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    Subjectqsbench, interesting results
    Date

    qsbench is a VM benchmark based on sorting a large array
    by quick sort.
    http://web.tiscali.it/allegrucci/qsbench-1.0.0.tar.gz

    Below are some results of qsbench sorting a 350Mb array
    on a 256+400Mb RAM+swap machine.
    Tested kernels: 2.4.19, 2.5.38 and 2.5.39
    All runs made with the same default seed, to compare
    apples with apples :)
    I used /usr/bin/time because it gives better statistics
    such as major and minor page faults etc.
    (Sorry for >72 cols).


    2.4.19
    bash-2.05# /usr/bin/time ./qsbench -m 350
    46.29user 3.54system 2:34.66elapsed 32%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (24739major+370199minor)pagefaults 0swaps
    bash-2.05# /usr/bin/time ./qsbench -m 350
    46.57user 3.27system 2:35.73elapsed 32%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (24493major+370706minor)pagefaults 0swaps
    bash-2.05# /usr/bin/time ./qsbench -m 350
    46.61user 3.09system 2:35.91elapsed 31%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (24560major+370571minor)pagefaults 0swaps

    Perfectly reproducible performance.


    2.5.38
    bash-2.05# /usr/bin/time ./qsbench -m 350
    ERROR: i = 7766682
    *** WARNING *** 1 errors.
    47.11user 3.57system 3:42.19elapsed 22%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (39875major+439626minor)pagefaults 0swaps
    bash-2.05# /usr/bin/time ./qsbench -m 350
    46.80user 3.68system 3:42.20elapsed 22%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (39336major+441350minor)pagefaults 0swaps
    bash-2.05# /usr/bin/time ./qsbench -m 350
    46.87user 3.70system 3:44.50elapsed 22%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (39926major+440091minor)pagefaults 0swaps

    This is interesting, qsbench got an array not "quite" sorted.
    I have run qsbench a lot of times in the past on many kernels
    and I have never seen such error.
    I don't think it's my hardware fault so I would like to know
    if somebody can reproduce it.
    Performance is worse than 2.4.19


    2.5.39
    bash-2.05# /usr/bin/time ./qsbench -m 350
    46.94user 4.41system 8:17.94elapsed 10%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (66343major+455167minor)pagefaults 0swaps
    bash-2.05# /usr/bin/time ./qsbench -m 350
    46.74user 4.64system 8:45.03elapsed 9%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (68600major+454782minor)pagefaults 0swaps
    bash-2.05# /usr/bin/time ./qsbench -m 350
    46.81user 4.31system 8:37.07elapsed 9%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (69090major+454355minor)pagefaults 0swaps

    Big performance drop.


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