Modeling load imbalance and fuzzy barriers for scalable shared-memory multiprocessors

Proposes an analytical model that quantifies the overall execution time of a parallel region in the presence of non-deterministic load imbalance introduced by network contention and by a random replacement policy in processor caches. We present a novel model that evaluates the expected hit ratio and variance introduced by a cache accessed with a cyclic access stream. We also model the performance improvement of fuzzy barriers, where the synchronization between processors at the end of a parallel region is relaxed. Experiments on a 64-processor KSR (Kendall Square Research) system which has random first-level caches confirms the general nature of the analytic results