Real-Time Operating Systems
Real-Time Operating Systems
Real-Time Operating Systems
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Jackson’s algorithm (3)<br />
¿ Example of feasible schedule:<br />
¿ Example of unfeasible schedule:<br />
51<br />
Horn’s algorithm<br />
¿ 1 | preem| L max<br />
¿ Principle: Earliest Deadline First (EDF)<br />
¿ It can be proved that:<br />
¿ Given a set of n independent tasks with arbitrary arrival<br />
times, any algorithm that at any instant executes the<br />
task with the earliest absolute deadline among all the<br />
ready tasks is optimal with respect to minimizing the<br />
maximum lateness.<br />
¿ Complexity:<br />
¿ per task: inserting a newly arriving task into an ordered<br />
list properly:<br />
¿ n tasks => total complexity O(n 2 )<br />
¿ Non preemptive EDF is not optimal!<br />
52<br />
26
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