Sech-1.pdf - Real Time Embedded Systems(EEE446 Lecture(16...

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Real Time Embedded Systems (EEE446) Lecture (16) Dr. Farman Ullah [email protected] Department of Electrical Engineering (Major in CE), COMSATS Attock
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“Monolithic approach” Good enough? No! For a complex system, it is really hard to design a single superloop Really hard to validate cross-related temporal requirements So, we need a more structured way to look at the problem Reference model: abstracted view (look at only core) of Workload Resource Easy to form a structured way of design and validation Can be generalized for many variations of problems
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The Objective of A Reference Model A Reference Model captures only relevant characteristics and categorize the problem space workload model resource model algorithms Like doctor’s reference handbook, a reference model help you classify a given real-time problem know if it is a solved problem or open problem know if it is a easy problem or hard problem
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Developing a Reference Model Modeling the system to focus on timing properties and resource requirements. Composed of three elements: workload model - describes supported applications Temporal parameters Precedence constraints and dependencies Functional parameters resource model - describes available system resources Modeling resources (Processors and Resources) Resource parameters algorithms - how application uses resources at all times Scheduling Hierarchy
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Overview Workload model (characterization of applications) Jobs and tasks Release time (periodic/aperiodic/sporadic) Deadline (absolute/relative, hard/soft, single stage/end to end) Execution time (deterministic/stochastic) Temporal distance and precedence constraints Resource model Processors and resources Utilization of resource Scheduling algorithms Priority/preemptability/blocking Scheduler and schedule
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Workload Model Task and job Task offset Release time of jobs (periodic, sporadic, aperiodic) Deadline of jobs (hard or soft) Execution time of jobs (deterministic or stochastic) 0 (system startup time)
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Jobs and Tasks A job is a unit of computation, e.g., handling the press of a keyboard or compute the control response in one instance of a control loop A task is a sequence of the same type of jobs, say, a control task or the keyboard handling task. Set of related jobs jointly provide function. job1 Job 2
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Jobs Job ( J ij ) : Unit of work, scheduled and executed by system. characterized by the following parameters: Temporal parameters: timing constraints and behavior Functional parameters: intrinsic properties of the job. Resource parameters: resource requirements.
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  • Spring '12
  • Adeel
  • Electrical Engineering, Scheduling algorithm, Round-robin scheduling, Scheduling algorithms

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