linux-kernel - Re: [.32-rc3] scheduler: iwlagn consistently high in "waiting for CPU"

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Date:	Fri, 09 Oct 2009 05:04:33 +0200
From:	Mike Galbraith <efault@....de>
To:	Frans Pop <elendil@...net.nl>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-wireless@...r.kernel.org
Subject: Re: [.32-rc3] scheduler: iwlagn consistently high in "waiting for
 CPU"

On Thu, 2009-10-08 at 22:59 +0200, Frans Pop wrote:
> On Thursday 08 October 2009, Mike Galbraith wrote:
> > I still see very high latencies coming out of idle (last noted was >
> > 300ms, NO_HZ) with this patch,
> >
> > Like this:
> >
> > Cause                                           Maximum    Percentage
> > Scheduler: waiting for cpu                   604.2 msec        49.0 %
> 
> I'm not seeing anything even remotely like that.
> 
> I've tried quieting the system down as much as possible, but that made
> no difference. I do have NO_HZ set; will send my full config privately.
> 
> If you'd still like me to try your patch I will, but I'm not sure if
> that has much value.

No, if you watch for a bit with box mostly idle, and don't see > 100ms
hits occasionally, testing patchlet is likely a waste of time.  To get
one like the above, I have to hold my tongue just right ;-) they're not
common.

	-Mike

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