Cell处理器访存特征研究

Cell处理器是一款异构多核处理器,拥有强大的计算能力。但是,在进行应用并行化时,却受到本地存储器容量、访存带宽和数据传输延时等的限制。DMA传输是隐藏长延时、提高存储带宽利用率的有效方法。本文在分析Cell处理器结构基础上,进行了一系列详细的DMA测试,并利用指数拟合技术得到DMA平均带宽模型,发现参与DMA传输的SPE数量和每次DMA传输规模是影响DMA访存带宽的主要因素。

The Memory Access Characteristics of the Cell Processor

The Cell processor is a typical heterogeneous multi-core processor with powerful computing ability.However,we are facing the challenges of 'memory wall' in developing parallel applications,such as,limited capacity of local memory,limited memory bandwidth for multi-cores and the large latency for data communication.The DMA transfer mechanism is often used to hide the large latency and improve the utilization of memory bandwidth.In the paper,we start with a series of DMA experimental tests in the context of the Cell processor architecture,and perform mathematical analysis to setup a unified formula on the average bandwidth of DMA by means of exponential fitting,which describes that SPE amount and DMA block size take main effects on DMA bandwidth in quantity.