DTACU: a global DVFS algorithm based on piece energy model
Considering the exclusive policy and poor energy benefits for multicore processor by Ondemand algorithm, a global DVFS (Dynamic Voltage and Frequency Scaling) algorithm DTACU based on piece energy model is proposed. In order to translate multicore problems to single core problems, an equivalent energy model, called piece energy model, was set up. It divided the time into several periods in which no task arrive or finish in each core, hence the multicore processor can be seen as a single core processor. Based on theoretical research on energy consumption and current published papers, analytical expressions of equivalent single core energy consumption were deduced. DTACU was proposed through analyzing the source of energy consumption in expression and implemented based on Userspace. Taking the number of active cores and dynamic thresholds into account, DTACU only change CPU speed during one period to both reduce energy consumption and satisfy the demand of task deadline. The final result of experiments show that DTACU can achieve lower energy consumption without sacrificing system performance compared with Ondemand. Introduction Nowadays, reducing the energy consumption is considered as one of the major research topics for computing system, especially for mobile computing system. Comparing with low power component design and manufacturing technology, processor low power design at system level is also meaningful. Dynamic Voltage and Frequency Scaling (DVFS) is one of feasible means of reducing energy consumption. It is a hardware technology used to dynamically scale up or down the frequency or voltage of processor according to the governor policy and the workload demand at the cost of an increased latency. For multicore processor, there are two main means of DVFS control, namely local DVFS and global DVFS. Local DVFS changes the clock frequency per core, while global DVFS makes these changes for the entire chip. Recently, clustered DVFS, which uses multiple of on chip regulators drive a set of DVFS domains, was proposed for multicore processors[1] Theoretically, local DVFS is the most effective way to reducing energy consumption. However, in practice global DVFS is the most common in processor design, since it is cheaper to implement, but there are still some issues on global DVFS, such as low energy benefits and complex algorithms. In this paper, we explore and propose a global DVFS algorithm DTACU (Dynamic Threshold and Active Cores based on Userspace) by analyzing the relationship between frequency and energy consumption based on piece energy model. Section 2 introduces the related works about global DVFS. After presenting the detailed process of setting up the piece energy model, the description and implementation of DTACU are presented in Section 4. The results of experiment are shown in section 5, and final conclusion is given in section 6.