4.1bsd accounting question

[ALMQUIST at SU-SCORE.ARPA]

From:  Philip Almquist <ALMQUIST at SU-SCORE.ARPA>

	I've never tried to do such analysis on a UNIX system, but such
problems (user time + system time /= real time) seems to be quite common.
Under Tops-20, for example, the sum of user time and system time seems to
vary between about 70% and 115% of real time.  The reasons seem to be both
due to numerical (rounding) problems and to data collection problems (some
time is counted as both kinds or not at all).  Solving the latter problem
is actually a rather subtle task, since you need an atomic way of
switching which clock you are charging the time to and since there are a
great many places where the average OS can switch between "user tasks" and
"system tasks".
					Philip
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