Percentage of total memory

configname: CONFIG_CMA_SIZE_PERCENTAGE

Linux Kernel Configuration
└─>Library routines
└─>Percentage of total memory
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Defines the size of the default memory area for Contiguous Memory
Allocator as a percentage of the total memory in the system.
If 0 percent is selected, CMA is disabled by default, but it can be
enabled by passing cma=size[MG] to the kernel.