the issue where N*frac(smt_capacity) >= 1 creates 'phantom' cores by
6191 * first dividing out the smt factor and computing the actual number of cores
6192 * and limit unit capacity with that.
6194 static inline int sg_capacity_factor(struct lb_env
*env
, struct sched_group
*group
)
6196 unsigned int capacity_factor
, smt
, cpus
;
6197 unsigned int capacity
, capacity_orig
;
6199 capacity
= group
->sgc
->capacity
;
6200 capacity_orig
= group
->sgc
->capacity_orig
;
6201 cpus
= group
->group_weight
;
6203 /* smt := ceil(cpus / capacity), assumes: 1 < smt_capacity < 2 */
6204 smt
= DIV_ROUND_UP(SCHED_CAPACITY_SCALE
* cpus
, capacity_orig
);
6205 capacity_factor
= cpus
/ smt
; /* cores */
6207 capacity_factor
= min_t(unsigned,
6208 capacity_factor
, DIV_ROUND_CLOSEST(capacity
, SCHED_CAPACITY_SCALE
));
6209 if (!capacity_factor
)
6210 capacity_factor
= fix_small_capacity(env
->sd
, group
);
6212 return capacity_factor
;
6215 static enum group_type
6216 group_classify(struct sched_group
*group
, struct sg_lb_stats
*sgs
)
6218 if (sgs
->sum_nr_running
> sgs
->group_capacity_factor
)
6219 return group_overloaded
;
6221 if (sg_imbalanced(group
))
6222 return group_imbalanced
;
6228 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6229 * @env: The load balancing environment.
6230 * @group: sched_group whose statistics are to be updated.
6231 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6232 * @local_group: Does group contain this_cpu.
6233 * @sgs: variable to hold the statistics for this group.
6234 * @overload: Indicate more than one runnable task for any CPU.
6236 static inline void update_sg_lb_stats(struct lb_env
*env
,
6237 struct sched_group
*group
, int load_idx
,
6238 int local_group
, struct sg_lb_stats
*sgs
,
6244 memset(sgs
, 0, sizeof(*sgs
));
6246 for_each_cpu_and(i
, sched_group_cpus(group
), env
->cpus
) {
6247 struct rq
*rq
= cpu_rq(i
);
6249 /* Bias balancing toward cpus of our domain */
6251 load
= target_load(i
, load_idx
);
6253 load
= source_load(i
, load_idx
);
6255 sgs
->group_load
+= load
;
6256 sgs
->sum_nr_running
+= rq
->cfs
.h_nr_running
;
6258 if (rq
->nr_running
> 1)
6261 #ifdef CONFIG_NUMA_BALANCING
6262 sgs
->nr_numa_running
+= rq
->nr_numa_running
;
6263 sgs
->nr_preferred_running
+= rq
->nr_preferred_running
;
6265 sgs
->sum_weighted_load
+= weighted_cpuload(i
);
6270 /* Adjust by relative CPU capacity of the group */
6271 sgs
->group_capacity
= group
->sgc
->capacity
;
6272 sgs
->avg_load
= (sgs
->group_load
*SCHED_CAPACITY_SCALE
) / sgs
->group_capacity
;
6274 if (sgs
->sum_nr_running
)
6275 sgs
->load_per_task
= sgs
->sum_weighted_load
/ sgs
->sum_nr_running
;
6277 sgs
->group_weight
= group
->group_weight
;
6278 sgs
->group_capacity_factor
= sg_capacity_factor(env
, group
);
6279 sgs
->group_type
= group_classify(group
, sgs
);
6281 if (sgs
->group_capacity_factor
> sgs
->sum_nr_running
)
6282 sgs
->group_has_free_capacity
= 1;
6286 * update_sd_pick_busiest - return 1 on busiest group
6287 * @env: The load balancing environment.
6288 * @sds: sched_domain statistics
6289 * @sg: sched_group candidate to be checked for being the busiest
6290 * @sgs: sched_group statistics
6292 * Determine if @sg is a busier group than the previously selected
6295 * Return: %true if @sg is a busier group than the previously selected
6296 * busiest group. %false otherwise.
6298 static bool update_sd_pick_busiest(struct lb_env
*env
,
6299 struct sd_lb_stats
*sds
,
6300 struct sched_group
*sg
,
6301 struct sg_lb_stats
*sgs
)
6303 struct sg_lb_stats
*busiest
= &sds
->busiest_stat
;
6305 if (sgs
->group_type
> busiest
->group_type
)
6308 if (sgs
->group_type
< busiest
->group_type
)
6311 if (sgs
->avg_load
<= busiest
->avg_load
)
6314 /* This is the busiest node in its class. */
6315 if (!(env
->sd
->flags
& SD_ASYM_PACKING
))
6319 * ASYM_PACKING needs to move all the work to the lowest
6320 * numbered CPUs in the group, therefore mark all groups
6321 * higher than ourself as busy.
6323 if (sgs
->sum_nr_running
&& env
->dst_cpu
< group_first_cpu(sg
)) {
6327 if (group_first_cpu(sds
->busiest
) > group_first_cpu(sg
))
6334 #ifdef CONFIG_NUMA_BALANCING
6335 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
6337 if (sgs
->sum_nr_running
> sgs
->nr_numa_running
)
6339 if (sgs
->sum_nr_running
> sgs
->nr_preferred_running
)
6344 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
6346 if (rq
->nr_running
> rq
->nr_numa_running
)
6348 if (rq
->nr_running
> rq
->nr_preferred_running
)
6353 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
6358 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
6362 #endif /* CONFIG_NUMA_BALANCING */
6365 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6366 * @env: The load balancing environment.
6367 * @sds: variable to hold the statistics for this sched_domain.
6369 static inline void update_sd_lb_stats(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6371 struct sched_domain
*child
= env
->sd
->child
;
6372 struct sched_group
*sg
= env
->sd
->groups
;
6373 struct sg_lb_stats tmp_sgs
;
6374 int load_idx
, prefer_sibling
= 0;
6375 bool overload
= false;
6377 if (child
&& child
->flags
& SD_PREFER_SIBLING
)
6380 load_idx
= get_sd_load_idx(env
->sd
, env
->idle
);
6383 struct sg_lb_stats
*sgs
= &tmp_sgs
;
6386 local_group
= cpumask_test_cpu(env
->dst_cpu
, sched_group_cpus(sg
));
6389 sgs
= &sds
->local_stat
;
6391 if (env
->idle
!= CPU_NEWLY_IDLE
||
6392 time_after_eq(jiffies
, sg
->sgc
->next_update
))
6393 update_group_capacity(env
->sd
, env
->dst_cpu
);
6396 update_sg_lb_stats(env
, sg
, load_idx
, local_group
, sgs
,
6403 * In case the child domain prefers tasks go to siblings
6404 * first, lower the sg capacity factor to one so that we'll try
6405 * and move all the excess tasks away. We lower the capacity
6406 * of a group only if the local group has the capacity to fit
6407 * these excess tasks, i.e. nr_running < group_capacity_factor. The
6408 * extra check prevents the case where you always pull from the
6409 * heaviest group when it is already under-utilized (possible
6410 * with a large weight task outweighs the tasks on the system).
6412 if (prefer_sibling
&& sds
->local
&&
6413 sds
->local_stat
.group_has_free_capacity
) {
6414 sgs
->group_capacity_factor
= min(sgs
->group_capacity_factor
, 1U);
6415 sgs
->group_type
= group_classify(sg
, sgs
);
6418 if (update_sd_pick_busiest(env
, sds
, sg
, sgs
)) {
6420 sds
->busiest_stat
= *sgs
;
6424 /* Now, start updating sd_lb_stats */
6425 sds
->total_load
+= sgs
->group_load
;
6426 sds
->total_capacity
+= sgs
->group_capacity
;
6429 } while (sg
!= env
->sd
->groups
);
6431 if (env
->sd
->flags
& SD_NUMA
)
6432 env
->fbq_type
= fbq_classify_group(&sds
->busiest_stat
);
6434 if (!env
->sd
->parent
) {
6435 /* update overload indicator if we are at root domain */
6436 if (env
->dst_rq
->rd
->overload
!= overload
)
6437 env
->dst_rq
->rd
->overload
= overload
;
6443 * check_asym_packing - Check to see if the group is packed into the
6446 * This is primarily intended to used at the sibling level. Some
6447 * cores like POWER7 prefer to use lower numbered SMT threads. In the
6448 * case of POWER7, it can move to lower SMT modes only when higher
6449 * threads are idle. When in lower SMT modes, the threads will
6450 * perform better since they share less core resources. Hence when we
6451 * have idle threads, we want them to be the higher ones.
6453 * This packing function is run on idle threads. It checks to see if
6454 * the busiest CPU in this domain (core in the P7 case) has a higher
6455 * CPU number than the packing function is being run on. Here we are
6456 * assuming lower CPU number will be equivalent to lower a SMT thread
6459 * Return: 1 when packing is required and a task should be moved to
6460 * this CPU. The amount of the imbalance is returned in *imbalance.
6462 * @env: The load balancing environment.
6463 * @sds: Statistics of the sched_domain which is to be packed
6465 static int check_asym_packing(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6469 if (!(env
->sd
->flags
& SD_ASYM_PACKING
))
6475 busiest_cpu
= group_first_cpu(sds
->busiest
);
6476 if (env
->dst_cpu
> busiest_cpu
)
6479 env
->imbalance
= DIV_ROUND_CLOSEST(
6480 sds
->busiest_stat
.avg_load
* sds
->busiest_stat
.group_capacity
,
6481 SCHED_CAPACITY_SCALE
);
6487 * fix_small_imbalance - Calculate the minor imbalance that exists
6488 * amongst the groups of a sched_domain, during
6490 * @env: The load balancing environment.
6491 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6494 void fix_small_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6496 unsigned long tmp
, capa_now
= 0, capa_move
= 0;
6497 unsigned int imbn
= 2;
6498 unsigned long scaled_busy_load_per_task
;
6499 struct sg_lb_stats
*local
, *busiest
;
6501 local
= &sds
->local_stat
;
6502 busiest
= &sds
->busiest_stat
;
6504 if (!local
->sum_nr_running
)
6505 local
->load_per_task
= cpu_avg_load_per_task(env
->dst_cpu
);
6506 else if (busiest
->load_per_task
> local
->load_per_task
)
6509 scaled_busy_load_per_task
=
6510 (busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) /
6511 busiest
->group_capacity
;
6513 if (busiest
->avg_load
+ scaled_busy_load_per_task
>=
6514 local
->avg_load
+ (scaled_busy_load_per_task
* imbn
)) {
6515 env
->imbalance
= busiest
->load_per_task
;
6520 * OK, we don't have enough imbalance to justify moving tasks,
6521 * however we may be able to increase total CPU capacity used by
6525 capa_now
+= busiest
->group_capacity
*
6526 min(busiest
->load_per_task
, busiest
->avg_load
);
6527 capa_now
+= local
->group_capacity
*
6528 min(local
->load_per_task
, local
->avg_load
);
6529 capa_now
/= SCHED_CAPACITY_SCALE
;
6531 /* Amount of load we'd subtract */
6532 if (busiest
->avg_load
> scaled_busy_load_per_task
) {
6533 capa_move
+= busiest
->group_capacity
*
6534 min(busiest
->load_per_task
,
6535 busiest
->avg_load
- scaled_busy_load_per_task
);
6538 /* Amount of load we'd add */
6539 if (busiest
->avg_load
* busiest
->group_capacity
<
6540 busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) {
6541 tmp
= (busiest
->avg_load
* busiest
->group_capacity
) /
6542 local
->group_capacity
;
6544 tmp
= (busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) /
6545 local
->group_capacity
;
6547 capa_move
+= local
->group_capacity
*
6548 min(local
->load_per_task
, local
->avg_load
+ tmp
);
6549 capa_move
/= SCHED_CAPACITY_SCALE
;
6551 /* Move if we gain throughput */
6552 if (capa_move
> capa_now
)
6553 env
->imbalance
= busiest
->load_per_task
;
6557 * calculate_imbalance - Calculate the amount of imbalance present within the
6558 * groups of a given sched_domain during load balance.
6559 * @env: load balance environment
6560 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
6562 static inline void calculate_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6564 unsigned long max_pull
, load_above_capacity
= ~0UL;
6565 struct sg_lb_stats
*local
, *busiest
;
6567 local
= &sds
->local_stat
;
6568 busiest
= &sds
->busiest_stat
;
6570 if (busiest
->group_type
== group_imbalanced
) {
6572 * In the group_imb case we cannot rely on group-wide averages
6573 * to ensure cpu-load equilibrium, look at wider averages. XXX
6575 busiest
->load_per_task
=
6576 min(busiest
->load_per_task
, sds
->avg_load
);
6580 * In the presence of smp nice balancing, certain scenarios can have
6581 * max load less than avg load(as we skip the groups at or below
6582 * its cpu_capacity, while calculating max_load..)
6584 if (busiest
->avg_load
<= sds
->avg_load
||
6585 local
->avg_load
>= sds
->avg_load
) {
6587 return fix_small_imbalance(env
, sds
);
6591 * If there aren't any idle cpus, avoid creating some.
6593 if (busiest
->group_type
== group_overloaded
&&
6594 local
->group_type
== group_overloaded
) {
6595 load_above_capacity
=
6596 (busiest
->sum_nr_running
- busiest
->group_capacity_factor
);
6598 load_above_capacity
*= (SCHED_LOAD_SCALE
* SCHED_CAPACITY_SCALE
);
6599 load_above_capacity
/= busiest
->group_capacity
;
6603 * We're trying to get all the cpus to the average_load, so we don't
6604 * want to push ourselves above the average load, nor do we wish to
6605 * reduce the max loaded cpu below the average load. At the same time,
6606 * we also don't want to reduce the group load below the group capacity
6607 * (so that we can implement power-savings policies etc). Thus we look
6608 * for the minimum possible imbalance.
6610 max_pull
= min(busiest
->avg_load
- sds
->avg_load
, load_above_capacity
);
6612 /* How much load to actually move to equalise the imbalance */
6613 env
->imbalance
= min(
6614 max_pull
* busiest
->group_capacity
,
6615 (sds
->avg_load
- local
->avg_load
) * local
->group_capacity
6616 ) / SCHED_CAPACITY_SCALE
;
6619 * if *imbalance is less than the average load per runnable task
6620 * there is no guarantee that any tasks will be moved so we'll have
6621 * a think about bumping its value to force at least one task to be
6624 if (env
->imbalance
< busiest
->load_per_task
)
6625 return fix_small_imbalance(env
, sds
);
6628 /******* find_busiest_group() helpers end here *********************/
6631 * find_busiest_group - Returns the busiest group within the sched_domain
6632 * if there is an imbalance. If there isn't an imbalance, and
6633 * the user has opted for power-savings, it returns a group whose
6634 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
6635 * such a group exists.
6637 * Also calculates the amount of weighted load which should be moved
6638 * to restore balance.
6640 * @env: The load balancing environment.
6642 * Return: - The busiest group if imbalance exists.
6643 * - If no imbalance and user has opted for power-savings balance,
6644 * return the least loaded group whose CPUs can be
6645 * put to idle by rebalancing its tasks onto our group.
6647 static struct sched_group
*find_busiest_group(struct lb_env
*env
)
6649 struct sg_lb_stats
*local
, *busiest
;
6650 struct sd_lb_stats sds
;
6652 init_sd_lb_stats(&sds
);
6655 * Compute the various statistics relavent for load balancing at
6658 update_sd_lb_stats(env
, &sds
);
6659 local
= &sds
.local_stat
;
6660 busiest
= &sds
.busiest_stat
;
6662 if ((env
->idle
== CPU_IDLE
|| env
->idle
== CPU_NEWLY_IDLE
) &&
6663 check_asym_packing(env
, &sds
))
6666 /* There is no busy sibling group to pull tasks from */
6667 if (!sds
.busiest
|| busiest
->sum_nr_running
== 0)
6670 sds
.avg_load
= (SCHED_CAPACITY_SCALE
* sds
.total_load
)
6671 / sds
.total_capacity
;
6674 * If the busiest group is imbalanced the below checks don't
6675 * work because they assume all things are equal, which typically
6676 * isn't true due to cpus_allowed constraints and the like.
6678 if (busiest
->group_type
== group_imbalanced
)
6681 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6682 if (env
->idle
== CPU_NEWLY_IDLE
&& local
->group_has_free_capacity
&&
6683 !busiest
->group_has_free_capacity
)
6687 * If the local group is busier than the selected busiest group
6688 * don't try and pull any tasks.
6690 if (local
->avg_load
>= busiest
->avg_load
)
6694 * Don't pull any tasks if this group is already above the domain
6697 if (local
->avg_load
>= sds
.avg_load
)
6700 if (env
->idle
== CPU_IDLE
) {
6702 * This cpu is idle. If the busiest group is not overloaded
6703 * and there is no imbalance between this and busiest group
6704 * wrt idle cpus, it is balanced. The imbalance becomes
6705 * significant if the diff is greater than 1 otherwise we
6706 * might end up to just move the imbalance on another group
6708 if ((busiest
->group_type
!= group_overloaded
) &&
6709 (local
->idle_cpus
<= (busiest
->idle_cpus
+ 1)))
6713 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
6714 * imbalance_pct to be conservative.
6716 if (100 * busiest
->avg_load
<=
6717 env
->sd
->imbalance_pct
* local
->avg_load
)
6722 /* Looks like there is an imbalance. Compute it */
6723 calculate_imbalance(env
, &sds
);
6732 * find_busiest_queue - find the busiest runqueue among the cpus in group.
6734 static struct rq
*find_busiest_queue(struct lb_env
*env
,
6735 struct sched_group
*group
)
6737 struct rq
*busiest
= NULL
, *rq
;
6738 unsigned long busiest_load
= 0, busiest_capacity
= 1;
6741 for_each_cpu_and(i
, sched_group_cpus(group
), env
->cpus
) {
6742 unsigned long capacity
, capacity_factor
, wl
;
6746 rt
= fbq_classify_rq(rq
);
6749 * We classify groups/runqueues into three groups:
6750 * - regular: there are !numa tasks
6751 * - remote: there are numa tasks that run on the 'wrong' node
6752 * - all: there is no distinction
6754 * In order to avoid migrating ideally placed numa tasks,
6755 * ignore those when there's better options.
6757 * If we ignore the actual busiest queue to migrate another
6758 * task, the next balance pass can still reduce the busiest
6759 * queue by moving tasks around inside the node.
6761 * If we cannot move enough load due to this classification
6762 * the next pass will adjust the group classification and
6763 * allow migration of more tasks.
6765 * Both cases only affect the total convergence complexity.
6767 if (rt
> env
->fbq_type
)
6770 capacity
= capacity_of(i
);
6771 capacity_factor
= DIV_ROUND_CLOSEST(capacity
, SCHED_CAPACITY_SCALE
);
6772 if (!capacity_factor
)
6773 capacity_factor
= fix_small_capacity(env
->sd
, group
);
6775 wl
= weighted_cpuload(i
);
6778 * When comparing with imbalance, use weighted_cpuload()
6779 * which is not scaled with the cpu capacity.
6781 if (capacity_factor
&& rq
->nr_running
== 1 && wl
> env
->imbalance
)
6785 * For the load comparisons with the other cpu's, consider
6786 * the weighted_cpuload() scaled with the cpu capacity, so
6787 * that the load can be moved away from the cpu that is
6788 * potentially running at a lower capacity.
6790 * Thus we're looking for max(wl_i / capacity_i), crosswise
6791 * multiplication to rid ourselves of the division works out
6792 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
6793 * our previous maximum.
6795 if (wl
* busiest_capacity
> busiest_load
* capacity
) {
6797 busiest_capacity
= capacity
;
6806 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
6807 * so long as it is large enough.
6809 #define MAX_PINNED_INTERVAL 512
6811 /* Working cpumask for load_balance and load_balance_newidle. */
6812 DEFINE_PER_CPU(cpumask_var_t
, load_balance_mask
);
6814 static int need_active_balance(struct lb_env
*env
)
6816 struct sched_domain
*sd
= env
->sd
;
6818 if (env
->idle
== CPU_NEWLY_IDLE
) {
6821 * ASYM_PACKING needs to force migrate tasks from busy but
6822 * higher numbered CPUs in order to pack all tasks in the
6823 * lowest numbered CPUs.
6825 if ((sd
->flags
& SD_ASYM_PACKING
) && env
->src_cpu
> env
->dst_cpu
)
6829 return unlikely(sd
->nr_balance_failed
> sd
->cache_nice_tries
+2);
6832 static int active_load_balance_cpu_stop(void *data
);
6834 static int should_we_balance(struct lb_env
*env
)
6836 struct sched_group
*sg
= env
->sd
->groups
;
6837 struct cpumask
*sg_cpus
, *sg_mask
;
6838 int cpu
, balance_cpu
= -1;
6841 * In the newly idle case, we will allow all the cpu's
6842 * to do the newly idle load balance.
6844 if (env
->idle
== CPU_NEWLY_IDLE
)
6847 sg_cpus
= sched_group_cpus(sg
);
6848 sg_mask
= sched_group_mask(sg
);
6849 /* Try to find first idle cpu */
6850 for_each_cpu_and(cpu
, sg_cpus
, env
->cpus
) {
6851 if (!cpumask_test_cpu(cpu
, sg_mask
) || !idle_cpu(cpu
))
6858 if (balance_cpu
== -1)
6859 balance_cpu
= group_balance_cpu(sg
);
6862 * First idle cpu or the first cpu(busiest) in this sched group
6863 * is eligible for doing load balancing at this and above domains.
6865 return balance_cpu
== env
->dst_cpu
;
6869 * Check this_cpu to ensure it is balanced within domain. Attempt to move
6870 * tasks if there is an imbalance.
6872 static int load_balance(int this_cpu
, struct rq
*this_rq
,
6873 struct sched_domain
*sd
, enum cpu_idle_type idle
,
6874 int *continue_balancing
)
6876 int ld_moved
, cur_ld_moved
, active_balance
= 0;
6877 struct sched_domain
*sd_parent
= sd
->parent
;
6878 struct sched_group
*group
;
6880 unsigned long flags
;
6881 struct cpumask
*cpus
= this_cpu_cpumask_var_ptr(load_balance_mask
);
6883 struct lb_env env
= {
6885 .dst_cpu
= this_cpu
,
6887 .dst_grpmask
= sched_group_cpus(sd
->groups
),
6889 .loop_break
= sched_nr_migrate_break
,
6892 .tasks
= LIST_HEAD_INIT(env
.tasks
),
6896 * For NEWLY_IDLE load_balancing, we don't need to consider
6897 * other cpus in our group
6899 if (idle
== CPU_NEWLY_IDLE
)
6900 env
.dst_grpmask
= NULL
;
6902 cpumask_copy(cpus
, cpu_active_mask
);
6904 schedstat_inc(sd
, lb_count
[idle
]);
6907 if (!should_we_balance(&env
)) {
6908 *continue_balancing
= 0;
6912 group
= find_busiest_group(&env
);
6914 schedstat_inc(sd
, lb_nobusyg
[idle
]);
6918 busiest
= find_busiest_queue(&env
, group
);
6920 schedstat_inc(sd
, lb_nobusyq
[idle
]);
6924 BUG_ON(busiest
== env
.dst_rq
);
6926 schedstat_add(sd
, lb_imbalance
[idle
], env
.imbalance
);
6929 if (busiest
->nr_running
> 1) {
6931 * Attempt to move tasks. If find_busiest_group has found
6932 * an imbalance but busiest->nr_running <= 1, the group is
6933 * still unbalanced. ld_moved simply stays zero, so it is
6934 * correctly treated as an imbalance.
6936 env
.flags
|= LBF_ALL_PINNED
;
6937 env
.src_cpu
= busiest
->cpu
;
6938 env
.src_rq
= busiest
;
6939 env
.loop_max
= min(sysctl_sched_nr_migrate
, busiest
->nr_running
);
6942 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
6945 * cur_ld_moved - load moved in current iteration
6946 * ld_moved - cumulative load moved across iterations
6948 cur_ld_moved
= detach_tasks(&env
);
6951 * We've detached some tasks from busiest_rq. Every
6952 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
6953 * unlock busiest->lock, and we are able to be sure
6954 * that nobody can manipulate the tasks in parallel.
6955 * See task_rq_lock() family for the details.
6958 raw_spin_unlock(&busiest
->lock
);
6962 ld_moved
+= cur_ld_moved
;
6965 local_irq_restore(flags
);
6967 if (env
.flags
& LBF_NEED_BREAK
) {
6968 env
.flags
&= ~LBF_NEED_BREAK
;
6973 * Revisit (affine) tasks on src_cpu that couldn't be moved to
6974 * us and move them to an alternate dst_cpu in our sched_group
6975 * where they can run. The upper limit on how many times we
6976 * iterate on same src_cpu is dependent on number of cpus in our
6979 * This changes load balance semantics a bit on who can move
6980 * load to a given_cpu. In addition to the given_cpu itself
6981 * (or a ilb_cpu acting on its behalf where given_cpu is
6982 * nohz-idle), we now have balance_cpu in a position to move
6983 * load to given_cpu. In rare situations, this may cause
6984 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
6985 * _independently_ and at _same_ time to move some load to
6986 * given_cpu) causing exceess load to be moved to given_cpu.
6987 * This however should not happen so much in practice and
6988 * moreover subsequent load balance cycles should correct the
6989 * excess load moved.
6991 if ((env
.flags
& LBF_DST_PINNED
) && env
.imbalance
> 0) {
6993 /* Prevent to re-select dst_cpu via env's cpus */
6994 cpumask_clear_cpu(env
.dst_cpu
, env
.cpus
);
6996 env
.dst_rq
= cpu_rq(env
.new_dst_cpu
);
6997 env
.dst_cpu
= env
.new_dst_cpu
;
6998 env
.flags
&= ~LBF_DST_PINNED
;
7000 env
.loop_break
= sched_nr_migrate_break
;
7003 * Go back to "more_balance" rather than "redo" since we
7004 * need to continue with same src_cpu.
7010 * We failed to reach balance because of affinity.
7013 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
7015 if ((env
.flags
& LBF_SOME_PINNED
) && env
.imbalance
> 0)
7016 *group_imbalance
= 1;
7019 /* All tasks on this runqueue were pinned by CPU affinity */
7020 if (unlikely(env
.flags
& LBF_ALL_PINNED
)) {
7021 cpumask_clear_cpu(cpu_of(busiest
), cpus
);
7022 if (!cpumask_empty(cpus
)) {
7024 env
.loop_break
= sched_nr_migrate_break
;
7027 goto out_all_pinned
;
7032 schedstat_inc(sd
, lb_failed
[idle
]);
7034 * Increment the failure counter only on periodic balance.
7035 * We do not want newidle balance, which can be very
7036 * frequent, pollute the failure counter causing
7037 * excessive cache_hot migrations and active balances.
7039 if (idle
!= CPU_NEWLY_IDLE
)
7040 sd
->nr_balance_failed
++;
7042 if (need_active_balance(&env
)) {
7043 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
7045 /* don't kick the active_load_balance_cpu_stop,
7046 * if the curr task on busiest cpu can't be
7049 if (!cpumask_test_cpu(this_cpu
,
7050 tsk_cpus_allowed(busiest
->curr
))) {
7051 raw_spin_unlock_irqrestore(&busiest
->lock
,
7053 env
.flags
|= LBF_ALL_PINNED
;
7054 goto out_one_pinned
;
7058 * ->active_balance synchronizes accesses to
7059 * ->active_balance_work. Once set, it's cleared
7060 * only after active load balance is finished.
7062 if (!busiest
->active_balance
) {
7063 busiest
->active_balance
= 1;
7064 busiest
->push_cpu
= this_cpu
;
7067 raw_spin_unlock_irqrestore(&busiest
->lock
, flags
);
7069 if (active_balance
) {
7070 stop_one_cpu_nowait(cpu_of(busiest
),
7071 active_load_balance_cpu_stop
, busiest
,
7072 &busiest
->active_balance_work
);
7076 * We've kicked active balancing, reset the failure
7079 sd
->nr_balance_failed
= sd
->cache_nice_tries
+1;
7082 sd
->nr_balance_failed
= 0;
7084 if (likely(!active_balance
)) {
7085 /* We were unbalanced, so reset the balancing interval */
7086 sd
->balance_interval
= sd
->min_interval
;
7089 * If we've begun active balancing, start to back off. This
7090 * case may not be covered by the all_pinned logic if there
7091 * is only 1 task on the busy runqueue (because we don't call
7094 if (sd
->balance_interval
< sd
->max_interval
)
7095 sd
->balance_interval
*= 2;
7102 * We reach balance although we may have faced some affinity
7103 * constraints. Clear the imbalance flag if it was set.
7106 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
7108 if (*group_imbalance
)
7109 *group_imbalance
= 0;
7114 * We reach balance because all tasks are pinned at this level so
7115 * we can't migrate them. Let the imbalance flag set so parent level
7116 * can try to migrate them.
7118 schedstat_inc(sd
, lb_balanced
[idle
]);
7120 sd
->nr_balance_failed
= 0;
7123 /* tune up the balancing interval */
7124 if (((env
.flags
& LBF_ALL_PINNED
) &&
7125 sd
->balance_interval
< MAX_PINNED_INTERVAL
) ||
7126 (sd
->balance_interval
< sd
->max_interval
))
7127 sd
->balance_interval
*= 2;
7134 static inline unsigned long
7135 get_sd_balance_interval(struct sched_domain
*sd
, int cpu_busy
)
7137 unsigned long interval
= sd
->balance_interval
;
7140 interval
*= sd
->busy_factor
;
7142 /* scale ms to jiffies */
7143 interval
= msecs_to_jiffies(interval
);
7144 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
7150 update_next_balance(struct sched_domain
*sd
, int cpu_busy
, unsigned long *next_balance
)
7152 unsigned long interval
, next
;
7154 interval
= get_sd_balance_interval(sd
, cpu_busy
);
7155 next
= sd
->last_balance
+ interval
;
7157 if (time_after(*next_balance
, next
))
7158 *next_balance
= next
;
7162 * idle_balance is called by schedule() if this_cpu is about to become
7163 * idle. Attempts to pull tasks from other CPUs.
7165 static int idle_balance(struct rq
*this_rq
)
7167 unsigned long next_balance
= jiffies
+ HZ
;
7168 int this_cpu
= this_rq
->cpu
;
7169 struct sched_domain
*sd
;
7170 int pulled_task
= 0;
7173 idle_enter_fair(this_rq
);
7176 * We must set idle_stamp _before_ calling idle_balance(), such that we
7177 * measure the duration of idle_balance() as idle time.
7179 this_rq
->idle_stamp
= rq_clock(this_rq
);
7181 if (this_rq
->avg_idle
< sysctl_sched_migration_cost
||
7182 !this_rq
->rd
->overload
) {
7184 sd
= rcu_dereference_check_sched_domain(this_rq
->sd
);
7186 update_next_balance(sd
, 0, &next_balance
);
7193 * Drop the rq->lock, but keep IRQ/preempt disabled.
7195 raw_spin_unlock(&this_rq
->lock
);
7197 update_blocked_averages(this_cpu
);
7199 for_each_domain(this_cpu
, sd
) {
7200 int continue_balancing
= 1;
7201 u64 t0
, domain_cost
;
7203 if (!(sd
->flags
& SD_LOAD_BALANCE
))
7206 if (this_rq
->avg_idle
< curr_cost
+ sd
->max_newidle_lb_cost
) {
7207 update_next_balance(sd
, 0, &next_balance
);
7211 if (sd
->flags
& SD_BALANCE_NEWIDLE
) {
7212 t0
= sched_clock_cpu(this_cpu
);
7214 pulled_task
= load_balance(this_cpu
, this_rq
,
7216 &continue_balancing
);
7218 domain_cost
= sched_clock_cpu(this_cpu
) - t0
;
7219 if (domain_cost
> sd
->max_newidle_lb_cost
)
7220 sd
->max_newidle_lb_cost
= domain_cost
;
7222 curr_cost
+= domain_cost
;
7225 update_next_balance(sd
, 0, &next_balance
);
7228 * Stop searching for tasks to pull if there are
7229 * now runnable tasks on this rq.
7231 if (pulled_task
|| this_rq
->nr_running
> 0)
7236 raw_spin_lock(&this_rq
->lock
);
7238 if (curr_cost
> this_rq
->max_idle_balance_cost
)
7239 this_rq
->max_idle_balance_cost
= curr_cost
;
7242 * While browsing the domains, we released the rq lock, a task could
7243 * have been enqueued in the meantime. Since we're not going idle,
7244 * pretend we pulled a task.
7246 if (this_rq
->cfs
.h_nr_running
&& !pulled_task
)
7250 /* Move the next balance forward */
7251 if (time_after(this_rq
->next_balance
, next_balance
))
7252 this_rq
->next_balance
= next_balance
;
7254 /* Is there a task of a high priority class? */
7255 if (this_rq
->nr_running
!= this_rq
->cfs
.h_nr_running
)
7259 idle_exit_fair(this_rq
);
7260 this_rq
->idle_stamp
= 0;
7267 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7268 * running tasks off the busiest CPU onto idle CPUs. It requires at
7269 * least 1 task to be running on each physical CPU where possible, and
7270 * avoids physical / logical imbalances.
7272 static int active_load_balance_cpu_stop(void *data
)
7274 struct rq
*busiest_rq
= data
;
7275 int busiest_cpu
= cpu_of(busiest_rq
);
7276 int target_cpu
= busiest_rq
->push_cpu
;
7277 struct rq
*target_rq
= cpu_rq(target_cpu
);
7278 struct sched_domain
*sd
;
7279 struct task_struct
*p
= NULL
;
7281 raw_spin_lock_irq(&busiest_rq
->lock
);
7283 /* make sure the requested cpu hasn't gone down in the meantime */
7284 if (unlikely(busiest_cpu
!= smp_processor_id() ||
7285 !busiest_rq
->active_balance
))
7288 /* Is there any task to move? */
7289 if (busiest_rq
->nr_running
<= 1)
7293 * This condition is "impossible", if it occurs
7294 * we need to fix it. Originally reported by
7295 * Bjorn Helgaas on a 128-cpu setup.
7297 BUG_ON(busiest_rq
== target_rq
);
7299 /* Search for an sd spanning us and the target CPU. */
7301 for_each_domain(target_cpu
, sd
) {
7302 if ((sd
->flags
& SD_LOAD_BALANCE
) &&
7303 cpumask_test_cpu(busiest_cpu
, sched_domain_span(sd
)))
7308 struct lb_env env
= {
7310 .dst_cpu
= target_cpu
,
7311 .dst_rq
= target_rq
,
7312 .src_cpu
= busiest_rq
->cpu
,
7313 .src_rq
= busiest_rq
,
7317 schedstat_inc(sd
, alb_count
);
7319 p
= detach_one_task(&env
);
7321 schedstat_inc(sd
, alb_pushed
);
7323 schedstat_inc(sd
, alb_failed
);
7327 busiest_rq
->active_balance
= 0;
7328 raw_spin_unlock(&busiest_rq
->lock
);
7331 attach_one_task(target_rq
, p
);
7338 static inline int on_null_domain(struct rq
*rq
)
7340 return unlikely(!rcu_dereference_sched(rq
->sd
));
7343 #ifdef CONFIG_NO_HZ_COMMON
7345 * idle load balancing details
7346 * - When one of the busy CPUs notice that there may be an idle rebalancing
7347 * needed, they will kick the idle load balancer, which then does idle
7348 * load balancing for all the idle CPUs.
7351 cpumask_var_t idle_cpus_mask
;
7353 unsigned long next_balance
; /* in jiffy units */
7354 } nohz ____cacheline_aligned
;
7356 static inline int find_new_ilb(void)
7358 int ilb
= cpumask_first(nohz
.idle_cpus_mask
);
7360 if (ilb
< nr_cpu_ids
&& idle_cpu(ilb
))
7367 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7368 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7369 * CPU (if there is one).
7371 static void nohz_balancer_kick(void)
7375 nohz
.next_balance
++;
7377 ilb_cpu
= find_new_ilb();
7379 if (ilb_cpu
>= nr_cpu_ids
)
7382 if (test_and_set_bit(NOHZ_BALANCE_KICK
, nohz_flags(ilb_cpu
)))
7385 * Use smp_send_reschedule() instead of resched_cpu().
7386 * This way we generate a sched IPI on the target cpu which
7387 * is idle. And the softirq performing nohz idle load balance
7388 * will be run before returning from the IPI.
7390 smp_send_reschedule(ilb_cpu
);
7394 static inline void nohz_balance_exit_idle(int cpu
)
7396 if (unlikely(test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))) {
7398 * Completely isolated CPUs don't ever set, so we must test.
7400 if (likely(cpumask_test_cpu(cpu
, nohz
.idle_cpus_mask
))) {
7401 cpumask_clear_cpu(cpu
, nohz
.idle_cpus_mask
);
7402 atomic_dec(&nohz
.nr_cpus
);
7404 clear_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
7408 static inline void set_cpu_sd_state_busy(void)
7410 struct sched_domain
*sd
;
7411 int cpu
= smp_processor_id();
7414 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
7416 if (!sd
|| !sd
->nohz_idle
)
7420 atomic_inc(&sd
->groups
->sgc
->nr_busy_cpus
);
7425 void set_cpu_sd_state_idle(void)
7427 struct sched_domain
*sd
;
7428 int cpu
= smp_processor_id();
7431 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
7433 if (!sd
|| sd
->nohz_idle
)
7437 atomic_dec(&sd
->groups
->sgc
->nr_busy_cpus
);
7443 * This routine will record that the cpu is going idle with tick stopped.
7444 * This info will be used in performing idle load balancing in the future.
7446 void nohz_balance_enter_idle(int cpu
)
7449 * If this cpu is going down, then nothing needs to be done.
7451 if (!cpu_active(cpu
))
7454 if (test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))
7458 * If we're a completely isolated CPU, we don't play.
7460 if (on_null_domain(cpu_rq(cpu
)))
7463 cpumask_set_cpu(cpu
, nohz
.idle_cpus_mask
);
7464 atomic_inc(&nohz
.nr_cpus
);
7465 set_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
7468 static int sched_ilb_notifier(struct notifier_block
*nfb
,
7469 unsigned long action
, void *hcpu
)
7471 switch (action
& ~CPU_TASKS_FROZEN
) {
7473 nohz_balance_exit_idle(smp_processor_id());
7481 static DEFINE_SPINLOCK(balancing
);
7484 * Scale the max load_balance interval with the number of CPUs in the system.
7485 * This trades load-balance latency on larger machines for less cross talk.
7487 void update_max_interval(void)
7489 max_load_balance_interval
= HZ
*num_online_cpus()/10;
7493 * It checks each scheduling domain to see if it is due to be balanced,
7494 * and initiates a balancing operation if so.
7496 * Balancing parameters are set up in init_sched_domains.
7498 static void rebalance_domains(struct rq
*rq
, enum cpu_idle_type idle
)
7500 int continue_balancing
= 1;
7502 unsigned long interval
;
7503 struct sched_domain
*sd
;
7504 /* Earliest time when we have to do rebalance again */
7505 unsigned long next_balance
= jiffies
+ 60*HZ
;
7506 int update_next_balance
= 0;
7507 int need_serialize
, need_decay
= 0;
7510 update_blocked_averages(cpu
);
7513 for_each_domain(cpu
, sd
) {
7515 * Decay the newidle max times here because this is a regular
7516 * visit to all the domains. Decay ~1% per second.
7518 if (time_after(jiffies
, sd
->next_decay_max_lb_cost
)) {
7519 sd
->max_newidle_lb_cost
=
7520 (sd
->max_newidle_lb_cost
* 253) / 256;
7521 sd
->next_decay_max_lb_cost
= jiffies
+ HZ
;
7524 max_cost
+= sd
->max_newidle_lb_cost
;
7526 if (!(sd
->flags
& SD_LOAD_BALANCE
))
7530 * Stop the load balance at this level. There is another
7531 * CPU in our sched group which is doing load balancing more
7534 if (!continue_balancing
) {
7540 interval
= get_sd_balance_interval(sd
, idle
!= CPU_IDLE
);
7542 need_serialize
= sd
->flags
& SD_SERIALIZE
;
7543 if (need_serialize
) {
7544 if (!spin_trylock(&balancing
))
7548 if (time_after_eq(jiffies
, sd
->last_balance
+ interval
)) {
7549 if (load_balance(cpu
, rq
, sd
, idle
, &continue_balancing
)) {
7551 * The LBF_DST_PINNED logic could have changed
7552 * env->dst_cpu, so we can't know our idle
7553 * state even if we migrated tasks. Update it.
7555 idle
= idle_cpu(cpu
) ? CPU_IDLE
: CPU_NOT_IDLE
;
7557 sd
->last_balance
= jiffies
;
7558 interval
= get_sd_balance_interval(sd
, idle
!= CPU_IDLE
);
7561 spin_unlock(&balancing
);
7563 if (time_after(next_balance
, sd
->last_balance
+ interval
)) {
7564 next_balance
= sd
->last_balance
+ interval
;
7565 update_next_balance
= 1;
7570 * Ensure the rq-wide value also decays but keep it at a
7571 * reasonable floor to avoid funnies with rq->avg_idle.
7573 rq
->max_idle_balance_cost
=
7574 max((u64
)sysctl_sched_migration_cost
, max_cost
);
7579 * next_balance will be updated only when there is a need.
7580 * When the cpu is attached to null domain for ex, it will not be
7583 if (likely(update_next_balance
))
7584 rq
->next_balance
= next_balance
;
7587 #ifdef CONFIG_NO_HZ_COMMON
7589 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7590 * rebalancing for all the cpus for whom scheduler ticks are stopped.
7592 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
)
7594 int this_cpu
= this_rq
->cpu
;
7598 if (idle
!= CPU_IDLE
||
7599 !test_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
)))
7602 for_each_cpu(balance_cpu
, nohz
.idle_cpus_mask
) {
7603 if (balance_cpu
== this_cpu
|| !idle_cpu(balance_cpu
))
7607 * If this cpu gets work to do, stop the load balancing
7608 * work being done for other cpus. Next load
7609 * balancing owner will pick it up.
7614 rq
= cpu_rq(balance_cpu
);
7617 * If time for next balance is due,
7620 if (time_after_eq(jiffies
, rq
->next_balance
)) {
7621 raw_spin_lock_irq(&rq
->lock
);
7622 update_rq_clock(rq
);
7623 update_idle_cpu_load(rq
);
7624 raw_spin_unlock_irq(&rq
->lock
);
7625 rebalance_domains(rq
, CPU_IDLE
);
7628 if (time_after(this_rq
->next_balance
, rq
->next_balance
))
7629 this_rq
->next_balance
= rq
->next_balance
;
7631 nohz
.next_balance
= this_rq
->next_balance
;
7633 clear_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
));
7637 * Current heuristic for kicking the idle load balancer in the presence
7638 * of an idle cpu is the system.
7639 * - This rq has more than one task.
7640 * - At any scheduler domain level, this cpu's scheduler group has multiple
7641 * busy cpu's exceeding the group's capacity.
7642 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
7643 * domain span are idle.
7645 static inline int nohz_kick_needed(struct rq
*rq
)
7647 unsigned long now
= jiffies
;
7648 struct sched_domain
*sd
;
7649 struct sched_group_capacity
*sgc
;
7650 int nr_busy
, cpu
= rq
->cpu
;
7652 if (unlikely(rq
->idle_balance
))
7656 * We may be recently in ticked or tickless idle mode. At the first
7657 * busy tick after returning from idle, we will update the busy stats.
7659 set_cpu_sd_state_busy();
7660 nohz_balance_exit_idle(cpu
);
7663 * None are in tickless mode and hence no need for NOHZ idle load
7666 if (likely(!atomic_read(&nohz
.nr_cpus
)))
7669 if (time_before(now
, nohz
.next_balance
))
7672 if (rq
->nr_running
>= 2)
7676 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
7679 sgc
= sd
->groups
->sgc
;
7680 nr_busy
= atomic_read(&sgc
->nr_busy_cpus
);
7683 goto need_kick_unlock
;
7686 sd
= rcu_dereference(per_cpu(sd_asym
, cpu
));
7688 if (sd
&& (cpumask_first_and(nohz
.idle_cpus_mask
,
7689 sched_domain_span(sd
)) < cpu
))
7690 goto need_kick_unlock
;
7701 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
) { }
7705 * run_rebalance_domains is triggered when needed from the scheduler tick.
7706 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
7708 static void run_rebalance_domains(struct softirq_action
*h
)
7710 struct rq
*this_rq
= this_rq();
7711 enum cpu_idle_type idle
= this_rq
->idle_balance
?
7712 CPU_IDLE
: CPU_NOT_IDLE
;
7714 rebalance_domains(this_rq
, idle
);
7717 * If this cpu has a pending nohz_balance_kick, then do the
7718 * balancing on behalf of the other idle cpus whose ticks are
7721 nohz_idle_balance(this_rq
, idle
);
7725 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
7727 void trigger_load_balance(struct rq
*rq
)
7729 /* Don't need to rebalance while attached to NULL domain */
7730 if (unlikely(on_null_domain(rq
)))
7733 if (time_after_eq(jiffies
, rq
->next_balance
))
7734 raise_softirq(SCHED_SOFTIRQ
);
7735 #ifdef CONFIG_NO_HZ_COMMON
7736 if (nohz_kick_needed(rq
))
7737 nohz_balancer_kick();
7741 static void rq_online_fair(struct rq
*rq
)
7745 update_runtime_enabled(rq
);
7748 static void rq_offline_fair(struct rq
*rq
)
7752 /* Ensure any throttled groups are reachable by pick_next_task */
7753 unthrottle_offline_cfs_rqs(rq
);
7756 #endif /* CONFIG_SMP */
7759 * scheduler tick hitting a task of our scheduling class:
7761 static void task_tick_fair(struct rq
*rq
, struct task_struct
*curr
, int queued
)
7763 struct cfs_rq
*cfs_rq
;
7764 struct sched_entity
*se
= &curr
->se
;
7766 for_each_sched_entity(se
) {
7767 cfs_rq
= cfs_rq_of(se
);
7768 entity_tick(cfs_rq
, se
, queued
);
7771 if (numabalancing_enabled
)
7772 task_tick_numa(rq
, curr
);
7774 update_rq_runnable_avg(rq
, 1);
7778 * called on fork with the child task as argument from the parent's context
7779 * - child not yet on the tasklist
7780 * - preemption disabled
7782 static void task_fork_fair(struct task_struct
*p
)
7784 struct cfs_rq
*cfs_rq
;
7785 struct sched_entity
*se
= &p
->se
, *curr
;
7786 int this_cpu
= smp_processor_id();
7787 struct rq
*rq
= this_rq();
7788 unsigned long flags
;
7790 raw_spin_lock_irqsave(&rq
->lock
, flags
);
7792 update_rq_clock(rq
);
7794 cfs_rq
= task_cfs_rq(current
);
7795 curr
= cfs_rq
->curr
;
7798 * Not only the cpu but also the task_group of the parent might have
7799 * been changed after parent->se.parent,cfs_rq were copied to
7800 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
7801 * of child point to valid ones.
7804 __set_task_cpu(p
, this_cpu
);
7807 update_curr(cfs_rq
);
7810 se
->vruntime
= curr
->vruntime
;
7811 place_entity(cfs_rq
, se
, 1);
7813 if (sysctl_sched_child_runs_first
&& curr
&& entity_before(curr
, se
)) {
7815 * Upon rescheduling, sched_class::put_prev_task() will place
7816 * 'current' within the tree based on its new key value.
7818 swap(curr
->vruntime
, se
->vruntime
);
7822 se
->vruntime
-= cfs_rq
->min_vruntime
;
7824 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
7828 * Priority of the task has changed. Check to see if we preempt
7832 prio_changed_fair(struct rq
*rq
, struct task_struct
*p
, int oldprio
)
7834 if (!task_on_rq_queued(p
))
7838 * Reschedule if we are currently running on this runqueue and
7839 * our priority decreased, or if we are not currently running on
7840 * this runqueue and our priority is higher than the current's
7842 if (rq
->curr
== p
) {
7843 if (p
->prio
> oldprio
)
7846 check_preempt_curr(rq
, p
, 0);
7849 static void switched_from_fair(struct rq
*rq
, struct task_struct
*p
)
7851 struct sched_entity
*se
= &p
->se
;
7852 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
7855 * Ensure the task's vruntime is normalized, so that when it's
7856 * switched back to the fair class the enqueue_entity(.flags=0) will
7857 * do the right thing.
7859 * If it's queued, then the dequeue_entity(.flags=0) will already
7860 * have normalized the vruntime, if it's !queued, then only when
7861 * the task is sleeping will it still have non-normalized vruntime.
7863 if (!task_on_rq_queued(p
) && p
->state
!= TASK_RUNNING
) {
7865 * Fix up our vruntime so that the current sleep doesn't
7866 * cause 'unlimited' sleep bonus.
7868 place_entity(cfs_rq
, se
, 0);
7869 se
->vruntime
-= cfs_rq
->min_vruntime
;
7874 * Remove our load from contribution when we leave sched_fair
7875 * and ensure we don't carry in an old decay_count if we
7878 if (se
->avg
.decay_count
) {
7879 __synchronize_entity_decay(se
);
7880 subtract_blocked_load_contrib(cfs_rq
, se
->avg
.load_avg_contrib
);
7886 * We switched to the sched_fair class.
7888 static void switched_to_fair(struct rq
*rq
, struct task_struct
*p
)
7890 #ifdef CONFIG_FAIR_GROUP_SCHED
7891 struct sched_entity
*se
= &p
->se
;
7893 * Since the real-depth could have been changed (only FAIR
7894 * class maintain depth value), reset depth properly.
7896 se
->depth
= se
->parent
? se
->parent
->depth
+ 1 : 0;
7898 if (!task_on_rq_queued(p
))
7902 * We were most likely switched from sched_rt, so
7903 * kick off the schedule if running, otherwise just see
7904 * if we can still preempt the current task.
7909 check_preempt_curr(rq
, p
, 0);
7912 /* Account for a task changing its policy or group.
7914 * This routine is mostly called to set cfs_rq->curr field when a task
7915 * migrates between groups/classes.
7917 static void set_curr_task_fair(struct rq
*rq
)
7919 struct sched_entity
*se
= &rq
->curr
->se
;
7921 for_each_sched_entity(se
) {
7922 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
7924 set_next_entity(cfs_rq
, se
);
7925 /* ensure bandwidth has been allocated on our new cfs_rq */
7926 account_cfs_rq_runtime(cfs_rq
, 0);
7930 void init_cfs_rq(struct cfs_rq
*cfs_rq
)
7932 cfs_rq
->tasks_timeline
= RB_ROOT
;
7933 cfs_rq
->min_vruntime
= (u64
)(-(1LL << 20));
7934 #ifndef CONFIG_64BIT
7935 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
7938 atomic64_set(&cfs_rq
->decay_counter
, 1);
7939 atomic_long_set(&cfs_rq
->removed_load
, 0);
7943 #ifdef CONFIG_FAIR_GROUP_SCHED
7944 static void task_move_group_fair(struct task_struct
*p
, int queued
)
7946 struct sched_entity
*se
= &p
->se
;
7947 struct cfs_rq
*cfs_rq
;
7950 * If the task was not on the rq at the time of this cgroup movement
7951 * it must have been asleep, sleeping tasks keep their ->vruntime
7952 * absolute on their old rq until wakeup (needed for the fair sleeper
7953 * bonus in place_entity()).
7955 * If it was on the rq, we've just 'preempted' it, which does convert
7956 * ->vruntime to a relative base.
7958 * Make sure both cases convert their relative position when migrating
7959 * to another cgroup's rq. This does somewhat interfere with the
7960 * fair sleeper stuff for the first placement, but who cares.
7963 * When !queued, vruntime of the task has usually NOT been normalized.
7964 * But there are some cases where it has already been normalized:
7966 * - Moving a forked child which is waiting for being woken up by
7967 * wake_up_new_task().
7968 * - Moving a task which has been woken up by try_to_wake_up() and
7969 * waiting for actually being woken up by sched_ttwu_pending().
7971 * To prevent boost or penalty in the new cfs_rq caused by delta
7972 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
7974 if (!queued
&& (!se
->sum_exec_runtime
|| p
->state
== TASK_WAKING
))
7978 se
->vruntime
-= cfs_rq_of(se
)->min_vruntime
;
7979 set_task_rq(p
, task_cpu(p
));
7980 se
->depth
= se
->parent
? se
->parent
->depth
+ 1 : 0;
7982 cfs_rq
= cfs_rq_of(se
);
7983 se
->vruntime
+= cfs_rq
->min_vruntime
;
7986 * migrate_task_rq_fair() will have removed our previous
7987 * contribution, but we must synchronize for ongoing future
7990 se
->avg
.decay_count
= atomic64_read(&cfs_rq
->decay_counter
);
7991 cfs_rq
->blocked_load_avg
+= se
->avg
.load_avg_contrib
;
7996 void free_fair_sched_group(struct task_group
*tg
)
8000 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg
));
8002 for_each_possible_cpu(i
) {
8004 kfree(tg
->cfs_rq
[i
]);
8013 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
8015 struct cfs_rq
*cfs_rq
;
8016 struct sched_entity
*se
;
8019 tg
->cfs_rq
= kzalloc(sizeof(cfs_rq
) * nr_cpu_ids
, GFP_KERNEL
);
8022 tg
->se
= kzalloc(sizeof(se
) * nr_cpu_ids
, GFP_KERNEL
);
8026 tg
->shares
= NICE_0_LOAD
;
8028 init_cfs_bandwidth(tg_cfs_bandwidth(tg
));
8030 for_each_possible_cpu(i
) {
8031 cfs_rq
= kzalloc_node(sizeof(struct cfs_rq
),
8032 GFP_KERNEL
, cpu_to_node(i
));
8036 se
= kzalloc_node(sizeof(struct sched_entity
),
8037 GFP_KERNEL
, cpu_to_node(i
));
8041 init_cfs_rq(cfs_rq
);
8042 init_tg_cfs_entry(tg
, cfs_rq
, se
, i
, parent
->se
[i
]);
8053 void unregister_fair_sched_group(struct task_group
*tg
, int cpu
)
8055 struct rq
*rq
= cpu_rq(cpu
);
8056 unsigned long flags
;
8059 * Only empty task groups can be destroyed; so we can speculatively
8060 * check on_list without danger of it being re-added.
8062 if (!tg
->cfs_rq
[cpu
]->on_list
)
8065 raw_spin_lock_irqsave(&rq
->lock
, flags
);
8066 list_del_leaf_cfs_rq(tg
->cfs_rq
[cpu
]);
8067 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
8070 void init_tg_cfs_entry(struct task_group
*tg
, struct cfs_rq
*cfs_rq
,
8071 struct sched_entity
*se
, int cpu
,
8072 struct sched_entity
*parent
)
8074 struct rq
*rq
= cpu_rq(cpu
);
8078 init_cfs_rq_runtime(cfs_rq
);
8080 tg
->cfs_rq
[cpu
] = cfs_rq
;
8083 /* se could be NULL for root_task_group */
8088 se
->cfs_rq
= &rq
->cfs
;
8091 se
->cfs_rq
= parent
->my_q
;
8092 se
->depth
= parent
->depth
+ 1;
8096 /* guarantee group entities always have weight */
8097 update_load_set(&se
->load
, NICE_0_LOAD
);
8098 se
->parent
= parent
;
8101 static DEFINE_MUTEX(shares_mutex
);
8103 int sched_group_set_shares(struct task_group
*tg
, unsigned long shares
)
8106 unsigned long flags
;
8109 * We can't change the weight of the root cgroup.
8114 shares
= clamp(shares
, scale_load(MIN_SHARES
), scale_load(MAX_SHARES
));
8116 mutex_lock(&shares_mutex
);
8117 if (tg
->shares
== shares
)
8120 tg
->shares
= shares
;
8121 for_each_possible_cpu(i
) {
8122 struct rq
*rq
= cpu_rq(i
);
8123 struct sched_entity
*se
;
8126 /* Propagate contribution to hierarchy */
8127 raw_spin_lock_irqsave(&rq
->lock
, flags
);
8129 /* Possible calls to update_curr() need rq clock */
8130 update_rq_clock(rq
);
8131 for_each_sched_entity(se
)
8132 update_cfs_shares(group_cfs_rq(se
));
8133 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
8137 mutex_unlock(&shares_mutex
);
8140 #else /* CONFIG_FAIR_GROUP_SCHED */
8142 void free_fair_sched_group(struct task_group
*tg
) { }
8144 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
8149 void unregister_fair_sched_group(struct task_group
*tg
, int cpu
) { }
8151 #endif /* CONFIG_FAIR_GROUP_SCHED */
8154 static unsigned int get_rr_interval_fair(struct rq
*rq
, struct task_struct
*task
)
8156 struct sched_entity
*se
= &task
->se
;
8157 unsigned int rr_interval
= 0;
8160 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8163 if (rq
->cfs
.load
.weight
)
8164 rr_interval
= NS_TO_JIFFIES(sched_slice(cfs_rq_of(se
), se
));
8170 * All the scheduling class methods:
8172 const struct sched_class fair_sched_class
= {
8173 .next
= &idle_sched_class
,
8174 .enqueue_task
= enqueue_task_fair
,
8175 .dequeue_task
= dequeue_task_fair
,
8176 .yield_task
= yield_task_fair
,
8177 .yield_to_task
= yield_to_task_fair
,
8179 .check_preempt_curr
= check_preempt_wakeup
,
8181 .pick_next_task
= pick_next_task_fair
,
8182 .put_prev_task
= put_prev_task_fair
,
8185 .select_task_rq
= select_task_rq_fair
,
8186 .migrate_task_rq
= migrate_task_rq_fair
,
8188 .rq_online
= rq_online_fair
,
8189 .rq_offline
= rq_offline_fair
,
8191 .task_waking
= task_waking_fair
,
8194 .set_curr_task
= set_curr_task_fair
,
8195 .task_tick
= task_tick_fair
,
8196 .task_fork
= task_fork_fair
,
8198 .prio_changed
= prio_changed_fair
,
8199 .switched_from
= switched_from_fair
,
8200 .switched_to
= switched_to_fair
,
8202 .get_rr_interval
= get_rr_interval_fair
,
8204 .update_curr
= update_curr_fair
,
8206 #ifdef CONFIG_FAIR_GROUP_SCHED
8207 .task_move_group
= task_move_group_fair
,
8211 #ifdef CONFIG_SCHED_DEBUG
8212 void print_cfs_stats(struct seq_file
*m
, int cpu
)
8214 struct cfs_rq
*cfs_rq
;
8217 for_each_leaf_cfs_rq(cpu_rq(cpu
), cfs_rq
)
8218 print_cfs_rq(m
, cpu
, cfs_rq
);
8223 __init
void init_sched_fair_class(void)
8226 open_softirq(SCHED_SOFTIRQ
, run_rebalance_domains
);
8228 #ifdef CONFIG_NO_HZ_COMMON
8229 nohz
.next_balance
= jiffies
;
8230 zalloc_cpumask_var(&nohz
.idle_cpus_mask
, GFP_NOWAIT
);
8231 cpu_notifier(sched_ilb_notifier
, 0);