llama4 post (#47)

* llama4 post

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_posts/2025-04-05-llama4.md

@@ -0,0 +1,108 @@
+---
+layout: post
+title: "Llama 4 in vLLM"
+author: "The vLLM Team"
+image: /assets/figures/llama4/perf.png
+thumbnail-img: /assets/figures/llama4/perf.png
+share-img: /assets/figures/llama4/perf.png
+---
+
+We're excited to announce that vLLM now supports the [Llama 4 herd of models](https://ai.meta.com/blog/llama-4-multimodal-intelligence/): **Scout** (17B-16E) and **Maverick** (17B-128E). You can run these powerful long-context, natively multi-modal (up to 8-10 images with good results), mixture-of-experts models in vLLM today by updating to version v0.8.3 or later:
+
+```
+pip install -U vllm
+```
+Below, you'll find sample commands to get started. Alternatively, you can replace the CLI command with docker run ([instructions here](https://docs.vllm.ai/en/latest/deployment/docker.html)) or use our Pythonic interface, the [`LLM` class](https://docs.vllm.ai/en/latest/getting_started/quickstart.html#offline-batched-inference), for local batch inference. We also recommend checking out the [demo from the Meta team](https://github.com/meta-llama/llama-cookbook/blob/main/getting-started/build_with_llama_4.ipynb) showcasing the 1M long context capability with vLLM.
+
+## Usage Guide
+
+Here's how you can serve the Llama 4 models using different hardware configurations.
+
+Using 8xH100, vLLM can serve Scout with 1M context and Maverick with about 430K. See more tips below for performance enhancement and leveraging long context.
+
+On 8x H100 GPUs:
+
+* Scout (up to 1M context):
+
+```
+vllm serve meta-llama/Llama-4-Scout-17B-16E-Instruct \
+  --tensor-parallel-size 8 \
+  --max-model-len 1000000
+```
+
+* Maverick (up to \~430K context):
+
+```
+vllm serve meta-llama/Llama-4-Maverick-17B-128E-Instruct-FP8 \
+  --tensor-parallel-size 8 \
+  --max-model-len 430000
+```
+
+On 8x H200 GPUs:
+
+* Scout (up to 3.6M context):
+
+```
+vllm serve meta-llama/Llama-4-Scout-17B-16E-Instruct \
+  --tensor-parallel-size 8 \
+  --max-model-len 3600000
+```
+
+* Maverick (up to 1M context):
+
+```
+vllm serve meta-llama/Llama-4-Maverick-17B-128E-Instruct-FP8 \
+  --tensor-parallel-size 8
+```
+**Multimodality:**
+
+The Llama 4 models excel at image understanding up to 8-10 images. By default, vLLM server accepts 1 image per request. Please pass `--limit-mm-per-prompt image=10` to serve up to 10 images per request with OpenAI-compatible API. We also recommend checking out our multi-image offline inference example with Llama-4 [here](https://github.com/vllm-project/vllm/blob/v0.8.3/examples/offline_inference/vision_language_multi_image.py).
+
+**Performance:**
+
+With the configurations above, we observe the following output tokens/s for Scout-BF16 and Maverick-FP8:
+
+![](/assets/figures/llama4/perf.png)
+
+While more performance enhancements are on the way, we believe the Llama 4 models' efficient architecture and relatively small size make them practical for scaled usage today.
+
+**Tips for Performance and Long Context:**
+
+* **Boost Performance & Context Length:** Set `--kv-cache-dtype fp8` to potentially double the usable context window and gain a performance boost. We observe little to no accuracy drop in relevant evaluations with this setting.
+* **Maximize Context Window (up to 10M):** To fully utilize the maximum context windows (up to 10M for Scout), we recommend serving across multiple nodes using tensor parallelism or pipeline parallelism. Follow our distributed inference guide [here](https://docs.vllm.ai/en/latest/serving/distributed_serving.html).
+* **Improve Long Context Accuracy (\>32K):** We highly recommend adding `--override-generation-config='{"attn_temperature_tuning": true}'` to improve accuracy for contexts longer than 32K tokens.
+
+**Other Hardware Support & Quantizations:**
+
+* A100: We have verified that the bf16 versions of the models work well on A100 GPUs.
+* INT4: An INT4-quantized version of the Scout model checkpoint that fits on a single H100 GPUis currently a work in progress. Stay tuned for updates.
+* AMD MI300X: You can run Llama 4 on AMD MI300X GPUs by building [vLLM from source](https://docs.vllm.ai/en/latest/getting_started/installation/gpu.html?device=rocm) and using the same commands as above.
+
+**Inference Accuracy Validation:**
+We validated inference accuracy against the official Meta report using lm-eval-harness. Here are the results for [meta-llama/Llama-4-Maverick-17B-128E-Instruct](https://huggingface.co/meta-llama/Llama-4-Maverick-17B-128E-Instruct):
+
+| | MMLU Pro | ChartQA |
+|----------|---------|---------|
+| Reported | 80.5 | 90 |
+| H100 FP8 | 80.4 | 89.4 |
+| AMD MI300x BF16 | 80.4 | 89.4 |
+| H200 BF16 | 80.2 | 89.3 |
+
+## Efficient Architecture and Cluster Scale Serving
+
+Llama 4’s model architecture is particularly well-suited for efficient long-context inference, thanks to features like:
+
+* **Mixture of Experts (MoE):** Scout uses 16 experts (17B activated parameters), and Maverick uses 128 experts (17B activated parameters). Only one expert is activated per token, maintaining efficiency.
+* **Interleaved RoPE (iRoPE):** Llama 4 interleaves global attention (without RoPE) with chunked local attention (with RoPE) in a 1:3 ratio. The local attention layer attends to tokens in non-overlapping chunks, significantly reducing the quadratic complexity of attention as context length scales.
+
+
+vLLM recently launched the [V1 engine](https://blog.vllm.ai/2025/01/27/v1-alpha-release.html), delivering major performance speedups on single nodes, along with native torch.compile support. Our [Q2 roadmap](https://github.com/vllm-project/vllm/issues/15735) focuses on enhancing vLLM’s multi-node scaling capabilities, aiming for disaggregated, cluster-scale serving. We are actively adding support for efficient expert parallelism, multi-node data parallelism, and cluster-wide prefill disaggregation.
+
+## Acknowledgement
+
+We extend our sincere thanks to the Meta team for their implementation of the model architecture, extensive accuracy evaluation, and performance benchmarking:  [Lucia (Lu) Fang](https://github.com/luccafong), [Ye (Charlotte) Qi](https://github.com/yeqcharlotte), [Lu Fang](https://github.com/houseroad), [Yang Chen](https://github.com/chenyang78), [Zijing Liu](https://github.com/liuzijing2014), [Yong Hoon Shin](https://github.com/sarckk), [Zhewen Li](https://github.com/zhewenl), [Jon Swenson](https://github.com/jmswen), [Kai Wu](https://github.com/wukaixingxp), [Xiaodong Wang](https://github.com/xw285cornell), [Shiyan Deng](https://github.com/842974287), [Wenchen Wang](https://github.com/wangwenchen0407), [Lai Wei](https://github.com/roywei), [Matthias Reso](https://github.com/mreso), [Chris Thi](https://github.com/cthi), [Keyun Tong](https://github.com/youngkent), [Jinho Hwang](https://github.com/jinhohwang-meta), [Driss Guessous](https://github.com/drisspg), [Aston Zhang](https://github.com/astonzhang).
+
+We also thank the AMD team for their support in enabling these models on MI300X:  [Hongxia Yang](https://github.com/hongxiayang) and Weijun Jiang.
+
+The vLLM team’s performance benchmarks were run on hardware generously provided by Nebius and NVIDIA.
+