ssh登录缓慢，使用ssh -v登录后，显示在 “pledge: network” 处卡顿：

This is probably an issue with D-Bus and systemd. If the dbus service is restarted for some reason, you will also need to restart systemd-logind.
You can check if this is the issue by opening the ssh daemon log (on Ubuntu it should be /var/log/auth.log) and check if it has these lines:
注：CentOS 下查看 

sshd[2721]: pam_systemd(sshd:session): Failed to create session: Connection timed out
如果找到以上信息，则在服务端执行: