[PD][Spec] Fix hidden state transfer for spec decode (#7516)

Signed-off-by: Shangming Cai <caishangming@linux.alibaba.com>

python/sglang/srt/disaggregation/decode.py

@@ -579,11 +579,11 @@ class DecodeTransferQueue:
                 idx = decode_req.metadata_buffer_index
                 (
                     output_id,
-                    output_hidden_states,
                     output_token_logprobs_val,
                     output_token_logprobs_idx,
                     output_top_logprobs_val,
                     output_top_logprobs_idx,
+                    output_hidden_states,
                 ) = self.metadata_buffers.get_buf(idx)
 
                 decode_req.req.output_ids.append(output_id[0].item())

python/sglang/srt/disaggregation/mooncake/conn.py

@@ -291,15 +291,21 @@ class MooncakeKVManager(BaseKVManager):
         dst_aux_ptrs: list[int],
         dst_aux_index: int,
     ):
-        aux_item_len = self.kv_args.aux_item_lens[0]
-        prefill_aux_addr = (
-            self.kv_args.aux_data_ptrs[0] + prefill_aux_index * aux_item_len
+        src_addr_list = []
+        dst_addr_list = []
+        length_list = []
+        prefill_aux_ptrs = self.kv_args.aux_data_ptrs
+        prefill_aux_item_lens = self.kv_args.aux_item_lens
+        for i, dst_aux_ptr in enumerate(dst_aux_ptrs):
+            length = prefill_aux_item_lens[i]
+            src_addr = prefill_aux_ptrs[i] + length * prefill_aux_index
+            dst_addr = dst_aux_ptrs[i] + length * dst_aux_index
+            src_addr_list.append(src_addr)
+            dst_addr_list.append(dst_addr)
+            length_list.append(length)
+        return self.engine.batch_transfer_sync(
+            mooncake_session_id, src_addr_list, dst_addr_list, length_list
         )
-        decode_aux_addr = dst_aux_ptrs[0] + dst_aux_index * aux_item_len
-        status = self.engine.transfer_sync(
-            mooncake_session_id, prefill_aux_addr, decode_aux_addr, aux_item_len
-        )
-        return status
 
     def sync_status_to_decode_endpoint(
         self, remote: str, dst_port: int, room: int, status: int

python/sglang/srt/disaggregation/utils.py

@@ -107,9 +107,6 @@ class MetadataBuffers:
             # The minimal size for RDMA is 64Bytes, so we pad it to > 64Bytes
             self.output_ids = torch.zeros((size, 16), dtype=torch.int32, device=device)
 
-            self.output_hidden_states = torch.zeros(
-                (size, hidden_size), dtype=dtype, device=device
-            )
             self.output_token_logprobs_val = torch.zeros(
                 (size, 16), dtype=torch.float32, device=device
             )
@@ -122,51 +119,50 @@ class MetadataBuffers:
             self.output_top_logprobs_idx = torch.zeros(
                 (size, max_top_logprobs_num), dtype=torch.int32, device=device
             )
+            self.output_hidden_states = torch.zeros(
+                (size, hidden_size), dtype=dtype, device=device
+            )
 
     def get_buf_infos(self):
         ptrs = [
             self.output_ids.data_ptr(),
-            self.output_hidden_states.data_ptr(),  # TODO: set None to avoid transfer hidden_states when spec_algorithm is None
             self.output_token_logprobs_val.data_ptr(),
             self.output_token_logprobs_idx.data_ptr(),
             self.output_top_logprobs_val.data_ptr(),
             self.output_top_logprobs_idx.data_ptr(),
+            self.output_hidden_states.data_ptr(),
         ]
         data_lens = [
             self.output_ids.nbytes,
-            self.output_hidden_states.nbytes,
             self.output_token_logprobs_val.nbytes,
             self.output_token_logprobs_idx.nbytes,
             self.output_top_logprobs_val.nbytes,
             self.output_top_logprobs_idx.nbytes,
+            self.output_hidden_states.nbytes,
         ]
         item_lens = [
             self.output_ids[0].nbytes,
-            self.output_hidden_states[0].nbytes,
             self.output_token_logprobs_val[0].nbytes,
             self.output_token_logprobs_idx[0].nbytes,
             self.output_top_logprobs_val[0].nbytes,
             self.output_top_logprobs_idx[0].nbytes,
+            self.output_hidden_states[0].nbytes,
         ]
         return ptrs, data_lens, item_lens
 
     def get_buf(self, idx: int):
         return (
             self.output_ids[idx],
-            self.output_hidden_states[idx],
             self.output_token_logprobs_val[idx],
             self.output_token_logprobs_idx[idx],
             self.output_top_logprobs_val[idx],
             self.output_top_logprobs_idx[idx],
+            self.output_hidden_states[idx],
         )
 
     def set_buf(self, req: Req):
 
         self.output_ids[req.metadata_buffer_index][0] = req.output_ids[0]
-        if req.hidden_states_tensor is not None:
-            self.output_hidden_states[req.metadata_buffer_index].copy_(
-                req.hidden_states_tensor
-            )
         if req.return_logprob:
             if req.output_token_logprobs_val:  # not none or empty list
                 self.output_token_logprobs_val[req.metadata_buffer_index][0] = (
@@ -189,6 +185,11 @@ class MetadataBuffers:
                 ] = torch.tensor(
                     req.output_top_logprobs_idx[0], dtype=torch.int32, device="cpu"
                 )
+        # for PD + spec decode
+        if req.hidden_states_tensor is not None:
+            self.output_hidden_states[req.metadata_buffer_index].copy_(
+                req.hidden_states_tensor
+            )
 
 
 #########################