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    SubjectRe: CFS review
    Date
    Ingo Molnar wrote:
    > * Al Boldi <a1426z@gawab.com> wrote:
    > > > ok. I think i might finally have found the bug causing this. Could
    > > > you try the fix below, does your webserver thread-startup test work
    > > > any better?
    > >
    > > It seems to help somewhat, but the problem is still visible. Even
    > > v20.3 on 2.6.22.5 didn't help.
    > >
    > > It does look related to ia-boosting, so I turned off __update_curr
    > > like Roman mentioned, which had an enormous smoothing effect, but then
    > > nice levels completely break down and lockup the system.
    >
    > you can turn sleeper-fairness off via:
    >
    > echo 28 > /proc/sys/kernel/sched_features
    >
    > another thing to try would be:
    >
    > echo 12 > /proc/sys/kernel/sched_features
    >
    > (that's the new-task penalty turned off.)
    >
    > Another thing to try would be to edit this:
    >
    > if (sysctl_sched_features & SCHED_FEAT_START_DEBIT)
    > p->se.wait_runtime = -(sched_granularity(cfs_rq) / 2);
    >
    > to:
    >
    > if (sysctl_sched_features & SCHED_FEAT_START_DEBIT)
    > p->se.wait_runtime = -(sched_granularity(cfs_rq);
    >
    > and could you also check 20.4 on 2.6.22.5 perhaps, or very latest -git?
    > (Peter has experienced smaller spikes with that.)

    Ok, I tried all your suggestions, but nothing works as smooth as removing
    __update_curr.

    Does the problem show on your machine with the 3x gears under X-vesa test?


    Thanks!

    --
    Al

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