Metal API validation can add multiple ms of overhead to applications with lots of little draws. This can cause confusing raster overhead for simple seeming applications like the one in #157827 . In this application raster time goes from ~1ms up to ~8ms with API validation enabled.

Metal API validation also appears to be active in both debug and profile modes. While this thankfully disappears in release modes, our users expect profile mode to be more representative of real performance.