I wrote:
A bit of further experimentation shows that my 4000/500 still can't use
swap without crashing. It seems to get a bit further than it used to: I
suspect that it survives swapping something out, but crashes when it
needs to pull something back in. I'm back to running with no swap
configured, now, and will try to get the world built that way.
Actually, I just noticed that the /etc/fstab I'd been using not only had
a swap partition enabled, but had an mfs on /tmp, as well. Seeing as
there have been reports on current-users of trouble with mfs lately,
I've now given the 4000/500 a swap partition, but no mfs.