虚拟机环境下软件按需部署中的预取机制  

Prefetch Mechanism for On-Demand Software Deployment in Virtual Machine Environments

作　　者：陈彬[1,2] 肖侬[1] 蔡志平[1] 王志英[1] 

机构地区：[1]国防科学技术大学计算机学院,湖南长沙410073 [2]北京军区司令部,北京100041

出　　处：《软件学报》2010年第12期3186-3198,共13页Journal of Software

基　　金：国家自然科学基金Nos.60736013;61025009;61070198;60903040;国家重点基础研究发展计划(973)No.2007CB310900;新世纪优秀人才支持计划No.NCET-08-0145~~

摘　　要：针对大规模虚拟机环境下软件的按需部署,提出了一种基于预取的按需软件部署优化机制,能够降低用户端虚拟机的启动延迟以及为用户提供更好的虚拟机本地运行性能.基于用户使用软件的行为特点以及虚拟磁盘映像的细粒度分割,预取机制在后台对服务器端存储的虚拟磁盘映像进行预取,通过一种基于访问频率和优先级的预取目标识别算法AFPTR(access frequency and priority-based prefetch target recognition)和一种预取量动态调节机制,将预取集中在用户使用的少数小尺寸的虚拟磁盘映像上,并在预取过程中对预取量进行动态自适应地调节,以提高虚拟磁盘访问的本地命中率,进而提高用户端虚拟机的运行性能.基于QEMU虚拟机和Linux平台,实现了基于预取的按需软件部署原型系统.实验结果表明,预取机制能够有效地降低虚拟机的启动延迟,并能提高虚拟机的本地运行性能,支持虚拟机环境下按需、快速的软件部署.To achieve on-demand software deployment in large-scale virtual machine （VM） environments, this paper presents a prefetch-based on-demand software deployment optimization mechanism to reduce the VM startup latency and to improve the VM running performance at user side. Based on the characteristics of user＇s behavior of using software and fine-grained splitting of virtual disk （VD） image, the paper prefetches those small-sized being-used VD images at user side from server side by using an access frequency and priority-based prefetch target recognition algorithm--AFPTR and uses a dynamic adjustment mechanism to adjust the prefetch amount during the prefetching process so as to improve the local hit ratio of virtual disk accessing and then the VM running performance at user side. Based on QEMU virtual machine monitor and Linux system, a prototype is built to implement the prefetch mechanism. Experiments on the prototype show that the prefetch mechanism can effectively reduce the VM startup latency and improve the VM running performance at user side, supporting on-demand, fast software deployment in virtual machine environments.

关 键 词：虚拟机 虚拟机管理器 COW(copy-on-write)磁盘 预取 按需软件部署 

分 类 号：TP393[自动化与计算机技术—计算机应用技术]