DeepServeCB: SLO-Aware and Cost-Aware Elastic Scheduling for Serverless Multi-Tenant LLM Inference

Deploying large language model (LLM) inference services in serverless, multi-tenant environments present compounding challenges: cold start latency, GPU memory fragmentation, inter-tenant resource contention, and unpredictable tail latency. Existing systems optimize individual aspects but fail to jointly address service-level objective (SLO) compliance and cost efficiency under dynamic, heterogeneous workloads. We present DeepServeCB, an elastic scheduling framework that formulates the joint SLO--cost optimization as a contextual bandit problem. The system introduces a Request Profiler that extracts online features---prompt length, historical KV-cache hit ratio, and predicted generation length---and feeds them into a contextual bandit agent that adaptively selects batch sizes, concurrency levels, KV-cache eviction policies, and warm-standby strategies. We evaluate DeepServeCB on ShareGPT and BurstGPT traces using LLaMA-2-13B and Mixtral-8x7B models on NVIDIA A100 GPUs. Results show that DeepServeCB reduces P99 latency by 38--62% compared to state-of-the-art baselines while improving GPU utilization by 14--23% and reducing per-request cost by up to 27%, with only a modest increase in scheduling overhead.