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

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Message-ID: <20110623115128.GF10238@sun>
Date:	Thu, 23 Jun 2011 15:51:29 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Don Zickus <dzickus@...hat.com>
Cc:	Stephane Eranian <eranian@...gle.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 07:40:55AM -0400, Don Zickus 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.

As only there will be second/third and so on implementation of hw_nmi_watchdog_set_attr
then indeed it become a problem, for a while it's not, only single
implementation. I personally don't like much __weak linking until there is
no other choise, so explicit general event for x86 in a sake of nmi-watchdog
(without any __weak functions) is my favorite but I'm fine with Stephane proposal
as well, so Don what is your choise?

	Cyrill
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