ResourceExchange: Latency-Aware Scheduling in Virtualized Environments with High Performance Fabrics

Virtualized infrastructures have seen strong acceptance in data center systems and applications, but have not yet seen adoptance for latency-sensitive codes which require I/O to arrive predictability, or response times to be generated within certain timeliness guarantees. Examples of such applications include certain classes of parallel HPC codes, server systems performing phonecall or multimedia delivery, or financial services in electronic trading platforms, like ICE and CME. In this paper, we argue that the use of high-performance, VMM-bypass capable devices can help create the virtualized infrastructures needed for the latency-sensitive applications listed above. However, to enable consolidation, problems to be solved go beyond efficient I/O virtualization, and include dealing with the shared use of I/O and compute resource, in ways that minimize or eliminate interference. Toward this end, we describe ResEx -- a resource management approach for virtualized RDMA-based platforms which incorporates concepts from supply-demand theory and congestion pricing to dynamically control the allocation of CPU and I/O resources of guest VMs. ResEx and its mechanisms and abstractions allow multiple 'pricing policies' to be deployed on these types of virtualized platforms, including such which reduce interference and enhance isolation by identifying and taxing VMs responsible for resource congestion. While the main ideas behind ResEx are more general, the design presented in this paper is specific for InfiniBand RDMA-based virtualized platforms due to the use of asynchronous monitoring needed to determine the VMs' I/O usage, and the methods to establish the trading rate for the underlying CPU and I/O resources. The latter is particularly necessary since the hypervisor's only mechanism to control I/O usage is by making appropriate adjustments in the VM's CPU resources. The experimental evaluation of our solution uses InfiniBand platforms virtualized with the open source Xen hyper visor, and an RDMA-based latency-sensitive benchmark, BenchEx, based on a model of a financial trading platform. The results demonstrate the utility of the ResEx approach in making RDMA-based virtualized platforms more manageable and better suited for hosting even latency-sensitive workloads. ResEx can reduce the latency interference by as much as 30% in some cases as shown.