linux-kernel - Re: Battery life difference

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Date:	Sat, 5 Jul 2008 08:23:52 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	"Felipe Balbi" <felipebalbi@...rs.sourceforge.net>
Cc:	"Kernel development list" <linux-kernel@...r.kernel.org>,
	linux-acpi@...r.kernel.org
Subject: Re: Battery life difference

On Sat, 5 Jul 2008 16:17:01 +0300
"Felipe Balbi" <felipebalbi@...rs.sourceforge.net> wrote:

> Hello all,
> 
> I bought two x61s for testing purposes. One of them is running
> windows XP and the other one is running clean ubuntu 8.04 with kernel
> 2.6.24-19. The problem is that on windows that battery lasts around
> 3h30min and with linux 1h30min.
> 
> 2 hours is a huge difference. Here's the scenario:
> 
> . x61s with windows xp
> wifi on but not connected to any network, bluetooth on,
> display is in the less brighten state.
> 
> . x61s with ubuntu 8.04
> all radios off (modules removed and hw switch off),

Which wireless is this? Same for graphics

> 
> Anyways, do we reach D2/D3 states anywhere ? I mean without
> context save/restore we can't reach D3 and almost no D2 as well.

these don't give you all that much nowadays
> 
> Any comments ?
> 

There's a few things you can do to help stuff along; make sure you're
using AHCI.

Also take a look at 
http://kerneltrap.org/mailarchive/linux-kernel/2008/5/8/1771024 because
these patches save like 0.75W in our lab.

To be honest, I'm surprised at your results; in our testing (with a
different distro though) we don't see such a difference and Linux is
doing rather well.


-- 
If you want to reach me at my work email, use arjan@...ux.intel.com
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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