Experimental Validation of Stochastic Performance Models of General Layered Task Systems

Performance analysis of synchronization mechanisms for simple layered task systems has recently been reported. In this paper, we develop and validate performance models for general layered task systems which are applicable to a wider range of synchronization mechanisms and parallel task systems. Synchronization mechanisms considered include both strong (barrier) synchronization and weak (partial) synchronization. The models explicitly consider overheads due to synchronization waiting time and contention for shared software and hardware resources. The models are solvable for a number of commonly used task computation time distributions and are experimentally validated on two different shared-memory multiprocessors. It is shown that the task computation behavior, the amount of intertask dependencies, synchronization overheads, and throughput of the processor-memory interconnection network interact in a multi-dimensional, but predictable, way to impact overall performance. Approximate and asymptotic models are used to demonstrate these relationships, in both qualitative and quantitative terms.