CONFIG_CACHE_WRITETHRU is not available for thedefaultarchitecture x86.
Result is shown for architecture m68k

Write-through

configname: CONFIG_CACHE_WRITETHRU

Data cache mode
└─>Write-through
In linux kernel since version 2.6.38 (release Date: 2011-03-14)  
The ColdFire CPU cache is set into Write-through mode.