虚拟机内存轻量级检查点研究

Lightweight checkpoint of virtual machine memory

针对传统的虚拟机检查点粒度大和做检查点时停机时间长的问题,采用空闲内存页面排空、写时复制和增量检查点来解决传统虚拟机检查点的问题,通过这三项技术使检查点技术轻量化.空闲内存页面排空通过在检查点中排除空闲页面,可以减少虚拟机检查点文件的大小;写时复制通过在虚拟机内存写入时进行内存页面复制,可以减少做检查点的时间;增量检查点通过内存增量页面的计算,检查点只包含增量信息,可以减少虚拟机检查点文件的大小.在虚拟化平台Xen上的实验结果表明:采用写时复制技术减少了做检查点过程中虚拟机的停机时间,停机时间不超过300ms,并可使检查点这一过程对上层应用透明;采用内存排空技术和增量技术来做检查点,使得检查点文件的大小减少20%.

The size of the traditional virtual machine (VM) checkpoint is very large and the downtime of VM is long .In order to solve the two problems of VM checkpoint ,page eviction ,copy-on-write , and incremental memory mechanism were proposed in this paper .Free page eviction can avoid saving useless page in checkpoint file ,so that the size of VM checkpoint can be reduced .By copying the memory page only w hen there is w riting operation on it ,copy-on-w rite can reduce the time of check-point .By computing the incremental memory page and only including the incremental information in checkpoint ,the size of VM checkpoint can be reduced .The experiment shows that with copy-on-write checkpoint mechanism ,the shutdow n time of VM is reduced to 300 ms .With free page eviction and incremental checkpoint ,the size of checkpoint file is reduced by 20% .