[compile] Consistent compiler config for saved/loaded vllm backends. (#35810)

Signed-off-by: zhxchen17 <zhxchen17@fb.com>

tests/compile/test_aot_compile.py

@@ -14,6 +14,7 @@ import pytest
 import torch
 
 import vllm.model_executor.layers.activation
+from vllm.compilation.backends import VllmBackend
 from vllm.compilation.caching import (
     StandaloneCompiledArtifacts,
     VllmSerializableFunction,
@@ -721,3 +722,44 @@ class TestStandaloneCompiledArtifactsIntegration:
             ("mod3", "shape3"),
         ]:
             assert cache.get(submod, shape) == shared_data
+
+    def test_functorch_config(self):
+        vllm_config = make_vllm_config()
+        example_inputs = (torch.randn(10, 10),)
+
+        def add_1(x: torch.Tensor):
+            return x + 1
+
+        gm = torch._dynamo.functional_export.dynamo_graph_capture_for_export(add_1)(
+            *example_inputs
+        )
+
+        gm.graph._codegen = torch.fx.graph.CodeGen()
+        gm._dynamo_bytecode_flatten = None
+        gm._dynamo_bytecode_unflatten = None
+
+        with (
+            torch._functorch.config.patch(bundled_autograd_cache=False),
+            set_current_vllm_config(vllm_config),
+        ):
+            with torch._functorch.config.patch(bundled_autograd_cache=True):
+                fn = VllmSerializableFunction(gm, example_inputs, "", add_1)
+
+            payload = VllmSerializableFunction.serialize_compile_artifacts(fn)
+
+            config = None
+
+            def backend(*args, **kwargs) -> VllmSerializableFunction:
+                nonlocal config
+                # bundled_autograd_cache should be True even compiler backend
+                # runs with bundled_autograd_cache=False in ambient context.
+                config = torch._functorch.config.save_config_portable()
+                return fn
+
+            loaded_fn = VllmSerializableFunction.deserialize_compile_artifacts(payload)
+            with patch.object(VllmBackend, "__call__", backend):
+                loaded_fn(*example_inputs)
+
+        assert isinstance(config, dict)
+        assert "bundled_autograd_cache" in config
+        assert config["bundled_autograd_cache"] is True

vllm/compilation/caching.py

@@ -178,6 +178,7 @@ class VllmSerializableFunction(SerializableCallable):  # type: ignore[misc]
         is_encoder: bool = False,
         vllm_backend: Any | None = None,
         sym_tensor_indices: list[int] | None = None,
+        aot_autograd_config: dict[str, Any] | None = None,
     ) -> None:
         assert isinstance(graph_module, torch.fx.GraphModule)
         self.graph_module = graph_module
@@ -188,6 +189,13 @@ class VllmSerializableFunction(SerializableCallable):  # type: ignore[misc]
         self.shape_env = None
         self.vllm_backend = vllm_backend
         self.sym_tensor_indices = sym_tensor_indices
+
+        import torch._functorch.config as functorch_config
+
+        self.aot_autograd_config = (
+            aot_autograd_config or functorch_config.save_config_portable()
+        )
+
         sym_input = next(
             (i for i in self.example_inputs if isinstance(i, torch.SymInt)), None
         )
@@ -286,6 +294,12 @@ class VllmSerializableFunction(SerializableCallable):  # type: ignore[misc]
         sym_shape_indices_map = state.pop("sym_shape_indices_map", {})
         returns_tuple_map = state.pop("returns_tuple_map", {})
 
+        saved_aot_autograd_config = state["aot_autograd_config"]
+        if saved_aot_autograd_config is not None:
+            functorch_ctx = torch._functorch.config.patch(saved_aot_autograd_config)
+        else:
+            functorch_ctx = contextlib.nullcontext()
+
         if envs.VLLM_USE_MEGA_AOT_ARTIFACT:
             assert standalone_compile_artifacts is not None
             submod_names = standalone_compile_artifacts.submodule_names()
@@ -299,6 +313,7 @@ class VllmSerializableFunction(SerializableCallable):  # type: ignore[misc]
                 num_submods,
             )
 
+            with functorch_ctx:
                 fn = reconstruct_serializable_fn_from_mega_artifact(
                     state=state,
                     standalone_compile_artifacts=standalone_compile_artifacts,
@@ -328,7 +343,7 @@ class VllmSerializableFunction(SerializableCallable):  # type: ignore[misc]
             vllm_backend: VllmBackend = VllmBackend(
                 vllm_config, state["prefix"], is_encoder
             )
-            with tracing(TracingContext(fake_mode)):
+            with tracing(TracingContext(fake_mode)), functorch_ctx:
                 fn.optimized_call = vllm_backend(
                     state["graph_module"], compile_inputs
                 ).optimized_call