LinuxPREEMPT-RT vs. commercial RTOSs: how big is the performance gap?

Real-time operating systems (RTOSs) are getting more and more important for different uses in industry and become an integral part of commercial products today. Currently, there are many types of RTOSs, either open source or commercial ones with less or more features and characteristics. The aim of this research is to benchmark the real-time (RT) behaviour and performance of an open source RTOS (Linux PREEMPT-RT v3.6.6-rt17) and two commercial ones (QNX and Windows Embedded Compact 7), where all of them fall in the same RTOS category: they use virtual memory techniques to protect the kernel from user space, and protect the user space applications from each other. Flat memory RTOS’s are not in this category. The benchmark is based on experimental measurements’ metrics such as thread switch latency, interrupt latency, sustained interrupt frequency, mutex and semaphore acquisition and release durations, and finally the locking behaviour of mutex. These tests are executed on an x86 platform (ATOM processor) following a test framework and using non-invasive measurement equipment. The results show that the Linux PREEMPT-RT in its current version 3.6.6 is starting to be a competitor against the tested commercial RTOSs.