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SubjectRe: perf: negative time_enabled issue
On Tue, 14 Mar 2017, Vince Weaver wrote:

> So another obscure rdpmc problem, turned up by the PAPI regression tests.
>
> If you use rdpmc, and your event is attached measuring another process,
> and then you ENABLE/DISABLE/ENABLE/rdpmc the event
>
> somehow the userpg->time_enabled field gets a weird value and that
> completely confuses code expecting enabled!=running to mean multiplexing
> is happening.

Still working on this issue. It turns out it's not rdpmc specific, you
can see it with a regular read() too.

So far I've traced it back far enough to see that shadow_ctx_time is
ending up negative for some reason if you do an enable/disable/enable on
an event attached to another process. I'm trying to trace it back further
but it's a slow process.

Vince

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