Re: [.32-rc3] scheduler: iwlagn consistently high in "waiting forCPU"

[Arjan van de Ven]

On Thu, 08 Oct 2009 06:05:43 +0200
Mike Galbraith <efault@xxxxxx> wrote:

> On Wed, 2009-10-07 at 20:34 +0200, Frans Pop wrote:
> > On Wednesday 07 October 2009, Frans Pop wrote:
> > > On Tuesday 06 October 2009, Frans Pop wrote:
> > > > I've checked for 2.6.31.1 now and iwlagn is listed high there
> > > > too when the system is idle, but with normal values of 60-100
> > > > ms. And phy0 has normal values of below 10 ms.
> > > > I've now rebooted with today's mainline git; phy0 now
> > > > frequently shows with values of around 100 ms too (i.e. higher
> > > > than last time).
> > >
> > > Mike privately sent me a script to try to capture the latencies
> > > with perf, but the perf output does not show any high latencies
> > > at all. It looks as if we may have found a bug in latencytop here
> > > instead.
> > 
> > Not sure if it's relevant nor what it means, but I frequently see
> > two lines for iwlagn, e.g:
> > 
> >     Scheduler: waiting for cpu              102.4 msec         99.7
> > % .                                         3.3 msec          0.3 %
> > 
> > I get the same results with both latencytop 0.4 and 0.5.
> 
> 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 ?