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Subject: Re: [RFC] [PATCH] perf, x86: Add PERF_COUNT_HW_NMI_WATCHDOG event
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: lkml <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
        Lin Ming <ming.m.lin@intel.com>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Frederic Weisbecker <fweisbec@gmail.com>
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Date: Fri, 01 Apr 2011 12:53:14 +0200
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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?