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    Subjectgettimeofday() cripples notsc system
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    John,

    Running a large application that issues many gettimeofday()
    system calls on a kernel running with notsc, results in time
    slowing way down. I've seen the system time advance only
    three minutes over a 30 minute period. The following program,
    executed twice demonstrates the problem. Three instances running
    in parallel made a 16 processor machine completely unusable.

    #include <sys/time.h>

    main()
    {
    struct timeval tv;
    struct timezone tz;
    while (1)
    if (gettimeofday(&tv, &tz))
    return;
    }

    I've recreated on 2.5.30, 2.5.44, and 2.5.47. Running a system that
    is using the tsc I've tried 100 instances of this test running in
    parallel with no problems - other than the normal incorrect time due
    to tsc skew. At least no time slowdowns or hangs. The system I'm
    using is a 4 node NUMAQ (x86) box.

    I assume there is a lock starvation problem happening here, correct?
    Any chance of fixing this?
    --

    Michael Hohnbaum 503-578-5486
    hohnbaum@us.ibm.com T/L 775-5486

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