How much memory the viewer uses under Linux

Perform

PS aux
The VSZ (or VSS) column indicates how much virtual memory the program occupies;
The RSS column indicates how much physical memory the program occupies;
Virtual memory is not considered, it does not occupy actual physical memory.

or execute the top command

The VIRT (or VSS) column indicates how much virtual memory the program occupies, with the vsz column in PS aux;
The Res column indicates how much physical memory the program occupies, with the RSS column in the PS aux.

Reference

Http://blog.chinaunix.net/uid-20492804-id-265809.html

How much memory the viewer uses under Linux