[Feature] Add DWDP (Distributed Weight Data Parallelism) for MoE prefill (#29778)

python/sglang/srt/managers/scheduler_components/dp_attn.py

@@ -226,6 +226,7 @@ def prepare_mlp_sync_batch_raw(
     require_mlp_tp_gather: bool,
     disable_overlap_schedule: bool,
     offload_tags: set[str],
+    dwdp: bool = False,
 ):
     # Check if other DP workers have running batches
     if (
@@ -327,8 +328,8 @@ def prepare_mlp_sync_batch_raw(
 
     # Decide whether to emit idle batch
     if skip_all_gather:
-        # Skip idle batch when attn-dp=1
-        need_idle_batch = dp_size > 1
+        # Skip idle batch when attn-dp=1 (and always under DWDP: ranks run independently)
+        need_idle_batch = not dwdp and dp_size > 1
     else:
         need_idle_batch = max(mlp_sync_info.global_num_tokens) > 0
 
@@ -386,6 +387,7 @@ class SchedulerDPAttnAdapter:
             require_mlp_tp_gather=require_mlp_tp_gather(self.server_args),
             disable_overlap_schedule=self.server_args.disable_overlap_schedule,
             offload_tags=self.offload_tags,
+            dwdp=self.server_args.dwdp_size > 1,
         )
 
     def maybe_prepare_mlp_sync_batch(