Re: windows 2003 smp guest

[Farkas Levente <lfarkas-lWVWdrzSO4GHXe+LvDLADg@public.gmane.org>]

Luca wrote:
> On 9/20/07, Farkas Levente <lfarkas-lWVWdrzSO4GHXe+LvDLADg@public.gmane.org> wrote:
>> Dor Laor wrote:
>>> Haydn Solomon wrote:
>>>> I have a question on guest smp performance. If I have a host with core
>>>> 2 duo, should a kvm guest perform better using -smp 2 as opposed to
>>>> not using -smp 2?
>>>>
>>> Well, it depends:
>>> In general Avi measured 40% performance increase for using a second cpu
>>> in the guest. This was long time ago,
>>> before the in-kernel-apic implementation. It might improve the gain of
>>> the additional cpu.
>>>
>>> On the other hand, for 32 bit windows, using ACPI HAL has pretty big
>>> overhead at the moment. Since it is a must
>>> for smp guest, it might be slower than running non-acpi single cpu VM.
>> can you tell me what does the HAL means here? and what's kind of HAL
>> exists what are the advantage/disadvantages them. how can i
>> change/configure this?
> 
> Hardware Abstraction Layer. See:
> http://support.microsoft.com/kb/99588
> http://en.wikipedia.org/wiki/Architecture_of_Windows_NT

but if it's part of the windows, how can a user of kvm can change or use
different version? or windows itself has more hal inside and if we run
single cpu versus smp kvm for windows the use different hal? and what
other hel can be indirectly selected by this way?

-- 
  Levente                               "Si vis pacem para bellum!"

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