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Re: [Xen-devel] Virtualization of the CPU Performance Monitoring Unit
- To: xen-devel@xxxxxxxxxxxxx
- From: Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>
- Date: Tue, 17 Apr 2012 08:11:19 +0200
- Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Lin Ming <mlin@xxxxxxxxxxxxx>, wei.huang2@xxxxxxx, marcus.granado@xxxxxxxxxx, wei.wang2@xxxxxxx, Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx>
- Delivery-date: Tue, 17 Apr 2012 06:11:57 +0000
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Am Montag 16 April 2012, 13:39:36 schrieb Konrad Rzeszutek Wilk:
> 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@xxxxxxxxxxxxx> 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?
This had to do with a problem in the intel nehalem processors which could cause
endless interrupt loops in the hypervisor if a hvm guest uses the performance
counters so Keir proposed to add the vpmu boot flag.
> > > Software event, for example, perf top -e cpu-clock, works.
> > So both hardware and software event work in DomU.
> > Great!
> > >
> > >>
> > >> > 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
> Xen-devel mailing list
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