Then you modify the following variables:

sysctl -w kern.ipc.nmbclusters=16384
sysctl -w kern.ipc.maxsockets=16384

Other tips:

• set httpd simultaneous connections very high
• you must know your performance characteristics, make graps with your performance, analyze your server parameters
• use a dedicate server for your web server (do not mix with other server, like mail server)
• httpd.conf (apache):StartServers should be high (default is 5, for a dedicate server make it higher
  
• MaxRequestPerChild= 10000
• Timeout (to get a TCP ACK for a GET request) should be 60 (default is 300)
• MaxClients (FreeBSD) = 256