[Devel] RE: kernel based checkpoint/restart: about X windows application checkpoint and restart support.

[Will Huang]

> -----Original Message-----
> From: Oren Laadan [mailto:orenl at librato.com]
> Sent: Thursday, October 29, 2009 12:18 AM
> To: Matt Helsley
> Cc: Will Huang; containers at lists.linux-foundation.org
> Subject: Re: kernel based checkpoint/restart: about X windows application
> checkpoint and restart support.
> 
> 
> 
> Matt Helsley wrote:
> > On Wed, Oct 28, 2009 at 11:02:43AM -0400, Oren Laadan wrote:
> >>
> >> Matt Helsley wrote:
> >>> On Wed, Oct 28, 2009 at 10:51:32AM +0800, Will Huang wrote:
> >>>> Dear All,
> >>>>
> >>>>          Did the Kernel based checkpoint/restart patch support X
> windows
> >>>> application such as firefox?
> >>> No, and I think it may be a long time before that happens.
> >> In short: not yet, but we're getting closer.
> >>
> >
> > <snip> (lots of good background)
> >
> >> Now back to your question: X applications cannot be checkpointed
> >> standalone (unless, of course, X windows is modified for that).
> >> Instead, one must checkpoint the entire user session, including
> >> the X server itself.
> >>
> >> The main problem is that the X server is "talking" to the bare
> >> hardware, and the task of recording the specific hardware state
> >> and restoring it later is daunting, and becomes impossible if the
> >> session is to be restarted on different hardware.
> >>
> >> The solution is to not run the regular X server. Instead, start
> >> a virtual X server, such as VNC, and run the user session in it.
> >> The main difference is that VNC server does not directly use any
> >> hardware resources, so it is not tied to specific hardware state.
> >> From the user's point of view - this setup is transparent with
> >> suitable use of a VNC client.
> >
> > VNC is all well and good but it's hardly the norm for local
> > desktops to run under an X server with a VNC display. That said,
> > VNC support is much closer than any of my hare-brained ideas so..
> 
> There is a lot of work on server/client split of the X server
> (of which VNC is one), and also work on embedding one display
> manager within another (e.g. nested X, and also similar ideas
> done with embedding a VM window in the desktop as a regular
> window etc).
> 
> So eventually, I believe, embedding a (virtualized) X server in
> an outside X server and running the entire desktop in a container
> will eventually be possible in a manner transparent to the user.
> 
> And this is much more likely than checkpoint the standard X
> server including all it's hardware related state...
> 
> Changing the norm starts now :)
> 
> Oren.


Yes, the difference between hardware will make the task crazy. I think the X
server should be modified to support the X based application c/r. This will
make the problem a little easy.

Yours sincerely,
Will Huang,
DeviceVM, Inc.

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