[PD Disaggregation] replace transfer with batch transfer for better performance (sgl-project#7236)

Author: ssssnow

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

@@ -251,17 +251,19 @@ def send_kvcache(
 
         # Worker function for processing a single layer
         def process_layer(src_ptr: int, dst_ptr: int, item_len: int) -> int:
+            src_addr_list = []
+            dst_addr_list = []
+            length_list = []
             for prefill_index, decode_index in zip(prefill_kv_blocks, dst_kv_blocks):
                 src_addr = src_ptr + int(prefill_index[0]) * item_len
                 dst_addr = dst_ptr + int(decode_index[0]) * item_len
                 length = item_len * len(prefill_index)
-
-                status = self.engine.transfer_sync(
-                    mooncake_session_id, src_addr, dst_addr, length
-                )
-                if status != 0:
-                    return status
-            return 0
+                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
+            )
 
         futures = [
             executor.submit(

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

@@ -1,7 +1,7 @@
 import json
 import logging
 from dataclasses import dataclass
-from typing import Optional
+from typing import List, Optional
 
 logger = logging.getLogger(__name__)
 
@@ -90,5 +90,29 @@ def transfer_sync(
 
         return ret
 
+    def batch_transfer_sync(
+        self,
+        session_id: str,
+        buffers: List[int],
+        peer_buffer_addresses: List[int],
+        lengths: List[int],
+    ) -> int:
+        """Synchronously transfer data to the specified address."""
+        try:
+            ret = self.engine.batch_transfer_sync_write(
+                session_id, buffers, peer_buffer_addresses, lengths
+            )
+        except Exception:
+            ret = -1
+
+        if ret < 0:
+            logger.debug(
+                "Failed to batch transfer data. Buffers: %s, Session: %s, Peer addresses: %s",
+                buffers,
+                session_id,
+                peer_buffer_addresses,
+            )
+        return ret
+
     def get_session_id(self):
         return self.session_id