Re: KVM Processor cache size

[Andre Przywara <andre.przywara@amd.com>]

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