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    SubjectRe: unresponsiveness on linux desktop during file copy
    On Sun, May 17, 2009 at 12:30:28PM +0800, Satish Eerpini wrote:
    > > I've prepared a rolled up patch for you, run time tested.  It should
    > > protect all of the above pages from being evicted by large file copies.
    > >
    > > The attached patch is for 2.6.29.
    >
    > I applied the patch , but the number don seem to show much difference

    The numbers listed in your email? No the most relevant numbers are
    memory and disk ones.

    For my part, the number of mapped pages keeps stable when there is an
    ongoing background file copy:

    % ls -l /b/sparse
    -rw-r--r-- 1 root root 98T 2009-04-29 22:38 /b/sparse
    % cp /b/sparse /dev/null&
    % for i in `seq 1 100`; do grep Mapped /proc/meminfo; sleep 1; done
    Mapped: 22764 kB
    Mapped: 22796 kB
    Mapped: 22756 kB
    Mapped: 22716 kB
    Mapped: 22800 kB
    Mapped: 22788 kB
    Mapped: 22804 kB
    Mapped: 22808 kB
    Mapped: 22748 kB
    Mapped: 22708 kB
    Mapped: 22916 kB
    Mapped: 22944 kB
    Mapped: 22944 kB
    Mapped: 22944 kB
    Mapped: 22944 kB
    Mapped: 22944 kB
    Mapped: 22832 kB
    Mapped: 22812 kB
    Mapped: 22812 kB
    Mapped: 22792 kB
    Mapped: 22772 kB
    Mapped: 22860 kB
    Mapped: 22860 kB
    Mapped: 22748 kB
    Mapped: 22808 kB
    Mapped: 22868 kB
    Mapped: 22956 kB
    Mapped: 22956 kB
    Mapped: 22832 kB
    Mapped: 22832 kB
    Mapped: 22980 kB
    Mapped: 22980 kB
    Mapped: 22980 kB
    Mapped: 22980 kB
    Mapped: 22872 kB
    Mapped: 22872 kB
    Mapped: 22900 kB
    Mapped: 22792 kB
    Mapped: 22920 kB
    Mapped: 22812 kB
    Mapped: 22812 kB
    Mapped: 22752 kB
    Mapped: 22864 kB
    Mapped: 22972 kB
    Mapped: 22860 kB
    Mapped: 22796 kB
    Mapped: 22900 kB
    Mapped: 22888 kB
    Mapped: 22888 kB
    Mapped: 22888 kB
    Mapped: 22764 kB

    > , following are the statistics with the patched kernel, could
    > something else be causing the huge iowait, :
    >
    > Linux 2.6.29 (satish) 05/17/2009
    >
    > 09:57:14 AM CPU %user %nice %system %iowait %steal %idle
    > 09:57:18 AM all 12.93 0.00 10.25 33.44 0.00 43.38
    > 09:57:21 AM all 13.32 0.00 28.09 24.40 0.00 34.19
    > 09:57:24 AM all 10.79 0.00 4.76 75.56 0.00 8.89
    > 09:57:26 AM all 11.46 0.00 8.01 35.64 0.00 44.90
    > 09:57:30 AM all 11.68 0.00 8.88 35.05 0.00 44.39
    > Average: all 12.03 0.00 11.94 40.81 0.00 35.22

    The iowait is high. Do you have "iostat -x 5' numbers?

    > and
    >
    > hdparm -tT /dev/sda
    >
    > /dev/sda:
    > Timing cached reads: 1332 MB in 2.00 seconds = 666.35 MB/sec
    > Timing buffered disk reads: 24 MB in 3.32 seconds = 7.23 MB/sec

    That's pretty slow numbers. On my laptop:

    # hdparm -tT /dev/sda

    /dev/sda:
    Timing cached reads: 10266 MB in 1.98 seconds = 5188.46 MB/sec
    Timing buffered disk reads: 138 MB in 3.01 seconds = 45.90 MB/sec

    Thanks,
    Fengguang
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