On Tue, 2008-12-16 at 01:49 +0100, Miklos Szeredi wrote:
> On Sat, 13 Dec 2008, Rafael J. Wysocki wrote:
> > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=12208
> > Subject : uml is very slow on 2.6.28 host
> > Submitter : Miklos Szeredi <mik...@szeredi.hu>
> > Date : 2008-12-12 9:35 (2 days old)
> > References : http://marc.info/?l=linux-kernel&m=122907463518593&w=4
>
> I did a bisection, and this is the commit which is responsible:
>
> commit 464b75273f64be7c81fee975bd6ca9593df3427b
> Author: Peter Zijlstra <a.p.zijls...@chello.nl>
> Date: Fri Oct 24 11:06:15 2008 +0200
>
> sched: re-instate vruntime based wakeup preemption
>
> The advantage is that vruntime based wakeup preemption has a better
> conceptual model. Here wakeup_gran = 0 means: preempt when 'fair'.
> Therefore wakeup_gran is the granularity of unfairness we allow in order
> to make progress.
>
> Signed-off-by: Peter Zijlstra <a.p.zijls...@chello.nl>
> Acked-by: Mike Galbraith <efa...@gmx.de>
> Signed-off-by: Ingo Molnar <mi...@elte.hu>
If that commit is responsible, then it should also be very slow in pre
28 kernels, where the same exists. Hm, there's another possibility.
Can you try echo NO_LAST_BUDDY > /sys/kernel/debug/sched_features?
-Mike
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