Real-time multi-core virtual machine scheduling in xen

IEICE Transactions on Information and Systems, 2012

Cheol-Ho HONG †a) , Young-Pil KIM †b) , Nonmembers, Seehwan YOO †c) , Student Member, Chi-Young LEE †d) , Nonmember, and Chuck YOO †e) , Member SUMMARY Facing practical limits to increasing processor frequencies, manufacturers have resorted to multi-core designs in their commercial products. In multi-core implementations, cores in a physical package share the last-level caches to improve inter-core communication. To efficiently exploit this facility, operating systems must employ cache-aware schedulers. Unfortunately, virtualization software, which is a foundation technology of cloud computing, is not yet cache-aware or does not fully exploit the locality of the last-level caches. In this paper, we propose a cache-aware virtual machine scheduler for multi-core architectures. The proposed scheduler exploits the locality of the last-level caches to improve the performance of concurrent applications running on virtual machines. For this purpose, we provide a space-partitioning algorithm that migrates and clusters communicating virtual CPUs (VCPUs) in the same cache domain. Second, we provide a time-partitioning algorithm that co-schedules or schedules in sequence clustered VCPUs. Finally, we present a theoretical analysis that proves our scheduling algorithm is more efficient in supporting concurrent applications than the default credit scheduler in Xen. We implemented our virtual machine scheduler in the recent Xen hypervisor with para-virtualized Linux-based operating systems. We show that our approach can improve performance of concurrent virtual machines by up to 19% compared to the credit scheduler.

With multi-core processors becoming popular, exploiting their computational potential becomes an urgent matter. The functionality of multiple standalone computer systems can be aggregated into a single hardware computer by virtualization, giving efficient usage of the hardware and decreased cost for power. Some principles of operating systems can be applied directly to virtual machine systems, however virtualization disrupts the basis of spinlock synchronization in the guest operating system, which results in performance degradation of concurrent workloads such as parallel programs or multi-threaded programs in virtual machines.

IEEE Real-Time Systems Symposium, 2008

This paper tackles the problem of guaranteeing appro- priate timeliness guarantees to real-time applications run- ning in a virtualised Operating System. Preliminary exper- imental results are presented, highlighting how the appro- priate use of well-established real-time scheduling strate- gies may be effective in facing with this challenging issue.

Future Generation Computer Systems, 2013

Para-virtualization features little performance degradation by presenting each virtual machine with an abstraction of hardware instead of fully emulating the hardware environment. A guest running atop Xen can achieve near-native performances. A critical part of Xen is its CPU scheduler which slices and dispatches physical CPU time to virtual machines. Xen's credit scheduler utilizes blocked-to-boosted mechanism to improve latency and throughput of I/O tasks. It boosts the scheduling priority of a blocked VCPU that receives an event. The boosted VCPU then preempts the current VCPU and gets executed straightaway. However, virtual CPUs that receive events while processing CPU-intensive tasks seldom block. Thus, the mechanism does not favor these VCPUs which process mixed workloads. Moreover, VCPUs that constantly send request events are not properly prioritized either. The two problems above can result in poor application performance to guest domains. We propose a novel approach to improve the credit scheduler, making it appropriately prioritize such domains. Our solution includes two aspects: 1) to schedule the VCPU that receives I/O events as soon as possible; 2) to switch in frequent event senders to let them initiate more I/O requests from time to time. The experimental evaluation demonstrates that our approach not only improves the responsiveness of domains doing mixed workloads, but also minimizes the possibly caused scheduling unfairness.

Proceedings of the 2011 International Conference on Parallel and Distributed Processing Techniques and Applications (PDPTA 2011), 2011

Abstract—Heterogeneous multicore processors could be the future trend of processors' industry due to their performance-power efficiency. In the operating systems domain, A heterogeneity-aware scheduler assigns a thread or an application to an appropriate core to realize this efficiency. Using virtualization technologies enables resource consolidation and achieves effective utilization of resources. Nevertheless, Hypervisors' scheduling-policy is based on the round robin algorithm to ensure fairness among VMs. Emerging ...

International Journal of Trend in Scientific Research and Development, 2017

virtualization is the creation of a virtual (rather than actual) version of something, such as a hardware platform, operating system (OS), storage device, or network resources. In a virtualized environment, computing environments can be produced in a forceful dynamic manner, enlarged, become smaller or go in a specified direction or manner as demand varies. Virtualization is therefore highly suitable to a dynamic cloud infrastructure, because it provides important advantages in isolation, manageability and sharing.

SIGBED review, 2019

In recent years, there has been a growing interest in supporting component-based software development of complex real-time embedded systems. Techniques such as machine virtualisation have emerged as interesting mechanisms to enhance the security of these platforms, while real-time scheduling techniques have been proposed to guarantee temporal isolation of different virtualised components sharing the same physical resources. This combination also highlighted criticalities due to overheads introduced by hypervisors, particularly for low-end embedded devices. This led to the need of investigating deeper into solutions based on lightweight virtualisation alternatives, such as containers. In this context, this paper proposes to use a real-time deadline-based scheduling policy built into the Linux kernel to provide temporal scheduling guarantees to different co-located containers. The proposed solution extends the SCHED_DEADLINE scheduling policy to schedule Linux control groups, allowing user threads to be scheduled with fixed priorities inside the control group scheduled by SCHED_DEADLINE. The proposed mechanism can be configured via control groups, and it is compatible with commonly used tools such as LXC, Docker and similar. This solution is compatible with existing hierarchical real-time scheduling analysis, and some experiments demonstrate consistency between theory and practice.

International Journal of Embedded Systems and Applications, 2013

Virtualization, together with real-time support emerges to be used in an increasing amount of use cases, varying from embedded systems to enterprise computing. One of the most popular open-source virtualization software's is Xen. Its current implementation does not qualify it to be a candidate for timecritical systems. Researchers and developers extended it and claim the efficient usage of their versions in such systems. RT-Xen is one of these versions. It is a virtualization platform based on Compositional Scheduling and uses a suite of fixed-priority schedulers. This paper evaluates the performance and scheduling behaviour of RT-Xen. The test results show that only two proposed schedulers are suitable to be used for soft real-time applications.

2011

We present a co-designed scheduling framework and platform architecture that support compositional scheduling of real-time systems. The architecture is built on Xen virtualization platform, and relies on compositional scheduling theory that uses periodic resource models as component interfaces. We implement resource models as periodic servers and consider enhancements to periodic server design that significantly improve response times of tasks and resource utilization in the system while preserving theoretical schedulability results. We present an extensive evaluation of our implementation using workloads from an avionics case study as well as synthetic ones.