Analyzing pages and Web Parts with SharePoint Developer Dashboard
When the Web browser renders a SharePoint page with its Web Parts, there is a lot of activity in the SharePoint Server and its related components. When a Silverlight application is part of a Web Part, it can use the Client OM or the WCF Data Services to interact with SharePoint, and therefore, it is very difficult to imagine all the things that happen in the server to render a complex SharePoint page.
SharePoint 2010 introduced a new instrumentation framework, the Developer Dashboard. It offers diagnostic information that can help us troubleshoot performance problems and explains what is going on behind the scenes in the SharePoint server.