Low-latency inter-domain communication on the Xen hypervisor

Designing mixed-critical systems that provide both safety-critical and best-effort functions is a major challenge. In embedded systems, hypervisors are increasingly used to separate sensitive real-time tasks from best-effort applications. To take advantage of hypervisors at the application level as well, there is an emerging trend to split large applications into multiple guest domains to make the software easier to analyze and maintain. However, having more partitions leads to increased communication overhead between guest domains, increasing the impact of latencies on performance. In this article, we propose a framework for Inter-Domain Communication (IDC) to tackle these issues by reducing IDC latencies. It is built upon established open-source implementations of the VIRTIO and RPMsg specifications, allowing to reuse existing drivers for guest OS or bare-metal software. We can show latency improvements of up to 3x compared to UDP communication between two guests, even faster than UDP communication using the loopback interface within one Linux guest. Splitting applications into separate guest domains is discussed, as a trace-off between communication latency and computational complexity exists. Further a service-oriented example application is analyzed, where our approach can lead to improvements through inherent concurrency. In addition, we demonstrate how to extend the original peer-to-peer scheme with a router component to allow multiple guests to exchange data.