linux-kernel - Re: suspend blockers & Android integration

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Date:	Fri, 4 Jun 2010 08:22:21 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	tytso@....edu, Brian Swetland <swetland@...gle.com>,
	Neil Brown <neilb@...e.de>, Arve Hj?nnev?g <arve@...roid.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Alan Stern <stern@...land.harvard.edu>,
	Felipe Balbi <felipe.balbi@...ia.com>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Florian Mickler <florian@...kler.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Linux PM <linux-pm@...ts.linux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	James Bottomley <James.Bottomley@...e.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Kevin Hilman <khilman@...prootsystems.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: suspend blockers & Android integration


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> [...]
> 
> And those two things go together. The /sys/power/state thing is a global 
> suspend - which I don't think is appropriate for a opportunistic thing in 
> the first place, especially for multi-core.
> 
> A well-designed opportunistic suspend should be a two-phase thing: an 
> opportunistc CPU hotunplug (shutting down cores one by one as the system is 
> idle), and not a "global" event in the first place. And only when you've 
> reached single-core state should you then say "do I suspend the system too".

Shutting a core down would be a natural idle level, and when the last one goes 
idle we can do the suspend. (it happens as part of suspend anyway)

So on systems that dont want to auto-suspend this would indeed behave like you 
suggest: the final core left would run as UP in essence.

	Ingo
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