Re: [Xen-devel] Questions about Using Perf at Dom0

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 08/29/2016 02:42 PM, Sanghyun Hong wrote:
> Hi Boris, 
>
> I’ve found the
> documentations(https://github.com/torvalds/linux/blob/master/Documentation/ABI/testing/sysfs-hypervisor-pmu)
> in the kernel source code, and it seems like if we change the mode
> from *self* to *all* then we can collect counters for all the domains,
> right?

Yes, this will allow the hypervisor to collect samples from multiple
guests. However, the tool (perf) probably won't be able to properly
process these samples. But you can try.

You will want to run dom0 on all physical processors (i.e. no
dom0_max_vcpus boot option) and pin all VCPUs for both dom0 and the guest.


-boris

>
> All the best,
> Sanghyun.
>
>
>> On Aug 29, 2016, at 12:36 PM, Boris Ostrovsky
>> <boris.ostrovsky@xxxxxxxxxx <mailto:boris.ostrovsky@xxxxxxxxxx>> wrote:
>>
>> On 08/29/2016 09:18 AM, Sanghyun Hong wrote:
>>> Dear Xen-Devel Community:
>>>
>>> I’m a grad student working on measuring performance counters at the
>>> Xen domains. I read this
>>> thread(https://wiki.xenproject.org/wiki/Xen_Profiling:_oprofile_and_perf)
>>> in
>>> web, and it says using Linux perf command will let us collecting
>>> performance counters in both dom0 and domU. Does it mean that we can
>>> collect both of them at once if we run perf command on the dom0? (If
>>> not, does it mean we can collect counters for each domain separately
>>> once we run the perf command in each domain?
>>
>> Profiling both guest and dom0 (and the hypervisor) requires changes to
>> perf and those are not there yet.
>>
>> But you can run perf in each guest (including dom0) separately. Make
>> sure you have vpmu=true boot option.
>>
>> -boris
>>
>>
>>
>>
>>
>



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