300 Int. J. Embedded Systems, Vol. 8, No. 4, 2016 Copyright © 2016 Inderscience Enterprises Ltd. Behaviour and performance comparison between FreeRTOS and μC/OS-III Long Peng*, Fei Guan, Luc Perneel and Martin Timmerman Electronics and Informatics Department, Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussel, Belgium Email: long.peng@vub.ac.be Email: fei.guan@vub.ac.be Email: luc.perneel@vub.ac.be Email: martin.timmerman@vub.ac.be *Corresponding author Abstract: As the prevalence of embedded systems in various fields has spread, real-time operating systems (RTOSs) have been widely used for many years satisfying real-time requirements and a multitasking design. The use of RTOS adds additional overhead to a system, which should be deliberately considered and evaluated in some critical systems. This paper presents a qualitative and quantitative comparison between an open-source RTOS (FreeRTOS V8.0.0) and a commercial one (μC/OS-III). Both RTOS use a preemptive multitasking kernel, with additional support for round robin scheduling. We aim to benchmark and evaluate their performance and behaviour, including seven performance tests and two behaviour tests. Comparing the measurement results shows that the commercial μC/OS-III does not behave much better than FreeRTOS. Furthermore, we discovered that the priority changing function of μC/OS- III does not behave correctly in some circumstances. Although FreeRTOS has no such problem in the latest version, it still has a problem with its dynamic memory management. Keywords: FreeRTOS; μC/OS-III; behaviour; performance; comparison. Reference to this paper should be made as follows: Peng, L., Guan, F., Perneel, L. and Timmerman, M. (2016) ‘Behaviour and performance comparison between FreeRTOS and μC/OS-III’, Int. J. Embedded Systems, Vol. 8, No. 4, pp.300–312. Biographical notes: Long Peng received his BS and MS in Computer Science and Technology from the National University of Defense Technology, China in 2009 and 2012. His areas of research were web programming, data mining, and distributed file system. Since November 2012, he has been awarded as a PhD candidate at the Embedded System Lab, ETRO, VUB. His research topics include real-time operating system benchmark, behaviour-based robotics and adaptive systems. Fei Guan received her BEng in Automatic Test and Control from Harbin Institute of Technology (HIT), China, in 2010. She received her MS degree at the same university in 2012 and is currently a PhD candidate at the Department of Electronics and Informatics (ETRO) of Vrije Universiteit Brussel (VUB). Her research interests are in the areas of real-time operating system and adaptive scheduling. Luc Perneel received his Master in Electrical Engineering from Catholic University Leuven (KUL), Belgium, in 1990. He has complemented with a Post Master in Industrial Management, awarded also by KUL, in 1991. He has more than 20 years of experience in embedded systems and real-time behaviour. He is specialised in operating systems and interactions between hardware and software. Besides performing research on real-time scheduling at VUB as a PhD candidate, he owns the company Luperco. Martin Timmerman obtained his Engineering Master in Telecommunications at the Royal Military Academy, Brussels in 1975 and PhD in Applied Science at the University of Gent in 1982. He is a Professor at the Royal Military Academy and VUB. His research focuses on real-time operating system and swarm robotics. He is the head of the Embedded Systems Lab at VUB.