>I've migrated to -current to test the auto-join, but since then, my system >is slow. Specially with libreoffice, firefox, ... > >By looking at top, I've saw that only 2 CPU are actually running.
You only have 2 real cpus. the others are HT, and we disable those due to a security hole called tlbleed. You can search for the rest of the information yourself.
