To get real time system information from most Linux systems, use the command top. Open up a command prompt and type top. You'll get a updating readout of processor percentage used, memory percentage used, the amount of memory used by process. There are many ways to sort the list and you can kill processes as well (if you run the command using sudo or root).
While top is running type h. Pressing one of these keys while top is displayed will produce the corresponding results. Be sure to exit top using q. There seems to be an issue if you only close the command prompt in kubuntu.