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Subject: Re: [RFC] para virt interface of perf to support kvm guest os
 statistics collection in guest os
From: Peter Zijlstra <peterz@infradead.org>
To: Avi Kivity <avi@redhat.com>
Cc: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
       LKML <linux-kernel@vger.kernel.org>, kvm@vger.kernel.org,
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       Zachary Amsden <zamsden@redhat.com>, zhiteng.huang@intel.com,
       tim.c.chen@intel.com
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Date: Wed, 09 Jun 2010 12:08:42 +0200
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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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