Re: Questing regarding KVM Guest PMU

[Gleb Natapov <gleb@redhat.com>]

On Wed, Apr 04, 2012 at 12:24:17AM +0530, shashank rachamalla wrote:
> On Wed, Apr 4, 2012 at 12:13 AM, shashank rachamalla
> <shashank.rachamalla@gmail.com> wrote:
> > On Tue, Apr 3, 2012 at 10:28 PM, Gleb Natapov <gleb@redhat.com> wrote:
> >> 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?
> >>
> > both. qemu command line below.
> > sudo /usr/local/bin/qemu-system-x86_64 -drive
> > file=vdisk1.img,if=virtio -cpu host -m 2000 -net nic,model=virtio -net
> > user
> >
> 
> please find more info ( /proc/cpuinfo and uname of both host and guest
> ) in attached files.
> 
oprofile does not work for me even on the host. After trying to use it I can
see why perf was written in the first place.

--
			Gleb.