DPU-Direct: Unleashing Remote Accelerators via Enhanced RDMA for Disaggregated Datacenters

This paper presents DPU-Direct, an accelerator disaggregation system that connects accelerator nodes (ANs) and CPU nodes (CNs) over a standard Remote Direct Memory Access (RDMA) network. DPU-Direct eliminates the latency introduced by the CPU-based network stack, and PCIe interconnects between network I/O and the accelerator. The DPU-Direct system architecture includes a DPU Wrapper hardware architecture, an RDMA-based Accelerator Access Pattern (RAAP), and a CN-side programming model. The DPU Wrapper connects accelerators directly with the RDMA engine, turning ANs into disaggregation-native devices. The RAAP provides the CN with low-latency and high throughput accelerator semantics based on standard RDMA operations. Our FPGA prototype demonstrates DPU-Direct's efficacy with two proof-of-concept applications: AES encryption and key-value cache, which are computationally intensive and latency-sensitive. DPU-Direct yields a 400x speedup in AES encryption over the CPU baseline and matches the performance of the locally integrated AES accelerator. For key-value cache, DPU-Direct reduces the average end-to-end latency by 1.66x for GETs and 1.30x for SETs over the CPU-RDMA-Polling baseline, reducing latency jitter by over 10x for both operations.