sfc: batch up RX delivery

Improves packet rate of 1-byte UDP receives by up to 10%.

Signed-off-by: Edward Cree <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/sfc/efx.c

···
 static int efx_process_channel(struct efx_channel *channel, int budget)
 {
 	struct efx_tx_queue *tx_queue;
+	struct list_head rx_list;
 	int spent;
 
 	if (unlikely(!channel->enabled))
 		return 0;
+
+	/* Prepare the batch receive list */
+	EFX_WARN_ON_PARANOID(channel->rx_list != NULL);
+	INIT_LIST_HEAD(&rx_list);
+	channel->rx_list = &rx_list;
 
 	efx_for_each_channel_tx_queue(tx_queue, channel) {
 		tx_queue->pkts_compl = 0;
···
 				tx_queue->pkts_compl, tx_queue->bytes_compl);
 		}
 	}
+
+	/* Receive any packets we queued up */
+	netif_receive_skb_list(channel->rx_list);
+	channel->rx_list = NULL;
 
 	return spent;
 }
···
 		if (rc)
 			goto fail;
 	}
+
+	channel->rx_list = NULL;
 
 	return 0;
 

drivers/net/ethernet/sfc/net_driver.h

···
  *	__efx_rx_packet(), or zero if there is none
  * @rx_pkt_index: Ring index of first buffer for next packet to be delivered
  *	by __efx_rx_packet(), if @rx_pkt_n_frags != 0
+ * @rx_list: list of SKBs from current RX, awaiting processing
  * @rx_queue: RX queue for this channel
  * @tx_queue: TX queues for this channel
  * @sync_events_state: Current state of sync events on this channel
···
 
 	unsigned int rx_pkt_n_frags;
 	unsigned int rx_pkt_index;
+
+	struct list_head *rx_list;
 
 	struct efx_rx_queue rx_queue;
 	struct efx_tx_queue tx_queue[EFX_TXQ_TYPES];

drivers/net/ethernet/sfc/rx.c

···
 			return;
 
 	/* Pass the packet up */
-	netif_receive_skb(skb);
+	if (channel->rx_list != NULL)
+		/* Add to list, will pass up later */
+		list_add_tail(&skb->list, channel->rx_list);
+	else
+		/* No list, so pass it up now */
+		netif_receive_skb(skb);
 }
 
 /* Handle a received packet.  Second half: Touches packet payload. */