LED activity Trigger

modulename: ledtrig-activity.ko

configname: CONFIG_LEDS_TRIGGER_ACTIVITY

Linux Kernel Configuration
└─>Device Drivers
└─>LED Support
└─>LED Trigger support
└─>LED activity Trigger
In linux kernel since version 4.2 (release Date: 2015-08-30)  
This allows LEDs to be controlled by an immediate CPU usage.
The flash frequency and duty cycle varies from faint flashes to
intense brightness depending on the instant CPU load.
If unsure, say N.

source code:
drivers/leds/trigger/ledtrig-activity.c