[Bug] Fix torch dynamo warning Dynamo detected a call to a `functools.lru_cache` (#29038)

Signed-off-by: yewentao256 <zhyanwentao@126.com>

tests/v1/determinism/conftest.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-
 import pytest
 
+import vllm.model_executor.layers.batch_invariant as batch_invariant
+
 
 @pytest.fixture(autouse=True)
 def enable_batch_invariant_mode(monkeypatch: pytest.MonkeyPatch):
     """Automatically enable batch invariant kernel overrides for all tests."""
+    monkeypatch.setattr(batch_invariant, "VLLM_BATCH_INVARIANT", True)
     monkeypatch.setenv("VLLM_BATCH_INVARIANT", "1")
-    yield

tests/v1/determinism/test_batch_invariance.py

@@ -6,29 +6,16 @@ import random
 
 import pytest
 import torch
-from utils import _extract_step_logprobs, _random_prompt, skip_unsupported
+from utils import (
+    BACKENDS,
+    _extract_step_logprobs,
+    _random_prompt,
+    resolve_model_name,
+    skip_unsupported,
+)
 
+import vllm.model_executor.layers.batch_invariant as batch_invariant
 from vllm import LLM, SamplingParams
-from vllm.platforms import current_platform
-
-BACKENDS: list[str] = [
-    "FLASH_ATTN",
-    "FLASHINFER",
-]
-
-if current_platform.is_cuda() and current_platform.is_device_capability(90):
-    BACKENDS.append("FLASH_ATTN_MLA")
-
-DEFAULT_MODEL = "Qwen/Qwen3-1.7B"
-MLA_MODEL = "deepseek-ai/DeepSeek-V2-Lite-Chat"
-
-
-def resolve_model_name(backend: str) -> str:
-    """Resolve the model name for the given backend, respecting env overrides."""
-    model = os.getenv("VLLM_TEST_MODEL", DEFAULT_MODEL)
-    if backend.endswith("MLA") and model == DEFAULT_MODEL:
-        return MLA_MODEL
-    return model
 
 
 @skip_unsupported
@@ -454,14 +441,10 @@ def test_logprobs_without_batch_invariance_should_fail(
     The test will PASS if we detect differences (proving batch invariance matters).
     The test will FAIL if everything matches (suggesting batch invariance isn't needed).
     """
-    from vllm.model_executor.layers.batch_invariant import vllm_is_batch_invariant
-
-    vllm_is_batch_invariant.cache_clear()
     monkeypatch.setenv("VLLM_ATTENTION_BACKEND", backend)
 
     # CRITICAL: Disable batch invariance for this test
-    monkeypatch.setenv("VLLM_BATCH_INVARIANT", "0")
-
+    monkeypatch.setattr(batch_invariant, "VLLM_BATCH_INVARIANT", False)
     seed = int(os.getenv("VLLM_TEST_SEED", "12345"))
     random.seed(seed)
     model_name = resolve_model_name(backend)

tests/v1/determinism/test_online_batch_invariance.py

@@ -16,7 +16,8 @@ import sys
 from typing import Any
 
 import openai
-from utils import _random_prompt, skip_unsupported
+import pytest
+from utils import BACKENDS, _random_prompt, resolve_model_name, skip_unsupported
 
 from tests.utils import RemoteOpenAIServer
 
@@ -133,9 +134,14 @@ def _compare_bs1_vs_bsn_single_process(
 
 
 @skip_unsupported
-def test_logprobs_bitwise_batch_invariance_bs1_vs_bsN():
+@pytest.mark.parametrize("backend", BACKENDS)
+def test_logprobs_bitwise_batch_invariance_bs1_vs_bsN(
+    backend: str, monkeypatch: pytest.MonkeyPatch
+) -> None:
     random.seed(int(os.getenv("VLLM_TEST_SEED", "12345")))
-    model_name = os.getenv("VLLM_TEST_MODEL", "Qwen/Qwen3-1.7B")
+    # Override backend for this test (and the RemoteOpenAIServer child process).
+    monkeypatch.setenv("VLLM_ATTENTION_BACKEND", backend)
+    model_name = resolve_model_name(backend)
     prompts_all = [_random_prompt(10, 50) for _ in range(32)]
 
     sp_kwargs: dict[str, Any] = {

tests/v1/determinism/utils.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+import os
 import random
 
 import pytest
@@ -12,6 +13,25 @@ skip_unsupported = pytest.mark.skipif(
     reason="Requires CUDA and >= Hopper (SM90)",
 )
 
+BACKENDS: list[str] = [
+    "FLASH_ATTN",
+    "FLASHINFER",
+]
+
+if current_platform.is_cuda() and current_platform.is_device_capability(90):
+    BACKENDS.append("FLASH_ATTN_MLA")
+
+DEFAULT_MODEL = "Qwen/Qwen3-1.7B"
+MLA_MODEL = "deepseek-ai/DeepSeek-V2-Lite-Chat"
+
+
+def resolve_model_name(backend: str) -> str:
+    """Resolve the model name for the given backend."""
+    model = os.getenv("VLLM_TEST_MODEL", DEFAULT_MODEL)
+    if backend.endswith("MLA") and model == DEFAULT_MODEL:
+        return MLA_MODEL
+    return model
+
 
 def _random_prompt(min_words: int = 1024, max_words: int = 1024 * 2) -> str:
     # Generate more realistic prompts that will actually produce varied tokens

vllm/model_executor/layers/batch_invariant.py

@@ -2,7 +2,6 @@
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 import os
 from collections.abc import Callable
-from functools import cache
 from typing import Any
 
 import torch
@@ -785,16 +784,19 @@ def enable_batch_invariant_mode():
     torch.backends.cuda.preferred_blas_library(backend="cublaslt")
 
 
-@cache
-def vllm_is_batch_invariant():
-    env_key = "VLLM_BATCH_INVARIANT"
-    is_overridden = False
-    val = os.getenv(env_key, "0")
+def _read_vllm_batch_invariant() -> bool:
+    val = os.getenv("VLLM_BATCH_INVARIANT", "0")
     try:
-        is_overridden = int(val) != 0
+        return int(val) != 0
     except ValueError:
-        is_overridden = False
-    return is_overridden
+        return False
+
+
+VLLM_BATCH_INVARIANT: bool = _read_vllm_batch_invariant()
+
+
+def vllm_is_batch_invariant() -> bool:
+    return VLLM_BATCH_INVARIANT
 
 
 def override_envs_for_invariance():