linux-kernel - Re: Very high CPU values in top on idle system (3.0-rc1)

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Message-ID: <20110530182356.GA1762@x4.trippels.de>
Date:	Mon, 30 May 2011 20:23:56 +0200
From:	Markus Trippelsdorf <markus@...ppelsdorf.de>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Very high CPU values in top on idle system (3.0-rc1)

On 2011.05.30 at 20:05 +0200, Peter Zijlstra wrote:
> On Mon, 2011-05-30 at 19:39 +0200, Markus Trippelsdorf wrote:
> > I get very high CPU values when I run 'top' on my (mostly) idle system
> > with 3.0-rc1. For example mpd was always in the 1-2% range and is now
> > constantly over 50%. 
> > 
> > This is caused by:
> > 
> > commit 317f394160e9beb97d19a84c39b7e5eb3d7815a8
> > Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > Date:   Tue Apr 5 17:23:58 2011 +0200
> > 
> >     sched: Move the second half of ttwu() to the remote cpu
> > 
> > When I revert the above I see sane CPU values again.
> 
> So: echo NO_TTWU_QUEUE > /debug/sched_features, also cures it?

Yes.

> What architecture, what .config, and can you see it with anything other
> than mpd (yum search mpd, only seems to result in mpd clients not the
> actual server).

Yes, mpd was just an example. _Every_ program that would normally show in
the 1-5% CPU range is now in the 30-70% range (X, xterm, etc.).

I'm running an AMD Phenom II X4 in 64-bit mode.
My config is attached.

-- 
Markus

View attachment "config" of type "text/plain" (52839 bytes)