SDL_OPENGLBLIT performance considerations

I was wondering if there was a performance hit with SDL_OPENGLBLIT on
every call to SDL_GL_SwapBuffers or only when SDL_Flip is called and
hence when it has to do this trick to convert the 2D surface to a
texture and draw it on top of the current 3D scene.

I’d really like to use 2D for the menus and prompts in my game. These
aren’t that frequent, however I do not want to re-initialize the video
subsystem (and back) every time I want to do 2D.

Any help or tips would be greatly appreciated, especially a tutorial
on SDL_OPENGLBLIT and how it was meant to be used.

Olivier A. Dagenais - Software Architect and Developer