Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1755515Ab0HBVfs (ORCPT <rfc822;w@1wt.eu>);
	Mon, 2 Aug 2010 17:35:48 -0400
Received: from ogre.sisk.pl ([217.79.144.158]:57640 "EHLO ogre.sisk.pl"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1751255Ab0HBVfq (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Mon, 2 Aug 2010 17:35:46 -0400
From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: paulmck@linux.vnet.ibm.com
Subject: Re: Attempted summary of suspend-blockers LKML thread
Date: Mon, 2 Aug 2010 23:33:32 +0200
User-Agent: KMail/1.13.5 (Linux/2.6.35-rjw+; KDE/4.4.4; x86_64; ; )
Cc: Arjan van de Ven <arjan@infradead.org>,
        linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        arve@android.com, mjg59@srcf.ucam.org, pavel@ucw.cz,
        florian@mickler.org, stern@rowland.harvard.edu, swetland@google.com,
        peterz@infradead.org, tglx@linutronix.de, alan@lxorguk.ukuu.org.uk
References: <20100731175841.GA9367@linux.vnet.ibm.com> <201008021552.20505.rjw@sisk.pl> <20100802203609.GG2405@linux.vnet.ibm.com>
In-Reply-To: <20100802203609.GG2405@linux.vnet.ibm.com>
MIME-Version: 1.0
Content-Type: Text/Plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Message-Id: <201008022333.32623.rjw@sisk.pl>
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 3406
Lines: 67

On Monday, August 02, 2010, Paul E. McKenney wrote:
> On Mon, Aug 02, 2010 at 03:52:20PM +0200, Rafael J. Wysocki wrote:
> > On Monday, August 02, 2010, Paul E. McKenney wrote:
> > > On Sun, Aug 01, 2010 at 03:47:08PM -0700, Arjan van de Ven wrote:
> > > > On Sun, 1 Aug 2010 12:12:28 -0700
> > > > "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:
> > ...
> > > > Another one: freezing whole cgroups..... we have that today. it
> > > > actually works quite well.... of course the hard part is the decision
> > > > what to put in which cgroup, and at what frequency and duration you let
> > > > cgroups run.
> > > 
> > > Indeed, the Android guys seemed to be quite excited by cgroup freezing
> > > until they thought about the application-classification problem.
> > > Seems like it should be easy for some types of applications, but I do
> > > admit that apps can have non-trivial and non-obvious dependencies.
> > 
> > This isn't more difficult than deciding which applications will be allowed to
> > use wakelocks (in the wakelocks world).  It actually seems to be pretty much
> > equivalent to me. :-)
> 
> If I understand correctly, the problem they were concerned about was
> instead "given that a certain set of apps are permitted to use wakelocks,
> which of the other apps can safely be frozen when the display blanks
> itself."

I _think_ the problem should be reformulated as "which of the other apps
can be safely frozen without causing the wakelocks-using ones to have
problems" instead (the particular scenario is that one of the wakelocks-using
apps may need one of the other apps to process something and therefore the
other app cannot be frozen; however, that may be resolved by thawing all of
the other apps in such situations IMO).

> > > > on the suspend blockers for drivers; the linux device runtime PM is
> > > > effectively doing the same things; it allows drivers to suspend/resume
> > > > individually (with a very nice API/programming model I should say) based
> > > > on usage. And it works on a tree level, so that it's relatively easy
> > > > to do things like "I want to go to <this magic deep idle state>, but
> > > > only if <this set of devices is suspended already>". This is obviously
> > > > an important functionality for all low power devices, ARM or x86. 
> > > > Suspend blockers had this functionality as part of what it did (they do
> > > > more obviously) but I'd wager that the current Linux infrastructure is
> > > > outright nicer. 
> > > 
> > > This is what Rafael has been working on?
> > 
> > If you mean the runtime PM framework, then yes, I've been working on it.
> > 
> > > Of course, the Android guys also want to pay attention to which apps
> > > are running as well as to the state of devices on the system.
> > 
> > In fact the runtime PM framework is also important to Android, because it
> > can be used in there, for example, to implement the "early suspend" thing
> > I referred to in one of my previous messages in this thread.
> 
> Now we just need to convince the Android guys of that.  ;-)

I believe there's no need for that, as we were talking about that a few months
ago.

Thanks,
Rafael
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/