** Changed in: pm-utils
Status: Confirmed => Won't Fix
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https://bugs.launchpad.net/bugs/911325
Title:
pm-utils: additonal power.d scripts to save power
Status in pm-utils:
Won't Fix
Status in pm-utils package in Ubuntu:
Fix Released
Bug description:
The kernel allows us to save power on a range of devices - currently
pm-utils power.d does not make full advantage of these power savings.
Tools like PowerTop provide advice on which devices can be set into a
"Good" power management state. Analysis on a selection of
representative modern mobile x86 based platforms (e.g. netbook,
laptop) has shown that a subset of devices can be safely put into a
power saving state.
Each of the "Good/Bad" PowerTop device recommendations were measured
accurately using a 6 digit digital multimeter. Each measurement was
based on measuring current drain over 5 x 60 second periods on the
Good and Bad settings and seeing which device shows the most promising
power saving. The resulting data can be found here:
http://zinc.canonical.com/~cking/power-benchmarking/powertop-good-bad-
recommendations/powertop-good-bad-recommendations.ods
And the write-up of the methodology and conclusions can be found here:
http://zinc.canonical.com/~cking/power-benchmarking/powertop-good-bad-
recommendations/results.txt
From this analysis we can draw a conclusion that the following devices
behave well to power savings as follows:
* Webcam
* Audio
* DRAM
* Ethernet
* Wifi
* Bluetooth
* SATA link
* MMC/SD
From this, two pm-utils power.d scripts were written to control the
power state of the above devices. The script pci_devices controls the
PCI specific devices and usb_bluetooth controls USB webcams into and
out of power saving modes.
These were then tested by community - see:
https://wiki.ubuntu.com/Kernel/PowerManagementPMUtils
Power savings were calculated from the ACPI battery information. The
characteristics and reliability of ACPI battery data to measure power
consumption has been studied here: http://zinc.canonical.com/~cking
/power-benchmarking/acpi-battery-results/results.txt - the test
scripts used by the community testing use a battery power measuring
tool that has been calibrated and checked using a 6 digit multimeter
and calculates the average power consumption and standard deviation
(to allow us to discriminate against unreliable samples).
From these results, I discarded data where the standard deviation was
rather high and also results where the savings or losses were smaller
than the standard deviation. This left me with a set of results where
we have conclusive data showing us power savings or losses with these
new scripts. The conclusion is that the vast majority of machines
save power. Also, users tested their machines to see if the devices
behaved correctly.
On the samples of machines I have (Dell Inspirion 6400, Lenovo X220i,
HP Mini 210 + HP Mini 10) I see no regressions. I therefore am
requesting that the two new pm-utils/power.d scripts are added to pm-
utils.
Typical savings: 0.38 W per machine with some machines seeing > 1-2W
savings.
Attached to this bug report are the two new scripts for pm-
utils/power.d
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