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    SubjectRE: [patch] sched: auto-tune migration costs [was: Re: Industry db benchmark result on recent 2.6 kernels]
    Ingo Molnar wrote on Sunday, April 03, 2005 11:24 PM

    > great! How long does the benchmark take (hours?), and is there any way
    > to speed up the benchmarking (without hurting accuracy), so that
    > multiple migration-cost settings could be tried? Would it be possible to
    > try a few other values via the migration_factor boot option, in 0.5 msec
    > steps or so, to find the current sweet spot? It used to be at 11 msec
    > previously, correct?

    It take days, each experiment is 5 hours. Previous experiments on 2.6.8
    shows that the sweet spot was 12.5ms.

    This time on 2.6.11, it got pushed into 16 ms. Results comparing to 10ms:

    8 ms -0.3%
    10 ms --
    12 ms +0.11%
    16 ms +0.14%
    20 ms +0.06%

    12ms and up all has about 1.5% idle time. We are not anywhere near the
    limits on what the disk storage can deliver. So there is a potential to
    to tune/optimize the scheduler and reap these extra idle time.

    - Ken

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