Re: [PATCH net-next V3 3/4] virtio_net: support per queue interrupt coalesce command

[Gavin Li <gavinl@xxxxxxxxxx>]

On 7/24/2023 3:32 PM, Michael S. Tsirkin wrote:
> On Mon, Jul 24, 2023 at 06:40:47AM +0300, Gavin Li wrote:
> > Add interrupt_coalesce config in send_queue and receive_queue to cache user
> > config.
> >
> > Send per virtqueue interrupt moderation config to underline device in order
> > to have more efficient interrupt moderation and cpu utilization of guest
> > VM.
> >
> > Signed-off-by: Gavin Li <gavinl@xxxxxxxxxx>
> > Reviewed-by: Dragos Tatulea <dtatulea@xxxxxxxxxx>
> > Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx>
> > Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > ---
> >   drivers/net/virtio_net.c        | 120 ++++++++++++++++++++++++++++----
> >   include/uapi/linux/virtio_net.h |  14 ++++
> >   2 files changed, 122 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 802ed21453f5..0c3ee1e26ece 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -144,6 +144,8 @@ struct send_queue {
> >   
> >   	struct virtnet_sq_stats stats;
> >   
> > +	struct virtnet_interrupt_coalesce intr_coal;
> > +
> >   	struct napi_struct napi;
> >   
> >   	/* Record whether sq is in reset state. */
> > @@ -161,6 +163,8 @@ struct receive_queue {
> >   
> >   	struct virtnet_rq_stats stats;
> >   
> > +	struct virtnet_interrupt_coalesce intr_coal;
> > +
> >   	/* Chain pages by the private ptr. */
> >   	struct page *pages;
> >   
> > @@ -212,6 +216,7 @@ struct control_buf {
> >   	struct virtio_net_ctrl_rss rss;
> >   	struct virtio_net_ctrl_coal_tx coal_tx;
> >   	struct virtio_net_ctrl_coal_rx coal_rx;
> > +	struct virtio_net_ctrl_coal_vq coal_vq;
> >   };
> >   
> >   struct virtnet_info {
> > @@ -3078,6 +3083,55 @@ static int virtnet_send_notf_coal_cmds(struct virtnet_info *vi,
> >   	return 0;
> >   }
> >   
> > +static int virtnet_send_ctrl_coal_vq_cmd(struct virtnet_info *vi,
> > +					 u16 vqn, u32 max_usecs, u32 max_packets)
> > +{
> > +	struct scatterlist sgs;
> > +
> > +	vi->ctrl->coal_vq.vqn = cpu_to_le16(vqn);
> > +	vi->ctrl->coal_vq.coal.max_usecs = cpu_to_le32(max_usecs);
> > +	vi->ctrl->coal_vq.coal.max_packets = cpu_to_le32(max_packets);
> > +	sg_init_one(&sgs, &vi->ctrl->coal_vq, sizeof(vi->ctrl->coal_vq));
> > +
> > +	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
> > +				  VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET,
> > +				  &sgs))
> > +		return -EINVAL;
> > +
> > +	return 0;
> > +}
> > +
> > +static int virtnet_send_notf_coal_vq_cmds(struct virtnet_info *vi,
> > +					  struct ethtool_coalesce *ec,
> > +					  u16 queue)
> > +{
> > +	int err;
> > +
> > +	if (ec->rx_coalesce_usecs || ec->rx_max_coalesced_frames) {
> > +		err = virtnet_send_ctrl_coal_vq_cmd(vi, rxq2vq(queue),
> > +						    ec->rx_coalesce_usecs,
> > +						    ec->rx_max_coalesced_frames);
> > +		if (err)
> > +			return err;
> > +		/* Save parameters */
> > +		vi->rq[queue].intr_coal.max_usecs = ec->rx_coalesce_usecs;
> > +		vi->rq[queue].intr_coal.max_packets = ec->rx_max_coalesced_frames;
> > +	}
> > +
> > +	if (ec->tx_coalesce_usecs || ec->tx_max_coalesced_frames) {
> > +		err = virtnet_send_ctrl_coal_vq_cmd(vi, txq2vq(queue),
> > +						    ec->tx_coalesce_usecs,
> > +						    ec->tx_max_coalesced_frames);
> > +		if (err)
> > +			return err;
> > +		/* Save parameters */
> > +		vi->sq[queue].intr_coal.max_usecs = ec->tx_coalesce_usecs;
> > +		vi->sq[queue].intr_coal.max_packets = ec->tx_max_coalesced_frames;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> >   static int virtnet_coal_params_supported(struct ethtool_coalesce *ec)
> >   {
> >   	/* usecs coalescing is supported only if VIRTIO_NET_F_NOTF_COAL
> > @@ -3094,23 +3148,39 @@ static int virtnet_coal_params_supported(struct ethtool_coalesce *ec)
> >   }
> >   
> >   static int virtnet_set_coalesce_one(struct net_device *dev,
> > -				    struct ethtool_coalesce *ec)
> > +				    struct ethtool_coalesce *ec,
> > +				    bool per_queue,
> > +				    u32 queue)
> >   {
> >   	struct virtnet_info *vi = netdev_priv(dev);
> > -	int ret, i, napi_weight;
> > +	int queue_count = per_queue ? 1 : vi->max_queue_pairs;
> > +	int queue_number = per_queue ? queue : 0;
>
> Actually can't we refactor this? This whole function is littered
> with if/else branches. just code it separately - the only
> common part is:
>
>          napi_weight = ec->tx_max_coalesced_frames ? NAPI_POLL_WEIGHT : 0;
>          if (napi_weight ^ vi->sq[0].napi.weight) {
>                  if (dev->flags & IFF_UP)
>                          return -EBUSY;
>                  else
>                          update_napi = true;
>          }
>
> so just move this to a helper and have two functions - global and
> per queue.
ACK
> >   	bool update_napi = false;
> > +	int ret, i, napi_weight;
> > +
> > +	if (queue >= vi->max_queue_pairs)
> > +		return -EINVAL;
> >   
> >   	/* Can't change NAPI weight if the link is up */
> >   	napi_weight = ec->tx_max_coalesced_frames ? NAPI_POLL_WEIGHT : 0;
> > -	if (napi_weight ^ vi->sq[0].napi.weight) {
> > -		if (dev->flags & IFF_UP)
> > -			return -EBUSY;
> > -		else
> > +	for (i = queue_number; i < queue_count; i++) {
> > +		if (napi_weight ^ vi->sq[i].napi.weight) {
> > +			if (dev->flags & IFF_UP)
> > +				return -EBUSY;
> > +
> >   			update_napi = true;
> > +			/* All queues that belong to [queue_number, queue_count] will be
> > +			 * updated for the sake of simplicity, which might not be necessary
> > +			 */
> > +			queue_number = i;
> > +			break;
> > +		}
> >   	}
> >   
> > -	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL))
> > +	if (!per_queue && virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL))
> >   		ret = virtnet_send_notf_coal_cmds(vi, ec);
> > +	else if (per_queue && virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL))
> > +		ret = virtnet_send_notf_coal_vq_cmds(vi, ec, queue);
> >   	else
> >   		ret = virtnet_coal_params_supported(ec);
> >   
> > @@ -3118,7 +3188,7 @@ static int virtnet_set_coalesce_one(struct net_device *dev,
> >   		return ret;
> >   
> >   	if (update_napi) {
> > -		for (i = 0; i < vi->max_queue_pairs; i++)
> > +		for (i = queue_number; i < queue_count; i++)
> >   			vi->sq[i].napi.weight = napi_weight;
> >   	}
> >   
> > @@ -3130,19 +3200,29 @@ static int virtnet_set_coalesce(struct net_device *dev,
> >   				struct kernel_ethtool_coalesce *kernel_coal,
> >   				struct netlink_ext_ack *extack)
> >   {
> > -	return virtnet_set_coalesce_one(dev, ec);
> > +	return virtnet_set_coalesce_one(dev, ec, false, 0);
> >   }
> >   
> >   static int virtnet_get_coalesce_one(struct net_device *dev,
> > -				    struct ethtool_coalesce *ec)
> > +				    struct ethtool_coalesce *ec,
> > +				    bool per_queue,
> > +				    u32 queue)
> >   {
> >   	struct virtnet_info *vi = netdev_priv(dev);
> >   
> > -	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL)) {
> > +	if (queue >= vi->max_queue_pairs)
> > +		return -EINVAL;
> > +
> > +	if (!per_queue && virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL)) {
> >   		ec->rx_coalesce_usecs = vi->intr_coal_rx.max_usecs;
> >   		ec->tx_coalesce_usecs = vi->intr_coal_tx.max_usecs;
> >   		ec->tx_max_coalesced_frames = vi->intr_coal_tx.max_packets;
> >   		ec->rx_max_coalesced_frames = vi->intr_coal_rx.max_packets;
> > +	} else if (per_queue && virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL)) {
> > +		ec->rx_coalesce_usecs = vi->rq[queue].intr_coal.max_usecs;
> > +		ec->tx_coalesce_usecs = vi->sq[queue].intr_coal.max_usecs;
> > +		ec->tx_max_coalesced_frames = vi->sq[queue].intr_coal.max_packets;
> > +		ec->rx_max_coalesced_frames = vi->rq[queue].intr_coal.max_packets;
> >   	} else {
> >   		ec->rx_max_coalesced_frames = 1;
> >   
> > @@ -3158,7 +3238,21 @@ static int virtnet_get_coalesce(struct net_device *dev,
> >   				struct kernel_ethtool_coalesce *kernel_coal,
> >   				struct netlink_ext_ack *extack)
> >   {
> > -	return virtnet_get_coalesce_one(dev, ec);
> > +	return virtnet_get_coalesce_one(dev, ec, false, 0);
> > +}
> > +
> > +static int virtnet_set_per_queue_coalesce(struct net_device *dev,
> > +					  u32 queue,
> > +					  struct ethtool_coalesce *ec)
> > +{
> > +	return virtnet_set_coalesce_one(dev, ec, true, queue);
> > +}
> > +
> > +static int virtnet_get_per_queue_coalesce(struct net_device *dev,
> > +					  u32 queue,
> > +					  struct ethtool_coalesce *ec)
> > +{
> > +	return virtnet_get_coalesce_one(dev, ec, true, queue);
> >   }
> >   
> >   static void virtnet_init_settings(struct net_device *dev)
> > @@ -3291,6 +3385,8 @@ static const struct ethtool_ops virtnet_ethtool_ops = {
> >   	.set_link_ksettings = virtnet_set_link_ksettings,
> >   	.set_coalesce = virtnet_set_coalesce,
> >   	.get_coalesce = virtnet_get_coalesce,
> > +	.set_per_queue_coalesce = virtnet_set_per_queue_coalesce,
> > +	.get_per_queue_coalesce = virtnet_get_per_queue_coalesce,
> >   	.get_rxfh_key_size = virtnet_get_rxfh_key_size,
> >   	.get_rxfh_indir_size = virtnet_get_rxfh_indir_size,
> >   	.get_rxfh = virtnet_get_rxfh,
> > diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
> > index 12c1c9699935..cc65ef0f3c3e 100644
> > --- a/include/uapi/linux/virtio_net.h
> > +++ b/include/uapi/linux/virtio_net.h
> > @@ -56,6 +56,7 @@
> >   #define VIRTIO_NET_F_MQ	22	/* Device supports Receive Flow
> >   					 * Steering */
> >   #define VIRTIO_NET_F_CTRL_MAC_ADDR 23	/* Set MAC address */
> > +#define VIRTIO_NET_F_VQ_NOTF_COAL 52	/* Device supports virtqueue notification coalescing */
> >   #define VIRTIO_NET_F_NOTF_COAL	53	/* Device supports notifications coalescing */
> >   #define VIRTIO_NET_F_GUEST_USO4	54	/* Guest can handle USOv4 in. */
> >   #define VIRTIO_NET_F_GUEST_USO6	55	/* Guest can handle USOv6 in. */
> > @@ -391,5 +392,18 @@ struct virtio_net_ctrl_coal_rx {
> >   };
> >   
> >   #define VIRTIO_NET_CTRL_NOTF_COAL_RX_SET		1
> > +#define VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET		2
> > +#define VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET		3
> > +
> > +struct virtio_net_ctrl_coal {
> > +	__le32 max_packets;
> > +	__le32 max_usecs;
> > +};
> > +
> > +struct  virtio_net_ctrl_coal_vq {
> > +	__le16 vqn;
> > +	__le16 reserved;
> > +	struct virtio_net_ctrl_coal coal;
> > +};
> >   
> >   #endif /* _UAPI_LINUX_VIRTIO_NET_H */
> > --
> > 2.39.1