To ascertain the overhead values and , we must measure the instrumentation code that calculates inclusive and exclusive performance. However, the and values may be at the same scale as the measurement precision. Thus, we must construct a test that guarantees statistical accuracy in our estimation of and .

Our approach is to conduct a two-level experiment where the inclusive
measurement code is executed number of times (in a tight loop) and
the performance data being profiled is measured and stored. This
procedure is then repeated times and the minimum performance value
across the experiments is retained. We use that value divided by
to compute . While this does not entirely insure
against anomalous timing artifacts, its statistical safety can be
improved by increasing . The two-level experiment is then
repeated, this time with the exclusive measurement code included,
resulting in an approximation of
. We can
substract our approximation to find . It is
important to note that we need to do this overhead evaluation at the
beginning of the application execution for the specific set of profile
performance data being measured.^{}