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Efficient Streaming Language Models with Attention Sinks

2023/09/29 by Guangxuan Xiao, Yuandong Tian, Xiao, Guangxuan +7 · 5 voices · 684 citations
Computer Science · #Algorithm #Artificial intelligence #Cache #Computer network #Computer science #Decoding methods #Language model #Natural Language Processing Techniques #Parallel computing #Security token #Sequence (biology) #Sink (geography) #Sliding window protocol #Speech Recognition and Synthesis #Speedup #Topic Modeling #Window (computing) #World Wide Web

paper · pdf · doi:10.48550/arxiv.2309.17453

published in arXiv (Cornell University) (Cornell University)

openalex publication_date 2023/09/29 · openalex created_date 2023/10/03 · openalex updated_date 2026/08/05

Abstract

Deploying Large Language Models (LLMs) in streaming applications such as multi-round dialogue, where long interactions are expected, is urgently needed but poses two major challenges. Firstly, during the decoding stage, caching previous tokens' Key and Value states (KV) consumes extensive memory. Secondly, popular LLMs cannot generalize to longer texts than the training sequence length. Window attention, where only the most recent KVs are cached, is a natural approach -- but we show that it fails when the text length surpasses the cache size. We observe an interesting phenomenon, namely attention sink, that keeping the KV of initial tokens will largely recover the performance of window attention. In this paper, we first demonstrate that the emergence of attention sink is due to the strong attention scores towards initial tokens as a "sink" even if they are not semantically important. Based on the above analysis, we introduce StreamingLLM, an efficient framework that enables LLMs trained with a finite length attention window to generalize to infinite sequence lengths without any fine-tuning. We show that StreamingLLM can enable Llama-2, MPT, Falcon, and Pythia to perform stable and efficient language modeling with up to 4 million tokens and more. In addition, we discover that adding a placeholder token as a dedicated attention sink during pre-training can further improve streaming deployment. In streaming settings, StreamingLLM outperforms the sliding window recomputation baseline by up to 22.2x speedup. Code and datasets are provided at https://github.com/mit-han-lab/streaming-llm.

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