linux-kernel - Re: Hibernation Redesign

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Date:	Mon, 09 Jul 2007 15:33:50 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	unlisted-recipients:; (no To-header on input)
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

Nick Piggin wrote:
> Jeremy Maitin-Shepard wrote:
> 
>> Nick Piggin <nickpiggin@...oo.com.au> writes:
> 
> 
>>> Yes, I have a rough idea about how page reclaim works. But I just
>>> mean it would not be trivial to load the new kernel into physically
>>> discontiguous memory. Possible of course, but I don't think kexec or
>>> the setup code could quite cope ATM.
>>
>>
>>
>> It would indeed be a pain for the new kernel to be loaded and have to
>> use discontiguous memory.  The trick is, though, that this is not
>> necessary.  Immediately before jumping to the new kernel, the first X
>> bytes (where X is the amount of memory the new kernel will get,
>> typically 16MB or 64MB) of physical memory are backed up into the
>> arbitrary discontiguous pages that are made available.  This will not
>> take very long, because copying even 64MB of memory is extremely fast.
>> Then the new kernel is free to use the first X bytes of contiguous
>> physical memory.  Problem solved.
> 
> 
> Ah, that sounds like it would be the right way to go. Good thinking.

Hmm, considering it is not a crash situation, it might even be
better again to simply reuse the exising kernel text and kernel
page table and memory map information if possible. That would
probably only require a meg or two to reinit drivers, load a
suspend-to-disk-init, and do the IO.

OTOH it would likely be more complex than just freeing up a bit
of memory and relocating it.

-- 
SUSE Labs, Novell Inc.
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