mlx5: free buffers immediately after completion

This lowers the amount of cache misses.

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

diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index b82017e..622ac17 100644 (file)
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -84,6 +84,7 @@ txq_complete(struct txq *txq)
 {
        unsigned int elts_comp = txq->elts_comp;
        unsigned int elts_tail = txq->elts_tail;
+       unsigned int elts_free = txq->elts_tail;
        const unsigned int elts_n = txq->elts_n;
        int wcs_n;
 
@@ -110,6 +111,25 @@ txq_complete(struct txq *txq)
        elts_tail += wcs_n * txq->elts_comp_cd_init;
        if (elts_tail >= elts_n)
                elts_tail -= elts_n;
+
+       while (elts_free != elts_tail) {
+               struct txq_elt *elt = &(*txq->elts)[elts_free];
+               unsigned int elts_free_next =
+                       (((elts_free + 1) == elts_n) ? 0 : elts_free + 1);
+               struct rte_mbuf *tmp = elt->buf;
+               struct txq_elt *elt_next = &(*txq->elts)[elts_free_next];
+
+               RTE_MBUF_PREFETCH_TO_FREE(elt_next->buf);
+               /* Faster than rte_pktmbuf_free(). */
+               do {
+                       struct rte_mbuf *next = NEXT(tmp);
+
+                       rte_pktmbuf_free_seg(tmp);
+                       tmp = next;
+               } while (tmp != NULL);
+               elts_free = elts_free_next;
+       }
+
        txq->elts_tail = elts_tail;
        txq->elts_comp = elts_comp;
        return 0;
@@ -464,7 +484,6 @@ mlx5_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
                struct rte_mbuf *buf_next = pkts[i + 1];
                unsigned int elts_head_next =
                        (((elts_head + 1) == elts_n) ? 0 : elts_head + 1);
-               struct txq_elt *elt_next = &(*txq->elts)[elts_head_next];
                struct txq_elt *elt = &(*txq->elts)[elts_head];
                unsigned int segs = NB_SEGS(buf);
 #ifdef MLX5_PMD_SOFT_COUNTERS
@@ -472,18 +491,6 @@ mlx5_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 #endif
                uint32_t send_flags = 0;
 
-               /* Clean up old buffer. */
-               if (likely(elt->buf != NULL)) {
-                       struct rte_mbuf *tmp = elt->buf;
-
-                       /* Faster than rte_pktmbuf_free(). */
-                       do {
-                               struct rte_mbuf *next = NEXT(tmp);
-
-                               rte_pktmbuf_free_seg(tmp);
-                               tmp = next;
-                       } while (tmp != NULL);
-               }
                if (i + 1 < max)
                        rte_prefetch0(buf_next);
                /* Request TX completion. */
@@ -517,7 +524,6 @@ mlx5_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
                        if (txq->priv->vf)
                                rte_prefetch0((volatile void *)
                                              (uintptr_t)addr);
-                       RTE_MBUF_PREFETCH_TO_FREE(elt_next->buf);
                        /* Prefetch next buffer data. */
                        if (i + 1 < max) {
                                buf_next_addr =
@@ -568,7 +574,6 @@ mlx5_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
                                          &sges);
                        if (ret.length == (unsigned int)-1)
                                goto stop;
-                       RTE_MBUF_PREFETCH_TO_FREE(elt_next->buf);
                        /* Put SG list into send queue. */
                        err = txq->send_pending_sg_list
                                (txq->qp,