Re: Virtualization of the CPU Performance Monitoring Unit

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Mon, Apr 16, 2012 at 04:16:07PM +0800, Lin Ming wrote:
> On Wed, Apr 11, 2012 at 10:30 PM, Lin Ming <mlin@ss.pku.edu.cn> wrote:
> 
> [....]
> 
> >> That isn't actually true. If you run it, you will see it working
> >> in the guest - it just that it does not use the performence counters
> >> but instead uses the timer to sample data.
> >
> > Right, I mean "hardware event" does not work.
> >
> > Hardware event, for example, perf top -e cycles, does not work.
> 
> Just found that vpmu is disabled by default.
> You need to pass xen boot parameter "vpmu" to make hardware event work.

Oh, I wonder why it was disabled by default? Wei, would you know
by any chance?

> 
> > Software event, for example, perf top -e cpu-clock, works.
> 
> So both hardware and software event work in DomU.
> Great!

Excellent!
> 
> >
> >>
> >> > Run "perf top", but no data was collected.
> >>
> >> Hm, I am able to collect data using Fedora Core 16 PV guest.
> >> For dom0 or domU? For dom0 there is a bug somewhere where
> >
> > For domU HVM guest.
> > I have problem to run domU PV guest. Still looking at it.
> >
> >> the machine crashes after 30 seconds or so - hadn't actually
> >> gotten to the bottom of it. There was an email thread:
> >> https://lkml.org/lkml/2012/2/12/74 about this.
> >>
> >> Patches are most welcome!
> 
> Here are the patches.
> https://lkml.org/lkml/2012/4/15/12

Let me play with them a bit. At first glance they look ok - but I recall
Peter Z saying something about not implementing the IRQ WORKER, but I can't
recall the reasons.
> 
> Regards,
> Lin Ming