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    SubjectSleep-Slowdown
    Hello,


    while developing a compiler (www.informatik.uni-kiel.de/~sacbase),
    a problem with newer linux-kernels occured.

    I tracked it down to the following:

    Using this small program to test it, the executiontime on Linux <= 2.1.126
    and on Sparc-Solaris is nearly 1ms.

    Since 2.1.127 the time is 5 seconds, whoch means 10ms per sleep(0).

    -------------------- 8< ------------------------

    int main()
    {
    int i;
    for (i=0; i<=500; i++)
    {
    sleep(0);
    }
    return(0);
    }
    -------------------- 8< ------------------------

    Viewing it in strace results in nanosleep(0,0).
    The manpage for nanosleep() says, the (sleep-)time may increase up to one
    cycle (10ms) (Linux-man and Solaris-man).

    I inserted a line like

    if(arg==0) return 0;

    to sys_nanosleep() in sched.c, and the "problem" was fixed.

    It surely does not make sense to call sleep(0), but in that case,
    it would be nice to return emmediatly.

    Are there any oposite oppinions ?
    Could that fix be included into the official kernel ?




    jfe@informatik.uni-kiel.de


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