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

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Date:	Tue, 20 Aug 2013 17:15:11 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Stanislaw Gruszka <sgruszka@...hat.com>
Cc:	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 Tue, Aug 20, 2013 at 02:14:26PM +0300, Sergey Senozhatsky wrote:
> Hello,
> 3.11.0-rc6-next-20130820
> 
> at some point an overflowed cpu time is reported in /proc/PID/stat
> 
> cat /proc/10/stat
> 10 (rcu_preempt) S 2 0 0 0 -1 2129984 0 0 0 0 0 406 0 0 20 0 1 0 10 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 18446744073709551615 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0
> cat /proc/10/stat
> 10 (rcu_preempt) S 2 0 0 0 -1 2129984 0 0 0 0 0 406 0 0 20 0 1 0 10 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 18446744073709551615 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0
> cat /proc/10/stat
> 10 (rcu_preempt) S 2 0 0 0 -1 2129984 0 0 0 0 0 407 0 0 20 0 1 0 10 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 18446744073709551615 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0
> cat /proc/10/stat
> 10 (rcu_preempt) S 2 0 0 0 -1 2129984 0 0 0 0 0 407 0 0 20 0 1 0 10 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 18446744073709551615 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0
> cat /proc/10/stat
> 10 (rcu_preempt) S 2 0 0 0 -1 2129984 0 0 0 0 1844674407370 477 0 0 20 0 1 0 10 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 18446744073709551615 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0
> 						^^^^^^^^^
> cat /proc/10/stat
> 10 (rcu_preempt) S 2 0 0 0 -1 2129984 0 0 0 0 1844674407370 597 0 0 20 0 1 0 10 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 18446744073709551615 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0
> 
> (seems there are several more -1UL in output)
> 
> 
> oddly enough, I see this happening only for RCU
> 
>  ps aux | grep rcu
>  root         8  0.0  0.0      0     0 ?        S    12:42   0:00  [rcuc/0]
>  root         9  0.0  0.0      0     0 ?        S    12:42   0:00  [rcub/0]
>  root        10 62422329  0.0  0     0 ?        R    12:42 21114581:37  [rcu_preempt]
>  root        11  0.1  0.0      0     0 ?        S    12:42   0:02  [rcuop/0]
>  root        12 62422329  0.0  0     0 ?        S    12:42 21114581:35  [rcuop/1]
> 
> 	-ss


Hello,

Please upload your config.

I'm adding Stanislaw in Cc in case it relates to cputime scaling.
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