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    SubjectInconsistent timing results of multithreaded program on an SMP machine.
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    Hi,

    I am trying, as part of my thesis, to make some improvement to the linux
    scheduler.
    Therefore I've written a small multithreaded application and tested how
    long on average it takes for it to complete.

    The results were very surprising. I expected to see the completion time
    vary 1 to 2 seconds at most.
    Instead what I've got was an oscillation where the maximum time was twice
    and more than the minimum!! For a short test results ranged ~7sec to ~16
    sec, and the same happened to longer tests where the min was ~1min and the
    max ~2:30min.

    Does anyone have any clue as to what might happen ?
    Is there anything I can do to get stable results ?

    Here is a small test case program:

    (See attached file: sched_test.c)

    The test was always done on a pretty much empty machine. I've tried both
    kernel 2.6.4-52 and 2.6.13.4 but the results were the same.

    I'm working on a Xeon Intel machine, dual processor, hyperthreaded.
    Below is the info from /proc/cpuinfo

    (See attached file: cpuinfo.log)

    The machine's configuration is as follows: (filtered with grep "=[y|m]" )

    (See attached file: conf_filtered)

    Please respond to either:
    marcel@il.ibm.com
    or
    marcel.mz@gmail.com
    as I am not subscribed to the mailing list.

    Thank you for your help,
    Marcel[unhandled content-type:application/octet-stream][unhandled content-type:application/octet-stream][unhandled content-type:application/octet-stream]
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