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

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Message-ID: <20130709081434.GI25631@dyad.programming.kicks-ass.net>
Date:	Tue, 9 Jul 2013 10:14:34 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	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
Subject: Re: [PATCH v2 2/2] perf tools: Make Power7 events available for perf

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.

> > For the cpu you can obviously just detect what processor you're on with
> > cpuid or whatever, but it's a bit of a hack. And that really doesn't
> > work for non-cpu PMUs.
> 
> why is it a hack to use cpuid?

I agree, for x86 cpuid is perfectly fine, as would /proc/cpuinfo be, I suspect
that just the model number is sufficient in most cases, even for uncore stuff.
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