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

Ingo Molnar
2010-03-16T16:36:00Z

* Frank Ch. Eigler <fche@redhat.com> wrote:

> 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. [...]

It means something like my example of 'extended to guest space'
/proc/kallsyms:

> > [...]
> >
> > ( 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.)

To me it sounds like an example supporting my point. /proc/kallsyms is a
service by the kernel, and 'perf kvm' desires this to be extended to guest
space as well.

Thanks,

Ingo