Messages in this thread | | | Date | Tue, 05 Aug 2003 20:04:54 +1000 | From | Nick Piggin <> | Subject | Re: [PATCH] O13int for interactivity |
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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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