net/mlx5: fix minimum number of Multi-Packet RQ buffers

If MPRQ is enabled, a PMD-private mempool is allocated. For ConnectX-4 Lx,
the minimum number of strides is 512 which ConnectX-5 supports 8. This
results in quite small number of elements for the MPRQ mempool. For
example, if the size of Rx ring is configured as 512, only one MPRQ buffer
can cover the whole ring. If there's only one Rx queue is configured. In
the following code in mlx5_mprq_alloc_mp(), desc is 1 and obj_num will be
36 as a result.

	desc *= 4;
	obj_num = desc + MLX5_MPRQ_MP_CACHE_SZ * priv->rxqs_n;

However, rte_mempool_create_empty() has a sanity check to refuse large
per-lcore cache size compared to the number of elements. Cache flush
threshold should not exceed the number of elements of a mempool. For the
above example, the threshold is 32 * 1.5 = 48 which is larger than 36 and
it fails to create the mempool.

Fixes: 7d6bf6b866b8 ("net/mlx5: add Multi-Packet Rx support")
Cc: stable@dpdk.org
Signed-off-by: Yongseok Koh <yskoh@mellanox.com>

diff --git a/drivers/net/mlx5/mlx5_defs.h b/drivers/net/mlx5/mlx5_defs.h
index 439cc159f6c74825c3c6b899b8789e8616bc38f8..f2a1679511d009df2358f928e4cb92f81fa19671 100644 (file)
--- a/drivers/net/mlx5/mlx5_defs.h
+++ b/drivers/net/mlx5/mlx5_defs.h
@@ -126,7 +126,7 @@
 #define MLX5_MPRQ_MIN_RXQS 12
 
 /* Cache size of mempool for Multi-Packet RQ. */
-#define MLX5_MPRQ_MP_CACHE_SZ 32
+#define MLX5_MPRQ_MP_CACHE_SZ 32U
 
 /* Definition of static_assert found in /usr/include/assert.h */
 #ifndef HAVE_STATIC_ASSERT

diff --git a/drivers/net/mlx5/mlx5_rxq.c b/drivers/net/mlx5/mlx5_rxq.c
index 97b3e8ef0c674e7b7ef93e3e7755f4eb32e6e809..8b4c1b1a14927e6db11c7d38ad9183ca887a9c7c 100644 (file)
--- a/drivers/net/mlx5/mlx5_rxq.c
+++ b/drivers/net/mlx5/mlx5_rxq.c
@@ -1234,6 +1234,13 @@ mlx5_mprq_alloc_mp(struct rte_eth_dev *dev)
         */
        desc *= 4;
        obj_num = desc + MLX5_MPRQ_MP_CACHE_SZ * priv->rxqs_n;
+       /*
+        * rte_mempool_create_empty() has sanity check to refuse large cache
+        * size compared to the number of elements.
+        * CACHE_FLUSHTHRESH_MULTIPLIER is defined in a C file, so using a
+        * constant number 2 instead.
+        */
+       obj_num = RTE_MAX(obj_num, MLX5_MPRQ_MP_CACHE_SZ * 2);
        /* Check a mempool is already allocated and if it can be resued. */
        if (mp != NULL && mp->elt_size >= obj_size && mp->size >= obj_num) {
                DRV_LOG(DEBUG, "port %u mempool %s is being reused",