The same as 'on', but print a message on every collection
(the message goes to toplevel_output):
GC ... global: 96208 - 88504 (92.0 %), trail: 500 - 476 (95.2 %), time: 0.017
It displays the area to be searched for garbage, the amount
and percentage of garbage, and the time for the collection.
The message of the dictionary collector is as follows:
DICTIONARY GC ... 2814 - 653, (23.2 %), time: 0.033
It displays the number of dictionary entries before the collection,
the number of collected entries, the percentage of reduction and
the collection time.