vllm/.buildkite/performance-benchmarks/README.md

vLLM benchmark suite

Introduction

This directory contains a benchmarking suite for developers to run locally and gain clarity on whether their PR improves/degrades vllm's performance. vLLM also maintains a continuous performance benchmark under perf.vllm.ai, hosted under PyTorch CI HUD.

Performance benchmark quick overview

Benchmarking Coverage: latency, throughput and fix-qps serving on B200, A100, H100, Intel® Xeon® Processors, Intel® Gaudi® 3 Accelerators and Arm® Neoverse™ with different models.

Benchmarking Duration: about 1hr.

For benchmarking developers: please try your best to constraint the duration of benchmarking to about 1 hr so that it won't take forever to run.

Trigger the benchmark

The benchmark needs to be triggered manually:

bash .buildkite/performance-benchmarks/scripts/run-performance-benchmarks.sh

Runtime environment variables:

• ON_CPU: set the value to '1' on Intel® Xeon® and Arm® Neoverse™ Processors. Default value is 0.
• SERVING_JSON: JSON file to use for the serving tests. Default value is empty string (use default file).
• LATENCY_JSON: JSON file to use for the latency tests. Default value is empty string (use default file).
• THROUGHPUT_JSON: JSON file to use for the throughout tests. Default value is empty string (use default file).
• REMOTE_HOST: IP for the remote vLLM service to benchmark. Default value is empty string.
• REMOTE_PORT: Port for the remote vLLM service to benchmark. Default value is empty string.

Performance benchmark details

See performance-benchmarks-descriptions.md for detailed descriptions, and use tests/latency-tests.json, tests/throughput-tests.json, tests/serving-tests.json to configure the test cases.

NOTE: For Intel® Xeon® Processors, use tests/latency-tests-cpu.json, tests/throughput-tests-cpu.json, tests/serving-tests-cpu.json instead. For Intel® Gaudi® 3 Accelerators, use tests/latency-tests-hpu.json, tests/throughput-tests-hpu.json, tests/serving-tests-hpu.json instead. For Arm® Neoverse™, use tests/latency-tests-arm64-cpu.json, tests/throughput-tests-arm64-cpu.json, tests/serving-tests-arm64-cpu.json instead.

Latency test

Here is an example of one test inside latency-tests.json:

[
    {
        "test_name": "latency_llama8B_tp1",
        "parameters": {
            "model": "meta-llama/Meta-Llama-3-8B",
            "tensor_parallel_size": 1,
            "load_format": "dummy",
            "num_iters_warmup": 5,
            "num_iters": 15
        }
    },
]

In this example:

• The test_name attributes is a unique identifier for the test. In latency-tests.json, it must start with latency_.
• The parameters attribute control the command line arguments to be used for vllm bench latency. Note that please use underline _ instead of the dash - when specifying the command line arguments, and run-performance-benchmarks.sh will convert the underline to dash when feeding the arguments to vllm bench latency. For example, the corresponding command line arguments for vllm bench latency will be --model meta-llama/Meta-Llama-3-8B --tensor-parallel-size 1 --load-format dummy --num-iters-warmup 5 --num-iters 15

Note that the performance numbers are highly sensitive to the value of the parameters. Please make sure the parameters are set correctly.

WARNING: The benchmarking script will save json results by itself, so please do not configure --output-json parameter in the json file.

Throughput test

The tests are specified in throughput-tests.json. The syntax is similar to latency-tests.json, except for that the parameters will be fed forward to vllm bench throughput.

The number of this test is also stable -- a slight change on the value of this number might vary the performance numbers by a lot.

Serving test

We test the throughput by using vllm bench serve with request rate = inf to cover the online serving overhead. The corresponding parameters are in serving-tests.json, and here is an example:

[
    {
        "test_name": "serving_llama8B_tp1_sharegpt",
        "qps_list": [1, 4, 16, "inf"],
        "server_parameters": {
            "model": "meta-llama/Meta-Llama-3-8B",
            "tensor_parallel_size": 1,
            "swap_space": 16,
            "disable_log_stats": "",
            "load_format": "dummy"
        },
        "client_parameters": {
            "model": "meta-llama/Meta-Llama-3-8B",
            "backend": "vllm",
            "dataset_name": "sharegpt",
            "dataset_path": "./ShareGPT_V3_unfiltered_cleaned_split.json",
            "num_prompts": 200
        }
    },
]

Inside this example:

• The test_name attribute is also a unique identifier for the test. It must start with serving_.
• The server-parameters includes the command line arguments for vLLM server.
• The client-parameters includes the command line arguments for vllm bench serve.
• The qps_list controls the list of qps for test. It will be used to configure the --request-rate parameter in vllm bench serve

The number of this test is less stable compared to the delay and latency benchmarks (due to randomized sharegpt dataset sampling inside benchmark_serving.py), but a large change on this number (e.g. 5% change) still vary the output greatly.

WARNING: The benchmarking script will save json results by itself, so please do not configure --save-results or other results-saving-related parameters in serving-tests.json.

Default Parameters Field

We can specify default parameters in a JSON field with key defaults. Parameters defined in the field are applied globally to all serving tests, and can be overridden in test case fields. Here is an example:

An Example of default parameters field

{
  "defaults": {
    "qps_list": [
      "inf"
    ],
    "server_environment_variables": {
      "VLLM_ALLOW_LONG_MAX_MODEL_LEN": 1
    },
    "server_parameters": {
      "tensor_parallel_size": 1,
      "dtype": "bfloat16",
      "block_size": 128,
      "disable_log_stats": "",
      "load_format": "dummy"
    },
    "client_parameters": {
      "backend": "vllm",
      "dataset_name": "random",
      "random-input-len": 128,
      "random-output-len": 128,
      "num_prompts": 200,
      "ignore-eos": ""
    }
  },
  "tests": [
    {
      "test_name": "serving_llama3B_tp2_random_128_128",
      "server_parameters": {
        "model": "meta-llama/Llama-3.2-3B-Instruct",
        "tensor_parallel_size": 2,
      },
      "client_parameters": {
        "model": "meta-llama/Llama-3.2-3B-Instruct",
      }
    },
    {
      "test_name": "serving_qwen3_tp4_random_128_128",
      "server_parameters": {
        "model": "Qwen/Qwen3-14B",
        "tensor_parallel_size": 4,
      },
      "client_parameters": {
        "model": "Qwen/Qwen3-14B",
      }
    },
  ]
}

Visualizing the results

The convert-results-json-to-markdown.py helps you put the benchmarking results inside a markdown table, by formatting descriptions.md with real benchmarking results. You can find the result presented as a table inside the buildkite/performance-benchmark job page. If you do not see the table, please wait till the benchmark finish running. The json version of the table (together with the json version of the benchmark) will be also attached to the markdown file. The raw benchmarking results (in the format of json files) are in the Artifacts tab of the benchmarking.

Performance Results Comparison

Follow the instructions in performance results comparison to analyze performance results and the sizing guide.