Janus: A cross-layer soft real-time architecture for virtualization

With the advent of video sharing websites (e.g. YouTube) and interactive 3D video systems (e.g. Teeve, Cave), multimedia based content delivery networks (CDN) have become ubiquitous. These CDN architectures comprise of several processing and disseminating entities (e.g. proxies and gateways) that require real-time processing and trans-coding of multimedia content that must be delivered before an established deadline. Furthermore, Virtual Machine Monitors (VMMs) emerged as a popular architecture for server consolidation and cost reduction in enterprise systems. CDN proxies and gateways would greatly benefit from the deployment of VMM architectures since VMMs allow virtualization of their resources for virtual private multimedia sessions in a cost-effective manner. However, current VMMs do not provide abstractions to efficiently map processes to CPU resources and they do not provide adequate Quality of Service (QoS) mechanisms for task prioritization and CPU management to guarantee the completion of multimedia sessions by their deadlines. In this paper, we present Janus, a soft real-time Cross-Layer CPU scheduling architecture for VMM used in CDN gateways. Janus allows CDN gateway services to obtain efficiently reservation-based CPU guarantees within VMM and across VMMs, based on their individual QoS requirements. Our results show that soft real-time multimedia services running on our scheduling architecture can more efficiently meet the job deadlines specified when compared to the Xen Credit Scheduler.