Subject: Re: power management
To: None <>
From: Miles Nordin <carton@Ivy.NET>
List: port-hpcarm
Date: 10/26/2004 11:32:35
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>>>>> "lt" == Lorant Toth <> writes:

    lt> dump ... memory including kernel ... to a ... 64MB CF card

solaris added something like this in 2.7.  It makes a state file
inside a filesystem, but the file is small, I think because solaris
dumps mostly to swap.  The NetBSD scheme could be largely MI.  In
fact, NetBSD already has the ability to dump to swap, sometimes.  You
need at least, (1) a way to dump to ``free'' swap if the dumpdevice ==
swapdevice and cleanly abort if there isn't enough free swap, and (2)
an undumper. :'

    lt> I am not sure what WinCE does besides erasing RAM

There's a lot of discussion in the list archives about this.  Most of
it is about installing a ``hook'' so WinCE does not start at all, and
RAM is not erased, and you can unsuspend just like WinCE does without
dumping anything to disk.  As with your alternative scheme, after you
find the hypothetical hook you still have to convince NetBSD to
re-init all the hardware.  The power-on hook might require some
surprise work that your scheme doesn't, because NetBSD might for now
depend on WinCE to initialize a lot of the hardware.

Personally I think power-off stuff is silly, because in the future
everything will be on all the time.  It's more interesting to me to
make a buffer cache that's safe and performant without spinning disks
up every 30sec on an idle machine, slow a CPU to 1MHz instead of
idling it, bring secondary CPUs on MP machines up and down
configurably according to an efficiency-maximizing rule (only one CPU
<100% used) or a latency-minimizing rule (only one mostly-idle CPU),
swap RAM to disk move around to squeeze yourself to one end of
physical memory and shut down a whole bank of RAM, shut off the video
controller instead of just blanking the screen.  but nothing that
shuts off CPU, network, or keyboard.  However I think this opinion
isn't widely-held or well-supported by existing laptops.

Le fascisme est la dictature ouverte de la bourgeoisie.
		-- Georg Dimitrov

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