LeanK: Learnable K Cache Channel Pruning for Efficient Decoding
Yike Zhang, Zhiyuan He, Huiqiang Jiang, Chengruidong Zhang, Yuqing Yang, Jianyong Wang, Lili Qiu
Abstract
Large language models (LLMs) enable long-context tasks but face efficiency challenges due to the growing key-value (KV) cache. We propose LeanK, a learning-based method that prunes unimportant key (K) cache channels by leveraging static channel sparsity. LeanK reduces GPU memory and accelerates decoding without sacrificing accuracy. Experiments demonstrate up to 70% K cache and 16%–18% V cache memory reduction, and 1.45× decoding speedup. We also provide insights into model channels and attention heads during long-context inference by analyzing the learned importance distribution. Our code is anonymously available at https://anonymous.4open.science/r/LeanK-7A87/README.md.- Anthology ID:
- 2025.emnlp-main.1584
- Volume:
- Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
- Month:
- November
- Year:
- 2025
- Address:
- Suzhou, China
- Editors:
- Christos Christodoulopoulos, Tanmoy Chakraborty, Carolyn Rose, Violet Peng
- Venue:
- EMNLP
- SIG:
- Publisher:
- Association for Computational Linguistics
- Note:
- Pages:
- 31110–31125
- Language:
- URL:
- https://preview.aclanthology.org/ingest-emnlp/2025.emnlp-main.1584/
- DOI:
- Cite (ACL):
- Yike Zhang, Zhiyuan He, Huiqiang Jiang, Chengruidong Zhang, Yuqing Yang, Jianyong Wang, and Lili Qiu. 2025. LeanK: Learnable K Cache Channel Pruning for Efficient Decoding. In Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing, pages 31110–31125, Suzhou, China. Association for Computational Linguistics.
- Cite (Informal):
- LeanK: Learnable K Cache Channel Pruning for Efficient Decoding (Zhang et al., EMNLP 2025)
- PDF:
- https://preview.aclanthology.org/ingest-emnlp/2025.emnlp-main.1584.pdf