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While researching, I came across powertop, pm-utils, tlp, laptop-power-mode and a whole pile of manual hacks...

I spent a while trying to figure out the merits of each method and whether they conflicted.. and then I saw this..

https://askubuntu.com/questions/172391/is-laptop-mode-tools-still-relevant-for-12-04-and-the-3-x-kernels

..which claims that on the latest Ubuntu, these are barely relevant anymore.

It always surprised me how poor Linux battery life is out of the box compared to other OSes, given that it is also often more light weight, so it makes sense that the kernel is integrating these new features and the other tools are just required if your kernel is too old for your hardware... but is that the case?

Is the reasoning in the link above that the kernel now handles all of this - or is it specific to Ubuntu as they have added extra scripts, etc. for a better user experience.

tl;dr - (1) is this also applicable to Debian Jessie / any other distribution from a certain kernel version?

And (2) for people in the future who have the same question for the latest power saving tweak on whatever kernel we are on then - what is the easiest way to find out what tweaks are now handled in a given kernel, to avoid people asking this question every 6 months or so? (Better to learn how to learn about it than keep bothering you all!)

  • Why the -1? Is this not a valid question? If I can improve it just let me know what's wrong with it.. – Mark May 28 '15 at 11:05
  • Probably people don't agree with your claim about poor Linux battery life. Anyway, avoid cross-posting and delete one of your two posts to avoid closure. – Karan May 29 '15 at 1:32
  • Interesting, I am sure that it can be optimised (hence the question) to be competitive but out of the box, I always get much less on a fresh linux install than Windows. I have read many accounts of the same for Macs. I thought that leaving both posts up might be best practice, with links to the other on each, in case different audiences had different inputs so apologies if this was incorrect. I will close the other, since this has the better answer. Thanks for the feedback. – Mark May 29 '15 at 7:58
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The problem is that power saving is highly complex. Various elements make a difference. The OS itself, the hardware and the software you run. Each need to think about how power is consumed.

The Linux Kernel (common across all Linux distributions) has gained some features that allow software to fine tune power use. By default, that is configured in a generic way to ensure compatibility with the widest range of hardware.

On top of that, the Ubuntu developers have spent a lot of time with the various tools and utilities trying to fine tune the parameters to get the best out of Ubuntu as an operating system.

However, even that is not really enough since each laptop model is built differently and so requires further tuning to get the best battery life. Tools such as Jupiter for example are able to make big differences on certain types of hardware, not so much on others.

When using Windows as an OS, all of this tuning is done by the manufacturer because it is worth their while. The use of Linux on the desktop is still marginal compared to the use of Windows and so manufacturers don't do the work. Even if they did, I don't think there is a single point of configuration so any optimisation would need to take the form of a - probably pretty complex - script that would need to be checked and maintained constantly. So to be honest, it will almost certainly never be a widespread option unless a common power tuning platform becomes available for Linux.

So: No, the kernel exposes certain capabilities and a standard configuration. Specific distributions can tune things to a certain degree. Hardware specific tuning is left up to the user. :(

  1. Yes, the above applies to other distributions using comparable versions of the kernel.

  2. While I can see that tweaks and general tuning will happen gradually so you should see improvements over time (though I'm guessing that specific distribution releases may undo that from time to time due to other software changes that consume more power), you are unlikely to see a big jump unless or until someone comes up with a single, coherent power management platform. That would be the thing to watch for (in my opinion at least).

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  • I understand that manufacturers can optimise for their hardware and driver support, etc is often better - but I thought that some of the tools mentioned in my original post have made significant improvements in the past. So there must be generic ways that can help, even if it isn't quite as good as more closed systems. – Mark May 28 '15 at 11:09
  • Just to clarify, when you say that it does also apply to Debian and others, do you mean the link I posted, saying that most power saving tweaks are no longer required? Because that seems to contradict the rest of your post.. – Mark May 28 '15 at 11:10
  • That isn't what it says. It says the Ubuntu team did a lot of tweaks for v12.04 not that the Kernel makes them redundant. Look at the link to the 2nd question in the comments too. As I've said, the Kernel exposes some capabilities and defaults some general settings. They can be massively improved upon by further tweaks which the Ubuntu team have done for Ubuntu. The Kernel features are available for ALL distros, the Ubuntu tweaks only for Ubuntu. My response to 1 wasn't clear - I'm referring to the Kernel features there. – Julian Knight May 28 '15 at 16:27
  • Ok thanks for the clarification. My understanding was that there are tweaks required which are later fixed in kernel updates, for example, i915-rc6, etc for some processors - these had to be manually applied and then were later fixed by kernel updates - so my query I guess is how to find out when this is the case - that a given tweak is no longer required because it is now handled by the kernel (not just providing a new capability) – Mark May 28 '15 at 16:35
  • I'm afraid that you will probably be faced with having to monitor the various power tweak tools for updates. This is what I was saying about the lack of a single power management platform. – Julian Knight May 28 '15 at 16:40

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