linux-kernel - Re: [RFC] [PATCH] perf, x86: Add PERF_COUNT_HW_NMI

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Date:	Fri, 01 Apr 2011 15:05:04 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	lkml <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Lin Ming <ming.m.lin@...el.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [RFC] [PATCH] perf, x86: Add PERF_COUNT_HW_NMI_WATCHDOG event

On 04/01/2011 02:53 PM, Peter Zijlstra wrote:
> On Fri, 2011-04-01 at 01:16 +0400, Cyrill Gorcunov wrote:
>> Because of Netburst HW restriction we can't move events arbitrary
>> between counters and this makes 'perf top' unable to run if nmi-watchdog
>> is running (since both uses PERF_COUNT_HW_CPU_CYCLES but such event is
>> bound to run on a few counters only). So as a workaround we could count that named
>> non-sleeping ticks (as oprofile does) and both perf top and nmi-watchdog would co-exsist
>> without conflicts but kernel needs to know about such specifics -- so PERF_COUNT_HW_NMI_WATCHDOG
>> event is introduced. This event is an alias of PERF_COUNT_HW_CPU_CYCLES for non-P4 x86
>> architecture so nothing much changed I think.
>>
>> Please review, I might be missing something. Also comments on idea is quite welcome since
>> it touches ABI part.
> 
> 
>>  arch/x86/kernel/cpu/perf_event_amd.c   |    1 +
>>  arch/x86/kernel/cpu/perf_event_intel.c |    1 +
>>  arch/x86/kernel/cpu/perf_event_p4.c    |   15 +++++++++++++++
>>  arch/x86/kernel/cpu/perf_event_p6.c    |    1 +
>>  include/linux/perf_event.h             |    1 +
>>  kernel/watchdog.c                      |    2 +-
>>  6 files changed, 20 insertions(+), 1 deletions(-)
> 
> is x86 the only arch using the watchdog things?

Hm, good question. The powerpc, sparc, sh, arm, mips have PERF_COUNT_HW_CPU_CYCLES.
Seems I've missed those archs. Thanks Peter, will take a look.

-- 
    Cyrill
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