linux-kernel - Re: [PATCH] Enhance perf to collect KVM guest os statistics from host side

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Message-ID: <20100316160822.GE9841@redhat.com>
Date:	Tue, 16 Mar 2010 12:08:22 -0400
From:	"Frank Ch. Eigler" <fche@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Avi Kivity <avi@...hat.com>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Sheng Yang <sheng@...ux.intel.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	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>, ziteng.huang@...el.com
Subject: Re: [PATCH] Enhance perf to collect KVM guest os statistics from host side

Hi -

On Tue, Mar 16, 2010 at 04:52:21PM +0100, Ingo Molnar wrote:
> [...]
> > Perhaps the fact that kvm happens to deal with an interesting application 
> > area (virtualization) is misleading here.  As far as the host kernel or 
> > other host userspace is concerned, qemu is just some random unprivileged 
> > userspace program [...]

> You are quite mistaken: KVM isnt really a 'random unprivileged
> application' in this context, it is clearly an extension of
> system/kernel services.

I don't know what "extension of system/kernel services" means in this
context, beyond something running on the system/kernel, like every
other process.  To clarify, to what extent do you consider your
classification similarly clear for a host is running

* multiple kvm instances run as unprivileged users
* non-kvm OS simulators such as vmware or xen or gdb
* kvm instances running something other than linux

> ( Which can be seen from the simple fact that what started the
> discussion was 'how do we get /proc/kallsyms from the
> guest'. I.e. an extension of the existing host-space /proc/kallsyms
> was desired. )

(Sorry, that smacks of circular reasoning.)

It may be a charming convenience function for perf users to give them
shortcuts for certain favoured configurations (kvm running freshest
linux), but that says more about perf than kvm.


- FChE
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