EWSJF: An Adaptive Scheduler with Hybrid Partitioning for Mixed-Workload LLM Inference

Fuente: arXiv
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Autores principales: Sidik, Bronislav, Levi, Chaya, Kampeas, Joseph
Formato: Preprint
Publicado: 2026
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author Sidik, Bronislav
Levi, Chaya
Kampeas, Joseph
author_facet Sidik, Bronislav
Levi, Chaya
Kampeas, Joseph
contents Serving Large Language Models (LLMs) under mixed workloads--short, latency-sensitive interactive queries alongside long, throughput-oriented batch requests--poses a fundamental scheduling challenge. Standard First-Come, First-Served (FCFS) policies suffer from severe head-of-line blocking, leading to high tail latency and underutilized hardware. We introduce EWSJF (Effective Workload-based Shortest Job First), an adaptive request-level scheduler that learns workload structure in real time to jointly improve fairness and throughput. EWSJF operates upstream of execution-level schedulers and integrates four components: (1) Refine-and-Prune, an unsupervised partitioning algorithm that discovers performance-homogeneous request groups; (2) Dynamic Queue Routing for assigning requests to these groups; (3) Density-Weighted Scoring, a context-aware prioritization function balancing urgency and fairness; and (4) Bayesian Meta-Optimization, which continuously tunes scoring and partitioning parameters based on live performance feedback. Implemented in vLLM, EWSJF improves end-to-end throughput by over 30% and reduces average Time-To-First-Token for short requests by up to 4x compared to FCFS. These results demonstrate that adaptive, learning-based request scheduling is a critical missing layer for efficient and responsive LLM serving. Implementation available at https://anonymous.4open.science/r/vllm_0110-32D8.
format Preprint
id arxiv_https___arxiv_org_abs_2601_21758
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle EWSJF: An Adaptive Scheduler with Hybrid Partitioning for Mixed-Workload LLM Inference
Sidik, Bronislav
Levi, Chaya
Kampeas, Joseph
Distributed, Parallel, and Cluster Computing
Artificial Intelligence
I.2.6; C.2.4
Serving Large Language Models (LLMs) under mixed workloads--short, latency-sensitive interactive queries alongside long, throughput-oriented batch requests--poses a fundamental scheduling challenge. Standard First-Come, First-Served (FCFS) policies suffer from severe head-of-line blocking, leading to high tail latency and underutilized hardware. We introduce EWSJF (Effective Workload-based Shortest Job First), an adaptive request-level scheduler that learns workload structure in real time to jointly improve fairness and throughput. EWSJF operates upstream of execution-level schedulers and integrates four components: (1) Refine-and-Prune, an unsupervised partitioning algorithm that discovers performance-homogeneous request groups; (2) Dynamic Queue Routing for assigning requests to these groups; (3) Density-Weighted Scoring, a context-aware prioritization function balancing urgency and fairness; and (4) Bayesian Meta-Optimization, which continuously tunes scoring and partitioning parameters based on live performance feedback. Implemented in vLLM, EWSJF improves end-to-end throughput by over 30% and reduces average Time-To-First-Token for short requests by up to 4x compared to FCFS. These results demonstrate that adaptive, learning-based request scheduling is a critical missing layer for efficient and responsive LLM serving. Implementation available at https://anonymous.4open.science/r/vllm_0110-32D8.
title EWSJF: An Adaptive Scheduler with Hybrid Partitioning for Mixed-Workload LLM Inference
topic Distributed, Parallel, and Cluster Computing
Artificial Intelligence
I.2.6; C.2.4
url https://arxiv.org/abs/2601.21758