[arch-general] Setting dirty ratio

What is the recommended way to set dirty ratio and dirty background ratio on boot? I added those in /etc/sysctl.d/99-sysctl.conf fileand then added a systemd service to fork a process "sysctl --system" on startup and it didn't seem to work. The command "sysctl --system" run as root is successful in setting the custom options set in /etc/sysctl.d/99-sysctl.conf.