Memory usage inspection

[macro]

Is there a command I can use, or other clue, to measure the RAM used at a given point in time while running a guest, be it Windows or Linux, but not within the guest itself.

[loukingjr]

Not sure I understand the question. A guest takes up whatever RAM it is assigned. So, no matter how much of the assigned RAM the guest is using at any given time, it is always using the full amount assigned.