I modified a virtual server's "Website and PHP options" from
- Run CGI scripts as domain owner?: no
- PHP script execution mode: (none enabled)
- Run CGI scripts as domain owner?: yes
- PHP script execution mode: FCGId (run as virtual server owner)
When saving the options the server stopped responsing at HTTP. I still got shell access using SSH but it took ~20 seconds to log in.
Using top I discovered the process /usr/share/webmin/virtual-server/save_phpmode.cgi was using much RAM, see the attached screenshot. When killing the process the server returned to be usable.
BTW: The virtual server in question also produces an error message when backing up:
Copying Apache virtual host configuration ..
.. no Apache virtual host found!
It has a conf file in /etc/apache2/sites-enabled though.