linux-kernel - Re: [PATCH] libata: Add an additional LPM policy to match Intel recommendations

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 13 Apr 2015 10:52:59 -0700
From:	Matthew Garrett <matthew.garrett@...eos.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Matthew Garrett <mjg59@...eos.com>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] libata: Add an additional LPM policy to match Intel recommendations

On Mon, Apr 13, 2015 at 7:32 AM, Tejun Heo <tj@...nel.org> wrote:
> On Fri, Apr 10, 2015 at 01:15:29PM -0700, Matthew Garrett wrote:
>> Intel publish a document on designing energy efficient SATA devices at
>> http://www.intel.com/content/dam/doc/reference-guide/sata-devices-implementation-recommendations.pdf
>> which recommends that ALPE be set, ASPE be cleared and that DIPM be enabled
>> on the device. Right now we have no policy that matches that - medium_power
>> does not enable DIPM and min_power sets ASPE. Add a new low_power policy to
>> implement these recommendations. I've left devslp disabled because I'm not
>> yet sure what Intel do in that case. With luck this will provide reasonable
>> power savings without causing the device breakages we occasionally see with
>> the min_power policy.
>
> I suspect the aggressive methods actually don't buy us much, except
> for the obsessive mode switchings, in terms of power saving compared
> to something more reasonable provided via DIPM and I'm not sure it's a
> good idea to introduce yet another mode.  I'd be all in for converting
> min_power mode to DIPM for cases where we know this actually works
> rather than introducing yet another mode.  Or if there's a clear power
> consumption disadvantage to DIPM, let's conver medium_power to that.

Ok - my only real concern there was that we might end up changing the
semantics of medium_power enough that it would break somebody. I'll
post a patch to do that instead and I guess we can see what happens -
worst case we revert it and add a new one.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/