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    SubjectRe: [PATCH] O13int for interactivity


    Oliver Neukum wrote:

    >Am Dienstag, 5. August 2003 09:26 schrieb Con Kolivas:
    >
    >>On Tue, 5 Aug 2003 16:03, Andrew Morton wrote:
    >>
    >>>We do prefer that TASK_UNINTERRUPTIBLE processes are woken promptly so they
    >>>can submit more IO and go back to sleep. Remember that we are artificially
    >>>leaving the disk head idle in the expectation that the task will submit
    >>>more I/O. It's pretty sad if the CPU scheduler leaves the anticipated task
    >>>in the doldrums for five milliseconds.
    >>>
    >>Indeed that has been on my mind. This change doesn't affect how long it takes
    >>to wake up. It simply prevents tasks from getting full interactive status
    >>during the period they are doing unint. sleep.
    >>
    >
    >If you take that to its logical conclusion, such tasks should be woken
    >immediately. Likewise, the io scheduler should be notified when you know
    >that the task won't do io or will do other io, like waiting on character
    >devices, go paging out or terminate.
    >

    I don't think that is the logical conclusion because you are balancing
    against other things.

    As for the io scheduler, no, there is a lot that can be done (including
    waiting on character devs) before it is no longer worth keeping the disk
    waiting. AS really doesn't care in the slightest what a process does
    between submitting IOs*, what is important is simply its IO pattern.

    * except exit which is an easy case of course.


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