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[V0 deprecation] Remove _set_default_args_v0 function #25409

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Merged
merged 1 commit into from
Sep 23, 2025
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[V0 deprecation] Remove _set_default_args_v0 function #25409

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83 changes: 11 additions & 72 deletions vllm/engine/arg_utils.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1147,20 +1147,15 @@ def create_engine_config(
else:
envs.set_vllm_use_v1(use_v1)

# Set default arguments for V0 or V1 Engine.
if use_v1:
self._set_default_args_v1(usage_context, model_config)
# Disable chunked prefill for POWER (ppc64le)/ARM/s390x CPUs in V1
if current_platform.is_cpu(
) and current_platform.get_cpu_architecture() in (
CpuArchEnum.POWERPC, CpuArchEnum.S390X, CpuArchEnum.ARM):
logger.info(
"Chunked prefill is not supported for ARM and POWER "
"and S390X CPUs; "
"disabling it for V1 backend.")
self.enable_chunked_prefill = False
else:
self._set_default_args_v0(model_config)
# Set default arguments for V1 Engine.
self._set_default_args(usage_context, model_config)
# Disable chunked prefill for POWER (ppc64le)/ARM/s390x CPUs in V1
if current_platform.is_cpu() and current_platform.get_cpu_architecture(
) in (CpuArchEnum.POWERPC, CpuArchEnum.S390X, CpuArchEnum.ARM):
logger.info("Chunked prefill is not supported for ARM and POWER "
"and S390X CPUs; "
"disabling it for V1 backend.")
self.enable_chunked_prefill = False
Comment on lines +1150 to +1158
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critical

While this change correctly removes the V0-specific default arguments, the removal of V0 components seems incomplete across the codebase. Several platform-specific files still contain logic that depends on VLLM_USE_V1 and might attempt to use V0 components, which are presumably removed. This could lead to runtime errors if a user sets VLLM_USE_V1=0.

For example, in vllm/platforms/cuda.py and vllm/platforms/rocm.py, the code still selects vllm.worker.worker.Worker if VLLM_USE_V1 is false. If this V0 worker has been removed, this will cause a crash.

It is recommended to update these files to either always use the V1 worker or raise an error if VLLM_USE_V1=0, similar to the approach in cpu.py, xpu.py, and tpu.py which explicitly disallow VLLM_USE_V1=0.

assert self.enable_chunked_prefill is not None

sliding_window: Optional[int] = None
Expand Down Expand Up @@ -1540,64 +1535,8 @@ def _is_v1_supported_oracle(self, model_config: ModelConfig) -> bool:

return True

def _set_default_args_v0(self, model_config: ModelConfig) -> None:
"""Set Default Arguments for V0 Engine."""

max_model_len = model_config.max_model_len
use_long_context = max_model_len > 32768
if self.enable_chunked_prefill is None:
# Chunked prefill not supported for Multimodal or MLA in V0.
if model_config.is_multimodal_model or model_config.use_mla:
self.enable_chunked_prefill = False

# Enable chunked prefill by default for long context (> 32K)
# models to avoid OOM errors in initial memory profiling phase.
elif use_long_context:
is_gpu = current_platform.is_cuda()
use_sliding_window = (model_config.get_sliding_window()
is not None)
use_spec_decode = self.speculative_config is not None

if (is_gpu and not use_sliding_window and not use_spec_decode
and not self.enable_lora):
self.enable_chunked_prefill = True
logger.warning(
"Chunked prefill is enabled by default for models "
"with max_model_len > 32K. Chunked prefill might "
"not work with some features or models. If you "
"encounter any issues, please disable by launching "
"with --enable-chunked-prefill=False.")

if self.enable_chunked_prefill is None:
self.enable_chunked_prefill = False

if not self.enable_chunked_prefill and use_long_context:
logger.warning(
"The model has a long context length (%s). This may cause"
"OOM during the initial memory profiling phase, or result "
"in low performance due to small KV cache size. Consider "
"setting --max-model-len to a smaller value.", max_model_len)

# Disable prefix caching for multimodal models for VLLM_V0.
if self.enable_prefix_caching and model_config.is_multimodal_model:
logger.warning(
"--enable-prefix-caching is not supported for multimodal "
"models in V0 and has been disabled.")
self.enable_prefix_caching = False

if self.enable_prompt_embeds:
logger.warning(
"--enable-prompt-embeds and --enable-prefix-caching "
"are not supported together in V0. Prefix caching has "
"been disabled.")
self.enable_prefix_caching = False

# Set max_num_seqs to 256 for VLLM_V0.
if self.max_num_seqs is None:
self.max_num_seqs = 256

def _set_default_args_v1(self, usage_context: UsageContext,
model_config: ModelConfig) -> None:
def _set_default_args(self, usage_context: UsageContext,
model_config: ModelConfig) -> None:
"""Set Default Arguments for V1 Engine."""

# V1 always uses chunked prefills and prefix caching
Expand Down