Introduction to Earliest Deadline First (EDF) Algorithm 7


  • It is an Optimal dynamic Priority Scheduling Algorithm
  • Priorities are assigned based on the absolute deadlines of the task, earlier the deadline, higher the priority.
  • It is also called as Deadline Monotonic Scheduling (DM).
  • If two tasks have the same deadline, then EDF randomly select ¬†one to execute next.
  • The Schedulability condition for EDF is edf

where U is the processor Utilisation Factor and it never be greater than 1.

In practical, no processor will be utilised for more than 100%.


About TS Pradeepkumar

I am a professor by profession and a learner by life. Working in VIT University, Chennai, India and love to code and do things in open source technologies. Though from electrical engineering, I am fond of doing things in Computing and its way.


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7 thoughts on “Introduction to Earliest Deadline First (EDF) Algorithm

  • buddha puneeth

    sir,
    This is buddha.As a part of my final year project i need to work on EDF algorithm.Can you provide me the code as soon as possible.

  • Dash

    I am pretty sure on the point you said, “EDF also same as Deadline monotonic” and EDF handled as absolute deadlines of task set. If it deals with absolute deadline then how it could be dynamic priority scheduler.

    My arguments :
    1. Deadline monotonic is a spacial case of rate monotonic(RMS) where
    deadline < periodicity
    2. EDF runs with relative deadlines i.e at certain time intervals or specified trigger points it checks ( relative deadline = absolute deadline – present time ). so any task which will be closest to miss its deadline will get highest priority. this way the priority will be assigned DYNAMICALLY.
    Any good book or ieee article could prove this.