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    SubjectRe: Time sliced CFQ io scheduler
    On Wed, 2004-12-08 at 01:37 +0100, Andrea Arcangeli wrote:
    > On Thu, Dec 02, 2004 at 08:52:36PM +0100, Jens Axboe wrote:
    > > with its default io scheduler has basically zero write performance in
    > IMHO the default io scheduler should be changed to cfq. as is all but
    > general purpose so it's a mistake to leave it the default (plus as Jens

    I think it is actually pretty good at general purpose stuff. For
    example, the old writes starve reads thing. It is especially bad
    when doing small dependent reads like `find | xargs grep`. (Although
    CFQ is probably better at this than deadline too).

    It also tends to degrade more gracefully under memory load because
    it doesn't require much readahead.

    > found the write bandwidth is not existent during reads, no surprise it
    > falls apart in any database load). We had to make the cfq the default
    > for the enterprise release already. The first thing I do is to add
    > elevator=cfq on a new install. I really like how well cfq has been
    > designed, implemented and turned, Jens's results with his last patch are
    > quite impressive.

    That is synch write bandwidth. Yes that seems to be a problem.

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