From version 207 on, systemd will not apply the settings from /etc/sysctl.conf anymore: it will only apply those from /etc/sysctl.d/*. Since the settings of our /etc/sysctl.conf shipped by procps-ng have become kernel defaults anyway, we have decided to deprecate this file.
Upon upgrading to procps-ng-3.3.8-3, you will be prompted to move any changes you made to /etc/sysctl.conf under /etc/sysctl.d. The easiest way to do this is to run:
pacman -Syu
mv /etc/sysctl.conf.pacsave /etc/sysctl.d/99-sysctl.conf
If you never customized /etc/sysctl.conf, you have nothing to do.