Run benchmarking with trtllm-serve#

TensorRT-LLM provides the OpenAI-compatiable API via trtllm-serve command. A complete reference for the API is available in the OpenAI API Reference.

This step-by-step tutorial covers the following topics for running online serving benchmarking with Llama 3.1 70B:

  • Methodology Introduction

  • Launch the OpenAI-Compatibale Server with NGC container

  • Run the performance benchmark

  • Using extra_llm_api_options

Methodology Introduction#

The overall performance benchmarking involves:

  1. Launch the OpenAI-compatible service with trtllm-serve

  2. Run the benchmark with benchmark_serving.py

Launch the NGC container#

TensorRT-LLM distributes the pre-built container on NGC Catalog.

You can launch the container using the following command:

docker run --rm --ipc host -p 8000:8000 --gpus all -it nvcr.io/nvidia/tensorrt-llm/release

Start the trtllm-serve service#

[!WARNING] The commands and configurations presented in this document are for illustrative purposes only. They serve as examples and may not deliver the optimal performance for your specific use case. Users are encouraged to tune the parameters based on their hardware and workload. For benchmarking purposes, first create a bash script using the following code and name it start.sh.

#! /bin/bash
model_path=/path/to/llama3.1_70B
extra_llm_api_file=/tmp/extra-llm-api-config.yml

cat << EOF > ${extra_llm_api_file}
enable_attention_dp: false
print_iter_log: true
cuda_graph_config:
  enable_padding: true
  max_batch_size: 1024
kv_cache_config:
  dtype: fp8
EOF

trtllm-serve ${model_path} \
    --max_batch_size 1024 \
    --max_num_tokens 2048 \
    --max_seq_len 1024 \
    --kv_cache_free_gpu_memory_fraction 0.9 \
    --tp_size 1 \
    --ep_size 1 \
    --trust_remote_code \
    --extra_llm_api_options ${extra_llm_api_file}

[!NOTE] The trtllm-llmapi-launch is a script that launches the LLM-API code on Slurm-like systems, and can support multi-node and multi-GPU setups. e.g, trtllm-llmapi-launch trtllm-serve …..

Run the start.sh script in the background with the following command:

bash -x start.sh &

Once the serving is set up, it will generate the output log as shown below.

INFO:     Started server process [80833]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://localhost:8000 (Press CTRL+C to quit)

Run the benchmark#

Similar to starting trtllm-serve, create a script to execute the benchmark using the following code and name it bench.sh.

concurrency_list="1 2 4 8 16 32 64 128 256"
multi_round=5
isl=1024
osl=1024
result_dir=/tmp/llama3.1_output
model_path=/path/to/llama3.1_70B

for concurrency in ${concurrency_list}; do
    num_prompts=$((concurrency * multi_round))
    python -m tensorrt_llm.serve.scripts.benchmark_serving \
        --model ${model_path} \
        --backend openai \
        --dataset-name "random" \
        --random-input-len ${isl} \
        --random-output-len ${osl} \
        --random-prefix-len 0 \
        --num-prompts ${num_prompts} \
        --max-concurrency ${concurrency} \
        --ignore-eos \
        --save-result \
        --result-dir "${result_dir}" \
        --result-filename "concurrency_${concurrency}.json" \
        --percentile-metrics "ttft,tpot,itl,e2el"
done

Then we can run the benchmark using the command below.

bash -x bench.sh &> output_bench.log

Below is some example TensorRT-LLM serving benchmark output. Your actual results may vary.

============ Serving Benchmark Result ============
Successful requests:                     1
Benchmark duration (s):                  1.64
Total input tokens:                      1024
Total generated tokens:                  1024
Request throughput (req/s):              0.61
Output token throughput (tok/s):         622.56
Total Token throughput (tok/s):          1245.12
User throughput (tok/s):                 623.08
Mean Request AR:                         0.9980
Median Request AR:                       0.9980
---------------Time to First Token----------------
Mean TTFT (ms):                          12.83
Median TTFT (ms):                        12.83
P99 TTFT (ms):                           12.83
-----Time per Output Token (excl. 1st token)------
Mean TPOT (ms):                          1.59
Median TPOT (ms):                        1.59
P99 TPOT (ms):                           1.59
---------------Inter-token Latency----------------
Mean ITL (ms):                           1.59
Median ITL (ms):                         1.59
P99 ITL (ms):                            1.77
----------------End-to-end Latency----------------
Mean E2EL (ms):                          1643.44
Median E2EL (ms):                        1643.44
P99 E2EL (ms):                           1643.44
==================================================

Key Metrics#

  • Median Time to First Token (TTFT)

    • The typical time elapsed from when a request is sent until the first output token is generated.

  • Median Time Per Output Token (TPOT)

    • The typical time required to generate each token after the first one.

  • Median Inter-Token Latency (ITL)

    • The typical time delay between the completion of one token and the completion of the next.

  • Median End-to-End Latency (E2EL)

    • The typical total time from when a request is submitted until the final token of the response is received.

  • Total Token Throughput

    • The combined rate at which the system processes both input (prompt) tokens and output (generated) tokens.

About extra_llm_api_options#

trtllm-serve provides extra_llm_api_options knob to overwrite the parameters specified by trtllm-serve. Generally, We create a YAML file that contains various performance switches. e.g

  cuda_graph_config:
   padding_enabled: true
  print_iter_log: true
  kv_cache_dtype: fp8
  enable_attention_dp: true

The following is a list of common performance switches.

kv_cache_config#

 Description: A section for configuring the Key-Value (KV) cache.

 Options:

  dtype: Sets the data type for the KV cache.

  Default: auto (uses the data type specified in the model checkpoint).

cuda_graph_config#

 Description: A section for configuring CUDA graphs to optimize performance.

 Options:

  enable_padding: If true, input batches are padded to the nearest cuda_graph_batch_size. This can significantly improve performance.

  Default: false

  max_batch_size: Sets the maximum batch size for which a CUDA graph will be created.

  Default: 0

  Recommendation: Set this to the same value as the –max_batch_size command-line option.

  batch_sizes: A specific list of batch sizes to create CUDA graphs for.

  Default: None

moe_config#

 Description: Configuration for Mixture-of-Experts (MoE) models.

 Options:

  backend: The backend to use for MoE operations.

  Default: CUTLASS

attention_backend#

 Description: The backend to use for attention calculations.

 Default: TRTLLM

See the TorchLlmArgs class for the full list of options which can be used in the extra_llm_api_options.