[dpdk-stable] [PATCH 43/67] net/mlx5: remove excessive data prefetch

[Yongseok Koh]

[ upstream commit f84411be9e307d2723052a8ae8ee80a1fd9f559b ]

In Enhanced Multi-Packet Send (eMPW), entire packet data is prefetched to
LLC if it isn't inlined. Even though this helps reducing jitter when HW
fetches data by DMA, this can thresh the LLC with evicting precious data.
And if the size of queue is large and there are many queues, this might not
be effective. Also, if application runs on a remote node from the PCIe
link, it may not be helpful and can even cause bad results.

Signed-off-by: Yongseok Koh <yskoh at mellanox.com>
Acked-by: Adrien Mazarguil <adrien.mazarguil at 6wind.com>
---
 drivers/net/mlx5/mlx5_rxtx.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index 9c571f160..2e003aeac 100644
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -1378,7 +1378,6 @@ mlx5_tx_burst_empw(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 	do {
 		struct rte_mbuf *buf = *(pkts++);
 		uintptr_t addr;
-		unsigned int n;
 		unsigned int do_inline = 0; /* Whether inline is possible. */
 		uint32_t length;
 		unsigned int segs_n = buf->nb_segs;
@@ -1555,11 +1554,8 @@ mlx5_tx_burst_empw(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 					((uintptr_t)mpw.data.raw +
 					 inl_pad);
 			(*txq->elts)[elts_head++ & elts_m] = buf;
-			addr = rte_pktmbuf_mtod(buf, uintptr_t);
-			for (n = 0; n * RTE_CACHE_LINE_SIZE < length; n++)
-				rte_prefetch2((void *)(addr +
-						n * RTE_CACHE_LINE_SIZE));
-			addr = rte_cpu_to_be_64(addr);
+			addr = rte_cpu_to_be_64(rte_pktmbuf_mtod(buf,
+								 uintptr_t));
 			*dseg = (rte_v128u32_t) {
 				rte_cpu_to_be_32(length),
 				mlx5_tx_mb2mr(txq, buf),
-- 
2.11.0