Re: code read problems

[Brendan Cully <brendan@cs.ubc.ca>]

Nice summary!

In part 3, you have:

  ? What does that checkpoint flag do ?

When that flag is set (through xm save -c), the domain resumes
operation after the save operation. Normally "save" destroys the
domain.

You might be interested in my presentation at xen summit 4 about
checkpointing, which goes into some detail about the save/migration
process:

http://xen.org/files/xensummit_4/talk_Cully.pdf

Since then we've increased the speed of checkpointing considerably,
but the code to do it isn't in Xen yet. We have a paper about it in
the next NSDI conference which has the details, if you're interested.

On Wednesday, 27 February 2008 at 14:23, Mike Sun wrote:
> I've had to trace through the migration code and made the following
> notes.  Hope it helps:
> 
> http://msun.bluespot.org/wiki/doku.php?id=xen_migration_notes
> 
> On Wed, Feb 27, 2008 at 4:37 AM, tgh <wwwwww4187@sina.com.cn> wrote:
> > hi
> >   thank you for your reply
> >   and i read the code of xc_save.c and xc_restore.c, which maybe do the
> >  function of VMsaving and VMrestoring, but i wander, if the code of
> >  xc_save.c and xc_restore.c is called by some python code or c code
> >  during migration or xm save and xm restore or not? the code of xc_save.c
> >  is a main function ,and is it called by other program to do migration or
> >  not ?
> >
> >   and in the code of xc_save.c, there seem no notification to the
> >  xenstore or devbackend, and how are these VMdevbackends destroyed in the
> >  dom0, when migration or save?
> >   and in the code of xc_restore.c,there seems to be an existing
> >  VMdomain,and the whole data from savefile or from  migration,will load
> >  into the VMdomain, is it？  then ,what code call these code of xc_save
> >  and xc_restore?  i am confused
> >
> >  could you help me out
> >
> >  Thanks in advance
> >
> >
> >  Daniel Stodden 写道:
> >
> >
> > > On Tue, 2008-02-26 at 19:22 +0800, tgh wrote:
> >  >
> >  >> could you reply in english, i could not read your letter
> >  >>
> >  >
> >  > Don't bother. Just an autoreply generated to tell you the guy is on
> >  > vacation.
> >  >
> >  > Regarding your problem: There is not much you can do to get some sort
> >  > execution traces enabled automatically. You probably want to enable
> >  > debugging when building Xen and the libraries. Then maybe add a couple
> >  > of debug-print statements to the code, whereever you see fit.
> >  >
> >  > I believe migration support in xend and libxc should be understandable
> >  > in isolation. The tricky parts are definitely done in C. Last time I
> >  > checked, xend mainly performed a single call to the tools and library.
> >  >
> >  > Also note that random instrumentation of all code executed for
> >  > translating and mapping of the domU address space within the hypervisor
> >  > would probably soon get more verbose than you asked for, since some of
> >  > the functions involved can be called at a comparatively high frequency.
> >  >
> >  > Rule 1 when digging your way through complex systems: Divide and
> >  > Conquer. Division comes first. Understand one thing at a time, starting
> >  > at a comparatively high-level, then selectively dig deeper.
> >  >
> >  > regards,
> >  > daniel
> >  >
> >  >
> >  >
> >  >> clp@eclinso.com 写道:
> >  >>
> >  >>> Vielen Dank für Ihre Nachricht.
> >  >>>
> >  >>> Ich bin vom 22-02-08 bis 07-03-08 nicht im Hause und werde Ihre
> >  >>>
> >  >> E-Mail ab dem 10-03-07  bearbeiten.
> >  >>
> >  >>> In dringenden Fällen wenden Sie sich bitte an Herrn Fabio Lüdi, er
> >  >>>
> >  >> wird Ihnen gerne weiterhelfen.
> >  >>
> >  >>> Sie erreichen Herrn Lüdi unter:
> >  >>> Phone +41 61 6666 406
> >  >>> E-Mail fl@eclinso.com
> >  >>>
> >  >
> >  >
> >
> >
> >
> >
> > _______________________________________________
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> >  Xen-devel@lists.xensource.com
> >  http://lists.xensource.com/xen-devel
> >

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