From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: [PATCH] Enhance perf to collect KVM guest os statistics from
 host side
Date: Wed, 17 Mar 2010 05:54:45 +0200
Message-ID: <4BA05285.3070903@redhat.com>
References: <20100316130840.GA24808@elte.hu> <4B9F84C0.70706@redhat.com> <20100316133114.GB575@elte.hu> <y0mbpeo1f1y.fsf@fche.csb> <20100316155221.GA19699@elte.hu> <4B9FC11A.1070507@linux.vnet.ibm.com> <20100316175243.GC23859@elte.hu> <4B9FC8B2.6070404@linux.vnet.ibm.com> <20100316182809.GA26602@elte.hu> <4BA00E6A.7080903@linux.vnet.ibm.com> <20100317004136.GC17472@redhat.com>
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Cc: Anthony Liguori <aliguori@linux.vnet.ibm.com>,
	Ingo Molnar <mingo@elte.hu>,
	"Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Sheng Yang <sheng@linux.intel.com>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	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>, ziteng.huang@intel.com
To: "Frank Ch. Eigler" <fche@redhat.com>
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On 03/17/2010 02:41 AM, Frank Ch. Eigler wrote:
> Hi -
>
> On Tue, Mar 16, 2010 at 06:04:10PM -0500, Anthony Liguori wrote:
>    
>> [...]
>> The only way to really address this is to change the interaction.
>> Instead of running perf externally to qemu, we should support a perf
>> command in the qemu monitor that can then tie directly to the perf
>> tooling.  That gives us the best possible user experience.
>>      
> To what extent could this be solved with less crossing of
> isolation/abstraction layers, if the perfctr facilities were properly
> virtualized?
>    

That's the more interesting (by far) usage model.  In general guest 
owners don't have access to the host, and host owners can't (and 
shouldn't) change guests.

Monitoring guests from the host is useful for kvm developers, but less 
so for users.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.