core: Add some documentation to the malloc_trim code

This adds documentation to handle_cli_malloc_trim() indicating how it
can be useful when debugging OOM conditions.

Change-Id: I1936185e78035bf123cd5e097b793a55eeebdc78

diff --git a/main/cli.c b/main/cli.c
index f980fc6397633d4a4d810c5e679d2dd603822ca3..412755681a37739dc07feef334f37a2220c36786 100644 (file)
--- a/main/cli.c
+++ b/main/cli.c
@@ -1793,30 +1793,43 @@ static char *handle_cli_wait_fullybooted(struct ast_cli_entry *e, int cmd, struc
 
 
 #ifdef HAVE_MALLOC_TRIM
-       /* BUGBUG malloc_trim() is a libc specific function.  Non-portable. */
-       static char *handle_cli_malloc_trim(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
-       {
-               extern int malloc_trim(size_t __pad) __THROW;
-
-               switch (cmd) {
-               case CLI_INIT:
-                       e->command = "malloc trim";
-                       e->usage =
-                               "Usage: malloc trim\n"
-                               "       Try to give excess memory back to the OS.\n";
-                       return NULL;
-               case CLI_GENERATE:
-                       return NULL;
-               }
 
-               if (malloc_trim(0)) {
-                       ast_cli(a->fd, "Returned some memory to the OS.\n");
-               } else {
-                       ast_cli(a->fd, "No memory returned to the OS.\n");
-               }
+/*!
+ * \internal
+ * \brief Attempt to reclaim unused heap memory.
+ *
+ * Users have reported that asterisk will sometimes be killed because it can't allocate
+ * more than around 3G of memory on a 32 bit system.
+ *
+ * Using malloc_trim() will help us to determine if it's because there's a leak or because
+ * the heap is so fragmented that there isn't enough contiguous memory available.
+ *
+ * \note malloc_trim() is a GNU extension and is therefore not portable.
+ */
+static char *handle_cli_malloc_trim(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
+{
+       extern int malloc_trim(size_t __pad) __THROW;
 
-               return CLI_SUCCESS;
+       switch (cmd) {
+       case CLI_INIT:
+               e->command = "malloc trim";
+               e->usage =
+                       "Usage: malloc trim\n"
+                       "       Try to give excess memory back to the OS.\n";
+               return NULL;
+       case CLI_GENERATE:
+               return NULL;
        }
+
+       if (malloc_trim(0)) {
+               ast_cli(a->fd, "Returned some memory to the OS.\n");
+       } else {
+               ast_cli(a->fd, "No memory returned to the OS.\n");
+       }
+
+       return CLI_SUCCESS;
+}
+
 #endif
 
 static char *handle_help(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a);