[root@2 ~]# time for i in `seq 1 100`;do dig @8.8.8.8 www.alidns.com > /dev/null 2>&1; done

real    0m14.733s
user    0m0.227s
sys     0m0.302s
[root@2 ~]# time for i in `seq 1 100`;do dig @119.29.29.29 www.alidns.com > /dev/null 2>&1; done

real    0m14.249s
user    0m0.224s
sys     0m0.327s
[root@2 ~]# time for i in `seq 1 100`;do dig @114.114.114.114 www.alidns.com > /dev/null 2>&1; done

real    0m14.856s
user    0m0.235s
sys     0m0.312s
[root@2 ~]# time for i in `seq 1 100`;do dig @223.5.5.5 www.alidns.com > /dev/null 2>&1; done

real    0m13.729s
user    0m0.235s
sys     0m0.309s
[root@2 ~]# time for i in `seq 1 100`;do dig @180.76.76.76 www.alidns.com > /dev/null 2>&1; done

real    1m8.154s
user    0m0.205s
sys     0m0.326s
[root@2 ~]# time for i in `seq 1 100`;do dig @101.226.4.6 www.alidns.com > /dev/null 2>&1; done

real    0m16.814s
user    0m0.225s
sys     0m0.307s
[root@2 ~]# time for i in `seq 1 100`;do dig @1.2.4.8 www.alidns.com > /dev/null 2>&1; done

real    0m14.493s
user    0m0.215s
sys     0m0.317s
[root@2 ~]# time for i in `seq 1 100`;do dig @208.67.222.222 www.alidns.com > /dev/null 2>&1; done

real    0m47.309s
user    0m0.228s
sys     0m0.326s
[root@2 ~]# time for i in `seq 1 100`;do dig @208.67.222.222 www.alidns.com > /dev/null 2>&1; done
c^C
real    1m36.730s
user    0m0.214s
sys     0m0.320s
[root@2 ~]# time for i in `seq 1 100`;do dig @4.2.2.1 www.alidns.com > /dev/null 2>&1; done

real    0m38.440s
user    0m0.224s
sys     0m0.303s
[root@2 ~]# time for i in `seq 1 100`;do dig @1.1.1.1 www.alidns.com > /dev/null 2>&1; done

real    0m27.393s
user    0m0.239s
sys     0m0.292s