Re: windows 2003 smp guest

[Dor Laor <dor.laor-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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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.

My guess is that you better use -smp 2.
Dor.
> On 9/18/07, *Haydn Solomon* <haydn.solomon-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
> <mailto:haydn.solomon-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>> wrote:
>
>     I'm going to try the acpi multiprocessor HAL and see how that
>     works. What kind of performance do you get with it?
>
>
>     On 9/18/07, * He, Qing* < qing.he-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org
>     <mailto:qing.he-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>> wrote:
>
>
>
>         >-----Original Message-----
>         >From: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
>         <mailto:kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>
>         >[mailto:kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
>         <mailto:kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>] On Behalf Of
>         Avi Kivity
>         >Sent: 2007年9月18日 22:06
>         >To: Haydn Solomon
>         >Cc: kvm-devel
>         >Subject: Re: [kvm-devel] windows 2003 smp guest
>         >
>         >Haydn Solomon wrote:
>         >> I am interested in installing smp windows 2003 server guest
>         and have
>         >> some questions.
>         >>
>         >> 1.Is windows smp guest working and performing well at this
>         point in kvm?
>         >
>         >It's working will with -no-kvm-irqchip.Not so sure without the
>         switch,
>         >but we're improving things.
>         >
>         >I haven't tested performance very thoroughly.What's your workload?
>
>         It's also working well on my side if the option is not
>         presented :-)
>
>         >
>         >> 2.If question 1 above is true, then what HAL should I choose
>         during
>         >> installation and what other flags should I use when running it?
>         >>
>         >
>         >Good question.What HALs are available for Windows 2003 SMP?
>
>         I'm using ACPI multiprocessor HAL, don't know how MPS
>         multiprocessor HAL works.
>
>         >
>         >--
>         >error compiling committee.c: too many arguments to function
>         >
>         >
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