linux-kernel - Re: [PATCH] perf_events: fix bug in hw_perf

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Date:	Mon, 01 Feb 2010 17:47:17 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, paulus@...ba.org,
	davem@...emloft.net, fweisbec@...il.com, robert.richter@....com,
	perfmon2-devel@...ts.sf.net, eranian@...il.com
Subject: Re: [PATCH] perf_events: fix bug in hw_perf_enable()

On Mon, 2010-02-01 at 17:12 +0100, Stephane Eranian wrote:
> > btw, I've also added the below, from what I can make from the docs
> fixed
> > counter 2 is identical to arch perf event 0x013c, as per table A-1
> and
> > A-7. Both are called CPU_CLK_UNHALTED.REF, except for Core2, where
> > 0x013c is called CPU_CLK_UNHALTED.BUS.
> >
> 
> If you measure 0x013c in a generic counter or in fixed counter 2
> it will count the same thing but not at the same rate.
> This is true on Core2, Atom, Nehalem, Westmere. The ratio is the
> clock/bus ratio.

But for Nehalem and Westmere event 0x3c umask 0x01 is referred to as
CPU_CLK_UNHALTED.REF_P (Tables A-2 and A-4), 

Fixed Counter 2 is referred to as CPU_CLK_UNHALTED.REF (Table A-7).

For Core2 and Atom (Table A-8, A-9) it is called CPU_CLK_UNHALTED.BUS,
for these entries there is talk about a fixed ratio.

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