It happens when rebuilding /script/fixdns on master-slave:
22312 root 20 0 169m 8924 5092 R 36.1 0.2 0:01.17 rpm -qa
22208 root 20 0 169m 8960 5092 R 33.0 0.2 0:01.95 rpm -qa
22211 root 20 0 328m 16m 2008 R 33.0 0.4 0:01.72 /opt/php54s/usr/bin/php -c /opt/php54s/custom/php54s.ini /usr/local/lxlabs/kloxo/sbin/kloxo.php slave
628 mysql 20 0 1335m 193m 9076 S 9.2 5.1 1:28.25 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib/mysql/plugin --user=mysql --log-error=/var/log/mysqld.log --pid-file
1804 root 20 0 115m 2100 652 R 7.4 0.1 23:55.70 crond
21558 pdns 20 0 882m 8944 5080 S 3.4 0.2 0:00.40 /usr/sbin/pdns_server-instance --daemon --guardian=yes
That's why /script/fixdns is so slow now - it can kill Intel Atom CPU with load.