Re: [PATCH net-next v6 2/5] veth: implement Byte Queue Limits (BQL) for latency reduction

[Paolo Abeni]

On 5/27/26 3:54 PM, hawk@xxxxxxxxxx wrote:
> @@ -348,10 +381,11 @@ static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
>  {
>  	struct veth_priv *rcv_priv, *priv = netdev_priv(dev);
>  	struct veth_rq *rq = NULL;
> -	struct netdev_queue *txq;
> +	struct netdev_queue *txq = NULL;

Minor nit: please fix the variables declaration order above.

> @@ -1092,6 +1137,24 @@ static void veth_napi_del_range(struct net_device *dev, int start, int end)
>  		ptr_ring_cleanup(&rq->xdp_ring, veth_ptr_free);
>  	}
>  
> +	/* Reset BQL and wake stopped peer txqs.  A concurrent veth_xmit()
> +	 * may have set DRV_XOFF between rcu_assign_pointer(napi, NULL) and
> +	 * synchronize_net(), and NAPI can no longer clear it.
> +	 * Only wake when the device is still up.
> +	 */
> +	peer = rtnl_dereference(priv->peer);
> +	if (peer) {
> +		int peer_end = min_t(int, end, peer->real_num_tx_queues);

Sashiko noted you may need to additionally complete/reset the tx queue
in the <old_real_num_tx_queues> .. <new_real_num_tx_queue> range, and I
think it's right.

/P