linux-kernel - Re: suspend2 merge (was Re: [Suspend2-devel] Re: CFS and suspend2: hang in atomic copy)

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Date:	Thu, 26 Apr 2007 11:48:41 +1000
From:	Nigel Cunningham <nigel@...el.suspend2.net>
To:	Pavel Machek <pavel@....cz>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Kenneth Crudup <kenny@...ix.com>,
	Nick Piggin <npiggin@...e.de>, Mike Galbraith <efault@....de>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Con Kolivas <kernel@...ivas.org>,
	suspend2-devel@...ts.suspend2.net, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: suspend2 merge (was Re: [Suspend2-devel] Re: CFS and suspend2:
	hang in atomic copy)

Hi.

On Thu, 2007-04-26 at 01:45 +0200, Pavel Machek wrote:
> > What's your argument? Your argument seems to be that it's not stupid, 
> > because it can work. Can't you see that that simply isn't an
> > argument at 
> 
> I tried keeping module_init/thaw/resume similar code, so that driver
> authors can debug suspend-to-disk, cross their fingers, and have
> suspend-to-ram work, too.

> Now, perhaps enough people do std/str these days so this is not
> important any longer... lets hope so.

Noooo! It's important and getting more important. More and more, people
are going to be demanding better power saving (climate change and all
that stuff). The best power saving is to have the thing completely off,
so STD is more important. The second best power saving is STR, so that's
important too. But even more important is good power saving all the
time.

For that reason, I agree completely with Linus. The current model is far
too limited. It shouldn't be so suspend-to-ram/disk centric, and should
instead focus on run-time power management, with suspend to ram and disk
as particular instances of run-time power management. It should make
appropriate differentiation between snapshotting and suspending to ram.

I do disagree that the current suspend-to-disk algorithm is broken. We
do need a point at which we say "Ok, drivers, record your state." - the
current device_suspend and device_resume calls. But that doesn't mean
the need to be called device_suspend/resume or do what they do now.

I'd love to help make this happen, but I'm afraid I just don't have the
time.

Nigel

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