On Fri, Feb 18, 2022 at 08:43:20AM -0700, Willem de Bruijn wrote:
> On Thu, Feb 17, 2022 at 12:05 PM Andrew Melnichenko <and...@daynix.com> wrote:
> >
> > Hi all,
> >
> > On Mon, Feb 14, 2022 at 12:09 AM Willem de Bruijn
> > <willemdebruijn.ker...@gmail.com> wrote:
> > >
> > > > > > @@ -3113,13 +3270,14 @@ static int virtnet_probe(struct
> > > > > > virtio_device *vdev)
> > > > > > u16 max_queue_pairs;
> > > > > > int mtu;
> > > > > >
> > > > > > - /* Find if host supports multiqueue virtio_net device */
> > > > > > - err = virtio_cread_feature(vdev, VIRTIO_NET_F_MQ,
> > > > > > - struct virtio_net_config,
> > > > > > - max_virtqueue_pairs,
> > > > > > &max_queue_pairs);
> > > > > > + /* Find if host supports multiqueue/rss virtio_net device */
> > > > > > + max_queue_pairs = 1;
> > > > > > + if (virtio_has_feature(vdev, VIRTIO_NET_F_MQ) ||
> > > > > > virtio_has_feature(vdev, VIRTIO_NET_F_RSS))
> > > > > > + max_queue_pairs =
> > > > > > + virtio_cread16(vdev, offsetof(struct
> > > > > > virtio_net_config, max_virtqueue_pairs));
> > > > >
> > > > > Instead of testing either feature and treating them as somewhat equal,
> > > > > shouldn't RSS be dependent on MQ?
> > > >
> > > > No, RSS is dependent on CTRL_VQ. Technically RSS and MQ are similar
> > > > features.
> > >
> > > RSS depends on having multiple queues.
> > >
> > > What would enabling VIRTIO_NET_F_RSS without VIRTIO_NET_F_MQ do?
> >
> > RSS would work.
>
> What does that mean, exactly? RSS is load balancing, does that not
> require multi-queue?
It does, but VIRTIO_NET_F_MQ is a misnomer.
\item[VIRTIO_NET_F_MQ(22)] Device supports multiqueue with automatic
receive steering.
VIRTIO_NET_F_RSS implies multi queue and does not depend on VIRTIO_NET_F_MQ.
--
MST
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