> > I've gotten some dup alloc crashes recently,
> This is usually caused by corrupt filesystems.

The filesystem in question (which wasn't the one I thought it was, it
turns out) had been clean the last time I ran fsck, and actually had
very little corruption when fsck was run on it after reboot.  What was
interesting, though, is that after being told that one must run fsck -c3
on filesystems when you adjust maxcontig (the tunefs manual page should
mention this, as well as the fact that this will ALSO change your filesystem
type if you tunefs an ancient filesytem!), I ran fsck and was told that one
filesystem had a corrupted directory, and that I should run fsck in manual
mode (having used -p).  When I re-ran fsck, *nothing was wrong*.  I now
suspect flaky hardware (I've had suspicions of flakiness for some time now).