Template-aware Live Migration of Virtual Machines

One of the key challenges of edge computing is working with a limited amount of resources available at the edge, especially memory and bandwidth. Virtual Machine (VM) Templating is a technique to start multiple VM instances quickly from a shared pre-configured read-only image (or template). The new VM instances share the memory of the template in a copy-on-write (COW) manner. In edge computing platforms, VM templating can help to reduce the collective memory footprint and deployment time of multiple VMs. Live migration of VMs can also improve task placement on edge nodes for latency reduction, service availability, and cost-effectiveness. However, existing live migration techniques fail to maintain memory sharing among multiple templated VMs that are migrated to a common destination. Consequently, identical pages at the source are replicated several times at the destination, increasing memory pressure on the destination node, network traffic during migration, and total migration time. Lack of templating awareness can also trigger migration failure if the destination lacks sufficient memory to accommodate the increased memory footprint. To address this shortcoming of live migration, we introduce Template-aware Live Migration (TLM), which preserves preexisting COW memory sharing between templated VMs that are migrated to a common destination machine. Specifically, TLM ensures that multiple virtual pages from different VMs that are mapped to the same template page at the source are mapped to the same page at the destination. We implement TLM on the QEMU/KVM virtualization platform and demonstrate a significant reduction in memory footprint, shorter migration time, and reduced network traffic.