LoRe: Supporting Non-deterministic Events Logging and Replay for KVM Virtual Machines

Cloud computing brings a loose-coupled resources integration paradigm with virtualized, elastic and cost-efficient resource management capabilities. Virtualization-based logging and replay technologies give users the ability to record the executions of the whole virtual machines and recover them at any time in a peer to peer mode, and it has become an important approach to analyze the system vulnerability, debug the system execution, or recover a failed system. In this paper, we design a logging and replay system named LoRe in KVM (Kernel-based Virtual Machine) which is a widely-used full virtualization solution. In LoRe, the logging of non-deterministic events is achieved based on the Virtual Machine Control Structure (VMCS), and a kernel notification chain is designed to reduce the time consumption of the branches counter matching procedure in the replay process. Moreover, to use less cache and reduce the overhead of log transmission, a reusable circular buffer queue is designed and IOCTL is used for the data transmission. We implemented LoRe in kvm-kmod-2.6.32, and experimental study show that the overhead of LoRe is lower than 8%, and only a small storage space is used.