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arXiv 2501.08192cs.AIcs.ARcs.DC
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PRESERVE:分布式LLM服务中的模型权重与KV缓存预取

PRESERVE: Prefetching Model Weights and KV-Cache in Distributed LLM Serving

Huawei Zurich Research Center Switzerland(华为苏黎世研究中心)

Ahmet Caner Yüzügüler, Jiawei Zhuang, Lukas Cavigelli

AI总结:

PRESERVE通过在通信期间预取模型权重和KV缓存到片上缓存,在商用AI加速器上实现高达1.6倍端到端加速,并优化硬件配置额外提升1.25倍性能成本比。

摘要:

大型语言模型(LLM)通常由包含大量设备的GPU/NPU集群提供服务。不幸的是,这些设备之间的通信会产生显著的开销,增加推理延迟和成本,同时限制可扩展性。先前的工作通过将通信与计算重叠来解决这个问题,但由于这些操作之间的数据依赖性,存在严重的局限性。在本文中,我们提出了PRESERVE,一种新颖的框架,在通信操作期间将模型权重和KV缓存从片外HBM内存预取到AI加速器的片上缓存,与先前方法相比,这提供了各种优势和性能改进。通过在商用AI加速器上进行的大量实验,我们在最先进的开源LLM上展示了高达1.6倍的端到端加速。此外,我们进行了设计空间探索,确定了所提出方法的最佳硬件配置,通过选择最佳的L2缓存大小,在性能每成本上进一步提升了1.25倍。我们的结果表明,PRESERVE有潜力缓解内存瓶颈和通信开销,为改善LLM推理系统的性能和可扩展性提供了一种解决方案。

英文摘要:

Large language models (LLMs) are typically served from clusters of GPUs/NPUs that consist of large number of devices. Unfortunately, communication between these devices incurs significant overhead, increasing the inference latency and cost while limiting the scalability. Prior work addressed this issue by overlapping communication with compute, but has severe limitations due to the data dependencies between these operations. In this paper, we propose PRESERVE, a novel framework that prefetches model weights and KV-cache from off-chip HBM memory to the on-chip cache of AI accelerators during the communication operations, which offers various advantages and performance improvements compared to prior methods. Through extensive experiments conducted on commercial AI accelerators, we demonstrate up to 1.6x end-to-end speedup on state-of-the-art, open-source LLMs. Additionally, we perform a design space exploration that identifies the optimal hardware configuration for the proposed method, showing a further 1.25x improvement in performance per cost by selecting the optimal L2 cache size. Our results show that PRESERVE has the potential to mitigate the memory bottlenecks and communication overheads, offering a solution to improve the performance and scalability of the LLM inference systems.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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