Research On Dynamic Frequency Technology For Time-Sharing System Based On Performance-Energy Tradeoff Model

Just like the description of Moore’s law, along with the rapid development and popu-larization of computer system, the performance of computer system has been greatly improved in a stable speed. However, the performance-improvement-only mode for de-velopment of computer has brought some severe problems. One of them is constantly increasing of power and energy consumption, which has been an obstacle holding back further development of performance for computer.Better performance of electronic computers need bigger scale integration, but more electrical consumption. Energy is transformed into heat. Electronic components will behave abnormal and even life-shortened when temperature is high. So the cooling sys-tem is indispensable. The total energy consumption of components and cooling devices is increasing. The question about how to reduce power and energy consumption has gradually been a hot spot of current researches.Part of energy is indeed wasted by current computer systems, because they are not always in fully-loaded status. And various new technologies provide abundant methods to reduce the energy consumption. In this dissertation, we focus on the widely used time-sharing system to reduce the energy consumption of processor whose energy is domi-nant. Using dynamic voltage and frequency scaling technology and from the operating system level, we propose a complete solution for the energy consumption of computer system. Using this solution, users’ performance requirement and the tasks’instruction characteristic are all in consideration. By controlling the working frequency of CPU, a balance status between performance and energy consumption is being kept.The main research works in this dissertation include:1. By summarizing the development status of current computer system, the badness of power and energy consumption is analyzed to prove the importance of reducing it. Current research results of relative fields are introduced to explain the necessity of focusing on the time-sharing system. Through analyzing the pros and cons of various researches in different levels of computer system, we propose a scheme to control power and energy in operating system level for time-sharing system.2. A Performance-Energy-Tradeoff model (T-model for short) is proposed in this dis-sertation. By theoretically analyzing the root cause of power/energy consumption and performance latency, we find out the relationship between CPU frequency and performance/energy. To make a balance between performance and energy, we de-fine a Best Energy-saving Condition. Using the T-model, a formula to get the Best Energy-saving Frequency is deduced by further analyzing.3. Integrating into practical computer system, we propose a T-model based Dynamic Frequency Governor (TDFG for short). Using the latest technologies, the schemes of collecting information dynamically and adjusting frequency in fine-grained way are adopted in TDFG. To solve difference between theory and practice, the condi-tions of Best Frequency Distribution are found out to approximate the Best Energy-saving Frequency in discrete-frequency system.4. By adding a Frequency Management Module (FMM for short) into Linux, an in-stance is given to realize the TDFG in practical system. FMM is adapted to the framework of frequency management in Linux, and is working with its process model. Some codes are added to collect informations, compute and change the CPU frequency, then a low-overhead method to manage frequency is realized to save energy efficiently, which is also an intuitive way to control performance.5. To resolve the high threshold to do experiments in this field, we also design a sim-ple Battery based Experiment Platform (BEP for short). A serial of experiments are provided not only for validating the research results in this dissertation, but also for the demonstration of how to use BEP.The contributions and innovations of our works include:1. Propose a complete power/energy solution for time-sharing system, which has the following advantage:· Design and use the System Performance Loss to represent performance intu-itively.· Use the Best Energy-Saving Condition to define the balance status between system performance and energy consuming.· Use theoretical analysis for the first time to find the Best Frequency Distri-bution to approximate the result of best frequency.2. TDFG is indeed realized. Adding TDFG into Linux, the system have the following features:· Add an user-frendly interface to control performance.· Can optimize power and energy consumption based on the performance re-quirement. · User performance requirement is satisfied with energy farthest saved.· The TDFG in Linux is efficient and low overhead.3. A new experiment platform is proposed. The platform have the following features:· The requirement of HW/SW is low. Greatly simplify experiments in this field.· The results of energy are directly measured.· It is naturally suitable to verify the efficiency of real system.In this dissertation, through theoretical analysis, a solution to decrease the power and energy consumption of time-sharing system is proposed, and it is realized in a real operating system. The correctness and efficiency of the system are verified by some experiments.