SDL_GL_SwapWindows status check

Is there a way to check if SDL_GL_SwapWindows is waiting on a queue from OpenGL? That seems to be where most of my application’s time is spent. (yes vsync is turn off SDL_GL_SetSwapInterval(0)).
It would be great if I could check if there is a queue in the pipeline without having a separate thread to handle rendering. I want to skip on to the next frame if OpenGL is still rendering the last frame.

while(running){

input();
simulate();

if(QUEUE_EMPTY){
render();
SDL_GL_SWAPWINDOW(myWindow);
}

}