Date: Wed, 1 Nov 2023 18:55:11 +0800
From: Heng Qi <hengqi@...ux.alibaba.com>
To: Jason Wang <jasowang@...hat.com>
Cc: "Michael S. Tsirkin" <mst@...hat.com>, netdev@...r.kernel.org,
 virtualization@...ts.linux-foundation.org,
 Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Eric Dumazet <edumazet@...gle.com>,
 "David S. Miller" <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 John Fastabend <john.fastabend@...il.com>,
 Alexei Starovoitov <ast@...nel.org>, Jakub Kicinski <kuba@...nel.org>,
 Simon Horman <horms@...nel.org>, "Liu, Yujie" <yujie.liu@...el.com>
Subject: Re: [PATCH net-next 4/5] virtio-net: support rx netdim



在 2023/10/25 上午11:34, Jason Wang 写道:
> On Thu, Oct 12, 2023 at 3:44 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>
>> ---
>>   drivers/net/virtio_net.c | 147 +++++++++++++++++++++++++++++++++------
>>   1 file changed, 126 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index caef78bb3963..6ad2890a7909 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);
>>   }
>>
>> @@ -2138,6 +2154,25 @@ 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 virtnet_rq_stats *stats = &rq->stats;
>> +       struct dim_sample cur_sample = {};
>> +
>> +       if (!rq->packets_in_napi)
>> +               return;
>> +
>> +       u64_stats_update_begin(&rq->stats.syncp);
>> +       dim_update_sample(rq->calls, stats->packets,
>> +                         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 =
>> @@ -2146,17 +2181,22 @@ 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);
>> @@ -2176,6 +2216,7 @@ 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)
>> @@ -2193,6 +2234,9 @@ 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);
>> +       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);
>>
>> @@ -3335,23 +3379,42 @@ 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;
>> +       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))
>> +       if (rx_ctrl_dim_on && (ec->rx_coalesce_usecs != vi->intr_coal_rx.max_usecs ||
>> +                              ec->rx_max_coalesced_frames != vi->intr_coal_rx.max_packets))
> Any reason we need to stick a check for usecs/packets? I think it
> might confuse the user since the value could be modified by netdim
> actually.

Yes, that's exactly what's done here.

When dim is enabled, the user is prohibited from manually configuring 
parameters because dim may modify the parameters.

>
>>                  return -EINVAL;
>>
>> -       /* 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 (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;
>> +
>> +               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;
>> @@ -3377,13 +3440,27 @@ static int virtnet_send_notf_coal_vq_cmds(struct virtnet_info *vi,
>>                                            struct ethtool_coalesce *ec,
>>                                            u16 queue)
>>   {
>> +       bool rx_ctrl_dim_on;
>> +       u32 max_usecs, max_packets;
>>          int err;
>>
>> -       err = virtnet_send_rx_ctrl_coal_vq_cmd(vi, queue,
>> -                                              ec->rx_coalesce_usecs,
>> -                                              ec->rx_max_coalesced_frames);
>> -       if (err)
>> -               return err;
>> +       rx_ctrl_dim_on = !!ec->use_adaptive_rx_coalesce;
>> +       max_usecs = vi->rq[queue].intr_coal.max_usecs;
>> +       max_packets = vi->rq[queue].intr_coal.max_packets;
>> +       if (rx_ctrl_dim_on && (ec->rx_coalesce_usecs != max_usecs ||
>> +                              ec->rx_max_coalesced_frames != max_packets))
>> +               return -EINVAL;
>> +
>> +       if (rx_ctrl_dim_on) {
>> +               vi->rq[queue].dim_enabled = true;
>> +       } else {
>> +               vi->rq[queue].dim_enabled = false;
>> +               err = virtnet_send_rx_ctrl_coal_vq_cmd(vi, queue,
>> +                                                      ec->rx_coalesce_usecs,
>> +                                                      ec->rx_max_coalesced_frames);
>> +               if (err)
>> +                       return err;
>> +       }
>>
>>          err = virtnet_send_tx_ctrl_coal_vq_cmd(vi, queue,
>>                                                 ec->tx_coalesce_usecs,
>> @@ -3394,6 +3471,32 @@ 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) {
> Is this safe across the e.g vq reset?

I think it might. This will be avoided in the next version using:
1. cancel virtnet_rx_dim_work before vq reset.
2. restore virtnet_rx_dim_work after vq re-enable.

Thanks a lot!

>
> Thanks
>
>> +               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
>> @@ -3475,6 +3578,7 @@ 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;
>>
>> @@ -3532,6 +3636,7 @@ 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;
>>
>> @@ -3657,7 +3762,7 @@ 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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