Online agentic reinforcement learning implemented with micro-services separates policy training from rollout generation, improving scalability and modularity while potentially making frequent policy-weight synchronization a critical systems overhead. Shared storage naturally connects these services across clusters, but vanilla dense policy weight synchronization could incur model-scale construction, transfer, and application costs. Sparse synchronization reduces transferred data, yet checkpoint-oriented approaches can still retain a previous model and materialize complete intermediates to bridge heterogeneous training and inference layouts. We present AReaL-DTE, a snapshot-free Delta Transfer Engine that translates inference-visible weight sparsity into end-to-end system efficiency. Across our evaluated workloads, fewer than 2% of BF16 weight elements change between consecutive policy versions. AReaL-DTE reconstructs overwritten weights on demand by inverting AdamW updates, streams reconstructed and current parameters through converter-aligned BF16 change detection, and remaps changed elements directly into receiver-local coordinates. AReaL-DTE supports manifest-committed sparse transfer through shared storage across clusters and a deadlock-safe two-round protocol within a cluster, followed by direct application to inference shards. We evaluate AReaL-DTE on Qwen3-8B and Qwen3-30B-A3B across four online RL workloads. AReaL-DTE achieves speedups of up to 19.9x over ByteCheckpoint and 3.2x over PULSE across clusters, and up to 7.6x and 7.4x, respectively, within a cluster. In the same-cluster Qwen3-30B-A3B experiments, it reduces peak GPU memory by approximately 41% and peak CPU memory by at least 87%.
Yingqi Peng, Jiawei Zhang, Wenhao Zhou et al.· 0 citations
Long-context inference is becoming a fundamental capability for modern LLM serving, especially driven by emerging agentic applications. Yet it faces a severe memory wall that the KV cache scales proportionally with increasing context length and request concurrency. Existing sparse KV cache methods offload most KV entries to host memory and retrieve only the critical KV entries needed by each decoding step. However, they commonly introduce substantial auxiliary states in GPU memory for KV retrieval management. Our measurements show that these often-overlooked auxiliary states introduce significant memory overhead and become a new bottleneck under high-concurrency workloads. In this paper, we present DualDecoder, a lightweight serving system for long-context LLM inference that enables efficient sparse KV cache retrieval from host memory. Our key insight is that the critical KV entries required for decoding the next token can be accurately predicted from the preceding speculated token. This predictability enables KV retrieval to be proactively prefetched and overlapped with decoding computation, effectively eliminating the GPU memory overhead of auxiliary states. To achieve this prefetching efficiently, DualDecoder leverages a novel dual-token decoding pipeline that accurately identifies critical KV entries with negligible computational overhead, and designs a layer-aware transfer schedule to overlap KV prefetching with model computation and a layer-scoped memory manager to reduce the GPU runtime buffer. Experimental results show that DualDecoder improves decoding throughput by up to 2.62$\times$ over state-of-the-art systems while preserving decoding latency and model quality.
Zuning Liang, Zhiyi Yao, Qi Chen et al.· 0 citations