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

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Message-ID: <BANLkTin5sN2FZaQYsnsEkH10OF-GES9MGw@mail.gmail.com>
Date:	Thu, 23 Jun 2011 14:03:50 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	Don Zickus <dzickus@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, Lin Ming <ming.m.lin@...el.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Vince Weaver <vweaver1@...s.utk.edu>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [RFC -tip] perf, x86: Add PERF_COUNT_HW_NMI_WATCHDOG event v2

On Thu, Jun 23, 2011 at 1:53 PM, Cyrill Gorcunov <gorcunov@...il.com> wrote:
> On Thu, Jun 23, 2011 at 01:44:36PM +0200, Stephane Eranian wrote:
>> On Thu, Jun 23, 2011 at 1:40 PM, Don Zickus <dzickus@...hat.com> wrote:
>> > On Thu, Jun 23, 2011 at 03:07:06PM +0400, Cyrill Gorcunov wrote:
>> >> On Thu, Jun 23, 2011 at 01:54:39PM +0400, Cyrill Gorcunov wrote:
>> >> ...
>> >> > >
>> >> > > No new hidden event, just a x86_pmu + a per-arch callbacks.
>> >> >
>> >> > Looks quite good for me, Don? (i'll cook some draft patch for review meanwhile).
>> >> >
>> >> >     Cyrill
>> >>
>> >> Since we are going to make __weak linking anyway maybe something like below
>> >> fit even beter? (untested)
>> >
>> > I don't think the compiler knows what platform you are running on and may
>> > just blindly link your new p4 function for all x86s, which is probably not
>> > what you want.
>> >
>> Don, is right. You need the level of indirection I had in my outline patch.
>>
>> You also don't need the:
>> +       if (wd_attr->type       != PERF_TYPE_HARDWARE ||
>> +          wd_attr->attr.config != PERF_COUNT_HW_CPU_CYCLES)
>> +               return;
>>
>> In the p4 callback given you know your coming in for the watchdog.
>>
>
> Yes, that is why in __weak implementation I dropped it. So guys,
> what we stick with -- __weak with second level indirection?
>
No, first level in watchdog.c, the other callback has to be implemented
from x86_pmu as you had it.

>        Cyrill
>
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