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SubjectRe: [net-next RFC V5 5/5] virtio_net: support negotiating the number of queues through ctrl vq
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On Thu, 2012-07-05 at 18:29 +0800, Jason Wang wrote:
> This patch let the virtio_net driver can negotiate the number of queues it
> wishes to use through control virtqueue and export an ethtool interface to let
> use tweak it.
>
> As current multiqueue virtio-net implementation has optimizations on per-cpu
> virtuqueues, so only two modes were support:
>
> - single queue pair mode
> - multiple queue paris mode, the number of queues matches the number of vcpus
>
> The single queue mode were used by default currently due to regression of
> multiqueue mode in some test (especially in stream test).
>
> Since virtio core does not support paritially deleting virtqueues, so during
> mode switching the whole virtqueue were deleted and the driver would re-create
> the virtqueues it would used.
>
> btw. The queue number negotiating were defered to .ndo_open(), this is because
> only after feature negotitaion could we send the command to control virtqueue
> (as it may also use event index).
[...]
> +static int virtnet_set_channels(struct net_device *dev,
> + struct ethtool_channels *channels)
> +{
> + struct virtnet_info *vi = netdev_priv(dev);
> + u16 queues = channels->rx_count;
> + unsigned status = VIRTIO_CONFIG_S_ACKNOWLEDGE | VIRTIO_CONFIG_S_DRIVER;
> +
> + if (channels->rx_count != channels->tx_count)
> + return -EINVAL;
[...]
> +static void virtnet_get_channels(struct net_device *dev,
> + struct ethtool_channels *channels)
> +{
> + struct virtnet_info *vi = netdev_priv(dev);
> +
> + channels->max_rx = vi->total_queue_pairs;
> + channels->max_tx = vi->total_queue_pairs;
> + channels->max_other = 0;
> + channels->max_combined = 0;
> + channels->rx_count = vi->num_queue_pairs;
> + channels->tx_count = vi->num_queue_pairs;
> + channels->other_count = 0;
> + channels->combined_count = 0;
> +}
[...]

It looks like the queue-pairs should be treated as 'combined channels',
not separate RX and TX channels. Also you don't need to clear the other
members; you can assume that the ethtool core will zero-initialise
structures for 'get' operations.

Ben.

--
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.



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