[ltp] short battery life on t40

[Theodore Ts'o]

On Thu, Sep 11, 2003 at 10:44:41AM -0400, Jason 'T' Rolfe wrote:
> 
> I know this should be an RTFM-type question, but I can't find a manual of 
> any sort: How do you adjust the display power in linux or otherwise?  

Fn-Home to increase the backlight, Fn-End to decrease the backlight.
It's well labelled onthe keyboard.

> Also, I am running ext3.  Do you have any idea how much power is saved by 
> switching to a non-journaling file system?  

If you use a non-journaling filesystem, you can use the noflushd
daemon to prevent trivial filesystem modifications (atime, mtime, log
updates, etc.) from causing the hard drive to spin up.  However, it's
not strictly necessary to use noflushd and a non-journaling filesystem.

You can also possible to simply reduce unneeded filesystem updates.
The main things to do is mount with the noatime option, so that access
time updates don't cause the hard drive to spin up, and to change the
syslog file to avoid logging low priorities to the files in /var/log.
Normally, I just set things up so the low priority messages get logged
to /dev/tty8, but you might also prefer logging them to a file on a
ramdisk.

At that point, make sure that your hard drive has its power save mode
turned on.  I usually use hdparm -S 18, which turns off the hard drive
motor after 90 seconds of inactivity.  Check and make sure the hard
drive isn't spinning up needlessly when you aren't doing anything on
the laptop.  If there is, then trick is to figure out what is running
in the background or daemon processes which is causing the hard drive
to spin up.

> Do I actually need to remove my wlan modules?  Why isn't turning off
> wireless with ifdown sufficient?  Thanks for your help.

It depends on the driver, but as long as you can turn off the radio,
that's most of it.  Using iwconfig to turn on power save mode (and
disabling multicast) while you *are* using the wireless will also
help to prologue your battery life.

						- Ted