linux-kernel - Re: [RFD] Automatic suspend

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Date:	Mon, 16 Feb 2009 23:58:31 +0100
From:	Pavel Machek <pavel@...e.cz>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	pm list <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Arve Hj?nnev?g <arve@...roid.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	mark gross <mgross@...ux.intel.com>,
	"Woodruff, Richard" <r-woodruff2@...com>,
	Uli Luckas <u.luckas@...d.de>,
	Igor Stoppa <igor.stoppa@...ia.com>,
	Brian Swetland <swetland@...gle.com>,
	Len Brown <lenb@...nel.org>
Subject: Re: [RFD] Automatic suspend

Hi!

> The recent descussion about the Android PM patches sent by Arve shows that
> there is a need to introduce a mechanism allowing us to:
> (1) automatically put the system as a whole into a sleep state (eg. suspend to
>     RAM) when it is found to be "idle", where the meaning of "idle" has to be
>     defined too,

Well; I'd prefer to keep the interface very minimal.

If no devices are being used, and next wakeup is far enough in the
future, just put system to sleep. Long enough == so far away that
suspend/wakeup is short compared to that... like 20 seconds on PC.

Ok, it probably needs to be opt-in: echo auto-mem > /sys/power/state
should do the trick.

This will need either fixing all the applications not to poll, or
maybe someone SIGSTOP-ing apps that are in background and poll too
often.

> (2) put given subset of devices into low power states whenever they are not
>     used, without putting the entire system into a sleep state.

Arjan said this nicely...

									Pavel

-- 
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