Re: [tip:perf/timer] perf: Add per event clockid support

[Stephane Eranian <eranian@google.com>]

On Fri, Mar 27, 2015 at 9:57 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Fri, Mar 27, 2015 at 09:52:25AM -0700, Stephane Eranian wrote:
>> Ok, I see. But on architectures which do not have NMI, they would all
>> be safe. And that would work if they set the PERF_PMU_CAP_NO_NMI flag
>> on their pmu->capabilities.
>
> Indeed so. I have not audited them all as the current 'default' is safe.
>
>> Next, I am trying to understand how perf is going to expose this. I am
>> thinking about this in the context of my jitted code patches.
>
> I send you some preliminary patches for this.
>
>> With this approach, the jit runtime and the perf tool need to agree on
>> the clock they are using. That mean they need to advertise or document
>> the clock they use
>
> This is indeed still missing, I put an XXX question in one of the
> emails to this effect. I suppose we should store the used clockid in the
> data file. I just haven't figured out how all that code works.
>
>> and there needs to be an option in perf record to pass that same
>> clockid.
>
> I did indeed post a patch to do that.

I will switch my jitted patches to your approach to verify that this
actually works.
Thanks.