Re: [PATCH v11 39/40] virtio_net: support tx queue resize

Jason Wang
2022-07-04T03:46:13Z

在 2022/6/29 14:56, Xuan Zhuo 写道:
> This patch implements the resize function of the tx queues.
> Based on this function, it is possible to modify the ring num of the
> queue.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> ---
> drivers/net/virtio_net.c | 48 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 48 insertions(+)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 6ab16fd193e5..fd358462f802 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -135,6 +135,9 @@ struct send_queue {
> struct virtnet_sq_stats stats;
>
> struct napi_struct napi;
> +
> + /* Record whether sq is in reset state. */
> + bool reset;
> };
>
> /* Internal representation of a receive virtqueue */
> @@ -279,6 +282,7 @@ struct padded_vnet_hdr {
> };
>
> static void virtnet_rq_free_unused_buf(struct virtqueue *vq, void *buf);
> +static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf);
>
> static bool is_xdp_frame(void *ptr)
> {
> @@ -1603,6 +1607,11 @@ static void virtnet_poll_cleantx(struct receive_queue *rq)
> return;
>
> if (__netif_tx_trylock(txq)) {
> + if (READ_ONCE(sq->reset)) {
> + __netif_tx_unlock(txq);
> + return;
> + }
> +
> do {
> virtqueue_disable_cb(sq->vq);
> free_old_xmit_skbs(sq, true);
> @@ -1868,6 +1877,45 @@ static int virtnet_rx_resize(struct virtnet_info *vi,
> return err;
> }
>
> +static int virtnet_tx_resize(struct virtnet_info *vi,
> + struct send_queue *sq, u32 ring_num)
> +{
> + struct netdev_queue *txq;
> + int err, qindex;
> +
> + qindex = sq - vi->sq;
> +
> + virtnet_napi_tx_disable(&sq->napi);
> +
> + txq = netdev_get_tx_queue(vi->dev, qindex);
> +
> + /* 1. wait all ximt complete
> + * 2. fix the race of netif_stop_subqueue() vs netif_start_subqueue()
> + */
> + __netif_tx_lock_bh(txq);
> +
> + /* Prevent rx poll from accessing sq. */
> + WRITE_ONCE(sq->reset, true);

Can we simply disable RX NAPI here?

Thanks

> +
> + /* Prevent the upper layer from trying to send packets. */
> + netif_stop_subqueue(vi->dev, qindex);
> +
> + __netif_tx_unlock_bh(txq);
> +
> + err = virtqueue_resize(sq->vq, ring_num, virtnet_sq_free_unused_buf);
> + if (err)
> + netdev_err(vi->dev, "resize tx fail: tx queue index: %d err: %d\n", qindex, err);
> +
> + /* Memory barrier before set reset and start subqueue. */
> + smp_mb();
> +
> + WRITE_ONCE(sq->reset, false);
> + netif_tx_wake_queue(txq);
> +
> + virtnet_napi_tx_enable(vi, sq->vq, &sq->napi);
> + return err;
> +}
> +
> /*
> * Send command via the control virtqueue and check status. Commands
> * supported by the hypervisor, as indicated by feature bits, should