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

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Date:	Tue, 14 Aug 2007 11:44:56 +1000
From:	Stewart Smith <stewart@...ql.com>
To:	Brice Figureau <brice+lklm@...sofwonder.com>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/23] per device dirty throttling -v8

On Mon, 2007-08-06 at 10:40 +0200, Brice Figureau wrote:
> Mysql accesses its database files in O_DIRECT mode.

binlog is written using buffered IO.

for InnoDB, binlog is synced first, then innodb log. on restart (in 5.0)
these are synced back up so you don't get inconsistencies.

and from a quick look at the innobase source, only data file is using
O_DIRECT.

> 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).
-- 
Stewart Smith, Senior Software Engineer
MySQL AB, www.mysql.com
Office: +14082136540 Ext: 6616
VoIP: 6616@....us.mysql.com
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