Messages in this thread | | | Date | Tue, 18 Jun 2002 06:55:48 +0200 (CEST) | From | Ingo Molnar <> | Subject | Re: Question about sched_yield() |
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On Mon, 17 Jun 2002, David Schwartz wrote:
> >I am seeing some strange linux scheduler behaviours, > >and I thought this'd be the best place to ask. > > > >I have two processes, one that loops forever and > >does nothing but calling sched_yield(), and the other > >is basically benchmarking how fast it can compute > >some long math calculation.
> [...] It is not a replacement for blocking or a scheduling priority > adjustment. It simply lets other ready-to-run tasks be scheduled before > returning to the current task.
and this is what the scheduler didnt do properly, it actually didnt schedule valid ready-to-run processes for long milliseconds, it switched between two sched_yield processes, starving the CPU-intensive process. I posted a patch for 2.5 that fixes this, and the 2.4.19-pre10-ac2 backport i did includes this fix as well:
http://redhat.com/~mingo/O(1)-scheduler/sched-2.4.19-pre10-ac2-A4
a good sched_yield() implementation should give *all* other tasks a chance to run, instead of switching between multiple sched_yield()-ing tasks. I don think this is specified anywhere, but it's a quality of implementation issue.
Ingo
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