即時系統中以可拓動態電壓排程法為基礎之節能技術

隨著嵌入式逐漸應用於各種手持裝置的發展，如何設計可以有效的利用有限電力能量裝置也日益重要，而動態電壓排程法（DVS, Dynamic Voltage Scaling）是其中一種被廣泛討論能夠有效減少能量消耗的技術。動態電壓排程法是一種利用系統鬆散時間（slack time）來調整降低系統工作執行電壓。然而如何有效的分配每個工作的工作電壓而使系統不會超過執行時限卻是一種NP-complete的問題。近年來許多學者分別提出數種不同的動態電壓排程演算法來解決此問題，但是這些研究都僅僅局限於靜態排程法，針對可預期的工作順序進行排程。在本論文中將會提出一種基於可拓工程方法來達到動態節能目的，稱之為 Excenics-based Dynamic Voltage Scaling (E-DVS)，E-DVS可針對無法確切預期工作順序進行排程。該方法為利用可拓關聯函數來計算並且預測每個工作的完成時間與執行電壓。在本論文中，將會針對所題出的E-DVS與目前常見平均分配法和貪婪法進行模擬實驗與比較。透過實驗結果得知E-DVS可以有效的減少約百分之72.94的能量消耗，其結果顯示優於常用的平均分配法和貪婪法等兩種動態電壓排程法。並且使用E-DVS時所產生的額外計算能量消耗是夠小而可以被忽略。

關鍵字

即時系統；動態電壓排程法；嵌入式系統；可拓工程方法

並列摘要

With the growing of applying the embedded system technology to the mobile systems, energy efficiency is becoming an important issue for designing a real-time embedded system. One of the possible techniques to reduce energy consumption is the Dynamic Voltage Scaling (DVS). DVS utilizes the slack time to adjust supplied voltage so as to reduce the energy expense. However, how to optimally adjust supplied voltage is a NP-complete problem. In recent years, many researchers have proposed several DVS-based algorithms for applying to hard real-time systems. However, those methods are all based on the static scheduling. In this thesis, a dynamic power saving scheduling scheme with the Excenics-based Dynamic Voltage Scaling (E-DVS) mechanism has been proposed. In the proposed method, an extenics relational function is derived to calculate and predict the completion time and the system supply voltage. The E-DVS will be compared with Proportional DVS and Greedy DVS in the experiments. The experimental results show that the proposed method can effectively decrease the energy consumption about 72.94 percent, the energy saving is better than the other DVS algorithms. Furthermore, the overheads with E-DVS are too small and it can be ignored.

並列關鍵字

Embedded System ； Real-time System ； Dynamic Voltage Scaling ； Extenics

參考文獻

[1] N. AbouGhazaleh, D. Mossé, B. Childers and R. Melhem, “Toward the Placement of Power Management Points in Real Time Applications,” Proceedings of Workshop Compilers and Operating Systems for Low Power, pp. 37-52, September 2001.

[2] H. Aydin, R. Melhem, D. Moose, and P. Mejia-Alvarez, “Power-Aware Scheduling for Periodic Real-Time Tasks,” IEEE Transactions on Computers, Volume 53, Issue 5, pp. 584-600, May 2004.

[3] T. D. Burd, T. A. Pering, A. J. Stratakos, and R. W. Brodersen, "A dynamic voltage scaled microprocessor system," IEEE Journal of Solid-State Circuits, Vol. 35, pp. 1571-1580, November 2000.

[8] M. Lin and C. Ding, "Parallel Genetic Algorithms for DVS Scheduling of Distributed Embedded Systems," Lecture Notes in Computer Science, vol. 4782, pp. 180-191, September 2007.

[9] M. Lombardi and M. Milano, Scheduling Conditional Task Graphs, Springer Berlin / Heidelberg, 2007.

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即時系統中以可拓動態電壓排程法為基礎之節能技術

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