CoINT2: A Heuristic Coordinator for Responsive Receive-Side Network I/O Virtualization in Overcommitment Cloud

Cloud computing providers are committed to CPU overcommitment for maximizing resource utilization. However, CPU overcommitment degrades network I/O performance by deferred interrupt acceptance as well as interruptibility holder preemption under CPU overcommitment scenarios. Previous research focused on bridging the semantic gap between the hypervisor scheduler and the source of interrupt delivery. However, unlike virtual interrupt delivery is highly mediated by the hypervisor in para-virtualization, pass-through I/O utilizes interrupt posting hardware for non-exit-to-hypervisor interrupt delivery. Therefore, the lack of exposed interfaces poses challenges in transferring existing solutions. In this paper, we implement a software and hardware co-design design, COPINT2. First, we reintroduces the hypervisor to interrupt delivery, leveraging its capability to select target vCPUs for interrupt delivery from hardware. Second, we heuristically divide the VCPU execution cycle into interruptibility holding and enabling phases to eliminating interrupt holding preemption. CoINT2 increase throughput by up to 126% and achieve up to 82% lower latency in both micro and macro benchmarks, which is proven to be a practical solution in that provides near non-overcommitment performance for I/O workloads in overcommitted cloud.