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SubjectRe: [RFC] perf: need to expose sched_clock to correlate user samples with kernel samples
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On Tue, 2013-02-05 at 22:13 +0000, Stephane Eranian wrote:
> The app requesting the timestamp may not necessarily have an active
> perf session. And by that I mean, it may not be self-monitoring. But it
> could be monitored by an external tool such as perf, without necessary
> knowing it.

Fair enough - I guess eg. JIT engine could generate a timestamped
information about generated symbols which could be then merged with a
stream recorded by the perf tool by yet another tool.

> The timestamp is global or at least per-cpu. It is not tied to a particular
> active event.

I know that the implementation does it now, but is it actually specified
as such? I could imagine a situation where perf_clock() returns time
elapsed since the "current" sys_perf_event_open()... (not that I'd like
it ;-)

Paweł


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