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Re: [Qemu-devel] multiprocessor on kvm
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] multiprocessor on kvm |
Date: |
Tue, 8 Nov 2011 12:23:26 +0000 |
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