netdev - Re: [PATCH net-next v2 2/2] virtio_net: get init coalesce value when probe

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Message-ID: <CACGkMEs9nrFTjLa18XN9ZAokgLsw4MtXM3O3kVmQv=ofP49coA@mail.gmail.com>
Date: Tue, 7 May 2024 14:24:12 +0800
From: Jason Wang <jasowang@...hat.com>
To: Heng Qi <hengqi@...ux.alibaba.com>
Cc: netdev@...r.kernel.org, virtualization@...ts.linux.dev, 
	"Michael S . Tsirkin" <mst@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, 
	Eric Dumazet <edumazet@...gle.com>, "David S . Miller" <davem@...emloft.net>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net-next v2 2/2] virtio_net: get init coalesce value when probe

On Fri, Apr 26, 2024 at 2:54 PM Heng Qi <hengqi@...ux.alibaba.com> wrote:
>
> Currently, virtio-net lacks a way to obtain the default coalesce
> values of the device during the probe phase. That is, the device
> may have default experience values, but the user uses "ethtool -c"
> to query that the values are still 0.
>
> Therefore, we reuse VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET to complete the goal.
>
> Signed-off-by: Heng Qi <hengqi@...ux.alibaba.com>
> ---
>  drivers/net/virtio_net.c | 68 +++++++++++++++++++++++++++++++++++-----
>  1 file changed, 61 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 3bc9b1e621db..fe0c15819dd3 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -4623,6 +4623,46 @@ static int virtnet_validate(struct virtio_device *vdev)
>         return 0;
>  }
>
> +static int virtnet_get_coal_init_value(struct virtnet_info *vi,
> +                                      u16 _vqn, bool is_tx)
> +{
> +       struct virtio_net_ctrl_coal *coal = &vi->ctrl->coal_vq.coal;
> +       __le16 *vqn = &vi->ctrl->coal_vq.vqn;
> +       struct scatterlist sgs_in, sgs_out;
> +       u32 usecs, pkts, i;
> +       bool ret;
> +
> +       *vqn = cpu_to_le16(_vqn);
> +
> +       sg_init_one(&sgs_out, vqn, sizeof(*vqn));
> +       sg_init_one(&sgs_in, coal, sizeof(*coal));
> +       ret = virtnet_send_command_reply(vi, VIRTIO_NET_CTRL_NOTF_COAL,
> +                                        VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET,
> +                                        &sgs_out, &sgs_in);
> +       if (!ret)
> +               return ret;
> +
> +       usecs = le32_to_cpu(coal->max_usecs);
> +       pkts = le32_to_cpu(coal->max_packets);
> +       if (is_tx) {
> +               vi->intr_coal_tx.max_usecs = usecs;
> +               vi->intr_coal_tx.max_packets = pkts;
> +               for (i = 0; i < vi->max_queue_pairs; i++) {
> +                       vi->sq[i].intr_coal.max_usecs = usecs;
> +                       vi->sq[i].intr_coal.max_packets = pkts;
> +               }
> +       } else {
> +               vi->intr_coal_rx.max_usecs = usecs;
> +               vi->intr_coal_rx.max_packets = pkts;
> +               for (i = 0; i < vi->max_queue_pairs; i++) {
> +                       vi->rq[i].intr_coal.max_usecs = usecs;
> +                       vi->rq[i].intr_coal.max_packets = pkts;
> +               }
> +       }
> +
> +       return 0;
> +}
> +
>  static bool virtnet_check_guest_gso(const struct virtnet_info *vi)
>  {
>         return virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) ||
> @@ -4885,13 +4925,6 @@ static int virtnet_probe(struct virtio_device *vdev)
>                         vi->intr_coal_tx.max_packets = 0;
>         }
>
> -       if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL)) {
> -               /* The reason is the same as VIRTIO_NET_F_NOTF_COAL. */
> -               for (i = 0; i < vi->max_queue_pairs; i++)
> -                       if (vi->sq[i].napi.weight)
> -                               vi->sq[i].intr_coal.max_packets = 1;
> -       }
> -
>  #ifdef CONFIG_SYSFS
>         if (vi->mergeable_rx_bufs)
>                 dev->sysfs_rx_queue_group = &virtio_net_mrg_rx_group;
> @@ -4926,6 +4959,27 @@ static int virtnet_probe(struct virtio_device *vdev)
>
>         virtio_device_ready(vdev);
>
> +       if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL)) {
> +               /* The reason is the same as VIRTIO_NET_F_NOTF_COAL. */
> +               for (i = 0; i < vi->max_queue_pairs; i++)
> +                       if (vi->sq[i].napi.weight)
> +                               vi->sq[i].intr_coal.max_packets = 1;
> +
> +               /* The loop exits if the default value from any
> +                * queue is successfully read.
> +                */

So this assumes the default values are the same. Is this something
required by the spec? If not, we probably need to iterate all the
queues.

Thanks


> +               for (i = 0; i < vi->max_queue_pairs; i++) {
> +                       err = virtnet_get_coal_init_value(vi, rxq2vq(i), false);
> +                       if (!err)
> +                               break;
> +               }
> +               for (i = 0; i < vi->max_queue_pairs; i++) {
> +                       err = virtnet_get_coal_init_value(vi, txq2vq(i), true);
> +                       if (!err)
> +                               break;
> +               }
> +       }
> +
>         _virtnet_set_queues(vi, vi->curr_queue_pairs);
>
>         /* a random MAC address has been assigned, notify the device.
> --
> 2.32.0.3.g01195cf9f
>