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* Consistent throughput challenge -- fragmentation?
@ 2013-02-25 16:01 Brian Cain
  2013-02-25 21:39 ` Stan Hoeppner
  2013-02-25 22:16 ` Dave Chinner
  0 siblings, 2 replies; 8+ messages in thread
From: Brian Cain @ 2013-02-25 16:01 UTC (permalink / raw)
  To: xfs


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All,

I have been observing some odd behavior regarding write throughput to an
XFS partition (the baseline kernel version is 2.6.32.27).  I see
consistently high write throughput (close to the performance of the raw
block device) to the filesystem immediately after a mkfs, but after a few
test cycles, there is sporadic poor performance.

The test mechanism is like so:

[mkfs.xfs <blockdev>] (no flags/options, xfsprogs ver 3.1.1-0.1.36)
...
1. remove a previous test cycle's directory
2. create a new directory
3. open/write/close a small file (4kb) in this directory
4. open/read/close this same small file (by the local NFS server)
5. open[O_DIRECT]/write/write/write/.../close a large file (anywhere from
~100MB to 200GB)

Step #5 contains the high-throughput metrics which becomes an order of
magnitude worse several test cycles after a mkfs.  Omitting steps 1-3 does
not show the poor performance behavior.

Can anyone provide any suggestions as to an explanation for the behavior or
a way to mitigate it?  Running xfs_fsr didn't seem to improve the results.

I'm happy to share benchmarks, specific results data, or describe the
hardware being used for the measurements if it's helpful.

-- 
-Brian

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^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2013-02-25 23:47 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2013-02-25 16:01 Consistent throughput challenge -- fragmentation? Brian Cain
2013-02-25 21:39 ` Stan Hoeppner
2013-02-25 22:06   ` Brian Cain
2013-02-25 22:38   ` Brian Cain
2013-02-25 22:16 ` Dave Chinner
2013-02-25 22:18   ` Brian Cain
2013-02-25 22:23     ` Brian Cain
2013-02-25 23:46     ` Dave Chinner

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