Reconfigurable Virtual Memory for FPGA-Driven I/O

FPGAs are increasingly used to accelerate modern applications, and cloud providers offer FPGA platforms on-demand with a variety of FPGAs, I/O peripherals, and memory options. FPGA vendors expose I/O with low-level interfaces that limit application portability. Current approaches to abstracting these interfaces trade level of abstraction against performance. We present FSRF, File System for Reconfigurable Fabrics, which abstracts FPGA I/O at a high level without sacrificing performance. Rather than exposing platform-specific I/O interfaces, FSRF enables files to be mapped directly into FPGA virtual memory from the host. On the FPGA, powerful OS-managed virtual memory hardware provides performant access to FPGA-local resources and helps coordinate access to remote data. FSRF leverages reconfigurability to specialize its virtual memory implementation to applications, including selecting between SRAM and DRAM TLBs, adapting FPGA DRAM striping, and tuning DMA I/O. On Amazon F1 FPGAs, FSRF outperforms techniques from FPGA OSes such as Coyote and AmorphOS with improvements of up to 64× and 2.3×, respectively (+75% and +27% geometric mean), and performance close to that of physical addressing (90% geometric mean).