Improving Responsiveness for Virtualized Networking Under Intensive Computing Workloads

In this paper the problem of providing network response guarantees to multiple Virtual Machines (VMs) co-scheduled on the same set of CPUs is tackled, where the VMs may have to host both responsive real-time applications and batch compute-intensive workloads. When trying to use a real-time reservation- based CPU scheduler for providing stable performance guarantees to such a VM, the compute-intensive workload would be scheduled better with high time granularities, to increase performance and reduce system overheads, whilst the real-time workload would need lower time granularities in order to keep the response-time under acceptable levels. The mechanism that is proposed in this paper mixes both concepts, allowing the scheduler to dynamically switch between fine-grain and coarse-grain scheduling intervals depending on whether the VM is performing network operations or not. A prototype implementation of the proposed mechanism has been realized for the KVM hypervisor when running on Linux, modifying a deadline-based real-time scheduling strategy for the Linux kernel developed previously. The gathered experimental results show that the proposed technique is effective in controlling the response-times of the real-time workload inside a VM while at the same time it allows for an efficient execution of the batch compute-intensive workload.