When you first time make a request for JSP, it will compile it and convert it in to the Servlet.
For the further request for the same JSP, application server will check whether JSP has changed after Servlet generated or not. If it has changed then it will again compile the Servlet, else execute the existing Servlet.
This process involves IO and it consumes time � a tiny amount but if you aggregate, it becomes significant.
In WebLogic you have option where by you turn off this option, and it will not check for the new version of JSP for each request. And whenever you update any JPS, you just have to restart the server.
I guess by turning of this option you can avoid some amount of delay, but don�t expect drastic performance gain by doing this.