How to benchmark a theme

In the theme configuration menu choose the profiler theme renderer.

Here is a typical output:

Profiling lvl:-1 cpsskins_main_template_profiler:
t       mark       delta t
0.0000: Start      + 0.0000
0.0000: --------- [top] ----------------------------------  + 0.0000
0.0100: CPSSkins: banner..................................  + 0.0100
0.0100: CPSSkins: welcome box.............................  + 0.0000
0.0100: CPSSkins: search box..............................  + 0.0000
0.0200: CPSSkins: Action Box Templet......................  + 0.0100
0.0200: --------- [Navigation] ---------------------------  + 0.0000
0.0300: CPSSkins: maintabs................................  + 0.0100
0.0300: CPSSkins: actionbox...............................  + 0.0000
0.0400: CPSSkins: Breadcrumbs.............................  + 0.0100
0.0400: --------- [Main Columns] -------------------------  + 0.0000
0.1200:           Left-column slot........................  + 0.0800
0.1300: CPSSkins: action tab..............................  + 0.0100
0.2000:           Content actions.........................  + 0.0700
0.2800:           Main Content............................  + 0.0800
0.3000: CPSSkins: Workflow actions........................  + 0.0200
0.4100:           Right-column slot.......................  + 0.1100
0.4100: --------- [bottom] -------------------------------  + 0.0000
0.4200: CPSSkins: footer..................................  + 0.0100
0.4200: Stop       + 0.0000