Use APKPure App
Get CpuNotify old version APK for Android
Lightweight CPU usage in notification bar
Simple notification icon that shows CPU usage percentage. Refreshing every two seconds.
Done to be small and fast with few options in order to not to cause CPU usage itself!!
Know why and when your device is slowing down and what apps are causing you troubles!
Premissions:
Boot permission to be able to auto start after device reset.