mlx4: 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: 7fae69eeff13 ("mlx4: new poll mode driver")

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

diff --git a/drivers/net/mlx4/mlx4.c b/drivers/net/mlx4/mlx4.c
index 3e05373..4f57e2d 100644 (file)
--- a/drivers/net/mlx4/mlx4.c
+++ b/drivers/net/mlx4/mlx4.c
@@ -1306,7 +1306,6 @@ mlx4_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;
@@ -1316,7 +1315,7 @@ mlx4_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);