[PATCH v2 bpf-next 03/14] ice: xsk: decorate ICE_XDP_REDIR with likely()

Maciej Fijalkowski
2022-04-13T15:30:40Z

ice_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
ice_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>
---
drivers/net/ethernet/intel/ice/ice_xsk.c | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
index 866ee4df9671..e9ff05de0084 100644
--- a/drivers/net/ethernet/intel/ice/ice_xsk.c
+++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
@@ -629,18 +629,19 @@ int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget)
xsk_buff_dma_sync_for_cpu(xdp, rx_ring->xsk_pool);

xdp_res = ice_run_xdp_zc(rx_ring, xdp, xdp_prog, xdp_ring);
- if (xdp_res) {
- if (xdp_res & (ICE_XDP_TX | ICE_XDP_REDIR))
- xdp_xmit |= xdp_res;
- else
- xsk_buff_free(xdp);
+ if (likely(xdp_res & (ICE_XDP_TX | ICE_XDP_REDIR)))
+ xdp_xmit |= xdp_res;
+ else if (xdp_res == ICE_XDP_CONSUMED)
+ xsk_buff_free(xdp);
+ else
+ goto construct_skb;

- total_rx_bytes += size;
- total_rx_packets++;
+ total_rx_bytes += size;
+ total_rx_packets++;
+
+ ice_bump_ntc(rx_ring);
+ continue;

- ice_bump_ntc(rx_ring);
- continue;
- }
construct_skb:
/* XDP_PASS path */
skb = ice_construct_skb_zc(rx_ring, xdp);
--
2.33.1