linux-kernel - Re: [REGRESSION] [Linux 3.2] top/htop and all other CPU usage metering applications has gone crackers

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Message-ID: <20111128195533.GA26460@mac.home>
Date:	Mon, 28 Nov 2011 20:55:34 +0100
From:	Tino Keitel <tino.keitel@...ei.de>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	linux-kernel@...r.kernel.org,
	"Artem S. Tashkinov" <t.artem@...os.com>
Subject: Re: [REGRESSION] [Linux 3.2] top/htop and all other CPU usage
 metering applications has gone crackers

On Sun, Nov 27, 2011 at 12:45:57 +0100, Rafael J. Wysocki wrote:
> On Sunday, November 27, 2011, Tino Keitel wrote:
> > On Thu, Nov 24, 2011 at 21:05:53 +0100, Tino Keitel wrote:
> > > On Thu, Nov 24, 2011 at 10:30:15 +0000, Artem S. Tashkinov wrote:
> > > > Hello,
> > > > 
> > > > I'd like to report a weird regression in Linux 3.2 (running rc3 now) - all CPU metering applications have gone terribly mad
> > > > under this kernel:
> > > 
> > > I get the same using top, htop and the gnome system monitor with kernel
> > > 3.2 on a Sandy Bridge quad core box, running Debian unstable.
> > 
> > I just tested 3.2-rc2, and see the same bug.
> 
> I'm seeing that too on one of my test boxes, but not all the time
> (i.e. there are periods in which the readings are correct).  The other boxes
> I've tested with 3.2-rc are fine in that respect.
> 
> Also, it seems that it shows 100%-(real load) when it is wrong.  So, it looks
> like there's an overflow somewhere in the CPU load measuring code, at least
> on some CPUs.

Hi,

I reverted this commit and so far it looks good:

commit a25cac5198d4ff2842ccca63b423962848ad24b2
Author: Michal Hocko <mhocko@...e.cz>
Date:   Wed Aug 24 09:40:25 2011 +0200

    proc: Consider NO_HZ when printing idle and iowait times

I'll report back tomorrow how the kernel behaves.

Regards,
Tino
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