Status update:

After applying the patch in PR26908, my desktop machine has not
frozen or paniced despite of normal use and the "huge image test"
in gimp.  I'm using the old 16 GB swap again and I re-enabled
softdeps on local partitions after applying the patch.

I applied the PR26908 patch to my laptop kernel and upgraded xine
(and almost every pkg including kde, gnome, and lots of smaller pkgs).
The laptop hasn't paniced, but when I quit xine, it froze for a
relatively long period of time.  I thought it froze for good, but when
I returned after some 10 minutes, the laptop was back alive again.

When the laptop was frozen, it didn't respong to ping or any keyboard
events - but when it came back alive, all the keys I had entered (some 20
of them) appeared in the xterm window.

  -jm