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

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Date:	Mon, 1 Feb 2010 18:22:06 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
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, Feb 1, 2010 at 5:47 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> 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),
>
_P means programmable (counter).

on my NHM:

pfmon -v -eunhalted_core_cycles,unhalted_reference_cycles,cpu_clk_unhalted:ref_p
 ./noploop 10
[FIXED_CTRL(pmc16)=0xaa0 pmi0=1 en0=0x0 any0=0 pmi1=1 en1=0x2 any1=0
pmi2=1 en2=0x2 any2=0] UNHALTED_CORE_CYCLES UNHALTED_REFERENCE_CYCLES
[PERFEVTSEL0(pmc0)=0x51013c event_sel=0x3c umask=0x1 os=0 usr=1
anythr=0 en=1 int=1 inv=0 edge=0 cnt_mask=0] CPU_CLK_UNHALTED
noploop for 10 seconds

29292225749 UNHALTED_CORE_CYCLES
29292249954 UNHALTED_REFERENCE_CYCLES
 1331465398 CPU_CLK_UNHALTED:REF_P

REF_P runs at 133MHz. Core at 2.93GHz.


> 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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Stephane Eranian  | EMEA Software Engineering
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