PipeArch

Abstract

Data processing systems based on FPGAs offer high performance and energy efficiency for a variety of applications. However, these advantages are achieved through highly specialized designs. The high degree of specialization leads to accelerators with narrow functionality and designs adhering to a rigid execution flow. For multi-tenant systems this limits the scope of applicability of FPGA-based accelerators, because, first, supporting a single operation is unlikely to have any significant impact on the overall performance of the system, and, second, serving multiple users satisfactorily is difficult due to simplistic scheduling policies enforced when using the accelerator. Standard operating system and database management system features that would help address these limitations, such as context-switching, preemptive scheduling, and thread migration are practically non-existent in current FPGA accelerator efforts. In this work, we propose PipeArch, an open-source project 1 for developing FPGA-based accelerators that combine the high efficiency of specialized hardware designs with the generality and functionality known from conventional CPU threads. PipeArch provides programmability and extensibility in the accelerator without losing the advantages of SIMD-parallelism and deep pipelining. PipeArch supports context-switching and thread migration, thereby enabling for the first time new capabilities such as preemptive scheduling in FPGA accelerators within a high-performance data processing setting. We have used PipeArch to implement a variety of machine learning methods for generalized linear model training and recommender systems showing empirically their advantages over a high-end CPU and even over fully specialized FPGA designs.