Messages in this thread | | | Date | Thu, 10 Jul 2008 06:18:22 -0700 | From | Andrew Morton <> | Subject | Re: Higher than expected disk write(2) latency |
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On Thu, 10 Jul 2008 15:17:47 +0200 Martin Sustrik <sustrik@fastmq.com> wrote:
> Hi Alan, > > >> What we see is that AIO performs rather bad while we are still > >> enqueueing more writes (it misses right position on the disk and has to > >> do superfluous disk revolvings), however, once we stop enqueueing new > >> write request, those already in the queue are processed swiftly. > > > > Which disk scheduler are you using - some of the disk schedulers > > intentionally delay writes to try and get better block merging. > > It's CFQ. Does it delay writes? And if so, what should we use instead? >
noop is the simplest scheduler. deadline is the simplest real scheduler, and deadline doesn't have any delaying logic.
If CFQ or anticipatory _are_ putting delays into this workload, that'd be a bug.
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