Measure time it takes to calculate state group ID

synapse/state.py

@@ -483,6 +483,7 @@ class StateResolutionHandler(object):
                     key: e_ids.pop() for key, e_ids in state.iteritems()
                 }
 
+            with Measure(self.clock, "state.create_group_ids"):
                 # if the new state matches any of the input state groups, we can
                 # use that state group again. Otherwise we will generate a state_id
                 # which will be used as a cache key for future resolutions, but