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    SubjectRe: [BUG] Serious scheduler starvation
    On Sun, 17 Aug 2003 22:11, Måns Rullgård wrote:
    > I'm reposting this, since I got no response last time.
    > First the machine details. It's a Pentium4 running at 2 GHz. Linux
    > version 2.6.0-test3 + O16int + softrr.

    Softrr ? Which patch? Davide's? Noone has tried to make them compatible
    (yet?). Even so, this may be unrelated to softrr.

    > I just experienced something that might be a scheduler problem. I was

    Almost certainly is.

    > working in XEmacs, when suddenly the machine became very
    > unresponsive. The mouse pointer in X moved sporadically. I could
    > switch to a text console and log in, though typing lagged tens of
    > seconds. Switching between text consoles was fast, though. I killed
    > xemacs, and the system was back to normal. Further investigation
    > showed that xemacs was stuck in a nasty regexp match. If I was quick
    > enough, I could interrupt it with C-g.
    > With X and the window manager reniced to -10, they seem to be able to
    > get their job done. This leads me to believe that maybe xemacs is
    > considered interactive, and given too high priority when it suddenly
    > starts burning the cpu.
    > I'll try it later with other kernel versions, but right now I don't
    > want to reboot.
    > What can I do to collect more information about the problem?

    Run top in batch mode as root reniced to -11 so it doesn't get preempted and
    capture it happening before you kill XEmacs. Then try running XEmacs niced
    +10 and see if it doesn't happen there. Also if it was lucky enough that you
    booted with profiling enabled you could profile it, but top will tell if it's
    a simple scheduler starvation error.


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