Re: [patch 0/3] AHCI Link Power Management

From: Arjan van de Ven
Date: Mon Jun 11 2007 - 23:14:32 EST

Jeff Garzik wrote:
Arjan van de Ven wrote:
Tejun Heo wrote:
Kristen Carlson Accardi wrote:
This series of patches enables Aggressive Link Power Management for AHCI devices, as documented in the AHCI spec. On my laptop (a Lenovo X60), this
saves me a full watt of power. On other systems, reported power savings
range from .5-1.5 Watts. It has been tested by the kind folks at #powertop
with similar results. Please give it a try and let me know what you think.

I'm not sure about this. We need better PM framework to support
powersaving in other controllers and some ahcis don't save much when
only link power management is used,

do you have data to support this? The data we have from this patch is that it saves typically a Watt of power (depends on the machine of course, but the range is 0.5W to 1.5W). If you want to also have an even more agressive thing where you want to start disabling the entire controller... I don't see how this is in conflict with saving power on the link level by "just" enabling a hardware feature ....

SATA standard defines lower power phy states. So the same argument you're using for AHCI applies there too -- "just" enabling an existing hardware feature.

yes I'm not arguing against that. I was trying to find out (and suggest-unless-proven-otherwise) that the 2 are not exclusive or conflicting... in fact I assume both are wanted concurrently.
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