I would say the preffered setting is True. In former days or without this setting active each realm has a dedicated thread with the only purpose to iterate over the complete map to find items to destroy. With this setting active it's only one thread for all realms.
(Only used with above setting also set)
Since iterating over the complete world to find items to destroy is really a big overhead the story is not over. I added this setting to print statistics per run how many items are able to decay currently and how many items got destroyed to find the best implementation. I hope I will find time again to finish this todo. I would be glad if any shardowner who reads this activates this for a few days and sends me the log prints.
Yes name is selfexplaining without other side effects (oh my god)
The current highest level is 22. All of them pretty senseless if you don't search a bug somewhere near these lines. Search for INFO_PRINT_TRACE in the sources to find the spots and what they print.
The tachometer "rotations per minute" prints some informations how busy the script scheduler was
I guess this is a left over, atleast the variables which get printed never change, plus our map is completely in RAM there cannot be a cache miss.