Design And Implementation Of A Page Migration Strategy Based On Physical Large Pages

In modern computers, physical memory is crucial and short. The situation of more and more processes in memory and of the increasing memory footprint of applications have made the relent-less persuit of more available memory continue. Among the methods of improving the utilization of physical memory,the use of large pages,or hugepages,is a typical one. Widely supported by modern computer systems, hugepaging can reduce the TLB (Translation Lookaside Buffer) miss rate and the number of page-table entries managed by the operating system.The current hugepage of the Linux system is a compound page based on several consecutive base pages. Because of its compatibility of original pages and effective enhancement of system performance, compound-hugepaging is immensely popular. However, we can see that compound-hugepaging does not reduce the metadata costs of physical memory management. Also, hugepage operations are often broken down into iterations of several base page operations. Consequently,hugepaging can be optimized in both aspects of time and space.A corresponding solution is the use of physical hugepages(page descriptors directly refer to hugepages), but we need to face challenges before using them. First of all, we cannot give up.physical base pages. Hugepages do have significant performance improvements and space savings in its applications, but the benefits of hugepages are not as universal as base pages. If we only use hugepages, it's possible to have overwhelming internal fragmentation. If we do not give up base pages, however, the physical hugepage will coexist with the physical base page, which puts forward a lot of problems for the design of the operating system.In this paper,we designed a page migration policy to support the runtime adjustment of the size of the page memory pools of different physical page sizes, based on a physical hugepaging solution sharing the interface with hugetlbf s in Linux. The main work of this paper:We analyzed hugepage technologies supported by Linux, including Shared Memory and Memory Mapping from system programers' perspective and Transparent Hugepage and hugetlbfs from Linux kernel developers' perspective. We also did a research and anal-ysis of a huget lbf s-oriented physical hugepage for Linux.We implemented a page migration mechanism on a physical hugepage and designed a page migration policy based on multiple physical page sizes.We evaluated the page migration policy and quantified the optimization of memory utiliza-tion.