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    SubjectRe: [git pull] scheduler fixes
    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.
    >
    > Below is the commit in question. Avi, any ideas what makes KVM special
    > here? Perhaps its use of "preempt notifiers" is causing a problem somehow?
    >

    preempt notifiers use should cause additional context switch costs of a
    few thousand cycles and possible an IPI (if a vcpu was migrated). So
    I'd suspect scheduling latency here.

    Is it possible to trace this (the time between a wake up and actual
    scheduling of a task)?

    --
    error compiling committee.c: too many arguments to function



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