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    SubjectRe: ext4 performance regression 2.6.27-stable versus 2.6.32 and later
    Am 30.07.2010 04:20, schrieb Ted Ts'o:
    > On Wed, Jul 28, 2010 at 09:51:48PM +0200, Kay Diederichs wrote:
    >>
    >> When looking at the I/O statistics while the benchmark is running, we
    >> see very choppy patterns for 2.6.32, but quite smooth stats for
    >> 2.6.27-stable.
    >
    > Could you try to do two things for me? Using (preferably from a
    > recent e2fsprogs, such as 1.41.11 or 12) run filefrag -v on the files
    > created from your 2.6.27 run and your 2.6.32 run?
    >
    > Secondly can capture blktrace results from 2.6.27 and 2.6.32? That
    > would be very helpful to understand what might be going on.
    >
    > Either would be helpful; both would be greatly appreciated.
    >
    > Thanks,
    >
    > - Ted

    Ted,

    a typical example of filefrag -v output for 2.6.27.48 is

    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 796160000 1024
    1 1024 826381312 796161023 497 eof

    (99 out of 100 files have 2 extents)

    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

    (99 out of 100 files have 1 extent)

    We'll try the blktrace ASAP and report back.

    thanks,

    Kay

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