docker统计显示“ – ”

当运行docker统计我看到：

CONTAINER CPU % MEM USAGE / LIMIT MEM % NET I/O BLOCK I/O PIDS 11e22031f0be -- -- / -- -- -- / -- -- / -- -- f55b3bbf6115 0.00% 26.98 MiB / 7.795 GiB 0.34% 0 B / 0 B 6.728 MB / 0 B 2 ff7800652fa1 0.30% 21.61 MiB / 7.795 GiB 0.27% 0 B / 0 B 16.69 MB / 270.2 MB 9 d422fe2d0f1a 0.12% 14.23 MiB / 7.795 GiB 0.18% 0 B / 0 B 7.055 MB / 0 B 5 86df65e7c195 0.04% 6.141 MiB / 7.795 GiB 0.08% 0 B / 0 B 6.192 MB / 0 B 2 1d0c20d5ea48 0.27% 32.51 MiB / 7.795 GiB 0.41% 0 B / 0 B 23.48 MB / 0 B 11 -- 

有谁知道什么 – 表示？ 容器正在运行，我可以使用top查看非零进程的统计信息。 这是什么意思？

docker ps的结果

 CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 11e22031f0be aaaaaaaaaaa "run master" 28 hours ago Up 28 hours agitated_bhaskara f55b3bbf6115 bbbbbbbbb "run ovn-controller" 28 hours ago Up 28 hours ovn-controller ff7800652fa1 quay.io/coreos/etcd:v3.0.2 "/usr/local/bin/etcd " 28 hours ago Up 28 hours etcd d422fe2d0f1a ccccc/ovs "run ovs-vswitchd" 28 hours ago Up 28 hours ovs-vswitchd 86df65e7c195 ddddd/ovs "run ovsdb-server" 28 hours ago Up 28 hours ovsdb-server 1d0c20d5ea48 eeeeeeeeeeeeeeee "abcde minino" 28 hours ago Up 28 hours minion