针对大模型代理并行任务,提出高效公平的调度器,提升完成速度且保障最差情况延迟。
Justitia: Fair and Efficient Scheduling of Task-parallel LLM Agents with Selective Pampering
- 按内存占用量化代理真实成本,实现精准调度
- 预测成本准确且轻量,支持快速决策
- 基于虚拟时间的公平队列,兼顾效率与公平
大模型代理常由并行推理任务构成,广泛用于解决实际问题。在共享GPU服务器上服务此类任务并行的大模型代理时,调度器需在保证最差情况延迟的前提下实现快速代理完成。我们的核心洞察是:根据理想化公平共享下的完成顺序,对代理进行选择性优待。为此,我们设计了Justitia,一种面向任务并行大模型代理的高效且公平的调度器。考虑到内存在大模型服务中普遍为瓶颈,Justitia以内存为中心量化代理的真实成本,并采用轻量但准确的方法预测代理成本。最后,通过基于虚拟时间的公平队列算法,降低整体延迟并保证最差情况延迟。我们在vLLM之上实现了Justitia,实验结果表明,其在多种代理场景下显著提升了调度效率,同时保持了公平性。
原文摘要 · Abstract (English)
LLM agents, which often comprise parallel inference tasks, are commonly adopted to solve real-world problems. When serving such task-parallel LLM agents in shared GPU servers, the scheduler is expected to attain fast agent completion with guaranteed worst-case performance. For that objective, our insight is to selectively pampering agents based on their completion order under idealized fair-sharing. We design Justitia, a fair and also efficient scheduler for task-parallel LLM agents. Noticing that memory is prevalently a bottleneck in LLM serving, Justitia quantifies the true agent cost in a memory-centric manner. It also adopts a light-weight yet accurate method to predict agent costs. Finally, Justitia adopts a virtual-time based fair queuing algorithm to reduce the overall performance with guaranteed worst-case delay. We have implemented Justitia atop vLLM, and experimental results involving diverse agents show that it can substantially enhance the scheduling efficiency with fairness preserved.
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