Re: [RFC] Performance monitoring units and KVM

[Avi Kivity <avi@qumranet.com>]

Markus Armbruster wrote:
> Balaji Rao <balajirrao@gmail.com> writes:
>
>   
>> Hi all!
>>
>> Earlier it was suggested that we go ahead with emulating Perf Mon Events in 
>> exposing it to the guest. The serious limitation in this approach is that we 
>> end up exposing only a small number of events to the guest, even though the 
>> host hardware is capable of much more. The only benefit this approach offers is 
>> that, it doesn't break live migration.
>>
>> The other option is to pass through the real PMU to the guest. I believe this 
>> approach is far better in the sense that,
>>     
>
> Do we really have an either/or alternative here?
>
>   

I think that PMU pass through makes more sense, due to the nature of 
existing non-paravirtualized tools.

> There are ways to use the PMU in guests that don't require costly
> virtualization of the real PMU.  They put the guest's performance
> monitoring interface at a level higher than hardware PMU.
>   

On the other hand, they will work only on very new guests.  Paravirt pmu 
makes sense, but it cannot replace the hardware pmu interface.


-- 
error compiling committee.c: too many arguments to function


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