[Bug 1650067] Re: qemu core dumps when unable to allocate ram for new virtual machine

[Dave Chiluk]

To be explicit as to what I tested.  I launched a machine with the
corresponding cloud archive.  Launched a VM, made sure it functioned.
Launched a VM with a massive memory over-commit, made sure it core
dumped.  Then upgraded to my proposed package.  Made sure I could launch
a vm.  Then made sure launching a VM with over-commit of memory would
not create a core.

I did notice that liberty required significantly more memory overcommit
by default before qemu would fail.  i.e. I was able to launch a 20G vm
on a 16G host using qemu out of liberty.  I ended up raising the VM to
48G to force the failure *(intermediate values were not tested).  It
might be beneficial to figure out what allows this additional overcommit
in liberty/qemu 2.3+.

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https://bugs.launchpad.net/bugs/1650067

Title:
  qemu core dumps when unable to allocate ram for new virtual machine

Status in Ubuntu Cloud Archive:
  Fix Released
Status in Ubuntu Cloud Archive kilo series:
  Triaged
Status in Ubuntu Cloud Archive liberty series:
  Triaged
Status in Ubuntu Cloud Archive mitaka series:
  Fix Released

Bug description:
  Qemu available in the kilo-staging cloud archive will cause an abort
  which will generate a core dump, if there is not enough memory
  available to satisfy creation of the new Virtual Machine.

  This becomes more critical if this happens over and over in highly
  resource constrained environments, as the core dumps start filling up
  the disk.

  This is resolved with upstream commit
  f8ed85ac992c48814d916d5df4d44f9a971c5de4

  I'm opening this case, while I decide if it's worthwhile to re-spin
  qemu to fix this issue.

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