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55 lines
1.9 KiB
Markdown
55 lines
1.9 KiB
Markdown
# Qwen2.5-14B OOM on RTX 3080 Ti (12GB)
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## Problem
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When attempting to run or fine-tune **Qwen2.5-14B** on an NVIDIA RTX 3080 Ti with 12GB of VRAM, the process fails with an Out of Memory (OOM) error:
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```
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torch.cuda.OutOfMemoryError: CUDA out of memory. Tried to allocate X GiB (GPU 0; 12.00 GiB total capacity; Y GiB already allocated; Z GiB free; ...)
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```
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The 12GB VRAM limit is hit during the initial model load or immediately upon starting the first training step.
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## Root Causes
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1. **Model Size:** A 14B parameter model in FP16/BF16 requires ~28GB of VRAM just for the weights.
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2. **Context Length:** High context lengths (e.g., 4096+) significantly increase VRAM usage during training.
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3. **Training Overhead:** Even with QLoRA (4-bit quantization), the overhead of gradients, optimizer states, and activations can exceed 12GB for a 14B model.
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---
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## Solutions
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### 1. Pivot to a 7B Model (Recommended)
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For a 12GB GPU, a 7B parameter model (like **Qwen2.5-7B-Instruct**) is the sweet spot. It provides excellent performance while leaving enough VRAM for high context lengths and larger batch sizes.
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- **VRAM Usage (7B QLoRA):** ~6-8GB
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- **Pros:** Stable, fast, supports long context.
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- **Cons:** Slightly lower reasoning capability than 14B.
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### 2. Aggressive Quantization
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If you MUST run 14B, use 4-bit quantization (GGUF or EXL2) for inference only. Training 14B on 12GB is not reliably possible even with extreme offloading.
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```bash
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# Example Ollama run (uses 4-bit quantization by default)
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ollama run qwen2.5:14b
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```
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### 3. Training Optimizations (if attempting 14B)
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If you have no choice but to try 14B training:
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- Set `max_seq_length` to 512 or 1024.
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- Use `Unsloth` (it is highly memory-efficient).
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- Enable `gradient_checkpointing`.
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- Set `per_device_train_batch_size = 1`.
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---
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## Maintenance
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Keep your NVIDIA drivers and CUDA toolkit updated. On Windows (MajorRig), ensure WSL2 has sufficient memory allocation in `.wslconfig`.
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---
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