RADIX_PMD_INDEX_SIZE    9 arch/powerpc/include/asm/book3s/64/radix-4k.h #define RADIX_PMD_INDEX_SIZE   9  // size: 8B <<  9 =  4KB, maps 2^9  x   2MB =   1GB
RADIX_PMD_INDEX_SIZE    9 arch/powerpc/include/asm/book3s/64/radix-64k.h #define RADIX_PMD_INDEX_SIZE   9  // size: 8B <<  9 =  4KB, maps 2^9  x   2MB =   1GB