Real-Time Operating Systems

Cyclic executive approach
¿ Schedule is essentially a table of procedure call
¿ Tasks are mapped onto a set of minor cycles
¿ The set of minor cycles constitute a major cycle (the
complete schedule)
¿ Typically:
¿ Major cycle M = max. period among task set
¿ Minor cycle m = min. period among task set
¿ Must be: M = k·m
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Cyclic executive approach: example
¿ Task set
Process period,T Computation Time. C
----------------------------------------------------------------
A 25 10
B 25 8
C 50 5
D 50 4
E 100 2
¿ Schedule:
Minor cycle
(25)
Minor cycle
(25)
Major cycle
(100)
Minor cycle
(25)
Minor cycle
(25)
A B C A B D E A B C A B
D
23 24 23
22
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