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SubjectRe: [patch] CFS scheduler, -v18

* Willy Tarreau <w@1wt.eu> wrote:

> > > I have no idea about what version brought that unexpected
> > > behaviour, but it's clearly something which needs to be tracked
> > > down.
> >
> > hm, the two problems might be related. Could you try v17 perhaps? In
> > v18 i have 'unified' all the sched.c's between the various kernel
> > releases, maybe that brought in something unexpected on 2.6.20.14.
> > (perhaps try v2.6.21.5 based cfs too?)
>
> Well, forget this, I'm nuts. I'm sorry, but I did not set any of the
> -R and -S parameter on ocbench, which means that all the processes ran
> at full speed and did not sleep. The load distribution was not fair,
> but since they put a lot of stress on the X server, I think it might
> be one of the reasons for the unfairness. I got the same behaviour
> with -v17, -v9 and even 2.4 ! It told me something was wrong on my
> side ;-)
>
> I've retried with 50%/50% run/sleep, and it now works like a charm.
> It's perfectly smooth with both small and long run/sleep times
> (between 1 and 100 ms). I think that with X saturated, it might
> explain why I only had one CPU running at 100% !

ah, great! :-) My testbox needs a 90% / 10% ratio between sleep/run for
an 8x8 matrix of ocbench tasks to not overload the X server. Once the
overload happens X starts penalizing certain clients it finds abusive (i
think), and that mechanism seems to be wall-clock based and it thus
brings in alot of non-determinism and skews the clients.

Ingo
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