Re: cfq misbehaving on 2.6.11-1.14_FC3

From: spaminos-ker
Date: Wed Jun 22 2005 - 13:04:05 EST

--- Jens Axboe <axboe@xxxxxxx> wrote:
> THe problem here is that cfq (and the other io schedulers) still
> consider the io async even if fsync() ends up waiting for it to
> complete. So there's no real QOS being applied to these pending writes,
> and I don't immediately see how we can improve that situation right now.
<I might sound stupid>
I still don't understand why async requests are in a different queue than the
sync ones?
Wouldn't it be simpler to consider all the IO the same, and like you pointed
out, consider synced IO to be equivalent to async + some sync (as in wait for
completion) call (fsync goes a little too far).
</I might sound stupid>

> What file system are you using? I ran your test on ext2, and it didn't
> give me more than ~2 seconds latency for the fsync. Tried reiserfs now,
> and it's in the 23-24 range.
I am using ext3 on Fedora Core 3.

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