Re: [net-next RFC V5 4/5] virtio_net: multiqueue support

[Jason Wang]

On 07/06/2012 04:02 AM, Amos Kong wrote:
> On 07/05/2012 06:29 PM, Jason Wang wrote:
> > This patch converts virtio_net to a multi queue device. After negotiated
> > VIRTIO_NET_F_MULTIQUEUE feature, the virtio device has many tx/rx queue pairs,
> > and driver could read the number from config space.
> >
> > The driver expects the number of rx/tx queue paris is equal to the number of
> > vcpus. To maximize the performance under this per-cpu rx/tx queue pairs, some
> > optimization were introduced:
> >
> > - Txq selection is based on the processor id in order to avoid contending a lock
> >    whose owner may exits to host.
> > - Since the txq/txq were per-cpu, affinity hint were set to the cpu that owns
> >    the queue pairs.
> >
> > Signed-off-by: Krishna Kumar<krkumar2@xxxxxxxxxx>
> > Signed-off-by: Jason Wang<jasowang@xxxxxxxxxx>
> > ---
> ...
>
> >   static int virtnet_probe(struct virtio_device *vdev)
> >   {
> > -	int err;
> > +	int i, err;
> >   	struct net_device *dev;
> >   	struct virtnet_info *vi;
> > +	u16 num_queues, num_queue_pairs;
> > +
> > +	/* Find if host supports multiqueue virtio_net device */
> > +	err = virtio_config_val(vdev, VIRTIO_NET_F_MULTIQUEUE,
> > +				offsetof(struct virtio_net_config,
> > +				num_queues),&num_queues);
> > +
> > +	/* We need atleast 2 queue's */
>
> s/atleast/at least/
>
>
> > +	if (err || num_queues<  2)
> > +		num_queues = 2;
> > +	if (num_queues>  MAX_QUEUES * 2)
> > +		num_queues = MAX_QUEUES;
>                  num_queues = MAX_QUEUES * 2;
>
> MAX_QUEUES is the limitation of RX or TX.

Right, it's a typo, thanks.
> > +
> > +	num_queue_pairs = num_queues / 2;
> ...

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