XenForo 2.1.1 is now available for download. We recommend that all users using previous versions of XenForo 2.1 upgrade to this version to improve stability.
Some improvements have been made to the import structure. It is noteworthy that it has now become possible to perform multithreaded imports in order to make better use of multi-core processors. If you run the import via the CLI and add the --processes option with a value greater than 1, then several PHP processes will be used to perform the import instead of one CPU core, which is used by default in PHP. Your results may vary, but with the number of processes set equal to the number of physical cores on a sufficiently powerful server, you should notice a significant increase in performance.
You can also run the import command with the new --finalize option, which will start the rebuild stage automatically after the data import is completed.