Parallel programs and background load: efficiency studies with the PAR-Bench system

Today most of the multiprocessor supercomputer systems are still used within a multiprogramming environment, where the individual processors execute different jobs which are totally independent. All programs compete for the available resources. With multitasking, processors may also execute different parts of one program in parallel. The behaviour of parallel programs within a multiprogramming environment and the influence of these programs on the overall workload is of great interest for the rating of multitasking concepts with respect to their efficiency in practice.While the efficiency of multitasking is proved for parallel programs running in a dedicated environment, this paper leads to a new approach for the assessment of multitasking. It shortly describes the benchmark generation environment PAR-Bench, which is implemented on a Cray Y-MP under the UNICOS operating system; based on full information about system activities, this system enables reasonable measurements of parallel programs in a multiprogramming mode. Additionally, a few typical results obtained from first measurements are summarized