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

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Message-ID: <alpine.DEB.2.20.1507221055520.32012@vincent-weaver-1.umelst.maine.edu>
Date:	Wed, 22 Jul 2015 10:57:23 -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 Wed, 22 Jul 2015, Peter Zijlstra wrote:

> On Tue, Jul 21, 2015 at 04:08:28PM -0400, Vince Weaver wrote:
> > 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.
> 
> Can you run with something like the below?

OK, so I have to admit I'm a bit weak on ftrace.  What type of command 
line are you interested in seeing?  The ones I've tried with trace-cmd
have  activated  your trace_printks but there's 500MB of other data mixed 
in so maybe I am doing something wrong.

Vince
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