net/mlx5: fix legacy non-inline multi-packet performance

The legacy multi-packet write is the feature allowing to
put multiple packets into one transmitting descriptor,
this feature is supported by only NIC ConnectX-4LX.
The number of packets should be limited to provide
optimal size descriptor and better performance.

Fixes: 18a1c20044c0 ("net/mlx5: implement Tx burst template")
Cc: stable@dpdk.org
Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>

diff --git a/drivers/net/mlx5/mlx5_prm.h b/drivers/net/mlx5/mlx5_prm.h
index 651006b..2bac6a7 100644 (file)
--- a/drivers/net/mlx5/mlx5_prm.h
+++ b/drivers/net/mlx5/mlx5_prm.h
@@ -99,6 +99,8 @@
  * in tx burst routine at the moment of freeing multiple mbufs.
  */
 #define MLX5_EMPW_MAX_PACKETS MLX5_TX_COMP_THRESH
+#define MLX5_MPW_MAX_PACKETS 6
+
 /*
  * Default packet length threshold to be inlined with
  * ordinary SEND. Inlining saves the MR key search

diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index 73c16de..25d915c 100644 (file)
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -3888,7 +3888,9 @@ mlx5_tx_burst_empw_simple(struct mlx5_txq_data *restrict txq,
 
 next_empw:
                assert(NB_SEGS(loc->mbuf) == 1);
-               part = RTE_MIN(pkts_n, MLX5_EMPW_MAX_PACKETS);
+               part = RTE_MIN(pkts_n, MLX5_TXOFF_CONFIG(MPW) ?
+                                      MLX5_MPW_MAX_PACKETS :
+                                      MLX5_EMPW_MAX_PACKETS);
                if (unlikely(loc->elts_free < part)) {
                        /* We have no enough elts to save all mbufs. */
                        if (unlikely(loc->elts_free < MLX5_EMPW_MIN_PACKETS))