linux-kernel - Re: [sched next] overflowed cpu time for kernel threads in /proc/PID/stat

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Message-ID: <20130821153957.GA2969@swordfish.minsk.epam.com>
Date:	Wed, 21 Aug 2013 18:39:57 +0300
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Stanislaw Gruszka <sgruszka@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org
Subject: Re: [sched next] overflowed cpu time for kernel threads in
 /proc/PID/stat

On (08/20/13 17:42), Frederic Weisbecker wrote:
> On Tue, Aug 20, 2013 at 06:35:50PM +0300, Sergey Senozhatsky wrote:
> > On (08/20/13 17:15), Frederic Weisbecker wrote:
> > > On Tue, Aug 20, 2013 at 02:14:26PM +0300, Sergey Senozhatsky wrote:
> > > Hello,
> > > 
> > > Please upload your config.
> > > 
> > > I'm adding Stanislaw in Cc in case it relates to cputime scaling.
> > >
> > 
> > please find attached.
> > 
> > 	-ss
> 
> > #
> > # CPU/Task time and stats accounting
> > #
> > CONFIG_VIRT_CPU_ACCOUNTING=y
> > CONFIG_VIRT_CPU_ACCOUNTING_GEN=y
> 
> So it happens with full dynticks cputime accounting.
> How reproducable is this? Does it always happen?
> Does it happen with CONFIG_TICK_CPU_ACCOUNTING as well? (you'll
> need to deactivate full dynticks.)

in cputime_adjust() `stime' is greater than `rtime', so `utime = rtime - stime'
sets wrong value.

	-ss
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