After the last weekly update of my Sabayon Notebook I encountered a high CPU load of one core caused by syslog-ng. The process was literally flooding /var/log/messages and within a couple of minutes tens of Megabyte accumulated. logrotate did not help. The messages were months old, it appeared as syslog-ng would be processing old logs from somewhere else.
I knew that journald was active too, complementing syslog-ng I thought. Some ddg searches later I stumbled over a Gentoo bug report confirming my issue.
Instead of masking syslog-ng-3.6.1 I headed to #sabayon and asked around. Someone explicitly mentioned that syslog-ng is likely pulling logs from journald.
I ended up editing /etc/syslog-ng/syslog-ng.conf and replacing the default source src: