measurements and prediction of contention in multiprocessor operating systems with scientific application workloads
This paper examines the effect of contention for a single shared semaphore protecting critical regions in a multiprocessor operating system on system performance as the number of processors increases. A simple queueing model is used to make predictions as a function of the expected demand for the semaphore by each processor. Measurements are then presented for 2 and 4 processor configurations of the CRAY X-MP running an experimental version of UNICOS. The measurements indicate that demand is highly dependent on the workload, and that contention can be somewhat higher than predicted by the model due to process scheduling effects and request interdependencies. One interesting point which is revealed in the measurement results, is that the UNIX scheduler gives preferential treatment to jobs that make frequent requests for the semaphore.
measurement predict contention multiprocessor processor process operating system systems applications workload paper effect sharing semaphores critic region performance queue model functional configurability experimentation version dependencies scheduling point