[None][chore] Make torch compiling and piecewise running flags thread-safe

    Control skip_maybe_compile behavior directly

Signed-off-by: Jonas Li <[email protected]>

Author: longlee0622

tensorrt_llm/_torch/compilation/piecewise_optimizer.py

@@ -14,7 +14,7 @@
 from ..utils import (get_model_extra_attrs,
                      get_per_request_piecewise_cuda_graph_flag,
                      get_piecewise_cuda_graph_flag, make_weak_ref,
-                     set_piecewise_running)
+                     skip_maybe_compile)
 from .multi_stream.auto_multi_stream import multi_stream_schedule
 from .utils import get_capture_piecewise_cuda_graph_flag, is_call_function
 
@@ -171,68 +171,75 @@ def __call__(self, *args):
                 or not get_per_request_piecewise_cuda_graph_flag()):
             return self.default_callable(*args)
 
-        if self.is_first_runner or self.is_last_runner:
-            if self.is_first_runner == self.is_last_runner:
-                set_piecewise_running(False)
-            else:
-                set_piecewise_running(self.is_first_runner)
-
-        entry = self.entries[runtime_num_of_token]
-
-        if entry.enable_inductor and not entry.compiled:
-            entry.callable = compile_fx(entry.callable, args)
-            entry.compiled = True
-
-        if entry.cuda_graph is None:
-
-            if not get_capture_piecewise_cuda_graph_flag():
-                return entry.callable(*args)
-
-            if entry.warmup_count < 3:
-                entry.warmup_count += 1
-                return entry.callable(*args)
-
-            entry.input_addresses = [
-                i.data_ptr() for i in args if isinstance(i, torch.Tensor)
-            ]
-
-            graph = torch.cuda.CUDAGraph()
-
-            # Torch's cuda graph will call gc.collect() internally. This will slow down the performance.
-            # We patch it to do nothing.
-            with patch("gc.collect", lambda: None):
-                # TODO: consider to use `make_graphed_callables()` when
-                # it's ready rather than capture it ourselves
-                # Graph Capture would override the stream. We need to setup the stream correctly.
-                extra_attrs = get_model_extra_attrs()
-                with torch.cuda.graph(graph, pool=self.graph_pool_handle):
+        # Determine if we should skip compilation in @maybe_compile decorated functions:
+        # - First runner only: skip compilation (to avoid overhead)
+        # - Last runner only: skip compilation (to avoid overhead)
+        # - Both first and last (single runner): allow compilation (normal mode)
+        # - Middle runner: allow compilation (normal mode)
+        should_skip = (self.is_first_runner or self.is_last_runner) and \
+                      not (self.is_first_runner and self.is_last_runner)
+
+        # Use context manager to directly control @maybe_compile behavior
+        # This makes the relationship explicit: PiecewiseRunner → skip_maybe_compile → @maybe_compile
+        with skip_maybe_compile(should_skip):
+            entry = self.entries[runtime_num_of_token]
+
+            if entry.enable_inductor and not entry.compiled:
+                entry.callable = compile_fx(entry.callable, args)
+                entry.compiled = True
+
+            if entry.cuda_graph is None:
+
+                if not get_capture_piecewise_cuda_graph_flag():
+                    return entry.callable(*args)
+
+                if entry.warmup_count < 3:
+                    entry.warmup_count += 1
+                    return entry.callable(*args)
+
+                entry.input_addresses = [
+                    i.data_ptr() for i in args if isinstance(i, torch.Tensor)
+                ]
+
+                graph = torch.cuda.CUDAGraph()
+
+                # Torch's cuda graph will call gc.collect() internally. This will slow down the performance.
+                # We patch it to do nothing.
+                with patch("gc.collect", lambda: None):
+                    # TODO: consider to use `make_graphed_callables()` when
+                    # it's ready rather than capture it ourselves
+                    # Graph Capture would override the stream. We need to setup the stream correctly.
+                    extra_attrs = get_model_extra_attrs()
+                    with torch.cuda.graph(graph, pool=self.graph_pool_handle):
+                        extra_attrs[
+                            "global_stream"] = torch.cuda.current_stream()
+                        output = entry.callable(*args)
                     extra_attrs["global_stream"] = torch.cuda.current_stream()
-                    output = entry.callable(*args)
-                extra_attrs["global_stream"] = torch.cuda.current_stream()
 
-            entry.cuda_graph = graph
-            # Mark weak ref here. The intermediate activation tensor should be freed properly.
-            # Here we don't use python native weakref since we still need the object to be alive when the graph is replayed.
-            entry.output = make_weak_ref(output)
-            entry.output_addresses = [
-                i.data_ptr() for i in output if isinstance(i, torch.Tensor)
-            ]
+                entry.cuda_graph = graph
+                # Mark weak ref here. The intermediate activation tensor should be freed properly.
+                # Here we don't use python native weakref since we still need the object to be alive when the graph is replayed.
+                entry.output = make_weak_ref(output)
+                entry.output_addresses = [
+                    i.data_ptr() for i in output if isinstance(i, torch.Tensor)
+                ]
 
-            entry.cuda_graph.replay()
+                entry.cuda_graph.replay()
 
-            return output
+                return output
 
-        if enable_llm_debug():
-            runtime_input_addresses = [
-                i.data_ptr() for i in args if isinstance(i, torch.Tensor)
-            ]
+            if enable_llm_debug():
+                runtime_input_addresses = [
+                    i.data_ptr() for i in args if isinstance(i, torch.Tensor)
+                ]
 
-            assert (entry.input_addresses == runtime_input_addresses
-                    ), f"{entry.input_addresses} vs\n {runtime_input_addresses}"
+                assert (
+                    entry.input_addresses == runtime_input_addresses
+                ), f"{entry.input_addresses} vs\n {runtime_input_addresses}"
 
-        entry.cuda_graph.replay()
+            entry.cuda_graph.replay()
 
-        return entry.output
+            return entry.output
 
 
 def piecewise_optimizer(

tensorrt_llm/_torch/utils.py

@@ -11,8 +11,10 @@
 from tensorrt_llm.math_utils import ceil_div, pad_up
 from tensorrt_llm.quantization.utils import fp4_utils
 
-is_torch_compiling_flag = False
-is_piecewise_running_flag = False
+_torch_compiling = threading.local()
+# Controls whether @maybe_compile decorator should skip compilation
+# Set directly by PiecewiseRunner to avoid compilation overhead
+_skip_maybe_compile = threading.local()
 
 aux_stream_name_list = [
     'Attention',
@@ -46,23 +48,42 @@ class ActivationType(IntEnum):
 
 
 def set_torch_compiling(enable: bool):
-    global is_torch_compiling_flag
-    is_torch_compiling_flag = enable
+    _torch_compiling.flag = enable
 
 
 def is_torch_compiling() -> bool:
-    global is_torch_compiling_flag
-    return is_torch_compiling_flag
+    return getattr(_torch_compiling, 'flag', False)
 
 
-def set_piecewise_running(enable: bool):
-    global is_piecewise_running_flag
-    is_piecewise_running_flag = enable
+@contextlib.contextmanager
+def skip_maybe_compile(skip: bool = True):
+    """
+    Context manager to directly control @maybe_compile decorator behavior.
+
+    When skip=True, functions decorated with @maybe_compile will skip torch.compile
+    to avoid compilation overhead. Used by PiecewiseRunner to control compilation.
+
+    This makes the relationship between PiecewiseRunner and @maybe_compile explicit.
+
+    Args:
+        skip: Whether to skip compilation in @maybe_compile decorated functions
+
+    Example:
+        with skip_maybe_compile(True):
+            # Functions with @maybe_compile will NOT be compiled
+            result = some_function()
+    """
+    old_state = getattr(_skip_maybe_compile, 'flag', False)
+    _skip_maybe_compile.flag = skip
+    try:
+        yield
+    finally:
+        _skip_maybe_compile.flag = old_state
 
 
-def is_piecewise_running() -> bool:
-    global is_piecewise_running_flag
-    return is_piecewise_running_flag
+def _should_skip_maybe_compile() -> bool:
+    """Check if @maybe_compile should skip compilation."""
+    return getattr(_skip_maybe_compile, 'flag', False)
 
 
 _global_attrs = threading.local()
@@ -344,19 +365,34 @@ def get_device_uuid(device_idx: int) -> str:
 def maybe_compile(func=None, **compile_kwargs):
     """
     Conditionally compile a function with torch.compile.
-    If is_piecewise_running() is True, the function will not be compiled to avoid host overhead in attention op.
+
+    Compilation is skipped when running within a skip_maybe_compile(True) context,
+    which is used by PiecewiseRunner to avoid compilation overhead.
+
     Args:
         func: The function to decorate (optional, for direct decoration).
         **compile_kwargs: Keyword arguments for torch.compile.
     Returns:
-        The conditionally compiled function..
+        The conditionally compiled function.
+
+    Example:
+        @maybe_compile
+        def my_function(x):
+            return x * 2
+
+        # Normal usage: function is compiled
+        result = my_function(tensor)
+
+        # With skip_maybe_compile: function runs uncompiled
+        with skip_maybe_compile(True):
+            result = my_function(tensor)  # Not compiled
     """
 
     def decorator(f):
         compiled_func = torch.compile(f, **compile_kwargs)
 
         def wrapper(*args, **kwargs):
-            if is_piecewise_running():
+            if _should_skip_maybe_compile():
                 return f(*args, **kwargs)
             return compiled_func(*args, **kwargs)