ps command is a great tool to get a relevant information for each process in the Linux system. The ps command is yet another tool among many which reads and interprets data located in the virtual directory /proc/. If you need to read raw process stats data head over /proc directory and locate directory named after process ID ( PID ) of the process you are looking for. Below as a sample output of the ps command:
The most obvious values here are USER, PID, etc. However, there are two additional columns which need more explanation:
VSZ - Virtual Set Size
The Virtual Set Size is a memory size assigned to a process ( program ) during the initial execution. The Virtual Set Size memory is simply a number of how much memory a process has available for its execution.
RSS - Resident Set Size
As oppose to VSZ ( Virtual Set Size ), RSS is a memory currently used by a process. This is a actual number in kilobytes of how much RAM the current process is using.