[torch.compile]: Disable Sequence Parallelism (SP) for piecewise compilation (#38373)

Signed-off-by: SouthWest7 <am1ao@qq.com>
Signed-off-by: Xinan Miao <1403572259@qq.com>
Co-authored-by: SouthWest7 <am1ao@qq.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
Co-authored-by: OpenAI Codex <codex@openai.com>
Co-authored-by: Wang Xingran <72983099+wangxingran222@users.noreply.github.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

tests/compile/correctness_e2e/test_sequence_parallel.py

@@ -261,6 +261,8 @@ def _compare_sp(
         },
         "use_inductor_graph_partition": use_inductor_graph_partition,
     }
+    if not use_inductor_graph_partition:
+        compilation_config["splitting_ops"] = []
 
     tp_sp_args = [
         *common_args,

tests/compile/passes/distributed/test_async_tp.py

@@ -19,6 +19,7 @@ from vllm.config import (
     VllmConfig,
     set_current_vllm_config,
 )
+from vllm.config.utils import Range
 from vllm.distributed import (
     tensor_model_parallel_all_gather,
     tensor_model_parallel_reduce_scatter,
@@ -288,6 +289,22 @@ def test_async_tp_pass_replace(
     run_torch_spawn(async_tp_pass_on_test_model, num_processes)
 
 
+def test_async_tp_pass_requires_full_graph_compilation():
+    vllm_config = VllmConfig()
+    vllm_config.compilation_config.use_inductor_graph_partition = False
+    vllm_config.compilation_config.splitting_ops = [
+        "vllm::unified_attention_with_output"
+    ]
+
+    async_tp_pass = object.__new__(AsyncTPPass)
+    async_tp_pass.compilation_config = vllm_config.compilation_config
+
+    with pytest.raises(
+        AssertionError, match="AsyncTPPass requires full-graph compilation"
+    ):
+        async_tp_pass.is_applicable_for_range(Range(start=8, end=8))
+
+
 def async_tp_pass_on_test_model(
     local_rank: int,
     world_size: int,

tests/compile/passes/distributed/test_sequence_parallelism.py

@@ -22,6 +22,7 @@ from vllm.config import (
     get_current_vllm_config,
     set_current_vllm_config,
 )
+from vllm.config.utils import Range
 from vllm.distributed import tensor_model_parallel_all_reduce
 from vllm.distributed.parallel_state import (
     init_distributed_environment,
@@ -216,6 +217,24 @@ def test_sequence_parallelism_pass(
     run_torch_spawn(sequence_parallelism_pass_on_test_model, num_processes)
 
 
+def test_sequence_parallelism_pass_requires_full_graph_compilation():
+    vllm_config = VllmConfig()
+    vllm_config.compilation_config.use_inductor_graph_partition = False
+    vllm_config.compilation_config.splitting_ops = [
+        "vllm::unified_attention_with_output"
+    ]
+
+    sequence_parallelism_pass = object.__new__(SequenceParallelismPass)
+    sequence_parallelism_pass.compilation_config = vllm_config.compilation_config
+    sequence_parallelism_pass.min_token_num = 1
+
+    with pytest.raises(
+        AssertionError,
+        match="SequenceParallelismPass requires full-graph compilation",
+    ):
+        sequence_parallelism_pass.is_applicable_for_range(Range(start=8, end=8))
+
+
 def sequence_parallelism_pass_on_test_model(
     local_rank: int,
     world_size: int,

tests/compile/test_config.py

@@ -407,7 +407,7 @@ def test_should_split():
         (None, 257, 1, False, 2048, CUDAGraphMode.FULL_AND_PIECEWISE, 256),
         # max from list
         ([1, 2, 4, 15], None, 1, False, 2048, CUDAGraphMode.FULL_AND_PIECEWISE, 15),
-        # filtered out 15 due to SP
+        # SP forces full-graph compilation, sizes are filtered by TP
         ([1, 2, 4, 15], None, 2, True, 2048, CUDAGraphMode.FULL_AND_PIECEWISE, 4),
         # limited by the max_tokens
         ([1, 2, 4, 15], None, 1, False, 8, CUDAGraphMode.FULL_AND_PIECEWISE, 4),
@@ -465,6 +465,123 @@ def test_cudagraph_sizes_post_init(
         )
 
 
+@pytest.mark.skipif(
+    not current_platform.support_static_graph_mode(),
+    reason="Skip if not cudagraph mode supported",
+)
+@pytest.mark.parametrize(
+    (
+        "cudagraph_mode",
+        "use_inductor_graph_partition",
+        "expected_enable_sp",
+        "expected_cudagraph_mode",
+        "expected_piecewise_compile",
+        "expected_capture_sizes",
+        "expected_max_size",
+    ),
+    [
+        (CUDAGraphMode.PIECEWISE, False, True, CUDAGraphMode.FULL, False, [2, 4], 4),
+        (
+            CUDAGraphMode.FULL_DECODE_ONLY,
+            False,
+            True,
+            CUDAGraphMode.FULL_DECODE_ONLY,
+            False,
+            [2, 4],
+            4,
+        ),
+        (
+            CUDAGraphMode.FULL_AND_PIECEWISE,
+            False,
+            True,
+            CUDAGraphMode.FULL,
+            False,
+            [2, 4],
+            4,
+        ),
+        (
+            CUDAGraphMode.FULL_AND_PIECEWISE,
+            True,
+            True,
+            CUDAGraphMode.FULL_AND_PIECEWISE,
+            True,
+            [2, 4],
+            4,
+        ),
+    ],
+)
+def test_sequence_parallelism_requires_full_graph_compilation(
+    cudagraph_mode: CUDAGraphMode,
+    use_inductor_graph_partition: bool,
+    expected_enable_sp: bool,
+    expected_cudagraph_mode: CUDAGraphMode,
+    expected_piecewise_compile: bool,
+    expected_capture_sizes: list[int],
+    expected_max_size: int,
+):
+    with patch.object(current_platform, "device_count", return_value=2):
+        vllm_config = VllmConfig(
+            parallel_config=ParallelConfig(tensor_parallel_size=2),
+            scheduler_config=SchedulerConfig(
+                max_num_seqs=128,
+                max_num_batched_tokens=2048,
+                max_model_len=2048,
+                is_encoder_decoder=False,
+            ),
+        )
+        vllm_config.model_config = MagicMock(
+            dtype=torch.float16,
+            enforce_eager=False,
+            is_moe=False,
+            disable_cascade_attn=False,
+            get_hidden_size=MagicMock(return_value=4096),
+        )
+        vllm_config.compilation_config = CompilationConfig(
+            mode=CompilationMode.VLLM_COMPILE,
+            cudagraph_capture_sizes=[1, 2, 4, 15],
+            max_cudagraph_capture_size=None,
+            compile_sizes=["cudagraph_capture_sizes"],
+            use_inductor_graph_partition=use_inductor_graph_partition,
+            pass_config=PassConfig(
+                enable_sp=True,
+                fuse_gemm_comms=True,
+                fuse_norm_quant=True,
+                fuse_act_quant=True,
+                eliminate_noops=True,
+                sp_min_token_num=512,
+            ),
+            cudagraph_mode=cudagraph_mode,
+        )
+        vllm_config.compilation_config.set_splitting_ops_for_v1(
+            all2all_backend=vllm_config.parallel_config.all2all_backend,
+            data_parallel_size=1,
+        )
+        vllm_config._set_compile_ranges()
+        vllm_config._set_cudagraph_sizes()
+
+    assert (
+        vllm_config.compilation_config.use_inductor_graph_partition
+        == use_inductor_graph_partition
+    )
+    assert (
+        bool(vllm_config.compilation_config.splitting_ops) == expected_piecewise_compile
+    )
+    assert vllm_config.compilation_config.pass_config.enable_sp == expected_enable_sp
+    assert (
+        vllm_config.compilation_config.pass_config.fuse_gemm_comms == expected_enable_sp
+    )
+    assert vllm_config.compilation_config.cudagraph_mode == expected_cudagraph_mode
+    assert (
+        vllm_config.compilation_config.cudagraph_capture_sizes == expected_capture_sizes
+    )
+    assert (
+        vllm_config.compilation_config.max_cudagraph_capture_size == expected_max_size
+    )
+    assert (
+        511 in vllm_config.compilation_config.compile_ranges_endpoints
+    ) == expected_enable_sp
+
+
 def test_cached_compilation_config(default_vllm_config):
     import torch
     from torch._inductor.utils import run_and_get_code

vllm/compilation/passes/fusion/collective_fusion.py

@@ -406,16 +406,13 @@ class AsyncTPPass(VllmPatternMatcherPass):
         self.dump_patterns(config, self.patterns)
 
     def is_applicable_for_range(self, compile_range: Range) -> bool:
-        # This pass is applied on top of the sequence parallelism pass.
-        # It inherits the same applicability condition as `SequenceParallelismPass`.
-        # See `SequenceParallelismPass.is_applicable` for more details.
-        if (
-            not self.compilation_config.splitting_ops
-            or self.compilation_config.use_inductor_graph_partition
-        ):
-            return True
-        tp_size = get_tensor_model_parallel_world_size()
-        return bool(compile_range.is_single_size() and compile_range.end % tp_size == 0)
+        # This pass is applied on top of the sequence parallelism pass,
+        # which is only supported in fullgraph compilation mode.
+        assert (
+            self.compilation_config.use_inductor_graph_partition
+            or not self.compilation_config.splitting_ops
+        ), "AsyncTPPass requires full-graph compilation"
+        return True
 
     @VllmInductorPass.time_and_log
     def __call__(self, graph: fx.Graph) -> None:

vllm/compilation/passes/fusion/sequence_parallelism.py

@@ -341,22 +341,18 @@ class SequenceParallelismPass(VllmPatternMatcherPass):
     significantly reduce communication overhead and improve overall model
     performance.
 
+    This pass is only supported when compiling the whole graph (fullgraph
+    mode, i.e. using Inductor graph partition or empty splitting_ops).
+    Piecewise compilation is not supported because the residual tensor
+    gets split across TP ranks, causing size mismatches at subgraph
+    boundaries.
 
-    This pass splits up the residual tensor across TP ranks and hence divides its size.
-    Because the pattern matcher starts at the end of the graph, the replacement
-    contains a slice that temporarily conforms the input residual to the correct size.
-    After all patterns have been matched, we use a NoOpEliminationPass to clean up
-    what have now become no-op slices.
-
-    Note that an older version of the pass did not need this as it operated only on
-    custom rms_norm and fused_rms_norm_add custom ops which did not complain about
-    mismatched shapes during replacement. So this approach has the same assumption that
-    correctness is only maintained if all rms_norm operations are split across ranks.
-
-    Correctness-wise, this is approach strictly better than before - before,
-    the graph was incorrect semantically and shape-wise during the pass.
-    With this approach there's only semantic incorrectness during the pass.
-    Both approaches restore a correct graph once all patterns are matched.
+    This pass splits up the residual tensor across TP ranks and hence
+    divides its size. Because the pattern matcher starts at the end of
+    the graph, the replacement contains a slice that temporarily conforms
+    the input residual to the correct size. After all patterns have been
+    matched, we use a NoOpEliminationPass to clean up what have now
+    become no-op slices.
     """
 
     @enable_fake_mode
@@ -419,19 +415,13 @@ class SequenceParallelismPass(VllmPatternMatcherPass):
         and gathering tensors across TP ranks outweighs the benefits.
 
         Returns False (SP disabled) when:
-        - Using piecewise compilation with non-concrete or TP-indivisible sizes
         - min_token_num is None (SP disabled for this device/config)
         - The compile range starts below the minimum token threshold
         """
-        # For piecewise compilation (not using inductor graph partition),
-        # we need concrete sizes that are divisible by TP for correct splitting
-        if (
-            not self.compilation_config.use_inductor_graph_partition
-            and self.compilation_config.splitting_ops
-        ):
-            tp_size = get_tensor_model_parallel_world_size()
-            if not compile_range.is_single_size() or compile_range.end % tp_size != 0:
-                return False
+        assert (
+            self.compilation_config.use_inductor_graph_partition
+            or not self.compilation_config.splitting_ops
+        ), "SequenceParallelismPass requires full-graph compilation"
 
         # min_token_num is None when SP is disabled for this device/config
         # (e.g., non-CUDA platform, unsupported GPU, or small hidden_size)

vllm/config/compilation.py

@@ -1148,6 +1148,25 @@ class CompilationConfig:
                     self.cudagraph_mode = CUDAGraphMode.FULL
                 self.splitting_ops = []
 
+        if (
+            not self.use_inductor_graph_partition
+            and (self.pass_config.enable_sp or self.pass_config.fuse_gemm_comms)
+            and self.splitting_ops
+        ):
+            logger.warning_once(
+                "Sequence parallelism requires full-graph compilation when "
+                "use_inductor_graph_partition is off. Setting splitting_ops "
+                "to an empty list to preserve SP and async TP."
+            )
+            self.splitting_ops = []
+            if self.cudagraph_mode.has_piecewise_cudagraphs():
+                logger.warning_once(
+                    "Sequence parallelism is incompatible with piecewise "
+                    "cudagraph when use_inductor_graph_partition is off. "
+                    "Setting cudagraph_mode to FULL."
+                )
+                self.cudagraph_mode = CUDAGraphMode.FULL
+
         # Disable CUDA graphs for DeepEP high-throughput since its not CG compatible
         if (
             all2all_backend == "deepep_high_throughput"

vllm/config/vllm.py

@@ -983,19 +983,16 @@ class VllmConfig:
             )
             self.compilation_config.cudagraph_mode = CUDAGraphMode.NONE
 
-        # async tp is built on top of sequence parallelism
-        # and requires it to be enabled.
-        if self.compilation_config.pass_config.fuse_gemm_comms:
-            self.compilation_config.pass_config.enable_sp = True
-        if self.compilation_config.pass_config.enable_sp:
+        # async tp is built on top of sequence parallelism and requires it.
+        pass_config = self.compilation_config.pass_config
+        if pass_config.fuse_gemm_comms:
+            pass_config.enable_sp = True
+        if pass_config.enable_sp:
             if self.parallel_config.tensor_parallel_size == 1:
                 logger.warning("Sequence Parallelism requires TP>1, disabling")
-                self.compilation_config.pass_config.enable_sp = False
-                self.compilation_config.pass_config.fuse_gemm_comms = False
+                pass_config.enable_sp = False
+                pass_config.fuse_gemm_comms = False
             else:
-                # Compute SP threshold early; disable if None (model too
-                # small for SP to be beneficial).
-                pass_config = self.compilation_config.pass_config
                 if pass_config.sp_min_token_num is None:
                     from vllm.compilation.passes.fusion.sequence_parallelism import (
                         get_sequence_parallelism_threshold,
@@ -1015,8 +1012,8 @@ class VllmConfig:
                         "threshold heuristic, disabling. To force SP, "
                         "set pass_config.sp_min_token_num manually."
                     )
-                    self.compilation_config.pass_config.enable_sp = False
-                    self.compilation_config.pass_config.fuse_gemm_comms = False
+                    pass_config.enable_sp = False
+                    pass_config.fuse_gemm_comms = False
 
         from vllm.utils.torch_utils import HAS_OPAQUE_TYPE
 
@@ -1098,6 +1095,7 @@ class VllmConfig:
                 self.compilation_config.cudagraph_num_of_warmups = 1
 
             self._set_cudagraph_sizes()
+
         else:
             self.compilation_config.cudagraph_mode = CUDAGraphMode.NONE
 
@@ -1171,8 +1169,8 @@ class VllmConfig:
         )
 
         if self.compilation_config.pass_config.enable_sp:
-            # With pipeline parallelism or dynamo partitioning,
-            # native rms norm tracing errors due to incorrect residual shape.
+            # With pipeline parallelism, native rms norm tracing errors due to
+            # incorrect residual shape.
             # Use custom rms norm to unblock. In the future,
             # the pass will operate on higher-level IR to avoid the issue.
             # TODO: https://github.com/vllm-project/vllm/issues/27894
@@ -1183,24 +1181,15 @@ class VllmConfig:
                     self.compilation_config.mode,
                 )
 
-            is_fullgraph = (
-                self.compilation_config.use_inductor_graph_partition
-                or len(self.compilation_config.splitting_ops or []) == 0
-            )
-            if self.parallel_config.pipeline_parallel_size > 1 or not is_fullgraph:
+            if self.parallel_config.pipeline_parallel_size > 1:
                 if "-rms_norm" not in self.compilation_config.custom_ops:
                     self.compilation_config.custom_ops.append("+rms_norm")
                 else:
-                    regime = (
-                        "Dynamo partition"
-                        if not is_fullgraph
-                        else "pipeline parallelism"
-                    )
                     logger.warning_once(
                         "Sequence parallelism not supported with "
                         "native rms_norm when using %s, "
                         "this will likely lead to an error.",
-                        regime,
+                        "pipeline parallelism",
                     )
 
         # final check of cudagraph mode after all possible updates
@@ -1212,9 +1201,9 @@ class VllmConfig:
                 and not self.compilation_config.cudagraph_mode.has_piecewise_cudagraphs()  # noqa: E501
             ):
                 logger.warning_once(
-                    "No piecewise cudagraph for executing cascade attention."
-                    " Will fall back to eager execution if a batch runs "
-                    "into cascade attentions."
+                    "No piecewise cudagraph for executing cascade attention. "
+                    "Will fall back to eager execution if a batch runs into "
+                    "cascade attentions."
                 )
 
             if self.compilation_config.cudagraph_mode.requires_piecewise_compilation():

vllm/v1/worker/utils.py

@@ -519,12 +519,8 @@ def is_residual_scattered_for_sp(
     """Check if the residual tensor is scattered for sequence parallelism.
 
     The residual tensor is scattered across tensor parallel ranks when sequence
-    parallelism and tensor parallelism is enabled.
-
-    This follows the same logic as SequenceParallelismPass.is_applicable_for_range():
-    - In full-graph compilation mode (no splitting ops or using inductor graph
-      partition), SP is always applied
-    - Otherwise, SP is only applied for specific shapes in compile_sizes
+    parallelism and tensor parallelism is enabled. SP is only supported in
+    full-graph compilation mode.
     """
     if not vllm_config.compilation_config.pass_config.enable_sp:
         return False
@@ -534,16 +530,13 @@ def is_residual_scattered_for_sp(
     if tp == 1:
         return False
 
+    assert (
+        vllm_config.compilation_config.use_inductor_graph_partition
+        or not vllm_config.compilation_config.splitting_ops
+    ), "Sequence parallelism requires full-graph compilation"
+
     # When sequence parallelism is enabled, we always pad num_input_tokens
     # to be a multiple of tensor_parallel_size (tp) earlier.
     assert num_input_tokens % tp == 0
 
-    if (
-        not vllm_config.compilation_config.splitting_ops
-        or vllm_config.compilation_config.use_inductor_graph_partition
-    ):
-        return True
-    compile_sizes = vllm_config.compilation_config.compile_sizes
-    if compile_sizes is None:
-        return False
-    return num_input_tokens in compile_sizes
+    return True