linux-kernel - Re: [PATCH 2/8] vtime: Use consistent clocks among nohz accounting

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Date:	Mon, 3 Jun 2013 21:48:08 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Stefan Seyfried <stefan.seyfried@...glemail.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>,
	Li Zhong <zhong@...ux.vnet.ibm.com>,
	Mike Galbraith <efault@....de>
Subject: Re: [PATCH 2/8] vtime: Use consistent clocks among nohz accounting

On Mon, Jun 03, 2013 at 11:47:17AM +0200, Stefan Seyfried wrote:
> Am 20.05.2013 18:01, schrieb Frederic Weisbecker:
> > While computing the cputime delta of dynticks CPUs,
> > we are mixing up clocks of differents natures:
> 
> [...]
> 
> > As a consequence, some strange behaviour with unstable tsc
> > has been observed such as non progressing constant zero cputime.
> > (The 'top' command showing no load).
> 
> This happens for example on my trusty ThinkPad X200s (family 6 model 23
> stepping 10 Core 2 duo), seriously confusing its user (me :-).
> 
> > Fix this by only using local_clock(), or its irq safe/remote
> > equivalent, in vtime code.
> > 
> > Reported-by: Mike Galbraith <efault@....de>
> > Suggested-by: Mike Galbraith <efault@....de>
> > Cc: Steven Rostedt <rostedt@...dmis.org>
> > Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> > Cc: Ingo Molnar <mingo@...nel.org>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Borislav Petkov <bp@...en8.de>
> > Cc: Li Zhong <zhong@...ux.vnet.ibm.com>
> > Cc: Mike Galbraith <efault@....de>
> > Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> 
> FWIW:
> Tested-by: Stefan Seyfried <seife+dev@...systems.com>
> 
> This patch fixes the 0% CPU issue on openSUSE Factory kernels for me.

Thanks! The patch has been committed already so I can't add your Tested-by:
but feedbacks on testing are always appeciated.
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