Exploiting parallelism in deterministic shared memory multiprocessing

Abstract

Multi-threaded programs on shared-memory hardware tend to be non-deterministic, which brings challenges to software debugging and testing. Current deterministic implementations eliminate nondeterminism of multi-threaded programs by trading much parallelism for determinism, which leads to low performance. Researchers typically improve parallelism by weakening determinism or introducing weak memory consistency models. However, weak determinism cannot deal with non-determinism caused by data races which are very common in multi-threaded programs. Weak memory consistency models impact the productivity of programming and may bring correctness problems of legacy programs. To address the problems, this paper presents a fully parallelized deterministic runtime, FPDet, which exploits parallelism of deterministic multi-threaded programs by preserving strong determinism and sequential memory consistency. FPDet creates a Working Set Memory (WSM) for each thread to make threads run independently for parallelism. FPDet guarantees determinism by redistributing memory blocks among threads’ WSMs in specified synchronization points. As a result, FPDet obtains parallelism and determinism simultaneously. To further exploit parallelism, we propose an Adaptive Budget Adjustment (ABA) mechanism to minimize wait time caused by thread synchronization.We evaluated FPDet using benchmarks from both the SPLASH-2 and PARSEC suits. The results show that FPDet can effectively improve parallelism (the average speedup is more than 1.4 compared with existing approaches) without weakening determinism or memory consistency.