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Uncertainty Based Scheduling: Energy-Efficient Ordering for Tasks with Variable Execution Time

Embedded Systems Design Laboratory. Lund Institute of Technology Sweden. Uncertainty Based Scheduling: Energy-Efficient Ordering for Tasks with Variable Execution Time. Flavius Gruian and Krzysztof Kuchcinski. Presentation Outline. Problem Set-up A Motivation Uncertainty Based Scheduling

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Uncertainty Based Scheduling: Energy-Efficient Ordering for Tasks with Variable Execution Time

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  1. Embedded Systems Design Laboratory Lund Institute of Technology Sweden Uncertainty Based Scheduling:Energy-Efficient OrderingforTasks with Variable Execution Time Flavius Gruian and Krzysztof Kuchcinski

  2. Presentation Outline • Problem Set-up • A Motivation • Uncertainty Based Scheduling • Experiments • comparison to FullSearch • measurements on EVB80200 platform • Summary & Conclusions ISLPED 2003 --- Uncertainty Based Scheduling…

  3. Problem Set-up • tasks: period=deadline, variable execution • off-line (static) ordering but • run-time speed selection • speed for the kth task • energy for a period(clock energy e(s)=Ks) • average energy ISLPED 2003 --- Uncertainty Based Scheduling…

  4. A Motivational Example Task Set: 3 tasks, uniform distribution (BCE,WCE) = {t1:(12,20),t2:(10,30),t3:(24,40)}A = 100, K=1, fref=1, b=2 ISLPED 2003 --- Uncertainty Based Scheduling…

  5. UBS in a Nutshell • Main ideas: • achieve a low speed ASAP by ordering tasks wisely • approximate by • Priority: • Observations: • prioritize short tasks • prioritize tasks with large variation in execution • prioritize power efficient tasks • algorithmic complexity O(N2) for ordering N tasks ISLPED 2003 --- Uncertainty Based Scheduling…

  6. UBS vs. Full Search • 300 sets of each size(3,4,5,6 tasks) • used the “real” E formula (4) • under 2% difference ISLPED 2003 --- Uncertainty Based Scheduling…

  7. The Test Platform: EVB80200 • Intel i80200 (XScale) • MAX1855 voltage regulator • 32MB SDRAM, 4MB Flash • RS232, JTAG, 7segLED ISLPED 2003 --- Uncertainty Based Scheduling…

  8. UBS example on i80200: m6 • 6 tasks • 2 LZ (K=770mW) • 2 QS (K=840mW) • 2 FOR (K=800mW) • max speed time 49ms • variation 17ms • runtime rescheduling after every 5 x H ISLPED 2003 --- Uncertainty Based Scheduling…

  9. More Experimental Results: m6 ISLPED 2003 --- Uncertainty Based Scheduling…

  10. Experimental Results: m15 5x LZ 5x QS 5x FOR ISLPED 2003 --- Uncertainty Based Scheduling…

  11. Summary & Conclusions • use more information to derive better methods • UBS: runtime, non-intrusive ordering for tasks with variable execution time • measurements on • a real platform: EVB80200 • realistic tasks: Lempel-Ziv codec & Quicksort • execution order matters! • random reordering: OK • UBS strategy: BEST ISLPED 2003 --- Uncertainty Based Scheduling…

  12. Thank You! ISLPED 2003 --- Uncertainty Based Scheduling…

  13. Measuring the core Power ISLPED 2003 --- Uncertainty Based Scheduling…

  14. i80200 I/O Power ISLPED 2003 --- Uncertainty Based Scheduling…

  15. i80200 Core Power ISLPED 2003 --- Uncertainty Based Scheduling…

  16. UBO extension to EDF • Use preemption to extract regions • Push forward uncertain regions • Algorithm: • Start from the latest deadline • Between two consecutive deadlines order the regions according to the already given priorities • Preempt the task which does not fit entirely • Proceed with the next consecutive deadlines ISLPED 2003 --- Uncertainty Based Scheduling…

  17. T=16 WCE=10 D=15 Task 1 mean=9 WCE=6 Task 2 m=3 D=16 10 6 Classic EDF Preemption for Reduced Energy 5 + 10 1 Reordering In the long run: 18% less energy than for the classic EDF! An Example of UBO EDF ISLPED 2003 --- Uncertainty Based Scheduling…

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