I tried to use VirtualBox settings to increase the number of processors used by my MediaWiki vagrant install (from 2 to 4), as suggested on
https://www.mediawiki.org/wiki/MediaWiki-Vagrant/Troubleshooting#If_vagrant_is_slow
I saved my changes, but after I executed vagrant up the number was reset to 2. Increasing the memory has the same problem, but increasing the video memory works fine.
Is this a bug preventing me to make this change permanent or did I miss something?