[GSoC] Making vkernels checkpointable - final report

Justin Sherrill justin at shiningsilence.com
Wed Sep 25 19:52:59 PDT 2013

This is open source, so you can pretty much work on whatever schedule you

Something that might be useful for the future, if you wanted to work on it:
a specific test that can be run to make sure vkernel checkpoint works.
 Given that checkpointing is complicated, and vkernels are going through
some changes, it is useful to have a tool that could regularly check to
make sure this hasn't been broken by other work.  This would be especially
useful near release times.

On Tue, Sep 24, 2013 at 9:17 PM, Pawel Dziepak <pdziepak at quarnos.org> wrote:

> Hello,
> During the last week of this year Google Summer of Code I continued
> testing the code, including more tests of 32 bit versions of both
> vkernel and the "host" kernel (during the GSoC I used mostly 64 bit
> versions). Fortunately, I didn't came across any serious problems.
> Moreover, I updated the sys_checkpoint(2) manpage removing information
> about the limitations that are no longer present and adding
> implementation notes that explain the format of the checkpoint files.
> The goal of my project is completed. It is possible now to chekpoint a
> running vkernel together with its virtual processes and then restore
> it. I tried to make it possible by enhancing checkpointing
> implementation rather than doing everything inside vkernel checkpoint
> signal handler so that not only vkernels can benefit from these
> modifications. Apart from some minor fixes, making checkpoint file
> format more flexible and future-proof, now all MAP_VPAGETABLE mappings
> are properly supported as well as kqueues and threaded programs.
> I've checked and there are no merge conflicts with the master. There
> also doesn't seem to be any problems with the kernels (and vkernels)
> built after merge, but undoubtedly vkernels taking advantage from
> visualizing extensions cannot be currently checkpointed. There is also
> matter of dirfs which was recently added. I haven't really looked into
> it yet but it seems like it will also require some work to get it
> working with checkpointed vkernels.
> I am willing to continue working on the checkpointing code and the
> vkernels and make it work with these recent additions hardware
> virtualization and dirfs. Due to previous arrangements in October I
> would have much less time for it that I'd wish to have but still I
> expect to make some progress.
> Paweł
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