Re: SATA powersave patches

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Hello,

Pavel Machek wrote:
If I understood correctly, the high power consumption of ahci controller can be solved by dynamically turning off command processing while the controller is idle, which fits nicely into link powersaving, right? So, I think full-fledged leveled dynamic PM would be an overkill for this particular problem, but then again, maybe the

It is single bit, and it should not even need a timeout, AFAICT, so
perhaps we should just fix it (no need for dynamic PM layers). It
probably does not even need to be configurable...

I think this has been discussed in linux-ide recently but just to add my 2 cents. ALPE and ASP can cause quite some problems. Many devices don't implement link powermanagement mode properly and some locks up completely (recent LG dvd-rams, only physical power removal/reapply can recover it) while others (wd raptors) spin down on slumber. If you turn on ALPE and ASP on such devices, all hell will break loose.

Even for devices which implement partial and slumber modes properly, I'm not very comfortable with ALPE. It puts the link into power save mode as soon as there is no command pending. IMHO, that's way too aggressive. It's not like being that aggressive will bring any noticeable difference in power consumption. Disk idle period is too long for that level of aggressiveness to be effective.

Thanks.

--
tejun
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