[dpdk-stable] [PATCH 18.11] net/mlx5: fix instruction hotspot on replenishing Rx buffer

[Yongseok Koh]

[ backported from upstream commit 12d468a62bc19ca08ee9964dcb923f67f87fba7d ]

On replenishing Rx buffers for vectorized Rx, mbuf->buf_addr isn't needed
to be accessed as it is static and easily calculated from the mbuf address.
Accessing the mbuf content causes unnecessary load stall and it is worsened
on ARM.

Fixes: 545b884b1da3 ("net/mlx5: fix buffer address posting in SSE Rx")

Signed-off-by: Yongseok Koh <yskoh at mellanox.com>
Acked-by: Shahaf Shuler <shahafs at mellanox.com>
---
 drivers/net/mlx5/mlx5_rxtx_vec.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_rxtx_vec.h b/drivers/net/mlx5/mlx5_rxtx_vec.h
index fda7004e2d..da447a63e2 100644
--- a/drivers/net/mlx5/mlx5_rxtx_vec.h
+++ b/drivers/net/mlx5/mlx5_rxtx_vec.h
@@ -102,8 +102,12 @@ mlx5_rx_replenish_bulk_mbuf(struct mlx5_rxq_data *rxq, uint16_t n)
 		return;
 	}
 	for (i = 0; i < n; ++i) {
-		wq[i].addr = rte_cpu_to_be_64((uintptr_t)elts[i]->buf_addr +
-					      RTE_PKTMBUF_HEADROOM);
+		uintptr_t buf_addr =
+			(uintptr_t)elts[i] + sizeof(struct rte_mbuf) +
+			rte_pktmbuf_priv_size(rxq->mp);
+
+		assert(buf_addr == (uintptr_t)elts[i]->buf_addr);
+		wq[i].addr = rte_cpu_to_be_64(buf_addr + RTE_PKTMBUF_HEADROOM);
 		/* If there's only one MR, no need to replace LKey in WQE. */
 		if (unlikely(mlx5_mr_btree_len(&rxq->mr_ctrl.cache_bh) > 1))
 			wq[i].lkey = mlx5_rx_mb2mr(rxq, elts[i]);
-- 
2.11.0