[BugFix] Fix DBO assert `assert B_block_table == B_q` (#29933)

Signed-off-by: Lucas Wilkinson <lwilkins@redhat.com>

tests/v1/attention/test_attention_splitting.py

@@ -13,7 +13,7 @@ from vllm.v1.attention.backends.utils import (
     split_attn_metadata,
     split_decodes_and_prefills,
 )
-from vllm.v1.worker.ubatch_utils import create_ubatch_slices
+from vllm.v1.worker.ubatch_utils import maybe_create_ubatch_slices
 
 
 @pytest.fixture
@@ -294,8 +294,14 @@ def test_prefill_split_across_ubatches(
     qsl_np = common.query_start_loc_cpu.numpy()
     num_tokens = common.num_actual_tokens
 
-    ubatch_slices = create_ubatch_slices(num_scheduled_tokens, split_point)
-    assert len(ubatch_slices) == 2
+    ubatch_slices, _ = maybe_create_ubatch_slices(
+        True,
+        num_scheduled_tokens,
+        num_tokens,
+        batch_spec.batch_size,
+        split_point=split_point,
+    )
+    assert ubatch_slices is not None and len(ubatch_slices) == 2
 
     first_meta = _make_metadata_with_slice(ubatch_slices[0], common)
     second_meta = _make_metadata_with_slice(ubatch_slices[1], common)

vllm/v1/spec_decode/eagle.py

@@ -1258,7 +1258,7 @@ class EagleProposer:
         num_tokens_padded: int,
     ) -> tuple[int, torch.Tensor]:
         # TODO(Flechman): support DBO ubatching
-        ubatch_slices, num_toks_across_dp = coordinate_batch_across_dp(
+        should_ubatch, num_toks_across_dp = coordinate_batch_across_dp(
             num_tokens_unpadded=num_tokens_unpadded,
             parallel_config=self.vllm_config.parallel_config,
             allow_microbatching=False,
@@ -1267,7 +1267,7 @@ class EagleProposer:
             uniform_decode=None,
             num_scheduled_tokens_per_request=None,
         )
-        assert ubatch_slices is None, "DBO ubatching not implemented for EAGLE"
+        assert not should_ubatch, "DBO ubatching not implemented for EAGLE"
 
         num_tokens_dp_padded = num_tokens_padded
         if num_toks_across_dp is not None:

vllm/v1/worker/dp_utils.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
+
 import numpy as np
 import torch
 import torch.distributed as dist
@@ -9,10 +10,7 @@ from vllm.config import ParallelConfig
 from vllm.distributed.parallel_state import get_dp_group
 from vllm.logger import init_logger
 from vllm.v1.worker.ubatch_utils import (
-    UBatchSlice,
-    UBatchSlices,
     check_ubatch_thresholds,
-    create_ubatch_slices,
     is_second_ubatch_empty,
 )
 
@@ -91,20 +89,6 @@ def _post_process_dp_padding(tensor: torch.Tensor, should_dp_pad: bool) -> torch
         return num_tokens_across_dp.cpu()
 
 
-# This just pads the second ubatch slice out to the total number of tokens
-# (num_tokens + padding) since we do `create_ubatch_slices` before applying DP padding.
-def _pad_out_ubatch_slice(
-    ubatch_slices: UBatchSlices, num_total_tokens: int
-) -> UBatchSlices:
-    padded_second_token_slice = slice(
-        ubatch_slices[1].token_slice.start, num_total_tokens
-    )
-    ubatch_slices[1] = UBatchSlice(
-        ubatch_slices[1].request_slice, padded_second_token_slice
-    )
-    return ubatch_slices
-
-
 def _synchronize_dp_ranks(
     num_tokens_unpadded: int,
     num_tokens_padded: int,
@@ -175,7 +159,7 @@ def coordinate_batch_across_dp(
     num_tokens_padded: int | None = None,
     uniform_decode: bool | None = None,
     num_scheduled_tokens_per_request: np.ndarray | None = None,
-) -> tuple[UBatchSlices | None, torch.Tensor | None]:
+) -> tuple[bool, torch.Tensor | None]:
     """
     Coordinates amongst all DP ranks to determine if and how the full batch
     should be split into microbatches.
@@ -204,7 +188,7 @@ def coordinate_batch_across_dp(
     """
     if parallel_config.data_parallel_size == 1:
         # Early exit.
-        return None, None
+        return False, None
 
     # If the caller has explicitly enabled microbatching.
     should_attempt_ubatching = False
@@ -228,23 +212,4 @@ def coordinate_batch_across_dp(
         parallel_config,
     )
 
-    # Don't microbatch unless every other DP worker is also microbatching
-    if not should_ubatch:
-        return (None, num_tokens_after_padding)
-
-    # This doesn't actually pad the ubatch slices. It just initializes the
-    # split point to the padded value so that padding can be applied
-    # to the second ubatch in pad_out_ubatch_slice after attention
-    # metadata creation
-    assert num_tokens_after_padding is not None
-    num_tokens_padded = int(num_tokens_after_padding[0].item())
-    token_split_point = int(num_tokens_padded) // 2
-
-    assert num_scheduled_tokens_per_request is not None
-    ubatch_slices = create_ubatch_slices(
-        num_scheduled_tokens_per_request, token_split_point
-    )
-    ubatch_slices = _pad_out_ubatch_slice(ubatch_slices, num_tokens_padded)
-    assert sum(s.num_tokens for s in ubatch_slices) == num_tokens_padded
-
-    return (ubatch_slices, num_tokens_after_padding)
+    return (should_ubatch, num_tokens_after_padding)

vllm/v1/worker/gpu_model_runner.py

@@ -153,6 +153,7 @@ from vllm.v1.worker.lora_model_runner_mixin import LoRAModelRunnerMixin
 from vllm.v1.worker.ubatch_utils import (
     UBatchSlices,
     check_ubatch_thresholds,
+    maybe_create_ubatch_slices,
 )
 from vllm.v1.worker.utils import is_residual_scattered_for_sp
 
@@ -2743,7 +2744,7 @@ class GPUModelRunner(
     ) -> tuple[
         CUDAGraphMode,
         BatchDescriptor,
-        UBatchSlices | None,
+        bool,
         torch.Tensor | None,
         CUDAGraphStat | None,
     ]:
@@ -2779,7 +2780,7 @@ class GPUModelRunner(
 
         # Extra coordination when running data-parallel since we need to coordinate
         # across ranks
-        ubatch_slices, num_tokens_across_dp = None, None
+        should_ubatch, num_tokens_across_dp = False, None
         if self.vllm_config.parallel_config.data_parallel_size > 1:
             # Disable DP padding when running eager to avoid excessive padding when
             # running prefills. This lets us set cudagraph_mode="NONE" on the prefiller
@@ -2789,8 +2790,8 @@ class GPUModelRunner(
                 self.compilation_config.cudagraph_mode != CUDAGraphMode.NONE
             )
 
-            ubatch_slices, num_tokens_across_dp = coordinate_batch_across_dp(
-                num_tokens_unpadded=num_tokens_padded,
+            should_ubatch, num_tokens_across_dp = coordinate_batch_across_dp(
+                num_tokens_unpadded=num_tokens,
                 parallel_config=self.parallel_config,
                 allow_microbatching=allow_microbatching,
                 allow_dp_padding=allow_dp_padding,
@@ -2822,7 +2823,7 @@ class GPUModelRunner(
         return (
             cudagraph_mode,
             batch_descriptor,
-            ubatch_slices,
+            should_ubatch,
             num_tokens_across_dp,
             cudagraph_stats,
         )
@@ -2921,7 +2922,7 @@ class GPUModelRunner(
                 (
                     cudagraph_mode,
                     batch_desc,
-                    ubatch_slices,
+                    should_ubatch,
                     num_tokens_across_dp,
                     cudagraph_stats,
                 ) = self._determine_batch_execution_and_padding(
@@ -2934,10 +2935,10 @@ class GPUModelRunner(
 
                 logger.debug(
                     "Running batch with cudagraph_mode: %s, batch_descriptor: %s, "
-                    "ubatch_slices: %s, num_tokens_across_dp: %s",
+                    "should_ubatch: %s, num_tokens_across_dp: %s",
                     cudagraph_mode,
                     batch_desc,
-                    ubatch_slices,
+                    should_ubatch,
                     num_tokens_across_dp,
                 )
 
@@ -2945,10 +2946,18 @@ class GPUModelRunner(
                 num_reqs_padded = (
                     batch_desc.num_reqs if batch_desc.num_reqs is not None else num_reqs
                 )
+                ubatch_slices, ubatch_slices_padded = maybe_create_ubatch_slices(
+                    should_ubatch,
+                    num_scheduled_tokens_np,
+                    num_tokens_padded,
+                    num_reqs_padded,
+                )
 
-                use_spec_decode = len(scheduler_output.scheduled_spec_decode_tokens) > 0
                 pad_attn = cudagraph_mode == CUDAGraphMode.FULL
 
+                use_spec_decode = len(scheduler_output.scheduled_spec_decode_tokens) > 0
+                ubatch_slices_attn = ubatch_slices_padded if pad_attn else ubatch_slices
+
                 (attn_metadata, spec_decode_common_attn_metadata) = (
                     self._build_attention_metadata(
                         num_tokens=num_tokens_unpadded,
@@ -2956,7 +2965,7 @@ class GPUModelRunner(
                         num_reqs=num_reqs,
                         num_reqs_padded=num_reqs_padded if pad_attn else None,
                         max_query_len=max_num_scheduled_tokens,
-                        ubatch_slices=ubatch_slices,
+                        ubatch_slices=ubatch_slices_attn,
                         logits_indices=logits_indices,
                         use_spec_decode=use_spec_decode,
                         num_scheduled_tokens=scheduler_output.num_scheduled_tokens,
@@ -2993,7 +3002,7 @@ class GPUModelRunner(
                 num_tokens_across_dp=num_tokens_across_dp,
                 cudagraph_runtime_mode=cudagraph_mode,
                 batch_descriptor=batch_desc,
-                ubatch_slices=ubatch_slices,
+                ubatch_slices=ubatch_slices_padded,
             ),
             record_function_or_nullcontext("gpu_model_runner: forward"),
             self.maybe_get_kv_connector_output(scheduler_output) as kv_connector_output,
@@ -3945,7 +3954,7 @@ class GPUModelRunner(
 
         num_sampled_tokens = np.ones(num_reqs, dtype=np.int32)
 
-        _cudagraph_mode, batch_desc, ubatch_slices, num_tokens_across_dp, _ = (
+        _cudagraph_mode, batch_desc, should_ubatch, num_tokens_across_dp, _ = (
             self._determine_batch_execution_and_padding(
                 num_tokens=num_tokens_unpadded,
                 num_reqs=num_reqs,
@@ -3979,6 +3988,9 @@ class GPUModelRunner(
         num_reqs_padded = (
             batch_desc.num_reqs if batch_desc.num_reqs is not None else num_reqs
         )
+        ubatch_slices, ubatch_slices_padded = maybe_create_ubatch_slices(
+            should_ubatch, num_scheduled_tokens, num_tokens_padded, num_reqs_padded
+        )
 
         attn_metadata: PerLayerAttnMetadata | None = None
 
@@ -4000,11 +4012,12 @@ class GPUModelRunner(
             self.query_start_loc.np[1 : num_reqs + 1] = cum_num_tokens
             self.query_start_loc.copy_to_gpu()
 
+            pad_attn = cudagraph_runtime_mode == CUDAGraphMode.FULL
             attn_metadata, _ = self._build_attention_metadata(
                 num_tokens=num_tokens_unpadded,
                 num_reqs=num_reqs_padded,
                 max_query_len=max_query_len,
-                ubatch_slices=ubatch_slices,
+                ubatch_slices=ubatch_slices_padded if pad_attn else ubatch_slices,
                 for_cudagraph_capture=is_graph_capturing,
             )
 
@@ -4056,11 +4069,11 @@ class GPUModelRunner(
                     num_tokens_padded, None, False
                 )
 
-            if ubatch_slices is not None:
+            if ubatch_slices_padded is not None:
                 # Adjust values to reflect a single ubatch.
                 # TODO(sage,lucas): this is cruft that should be addressed in
                 #  the padding refactor.
-                num_tokens_padded = ubatch_slices[0].num_tokens
+                num_tokens_padded = ubatch_slices_padded[0].num_tokens
                 if num_tokens_across_dp is not None:
                     num_tokens_across_dp[:] = num_tokens_padded
 
@@ -4073,7 +4086,7 @@ class GPUModelRunner(
                     num_tokens_across_dp=num_tokens_across_dp,
                     cudagraph_runtime_mode=cudagraph_runtime_mode,
                     batch_descriptor=batch_desc,
-                    ubatch_slices=ubatch_slices,
+                    ubatch_slices=ubatch_slices_padded,
                 ),
             ):
                 outputs = self.model(

vllm/v1/worker/ubatch_utils.py

@@ -42,9 +42,37 @@ def check_ubatch_thresholds(
         return num_tokens >= config.dbo_prefill_token_threshold
 
 
-def create_ubatch_slices(
-    num_scheduled_tokens: np.ndarray, split_point: int
+# This just pads the second ubatch slice out to the total number of tokens
+# (num_tokens + padding) since we do `create_ubatch_slices` before applying DP padding.
+def _pad_out_ubatch_slices(
+    ubatch_slices: UBatchSlices, num_total_tokens: int, num_reqs_padded: int
 ) -> UBatchSlices:
+    # TODO(lucas): handle empty second ubatch
+    padded_second_request_slice = slice(
+        ubatch_slices[1].request_slice.start, num_reqs_padded
+    )
+    padded_second_token_slice = slice(
+        ubatch_slices[1].token_slice.start, num_total_tokens
+    )
+    return [
+        ubatch_slices[0],
+        UBatchSlice(padded_second_request_slice, padded_second_token_slice),
+    ]
+
+
+def maybe_create_ubatch_slices(
+    should_ubatch: bool,
+    num_scheduled_tokens: np.ndarray,
+    num_tokens_padded: int,
+    num_reqs_padded: int,
+    split_point: int | None = None,
+) -> tuple[UBatchSlices | None, UBatchSlices | None]:
+    if not should_ubatch:
+        return None, None
+
+    if split_point is None:
+        split_point = int(num_tokens_padded) // 2
+
     # TODO(lucas): Refactor the gpu_model_runner.py so we can pass
     # in cu_num_tokens directly (i.e. query_start_loc)
     cu_num_tokens = np.zeros(len(num_scheduled_tokens) + 1, dtype=np.int32)
@@ -67,7 +95,15 @@ def create_ubatch_slices(
     )
     second_ubatch_req_slice = slice(second_ubatch_req_start, len(cu_num_tokens) - 1)
 
-    return [
+    ubatch_slices = [
         UBatchSlice(first_ubatch_req_slice, first_ubatch_token_slice),
         UBatchSlice(second_ubatch_req_slice, second_ubatch_token_slice),
     ]
+
+    ubatch_slices_padded = _pad_out_ubatch_slices(
+        ubatch_slices, num_tokens_padded, num_reqs_padded
+    )
+
+    assert sum(s.num_tokens for s in ubatch_slices_padded) == num_tokens_padded
+
+    return ubatch_slices, ubatch_slices_padded