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[V1] Raise error if chunked prefill is explicitly disabled #21645

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22quinn wants to merge 2 commits into from
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[V1] Raise error if chunked prefill is explicitly disabled #21645

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8802e82
raise error if disable chunked prefill for v1
22quinn Jul 26, 2025
e685025
test
22quinn Jul 26, 2025
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5 changes: 2 additions & 3 deletions tests/conftest.py
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Original file line number Diff line number Diff line change
Expand Up @@ -761,8 +761,7 @@ class VllmRunner:
- `max_model_len`: Set to `1024` instead of `None` to reduce memory usage.
- `block_size`: To reduce memory usage, set default to `64` if on XPU
devices, otherwise default to `16`.
- `enable_chunked_prefill`: Set to `False` instead of `None` for
test reproducibility.
- `enable_chunked_prefill`: Set to `None` to support V1 tests.

@22quinn 22quinn Jul 26, 2025

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@DarkLight1337 do you know the context for this? Feels we can set False individually for tests that need them?

@DarkLight1337 DarkLight1337 Jul 26, 2025

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I forgot, it has been so long ago

- `enforce_eager`: Set to `False` to test CUDA graph.
"""

Expand All @@ -779,7 +778,7 @@ def __init__(
disable_log_stats: bool = True,
tensor_parallel_size: int = 1,
block_size: int = 16 if not torch.xpu.is_available() else 64,
enable_chunked_prefill: Optional[bool] = False,
enable_chunked_prefill: Optional[bool] = None,
swap_space: int = 4,
enforce_eager: Optional[bool] = False,
**kwargs,
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3 changes: 3 additions & 0 deletions vllm/engine/arg_utils.py
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Expand Up @@ -1529,6 +1529,9 @@ def _set_default_args_v1(self, usage_context: UsageContext,
# for non-pooling tasks.
# For pooling tasks the default is False
if model_config.runner_type != "pooling":
if self.enable_chunked_prefill is False:

@DarkLight1337 DarkLight1337 Jul 26, 2025

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@WoosukKwon does it make sense to disable this completely?

raise ValueError(
"Cannot disable chunked prefill for V1 engine.")
self.enable_chunked_prefill = True
if self.enable_prefix_caching is None:
self.enable_prefix_caching = True
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