Re: Back to the future.

Rafael J. Wysocki
2007-04-27T21:25:53Z

On Friday, 27 April 2007 14:49, Pavel Machek wrote:
> Hi!
>
> > > * Doing things in the right order? (Prepare the image, then do the
> > > atomic copy, then save).
> >
> > I'd actually like to discuss this a bit..
> >
> > I'm obviously not a huge fan of the whole user/kernel level split and
> > interfaces, but I actually do think that there is *one* split that makes
> > sense:
> >
> > - generate the (whole) snapshot image entirely inside the kernel
> >
> > - do nothing else (ie no IO at all), and just export it as a single image
> > to user space (literally just mapping the pages into user space).
> > *one* interface. None of the "pretty UI update" crap. Just a single
> > system call:
> >
> > void *snapshot_system(u32 *size);
> >
> > which will map in the snapshot, return the mapped address and the size
> > (and if you want to support snapshots > 4GB, be my guest, but I suspect
> > you're actually *better* off just admitting that if you cannot shrink
> > the snapshot to less than 32 bits, it's not worth doing)
>
> I think this is very similar to current uswsusp design; except that we
> are using read on /dev/snapshot to read the snapshot (not memory
> mapping) and that we freeze the system

Yes, it seems so.

> (because I do not think killall _SIGSTOP is enough).

Agreed.

Greetings,
Rafael