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    SubjectRe: [patch] Give kjournald a IOPRIO_CLASS_RT io priority
    On Nov 16, 2007 8:25 AM, Alan D. Brunelle <alan.brunelle@hp.com> wrote:
    > Here are the results for the latest tests, some notes:
    >
    > o The machine actually has 8GiB of RAM, so the tests still may end up
    > using (some) page cache. (But at least it was the same for both kernels!
    > :-) )
    >
    > o Sorry the results took so long - the updated tree size caused the
    > runs to take > 12 hours...
    >
    > o The longer runs seemed to bring down the standard deviation a bit,
    > although they are still quite large.
    >
    > o 10 runs per test (read large file, read a tree, overwrite large
    > file), with averages presented.
    >
    > o 1st 4 columns (min, avg, max, std dev) refer to the average run
    > lengths for the tests - real time, in seconds
    >
    > o The last 3 columns are extracted from iostat results over the course
    > of the whole run.
    >
    > o The read a tree test certainly stands out - the other 2 large file
    > manipulations have the two kernels within a couple of percent, but the
    > read a tree test has Arjan's patch taking about 47%(!) longer on
    > average. The increased %iowait & %system time in all 3 cases is interesting.
    >
    >
    > Read large file:
    >
    > Kernel Min Avg Max Std Dev %user %system %iowait
    > --------------------------------------------------------------
    > base : 201.6 215.1 275.5 22.8 0.26% 4.69% 33.54%
    > arjan: 198.0 210.3 261.5 18.5 0.33% 10.24% 54.00%
    >
    > Read a tree:
    >
    > Kernel Min Avg Max Std Dev %user %system %iowait
    > --------------------------------------------------------------
    > base : 3518.2 4631.3 5991.3 784.6 0.19% 3.29% 23.56%
    > arjan: 5731.6 6849.8 7777.4 731.6 0.32% 9.90% 52.70%
    >
    > Overwrite large file:
    >
    > Kernel Min Avg Max Std Dev %user %system %iowait
    > --------------------------------------------------------------
    > base : 104.2 147.7 239.5 38.4 0.02% 0.05% 1.08%
    > arjan: 106.2 149.7 239.2 38.4 0.25% 0.79% 14.97%
    >
    > Let me know if there is anything else I can do to elaborate, or if you
    > have suggestions for further testing.

    Out of curiosity, what are the mount options for the freshly created
    ext3 fs? In particular, are you using noatime, nodiratime?

    Ray
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