Re: [GIT PULL] cputime: Full dynticks task/cputime accounting v7

From: Frederic Weisbecker
Date: Mon Jan 28 2013 - 21:38:58 EST


2013/1/29 Steven Rostedt <rostedt@xxxxxxxxxxx>:
> On Mon, 2013-01-28 at 19:02 -0500, Steven Rostedt wrote:
>
>> I've ran these through some basic tests and I don't see any issues. But
>> why did you drop the 'comment' patch that you had in v6?
>>
>> Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
>>
>
> I'm sorry but I need to un-Ack. Due to a test machine setup error, I've
> been testing the same config over and over and not other configs.
>
> Everything works great up until I enabled the dynamic tick and force
> context tracking.
>
> User time seems to be pretty much the same, but the kernel time is
> screwed:
>
> For all my other tests (I finally tested other configs and without your
> patches) I had my kernel time test report something like this:
>
> [root@bxtest ~]# time /work/c/kernelspin 10
>
> real 0m10.001s
> user 0m1.114s
> sys 0m8.886s
>
>
> But after enabling the force context_tracking I get this:
>
> [root@bxtest ~]# time /work/c/kernelspin 10
>
> real 0m10.001s
> user 0m3.769s
> sys 0m6.203s
>
>
> Consistently. All the other runs always had a 1.X 8.X ratio. This seems
> to give 3.7x 6.2x ratio consistently. Maybe it's more accurate then the
> others. Or something else is broken.
>
> I'll look deeper into it.

Please send me your kernelspin so I can test as well.

Thanks.

>
> -- Steve
>
>
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