Research On Godson-2 Multithreading Processor Technique

With the development of VLSI technology, a single chip can contain over one billiontransistor. How to utilize the available transistor to design high performance processor hasbecome a hot spot of research activities in computer architecture area currently. Multithreadingtechnique is the developing trend of high performance processor in the future, which canexploit thread-level parallelism to improve the performance of processor by utilizing transistorresources.From the point of view of improving performance of processor and decreasing hardwareoverhead, this dissertation gives a systematic research on the Godson-2 multithreadingprocessor design, simultaneous multi-microthreading architecture, memory consistency as wellas register synchronization and sharing by exploiting thread-level parallelism and optimizingthe utilization of the functional units. Following contributions are presented in this dissertation.1. Based on the analysis of multithreading technique and the characteristic of Godson-2processor, a design model and microarchitecture implement scheme of Godson-2multithreading processor is proposed. The logic design of Godson-2 multithreading processorhas been completed. The design of the Godson-2 multithreading processor has been physicallyimplemented based on 0.18um CMOS process. The area of the chip is evaluated. Godson-2multithreading processor supports three running models including superscalar model,simultaneous multithreading model and simultaneous multi-microthreading model. Thesoftware system is allowed to choose the running models in accordane with applicationprograms to reach the maximum performance of processor.2. A novel processor architecture and implement scheme of the simultaneousmulti-microthreading that combines simultaneous multithreading technique withmicrothreading technique is proposed. Simultaneous multi-microthreading efficientlycombines the advantage of little hardware overhead in simultaneous multithreading with theability of speeding up single program in microthreading. Simultaneous multi-microthreadingexploits the microthreading-level parallelism of single program fully by means of software andhardware co-design.3. A novel memory consistency of chip multithreading consistency model is proposed.Chip multithreading consistency model improves the performance and reduces the complexityand cost of the processor design. Uniprocessor program can run on multithreading processorcorrectly without modification by adopting chip multithreading consistency model. A solutionof maintaining memory consistency by exception scheme is presented. And implement schemeof chip multithreading consistency model on Godson-2 processor is designed andimplemented.4. Fast register sharing and synchronization scheme is proposed. Godson-2 multithreadingprocessor adopts full/empty synchronization to pass messages between threads at register level.Each register has an associated full/empty bit. Running condition is checked in decode stage.This scheme not only avoids blocking the whole pipeline, but also avoids the complex logic ofcorrecting physical register number. Full/empty synchronization not only can pass messagesfast at register level, but also can synchronize between two microthreads efficiently.5. Hardware/Software interface and operating system design of Godson-2 multithreadingprocessor is proposed based on the analysis of software requirement. The related Linuxoperating systems for Godson-2 simultaneous multithreading and simultaneousmulti-microthreading are designed and implemented. The Godson-2 simultaneousmultithreading Linux operating system is able to schedule multiple processes to run on theprocessor, which will improve the performance of the whole software system. The Godson-2simultaneous microthreading Linux can support the microthreading applications, soprogrammers can recompile or rewrite the application and create multiple microthreads tofinish the same work, which will improve the performance of this application. Linux operatingsystem is booted in Godson-2 multithreading processor and application programs are executedin it to evaluate performance.The experimental results indicate that the performance of multithreading Godson-2processor is improved significantly by full exploitation of thread-level parallelism. The averagespeedup is 31.3% with only 18.8% area overhead.