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    SubjectRe: [Ksummit-2010-discuss] checkpoint-restart: naked patch
    On Sun, 21 Nov 2010, Gene Cooperman wrote:

    > Below, we'll summarize the four major questions that we've understood from
    > this discussion so far. But before doing so, I want to point out that a single
    > process or process tree will always have many possible interactions with
    > the rest of the world. Within our own group, we have an internal slogan:
    > "You can't checkpoint the world."
    > A virtual machine can have a relatively closed world, which makes it more
    > robust, but checkpointing will always have some fragile parts.

    That depends of what your definition of "world". One definition
    is "world := VM", as you state above. Another is "world := container"
    which I stated in my post(s). You can checkpoint both.

    For those cases where the "world" cannot be fully checkpointed,
    I explicitly pointed that we should focus on the core c/r
    functionality, because the "glue" can be done either way.

    > We give four examples below:
    > a. time virtualization

    IMHO, irrelevant to current discussion. And btw, this is done in
    linux-cr for live migration of tcp connections.

    > b. external database
    > c. NSCD daemon

    This falls within the category of "glue", and is - as I try once
    again to remind - tentirely oorthogonal to the topic of where
    to do c/r.

    > d. screen and other full-screen text programs
    > These are not the only examples of difficult interactions with the
    > rest of the world.

    This actually never required a userspace "component" with Zap
    or linux-cr (to the best of my knowledge)..

    Even if it did - the question is not how to deal with "glue"
    (you demonstrated quite well how to do that with DMTCP), but
    how should teh basic, core c/r functionality work - which is
    below, and orthogonal to the "glue".

    Let us please focus on the base c/r engine functionality...

    (gotta disconnect now .. more later)

    Oren.


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