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[V1] Revert the default max_num_seqs to V0 values for most hardware (#16158)

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Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>
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Cyrus Leung 2025-04-08 01:54:36 +08:00 committed by GitHub
parent 027b204ff1
commit 66d433b94f
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3 changed files with 6 additions and 10 deletions
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7
docs/source/getting_started/v1_user_guide.md
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@ -156,10 +156,3 @@ vLLM V1 is currently optimized for decoder-only transformers. Models requiring
cross-attention between separate encoder and decoder are not yet supported (e.g., `BartForConditionalGeneration`, `MllamaForConditionalGeneration`).
For a complete list of supported models, see the [list of supported models](https://docs.vllm.ai/en/latest/models/supported_models.html).
## Frequently Asked Questions
**I'm using vLLM V1 and I'm getting CUDA OOM errors. What should I do?**
The default `max_num_seqs` has been raised from `256` in V0 to `1024` in V1. If you encounter CUDA OOM only when using V1 engine, try setting a lower value of `max_num_seqs` or `gpu_memory_utilization`.
On the other hand, if you get an error about insufficient memory for the cache blocks, you should increase `gpu_memory_utilization` as this indicates that your GPU has sufficient memory but you're not allocating enough to vLLM for KV cache blocks.

6
tests/v1/engine/test_engine_args.py
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@ -64,15 +64,17 @@ def test_defaults_with_usage_context():
# For H100 and H200, we use larger default values.
default_llm_tokens = 16384
default_server_tokens = 8192
default_max_num_seqs = 1024
else:
default_llm_tokens = 8192
default_server_tokens = 2048
default_max_num_seqs = 256
assert vllm_config.scheduler_config.max_num_seqs == 1024
assert vllm_config.scheduler_config.max_num_seqs == default_max_num_seqs
assert vllm_config.scheduler_config.max_num_batched_tokens == default_llm_tokens # noqa: E501
engine_args = EngineArgs(model="facebook/opt-125m")
vllm_config = engine_args.create_engine_config(
UsageContext.OPENAI_API_SERVER)
assert vllm_config.scheduler_config.max_num_seqs == 1024
assert vllm_config.scheduler_config.max_num_seqs == default_max_num_seqs
assert vllm_config.scheduler_config.max_num_batched_tokens == default_server_tokens # noqa: E501

3
vllm/engine/arg_utils.py
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@ -1666,12 +1666,14 @@ class EngineArgs:
UsageContext.LLM_CLASS: 16384,
UsageContext.OPENAI_API_SERVER: 8192,
}
default_max_num_seqs = 1024
else:
# TODO(woosuk): Tune the default values for other hardware.
default_max_num_batched_tokens = {
UsageContext.LLM_CLASS: 8192,
UsageContext.OPENAI_API_SERVER: 2048,
}
default_max_num_seqs = 256
use_context_value = usage_context.value if usage_context else None
if (self.max_num_batched_tokens is None
@ -1682,7 +1684,6 @@ class EngineArgs:
"Setting max_num_batched_tokens to %d for %s usage context.",
self.max_num_batched_tokens, use_context_value)
default_max_num_seqs = 1024
if self.max_num_seqs is None:
self.max_num_seqs = default_max_num_seqs