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    SubjectRe: [PATCH] O13int for interactivity


    Gene Heskett wrote:

    >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.
    >

    Boot with "elevator=deadline" to use the more conventional elevator.

    It would be good if you could get some numbers 2.4 vs 2.6, with and
    without seti running. Sounds like a long cycle though so you probably
    can't be bothered!


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