Re: Hibernation considerations

[david@lang.hm]

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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