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Commit b3137bc8 authored by Mike Galbraith's avatar Mike Galbraith Committed by Ingo Molnar
Browse files

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: default avatarMike Galbraith <efault@gmx.de>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent a381759d

kernel/sched_fair.c

+14 −11
Original line number Diff line number Diff line
@@ -996,16 +996,27 @@ 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 sync wakeup then subtract the (maximum possible)

	 * effect of the currently running task from the load

	 * of the current CPU:

	 */

	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 && curr->sched_class == &fair_sched_class) {

	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;
@@ -1014,16 +1025,8 @@ wake_affine(struct rq *rq, struct sched_domain *this_sd, struct rq *this_rq, 
	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

	 * of the current CPU:

	 */

	if (sync)

		tl -= current->se.load.weight;



	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