分析大模型推理的硬件成本,发现低精度计算效率比理论算力更关键。
An Inquiry into Datacenter TCO for LLM Inference with FP8
- 从实际负载出发,评估不同芯片在低精度下的真实性能表现。
- FP8下,Gaudi处理器在稀疏矩阵运算中利用率显著优于NVIDIA H100/H200。
- 适合关注云服务部署成本与硬件选型的研究者和工程师。
随着大语言模型持续扩大,数据中心中AI加速器的高功耗给云服务商带来巨大挑战,显著推高了大模型推理的总拥有成本(TCO)。本文从TCO角度分析大模型推理的计算特性,提出一个可泛化的框架,用于比较不同硬件在多样化业务需求下的表现。基于该框架,我们研究了Intel Gaudi 2 & 3和NVIDIA H100 & H200在稀疏矩阵乘法(thin GEMM)利用和FP8量化方面的关键影响因素。尤其在FP8成为下一代大模型基线精度的背景下,理解不同架构如何实现并受益于低精度计算愈发重要。结果表明,由于解码阶段以内存受限的GEMV类计算为主,薄矩阵乘法的吞吐量对TCO的影响超过理论峰值算力。Gaudi HPU在FP8量化模型中表现出更优的稀疏矩阵运算利用率。研究强调应通过工作负载级实证分析评估加速器性能,而非仅依赖理论规格。通过分析功耗、量化策略与硬件架构间的交互关系,为优化部署决策和指导未来加速器设计提供依据。
原文摘要 · Abstract (English)
As large language models (LLMs) continue to scale, the high power consumption of AI accelerators in datacenters presents significant challenges, substantially increasing the total cost of ownership (TCO) for cloud service providers (CSPs) that provide LLM inference. In this work, we analyze the computational characteristics of LLM inference from a TCO perspective and present a generalizable framework to compare AI accelerators across diverse operational requirements. Using this model, we investigate key workload characteristics influencing TCO for AI accelerators from Intel (Gaudi 2 & 3) and NVIDIA (H100 & H200), especially thin GEMM utilization and FP8 quantization. In particular, as FP8 emerges as the baseline precision for next-generation LLMs, understanding how different architectures implement and benefit from low-precision computation is increasingly critical. Throughput on thin GEMMs has a greater impact on TCO than theoretical hardware peak throughput because the memory-bound decode phase is dominated by GEMV-like computations. We find that Gaudi HPUs achieve superior utilization on thin GEMMs compared to their counterparts, especially in FP8-quantized models. Our result underscores the importance of empirical, workload-level analysis in evaluating accelerator performance, rather than relying solely on theoretical hardware specifications. By studying the interaction between power consumption, quantization strategies, and hardware architecture, we provide insights to support informed deployment decisions and guide future accelerator designs aimed at improving the TCO of LLM inference workloads.
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