基于IEEE 802.1 AS和ACRN的虚拟化分布式实时的系统时钟同步
Clock Synchronization in Virtualized Distributed Real-Time Systems using IEEE 802.1AS and ACRN
摘要：
分布式实时的【形】系统的虚拟化使得在共享硬件平台上整合混合关键性功能成为可能，从而简化了系统集成。时间触发的通信和计算可以作为安全的硬实时的【形】系统的使能者。根据全局调度来激活虚拟CPU的时间触发的管理程序可以提供允许在虚拟化分布式实时的【形】系统中的时间触发范例的资源高效实现的手段。对于硬实时的【形】系统，时间触发虚拟化的先决条件是为VM以及管理程序提供对全局时间基准的访问。全局时基是时钟同步的结果，具有时钟同步精度的上限。我们提出了一个形式化的虚拟化实时的【形】系统中的时间概念。我们使用这种形式化提出了一个虚拟时钟条件，使我们能够测试的虚拟时钟的虚拟时间触发的实时的【形】系统的设计的适用性。我们讨论和模拟虚拟化，特别是资源整合与资源分区，降低时钟同步精度。最后，我们应用我们的见解建模的IEEE 802.1AS时钟同步协议，并推导出一个上界的IEEE 802.1AS的时钟同步精度。我们提出了一个依赖的ACRN时钟，可以同步到一个大师时钟的实现。我们的实验结果表明，1型虚拟机管理程序实现依赖的时钟产生本机时钟同步精度。此外，我们表明，来自我们的模型的上限举行了一系列的实验，具有本地以及虚拟化的设置。
英文摘要：
Virtualization of distributed real-time systems enables the consolidation of mixed-criticality functions on a shared hardware platform thus easing system integration. Time-triggered communication and computation can act as an enabler of safe hard real-time systems. A time-triggered hypervisor that activates virtual CPUs according to a global schedule can provide the means to allow for a resource efficient implementation of the time-triggered paradigm in virtualized distributed real-time systems. A prerequisite of time-triggered virtualization for hard real-time systems is providing access to a global time base to VMs as well as to the hypervisor. A global time base is the result of clock synchronization with an upper bound on the clock synchronization precision. We present a formalization of the notion of time in virtualized real-time systems. We use this formalization to propose a virtual clock condition that enables us to test the suitability of a virtual clock for the design of virtualized time-triggered real-time systems. We discuss and model how virtualization, in particular resource consolidation versus resource partitioning, degrades clock synchronization precision. Finally, we apply our insights to model the IEEE~802.1AS clock synchronization protocol and derive an upper bound on the clock synchronization precision of IEEE 802.1AS. We present our implementation of a dependent clock for ACRN that can be synchronized to a grandmaster clock. The results of our experiments illustrate that a type-1 hypervisor implementing a dependent clock yields native clock synchronization precision. Furthermore, we show that the upper bound derived from our model holds for a series of experiments featuring native as well as virtualized setups.
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