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sched: fix calc_delta_asym()

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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: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2008-06-27 13:41:12 +02:00 committed by Ingo Molnar
parent a7be37ac8e
commit c9c294a630
2 changed files with 28 additions and 1 deletions
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28
kernel/sched_fair.c
View file

@ -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.
*/
gran = calc_delta_asym(sysctl_sched_wakeup_granularity, se);
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;
}

1
kernel/sched_features.h
View file

@ -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)