Subject: Re: [OPSAWG] : Power state naming

From: Bruce Nordman <[email-masked]>
Date: Wed, 09 Jun 2010 00:44:56 -0700

< My apologies in advance for not having closely read the drafts yet,
but I want to engage the current discussion today in a timely fashion >

The current DMTF doc that Juergen references us to:
http://www.dmtf.org/standards/published_documents/DSP1027_2.0.0.pdf
has one On state, two Sleep states, and three Off states (Table 3, page 12).
The only definition that is particularly informative is the Hibernate for
of Off, which clarifies that the OS state is preserved.
I think this supports my contention that power states are best
understood as being in three broad categories (“buckets”) of
On, Sleep, and Off that should be hard-wired into the standard.
Differentiation within these categories varies from system to system
and so will inevitably be less well-defined.

In my email of 4/23, I discussed some of the history of power state naming;
over the last 25 years much has been learned. In the context of regulating
energy use in low-power modes, some of us have come to believe that it
is most useful to focus on functions that are present/active in a 
particular
mode, and describe modes that way rather than trying to load a lot of 
specific
meaning into names. This approach is described in the “EEDAL” paper on:
http://eetd.lbl.gov/ea/nordman/

I do agree it is helpful to cite ACPI states to show how a common 
implementation
maps to generic power states, but the RFC should be generic. Also, my 
understanding
is that very few if any ACPI devices implement S1 and S2, so devices in 
practice
are somewhat simpler than the ACPI table alone suggests.

For power control, I am a great believer that most devices will manage
their own power state, not be controlled by others. I am not opposed
to including an optional facility to set power state (in addition to 
reporting it),
but I believe it will get much less use.

I am quite interested in this facility being used for both electronic 
devices
like computers, as well as other devices that will increasingly become
networked such as appliances, lights, cars, etc.

--Bruce

-- 
Bruce Nordman
Lawrence Berkeley National Laboratory
[email-masked] -- 510-486-7089
eetd.lbl.gov/ea/nordman/

---

From: "Brad Schoening" <[email-masked]>
Date: Wed, 9 Jun 2010 08:31:42 -0400

Hi Bruce,

I completely agree with your broad categories for power states, but see these more as classification trees than flat "buckets". 

For example, "mechanically off" and "soft-off" are well-defined sub-classification of "off".  For sleep, Light-sleep (standby), Deep-sleep (save-to-ram) and Hibernate (save-to-disk) are commonly recognized sub-classifications.  I guess we can all agree that the top classification is Off, Sleep, and On.

Therefore, the classification in the ACPI/DMTF draft is:

	Off:  	two states, mechanically off and soft off
	Sleep: 	four Sleep states S1...S4 with increased latency in "deeper" states

You're correct that the DMTF doc @ http://www.dmtf.org/standards/published_documents/DSP1027_2.0.0.pdf does not go into much details about these well-known states, deferring the details to the ACPI definition.  Specifically, please see Table 2-1 (Summary of Global Power States) and section 2-4 (Sleep State Definitions) of the ACPI spec 4.0 which can be found here: http://www.acpi.info/spec.htm?info=EXLINK.  ACPI Figure 3-1 (attached) illustrates the broad categories you mention.

Please do review the actual MIBs drafts themselves when you have a chance and we welcome your further feedback.

Regards,

Brad Schoening

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Bruce Nordman
Sent: Wednesday, June 09, 2010 3:45 AM
To: [email-masked]
Subject: Re: [OPSAWG] : Power state naming

--Bruce

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