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    SubjectRe: CFS review
    Date
    Ingo Molnar wrote:
    > * Al Boldi <a1426z@gawab.com> wrote:
    > > > could you send the exact patch that shows what you did?
    > >
    > > On 2.6.22.5-v20.3 (not v20.4):
    > >
    > > 340- curr->delta_exec += delta_exec;
    > > 341-
    > > 342- if (unlikely(curr->delta_exec > sysctl_sched_stat_granularity))
    > > { 343:// __update_curr(cfs_rq, curr);
    > > 344- curr->delta_exec = 0;
    > > 345- }
    > > 346- curr->exec_start = rq_of(cfs_rq)->clock;
    >
    > ouch - this produces a really broken scheduler - with this we dont do
    > any run-time accounting (!).

    Of course it's broken, and it's not meant as a fix, but this change allows
    you to see the amount of overhead as well as any miscalculations
    __update_curr incurs.

    In terms of overhead, __update_curr incurs ~3x slowdown, and in terms of
    run-time accounting it exhibits a ~10sec task-startup miscalculation.

    > Could you try the patch below instead, does this make 3x glxgears smooth
    > again? (if yes, could you send me your Signed-off-by line as well.)

    The task-startup stalling is still there for ~10sec.

    Can you see the problem on your machine?


    Thanks!

    --
    Al

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