[Misc] [CI/Build] Speed up block manager CPU-only unit tests ~10x by …

…opting-out of GPU cleanup (#3783)

tests/conftest.py

@@ -55,10 +55,20 @@ def cleanup():
     torch.cuda.empty_cache()
 
 
+@pytest.fixture()
+def should_do_global_cleanup_after_test() -> bool:
+    """Allow subdirectories to skip global cleanup by overriding this fixture.
+    This can provide a ~10x speedup for non-GPU unit tests since they don't need
+    to initialize torch.
+    """
+    return True
+
+
 @pytest.fixture(autouse=True)
-def cleanup_fixture():
+def cleanup_fixture(should_do_global_cleanup_after_test: bool):
     yield
-    cleanup()
+    if should_do_global_cleanup_after_test:
+        cleanup()
 
 
 @pytest.fixture(scope="session")

tests/core/block/conftest.py

@@ -0,0 +1,12 @@
+import pytest
+
+
+@pytest.fixture()
+def should_do_global_cleanup_after_test() -> bool:
+    """Disable the global cleanup fixture for tests in this directory. This
+    provides a ~10x speedup for unit tests that don't load a model to GPU.
+
+    This requires that tests in this directory clean up after themselves if they
+    use the GPU.
+    """
+    return False

tests/core/block/e2e/conftest.py

@@ -1,25 +1,10 @@
-import contextlib
-import gc
-
 import pytest
-import ray
-import torch
 
+from tests.conftest import cleanup
 from vllm import LLM
-from vllm.model_executor.parallel_utils.parallel_state import (
-    destroy_model_parallel)
 from vllm.model_executor.utils import set_random_seed
 
 
-def cleanup():
-    destroy_model_parallel()
-    with contextlib.suppress(AssertionError):
-        torch.distributed.destroy_process_group()
-    gc.collect()
-    torch.cuda.empty_cache()
-    ray.shutdown()
-
-
 @pytest.fixture
 def baseline_llm_generator(common_llm_kwargs, per_test_common_llm_kwargs,
                            baseline_llm_kwargs, seed):