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

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Message-ID: <20100812034435.GA7403@linux.vnet.ibm.com>
Date:	Wed, 11 Aug 2010 20:44:35 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Felipe Contreras <felipe.contreras@...il.com>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, "Ted Ts'o" <tytso@....edu>,
	david@...g.hm, Brian Swetland <swetland@...gle.com>,
	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,
	peterz@...radead.org, tglx@...utronix.de, menage@...gle.com,
	david-b@...bell.net, James.Bottomley@...e.de, arjan@...radead.org,
	swmike@....pp.se, galibert@...ox.com, dipankar@...ibm.com
Subject: Re: Attempted summary of suspend-blockers LKML thread, take three

On Thu, Aug 12, 2010 at 04:25:21AM +0300, Felipe Contreras wrote:
> On Thu, Aug 12, 2010 at 4:06 AM, Paul E. McKenney
> <paulmck@...ux.vnet.ibm.com> wrote:
> > On Thu, Aug 12, 2010 at 03:28:00AM +0300, Felipe Contreras wrote:
> >> On Thu, Aug 12, 2010 at 1:28 AM, Paul E. McKenney
> >> <paulmck@...ux.vnet.ibm.com> wrote:
> >> > On Wed, Aug 11, 2010 at 10:18:51PM +0300, Felipe Contreras wrote:
> >> >> On Mon, Aug 9, 2010 at 9:16 PM, Paul E. McKenney
> >> >> <paulmck@...ux.vnet.ibm.com> wrote:
> >> >> > But wouldn't an office suite run as a power-oblivious application on an
> >> >> > Android device?  After all, office applications do not need to run when
> >> >> > the screen is turned off, so these the applications do not need to use
> >> >> > suspend blockers.
> >> >>
> >> >> Ideally the system would be suspended even when the screen is on. If
> >> >> there are no "trusted" applications running at the same time, then
> >> >> openoffice wouldn't load at all. Right?
> >> >
> >> > My understanding is that Android systems in fact do not suspend when
> >> > the screen is on, and that most (perhaps all) other systems do not
> >> > opportunistically suspend at all.  There has been some speculation about
> >> > what a hypothetical Android having a non-volatile display might do,
> >> > but as far as I know, this is just speculation.
> >>
> >> I have a desktop system in mind. If opportunistic suspend is only
> >> triggered when the display is off, then it's no good for normal usage,
> >> and therefore dynamic PC needs to get its act together... specially
> >> for laptops.
> >
> > If I understand you correctly, you are saying that both opportunistic
> > suspend and dynamic power control should be used together, with dynamic
> > power control being used for short non-busy periods (as in between
> > keystrokes) and opportunistic suspend being used for longer non-busy
> > periods (as in while grabbing a coffee).  That combination of usage
> > sounds promising to me.
> 
> No. In the future x86 will be fixed, but for now let's imagine an ARM laptop.

Hmmm...  OK...

> > That said, I don't know that anyone has really sat down and thought
> > through how one might apply suspend blockers to a desktop system.
> > I suspect that there are several ways to go about it.
> 
> Think in terms of an ARM laptop. What good is opportunistic suspend if
> it's not going to help when the laptop is being used?

For when the laptop is not being used, presumably.

							Thanx, Paul
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