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fakultät für informatik informatik 12 technische universität dortmund Lab 3: Scheduling Solution - Session 10 - Heiko Falk TU Dortmund Informatik 12 Germany
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- 2 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 1: Rate Monotonic Scheduling Parameters: p 1 = 5, c 1 = 3p 2 = 8, c 2 = 3 Processor Utilization: μ = Σ ( c i / p i ) n( 2 (1/n) – 1) μ = 3/5 + 3/8 = 39/40 = 0.975 > 2( 2 (1/2) - 1) = 0.828 A process may miss its deadline. i =1 n
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- 3 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 1: Rate Monotonic Scheduling Schedule:
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- 4 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 2: Aperiodic Scheduling Least Laxity Schedule: Laxity l i = d i - c i
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- 5 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 2: Aperiodic Scheduling Earliest Deadline First Schedule:
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- 6 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 3: Latest Deadline First Scheduling T2T3 T1T4 T5 c 1 = 2d 1 = 15 c 2 = 5d 2 = 20 c 3 = 4d 3 = 12 c 4 = 3d 4 = 15 c 5 = 3d 5 = 20 Stack:
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- 7 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 3: Latest Deadline First Scheduling T2T3 T1T4 T5 c 1 = 2d 1 = 15 c 2 = 5d 2 = 20 c 3 = 4d 3 = 12 c 4 = 3d 4 = 15 c 5 = 3d 5 = 20 Stack:
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- 8 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 3: Latest Deadline First Scheduling T2T3 T1T4 T5 c 1 = 2d 1 = 15 c 2 = 5d 2 = 20 c 3 = 4d 3 = 12 c 4 = 3d 4 = 15 c 5 = 3d 5 = 20 Stack:
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- 9 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 3: Latest Deadline First Scheduling T2T3 T1T4 T5 c 1 = 2d 1 = 15 c 2 = 5d 2 = 20 c 3 = 4d 3 = 12 c 4 = 3d 4 = 15 c 5 = 3d 5 = 20 Stack:
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- 10 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 3: Latest Deadline First Scheduling T2T3 T1 T4 T5 c 1 = 2d 1 = 15 c 2 = 5d 2 = 20 c 3 = 4d 3 = 12 c 4 = 3d 4 = 15 c 5 = 3d 5 = 20 Stack:
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- 11 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 3: Latest Deadline First Scheduling T2T3 T1 T4 T5 c 1 = 2d 1 = 15 c 2 = 5d 2 = 20 c 3 = 4d 3 = 12 c 4 = 3d 4 = 15 c 5 = 3d 5 = 20 Stack:
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- 12 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 3: Latest Deadline First Scheduling T2T3 T1 T4 T5 c 1 = 2d 1 = 15 c 2 = 5d 2 = 20 c 3 = 4d 3 = 12 c 4 = 3d 4 = 15 c 5 = 3d 5 = 20 Stack:
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- 13 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 3: Latest Deadline First Scheduling T2T3 T1 T4 T5 c 1 = 2d 1 = 15 c 2 = 5d 2 = 20 c 3 = 4d 3 = 12 c 4 = 3d 4 = 15 c 5 = 3d 5 = 20 Stack:
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- 14 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 3: Latest Deadline First Scheduling T2 T3 T1 T4 T5 c 1 = 2d 1 = 15 c 2 = 5d 2 = 20 c 3 = 4d 3 = 12 c 4 = 3d 4 = 15 c 5 = 3d 5 = 20 Stack:
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- 15 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 3: Latest Deadline First Scheduling T2 T3 T1 T4 T5 c 1 = 2d 1 = 15 c 2 = 5d 2 = 20 c 3 = 4d 3 = 12 c 4 = 3d 4 = 15 c 5 = 3d 5 = 20 Stack:
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- 16 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 3: Latest Deadline First Scheduling T2 T3 T1 T4 T5 c 1 = 2d 1 = 15 c 2 = 5d 2 = 20 c 3 = 4d 3 = 12 c 4 = 3d 4 = 15 c 5 = 3d 5 = 20 Stack:
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- 17 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 3: Latest Deadline First Scheduling T2 T3 T1 T4 T5 c 1 = 2d 1 = 15 c 2 = 5d 2 = 20 c 3 = 4d 3 = 12 c 4 = 3d 4 = 15 c 5 = 3d 5 = 20 Stack: Execution order: In opposite order! T2T3T5T4T1 Resulting Schedule:
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- 18 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 4: Resource Constrained Scheduling
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- 19 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 4: Resource Constrained Scheduling Problems of this Schedule Task T4 of highest Priority thwarted by T1, T2 and T3: At time 5, T4 has to wait until T1 frees the printer. T1 can only free the printer after T2 and T3 finished execution Despite highest priority, T4 terminates very late at time 34 Priority Inversion! Ways out: Scheduling with Priority Inheritance
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- 20 - technische universität dortmund fakultät für informatik h. falk, informatik 12, 2008 TU Dortmund Exercise 4: Resource Constrained Scheduling
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