| Summary: | 碩士 === 國立臺北科技大學 === 資訊工程系研究所 === 99 === Saving energy is an important target for portable devices which are powered by batteries. Among low power mechanisms, DVFS is an efficient method which can reduce energy consumption while tasks are running. In our previous studies, we found a relationship between the memory access rate and the frequency which minimizes the energy consumption. We have proposed an equation named MAR-CSE which represents this relationship and is used to perform dynamic frequency selection.
However, the MAR-CSE equation cannot handle all the cases. It may cause the energy consumption to be increased inversely. For example, if both of the memory access rate and the number of instruction executed are low, the system will scale up the frequency according to the MAR-CSE equation. This may not be correct, because the system could be in an I/O state. A low frequency will be more suitable for this case.
In this thesis, we improve our MAR-CSE-based DVFS algorithm. The CPU utilization is considered in the algorithm. We use the MiBench benchmarks and some utility programs in Linux to find the thresholds which can distinguish among I/O bound, memory bound, and CPU bound according to the memory access rate and the CPU utilization information. We have implemented the algorithm in the Linux kernel based on the CPUfreq subsystem, a processor power management architecture for Linux. The EDP metric is used to prove our algorithm is good at energy saving and low performance loss.
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