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Mixing Importance with Diversity: Joint Optimization for KV Cache Compression in Large Vision-Language Models
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Proposes MixKV, a plug-and-play KV cache compression method for LVLMs that adaptively mixes per-head importance scores with key-diversity scores, weighted by each head's measured key redundancy.
Problem
KV cache growth from long multimodal sequences in LVLMs creates a memory bottleneck; existing importance-based eviction methods retain semantically redundant KV pairs and lose coverage of the full KV distribution.
Approach
Measure per-head key redundancy in closed form (average off-diagonal cosine similarity via the global mean key) and use it as an adaptive weight that interpolates between importance scores (VNorm plus attention) and a key-diversity score, so redundant heads favor diversity and less redundant heads favor importance.
Key results
- At budget 64, MixKV improves SnapKV and AdaKV by 8.0% and 9.0% average on ScreenSpot-v2 GUI grounding with Qwen2.5-VL-7B.
- MixKV improves baseline methods by an average of 5.1% across five multi-modal understanding benchmarks at extreme compression (budget 64), per the abstract.
- On Qwen3-VL-30B-A3B, MixKV boosts SnapKV on OCRBench by 13.6% at budget 64.
Surprising findings
- Adding diversity alone (s_div) substantially degrades performance relative to importance-based baselines, showing diversity cannot replace importance.
- MixKV gives slight declines on some LongBench information-localization tasks for LLMs, where head-wise redundancy is lower.
Limitations
- Evaluated only on models up to 8B in the main analysis (plus 30B MoE and 38B in additional tables); generalization to 70B+ untested.
- Head-wise redundancy is measured per sample on-the-fly, with diversity computed from key vectors only.
Experimental setup
Datasets: OCRBench
Benchmarks: DocVQA OCRBench TextVQA ChartQA TextCaps ScreenSpot-v2 LongBench
Metrics: accuracy (%) CIDEr-style captioning score average precision on GUI grounding
Baselines: SnapKV PyramidKV AdaKV SparseMM KNorm VNorm HeadKV
Builds on: SnapKV PyramidKV AdaKV SparseMM VNorm
Closest papers by meaning
- VL-Cache: Sparsity and Modality-Aware KV Cache Compression for Vision-Language Model Inference Acceleration (ICLR 2025 · similarity 0.93)
- EchoKV: Efficient KV Cache Compression via Similarity-Based Reconstruction (NeurIPS 2026 · similarity 0.91)
- Q Cache: Visual Attention Is Valuable in Less than Half of Decode Layers for Multimodal Large Language Model (AAAI 2026 · similarity 0.90)
- PrefixKV: Adaptive Prefix KV Cache is What Vision Instruction-Following Models Need for Efficient Generation (NeurIPS 2025 · similarity 0.90)
- Prune Redundancy, Preserve Essence: Vision Token Compression in VLMs via Synergistic Importance-Diversity (ICLR 2026 · similarity 0.89)
- SqueezeAttention: 2D Management of KV-Cache in LLM Inference via Layer-wise Optimal Budget (ICLR 2025 · similarity 0.89)
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