[dpdk-stable] [PATCH] net/mlx5: fix multi-segment inline for the first segment

[Viacheslav Ovsiienko <viacheslavo@nvidia.com>]

If the first segment in the multi-segment packet is short
and below the inline threshold it should be inline into
the WQE to improve the performance. For example, the T-Rex
traffic generator might use small leading segments to
handle packet headers and performance was affected.

Fixes: cacb44a09962 ("net/mlx5: add no-inline Tx flag")
Cc: stable@dpdk.org

Signed-off-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
---
 drivers/net/mlx5/mlx5_tx.h | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_tx.h b/drivers/net/mlx5/mlx5_tx.h
index e8b1c0f108..1a35919371 100644
--- a/drivers/net/mlx5/mlx5_tx.h
+++ b/drivers/net/mlx5/mlx5_tx.h
@@ -2041,6 +2041,8 @@ mlx5_tx_packet_multi_inline(struct mlx5_txq_data *__rte_restrict txq,
 		unsigned int nxlen;
 		uintptr_t start;
 
+		mbuf = loc->mbuf;
+		nxlen = rte_pktmbuf_data_len(mbuf);
 		/*
 		 * Packet length exceeds the allowed inline data length,
 		 * check whether the minimal inlining is required.
@@ -2050,28 +2052,23 @@ mlx5_tx_packet_multi_inline(struct mlx5_txq_data *__rte_restrict txq,
 				    MLX5_ESEG_MIN_INLINE_SIZE);
 			MLX5_ASSERT(txq->inlen_mode <= txq->inlen_send);
 			inlen = txq->inlen_mode;
-		} else {
-			if (loc->mbuf->ol_flags & PKT_TX_DYNF_NOINLINE ||
-			    !vlan || txq->vlan_en) {
-				/*
-				 * VLAN insertion will be done inside by HW.
-				 * It is not utmost effective - VLAN flag is
-				 * checked twice, but we should proceed the
-				 * inlining length correctly and take into
-				 * account the VLAN header being inserted.
-				 */
-				return mlx5_tx_packet_multi_send
-							(txq, loc, olx);
-			}
+		} else if (vlan && !txq->vlan_en) {
+			/*
+			 * VLAN insertion is requested and hardware does not
+			 * support the offload, will do with software inline.
+			 */
 			inlen = MLX5_ESEG_MIN_INLINE_SIZE;
+		} else if (mbuf->ol_flags & PKT_TX_DYNF_NOINLINE ||
+			   nxlen > txq->inlen_send) {
+			return mlx5_tx_packet_multi_send(txq, loc, olx);
+		} else {
+			goto do_first;
 		}
 		/*
 		 * Now we know the minimal amount of data is requested
 		 * to inline. Check whether we should inline the buffers
 		 * from the chain beginning to eliminate some mbufs.
 		 */
-		mbuf = loc->mbuf;
-		nxlen = rte_pktmbuf_data_len(mbuf);
 		if (unlikely(nxlen <= txq->inlen_send)) {
 			/* We can inline first mbuf at least. */
 			if (nxlen < inlen) {
@@ -2093,6 +2090,7 @@ mlx5_tx_packet_multi_inline(struct mlx5_txq_data *__rte_restrict txq,
 					goto do_align;
 				}
 			}
+do_first:
 			do {
 				inlen = nxlen;
 				mbuf = NEXT(mbuf);
-- 
2.18.1