linux-kernel - Re: [RFC][PATCH 00/11] perf pmu interface -v2

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Date:	Fri, 02 Jul 2010 13:55:38 +0100
From:	Will Deacon <will.deacon@....com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	paulus <paulus@...ba.org>,
	stephane eranian <eranian@...glemail.com>,
	Robert Richter <robert.richter@....com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Lin Ming <ming.m.lin@...el.com>,
	Yanmin <yanmin_zhang@...ux.intel.com>,
	Deng-Cheng Zhu <dengcheng.zhu@...il.com>,
	David Miller <davem@...emloft.net>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 00/11] perf pmu interface -v2

Hi Peter,

On Thu, 2010-07-01 at 15:36 +0100, Peter Zijlstra wrote:
> On Fri, 2010-06-25 at 16:50 +0200, Peter Zijlstra wrote:
> 
> > Not exactly sure how I could have messed up the ARM architecture code to
> > make this happen though... will have a peek.
> 
> I did find a bug in there, not sure it could have been responsible for
> this but who knows...
> 
> Pushed out a new git tree with the below delta folded in.
> 
I had a look at this yesterday and discovered a bug in the ARM
backend code, which I've posted a patch for to ALKML:

http://lists.infradead.org/pipermail/linux-arm-kernel/2010-July/019461.html

Unfortunately, with this applied and your latest changes I still
get 0 from pinned hardware counters:

# perf stat -r 5 -e cycles -e instructions -e cs -e faults -e branches -a -- git status

Performance counter stats for 'git status' (5 runs):

                  0  cycles                     ( +-     nan% )
                  0  instructions             #      0.000 IPC     ( +-     nan% )
              88447  context-switches           ( +-  12.624% )
              13647  page-faults                ( +-   0.015% )
                  0  branches                   ( +-     nan% )

The changes you've made to arch/arm/kernel/perf_event.c
look sane. If I get some time I'll try and dig deeper.

Will

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