Displaying
Data
The raw value
of many counters is not what the user would expect to see. To get the
information in the form described by most counter names, you need to compute
the displayable value based on this raw data. PDH does this for you. For
example, the Page Faults/Sec counter simply counts page faults, so if you view
the raw data, you see a running total of page faults. To get the rate implied
by the counter name, page faults per second, you need to call the PdhGetFormattedCounterValue function. In this case, the
function divides the difference between two samples by the time between the
samples.
The PdhGetFormattedCounterValue
function performs its computations on the most recent sample. If you need to
recalculate and redisplay a sample, you must store the raw data and then call
the PdhCalculateCounterFromRawValue function to perform the calculation on the
stored data.