[Spec Decode] Update extract_hidden_states to use deferred kv_connector clear (#37013)

vllm/distributed/kv_transfer/kv_connector/v1/example_hidden_states_connector.py

@@ -286,7 +286,9 @@ class ExampleHiddenStatesConnector(KVConnectorBase_V1):
             cached_req = self._active_requests[req_id]
             req_block_ids = self._req_blocks[req_id]
 
-            assert new_block_ids is not None
+            if new_block_ids is None:
+                continue
+
             block_ids = new_block_ids[0]
 
             req_block_ids.extend(block_ids)

vllm/v1/spec_decode/extract_hidden_states.py

@@ -3,26 +3,21 @@
 
 from __future__ import annotations
 
-from contextlib import nullcontext
 from typing import TYPE_CHECKING
 
 import torch
 import torch.nn as nn
 
 from vllm.config import CUDAGraphMode, VllmConfig, get_layers_from_vllm_config
-from vllm.distributed.kv_transfer import has_kv_transfer_group
 from vllm.forward_context import set_forward_context
 from vllm.model_executor.layers.attention_layer_base import AttentionLayerBase
 from vllm.model_executor.model_loader import get_model
 from vllm.v1.attention.backend import AttentionMetadataBuilder, CommonAttentionMetadata
 from vllm.v1.cudagraph_dispatcher import CudagraphDispatcher
-from vllm.v1.outputs import KVConnectorOutput
 from vllm.v1.worker.dp_utils import coordinate_batch_across_dp
 from vllm.v1.worker.gpu_input_batch import CachedRequestState, InputBatch
-from vllm.v1.worker.kv_connector_model_runner_mixin import KVConnectorModelRunnerMixin
 
 if TYPE_CHECKING:
-    from vllm.v1.core.sched.output import SchedulerOutput
     from vllm.v1.kv_cache_interface import KVCacheConfig
 
 PADDING_SLOT_ID = -1
@@ -79,11 +74,10 @@ class ExtractHiddenStatesProposer:
         sampled_token_ids: torch.Tensor,
         target_hidden_states: list[torch.Tensor],
         common_attn_metadata: CommonAttentionMetadata,
-        scheduler_output: SchedulerOutput,
         slot_mappings: dict[str, torch.Tensor]
         | list[dict[str, torch.Tensor]]
         | None = None,
-    ) -> tuple[torch.Tensor, KVConnectorOutput | None]:
+    ) -> torch.Tensor:
         """Propose draft tokens by calling the ExtractHiddenStatesModel model.
 
         The ExtractHiddenStatesModel caches the hidden states in the KV cache
@@ -99,7 +93,6 @@ class ExtractHiddenStatesProposer:
             target_hidden_states: List of hidden state tensors from target model
                                 (one per aux hidden state layer)
             common_attn_metadata: Attention metadata
-            scheduler_output: Scheduler output for KV connector
             slot_mappings: Slot mappings for KV cache (unused, provided for
                           interface compatibility)
 
@@ -136,22 +129,15 @@ class ExtractHiddenStatesProposer:
         if num_tokens_across_dp is not None:
             num_tokens_across_dp[self.dp_rank] = num_input_tokens
 
-        with (
-            set_forward_context(
-                per_layer_attn_metadata,
-                self.vllm_config,
-                num_tokens=num_input_tokens,
-                num_tokens_across_dp=num_tokens_across_dp,
-                cudagraph_runtime_mode=cudagraph_runtime_mode,
-                slot_mapping=self._get_slot_mapping(
-                    num_input_tokens, common_attn_metadata.slot_mapping
-                ),
+        with set_forward_context(
+            per_layer_attn_metadata,
+            self.vllm_config,
+            num_tokens=num_input_tokens,
+            num_tokens_across_dp=num_tokens_across_dp,
+            cudagraph_runtime_mode=cudagraph_runtime_mode,
+            slot_mapping=self._get_slot_mapping(
+                num_input_tokens, common_attn_metadata.slot_mapping
             ),
-            (
-                KVConnectorModelRunnerMixin._get_kv_connector_output(scheduler_output)
-                if has_kv_transfer_group()
-                else nullcontext()
-            ) as kv_connector_output,
         ):
             self.model(
                 hidden_states=self.hidden_states[:num_input_tokens],
@@ -159,7 +145,7 @@ class ExtractHiddenStatesProposer:
 
         # Return the sampled tokens as "draft" tokens
         # Shape: [batch_size, 1] to match num_speculative_tokens=1
-        return sampled_token_ids.unsqueeze(-1), kv_connector_output
+        return sampled_token_ids
 
     def _get_slot_mapping(
         self,

vllm/v1/worker/gpu_model_runner.py

@@ -4328,23 +4328,12 @@ class GPUModelRunner(
                 )
             target_hidden_states = [h[:num_scheduled_tokens] for h in aux_hidden_states]
 
-            draft_token_ids, drafter_kv_connector_output = self.drafter.propose(
+            draft_token_ids = self.drafter.propose(
                 sampled_token_ids=sampled_token_ids,
                 target_hidden_states=target_hidden_states,
                 common_attn_metadata=common_attn_metadata,
-                scheduler_output=scheduler_output,
                 slot_mappings=slot_mappings,
             )
-            # Combine KVConnectorOutputs or select the non-empty one
-            if self.kv_connector_output and drafter_kv_connector_output:
-                self.kv_connector_output = KVConnectorOutput.merge(
-                    self.kv_connector_output, drafter_kv_connector_output
-                )
-            else:
-                self.kv_connector_output = (
-                    self.kv_connector_output or drafter_kv_connector_output
-                )
-
             next_token_ids, valid_sampled_tokens_count = (
                 self.drafter.prepare_next_token_ids_padded(
                     common_attn_metadata,