Re: RFA: acpi-support -- glue layer for translating laptop buttons, plus legacy suspend support

[Bjørn Mork <bjorn@mork.no>]

Matthew Garrett <mgarrett@chiark.greenend.org.uk> writes:

> powertop makes various recommendations that are only useful in very
> specific circumstances. Disabling polling in hal saves you a small (and
> probably not useful in the real world) amount of power, but is required
> to get to the number of wakeups per second that Arjan was aiming for. I 
> haven't been able to measure any difference in power consumption on a 
> typical system.

I'm sure you know this, but others may not be aware of it...

Modern systems have the ability to put inactive devices in a low power
state to save power.  See for example
http://www.lesswatts.org/projects/devices-power-management/

You'll save between 0.5 and 1.5 W by enabling SATA Aggressive Link Power
Management according to http://www.lesswatts.org/tips/disks.php As this
definitely is measurable, I assume that your measurements have been done
without enabling ALPM?  Or maybe the power saving estimated by lesswatts
is based on normal hard drive usage?

Could you please share the details of what you've measured?  Which type
of drives, controllers and drivers are used in a "typical system"?  How
about a "typical laptop" (which in my world is the only system class
where this matters anyway)?  How about "modern laptop" (AHCI controller,
SATA DVD)?



Bjørn