Messages in this thread | | | From | Vince Weaver <> | Date | Fri, 17 Mar 2017 10:37:48 -0400 (EDT) | Subject | Re: perf: negative time_enabled issue |
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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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