In a project I am working on I am structuring my code as follows

MyLib = {
    AField:0,

    ASubNamespace:{
        AnotherField:"value",

        AClass:function(param) {
            this.classField = param;

            this.classFunction = function(){
                // stuff
            }
        }
    },

    AnotherClass:function(param) {
        this.classField = param;

        this.classFunction = function(){
            // stuff
        }
    }
}

and so on like that to do stuff like:

var anInstance = new MyLib.ASubNamespace.AClass("A parameter.");

Is this the right way to go about achieving namespacing? Are there performance hits, and if so, how drastic? Do performance degradations stack as I nest deeper? Are there any other issues I should be aware of when using this structure?

I care about every little bit of performance because it's a library for realtime graphics, so I'm taking any overhead very seriously.