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The Hybrid Scheduling Framework for Virtual Machine Systems

The Hybrid Scheduling Framework for Virtual Machine Systems. Authors. 翁楚良，男，博士，副教授。 2001 年进入上海交通大学计算机系学习，从事并行与分布计算、集群计算与网格计算等研究工作。 2004 年博士毕业留校工作。 研究兴趣涉及 虚拟化技术 、并行与分布计算、网格计算与集群计算、高性能计算、系统安全等。同时负责网格计算中心的 IBM P690 、 IBM e1350 集群、 Intel Itanium2 服务器等高性能计算机的系统管理和相关开发工作。. This team’s work.

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The Hybrid Scheduling Framework for Virtual Machine Systems

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  1. The Hybrid Scheduling Framework for Virtual Machine Systems

  2. Authors • 翁楚良，男，博士，副教授。 • 2001年进入上海交通大学计算机系学习，从事并行与分布计算、集群计算与网格计算等研究工作。2004年博士毕业留校工作。 • 研究兴趣涉及虚拟化技术、并行与分布计算、网格计算与集群计算、高性能计算、系统安全等。同时负责网格计算中心的 IBM P690 、 IBM e1350 集群、 Intel Itanium2 服务器等高性能计算机的系统管理和相关开发工作。

  3. This team’s work • Automatic Performance Tuning for the Virtualized Cluster System ---- ICDCS2009

  4. The Problem • The scheduling strategy in Xen (Asynchronous CPU scheduling strategy) may deteriorate the performance when the virtual machine is used to execute the concurrent applications such as parallel programs or multithreaded programs.

  5. Why? • All virtual CPUs in a SMP virtual machine are usually not online all the time, and possibly not online at the same time(多线程程序需要相关所有CPU当前online才能继续运行), so the scheduling methods may deteriorate the performance.

  6. Why? VM VM Guest App. Guest App. vCPU vCPU vCPU pCPU pCPU ? Physical Hardware

  7. Why? • In the worst case, all the VMs are suspended even in the condition of enough physical CPUs. Just imagine 4 VMs have 2 vCPUs each on a 4-core platform.

  8. Solution • Recognize two types of virtual machines in the system: • the high-throughput type -- default • the concurrent type -- when the majority of its workload is concurrent applications

  9. Solution • When it is a concurrent VM, its virtual CPUs are mapped into physical CPUs synchronously ---- VM granularity schedule (Coscheduling) • Otherwise its virtual CPUs are mapped asynchronously. ---- vCPU granularity schedule

  10. Hybrid Schedule Framework

  11. Design Key Notes • To maximize the performance in the virtual machine system, the following design issues should be considered for the scheduler in the VMM. • Fairness • Workload Balancing • Wasted CPU Time • Adaptiveness

  12. Xen Scheduler • Three scheduling algorithms in Xen: • Borrowed Virtual Time (BVT) • Simple Earliest Deadline First (SEDF) • Credit Scheduling

  13. Borrowed Virtual Time (BVT) • Fair-share scheduling algorithm • Schedule the runnable VM with the smallest virtual time firstly • The client can effectively borrow virtual time from its future CPU allocation. • Low latency support ---- for realtime and interactive applications • Shortage : lack of the non work -conserving (NWC) mode

  14. Simple Earliest Deadline First (SEDF) • The real time property is used to ensure time guarantees • a VM will receive at least the slice specified by the VM in each period of the length specified by the VM. • Can indicate whether the VM is eligible to receive extra CPU time (work-conserving mode).

  15. Simple Earliest Deadline First (SEDF) • Shortage: • Lack of global workload balancing on multiprocessors • The CPU fairness depends on the value of the period.

  16. Credit Scheduling • One of proportional share (PS) strategies • Automatic workload balancing • This algorithm can efficiently achieve a global workload balancing on a SMP system when the majority of the workload is not the high concurrent application. • Default scheduling algorithm in Xen

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