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[GPT-NeoX] Add SDPA support (#31031)

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* starting support for sdpa in `gptneox` models

* small comment on tests

* fix dropout

* documentation and style

* clarify concrete paths for reference

* generalise attn projections and rope application

added head mask check to sdpa mask creation

handle sdpa memory backend bug via own version flag

* update docs and style

* move dtype casting outside of general attn_projection_and_rope function

fix flash_attn_2 stuff

* more generic attn warning if output_attns or head_mask

* simplify head mask check by moving head mask creation to a later point

* remove copied llama artifact

* remove padding_mask from attention function signature

* removing unnecessary comments, only "save" attn implementation once

* [run_slow] gpt_neox
This commit is contained in:
Anton Vlasjuk
2024-06-26 14:56:36 +02:00
committed by GitHub
parent 1218e439b5
commit b07770c5eb
4 changed files with 289 additions and 98 deletions
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@@ -95,6 +95,68 @@ Below is an expected speedup diagram that compares pure inference time between t
<img src="https://huggingface.co/datasets/ybelkada/documentation-images/resolve/main/gpt-neox-1.8b-speedup.jpg">
</div>
## Using Scaled Dot Product Attention (SDPA)
PyTorch includes a native scaled dot-product attention (SDPA) operator as part of `torch.nn.functional`. This function
encompasses several implementations that can be applied depending on the inputs and the hardware in use. See the
[official documentation](https://pytorch.org/docs/stable/generated/torch.nn.functional.scaled_dot_product_attention.html)
or the [GPU Inference](https://huggingface.co/docs/transformers/main/en/perf_infer_gpu_one#pytorch-scaled-dot-product-attention)
page for more information.
SDPA is used by default for `torch>=2.1.1` when an implementation is available, but you may also set
`attn_implementation="sdpa"` in `from_pretrained()` to explicitly request SDPA to be used.
```python
from transformers import GPTNeoXForCausalLM
model = GPTNeoXForCausalLM.from_pretrained("EleutherAI/gpt-neox-20b", torch_dtype=torch.float16, attn_implementation="sdpa")
...
```
For the best speedups, we recommend loading the model in half-precision (e.g. `torch.float16` or `torch.bfloat16`).
On a local benchmark (rtx3080ti-16GB, PyTorch 2.2.1, OS Ubuntu 22.04) using `float16` with
[pythia-410m-deduped](https://huggingface.co/EleutherAI/pythia-410m-deduped), we saw the
following speedups during training and inference.
### Training
| Batch size | Seq len | Time per batch (Eager - s) | Time per batch (SDPA - s) | Speedup (%) | Eager peak mem (MB) | SDPA peak mem (MB) | Mem saving (%) |
|-----------:|-----------:|---------------------------:|-----------------------------:|------------:|--------------------:|-------------------:|------------------:|
| 1 | 128 | 0.024 | 0.019 | 28.945 | 1789.95 | 1789.95 | 0 |
| 1 | 256 | 0.039 | 0.031 | 23.18 | 1845.83 | 1844.84 | 0.053 |
| 1 | 512 | 0.08 | 0.055 | 45.524 | 2278.38 | 1953.76 | 16.615 |
| 1 | 1024 | 0.19 | 0.102 | 86.777 | 4772.36 | 2408.35 | 98.159 |
| 1 | 2048 | 0.565 | 0.204 | 177.098 | 13484.1 | 3882.01 | 247.348 |
| 2 | 128 | 0.037 | 0.032 | 15.121 | 1843.86 | 1844.78 | -0.05 |
| 2 | 256 | 0.067 | 0.055 | 21.706 | 1999.72 | 1951.67 | 2.462 |
| 2 | 512 | 0.144 | 0.096 | 50.046 | 3613.16 | 2406.77 | 50.125 |
| 2 | 1024 | 0.366 | 0.193 | 89.666 | 8707.55 | 3878.86 | 124.487 |
| 2 | 2048 | OOM | 0.379 | / | OOM | 6825.13 | SDPA does not OOM |
| 4 | 128 | 0.06 | 0.054 | 11.539 | 1947.6 | 1952.06 | -0.228 |
| 4 | 256 | 0.119 | 0.093 | 28.072 | 3008.39 | 2405.99 | 25.038 |
| 4 | 512 | 0.275 | 0.187 | 47.145 | 6290.58 | 3877.29 | 62.242 |
| 4 | 1024 | OOM | 0.36 | / | OOM | 6821.98 | SDPA does not OOM |
| 4 | 2048 | OOM | 0.731 | / | OOM | 12705.1 | SDPA does not OOM |
### Inference
| Batch size | Seq len | Per token latency Eager (ms) | Per token latency SDPA (ms) | Speedup (%) | Mem Eager (MB) | Mem SDPA (MB) | Mem saved (%) |
|--------------:|-------------:|--------------------------------:|-------------------------------:|---------------:|------------------:|----------------:|-----------------:|
| 1 | 128 | 6.569 | 5.858 | 12.14 | 974.831 | 974.826 | 0 |
| 1 | 256 | 7.009 | 5.863 | 19.542 | 1029.01 | 1028.08 | 0.09 |
| 1 | 512 | 7.157 | 5.965 | 19.983 | 1137.54 | 1137.52 | 0.001 |
| 1 | 1024 | 7.523 | 6.506 | 15.637 | 1329.3 | 1329.26 | 0.003 |
| 1 | 2048 | 9.271 | 9.205 | 0.713 | 1752.47 | 1734.51 | 1.036 |
| 2 | 128 | 7.239 | 5.959 | 21.493 | 1044.8 | 1028.37 | 1.597 |
| 2 | 256 | 7.228 | 6.036 | 19.757 | 1167.32 | 1137.73 | 2.601 |
| 2 | 512 | 7.538 | 6.693 | 12.628 | 1352.93 | 1329.55 | 1.758 |
| 2 | 1024 | 8.916 | 8.632 | 3.291 | 1752.56 | 1734.62 | 1.034 |
| 2 | 2048 | 12.628 | 12.606 | 0.181 | 2558.72 | 2545.8 | 0.508 |
| 4 | 128 | 7.278 | 6.046 | 20.373 | 1168.41 | 1137.79 | 2.691 |
| 4 | 256 | 7.614 | 6.588 | 15.574 | 1353.1 | 1329.79 | 1.753 |
| 4 | 512 | 8.798 | 8.144 | 8.028 | 1752.76 | 1734.85 | 1.032 |
| 4 | 1024 | 11.765 | 11.303 | 4.09 | 2558.96 | 2546.04 | 0.508 |
| 4 | 2048 | 19.568 | 17.735 | 10.33 | 4175.5 | 4165.26 | 0.246 |
## Resources
- [Causal language modeling task guide](../tasks/language_modeling)