net/mlx5: fix Rx buffer replenishment threshold

The threshold of buffer replenishment for vectorized Rx burst is a constant
value (64). If the size of Rx queue is comparatively small, device could
run out of buffers. For example, if the size of Rx queue is 128, buffers
are replenished only twice per a wraparound. This can cause jitter in
receiving packets and the jitter can cause unnecessary retransmission for
TCP connections.

Fixes: 6cb559d67b83 ("net/mlx5: add vectorized Rx/Tx burst for x86")
Fixes: 570acdb1da8a ("net/mlx5: add vectorized Rx/Tx burst for ARM")
Cc: stable@dpdk.org
Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
Acked-by: Shahaf Shuler <shahafs@mellanox.com>

diff --git a/drivers/net/mlx5/mlx5_defs.h b/drivers/net/mlx5/mlx5_defs.h
index 51124cd..b52f7dc 100644 (file)
--- a/drivers/net/mlx5/mlx5_defs.h
+++ b/drivers/net/mlx5/mlx5_defs.h
@@ -64,10 +64,11 @@
 #define MLX5_VPMD_MIN_TXQS 4
 
 /* Threshold of buffer replenishment for vectorized Rx. */
-#define MLX5_VPMD_RXQ_RPLNSH_THRESH   64U
+#define MLX5_VPMD_RXQ_RPLNSH_THRESH(n) \
+       (RTE_MIN(MLX5_VPMD_RX_MAX_BURST, (unsigned int)(n) >> 2))
 
 /* Maximum size of burst for vectorized Rx. */
-#define MLX5_VPMD_RX_MAX_BURST        MLX5_VPMD_RXQ_RPLNSH_THRESH
+#define MLX5_VPMD_RX_MAX_BURST 64U
 
 /*
  * Maximum size of burst for vectorized Tx. This is related to the maximum size

diff --git a/drivers/net/mlx5/mlx5_rxtx_vec.h b/drivers/net/mlx5/mlx5_rxtx_vec.h
index 598dc75..fb884f9 100644 (file)
--- a/drivers/net/mlx5/mlx5_rxtx_vec.h
+++ b/drivers/net/mlx5/mlx5_rxtx_vec.h
@@ -91,9 +91,9 @@ mlx5_rx_replenish_bulk_mbuf(struct mlx5_rxq_data *rxq, uint16_t n)
                &((volatile struct mlx5_wqe_data_seg *)rxq->wqes)[elts_idx];
        unsigned int i;
 
-       assert(n >= MLX5_VPMD_RXQ_RPLNSH_THRESH);
+       assert(n >= MLX5_VPMD_RXQ_RPLNSH_THRESH(q_n));
        assert(n <= (uint16_t)(q_n - (rxq->rq_ci - rxq->rq_pi)));
-       assert(MLX5_VPMD_RXQ_RPLNSH_THRESH > MLX5_VPMD_DESCS_PER_LOOP);
+       assert(MLX5_VPMD_RXQ_RPLNSH_THRESH(q_n) > MLX5_VPMD_DESCS_PER_LOOP);
        /* Not to cross queue end. */
        n = RTE_MIN(n - MLX5_VPMD_DESCS_PER_LOOP, q_n - elts_idx);
        if (rte_mempool_get_bulk(rxq->mp, (void *)elts, n) < 0) {

diff --git a/drivers/net/mlx5/mlx5_rxtx_vec_neon.h b/drivers/net/mlx5/mlx5_rxtx_vec_neon.h
index 71a5eaf..3ebf348 100644 (file)
--- a/drivers/net/mlx5/mlx5_rxtx_vec_neon.h
+++ b/drivers/net/mlx5/mlx5_rxtx_vec_neon.h
@@ -739,7 +739,7 @@ rxq_burst_v(struct mlx5_rxq_data *rxq, struct rte_mbuf **pkts, uint16_t pkts_n,
         *   N - (rq_ci - rq_pi) := # of buffers consumed (to be replenished).
         */
        repl_n = q_n - (rxq->rq_ci - rxq->rq_pi);
-       if (repl_n >= MLX5_VPMD_RXQ_RPLNSH_THRESH)
+       if (repl_n >= MLX5_VPMD_RXQ_RPLNSH_THRESH(q_n))
                mlx5_rx_replenish_bulk_mbuf(rxq, repl_n);
        /* See if there're unreturned mbufs from compressed CQE. */
        rcvd_pkt = rxq->cq_ci - rxq->rq_pi;

diff --git a/drivers/net/mlx5/mlx5_rxtx_vec_sse.h b/drivers/net/mlx5/mlx5_rxtx_vec_sse.h
index 3e985d6..f0d8888 100644 (file)
--- a/drivers/net/mlx5/mlx5_rxtx_vec_sse.h
+++ b/drivers/net/mlx5/mlx5_rxtx_vec_sse.h
@@ -724,7 +724,7 @@ rxq_burst_v(struct mlx5_rxq_data *rxq, struct rte_mbuf **pkts, uint16_t pkts_n,
         *   N - (rq_ci - rq_pi) := # of buffers consumed (to be replenished).
         */
        repl_n = q_n - (rxq->rq_ci - rxq->rq_pi);
-       if (repl_n >= MLX5_VPMD_RXQ_RPLNSH_THRESH)
+       if (repl_n >= MLX5_VPMD_RXQ_RPLNSH_THRESH(q_n))
                mlx5_rx_replenish_bulk_mbuf(rxq, repl_n);
        /* See if there're unreturned mbufs from compressed CQE. */
        rcvd_pkt = rxq->cq_ci - rxq->rq_pi;