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Date: Thu, 23 Jun 2005 19:33:56 -0700 (PDT)
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Reply-To: spaminos-ker@yahoo.com
Subject: Re: cfq misbehaving on 2.6.11-1.14_FC3
To: Con Kolivas <kernel@kolivas.org>, linux-kernel@vger.kernel.org
Cc: Jens Axboe <axboe@suse.de>, Andrew Morton <akpm@osdl.org>
In-Reply-To: <200506240933.55951.kernel@kolivas.org>
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--- Con Kolivas <kernel@kolivas.org> wrote:
> I found the same, and the effect was blunted by noatime and 
> journal_data_writeback (on ext3). Try them one at a time and see what you 
> get.

I had to move to a different box, but get the same kind of results (for ext3
default mount options).

Here are the latencies (all cfq) I get with different values for the mount
parameters

ext2 default
0.1s

ext3 default
52.6s avg

reiser defaults
29s avg 5 minutes
then, 
12.9s avg

ext3 rw,noatime,data=writeback
0.1s avg

reiser rw,noatime,data=writeback
4s avg for 20 seconds
then 0.1 seconds avg


So, indeed adding noatime,data=writeback to the mount options improves things a
lot.
I also tried without the noatime, and that doesn't make much difference to me.

That looks like a good workaround, I'll now try with the actual server and see
how things go.

Nicolas