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

“这项奖励是根据2009年美国复苏和再投资法案（公法111-5）资助的。”在21世纪，占主导地位的计算平台已经转向实现缓存一致共享内存和运行多线程应用程序的多核芯片。不幸的是，这些芯片并没有为软件或硬件开发人员提供一个确定的模型。推理和测试多个可能的执行比推理和测试一个正确的顺序执行要困难得多，因为在20世纪占主导地位的冯·诺伊曼模型下，这是可能的。减轻多核芯片编程的负担对于为社会提供我们所期望的快速、经济高效的性能提升至关重要。此外，广泛的影响需要实际的解决方案，这些解决方案不要求行业丢弃或重写数十亿行现有的基于通用线程的软件。为此目的，本提案下的研究将制定管理不确定性的解决办法，采用提供互补利益和机会的备选执行方法。(1)工作将扩展确定性重播的记录执行技术，以提高重播并行性，并将记录/重播的范围扩展到硬件调试和容错。(2)工作将发展和推进确定性一致性模型，消除共享内存多处理器系统中非确定性的主要来源：内存竞争。(3)工作将开发确定性一致性的全软件和硬件加速实现，部分通过扩展威斯康星GEMS模拟基础设施。(4)最后，工作将探索在形式确定性基础上重建一致性。更广泛的影响将包括在公共软件发布（例如GEMS）中体现拟议的工作，以及通过课程、讲座、工业附属机构和商业影响向学生传播。

"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.