Subject: Re: True  fsync() in Linux (on IDE)
From: Peter Zaitsev <peter@mysql.com>
To: Chris Mason <mason@suse.com>
Cc: Jens Axboe <axboe@suse.de>, Linux Kernel <linux-kernel@vger.kernel.org>
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Date: Thu, 18 Mar 2004 13:09:52 -0800
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On Thu, 2004-03-18 at 13:02, Chris Mason wrote:

> > In the former case cache is surely not flushed. 
> > 
> Hmmm, is it reiser?  For both 2.4 reiserfs and ext3, the flush happens
> when you commit.  ext3 always commits on fsync and reiser only commits
> when you've changed metadata.

Oh. Yes. This is Reiser, I did not think it is FS issue.
I'll know to stay away from ReiserFS now.

> 
> Thanks to Jens, the 2.6 barrier patch has a nice clean way to allow
> barriers on fsync, O_SYNC, O_DIRECT, etc, so we can make IDE drives much
> safer than the 2.4 code did.  

Great.

> > I was also surprised to see this simple test case has so different
> > performance with default and "deadline" IO scheduler   -  1.6 vs 0.5 sec
> > per 1000 fsync's.
> 
> Not sure on that one, both cases are generating tons of unplugs, the
> drive is just responding insanely fast.

Well why it would be slow if it has write cache off.


-- 
Peter Zaitsev, Senior Support Engineer
MySQL AB, www.mysql.com

Meet the MySQL Team at User Conference 2004! (April 14-16, Orlando,FL)
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