linux-ext4 - Re: delalloc fragmenting files?

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Message-ID: <472A2384.2010001@redhat.com>
Date:	Thu, 01 Nov 2007 14:05:40 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Eric Sandeen <sandeen@...hat.com>
CC:	Alex Tomas <bzzz.tomas@...il.com>,
	Andreas Dilger <adilger@....COM>,
	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: delalloc fragmenting files?

Eric Sandeen wrote:
> Alex Tomas wrote:
>> please, try the patch attached.
> 
> Looks quite a bit better:
> 
> http://people.redhat.com/esandeen/seekwatcher/ext4-alex.png
> http://people.redhat.com/esandeen/seekwatcher/ext4-alex-ext4-dd-write.png
> http://people.redhat.com/esandeen/seekwatcher/ext4-alex-ext4-xfs-dd-write.png
> 
> It is much less fragmented, although still not exactly the nice linear
> allocation I'd expect from a single threaded large write on a fresh fs...

Note, we're still getting out-of-order extents, too:

First block: 122880
Last block: 2694143
Discontinuity: Block 7424 is at 101376 (was 130303)
Discontinuity: Block 28160 is at 133120 (was 122111)
Discontinuity: Block 58368 is at 188416 (was 163327)
Discontinuity: Block 66304 is at 180224 (was 196351)
Discontinuity: Block 73984 is at 172032 (was 187903)
Discontinuity: Block 81664 is at 167936 (was 179711)
Discontinuity: Block 84736 is at 221184 (was 171007)
Discontinuity: Block 92416 is at 212992 (was 228863)
Discontinuity: Block 100096 is at 204800 (was 220671)
Discontinuity: Block 107776 is at 198656 (was 212479)
...

I'm trying to find time to look into this but other things are knocking
at my door so no promises...

-Eric
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