With the development of cloud computing and virtualization technologies, more and more soft real-time applications, such as Voice over Internet Protocol (VoIP) server and cloud gaming, are running in virtualized data centers. Though previous studies optimize CPU schedulers of hypervisors to support these applications in virtualized environments, there are some important challenges in designing an efficient CPU scheduler which is suitable for real-world clouds. On one hand, hypervisors do not know whether an application in a virtual machine (VM) has real-time requirements, so manually setting the scheduling parameters is a common case for CPU schedulers, which probably increases users’ burden, lacks flexibility, and causes misconfigurations. On the other hand, it has been reported that most of existing CPU schedulers designed for soft real-time applications have an obvious propensity to such applications which prevents them from being applied in practical multi-tenant cloud environments. In this paper, we design and implement an adaptive soft real-time scheduler based on Xen, named Doris, to address these challenges. It identifies the VMs running soft real-time applications (RT-VMs) and infers their scheduling parameters according to the communication behaviors of VMs adaptively. Then, it promotes the priorities of VCPUs of the RT-VMs temporarily according to I/O events and the inferred scheduling parameters of RT-VMs to support soft real-time applications adaptively while minimizing the impacts on non-real-time applications. Finally, considering the importance of privileged entities (such as Domain0 in Xen) in I/O processing, Doris sets their types and scheduling parameters dynamically, which enables the adaptive scheduling of them to guarantee the performance of soft real-time applications. Our evaluation shows Doris can support soft real-time applications adaptively and efficiently, and only introduces very slight overhead.

中文翻译：

---

Doris：虚拟化环境中的自适应软实时调度程序

随着云计算和虚拟化技术的发展，越来越多的软实时应用，如网络电话（VoIP）服务器、云游戏等，都在虚拟化数据中心运行。尽管之前的研究优化了管理程序的 CPU 调度程序以支持虚拟化环境中的这些应用程序，但在设计适用于现实世界云的高效 CPU 调度程序方面存在一些重要挑战。一方面，管理程序不知道虚拟机（VM）中的应用程序是否有实时性要求，因此手动设置调度参数是 CPU 调度程序的常见情况，这可能会增加用户的负担，缺乏灵活性，并导致错误配置。另一方面，据报道，大多数现有的为软实时应用程序设计的 CPU 调度程序都明显倾向于此类应用程序，这阻碍了它们在实际多租户云环境中的应用。在本文中，我们设计并实现了一个基于 Xen 的自适应软实时调度器，名为 Doris，以应对这些挑战。它识别运行软实时应用程序 (RT-VM) 的 VM，并根据 VM 的通信行为自适应地推断它们的调度参数。然后，它根据 I/O 事件和 RT-VM 推断的调度参数临时提升 RT-VM 的 VCPU 的优先级，以自适应地支持软实时应用程序，同时最小化对非实时应用程序的影响。最后，考虑到特权实体（如 Xen 中的 Domain0）在 I/O 处理中的重要性，Doris 动态设置它们的类型和调度参数，使得它们的自适应调度能够保证软实时应用程序的性能。我们的评估表明 Doris 可以自适应和高效地支持软实时应用程序，并且只引入了非常小的开销。