Research On Data Value Prediction And Memory Prefetching Techniques

The speed difference between processor and memory is not reduced by the development of modern semiconductor technology. Actually, it deteriorates due to the wide employment of instruction parallelism technology in modern high performance processors.No matter how large the Cache is or how many hierarchies the memory system adopts, there are always two inevitable problems: firstly, if the data requested by the processor is not in the Cache, a Cache miss happens and consequently the pipeline is stalled until the requested data is retrieved from the lower hierarchy; secondly, if data dependency occurs between instructions, the pipeline must be blocked until the data requested by the consumer instruction can be provided by the producer instruction.Up to now, the best method to solve the above problems is data prefetching. According to the problem it solves, data prefetching can be classified into two types. The one focusing on prefetching the data requested by the Load instruction from the Cache into the pipeline before the effective address is calculated is defined as Cache Prefetching Method herein, the other focusing on prefetching the data requested by the Load instruction from the memory into the Cache before the Load instruction is issued is defined as Memory Prefetching Method. This paper studied the Cache Prefetching Method and Memory Prefetching Method in the following aspects:1) Cache prefetching based on Markov modelThis work analyzed the instruction stream and data prefetching mathematically and accordingly established a Markov model for data prefetching. The different methods employed to extract the status require different amounts of calculation and bring about different results, so the definition of status is a key point when data prefetching is described mathematically. According to the characteristics of data stream, in this work, the status of Markov model was defined as a characteristic vector consisting of a set of data in a sliding window. Data prefetching was then carried out according to the possibility of status...