RADIX_PMD_FRAG_SIZE_SHIFT   19 arch/powerpc/include/asm/book3s/64/radix-4k.h #define RADIX_PMD_FRAG_SIZE_SHIFT  (RADIX_PMD_INDEX_SIZE + 3)
RADIX_PMD_FRAG_SIZE_SHIFT   20 arch/powerpc/include/asm/book3s/64/radix-64k.h #define RADIX_PMD_FRAG_SIZE_SHIFT  (RADIX_PMD_INDEX_SIZE + 3)