An evaluation of the potential of flash SSD as large and slow memory for stencil computations

This paper investigates the potential of flash as a large and slow memory behind dynamic random-access memory (DRAM) for stencil computation, which is one of the most common and important computation kernels in various scientific and engineering simulations. We evaluate the performance of a fastswap kernel, which was recently incorporated into Linux, in stencil computation using flash as a swap device. Moreover, we propose a locality-aware, hierarchical out-of-core computation algorithm by employing data structure blocking techniques in stencil computations to bridge the DRAM-flash latency divide. We find that 7-point and 27-point stencil computations for a 1-TiB problem size (32 times that of the DRAM), using only a 32-GiB DRAM and a flash solid-state drive (SSD), in Mflops attain 24% and 47%, respectively, of the performance achieved in execution using only DRAM.