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Old 07-02-2011, 08:39 AM   #1
Knightron
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battery performance inconsistent, per distro/os


Hi, i'm sure i saw a thread like this, but i couldn't find it, and no offence to the sight, but i don't think it's search function is to good. (either that or i'm just not working it)

Anyways, full battery for each distro/os, when i hover the cursor over the battery icon, it gives me an estimation of how long it'll last, but they're a fare bit different.
In Windows7, it tells me something like 8 hours (i normally get about 6). In Slackware, it tells me something like 3 hours, 50 minutes, (I normally get about a little over 3). And in Ubuntu it says something like 4 hours, 20 minutes, (i get about a little under 4).

I was just wondering why.
 
Old 07-02-2011, 08:48 AM   #2
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If you are using the laptop you mentioned in this thread-

http://www.linuxquestions.org/questi...-start-887136/

Then part of the reason why you are getting lower battery life in linux compared to windows is because the nVidia GT520M will be drawing power under linux, even though its not in use. Disabling the nVidia GPU under linux should lengthen battery life.

Another reason could (would?) be if you are still running a kernel and/or xrog without 'sandy bridge' support.
 
Old 07-02-2011, 09:15 AM   #3
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lol, thanks cascade, you're awesome. Yes it's the same laptop. Is the .6.38 kernel the only one with Sandy bridge support?
 
Old 07-03-2011, 05:17 AM   #4
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Nah, I'm pretty sure that they started adding support for sandy bridge in 2.6.35. Even 2.6.38 isnt really finished as far as sandy bridge goes, 2.6.39 and 2.6.40 are still having sandy bridge parts added.
 
Old 07-04-2011, 01:19 AM   #5
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I use the 2.6.37 kernel in Slackware, and it doesn't appear to be much different in regards to battery use compared to other distros running lower kernels, that i've tried. Are you sure that this is the issue? I don't mean to sound ignorant, it's just that i don't want to upgrade away from the supported kernel unless i have to.
 
Old 07-05-2011, 12:43 AM   #6
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The newer kernels (2.6.35+ if I recall correctly) have a power regression, so while you might save a little power due to better drivers, you can also lose as well due to the regression.
 
Old 07-05-2011, 04:33 AM   #7
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that still doesn't explain why i get such short amount of time on linux compared to windows. This isn't the first time i've experienced this either. I had linux installed on a mac before this computer and linux only got 3 hours out of that machine while os x would get about 5
 
Old 07-05-2011, 04:45 AM   #8
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Optimus will be eating power, like I said above. Its not only a case of optimus eating the battery, when using a OS with optimus support the intel video will use more power than the nVidia GPU for accelerated/3D use. So its a double hit.

As for the mac.....I have no idea of the hardware setup, what distro you ran, or anything else.
 
Old 07-05-2011, 07:30 PM   #9
Knightron
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I was running Ubuntu with all the proper drivers installed (I followed a guide to set up Ubuntu on Mac). I searched google and there seems to be a few people that have reported that they don't get the hours with Linux that they do on Windows; but there seems to be no reason why.
 
Old 07-06-2011, 04:37 AM   #10
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Without knowing what model laptop, which version ubuntu you used, and the guide you followed, I have no idea what was happening in that case. Macs arent that linux friendly, which could be part of the cause.....

Its possible that like your 'optimus' laptop you were running bleeding edge hardware with an older linux version, which is never a good idea.
 
Old 07-06-2011, 09:35 AM   #11
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Try installing PowerTop, it will offer suggestions that will help conserve power. Also, if you're using an nVidia card with either the nv or nouveau driver, try using the proprietary nVidia driver instead (this saves me about 3 watts). Of course, if you're not using that card at all, disable it as cascade suggests.

By using PowerTop and turning down my backlight a little, I'm able to extend my battery life by 50%.

To answer your original question, I think your estimates vary from your actual battery life for a couple of reasons: the remaining battery life is an estimate based on how quickly the system thinks the battery is being discharged -- the estimates are not entirely accurate. Your system might also be set to turn itself off before the battery reaches 0% charge, for safety reasons, while the estimate provided might be calculating to 0% (I don't know this for sure, but I suspect that's the case). Finally, your actual power usage varies from one moment to the next. If I do something that is resource intensive (like compiling or compressing something), I might use 50 Watts instead of 17. My battery certainly won't last as long in this case.
 
  


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