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Date: Fri, 17 Jul 2009 07:31:51 +0200
From: Stephan Kulow <coolo@...e.de>
To: Andreas Dilger <adilger@....com>, linux-ext4@...r.kernel.org
Subject: Re: file allocation problem
On Friday 17 July 2009 06:32:42 Andreas Dilger wrote:
Hi,
> It seems quite odd to me that mballoc didn't find enough contiguous
> free space for this relatively small file. It might be worthwhile
> to look at (though not necessarily post) the output from the file
> /sys/fs/ext4/{dev}/mb_groups (or "dumpe2fs" has equivalent data)
> and see if there are groups with a lot of contiguous free space.
> In the mb_groups file this would be numbers in the 2^{high} column.
I'm not sure what you expect with "a lot", so I pasted the full file (that
happens to be in /proc/fs here): http://ktown.kde.org/~coolo/sda6
>
> I don't agree that flex_bg is necessary to have good block allocation,
> since we do get about 125MB per group. Maybe mballoc is being
> constrained to look at too few block groups in this case? Looking at
> /sys/fs/ext4/{dev}/mb_history under the "groups" column will tell how
> many groups were scanned to find that allocation, and the "original"
> and "result" will show group/grpblock/count@...block for recent writes.
>
> $ dd if=/dev/zero of=/myth/tmp/foo bs=1M count=1
>
> pid inode original goal result
> 4423 110359 3448/14336/256@0 1646/18944/256@0 1646/19456/256@0
>
> You might also try to create a new temp directory elsewhere on the
> filesystem, copy the file over to the temp directory, and then see
> if it is less fragmented in the new directory.
>
cp /usr/bin/gimp-2.6{.defrag}:
31548 106916 13/0/1142@0 13/0/1024@0 13/24152/59@0
201 1 2 1056 0 0
31548 106916 13/24211/1083@59 13/24211/965@59 13/26192/41@59
201 1 2 1568 0 0
31548 106916 13/26233/1042@100 13/26233/924@100 13/21777/34@100
201 1 2 1568 0 0
31548 106916 13/21811/1008@134 13/21811/890@134 13/6688/32@134
201 1 2 1568 0 0
31548 106916 13/6720/976@166 13/6720/858@166 13/10944/32@166
201 1 2 1568 0 0
31548 106916 13/6720/1@0 13/6720/1@0 13/513/1@0
1 1 1 1024 0 0
31548 106916 13/10976/944@198 13/10976/826@198 13/16896/32@198
201 1 2 1568 0 0
31548 106916 13/16928/912@230 13/16928/794@230 13/12564/31@230
201 1 2 1568 0 0
31548 106916 13/12595/881@261 13/12595/763@261 13/12724/31@261
201 1 2 1568 0 0
31548 106916 13/12755/850@292 13/12755/732@292 13/31700/31@292
201 1 2 1568 0 0
31548 106916 13/31731/819@323 13/31731/701@323 13/18103/30@323
201 1 2 1568 0 0
31548 106916 13/18133/789@353 13/18133/671@353 13/21691/30@353
201 1 2 1568 0 0
31548 106916 13/21721/759@383 13/21721/641@383 13/25881/30@383
201 1 2 1568 0 0
31548 106916 13/25911/729@413 13/25911/611@413 13/22196/29@413
201 1 2 1568 0 0
31548 106916 13/22225/700@442 13/22225/582@442 13/31380/29@442
201 1 2 1568 0 0
31548 106916 13/31409/671@471 13/31409/553@471 13/12954/27@471
201 2 2 1568 0 0
31548 106916 13/12981/644@498 13/12981/526@498 13/18176/27@498
201 2 2 1568 0 0
31548 106916 13/18203/617@525 13/18203/499@525 13/15161/26@525
201 2 2 1568 0 0
31548 106916 13/15187/591@551 13/15187/473@551 13/17625/26@551
201 2 2 1568 0 0
31548 106916 13/17651/565@577 13/17651/447@577 13/19936/26@577
201 2 2 1568 0 0
31548 106916 13/19962/539@603 13/19962/421@603 13/20247/26@603
201 2 2 1568 0 0
31548 106916 13/20273/513@629 13/20273/395@629 13/23515/26@629
201 2 2 1568 0 0
31548 106916 13/23541/487@655 13/23541/369@655 13/9949/25@655
201 2 2 1568 0 0
31548 106916 13/9974/462@680 13/9974/344@680 13/19832/25@680
201 2 2 1568 0 0
31548 106916 13/19857/437@705 13/19857/319@705 13/29244/25@705
201 2 2 1568 0 0
31548 106916 13/29269/412@730 13/29269/294@730 13/1344/24@730
201 2 2 1568 0 0
31548 106916 13/1368/388@754 13/1368/270@754 13/11776/23@754
201 2 2 1568 0 0
31548 106916 13/11799/365@777 13/11799/247@777 14/3104/26@777
201 2 2 1568 0 0
31548 106916 14/3130/339@803 14/3130/221@803 14/9984/50@803
201 1 2 1568 0 0
31548 106916 14/10034/289@853 14/10034/171@853 14/11264/46@853
201 1 2 1568 0 0
31548 106916 14/11310/243@899 14/11310/125@899 58/1024/125@899
11 1 1 1568 125 128
31548 106916 58/1149/118@...4 58/1149/1024@...4
58/17408/445@...4 201 2 2 1568 0 0
filefrag: 59 extents.
cp /usr/bin/gimp-2.6 /tmp/nd/
25449 650578 80/0/1@0 80/0/1@0 80/589/1@0
4 1 1 0 0 0
Filesystem type is: ef53
File size of /tmp/nd/gimp-2.6 is 4677400 (1142 blocks, blocksize 4096)
ext logical physical expected length flags
0 0 2638592 588
1 588 2628896 2639179 436
2 1024 2637846 2629331 118 eof
/tmp/nd/gimp-2.6: 3 extents found
Greetings, Stephan
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