Re: [RFC][PATCH 1/2 -mm] kexec based hibernation -v3: kexec jump

Andrew Morton
2007-09-21T04:16:27Z

On Fri, 21 Sep 2007 11:57:26 +1000 Nigel Cunningham <nigel@nigel.suspend2.net> wrote:

> Hi.
>
> On Friday 21 September 2007 11:41:06 Andrew Morton wrote:
> > > On Friday 21 September 2007 11:06:23 Andrew Morton wrote:
> > > > On Fri, 21 Sep 2007 10:24:34 +1000 Nigel Cunningham
> > > <nigel@nigel.suspend2.net> wrote:
> > > >
> > > > > Hi Andrew.
> > > > >
> > > > > On Thursday 20 September 2007 20:09:41 Pavel Machek wrote:
> > > > > > Seems like good enough for -mm to me.
> > > > > >
> > > > > > Pavel
> > > > >
> > > > > Andrew, if I recall correctly, you said a while ago that you didn't
> want
> > > > > another hibernation implementation in the vanilla kernel. If you're
> going
> > > to
> > > > > consider merging this kexec code, will you also please consider
> merging
> > > > > TuxOnIce?
> > > > >
> > > >
> > > > The theory is that kexec-based hibernation will mainly use preexisting
> > > > kexec code and will permit us to delete the existing hibernation
> > > > implementation.
> > > >
> > > > That's different from replacing it.
> > >
> > > TuxOnIce doesn't remove the existing implementation either. It can
> > > transparently replace it, but you can enable/disable that at compile time.
> >
> > Right. So we end up with two implementations in-tree. Whereas
> > kexec-based-hibernation leads us to having zero implementations in-tree.
> >
> > See, it's different.
>
> That's not true. Kexec will itself be an implementation, otherwise you'd end
> up with people screaming about no hibernation support. And it won't result in
> the complete removal of the existing hibernation code from the kernel. At the
> very least, it's going to want the kernel being hibernated to have an
> interface by which it can find out which pages need to be saved. I wouldn't
> be surprised if it also ends up with an interface in which the kernel being
> hibernated tells it what bdev/sectors in which to save the image as well
> (otherwise you're going to need a dedicated, otherwise untouched partition
> exclusively for the kexec'd kernel to use), or what network settings to use
> if it wants to try to save the image to a network storage device. On top of
> that, there are all the issues related to device reinitialisation and so on,
> and it looks like there's greatly increased pain for users wanting to
> configure this new implementation. Kexec is by no means proven to be the
> panacea for all the issues.
>

Maybe, maybe not, dunno. That's why we haven't merged it yet. If it ends
up being no good, we won't merge it!