Apache Performance analysis

I am having really difficult time with my web server. I have been tweaking things as per the suggestions on web, yet not able to find anything concrete.

My Apache process was eating 450MB under Virtual Memory column when I did htop. I searched on internet and people said that installing eaccelerator the system will become faster and efficient and would eat lesser memory and CPU. Unfortunately, this turned out to be worse than before. Now my apache processes showing 1488MB memory under Virtual Memory column.

1. Although each process shows 1488MB memory, I can see that total RAM consumption is just 7GB that too when 4GB has been taken away by Varnish Cache (I am using it as reverse proxy).




2. I am not sure if I should worry about Virtual Memory column or not.




3. After installing eaccelerator, my server has not went down due to consumption of complete RAM of 18GB and 2GB of SWAP space. This used to happen before. But again, its been just 1 day since I have installed eaccelerator so may be issues will start coming in day or two.




4. Please do not suggest me to use APC...its not installing on my server.




5. I have checked on phpinfo page of my server and found that Eaccelerator is caching the scripts. As of now it has used up some 80MB of memory (out of 1Gb assigned by me) and has cached some 900 scripts.




6. As of now my prefork settings are -

   
   
   

   
   StartServers 8
   MinSpareServers 5
   MaxSpareServers 20
   ServerLimit 256
   MaxClients 256
   MaxRequestsPerChild 100
   

Please find below the screenshot of htop.

FYI -
Its a dedicated server and has 8 core CPU.
Till the time my server is up and running my site performance is excellent. It loads in around 8 sec for the first time and second view is 2.5 seconds. The site is image heavy as its an ecommerce site.