CONFIG_HUGETLB_PAGE_SIZE_256K is not available for thedefaultarchitecture x86.
Result is shown for architecture sh

256kB

configname: CONFIG_HUGETLB_PAGE_SIZE_256K

HugeTLB page size
└─>256kB
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
depends
CONFIG_X2TLB