RPFF: A Remote Page-Fault Filter for Post-copy Live Migration

Abstract

Live migration of virtual machine has attracted significant attention in recent years. It facilitates system online maintenance, load balancing, fault tolerance and power management. Existing pre-copy live migration approach has to iteratively copy redundant memory pages, which causes high network overhead and slow migration. Another post-copy live migration approach can provide quick migration with low network overhead but would lead to a lot of remote page faults which greatly degrade application performance. In this paper, we improve the post-copy approach by eliminating unnecessary remote page faults. In our improved post-copy approach, page faults caused by guest's overwriting operations on remote memory pages are intercepted and handled by allocating new local memory pages, instead of fetching memory pages from the source host across the network. We have implemented our approach into the KVM/QEMU hypervisor and ran a series of experiments with Linux guests. The experimental results demonstrate that our improved approach performs much better than traditional post-copy approach.