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

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521 points OlympicMarmoto | 1 comments | 29 Aug 25 16:45 UTC | HN request time: 0s | source
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jnwatson ◴[29 Aug 25 17:46 UTC] No.45067216[source]▶
I've written a lot of low level software, BSPs, and most of an OS, and the main reason to not write your own OS these days is silicon vendors. Back in the day, they would provide you a spec detailed enough that you could feasibly write your own drivers.

These days, you get a medium-level description and a Linux driver of questionable quality. Part of this is just laziness, but mostly this is a function of complexity. Modern hardware is just so complicated it would take a long time to completely document, and even longer to write a driver for.

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mbac32768 ◴[29 Aug 25 20:54 UTC] No.45069287[source]▶
Yeah this. I tried to modify a hobby OS recently so it would process the "soft reboot" button (to speed up being rebooted in GCP) and it was so unbelievably hard to figure out how to support it. I tried following the instructions on the OS Dev Wiki and straight up reading what both Linux and FreeBSD do and still couldn't make progress. Yes. The thing that happens when you tell Windows or Linux to "restart". Gave up on this after spending days on it.

The people who develop OSes are cut from a different cloth and are not under the usual economic pressures.

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toast0 ◴[29 Aug 25 23:14 UTC] No.45070466[source]▶
To clarify, are you having trouble getting the signal to reboot from the gcp console into your OS? Or are you having trouble rebooting on gcp?
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1. mbac32768 ◴[30 Aug 25 14:55 UTC] No.45075193[source]▶
I mean when the hobby OS wants to shut down, it can power the machine it's running on down. Not unlike what would happen if you clicked power off on your desktop OS menu.

Getting it to work on GCP meant properly driving something called the Intel PIIX4 controller which was emulated into the VM.

Separately from the OS being able to turn itself off, the OS needs to process a signal received by the hypervisor on this controller to support the hypervisor gracefully shutting it down. Otherwise GCP will wait 90 seconds after it has sent the shut down signal to give up and terminate the VM itself.

The problem I was trying to solve was (a) OS can shut itself down in GCP (b) restarts in GCP from the GCP console would be instant, rather than take 90+ seconds