[Qemu-devel] COLO hybrid mode and other changes

[Dr. David Alan Gilbert]

Hi,
  I've got a world with a few COLO changes in that you might
like to look at; they're all experimental, but it seems
to be working for me.

  The world is at:
    https://github.com/orbitfp7/qemu/commits/orbit-wp4-colo-jan16

It's based off:
    The December/2.4 colo framework world with periodic checkpoints
    + The december user space colo-proxy
    + The integration code that was in the colo-proxy git repo
    (those needed some updates to go into the 2.4-periodic world)

And then I've added:
   - An updated version of my hybrid mode code that switches between
     COLO and periodic checkpoints depending on the frequency of
     miscompares
   - A minimum checkpoint time, so that on fast miscompares
     we do get some runtime (as in the earlier colo series)
   - I'm using a condition-variable to flag the miscompares from
     the colo-proxy to the colo thread; this seems cleaner and it
     avoids having to do short waits;  it might be a bit tricky
     to make portable.
   - Add back some statistcs in 'info migrate'
   - An HMP command equivalent to x-blockdev-change.
   - RDMA transport for COLO

I don't intend to post any of these changes in full to the list
until your main COLO code is in; although if any of my changes
are useful to you, then feel free to include them in sets you post.

Dave
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK