Re: [PATCH v3 0/3] perf: User/kernel time correlation and event generation

[Andy Lutomirski]

On Mon, Nov 3, 2014 at 4:28 PM, Pawel Moll <pawel.moll@xxxxxxx> wrote:
> From: Pawel Moll <mail@xxxxxxxxxxxxx>
> Thomas suggested solution which gets down to my original proposal for
> sched/monotonic clock correlation - an additional sample type so events
> can be "double stamped" using different clock sources providing
> synchronisation points for later time approximation. I've just extended
> the implementation with configuration value to select the clock source.
> If the first patch (making perf timestamps monotonic) gets accepted,
> there will be no immediate need for this one, but I'd like to gain some
> feedback anyway.
>

I have nothing intelligent to add to the potentional Thomas/Ingo
showdown, but I do have a related thought. :)

If you're going to add double-stamped packets, can you also add a
syscall to read multiple clocks at once, atomically?  Or can you
otherwise add a non-perf mechanism to get at this data?

Because the realtime to monotonic offset is really quite useful for
things like this, and it seems silly to make people actually open a
perf_event to get at it.

--Andy
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