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The added profiling code takes time to run every time that the profiled function is called, which can disrupt the attempt to collect timing information. In order to avoid serious inflation of the times for functions that take little time to run, an estimate of the overhead due to profiling is subtracted from the times reported for each function.
Although this correction works fairly well, it is not totally accurate, resulting in times that become increasingly meaningless for functions with short runtimes. This is only a concern when the estimated profiling overhead is many times larger than reported total CPU time.
The estimated profiling overhead is not represented in the reported total CPU
time. The sum of total CPU time and the estimated profiling overhead should be
close to the total CPU time for the entire profiling run (as determined by the
time macro.) Time unaccounted for is probably being used by functions that
you forgot to profile.
Next: Additional Timing Utilities, Previous: Clock resolution, Up: Profiling [Contents][Index]