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Proceedings of the 22nd International Conference on Parallel Architectures and Compilation Techniques (2011)
Galveston, Texas USA
Oct. 10, 2011 to Oct. 14, 2011
ISSN: 1089-795X
ISBN: 978-0-7695-4566-0
pp: 155-166
For parallelism to become tractable for mass programmers, shared-memory languages and environments must evolve to enforce disciplined practices that ban "wild shared-memory behaviors;'' e.g., unstructured parallelism, arbitrary data races, and ubiquitous non-determinism. This software evolution is a rare opportunity for hardware designers to rethink hardware from the ground up to exploit opportunities exposed by such disciplined software models. Such a co-designed effort is more likely to achieve many-core scalability than a software-oblivious hardware evolution. This paper presents DeNovo, a hardware architecture motivated by these observations. We show how a disciplined parallel programming model greatly simplifies cache coherence and consistency, while enabling a more efficient communication and cache architecture. The DeNovo coherence protocol is simple because it eliminates transient states -- verification using model checking shows 15X fewer reachable states than a state-of-the-art implementation of the conventional MESI protocol. The DeNovo protocol is also more extensible. Adding two sophisticated optimizations, flexible communication granularity and direct cache-to-cache transfers, did not introduce additional protocol states (unlike MESI). Finally, DeNovo shows better cache hit rates and network traffic, translating to better performance and energy. Overall, a disciplined shared-memory programming model allows DeNovo to seamlessly integrate message passing-like interactions within a global address space for improved design complexity, performance, and efficiency.
Hyojin Sung, Robert Smolinski, Byn Choi, Rakesh Komuravelli, Nicholas P. Carter, Sarita V. Adve, Nima Honarmand, Vikram S. Adve, Ching-Tsun Chou, "DeNovo: Rethinking the Memory Hierarchy for Disciplined Parallelism", Proceedings of the 22nd International Conference on Parallel Architectures and Compilation Techniques, vol. 00, no. , pp. 155-166, 2011, doi:10.1109/PACT.2011.21
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