display noise level

ok we have now adaptive sampling since 2.83 is here. i would suggest to make cycles to display noise level while rendering of tile or entire image. or even viewport. why do we need that ? many render engines have this feature. it's the best way to define what noise treshold do we need to set in the adaptivity relating the acceptable visual quality of image. instead of guessing the noise level i would need to see it in realtime while rendering and definig it by stopping the render, set the treshold and start render again with the right optimised treshold. the corona render is a good example of this feature