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Commit d942fb6c authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: fix sync wakeups 



Pawel Dziekonski reported that the openssl benchmark and his
quantum chemistry application both show slowdowns due to the
scheduler under-parallelizing execution.

The reason are pipe wakeups still doing 'sync' wakeups which
overrides the normal buddy wakeup logic - even if waker and
wakee are loosely coupled.

Fix an inversion of logic in the buddy wakeup code.

Reported-by: default avatarPawel Dziekonski <dzieko@gmail.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent f90d4118

kernel/sched.c

+4 −0
Original line number Diff line number Diff line
@@ -2266,6 +2266,10 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync) 
	if (!sched_feat(SYNC_WAKEUPS))

		sync = 0;



	if (!sync && (current->se.avg_overlap < sysctl_sched_migration_cost &&

			    p->se.avg_overlap < sysctl_sched_migration_cost))

		sync = 1;



#ifdef CONFIG_SMP

	if (sched_feat(LB_WAKEUP_UPDATE)) {

		struct sched_domain *sd;

kernel/sched_fair.c

+2 −9
Original line number Diff line number Diff line
@@ -1179,20 +1179,15 @@ wake_affine(struct sched_domain *this_sd, struct rq *this_rq, 
	    int idx, unsigned long load, unsigned long this_load,

	    unsigned int imbalance)

{

	struct task_struct *curr = this_rq->curr;

	struct task_group *tg;

	unsigned long tl = this_load;

	unsigned long tl_per_task;

	struct task_group *tg;

	unsigned long weight;

	int balanced;



	if (!(this_sd->flags & SD_WAKE_AFFINE) || !sched_feat(AFFINE_WAKEUPS))

		return 0;



	if (sync && (curr->se.avg_overlap > sysctl_sched_migration_cost ||

			p->se.avg_overlap > sysctl_sched_migration_cost))

		sync = 0;



	/*

	 * If sync wakeup then subtract the (maximum possible)

	 * effect of the currently running task from the load
@@ -1419,9 +1414,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync) 
	if (!sched_feat(WAKEUP_PREEMPT))

		return;



	if (sched_feat(WAKEUP_OVERLAP) && (sync ||

			(se->avg_overlap < sysctl_sched_migration_cost &&

			 pse->avg_overlap < sysctl_sched_migration_cost))) {

	if (sched_feat(WAKEUP_OVERLAP) && sync) {

		resched_task(curr);

		return;

	}