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Commit c9c294a6 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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sched: fix calc_delta_asym() 



calc_delta_asym() is supposed to do the same as calc_delta_fair() except
linearly shrink the result for negative nice processes - this causes them
to have a smaller preemption threshold so that they are more easily preempted.

The problem is that for task groups se->load.weight is the per cpu share of
the actual task group weight; take that into account.

Also provide a debug switch to disable the asymmetry (which I still don't
like - but it does greatly benefit some workloads)

This would explain the interactivity issues reported against group scheduling.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent a7be37ac

kernel/sched_fair.c

+27 −1
Original line number Diff line number Diff line
@@ -430,6 +430,29 @@ calc_delta_asym(unsigned long delta, struct sched_entity *se) 
	for_each_sched_entity(se) {

		struct load_weight *se_lw = &se->load;



#ifdef CONFIG_FAIR_SCHED_GROUP

		struct cfs_rq *cfs_rq = se->my_q;

		struct task_group *tg = NULL



		if (cfs_rq)

			tg = cfs_rq->tg;



		if (tg && tg->shares < NICE_0_LOAD) {

			/*

			 * scale shares to what it would have been had

			 * tg->weight been NICE_0_LOAD:

			 *

			 *   weight = 1024 * shares / tg->weight

			 */

			lw.weight *= se->load.weight;

			lw.weight /= tg->shares;



			lw.inv_weight = 0;



			se_lw = &lw;

		} else

#endif



		if (se->load.weight < NICE_0_LOAD)

			se_lw = &lw;
@@ -1154,7 +1177,10 @@ static unsigned long wakeup_gran(struct sched_entity *se) 
	 * More easily preempt - nice tasks, while not making it harder for

	 * + nice tasks.

	 */

	if (sched_feat(ASYM_GRAN))

		gran = calc_delta_asym(sysctl_sched_wakeup_granularity, se);

	else

		gran = calc_delta_fair(sysctl_sched_wakeup_granularity, se);



	return gran;

}

kernel/sched_features.h

+1 −0
Original line number Diff line number Diff line
@@ -7,3 +7,4 @@ SCHED_FEAT(CACHE_HOT_BUDDY, 1) 
SCHED_FEAT(SYNC_WAKEUPS, 1)

SCHED_FEAT(HRTICK, 1)

SCHED_FEAT(DOUBLE_TICK, 0)

SCHED_FEAT(ASYM_GRAN, 1)