I _finally_ got my laptop upgraded and in a reasonable state, so I tried
playing with the soft update code to see if it affects power management at
all.  This is 1.5_ALPHA.

To my surprise, I discovered that when I mounted my filesystems with
soft updates turned on, I got a disk write once every 5-8 seconds, which
interacted with power management very badly (as you can imagine).

The same setup _without_ soft updates:

- Running X
- Filesystems mounted with async,noatime,nodevmtime ("async" is ignored
  when you're using soft updates, of course),
- Connected to the network

Doesn't result in any disk I/O.  In fact, I still get occasional disk
writes when I've exited X and I'm using soft updates.

I'm scratching my head on this one.  Anyone got any ideas?  I have no
fear in diving into the kernel and inserting various debugging printfs
to track down what's being written; I'm just wondering if anyone has
any ideas.

--Ken