linux-kernel - Re: [PATCH 4/4] perf, x86: Add PERF_COUNT_HW_NMI

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Message-ID: <BANLkTimh80LorfC8O-HOPAAWK9BLYNjcXA@mail.gmail.com>
Date:	Fri, 22 Apr 2011 12:43:38 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Don Zickus <dzickus@...hat.com>, "x86@...nel.org" <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 4/4] perf, x86: Add PERF_COUNT_HW_NMI_WATCHDOG event

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@...e.hu> wrote:
>
> * Don Zickus <dzickus@...hat.com> wrote:
>
>> From: Cyrill Gorcunov <gorcunov@...il.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
>
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