CprE 458/558: Real-Time SystemsDynamic Planning-Based SchedulerSpring Scheduling AlgorithmSpring Scheduling – ExampleCprE 458/558: Real-Time Systems (G. Manimaran) 1CprE 458/558: Real-Time Systems Dynamic Planning Based SchedulingCprE 458/558: Real-Time Systems (G. Manimaran) 2Dynamic Planning-Based Scheduler•Schedulability checking (on-line) - by the scheduler •Schedule construction (on-line) - by the scheduler •Dispatching & Resource reclaiming - by the processors Sched-check at a most opportune time (punctual point).CprE 458/558: Real-Time Systems (G. Manimaran) 3Spring Scheduling AlgorithmHeuristic search algorithm based on a notion of strong feasibility. 1. Check for strong feasibility for tasks within feasibility check window (K tasks). (ie., Check for all K tasks, EST(Ti) + Ci <= di)2. If the current vertex is strongly feasible –Compute heuristic value Hi = di + W . EST(Ti) –Choose the best (smallest) H value, let it be Hx. –Extend the schedule with task Tx. 3. Else Backtrack to the previous vertex, Extend the schedule with next best task. 4. Repeat steps 1-3 until one of the conditions is met: –Feasible schedule is obtained. –Maximum backtracks reached. –No more backtracking is possible.CprE 458/558: Real-Time Systems (G. Manimaran) 4Spring Scheduling –
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