A lot of times busy servers will have this issue and you cannot even force kill -9 the apachectl or httpd process:
[root@apachebox stats]# ps aux|grep httpd
root 1547 0.0 0.2 495452 32396 ? Ds Sep08 3:23 /usr/sbin/httpd
root 3543 0.0 0.0 6448 724 pts/1 S+ 13:11&nbs........
apachectl -l
Compiled in modules:
core.c
prefork.c
http_core.c
mod_so.c
It is "prefork.c" so in httpd.conf these settings are what you would use (if you use worker.c it won't have any impact):
StartServers 2
MinSpareServers 5
MaxSpareServers&nb........
find what MPM Apache is using, it will either be using "worker" or "prefork"
apachectl -l
Compiled in modules:
core.c
prefork.c
http_core.c
mod_so.c
In my case it is "prefork"
vi /etc/httpd/conf/httpd.conf
Find the section that looks like this (by default one will normally exist for prefork and for worker, but in my case I only care a........