[CI/Build] Also check DP in benchmarks throughput script

[zhewenl]

Purpose

Like #16737, DP is not really supported in the throughput benchmarking, adding a checks to raise the issue. (See discussions in #16222)

Test Plan

CUDA_VISIBLE_DEVICES=0,1 VLLM_LOGGING_LEVEL=DEBUG CUDA_LAUNCH_BLOCKING=1 VLLM_TRUST_REMOTE_CODE=1 SAFETENSORS_FAST_GPU=1 TORCH_SHOW_CPP_STACKTRACES=1 CUDA_ENABLE_CORE_DUMP_ON_EXCEPTION=1 \
vllm bench throughput --model /data/users/zhewenli/models/qwen_moe \
--tensor-parallel-size 1 --data-parallel-size 2   --enable-expert-parallel \
--max-model-len 2048 --input-len 1000 --output-len 1000 --num-prompts 50 --trust-remote-code

Test Result

before: test will hang at Processed prompts:

(EngineCore_0 pid=3839314) DEBUG 08-16 14:07:38 [core.py:728] EngineCore waiting for work.
(EngineCore_0 pid=3839314) DEBUG 08-16 14:07:38 [core.py:728] EngineCore waiting for work.
INFO 08-16 14:07:38 [llm.py:298] Supported_tasks: ['generate']
Adding requests:   0%|                                                                                                        | 0/50 [00:00<?, ?it/s](EngineCore_0 pid=3839314) DEBUG 08-16 14:07:38 [core.py:734] EngineCore loop active.
Adding requests: 100%|██████████████████████████████████████████████████████████████████████████████████████████████| 50/50 [00:00<00:00, 285.04it/s]
Processed prompts:   0%|   

after: raise errors

Traceback (most recent call last):
  File "/home/zhewenli/uv_env/vllm/bin/vllm", line 10, in <module>
    sys.exit(main())
             ^^^^^^
  File "/data/users/zhewenli/gitrepos/vllm/vllm/entrypoints/cli/main.py", line 54, in main
    args.dispatch_function(args)
  File "/data/users/zhewenli/gitrepos/vllm/vllm/entrypoints/cli/benchmark/throughput.py", line 21, in cmd
    main(args)
  File "/data/users/zhewenli/gitrepos/vllm/vllm/benchmarks/throughput.py", line 585, in main
    validate_args(args)
  File "/data/users/zhewenli/gitrepos/vllm/vllm/benchmarks/throughput.py", line 441, in validate_args
    raise ValueError(
ValueError: Data parallel is not supported in offline benchmark,             please use benchmark serving instead

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[gemini-code-assist]

Code Review

This pull request adds a check to the throughput benchmark script to prevent the use of data parallelism, which is unsupported and causes the script to hang. The change correctly raises a ValueError when data_parallel_size is greater than 1. My feedback focuses on improving the formatting of the error message string to adhere to PEP 8 style guidelines and produce a cleaner, more readable error for the user.

[gemini-code-assist]

The string continuation using a backslash (\) includes the leading whitespace from the next line in the final string, resulting in a poorly formatted error message. According to PEP 8, the preferred way to wrap long lines is by using Python's implied line continuation inside parentheses. This improves readability and avoids unintended whitespace in the string.¹

Suggested change

	raise ValueError(
	"Data parallel is not supported in offline benchmark, \
	please use benchmark serving instead"
	)
	raise ValueError(
	"Data parallel is not supported in offline benchmark, "
	"please use benchmark serving instead"
	)

Style Guide References

Footnotes

1. PEP 8 recommends using implied line continuation within parentheses for long lines over using a backslash, especially for strings, to improve readability and prevent issues with extraneous whitespace. ↩