On Thu, Jun 20, 2024 at 3:35 PM Heng Qi <hengqi@xxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, 19 Jun 2024 17:19:12 -0400, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote:
> > On Thu, Jun 20, 2024 at 12:19:05AM +0800, Heng Qi wrote:
> > > @@ -5312,7 +5315,7 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
> > >
> > > /* Parameters for control virtqueue, if any */
> > > if (vi->has_cvq) {
> > > - callbacks[total_vqs - 1] = NULL;
> > > + callbacks[total_vqs - 1] = virtnet_cvq_done;
> > > names[total_vqs - 1] = "control";
> > > }
> > >
> >
> > If the # of MSIX vectors is exactly for data path VQs,
> > this will cause irq sharing between VQs which will degrade
> > performance significantly.
> >
Why do we need to care about buggy management? I think libvirt has
been teached to use 2N+2 since the introduction of the multiqueue[1].
> > So no, you can not just do it unconditionally.
> >
> > The correct fix probably requires virtio core/API extensions.
>
> If the introduction of cvq irq causes interrupts to become shared, then
> ctrlq need to fall back to polling mode and keep the status quo.
Having to path sounds a burden.
>
> Thanks.
>
Thanks
[1] https://www.linux-kvm.org/page/Multiqueue
> >
> > --
> > MST
> >
>
