CONFIG_CONSISTENT_SIZE is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc
default or selected kernelversion does not have config value CONFIG_CONSISTENT_SIZE.
Result is shown for kernelversion 6.9.9

Size of consistent memory pool

configname: CONFIG_CONSISTENT_SIZE

Linux Kernel Configuration
└─>Advanced setup
└─>Size of consistent memory pool
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  
depends
CONFIG_PPC32