Checkpointing vkernels

Matthew Dillon dillon at
Thu Feb 15 10:57:39 PST 2007

:Cool, I didn't think that it would be relatively easy to
:implement that.
:I think it would be quite useful to be able to suspend a
:vkernel and later resume it, e.g. after a reboot of the
:physical machine, or even after moving the checkpoint file
:and the vkernel's FS image to a different physical machine.
:It would break any existing network connections, though,
:I guess (i.e. through vke).
:Best regards
:   Oliver

    You would have to copy over the vkernel's memory image file, disk
    image file, and checkpoint file.  TCP connections would likely be lost, 
    since you have no control over the timeouts of external TCP links.

    Oh, I guess the vkernel would also have to reconfigure its TAP 
    interface... but that is easy to do as well.

    The checkpoint code would also have to be made to understand mailbox
    signal handlers.  Also easy to do.

    There is something to be said for having a single memory image file
    that the virtual kernel and its entire process set uses to map memory.
    From the checkpoint code's point of view, a virtual kernel doesn't
    really do anything esoteric.


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