On Tue, Nov 8, 2011 at 12:10 PM, 陳韋任 <che...@iis.sinica.edu.tw> 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