linux-kernel - Re: [RFC] para virt interface of perf to support kvm guest os statistics collection in guest os

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Date:	Wed, 9 Jun 2010 12:27:43 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Avi Kivity <avi@...hat.com>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>, kvm@...r.kernel.org,
	Fr??d??ric Weisbecker <fweisbec@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Lin Ming <ming.m.lin@...el.com>,
	Sheng Yang <sheng@...ux.intel.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	oerg Roedel <joro@...tes.org>,
	Jes Sorensen <Jes.Sorensen@...hat.com>,
	Gleb Natapov <gleb@...hat.com>,
	Zachary Amsden <zamsden@...hat.com>, zhiteng.huang@...el.com,
	tim.c.chen@...el.com
Subject: Re: [RFC] para virt interface of perf to support kvm guest os
 statistics collection in guest os


* Peter Zijlstra <peterz@...radead.org> wrote:

> On Wed, 2010-06-09 at 12:41 +0300, Avi Kivity wrote:
> > 
> > >> Disabling the watchdog is unfortunate.  Why is it necessary?
> > >>      
> > > perf always uses NMI, so we disable the nmi_watchdog when a perf_event is
> > > set up in case they might have impact.
> > >    
> > 
> > Ok.  Is that the case for the hardware pmus as well?  If so it might be 
> > done in common code. 
> 
> The x86 hardware pmu implementation disables the lapic watchdog too, but 
> recent kernels come with a watchdog implementation on top of perf, the old 
> lapic one will be depricated.

Note, that code is in -tip, queued for v2.6.36.

	Ingo
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