Measuring cpu time using getrusage

[Johann Schuster <johann.schuster@unibw.de>]

Hello,

currently i'm trying to measure the cpu times for
numerical algorithms written in C using two calls of
getrusage() and then calculating the time difference.

According to the man page of getrusage i looked at the
user time of my process. Surprisingly the measured user
times vary strongly depending on the system load of the
machine.
A heavy system load nearly doubles the measured time
for my routine.

Does anyone know a better way to measure the used
cpu cycles of a given process (or part of a program)
or can anyone give me a hint if i missed some important
fact.

Any help appreciated. Thank you in advance.


Johann Schuster