mlx5: fix available entries in Tx rings

The number of available entries in TX rings is taken before performing
completion, effectively making rings smaller than they are and causing
TX performance issues under load.

Fixes: 2e22920b85d9 ("mlx5: support non-scattered Tx and Rx")

Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>

diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index eb6c9f7..fa5e648 100644 (file)
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -436,7 +436,6 @@ mlx5_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 {
        struct txq *txq = (struct txq *)dpdk_txq;
        unsigned int elts_head = txq->elts_head;
-       const unsigned int elts_tail = txq->elts_tail;
        const unsigned int elts_n = txq->elts_n;
        unsigned int elts_comp_cd = txq->elts_comp_cd;
        unsigned int elts_comp = 0;
@@ -446,7 +445,7 @@ mlx5_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 
        assert(elts_comp_cd != 0);
        txq_complete(txq);
-       max = (elts_n - (elts_head - elts_tail));
+       max = (elts_n - (elts_head - txq->elts_tail));
        if (max > elts_n)
                max -= elts_n;
        assert(max >= 1);