Messages in this thread | | | Subject | Re: PostgreSQL pgbench performance regression in 2.6.23+ | From | Mike Galbraith <> | Date | Thu, 22 May 2008 15:16:49 +0200 |
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On Thu, 2008-05-22 at 14:24 +0200, Peter Zijlstra wrote: > On Thu, 2008-05-22 at 14:09 +0200, Mike Galbraith wrote: > > On Thu, 2008-05-22 at 13:44 +0200, Peter Zijlstra wrote: > > > > > Humm,.. how to fix this.. we'd need to somehow detect the 1:n nature of > > > its operation - I'm sure there are other scenarios that could benefit > > > from this. > > > > Maybe simple (minded): cache waker's last non-interrupt context wakee, > > if the wakee != cached, ignore SYNC_WAKEUP unless sync was requested at > > call time? > > Yeah, something like so - or perhaps like you say cache the wakee. > > I picked the wake_affine() condition, because I think that is the > biggest factor in this behaviour. You could of course also disable all > of sync.
Works fine (modulo booboo).
-Mike
> diff --git a/include/linux/sched.h b/include/linux/sched.h > index c86c5c5..856c2a8 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -950,6 +950,8 @@ struct sched_entity { > u64 last_wakeup; > u64 avg_overlap; > > + struct sched_entity *waker; > + > #ifdef CONFIG_SCHEDSTATS > u64 wait_start; > u64 wait_max; > diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c > index 894a702..8971044 100644 > --- a/kernel/sched_fair.c > +++ b/kernel/sched_fair.c > @@ -1036,7 +1036,8 @@ wake_affine(struct rq *rq, struct sched_domain *this_sd, struct rq *this_rq, > * a reasonable amount of time then attract this newly > * woken task: > */ > - if (sync && curr->sched_class == &fair_sched_class) { > + if (sync && curr->sched_class == &fair_sched_class && > + p->se.waker == curr->se->waker) { > if (curr->se.avg_overlap < sysctl_sched_migration_cost && > p->se.avg_overlap < sysctl_sched_migration_cost) > return 1; > @@ -1210,6 +1211,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p) > if (unlikely(se == pse)) > return; > > + se->waker = pse; > cfs_rq_of(pse)->next = pse; > > /* > >
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