linux-kernel - Re: Hibernation Redesign

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Message-ID: <20070709135205.GB3216@elf.ucw.cz>
Date:	Mon, 9 Jul 2007 15:52:05 +0200
From:	Pavel Machek <pavel@....cz>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Jeremy Maitin-Shepard <jbms@....edu>, Al Boldi <a1426z@...ab.com>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Hibernation Redesign

Hi!

> >>from a *new* kernel space/user space that is created by loading a new
> >>kernel in a manner similar to what is done for kexec crashdumps.  Unlike
> >>kexec crashdumps, however, it would not require reserving any memory at
> >>boot, because the necessary memory (maybe 16MB or 64MB) can be freed
> >>just before hibernating, and device drivers can be properly stopped so
> >>that DMAs don't stomp over certain memory.
> >
> >
> >This is the Morton method, isn't it? :) I remember it sounding like a
> >very good idea when he brought it up, but I can't remember the details
> >of why it was rejected or what the problems were.
> 
> Hmm, and it seems like I won't get to know without reliving what
> looks like an epic flamewar starting.... here:
> 
>   http://thread.gmane.org/gmane.linux.kernel/374889
> 
> However from a quick look it seems like the only reason is the RAM
> overhead of a reserve area. It seems unfortunate that it was
> dismissed so quickly because of that problem (which could be
> improved).

Well, the kexec thingy should be able to hibernate a machine, but it
will not be "software-suspend" any more, and it may be quite a lot of
work to get it going.

In the end, you'll get rid of freezer problems, but will have two
kernels to care about, and certainly more conventional design. I do
not think I have time to try that (and don't think freezer problems
are _that_ bad in the first place), but some interested soul could
certainly try it.

If we deprecate swsusp in 2.6.45 or so, I do not think I'll be crying.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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