Scheduling Analysis of UAV Flight Control Workloads using Raspberry Pi 5 Using PREEMPT_RT Linux

2026-04-21

AI Summary

This study addresses the severe timing unpredictability arising from shared resource contention in multicore SoCs when integrating high-level autonomy with low-level flight control on general-purpose operating systems for modern drones. For the first time, it quantitatively evaluates the impact of the PREEMPT_RT Linux kernel on worst-case latency of a 250 Hz flight control task on the Raspberry Pi 5 platform, comparing scheduling performance between SoftIRQ deferred execution and real-time direct-wakeup pathways. Through kernel activation path analysis, system stress testing, and temporal determinism assessment, the work demonstrates that the standard Linux kernel exhibits worst-case latencies exceeding 9 ms, whereas PREEMPT_RT reduces this by 88% to below 225 µs. The study further identifies hardware memory contention as the primary source of residual jitter, significantly enhancing the temporal reliability of flight control tasks.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Machine Learning: Hardware-aware ML
• Intelligent Robots: Multi-Robot Systems

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Security and Privacy: Large-scale security measurements

Abstract

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.

Problem

• UAV
• real-time scheduling
• timing indeterminism
• resource contention
• flight control

Innovation

• PREEMPT_RT
• UAV flight control
• real-time scheduling
• Raspberry Pi 5
• memory contention