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    SubjectRe: CPU scheduler weirdness?
    On Tue, 2009-08-18 at 21:49 +0200, Marton Balint wrote:

    > In the meantime, I was able to create a tiny C program which always
    > succesfully reproduces the bug. It's basically an endless loop which does
    > not stop while the process is running on the last CPU core. The program
    > creates multiple instances of itself, to be able to keep all of the CPU
    > cores busy. After 1 second, the processes running on other than the last
    > CPU core die, the processes running on the last CPU core remain stuck
    > there...
    > I tested it on my dual core system, if someone could test it on a quad
    > core and report back that would probably be useful.
    > Usage: ./schedtest <number of CPU cores>
    > And don't forget to kill the stuck processes after using the program! :)

    So what's the bug? Sure one task will stay on the cpu, and because there
    is no contention it doesn't get migrated, and therefore won't quit,
    how's that a problem?

    If you start a bunch of loops (enough to fill all cpus) you'll find
    it'll get migrated and die pretty quickly.

    Those same loops `while :; do :; done &` get spread around the available
    cores just fine, still no bug.

    btw: sysconf(_SC_NPROCESSORS_ONLN);

     \ /
      Last update: 2009-08-19 09:07    [W:0.022 / U:5.492 seconds]
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