class ActionView::Template

def render(view, locals, buffer=nil, &block)

consume this in production. This is only slow if it's being listened to.
we use a bang in this instrumentation because you don't want to
This method is instrumented as "!render_template.action_view". Notice that

exactly before rendering.
Render a template. If the template was not compiled yet, it is done 
def render(view, locals, buffer=nil, &block)
  instrument("!render_template") do
    compile!(view)
    view.send(method_name, locals, buffer, &block)
  end
rescue => e
  handle_render_error(view, e)
end