Selecting the right RTOS scheduling algorithms using system modelling

Ranjit Adiga, CMR Design Automation
embeded.com (August 26, 2013)

Most high-performance embedded systems do not need an expensive and full-functionality real-time operating system (RTOS). A dedicated scheduler such as those used in arbitration processes and traffic management is sufficient, extremely efficient, and has a low memory footprint. This approach is particularly preferred where memory size is limited and timing deadlines must be strictly enforced.

Typical applications are in defence, aerospace, industrial, and automotive. There are a number of standard scheduling algorithms such as First Come, First Served (FCFS); Shortest Job First (SJF); Preemptive; and Round Robin.

How do we select the right scheduler at the start of the project when the software is not ready and we have only the guideline specification of the hardware? There are many approaches, such as rate monotonic analysis (RMA), worst case execution time analysis, and system-level performance modelling analysis. When you combine the requirements of current software architectures such as non-periodic arrivals, pre-emption, and variable start times, deploying RMA is extremely difficult and in many cases impossible to configure.

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