Re: Questing regarding KVM Guest PMU

[Gleb Natapov <gleb@redhat.com>]

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.

--
			Gleb.