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

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Message-ID: <20130711105843.GG32197@mudshark.cambridge.arm.com>
Date:	Thu, 11 Jul 2013 11:58:43 +0100
From:	Will Deacon <will.deacon@....com>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Michael Ellerman <michael@...erman.id.au>,
	Vince Weaver <vince@...ter.net>,
	Runzhen Wang <runzhen@...ux.vnet.ibm.com>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"paulus@...ba.org" <paulus@...ba.org>,
	"acme@...hat.com" <acme@...hat.com>,
	"mingo@...nel.org" <mingo@...nel.org>,
	Stephane Eranian <eranian@...gle.com>,
	"sukadev@...ux.vnet.ibm.com" <sukadev@...ux.vnet.ibm.com>,
	"xiaoguangrong@...ux.vnet.ibm.com" <xiaoguangrong@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 2/2] perf tools: Make Power7 events available for perf

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@...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.

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
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