Re: [Qemu-devel] multiprocessor on kvm

[Stefan Hajnoczi]

On Tue, Nov 8, 2011 at 12:10 PM, 陳韋任 <address@hidden> wrote:
> On Tue, Nov 08, 2011 at 08:04:44PM +0800, 陳韋任 wrote:
>> > I am wondering that when one uses qemu with kvm. How many cores are
>> > exposed and available to the guest os ( assuming the host has 4 cores
>> > ). is this configurable ?
>>
>>   QEMU provides "-smp" option, but those virtual cpus are scheduled in
>> round-robin fashion. In other words, it's not real parallelism. I don't
>> know if there is any difference with kvm enabled.
>
>  IIRC, kvm uses QEMU for device emulation only. Those virtual cpus are
> ran on physical cpus simultaneously.

Right, qemu -enable-kvm will run a thread for each vCPU.  So you get
true SMP parallelism.

QEMU without KVM mode, on the other hand, does round-robin scheduling
of vCPUs and does not take advantage of multiprocessor hosts.

Stefan