linux-kernel - RE: [Ptools-perfapi] [perfmon2] [PATCH] perf

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Date:	Fri, 22 Jan 2010 18:42:01 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	John McCalpin <mccalpin@...c.utexas.edu>
Cc:	'Dan Terpstra' <terpstra@...s.utk.edu>,
	"eranian@...gle.com" <eranian@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"ptools-perfapi@...s.utk.edu" <ptools-perfapi@...s.utk.edu>,
	"perfmon2-devel@...ts.sf.net" <perfmon2-devel@...ts.sf.net>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"paulus@...ba.org" <paulus@...ba.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"davem@...emloft.net" <davem@...emloft.net>
Subject: RE: [Ptools-perfapi] [perfmon2] [PATCH] perf_events: AMD event
 scheduling (v1)

On Fri, 2010-01-22 at 11:33 -0600, John McCalpin wrote:

> * Think of the system as having four performance monitors per core
> *plus* four performance monitors for the "shared" structures on the
> chip (L3, crossbar, HyperTransport links, memory controllers).

Would have been nice to have them as a separately addressable pmu
instead of shadowing the logical cpu's pmu.

But that's all ancient history of course..

> There is an additional hazard when working with early K8 processors --
> a hardware bug causes the counts of all shared counters to be reset to
> zero any time any shared register is programmed.  This makes
> "protecting" users somewhat more difficult....

Could you qualify early k8 a bit more, it shouldn't be hard to add a
quirk for a specific set of cpus to read/reset all counters before
writing to the shared pmu.

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