Accelerator-in-switch: A framework for tightly coupled switching hub and an accelerator with FPGA

Accelerator-in-Switch (AiS) is a framework for building an accelerator logic tightly coupled with a switching hub in a single FPGA for high performance computation with heterogeneous environment with CPUs and GPUs. AiS is implemented on a partial reconfigurable region of an FPGA whose permanent region is used for a switching hub. A port of the switching hub is connected to the registers and local memory of AiS directly. AiS has a standard interface for a standard bus (Avalon MM bus, here) to exchange data between on-board DDR SDRAM and the local memory, and various types of accelerators can be implemented just by providing such an interface. The data input and output are performed with the DMA controller inside the switching hub with the shared memory model between host CPUs and GPUs. We implemented two example accelerators: a reduction calculator for a radiation transfer equations solver (RED) and LET generator for N-body simulation (LET) were implemented as the AiS on PEACH3, a switching hub for a PCIe direct interconnection network with Altera's Stratix V. The use of partial reconfiguration makes it possible to switch multiple accelerators without stopping the switching hub. As a result, we reduced the time for place&route of an accelerator by 47% compared to the case of the design combining the accelerator into the switching hub.