linux-kernel - Re: [PATCH 00/10] perf, x86: Add northbridge counter support for AMD family 15h

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Date:	Wed, 20 Jun 2012 10:54:53 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	Robert Richter <robert.richter@....com>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 00/10] perf, x86: Add northbridge counter support for
 AMD family 15h

On Wed, 2012-06-20 at 10:36 +0200, Stephane Eranian wrote:
> 
> I dont' quite understand the design choice here. In Fam15h, there is a clean
> design for the uncore PMU. It has its own distinct set of 4 counters. Unlike
> Fam10h, where you program core counters to access the NB counters. So
> why not like with Intel uncore, create a separate NB PMU which would
> advertise its characteristics? That does not preclude re-using the existing
> AMD-specific routines wherever possible. I think the advantage is that
> muxing or starting/stopping of the core PMU would not affect uncore and
> vice-versa for instance. Wouldn't this also alleviate the problems with
> assigning indexes to uncore PMU counters? 

Quite agreed, it also avoids making a trainwreck of the counter rotation
on overload.


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