龙芯2F上的访存优化

Optimization of Memory Access Based on Loongson2F

一般的数据处理程序中,计算时间在其中往往只起次要作用,因此访存方式是否有效对程序的性能影响很大。在基于龙芯2F处理器研制的高性能计算机系统KD-50-I上安装ATLAS,经测试其性能只达到龙芯2F理论峰值的30%。通过循环展开减少函数存储访问次数,增大计算访存比;采用数据分块、部分拷贝以增强访存局部性,减少cache失效;利用非阻塞cache加快内存访问速度等访存优化技术,将ATLAS性能提高50%以上。

In most cases,compared to computing time,memory access time takes a much larger proportion of program running time.Therefore,memory access approach can affect the program performance significantly.Testing results show that the performance of ATLAS transplanted on KD-50-I,which is based on Loongson 2F, reaches only 30%of its theoretical peak.In this paper,by exploiting Loop Unrolling technique to decrease memory access frequency,enhancing time and space locality to reduce cache misses and nonblocking cache mechanism to form memory access pipeline,the performance of optimized ATLAS can be improved to 50% higher.