performance -- depends on the deployment.  For me -- primarily not.  But we had already complaints where users had to come up with ad-hoc setups to run multiple fail2bans on the same box to be able to avoid GIL and still be capable to parse all the log files.  sure thing those are not directly related to performance of actually running the commands, but more of parsing, but better to just keep performance in mind.

As for vbench -- it might be fun to see either we impaired parsing performance by e.g. introducing more of time formats etc.