[dpdk-dev] [RFC ][PATCH] Introduce RTE_ARCH_STRONGLY_ORDERED_MEM_OPS configuration parameter

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

rte_ring implementation needs explicit memory barrier
in weakly ordered architecture like ARM unlike
strongly ordered architecture like X86

Introducing RTE_ARCH_STRONGLY_ORDERED_MEM_OPS
configuration to abstract such dependency so that other
weakly ordered architectures can reuse this infrastructure.

Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
---
 config/common_bsdapp                         |  5 +++++
 config/common_linuxapp                       |  5 +++++
 config/defconfig_arm64-armv8a-linuxapp-gcc   |  1 +
 config/defconfig_arm64-thunderx-linuxapp-gcc |  1 +
 lib/librte_ring/rte_ring.h                   | 20 ++++++++++++++++++++
 5 files changed, 32 insertions(+)

diff --git a/config/common_bsdapp b/config/common_bsdapp
index b37dcf4..c8d1f63 100644
--- a/config/common_bsdapp
+++ b/config/common_bsdapp
@@ -79,6 +79,11 @@ CONFIG_RTE_FORCE_INTRINSICS=n
 CONFIG_RTE_ARCH_STRICT_ALIGN=n
 
 #
+# Machine has strongly-ordered memory operations on normal memory like x86
+#
+CONFIG_RTE_ARCH_STRONGLY_ORDERED_MEM_OPS=y
+
+#
 # Compile to share library
 #
 CONFIG_RTE_BUILD_SHARED_LIB=n
diff --git a/config/common_linuxapp b/config/common_linuxapp
index 0de43d5..d040a74 100644
--- a/config/common_linuxapp
+++ b/config/common_linuxapp
@@ -79,6 +79,11 @@ CONFIG_RTE_FORCE_INTRINSICS=n
 CONFIG_RTE_ARCH_STRICT_ALIGN=n
 
 #
+# Machine has strongly-ordered memory operations on normal memory like x86
+#
+CONFIG_RTE_ARCH_STRONGLY_ORDERED_MEM_OPS=y
+
+#
 # Compile to share library
 #
 CONFIG_RTE_BUILD_SHARED_LIB=n
diff --git a/config/defconfig_arm64-armv8a-linuxapp-gcc b/config/defconfig_arm64-armv8a-linuxapp-gcc
index 6ea38a5..5289152 100644
--- a/config/defconfig_arm64-armv8a-linuxapp-gcc
+++ b/config/defconfig_arm64-armv8a-linuxapp-gcc
@@ -37,6 +37,7 @@ CONFIG_RTE_ARCH="arm64"
 CONFIG_RTE_ARCH_ARM64=y
 CONFIG_RTE_ARCH_64=y
 CONFIG_RTE_ARCH_ARM_NEON=y
+CONFIG_RTE_ARCH_STRONGLY_ORDERED_MEM_OPS=n
 
 CONFIG_RTE_FORCE_INTRINSICS=y
 
diff --git a/config/defconfig_arm64-thunderx-linuxapp-gcc b/config/defconfig_arm64-thunderx-linuxapp-gcc
index e8fccc7..79fa9e6 100644
--- a/config/defconfig_arm64-thunderx-linuxapp-gcc
+++ b/config/defconfig_arm64-thunderx-linuxapp-gcc
@@ -37,6 +37,7 @@ CONFIG_RTE_ARCH="arm64"
 CONFIG_RTE_ARCH_ARM64=y
 CONFIG_RTE_ARCH_64=y
 CONFIG_RTE_ARCH_ARM_NEON=y
+CONFIG_RTE_ARCH_STRONGLY_ORDERED_MEM_OPS=n
 
 CONFIG_RTE_FORCE_INTRINSICS=y
 
diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h
index af68888..1ccd186 100644
--- a/lib/librte_ring/rte_ring.h
+++ b/lib/librte_ring/rte_ring.h
@@ -457,7 +457,12 @@ __rte_ring_mp_do_enqueue(struct rte_ring *r, void * const *obj_table,
 
 	/* write entries in ring */
 	ENQUEUE_PTRS();
+
+#ifdef RTE_ARCH_STRONGLY_ORDERED_MEM_OPS
 	rte_compiler_barrier();
+#else
+	rte_wmb();
+#endif
 
 	/* if we exceed the watermark */
 	if (unlikely(((mask + 1) - free_entries + n) > r->prod.watermark)) {
@@ -552,7 +557,12 @@ __rte_ring_sp_do_enqueue(struct rte_ring *r, void * const *obj_table,
 
 	/* write entries in ring */
 	ENQUEUE_PTRS();
+
+#ifdef RTE_ARCH_STRONGLY_ORDERED_MEM_OPS
 	rte_compiler_barrier();
+#else
+	rte_wmb();
+#endif
 
 	/* if we exceed the watermark */
 	if (unlikely(((mask + 1) - free_entries + n) > r->prod.watermark)) {
@@ -643,7 +653,12 @@ __rte_ring_mc_do_dequeue(struct rte_ring *r, void **obj_table,
 
 	/* copy in table */
 	DEQUEUE_PTRS();
+
+#ifdef RTE_ARCH_STRONGLY_ORDERED_MEM_OPS
 	rte_compiler_barrier();
+#else
+	rte_rmb();
+#endif
 
 	/*
 	 * If there are other dequeues in progress that preceded us,
@@ -727,7 +742,12 @@ __rte_ring_sc_do_dequeue(struct rte_ring *r, void **obj_table,
 
 	/* copy in table */
 	DEQUEUE_PTRS();
+
+#ifdef RTE_ARCH_STRONGLY_ORDERED_MEM_OPS
 	rte_compiler_barrier();
+#else
+	rte_rmb();
+#endif
 
 	__RING_STAT_ADD(r, deq_success, n);
 	r->cons.tail = cons_next;
-- 
2.1.0