I was able to reproduce this issue with a recent (as of today) install of devstack:
$ pstree -Aapn
| |-bash,26889 | | `-python,30368 ./utils/nova-novncproxy --config-file /etc/nova/nova.conf ... | | |-(python,31700) | | `-(python,31701)
$ ps aux | grep Z
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND ubuntu 31894 0.0 0.0 0 0 pts/12 Z+ 03:01 0:00 [python] <defunct> ubuntu 31895 0.0 0.0 0 0 pts/12 Z+ 03:01 0:00 [python] <defunct>
I was able to reproduce this issue with a recent (as of today) install of devstack:
$ pstree -Aapn
| |-bash,26889 nova-novncproxy --config-file /etc/nova/nova.conf ...
| | `-python,30368 ./utils/
| | |-(python,31700)
| | `-(python,31701)
$ ps aux | grep Z
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
ubuntu 31894 0.0 0.0 0 0 pts/12 Z+ 03:01 0:00 [python] <defunct>
ubuntu 31895 0.0 0.0 0 0 pts/12 Z+ 03:01 0:00 [python] <defunct>