SHF: Small: Managing Non-Determinism in Multithreaded Software and Hardware

该奖项是根据2009年《美国复苏和再投资法案》(Public Law 111-5)资助的。在21世纪，占主导地位的计算平台已转向多核芯片，这些芯片实现高速缓存一致性共享内存并运行多线程应用程序。不幸的是，这些芯片不能为软件或硬件开发人员提供确定性模型。对多个可能的执行进行推理和测试，比对单一正确的顺序执行进行推理和测试要困难得多，这在20世纪占主导地位的冯·诺伊曼模式下是可能的。减轻编程多核芯片的负担对于为社会提供我们都期待的快速、经济高效的性能收益至关重要。此外，广泛的影响需要实用的解决方案，不要求业界丢弃或重写数十亿行现有的基于线程的通用软件。为此，根据这一提议进行的研究将开发出管理非确定性的解决方案，并采用提供互补好处和机会的替代实现方法。(1)扩展确定性回放的记录执行技术，提高回放并行性，将记录/回放的范围扩展到硬件调试和容错。(2)工作将开发和推进确定性一致性模型，以消除共享内存多处理器系统中的一个主要不确定性来源：内存竞赛。(3)将部分通过扩展威斯康星州的GEMS模拟基础设施，开发确定性一致性的全软件和硬件加速实施。(4)最后，工作将探索在正式的决定论基础上重建一致性。更广泛的影响将包括将拟议的工作体现在公共软件发布中(例如，GEM)，以及通过课程、讲座、行业分支机构和商业影响力向学生传播。

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."In the 21st century, the dominant computing platform has shifted to multicore chips that implement cache-coherent shared memory and run multi-threaded applications. Unfortunately, these chips do not provide a deterministic model to either software or hardware developers. Reasoning about and testing for multiple possible executions is much harder than reasoning about and testing for a single correct sequential execution, as was possible under the von Neumann model that dominated in the 20th century. Easing the burden of programming multicore chips is critical to provide society with the rapid, cost-effective performance gains that we have all come to expect. Moreover, broad impact requires practical solutions that do not ask industry to discard or rewrite billions of lines of existing general-purpose thread-based software.To this end, research under this proposal will develop solutions for managing non-determinism with alterative implementation approaches that provide complementary benefits and opportunities. (1) Work will expand techniques of recording executions for deterministic replay to improve replay parallelism and extend the scope of record/replay to hardware debugging and fault-tolerance. (2) Work will develop and advance a deterministic coherence model that eliminates a major source of non-determinism in shared-memory multiprocessor systems: memory races. (3) Work will develop both all-software and hardware-accelerated implementations of deterministic coherence, in part, through extensions to the Wisconsin GEMS simulation infrastructure. (4) Finally, work will explore rebuilding coherence upon a formal deterministic foundation. Broader impacts will include embodying the proposed work in public software releases (e.g., GEMS) as well as dissemination to students and through courses, talks, industrial affiliates, and commercial influence.