[plug] power saving features? sleep etc.

[Craig Ringer]

Sham Chukoury wrote:

> About the Sleep and Wake Up buttons.. I assume these are meant to
> suspend and resume the computer? APM and ACPI can put the system on
> standby.

APM tends to work very well for it on older laptops, but isn't supported 
on newer ones. APM on desktops has always been a bit iffy, depending on 
your exact hardware.

ACPI also works OK (you'll need 2.6 for ACPI sleep, etc), but can be 
fiddly to get going. Lots of hardware has ACPI BIOS bugs that must be 
worked around.

> However doing a Hibernation-type thing, where the contents of
> memory are written to disk and the system powered off, then having the
> memory restored when powered on again, is still quite dodgy.

Works for me :-)

There's an swsusp implementation in the 2.6 kernel that works pretty 
well for many, and an external one at swsusp.sf.net that gets extremely 
good ratings from a lot of people.

Some users get better results if they switch away from X before 
hibernating. Unloading certain modules and bringing down network 
interfaces can also help. I find everything "just works" myself.

Additionally, I hear software suspend is currently more robust in 2.4 
than 2.6. It works perfectly for me in 2.6 so I'm not complaining, but 
its worth keeping in mind for if you have trouble.

> Last time i
> tried the feature (swsusp?), it managed to suspend properly, but failed
> to resume. That was back on kernel 2.6.0 or 2.6.1.. I might try it again
> some time, with 2.6.6. :P

Worth a try - its REALLY nice to be able to completely hibernate the 
machine. I just need to try out the compressed RAM dump support, and see 
if there's a patch out there that makes the RAM freeing a bit less 
agressive (slower suspend/resume, more immediately useable machine after 
resume).

Craig Ringer