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    SubjectRe: [RFC v6][PATCH 0/9] Kernel based checkpoint/restart

    * Oren Laadan <> wrote:

    > These patches implement basic checkpoint-restart [CR]. This version
    > (v6) supports basic tasks with simple private memory, and open files
    > (regular files and directories only). Changes mainly cleanups. See
    > original announcements below.

    i'm wondering about the following productization aspect: it would be
    very useful to applications and users if they knew whether it is safe to
    checkpoint a given app. I.e. whether that app has any state that cannot
    be stored/restored yet.

    Once we can do that, if the kernel can reliably tell whether it can
    safely checkpoint an application, we could start adding a kernel driven
    self-test of sorts: a self-propelled kernel feature that would
    transparently try to checkpoint various applications as it goes, and
    restore them immediately.

    When such a test-kernel is booted then all that should be visible is an
    occasional slowdown due to the random save/restore cycles of various
    processes - but no actual application breakage should ever occur, and
    the kernel must not crash either. This would work a bit like
    CONFIG_RCUTORTURE: a constant test that should be transparent in terms
    of functionality.

    Also, the ability to tell whether a process can be safely checkpointed
    would allow apps to rely on it - they cannot accidentally use some
    kernel feature that is not saved/restored and then lose state across a
    CR cycle.

    Plus, as a bonus, the inability to CR a given application would sure
    spur the development of proper checkpointing of that given kernel state.
    We could print some once-per-boot debug warning about exactly what bit
    cannot be checkpointed yet. This would create proper pressure from
    actual users of CR.


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