Time Critical Messaging Using a Real-Time Operating System

Abstract

This thesis evaluates the possibility and the effects on performance of running an existing software, not designed for real-time operation, on a real-time operating system. The software being investigated is Unite Communication Server developed by Ascom Wireless Solutions, and is used for wireless communication within the healthcare sector. The software, which originally runs on Red Hat Enterprise Linux 7 with stock kernel, was installed on a Red Hat Enterprise Linux 7 system (the host) running a kernel patched with the real-time patch RT-Preempt. Performance was then measured by an external computer (the client) connected directly through wired Ethernet. The host was also put under a number of different loads to further amplify the effects of the real-time runtime. The real-time kernel is shown to give equal or better determinism under all loads, albeit only marginally if one considers how the software is used. The stock kernel is deemed good enough regarding performance and determinism while also being more stable, and migration to the real-time kernel is therefore advised against for this particular software. Furthermore, the standard Intel Ethernet driver for Linux is identified as a substantial source of nondeterminism that should preferably be avoided in networking applications with strict timing constraints. Nonetheless, switching to the RT-Preempt based real-time kernel showed to be a simple way to increase determinism for this system, especially since no changes to the software were required.