Messages in this thread |  | | | Subject | Re: Time sliced CFQ io scheduler | | From | Nick Piggin <> | | Date | Wed, 08 Dec 2004 11:54:13 +1100 |
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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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