Mark remote device list updates as already handled

changelog.d/12557.misc

@@ -0,0 +1 @@
+Reduce unnecessary work when handling remote device list updates.

synapse/handlers/device.py

@@ -505,8 +505,9 @@ async def notify_device_update(
             "device_list_key", position, users={user_id}, rooms=room_ids
         )
 
-        # We may need to do some processing asynchronously.
-        self._handle_new_device_update_async()
+        # We may need to do some processing asynchronously for local user IDs.
+        if self.hs.is_mine_id(user_id):
+            self._handle_new_device_update_async()
 
     async def notify_user_signature_update(
         self, from_user_id: str, user_ids: List[str]

synapse/storage/databases/main/devices.py

@@ -1748,7 +1748,8 @@ def _add_device_outbound_room_poke_txn(
                     device_id,
                     room_id,
                     stream_id,
-                    False,
+                    # We only need to calculate outbound pokes for local users
+                    not self.hs.is_mine_id(user_id),
                     encoded_context,
                 )
                 for room_id in room_ids

tests/storage/test_devices.py

@@ -29,7 +29,7 @@ def add_device_change(self, user_id, device_ids, host):
         for device_id in device_ids:
             stream_id = self.get_success(
                 self.store.add_device_change_to_streams(
-                    "user_id", [device_id], ["!some:room"]
+                    user_id, [device_id], ["!some:room"]
                 )
             )