getRunningAppProcesses on Android >5.1 ?

I want to know process on background in Android 5.1 but doesnt work with getRunningAppProcesses (deprecated)

Any solution ???

This app doesnt work with 5.1 : https://play.google.com/store/apps/details?id=com.rechild.advancedtaskkiller
This app work with 5.1 : https://play.google.com/store/apps/details?id=mobi.infolife.taskmanager

How do they get it? (https://play.google.com/store/apps/details?id=mobi.infolife.taskmanager) ???