Re: [PATCH 4/4] perf, x86: Add PERF_COUNT_HW_NMI_WATCHDOG event

[Cyrill Gorcunov <gorcunov@gmail.com>]

P4 cant move events between counters in compare with architectural
event so when nmi-watchdog is used perf top is blocked because it
needs same counters but the counters already borrowed for watchdog. as
result we need a different event and counters for watchdog.

Ingo, nonsleeping cycles is from intel sdm, so when someone start
reading this code in future will find this term in sdm fast. or i
could put the reference from sdm itself here, hm?

On Friday, April 22, 2011, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Don Zickus <dzickus@redhat.com> wrote:
>
>> From: Cyrill Gorcunov <gorcunov@gmail.com>
>>
>> Due to restriction and specifics of Netburst PMU we need
>> a separated event for NMI watchdog. Note that on all other
>> than P4 PMU cpus this event is a simple alias for PERF_COUNT_HW_CPU_CYCLES.
>>
>> This event is only used by x86 for now so no other archs involved.
>
> hm, there's no explanation exactly why this is needed and what the alternatives
> are.
>
> This sentence:
>
>> +  /* we use that named non-sleeping calls */
>
> does not parse for me.
>
> Thanks,
>
>         Ingo
>