linux-kernel - Re: [PATCH 00/23] per device dirty throttling -v8

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Message-Id: <1187078375.11811.7.camel@localhost.localdomain>
Date:	Tue, 14 Aug 2007 09:59:35 +0200
From:	Brice Figureau <brice+lklm@...sofwonder.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Stewart Smith <stewart@...ql.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/23] per device dirty throttling -v8

On Tue, 2007-08-14 at 04:25 +0200, Andi Kleen wrote:
> On Tue, Aug 14, 2007 at 11:44:56AM +1000, Stewart Smith wrote:
> > > Since the database fits in RAM, the only kind of access Mysql is doing
> > > is writing to the innodb log, the mysql binlog and finally to the innodb
> > > database files.
> > > There are certainly a whole lot of fsync'ing happening.
> > 
> > yes. Keep in mind that the binlog grows in file size too... so this has
> > to sync all the metadata as well (ick, i know).

Back in the first days of my original bug report I moved the binlogs to
another disk and it didn't change anything to my issue.

On Tue, 2007-08-14 at 04:25 +0200, Andi Kleen wrote:
> It might be an interesting experiment to see if it still happens
> with the file system remounted as ext2. ext2 has a much more 
> benign fsync than ext3.

Is it possible to perform a live remount of the fs on ext2 ?

Beside that, the RAID card has a battery backed RAM in write-back mode,
I was told that fsync don't really hurt in this case (moreover the fs is
mounted in journal=writeback mode).

I'll post soon blktrace files in the original bug report, this will show
exactly what is the disk workload in the baseline case _and_ in the
underload atypical case. Maybe that will help to shed some lights on the
issue?

Anyway, thanks,
-- 
Brice Figureau <brice+lklm@...sofwonder.com>

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