linux-kernel - Re: [PATCH 1/8] PM: Opportunistic suspend support.

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Message-ID: <1274894602.1674.1780.camel@laptop>
Date:	Wed, 26 May 2010 19:23:22 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	James Bottomley <James.Bottomley@...e.de>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	Arve Hjønnevåg <arve@...roid.com>,
	Florian Mickler <florian@...kler.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Alan Stern <stern@...land.harvard.edu>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Randy Dunlap <rdunlap@...otime.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	Tejun Heo <tj@...nel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Nigel Cunningham <nigel@...onice.net>,
	Ming Lei <tom.leiming@...il.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Maxim Levitsky <maximlevitsky@...il.com>,
	linux-doc@...r.kernel.org, Matthew Garrett <mjg59@...f.ucam.org>,
	Greg KH <gregkh@...e.de>, tytso@....edu
Subject: Re: [PATCH 1/8] PM: Opportunistic suspend support.

On Wed, 2010-05-26 at 12:14 -0500, James Bottomley wrote:
> On Wed, 2010-05-26 at 19:00 +0200, Peter Zijlstra wrote:
> > On Wed, 2010-05-26 at 11:54 -0500, James Bottomley wrote:
> > > Given that I'm in the latter category, I think suspend blockers is a
> > > reasonable solution to an existing problem.  I like Alan's idea of
> > > restricting the API into a single user space program so we contain the
> > > API contamination ... but realistically that's mostly the current
> > > suspend blockers anyway. 
> > 
> > There's a _large_ difference between resource limits and these wonky
> > suspend blockers.
> 
> Well, you have policy and then you have implementation ... suspend
> blockers just looks like an implementation to me.  It seems to be
> reasonably well suited in that regard ... after all, we kill processes
> that exhaust memory for instance or cut off write privileges to those
> that go over quota.  Preventing power hungry processes from consuming
> power by not allowing them to run until there's a wakeup event is fairly
> gentle by those standards.

The difference is that the limit should be per task. In this model a
process that only runs a little still gets suspended.

> > The main and most important one being that suspend is a global property
> > and can/will hurt sensible tasks. It puts the whole task model upside
> > down.
> 
> OK, so I believe you have an android phone ... it already implements
> this model ... specifically what are the problems on that platform this
> causes?

I do not have one, nor have I ever written an application for it (nor
will I likely ever do that, since I detest Java), but I would expect an
application to run when its runnable.

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