On Thu, Jun 6, 2024 at 2:15 PM Heng Qi <hengqi@xxxxxxxxxxxxxxxxx> wrote:
>
> Currently, control vq handles commands synchronously,
> leading to increased delays for dim commands during multi-queue
> VM configuration and directly impacting dim performance.
>
> To address this, we are shifting to asynchronous processing of
> ctrlq's dim commands.
>
> Signed-off-by: Heng Qi <hengqi@xxxxxxxxxxxxxxxxx>
> ---
> drivers/net/virtio_net.c | 233 ++++++++++++++++++++++++++++++++++-----
> 1 file changed, 208 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index e59e12bb7601..0338528993ab 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -376,6 +376,13 @@ struct control_buf {
> struct completion completion;
> };
>
> +struct virtnet_coal_node {
> + struct control_buf ctrl;
> + struct virtio_net_ctrl_coal_vq coal_vqs;
> + bool is_coal_wait;
> + struct list_head list;
> +};
> +
> struct virtnet_info {
> struct virtio_device *vdev;
> struct virtqueue *cvq;
> @@ -420,6 +427,9 @@ struct virtnet_info {
> /* Lock to protect the control VQ */
> struct mutex cvq_lock;
>
> + /* Work struct for acquisition of cvq processing results. */
> + struct work_struct get_cvq;
> +
> /* Host can handle any s/g split between our header and packet data */
> bool any_header_sg;
>
> @@ -464,6 +474,14 @@ struct virtnet_info {
> struct virtnet_interrupt_coalesce intr_coal_tx;
> struct virtnet_interrupt_coalesce intr_coal_rx;
>
> + /* Free nodes used for concurrent delivery */
> + struct mutex coal_free_lock;
> + struct list_head coal_free_list;
> +
> + /* Filled when there are no free nodes or cvq buffers */
> + struct mutex coal_wait_lock;
> + struct list_head coal_wait_list;
> +
> unsigned long guest_offloads;
> unsigned long guest_offloads_capable;
>
> @@ -670,7 +688,7 @@ static void virtnet_cvq_done(struct virtqueue *cvq)
> {
> struct virtnet_info *vi = cvq->vdev->priv;
>
> - complete(&vi->ctrl->completion);
> + schedule_work(&vi->get_cvq);
> }
>
> static void skb_xmit_done(struct virtqueue *vq)
> @@ -2696,7 +2714,7 @@ static bool virtnet_send_command_reply(struct virtnet_info *vi,
> struct scatterlist *in)
> {
> struct scatterlist *sgs[5], hdr, stat;
> - u32 out_num = 0, tmp, in_num = 0;
> + u32 out_num = 0, in_num = 0;
> int ret;
>
> /* Caller should know better */
> @@ -2730,14 +2748,14 @@ static bool virtnet_send_command_reply(struct virtnet_info *vi,
> return false;
> }
>
> - if (unlikely(!virtqueue_kick(vi->cvq)))
> - goto unlock;
> + if (unlikely(!virtqueue_kick(vi->cvq))) {
> + mutex_unlock(&vi->cvq_lock);
> + return false;
> + }
> + mutex_unlock(&vi->cvq_lock);
>
> - wait_for_completion(&vi->ctrl->completion);
> - virtqueue_get_buf(vi->cvq, &tmp);
> + wait_for_completion(&ctrl->completion);
>
> -unlock:
> - mutex_unlock(&vi->cvq_lock);
> return ctrl->status == VIRTIO_NET_OK;
> }
>
> @@ -2747,6 +2765,86 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
> return virtnet_send_command_reply(vi, class, cmd, vi->ctrl, out, NULL);
> }
>
> +static void virtnet_process_dim_cmd(struct virtnet_info *vi,
> + struct virtnet_coal_node *node)
> +{
> + u16 qnum = le16_to_cpu(node->coal_vqs.vqn) / 2;
> +
> + mutex_lock(&vi->rq[qnum].dim_lock);
> + vi->rq[qnum].intr_coal.max_usecs =
> + le32_to_cpu(node->coal_vqs.coal.max_usecs);
> + vi->rq[qnum].intr_coal.max_packets =
> + le32_to_cpu(node->coal_vqs.coal.max_packets);
> + vi->rq[qnum].dim.state = DIM_START_MEASURE;
> + mutex_unlock(&vi->rq[qnum].dim_lock);
> +
> + if (node->is_coal_wait) {
> + mutex_lock(&vi->coal_wait_lock);
> + list_del(&node->list);
> + mutex_unlock(&vi->coal_wait_lock);
> + kfree(node);
> + } else {
> + mutex_lock(&vi->coal_free_lock);
> + list_add(&node->list, &vi->coal_free_list);
> + mutex_unlock(&vi->coal_free_lock);
> + }
> +}
> +
> +static int virtnet_add_dim_command(struct virtnet_info *vi,
> + struct virtnet_coal_node *coal_node)
> +{
> + struct scatterlist sg;
> + int ret;
> +
> + sg_init_one(&sg, &coal_node->coal_vqs, sizeof(coal_node->coal_vqs));
> + ret = virtnet_send_command_reply(vi, VIRTIO_NET_CTRL_NOTF_COAL,
> + VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET,
> + &coal_node->ctrl, &sg, NULL);
> + if (!ret) {
> + dev_warn(&vi->dev->dev,
> + "Failed to change coalescing params.\n");
> + return ret;
> + }
> +
> + virtnet_process_dim_cmd(vi, coal_node);
> +
> + return 0;
> +}
> +
> +static void virtnet_get_cvq_work(struct work_struct *work)
> +{
> + struct virtnet_info *vi =
> + container_of(work, struct virtnet_info, get_cvq);
> + struct virtnet_coal_node *wait_coal;
> + bool valid = false;
> + unsigned int tmp;
> + void *res;
> +
> + mutex_lock(&vi->cvq_lock);
> + while ((res = virtqueue_get_buf(vi->cvq, &tmp)) != NULL) {
> + complete((struct completion *)res);
> + valid = true;
> + }
> + mutex_unlock(&vi->cvq_lock);
How could we synchronize with the device in this case?
E.g what happens if the device finishes another buf here?
> +
> + if (!valid)
> + return;
> +
> + while (true) {
> + wait_coal = NULL;
> + mutex_lock(&vi->coal_wait_lock);
> + if (!list_empty(&vi->coal_wait_list))
> + wait_coal = list_first_entry(&vi->coal_wait_list,
> + struct virtnet_coal_node,
> + list);
> + mutex_unlock(&vi->coal_wait_lock);
> + if (wait_coal)
> + if (virtnet_add_dim_command(vi, wait_coal))
> + break;
> + else
> + break;
> + }
This is still an ad-hoc optimization for dim in the general path here.
Could we have a fn callback so for non dim it's just a completion and
for dim it would be a schedule_work()?
> +}
> static int virtnet_set_mac_address(struct net_device *dev, void *p)
> {
> struct virtnet_info *vi = netdev_priv(dev);
> @@ -4398,35 +4496,73 @@ static int virtnet_send_notf_coal_vq_cmds(struct virtnet_info *vi,
> return 0;
> }
>
> +static void virtnet_put_wait_coal(struct virtnet_info *vi,
> + struct receive_queue *rq,
> + struct dim_cq_moder moder)
> +{
> + struct virtnet_coal_node *wait_node;
> +
> + wait_node = kzalloc(sizeof(*wait_node), GFP_KERNEL);
> + if (!wait_node) {
> + rq->dim.state = DIM_START_MEASURE;
> + return;
> + }
> +
> + wait_node->is_coal_wait = true;
> + wait_node->coal_vqs.vqn = cpu_to_le16(rxq2vq(rq - vi->rq));
> + wait_node->coal_vqs.coal.max_usecs = cpu_to_le32(moder.usec);
> + wait_node->coal_vqs.coal.max_packets = cpu_to_le32(moder.pkts);
> + mutex_lock(&vi->coal_wait_lock);
> + list_add_tail(&wait_node->list, &vi->coal_wait_list);
> + mutex_unlock(&vi->coal_wait_lock);
> +}
> +
> static void virtnet_rx_dim_work(struct work_struct *work)
> {
> struct dim *dim = container_of(work, struct dim, work);
> struct receive_queue *rq = container_of(dim,
> struct receive_queue, dim);
> struct virtnet_info *vi = rq->vq->vdev->priv;
> - struct net_device *dev = vi->dev;
> + struct virtnet_coal_node *avail_coal;
> struct dim_cq_moder update_moder;
> - int qnum, err;
>
> - qnum = rq - vi->rq;
> + update_moder = net_dim_get_rx_moderation(dim->mode, dim->profile_ix);
>
> mutex_lock(&rq->dim_lock);
> - if (!rq->dim_enabled)
> - goto out;
> -
> - update_moder = net_dim_get_rx_moderation(dim->mode, dim->profile_ix);
> - if (update_moder.usec != rq->intr_coal.max_usecs ||
> - update_moder.pkts != rq->intr_coal.max_packets) {
> - err = virtnet_send_rx_ctrl_coal_vq_cmd(vi, qnum,
> - update_moder.usec,
> - update_moder.pkts);
> - if (err)
> - pr_debug("%s: Failed to send dim parameters on rxq%d\n",
> - dev->name, qnum);
> - dim->state = DIM_START_MEASURE;
> + if (!rq->dim_enabled ||
> + (update_moder.usec == rq->intr_coal.max_usecs &&
> + update_moder.pkts == rq->intr_coal.max_packets)) {
> + rq->dim.state = DIM_START_MEASURE;
> + mutex_unlock(&rq->dim_lock);
> + return;
> }
> -out:
> mutex_unlock(&rq->dim_lock);
> +
> + mutex_lock(&vi->cvq_lock);
> + if (vi->cvq->num_free < 3) {
> + virtnet_put_wait_coal(vi, rq, update_moder);
> + mutex_unlock(&vi->cvq_lock);
> + return;
> + }
Could we simply sleep instead of using a list here?
> + mutex_unlock(&vi->cvq_lock);
> +
> + mutex_lock(&vi->coal_free_lock);
> + if (list_empty(&vi->coal_free_list)) {
> + virtnet_put_wait_coal(vi, rq, update_moder);
> + mutex_unlock(&vi->coal_free_lock);
> + return;
> + }
> +
> + avail_coal = list_first_entry(&vi->coal_free_list,
> + struct virtnet_coal_node, list);
> + avail_coal->coal_vqs.vqn = cpu_to_le16(rxq2vq(rq - vi->rq));
> + avail_coal->coal_vqs.coal.max_usecs = cpu_to_le32(update_moder.usec);
> + avail_coal->coal_vqs.coal.max_packets = cpu_to_le32(update_moder.pkts);
> +
> + list_del(&avail_coal->list);
> + mutex_unlock(&vi->coal_free_lock);
> +
> + virtnet_add_dim_command(vi, avail_coal);
> }
>
> static int virtnet_coal_params_supported(struct ethtool_coalesce *ec)
> @@ -4839,6 +4975,7 @@ static void virtnet_freeze_down(struct virtio_device *vdev)
> flush_work(&vi->config_work);
> disable_rx_mode_work(vi);
> flush_work(&vi->rx_mode_work);
> + flush_work(&vi->get_cvq);
>
> netif_tx_lock_bh(vi->dev);
> netif_device_detach(vi->dev);
> @@ -5612,6 +5749,45 @@ static const struct xdp_metadata_ops virtnet_xdp_metadata_ops = {
> .xmo_rx_hash = virtnet_xdp_rx_hash,
> };
>
> +static void virtnet_del_coal_free_list(struct virtnet_info *vi)
> +{
> + struct virtnet_coal_node *coal_node, *tmp;
> +
> + list_for_each_entry_safe(coal_node, tmp, &vi->coal_free_list, list) {
> + list_del(&coal_node->list);
> + kfree(coal_node);
> + }
> +}
> +
> +static int virtnet_init_coal_list(struct virtnet_info *vi)
> +{
> + struct virtnet_coal_node *coal_node;
> + int batch_dim_nums;
> + int i;
> +
> + INIT_LIST_HEAD(&vi->coal_free_list);
> + mutex_init(&vi->coal_free_lock);
> +
> + INIT_LIST_HEAD(&vi->coal_wait_list);
> + mutex_init(&vi->coal_wait_lock);
> +
> + if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL))
> + return 0;
> +
> + batch_dim_nums = min((unsigned int)vi->max_queue_pairs,
> + virtqueue_get_vring_size(vi->cvq) / 3);
> + for (i = 0; i < batch_dim_nums; i++) {
> + coal_node = kzalloc(sizeof(*coal_node), GFP_KERNEL);
> + if (!coal_node) {
> + virtnet_del_coal_free_list(vi);
> + return -ENOMEM;
> + }
> + list_add(&coal_node->list, &vi->coal_free_list);
> + }
> +
> + return 0;
> +}
> +
> static int virtnet_probe(struct virtio_device *vdev)
> {
> int i, err = -ENOMEM;
> @@ -5797,6 +5973,9 @@ static int virtnet_probe(struct virtio_device *vdev)
> if (err)
> goto free;
>
> + if (virtnet_init_coal_list(vi))
> + goto free;
> +
> if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL)) {
> vi->intr_coal_rx.max_usecs = 0;
> vi->intr_coal_tx.max_usecs = 0;
> @@ -5838,6 +6017,7 @@ static int virtnet_probe(struct virtio_device *vdev)
> if (vi->has_rss || vi->has_rss_hash_report)
> virtnet_init_default_rss(vi);
>
> + INIT_WORK(&vi->get_cvq, virtnet_get_cvq_work);
> init_completion(&vi->ctrl->completion);
> enable_rx_mode_work(vi);
>
> @@ -5967,11 +6147,14 @@ static void virtnet_remove(struct virtio_device *vdev)
> flush_work(&vi->config_work);
> disable_rx_mode_work(vi);
> flush_work(&vi->rx_mode_work);
> + flush_work(&vi->get_cvq);
Do we need to prevent cvq work from being scheduled here?
Thanks
>
> unregister_netdev(vi->dev);
>
> net_failover_destroy(vi->failover);
>
> + virtnet_del_coal_free_list(vi);
> +
> remove_vq_common(vi);
>
> free_netdev(vi->dev);
> --
> 2.32.0.3.g01195cf9f
>
