Priority-based pre-emptive scheduling, rate-monotonic and EDF algorithms.
Rate-monotonic scheduling assigns higher priority to shorter periods and is feasible if utilisation U≤n(2^{1/n}-1) (≈69%). EDF schedules by earliest deadline up to 100% utilisation. Round-robin shares time among equal priorities.
Three tasks with periods 10, 20 and 50 ms get priorities in that order under RMS.
Scheduling decides which task runs when, and the chosen algorithm determines whether all deadlines are met.
Priority-based pre-emptive scheduling, rate-monotonic and EDF algorithms.
Scheduling decides which task runs when, and the chosen algorithm determines whether all deadlines are met.
Fixed priorities assigned by period, with shorter periods getting higher priority, which is optimal among fixed-priority schemes for periodic tasks.
About 69 percent for many tasks, so a set below this bound is always schedulable under the standard assumptions.
Typical applications include checking whether a set of periodic control tasks is schedulable with rate-monotonic analysis, assigning priorities to sensor, control and logging tasks and using earliest-deadline-first to maximise utilisation for variable tasks.
Study "Real-time operating systems" first (topic 77 of 104 in Electronics & Embedded). It covers the groundwork this topic builds on.
Preemptive vs cooperative. Deadline misses. Response-time analysis.
Three tasks with periods 10, 20 and 50 ms get priorities in that order under RMS.
The next topic is "Mutexes and semaphores", which builds directly on this one.
It is classed as Advanced in Electronics & Embedded (topic 78 of 104). It is an advanced topic. It assumes you are comfortable with the intermediate topics in Electronics & Embedded.
Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.