arXiv Machine Learning

Deterministic Regime Switching and Feasibility Inversion in Dynamic Tensor Rematerialization

The paper reports fine‑grained, deterministic instability in Dynamic Tensor Rematerialization (DTR), an online eviction policy for memory‑constrained DNN training. On an LSTM trace, tiny changes in memory budget (0.10% of peak) switch the system between fast and slow execution regimes with up to 7.3× overhead differences, driven by repeated re‑eviction of the same storages. On a ResNet‑32 trace, a deterministic feasibility inversion is observed: the run is feasible at a 0.101 budget ratio, infeasible (OOM) between 0.102–0.106, and feasible again from 0.107, caused by a fully pinned recursive rematerialization frontier exceeding the budget after all evictable tensors are removed. The authors attribute the LSTM instability to the joint size‑staleness scoring term and argue that these represent two distinct budget‑sensitive pathologies rather than a single mechanism.

arXiv AI
Aug 25

SANE: State Anomaly Neutralization for Stable Extreme-Context Delta-Rule Models

The paper introduces SANE, a method for stabilizing Delta‑Rule recurrent models that maintain a fixed‑size state. By applying adaptive tanh compression at chunk boundaries, SANE prevents localized norm explosions observed in long‑sequence experiments while preserving reasoning performance on short‑context benchmarks. Experiments on a 100M‑token prefix show that SANE retains functional reasoning where the baseline fails, but overly aggressive compression sacrifices reasoning ability, highlighting a capacity–stability trade‑off.

By Qingwen Lin, Boyan Xu, Xiao Liu, Zhifeng Hao, Ruichu Cai
arXiv AI
Aug 26

Elastic KV Cache for LLM Serving:A Working Reclamation Mechanism, and Why Chunked Prefill Already Closes the Gap

The paper introduces an elastic key‑value (KV) cache for large language model (LLM) serving that dynamically reclaims a pre‑allocated reserve during decode‑heavy phases and restores it before prefill, using a userspace CUDA virtual‑memory trick that requires no driver changes. The authors implement this mechanism, test it under realistic workloads, and find that it offers only marginal benefits—about a 1 % difference in time‑to‑first‑token for large prefill chunks—and that simpler strategies such as lowering the maximum batch size can achieve similar results. The study also notes that the reserve’s impact diminishes with higher tensor‑parallelism levels. whyItMatters":"The work demonstrates that a dynamic KV cache reclamation strategy can be implemented without driver patches and that its practical benefits are limited, guiding future LLM serving optimizations toward simpler approaches."

By Sathishkumar Sivashanmugam