My understanding is that real-time isn't so much about lower latency (though that is also desirable), but rather about predictable, bounded latency. For the purposes of gaming, no amount of predictability at the kernel level will reduce the amount of work you need to perform to draw a frame, and that is the real limiting factor for most games.
> For the purposes of gaming, no amount of predictability at the kernel level will reduce the amount of work you need to perform to draw a frame, and that is the real limiting factor for most games.
It all depends on what you're trying to optimize for. You can maximize raw framerate numbers by having an unlimited frame queue depth, but it'll feel like shit because you won't have even frame pacing and your input latency will vary wildly. The ideal scenario in gaming is for your draw time to be perfectly deterministic, and be able to schedule things so you can read input and do your render calls just before vsync.
