[Core/DBO][2/N] Dual-Batch Overlap add DeepEP High Throughput support and Prefill support (#24845)

Signed-off-by: Sage Moore <sage@neuralmagic.com>
Signed-off-by: Lucas Wilkinson <lwilkins@redhat.com>
Signed-off-by: yewentao256 <zhyanwentao@126.com>
Signed-off-by: Lucas Wilkinson <LucasWilkinson@users.noreply.github.com>
Signed-off-by: Tyler Michael Smith <tyler@neuralmagic.com>
Co-authored-by: Sage Moore <sage@neuralmagic.com>
Co-authored-by: yewentao256 <zhyanwentao@126.com>
Co-authored-by: Tyler Michael Smith <tyler@neuralmagic.com>

tests/v1/attention/test_attention_splitting.py

@@ -5,11 +5,12 @@ import pytest
 import torch
 
 from tests.v1.attention.test_attention_backends import BATCH_SPECS
-from tests.v1.attention.utils import create_common_attn_metadata
+from tests.v1.attention.utils import BatchSpec, create_common_attn_metadata
 from vllm.v1.attention.backends.utils import (UBatchSlice,
                                               _make_metadata_with_slice,
                                               slice_query_start_locs,
                                               split_attn_metadata)
+from vllm.v1.worker.ubatch_utils import create_ubatch_slices
 
 
 @pytest.fixture
@@ -155,3 +156,83 @@ def test_split_attn_metadata_decode_batch(large_decode_metadata):
     assert results[1].num_reqs == mid_point
     assert results[1].num_actual_tokens == mid_point
     assert torch.equal(results[1].seq_lens, torch.tensor([2048] * mid_point))
+
+
+@pytest.mark.parametrize(
+    "seq_lens,query_lens,split_point,expected_first_reqs,expected_second_reqs",
+    [
+        # Split in the middle of request 1
+        ([32, 40], [8, 8], 12, 2, 1),
+        # Split inside the first request
+        ([32, 40], [8, 8], 4, 1, 2),
+    ],
+)
+def test_prefill_split_across_ubatches(seq_lens, query_lens, split_point,
+                                       expected_first_reqs,
+                                       expected_second_reqs):
+    """Test splitting a prefill across ubatches"""
+    import numpy as np
+
+    device = torch.device("cpu")
+    batch_spec = BatchSpec(seq_lens=seq_lens, query_lens=query_lens)
+    common = create_common_attn_metadata(batch_spec,
+                                         block_size=16,
+                                         device=device)
+
+    num_scheduled_tokens = np.array(query_lens, dtype=np.int32)
+    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
+
+    first_meta = _make_metadata_with_slice(ubatch_slices[0], common)
+    second_meta = _make_metadata_with_slice(ubatch_slices[1], common)
+
+    # Token counts match the split
+    assert first_meta.num_actual_tokens == split_point
+    assert second_meta.num_actual_tokens == num_tokens - split_point
+
+    # Number of requests per ubatch
+    assert first_meta.num_reqs == expected_first_reqs
+    assert second_meta.num_reqs == expected_second_reqs
+
+    # Identify which request is split and how many tokens are in the first chunk
+    split_req_idx = int(np.searchsorted(qsl_np, split_point, side="right") - 1)
+    tokens_in_first_chunk = split_point - int(qsl_np[split_req_idx])
+    orig_q_lens = (common.query_start_loc_cpu[1:] -
+                   common.query_start_loc_cpu[:-1])
+
+    # Check query length continuity: first-chunk + second-chunk == original qlen
+    # First ubatch last request query length
+    qlen_first_last = int(first_meta.query_start_loc_cpu[-1] -
+                          first_meta.query_start_loc_cpu[-2])
+    # Second ubatch first request query length
+    qlen_second_first = int(second_meta.query_start_loc_cpu[1] -
+                            second_meta.query_start_loc_cpu[0])
+    assert qlen_first_last == tokens_in_first_chunk
+    assert qlen_first_last + qlen_second_first == int(
+        orig_q_lens[split_req_idx])
+
+    # Check seq_lens adjustments
+    # Context lengths per original request
+    context_lens = [s - q for s, q in zip(seq_lens, query_lens)]
+
+    # First ubatch: last request's seq_len should be
+    #  context + tokens_in_first_chunk
+    expected_seqlen = context_lens[split_req_idx] + tokens_in_first_chunk
+    assert int(first_meta.seq_lens[-1]) == expected_seqlen
+
+    # For full preceding requests in first ubatch, seq_lens should match
+    #  originals
+    for i in range(first_meta.num_reqs - 1):
+        assert int(first_meta.seq_lens[i]) == seq_lens[i]
+
+    # Second ubatch: first request (continuation) seq_len should be full
+    #  original
+    assert int(second_meta.seq_lens[0]) == seq_lens[split_req_idx]
+    # Any following full requests in second ubatch should match originals
+    for j in range(1, second_meta.num_reqs):
+        # Map to original request index
+        orig_idx = split_req_idx + j
+        assert int(second_meta.seq_lens[j]) == seq_lens[orig_idx]

tests/v1/spec_decode/test_eagle.py

@@ -532,9 +532,8 @@ def test_propose(method, attn_backend, num_speculative_tokens, monkeypatch):
     # Mock runner for attention metadata building
     proposer.runner = mock.MagicMock()
     proposer.runner.attn_groups.append([mock.MagicMock()])
-    proposer.runner.attn_groups[0][0].metadata_builders = [
+    proposer.runner.attn_groups[0][0].get_metadata_builder.return_value = \
         attn_metadata_builder
-    ]
 
     result = proposer.propose(target_token_ids=target_token_ids,
                               target_positions=target_positions,
@@ -659,9 +658,8 @@ def test_propose_tree(spec_token_tree):
     # Mock runner for attention metadata building.
     proposer.runner = mock.MagicMock()
     proposer.runner.attn_groups.append([mock.MagicMock()])
-    proposer.runner.attn_groups[0][0].metadata_builders = [
+    proposer.runner.attn_groups[0][0].get_metadata_builder.return_value = \
         attn_metadata_builder
-    ]
 
     # Setup inputs for the proposer.
     target_token_ids = torch.randint(0,

vllm/config/__init__.py

@@ -638,11 +638,13 @@ class VllmConfig:
 
         if self.parallel_config.enable_dbo:
             a2a_backend = envs.VLLM_ALL2ALL_BACKEND
-            assert a2a_backend == "deepep_low_latency", \
-            "Microbatching currently only supports the deepep_low_latency "\
-            f"all2all backend. {a2a_backend} is not supported. To fix set "\
-            "the VLLM_ALL2ALL_BACKEND environment variable to "\
-            "deepep_low_latency and install the DeepEP kerenls."
+            assert a2a_backend in \
+                ["deepep_low_latency", "deepep_high_throughput"], \
+            "Microbatching currently only supports the deepep_low_latency and "\
+            f"deepep_high_throughput all2all backend. {a2a_backend} is not "\
+            "supported. To fix set the VLLM_ALL2ALL_BACKEND environment "\
+            "variable to deepep_low_latency or deepep_high_throughput and "\
+            "install the DeepEP kernels."
 
         if not self.instance_id:
             self.instance_id = random_uuid()[:5]

vllm/config/parallel.py

@@ -139,12 +139,18 @@ class ParallelConfig:
     """Disable the custom all-reduce kernel and fall back to NCCL."""
 
     enable_dbo: bool = False
-    """Enable microbatching for the model executor."""
+    """Enable dual batch overlap for the model executor."""
 
     dbo_decode_token_threshold: int = 32
-    """The threshold for microbatching. If the number of tokens in the
-    request is greater than this threshold, microbatching will be used.
-    Otherwise, the request will be processed in a single batch."""
+    """The threshold for dual batch overlap for batches only containing decodes.
+    If the number of tokens in the request is greater than this threshold,
+    microbatching will be used. Otherwise, the request will be processed in a
+    single batch."""
+    dbo_prefill_token_threshold: int = 512  # TODO(lucas): tune
+    """The threshold for dual batch overlap for batches that contain one or more
+    prefills. If the number of tokens in the request is greater than this
+    threshold, microbatching will be used. Otherwise, the request will be
+    processed in a single batch."""
 
     ray_workers_use_nsight: bool = False
     """Whether to profile Ray workers with nsight, see https://docs.ray.io/en/latest/ray-observability/user-guides/profiling.html#profiling-nsight-profiler."""

vllm/distributed/device_communicators/all2all.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-from typing import Any
+from typing import Any, Optional
 
 import torch
 import torch.distributed as dist
 
+import vllm.envs as envs
 from vllm.distributed import get_dp_group
 from vllm.forward_context import get_forward_context
 from vllm.logger import init_logger
@@ -200,12 +201,12 @@ class DeepEPHTAll2AllManager(DeepEPAll2AllManagerBase):
 
     def _make_all2all_kwargs(self) -> dict[Any, Any]:
         # Defaults for internode and intranode are taken from DeepEP tests.
-        num_nvl_bytes = 1024 * 1024 * 1024
+        num_nvl_bytes = envs.VLLM_DEEPEP_BUFFER_SIZE_MB * 1024 * 1024
         num_rdma_bytes = None
         num_qps_per_rank = None
 
         if self.internode:
-            num_rdma_bytes = 1024 * 1024 * 1024
+            num_rdma_bytes = envs.VLLM_DEEPEP_BUFFER_SIZE_MB * 1024 * 1024
             num_qps_per_rank = self.num_sms // 2
         else:
             num_rdma_bytes = 0
@@ -230,13 +231,18 @@ class DeepEPHTAll2AllManager(DeepEPAll2AllManagerBase):
         logger.debug("DeepEP all2all args %s", buffer_kwargs)
         handle: deep_ep.Buffer = self.handle_cache.get_or_create(
             buffer_kwargs, deep_ep.Buffer)
-        # It is dangerous to set num sms outside this function. num_sms is not
-        # a part of the hash-key that identifies this object. If we are in a
-        # situation where we make objects with different num_sms, the hash key
-        # in get_or_create must be updated.
-        handle.set_num_sms(self.num_sms)
         return handle
 
+    def set_num_sms(self, num_sms: int):
+        import deep_ep
+
+        # Right now the buffers are sized for only what the kernels were
+        # created with. So we can only reduce the number of SMS used
+        # but not increase it.
+        if num_sms > self.num_sms:
+            num_sms = self.num_sms
+        deep_ep.Buffer.set_num_sms(num_sms)
+
 
 class DeepEPLLAll2AllManager(DeepEPAll2AllManagerBase):
     """
@@ -265,7 +271,7 @@ class DeepEPLLAll2AllManager(DeepEPAll2AllManagerBase):
         import deep_ep
 
         # Defaults for internode and intranode are taken from DeepEP tests.
-        num_nvl_bytes = 1024 * 1024 * 1024
+        num_nvl_bytes = envs.VLLM_DEEPEP_BUFFER_SIZE_MB * 1024 * 1024
         num_qps_per_rank = num_local_experts
         num_rdma_bytes = deep_ep.Buffer.get_low_latency_rdma_size_hint(
             num_max_dispatch_tokens_per_rank=max_num_tokens_per_dp_rank,
@@ -291,3 +297,7 @@ class DeepEPLLAll2AllManager(DeepEPAll2AllManagerBase):
         handle: deep_ep.Buffer = self.handle_cache.get_or_create(
             buffer_kwargs, deep_ep.Buffer)
         return handle
+
+    # DeepEP LL uses RDMA so no SMs are used for communication
+    def max_sms_used(self) -> Optional[int]:
+        return 0
\ No newline at end of file

vllm/distributed/device_communicators/base_device_communicator.py

@@ -60,6 +60,12 @@ class All2AllManagerBase:
         # and reuse it for the same config.
         raise NotImplementedError
 
+    def set_num_sms(self, num_sms: int):
+        pass
+
+    def max_sms_used(self) -> Optional[int]:
+        return None  # None means it could use the whole GPU
+
     def dispatch(self, hidden_states: torch.Tensor,
                  router_logits: torch.Tensor):
         raise NotImplementedError

vllm/engine/arg_utils.py

@@ -330,6 +330,8 @@ class EngineArgs:
     enable_dbo: bool = ParallelConfig.enable_dbo
     dbo_decode_token_threshold: int = \
         ParallelConfig.dbo_decode_token_threshold
+    dbo_prefill_token_threshold: int = \
+        ParallelConfig.dbo_prefill_token_threshold
     eplb_config: EPLBConfig = get_field(ParallelConfig, "eplb_config")
     enable_eplb: bool = ParallelConfig.enable_eplb
     expert_placement_strategy: ExpertPlacementStrategy = \
@@ -698,6 +700,9 @@ class EngineArgs:
         parallel_group.add_argument(
             "--dbo-decode-token-threshold",
             **parallel_kwargs["dbo_decode_token_threshold"])
+        parallel_group.add_argument(
+            "--dbo-prefill-token-threshold",
+            **parallel_kwargs["dbo_prefill_token_threshold"])
         parallel_group.add_argument("--enable-eplb",
                                     **parallel_kwargs["enable_eplb"])
         parallel_group.add_argument("--eplb-config",
@@ -1316,6 +1321,7 @@ class EngineArgs:
             enable_expert_parallel=self.enable_expert_parallel,
             enable_dbo=self.enable_dbo,
             dbo_decode_token_threshold=self.dbo_decode_token_threshold,
+            dbo_prefill_token_threshold=self.dbo_prefill_token_threshold,
             enable_eplb=self.enable_eplb,
             eplb_config=self.eplb_config,
             expert_placement_strategy=self.expert_placement_strategy,

vllm/envs.py

@@ -189,6 +189,8 @@ if TYPE_CHECKING:
     VLLM_CUSTOM_SCOPES_FOR_PROFILING: bool = False
     VLLM_KV_EVENTS_USE_INT_BLOCK_HASHES: bool = True
     VLLM_OBJECT_STORAGE_SHM_BUFFER_NAME: str = "VLLM_OBJECT_STORAGE_SHM_BUFFER"
+    VLLM_DEEPEP_BUFFER_SIZE_MB: int = 1024
+    VLLM_DBO_COMM_SMS: int = 20
     GPT_OSS_SYSTEM_TOOL_MCP_LABELS: list[str] = []
     VLLM_PATTERN_MATCH_DEBUG: Optional[str] = None
 
@@ -1392,6 +1394,15 @@ environment_variables: dict[str, Callable[[], Any]] = {
     lambda: os.getenv("VLLM_OBJECT_STORAGE_SHM_BUFFER_NAME",
                       "VLLM_OBJECT_STORAGE_SHM_BUFFER"),
 
+    # The size in MB of the buffers (NVL and RDMA) used by DeepEP
+    "VLLM_DEEPEP_BUFFER_SIZE_MB":
+    lambda: int(os.getenv("VLLM_DEEPEP_BUFFER_SIZE_MB", "1024")),
+
+    # The number of SMs to allocate for communication kernels when running DBO
+    # the rest of the SMs on the device will be allocated to compute
+    "VLLM_DBO_COMM_SMS":
+    lambda: int(os.getenv("VLLM_DBO_COMM_SMS", "20")),
+
     # Valid values are container,code_interpreter,web_search_preview
     # ex GPT_OSS_SYSTEM_TOOL_MCP_LABELS=container,code_interpreter
     "GPT_OSS_SYSTEM_TOOL_MCP_LABELS":

vllm/model_executor/layers/fused_moe/deepep_ht_prepare_finalize.py

@@ -12,6 +12,11 @@ from vllm.model_executor.layers.fused_moe.topk_weight_and_reduce import (
 from vllm.model_executor.layers.fused_moe.utils import (
     moe_kernel_quantize_input)
 from vllm.utils import round_up
+from vllm.v1.worker.ubatching import (
+    dbo_current_ubatch_id, dbo_enabled, dbo_switch_to_comm,
+    dbo_switch_to_compute, dbo_switch_to_compute_sync,
+    dbo_yield_and_switch_from_comm_to_compute,
+    dbo_yield_and_switch_from_compute_to_comm)
 
 
 class DeepEPHTPrepareAndFinalize(mk.FusedMoEPrepareAndFinalize):
@@ -46,9 +51,9 @@ class DeepEPHTPrepareAndFinalize(mk.FusedMoEPrepareAndFinalize):
         self.async_prepare = True
 
         # The dispatch function returns a handle that the combine function
-        # requires. We store the handle here so it is available to the
-        # combine function.
-        self.handle = None
+        # requires. Under DBO microbatching we must track one handle per
+        # micro-batch to avoid races between threads.
+        self.handles = [None, None]
 
         # From https://github.com/deepseek-ai/DeepEP/blob/9fe9021f29c9083cd1808ab36b740208524d9f63/deep_ep/buffer.py#L164
         self.available_rank_configs = [2, 4, 8, 16, 24, 32, 64, 128, 144, 160]
@@ -89,6 +94,11 @@ class DeepEPHTPrepareAndFinalize(mk.FusedMoEPrepareAndFinalize):
 
         has_scales = token_scales is not None
 
+        # We yield before launching the dispatch kernel since the dispatch
+        # kernel will block the CPU so we want to queue up all the compute
+        # for the other ubatch before the dispatch kernel starts.
+        dbo_yield_and_switch_from_compute_to_comm()
+
         (num_tokens_per_rank, num_tokens_per_rdma_rank,
          dispatch_expert_num_tokens, is_token_in_rank,
          event) = self.buffer.get_dispatch_layout(
@@ -104,7 +114,7 @@ class DeepEPHTPrepareAndFinalize(mk.FusedMoEPrepareAndFinalize):
 
         (
             token_data, expert_topk_ids, expert_topk_weights,
-            expert_num_tokens_per_expert_list, self.handle, event
+            expert_num_tokens_per_expert_list, handle, event
         ) = self.buffer.dispatch(
             x=token_data,
             handle=None,
@@ -119,9 +129,15 @@ class DeepEPHTPrepareAndFinalize(mk.FusedMoEPrepareAndFinalize):
             expert_alignment=1,
             config=self._get_dispatch_config(),
             previous_event=None,
-            async_finish=self.async_prepare,
+            async_finish=self.async_prepare and not dbo_enabled(),
             allocate_on_comm_stream=False)
 
+        # record the handle for this ubatch
+        a2a_idx = dbo_current_ubatch_id()
+        self.handles[a2a_idx] = handle
+
+        dbo_switch_to_compute_sync()
+
         return lambda: self._receiver(
             event,
             has_scales,
@@ -146,7 +162,7 @@ class DeepEPHTPrepareAndFinalize(mk.FusedMoEPrepareAndFinalize):
         a1_scale: Optional[torch.Tensor],
         quant_config: FusedMoEQuantConfig,
     ) -> mk.PrepareResultType:
-        if self.async_prepare:
+        if event.event is not None:
             event.current_stream_wait()
 
         if has_scales:
@@ -207,7 +223,7 @@ class DeepEPHTPrepareAndFinalize(mk.FusedMoEPrepareAndFinalize):
         expert_map: Optional[torch.Tensor],
         apply_router_weight_on_input: bool,
         quant_config: FusedMoEQuantConfig,
-    ) -> tuple[Callable, mk.ReceiverType]:
+    ) -> mk.ReceiverType:
 
         if apply_router_weight_on_input:
             topk = topk_ids.size(1)
@@ -233,14 +249,13 @@ class DeepEPHTPrepareAndFinalize(mk.FusedMoEPrepareAndFinalize):
             a1q_scale = None
             a1_post_scale = quant_config.a1_scale
 
-        return (lambda *args: None,
-                self._do_dispatch(tokens=a1q,
+        return self._do_dispatch(tokens=a1q,
                                  token_scales=a1q_scale,
                                  rank_topk_ids=topk_ids,
                                  rank_topk_weights=topk_weights,
                                  num_experts=num_experts,
                                  a1_scale=a1_post_scale,
-                                  quant_config=quant_config))
+                                 quant_config=quant_config)
 
     def prepare(
         self,
@@ -252,9 +267,8 @@ class DeepEPHTPrepareAndFinalize(mk.FusedMoEPrepareAndFinalize):
         apply_router_weight_on_input: bool,
         quant_config: FusedMoEQuantConfig,
     ) -> mk.PrepareResultType:
-        (_, receiver) = self.prepare_async(a1, topk_weights, topk_ids,
-                                           num_experts, expert_map,
-                                           apply_router_weight_on_input,
+        receiver = self.prepare_async(a1, topk_weights, topk_ids, num_experts,
+                                      expert_map, apply_router_weight_on_input,
                                       quant_config)
         return receiver()
 
@@ -269,7 +283,9 @@ class DeepEPHTPrepareAndFinalize(mk.FusedMoEPrepareAndFinalize):
         do_async: bool,
     ) -> Optional[Callable]:
 
-        assert self.handle is not None
+        a2a_idx = dbo_current_ubatch_id()
+        handle = self.handles[a2a_idx]
+        assert handle is not None
 
         # fused_expert_output can have 0 tokens - This happens when none of the
         # tokens from the all2all reach this EP rank.
@@ -283,25 +299,35 @@ class DeepEPHTPrepareAndFinalize(mk.FusedMoEPrepareAndFinalize):
                 topk_ids=topk_ids,
                 apply_router_weight_on_input=apply_router_weight_on_input,
             )
-
+        dbo_yield_and_switch_from_compute_to_comm()
         combined_x, _, event = self.buffer.combine(
             x=fused_expert_output,
-            handle=self.handle,
+            handle=handle,
             topk_weights=None,
             config=self._get_combine_config(),
             previous_event=None,
-            async_finish=do_async,
+            async_finish=do_async and not dbo_enabled(),
             allocate_on_comm_stream=False)
 
+        dbo_switch_to_compute()
+
         if do_async:
 
             def _receiver():
+                if event.event is not None:
                     event.current_stream_wait()
+                dbo_switch_to_comm()
                 # Respect inplace outputs.
                 output.copy_(combined_x, non_blocking=True)
 
-            return lambda: _receiver()
+                # TODO(lucas): refactor the modular kernel so this will be
+                # handled there
+                dbo_yield_and_switch_from_comm_to_compute()
+
+            return _receiver
         else:
+            # TODO(lucas): support this case with the refactored modular kernel
+            assert not dbo_enabled()
             # Respect inplace outputs.
             output.copy_(combined_x, non_blocking=True)
             return None

vllm/model_executor/layers/fused_moe/deepep_ll_prepare_finalize.py

@@ -206,7 +206,7 @@ class DeepEPLLPrepareAndFinalize(mk.FusedMoEPrepareAndFinalize):
         apply_router_weight_on_input: bool,
         weight_and_reduce_impl: mk.TopKWeightAndReduce,
         do_async: bool,
-    ) -> Optional[Callable]:
+    ) -> tuple[Callable, Callable]:
         assert isinstance(
             weight_and_reduce_impl, TopKWeightAndReduceDelegate
         ), ("Weight application and reduction happens in the combine kernel.")
@@ -233,7 +233,7 @@ class DeepEPLLPrepareAndFinalize(mk.FusedMoEPrepareAndFinalize):
             return_recv_hook=do_recv_hook,
             out=output)
 
-        return recv_hook
+        return recv_hook, lambda: None
 
     def finalize_async(
         self,
@@ -243,8 +243,8 @@ class DeepEPLLPrepareAndFinalize(mk.FusedMoEPrepareAndFinalize):
         topk_ids: torch.Tensor,
         apply_router_weight_on_input: bool,
         weight_and_reduce_impl: mk.TopKWeightAndReduce,
-    ) -> Callable:
-        recv_hook = self._finalize(
+    ) -> tuple[Callable, Callable]:
+        return self._finalize(
             output,
             fused_expert_output,
             topk_weights,
@@ -253,8 +253,6 @@ class DeepEPLLPrepareAndFinalize(mk.FusedMoEPrepareAndFinalize):
             weight_and_reduce_impl,
             do_async=True,
         )
-        assert recv_hook is not None
-        return recv_hook
 
     def finalize(
         self,

vllm/model_executor/layers/fused_moe/modular_kernel.py

@@ -13,7 +13,8 @@ from vllm.model_executor.layers.fused_moe.config import FusedMoEQuantConfig
 from vllm.model_executor.layers.fused_moe.utils import (  # yapf: disable
     _resize_cache, count_expert_num_tokens)
 from vllm.utils import cdiv
-from vllm.v1.worker.ubatching import (dbo_enabled, dbo_maybe_run_recv_hook,
+from vllm.v1.worker.ubatching import (dbo_current_ubatch_id, dbo_enabled,
+                                      dbo_maybe_run_recv_hook,
                                       dbo_register_recv_hook, dbo_yield)
 
 #
@@ -223,7 +224,7 @@ class FusedMoEPrepareAndFinalize(ABC):
         expert_map: Optional[torch.Tensor],
         apply_router_weight_on_input: bool,
         quant_config: FusedMoEQuantConfig,
-    ) -> tuple[Callable, ReceiverType]:
+    ) -> Union[tuple[Callable, ReceiverType], ReceiverType]:
         """
         Perform any quantization (and/or) dispatching needed for this kernel
         but do not wait for results from other workers.
@@ -239,10 +240,21 @@ class FusedMoEPrepareAndFinalize(ABC):
         - apply_router_weight_on_input: When True, apply the weights to the
           activations, before quantization + dispatching.
 
-        Returns a callback that when invoked waits for results from other
-        workers and has the same return signature as `prepare`, e.g.
+        Returns a callback or a hook callback pair that when invoked waits for 
+        results from other workers and has the same return signature as 
+        `prepare`, if a hook is returned this is more lightweight check that
+        the recv is complete without doing extra work (used by DBO, will be 
+        refactored in the very near future)
         
-        receiver = obj.prepare_async(...)
+        e.g.
+
+        ret = obj.prepare_async(...)
+        
+        if isinstance(ret, tuple):
+            hook, receiver = ret
+            hook()
+
+        if hook is not None:
         a, a_scales, expert_meta, topk_ids, topk_weights = receiver()
 
         is equivalent to:
@@ -284,7 +296,7 @@ class FusedMoEPrepareAndFinalize(ABC):
         topk_ids: torch.Tensor,
         apply_router_weight_on_input: bool,
         weight_and_reduce_impl: TopKWeightAndReduce,
-    ) -> Callable:
+    ) -> Union[tuple[Callable, Callable], Callable]:
         """
         Perform any combine plus apply weights and perform a reduction on the
         fused experts output but do not wait for results from other workers.
@@ -298,11 +310,17 @@ class FusedMoEPrepareAndFinalize(ABC):
         - weight_and_reduce_impl: An optional TopKWeightAndReduce
           implementation.
 
-        Returns a callback that when invoked waits for results from other
-        workers and has the same return signature as `finalize`, e.g.
+        Returns a callback or a hook callback pair that when invoked waits for 
+        results from other workers and has the same return signature as 
+        `finalize`, if a hook is returned this is more lightweight check that
+        the recv is complete without doing extra work (used by DBO, will be 
+        refactored in the very near future)
 
-        receiver = obj.finalize_async(output, ...)
+        ret = obj.finalize_async(output, ...)
         ... output not valid yet ...
+        if isinstance(ret, tuple):
+            hook, receiver = ret
+            hook()
         receiver()
         ... output valid here ...
 
@@ -600,9 +618,23 @@ class FusedMoEModularKernel(torch.nn.Module):
     layer due to any layer specific state that may be used by the component
     objects.
     """
-    fused_out_buffer = SharedResizableBuffer()
-    workspace13_buffer = SharedResizableBuffer()
-    workspace2_buffer = SharedResizableBuffer()
+
+    class SharedBuffers:
+
+        def __init__(self) -> None:
+            self.fused_out = SharedResizableBuffer()
+            self.workspace13 = SharedResizableBuffer()
+            self.workspace2 = SharedResizableBuffer()
+
+    # Persistent buffers that are shared across `FusedMoEModularKernel`
+    # instances (layers), to save memory and allocattions.
+    #
+    # We have two sets of buffers to support dual batch overlap (DBO) where each
+    # microbatch (ubatch) should use its own set of buffers to avoid
+    # cross-ubatch contimination.
+    # NOTE that memory is lazily allocated for these buffers, meaning that if
+    # DBO isn't being used, the second SharedBuffers will be empty.
+    shared_buffers: list[SharedBuffers] = [SharedBuffers(), SharedBuffers()]
 
     def __init__(
         self,
@@ -647,12 +679,16 @@ class FusedMoEModularKernel(torch.nn.Module):
              a1, a1q, M, N, K, top_k, global_num_experts, local_num_experts,
              expert_tokens_meta)
 
+        # select per-ubatch buffers to avoid cross-ubatch reuse under DBO
+        ubatch_idx = dbo_current_ubatch_id()
+        buffers = self.shared_buffers[ubatch_idx]
+
         # We can reuse the memory between cache1 and cache3 because by the
         # time we need cache3, we're done with cache1.
-        workspace13 = self.workspace13_buffer.get(workspace13_shape,
+        workspace13 = buffers.workspace13.get(workspace13_shape,
                                               device=a1.device,
                                               dtype=workspace_dtype)
-        workspace2 = self.workspace2_buffer.get(workspace2_shape,
+        workspace2 = buffers.workspace2.get(workspace2_shape,
                                             device=a1.device,
                                             dtype=workspace_dtype)
 
@@ -733,7 +769,9 @@ class FusedMoEModularKernel(torch.nn.Module):
         (_, _, fused_out_shape, _) = self.fused_experts.workspace_shapes(
             a1, a1q, M, N, K, top_k, global_num_experts, local_num_experts,
             expert_tokens_meta)
-        fused_out = self.fused_out_buffer.get(fused_out_shape,
+        ubatch_idx = dbo_current_ubatch_id()
+        buffers = self.shared_buffers[ubatch_idx]
+        fused_out = buffers.fused_out.get(fused_out_shape,
                                           device=a1q.device,
                                           dtype=a1.dtype)
 
@@ -868,6 +906,7 @@ class FusedMoEModularKernel(torch.nn.Module):
         if not self.prepare_finalize.supports_async():
             # We shouldn't be running an a2a kernel that doesn't
             # support async prepare/finalize
+            # TODO(lucas): enable in follow-up
             assert not dbo_enabled()
 
             (a1q, a1q_scale, expert_tokens_meta, _expert_topk_ids,
@@ -883,7 +922,7 @@ class FusedMoEModularKernel(torch.nn.Module):
         else:
             # Overlap shared expert compute with all2all dispatch.
             dbo_maybe_run_recv_hook()
-            hook, receiver = self.prepare_finalize.prepare_async(
+            prepare_ret = self.prepare_finalize.prepare_async(
                 a1,
                 topk_weights,
                 topk_ids,
@@ -893,12 +932,20 @@ class FusedMoEModularKernel(torch.nn.Module):
                 self.fused_experts.quant_config,
             )
 
-            # If DBO is being used, register the hook with the ubatch context
-            # and call it in dbo_maybe_run_recv_hook instead of passing it to
-            # the receiver.
+            # TODO(lucas): refactor this in the alternative schedules followup
+            # currently unpack if we have hook + receiver pair or just
+            # receiver (see finalize_async docstring)
+            hook, receiver = prepare_ret \
+                if isinstance(prepare_ret, tuple) else (None, prepare_ret)
+
+            if hook is not None:
+                if dbo_enabled():
+                    # If DBO is being used, register the hook with the ubatch
+                    # context and call it in dbo_maybe_run_recv_hook instead of
+                    #  passing it to the receiver.
                     dbo_register_recv_hook(hook)
                     dbo_yield()
-            if not dbo_enabled():
+                else:
                     hook()
 
             (a1q, a1q_scale, expert_tokens_meta, _expert_topk_ids,
@@ -952,7 +999,7 @@ class FusedMoEModularKernel(torch.nn.Module):
             if self.shared_experts is not None:
                 shared_output = self.shared_experts(a1)
         else:
-            recv_hook = self.prepare_finalize.finalize_async(
+            finalize_ret = self.prepare_finalize.finalize_async(
                 output,
                 fused_out,
                 topk_weights,
@@ -964,11 +1011,23 @@ class FusedMoEModularKernel(torch.nn.Module):
             if self.shared_experts is not None:
                 shared_output = self.shared_experts(a1)
 
-            assert recv_hook is not None
-            dbo_register_recv_hook(recv_hook)
+            # TODO(lucas): refactor this in the alternative schedules followup
+            # currently unpack if we have hook + receiver pair or just
+            # receiver (see finalize_async docstring)
+            hook, receiver = finalize_ret \
+                if isinstance(finalize_ret, tuple) else (None, finalize_ret)
+
+            if hook is not None:
+                if dbo_enabled():
+                    # If DBO is being used, register the hook with the ubatch
+                    # context and call it in dbo_maybe_run_recv_hook instead of
+                    #  passing it to the receiver.
+                    dbo_register_recv_hook(hook)
                     dbo_yield()
-            if not dbo_enabled():
-                recv_hook()
+                else:
+                    hook()
+
+            receiver()
 
         if self.shared_experts is None:
             return output

vllm/v1/attention/backends/utils.py

@@ -107,19 +107,57 @@ def _make_metadata_with_slice(
     the requests included in ubatch_slice
     """
 
+    assert not ubatch_slice.is_empty(), (
+        f"Ubatch slice {ubatch_slice} is empty")
+
     request_slice = ubatch_slice.request_slice
     token_slice = ubatch_slice.token_slice
 
+    start_locs = attn_metadata.query_start_loc_cpu
+    first_req = request_slice.start
+    first_tok = token_slice.start
+    last_req = request_slice.stop - 1
+    last_tok = token_slice.stop - 1
+
+    assert start_locs[first_req] <= first_tok < start_locs[first_req + 1], \
+        "Token slice start outside of first request"
+    assert start_locs[last_req] <= last_tok < start_locs[last_req+1], \
+        "Token slice end outside of last request"
+
+    # If the "middle" request has tokens in both ubatches, we have to split it.
+    # If ubatch_slice is the first ubatch then we will be splitting the last
+    # request. If it's the second microbatch, then we will be splitting the
+    # first request
+    splits_first_request = first_tok > start_locs[first_req]
+    splits_last_request = last_tok < start_locs[last_req + 1] - 1
+
+    query_start_loc_cpu = slice_query_start_locs(start_locs, request_slice)
     query_start_loc = slice_query_start_locs(attn_metadata.query_start_loc,
                                              request_slice)
+
     assert len(query_start_loc) >= 2, (
         f"query_start_loc must have at least 2 elements, "
         f"got {len(query_start_loc)}")
-    query_start_loc_cpu = slice_query_start_locs(
-        attn_metadata.query_start_loc_cpu, request_slice)
 
+    if splits_first_request:
+        tokens_skipped = first_tok - start_locs[first_req]
+        query_start_loc[1:] -= tokens_skipped
+        query_start_loc_cpu[1:] -= tokens_skipped
     seq_lens = attn_metadata.seq_lens[request_slice]
     seq_lens_cpu = attn_metadata.seq_lens_cpu[request_slice]
+
+    if splits_last_request:
+        tokens_skipped = query_start_loc_cpu[-1] - token_slice.stop
+        query_start_loc[-1] -= tokens_skipped
+        query_start_loc_cpu[-1] -= tokens_skipped
+
+        # Make sure we don't modify the seq_lens tensors
+        #  (not cudagraph compatible)
+        seq_lens = seq_lens.clone()
+        seq_lens_cpu = seq_lens_cpu.clone()
+        seq_lens[-1] -= tokens_skipped
+        seq_lens_cpu[-1] -= tokens_skipped
+
     max_seq_len = int(seq_lens_cpu.max())
     num_computed_tokens_cpu = attn_metadata.num_computed_tokens_cpu[
         request_slice]
@@ -167,6 +205,7 @@ def split_attn_metadata(
     for ubatch_slice in ubatch_slices:
         results.append(
             _make_metadata_with_slice(ubatch_slice, common_attn_metadata))
+
     return results
 
 
@@ -696,7 +735,6 @@ def split_decodes_and_prefills(
         return num_reqs, 0, num_tokens, 0
 
     first_prefill = is_prefill.int().argmax(dim=-1).item()
-    assert torch.all(query_lens[first_prefill:] > decode_threshold)
     assert torch.all(query_lens[:first_prefill] <= decode_threshold)
     num_decodes = first_prefill
     num_prefills = num_reqs - num_decodes

vllm/v1/spec_decode/eagle.py

@@ -30,7 +30,6 @@ from vllm.v1.sample.metadata import SamplingMetadata
 from vllm.v1.spec_decode.metadata import SpecDecodeMetadata
 from vllm.v1.utils import CpuGpuBuffer
 from vllm.v1.worker.gpu_input_batch import CachedRequestState, InputBatch
-from vllm.v1.worker.ubatching import dbo_current_ubatch_id
 
 logger = init_logger(__name__)
 
@@ -192,9 +191,8 @@ class EagleProposer:
         assert self.runner is not None
 
         # FIXME: need to consider multiple kv_cache_groups
-        ubatch_id = dbo_current_ubatch_id()
         attn_metadata_builder = \
-            self.runner.attn_groups[0][0].metadata_builders[ubatch_id]
+            self.runner.attn_groups[0][0].get_metadata_builder()
         attn_metadata = attn_metadata_builder.build_for_drafting(
             common_attn_metadata=common_attn_metadata, draft_index=0)
 
@@ -330,7 +328,7 @@ class EagleProposer:
 
             # Rebuild attention metadata
             attn_metadata_builder = \
-                self.runner.attn_groups[0][0].metadata_builders[ubatch_id]
+                self.runner.attn_groups[0][0].get_metadata_builder()
             attn_metadata = attn_metadata_builder\
                 .build_for_drafting(common_attn_metadata=common_attn_metadata,
                                 draft_index=token_index + 1)
@@ -538,9 +536,8 @@ class EagleProposer:
         hidden_states: torch.Tensor,
         common_attn_metadata: CommonAttentionMetadata,
     ) -> list[torch.Tensor]:
-        ubatch_id = dbo_current_ubatch_id()
         tree_attn_metadata_builder = \
-            self.runner.attn_groups[0][0].metadata_builders[ubatch_id]
+            self.runner.attn_groups[0][0].get_metadata_builder()
         assert isinstance(tree_attn_metadata_builder,
                           TreeAttentionMetadataBuilder)
 

vllm/v1/worker/gpu_model_runner.py

@@ -96,7 +96,8 @@ from vllm.v1.worker.gpu_ubatch_wrapper import UBatchWrapper
 from vllm.v1.worker.kv_connector_model_runner_mixin import (
     KVConnectorModelRunnerMixin)
 from vllm.v1.worker.lora_model_runner_mixin import LoRAModelRunnerMixin
-from vllm.v1.worker.ubatch_splitting import get_dp_padding_ubatch, ubatch_split
+from vllm.v1.worker.ubatch_splitting import (check_ubatch_thresholds,
+                                             ubatch_split)
 from vllm.v1.worker.ubatch_utils import UBatchSlice, UBatchSlices
 from vllm.v1.worker.utils import is_residual_scattered_for_sp
 
@@ -1032,7 +1033,7 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
         num_tokens_padded = num_tokens_unpadded + self.get_local_padding(
             num_tokens_unpadded)
         ubatch_slices, num_tokens_after_padding = \
-            ubatch_split(max_num_scheduled_tokens,
+            ubatch_split(num_scheduled_tokens,
                          num_tokens_unpadded,
                          num_tokens_padded,
                          self.vllm_config)
@@ -1206,7 +1207,6 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
                         ubatch_slices, common_attn_metadata)
                     for ubid, common_attn_metadata in enumerate(
                             common_attn_metadata_list):
-                        assert common_attn_metadata.max_query_len == 1
                         attn_metadata_i = (attn_group.get_metadata_builder(
                             ubatch_id=ubid).build(
                                 common_prefix_len=common_prefix_len,
@@ -2182,9 +2182,6 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
             ) = self._preprocess(scheduler_output, intermediate_tensors,
                                  ubatch_slices, num_tokens_after_padding)
 
-            if ubatch_slices is not None:
-                num_input_tokens = num_input_tokens // 2
-
             uniform_decode = (max_query_len
                               == self.uniform_decode_query_len) and (
                                   num_scheduled_tokens
@@ -2194,6 +2191,11 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
             cudagraph_runtime_mode, batch_descriptor = \
                 self.cudagraph_dispatcher.dispatch(batch_descriptor)
 
+        # This is currently to get around the assert in the DPMetadata
+        # where it wants `num_tokens_across_dp` to align with `num_tokens`
+        if ubatch_slices is not None:
+            num_input_tokens = ubatch_slices[0].num_tokens
+
         # Run the model.
         # Use persistent buffers for CUDA graphs.
         with (set_forward_context(
@@ -2821,7 +2823,7 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
         cudagraph_runtime_mode: CUDAGraphMode = CUDAGraphMode.NONE,
         force_attention: bool = False,
         uniform_decode: bool = False,
-        allow_microbatching: bool = False,
+        allow_microbatching: bool = True,
         skip_eplb: bool = False,
         is_profile: bool = False,
         create_mixed_batch: bool = False,
@@ -2847,32 +2849,10 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
                 (1 token) and prefill (multiple tokens) requests.
             remove_lora: If False, dummy LoRAs are not destroyed after the run
         """
-        ubatch_enabled = self.parallel_config.enable_dbo
-        num_tokens_across_dp = None
-        num_pad = 0
-        should_ubatch = False
-        if ubatch_enabled:
-            should_ubatch = num_tokens >= \
-                self.parallel_config.dbo_decode_token_threshold and \
-                allow_microbatching
-
-            (should_ubatch, num_tokens_across_dp) = get_dp_padding_ubatch(
-                num_tokens, num_tokens, should_ubatch, self.vllm_config)
-
-            # Currently the dummy run should only be ubatching during
-            # cuda graph capture, meaning all DP ranks should already
-            # have the same batch size
-            if num_tokens_across_dp is not None:
-                assert int(num_tokens_across_dp[0]) == num_tokens // 2
-
         assert cudagraph_runtime_mode in {
             CUDAGraphMode.NONE, CUDAGraphMode.PIECEWISE, CUDAGraphMode.FULL
         }
 
-        if not should_ubatch:
-            num_pad, num_tokens_across_dp = self.get_dp_padding(num_tokens)
-        num_tokens += num_pad
-
         # If cudagraph_mode.decode_mode() == FULL and
         # cudagraph_mode.separate_routine(). This means that we are using
         # different graphs and/or modes for mixed prefill-decode batches vs.
@@ -2888,10 +2868,6 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
         # for GQA/MQA.
         max_query_len = self.uniform_decode_query_len if uniform_decode else \
                                                                 num_tokens
-        if allow_microbatching:
-            assert self.uniform_decode_query_len == 1
-            assert uniform_decode is True
-            assert max_query_len == 1
 
         # Set num_scheduled_tokens based on num_tokens and max_num_seqs
         # for dummy run with LoRA so that the num_reqs collectively
@@ -2930,20 +2906,31 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
         assert len(num_scheduled_tokens_list) == num_reqs
         num_scheduled_tokens = np.array(num_scheduled_tokens_list,
                                         dtype=np.int32)
+        total_num_scheduled_tokens = int(num_scheduled_tokens.sum())
 
         ubatch_slices = None
+        num_tokens_after_padding = None
+
         # We currently only microbatch if the number of tokens is
         # over a certain threshold.
-        if should_ubatch:
-            # We only support decode-only cudagraphs
-            assert num_reqs == num_tokens
-            assert num_tokens % 2 == 0
-            ubatch_slices = [
-                UBatchSlice(slice(0, num_reqs // 2), slice(0,
-                                                           num_tokens // 2)),
-                UBatchSlice(slice(num_reqs // 2, num_reqs),
-                            slice(num_tokens // 2, num_tokens))
-            ]
+        if self.parallel_config.enable_dbo and allow_microbatching:
+            ubatch_slices, num_tokens_after_padding = ubatch_split(
+                num_scheduled_tokens,
+                total_num_scheduled_tokens,
+                total_num_scheduled_tokens,
+                self.vllm_config,
+            )
+
+        # If we failed to microbatch, currently need to resynchronize
+        # TODO(lucas,sage): we should be able to avoid this second sync by
+        #  refactoring `get_dp_padding_ubatch` and `get_dp_padding` into
+        #  a single `coordinate_batch_across_dp` function.
+        if num_tokens_after_padding is None:
+            num_pad, num_tokens_across_dp = self.get_dp_padding(num_tokens)
+            num_tokens_after_padding = num_tokens + num_pad
+        else:
+            num_tokens_across_dp = num_tokens_after_padding
+            num_tokens_after_padding = int(num_tokens_after_padding[0].item())
 
         attn_metadata: Optional[PerLayerAttnMetadata] = None
 
@@ -2966,6 +2953,11 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
             self.seq_lens.np[num_reqs:] = 0
             self.seq_lens.copy_to_gpu()
 
+            cum_num_tokens, _ = self._get_cumsum_and_arange(
+                num_scheduled_tokens)
+            self.query_start_loc.np[1:num_reqs + 1] = cum_num_tokens
+            self.query_start_loc.copy_to_gpu()
+
             for kv_cache_group_id, kv_cache_group_spec in enumerate(
                     self.kv_cache_config.kv_cache_groups):
                 common_attn_metadata = CommonAttentionMetadata(
@@ -3060,7 +3052,7 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
             with self.maybe_randomize_inputs(input_ids), set_forward_context(
                     attn_metadata,
                     self.vllm_config,
-                    num_tokens=num_tokens,
+                    num_tokens=num_tokens_after_padding,
                     num_tokens_across_dp=num_tokens_across_dp,
                     cudagraph_runtime_mode=cudagraph_runtime_mode,
                     batch_descriptor=batch_descriptor,
@@ -3395,38 +3387,31 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
                 desc="Capturing CUDA graphs ({}, {})".format(
                     "decode" if uniform_decode else "mixed prefill-decode",
                     cudagraph_runtime_mode.name))
-        enable_dbo = self.parallel_config.enable_dbo
-        # DBO Only supports running Full cudagraphs with uniform
-        # decode lengths
-        if enable_dbo and uniform_decode:
+
+        # We skip EPLB here since we don't want to record dummy metrics
         for num_tokens in compilation_cases:
-                # If the number of tokens is greater than the microbatching
-                # threshold, don't generate a microbatched cudagraph
-                if (num_tokens
-                        < self.parallel_config.dbo_decode_token_threshold):
-                    continue
+            # We currently only capture ubatched graphs when its a FULL
+            # cudagraph and for uniform decode batches.
+            capture_ubatched_graph = self.parallel_config.enable_dbo \
+                and cudagraph_runtime_mode == CUDAGraphMode.FULL \
+                and uniform_decode \
+                and check_ubatch_thresholds(
+                    config=self.vllm_config.parallel_config,
+                    num_tokens=num_tokens,
+                    uniform_decode=uniform_decode,
+                )
 
-                # Warmup
+            # Currently we capture both microbatched and non-microbatched
+            # graphs when capture_ubatched_graph is True, this is because
+            # occasionally we will be forced out of microbatching due to other
+            # DP ranks not microbatching (usually caused by an empty second
+            # microbatch; once we resolve this, we can remove the
+            # non-microbatched graph capture).
+            allow_microbatching_options = [True, False] if \
+                capture_ubatched_graph else [False]
+            for allow_microbatching in allow_microbatching_options:
                 for _ in range(
                         self.compilation_config.cudagraph_num_of_warmups):
-                    force_attention = (
-                        cudagraph_runtime_mode == CUDAGraphMode.FULL)
-                    self._dummy_run(num_tokens,
-                                    cudagraph_runtime_mode=CUDAGraphMode.NONE,
-                                    force_attention=force_attention,
-                                    uniform_decode=True,
-                                    allow_microbatching=True,
-                                    skip_eplb=True)
-
-                # Graph Capture
-                self._dummy_run(num_tokens,
-                                cudagraph_runtime_mode=CUDAGraphMode.FULL,
-                                uniform_decode=True,
-                                allow_microbatching=True,
-                                skip_eplb=True)
-        # We skip EPLB here since we don't want to record dummy metrics
-        for num_tokens in compilation_cases:
-            for _ in range(self.compilation_config.cudagraph_num_of_warmups):
                     # Use CUDAGraphRuntimeStyle.NONE (default) for warmup.
                     # But be careful, warm up with `NONE`is orthogonal to
                     # if we want to warm up attention or not. This is
@@ -3438,11 +3423,13 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
                                     cudagraph_runtime_mode=CUDAGraphMode.NONE,
                                     force_attention=force_attention,
                                     uniform_decode=uniform_decode,
+                                    allow_microbatching=allow_microbatching,
                                     skip_eplb=True,
                                     remove_lora=False)
                 self._dummy_run(num_tokens,
                                 cudagraph_runtime_mode=cudagraph_runtime_mode,
                                 uniform_decode=uniform_decode,
+                                allow_microbatching=allow_microbatching,
                                 skip_eplb=True,
                                 remove_lora=False)
         self.maybe_remove_all_loras(self.lora_config)
@@ -3500,24 +3487,16 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
             attn_groups: list[AttentionGroup] = []
             for (attn_backend,
                  kv_cache_spec), layer_names in attn_backends_map.items():
-                attn_metadata_builders = []
-                attn_metadata_builders.append(attn_backend.get_builder_cls()(
-                    kv_cache_spec,
+                attn_group = AttentionGroup.create_with_metadata_builders(
+                    attn_backend,
                     layer_names,
-                    self.vllm_config,
-                    self.device,
-                ))
-                if self.parallel_config.enable_dbo:
-                    attn_metadata_builders.append(
-                        attn_backend.get_builder_cls()(
                     kv_cache_spec,
-                            layer_names,
                     self.vllm_config,
                     self.device,
-                        ))
-                attn_group = AttentionGroup(attn_backend,
-                                            attn_metadata_builders,
-                                            layer_names, kv_cache_spec)
+                    num_metadata_builders=1
+                    if not self.parallel_config.enable_dbo else 2,
+                )
+
                 attn_groups.append(attn_group)
             return attn_groups
 

vllm/v1/worker/gpu_ubatch_wrapper.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
-import dataclasses
 import threading
+from dataclasses import dataclass
 from typing import Any, Callable, Optional
 
 import torch
 
+import vllm.envs as envs
 from vllm.compilation.cuda_graph import CUDAGraphWrapper
 from vllm.config import CUDAGraphMode, VllmConfig
+from vllm.distributed import get_ep_group
 from vllm.forward_context import (create_forward_context, get_forward_context,
                                   override_forward_context)
 from vllm.logger import init_logger
 from vllm.platforms import current_platform
 from vllm.sequence import IntermediateTensors
+from vllm.utils import has_deep_gemm
 from vllm.v1.worker.ubatching import UBatchContext, make_ubatch_contexts
 
 logger = init_logger(__name__)
 
 
-@dataclasses.dataclass
+@dataclass
 class UbatchMetadata:
     context: UBatchContext
     input_ids: torch.Tensor
@@ -29,13 +32,55 @@ class UbatchMetadata:
     num_tokens: int
 
 
-@dataclasses.dataclass
+@dataclass
 class CUDAGraphMetaData:
     cudagraph: torch.cuda.CUDAGraph
     ubatch_metadata: UbatchMetadata
     outputs: Optional[Any] = None
 
 
+class SMControlContextManager:
+
+    def __init__(self, comm_sms: int, set_comm_sms: Callable[[int], None],
+                 set_compute_sms: Callable[[int], None]):
+        """
+        Context manager for controlling SM (Streaming Multiprocessor) 
+        allocation. Upon entering the context, it sets the number of SMs
+        allocated for communication and computation to comm_sms and
+        total_sms - comm_sms respectively. Upon exiting, it restores the
+        allocation to use all available SMs (i.e. total_sms).
+
+        Args:
+            comm_sms (int): The number of SMs to allocate for communication. 
+                (The remainder will be used for computation.)
+            set_comm_sms (Callable[[int], None]): 
+                A function that sets the number of SMs for communication.
+            set_compute_sms (Callable[[int], None]): 
+                A function that sets the number of SMs for computation.
+        """
+
+        assert current_platform.is_cuda(), \
+            "SM control is currently only supported on CUDA"
+
+        props = torch.cuda.get_device_properties(torch.cuda.current_device())
+        total_sms = props.multi_processor_count
+
+        assert comm_sms < total_sms
+        self.total_sms = total_sms
+        self.compute_sms = total_sms - comm_sms
+        self.comm_sms = comm_sms
+        self.set_comm_sms = set_comm_sms
+        self.set_compute_sms = set_compute_sms
+
+    def __enter__(self):
+        self.set_comm_sms(self.comm_sms)
+        self.set_compute_sms(self.compute_sms)
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        self.set_comm_sms(self.total_sms)
+        self.set_compute_sms(self.total_sms)
+
+
 class UBatchWrapper:
 
     def __init__(self, runnable: Callable, vllm_config: VllmConfig,
@@ -56,6 +101,35 @@ class UBatchWrapper:
                 runnable, vllm_config, runtime_mode=runtime_mode)
             self.graph_pool = current_platform.get_global_graph_pool()
 
+        self.sm_control = self._create_sm_control_context(vllm_config)
+
+    @staticmethod
+    def _create_sm_control_context(vllm_config: VllmConfig):
+        comm_sms = envs.VLLM_DBO_COMM_SMS
+
+        set_comm_sms = lambda sms: None
+        if vllm_config.parallel_config.enable_expert_parallel:
+            # Currently only DeepEP highthroughput supports SM control so this
+            # only affects that case.
+            all2all_manager = get_ep_group(
+            ).device_communicator.all2all_manager
+
+            if all2all_manager.max_sms_used() is not None:
+                comm_sms = min(comm_sms, all2all_manager.max_sms_used())
+
+            if comm_sms > 0:
+                set_comm_sms = lambda sms: all2all_manager.set_num_sms(sms)
+
+        # TODO(lucas): support other kernels besides DeepGEMM
+        set_compute_sms = lambda sms: None
+        if has_deep_gemm() and comm_sms > 0:
+            import deep_gemm as dg
+            set_compute_sms = lambda sms: dg.set_num_sms(sms)
+
+        return SMControlContextManager(comm_sms=comm_sms,
+                                       set_comm_sms=set_comm_sms,
+                                       set_compute_sms=set_compute_sms)
+
     def __getattr__(self, key: str):
         # allow accessing the attributes of the runnable.
         if hasattr(self.runnable, key):
@@ -282,7 +356,7 @@ class UBatchWrapper:
                 dp_metadata=dp_metadata,
                 batch_descriptor=batch_descriptor,
                 cudagraph_runtime_mode=CUDAGraphMode.NONE)
-
+            with self.sm_control:
                 return self._capture_ubatches(ubatch_metadata, self.model)
         elif num_tokens in self.cudagraphs:
             cudagraph_metadata = self.cudagraphs[num_tokens]
@@ -300,4 +374,5 @@ class UBatchWrapper:
                 dp_metadata=dp_metadata,
                 batch_descriptor=batch_descriptor,
                 cudagraph_runtime_mode=CUDAGraphMode.NONE)
+            with self.sm_control:
                 return self._run_ubatches(ubatch_metadata, self.model)

vllm/v1/worker/ubatch_splitting.py

@@ -3,9 +3,10 @@
 
 from typing import Optional
 
+import numpy as np
 import torch
 
-from vllm.config import VllmConfig
+from vllm.config import ParallelConfig, VllmConfig
 from vllm.forward_context import DPMetadata
 from vllm.logger import init_logger
 from vllm.utils import round_up
@@ -29,6 +30,16 @@ def should_ubatch_with_num_tokens(
                                               dp_size, dp_rank)
 
 
+def check_ubatch_thresholds(config: ParallelConfig, num_tokens: int,
+                            uniform_decode: bool) -> bool:
+    if not config.enable_dbo:
+        return False
+    if uniform_decode:
+        return num_tokens >= config.dbo_decode_token_threshold
+    else:
+        return num_tokens >= config.dbo_prefill_token_threshold
+
+
 def get_dp_padding_ubatch(
         num_tokens_unpadded: int, num_tokens_padded: int,
         should_attempt_ubatching: bool,
@@ -95,9 +106,37 @@ def get_dp_padding_ubatch(
                                             dtype=torch.int32)
     return should_ubatch, num_tokens_after_padding
 
+def create_ubatch_slices(num_scheduled_tokens: np.ndarray, split_point: int) \
+    -> UBatchSlices:
+    # 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)
+    np.cumsum(num_scheduled_tokens, dtype=np.int32, out=cu_num_tokens[1:])
+
+    first_ubatch_token_slice = slice(0, split_point)
+    second_ubatch_token_slice = slice(split_point, cu_num_tokens[-1])
+
+    # Determine request slices using exclusive stop semantics
+    # First ubatch includes requests whose tokens overlap [0, split_point)
+    first_ubatch_req_stop = int(
+        np.searchsorted(cu_num_tokens, split_point, side="left"))
+    first_ubatch_req_slice = slice(0, first_ubatch_req_stop)
+
+    # Second ubatch starts at the request that contains the split_point
+    # or the request starting exactly at split_point (if on boundary)
+    second_ubatch_req_start = int(
+        np.searchsorted(cu_num_tokens, split_point, side="right") - 1)
+    second_ubatch_req_slice = slice(second_ubatch_req_start,
+                                    len(cu_num_tokens) - 1)
+
+    return [
+        UBatchSlice(first_ubatch_req_slice, first_ubatch_token_slice),
+        UBatchSlice(second_ubatch_req_slice, second_ubatch_token_slice)
+    ]
+
 
 def ubatch_split(
-    max_num_scheduled_tokens: int,
+    num_scheduled_tokens_per_request: np.ndarray,
     num_tokens_unpadded: int,
     num_tokens_padded: int,
     vllm_config: VllmConfig,
@@ -122,17 +161,20 @@ def ubatch_split(
         return (None, None)
 
     # Check preconditions for microbatching
-    should_attempt_ubatching = \
-        parallel_config.enable_dbo and \
-        num_tokens_unpadded >= \
-        parallel_config.dbo_decode_token_threshold \
-        and max_num_scheduled_tokens == 1
+    should_attempt_ubatching = check_ubatch_thresholds(
+        parallel_config,
+        num_tokens_unpadded,
+        vllm_config,
+    )
 
     # Don't microbatch unless every other DP worker is also microbatching
-    num_tokens_after_padding = None
-    (should_ubatch, num_tokens_after_padding) = get_dp_padding_ubatch(
-        num_tokens_unpadded, num_tokens_padded, should_attempt_ubatching,
-        vllm_config)
+    should_ubatch, num_tokens_after_padding = get_dp_padding_ubatch(
+        num_tokens_unpadded,
+        num_tokens_padded,
+        should_attempt_ubatching,
+        vllm_config,
+    )
+
     if not should_ubatch:
         return (None, None)
 
@@ -141,15 +183,9 @@ def ubatch_split(
     # to the second ubatch in pad_out_ubatch_slice after attention
     # metadata creation
     assert num_tokens_after_padding is not None
-    total_num_tokens_per_ubatch = int(num_tokens_after_padding[0].item())
-    padded_first_ubatch_slice = slice(0, total_num_tokens_per_ubatch)
-    padded_second_ubatch_slice = slice(total_num_tokens_per_ubatch,
-                                       num_tokens_unpadded)
-
-    # Note there's an assumption here that there's 1 token per request
-    ubatch_slices = [
-        UBatchSlice(padded_first_ubatch_slice, padded_first_ubatch_slice),
-        UBatchSlice(padded_second_ubatch_slice, padded_second_ubatch_slice)
-    ]
+    token_split_point = int(num_tokens_after_padding[0].item())
+
+    ubatch_slices = create_ubatch_slices(num_scheduled_tokens_per_request,
+                                         token_split_point)
 
     return (ubatch_slices, num_tokens_after_padding)

vllm/v1/worker/ubatch_utils.py

@@ -10,6 +10,14 @@ class UBatchSlice:
     request_slice: slice
     token_slice: slice
 
+    def is_empty(self) -> bool:
+        return self.request_slice.start == self.request_slice.stop \
+            or self.token_slice.start == self.token_slice.stop
+
+    @property
+    def num_tokens(self) -> int:
+        return self.token_slice.stop - self.token_slice.start
+
 
 UBatchSlices: TypeAlias = list[UBatchSlice]
 

vllm/v1/worker/ubatching.py

@@ -51,8 +51,8 @@ class UBatchContext:
         self.cpu_wait_event.wait()
         self.cpu_wait_event.clear()
         self._restore_context()
-        # Assume we start on the compute stream
-        assert current_stream() == self.compute_stream
+        # Assume we want to start on the compute stream
+        self.update_stream(self.compute_stream)
         return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
@@ -62,16 +62,14 @@ class UBatchContext:
         self.maybe_run_recv_hook()
         self.cpu_signal_event.set()
         self.cpu_wait_event.clear()
-        self.current_stream = self.compute_stream
-        torch.cuda.set_stream(self.current_stream)
         return False
 
     def _restore_context(self):
         forward_context._forward_context = self.forward_context
-        torch.cuda.set_stream(self.current_stream)
 
     def update_stream(self, stream):
         self.current_stream = stream
+        if current_stream() != self.current_stream:
             torch.cuda.set_stream(self.current_stream)
 
     def _signal_comm_done(self):
@@ -99,9 +97,20 @@ class UBatchContext:
         self.cpu_wait_event.clear()
         self._restore_context()
 
+    def switch_to_comm(self):
+        self.update_stream(self.comm_stream)
+
+    def switch_to_compute(self):
+        self.update_stream(self.compute_stream)
+
     def switch_to_comm_sync(self):
         self._signal_compute_done()
         self.update_stream(self.comm_stream)
+        self._wait_compute_done()
+
+    def switch_to_compute_sync(self):
+        self._signal_comm_done()
+        self.update_stream(self.compute_stream)
         self._wait_comm_done()
 
     def maybe_run_recv_hook(self):
@@ -112,7 +121,6 @@ class UBatchContext:
     def yield_(self):
         self.current_stream = current_stream()
         self._cpu_yield()
-        if self.current_stream != current_stream():
         self.update_stream(self.current_stream)
 
     def yield_and_switch_from_compute_to_comm(self):
@@ -153,15 +161,20 @@ def _register_ubatch_function(func):
     return wrapper
 
 
+dbo_maybe_run_recv_hook = _register_ubatch_function(
+    UBatchContext.maybe_run_recv_hook)
+dbo_yield = _register_ubatch_function(UBatchContext.yield_)
 dbo_yield_and_switch_from_compute_to_comm = _register_ubatch_function(
     UBatchContext.yield_and_switch_from_compute_to_comm)
 dbo_yield_and_switch_from_comm_to_compute = _register_ubatch_function(
     UBatchContext.yield_and_switch_from_comm_to_compute)
-dbo_yield = _register_ubatch_function(UBatchContext.yield_)
-dbo_maybe_run_recv_hook = _register_ubatch_function(
-    UBatchContext.maybe_run_recv_hook)
+dbo_switch_to_comm = _register_ubatch_function(UBatchContext.switch_to_comm)
+dbo_switch_to_compute = _register_ubatch_function(
+    UBatchContext.switch_to_compute)
 dbo_switch_to_comm_sync = _register_ubatch_function(
     UBatchContext.switch_to_comm_sync)
+dbo_switch_to_compute_sync = _register_ubatch_function(
+    UBatchContext.switch_to_compute_sync)
 
 
 def dbo_register_recv_hook(recv_hook):

vllm/v1/worker/utils.py

@@ -130,15 +130,32 @@ class MultiModalBudget:
 @dataclass
 class AttentionGroup:
     backend: type[AttentionBackend]
+    # When ubatching is enabled we will have a metadata builder for each ubatch
+    # so that if they use internal persistant buffers for cudagraphs, and they
+    # won't have to worry about conflicting with the other ubatches.
     metadata_builders: list[AttentionMetadataBuilder]
     layer_names: list[str]
     kv_cache_spec: KVCacheSpec
 
+    @staticmethod
+    def create_with_metadata_builders(
+        backend: type[AttentionBackend],
+        layer_names: list[str],
+        kv_cache_spec: KVCacheSpec,
+        vllm_config: VllmConfig,
+        device: torch.device,
+        num_metadata_builders: int = 1,
+    ) -> 'AttentionGroup':
+        metadata_builders = [
+            backend.get_builder_cls()(kv_cache_spec, layer_names, vllm_config,
+                                      device)
+            for _ in range(num_metadata_builders)
+        ]
+        return AttentionGroup(backend, metadata_builders, layer_names,
+                              kv_cache_spec)
+
     def get_metadata_builder(self,
-                             ubatch_id: Optional[int] = None
-                             ) -> AttentionMetadataBuilder:
-        if ubatch_id is None:
-            return self.metadata_builders[0]
+                             ubatch_id: int = 0) -> AttentionMetadataBuilder:
         assert len(self.metadata_builders) > ubatch_id
         return self.metadata_builders[ubatch_id]