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

Will Deacon
2010-07-02T12:57:15Z

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