How To Bench Mark A Webserver For HTTP Requests

Well Have U Ever Wondered How Much Traffic ,Users and HTTP Request Your Webserver Can handle ,Well I Came across This problem with One of My Website its traffic gone viral like i was hitting 1000 users every minute which is equivalent to 5 times http requests now i was suspecting that these is some problem because no matter what I tried that number is not increasing at all so i thought there is some limit on max http request which my Apache webserver can handle and by doing a little research i came across some pretty useful things by which i can benchmark my server performance here is the list

1.Httperf: A Good Open Source utility by HP, for Linux operating systems only
2.Autobench: Perl wrapper for httperf improving the testing mechanisms and generating detailed reports
3.OpenWebLoad: Smaller scale open source load testing application; supports both Windows and Linux platforms
These Tools Can BenchMark Your Webserver For Performance Load with Detailed Stats