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John Carmack's arguments against building a custom XR OS at Meta

(twitter.com)
520 points OlympicMarmoto | 2 comments | 29 Aug 25 16:45 UTC | HN request time: 0.001s | source
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armchairhacker ◴[29 Aug 25 17:37 UTC] No.45067092[source]▶
What would be the real advantage of a custom OS over a Linux distribution?

The OS does process scheduling, program management, etc. Ok, you don’t want a VR headset to run certain things slowly or crash. But some Linux distributions are battle-tested and stable, and fast, so can’t you write ordinary programs that are fast and reliable (e.g. the camera movement and passthrough use RTLinux and have a failsafe that has been formally verified or extensively tested) and that’s enough?

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Nuthen ◴[29 Aug 25 18:03 UTC] No.45067419[source]▶
Based on the latter tweet in the chain, I'm wondering if Carmack is hinting that Foveated Rendering (more processing power is diverted towards the specific part of the screen you're looking at) was one advantage envisioned for it. But perhaps he's saying that he's not so sure if the performance gains from it actually justify building a custom OS instead of just overclocking the GPU along with an existing OS?
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1. mook ◴[29 Aug 25 22:14 UTC] No.45070034[source]▶
Wouldn't that be an application (or at most system library) concern though? The OS is just there to sling pixels, it wouldn't have any idea whether those pixels are blurry… well for VR it would all be OpenGL or equivalent so the OS just did hardware access permissions.
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2. hedgehog ◴[30 Aug 25 02:03 UTC] No.45071302[source]▶
I think the context is that foveated rendering ties sensor input (measuring gaze direction) to the rendering pipeline in a way that requires very low latency. Past a certain point reducing latency requires optimizations that break normal abstractions made by user land, so you end up with something more custom. I'm not sure why that would require a whole new OS, the obvious path would be to put the latency-sensitive code onto dedicated hardware and leave the rest managed by Linux. If a bunch of smart people thought XROS was a good idea there's probably something there though, even if it didn't pan out.