Power consumption Linux vs. Windows

[piete]

Hi! I found Phoronix when I bought a used HP NC8430 laptop that was my first laptop with a dedicated GPU, Mobility Radeon X1600. Unfortunately it was around the time the GPU was deemed as "legacy" and left without proper power management. Soon I got fed up with cooking my laptop and settled with good and steady Debian Lenny whose Catalyst version still supports my chip. A few weeks ago I got interested in the power management advances and to my delight the newest kernel is doing a good job in keeping the temperature of the GPU down.

However, this is not reflected in the power consumption. To be honest, during the times my laptop was cooking, I didn't even measure the consumption, but now that everything should be more or less ok, I'm still getting almost double power consumption (22-27 W in Linux vs. 13-14 W in Windows Vista). I keep reading that Windows power management is better, the dedicated device drivers are available only to Windows etc.

However, I'm unable to understand the difference. I'm not a programmer, but let's say I "turn off" all my unnecessary devices like serial ports, cd-rom, USB etc. If I'm running only the core devices, shouldn't the power consumption be minimized? When I have time, I am going to experiment compiling my kernel with the minimal amount of devices to see if it has any effect. But if someone already has done this, or has the knowledge to answer, please reply.

The funniest thing is that in Windows Vista to get 13-14 W I have Aero running, changing to "classic" theme actually increases the consumption. I haven't succeeded in lowering the consumption by tweaking, only making sure that the processor is not in performance mode and GPU is in battery saving mode is enough. With linux I am doing all the possible tweaks plus what Powertop says, and still get over 20 W.

My mission is not accomplished (and I can't get rid of Windows) until I get linux at the same level. Until then, I only have a Desktop linux, but a Windows laptop.

Needless to say, I welcome all benchmarks related to power consumption. And I hope to read some good advice from the expert tweakers here

[movieman]

Power management doesn't just mean turning things off, but also changing clock speeds, etc. So if the Windows driver is dropping the clock speed of the GPU when it's not working hard and the Linux driver isn't, you'll see a significant difference in power consumption.

[piete]

Power management doesn't just mean turning things off, but also changing clock speeds, etc. So if the Windows driver is dropping the clock speed of the GPU when it's not working hard and the Linux driver isn't, you'll see a significant difference in power consumption.

Of course I can't turn off my GPU (or maybe I even could, but then I couldn't see the current power consumption). The recent OSS radeon driver reaches the same clock speeds as the Windows driver (can't tell about the voltage), so in theory it at least could reach the same power consumption level. But with other devices, maybe linux can't idle them and Windows can, but turning them off should allow me to reach the same power consumption.

This all is at the moment just a fun experiment, but it would be nice to get even an unusable linux to the same power consumption level. After that I could see how each device would increase the power consumption, and maybe draw some attention to the drivers that could save power (or if I could program, do something even by myself).

[piete]

Did I write on a wrong subforum? Or is the subject so well discussed that nobody has anything to add? For me this is the last thing keeping me using windows. Surely somebody else is interested in getting linux power consumption to Windows level?

Please, all comments help me in my mission. I tried to google "laptop linux", did not find such distro but obviously we need one If I only had spare time...

[HokTar]

Actually you have a good point. I never really used my notebook with windows, but I think I could get at least 2 hours on battery if I didn't do anything.
With Linux I set the lowest cpu frequency as well as the low profile for my radeon rv730 and dim the display as much as I can. With all this I can't get more than 1.5 hours.

No idea why...

[kernelOfTruth]

battery runtime for Dell XPS m1330:

Gentoo Linux with my own power tweaks: 7 hours max.

Windows XP: 4.5-6 hours max.

Windows Vista: 4-5 hours

you might want to take a look at:

[ubuntu] HOWTO: XPS m1330 power savings

when you're through with that thread - shout if you need more info on tweaks

[yotambien]

I haven't read that link in detail, but it seems over the top. Come on, closing Firefox tabs? I want to use my computer, power saving shouldn't be on my way nor require my constant intervention to see whether something is writing stuff to disk or what not.

Anyway, I just wanted to point out that the conservative governor may be better than the ondemand one:

http://www.ibm.com/developerworks/li...y/l-cpufreq-3/

[piete]

Thanks for the link, kernelOfTruth. When I have time I'll try all the scripts and report how it went.

I partially agree with yotambien, the computer needs to be usable. But on the other hand I'm really interested in what causes power consumption. If I need to have more battery life I have no problem to keep only the essentials running.