Evaluating the real-time capabilities of Zephyr on UP Squared - a pilot study with Zephyr and ACRN

Abstract: In this study we have investigated if using Zephyr (User VM) and ACRN (Hypervisor) on the UPSquared (N3350) board are suitable for use in real-time scenarios. This was achieved by conductinga series of tests on Zephyr’s scheduling API functions such as busy-wait and sleep under differentsystem configurations. The tests involved running a task in isolation and taking timestamps ofthe current system cycle count before and after each function. To do this, we used the CommonTrace Format functionality in Zephyr to collect execution traces, which were then analyzed usingBabeltrace to convert the binary trace into human-readable form. The difference between the beforeand after timestamp were compared to the configured clock frequency to see if the system behaved asexpected. Our findings in this report suggest that Zephyr and ACRN on the UP Squared board arenot suitable for use in real-time scenarios due to large differences in system cycle count dependingon the configuration.