Synchronization support for parallel applications in virtualized clouds

Cloud computing platforms have become very attractive for parallel applications, thanks to the system virtualization technology that allows versatile and pliable computing environments. However, owing to the virtualization overhead, parallel applications can suffer from poor performance when executing synchronization operations. In this paper, we propose sc scheduling, which is a synchronization-conscious scheduling algorithm that can mitigate the existing virtualization overhead. For this purpose, the proposed scheduler understands the synchronization phases of each parallel application. Based on this comprehension, it then eliminates unnecessary CPU spinning of parallel threads and its incurred waste of valuable CPU time. In addition, it prevents their long blocking, which otherwise causes unfairness between concurrent virtual machines (VMs) and other VMs. We implemented these simple concepts and thoroughly evaluated them in a recent Xen hypervisor release. Our results demonstrate that our approach can significantly improve the speed of concurrent virtual machines compared to the original credit scheduler in Xen.