hibernation support - lack of distro-wide coordination between systemd, dracut, anaconda, pm-utils and maybe more?

[Zbigniew Jędrzejewski-Szmek]

On Tue, Apr 14, 2015 at 09:30:31AM -0600, Chris Murphy wrote:
> On Tue, Apr 14, 2015 at 3:07 AM, Bastien Nocera <bnocera at redhat.com> wrote:
> >
> >
> > ----- Original Message -----
> >> OK not everyone is on the same page, apparently. This bug was just
> >> closed by Anaconda as WONTFIX.
> >>
> >> suggested swap for laptop seems low
> >> https://bugzilla.redhat.com/show_bug.cgi?id=1037472
> >>
> >> I don't see how hibernation works reliably with such a low default swap size.
> >
> > This isn't the way to fix it. The hibernation file/partition should really be independent
> > of swap, because 1) you can't be sure how much swap will actually be used by the applications
> > so you can't be sure you'll ever have enough swap to save the RAM 2) Too much swap and the
> > (lack of) interactivity will make you want to advocate physical violence when your machine
> > is unusable for an hour because of a hungry Javascript in your 50th Firefox tab.
> 
> Windows and OS X both use swapfiles rather than swap partition, and a
> sleep image file rather than a partition. OS X's swapfiles are
> dynamically created on demand in variable size increments.
I think the problem is in the ways filesystems are implemented.  The
fs has to be mounted to access the swap file, and this can change the
fs, even with a read-only mount. Because we don't have
really-read-only fs mounting, we need to support swap-as-partition, so
we might just as well use it by default.

> Both OS's have a feature that I find invaluable on a laptop which is
> the automatic switch from suspend-to-RAM to suspend-to-disk.
Yes, integrating with firmware would be great. So far this hasn't been hapenning...
What we can do instead is use hybrid sleep. It's not smart at all,
and doesn't prevent your battery from draining completely, but it does protect
your data.

Systemd supports hybrid-sleep as another option analogous to suspend
and hibernation, so for anything using systemd to suspend swithing to
hybrid should be trivial. Maybe we should make this an F23 goal:
- use hybrid-sleep from Gnome and other DE by default

Zbyszek