On Tue, Sep 04, 2012 at 04:55:56PM +0200, Paolo Bonzini wrote:
> Il 04/09/2012 16:47, Michael S. Tsirkin ha scritto:
> >> > static void virtscsi_init_vq(struct virtio_scsi_vq *virtscsi_vq,
> >> > - struct virtqueue *vq)
> >> > + struct virtqueue *vq, bool affinity)
> >> > {
> >> > spin_lock_init(&virtscsi_vq->vq_lock);
> >> > virtscsi_vq->vq = vq;
> >> > + if (affinity)
> >> > + virtqueue_set_affinity(vq, virtqueue_get_queue_index(vq) -
> >> > + VIRTIO_SCSI_VQ_BASE);
> >> > }
> >> >
> > This means in practice if you have less virtqueues than CPUs,
> > things are not going to work well, will they?
>
> Not particularly. It could be better or worse than single queue
> depending on the workload.
Well interrupts will go to CPU different from the one
that sends commands so ...
> > Any idea what to do?
>
> Two possibilities:
>
> 1) Add a stride argument to virtqueue_set_affinity, and make it equal to
> the number of queues.
>
> 2) Make multiqueue the default in QEMU, and make the default number of
> queues equal to the number of VCPUs.
>
> I was going for (2).
>
> Paolo
3. use per target queue if less targets than cpus?
--
MST
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