Optimal dynamic data layouts for 2D FFT on 3D memory integrated FPGA

Abstract

FPGAs have been widely used for accelerating various applications. For many data intensive applications, the memory bandwidth limits the performance. 3D memories with through-silicon-via connections provide potential solutions to the latency and bandwidth limitations. In this paper, we revisit the classic 2D FFT problem to evaluate the performance of 3D memory integrated FPGA. To fully utilize the fine-grained parallelism in 3D memory, data layouts which take into account the structure and organization of the memory are required. We propose dynamic data layouts for optimizing the performance of the 3D architecture. In 2D FFT, data are accessed in row major order in the first phase, whereas the data are accessed in column major order in the second phase. This column major order results in high memory latency and low bandwidth due to high row activation overhead of memory. Using the proposed dynamic data layouts, we improve memory access performance in the second phase without degrading the performance of the first phase. With parallelism employed in the third dimension of the memory, data parallelism can be increased to further improve the performance. We adopt a model-based approach for 3D memory and we perform experiments on the FPGA to validate our analysis and evaluate the performance. Compared with the baseline architecture, our approach achieves up to $40\times$ peak memory bandwidth utilization for columnwise FFT, thus resulting in approximately $97\,\,\%$ improvement in throughput for the complete 2D FFT application.