Virtual Machine Scheduling for Parallel Soft Real-Time Applications

With the prevalence of multicore processors in computer systems, many soft real-time applications, such as media-based ones, use parallel programming models to utilize hardware resources better and possibly shorten response time. Meanwhile, virtualization technology is widely used in cloud data centers. More and more cloud services including such parallel soft real-time applications are running in virtualized environment. However, current hyper visors do not provide adequate support for them because of soft real-time constraints and synchronization problems, which result in frequent deadline misses and serious performance degradation. CPU schedulers in underlying hyper visors are central to these issues. In this paper, we identify and analyze CPU scheduling problems in hyper visors, and propose a novel scheduling algorithm considering both soft real-time constraints and synchronization problems. In our proposed method, real-time priority is introduced to accelerate event processing of parallel soft real-time applications, and dynamic time slice is used to schedule virtual CPUs. Besides, all runnable virtual CPUs of virtual machines running parallel soft real-time applications are scheduled simultaneously to address synchronization problems. We implement a parallel soft real-time scheduler, named Poris, based on Xen. Our evaluation shows Poris can significantly improve the performance of parallel soft real-time applications. For example, compared to the Credit scheduler, Poris improves the performance of media player by up to a factor of 1.35, and shortens the execution time of PARSEC benchmark by up to 44.12%.