linux-kernel - Re: Very high CPU load when idle with 3.0-rc1

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Message-ID: <1306761043.7415.5.camel@marge.simson.net>
Date:	Mon, 30 May 2011 15:10:43 +0200
From:	Mike Galbraith <efault@....de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Damien Wyart <damien.wyart@...e.fr>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org, paulmck <paulmck@...ux.vnet.ibm.com>
Subject: Re: Very high CPU load when idle with 3.0-rc1

On Mon, 2011-05-30 at 13:34 +0200, Peter Zijlstra wrote:
> On Mon, 2011-05-30 at 07:59 +0200, Damien Wyart wrote:
> > Hi,
> > 
> > Testing 3.0-rc1 on a core i7 (4 cores + HT), I get a load average of 9.0
> > when idle. No process is shown running or in "D state" in htop. The box
> > is behaving normal, no impression of lag or slowness.
> > 
> > Not sure what other info to include, I guess this should be quite easy
> > to reproduce.
> 
> 
> ---
> Subject: rcu: Cure load woes
> 
> Commit cc3ce5176d83 (rcu: Start RCU kthreads in TASK_INTERRUPTIBLE
> state) fudges a sleeping task' state, resulting in the scheduler seeing
> a TASK_UNINTERRUPTIBLE task going to sleep, but a TASK_INTERRUPTIBLE
> task waking up. The result is unbalanced load calculation.

(darn, 'which' poked me in the eye, but 'how' didn't)

Yup, all better.

	-Mike

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