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

From: Frederic Weisbecker
Date: Tue Aug 20 2013 - 11:15:23 EST


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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