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Date: Tue, 21 Jul 2015 16:08:28 -0400 (EDT) From: Vince Weaver <vincent.weaver@...ne.edu> To: Peter Zijlstra <peterz@...radead.org> cc: Vince Weaver <vincent.weaver@...ne.edu>, linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org> Subject: Re: perf: multiplexing broken on amd fam16h? On Tue, 21 Jul 2015, Peter Zijlstra wrote: > On Tue, Jul 21, 2015 at 02:14:54PM -0400, Vince Weaver wrote: > > Hello > > > > I have a new AMD A8 system and perf multiplexing support is acting weird. > > > > If I run the perf_event_tests check_multiplexing test it fails like this: > > > > Event TotalCount RawCount Scale ScaledCount Error > > 0 500282143 150403975 -2.00 (c8050b5 fffffffff9c224ef) -300807950 160.13% > > > > So the problem is that the TOTAL_TIME_RUNNING value is negative, which as > > far as I know shouldn't be possible. > > Correct, that should not happen. I don't have a Fam16 machine, but I can > try and stare at the code a wee bit. Although there's another few perf > issues I am still looking into as well :/ well I've traced it back to see that in update_event_times() run_end is less than event->tstamp_running, which is why the result is negative. [ 1279.857205] VMW: 1 run_end=1279846999345 tstamp_running=1279929016607 [ 1279.857222] VMW: 0 run_end=1279855184453 tstamp_running=1279931111760 It seems to happen both in the PERF_EVENT_STATE_INACTIVE and !PERF_EVENT_STATE_INACTIVE cases. tracking back why those values are wrong is proving to be a bit trickier. Vince -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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