linux-kernel - Re: [RFC] perf_events: support for uncore a.k.a. nest units

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Message-ID: <1265054061.24455.244.camel@laptop>
Date:	Mon, 01 Feb 2010 20:54:21 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Corey Ashford <cjashfor@...ux.vnet.ibm.com>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...glemail.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Xiao Guangrong <xiaoguangrong@...fujitsu.com>,
	Dan Terpstra <terpstra@...s.utk.edu>,
	Philip Mucci <mucci@...s.utk.edu>,
	Maynard Johnson <mpjohn@...ibm.com>,
	Carl Love <cel@...ibm.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Masami Hiramatsu <mhiramat@...hat.com>
Subject: Re: [RFC] perf_events: support for uncore a.k.a. nest units

On Mon, 2010-02-01 at 11:39 -0800, Corey Ashford wrote:
> 
> On 1/30/2010 12:42 AM, Peter Zijlstra wrote:
> > On Fri, 2010-01-29 at 15:05 -0800, Corey Ashford wrote:
> >> So you'd read the id from the sysfs topology tree, and then pass that id to the
> >> interface?  That's an interesting approach that eliminates the need to pass a
> >> string pmu path to the kernel.
> >
> > No, the attr.pmu_id would reflect the location in the tree (pci
> > location, or spu number), the pmu id reported would identify the kind of
> > pmu driver used for that particular device.
> >
> > I realized this confusion after sending but didn't clarify, we should
> > come up with a good alternative name for either (or both) uses.
> >
> 
> Ok, just so I'm clear here, is attr.pmu_id a (char *) or some sort of encoded 
> bit field?

Right, currently on x86 we have x86_pmu.name which basically tells us
what kind of pmu it is, but we really don't export that since its
trivial to see that from /proc/cpuinfo, but the ARM people expressed
interest in this because decoding the cpuid equivalent on arm is like
nasty business.

But once we go add other funny pmu's, it becomes interesting to know
what kind of pmu it is and tie possible event sets to them.

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