LLMTailor: A Layer-wise Tailoring Tool for Efficient Checkpointing of Large Language Models

TL;DR

LLMTailor is a new framework that reduces storage and time overhead in checkpointing large language models by selectively saving only the most changed layers, without sacrificing model quality.

Contribution

It introduces a layer-wise selective checkpointing method that assembles checkpoints from different layers, a capability not available in existing tools.

Findings

Reduces checkpoint size by up to 4.3 times

Speeds up checkpointing by up to 2.8 times

Maintains model quality despite selective checkpointing

Abstract

Checkpointing is essential for fault tolerance in training large language models (LLMs). However, existing methods, regardless of their I/O strategies, periodically store the entire model and optimizer states, incurring substantial storage overhead and resource contention. Recent studies reveal that updates across LLM layers are highly non-uniform. Across training steps, some layers may undergo more significant changes, while others remain relatively stable or even unchanged. This suggests that selectively checkpointing only layers with significant updates could reduce overhead without harming training. Implementing such selective strategies requires fine-grained control over both weights and optimizer states, which no current tool provides. To address this gap, we propose \texttt{LLMTailor}, a checkpoint-merging framework that filters and assembles layers from different checkpoints to form a composite checkpoint. Our evaluation indicates that LLMTailor can work with different selective checkpointing strategies and effectively reduce checkpoint size (e.g., 4.3 times smaller for Llama3.1-8B) and checkpoint time (e.g., 2.8 times faster for Qwen2.5-7B) while maintaining model quality.