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

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Message-ID: <alpine.DEB.2.10.1307082204550.26280@vincent-weaver-1.um.maine.edu>
Date:	Mon, 8 Jul 2013 22:24:34 -0400 (EDT)
From:	Vince Weaver <vincent.weaver@...ne.edu>
To:	Michael Ellerman <michael@...erman.id.au>
cc:	Peter Zijlstra <peterz@...radead.org>,
	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,
	vincent.weaver@...ne.edu, 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 Tue, 9 Jul 2013, Michael Ellerman wrote:

> On Thu, Jul 04, 2013 at 02:57:00PM +0200, Peter Zijlstra wrote:
> > 
> > Right; I think Stephane and Jiri are in favour of creating a 'new' project that
> > includes just the event definitions in a plain text format and a little library
> > with parser to be used by all interested parties.
> 
> OK that would be great.
> 
> The part that seems to be missing to make that work is we have no way of
> matching the PMU that appears in /sys with a list of events.
> 
> Eg. on my system I have /sys/bus/event_source/devices/cpu - but there's
> nothing in there to identify that it's a Sandy Bridge.

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

> 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?

People have done event lists in userspace for years.  Why must it be the 
kernel's job?

Vince Weaver
vincent.weaver@...ne.edu
http://www.eece.maine.edu/~vweaver/
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