[PATCH] reorder: introduce API to obtain memory footprint

[Volodymyr Fialko]

At present, it is not easy to determine the memory requirement for the
reorder buffer without delving into its implementation details.
To facilitate the use of reorder buffer with user allocation, a new API
`rte_reorder_memory_footprint_get()` is introduced.
This API will provide the amount of required memory for reorder buffer.

Signed-off-by: Volodymyr Fialko <vfialko at marvell.com>
---
 app/test/test_reorder.c   |  8 ++++----
 lib/reorder/rte_reorder.c | 13 +++++++++----
 lib/reorder/rte_reorder.h | 16 ++++++++++++++++
 lib/reorder/version.map   |  2 ++
 4 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/app/test/test_reorder.c b/app/test/test_reorder.c
index f391597a78..6daa913ef9 100644
--- a/app/test/test_reorder.c
+++ b/app/test/test_reorder.c
@@ -68,12 +68,12 @@ test_reorder_init(void)
 	struct rte_reorder_buffer *b = NULL;
 	unsigned int size;
 	/*
-	 * The minimum memory area size that should be passed to library is,
-	 * sizeof(struct rte_reorder_buffer) + (2 * size * sizeof(struct rte_mbuf *));
+	 * The minimum memory area size that should be passed to library determined
+	 * by rte_reorder_memory_footprint_get().
 	 * Otherwise error will be thrown
 	 */
 
-	size = 100;
+	size = rte_reorder_memory_footprint_get(REORDER_BUFFER_SIZE) - 1;
 	b = rte_reorder_init(b, size, "PKT1", REORDER_BUFFER_SIZE);
 	TEST_ASSERT((b == NULL) && (rte_errno == EINVAL),
 			"No error on init with NULL buffer.");
@@ -84,7 +84,7 @@ test_reorder_init(void)
 			"No error on init with invalid mem zone size.");
 	rte_free(b);
 
-	size = 262336;
+	size = rte_reorder_memory_footprint_get(REORDER_BUFFER_SIZE);
 	b = rte_malloc(NULL, size, 0);
 	b = rte_reorder_init(b, size, "PKT1", REORDER_BUFFER_SIZE_INVALID);
 	TEST_ASSERT((b == NULL) && (rte_errno == EINVAL),
diff --git a/lib/reorder/rte_reorder.c b/lib/reorder/rte_reorder.c
index 66d2cc07b7..f55f383700 100644
--- a/lib/reorder/rte_reorder.c
+++ b/lib/reorder/rte_reorder.c
@@ -54,12 +54,17 @@ struct rte_reorder_buffer {
 static void
 rte_reorder_free_mbufs(struct rte_reorder_buffer *b);
 
+unsigned int
+rte_reorder_memory_footprint_get(unsigned int size)
+{
+	return sizeof(struct rte_reorder_buffer) + (2 * size * sizeof(struct rte_mbuf *));
+}
+
 struct rte_reorder_buffer *
 rte_reorder_init(struct rte_reorder_buffer *b, unsigned int bufsize,
 		const char *name, unsigned int size)
 {
-	const unsigned int min_bufsize = sizeof(*b) +
-					(2 * size * sizeof(struct rte_mbuf *));
+	const unsigned int min_bufsize = rte_reorder_memory_footprint_get(size);
 	static const struct rte_mbuf_dynfield reorder_seqn_dynfield_desc = {
 		.name = RTE_REORDER_SEQN_DYNFIELD_NAME,
 		.size = sizeof(rte_reorder_seqn_t),
@@ -148,8 +153,8 @@ rte_reorder_create(const char *name, unsigned socket_id, unsigned int size)
 {
 	struct rte_reorder_buffer *b = NULL;
 	struct rte_tailq_entry *te, *te_inserted;
-	const unsigned int bufsize = sizeof(struct rte_reorder_buffer) +
-					(2 * size * sizeof(struct rte_mbuf *));
+
+	const unsigned int bufsize = rte_reorder_memory_footprint_get(size);
 
 	/* Check user arguments. */
 	if (!rte_is_power_of_2(size)) {
diff --git a/lib/reorder/rte_reorder.h b/lib/reorder/rte_reorder.h
index 9a5998f2f6..16dc4ee400 100644
--- a/lib/reorder/rte_reorder.h
+++ b/lib/reorder/rte_reorder.h
@@ -212,6 +212,22 @@ __rte_experimental
 unsigned int
 rte_reorder_min_seqn_set(struct rte_reorder_buffer *b, rte_reorder_seqn_t min_seqn);
 
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice
+ *
+ * Determine the amount of memory needed by the reorder buffer to accommodate a given number of
+ * elements. @see rte_reorder_init()
+ *
+ * @param size
+ *   Number of elements that can be stored in reorder buffer.
+ * @return
+ *   Reorder buffer footprint measured in bytes.
+ */
+__rte_experimental
+unsigned int
+rte_reorder_memory_footprint_get(unsigned int size);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/reorder/version.map b/lib/reorder/version.map
index e21b91f526..7ff6a622f4 100644
--- a/lib/reorder/version.map
+++ b/lib/reorder/version.map
@@ -19,4 +19,6 @@ EXPERIMENTAL {
 	# added in 23.03
 	rte_reorder_drain_up_to_seqn;
 	rte_reorder_min_seqn_set;
+	# added in 23.07
+	rte_reorder_memory_footprint_get;
 };
-- 
2.34.1