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Date: Thu, 21 Dec 2023 22:34:29 +0800
From: Zhu Yanjun <yanjun.zhu@...ux.dev>
To: Heng Qi <hengqi@...ux.alibaba.com>
Cc: Jason Wang <jasowang@...hat.com>, "Michael S. Tsirkin" <mst@...hat.com>,
"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Alexei Starovoitov <ast@...nel.org>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH net-next] virtio-net: switch napi_tx without downing nic
在 2023/12/21 13:20, Heng Qi 写道:
>
>
> 在 2023/12/21 上午11:02, Zhu Yanjun 写道:
>> 在 2023/12/20 16:07, Heng Qi 写道:
>>> virtio-net has two ways to switch napi_tx: one is through the
>>> module parameter, and the other is through coalescing parameter
>>> settings (provided that the nic status is down).
>>>
>>> Sometimes we face performance regression caused by napi_tx,
>>> then we need to switch napi_tx when debugging. However, the
>>> existing methods are a bit troublesome, such as needing to
>>> reload the driver or turn off the network card. So try to make
>>> this update.
>>
>> What scenario can trigger this? We want to make tests on our device.
>
> Hi Zhu Yanjun, you can use the following cmds:
>
> ethtool -C tx-frames 0, to disable napi_tx
> ethtool -C tx-frames 1, to enable napi_tx
Thanks a lot. Just now I made tests on our device. I confirmed that
virtion_net driver can work well after running "ethtool -C NIC tx-frames
0 && sleep 3 && ethtool -C NIC tx-frames 1".
You can add "Reviewed-and-tested-by: Zhu Yanjun <yanjun.zhu@...ux.dev>"
Thanks,
Zhu Yanjun
>
> Thanks.
>
>>
>> Zhu Yanjun
>>
>>>
>>> Signed-off-by: Heng Qi <hengqi@...ux.alibaba.com>
>>> Reviewed-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
>>> ---
>>> drivers/net/virtio_net.c | 81
>>> ++++++++++++++++++----------------------
>>> 1 file changed, 37 insertions(+), 44 deletions(-)
>>>
>>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>>> index 10614e9f7cad..12f8e1f9971c 100644
>>> --- a/drivers/net/virtio_net.c
>>> +++ b/drivers/net/virtio_net.c
>>> @@ -3559,16 +3559,37 @@ static int
>>> virtnet_coal_params_supported(struct ethtool_coalesce *ec)
>>> return 0;
>>> }
>>> -static int virtnet_should_update_vq_weight(int dev_flags, int
>>> weight,
>>> - int vq_weight, bool *should_update)
>>> +static void virtnet_switch_napi_tx(struct virtnet_info *vi, u32
>>> qstart,
>>> + u32 qend, u32 tx_frames)
>>> {
>>> - if (weight ^ vq_weight) {
>>> - if (dev_flags & IFF_UP)
>>> - return -EBUSY;
>>> - *should_update = true;
>>> - }
>>> + struct net_device *dev = vi->dev;
>>> + int new_weight, cur_weight;
>>> + struct netdev_queue *txq;
>>> + struct send_queue *sq;
>>> - return 0;
>>> + new_weight = tx_frames ? NAPI_POLL_WEIGHT : 0;
>>> + for (; qstart < qend; qstart++) {
>>> + sq = &vi->sq[qstart];
>>> + cur_weight = sq->napi.weight;
>>> + if (!(new_weight ^ cur_weight))
>>> + continue;
>>> +
>>> + if (!(dev->flags & IFF_UP)) {
>>> + sq->napi.weight = new_weight;
>>> + continue;
>>> + }
>>> +
>>> + if (cur_weight)
>>> + virtnet_napi_tx_disable(&sq->napi);
>>> +
>>> + txq = netdev_get_tx_queue(dev, qstart);
>>> + __netif_tx_lock_bh(txq);
>>> + sq->napi.weight = new_weight;
>>> + __netif_tx_unlock_bh(txq);
>>> +
>>> + if (!cur_weight)
>>> + virtnet_napi_tx_enable(vi, sq->vq, &sq->napi);
>>> + }
>>> }
>>> static int virtnet_set_coalesce(struct net_device *dev,
>>> @@ -3577,25 +3598,11 @@ static int virtnet_set_coalesce(struct
>>> net_device *dev,
>>> struct netlink_ext_ack *extack)
>>> {
>>> struct virtnet_info *vi = netdev_priv(dev);
>>> - int ret, queue_number, napi_weight;
>>> - bool update_napi = false;
>>> -
>>> - /* Can't change NAPI weight if the link is up */
>>> - napi_weight = ec->tx_max_coalesced_frames ? NAPI_POLL_WEIGHT : 0;
>>> - for (queue_number = 0; queue_number < vi->max_queue_pairs;
>>> queue_number++) {
>>> - ret = virtnet_should_update_vq_weight(dev->flags, napi_weight,
>>> - vi->sq[queue_number].napi.weight,
>>> - &update_napi);
>>> - if (ret)
>>> - return ret;
>>> -
>>> - if (update_napi) {
>>> - /* All queues that belong to [queue_number,
>>> vi->max_queue_pairs] will be
>>> - * updated for the sake of simplicity, which might not
>>> be necessary
>>> - */
>>> - break;
>>> - }
>>> - }
>>> + int ret;
>>> +
>>> + /* Param tx_frames can be used to switch napi_tx */
>>> + virtnet_switch_napi_tx(vi, 0, vi->max_queue_pairs,
>>> + ec->tx_max_coalesced_frames);
>>> if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL))
>>> ret = virtnet_send_notf_coal_cmds(vi, ec);
>>> @@ -3605,11 +3612,6 @@ static int virtnet_set_coalesce(struct
>>> net_device *dev,
>>> if (ret)
>>> return ret;
>>> - if (update_napi) {
>>> - for (; queue_number < vi->max_queue_pairs; queue_number++)
>>> - vi->sq[queue_number].napi.weight = napi_weight;
>>> - }
>>> -
>>> return ret;
>>> }
>>> @@ -3641,19 +3643,13 @@ static int
>>> virtnet_set_per_queue_coalesce(struct net_device *dev,
>>> struct ethtool_coalesce *ec)
>>> {
>>> struct virtnet_info *vi = netdev_priv(dev);
>>> - int ret, napi_weight;
>>> - bool update_napi = false;
>>> + int ret;
>>> 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;
>>> - ret = virtnet_should_update_vq_weight(dev->flags, napi_weight,
>>> - vi->sq[queue].napi.weight,
>>> - &update_napi);
>>> - if (ret)
>>> - return ret;
>>> + /* Param tx_frames can be used to switch napi_tx */
>>> + virtnet_switch_napi_tx(vi, queue, queue,
>>> ec->tx_max_coalesced_frames);
>>> if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL))
>>> ret = virtnet_send_notf_coal_vq_cmds(vi, ec, queue);
>>> @@ -3663,9 +3659,6 @@ static int
>>> virtnet_set_per_queue_coalesce(struct net_device *dev,
>>> if (ret)
>>> return ret;
>>> - if (update_napi)
>>> - vi->sq[queue].napi.weight = napi_weight;
>>> -
>>> return 0;
>>> }
>
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