Re: Hibernation considerations

From: david
Date: Tue Jul 17 2007 - 00:48:55 EST


On Mon, 16 Jul 2007, Al Boldi wrote:

Alan Stern wrote:
On Mon, 16 Jul 2007, Al Boldi wrote:
From a kexec'd hibernation kernel pov, both S3 and S4 look conceptually
exactly the same. The only difference is, in S3 the memory is in memory
and in S4 the memory is on storage. All device handling is exactly the
same, so if there is a problem with device handling between the kexec'd
hibernation kernel and the normal kernel, then that would have made
itself visible.

You have contradicted yourself. "In S3 the memory is in memory and in
S4 the memory is on storage". How does the memory get onto storage?
The kexec'd hibernation kernel writes it there. To do so it accesses a
storage device.

Consequently the device handling _cannot_ be exactly the same in S3 and
S4.

Ok, you should have read this in the context of suspending/resuming from/to
the normal kernel, and in that case they are exactly the same, i.e. kexec -e
for suspend and kexec -j for resume.

BTW, it would be really helpful if people would actually try the kexec
hibernation patches, as this may yield a much more constructive discussion.

I would love to, but so far I don't see the nessasary pieces

once I kexec to the new kernel, how can it find out what pages of memory (and swap) need to be saved?

If i knew that then I could write a trivial perl program to save those pages with the appropriate headers to make a suspend file.

however, I'm now being told that that suspend file won't work if the machine is actually powered off, so there's a need to something more for the wake-up side of things as well.

David Lang
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