The proliferation of system virtualization poses a new challenge for the coarse-grained time sharing techniques for consolidation, since operating systems are running on virtual CPUs. The current system stack was designed under the assumption that operating systems can seize CPU resources at any moment. However, for the guest operating system on a virtual machine (VM), such assumption cannot be guaranteed, since virtual CPUs of VMs share a limited number of physical cores. Due to the time-sharing of physical cores, the execution of a virtual CPU is not contiguous, with a gap between the virtual and real time spaces. Such a virtual time discontinuity problem leads to significant inefficiency for lock and interrupt handling, which rely on the immediate availability of CPUs whenever the operating system requires computation. To reduce scheduling latencies of virtual CPUs, shortening time slices can be a straightforward strategy, but it may lead to the increased overhead of context switching costs across virtual machines for some workloads. It is challenging to determine a single time slice to satisfy all the VMs. In this article, we propose to have dual time slice to resolve the time slice conflict problem occurred in different types of virtual machines.

中文翻译：

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使用云的双时间片协调虚拟机的时间片冲突

系统虚拟化的激增对用于整合的粗粒度分时技术提出了新的挑战，因为操作系统是在虚拟 CPU 上运行的。当前的系统堆栈是在操作系统可以随时抢占 CPU 资源的假设下设计的。但是，对于虚拟机（VM）上的来宾操作系统，无法保证这种假设，因为 VM 的虚拟 CPU 共享有限数量的物理内核。由于物理内核的分时，虚拟 CPU 的执行不是连续的，虚拟和实时空间之间存在间隙。这种虚拟时间不连续性问题导致锁定和中断处理的效率显着低下，这依赖于每当操作系统需要计算时 CPU 的即时可用性。为了减少虚拟 CPU 的调度延迟，缩短时间片可能是一个简单的策略，但它可能会导致某些工作负载跨虚拟机的上下文切换开销增加。确定满足所有 VM 的单个时间片是具有挑战性的。在本文中，我们建议使用双时间片来解决不同类型虚拟机中出现的时间片冲突问题。