No process has run up against the memory limits I put in place on Iglulik and memory usage has remained stable since the kernel upgrade to 4.8.

     This makes it likely that the issue was a bug in the 4.4 kernel on that machine.  It was the only machine I had running that particular kernel.

     It is possible that whatever went wrong before just hasn’t happened again yet, but if it does hopefully the limits in place will identify the process, prevent the virtual machines being killed by the Linux OOM killer, and provide some diagnostic information.