Re: [PATCH net-next V1 3/4] virtio_net: support per queue interrupt coalesce command

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On Mon, Jul 10, 2023 at 5:21 PM Gavin Li <gavinl@xxxxxxxxxx> 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>
---
 drivers/net/virtio_net.c        | 117 ++++++++++++++++++++++++++++----
 include/uapi/linux/virtio_net.h |  14 ++++
 2 files changed, 119 insertions(+), 12 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 802ed21453f5..333a38e1941f 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;

@@ -3078,6 +3082,56 @@ 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 virtio_net_ctrl_coal_vq coal_vq = {};
+       struct scatterlist sgs;
+
+       coal_vq.vqn = cpu_to_le16(vqn);
+       coal_vq.coal.max_usecs = cpu_to_le32(max_usecs);
+       coal_vq.coal.max_packets = cpu_to_le32(max_packets);
+       sg_init_one(&sgs, &coal_vq, sizeof(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 +3148,36 @@ 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;
        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;
+                       queue_number = i;


This seems to assume all queues that belong to [queue_number, queue_count) need an updating of the NAPI which is not necessarily the case.  Worth a comment to mention that the updating of the NAPI might not be necessary.

Thanks
 
+                       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 +3185,7 @@ 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 +3197,29 @@ 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 +3235,21 @@ 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 +3382,8 @@ 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

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