[torch.compile] fix functionalization (vllm-project#8480)

tests/compile/test_full_graph.py

@@ -16,7 +16,12 @@ def test_full_graph(model):
         "The future of AI is",
     ]
     sampling_params = SamplingParams(temperature=0)
-    llm = LLM(model="meta-llama/Meta-Llama-3-8B",
-              enforce_eager=True,
-              load_format="dummy")
-    llm.generate(prompts, sampling_params)
+    llm = LLM(model=model, enforce_eager=True)
+
+    outputs = llm.generate(prompts, sampling_params)
+
+    # Print the outputs.
+    for output in outputs:
+        prompt = output.prompt
+        generated_text = output.outputs[0].text
+        print(f"Prompt: {prompt!r}, Generated text: {generated_text!r}")

vllm/compilation/backends.py

@@ -0,0 +1,156 @@
+import operator
+
+import torch
+import torch.fx as fx
+
+
+def fix_functionalization(graph: fx.Graph):
+    """
+    Rewrite the graph module to replace the pattern involving
+    torch._higher_order_ops.auto_functionalize.auto_functionalized
+    with a direct call to the inplace custom op.
+
+    # TODO: check if PyTorch nightly has fixed this issue
+    """
+
+    # debug code, if we want to see the graph before the transformation
+    # with open("before.py", "w") as f:
+    #     print(graph.python_code(root_module="self", verbose=True).src, file=f)
+
+    nodes_to_remove = []
+
+    for node in graph.nodes:
+        # Identify the auto_functionalized node
+        if node.op == 'call_function' and node.target == torch._higher_order_ops.auto_functionalize.auto_functionalized:  # noqa
+            if node.args[0] == torch.ops._C.rotary_embedding.default:
+                # manual replace for rotary_embedding
+
+                # Now, collect the arguments
+                kwargs = node.kwargs
+
+                query = kwargs['query']
+                mm_node = query.args[0].args[0]
+
+                # Create a new call to torch.ops._C.rotary_embedding.default
+                with graph.inserting_before(node):
+                    # just insert the call to the custom op
+                    # NOTE: don't run dead code elimination,
+                    # otherwise this op will be removed
+                    graph.call_function(torch.ops._C.rotary_embedding.default,
+                                        kwargs=kwargs)
+
+                # Remove the auto_functionalized node
+                # Since the node may have outputs, we need to handle its users
+                # Replace uses of the outputs (getitem nodes) with mm_node
+                for user in list(node.users):
+                    if user.op == 'call_function' and user.target == operator.getitem:  # noqa
+                        # Remove the getitem node
+                        for getitem_user in list(user.users):
+                            if (getitem_user.op == 'call_function'
+                                    and getitem_user.target
+                                    == torch.ops.aten.slice_scatter.default):
+                                # Replace the uses of slice_scatter node
+                                # with mm_node
+                                getitem_user.replace_all_uses_with(mm_node)
+                                nodes_to_remove.append(getitem_user)
+                        nodes_to_remove.append(user)
+                nodes_to_remove.append(node)
+
+            elif node.args[0] == torch.ops._C.fused_add_rms_norm.default:
+                # manual replace for fused_add_rms_norm
+                # this is the most effective optimization for llama
+                # failing to do this will result in many unnecessary copies
+
+                kwargs = node.kwargs
+
+                input = kwargs['input']
+                residual = kwargs['residual']
+
+                # Create a new call to torch.ops._C.rotary_embedding.default
+                with graph.inserting_before(node):
+                    # just insert the call to the custom op
+                    # NOTE: don't run dead code elimination,
+                    # otherwise this op will be removed
+                    graph.call_function(
+                        torch.ops._C.fused_add_rms_norm.default, kwargs=kwargs)
+
+                for user in list(node.users):
+                    if user.op == 'call_function' and user.target == operator.getitem:  # noqa
+                        # Remove the getitem node
+                        if user.args[1] == 1:
+                            replace_node = input
+                        elif user.args[1] == 2:
+                            replace_node = residual
+                        user.replace_all_uses_with(replace_node)
+                        nodes_to_remove.append(user)
+                nodes_to_remove.append(node)
+
+            elif node.args[0] == torch.ops._C.rms_norm.default:
+                # manual replace for rms_norm
+
+                kwargs = node.kwargs
+
+                input = kwargs['input']
+                out = kwargs['out']
+                weight = kwargs['weight']
+                epsilon = kwargs['epsilon']
+                # Create a new call to torch.ops._C.rotary_embedding.default
+                # cannot use kwargs, because we have an `out`, see https://github.com/pytorch/pytorch/blob/a00faf440888ffb724bad413f329a49e2b6388e7/torch/_inductor/lowering.py#L351 # noqa
+                with graph.inserting_before(node):
+                    # just insert the call to the custom op
+                    # NOTE: don't run dead code elimination,
+                    # otherwise this op will be removed
+                    graph.call_function(
+                        torch.ops._C.rms_norm.default,
+                        args=(out, input, weight, epsilon),
+                    )
+
+                replace_node = out
+
+                for user in list(node.users):
+                    if user.op == 'call_function' and user.target == operator.getitem:  # noqa
+                        user.replace_all_uses_with(replace_node)
+                        nodes_to_remove.append(user)
+                nodes_to_remove.append(node)
+
+            elif node.args[0] == torch.ops._C.silu_and_mul.default:
+                # manual replace for silu_and_mul
+
+                kwargs = node.kwargs
+
+                input = kwargs['input']
+                out = kwargs['out']
+
+                # Create a new call to torch.ops._C.rotary_embedding.default
+                # cannot use kwargs, because we have an `out`, see https://github.com/pytorch/pytorch/blob/a00faf440888ffb724bad413f329a49e2b6388e7/torch/_inductor/lowering.py#L351 # noqa
+                with graph.inserting_before(node):
+                    # just insert the call to the custom op
+                    # NOTE: don't run dead code elimination,
+                    # otherwise this op will be removed
+                    graph.call_function(
+                        torch.ops._C.silu_and_mul.default,
+                        args=(out, input),
+                    )
+                replace_node = out
+
+                for user in list(node.users):
+                    if user.op == 'call_function' and user.target == operator.getitem:  # noqa
+                        user.replace_all_uses_with(replace_node)
+                        nodes_to_remove.append(user)
+                nodes_to_remove.append(node)
+
+    # Remove the nodes all at once
+    for node in nodes_to_remove:
+        graph.erase_node(node)
+
+    # debug code, if we want to see the graph after the transformation
+    # with open("after.py", "w") as f:
+    #     print(graph.python_code(root_module="self", verbose=True).src, file=f)
+
+
+def vllm_backend(graph, example_inputs):
+    from torch._inductor import config
+    current_config = config.shallow_copy_dict()
+    from torch._inductor.compile_fx import compile_fx
+    current_config['post_grad_custom_post_pass'] = fix_functionalization
+    return compile_fx(graph, example_inputs, config_patches=current_config)

vllm/worker/model_runner.py

@@ -1064,8 +1064,9 @@ def load_model(self) -> None:
                     "This may lead to less accurate results!")
 
         if envs.VLLM_TEST_DYNAMO_GRAPH_CAPTURE and supports_dynamo():
+            from vllm.compilation.backends import vllm_backend
             from vllm.plugins import get_torch_compile_backend
-            backend = get_torch_compile_backend() or "eager"
+            backend = get_torch_compile_backend() or vllm_backend
             self.model = torch.compile(
                 self.model,
                 fullgraph=envs.VLLM_TEST_DYNAMO_FULLGRAPH_CAPTURE,