[libvirt-users] virsh responds slowly

Dear all, I have observed the virsh responds slowly with "virsh list" and used "strace virsh list" will find that it is waiting on the socket. I also use "netstat |grep libvirt" and see an opened socket /var/run/libvirt-sock-ro is always on and will not disappear. Is it caused by an abnormal termination of virsh API? Otherwise, if there is any possible issue? I have checked the cpu utilization, it is low and no waiting io. Regards, Chun-Hung