linux-kernel - Re: Strange behavior of perf top with PEBS

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Message-ID: <20160720143842.GB25992@krava>
Date:	Wed, 20 Jul 2016 16:38:42 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Nikolay Borisov <kernel@...p.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	andi@...stfloor.org
Subject: Re: Strange behavior of perf top with PEBS

On Wed, Jul 20, 2016 at 04:34:17PM +0200, Jiri Olsa wrote:
> On Wed, Jul 20, 2016 at 04:28:34PM +0300, Nikolay Borisov wrote:
> > Hello,
> > 
> > Running perf version 4.4.14.g0cb188d (no modification to the PMU/perf
> > code) I observed that "perf top" counts no cycles and produces no
> > output. After a bit of head scratching and testing I figured that
> > running "perf top -e cycles" actually works whereas the default option
> > is equivalent to running "perf top -e cycles:p". So the latter version
> > seems to not work on my machine.
> 
> hum, I think Core2 has PEBs valid only for instructions not cycles..
> 
> I'll check why perf top forcing the precise for cycles
> I thought we had that automated already

oops, too soon ;) we have:

perf/x86/intel: Fix Core2,Atom,NHM,WSM cycles:pp events
commit 517e6341fa123ec3a2f9ea78ad547be910529881
Author: Peter Zijlstra <peterz@...radead.org>
Date:   Sat Apr 11 12:16:22 2015 +0200


so i guess it should work.. checking ;-)

jirka