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    SubjectRe: [git pull] scheduler changes for v2.6.26
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    On Tue, 2008-04-22 at 10:59 +0200, Ingo Molnar wrote:
    > * Mike Galbraith <efault@gmx.de> wrote:
    >
    > > > the 700-800 msecs of delays you see are very "brutal" so there must
    > > > be something fundamentally wrong going on here.
    > >
    > > I'm seeing latency hits with 26.git, whereas 25 is hit free.
    >
    > ok. I think what happens is that your broken sched-clock hid the real
    > breakage. Lets try fix the real breakage now.
    >
    > I've uploaded a new sched-devel.git that is against very latest -git,
    > could you try ftrace (with a sufficiently large
    > /debug/tracing/tracing_max_entries value) - perhaps the
    > worst-case-wakeup-latency tracer shows large latencies? If not, then
    > maybe the sched_switch tracer gives a better insight into what's
    > happening?
    >
    > > Erm, should my Q6600 emit such?
    >
    > on nohz it could happen - and fixed in -git. Patch looked too dangerous
    > for late-2.6.25 to merge.

    Also, it only happens when the cpu has idle time; and that typically
    happens when its well,. idle - so not much to schedule wrong.

    That said; yes there are boundary effect that could make it show up.

    > > On 26.git, I get numbers like yours, but with occasional dips down to
    > > ~700, though the latency hits don't _seem_ to be synchronous with
    > > watch-rq-clock.sh glitchies.
    >
    > hm, the dips shouldnt be happening normally.

    Agreed, those ought to be gone.. Guillaume do you see any holes in the
    current rq clock code?



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