arXiv Computation and Language

Compression Does Not End at Selection: Post-Selection Positional Geometry for Sparse KV Caches

The paper investigates how the positional geometry of cached key‑value (KV) states affects inference quality in sparse KV compression. It introduces RoPERelay, a method that reassigns compact, order‑preserving RoPE coordinates and re‑rotates cached key phases to better align with current queries, without requiring new selection or extra cache budget. Experiments on two models and multiple selectors show that RoPERelay improves answer quality in most cases, notably raising Llama‑3.1‑8B‑Instruct accuracy from 23.6% to 35.4% on LongMemEval‑S with only a 1–3% runtime overhead.

arXiv AI
Jul 8

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

arXiv:2607. 06519v1 Announce Type: new Abstract: Long-context LLM inference is increasingly limited by the memory and bandwidth cost of KV caches, yet aggressive compression can remove the layer-specific evidence needed for retrieval and multi-step reasoning.

By Anna C\'ordoba, Adam Puente Tercero, Nerea Angulo Hijo, Mar Linares Tercero, Julia Barrientos, Ainhoa Miranda, Jes\'us Olivera
arXiv AI
Oct 5

KV$^2$: A Self-Refining KV Cache

KV$^2$ is a query‑agnostic key‑value cache compression technique that selectively reconstructs only informative in‑context tokens using a lightweight proxy scorer before final eviction scoring. On benchmarks such as RULER, Needle‑in‑a‑Haystack, and LongBench, KV$^2$ outperforms baseline methods, especially under tight memory budgets, achieving higher scores with lower runtime and peak memory than full‑context reconstruction. The approach demonstrates that reusable KV‑cache compression can avoid reprocessing the entire prompt while maintaining quality.

By Johannes Wesch, Danni Liu, Jan Niehues
arXiv AI
Oct 5

iS-KV: Online Low-Rank KV Cache Compression via Block-Incremental SVD

The paper introduces iS-KV, an online low‑rank KV‑cache compression technique that uses block‑incremental SVD to manage memory during long‑horizon autoregressive decoding. Unlike token‑eviction methods, iS‑KV retains all positions in a compact representation by keeping a recent window exact and incrementally folding older states into bounded‑rank bases, synchronizing coordinates as the basis evolves. Experiments on DeepSeek‑R1‑Distill‑Llama‑8B and Qwen3‑8B show that iS‑KV achieves high accuracy (82.6% and 89.2% respectively) while providing 4.06‑fold and 5.64‑fold compression, outperforming token‑eviction baselines under matched memory budgets.

By Yiren Zhao, Guanghui Song, Tianrui Qin, Kejiang Ye, Cheng-zhong Xu, Xitong Gao
arXiv Computation and Language
Sep 10

Fine-Tuning a KV Cache Concatenation-Aware Model or Recomputing KV Caches? Why Not Both?

The paper addresses the challenge of long input contexts in Retrieval-Augmented Generation (RAG) systems, where concatenating many retrieved chunks increases prefill workload and time to first token (TTFT). It proposes a dual strategy: fine‑tuning the model to be aware of KV cache concatenation and selectively recomputing only part of the KV caches. Experiments on the RULER benchmark show that for a 124k‑token input, this combined method boosts the RULER score by 9.7 points over a baseline that recomputes caches only, while cutting TTFT by 80% compared with full attention.

By Fumihiko Tachibana, Daisuke Miyashita, Jun Deguchi