[dpdk-stable] patch 'net/mlx5: fix multi-segment inline for the first segments' has been queued to stable release 20.11.3

[luca.boccassi at gmail.com]

Hi,

FYI, your patch has been queued to stable release 20.11.3

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 07/14/21. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/bluca/dpdk-stable

This queued commit can be viewed at:
https://github.com/bluca/dpdk-stable/commit/50ad5c68ce041b5258278d041ea1052bb3fa6709

Thanks.

Luca Boccassi

---
>From 50ad5c68ce041b5258278d041ea1052bb3fa6709 Mon Sep 17 00:00:00 2001
From: Viacheslav Ovsiienko <viacheslavo at nvidia.com>
Date: Tue, 22 Jun 2021 19:40:49 +0300
Subject: [PATCH] net/mlx5: fix multi-segment inline for the first segments

[ upstream commit ec837ad0fc7c6df4912cc2706b9cd54b225f4a34 ]

Before 19.08 release the Tx burst routines of mlx5 PMD
provided data inline for the first short segments of the
multi-segment packets. In the release 19.08 mlx5 Tx datapath
was refactored and this behavior was broken, affecting the
performance.

For example, the T-Rex traffic generator might use small
leading segments to handle packet headers and performance
degradation was noticed.

If the first segments of the multi-segment packet are short
and the overall length is below the inline threshold it
should be inline into the WQE to fix the performance.

Fixes: 18a1c20044c0 ("net/mlx5: implement Tx burst template")

Signed-off-by: Viacheslav Ovsiienko <viacheslavo at nvidia.com>
---
 drivers/net/mlx5/mlx5_rxtx.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index c765314068..64bba34ffc 100644
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -3456,6 +3456,8 @@ 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
@@ -3466,28 +3468,23 @@ 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) {
@@ -3509,6 +3506,7 @@ mlx5_tx_packet_multi_inline(struct mlx5_txq_data *__rte_restrict txq,
 					goto do_align;
 				}
 			}
+do_first:
 			do {
 				inlen = nxlen;
 				mbuf = NEXT(mbuf);
-- 
2.30.2

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2021-07-12 13:41:41.341503969 +0100
+++ 0092-net-mlx5-fix-multi-segment-inline-for-the-first-segm.patch	2021-07-12 13:41:36.778128610 +0100
@@ -1 +1 @@
-From ec837ad0fc7c6df4912cc2706b9cd54b225f4a34 Mon Sep 17 00:00:00 2001
+From 50ad5c68ce041b5258278d041ea1052bb3fa6709 Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit ec837ad0fc7c6df4912cc2706b9cd54b225f4a34 ]
+
@@ -21 +22,0 @@
-Cc: stable at dpdk.org
@@ -25 +26 @@
- drivers/net/mlx5/mlx5_tx.h | 28 +++++++++++++---------------
+ drivers/net/mlx5/mlx5_rxtx.c | 28 +++++++++++++---------------
@@ -28,5 +29,5 @@
-diff --git a/drivers/net/mlx5/mlx5_tx.h b/drivers/net/mlx5/mlx5_tx.h
-index 7d3ff8407c..634c9d754a 100644
---- a/drivers/net/mlx5/mlx5_tx.h
-+++ b/drivers/net/mlx5/mlx5_tx.h
-@@ -2040,6 +2040,8 @@ mlx5_tx_packet_multi_inline(struct mlx5_txq_data *__rte_restrict txq,
+diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
+index c765314068..64bba34ffc 100644
+--- a/drivers/net/mlx5/mlx5_rxtx.c
++++ b/drivers/net/mlx5/mlx5_rxtx.c
+@@ -3456,6 +3456,8 @@ mlx5_tx_packet_multi_inline(struct mlx5_txq_data *__rte_restrict txq,
@@ -39,3 +40,3 @@
- 		 * Packet length exceeds the allowed inline data length,
- 		 * check whether the minimal inlining is required.
-@@ -2049,28 +2051,23 @@ mlx5_tx_packet_multi_inline(struct mlx5_txq_data *__rte_restrict txq,
+ 		 * Packet length exceeds the allowed inline
+ 		 * data length, check whether the minimal
+@@ -3466,28 +3468,23 @@ mlx5_tx_packet_multi_inline(struct mlx5_txq_data *__rte_restrict txq,
@@ -80 +81 @@
-@@ -2092,6 +2089,7 @@ mlx5_tx_packet_multi_inline(struct mlx5_txq_data *__rte_restrict txq,
+@@ -3509,6 +3506,7 @@ mlx5_tx_packet_multi_inline(struct mlx5_txq_data *__rte_restrict txq,