S-memV: Split Migration of Large-Memory Virtual Machines in IaaS Clouds

Recently, Infrastructure-as-a-Service clouds provide virtual machines (VMs) with a large amount of memory. Such large-memory VMs make VM migration difficult because it is costly to reserve large-memory hosts as the destination. Using virtual memory is a remedy for this problem, but virtual memory is incompatible with the memory access pattern in VM migration. Consequently, large performance degradation occurs during and after VM migration due to excessive paging. This paper proposes split migration of large-memory VMs with S-memV. Split migration migrates a VM to one main host and one or more sub-hosts. It divides the memory of a VM and transfers memory likely to be accessed to the main host. Since it transfers the rest of the memory directly to the sub-hosts, no paging occurs during VM migration. After split migration, remote paging is performed between the main host and the sub-hosts, but its frequency is lower thanks to memory splitting that is aware of remote paging. We have implemented S-memV in KVM and showed that the performance of split migration and application performance after VM migration were comparable to that of traditional VM migration with sufficient memory.