Tag Archives: power management

Linux 4.1 = +50% power efficiency (when idle)

Increased battery efficiency

Increased battery efficiency

On my laptop, I’m running Fedora 22 which was shipped initially with a Linux 4.0 kernel. It was difficult to get 4h of battery life (3h30 was usually enough to deplete the battery down to 5%). Recently, the kernel was changed to 4.1 and because after 5h working on my laptop I got notified that I still had 10% power I got curious,

Therefore with a fully charged battery, I booted with Fedora 22 Linux kernel 4.0.4-301. I used powertop to measure the battery power usage in Watt in graphical (ex-init 5 level) and multi-user target (ex-init 3 level). I then rebooted using Linux kernel 4.1.3-201 and did the same measurement. I waited each time that the system settled down and that successive measurements where constant. Nothing was running, WiFi was ON and connected (Link Quality=64/70), screen brightness at 30%, Graphical target is using Gnome 3.

SystemD Target (~init level) Linux 4.0 (in W) Linux 4.1 (in W) Progress
Multi-User (init 3) 12,8 8,66 -32%
Graphical (init 5) 13,1 8,51 -35%

Wow! That’s great. And the estimated battery power is now up from 4h to 6h30 with WiFi ON. But with light browsing usage and some Arduino development, I got a bit more than 5h15 without requiring a wall power connection!! That close to 50% more battery life than with earlier kernels.

Where does this come from? I don’t know. There seems to have been a few pull requests about power management for kernel 4,1 but none stroke me as relevant for such a huge improvement, Matthew Garrett has proposed a patch to improve dramatically the power efficiency of Intel’s Haswell and Broadwell CPUs (and I happen to have an Haswell one), so that could have been that patch, but I did not find it in the kernel 4.1 changelog, so I doubt it was yet implemented. So I really don’t know what made change in the kernel bring such an improvement. (note: I’m running Fedora 22 and without software update, just by selecting kernel 4.0 or 4.1 at boot, I can see the difference in power consumption. So this is really a kernel-side improvement).

Did you also witness improvement when switching to Linux kernel 4.1? Let me know using any social media means!

Note to self: telinit is now deprecated in favour of systemd targets. Runlevel 3 can be reached by invoking sudo systemctl isolate multi-user.target and the switch to the “runlevel 5” can be triggered using sudo systemctl isolate graphical.target.

Picture credits: Picture was created by me using elements from the KDE project. The original materials were licensed under GNU LGPLv3, and the picture is also provided under this license terms and conditions.

Increasing laptop battery life in Ubuntu

Gnome Power Management logoThe nature is getting greener everyday, so why can’t we? I decided to invest a bit of my time solving a problem with Dell laptops running Ubuntu and the LCD brightness. The root of this problem is detailed in the Dell Latitude D600 laptop page on the Ubuntu Wiki. To shortly summarise the current release (7.04) of Ubuntu does not manage to talk with the Dell hardware properly to get the brightness state and to modify it. Therefore, Ubuntu cannot dim the LCD brightness to save energy on such laptop.

This post briefly offers some technical background before pointing to a guide in wikishelf, which will explain how to activate the control of the LCD brightness and take advantage of the Gnome Power Manager facilities to save some more battery life.

For other tips and tricks to lower your power consumption on Linux in general, try this article about Linux power management, how to optimise power consumption, most of these information are not specific to Dell laptops or Ubuntu, they can even be applied on desktop computers to save energy.
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Linux is going to be super green

Gnome Power Management logoEcology, this is a kind of marketing and political buzz word now-a-day. When someone says “I am an ecologist”, what does he really want to say? Thus, I will not use it but rather say that I love hiking and cycling, and the best place to do so is Nature, especially far from any road or city. Therefore, I love Nature (at large) and I am doing my bit and my best to protect it and today I was quite happy to read an article on future improvements on the power management of Linux.

To shortly summarise (I heavily advise you to read the above linked article): the new kernel (2.6.21 with the tickless timer) and Intel involvement will mainly help reducing power consumption. Also, it seems that KDE (another Linux desktop environment) has some nice improvements in sleep states area.

Now linking the article conclusion about AMD/ATI drivers and the dream that perhaps AMD/ATI will help the open source community creating new drivers. There are hopes to save even more energy.

Getting more from your battery

Gnome Power Management logoFollowing my previous article on the Gnome Power Management applet, I want to talk about another new functionality of this tool that got added with the latest version of Gnome (2.18 available with the coming Ubuntu Release).

This new facility helps you getting more information from your battery and is available via the menu of the Gnome Power Management applet when clicking on it with the left button. In the menu, the first entry should be about your battery with the charge information.

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Gnome Power Management

Gnome Power Management logoIn the up coming Gnome 2.18, there have been several improvement of the Gnome Power Management applet. It still does the job of easily configuring many options that reduce power consumption. But recently it offers a power history.

This functionality is accessible upon right click on the applet icon. It displays a neat little plot of the power level of your battery and of various ACPI-related events (like session idle, suspend, etc.) Gnome Power Management - Power History exampleI find it quite useful to see if the power management policies chosen are applied and if they could be optimised.

On your right is a screenshot of the power history (click the image to enlarge).