Re: [PATCH bpf-next] xsk: avoid double checking against rx queue being full

[Stanislav Fomichev <stfomichev@gmail.com>]

On 02/18, Maciej Fijalkowski wrote:
> Currently non-zc xsk rx path for multi-buffer case checks twice if xsk
> rx queue has enough space for producing descriptors:
> 1.
> 	if (xskq_prod_nb_free(xs->rx, num_desc) < num_desc) {
> 		xs->rx_queue_full++;
> 		return -ENOBUFS;
> 	}
> 2.
> 	__xsk_rcv_zc(xs, xskb, copied - meta_len, rem ? XDP_PKT_CONTD : 0);
> 	-> err = xskq_prod_reserve_desc(xs->rx, addr, len, flags);
> 	  -> if (xskq_prod_is_full(q))
> 
> Second part is redundant as in 1. we already peeked onto rx queue and
> checked that there is enough space to produce given amount of
> descriptors.
> 
> Provide helper functions that will skip it and therefore optimize code.
> 
> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>

Acked-by: Stanislav Fomichev <sdf@fomichev.me>