Re: faster boot with -no-kvm?

Avi Kivity
2007-04-12T14:35:19Z

David Abrahams wrote:
> on Thu Apr 12 2007, Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w-AT-public.gmane.org> wrote:
>
>
>> David Abrahams wrote:
>>
>>> When I start my Windows VM with -no-kvm, it seems to boot much more
>>> quickly than without.
>>>
>> You probably have acpi enabled in Windows. This causes massive
>> slowdowns in kvm; the real fix will unfortunately require you to upgrade
>> your hardware.
>>
>
> My physical hardware? Which part?
>

The part that currently doesn't virtualize the apic tpr: the cpu.

It happens that Windows in acpi mode likes to bang on this register
quite a lot, and that the penalty for accessing this register is several
microseconds (instead of nanoseconds). Most of the time in a (virtual)
Windows boot is spent on reading and writing this register.

> Is starting the vm with -no-acpi insufficient? I just realized, I
> haven't been doing that.
>

It won't help if Windows wants acpi, I think.

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