The Maya Learning Channel has a look into working with the Profiler in Maya that can help diagnose scene slowdowns.

The Maya Profiler Tools have been around for a while, allowing you to visualize performance on your scene. The Maya Profiler Tools will allow you to measure and debug the implementation of character rigs, individual nodes, and Maya scenes.

Here, The Maya Learning Channel posts a look into working with the Profiler in Maya to help show how to root out slow operations and find where the bottlenecks are with your scene.

The Maya Profiler Tools also offer an API allowing you to use it with custom tools and plugins.