Buildworlds are now much faster, because they can run themselves in parallel. Invoke it using the -j option to make. Matthew Dillon saw a 25% reduction in time when using ‘make -j 12 buildworld’ on a 4-core system. You may need to manually update xinstall and mkdir:
cd /usr/src/usr.bin/xinstall make clean; make obj; make all install cd /usr/src/bin/mkdir make clean; make obj; make all install
It’ll also use more memory than a non-parallel build, but heck, that’s cheap these days.