Add arena.i.retain_grow_limit

This option controls the max size when grow_retained.  This is useful when we
have customized extent hooks reserving physical memory (e.g. 1G huge pages).
Without this feature, the default increasing sequence could result in fragmented
and wasted physical memory.

include/jemalloc/internal/arena_externs.h

@@ -77,6 +77,8 @@ 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);
 bool arena_muzzy_decay_ms_default_set(ssize_t decay_ms);
+bool arena_retain_grow_limit_get_set(tsd_t *tsd, arena_t *arena,
+    size_t *old_limit, size_t *new_limit);
 unsigned arena_nthreads_get(arena_t *arena, bool internal);
 void arena_nthreads_inc(arena_t *arena, bool internal);
 void arena_nthreads_dec(arena_t *arena, bool internal);

include/jemalloc/internal/arena_structs_b.h

@@ -240,9 +240,14 @@ struct arena_s {
 	 * be effective even if multiple arenas' extent allocation requests are
 	 * highly interleaved.
 	 *
+	 * retain_grow_limit is the max allowed size ind to expand (unless the
+	 * required size is greater).  Default is no limit, and controlled
+	 * through mallctl only.
+	 *
 	 * Synchronization: extent_grow_mtx
 	 */
 	pszind_t		extent_grow_next;
+	pszind_t		retain_grow_limit;
 	malloc_mutex_t		extent_grow_mtx;
 
 	/*

include/jemalloc/internal/extent_types.h

@@ -6,4 +6,6 @@ typedef struct extents_s extents_t;
 
 #define EXTENT_HOOKS_INITIALIZER	NULL
 
+#define EXTENT_GROW_MAX_PIND (NPSIZES - 1)
+
 #endif /* JEMALLOC_INTERNAL_EXTENT_TYPES_H */