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

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Message-Id: <200910072034.57511.elendil@planet.nl>
Date:	Wed, 7 Oct 2009 20:34:55 +0200
From:	Frans Pop <elendil@...net.nl>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	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 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.
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