Comment 1 for bug 900923

Since the posting was on a private list, I'm putting a link into the results and spreadsheet data that covers the analysis:

Results: http://zinc.canonical.com/~cking/power-benchmarking/pm-utils-results/results.txt
Data: http://zinc.canonical.com/~cking/power-benchmarking/pm-utils-results/pm-tests.ods

== Journal-commit ==

script: power.d/journal-commit

For ext3/ext4 file systems this sets the journal commit time to 600
seconds(!) when on battery power.

Test: build busybox
Results: NO power savings on HDD drives, with biggest loss of 1.5% on
  SSD based netbook.

Recommendation: We remove this script for two reasons:
 1) It is shown not to save power on a busy system
 2) It is a dangerous option - pushing the commit timeout to 10 minutes
    increases the likely of filesystem errors on a system hang.

== Readahead ===

script: power.d/readahead

This script tries to trade off the number of times we spin up a drive to
read for potentially wasted cache. For AC power, set to 256KB, for battery
power, set to 3072KB.

Test: build busybox
Results: All systems fail to show any power savings, in fact SSD loses
  ~1.7% more power with this enabled.
Recommendation: Remove this script

Please refer to the pm-tests.ods for the results from some thorough testing on 3 representative machines.