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

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Message-ID: <20160720143417.GA25992@krava>
Date:	Wed, 20 Jul 2016 16:34:17 +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 04:28:34PM +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

jirka