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

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Date:	Wed, 26 May 2010 13:09:48 -0500
From:	James Bottomley <James.Bottomley@...e.de>
To:	Pavel Machek <pavel@....cz>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Arve Hj?nnev?g <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>,
	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 19:42 +0200, Pavel Machek wrote:
> Hi!
> 
> > > > > 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.
> > 
> > OK, so I've got one ... tell me what I should see and I'll try to
> > reproduce.
> 
> Umm... try to boot ordinary distro and see how it copes with
> opportunistic suspend?

That's not really going to help, is it?  The issue I was curious are
what are the bad things that result from interfering with the regular
scheduling of processes ... because undeniably suspend (whether
opportunistic or ordinary) does produce this interference.

I could boot debian on an android and have it suspend ... that's still
not going to answer my question.

> I do have android here, and of course it work well with custom
> userland. Question is: can common distro be reasonably modified to
> work with suspend blockers, in a way that's backward compatible?

You mean how an app could run if it was compiled with suspend blockers
but the platform doesn't support it?  That's a simple runtime switch in
the library surely?

James


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