Q:

An application named X uses too much CPU

My OS is openSUSE Leap 42.1.  When I check the System Monitor, I see an app called 'X' consumes system resources. 
I right-click to see detailed info. Here is the result that is not satisfying:
Process 941 - X

    Sorry

    You do not have permissions to read detailed memory information about this process (/proc/941/smaps could not be read)

A:

Depending on your setup, this is very likely the X server (sometimes, it's Xorg rather than just X).
If you're doing a lot of things that requires it to work heavily, its CPU usage will go up. Sometimes, switching to a lighter window manager will help, or turning off "special effects" such as window zooming, window shadows, etc.

