Re: [Xen-devel] How to make tracking CPU cache-miss on Xen?

[George Dunlap <dunlapg@xxxxxxxxx>]

On Mon, Dec 11, 2017 at 3:05 PM, Boris Ostrovsky
<boris.ostrovsky@xxxxxxxxxx> wrote:
> On 12/11/2017 09:36 AM, Meng Xu wrote:
>> On Mon, Dec 11, 2017 at 8:14 AM, Minjun Hong <nickeysgo@xxxxxxxxx> wrote:
>>> Thanks for your answer, George.
>>>
>>> What I want ultimately is cache misses from the guest, but even I could not 
>>> get the cache misses from dom0 also.
>>> That's why I'm confused as I know, it should be possible to get 
>>> cache-misses from dom0 (is it right??).
>>> I already enabled CONFIG_XEN_HAVE_VPMU of current kernel to get cache 
>>> misses. Is there anything what I miss during Xen install?
>>>
>> If this is for a research project, I would suggest you to write your
>> own code to monitor the cache misses for domU. This could be faster,
>> since it's not complicated to do so.
>>
>> IIRC, PMU in Xen can only monitor the cache misses when VCPUs are
>> pinned to cores.
>
> Counters are virtualized for guests (including dom0) so I am not sure
> pinning is required. Pinning is only needed when you try to collect
> counters for full system.
>
> OTOH, when a VCPU is migrated you start running with a new cache,
> something to keep in mind.

Well if his goal was to measure cache misses based on different Xen
scheduling algorithms, that might be the point. :-)

Minjun: BTW, it's standard on this list to quote inline (as I'm
doing), rather than top-posting (having your reply at the top and the
original mail entirely beneath it).

Thanks,
 -George

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