OpenStack instances and compute node crash

Issue

• Several instances across multiple compute nodes have crashed
• A compute node also crashed
• Messages seen in /var/log/messages of the affected compute nodes:

Apr 27 14:08:34 compute kernel: ksmd invoked oom-killer: gfp_mask=0x2000d0, order=0, oom_score_adj=0
...
Apr 27 14:08:34 compute kernel: Out of memory: Kill process 7928 (qemu-kvm) score 479 or sacrifice child
Apr 27 14:08:34 compute kernel: Killed process 7928 (qemu-kvm) total-vm:65985372kB, anon-rss:63278796kB, file-rss:1876kB