WindServe: Efficient Phase-Disaggregated LLM Serving with Stream-based Dynamic Scheduling

Existing large language model (LLM) serving systems typically batch the compute-bound prefill and I/O-bound decoding phases together.This co-location approach not only leads to significant interference between the two phases but also limits resource allocation and placements.To address these limitations, recent work proposes disaggregating the prefill and decoding phases to enhance performance.However, these works often rely on coarse-grained static scheduling strategies, resulting in imbalanced and insufficient resource utilization.For instance, compute resources for the prefill phase may be overloaded while those for the decoding phase remain idle, resulting in performance bottlenecks.In this paper, we propose WindServe, an efficient phase disaggregated LLM serving system that leverages stream-based, finegrained dynamic scheduling to enhance resource utilization and performance.WindServe features a global scheduler that monitors compute and memory resource usage to dynamically orchestrate cross-phase jobs, effectively reducing queuing delay and KV cache swapping overhead.We also introduce a stall-free rescheduling strategy to saturate the memory resources while minimizing the scheduling overhead from KV cache transfers.Furthermore, we design a stream-based approach to mitigate interference between prefill and decoding jobs.Our evaluation demonstrates that Wind-Serve achieves remarkable stability and SLO attainment under highload scenarios, outperforming state-of-the-art phase-disaggregated LLM serving systems by delivering a 4.28× improvement in TTFT median latency and a 1.5× reduction in TPOT P99 latency.