CSR-PDOS: Out-of-Context Prefetching for L2 Caches

CSR-PDOS：L2 缓存的上下文外预取

• 批准号: 0720741
• 负责人: Sohum Sohoni
• 金额: --
• 依托单位: Oklahoma State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-01 至 2010-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0720741&HistoricalAwards=false
• 关键词: CSR; PDOS; Out; Context; Prefetching

On a multi-tasked system, the CPU cycles through a number of processes every few milliseconds. Some of the processes are memory-intensive, but most are non-intensive support processes and other user programs such as text-editors, email clients, and instant messengers. A typical system cycles through a few memory-intensive processes, each of which replaces several cache blocks from the level-2 cache from other processes. This results in a large number of demand misses for the L2, and ties up the memory subsystem preventing effective prefetching.This project investigates a possible solution to this problem by modifying the OS to prefetch to the L2 out of context, i.e. when the CPU is executing a non memory-intensive process. (ideally, just before the memory-intensive process will be brought in for execution). Thus, when this process resumes execution, it will have low L2 cache misses which in turn will keep the memory-bus free in order to prefetch even more blocks. Out-of-context prefetching aims to shift from a predominantly demand-fetched paradigm to a predominantly prefetched paradigm.In conjunction with accurate predictors for prefetching, this work has the potential to greatly mitigate the performance CPU-memory gap problem on a system-wide level. The expected outcome of the project is a Linux implementation of out-of-context prefetching on a full-system simulator, and a website that documents all the assumptions, the source code, and extensive project results beyond those published in the corresponding research literature. All researchers, operating system designers, and processor manufacturers will have access to the website and the research findings to freely incorporate them as they wish.

在多任务系统上，CPU每隔几毫秒就通过许多过程进行了循环。其中一些过程是内存密集型的，但大多数是非密集型支持流程和其他用户程序，例如文本编辑，电子邮件客户端和即时信使。一个典型的系统通过一些内存密集的过程循环，每个过程都取代了来自其他过程的级别-2高速缓存的几个缓存块。这导致了L2的大量需求，并绑定了内存子系统，以防止有效预取。 （理想情况下，将在记忆密集型过程之前进行执行之前）。因此，当此过程恢复执行时，它将具有较低的L2高速缓存失误，从而使内存库免费以预取更多块。远方的预摘要旨在从主要需求的范式转变为主要预取的范式。与准确的预测指标结合使用，这项工作有可能极大地减轻系统范围内的性能CPU-Memory Gap问题。该项目的预期结果是在完整系统模拟器上预摘要的Linux实施，以及一个记录所有假设，源代码和广泛项目结果的网站，超出了相应的研究文献中发布的项目。所有研究人员，操作系统设计师和处理器制造商都将可以访问该网站以及研究结果，以根据自己的意愿自由合并它们。