Scheduling Analysis of UAV Flight Control Workloads using Raspberry Pi 5 Using PREEMPT_RT Linux
For UAV developers seeking to consolidate autonomy and flight control on a single GPOS, this work provides a quantitative evaluation of PREEMPT_RT's effectiveness on a modern SoC.
This paper analyzes PREEMPT_RT Linux on a Raspberry Pi 5 for UAV flight control, showing that under heavy stress, standard Linux has worst-case latencies exceeding 9 ms, while PREEMPT_RT reduces them by 88% to under 225 μs, though residual jitter from hardware memory contention remains.
Modern UAV architectures increasingly aim to unify high-level autonomy and low-level flight control on a single General-Purpose Operating System (GPOS). However, complex multi-core System-on-Chips (SoCs) introduce significant timing indeterminism due to shared resource contention. This paper performs an architectural analysis of the PREEMPT RT Linux kernel on a Raspberry Pi 5, specifically isolating the impact of kernel activation paths (deferred execution SoftIRQs versus real-time direct activation) on a 250 Hz control loop. Results show that under heavy stress, the standard kernel is unsuitable, exhibiting worst-case latencies exceeding 9 ms. In contrast, PREEMPT RT reduced the worst-case latency by nearly 88 percent to under 225 microseconds, enforcing a direct wake-up path that mitigates OS noise. These findings demonstrate that while PREEMPT RT resolves scheduling variance, the residual jitter on modern SoCs is primarily driven by hardware memory contention.