memory usage

[Michael Fortin]

We've recently been trying to get an accurate account of how memory is
being utilized on some Sun 3/50's. When using top, ps, and vmmeter,
we consistently get strange results.

For example, at one moment top might tell me that the real memory
in the system was X, and that the free memory in the system was Y. So, one
could hazard a guess that X+Y represents the total amount of memory that
exists.

But, another execution of top might produce a real memory total of Q and
and free memory total of R. 

The problem is that Q+R does not equal X+Y.

(Please note that I have been talking about the total real memory, not the
active real memory in use. Total Real should be a superset of active real.)


The same problem occurs when ps is run a couple of times, or when vmmeter
is. 

My question is why don't the numbers add up? Is there some other way
to detemine how much memory is being used?

Thanks Mike