SATA Aggressive Link Power Management (ALPM) - call for testing

[Colin Ian King]

On 06/12/11 17:14, Tim Gardner wrote:
> On 12/06/2011 06:25 AM, Colin Ian King wrote:
>> Hi there,
>>
>> Aggressive Link Power Management (ALPM) is a mechanism where a SATA AHCI
>> controller can put the SATA link that connects to the disk into a very
>> low power mode during periods of zero I/O activity and into an active
>> power state when work needs to be done. Tests show that this can save
>> around 0.5-1.5 Watts of power on a typical system.
>>
>> ALPM is now available in several SATA controllers that use the Advanced
>> Host Controller Interface (AHCI). However, there is some anecdotal
>> evidence that some controllers may go into a low power state incorrectly
>> and this ends up causing data loss. Ubuntu has the ability to use ALPM
>> but it it disabled by default since it can cause data loss on some
>> machines.
>>
>> We are looking for (brave?) volunteers to test ALPM for 2 reasons:
>>
>> 1) help to identify typical power savings on a range of machines
>> 2) help to identify chipsets (and machines) where ALPM works reliably
>> and also where it is broken and needs fixing.
>>
>> An ALPM crowd-sourcing testing Wiki page has been created that describes
>> a testing methodology and has a table for test results:
>> https://wiki.ubuntu.com/Kernel/PowerManagementALPM
>>
>> Please note that there is a possibility that ALPM MAY CAUSE DATA LOSS on
>> some machines, so please ensure you have backed up your data or don't
>> mind the risk in losing your data.
>>
>> Colin
>>
>
> How about screen backlight management? I've noticed that my screen at 
> full brightness consumes about 4W compared to screen off. Should we at 
> least be measuring that ?
>
It's on my very long list of things to measure