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    SubjectRe: [PATCH] Time sliced CFQ #2
    On Sat, Dec 04 2004, Jeff Sipek wrote:
    > On Sat, Dec 04, 2004 at 11:49:21AM +0100, Jens Axboe wrote:
    > > Hi,
    > >
    > > Second version of the time sliced CFQ. Changes:
    > >
    > > - Sync io has a fixed time slice like before, async io has both a time
    > > based and a request based slice limit. The queue slice is expired when
    > > one of these limits are reached.
    > >
    > > - Fix a bug in invoking the request handler on a plugged queue.
    > >
    > > - Drop the ->alloc_limit wakeup stuff, I'm not so sure it's a good idea
    > > and there are probably wakeup races buried there.
    > >
    > > With the async rq slice limit, it behaves perfectly here for me with
    > > readers competing with async writers. The main slice settings for a
    > > queue are:
    > >
    > > - slice_sync: How many msec a sync disk slice lasts
    > > - slice_idle: How long a sync slice is allowed to idle
    > > - slice_async: How many msec an async disk slice lasts
    > > - slice_async_rq: How many requests an async disk slice lasts
    >
    > This looks very nice. And from your previous post (with version #1) it
    > would look like you made my attempt at io priorities easier. We'll see
    > ;-)

    It should be really easy to try some rudimentary prio io support - just
    scale the time slice based on process priority. A few lines of code
    change, and io priority now follows process cpu scheduler priority. To
    work really well, the code probably needs a few more limits besides just
    slice time.

    --
    Jens Axboe

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