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

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Message-ID: <bd4cb8901002010923q79fa82f5s90a8430b4c037a19@mail.gmail.com>
Date:	Mon, 1 Feb 2010 18:23:29 +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,
	Arjan van de Ven <arjan@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] perf_events: fix bug in hw_perf_enable()

On Mon, Feb 1, 2010 at 5:45 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Mon, 2010-02-01 at 17:14 +0100, Stephane Eranian wrote:
>
>> Using perfmon on Core 2 on a 10s noploop:
>>
>> pfmon -eunhalted_reference_cycles,unhalted_core_cycles,cpu_clk_unhalted:bus
>>  noploop 10
>> noploop for 10 seconds
>> 23869090125 UNHALTED_REFERENCE_CYCLES
>> 23849336873 UNHALTED_CORE_CYCLES
>>  2652122099 CPU_CLK_UNHALTED:BUS
>
> Weird, I used:
>
>  while :; do :; done &
>  while :; do :; done &
>  while :; do :; done &
>  while :; do :; done &
>  perf stat -a -e r013c -e r013c sleep 4
>  killall bash
>
> Which gives:
>
>  Performance counter stats for 'sleep 4':
>
>  244235699509090  raw 0x13c
>  244235695558036  raw 0x13c
>
Strange. I am running mine on a Q6600.
What's yours?

>    4.005485333  seconds time elapsed
>
> And verified it used fixed counter 2 and general purpose counter 0 using
> sysrq-p.
>
> [523417.108402] CPU#0:   gen-PMC0 ctrl:  000000000053013c
> [523417.108403] CPU#0:   gen-PMC0 count: 000000ff80019948
> [523417.108405] CPU#0:   gen-PMC0 left:  000000007fffffff
> [523417.108407] CPU#0:   gen-PMC1 ctrl:  0000000000000000
> [523417.108409] CPU#0:   gen-PMC1 count: 0000000000000000
> [523417.108411] CPU#0:   gen-PMC1 left:  000000007fffb8a8
> [523417.108412] CPU#0: fixed-PMC0 count: 0000000000000000
> [523417.108414] CPU#0: fixed-PMC1 count: 0000000000000000
> [523417.108416] CPU#0: fixed-PMC2 count: 0000010db1db2117
>
> Using -linus, since that doesn't have any of the recent constraint
> patches in that would avoid us from using fixed-PMC2.
>
>



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