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sched: stop wake_affine from causing serious imbalance 

Prevent short-running wakers of short-running threads from overloading a single
cpu via wakeup affinity, and wire up disconnected debug option.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Mike Galbraith 2008-05-29 11:11:41 +02:00 committed by Ingo Molnar
parent a381759d6a
commit b3137bc8e7
1 changed files with 19 additions and 16 deletions
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35
kernel/sched_fair.c
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@ -996,24 +996,11 @@ wake_affine(struct rq *rq, struct sched_domain *this_sd, struct rq *this_rq,
struct task_struct *curr = this_rq->curr;
unsigned long tl = this_load;
unsigned long tl_per_task;
int balanced;
if (!(this_sd->flags & SD_WAKE_AFFINE))
if (!(this_sd->flags & SD_WAKE_AFFINE) || !sched_feat(AFFINE_WAKEUPS))
return 0;
/*
* If the currently running task will sleep within
* a reasonable amount of time then attract this newly
* woken task:
*/
if (sync && curr->sched_class == &fair_sched_class) {
if (curr->se.avg_overlap < sysctl_sched_migration_cost &&
p->se.avg_overlap < sysctl_sched_migration_cost)
return 1;
}
schedstat_inc(p, se.nr_wakeups_affine_attempts);
tl_per_task = cpu_avg_load_per_task(this_cpu);
/*
* If sync wakeup then subtract the (maximum possible)
* effect of the currently running task from the load
@ -1022,8 +1009,24 @@ wake_affine(struct rq *rq, struct sched_domain *this_sd, struct rq *this_rq,
if (sync)
tl -= current->se.load.weight;
balanced = 100*(tl + p->se.load.weight) <= imbalance*load;
/*
* If the currently running task will sleep within
* a reasonable amount of time then attract this newly
* woken task:
*/
if (sync && balanced && curr->sched_class == &fair_sched_class) {
if (curr->se.avg_overlap < sysctl_sched_migration_cost &&
p->se.avg_overlap < sysctl_sched_migration_cost)
return 1;
}
schedstat_inc(p, se.nr_wakeups_affine_attempts);
tl_per_task = cpu_avg_load_per_task(this_cpu);
if ((tl <= load && tl + target_load(prev_cpu, idx) <= tl_per_task) ||
100*(tl + p->se.load.weight) <= imbalance*load) {
balanced) {
/*
* This domain has SD_WAKE_AFFINE and
* p is cache cold in this domain, and