CONFIG_ARC_CURR_IN_REG is not available for thedefaultarchitecture x86.
Result is shown for architecture arc

Dedicate Register r25 for current_task pointer

configname: CONFIG_ARC_CURR_IN_REG

Linux Kernel Configuration
└─>ARC Architecture Configuration
└─>Dedicate Register r25 for current_task pointer
In linux kernel since version 3.1 (release Date: 2011-10-24)  
This reserved Register R25 to point to Current Task in
kernel mode. This saves memory access for each such access