[dpdk-dev] [PATCH v2] net/mlx5: fix threshold for mbuf replenishment in MPRQ

Alexander Kozyrev akozyrev at nvidia.com
Tue Jul 13 17:21:12 CEST 2021


The replenishment scheme for the vectorized MPRQ Rx burst aims
to improve the cache locality by allocating new mbufs only when
there are almost no mbufs left: one burst gap between allocated
and consumed indexes.

This gap is not big enough to accommodate a corner case when we
have a very aggressive CQE compression with multiple regular CQEs
at the beginning and 64 zipped CQEs at the end.

Need to keep in mind this case and extend the replenishment
threshold by MLX5_VPMD_RX_MAX_BURST (64) to avoid mbuf overflow.

Fixes: 5fc2e5c27d6 ("net/mlx5: fix mbuf overflow in vectorized MPRQ")
Cc: stable at dpdk.org

Signed-off-by: Alexander Kozyrev <akozyrev at nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo at nvidia.com>
---

v2: increased the replenishment gap to MLX5_VPMD_RX_MAX_BURST
v1: https://patchwork.dpdk.org/project/dpdk/patch/20210712142910.314572-1-akozyrev@nvidia.com/

 drivers/net/mlx5/mlx5_rxtx_vec.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/mlx5/mlx5_rxtx_vec.c b/drivers/net/mlx5/mlx5_rxtx_vec.c
index e64ef70181..e1b6d5422a 100644
--- a/drivers/net/mlx5/mlx5_rxtx_vec.c
+++ b/drivers/net/mlx5/mlx5_rxtx_vec.c
@@ -157,7 +157,8 @@ mlx5_rx_mprq_replenish_bulk_mbuf(struct mlx5_rxq_data *rxq)
 	unsigned int i;
 
 	if (n >= rxq->rq_repl_thresh &&
-	    rxq->elts_ci - rxq->rq_pi <= rxq->rq_repl_thresh) {
+	    rxq->elts_ci - rxq->rq_pi <=
+	    rxq->rq_repl_thresh + MLX5_VPMD_RX_MAX_BURST) {
 		MLX5_ASSERT(n >= MLX5_VPMD_RXQ_RPLNSH_THRESH(elts_n));
 		MLX5_ASSERT(MLX5_VPMD_RXQ_RPLNSH_THRESH(elts_n) >
 			     MLX5_VPMD_DESCS_PER_LOOP);
-- 
2.18.2



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