Re: KVM Processor cache size

Andre Przywara
2010-08-02T22:42:19Z

Anthony Liguori wrote:
> On 08/02/2010 08:49 AM, Ulrich Drepper wrote:
>> glibc uses the cache size information returned by cpuid to perform
>> optimizations. For instance, copy operations which would pollute too
>> much of the cache because they are large will use non-temporal
>> instructions. There are real performance benefits.
>
> I imagine that there would be real performance problems from doing live
> migration with -cpu host too if we don't guarantee these values remain
> stable across migration...
Again, -cpu host is not meant to be migrated. There are other
virtualization use cases than cloud-like server virtualization.
Sometimes users don't care about migration (or even the live version),
but want full CPU exposure for performance reasons (think of
virtualizing Windows on a Linux desktop).
I agree that -cpu host and migration should be addressed, but only to a
certain degree. And missing migration experience should not be a road
blocker for -cpu host.

Regards,
Andre.

--
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 488-3567-12