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

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Message-ID: <AANLkTinVV1NVHFPeO0p_e2pCtNwTNB932q9tbu9MMD3_@mail.gmail.com>
Date:	Thu, 12 Aug 2010 04:25:21 +0300
From:	Felipe Contreras <felipe.contreras@...il.com>
To:	paulmck@...ux.vnet.ibm.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 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.

> 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?

-- 
Felipe Contreras
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