We are using the threaded apache and to know how much memory and cpu processors and the cpu load used by apache per thread.
Basically to do this things we will optimize well and improve the server and apache health.
We have running 1100 sites over just 70 servers so it's need to look better towards all these things
We are using memcached and as well varnish and ha for load balancing, really we are doing well, now we will allocating number of cpu's from total cpu processor to apache to run better.
that's the story ......