CONFIG_DCACHE_WRITETHROUGH is not available for thedefaultarchitecture x86.
Result is shown for architecture openrisc

Have write through data caches

configname: CONFIG_DCACHE_WRITETHROUGH

Linux Kernel Configuration
└─>Processor type and features
└─>Have write through data caches
In linux kernel since version 4.2 (release Date: 2015-08-30)  
Select this if your implementation features write through data caches.
Selecting 'N' here will allow the kernel to force flushing of data
caches at relevant times. Most OpenRISC implementations support write-
through data caches.

If unsure say N here