RADIX_TREE_MAP_SHIFT   64 include/linux/radix-tree.h #define RADIX_TREE_MAP_SHIFT	(CONFIG_BASE_SMALL ? 4 : 6)
RADIX_TREE_MAP_SHIFT   66 include/linux/radix-tree.h #define RADIX_TREE_MAP_SHIFT	3	/* For more stressful testing */