@SanAndreasP, with all due respect, this is a Java modification to a Java application community forum.
I sincerely believe, that an average person visiting these parts of internet could add 2 to 2 and get the answer, that, indeed, I'm looking for memory usage of the application itself, not VM. As it is apparent that under Linux, VM always claim entire -Xmx region without a hesitation.
I'll take a look into that app you linked, thank you.