ixgbe, xsk: Decorate IXGBE_XDP_REDIR with likely()

ixgbe_run_xdp_zc() suggests to compiler that XDP_REDIRECT is the most
probable action returned from BPF program that AF_XDP has in its
pipeline. Let's also bring this suggestion up to the callsite of
ixgbe_run_xdp_zc() so that compiler will be able to generate more
optimized code which in turn will make branch predictor happy.

Suggested-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220413153015.453864-5-maciej.fijalkowski@intel.com

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
index dd7ff66..85497bf 100644 (file)
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
@@ -303,21 +303,22 @@ int ixgbe_clean_rx_irq_zc(struct ixgbe_q_vector *q_vector,
                xsk_buff_dma_sync_for_cpu(bi->xdp, rx_ring->xsk_pool);
                xdp_res = ixgbe_run_xdp_zc(adapter, rx_ring, bi->xdp);
 
-               if (xdp_res) {
-                       if (xdp_res & (IXGBE_XDP_TX | IXGBE_XDP_REDIR))
-                               xdp_xmit |= xdp_res;
-                       else
-                               xsk_buff_free(bi->xdp);
+               if (likely(xdp_res & (IXGBE_XDP_TX | IXGBE_XDP_REDIR)))
+                       xdp_xmit |= xdp_res;
+               else if (xdp_res == IXGBE_XDP_CONSUMED)
+                       xsk_buff_free(bi->xdp);
+               else
+                       goto construct_skb;
 
-                       bi->xdp = NULL;
-                       total_rx_packets++;
-                       total_rx_bytes += size;
+               bi->xdp = NULL;
+               total_rx_packets++;
+               total_rx_bytes += size;
 
-                       cleaned_count++;
-                       ixgbe_inc_ntc(rx_ring);
-                       continue;
-               }
+               cleaned_count++;
+               ixgbe_inc_ntc(rx_ring);
+               continue;
 
+construct_skb:
                /* XDP_PASS path */
                skb = ixgbe_construct_skb_zc(rx_ring, bi->xdp);
                if (!skb) {