Benchmark C++ Runtime

This document explains how to benchmark the models supported by TensorRT-LLM on a single GPU, a single node with multiple GPUs or multiple nodes with multiple GPUs using the C++ runtime.

Usage

1. Build TensorRT-LLM and benchmarking source code

Please follow the installation document to build TensorRT-LLM.

Note that the benchmarking source code for C++ runtime is not built by default, you can use the argument --benchmarks in build_wheel.py to build the corresponding executable.

2. Launch C++ benchmarking (Inflight/V1 batching)

Prepare dataset

Run a preprocessing script to prepare/generate dataset into a json that gptManagerBenchmark can consume later. The processed output json has input tokens length, input token ids and output tokens length.

For tokenizer, specifying the path to the local tokenizer that have already been downloaded, or simply the name of the tokenizer from HuggingFace like meta-llama/Llama-2-7b will both work. The tokenizer will be downloaded automatically for the latter case.

This tool can be used in 3 different modes of traffic generation: dataset, token-norm-dist and token-unif-dist.

1 – Dataset

The tool will tokenize the words and instruct the model to generate a specified number of output tokens for a request.

python3 prepare_dataset.py \
    --tokenizer <path/to/tokenizer> \
    --output preprocessed_dataset.json
    dataset
    --dataset-name <name of the dataset> \
    --dataset-split <split of the dataset to use> \
    --dataset-input-key <dataset dictionary key for input> \
    --dataset-prompt-key <dataset dictionary key for prompt> \
    --dataset-output-key <dataset dictionary key for output> \
    [--num-requests 100] \
    [--max-input-len 1000] \
    [--output-len-dist 100,10]

For datasets that don't have prompt key, set --dataset-prompt instead. Take cnn_dailymail dataset for example:

python3 prepare_dataset.py \
    --tokenizer <path/to/tokenizer> \
    --output cnn_dailymail.json
    dataset
    --dataset-name cnn_dailymail \
    --dataset-split validation \
    --dataset-config-name 3.0.0 \
    --dataset-input-key article \
    --dataset-prompt "Summarize the following article:" \
    --dataset-output-key "highlights" \
    [--num-requests 100] \
    [--max-input-len 1000] \
    [--output-len-dist 100,10]

2 – Normal token length distribution

This mode allows the user to generate normally distributed token lengths with a mean and std deviation specified. For example, setting mean=100 and stdev=10 would generate requests where 95.4% of values are in <80,120> range following the normal probability distribution. Setting stdev=0 will generate all requests with the same mean number of tokens.

python prepare_dataset.py \
  --output token-norm-dist.json \
  --tokenizer <path/to/tokenizer> \
   token-norm-dist \
   --num-requests 100 \
   --input-mean 100 --input-stdev 10 \
   --output-mean 15 --output-stdev 0

2 – Uniform token length distribution

This mode allows the user to generate uniformly distributed token lengths with min and max lengths specified. For example, setting min=50 and max=100 would generate requests where lengths are in the range [50, 100] following the uniform probability distribution. Setting min=x and max=x will generate all requests with the same mean number of tokens x.

python prepare_dataset.py \
  --output token-norm-dist.json \
  --tokenizer <path/to/tokenizer> \
   token-unif-dist \
   --num-requests 100 \
   --input-min 50 --input-max 100 \
   --output-min 10 --output-max 15

Prepare TensorRT-LLM engines

Before you launch C++ benchmarking, please make sure that you have already built engine(s) using trtllm-build command. For more details on building engine(s), please refer to the Quick Start Guide.

Launch benchmarking

For detailed usage, you can do the following

cd cpp/build

# You can directly execute the binary for help information
./benchmarks/gptManagerBenchmark --help

gptManagerBenchmark now supports decoder-only models and encoder-decoder models.

Decoder-only Models

To benchmark decoder-only models, pass in the engine path with --engine_dir as executable input argument.

Take GPT-350M as an example for 2-GPU inflight batching
```
mpirun -n 2 ./benchmarks/gptManagerBenchmark \
    --engine_dir ../../examples/models/core/gpt/trt_engine/gpt2-ib/fp16/2-gpu/ \
    --request_rate 10 \
    --dataset ../../benchmarks/cpp/preprocessed_dataset.json \
    --max_num_samples 500
```
gptManagerBenchmark by default uses the high-level C++ API defined by the executor::Executor class (see cpp/include/tensorrt_llm/executor/executor.h).

Encoder-Decoder Models To benchmark encoder-decoder models, pass in the encoder engine path with --encoder_engine_dir and the decoder engine path with --decoder_engine_dir as executable input arguments. --decoder_engine_dir is an alias of --engine_dir.

Currently encoder-decoder engines only support --api executor, --type IFB, --enable_kv_cache_reuse false, which are all default values so no specific settings required.

Prepare t5-small engine from examples/models/core/enc_dec for the encoder-decoder 4-GPU inflight batching example.

Prepare the dataset suitable for engine input lengths.

python prepare_dataset.py \
    --tokenizer <path/to/tokenizer> \
    --output cnn_dailymail.json \
    dataset \
    --dataset-name cnn_dailymail \
    --dataset-split validation \
    --dataset-config-name 3.0.0 \
    --dataset-input-key article \
    --dataset-prompt "Summarize the following article:" \
    --dataset-output-key "highlights" \
    --num-requests 100 \
    --max-input-len 512 \
    --output-len-dist 128,20

Run the benchmark

mpirun --allow-run-as-root -np 4 ./benchmarks/gptManagerBenchmark \
    --encoder_engine_dir ../../examples/models/core/enc_dec/tmp/trt_engines/t5-small-4gpu/bfloat16/encoder \
    --decoder_engine_dir ../../examples/models/core/enc_dec/tmp/trt_engines/t5-small-4gpu/bfloat16/decoder \
    --dataset cnn_dailymail.json

Emulated static batching

To emulate the deprecated gptSessionBenchmark static batching, you can use gptManagerBenchmark with the --static_emulated_batch_size and --static_emulated-timeout arguments.

Given a static_emulated_batch_size of n the server will wait for n requests to arrive before submitting them to the batch manager at once. If the static_emulated_timeout (in ms) is reached before n requests are collected, the batch will be submitted prematurely with the current request count. New batches will only be submitted once the previous batch has been processed comepletely.

Datasets with fixed input/output lengths for benchmarking can be generated with the preprocessing script, e.g.

 python prepare_dataset.py \
  --output tokens-fixed-lengths.json \
  --tokenizer <path/to/tokenizer> \
   token-norm-dist \
   --num-requests 128 \
   --input-mean 60 --input-stdev 0 \
   --output-mean 20 --output-stdev 0

Take GPT-350M as an example for single GPU with static batching

./benchmarks/gptManagerBenchmark \
    --engine_dir ../../examples/models/core/gpt/trt_engine/gpt2/fp16/1-gpu/ \
    --request_rate -1 \
    --static_emulated_batch_size 32 \
    --static_emulated_timeout 100 \
    --dataset ../../benchmarks/cpp/tokens-fixed-lengths.json

Benchmarking LoRA

Using either of the prepare_dataset.py methods above, add --rand-task-id <start-id> <end-id> to the command. This will add a random task_id from <start-id> to <end-id> inclusive. You can then use utils/generate_rand_loras.py to generate random LoRA weights for benchmarking purposes. utils/generate_rand_loras.py takes an example LoRA for the model you are benchmarking. Then you can run gptManagerBenchmark with --type IFB and --lora_dir /path/to/utils/generate_rand_loras/output

End-to-end LoRA benchmarking script

git-lfs clone https://huggingface.co/meta-llama/Llama-2-13b-hf
git-lfs clone https://huggingface.co/hfl/chinese-llama-2-lora-13b

MODEL_CHECKPOINT=Llama-2-13b-hf
CONVERTED_CHECKPOINT=Llama-2-13b-hf-ckpt
TOKENIZER=Llama-2-13b-hf
LORA_ENGINE=Llama-2-13b-hf-engine

DTYPE=float16
TP=2
PP=1
MAX_LEN=1024
MAX_BATCH=32
NUM_LAYERS=40
MAX_LORA_RANK=64
NUM_LORA_MODS=7
EOS_ID=2

SOURCE_LORA=chinese-llama-2-lora-13b
CPP_LORA=chinese-llama-2-lora-13b-cpp

EG_DIR=/tmp/lora-eg

# Build lora enabled engine
python examples/models/core/llama/convert_checkpoint.py --model_dir ${MODEL_CHECKPOINT} \
                              --output_dir ${CONVERTED_CHECKPOINT} \
                              --dtype ${DTYPE} \
                              --tp_size ${TP} \
                              --pp_size 1

${HOME}/.local/bin/trtllm-build \
    --checkpoint_dir ${CONVERTED_CHECKPOINT} \
    --output_dir ${LORA_ENGINE} \
    --max_batch_size ${MAX_BATCH} \
    --max_input_len $MAX_LEN \
    --max_seq_len $((2*${MAX_LEN})) \
    --gemm_plugin float16 \
    --lora_plugin float16 \
    --use_paged_context_fmha enable \
    --lora_target_modules attn_q attn_k attn_v attn_dense mlp_h_to_4h mlp_4h_to_h mlp_gate \
    --max_lora_rank ${MAX_LORA_RANK}

NUM_LORAS=(8 16)
NUM_REQUESTS=1024

# Convert LoRA to cpp format
python examples/hf_lora_convert.py \
    -i $SOURCE_LORA \
    --storage-type $DTYPE \
    -o $CPP_LORA

# Prepare datasets
mkdir -p $EG_DIR/data

# Prepare dataset without lora_task_id
python benchmarks/cpp/prepare_dataset.py \
    --output "${EG_DIR}/data/token-norm-dist.json" \
    --tokenizer $TOKENIZER \
    token-norm-dist \
    --num-requests $NUM_REQUESTS \
    --input-mean 256 --input-stdev 16 --output-mean 128 --output-stdev 24

# Prepare dataset with lora_task_ids from 0 - $nloras
for nloras in ${NUM_LORAS[@]}; do
    python benchmarks/cpp/prepare_dataset.py \
        --output "${EG_DIR}/data/token-norm-dist-lora-${nloras}.json" \
        --rand-task-id 0 $(( $nloras - 1 )) \
        --tokenizer $TOKENIZER \
        token-norm-dist \
        --num-requests $NUM_REQUESTS \
        --input-mean 256 --input-stdev 16 --output-mean 128 --output-stdev 24
done

# Generate random lora weights for 16 adapters
python benchmarks/cpp/utils/generate_rand_loras.py ${CPP_LORA} ${EG_DIR}/loras 16

# Perform benchmarking

# First run inference without LoRAs
mkdir -p ${EG_DIR}/log-base-lora
mpirun -n ${TP} --output-filename ${EG_DIR}/log-base-lora \
    cpp/build/benchmarks/gptManagerBenchmark \
    --engine_dir $LORA_ENGINE \
    --type IFB \
    --dataset "${EG_DIR}/data/token-norm-dist.json" \
    --lora_host_cache_bytes 8589934592 \
    --lora_num_device_mod_layers $(( 32 * $NUM_LAYERS * $NUM_LORA_MODS * $MAX_LORA_RANK )) \
    --kv_cache_free_gpu_mem_fraction 0.70 \
    --log_level info \
    --eos_id ${EOS_ID}

# Now run inference with various numbers or loras
# The host cache is set large enough to hold all the LoRAs in lora_dir
# GPU cache is set to hold 16 LoRAs
# This benchmark will preload all the LoRAs into the host cache
# We run inference on a range of active LoRAs exercising different cache miss rates.
for nloras in ${NUM_LORAS[@]}; do
    mkdir -p ${EG_DIR}/log-lora-${nloras}
    mpirun -n ${TP} --output-filename "${EG_DIR}/log-lora-${nloras}" \
        cpp/build/benchmarks/gptManagerBenchmark \
        --engine_dir $LORA_ENGINE \
        --type IFB \
        --dataset "${EG_DIR}/data/token-norm-dist-lora-${nloras}.json" \
        --lora_host_cache_bytes 8589934592 \
        --lora_num_device_mod_layers $(( 16 * $NUM_LAYERS * $NUM_LORA_MODS * $MAX_LORA_RANK )) \
        --kv_cache_free_gpu_mem_fraction 0.70 \
        --log_level info \
        --eos_id ${EOS_ID} \
        --lora_dir ${EG_DIR}/loras
done

3. [DEPRECATED] Launch C++ static batching benchmarking (Fixed BatchSize/InputLen/OutputLen)

Prepare TensorRT-LLM engine(s)

Before you launch C++ benchmarking, please make sure that you have already built engine(s) using TensorRT-LLM API, C++ benchmarking code cannot generate engine(s) for you.

Use trtllm-build to build the TRT-LLM engine. Alternatively, if you have already benchmarked Python Runtime, you can reuse the engine(s) built previously, please see that document.

Launch benchmarking

For detailed usage, you can do the following

cd cpp/build

# You can directly execute the binary for help information
./benchmarks/bertBenchmark --help

Please note that the expected outputs in that document are only for reference, specific performance numbers depend on the GPU you're using.

4.launch C++ disaggServerBenchmark

Currently ,TensorRT-LLM has limited support for disaggregated inference, where context and generation phases of a request can run on different executors. disaggServerBenchmark is a tool to benchmark disaggregated inference.

Usage

For detailed usage, you can do the following

cd cpp/build

# You can directly execute the binary for help information
./benchmarks/disaggServerBenchmark --help

disaggServerBenchmark only supports decoder-only models. Here is the basic usage:

export TRTLLM_USE_UCX_KVCACHE=1
mpirun -n ${proc} benchmarks/disaggServerBenchmark --context_engine_dirs ${context_engine_0},${context_engine_1}...,${context_engine_{m-1}} \
--generation_engine_dirs ${generation_engine_0},${generation_engine_1}...,${generation_engine_{n-1}} --dataset ${dataset_path}

This command will launch m context engines and n generation engines. You need to ensure proc is equal to the sum of the number of processes required for each engine plus 1. Since we use orchestrator mode for disaggServerBenchmark we need an additional process as the orchestrator. For example, if there are two context engines (one is TP2_PP1,another is TP1_PP1) and two generation engines(one is TP2_PP1,another is TP1_PP1), then the proc value should be set to 7.

for example:

export TRTLLM_USE_UCX_KVCACHE=1
mpirun -n 7 benchmarks/disaggServerBenchmark --context_engine_dirs ${llama_7b_tp2_pp1_dir},${llama_7b_tp1_pp1_dir} --generation_engine_dirs ${llama_7b_tp1_pp1_dir},${llama_7b_tp2_pp1_dir} --dataset ${dataset_path}

# need 6 gpus and 7 processes to launch the benchmark.

Known Issues

1. error `All available sequence slots are used`

If generation_engine's pp_size >1, the error "All available sequence slots are used" may occur, setting and adjusting the parameter --request_rate may help alleviate the problem.

2.KVCache transfers are by default via PCIE on single node.

Currently, because of the dependency libraries,KVCache transfers are by default via PCIE on single node.

If you want to use NVLink, please check the UCX version in the container by running:

ucx_info -v

If the UCX version is less than or equal to 1.17, set UCX_RNDV_FRAG_MEM_TYPE=cuda to enable KvCache transfers using NVLink. If the UCX version is 1.18, please set UCX_CUDA_COPY_ASYNC_MEM_TYPE=cuda to enable KvCache transfers using NVLink.