Efficient Pre-copy Live Migration with Memory Compaction and Adaptive VM Downtime Control

Virtual machine (VM) live migration is an important feature of the virtualization technique. Pre-copy method is typically used to support live migration in most virtualization environments. It is observed that pre-copy may not work in some situation where memory-intensive applications are running in KVM. Moreover, pre-copy live migration does not consider high duplication ratio between memory and root file system as well as between memory snapshots. This paper proposes two techniques to improve pre-copy live migrations: 1) memory compaction technique based on disk cache and memory snapshot, 2) adaptive downtime control scheme based on the history of VM´s memory update information called WWS (Writable Working Set). We have successfully implemented the proposed method in KVM. It is shown that the proposed method can support live migration under any circumstances with little overhead.