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[Bugfix][DCP] Set default CUDAGraphMode to PIECEWISE for DCP #26574

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Merged
merged 4 commits into from
Oct 12, 2025
Merged

[Bugfix][DCP] Set default CUDAGraphMode to PIECEWISE for DCP #26574

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fd6b08b
Set default cudagraph mode to piecewise for DCP
FENP Oct 10, 2025
d97095f
add warning logs
FENP Oct 10, 2025
dace6f0
pre-commit check fix
FENP Oct 10, 2025
a022317
remove redundant check
FENP Oct 10, 2025
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4 changes: 4 additions & 0 deletions vllm/config/vllm.py
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Original file line number Diff line number Diff line change
Expand Up @@ -346,6 +346,10 @@ def __post_init__(self):
or self.model_config.is_encoder_decoder
):
self.compilation_config.cudagraph_mode = CUDAGraphMode.PIECEWISE

# decode context parallel do not support full cudagraphs now.
if self.parallel_config.decode_context_parallel_size > 1:
self.compilation_config.cudagraph_mode = CUDAGraphMode.PIECEWISE
Comment on lines 351 to 357
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@gemini-code-assist gemini-code-assist bot Oct 10, 2025

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critical

This implementation unconditionally sets cudagraph_mode to PIECEWISE if decode context parallelism (DCP) is enabled. This is too aggressive as it will override a user's explicit choice to disable CUDA graphs (e.g., cudagraph_mode=NONE), which might be done for debugging purposes.

A better approach is to only downgrade the mode to PIECEWISE if a FULL CUDA graph mode was requested, as those are the ones incompatible with DCP. This change also adds a warning to inform the user about the automatic adjustment.

if self.parallel_config.decode_context_parallel_size > 1 and \
                    self.compilation_config.cudagraph_mode.has_full_cudagraphs():
                    logger.warning(
                        "Decode context parallel (DCP) is enabled, which is "
                        "incompatible with full CUDA graphs. Downgrading "
                        "cudagraph_mode from %s to PIECEWISE.",
                        self.compilation_config.cudagraph_mode.name)
                    self.compilation_config.cudagraph_mode = CUDAGraphMode.PIECEWISE

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@FENP FENP Oct 10, 2025

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These code snippets will only execute when cudagraph_mode is not explicitly set by users.

else:
self.compilation_config.cudagraph_mode = CUDAGraphMode.NONE

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