[lug] laptop mode thinkering (2.6.6 kernel)

[Kevin Fenzi]

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Since I am running the 2.6.6 kernel on my laptop now, I decided to
take a look at http://www.xs4all.nl/~bsamwel/laptop_mode/ since it's
included in the kernel now. The laptop-mode.txt readme that comes with
the kernel has the approprate scripts in it, so I copied out the
/sbin/laptop-mode script and ran it.

I saw no mention of JFS support in the readme or the script however
(my laptop uses JFS), so decided to go look on the net. The
laptop_mode page does say that JFS is supported, but thats it. Digging
around on google got me a discussion about JFS and laptop mode on the
JFS list. Looks like JFS didn't need any modifications to work with
laptop mode, it just works. So, then I did a '/sbin/laptop-mode start'
and a 'hdparm -S 4 /dev/hda' to set the spindown time on my drive low
and start laptop mode. Nothing happened.

To figure out what was keeping my drive spun up, I used: "echo 1 >
/proc/sys/vm/block_dump". That spews out every process that hits the
disk and if it's a read/write or a cache hit. Using that I fixed a few
things: Set syslog to not sync after each log (a - before the
filename), closed some firefox windows that were autorefreshing and
writing to cache, setup syslog not to log my fetchnews jobs on each
run. 

Tried laptop mode again, but it still wouldn't spin down. The
drive was inactive as far as I could tell. Perhaps it's an issue with
my drive somehow, so I looked around a bit more and pulled down 
http://www.xs4all.nl/~bsamwel/smart_spindown/
which is a handy script that checks for activity and then spins down
your drive if there isn't any. It has backoff so that if things seem
busy it will wait longer and longer to spin it down. Using that script
things spun down and appeared to work ok. Running it overnight I was
able to see up to about 10min of spin down time at various points,
sometimes as little as 30 seconds. I think this might be worth the
savings if you were really hurting for power, but otherwise seems
kinda pointless.

kevin
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