sys: heap: support maximum allocated bytes statistic

Besides the current allocated/free bytes, keep track of
the maximum allocated bytes to help determine the heap
size requirements. Also, provide a function to reset
the statistic.

Signed-off-by: Damian Krolik <damian.krolik@nordicsemi.no>

include/zephyr/sys/sys_heap.h

@@ -70,6 +70,7 @@ struct z_heap_stress_result {
 struct sys_heap_runtime_stats {
 	size_t free_bytes;
 	size_t allocated_bytes;
+	size_t max_allocated_bytes;
 };
 
 /**
@@ -82,6 +83,17 @@ struct sys_heap_runtime_stats {
 int sys_heap_runtime_stats_get(struct sys_heap *heap,
 		struct sys_heap_runtime_stats *stats);
 
+/**
+ * @brief Reset the maximum heap usage.
+ *
+ * Set the statistic measuring the maximum number of allocated bytes to the
+ * current number of allocated bytes.
+ *
+ * @param heap Pointer to sys_heap
+ * @return -EINVAL if null pointer was passed, otherwise 0
+ */
+int sys_heap_runtime_stats_reset_max(struct sys_heap *heap);
+
 #endif
 
 /** @brief Initialize sys_heap

lib/os/heap-validate.c

@@ -422,6 +422,18 @@ int sys_heap_runtime_stats_get(struct sys_heap *heap,
 
 	stats->free_bytes = heap->heap->free_bytes;
 	stats->allocated_bytes = heap->heap->allocated_bytes;
+	stats->max_allocated_bytes = heap->heap->max_allocated_bytes;
+
+	return 0;
+}
+
+int sys_heap_runtime_stats_reset_max(struct sys_heap *heap)
+{
+	if (heap == NULL) {
+		return -EINVAL;
+	}
+
+	heap->heap->max_allocated_bytes = heap->heap->allocated_bytes;
 
 	return 0;
 }

lib/os/heap.c

@@ -10,6 +10,14 @@
 #include <string.h>
 #include "heap.h"
 
+#ifdef CONFIG_SYS_HEAP_RUNTIME_STATS
+static inline void increase_allocated_bytes(struct z_heap *h, size_t num_bytes)
+{
+	h->allocated_bytes += num_bytes;
+	h->max_allocated_bytes = MAX(h->max_allocated_bytes, h->allocated_bytes);
+}
+#endif
+
 static void *chunk_mem(struct z_heap *h, chunkid_t c)
 {
 	chunk_unit_t *buf = chunk_buf(h);
@@ -275,7 +283,7 @@ void *sys_heap_alloc(struct sys_heap *heap, size_t bytes)
 	mem = chunk_mem(h, c);
 
 #ifdef CONFIG_SYS_HEAP_RUNTIME_STATS
-	h->allocated_bytes += chunksz_to_bytes(h, chunk_size(h, c));
+	increase_allocated_bytes(h, chunksz_to_bytes(h, chunk_size(h, c)));
 #endif
 
 #ifdef CONFIG_SYS_HEAP_LISTENER
@@ -351,7 +359,7 @@ void *sys_heap_aligned_alloc(struct sys_heap *heap, size_t align, size_t bytes)
 
 	set_chunk_used(h, c, true);
 #ifdef CONFIG_SYS_HEAP_RUNTIME_STATS
-	h->allocated_bytes += chunksz_to_bytes(h, chunk_size(h, c));
+	increase_allocated_bytes(h, chunksz_to_bytes(h, chunk_size(h, c)));
 #endif
 
 #ifdef CONFIG_SYS_HEAP_LISTENER
@@ -425,7 +433,7 @@ void *sys_heap_aligned_realloc(struct sys_heap *heap, void *ptr,
 #endif
 
 #ifdef CONFIG_SYS_HEAP_RUNTIME_STATS
-		h->allocated_bytes += split_size * CHUNK_UNIT;
+		increase_allocated_bytes(h, split_size * CHUNK_UNIT);
 #endif
 
 		free_list_remove(h, rc);
@@ -498,6 +506,7 @@ void sys_heap_init(struct sys_heap *heap, void *mem, size_t bytes)
 #ifdef CONFIG_SYS_HEAP_RUNTIME_STATS
 	h->free_bytes = 0;
 	h->allocated_bytes = 0;
+	h->max_allocated_bytes = 0;
 #endif
 
 	int nb_buckets = bucket_idx(h, heap_sz) + 1;

lib/os/heap.h

@@ -72,6 +72,7 @@ struct z_heap {
 #ifdef CONFIG_SYS_HEAP_RUNTIME_STATS
 	size_t free_bytes;
 	size_t allocated_bytes;
+	size_t max_allocated_bytes;
 #endif
 	struct z_heap_bucket buckets[0];
 };