Rate monotonic algorithm

• Well-known fixed-priority algorithm is rate monotonic scheduling

• It assigns priorities to tasks based on their periods

– Priority is assigned as "The shorter the period, the higher the priority"

– The rate (of job releases) is the inverse of the period, so jobs with higher
rate have higher priority

• It is very widely studied and used
• For example, let us consider a system of 3 tasks:

– T1 = (4, 1)
– T2 = (5, 2)
– T3 = (20, 5)

⇒ rate = 1/4
⇒ rate = 1/5
⇒ rate = 1/20

– Relative priorities assigned by the rate monotonic scheduling is : T1 > T2 > T3