CSR: Small: A Unified Many-Core Architecture for Enabling Speculative Multithreading and Transactional Memory

随着多核和多核处理器逐渐成为所有类型计算平台的事实上的标准，投机性多线程（SpecMT）和事务性内存（TM）这两种技术在这些平台上得到了深入的研究，以提高单线程性能并简化并行编程模型。这两种计算模型分别被提出，在它们的底层实现中共享许多共同的特性。在这项研究中，我们给出了一个整体的观点，并研究了一个统一的多核架构，以在一个实现下支持这两种技术。我们首先将SpecMT映射到基于硬件的TM体系结构上，并开发启用技术来展示性能潜力，同时保持TM编程模型的好处。每个以投机或非投机方式生成的线程都被事务化到一个事务中。编译器用于确定何时何地用硬件启动SpecMT，以动态地引导决策并限制SpecMT的范围。这些事务执行不同的代码区域，可以在顺序程序顺序之外启动，但必须在硬件支持下以原始顺序提交。本研究着重于(1)支持SpecMT和TM的架构支持；(2)编译器对SpecMT和线程事务的支持；(3)量化不同类型事务的好处；(4)在异构多核平台（如即将到来的集成CPU-GPU系统）上支持SpecMT的经济可行机制。这种统一的多核体系结构的成功将为单线程应用程序的高性能提供基础，同时大大提高软件开发人员的生产力。

As multi-core and many-core processors are consensually becoming the de facto standard for all types of computing platforms, two techniques, Speculative Multithreading (SpecMT) and Transactional Memory (TM), have been intensively investigated on such platforms to enhance single-thread performance and to simplify the parallel programming model. These two computing models, proposed separately, share many common features in their underlying implementations. In this research, we give a holistic view and investigate a unified many-core architecture to support both technologies under one implementation. We first map SpecMT onto a hardware-based TM architecture and develop enabling techniques to showcase the performance potential while maintaining the benefit of a TM programming model. Each thread spawned speculatively or non-speculatively is transactified into a transaction. Compilers are used to determine when and where to initiate SpecMT with hardware to dynamically shepherd the decisions and throttle the extent of SpecMT. These transactions, executing different code regions, can be launched out of the sequential program order but must be committed in the original order with hardware support. This research focuses on (1) architectural support for enabling both SpecMT and TM, (2) compiler's support for SpecMT and thread transactification, (3) quantifying the benefits of different types of transactions, and (4) economical and feasible mechanisms to support SpecMT on heterogeneous many-core platforms such as the incoming integrated CPU-GPU systems. The success of such a unified many-core architecture will provide a foundation for delivering high performance for single-thread applications while improving the productivity for software developers substantially.