Earliest deadline first scheduling

Earliest Deadline First ( EDF ) is a scheduling method of operating systems, by means of which it processes (English tasks) allocates processor time. It belongs to the time-based method, because it makes its decisions so that completion dates ( deadlines ) are met. The preemptive variant of earliest deadline first is mainly used for real-time systems.

Operation

• All of the considered time waiting tasks are sorted in ascending order of completion dates (English deadlines )
• The task that must be done first, receives the processor

There will always be the time points for scheduling considered, where a new task is started either or just active task is terminated.

EDF is very flexible because it can be used both for preemptive, such as used for cooperative multitasking. It can also be used in aperiodic and periodic schedules.

Processor utilization

EDF can schedule the processor up to the maximum processor utilization. However, this applies only to task systems in which the time is always greater than or equal to the period of the respective task even before the deadline of a task. In addition, must be no dependencies between tasks and no shared resource can be used, as this is a deadlock could occur.