DMA Performance Analysis and Multi-core Memory Optimization for SWIM Benchmark on the Cell Processor

The Cell processor is a typical heterogeneous multi-core processor, which owns powerful computing capability. But 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 long latency for data communication. The DMA transfer mechanism is often used to hide the long latency and improve the effective usage 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. With the supports of the DMA performance formula, we perform 4 types of memory optimization in the process of parallelizing the SWIM benchmark program into a multi-core version. We take Sony PlayStation 3 (PS3) as our test-bed. For SWIM benchmark, with 6 SPE cores, we obtain over 13 times of speedup compared to single PPE, and 3.3 to 6.18 times to AMD and Intel CPU.