Re: Questing regarding KVM Guest PMU

[Gleb Natapov <gleb@redhat.com>]

On Tue, Apr 03, 2012 at 07:20:04PM +0530, shashank rachamalla wrote:
> On Mon, Mar 19, 2012 at 12:37 PM, Gleb Natapov <gleb@redhat.com> wrote:
> > On Mon, Mar 19, 2012 at 12:20:30PM +0530, shashank rachamalla wrote:
> >> On Sun, Mar 18, 2012 at 10:21 PM, Gleb Natapov <gleb@redhat.com> wrote:
> >> > On Sun, Mar 18, 2012 at 09:47:55PM +0530, shashank rachamalla wrote:
> >> >> >> I guess things are working fine with perf. But why not with oprofile ?
> >> >> >>
> >> >> > Looks like it. I never tried oprofile. Will try to reproduce your
> >> >> > problem and see what oprofile is doing.
> >> >>
> >> >> I am using ubuntu 10.04 with 2.6.32-21-generic kernel as guest and
> >> >> oprofile 0.9.6.
> >> >> Also, I have tried to capture kvm-events ( perf patch ) in host while
> >> >> running oprofile and perf in guest.
> >> >> Please see the attachment. I have run the tests in three cases for the
> >> >> around 5 secs.
> >> >>
> >> >> There are more number of MSR reads and writes in case of perf which I
> >> >> think is normal. However, there are very few MSR reads and writes with
> >> >> oprofile. Also, the number of NMI exceptions are too high in case of
> >> >> oprofile.
> >> >>
> >> > Which host kernel are you using? Try latest kvm.git and check if you see
> >> > something unusual in dmesg.
> >>
> >> Currenly running 3.3.0-rc5. will try with the latest source from kvm
> >> git and let you know.
> >>
> >>
> > Thanks, there were some fixes that didn't make it into 3.3. rdpmc
> > instruction emulation fix is one of them. If oprofile uses it this can
> > explain the problem.
> >
> I have tried with latest kvm source from git and also with 3.0 guest
> kernel but oprofile fails to collect any samples on guest. I am using
> a core2duo processor which is considered by oprofile as pentium pro
> model.
> 
core2duo on the host or the guest? What is your qemu command line?

--
			Gleb.