Providing Multi-tenant Services with FPGAs: Case Study on a Key-Value Store

FPGAs can be used to speed up computation and data management tasks in various application domains. In cloud settings, however, high utilization is as important as high performance. In software it is common to co-locate different tenants' workloads on the same servers to increase utilization. Sharing an FPGA is more complex because applications take up physical space on the chip. Even though it is possible to physically partition the FPGA, tenants can have widely different requirements and their needs can also fluctuate over time. In this paper, we take a different approach and provide flexibility to the tenants who are interested in the same type of application but have different workloads and quality of service requirements. We demonstrate our approach of multi-tenant design using a key-value store service but the ideas generalize to other network-facing services as well. A key challenge of multi-tenancy is to efficiently share the underlying hardware while enforcing strict data and performance isolation between tenants. In this paper we demonstrate that, by following a single-pipeline design principle, it is possible to control each tenant's share of network bandwidth and computational resources even for complex, distributed operations. Furthermore, we show how state-machine based logic on the FPGA can be made tenant-aware without introducing significant context-switching overhead. Finally, our hardware design provides flexibility for changing per-tenant shares, allowing the same circuit to be used by one or multiple tenants without performance loss.