Performance degradation due to multiprogramming and system overheads in real workloads. Case study on a shared memory multiprocessor

In this paper, performance degradation specifically due to the multiprogramming (MP) overhead in a parallel execution environment is quantified. In addition, total system overhead is also measured. A methodology, which estimates the MP overhead present in real workloads, is illustrated with real measurements taken on an Alliant FX/80 running Xylem (Cedar's operating system). It is found that MP overhead usually consumes between 10% and 23% of the processing power available to parallel programs. Total system overhead usually consumes between 12% and 30% of the parallel environment processing power, but is found to be as high as 82.1%. The mean MP overhead is determined to be 16% which is well over half the total system overhead executed on the system (the mean system overhead is determined to be 24% of the processing power). It is found that MP overhead, total system overhead, and application completion time are all moderately correlated. Relationships between the characteristics of a workload and the overhead measurements indicate that processor utilization and to a lesser degree paging are moderately correlated with the overhead present in the workload. It is also found that MP overhead is statistically independent of the number of parallel jobs in the system, while total system overhead is not.