this post was submitted on 20 Aug 2023
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Why does Linux run so well on ARM (ls.buckodr.ink)
submitted 1 year ago by xusontha@ls.buckodr.ink to c/linux@lemmy.ml
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I've seen people talking about it and experienced it myself with a server, but why does Linux run so well on ARM (especially compared to Windows)?

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[–] carl_the_grackle@lemmy.world 18 points 1 year ago (2 children)

Apple designed the silicon to have an "x86 mode" for the memory model ordering, as well as an undocumented mode that makes certain arm instructions set flags similarly to x86. There's a good write up of the reasons here: https://dougallj.wordpress.com/2022/11/09/why-is-rosetta-2-fast/

[–] kimpilled@infosec.pub 13 points 1 year ago

Apple hit a sweet spot with this. x86_64 applications run at acceptable speed (making the transition easy for people who buy the hardware) while not being SO good that there's zero reason for developers to start porting their software.

[–] pivot_root@lemmy.world 11 points 1 year ago (1 children)

Small correction: the flag setting modes aren't undocumented. They're standardized extensions. ARMv8.4 added FEAT_FlagM, and ARMv8.5 added FEAT_FlagM2.

https://developer.arm.com/downloads/-/exploration-tools/feature-names-for-a-profile

IIRC, the only nonstandard ARM extension used by Rosetta 2 in Apple's processors is TSO, and that's also implemented by other manufacturers. It's also not a hard requirement to run amd64 under ARM. You can emulate it very slowly or restrict the application to a single core.

Apologies for the tangent, but I needed to make sure nobody could defend Microsoft's prior failings by saying "but Apple has secret hardware sauce".

[–] carl_the_grackle@lemmy.world 3 points 1 year ago

So while not technically "secret sauce," it's certainly "special sauce." Good point.