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    SubjectRe: 2.2.1 scheduler behavior

    On Fri, 19 Feb 1999, Neil Conway wrote:

    > > i've changed it back to 15 around pre9-2.2.0. Your original reasoning for
    > > reducing PROC_CHANGE_PENALTY was interactive feel, but this became a
    > > non-issue with my smp_reschedule patches, so i empirically adjusted
    > > PROC_CHANGE_PENALTY to maximize kernel compilation speed.
    > Ah the irony... My patch for 2.1.131 changed it to 15, but Linus chose
    > 10 :-)) Lucky guess!
    > I must read the new scheduling code and try to figure out the effects of
    > smp_reschedule(). I wasn't aware that it removed the interactive
    > problem. Also note that I changed it from *20* to 15, so don't be
    > completely sure you've killed the interactive problem unless it's gone
    > when you build a kernel with it set to 20. Basically, due to the nature
    > of the problem, even reducing it to 19 was enough to prevent it hurting
    > interactive response time.

    (yes but the real interactive problems were still there. It's a whole
    different issue, PROC_CHANGE_PENALTY is now only a way to measure
    processor changing penalty, without any interactivity issue.) I have made
    it a sysctl and i've tried lots of settings (including 20), and for pure
    CPU-intensive work (kernel compilation) 15 proved to be the best.

    -- mingo

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