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    SubjectRe: [PATCH] O13int for interactivity
    Date
    On Tuesday 12 August 2003 22:08, jw schultz wrote:
    >On Tue, Aug 12, 2003 at 09:58:04PM +1000, Nick Piggin wrote:
    >> I have been hearing of people complaining the scheduler is worse
    >> than 2.4 so its not entirely obvious to me. But yeah lots of it is
    >> trial and error, so I'm not saying Con is wasting his time.
    >
    >I've been watching Con and Ingo's efforts with the process
    >scheduler and i haven't seen people complaining that the
    >process scheduler is worse. They have complained that
    >interactive processes seem to have more latency. Con has
    >rightly questioned whether that might be because the process
    >scheduler has less control over CPU time allocation than in
    >2.4. Remember that the process scheduler only manages the
    >CPU time not spent in I/O and other overhead.
    >
    >If there is something in BIO chewing cycles it will wreak
    >havoc with latency no matter what you do about process
    >scheduling. The work on BIO to improve bandwidth and reduce
    >latency was Herculean but the growing performance gap
    >between CPU and I/O is a formidable challenge.

    In thinking about this from the aspect of what I do here, this makes
    quite a bit of sense. In running 2.6.0-test3, with anticipatory
    scheduler, it appears the i/o intensive tasks are being pushed back
    in favor of interactivity, perhaps a bit too aggressively. An amanda
    estimate phase, which turns tar loose on the drives, had to be
    advanced to a -10 niceness for the whole tree of processes amanda
    spawns before it began to impact the setiathome use as shown by the
    nice display in gkrellm. Normally there is a period for maybe 20
    minutes before the tape drive fires up where the machine is virtually
    unusable due to gzip hogging things, like the cpu, during which time
    seti could just as easily be swapped out. It remained at around 60%!

    It did not hog/lag near as badly as usual, and the amanda run was over
    an hour longer than it would have been in 2.4.22-rc2.

    It is my opinion that all this should have been at setiathomes
    expense, which is also rather cpu intensive, but it didn't seem to be
    without lots of forceing. This is what the original concept of
    niceness was all about. Or at least that was my impression. From
    what it feels like here, it seems the i/o stuff is whats being
    choked, and choked pretty badly when using the anticipatory
    scheduler.

    I've read rumors that a boottime option can switch it to somethng
    else, so what do I do to switch it from the anticipatory scheduler to
    whatever the alternate is?, so that I can get a feel for the other
    methods and results.

    --
    Cheers, Gene
    AMD K6-III@500mhz 320M
    Athlon1600XP@1400mhz 512M
    99.27% setiathome rank, not too shabby for a WV hillbilly
    Yahoo.com attornies please note, additions to this message
    by Gene Heskett are:
    Copyright 2003 by Maurice Eugene Heskett, all rights reserved.

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