Add arena-level name.

An arena-level name can help identify manual arenas.

include/jemalloc/internal/arena_externs.h

@@ -88,6 +88,8 @@ ehooks_t *arena_get_ehooks(arena_t *arena);
 extent_hooks_t *arena_set_extent_hooks(tsd_t *tsd, arena_t *arena,
     extent_hooks_t *extent_hooks);
 bool arena_dss_prec_set(arena_t *arena, dss_prec_t dss_prec);
+void arena_name_get(arena_t *arena, char *name);
+void arena_name_set(arena_t *arena, const char *name);
 ssize_t arena_dirty_decay_ms_default_get(void);
 bool arena_dirty_decay_ms_default_set(ssize_t decay_ms);
 ssize_t arena_muzzy_decay_ms_default_get(void);

include/jemalloc/internal/arena_structs.h

@@ -91,6 +91,9 @@ struct arena_s {
 	/* Used to determine uptime.  Read-only after initialization. */
 	nstime_t		create_time;
 
+	/* The name of the arena. */
+	char 			name[ARENA_NAME_LEN];
+
 	/*
 	 * The arena is allocated alongside its bins; really this is a
 	 * dynamically sized array determined by the binshard settings.

include/jemalloc/internal/arena_types.h

@@ -8,6 +8,8 @@
 #define MUZZY_DECAY_MS_DEFAULT	(0)
 /* Number of event ticks between time checks. */
 #define ARENA_DECAY_NTICKS_PER_UPDATE	1000
+/* Maximum length of the arena name. */
+#define ARENA_NAME_LEN 32
 
 typedef struct arena_decay_s arena_decay_t;
 typedef struct arena_s arena_t;