Debugging the graphic performance of a level is vital to understand which parts are causing the bottleneck. It can also be used to find bugged/incorrect meshes or entities.
Start Depth.exe in Dev mode and then press F1 to bring up the Debug Toolbar. The two groups that are important are the “Debug texts” and “Graphics Debug”.
The important checkboxes here are Show FPS, Show Memory Usage and Show Render Info. These will tell you how costly the rendering of the scene is.
Shows how fast the level is running.