Messages in this thread |  | | | Date | Sun, 1 Aug 2010 19:02:25 -0400 | | From | Ted Ts'o <> | | Subject | Re: ext4 performance regression 2.6.27-stable versus 2.6.32 and later |
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On Fri, Jul 30, 2010 at 11:01:36PM +0200, Kay Diederichs wrote: > whereas for 2.6.32.16 the result is typically > Filesystem type is: ef53 > File size of > /mnt/md5/scratch/nfs-test/tmp/xds/frames/h2g28_1_00000.cbf is > 6229688 (1521 blocks, blocksize 4096) > ext logical physical expected length flags > 0 0 826376200 1521 eof > /mnt/md5/scratch/nfs-test/tmp/xds/frames/h2g28_1_00000.cbf: 1 extent found
OK, so 2.6.32 is actually doing a better job laying out the files.... The blktrace will be interesting, but at this point I'm wondering if this is a generic kernel-wide writeback regression. At $WORK we've noticed some performance regressions between 2.6.26-based kernels and 2.6.33- and 2.6.34-based kernels with both ext2 and ext4 (in no journal mode) that we've been trying to track down. We have a pretty large number of patches applied to both 2.6.26 and 2.6.33/34 which is why I haven't mentioned it up until now, but at this point it seems pretty clear there are some writeback issues in the mainline kernel.
There are half a dozen or so patch series on LKML that are addressing writeback in one way or another, and writeback is a major topic at the upcoming Linux Storage and Filesystem workshop. So if this is the cause, hopefully there will be some improvements in this area in the near future.
- Ted
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