Re: [PATCH v2 2/2] perf tools: Make Power7 events available for perf

[Will Deacon <will.deacon@arm.com>]

On Tue, Jul 09, 2013 at 04:05:30PM +0100, Vince Weaver wrote:
> On Tue, 9 Jul 2013, Peter Zijlstra wrote:
> 
> > On Mon, Jul 08, 2013 at 10:24:34PM -0400, Vince Weaver wrote:
> > > 
> > > So something like they have on ARM?
> > > 
> > > vince@pandaboard:/sys/bus/event_source/devices$ ls -l
> > > lrwxrwxrwx 1 root root 0 Jul  8 21:57 ARMv7 Cortex-A9 -> ../../../devices/ARMv7 Cortex-A9
> > > lrwxrwxrwx 1 root root 0 Jul  8 21:57 breakpoint -> ../../../devices/breakpoint
> > > lrwxrwxrwx 1 root root 0 Jul  8 21:57 software -> ../../../devices/software
> > > lrwxrwxrwx 1 root root 0 Jul  8 21:57 tracepoint -> ../../../devices/tracepoint
> > 
> > Right so what I remember of the ARM case is that their /proc/cpuinfo isn't
> > sufficient to identify their PMU. And they don't have a cpuid like instruction
> > at all.
> 
> libpfm4 uses the
>    CPU part	: 0xc09
> line in /proc/cpuinfo on ARM, and that's enough for the processors PAPI 
> supports (Cortex A8/A9/A15 plus the 1176 on the raspberry-pi).  I'm 
> guessing it wouldn't be enough if we wanted to support *all* ARMs with
> PMUs.

The CPU part you cite is actually A9-specific, so you probably want to
probe each CPU specifically. Take a look at the cpuinfo parsing in OProfile
(used by operf).

> And speaking of ARM, I should be railing at them for breaking the ABI too, 
> with their (understandable yet still ABI breaking) decision to remove 
> BogoMIPS from /proc/cpuinfo.  That change will impact PAPI as well as 
> various other programs I maintain that have the misfortune of parsing that 
> file.

Really? Why are you checking for that line at all?

Will