6.7 Evaluating Operating System Performance

The scheduling policy does not tell us all that we would like to know about the performance of a real system running processes. Our analysis of scheduling policies makes some simplifying assumptions:

• We have assumed that context switches require zero time. Although it is often reasonable to neglect context switch time when it is much smaller than the process execution time, context switching can add significant delay in some cases.

• We have largely ignored interrupts. The latency from when an interrupt is requested to when the device’s service is complete is a critical parameter of real-time performance.

• We have assumed that we know the execution time of the processes. In fact, we learned in ...

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