PGDIR_SIZE         17 arch/x86/include/asm/pgtable_32_types.h #define PGDIR_SIZE	(1UL << PGDIR_SHIFT)
PGDIR_SIZE         53 arch/x86/include/asm/pgtable_64_types.h #define PGDIR_SIZE	(_AC(1, UL) << PGDIR_SHIFT)