CPU utilization
The term “percentage deviation” used in the following always denotes the absolute deviation, in other words:
X and Y have a deviation of P if abs (X-Y) ≤ P.
TU/TPR/SIH time, IDLE time
The operating system uses timers to determine three time components: the total for TU and TPR times, the SIH time and the IDLE time. Consequently, falsifications due to the noninterruptible SIH code cannot occur. Investigations have shown that this timer is sufficiently precise for realistic monitoring cycles. As a rule, comparative measurements made with hardware monitors under typical load conditions have shown deviations of less than 1%.
SM2 divides the total for TU and TPR times into separate values for the TU time and the TPR time on the basis of samples taken during the sampling period. The accuracy of this procedure depends on the number of samples, which means that large deviations are possible if few samples are taken.