CSR: Small: Performance and Fairness with Multiple Page Sizes

机器学习、大数据分析和科学计算等现代计算工作负载需要巨大的内存容量。管理内存的系统软件是为更小的系统设计的，因此，它对现代系统施加了巨大的性能和功耗损失。现在是偿还技术债务的时候了。这项工作全面重新设计了操作系统和虚拟机内存管理，以适应大内存，使应用程序获得当前硬件所承诺的性能和效率。本研究的目标是为操作系统和管理程序提供一组原则和框架，以透明地支持大小内存页面。大内存页（例如，流行的x86架构的2MB页而不是标准的4KB页）可以通过显著减少地址转换开销来提供显著的性能优势。然而，它们的支持和采用一直受到由碎片和内存访问可视性差引起的基本管理问题的阻碍。当前的大页面管理存在各种各样的问题，比如内存膨胀和进程和/或虚拟机之间的不公平，系统管理员通常在生产系统中禁用大页面。依赖于将连续性管理作为一级资源并跟踪内存页的利用率和访问频率的框架将使操作系统能够协调其当前不同的机制，避免性能病态，并使应用程序能够享受大页面的性能优势。

Modern computing workloads such as machine learning, big data analytics, and scientific computing require enormous memory capacities. The system software that manages memory was designed for much smaller systems, and consequently, it imposes hefty performance and power penalties on modern systems. The time has come to pay this technical debt. This work comprehensively redesigns operating system and virtual machine memory management to accommodate large memories, enabling applications to obtain the performance and efficiency promised by current hardware.The goal of this research is a set of principles and a framework for the operating system and hypervisor to transparently support small and large memory pages. Large memory pages (e.g., 2MB pages for the popular x86 architecture instead of the standard 4KB) can provide significant performance benefit by dramatically reducing address translation over- heads. However, their support and adoption has been hindered by fundamental management problems arising from fragmentation and poor visibility into memory accesses. Current large page management suffers a variety of pathologies such as memory bloat and unfairness across processes and/or virtual machines, and system administrators generally disable large pages in production systems. A framework that relies on managing contiguity as a first-class resource and on tracking utilization and access frequency of memory pages will enable an OS to coordinate its currently disparate mechanisms, avoid performance pathologies, and enable applications to enjoy the performance benefits of large pages.