Suppose I inserted an empty loop in the middle of my game loop such that I can be sure that the time spent outside of rendering amounts to over 95% of the run time of the program and the framerate never exceeds 40 fps. What does it mean if the framerate still drops quite visibly?
I can also monitor GPU usage from Process Explorer and it practically idles to run my program.

EDIT: If the answer to the above question is "it doesn't mean anything", is there any way I can improve my code? My target is being able to draw as many sprites as possible as efficiently as possible, considering that they'll be moving constantly and independently, and that sprites may be created or destroyed at any time.

Suppose I inserted an empty loop in the middle of my game loop such that I can be sure that the time spent outside of rendering amounts to over 95% of the run time of the program and the framerate never exceeds 40 fps. What does it mean if the framerate still drops quite visibly?
I can also monitor GPU usage from Process Explorer and it practically idles to run my program.