Performance Implications of Extended Page Tables on Virtualized x86 Processors

Timothy Merrifield, H. Taheri
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引用次数: 1

Abstract

Managing virtual memory is an expensive operation, and becomes even more expensive on virtualized servers. Processing TLB misses on a virtualized x86 server requires a twodimensional page walk that can have 6x more page table lookups, hence 6x more memory references, than a native page table walk. Thus much of the recent research on the subject starts from the assumption that TLB miss processing in virtual environments is significantly more expensive than on native servers. However, we will show that with the latest software stack on modern x86 processors, most of these page table lookups are satisfied by internal paging structure caches and the L1/L2 data caches, and the actual virtualization overhead of TLB miss processing is a modest fraction of the overall time spent processing TLB misses. We show that even for the heaviest workloads, a welltuned application that uses large pages on a recent OS release with a modern hypervisor running on the latest x86 processors sees only minimal degradation from the additional overhead of the two-dimensional page walks in a virtualized server.
扩展页表在虚拟化x86处理器上的性能影响
管理虚拟内存是一项昂贵的操作,在虚拟化服务器上甚至会变得更加昂贵。在虚拟化的x86服务器上处理TLB缺失需要一个二维页遍历,它可以有6倍多的页表查找,因此比本机页表遍历多6倍的内存引用。因此,最近关于该主题的许多研究都基于这样的假设,即虚拟环境中的TLB遗漏处理比本地服务器上的TLB遗漏处理要昂贵得多。但是,我们将展示,使用现代x86处理器上的最新软件堆栈,大多数页表查找都可以通过内部分页结构缓存和L1/L2数据缓存来满足,并且TLB丢失处理的实际虚拟化开销只是处理TLB丢失所花费的总时间的一小部分。我们表明,即使对于最繁重的工作负载,在最新的操作系统版本上使用大型页面,并在最新的x86处理器上运行现代管理程序的经过优化的应用程序,在虚拟服务器中二维页面遍历的额外开销也只会带来最小的性能下降。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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