linux-ext4 - Re: ext4 unlink performance

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Message-ID: <491F5659.7010206@redhat.com>
Date:	Sat, 15 Nov 2008 17:08:09 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	linux-ext4@...r.kernel.org
Subject: Re: ext4 unlink performance

Bruce Guenter wrote:
> On Fri, Nov 14, 2008 at 09:59:14AM -0500, Theodore Tso wrote:
>> This is beginning to perhaps sound like a layout problem of some kind.
> 
> To test this theory, I ran one test where I populated the filesystem
> with ext3 and then mounted as ext4 to do the unlinking.  This produced
> unlink times comparable with ext3.  That is, the degredation is occuring
> when the filesystem is populated, not when it is cleaned.

Maybe run the unlinking activity through seekwatcher* in both cases, to
see where the IO is happening.

(also, you're right w.r.t. lvm/dm; barriers don't pass and should get
disabled after the first attempt at a barrier write).

-Eric

*http://oss.oracle.com/~mason/seekwatcher/ (also packaged for fedora,
maybe other distros as well)
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