add comments in malloc()

src/malloc.c

@@ -67,6 +67,9 @@ void * malloc(size_t size) {
     }
 
     if(ptr == NULL) {
+        /* No suitable memory block has been found, a new raw block shall be
+         * created. */
+
         size_t sys_alloc_size;
 
 #ifdef WITH_KNOBS
@@ -94,6 +97,10 @@ void * malloc(size_t size) {
                 sizeof(freelist_rb_t)) {
 #endif /* FL_RB_ONLY */
 
+            /* The memory request size is too large to serve it inside a raw
+             * block which contains multiple memory blocks, a big raw block
+             * shall be used. */
+
             ptr = create_raw_block(size + sizeof(raw_block_header_t),
                         BIGBLOCK);
             if(ptr != NULL) {
@@ -120,8 +127,7 @@ void * malloc(size_t size) {
             /* Try to create a new raw block and allocate a memory block from
              * there */
 
-            new_raw_block = create_raw_block((size_t) sys_alloc_size,
-                    DEFAULT_RB_TYPE);
+            new_raw_block = create_raw_block(sys_alloc_size, DEFAULT_RB_TYPE);
             if(new_raw_block != NULL) {
                 LOCK_GLOBAL();
                 LOCK_RAW_BLOCK(new_raw_block);