A Study Of Software/Hardware Cooperative Prefetch Technique

Memory-Wall is a difficult problem that reduce the efficiency of computer system at all time. The gap between cpu and memory is more broader as technique develop, meanwhile multicore made this more acute. Traditional hardware pre-fetch or software prefetch can't improve compulsive miss and capability miss more. Because hardware pre-fetch predict the future behavior of the application by the past information about it, while software pre-fetch insert a lot of instruction for pre-fetch purpose and reduce the efficiency of pre-fetch. Software/hardware cooperative approach can get the benefit of them, but now is under researching. And we deeply researched the Software/hardware cooperative pre-fetch.In this paper, we proposed a visual method to study the rule of cache's behavior for better use of the information that the compiler gets. The result shows that the sequential access to the big array is a key factor of cache miss. To improve the cache efficiency, we proposed compiler directed reference prediction table based pre-fetch, and decoded the information about access patten into reference instruction to direct the process of pre-fetch. Our approach can avoid the low efficiency problem that traditional pre-fetch meet and reduces miss-rate a lot. Also, we proposed integrate Evict Me and compiler directed reference prediction table based pre-fetch together, for the purpose of improving cache block replacement. This can avoid incorrect cache replacement and reduce the demand to memory bandwidth.At the end, we implement the architect proposed in simplescalar simulator, and use the NPB benchmarks for performance testing. The result shows compiler directed reference prediction table based pre-fetch can hide the the memory delay effectively, reduce cache miss-rate, and .improve performance. The memory system preformance can further improve after combined the Evict Me.