Memory Hotplug

configname: CONFIG_ACPI_HOTPLUG_MEMORY

Linux Kernel Configuration
└─>Power management and ACPI options
└─>ACPI (Advanced Configuration and Power Interface) Support
└─>Memory Hotplug
In linux kernel since version 4.2 (release Date: 2015-08-30)  
This driver supports ACPI memory hotplug. The driver
fields notifications on ACPI memory devices (PNP0C80),
which represent memory ranges that may be onlined or
offlined during runtime.

If your hardware and firmware do not support adding or
removing memory devices at runtime, you need not enable
this driver.