net/mlx5e: Optimize XDP frame xmit
XDP SQ has a fixed size WQE (MLX5E_XDP_TX_WQEBBS = 1) and only posts
one kind of WQE (MLX5_OPCODE_SEND),
Also we initialize SQ descriptors static fields once on open_xdpsq,
rather than every time on critical path.
Optimize the code in light of those facts and add a prefetch of the TX
descriptor first thing in the xdp xmit function.
Performance improvement:
System: Intel(R) Xeon(R) CPU E5-2620 v3 @ 2.40GHz
Test case Before Now improvement
---------------------------------------------------------------
XDP TX (1 core) 13Mpps 13.7Mpps 5%
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>