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Explain clock - Driven Scheduling.
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Clock - Driven Scheduling:

  • The scheduling in which the scheduling points are determined by the interrupts received from a clock, It's known as Clock-driven Scheduling.

  • Clock-driven scheduling handles which task is to be processed next is dependent at clock interrupt point. In a clock-driven scheduler, the scheduling points are defined at the time instants marked by interrupts generated by a periodic timer.

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  • When workload is mostly periodic and the schedule is cyclic, timing constraints can be checked and enforced at each frame boundary

  • That is, the scheduler pre-determines which task will run when. Therefore, these schedulers incur very little run Time overhead.

  • However, a prominent shortcoming of this class of schedulers is that they can not satisfactorily handle aperiodic and sporadic tasks since the exact Time of occurrence of these tasks can not be predicted.

Advantages:

  • The important advantage is conceptual simplicity.
  • Time triggered System Based on clock driven scheduling is easy to validate, test and certify.

  • Clock driven scheduling paradigm are time triggered. in this systems interrupts to external events are queued and polled periodically.

Disadvantages:

  • The system based on clock driven approach is Brittle (soft).

  • The release time of all jobs must be fixed.

  • The pure clock driven approach is not suitable for many systems that contain both hard and soft real time applications.

  • In this system all combinations of periodic task that might execute at same time.

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