MDEV-19229 allows the parameter innodb_undo_tablespaces to be increased from its current default value 0, we should enable multiple undo tablespaces by default. Likewise, we should set innodb_undo_log_truncate=ON by default, so that the space occupied by possible bursts of undo log records will be eventually reclaimed.
Edit: Based on some preliminary performance test results presented by axel, innodb_undo_log_truncate=ON seems to reduce throughput. That setting can be changed by SET GLOBAL while the server is running. The main thing here is to run the server with multiple tablespaces by default, so that it will be possible to truncate the undo tablespaces while the server is running.
Space that was occupied by undo logs in the system tablespace will not be reclaimed until
MDEV-14795 has been implemented.