SHF: Small: DeNovo: Rethinking Hardware for Disciplined Parallelism

SHF：小型：DeNovo：重新思考硬件以实现严格的并行性

• 批准号: 1018796
• 负责人: Sarita Adve
• 金额: $ 50万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-15 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1018796&HistoricalAwards=false
• 关键词: SHF; Small; DeNovo; Rethinking; Hardware

Designing parallel systems that are scalable, low-cost, and power efficient, and yet easily programmable, is arguably one of the biggest challenges facing the computing industry today. This proposal describes DeNovo, a hardware architecture and framework that rethinks shared memory system design from the ground up to take advantage of long term trends in disciplined parallel software. It takes the stance that, if shared memory multicore systems with hundreds of cores are to become widely used, programming languages and environments must evolve to enforce highly disciplined programming practices that greatly simplify the programmer's view of shared memory. Such languages must restrict shared memory interactions, enforcing data-race-freedom and determinism-by-default. Moreover, disciplined programming models communicate extensive information about shared memory access patterns (so the discipline can be enforced). Exploiting the parallelism discipline and the communicated information can enable far simpler and more efficient hardware design than possible today.DeNovo proposes an extensive redesign of the memory hierarchy based on three ideas. First, the coherence protocol can be vastly simplified by taking advantage of the absence of software races to virtually eliminate races from the protocol and greatly reduce the number of hidden protocol states. Second, DeNovo uses application-level data sharing granularity (rather than software-oblivious cache lines) as the organizing principle for addressing, communication, and coherence granularities. Third, DeNovo uses more efficient, point-to-point communication (close to explicit message passing) even for shared memory programs, by minimizing indirections through the directory and exploiting information about sharing granularity for bulk data transfers. These changes will simultaneously simplify the hardware design, reduce power consumption, and improve performance. Such a solution is highly unlikely without a fundamental rethinking of the memory system design, but is required to continue to reap the benefits of Moore's law.

设计可扩展、低成本、高能效且易于编程的并行系统可以说是当今计算行业面临的最大挑战之一。 该提案描述了DeNovo，一种硬件架构和框架，它从头开始重新考虑共享内存系统设计，以利用纪律并行软件的长期趋势。它采取的立场是，如果具有数百个核心的共享内存多核系统被广泛使用，编程语言和环境必须发展到执行高度规范的编程实践，大大简化程序员对共享内存的看法。这些语言必须限制共享内存交互，强制执行数据竞争自由和默认确定性。此外，规范化的编程模型传达了关于共享内存访问模式的大量信息（因此可以强制执行规范）。 利用并行性原则和通信信息可以实现比今天更简单，更有效的硬件设计。DeNovo提出了基于三个想法的内存层次结构的广泛重新设计。首先，一致性协议可以大大简化，利用软件竞争的情况下，从协议中几乎消除竞争，大大减少了隐藏的协议状态的数量。其次，DeNovo使用应用程序级数据共享粒度（而不是软件无关的缓存行）作为寻址、通信和一致性粒度的组织原则。 第三，DeNovo使用更有效的点对点通信（接近显式消息传递），即使是共享内存程序，通过最大限度地减少通过目录的间接访问，并利用有关批量数据传输的共享粒度的信息。 这些变化将同时简化硬件设计，降低功耗，并提高性能。 如果不从根本上重新考虑存储器系统设计，这种解决方案是极不可能的，但需要继续获得摩尔定律的好处。