[dpdk-dev,v3,3/3] memzone: improve zero-length memzone reserve

diff --git a/lib/librte_eal/common/eal_common_memzone.c b/lib/librte_eal/common/eal_common_memzone.c
index bce3321..18e2349 100644
--- a/lib/librte_eal/common/eal_common_memzone.c
+++ b/lib/librte_eal/common/eal_common_memzone.c
@@ -52,38 +52,6 @@  memzone_lookup_thread_unsafe(const char *name)
 	return NULL;
 }
 
-
-/* This function will return the greatest free block if a heap has been
- * specified. If no heap has been specified, it will return the heap and
- * length of the greatest free block available in all heaps */
-static size_t
-find_heap_max_free_elem(int *s, unsigned align)
-{
-	struct rte_mem_config *mcfg;
-	struct rte_malloc_socket_stats stats;
-	int i, socket = *s;
-	size_t len = 0;
-
-	/* get pointer to global configuration */
-	mcfg = rte_eal_get_configuration()->mem_config;
-
-	for (i = 0; i < RTE_MAX_NUMA_NODES; i++) {
-		if ((socket != SOCKET_ID_ANY) && (socket != i))
-			continue;
-
-		malloc_heap_get_stats(&mcfg->malloc_heaps[i], &stats);
-		if (stats.greatest_free_size > len) {
-			len = stats.greatest_free_size;
-			*s = i;
-		}
-	}
-
-	if (len < MALLOC_ELEM_OVERHEAD + align)
-		return 0;
-
-	return len - MALLOC_ELEM_OVERHEAD - align;
-}
-
 static const struct rte_memzone *
 memzone_reserve_aligned_thread_unsafe(const char *name, size_t len,
 		int socket_id, unsigned int flags, unsigned int align,
@@ -92,6 +60,7 @@  memzone_reserve_aligned_thread_unsafe(const char *name, size_t len,
 	struct rte_memzone *mz;
 	struct rte_mem_config *mcfg;
 	struct rte_fbarray *arr;
+	void *mz_addr;
 	size_t requested_len;
 	int mz_idx;
 	bool contig;
@@ -165,27 +134,16 @@  memzone_reserve_aligned_thread_unsafe(const char *name, size_t len,
 	/* malloc only cares about size flags, remove contig flag from flags */
 	flags &= ~RTE_MEMZONE_IOVA_CONTIG;
 
-	if (len == 0) {
-		/* len == 0 is only allowed for non-contiguous zones */
-		if (contig) {
-			RTE_LOG(DEBUG, EAL, "Reserving zero-length contiguous memzones is not supported\n");
-			rte_errno = EINVAL;
-			return NULL;
-		}
-		if (bound != 0)
+	if (len == 0 && bound == 0) {
+		mz_addr = malloc_heap_alloc_biggest(NULL, socket_id, flags,
+				align, contig);
+	} else {
+		if (len == 0)
 			requested_len = bound;
-		else {
-			requested_len = find_heap_max_free_elem(&socket_id, align);
-			if (requested_len == 0) {
-				rte_errno = ENOMEM;
-				return NULL;
-			}
-		}
+		/* allocate memory on heap */
+		mz_addr = malloc_heap_alloc(NULL, requested_len, socket_id,
+				flags, align, bound, contig);
 	}
-
-	/* allocate memory on heap */
-	void *mz_addr = malloc_heap_alloc(NULL, requested_len, socket_id, flags,
-			align, bound, contig);
 	if (mz_addr == NULL) {
 		rte_errno = ENOMEM;
 		return NULL;
@@ -213,7 +171,7 @@  memzone_reserve_aligned_thread_unsafe(const char *name, size_t len,
 	snprintf(mz->name, sizeof(mz->name), "%s", name);
 	mz->iova = rte_malloc_virt2iova(mz_addr);
 	mz->addr = mz_addr;
-	mz->len = (requested_len == 0 ? elem->size : requested_len);
+	mz->len = elem->size - MALLOC_ELEM_OVERHEAD;
 	mz->hugepage_sz = elem->msl->page_sz;
 	mz->socket_id = elem->msl->socket_id;
 	mz->flags = 0;
diff --git a/lib/librte_eal/common/include/rte_memzone.h b/lib/librte_eal/common/include/rte_memzone.h
index 0eeb94f..beb591e 100644
--- a/lib/librte_eal/common/include/rte_memzone.h
+++ b/lib/librte_eal/common/include/rte_memzone.h
@@ -77,6 +77,12 @@  struct rte_memzone {
  * correctly filled memzone descriptor. If the allocation cannot be
  * done, return NULL.
  *
+ * @note: It is preferable to reserve memzones with len set to 0 and a valid
+ *   socket_id. Setting socket_id to SOCKET_ID_ANY is supported, but will likely
+ *   not yield expected results. Specifically, the resulting memzone may not
+ *   necessarily be the biggest memzone, but rather biggest memzone on socket id
+ *   corresponding to an lcore from which reservation was called.
+ *
  * @param name
  *   The name of the memzone. If it already exists, the function will
  *   fail and return NULL.
@@ -130,6 +136,12 @@  const struct rte_memzone *rte_memzone_reserve(const char *name,
  * descriptor. If the allocation cannot be done or if the alignment
  * is not a power of 2, returns NULL.
  *
+ * @note: It is preferable to reserve memzones with len set to 0 and a valid
+ *   socket_id. Setting socket_id to SOCKET_ID_ANY is supported, but will likely
+ *   not yield expected results. Specifically, the resulting memzone may not
+ *   necessarily be the biggest memzone, but rather biggest memzone on socket id
+ *   corresponding to an lcore from which reservation was called.
+ *
  * @param name
  *   The name of the memzone. If it already exists, the function will
  *   fail and return NULL.
@@ -188,6 +200,12 @@  const struct rte_memzone *rte_memzone_reserve_aligned(const char *name,
  * boundary. That implies that requested length should be less or equal
  * then boundary.
  *
+ * @note: It is preferable to reserve memzones with len set to 0 and a valid
+ *   socket_id. Setting socket_id to SOCKET_ID_ANY is supported, but will likely
+ *   not yield expected results. Specifically, the resulting memzone may not
+ *   necessarily be the biggest memzone, but rather biggest memzone on socket id
+ *   corresponding to an lcore from which reservation was called.
+ *
  * @param name
  *   The name of the memzone. If it already exists, the function will
  *   fail and return NULL.
diff --git a/test/test/test_memzone.c b/test/test/test_memzone.c
index efcf732..696a7e9 100644
--- a/test/test/test_memzone.c
+++ b/test/test/test_memzone.c
@@ -467,23 +467,16 @@  test_memzone_reserve_flags(void)
 
 /* Find the heap with the greatest free block size */
 static size_t
-find_max_block_free_size(const unsigned _align)
+find_max_block_free_size(unsigned align, unsigned int socket_id)
 {
 	struct rte_malloc_socket_stats stats;
-	unsigned i, align = _align;
-	size_t len = 0;
+	size_t len;
 
-	for (i = 0; i < RTE_MAX_NUMA_NODES; i++) {
-		rte_malloc_get_socket_stats(i, &stats);
-		if (stats.greatest_free_size > len)
-			len = stats.greatest_free_size;
-	}
+	rte_malloc_get_socket_stats(socket_id, &stats);
 
-	if (align < RTE_CACHE_LINE_SIZE)
-		align = RTE_CACHE_LINE_ROUNDUP(align+1);
+	len = stats.greatest_free_size;
 
-	if (len <= MALLOC_ELEM_OVERHEAD + align)
-		return 0;
+	align = RTE_CACHE_LINE_ROUNDUP(align);
 
 	return len - MALLOC_ELEM_OVERHEAD - align;
 }
@@ -491,37 +484,44 @@  find_max_block_free_size(const unsigned _align)
 static int
 test_memzone_reserve_max(void)
 {
-	const struct rte_memzone *mz;
-	size_t maxlen;
+	unsigned int i;
 
-	maxlen = find_max_block_free_size(0);
+	for (i = 0; i < rte_socket_count(); i++) {
+		const struct rte_memzone *mz;
+		size_t maxlen;
+		int socket;
 
-	if (maxlen == 0) {
-		printf("There is no space left!\n");
-		return 0;
-	}
+		socket = rte_socket_id_by_idx(i);
+		maxlen = find_max_block_free_size(0, socket);
 
-	mz = rte_memzone_reserve(TEST_MEMZONE_NAME("max_zone"), 0,
-			SOCKET_ID_ANY, 0);
-	if (mz == NULL){
-		printf("Failed to reserve a big chunk of memory - %s\n",
-				rte_strerror(rte_errno));
-		rte_dump_physmem_layout(stdout);
-		rte_memzone_dump(stdout);
-		return -1;
-	}
+		if (maxlen == 0) {
+			printf("There is no space left!\n");
+			return 0;
+		}
 
-	if (mz->len != maxlen) {
-		printf("Memzone reserve with 0 size did not return bigest block\n");
-		printf("Expected size = %zu, actual size = %zu\n", maxlen, mz->len);
-		rte_dump_physmem_layout(stdout);
-		rte_memzone_dump(stdout);
-		return -1;
-	}
+		mz = rte_memzone_reserve(TEST_MEMZONE_NAME("max_zone"), 0,
+				socket, 0);
+		if (mz == NULL) {
+			printf("Failed to reserve a big chunk of memory - %s\n",
+					rte_strerror(rte_errno));
+			rte_dump_physmem_layout(stdout);
+			rte_memzone_dump(stdout);
+			return -1;
+		}
 
-	if (rte_memzone_free(mz)) {
-		printf("Fail memzone free\n");
-		return -1;
+		if (mz->len != maxlen) {
+			printf("Memzone reserve with 0 size did not return bigest block\n");
+			printf("Expected size = %zu, actual size = %zu\n",
+					maxlen, mz->len);
+			rte_dump_physmem_layout(stdout);
+			rte_memzone_dump(stdout);
+			return -1;
+		}
+
+		if (rte_memzone_free(mz)) {
+			printf("Fail memzone free\n");
+			return -1;
+		}
 	}
 
 	return 0;
@@ -530,45 +530,62 @@  test_memzone_reserve_max(void)
 static int
 test_memzone_reserve_max_aligned(void)
 {
-	const struct rte_memzone *mz;
-	size_t maxlen = 0;
+	unsigned int i;
 
-	/* random alignment */
-	rte_srand((unsigned)rte_rdtsc());
-	const unsigned align = 1 << ((rte_rand() % 8) + 5); /* from 128 up to 4k alignment */
+	for (i = 0; i < rte_socket_count(); i++) {
+		const struct rte_memzone *mz;
+		size_t max_len, min_len = 0;
+		int socket;
 
-	maxlen = find_max_block_free_size(align);
+		socket = rte_socket_id_by_idx(i);
 
-	if (maxlen == 0) {
-		printf("There is no space left for biggest %u-aligned memzone!\n", align);
-		return 0;
-	}
+		/* random alignment */
+		rte_srand((unsigned)rte_rdtsc());
+		const unsigned int align = 1 << ((rte_rand() % 8) + 5); /* from 128 up to 4k alignment */
 
-	mz = rte_memzone_reserve_aligned(TEST_MEMZONE_NAME("max_zone_aligned"),
-			0, SOCKET_ID_ANY, 0, align);
-	if (mz == NULL){
-		printf("Failed to reserve a big chunk of memory - %s\n",
-				rte_strerror(rte_errno));
-		rte_dump_physmem_layout(stdout);
-		rte_memzone_dump(stdout);
-		return -1;
-	}
+		/* memzone size may be between size and size - align */
+		min_len = find_max_block_free_size(align, socket);
+		max_len = find_max_block_free_size(0, socket);
 
-	if (mz->len != maxlen) {
-		printf("Memzone reserve with 0 size and alignment %u did not return"
-				" bigest block\n", align);
-		printf("Expected size = %zu, actual size = %zu\n",
-				maxlen, mz->len);
-		rte_dump_physmem_layout(stdout);
-		rte_memzone_dump(stdout);
-		return -1;
-	}
+		if (min_len == 0 || max_len == 0) {
+			printf("There is no space left for biggest %u-aligned memzone!\n",
+					align);
+			return 0;
+		}
 
-	if (rte_memzone_free(mz)) {
-		printf("Fail memzone free\n");
-		return -1;
-	}
+		mz = rte_memzone_reserve_aligned(
+				TEST_MEMZONE_NAME("max_zone_aligned"),
+				0, socket, 0, align);
+		if (mz == NULL) {
+			printf("Failed to reserve a big chunk of memory - %s\n",
+					rte_strerror(rte_errno));
+			rte_dump_physmem_layout(stdout);
+			rte_memzone_dump(stdout);
+			return -1;
+		}
+		if (mz->addr != RTE_PTR_ALIGN(mz->addr, align)) {
+			printf("Memzone reserve with 0 size and alignment %u did not return aligned block\n",
+					align);
+			rte_dump_physmem_layout(stdout);
+			rte_memzone_dump(stdout);
+			return -1;
+		}
+
+		if (mz->len < min_len || mz->len > max_len) {
+			printf("Memzone reserve with 0 size and alignment %u did not return"
+					" bigest block\n", align);
+			printf("Expected size = %zu-%zu, actual size = %zu\n",
+					min_len, max_len, mz->len);
+			rte_dump_physmem_layout(stdout);
+			rte_memzone_dump(stdout);
+			return -1;
+		}
 
+		if (rte_memzone_free(mz)) {
+			printf("Fail memzone free\n");
+			return -1;
+		}
+	}
 	return 0;
 }