From 1a0f4defb76c5c6d3b6ba49ca2f560aad5afdab4 Mon Sep 17 00:00:00 2001 From: Wentao Ye <44945378+yewentao256@users.noreply.github.com> Date: Wed, 22 Oct 2025 08:12:21 -0400 Subject: [PATCH] [Log] Add Warning for `LLM(data_parallel_size=k)` single-process DP Usage (#27282) Signed-off-by: yewentao256 --- vllm/entrypoints/llm.py | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/vllm/entrypoints/llm.py b/vllm/entrypoints/llm.py index e82db693c92db..7cf0ad671cf2e 100644 --- a/vllm/entrypoints/llm.py +++ b/vllm/entrypoints/llm.py @@ -285,6 +285,16 @@ class LLM: else: structured_outputs_instance = StructuredOutputsConfig() + # warn about single-process data parallel usage. + _dps = int(kwargs.get("data_parallel_size", 1)) + if _dps > 1: + raise ValueError( + f"LLM(data_parallel_size={_dps}) is not supported for single-" + "process usage and may hang. Please use " + "the explicit multi-process data-parallel example at " + "'examples/offline_inference/data_parallel.py'." + ) + engine_args = EngineArgs( model=model, runner=runner,