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    SubjectRe: [git pull] scheduler fixes
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    On Sat, 2009-01-17 at 17:25 +0100, Ingo Molnar wrote:
    > * Mike Galbraith <efault@gmx.de> wrote:
    >
    > > On Sat, 2009-01-17 at 17:01 +0100, Ingo Molnar wrote:
    > > > * Mike Galbraith <efault@gmx.de> wrote:
    > > >
    > > > > On Sat, 2009-01-17 at 04:43 -0800, Andrew Morton wrote:
    > > > > > http://bugzilla.kernel.org/show_bug.cgi?id=12465 just popped up - another
    > > > > > scheduler regression. It has been bisected.
    > > > >
    > > > > Seems pretty clear. I'd suggest reverting it.
    > > >
    > > > We can revert it (and will revert it if no solution is found), but i'd
    > > > also like to understand why it happens, because that kind of
    > > > regression from this change is unexpected - we might be hiding some
    > > > bug that could pop up under less debuggable circumstances, so we need
    > > > to understand it while we have a chance.
    > >
    > > Agree. However, with the sched_mc stuff, mysql+oltp now does better
    > > with NEWIDLE on than off as well, as does an nfs kbuild.
    >
    > Didnt you come up with the verdict that sched_mc=2 is not a win - or has
    > that changed? If we should change the defaults then please send a
    > re-tuning patch against the latest code.

    sched_mc=2 was better than sched_mc=1. The other balancing changes put
    a dent in mysql+oltp peak and immediately after peak. Setting
    sched_mc=2 brought back the loss that was otherwise there all the way
    through the curve back to 28 level, so with sched_mc=2, there was only
    the slight loss of peak, and larger loss of post-peak.

    > Still, the ping delays of multiple seconds are completely unacceptable and
    > need to be understood, or these will come back and might bite us in a lot
    > less fortunate place. NEWIDLE and WAKE_BALANCE has micro-effects on
    > latencies - anything in the user-visible range is highly anomalous at
    > these low load levels.
    >
    > Ingo



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