[PATCH v2] mbuf perf test, please ignore

["Morten Brørup" <mb@smartsharesystems.com>]

Playing around with the mbuf structure, trying to reduce the use of the
second cache line in some common scenarios.

v2:
* Remove BUILD_BUG_ON in cnxk PMD.

Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
---
 drivers/net/cnxk/cn10k_ethdev.c |  2 ++
 drivers/net/cnxk/cn9k_ethdev.c  |  2 ++
 lib/mbuf/rte_mbuf_core.h        | 38 ++++++++++++++++-----------------
 3 files changed, 23 insertions(+), 19 deletions(-)

diff --git a/drivers/net/cnxk/cn10k_ethdev.c b/drivers/net/cnxk/cn10k_ethdev.c
index 4658713591..9f6086efe6 100644
--- a/drivers/net/cnxk/cn10k_ethdev.c
+++ b/drivers/net/cnxk/cn10k_ethdev.c
@@ -72,8 +72,10 @@ nix_tx_offload_flags(struct rte_eth_dev *eth_dev)
 			 offsetof(struct rte_mbuf, buf_addr) + 24);
 	RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, pkt_len) !=
 			 offsetof(struct rte_mbuf, ol_flags) + 12);
+/*
 	RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, tx_offload) !=
 			 offsetof(struct rte_mbuf, pool) + 2 * sizeof(void *));
+*/
 
 	if (conf & RTE_ETH_TX_OFFLOAD_VLAN_INSERT ||
 	    conf & RTE_ETH_TX_OFFLOAD_QINQ_INSERT)
diff --git a/drivers/net/cnxk/cn9k_ethdev.c b/drivers/net/cnxk/cn9k_ethdev.c
index 3b702d9696..3e9161ca79 100644
--- a/drivers/net/cnxk/cn9k_ethdev.c
+++ b/drivers/net/cnxk/cn9k_ethdev.c
@@ -72,8 +72,10 @@ nix_tx_offload_flags(struct rte_eth_dev *eth_dev)
 			 offsetof(struct rte_mbuf, buf_addr) + 24);
 	RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, pkt_len) !=
 			 offsetof(struct rte_mbuf, ol_flags) + 12);
+/*
 	RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, tx_offload) !=
 			 offsetof(struct rte_mbuf, pool) + 2 * sizeof(void *));
+*/
 
 	if (conf & RTE_ETH_TX_OFFLOAD_VLAN_INSERT ||
 	    conf & RTE_ETH_TX_OFFLOAD_QINQ_INSERT)
diff --git a/lib/mbuf/rte_mbuf_core.h b/lib/mbuf/rte_mbuf_core.h
index a30e1e0eaf..c0c3b45024 100644
--- a/lib/mbuf/rte_mbuf_core.h
+++ b/lib/mbuf/rte_mbuf_core.h
@@ -594,25 +594,6 @@ struct rte_mbuf {
 
 	uint16_t buf_len;         /**< Length of segment buffer. */
 
-	struct rte_mempool *pool; /**< Pool from which mbuf was allocated. */
-
-	/* second cache line - fields only used in slow path or on TX */
-	RTE_MARKER cacheline1 __rte_cache_min_aligned;
-
-#if RTE_IOVA_AS_PA
-	/**
-	 * Next segment of scattered packet. Must be NULL in the last
-	 * segment or in case of non-segmented packet.
-	 */
-	struct rte_mbuf *next;
-#else
-	/**
-	 * Reserved for dynamic fields
-	 * when the next pointer is in first cache line (i.e. RTE_IOVA_AS_PA is 0).
-	 */
-	uint64_t dynfield2;
-#endif
-
 	/* fields to support TX offloads */
 	RTE_STD_C11
 	union {
@@ -651,6 +632,25 @@ struct rte_mbuf {
 		};
 	};
 
+	/* second cache line - fields only used in slow path or on TX */
+	RTE_MARKER cacheline1 __rte_cache_min_aligned;
+
+#if RTE_IOVA_AS_PA
+	/**
+	 * Next segment of scattered packet. Must be NULL in the last
+	 * segment or in case of non-segmented packet.
+	 */
+	struct rte_mbuf *next;
+#else
+	/**
+	 * Reserved for dynamic fields
+	 * when the next pointer is in first cache line (i.e. RTE_IOVA_AS_PA is 0).
+	 */
+	uint64_t dynfield2;
+#endif
+
+	struct rte_mempool *pool; /**< Pool from which mbuf was allocated. */
+
 	/** Shared data for external buffer attached to mbuf. See
 	 * rte_pktmbuf_attach_extbuf().
 	 */
-- 
2.17.1