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

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Message-ID: <alpine.DEB.2.10.1307091059270.675@vincent-weaver-1.um.maine.edu>
Date:	Tue, 9 Jul 2013 11:05:30 -0400 (EDT)
From:	Vince Weaver <vincent.weaver@...ne.edu>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Vince Weaver <vincent.weaver@...ne.edu>,
	Michael Ellerman <michael@...erman.id.au>,
	Vince Weaver <vince@...ter.net>,
	Runzhen Wang <runzhen@...ux.vnet.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	paulus@...ba.org, acme@...hat.com, mingo@...nel.org,
	Stephane Eranian <eranian@...gle.com>,
	sukadev@...ux.vnet.ibm.com, xiaoguangrong@...ux.vnet.ibm.com,
	Will Deacon <will.deacon@....com>
Subject: Re: [PATCH v2 2/2] perf tools: Make Power7 events available for
 perf

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@...daboard:/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.

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.

Vince
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