Performance overlay showing the raster thread (top),
and UI thread (bottom).The vertical green bars
represent the current frame.

Interpreting the graphs

The top graph (marked “GPU”) shows the time spent by 
the raster thread, the bottom one graph shows the time 
spent by the UI thread.
The white lines across the graphs show 16ms increments
along the vertical axis; if the graph ever goes over one
of these lines then you are running at less than 60Hz.
The horizontal axis represents frames. The graph is
only updated when your application paints,
so if it’s idle the graph stops moving.

The overlay should always be viewed in profile mode,
since debug mode performance is intentionally sacrificed
in exchange for expensive asserts that are intended to aid
development, and thus the results are misleading.