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Date: Thu, 9 Nov 2023 12:43:29 +0800
From: Jason Wang <jasowang@...hat.com>
To: Heng Qi <hengqi@...ux.alibaba.com>
Cc: netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org, 
	"Michael S. Tsirkin" <mst@...hat.com>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, 
	"David S. Miller" <davem@...emloft.net>, Jesper Dangaard Brouer <hawk@...nel.org>, 
	John Fastabend <john.fastabend@...il.com>, Alexei Starovoitov <ast@...nel.org>, 
	Simon Horman <horms@...nel.org>, Jakub Kicinski <kuba@...nel.org>, "Liu, Yujie" <yujie.liu@...el.com>
Subject: Re: [PATCH net-next v2 4/5] virtio-net: support rx netdim

On Thu, Nov 2, 2023 at 9:10 PM Heng Qi <hengqi@...ux.alibaba.com> wrote:
>
> By comparing the traffic information in the complete napi processes,
> let the virtio-net driver automatically adjust the coalescing
> moderation parameters of each receive queue.
>
> Signed-off-by: Heng Qi <hengqi@...ux.alibaba.com>
> ---
> v1->v2:
> - Improved the judgment of dim switch conditions.
> - Fix the safe problem of work thread.

Nit: it's better to be more concrete here, e.g what kind of "safe
problem" it is.


>
>  drivers/net/virtio_net.c | 187 ++++++++++++++++++++++++++++++++++-----
>  1 file changed, 165 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 69fe09e99b3c..5473aa1ee5cd 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -19,6 +19,7 @@
>  #include <linux/average.h>
>  #include <linux/filter.h>
>  #include <linux/kernel.h>
> +#include <linux/dim.h>
>  #include <net/route.h>
>  #include <net/xdp.h>
>  #include <net/net_failover.h>
> @@ -172,6 +173,17 @@ struct receive_queue {
>
>         struct virtnet_rq_stats stats;
>
> +       /* The number of rx notifications */
> +       u16 calls;
> +
> +       /* Is dynamic interrupt moderation enabled? */
> +       bool dim_enabled;
> +
> +       /* Dynamic Interrupt Moderation */
> +       struct dim dim;
> +
> +       u32 packets_in_napi;
> +
>         struct virtnet_interrupt_coalesce intr_coal;
>
>         /* Chain pages by the private ptr. */
> @@ -305,6 +317,9 @@ struct virtnet_info {
>         u8 duplex;
>         u32 speed;
>
> +       /* Is rx dynamic interrupt moderation enabled? */
> +       bool rx_dim_enabled;
> +
>         /* Interrupt coalescing settings */
>         struct virtnet_interrupt_coalesce intr_coal_tx;
>         struct virtnet_interrupt_coalesce intr_coal_rx;
> @@ -2001,6 +2016,7 @@ static void skb_recv_done(struct virtqueue *rvq)
>         struct virtnet_info *vi = rvq->vdev->priv;
>         struct receive_queue *rq = &vi->rq[vq2rxq(rvq)];
>
> +       rq->calls++;
>         virtqueue_napi_schedule(&rq->napi, rvq);
>  }
>
> @@ -2141,6 +2157,26 @@ static void virtnet_poll_cleantx(struct receive_queue *rq)
>         }
>  }
>
> +static void virtnet_rx_dim_work(struct work_struct *work);
> +
> +static void virtnet_rx_dim_update(struct virtnet_info *vi, struct receive_queue *rq)
> +{
> +       struct dim_sample cur_sample = {};
> +
> +       if (!rq->packets_in_napi)
> +               return;
> +
> +       u64_stats_update_begin(&rq->stats.syncp);
> +       dim_update_sample(rq->calls,
> +                         u64_stats_read(&rq->stats.packets),
> +                         u64_stats_read(&rq->stats.bytes),
> +                         &cur_sample);
> +       u64_stats_update_end(&rq->stats.syncp);
> +
> +       net_dim(&rq->dim, cur_sample);
> +       rq->packets_in_napi = 0;
> +}
> +
>  static int virtnet_poll(struct napi_struct *napi, int budget)
>  {
>         struct receive_queue *rq =
> @@ -2149,17 +2185,22 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
>         struct send_queue *sq;
>         unsigned int received;
>         unsigned int xdp_xmit = 0;
> +       bool napi_complete;
>
>         virtnet_poll_cleantx(rq);
>
>         received = virtnet_receive(rq, budget, &xdp_xmit);
> +       rq->packets_in_napi += received;
>
>         if (xdp_xmit & VIRTIO_XDP_REDIR)
>                 xdp_do_flush();
>
>         /* Out of packets? */
> -       if (received < budget)
> -               virtqueue_napi_complete(napi, rq->vq, received);
> +       if (received < budget) {
> +               napi_complete = virtqueue_napi_complete(napi, rq->vq, received);
> +               if (napi_complete && rq->dim_enabled)
> +                       virtnet_rx_dim_update(vi, rq);
> +       }
>
>         if (xdp_xmit & VIRTIO_XDP_TX) {
>                 sq = virtnet_xdp_get_sq(vi);
> @@ -2179,6 +2220,7 @@ static void virtnet_disable_queue_pair(struct virtnet_info *vi, int qp_index)
>         virtnet_napi_tx_disable(&vi->sq[qp_index].napi);
>         napi_disable(&vi->rq[qp_index].napi);
>         xdp_rxq_info_unreg(&vi->rq[qp_index].xdp_rxq);
> +       cancel_work_sync(&vi->rq[qp_index].dim.work);
>  }
>
>  static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index)
> @@ -2196,6 +2238,9 @@ static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index)
>         if (err < 0)
>                 goto err_xdp_reg_mem_model;
>
> +       INIT_WORK(&vi->rq[qp_index].dim.work, virtnet_rx_dim_work);

Any reason we need to do the INIT_WORK here but not probe?

> +       vi->rq[qp_index].dim.mode = DIM_CQ_PERIOD_MODE_START_FROM_EQE;
> +
>         virtnet_napi_enable(vi->rq[qp_index].vq, &vi->rq[qp_index].napi);
>         virtnet_napi_tx_enable(vi, vi->sq[qp_index].vq, &vi->sq[qp_index].napi);
>
> @@ -2393,8 +2438,10 @@ static int virtnet_rx_resize(struct virtnet_info *vi,
>
>         qindex = rq - vi->rq;
>
> -       if (running)
> +       if (running) {
>                 napi_disable(&rq->napi);
> +               cancel_work_sync(&rq->dim.work);
> +       }
>
>         err = virtqueue_resize(rq->vq, ring_num, virtnet_rq_free_unused_buf);
>         if (err)
> @@ -2403,8 +2450,10 @@ static int virtnet_rx_resize(struct virtnet_info *vi,
>         if (!try_fill_recv(vi, rq, GFP_KERNEL))
>                 schedule_delayed_work(&vi->refill, 0);
>
> -       if (running)
> +       if (running) {
> +               INIT_WORK(&rq->dim.work, virtnet_rx_dim_work);
>                 virtnet_napi_enable(rq->vq, &rq->napi);
> +       }
>         return err;
>  }
>
> @@ -3341,24 +3390,51 @@ static int virtnet_send_tx_notf_coal_cmds(struct virtnet_info *vi,
>  static int virtnet_send_rx_notf_coal_cmds(struct virtnet_info *vi,
>                                           struct ethtool_coalesce *ec)
>  {
> +       bool rx_ctrl_dim_on = !!ec->use_adaptive_rx_coalesce;
>         struct scatterlist sgs_rx;
> +       bool switch_dim, update;
>         int i;
>
> -       vi->ctrl->coal_rx.rx_usecs = cpu_to_le32(ec->rx_coalesce_usecs);
> -       vi->ctrl->coal_rx.rx_max_packets = cpu_to_le32(ec->rx_max_coalesced_frames);
> -       sg_init_one(&sgs_rx, &vi->ctrl->coal_rx, sizeof(vi->ctrl->coal_rx));
> -
> -       if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
> -                                 VIRTIO_NET_CTRL_NOTF_COAL_RX_SET,
> -                                 &sgs_rx))
> -               return -EINVAL;
> +       switch_dim = rx_ctrl_dim_on != vi->rx_dim_enabled;
> +       if (switch_dim) {
> +               if (rx_ctrl_dim_on) {
> +                       if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL)) {
> +                               vi->rx_dim_enabled = true;
> +                               for (i = 0; i < vi->max_queue_pairs; i++)
> +                                       vi->rq[i].dim_enabled = true;
> +                       } else {
> +                               return -EOPNOTSUPP;
> +                       }
> +               } else {
> +                       vi->rx_dim_enabled = false;
> +                       for (i = 0; i < vi->max_queue_pairs; i++)
> +                               vi->rq[i].dim_enabled = false;
> +               }
> +       } else {
> +               if (ec->rx_coalesce_usecs != vi->intr_coal_rx.max_usecs ||
> +                   ec->rx_max_coalesced_frames != vi->intr_coal_rx.max_packets)
> +                       update = true;
>
> -       /* Save parameters */
> -       vi->intr_coal_rx.max_usecs = ec->rx_coalesce_usecs;
> -       vi->intr_coal_rx.max_packets = ec->rx_max_coalesced_frames;
> -       for (i = 0; i < vi->max_queue_pairs; i++) {
> -               vi->rq[i].intr_coal.max_usecs = ec->rx_coalesce_usecs;
> -               vi->rq[i].intr_coal.max_packets = ec->rx_max_coalesced_frames;
> +               if (vi->rx_dim_enabled) {
> +                       if (update)
> +                               return -EINVAL;

update could be used without initialization?

Btw under what condition could we reach here?

Thanks

> +               } else {
> +                       vi->ctrl->coal_rx.rx_usecs = cpu_to_le32(ec->rx_coalesce_usecs);
> +                       vi->ctrl->coal_rx.rx_max_packets = cpu_to_le32(ec->rx_max_coalesced_frames);
> +                       sg_init_one(&sgs_rx, &vi->ctrl->coal_rx, sizeof(vi->ctrl->coal_rx));
> +
> +                       if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
> +                                                 VIRTIO_NET_CTRL_NOTF_COAL_RX_SET,
> +                                                 &sgs_rx))
> +                               return -EINVAL;
> +
> +                       vi->intr_coal_rx.max_usecs = ec->rx_coalesce_usecs;
> +                       vi->intr_coal_rx.max_packets = ec->rx_max_coalesced_frames;
> +                       for (i = 0; i < vi->max_queue_pairs; i++) {
> +                               vi->rq[i].intr_coal.max_usecs = ec->rx_coalesce_usecs;
> +                               vi->rq[i].intr_coal.max_packets = ec->rx_max_coalesced_frames;
> +                       }
> +               }
>         }
>
>         return 0;
> @@ -3380,15 +3456,54 @@ static int virtnet_send_notf_coal_cmds(struct virtnet_info *vi,
>         return 0;
>  }
>
> +static int virtnet_send_rx_notf_coal_vq_cmds(struct virtnet_info *vi,
> +                                            struct ethtool_coalesce *ec,
> +                                            u16 queue)
> +{
> +       bool rx_ctrl_dim_on = !!ec->use_adaptive_rx_coalesce;
> +       bool cur_rx_dim = vi->rq[queue].dim_enabled;
> +       u32 max_usecs, max_packets;
> +       bool switch_dim, update;
> +       int err;
> +
> +       switch_dim = rx_ctrl_dim_on != cur_rx_dim;
> +       if (switch_dim) {
> +               if (rx_ctrl_dim_on)
> +                       vi->rq[queue].dim_enabled = true;
> +               else
> +                       vi->rq[queue].dim_enabled = false;
> +       } else {
> +               max_usecs = vi->rq[queue].intr_coal.max_usecs;
> +               max_packets = vi->rq[queue].intr_coal.max_packets;
> +               if (ec->rx_coalesce_usecs != max_usecs ||
> +                   ec->rx_max_coalesced_frames != max_packets)
> +                       update = true;
> +
> +               if (cur_rx_dim) {
> +                       if (update)
> +                               return -EINVAL;
> +               } else {
> +                       if (!update)
> +                               return 0;
> +
> +                       err = virtnet_send_rx_ctrl_coal_vq_cmd(vi, queue,
> +                                                              ec->rx_coalesce_usecs,
> +                                                              ec->rx_max_coalesced_frames);
> +                       if (err)
> +                               return err;
> +               }
> +       }
> +
> +       return 0;
> +}
> +
>  static int virtnet_send_notf_coal_vq_cmds(struct virtnet_info *vi,
>                                           struct ethtool_coalesce *ec,
>                                           u16 queue)
>  {
>         int err;
>
> -       err = virtnet_send_rx_ctrl_coal_vq_cmd(vi, queue,
> -                                              ec->rx_coalesce_usecs,
> -                                              ec->rx_max_coalesced_frames);
> +       err = virtnet_send_rx_notf_coal_vq_cmds(vi, ec, queue);
>         if (err)
>                 return err;
>
> @@ -3401,6 +3516,32 @@ static int virtnet_send_notf_coal_vq_cmds(struct virtnet_info *vi,
>         return 0;
>  }
>
> +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 dim_cq_moder update_moder;
> +       int qnum = rq - vi->rq, err;
> +
> +       update_moder = net_dim_get_rx_moderation(dim->mode, dim->profile_ix);
> +       if (update_moder.usec != vi->rq[qnum].intr_coal.max_usecs ||
> +           update_moder.pkts != vi->rq[qnum].intr_coal.max_packets) {
> +               rtnl_lock();
> +               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, (int)(rq - vi->rq));
> +               rtnl_unlock();
> +       }
> +
> +       dim->state = DIM_START_MEASURE;
> +}
> +
>  static int virtnet_coal_params_supported(struct ethtool_coalesce *ec)
>  {
>         /* usecs coalescing is supported only if VIRTIO_NET_F_NOTF_COAL
> @@ -3482,6 +3623,7 @@ static int virtnet_get_coalesce(struct net_device *dev,
>                 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;
> +               ec->use_adaptive_rx_coalesce = vi->rx_dim_enabled;
>         } else {
>                 ec->rx_max_coalesced_frames = 1;
>
> @@ -3539,6 +3681,7 @@ static int virtnet_get_per_queue_coalesce(struct net_device *dev,
>                 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;
> +               ec->use_adaptive_rx_coalesce = vi->rq[queue].dim_enabled;
>         } else {
>                 ec->rx_max_coalesced_frames = 1;
>
> @@ -3664,7 +3807,7 @@ static int virtnet_set_rxnfc(struct net_device *dev, struct ethtool_rxnfc *info)
>
>  static const struct ethtool_ops virtnet_ethtool_ops = {
>         .supported_coalesce_params = ETHTOOL_COALESCE_MAX_FRAMES |
> -               ETHTOOL_COALESCE_USECS,
> +               ETHTOOL_COALESCE_USECS | ETHTOOL_COALESCE_USE_ADAPTIVE_RX,
>         .get_drvinfo = virtnet_get_drvinfo,
>         .get_link = ethtool_op_get_link,
>         .get_ringparam = virtnet_get_ringparam,
> --
> 2.19.1.6.gb485710b
>


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