From my understanding, the EDF (Earliest Deadline First) rule is essentially an iterative "version" of the EDD (Earliest Due Date) rule, which allows for preemption. At every point in time, EDF looks at all the processes present and sorts them into the processes with the earliest deadlines first and the latest deadlines the last.

This means that if at time t1 we only have a process P1 with deadline d1 running, and no other processes; then P1 will run. But if at t2 we have a new process P2 with deadline d2 (such that d1 > d2), then P1 will be interrupted and P2 will be executed. Once P2 is finished, if only P1 is present then it is executed otherwise the deadlines of P1 and the next process are compared and the one with the earliest deadline is executed.

Is this the only difference or any there any more?


1 Answer 1


Yes, that's right. In fact I think we can say that EDD is a special case of EDF, where all the processes have arrived at the same time.


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