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

ISLPED 2003 --- Uncertainty Based Scheduling… Presentation Outline Problem Set-up A Motivation Uncertainty Based Scheduling Experiments comparison to FullSearch measurements on EVB80200 platform Summary & Conclusions 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…

ISLPED 2003 --- Uncertainty Based Scheduling… 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 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…

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 Execution Type <1, 3, 2> 42.094 41.839 134% <2, 3, 1> 37.482 36.978 119% Ideal: always mean 31.443 (speed 0.68) 100% Offline WCE 55.080 (speed 0.90) 175% 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…

ISLPED 2003 --- Uncertainty Based Scheduling… 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 Explain how we obtained the formula for the priority. Also why we approximate E like that. 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…

ISLPED 2003 --- Uncertainty Based Scheduling… UBS vs. Full Search 300 sets of each size (3,4,5,6 tasks) used the “real” E formula (4) under 2% difference 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…

ISLPED 2003 --- Uncertainty Based Scheduling… The Test Platform: EVB80200 Intel i80200 (XScale) MAX1855 voltage regulator 32MB SDRAM, 4MB Flash RS232, JTAG, 7segLED 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…

ISLPED 2003 --- Uncertainty Based Scheduling… 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 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…

More Experimental Results: m6 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…

Experimental Results: m15 5x LZ 5x QS 5x FOR 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…

ISLPED 2003 --- Uncertainty Based Scheduling… 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 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…

ISLPED 2003 --- Uncertainty Based Scheduling… Thank You! 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…

Measuring the core Power 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…

ISLPED 2003 --- Uncertainty Based Scheduling… i80200 I/O Power use the graph from Intel doc… 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…

ISLPED 2003 --- Uncertainty Based Scheduling… i80200 Core Power 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…

ISLPED 2003 --- Uncertainty Based Scheduling… 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 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…

An Example of UBO EDF m=3 mean=9 Task 1 Task 2 WCE=10 WCE=6 T=16 D=15 Classic EDF 10 6 Preemption for Reduced Energy Reordering 5 + 1 In the long run: 18% less energy than for the classic EDF! 04/12/2018 ISLPED 2003 --- Uncertainty Based Scheduling…