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This research challenges the prevailing assumption that cross-context KV-cache reuse incurs no quality loss, revealing significant accuracy degradation on benchmarks like MMLU and GSM8K when relying solely on prediction. The authors introduce Budgeted Cache Repair (BCR), a method that strategically recomputes specific cache rows based on attention metrics to recover lost precision without sacrificing the efficiency gains of caching. By operating at the token-row level rather than larger chunks, BCR effectively balances inference speed with model fidelity, offering a practical solution for deploying large language models in resource-constrained environments.
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Budgeted Cache Repair for Cross-Context KV-Cache Reuse

arXiv3 min read

arXiv:2610.02233v1 Announce Type: cross Abstract: Cross-context KV-cache reuse predicts a shared segment's keys and values under a new prefix instead of recomputing them, and has been reported to do so without quality loss. We find otherwise, and identify two problems. (1) A hidden cost: on MMLU and GSM8K, reuse costs substantial accuracy. (2) A decision at the wrong unit: no rule for deciding whether to reuse a cache removes that cost. What does help is choosing which parts of the cache to recompute, and the value of choosing well falls as the unit of choice grows: informed selection removes 49.5% of the cache error beyond chance at single rows (one token's keys and values), 10.6% at 64-token chunks, and nothing at the level of whole calls. Budgeted Cache Repair (BCR) acts at the unit where selection still pays. It drafts two tokens from the assembled cache, ranks cache rows by the attention those tokens pay them, and recomputes a fixed budget of rows exactly, in one of three layouts. The cost is paid rather than predicted away, and the draft that fails as a gate succeeds as a selector. BCR restores GSM8K to dense-prefill accuracy while still serving most calls from cache, and its best layout outperforms every reuse baseline's mean in the reference grid. The draft also beats a coin-flip selector at the same budget - a control prior evaluations lack.

Abstract:Cross-context KV-cache reuse predicts a shared segment's keys and values under a new prefix instead of recomputing them, and has been reported to do so without quality loss. We find otherwise, and identify two problems. (1) A hidden cost: on MMLU and GSM8K, reuse costs substantial accuracy. (2) A decision at the wrong unit: no rule for deciding whether to reuse a cache removes that cost. What does help is choosing which parts of the cache to recompute, and the value of choosing well falls as the unit of choice grows: informed selection removes 49.5% of the cache error beyond chance at single rows (one token's keys and values), 10.6% at 64-token chunks, and nothing at the level of whole calls. Budgeted Cache Repair (BCR) acts at the unit where selection still pays. It drafts two tokens from the assembled cache, ranks cache rows by the attention those tokens pay them, and recomputes a fixed budget of rows exactly, in one of three layouts. The cost is paid rather than predicted away, and the draft that fails as a gate succeeds as a selector. BCR restores GSM8K to dense-prefill accuracy while still serving most calls from cache, and its best layout outperforms every reuse baseline's mean in the reference grid. The draft also beats a coin-flip selector at the same budget - a control prior evaluations lack.

Hardware Architecture (cs.AR); Computation and Language (cs.CL); Machine Learning (cs.LG)

arXiv:2610.02233 [cs.AR]

(or arXiv:2610.02233v1 [cs.AR] for this version)

https://doi.org/10.48550/arXiv.2610.02233 Focus to learn more arXiv-issued DOI via DataCite

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Full text under the publisher's open licence · 326 words

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