From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ingo Molnar <mingo@elte.hu>
Subject: Re: [RFC] para virt interface of perf to support kvm guest os
 statistics collection in guest os
Date: Wed, 9 Jun 2010 12:27:43 +0200
Message-ID: <20100609102743.GC1150@elte.hu>
References: <1276054214.2096.383.camel@ymzhang.sh.intel.com>
 <4C0F51DD.3080200@redhat.com>
 <1276075280.2096.427.camel@ymzhang.sh.intel.com>
 <4C0F61D3.9000402@redhat.com>
 <1276078122.2046.1227.camel@twins>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
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>,
	Arnaldo Carvalho de Melo <acme@redhat.com>,
	Cyrill Gorcunov <gorcunov@gmail.com>,
	Lin Ming <ming.m.lin@intel.com>,
	Sheng Yang <sheng@linux.intel.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	oerg Roedel <joro@8bytes.org>,
	Jes Sorensen <Jes.Sorensen@redhat.com>,
	Gleb Natapov <gleb@redhat.com>,
	Zachary Amsden <zamsden@redhat.com>, zhiteng.huang@intel.com,
	tim.c.chen@intel.com
To: Peter Zijlstra <peterz@infradead.org>
Return-path: <linux-kernel-owner@vger.kernel.org>
Content-Disposition: inline
In-Reply-To: <1276078122.2046.1227.camel@twins>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org


* 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