1. 1 What is the meaning of preemption in utility based real-time scheduling? Raphael Guerra Gerhard Fohler TU Kaiserslautern Germany

2. 2 Utility based models task 2 utility model execution window task 1 deadline earliest start time utility utility accrual + _

3. Calculate utility accrual  Reference point?  Which? 3 Preemptions in utility model task 2 execution window task 1 utility utility accrual + _

4. 4 Preemptions in utility model task 2 execution window task 1 utility Calculate utility accrual  Reference point?  Which?  What happens on preemption? utility accrual + _

5. 5 Preemptions in utility model task 2 execution window task 1 utility Calculate utility accrual  Reference point?  Which?  What happens on preemption?  How many? same utility accrual? utility accrual + _

6. 6 Preemptions in utility model task 2 execution window task 1 Calculate utility accrual  Reference point?  Which?  What happens on preemption?  How many?  Integral over execution? utility utility accrual + _

7. 7 Motivating applications Calculate utility accrual  Reference point  Multimedia  display time dictates video quality  Control  Input/output dictate control performance  Integral over execution  ???

8. decoding 2decoding 1decoding 3 decoding 2decoding 1decoding 3 ddl 2 est 3 PQV + _ est 1 est 2 ddl 1 ddl 3 off 2 off 1 off 3 Example: multimedia applications Frame display at target points  Maximum Perceived Quality of Video (PQV)  No buffering – display right after decoding Tasks express execution windows  Frame display jitter degrades PQV  Tight execution windows (deadlines and offsets)

9. Problem PQV + _ decoding abortion decoding 1decoding 3 ddl 2 ddl 1 ddl 3 off 2 off 1 off 3 job 1 decoding 2 RW Tight execution windows limit feasibility Decoding aborted on deadline miss  Resource waste (RW)  High degradation of PQV

10. Express target points  Display at target points when possible  Flexibility to delay display if needed  Skip frames that cannot meet constraints No resource waste decoding 2decoding 1 decoding 3 est 3 PQV + _ est 1 est 2 Ideal behavior job 1 job 2

11. 11 Discussion Utility accrualApplications Reference point Integral model

12. 12 Discussion Utility accrualApplications Reference point multimedia and control Integral model does not ignore preemption

13. 13 Discussion Utility accrualApplications Reference point  can we ignore preemptions? multimedia and control Integral model does not ignore preemption  are there any?

14. 14 Discussion Utility accrualApplications Reference point  can we ignore preemptions? multimedia and control Integral model does not ignore preemption  are there any?