RetentiveKV: State-Space Memory for Uncertainty-Aware Multimodal KV Cache Eviction

TL;DR

RetentiveKV introduces a state-space memory approach for more effective, uncertainty-aware cache eviction in multimodal large language models, significantly improving efficiency and preserving important visual tokens.

Contribution

It proposes an entropy-driven, continuous memory evolution method for KV cache eviction, addressing limitations of existing pruning techniques in multimodal settings.

Findings

Achieves 5.0× KV cache compression

Provides 1.5× decoding acceleration

Effectively preserves important visual tokens during decoding

Abstract

Multimodal Large Language Models face severe challenges in computational efficiency and memory consumption due to the substantial expansion of the visual KV cache when processing long visual contexts. Existing KV cache compression methods typically rely on the "persistence of importance" hypothesis to prune tokens. However, this approach proves fragile in multimodal settings due to two key issues: 1) Visual tokens display "deferred importance," initially exhibiting low salience but becoming pivotal during later decoding, which can lead to premature eviction. 2) Discrete pruning disrupts the inherent spatial continuity of visual cues. To address these challenges, we propose RetentiveKV, an entropy-driven KV cache optimization method that reformulates KV eviction from "discrete context truncation" to "continuous memory evolution" based on State Space Models. Our method leverages information entropy to quantify the information potential of low-attention tokens and integrates tokens scheduled for eviction into a continuous state space through entropy-guided state transitions, enabling their dynamic reactivation when semantic relevance arises during subsequent decoding. Extensive experiments on multimodal benchmarks demonstrate that RetentiveKV achieves 5.0 times KV cache compression and 1.5 times decoding acceleration.