SweetspotVM: Oversubscribing CPU without Sacrificing VM Performance

Abstract

The adoption of computing resources oversubscription in cloud environments is conventionally limited to a restricted subset of Virtual Machines (VMs) within the providers' offerings, primarily driven by performance considerations. So far, VMs schedulers mostly implement all-or-nothing oversubscription strategies, wherein all VM resources are either oversubscribed or remain unaltered. While the former strategy offers higher consolidation rates, the latter delivers better performance guarantees.In this paper, we conducted an empirical study of the individual usage of virtual CPUs (vCPUs) in the OVHCLOUD production environment and we demonstrate that, as they are not uniformly utilized, the current holistic approach may not be appropriate. Based on these observations, we introduce a novel approach, named SWEETSPOTVM, where oversubscription ratios are applied at the granularity of individual vCPU, instead of the whole VMs. This novel paradigm unlocks a more flexible oversubscription management strategy, pinning oversubscription ratios per vCPU within VMs. We present a prototype of SWEETSPOTVM to illustrate the feasibility of accommodating multiple oversubscription levels within a single host and assigning them to individual vCPU.We assess the viability of our approach on a physical platform, demonstrating the possibility of dividing the cost of hosting VMs by 3, while maintaining the VMs performance at the level of non-oversubscribed platforms. We, therefore, believe that SWEETSPOTVM opens new avenues to boost the consolidation of VMs on a reduced number of servers, with positive impacts on the environmental footprint of cloud computing.