Re: [gentoo-user] Tips for saving power needed... particulary on laptops

[Michael Mol <mikemol@gmail.com>]

On Fri, Apr 6, 2012 at 1:05 PM, Frank Steinmetzger <Warp_7@gmx.de> wrote:
> On Mon, Apr 02, 2012 at 01:22:50AM -0400, Walter Dnes wrote:
>
>> > > Hi,
>> > >
>> > > admin of a colo-center keeps complaining my server is going
>> > > a little over power-limit (which they have set as ~120W per
>> > > 24h/avg, while my server needs ~130-135W). So I need to find
>> > > a way to save at least those 15W, or I will be moved to
>> > > higher tarif (which means higher costs for server-housing).
>> […]
>> The following may seem obvious, but here goes...
>>
>> * remove unnecessary video cards, and drivers.  Most colo machines
>>   should do OK with just a text console running on the onboard GPU.
>>   Dump all video driver stuff "/dev/agpgart (AGP Support)" and
>>   "Direct Rendering Manager".  This assumes you're not running X on
>>   your colo machines.  mc (Midnight Commander) is a great text-based
>>   tool, along the lines of ye olde Norton Commander.
>>
>> * disable sound cards/chips in BIOS and remove drivers and kernel
>>   support.
>
> As a follow-up question that’s been on my mind for a long time: can I always
> assume that when there is no driver loaded, the device is really (physically)
> off, so it doesn't use any power (at all)?  Or are there exceptions to that
> rule (like hardware known to be buggy)?

The hardware will be energized, but won't typically consume as much
energy as it would were it under active use and load.

>  My concern comes from having an
> ageing laptop whose battery I want to preserve as well as I can.
>
> In my case, that would be bluetooth, ethernet, possibly even the optical
> drive, and even the touchpad. I can switch the latter off using Fn+F9, which
> even works on the tty. But does that really switch it off, or does the kernel
> merely ignore its input then?

For wireless devices, I believe the radio is switched off if you use
the hardware or software switches, but controlling hardware would
still be energized.

For ethernet, you probably want the driver installed, so you can
access any power-saving modes available to it. (Ditto most other
things)

Regarding touchpad...no idea.

Most of this is probably very case-by-case. Check the kernel configs.
Perhaps even measure power consumption changes after doing things like
disabling devices via sysfs.

-- 
:wq