vllm

vLLM: Easy, Fast, and Cheap LLM Serving with PagedAttention

This README contains instructions to run a demo for vLLM, an open-source library for fast LLM inference and serving, which improves the throughput compared to HuggingFace by up to 24x.

• Blog post
• Repo

Prerequisites

Install the latest SkyPilot and check your setup of the cloud credentials:

pip install git+https://github.com/skypilot-org/skypilot.git
sky check

See the vLLM SkyPilot YAML for serving.

Serve a model with vLLM, launched on the cloud by SkyPilot

1. Start the serving the LLaMA-65B model on 8 A100 GPUs:

sky launch -c vllm-serve -s serve.yaml

2. Check the output of the command. There will be a sharable gradio link (like the last line of the following). Open it in your browser to use the LLaMA model to do the text completion.

(task, pid=7431) Running on public URL: https://a8531352b74d74c7d2.gradio.live

3. Optional: Serve the 13B model instead of the default 65B and use less GPU:

sky launch -c vllm-serve -s serve.yaml --gpus A100:1 --env MODEL_NAME=decapoda-research/llama-13b-hf

Serving Llama-2 with vLLM's OpenAI-compatible API server

Before you get started, you need to have access to the Llama-2 model weights on huggingface. Please check the prerequisites section in Llama-2 example for more details.

1. Start serving the Llama-2 model:

sky launch -c vllm-llama2 serve-openai-api.yaml

Optional: Only GCP offers the specified L4 GPUs currently. To use other clouds, use the --gpus flag to request other GPUs. For example, to use V100 GPUs:

sky launch -c vllm-llama2 serve-openai-api.yaml --gpus V100:1

2. Check the IP for the cluster with:

IP=$(sky status --ip vllm-llama2)

3. You can now use the OpenAI API to interact with the model.

• Query the models hosted on the cluster:

curl http://$IP:8000/v1/models

• Query a model with input prompts for text completion:

curl http://$IP:8000/v1/completions \
  -H "Content-Type: application/json" \
  -d '{
      "model": "meta-llama/Llama-2-7b-chat-hf",
      "prompt": "San Francisco is a",
      "max_tokens": 7,
      "temperature": 0
  }'

You should get a similar response as the following:

{
    "id":"cmpl-50a231f7f06a4115a1e4bd38c589cd8f",
    "object":"text_completion","created":1692427390,
    "model":"meta-llama/Llama-2-7b-chat-hf",
    "choices":[{
        "index":0,
        "text":"city in Northern California that is known",
        "logprobs":null,"finish_reason":"length"
    }],
    "usage":{"prompt_tokens":5,"total_tokens":12,"completion_tokens":7}
}

• Query a model with input prompts for chat completion:

curl http://$IP:8000/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "meta-llama/Llama-2-7b-chat-hf",
    "messages": [
      {
        "role": "system",
        "content": "You are a helpful assistant."
      },
      {
        "role": "user",
        "content": "Who are you?"
      }
    ]
  }'

You should get a similar response as the following:

{
  "id": "cmpl-879a58992d704caf80771b4651ff8cb6",
  "object": "chat.completion",
  "created": 1692650569,
  "model": "meta-llama/Llama-2-7b-chat-hf",
  "choices": [{
    "index": 0,
    "message": {
      "role": "assistant",
      "content": " Hello! I'm just an AI assistant, here to help you"
    },
    "finish_reason": "length"
  }],
  "usage": {
    "prompt_tokens": 31,
    "total_tokens": 47,
    "completion_tokens": 16
  }
}