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Model Tells You Where to Merge: Adaptive KV Cache Merging for LLMs on Long-Context Tasks

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arxiv 2407.08454 v2 pith:4IHXDMYO submitted 2024-07-11 cs.CL

classification cs.CL
keywords cachemerginglong-contextllmstasksalgorithmbudgetscomputational
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How to efficiently serve Large Language Models (LLMs) has become a pressing issue because of their huge computational cost in their autoregressive generation process. To mitigate computational costs, LLMs often employ the KV Cache technique to improve the generation speed. While improving the computational efficiency, the storage requirements of the KV cache are substantial, particularly in long-context scenarios, leading to significant memory consumption. Existing KV cache eviction methods often degrade the performance of LLMs in long-context scenarios due to the information loss introduced by eviction. In this paper, we propose a novel KV cache merging approach, called KVMerger, to achieve adaptive KV cache compression for long-context tasks without significant performance degradation under constrained memory budgets. Our approach is inspired by the intriguing observation that key states exhibit high similarity at the token level within a single sequence. To facilitate merging, we develop an effective yet straightforward merging set identification algorithm to identify suitable KV states for merging. Our merging set identification algorithm stimulates the second observation that KV cache sparsity, from similarity perspective, is independent of the dataset and remains persistent at the model level. Subsequently, we propose a Gaussian kernel weighted merging algorithm to selectively merge all states within each merging set. We conduct extensive experiments to demonstrate the effectiveness of KVMerger for long-context tasks under constrained memory budgets, applying it to models including Llama2-7B-chat and Llama2-13B-chat. Using the LongBench and ZeroScroll benchmarks, we compare our method with other KV cache compression techniques, including H2O and CaM, showing that our method achieves superior performance across tasks with both 50% and 35% KV cache budgets.

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Cited by 29 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

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  2. Fast KV Compaction via Attention Matching

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    Attention Matching compacts LLM key–value caches by matching per-head attention outputs and mass over reference queries, reaching 50× compression in seconds-to-minutes with modest task loss.

  3. From Tensor Buffer to Distributed Memory Hierarchy: A Survey of KV Cache Management for LLM Serving

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    ReCo coordinates KV-cache compression, reflection-token logit penalties, and confidence-based early stopping under one per-step process reward, reducing tokens and latency while largely preserving accuracy.

  5. AnchorKV: Anchor-Residual KV Cache Compression

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    AnchorKV compresses the KV cache 20x with near-lossless accuracy by representing each token as an anchor projection plus selectively allocated quantized residuals, beating eviction baselines at matched byte budgets on...

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    Learned pooling of speech KV caches from an intermediate LLM layer compresses speech to text-level length while matching or exceeding the uncompressed baseline on ASR and entity recognition, with 1.49–2× decoding speedup.

  8. DepthWeave-KV: Token-Adaptive Cross-Layer Residual Factorization for Long-Context KV Cache Compression

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  10. CaliDrop: KV Cache Compression with Calibration

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    CaliDrop adds a stale-query calibration term on top of token eviction, improving accuracy at high KV compression ratios with modest throughput overhead.

  11. IAM: Efficient Inference through Attention Mapping between Different-scale LLMs

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  13. HGCA: Hybrid GPU-CPU Attention for Long Context LLM Inference

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  14. RCStat: A Statistical Framework for using Relative Contextualization in Transformers

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  15. Cartridges: Lightweight and general-purpose long context representations via self-study

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    HashEvict uses locality-sensitive hashing to evict the KV-cache token least similar to the current query, compressing 30-70% with modest quality loss across several LLM benchmarks.

  17. FreqDepthKV: Frequency-Guided Depth Sharing for Robust KV Cache Compression in Long-Context LLM Inference

    cs.AI 2026-07 conditional novelty 5.0 of 10

    Frequency-guided inter-layer KV sharing with logit-aware head routing nearly matches full-cache long-context accuracy at about 3.9× lower peak KV memory.

  18. SelKV: Selective KV Cache Merging with Per-Token Merge-or-Drop and Attention Compensation

    cs.AI 2026-05 conditional novelty 5.0 of 10

    SelKV compresses the KV cache to 25% with per-token cosine-gated merging and an attention-ratio logit bias, staying within ~0.7 points of full-cache LongBench accuracy on GQA models.

  19. GraphKV: Breaking the Static Selection Paradigm with Graph-Based KV Cache Eviction

    cs.CL 2025-08 conditional novelty 5.0 of 10

    GraphKV adds a similarity-based decay penalty to existing top-k KV cache eviction scores, improving retention diversity and accuracy on LongBench and needle-in-a-haystack tasks.

  20. TPLA: Tensor Parallel Latent Attention for Efficient Disaggregated Prefill and Decode Inference

    cs.LG 2025-08 conditional novelty 5.0 of 10

    TPLA splits the latent KV cache across tensor-parallel GPUs while keeping every head's full view, yielding 1.79x and 1.93x decode speedups on DeepSeek-V3 and Kimi-K2 at 32K context with modest accuracy loss.

  21. LaCache: Ladder-Shaped KV Caching for Efficient Long-Context Modeling of Large Language Models

    cs.LG 2025-07 conditional novelty 5.0 of 10

    LaCache keeps a layer-dependent diagonal slice of the KV cache and iteratively compacts old entries, improving long-context perplexity and retrieval accuracy versus StreamingLLM at fixed cache sizes.

  22. Krul: Efficient State Restoration for Multi-turn Conversations with Dynamic Cross-layer KV Sharing

    cs.CL 2025-07 conditional novelty 5.0 of 10

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  23. SpindleKV: A Novel KV Cache Reduction Method Balancing Both Shallow and Deep Layers

    cs.CL 2025-07 conditional novelty 5.0 of 10

    SpindleKV compresses LLM KV cache by evicting low-attention tokens in deep layers and replacing near-duplicate key and value vectors in shallow layers with a shared codebook, while preserving benchmark accuracy at 15 ...

  24. Learn from the Past: Fast Sparse Indexing for Large Language Model Decoding

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  25. Curse of High Dimensionality Issue in Transformer for Long-context Modeling

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  27. PagedEviction: Structured Block-wise KV Cache Pruning for Efficient Large Language Model Inference

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  28. A Survey on Large Language Model Acceleration based on KV Cache Management

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