in reply to
Re^4: leak detection in other (non-perl) processes
in thread leak detection in other (non-perl) processes
As long as you don't set a fixed time frame for the observation/analysis, everything will be just a more or less useful heuristic.
Anyhow, I think you want to fit a trend line through the entire data1, and if it isn't flat, you likely have a leak. This assumes the evaluation interval is (considerably) longer than the period of any cyclic behavior you might observe.
1 if you're worried about outliers, you might want to look for a statistics package that can compute the fit based on minimizing linear deviations, instead of squared deviations, as done in a standard "least squares" fit (see also LAD).