Short circuit if presence is the same

synapse/handlers/presence.py

@@ -941,6 +941,9 @@ class PresenceHandler(object):
 def should_notify(old_state, new_state):
     """Decides if a presence state change should be sent to interested parties.
     """
+    if old_state == new_state:
+        return False
+
     if old_state.status_msg != new_state.status_msg:
         notify_reason_counter.inc("status_msg_change")
         return True