LMSYS 为 SGLang 引入 RDMA P2P 权重传输,1T 参数模型更新提速 7 倍
LMSYS 为 SGLang 的 RL 工作负载引入基于 RDMA 的点对点权重更新机制,作为传统 NCCL broadcast 的补充,兼容所有主流开源模型。在 1T 参数的 Kimi-K2 上,权重传输时间从 53 秒降至 7.2 秒,代价是每个训练 rank 在 CPU 内存上多占用一个 32G 的推理引擎副本。该设计通过源侧 CPU 引擎副本和 Mooncake TransferEngine 的零拷贝传输,让所有训练 rank 参与发送各自分片,减少网络冗余并让推理服务更快恢复 rollout。

ngine replica (32G) per training rank on CPU memory. These optimizations minimize network redundancy and allow inference servers to resume rollout significantly faster. Background NVIDIA's NCCL optimizes primitives like all-gather and broadcast by auto-detecting hardware topology and coordinating data flow via ring or tree algorithms. As the default communication backend for PyTorch FSDP, DeepSpeed, and Megatron-LM, it is the industry standard for symmetric training. However, it relies on collec
匹配字段正文
