Energy-Efficient LLM Inference with SLA-Constrained Adaptive GPU Power Capping
GPU energy consumption represents a primary operational cost for Large Language Model (LLM) inference services. Despite the inherent variability of production workloads, most deployments rely on static power configurations that fail to exploit the non-linear relationship between power limits and performance. Consequently, opportunities to reduce energy overhead while maintaining Service Level Agreements (SLAs) are often missed. While modern GPUs provide hardware-level powercapping interfaces, their systematic application in a feedbackdriven manner to satisfy stringent latency guarantees remains significantly underexplored. This paper proposes a lightweight, non-intrusive adaptive GPU power-capping mechanism based on a PID controller that dynamically adjusts power limits using SLA feedback. The controller operates directly through vendor power-limit interfaces and incorporates guardrails such as deadbands, rate limiting, utilization-aware gating, and antiwindup protection. We evaluate the approach on a server with eight NVIDIA H200 GPUs running the qwen3:32b model under a time-varying Poisson workload, with SLA compliance defined over TTFT. Results show that static caps expose a rigid energy-SLA trade-off, whereas the adaptive controller achieves a 3.84% reduction in total energy consumption relative to a 700 W baseline while maintaining empirical SLA non-inferiority. These findings demonstrate that feedback-driven GPU power modulation can improve energy efficiency without compromising latency stability.