2012/3/3 Jacek Luczak [off-list ref]:

2012/3/2 Chris Mason [off-list ref]:

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On Fri, Mar 02, 2012 at 03:16:12PM +0100, Jacek Luczak wrote:

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2012/3/2 Chris Mason [off-list ref]:

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On Fri, Mar 02, 2012 at 11:05:56AM +0100, Jacek Luczak wrote:

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I've took both on tests. The subject is acp and spd_readdir used=

 with

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tar, all on ext4:
1) acp: http://91.234.146.107/~difrost/seekwatcher/acp_ext4.png
2) spd_readdir: http://91.234.146.107/~difrost/seekwatcher/tar_e=

xt4_readir.png

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3) both: http://91.234.146.107/~difrost/seekwatcher/acp_vs_spd_e=

xt4.png

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The acp looks much better than spd_readdir but directory copy wi=

th

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spd_readdir decreased to 52m 39sec (30 min less).

Do you have stats on how big these files are, and how fragmented =

they

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are? =A0For acp and spd to give us this, I think something has go=

ne wrong

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at writeback time (creating individual fragmented files).

How big? Which files?

All the files you're reading ;)

filefrag will tell you how many extents each file has, any file with
more than one extent is interesting. =A0(The ext4 crowd may have bet=

ter

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suggestions on measuring fragmentation).

Since you mention this is a compile farm, I'm guessing there are a b=

unch

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of .o files created by parallel builds. =A0There are a lot of chance=

s for

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delalloc and the kernel writeback code to do the wrong thing here.

[Most of files are B and K size]

All files scanned: 1978149
Files fragmented: 313 (0.015%) where 11 have 3+ extents
Total size of fragmented files: 7GB (~13% of dir size)

BTRFS: Non of files according to filefrag are fragmented - all fit
into one extent.

tar cf on fragmented files:
1) time: 7sec
2) sw graph: http://91.234.146.107/~difrost/seekwatcher/tar_fragmente=

d.png

3) sw graph with spd_readdir:
http://91.234.146.107/~difrost/seekwatcher/tar_fragmented_spd.png
4) both on one:
http://91.234.146.107/~difrost/seekwatcher/tar_fragmented_pure_spd.pn=

g

BTRFS: tar on ext4 fragmented files
1) time: 6sec
2) sw graph: http://91.234.146.107/~difrost/seekwatcher/tar_fragmented_=
btrfs.png

tar cf of fragmented files disturbed with [40,50) K files (in total
4373 files). K files before fragmented M files:
1) size: 7.2GB
2) time: 1m 14sec
3) sw graph: http://91.234.146.107/~difrost/seekwatcher/tar_disturbed=

=2Epng

4) sw graph with spd_readdir:
http://91.234.146.107/~difrost/seekwatcher/tar_disturbed_spd.png
5) both on one:
http://91.234.146.107/~difrost/seekwatcher/tar_disturbed_pure_spd.png

BTRFS: tar on [40,50) K and ext4 fragmented
1) time: 56sec
2) sw graph: http://91.234.146.107/~difrost/seekwatcher/tar_disturbed_b=
trfs.png

New test I've included - randomly selected files:
- size 240MB
1) ext4 (time: 34sec) sw graph:
http://91.234.146.107/~difrost/seekwatcher/tar_random_ext4.png
2) btrfs (time: 55sec) sw graph:
http://91.234.146.107/~difrost/seekwatcher/tar_random_btrfs.png

-Jacek