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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).

Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.

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Why does Linux run so well on ARM (ls.buckodr.ink)

submitted 1 year ago by [email protected] to c/[email protected]

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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 20 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/

[–] [email protected] 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 12 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 3 points 1 year ago

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