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    SubjectRe: [git pull] scheduler fixes
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    On Sat, 2009-01-17 at 13:00 +0100, Peter Zijlstra wrote:
    > On Sat, 2009-01-17 at 11:34 +0100, Mike Galbraith wrote:
    > > > Right, how about we flip the 'initial' case in place_entity() for !
    > > > nr_exclusive wakeups.
    > >
    > > Wouldn't that be more drastic than sleep denial?
    >
    > Strictly speaking that DEBIT thing is valid for each wakeup, IIRC we
    > restricted it to clone() only because that was where we could actually
    > observe these latency spikes using a fork-bomb.
    >
    > This reduces the latency hits to around 400ms, which is about right for
    > the given load.
    >
    > ---
    > diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
    > index f34cf42..d344605 100644
    > --- a/kernel/sched_fair.c
    > +++ b/kernel/sched_fair.c
    > @@ -671,7 +671,8 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
    > * little, place the new task so that it fits in the slot that
    > * stays open at the end.
    > */
    > - if (initial && sched_feat(START_DEBIT))
    > + if ((initial && sched_feat(START_DEBIT)) ||
    > + (!initial && sched_feat(WAKER_DEBIT)))
    > vruntime += sched_vslice(cfs_rq, se);
    >
    > if (!initial) {
    > diff --git a/kernel/sched_features.h b/kernel/sched_features.h
    > index 4569bfa..b5fddf0 100644
    > --- a/kernel/sched_features.h
    > +++ b/kernel/sched_features.h
    > @@ -1,4 +1,4 @@
    > -SCHED_FEAT(NEW_FAIR_SLEEPERS, 1)
    > +SCHED_FEAT(NEW_FAIR_SLEEPERS, 0)
    > SCHED_FEAT(NORMALIZED_SLEEPER, 0)
    > SCHED_FEAT(ADAPTIVE_GRAN, 1)
    > SCHED_FEAT(WAKEUP_PREEMPT, 1)
    > @@ -15,3 +15,4 @@ SCHED_FEAT(ASYM_EFF_LOAD, 1)
    > SCHED_FEAT(WAKEUP_OVERLAP, 0)
    > SCHED_FEAT(LAST_BUDDY, 1)
    > SCHED_FEAT(OWNER_SPIN, 1)
    > +SCHED_FEAT(WAKER_DEBIT, 1)

    Ouch, that doesn't look like it will be nice at all for interactivity.

    (which btw was terrible with my hackery, even with booboos fixed)

    -Mike



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