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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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