[plugin][torch.compile] allow to add custom compile backend (#8445)

vllm/plugins/__init__.py

 import logging
+from typing import Callable, Optional, Union
 
 import vllm.envs as envs
 
@@ -29,3 +30,15 @@ def load_general_plugins():
             except Exception:
                 logger.exception("Failed to load general plugin: %s",
                                  plugin.name)
+
+
+_torch_compile_backend: Optional[Union[Callable, str]] = None
+
+
+def set_torch_compile_backend(backend: Union[Callable, str]):
+    global _torch_compile_backend
+    _torch_compile_backend = backend
+
+
+def get_torch_compile_backend() -> Optional[Union[Callable, str]]:
+    return _torch_compile_backend

vllm/worker/model_runner.py

@@ -1064,10 +1064,12 @@ class GPUModelRunnerBase(ModelRunnerBase[TModelInputForGPU]):
                     "This may lead to less accurate results!")
 
         if envs.VLLM_TEST_DYNAMO_GRAPH_CAPTURE and supports_dynamo():
+            from vllm.plugins import get_torch_compile_backend
+            backend = get_torch_compile_backend() or "eager"
             self.model = torch.compile(
                 self.model,
                 fullgraph=envs.VLLM_TEST_DYNAMO_FULLGRAPH_CAPTURE,
-                backend="eager")
+                backend=backend)
 
     def save_sharded_state(
         self,