linux-kernel - Re: perf: multiplexing broken on amd fam16h?

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Message-ID: <20150721193224.GW19282@twins.programming.kicks-ass.net>
Date:	Tue, 21 Jul 2015 21:32:24 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	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, 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 :/
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