Hello Ramkumar -
The answer really depends on the client, but for entry-level, typical requirements are some background with functional testing, a knowldge of the stack - HTML, javascript, TCP/IP, operating systems, databases, SQL, etc will help. Some programming knowledge, especially web and operations programming ruby etc will help.
Mid-level performance testers should have done it, while senior performance testers have done it on a wide variety of environments for several years, implemented performance testing on an environment that started without it, probably several - let performance testing implementations, acting more like a coach. Probably 5+ years experience.
Good luck!
