linux-kernel - Re: Attempted summary of suspend-blockers LKML thread, take two

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Message-ID: <20100805144012.GE2447@linux.vnet.ibm.com>
Date:	Thu, 5 Aug 2010 07:40:12 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	david@...g.hm
Cc:	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	arve@...roid.com, mjg59@...f.ucam.org, pavel@....cz,
	florian@...kler.org, rjw@...k.pl, stern@...land.harvard.edu,
	swetland@...gle.com, peterz@...radead.org, tglx@...utronix.de,
	alan@...rguk.ukuu.org.uk, menage@...gle.com, david-b@...bell.net,
	James.Bottomley@...e.de, tytso@....edu, arjan@...radead.org,
	swmike@....pp.se, galibert@...ox.com, dipankar@...ibm.com
Subject: Re: Attempted summary of suspend-blockers LKML thread, take two

On Thu, Aug 05, 2010 at 06:18:42AM -0700, david@...g.hm wrote:
> On Wed, 4 Aug 2010, Paul E. McKenney wrote:
> 
> >Continuing to rush in where angels fear to tread...
> 
> here here :-)
> 
> >o	"PM-driving application" are applications that are permitted
> >	to acquire suspend blockers on Android.  Verion 8 of the
> >	suspend-blocker patch seems to use group permissions to determine
> >	which applications are classified as power aware.  More generally,
> >	PM-driving applications seem to be those that have permission
> >	to exert some control over the system's sleep state.
> >
> >	Note that an application might be power-oblivious on one Android
> >	device and PM-driving on another, depending on whether the user
> >	allows that application to acquire suspend blockers.  The
> >	classification might even change over time.  For example, a
> >	user might give an application PM-driving status initially,
> >	but change his or her mind after some experience with that
> >	application.
> 
> One thing that I think it's important to document here is
> theinformation that Brian provided in response to your question
> about how many (or actually how few) applications fall into this
> catefory

Agreed!!!  I have added this, and it will appear in the next version.

							Thanx, Paul

> David Lang
> 
> Quote:
> 
> >I should have asked this earlier...  What exactly are the apps'
> >compatibility constraints?  Source-level APIs?  Byte-code class-library
> >invocations?  C/C++ dynamic linking?  C/C++ static linking (in other
> >words, syscall)?
> 
> For Java/Dalvik apps, the wakelock API is pertty high level -- it
> talks to a service via RPC (Binder) that actually interacts with the
> kernel.  Changing the basic kernel<->userspace interface (within
> reason) is not unthinkable.  For example, Arve's suspend_blocker patch
> provides a device interface rather than the proc interface the older
> wakelock patches use.  We'd have to make some userspace changes to
> support that but they're pretty low level and minor.
> 
> In the current model, only a few processes need to specifically
> interact with the kernel (the power management service in the
> system_server, possibly the media_server and the radio interface
> glue).  A model where every process needs to have a bunch of
> instrumentation is not very desirable from our point of view.  We
> definitely do need reasonable statistics in order to enable debugging
> and to enable reporting to endusers (through the Battery Usage UI)
> what's keeping the device awake.
> 
> Brian
> 
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