一句话：首个共享内存FPGA虚拟化hypervisor，用多路复用器树、页表切片与抢占接口实现空间/时间复用。
云厂商用FPGA作加速器并虚拟化复用，但现有虚拟化多限于主机中心模型，加速器不能发DMA，指针追逐负载开销高；共享内存FPGA允许DMA但缺乏虚拟化支持。方法：提出Optimus，首个可扩展共享内存FPGA虚拟化hypervisor，提供空间/时间复用，实现多路复用器树共享FPGA-CPU互连，以页表切片软硬件协同隔离客户地址空间，提供加速器抢占接口。结果：单FPGA支持八个加速器，十二个基准聚合吞吐提升1.98-7倍。
Cloud providers widely deploy FPGAs as application-specific accelerators for customer use. These providers seek to multiplex their FPGAs among customers via virtualization, thereby reducing running costs. Unfortunately, most virtualization support is confined to FPGAs that expose a restrictive, host-centric programming model in which accelerators cannot issue direct memory accesses (DMAs). The host-centric model incurs high runtime overhead for workloads that exhibit pointer chasing. Thus, FPGAs are beginning to support a shared-memory programming model in which accelerators can issue DMAs. However, virtualization support for shared-memory FPGAs is limited. This paper presents Optimus, the first hypervisor that supports scalable shared-memory FPGA virtualization. Optimus offers both spatial multiplexing and temporal multiplexing to provide efficient and flexible sharing of each accelerator on an FPGA. To share the FPGA-CPU interconnect at a high clock frequency, Optimus implements a multiplexer tree. To isolate each guest's address space, Optimus introduces the technique of page table slicing as a hardware-software co-design. To support preemptive temporal multiplexing, Optimus provides an accelerator preemption interface. We show that Optimus supports eight physical accelerators on a single FPGA and improves the aggregate throughput of twelve real-world benchmarks by 1.98x-7x.
DOI 原文 ·
@inproceedings{paperbot5429,
title = {A Hypervisor for Shared-Memory FPGA Platforms},
author = {Jiacheng Ma and Gefei Zuo and Kevin Loughlin and Xiaohe Cheng and Yanqiang Liu and Abel Mulugeta Eneyew and Zhengwei Qi and Baris Kasikci},
booktitle = {ASPLOS},
year = {2020},
doi = {10.1145/3373376.3378482}
}