Re: [PATCH] Perf: Correct Assumptions about Sample Timestamps inPasses

From: Frederic Weisbecker
Date: Thu Dec 26 2013 - 10:30:46 EST


On Thu, Dec 26, 2013 at 10:24:03AM -0500, David Ahern wrote:
> On 12/26/13, 10:14 AM, Frederic Weisbecker wrote:
> >>I was carrying that patch while working on perf-kvm-stat-live last
> >>Fall. It does not solve the problem for live commands, so ended up
> >>dropping it and going with local (to the command) hacks. I still
> >>think for live commands getting a perf_clock timestamp at the start
> >>of a round and using that as the flush time will work best.
> >
> >Ok, but how would you fetch this perf clock timestamp, with an explicit read?
>
> One option is exporting perf_clock to userspace.
>
> Preferably a built-in option, https://lkml.org/lkml/2013/12/10/781,
> but I can go the module route if I have to:
> https://github.com/dsahern/linux/blob/perf-full-monty/README.ahern

I see, that's one of the very verbose threads I've seen lately ;)
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