Re: Random abnormal high CPU sys usage related to timer

[Thomas Gleixner]

On Sat, 27 Aug 2016, Mac Lin wrote:
> Hi Vegard,
> Thanks for the prompt response.
> The commit is introduced since 4.6, but the issue can be reproduced at
> 3.10 (earliest I have ever test). And testing on buildroot+4.7 with
> the commit reverted, the issue still happen.
> 
> In fact, I did a test that ran a script that keep increase a counter
> for 10 seconds on the same CPU. If I ran 2 of it, the number is half
> of running 1. But if I ran it while the issue happened, the counter
> reported is around the same value as the 1 process case. So I doubt
> that it might be an issue of reported number.
> 
> Is there other way to ensure the CPU is "really" doing something?

Tracing will tell you exactly what's going on in the system.

Thanks,

	tglx