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

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Date:	Thu, 08 Oct 2009 15:18:33 +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 15:09 +0200, Frans Pop wrote:
> On Thursday 08 October 2009, Mike Galbraith wrote:
> > Care to try a patch?
> >
> > latencytop: only account on-runqueue wait time as being scheduler
> > latency.
> >
> > Latencytop was accounting uninterruptible and interruptible sleep time
> > up to 5ms, which is not the latency the user is looking for.  Account
> > time waiting on-runqueue instead.  Also add a clock update to
> > update_curr() for the case where there's nobody home.  When coming out
> > of idle with NO_HZ, not updating the clock leads to bogus max latency
> > report.
> 
> With this patch the high values for iwlagn and phy0 are gone. The values 
> now match roughly with the output of your script.
> 
> If (un)interruptible sleep is worth displaying in latencytop then maybe it 
> should be identified as a separate cause instead of lumped under "waiting 
> for CPU"?

That's what I was just thing about trying, add a cause sleep.

> > TODO: Figure out where the heck empty braces come from.
> 
> I also see these lines with "[]" sometimes; looks to come from 'sleep'.
> 
> And I still see lines with only a "." as the cause; this seems specific to 
> targets marked with the penguin (work queues?).
> 
> > Signed-off-by: Mike Galbraith <efault@....de>
> > Arjan van de Ven <arjan@...radead.org>
> > Cc: Ingo Molnar <mingo@...e.hu>
> > Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > LKML-Reference: <new-submission>
> 
> If Arjan is happy with the patch, please add my:

Probably just a diagnostic, but...

> Reported-and-tested-by: Frans Pop <elendil@...net.nl>

Saved.

	-Mike

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