[Apache2] Too many processes

If you have a lot of instances of apache2, you can update the values for StartServers, MinSpareServers and MaxSpareServers:

<IfModule mpm_prefork_module> 
StartServers 5 #at the begining
MinSpareServers 5  #min servers spare
MaxSpareServers 10  #max servers spare
MaxClients 150 
MaxRequestsPerChild 0 
</IfModule>

Source : https://fuscata.com/kb/set-maxclients-apache-prefork