Consider the same task set as in the previous assignment. Use earliest deadline first (EDF) for scheduling. Can any of the tasks miss its deadline? If not, why not? Generate a graphical representation of the resulting schedule!

Suppose that tasks will always run to their completion.

Previous assignment

Suppose that we have a system comprising two tasks. Task 1 has a period of 5 and an execution time of 2. The second task has a period of 7 and an execution time of 4. Let the deadlines be equal to the periods.

Assume that we are using rate monotonic scheduling (RMS). Could any of the two tasks miss its deadline, due to a too high processor utilization?

Compute this utilization, and compare it to a bound which would guarantee schedulability! Generate a graphical representation of the resulting schedule! Suppose that tasks will always run to their completion, even if they missed their deadline.

Earliest Deadline First Scheduling EDF can also be applied to periodic task sets. Obviously, it is sufficient to solve the scheduling problem for a single hyper-period. This schedule can then be repeated for the other hyper-periods. The hyper-period for the example of Fig. 6.14 is 40. It follows from the optimality of EDF for nonperiodic schedules that EDF is also optimal for a single hyper-period and therefore also for the entire scheduling problem. No additional constraints must be met to guarantee optimality. This implies that EDF is optimal also for the case of U sum = 1. Example 6.9 No deadline is missed if the example of Fig. 6.14 is scheduled with EDF (see Fig. 6.17). At time 5, the behavior is different from that of RM scheduling: due to the earlier deadline of T 2, it is not preempted. V T1 T2 T 0 2 4 6 8 10 12 14 16 18 20 22 24 t Fig. 6.17 EDF generated schedule for the example of 6.14