RADIX_PUD_INDEX_SIZE   10 arch/powerpc/include/asm/book3s/64/radix-4k.h #define RADIX_PUD_INDEX_SIZE   9  // size: 8B <<  9 =  4KB, maps 2^9  x   1GB = 512GB
RADIX_PUD_INDEX_SIZE   10 arch/powerpc/include/asm/book3s/64/radix-64k.h #define RADIX_PUD_INDEX_SIZE   9  // size: 8B <<  9 =  4KB, maps 2^9  x   1GB = 512GB