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Date: Wed, 9 Jun 2010 12:27:43 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Avi Kivity <avi@redhat.com>,
       "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
       LKML <linux-kernel@vger.kernel.org>, kvm@vger.kernel.org,
       Fr??d??ric Weisbecker <fweisbec@gmail.com>,
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       Sheng Yang <sheng@linux.intel.com>,
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       Zachary Amsden <zamsden@redhat.com>, zhiteng.huang@intel.com,
       tim.c.chen@intel.com
Subject: Re: [RFC] para virt interface of perf to support kvm guest os
 statistics collection in guest os
Message-ID: <20100609102743.GC1150@elte.hu>
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* Peter Zijlstra <peterz@infradead.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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