CONFIG_THREAD_SHIFT is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

Thread shift


Linux Kernel Configuration
└─>Kernel options
└─>Thread shift
In linux kernel since version 4.2 (release Date: 2015-08-30)  
Used to define the stack size. The default is almost always what you
want. Only change this if you know what you are doing.