import copy import dataclasses import time from contextlib import ExitStack from typing import Any, Callable, Dict, List, Optional, Sequence, Set, Tuple from unittest.mock import patch import torch import torch.fx as fx import vllm.envs as envs from vllm.config import CompilationConfig from vllm.logger import init_logger from vllm.utils import weak_ref_tensors from .counter import compilation_counter from .inductor_pass import InductorPass from .monitor import end_monitoring_torch_compile from .pass_manager import PostGradPassManager logger = init_logger(__name__) def wrap_inductor(graph, example_inputs, additional_inductor_config, compilation_config: CompilationConfig, graph_index: int = 0, num_graphs: int = 1, runtime_shape: Optional[int] = None, use_inductor: bool = True): if graph_index == 0: # before compiling the first graph, record the start time global compilation_start_time compilation_start_time = time.time() if not use_inductor: return graph compilation_counter.num_inductor_compilations += 1 from torch._inductor import config current_config = config.get_config_copy() from torch._inductor.compile_fx import compile_fx if additional_inductor_config is not None: current_config.update(additional_inductor_config) if isinstance(runtime_shape, int): # for a specific batchsize, tuning triton kernel parameters # can be beneficial current_config["max_autotune"] = True current_config["coordinate_descent_tuning"] = True # inductor can inplace modify the graph, so we need to copy it # see https://github.com/pytorch/pytorch/issues/138980 graph = copy.deepcopy(graph) compiled_graph = compile_fx(graph, example_inputs, config_patches=current_config) # after compiling the last graph, record the end time if graph_index == num_graphs - 1: now = time.time() elapsed = now - compilation_start_time compilation_config.compilation_time += elapsed if runtime_shape is None: logger.info("Compiling a graph for general shape takes %.2f s", elapsed) else: logger.info("Compiling a graph for shape %s takes %.2f s", runtime_shape, elapsed) return compiled_graph @dataclasses.dataclass class SplitItem: submod_name: str graph_id: int is_splitting_graph: bool graph: fx.GraphModule def split_graph(graph: fx.GraphModule, ops: List[str]) -> Tuple[fx.GraphModule, List[SplitItem]]: # split graph by ops subgraph_id = 0 node_to_subgraph_id = {} split_op_graphs = [] for node in graph.graph.nodes: if node.op in ("output", "placeholder"): continue if node.op == 'call_function' and str(node.target) in ops: subgraph_id += 1 node_to_subgraph_id[node] = subgraph_id split_op_graphs.append(subgraph_id) subgraph_id += 1 else: node_to_subgraph_id[node] = subgraph_id # `keep_original_order` is important! # otherwise pytorch might reorder the nodes and # the semantics of the graph will change when we # have mutations in the graph split_gm = torch.fx.passes.split_module.split_module( graph, None, lambda node: node_to_subgraph_id[node], keep_original_order=True) outputs = [] names = [name for (name, module) in split_gm.named_modules()] for name in names: if "." in name or name == "": # recursive child module or the root module continue module = getattr(split_gm, name) graph_id = int(name.replace("submod_", "")) outputs.append( SplitItem(name, graph_id, (graph_id in split_op_graphs), module)) # sort by intetger graph_id, rather than string name outputs.sort(key=lambda x: x.graph_id) return split_gm, outputs # we share the global graph pool among all the backends global_graph_pool = None compilation_start_time = 0.0 class PiecewiseCompileInterpreter(torch.fx.Interpreter): """Code adapted from `torch.fx.passes.shape_prop.ShapeProp`. It runs the given graph with fake inputs, and compile some submodules specified by `compile_submod_names` with the given compilation configs. NOTE: the order in `compile_submod_names` matters, because it will be used to determine the order of the compiled piecewise graphs. The first graph will handle logging, and the last graph has some special cudagraph output handling. """ def __init__(self, module: torch.fx.GraphModule, compile_submod_names: List[str], compilation_configs: CompilationConfig, graph_pool): super().__init__(module) from torch._guards import detect_fake_mode self.fake_mode = detect_fake_mode() self.compile_submod_names = compile_submod_names self.compilation_configs = compilation_configs self.graph_pool = graph_pool def run(self, *args): fake_args = [ self.fake_mode.from_tensor(t) if isinstance(t, torch.Tensor) else t for t in args ] with self.fake_mode: return super().run(*fake_args) def call_module(self, target: torch.fx.node.Target, args: Tuple[torch.fx.node.Argument, ...], kwargs: Dict[str, Any]) -> Any: assert isinstance(target, str) output = super().call_module(target, args, kwargs) if target in self.compile_submod_names: index = self.compile_submod_names.index(target) submod = self.fetch_attr(target) sym_shape_indices = [ i for i, x in enumerate(args) if isinstance(x, torch.SymInt) ] global compilation_start_time compiled_graph_for_general_shape = wrap_inductor( submod, args, self.compilation_configs.inductor_compile_config, self.compilation_configs, graph_index=index, num_graphs=len(self.compile_submod_names), runtime_shape=None, use_inductor=self.compilation_configs.use_inductor) self.module.__dict__[target] = PiecewiseBackend( submod, self.compilation_configs, self.graph_pool, index, len(self.compile_submod_names), sym_shape_indices, compiled_graph_for_general_shape) compilation_counter.num_piecewise_capturable_graphs_seen += 1 return output class VllmBackend: """The compilation backend for `torch.compile` with VLLM. It is used for compilation level of `CompilationLevel.PIECEWISE`, where we customize the compilation. The major work of this backend is to split the graph into piecewise graphs, and pass them to the piecewise backend. This backend also adds the PostGradPassManager to Inductor config, which handles the post-grad passes. """ compilation_configs: CompilationConfig graph_pool: Any _called: bool = False # the graph we compiled graph: fx.GraphModule # the stiching graph module for all the piecewise graphs split_gm: fx.GraphModule piecewise_graphs: List[SplitItem] returned_callable: Callable # Inductor passes to run on the graph pre-defunctionalization post_grad_passes: Sequence[Callable] sym_tensor_indices: List[int] input_buffers: List[torch.Tensor] def __init__( self, compilation_configs: CompilationConfig, ): global global_graph_pool if global_graph_pool is None: global_graph_pool = torch.cuda.graph_pool_handle() # TODO: in the future, if we want to use multiple # streams, it might not be safe to share a global pool. # only investigate this when we use multiple streams self.graph_pool = global_graph_pool # Passes to run on the graph post-grad. self.post_grad_pass_manager = PostGradPassManager() self.sym_tensor_indices = [] self.input_buffers = [] self.compilation_configs = compilation_configs # `torch.compile` is JIT compiled, so we don't need to # do anything here def configure_post_pass(self): config = self.compilation_configs self.post_grad_pass_manager.configure(config.pass_config) # Post-grad custom passes are run using the post_grad_custom_post_pass # hook. If a pass for that hook exists, add it to the pass manager. inductor_config = config.inductor_compile_config PASS_KEY = "post_grad_custom_post_pass" if PASS_KEY in inductor_config: # Config should automatically wrap all inductor passes assert isinstance(inductor_config[PASS_KEY], InductorPass) self.post_grad_pass_manager.add(inductor_config[PASS_KEY]) inductor_config[PASS_KEY] = self.post_grad_pass_manager def __call__(self, graph: fx.GraphModule, example_inputs) -> Callable: # when dynamo calls the backend, it means the bytecode # transform and analysis are done compilation_counter.num_graphs_seen += 1 from .monitor import torch_compile_start_time dynamo_time = time.time() - torch_compile_start_time logger.info("Dynamo bytecode transform time: %.2f s", dynamo_time) self.compilation_configs.compilation_time += dynamo_time # we control the compilation process, each instance can only be # called once assert not self._called, "VllmBackend can only be called once" self.graph = graph self.configure_post_pass() self.split_gm, self.piecewise_graphs = split_graph( graph, self.compilation_configs.splitting_ops) from torch._dynamo.utils import lazy_format_graph_code logger.debug("%s", lazy_format_graph_code("before split", self.graph)) logger.debug("%s", lazy_format_graph_code("after split", self.split_gm)) compilation_counter.num_piecewise_graphs_seen += len( self.piecewise_graphs) submod_names_to_compile = [ item.submod_name for item in self.piecewise_graphs if not item.is_splitting_graph ] # propagate the split graph to the piecewise backend, # compile submodules with symbolic shapes PiecewiseCompileInterpreter(self.split_gm, submod_names_to_compile, self.compilation_configs, self.graph_pool).run(*example_inputs) self._called = True if not self.compilation_configs.use_cudagraph or \ not self.compilation_configs.cudagraph_copy_inputs: return self.split_gm # if we need to copy input buffers for cudagraph from torch._guards import detect_fake_mode fake_mode = detect_fake_mode() fake_args = [ fake_mode.from_tensor(t) if isinstance(t, torch.Tensor) else t for t in example_inputs ] # index of tensors that have symbolic shapes (batch size) self.sym_tensor_indices = [ i for i, x in enumerate(fake_args) if isinstance(x, torch._subclasses.fake_tensor.FakeTensor) ] # compiler managed cudagraph input buffers # we assume the first run with symbolic shapes # has the maximum size among all the tensors self.input_buffers = [ example_inputs[x].clone() for x in self.sym_tensor_indices ] def copy_and_call(*args): list_args = list(args) for i, index in enumerate(self.sym_tensor_indices): runtime_tensor = list_args[index] runtime_shape = runtime_tensor.shape[0] static_tensor = self.input_buffers[i][:runtime_shape] # copy the tensor to the static buffer static_tensor.copy_(runtime_tensor) # replace the tensor in the list_args to the static buffer list_args[index] = static_tensor return self.split_gm(*list_args) return copy_and_call @dataclasses.dataclass class ConcreteSizeEntry: runtime_shape: int need_to_compile: bool # the size is in compile_sizes use_cudagraph: bool # the size is in capture_sizes compiled: bool = False runnable: Callable = None # type: ignore num_finished_warmup: int = 0 cudagraph: Optional[torch.cuda.CUDAGraph] = None output: Optional[Any] = None # for cudagraph debugging, track the input addresses # during capture, and check if they are the same during replay input_addresses: Optional[List[int]] = None class PiecewiseBackend: def __init__(self, graph: fx.GraphModule, compilation_configs: CompilationConfig, graph_pool: Any, piecewise_compile_index: int, total_piecewise_compiles: int, sym_shape_indices: List[int], compiled_graph_for_general_shape: Callable): """ The backend for piecewise compilation. It mainly handles the compilation and cudagraph capturing. We will compile `self.graph` once for the general shape, and then compile for different shapes specified in `compilation_configs.compile_sizes`. Independently, we will capture cudagraph for different shapes. If a shape needs both compilation and cudagraph, we will compile it first, and then capture cudagraph. """ self.graph = graph self.compilation_configs = compilation_configs self.graph_pool = graph_pool self.piecewise_compile_index = piecewise_compile_index self.total_piecewise_compiles = total_piecewise_compiles self.is_first_graph = piecewise_compile_index == 0 self.is_last_graph = ( piecewise_compile_index == total_piecewise_compiles - 1) self.compile_sizes: Set[int] = set( self.compilation_configs.compile_sizes) self.capture_sizes: Set[int] = set( self.compilation_configs.capture_sizes ) if self.compilation_configs.use_cudagraph else set() self.first_run_finished = False self.compiled_graph_for_general_shape = compiled_graph_for_general_shape # noqa self.sym_shape_indices = sym_shape_indices self.is_debugging_mode = envs.VLLM_LOGGING_LEVEL == "DEBUG" # the entries for different shapes that we need to either # compile or capture cudagraph self.concrete_size_entries: Dict[int, ConcreteSizeEntry] = {} self.to_be_compiled_sizes: Set[int] = self.compile_sizes.union( self.capture_sizes) for shape in self.compile_sizes.union(self.capture_sizes): self.concrete_size_entries[shape] = ConcreteSizeEntry( runtime_shape=shape, need_to_compile=shape in self.compile_sizes, use_cudagraph=shape in self.capture_sizes, ) def __call__(self, *args) -> Any: if not self.first_run_finished: self.first_run_finished = True # no specific sizes to compile if self.is_last_graph and not self.to_be_compiled_sizes: end_monitoring_torch_compile(self.compilation_configs) return self.compiled_graph_for_general_shape(*args) runtime_shape = args[self.sym_shape_indices[0]] if runtime_shape not in self.concrete_size_entries: # we don't need to do anything for this shape return self.compiled_graph_for_general_shape(*args) entry = self.concrete_size_entries[runtime_shape] if entry.runnable is None: entry.runnable = self.compiled_graph_for_general_shape if entry.need_to_compile and not entry.compiled: entry.compiled = True self.to_be_compiled_sizes.remove(runtime_shape) # args are real arguments entry.runnable = wrap_inductor( self.graph, args, self.compilation_configs.inductor_compile_config, self.compilation_configs, graph_index=self.piecewise_compile_index, num_graphs=self.total_piecewise_compiles, runtime_shape=runtime_shape, use_inductor=self.compilation_configs.use_inductor) # finished compilations for all required shapes if self.is_last_graph and not self.to_be_compiled_sizes: end_monitoring_torch_compile(self.compilation_configs) if not entry.use_cudagraph: return entry.runnable(*args) if entry.cudagraph is None: if entry.num_finished_warmup < self.compilation_configs.cudagraph_num_of_warmups: # noqa entry.num_finished_warmup += 1 if self.is_first_graph: logger.debug( "Warming up %s/%s for shape %s", entry.num_finished_warmup, self.compilation_configs.cudagraph_num_of_warmups, runtime_shape) return entry.runnable(*args) if self.is_first_graph: # Since we capture cudagraph for many different shapes and # capturing is fast, we don't need to log it for every shape. # We only log it in the debug mode. logger.debug("Capturing a cudagraph for shape %s", runtime_shape) input_addresses = [ x.data_ptr() for x in args if isinstance(x, torch.Tensor) ] entry.input_addresses = input_addresses cudagraph = torch.cuda.CUDAGraph() with ExitStack() as stack: if not self.is_first_graph: # during every model forward, we will capture # many pieces of cudagraphs (roughly one per layer). # running gc again and again across layers will # make the cudagraph capture very slow. # therefore, we only run gc for the first graph, # and disable gc for the rest of the graphs. stack.enter_context(patch("gc.collect", lambda: None)) stack.enter_context( patch("torch.cuda.empty_cache", lambda: None)) # mind-exploding: carefully manage the reference and memory. with torch.cuda.graph(cudagraph, pool=self.graph_pool): # `output` is managed by pytorch's cudagraph pool output = entry.runnable(*args) if self.is_last_graph: # by converting it to weak ref, # the original `output` will immediately be released # to save memory. It is only safe to do this for # the last graph, because the output of the last graph # will not be used by any other cuda graph. output = weak_ref_tensors(output) # here we always use weak ref for the output # to save memory entry.output = weak_ref_tensors(output) entry.cudagraph = cudagraph compilation_counter.num_cudagraph_caputured += 1 # important: we need to return the output, rather than # the weak ref of the output, so that pytorch can correctly # manage the memory during cuda graph capture return output if self.is_debugging_mode: # check if the input addresses are the same new_input_addresses = [ x.data_ptr() for x in args if isinstance(x, torch.Tensor) ] assert new_input_addresses == entry.input_addresses, ( "Input addresses for cudagraphs are different during replay." f" Expected {entry.input_addresses}, got {new_input_addresses}" ) entry.cudagraph.replay() return entry.output