The future of Power Management - together with Activities

Dario Freddi drf54321 at
Sat Oct 1 22:13:06 BST 2011

On Saturday 01 October 2011 21:21:40 Andras Mantia wrote:
> [Please reply on both lists if you cross-posted, otherwise dicussion will
> be more fragmented. I just looked up the plasma list out of curiosity,
> normally I don't follow, so your mail would have been missed.]
> Dario Freddi wrote:
> >> I can't comment on activities, never used them, nor feel the need to use
> >> them. So this sounds more like the power management applet would force
> >> me to create and use activites.
> > 
> > Well, if you like to see it that way, yes. Or better, we are trying to
> > drive forward the concept of "one environment, one setting", where
> > depending on what you do, the system is going to adapt.
> I don't like if software forces me to work in a certain way. And with
> activities I'm not alone. I'm happy without them, even if they are useful
> for others. Just as I'm mostly happy also without virtual desktops (which
> are a must for others). People are different, they have different workflows
> that they don't want to change if there is no *good* reason to do it.

Sorry, but software forces you to work in certain ways everytime - it's just 
that you don't like how it's being laid down atm. Previously, you had to 
create a profile, I could have argued that I don't like a software which 
forces me to work in a certain way (profiles).

I agree on the fact that people are different, but a huge percentage of them 
is not needing to change a profile manually, so delivering such a possibility 
in the only place where it might make sense is the rationale behind this idea.

> > There is still a rationale behind that. If you are in a situation where
> > you are actually *using* your PC, the only setting available (at the
> > moment) which is going to affect your battery life is brightness -
> > everything else is depending on the idle time, and in an emergency
> > situation one would simply close the lid and suspend straight away.
> Is it? Certainly disabling desktop effects and 3D acceleration has an
> impact.

Sorry to disappoint you, but this action will be removed in 4.8. Martin has 
explicitely stated that for how compositing in KDE works now turning off 
compositing is actually going to harm your battery instead of saving it - feel 
free to get in touch with him to expand on this topic, which is not exactly 
relevant to this discussion.

> And there are other things like when to suspend automatically (if
> do it at all), when to dim the display, etc.

I agree, but are you sure you need to configure these things separately 
depending on where you are? If you are, say, working on a train, you're very 
likely to never be idle, and to suspend the PC on your own by closing the lid 
when not active to save the most power. How can a different profile help you 

> I remember some time ago
> there was also a possibility to set how fast a CPU would run or throttle
> down a CPU manually, but I can't see anything like that in the current
> applet.

Nowadays the ondemand governor handles that properly, feel free to search 
these lists or b.k.o for flames/discussions about it.

> So I think there are more settings then display brightness (that
> you usually can control anyway with an Fn shortcut on laptops).

Again, as I said before, I am pretty sure there are no settings except 
brightness which require you to change to a different profile - in fact, there 
is a reason why brightness handling works this way at the moment.

> If we only talk about the above, and my development example (e.g travelling
> in an airplane): I know my travel takes 1 hour, my battery can last 2
> hours, so I want to use the laptop just as plugged into the wall. I start
> it, but then it becomes clear there is a delay, so I need to save battery
> life. Right now I just select a new profile, everything else remains the
> same on the desktop.

And what does it change? Yeah, brightness. You are working, and you'll never 
be idle. It might give you the illusion you are saving more energy, but I'd 
urge you to try lowering brightness and leave the profile unaltered - you 
might be surprised.

> Why would I need to switch to a new activity in such
> case? My work will be the same, just the conditions change.
> Or while developing I realize I compile more often then needed and this
> takes more power. So I need to save power in other way, again this would be
> possible with a simple change in the applet.

Which settings configurable from KDE's power manager are exactly affecting 
your battery besides brightness in this case?

> Please, keep this option. Having a way to control the power magament
> setting per activity is fine, but leave the possibility to change (and
> configure) the settings without having to use activities

Provided some good reasons, I will. But I think atm you are wasting your time 
creating new profiles, while you could achieve the same by tweaking your 
brightness. This kind of placebo-effect of switching to a profile with a 
different name is something I was fearing from day 1.

> .
> Andras
> _______________________________________________
> Plasma-devel mailing list
> Plasma-devel at


Dario Freddi
KDE Developer
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