I have installed PHP as an Apache module. I have had prefork running all this while. I've read that worker would consume less memory while offer higher performance]1. So, I've edited /etc/sysconfig/httpd and uncommented:
Last Friday (10/7/2011) we started having httpd.worker processes grow from the
typical 10-15M memory reserved to 10G+ (gigabytes) in a matter of 1-2 minutes. This obviously brings the server to a halt as it starts swapping etc. We have to reboot the server in order to get it running again.
We recently tried switching one of our servers over from the default MPM prefork to worker. The savings in memory were really surprising but we have no experience of tuning with worker. Can anyone give us a rough idea of any changes we could make to the default worker setting? This server has 8 cores and 12GB ram also running varnish.