Re: [Xen-devel] Virtualization of the CPU Performance Monitoring Unit

[Lin Ming <mlin@xxxxxxxxxxxxx>]

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.

> 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

Regards,
Lin Ming

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