Jonathan de Boyne Pollard wrote in a message to Paul Edwards:

 JdBP> Stop and think.  Your profiler cannot register time spent
 JdBP> in a device   or filesystem driver, nor does it register
 JdBP> time spent blocked waiting   for I/O requests to complete in
 JdBP> the bottom half of the kernel. 

A profiler should timestamp when calls enter the operating system API and
then when they leave, and should therefore be able to compute the elapsed
time.  While this sort of measurement can be skewed by other processes
running on the machine, real-world performance measurement is the whole
point of a profiler.  This is how the original determination was made that
the program is spending a lot of time in DosSubSet() or whatever.  If the
program was waiting on I/O a lot, it would show as in DosWrite(), for
example.
 
-- Mike


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