linux-kernel - Re: suspend blockers & Android integration

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Message-ID: <20100605092851.6ee15f13@infradead.org>
Date:	Sat, 5 Jun 2010 09:28:51 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Arve Hjønnevåg <arve@...roid.com>,
	Ingo Molnar <mingo@...e.hu>, tytso@....edu,
	Brian Swetland <swetland@...gle.com>,
	Neil Brown <neilb@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Alan Stern <stern@...land.harvard.edu>,
	Felipe Balbi <felipe.balbi@...ia.com>,
	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>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Kevin Hilman <khilman@...prootsystems.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: suspend blockers & Android integration

On Sat, 05 Jun 2010 11:54:13 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> On Fri, 2010-06-04 at 17:10 -0700, Arve Hjønnevåg wrote:
> > > Trusted processes are assumed to be sane and idle when there is
> > > nothing for them to do, allowing the machine to go into deep idle
> > > states.
> > >
> > 
> > Neither the kernel nor our trusted user-space code currently meets
> > this criteria. 
> 
> Then both need fixing. Really, that's the only sane approach.

fwiw... in MeeGo we're seeing quite good idle times (> 1 seconds)
without really bad hacks.

the kernel has a set of infrastructure already to help here (range
timers, with which you can wakeup-limit untrusted userspace crap),
timer slack for legacy background timers, etc etc.

getting to 10 seconds is not in the range of impossibilities to be
honest... and that's even without doing things like putting untrusted
junk (read: Appstore apps) into a cgroup and do wakeup limiting and cpu
time limiting on a cgroup level....


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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