On Mon, Oct 26, 2015 at 10:52:47AM -0700, Ravi Kerur wrote:
> Ported earlier patch from Jason Wang (dated 12/26/2014).
>
> This patch tries to reduce the number of MSIX irqs required for
> virtio-net by sharing a MSIX irq for each TX/RX queue pair through
> channels. If transport support channel, about half of the MSIX irqs
> were reduced.
>
> Signed-off-by: Ravi Kerur <rke...@gmail.com>
Why bother BTW? Looks like this is adding a bunch of overhead
on data path - to what end?
Maybe you have a huge number of these devices ... but in that case, how
about sharing the config interrupt instead?
That's only possible if host supports VIRTIO_1
(so we can detect config interrupt by reading the ISR).
> ---
> drivers/net/virtio_net.c | 29 ++++++++++++++++++++++++++++-
> 1 file changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index d8838ded..d705cce 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -72,6 +72,9 @@ struct send_queue {
>
> /* Name of the send queue: output.$index */
> char name[40];
> +
> + /* Name of the channel, shared with irq. */
> + char channel_name[40];
> };
>
> /* Internal representation of a receive virtqueue */
> @@ -1529,6 +1532,8 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
> int ret = -ENOMEM;
> int i, total_vqs;
> const char **names;
> + const char **channel_names;
> + unsigned *channels;
>
> /* We expect 1 RX virtqueue followed by 1 TX virtqueue, followed by
> * possible N-1 RX/TX queue pairs used in multiqueue mode, followed by
> @@ -1548,6 +1553,17 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
> if (!names)
> goto err_names;
>
> + channel_names = kmalloc_array(vi->max_queue_pairs,
> + sizeof(*channel_names),
> + GFP_KERNEL);
> + if (!channel_names)
> + goto err_channel_names;
> +
> + channels = kmalloc_array(total_vqs, sizeof(*channels),
> + GFP_KERNEL);
> + if (!channels)
> + goto err_channels;
> +
> /* Parameters for control virtqueue, if any */
> if (vi->has_cvq) {
> callbacks[total_vqs - 1] = NULL;
> @@ -1562,10 +1578,15 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
> sprintf(vi->sq[i].name, "output.%d", i);
> names[rxq2vq(i)] = vi->rq[i].name;
> names[txq2vq(i)] = vi->sq[i].name;
> + sprintf(vi->sq[i].channel_name, "txrx.%d", i);
> + channel_names[i] = vi->sq[i].channel_name;
> + channels[rxq2vq(i)] = i;
> + channels[txq2vq(i)] = i;
> }
>
> ret = vi->vdev->config->find_vqs(vi->vdev, total_vqs, vqs, callbacks,
> - names);
> + names, channels, channel_names,
> + vi->max_queue_pairs);
> if (ret)
> goto err_find;
>
> @@ -1580,6 +1601,8 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
> vi->sq[i].vq = vqs[txq2vq(i)];
> }
>
> + kfree(channels);
> + kfree(channel_names);
> kfree(names);
> kfree(callbacks);
> kfree(vqs);
> @@ -1587,6 +1610,10 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
> return 0;
>
> err_find:
> + kfree(channels);
> +err_channels:
> + kfree(channel_names);
> +err_channel_names:
> kfree(names);
> err_names:
> kfree(callbacks);
> --
> 1.9.1
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