本論文探討多核心系統中執行多執行緒程式之電源消耗與省電議題，並提出一高效率之動態電源管理機制動態調整處理器頻率以節省處理器電源消耗。過去的研究以單一執行緒為單位進行頻率調整，然而在大量的工作中(多執行緒系統)，過去機制將導致大量的處理器暫停，並降低系統效能。本論文針對多執行緒系統，將執行緒分群，並以群組為單位進行頻率調節以減少處理器負擔 (Overhead)。

本機制主要包含三部份：
壹、利用處理器中效能計數器監視並預測程式行為，並判斷適合各程式之處理器頻率，使該程式在較低的頻率中執行並不失其執行效能。
貳、將各處理器所要執行的執行緒分群，並以一工作平衡演算法將相同行為之程式移至同一群組，並平衡各處理器之工作量。
參、分析每一群組，調整一適合該群組之處理器頻率。

在此研究中，我們分析諸多程式之執行行為，並提出一數學模型以辦別執行緒行為，以此模型探討執行頻率與執行緒行為間之交互關係，並進一步定義不同行為之適合執行頻率。我們將此電源管理機制實現於Linux 2.6 作業系統中，並測試具公信標準之測試程式。根據實驗結果，此機制平均僅造成4.8%之效能降低的影響下，可節省近20%電源消耗。

In the green computing field, Dynamic voltage and frequency scaling (DVFS) is widely used to adjust the operating frequency of processor to reduce energy consumption. However, relatively fewer studies have addressed the issue of overhead introduced by the DVFS. Current technology employing DVFS renders processor cores unavailable for 10s to 650 s, and adjusting the frequency of each thread often incurs considerable overhead, particularly in multi-threaded operations.

This study addresses the problem of energy consumption and DVFS induced overhead by proposing a low overhead, Grouping-Based dynamic Power Management (GDPM) system. This system provides strategies for determining the appropriate processor frequency, such that energy consumption is reduced with only a negligible degradation in performance. To decrease the overhead of DVFS, threads requiring the same frequency are then clustered into a group, and processor frequency is adjusted for each group. The proposed approach was implemented on a quad-core processor running a Linux operating system. Comparisons using industry standard benchmarks show that the proposed approach is capable of improving energy consumption by an average of 20%, with only a 4.8% penalty in performance.

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