PatrickStar: Parallel Training of Pre-trained Models via a Chunk-based Memory Management
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The pre-trained model (PTM) is revolutionizing Artificial intelligence (AI) technology. It learns a model with general language features on the vast text and then fine-tunes the model using a task-specific dataset. Unfortunately, PTM training requires prohibitively expensive computing devices, especially fine-tuning, which is still a game for a small proportion of people in the AI community. Enabling PTMs training on low-quality devices, PatrickStar now makes PTM accessible to everyone. PatrickStar reduces memory requirements of computing platforms by using the CPU-GPU heterogeneous memory space to store model data, consisting of parameters, gradients, and optimizer states. We observe that the GPU memory available for model data changes regularly, in a tide-like pattern, decreasing and increasing iteratively. However, the existing heterogeneous training works do not take advantage of this pattern. Instead, they statically partition the model data among CPU and GPU, leading to both memory waste and memory abuse. In contrast, PatrickStar manages model data in chunks, which are dynamically distributed in heterogeneous memory spaces. Chunks consist of stateful tensors which run as finite state machines during training. Guided by the runtime memory statistics collected in a warm-up iteration, chunks are orchestrated efficiently in heterogeneous memory and generate lower CPU-GPU data transmission volume. Symbiosis with the Zero Redundancy Optimizer, PatrickStar scales to multiple GPUs using data parallelism, with the lowest communication bandwidth requirements and more efficient bandwidth utilization. Experimental results show PatrickStar trains a 12 billion parameters GPT model, 2x larger than the STOA work, on an 8-V100 and 240GB CPU memory node, and is also more efficient on the same model size.
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