The 130ms is "the time from light hitting the camera to when it appears on-screen on the other side". The article doesn't really specify where the latency happens, but with just the encoding/decoding of video alone I think you'll very quickly get latencies in roughly the ~100ms ballpark no matter what.
Adding latency is always bad. You're seldom in control of the full stack. Latency will come from hardware, firmware, your OS, the network, everywhere. The responsibilities are split. But if even a single node of the chain doesn't take latency seriously, it screws up the whole, because every link of the chain adds latency.
That said, 130ms is a lot for a single link of the chain other than the network (physical distance will of course incur latency).
seL4[0] will guarantee (with formal proof) a low maximum latency despite multitasking.
Negligible, compared to that of the network.
>What improvements in "the stack" would be needed?
It would have to take latency seriously, thoroughly.
>The article doesn't really specify where the latency happens,
It really happens everywhere. The rust code likely accounts for very little of the overall latency anymore, but the overall latency is still bad.
I would pick seL4 because of their WCET proof.
It depends on the implementation. Most protected RTOSs are vastly inefficient but it doesn't have to be so.
For an example, many multitasking RTOSs do reserve CPU time for the "important" tasks, whether they use it or not. That's the industry standard for "mixed criticality", where less and more critical tasks share the same CPU.
But there's better ways to do this. Refer to the seL4 whitepaper[0].
>desktop OS
I'd rather not WaitForever™ for the computer to react to my input due to unbounded latency on my Desktop OS. We might be used to trash responsiveness, but interacting with a computer does not have to be this bad. We should stop pretending non-RTOS systems are okay to build a desktop around.