These links might be worth checking out:
http://ez.no/ez_publish/documentation/configuration/optimization/configuration_tuning
http://ez.no/community/forum/developer/ez_what_is_ripping_our_resources http://ez.no/community/forum/developer/performance_mysql_add_index
Apache 2 is not recommended to use with eZ publish. This is not a eZ publish problem, but a PHP one. You will find lots of information about apache 2 in the forums.