An exercise in resource allocation

In a large operating system the probability that bottlenecks exist is high. The outcome of modifications to the system attempting to overcome these bottlenecks are often not easy to predict. It is frequently difficult to discover: 1) whether an improvement has actually been made to the system, 2) where exactly the improvements in system performance if any is occurring, 3) how to adjust parameters of the system to achieve an improved performance. Performance tools are described in this paper which were used to help resolve these points in the implementation of Peripheral Processor and Channel Scheduling mechanism in the operating system used at CERN on a CDC 6000 system. The paper shows how analysis of the performance data provided a clearer appreciation of the performance of the scheduling mechanism. (12 refs).