[Nix-dev] powertop kernel

[Mathijs Kwik]

On Tue, Feb 14, 2012 at 12:06 PM, Arie Middelkoop <amiddelk at gmail.com> wrote:
> On 13-02-12 22:24, Mathijs Kwik wrote:
>>
>> Hi all,
>>
>> I want to do some power usage tuning for my laptop, or at least gain
>> some insights into how my battery is spent.
>> I understand I need the powertop tool to do this, and I found that it
>> complains about some kernel config options.
>
>
> Compare the options with those listed at the top here:
> http://www.lesswatts.org/projects/powertop/faq.php
>
> CONFIG_TIMER_STATS is probably what powertop needs. The others are intended
> to reduce power, and seem a good idea to enable anyway.
> (except that CONFIG_SND_AC97_POWER_SAVE may give problems on some systems:
> but that option can be switched on/off at runtime I think).
>
> Arie

Yes, those are the options.
I did not see CONFIG_DEBUG_KERNEL there at first, so I was afraid
debugging would mean slowing stuff down for normal use. But it turns
out the option itself is just there to enable other options.

Furthermore, most options are already enabled in the current default
kernel (even the CONFIG_SND_AC97_POWER_SAVE you warned about, but off
by default, runtime switch).

Reading the description of the options, and some googling, I'm pretty
sure they are all quite harmless by default.
Most stuff needs to be enabled at runtime, while other settings offer
some more insights through /proc and /sys, which will only cause
overhead when actively polling for them (running the powertop tool).

So probably we can merge these options with our default config.
Let's say we do this by default when 3.3 comes out.
I will start using 3.2-powertop from now on and report if I run into issues.
If a few others will try this as well, we can make a solid decision about it.

Mathijs