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SubjectRe: [.32-rc3] scheduler: iwlagn consistently high in "waiting for CPU"
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On Thu, 2009-10-08 at 16:13 +0200, Mike Galbraith wrote:
> On Thu, 2009-10-08 at 06:40 -0700, Arjan van de Ven wrote:
> > On Thu, 08 Oct 2009 06:05:43 +0200
> > Mike Galbraith <efault@gmx.de> wrote:
>
> > > OK, I see latencytop spikes here on an idle box too, to the tune of up
> > > to a _second_. Booting with nohz=off seems to have cured it.
> >
> > interesting..
> >
> >
> > by chance, does this patch fix it ?
>
> I haven't seen incredible yet, but with idle box, have seen > 200ms, so
> would say no.

But this dinky hunk of my patchlet does indeed still fix it right up.

Index: linux-2.6/kernel/sched_fair.c
===================================================================
--- linux-2.6.orig/kernel/sched_fair.c
+++ linux-2.6/kernel/sched_fair.c
@@ -495,8 +495,10 @@ static void update_curr(struct cfs_rq *c
u64 now = rq_of(cfs_rq)->clock;
unsigned long delta_exec;

- if (unlikely(!curr))
+ if (unlikely(!curr)) {
+ update_rq_clock(rq_of(cfs_rq));
return;
+ }

/*
* Get the amount of time the current task was running
We have a clock problem with NO_HZ coming out of idle, so we may well
have real latency issues at the same time, not bogons.

-Mike



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