Mobile devices can operate under severe resource constraints. Not only do the devices themselves have limited resources, the OS can impose further restrictions. Running out of memory can cause applications to slow down or refuse to run.
ADB provides the ability to monitor devices while in operation, using ADB commands:
adb shell dumpsys cpuinfo
adb shell dumpsys meminfo 'app package name'
It would be useful to have this done automatically before and after an app is launched, to see the real impact of an application on a device's resources.