Linux power saving for the road warrior.

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kode-niner
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Linux power saving for the road warrior.

#1 Post by kode-niner »

This is the thread to share techniques for saving battery life and compare notes.
Daily drives a CF-31

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SHEEPMAN!
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Re: Linux power saving for the road warrior.

#2 Post by SHEEPMAN! »

Quote from Shawn:
The led backlit lcd makes about a 20% power savings according to the SWAG test procedure...

I am a certified SWAG test technician. I have held the certification for over ten years..
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kode-niner
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Re: Linux power saving for the road warrior.

#3 Post by kode-niner »

The first thing to do is to install powertop.

Run as root or sudo

Code: Select all

apt-get install powertop
Re-enable anything you may have disabled in BIOS like DVD drive, networking, bluetooth, modem and touch screen. Unplug your laptop from the AC adapter, run it on a 100% charged battery then calibrate powertop with everything enabled, screen brightness at full. It will dim your screen while running tests.

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powertop --calibrate
Recharge your battery or use another one that is closer to 100% charge and run powertop with refresh every 1 seconds

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powertop --time=1
In the Overview, the discharge rate and remaining time will fluctuate depending on the tasks running, so close as many applications as you can to get a good baseline reading with all your hardware enabled. Use the TAB key to cycle among the powertop views. We can compare our power usage among us with this tool with our respective TB models. The aim (or competition, if you will) is to get the discharge rate as low as you can while still maintaining an actual usable system.

Later we can discuss things we can do to improve these numbers, such as playing around with powertop's tunables, tweaking software and hardware.
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SHEEPMAN!
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Re: Linux power saving for the road warrior.

#4 Post by SHEEPMAN! »

First Look and Comments:

1. First time users, this is not instantaneous. Not complaining, be prepared for a few minutes of "off" time.
2. Charging now for second go. (powertop --time=1)
3. Are we going to do a chart or something?

Thanks kode,

J'd :salute:
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Re: Linux power saving for the road warrior.

#5 Post by kode-niner »

To keep things simple, the discharge rate is probably what we should focus on. Now that I think of it, charging the battery to 100% is not necessary. We're not testing battery performance, but power draw. For example, on my CF-30 I want to keep it below 10W.

It's getting late and I need to disconnect my brain.
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Re: Linux power saving for the road warrior.

#6 Post by kode-niner »

A few of the most obvious power saving techniques:

In BIOS I routinely disable everything I don't need. Normally you don't have to since most components will power themselves down when not in use, but I don't want them to be accidentally awaken by some silly script or program. And in my experience, auto-suspend doesn't always work properly.
On the CF-30 I disable:
LAN (ethernet) since I use wwan or wlan most of the time and activate these only when I need them.
bluetooth
dvd media bay
Express card slot
PC card slot
SD slot
IEEE1394 firewire
modem


Currently debating with myself over disabling touchscreen since I occasionally take a stab at the screen with my fingernail to click on buttons. But the damned thing can draw around 2W. What I'm really trying to do is to make it auto-suspend as quickly as possible but according to powertop it seems to linger on and won't power down once I start using it. This may be a bug and I need to figure that out or stop using it altogether.


LCD Brightness Mode seems like a goofy feature in BIOS. It basically cuts the maximum brightness level in half. I think I can control myself and adjust brightness manually and not keep it on full blast all the time. Sometimes in direct sunlight I need my 10000 nits. At night I can use it on one or two ticks above the lowest setting or completely low in total darkness. Power draw is around 3W including controller when at 100% brightness. At its lowest setting it's less than 700mW.


A bit less obvious: If you noticed the Tunables section of powertune, it does help a bit to set everything from BAD to GOOD in that list. I automate the process by using

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powertop --auto-tune
and run it automatically when I log in. I'm almost sure that this works better than the pm-utils powersave mode.
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Re: Linux power saving for the road warrior.

#7 Post by SHEEPMAN! »

How about "NMI WATCHDOG SHOULD BE TURNED OFF"?
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Re: Linux power saving for the road warrior.

#8 Post by kode-niner »

Sadlmkr wrote:How about "NMI WATCHDOG SHOULD BE TURNED OFF"?
I guess you might save a few CPU cycles by disabling that, assuming it's enabled by default.
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Re: Linux power saving for the road warrior.

#9 Post by SHEEPMAN! »

Looks like disabled by default in 64 bit. (did some reading)

Three instances of [display back-light] 1.17 ea ??????????????????

Baseline 12.4W with comfortable backlight.

Bluetooth disabled in bios. +- 1.25W Disabling WWAN will Knock it down another 414mW.
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Re: Linux power saving for the road warrior.

#10 Post by kode-niner »

Sadlmkr wrote:Three instances of [display back-light] 1.17 ea ??????????????????
I think that's a bug. I've always seen multiple back-light lines. I think you can still tweak it go get it down closer to 10W. My baseline hovers around the 13W with display at full blast.
Daily drives a CF-31

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