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    SubjectRe: BFS vs. mainline scheduler benchmarks and measurements
    On 09/09/2009 11:52 AM, Mike Galbraith wrote:
    > On Wed, 2009-09-09 at 08:13 +0200, Ingo Molnar wrote:
    >> * Jens Axboe<> wrote:
    >>> On Tue, Sep 08 2009, Peter Zijlstra wrote:
    >>>> On Tue, 2009-09-08 at 11:13 +0200, Jens Axboe wrote:
    >>>>> And here's a newer version.
    >>>> I tinkered a bit with your proglet and finally found the
    >>>> problem.
    >>>> You used a single pipe per child, this means the loop in
    >>>> run_child() would consume what it just wrote out until it got
    >>>> force preempted by the parent which would also get woken.
    >>>> This results in the child spinning a while (its full quota) and
    >>>> only reporting the last timestamp to the parent.
    >>> Oh doh, that's not well thought out. Well it was a quick hack :-)
    >>> Thanks for the fixup, now it's at least usable to some degree.
    >> What kind of latencies does it report on your box?
    >> Our vanilla scheduler default latency targets are:
    >> single-core: 20 msecs
    >> dual-core: 40 msecs
    >> quad-core: 60 msecs
    >> opto-core: 80 msecs
    >> You can enable CONFIG_SCHED_DEBUG=y and set it directly as well via
    >> /proc/sys/kernel/sched_latency_ns:
    >> echo 10000000> /proc/sys/kernel/sched_latency_ns
    > He would also need to lower min_granularity, otherwise, it'd be larger
    > than the whole latency target.

    Thank you for mentioning min_granularity. After:

    echo 10000000 > /proc/sys/kernel/sched_latency_ns
    echo 2000000 > /proc/sys/kernel/sched_min_granularity_ns

    I can clearly see an improvement: animations that are supposed to be
    fluid "skip" much less now, and in one occasion (simply moving the video
    window around) have been eliminated completely. However, there seems to
    be a side effect from having CONFIG_SCHED_DEBUG enabled; things seem to
    be generally a tad more "jerky" with that option enabled, even when not
    even touching the latency and granularity defaults.

    I'll try the patch you posted and see if this further improves things.

     \ /
      Last update: 2009-09-09 11:07    [W:0.024 / U:12.692 seconds]
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