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, 09 Jun 2010 12:08:42 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Avi Kivity <avi@...hat.com>
Cc:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>, kvm@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	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

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.


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