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    Subjectiosched: concurrent reads of many small files

    This test is very approximately the "busy web server" workload. We set up a
    number of processes each of which are reading many small files from different
    parts of the disk.

    Set up six separate copies of the 2.4.19 kernel tree, and then run, in
    parallel, six processes which are reading them:

    for i in 1 2 3 4 5 6
    do
    time (find kernel-tree-$i -type f | xargs cat > /dev/null ) &
    done

    With this test we have six read requests in the queue all the time. It's
    what the anticipatory scheduler was designed for.


    2.4.21-pre4:
    6m57.537s
    6m57.620s
    6m57.741s
    6m57.891s
    6m57.909s
    6m57.916s

    2.5.61+hacks:
    3m40.188s
    3m51.332s
    3m55.110s
    3m56.186s
    3m56.757s
    3m56.791s

    2.5.61+CFQ:
    5m15.932s
    5m16.219s
    5m16.386s
    5m17.407s
    5m50.233s
    5m50.602s

    2.5.61+AS:
    0m44.573s
    0m45.119s
    0m46.559s
    0m49.202s
    0m51.884s
    0m53.087s

    This was a little unfair to 2.4 because three of the trees were laid out by
    the pre-Orlov ext2. So I reran the test with 2.4.21-pre4 when all six trees
    were laid out by 2.5's Orlov allocator:

    6m12.767s
    6m12.974s
    6m13.001s
    6m13.045s
    6m13.062s
    6m13.085s

    Not much difference there, although Orlov is worth a 4x speedup in this test
    when there is only a single reader (or multiple readers + anticipatory
    scheduler)



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