Hi Nagaraju,
I am not aware of any tool to calculat the processing time of the request but there is another way of calculating it.

Write a Class which implements the javax.servlet.ServletRequestListener and implement the methods requestInitialized() and requestDestroyed().So when ever a request comes in requestInitialized will be called and when ever it's done the requestDestroyed will be called so you can write the logic in these to methods to calculate the request processing time.

Don't forget to register this listener in the web.xml of the Application.
Regards,
Krishna Rajendra A.