Why does Linux run so well on ARM
Why does Linux run so well on ARM
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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Windows’s achilles heel is arguably its chief benefit - legacy compatibility and being the de facto platform for applications.
Back when I had a Surface RT, I thought it was awfully neat, ARM-compiled versions of Office, IE, Windows 8.x bits ran well and it was fanless with fine battery life. (although I surely sound weird, I had a Windows Phone back then too and the syncing with IE on both was a nice feature) It’s just they were pushing the Store then and if you jailbroke it, ARM applications were rare.
Apple is a pro at architecture transitions and can steer the whole ship, MS can put Windows on ARM all they want but OEM’s will be reluctant since it’ll be a relatively big risk to sell a “Windows, buuut…” computer and the popular closed-source applications probably won’t bother with ARM for a while
Apple is a "pro" because it is a forced-migration, the eventual upgrade path is forced so the vendors have to follow if they want to support Mac. This is the reason there is vendor adoption on Mac, and not on Windows. I think until ARM has a significant market share on Windows the vendors will not port their software.
I know the cool thing is to hate on Apple for being Apple, but they have actually done a solid job with their transitions between instruction set architectures.
Ultimately, software developers and end users are forced to use the newer architecture, yes. But credit where credit is due, Apple chose to take the path of providing both hardware and software level facilities to make the transitions as seamless as possible over years-long timespans. They could have simply refused to support older architectures to force a migration down our throats, and indoctrinated fanboys would have opened their wallets anyway.
What they actually did was create compatibility layers, a multi-architecture executable file format, and binary translation frameworks built into the operating system. I fucking despise them for creating a walled-garden ecosystem and cult around their products, but I genuinely have to respect them for Rosetta and Rosetta 2. Developing a binary translation layer is a whole different beast than high-level emulation, and it's significantly more difficult to pull off correctly. The fact that they managed to do it twice, and do it damn-near seamlessly is impressive. Rosetta 2 even supports translating just-in-time compiled code, which is a huge pain point for that kind of thing.
If you follow the history of the Mac, it went through a number of major architecture transitions from 680x0 -> PowerPC -> Intel -> ARM. Each time, Apple supplied a decent emulator to support applications during the transition.
From a developer perspective, these were huge upheavals that came with a lot of drama but also offered some opportunities. The latter came from the fact that the bar was in some way set higher on the new platform and you could count on any code you compiled for it supporting certain base features. Every PowerPC, for example, had hardware floating-point. Before that, some CPUs did, some didn't. The Intel transition happened at the time when dual core had become standard and SIMD had become serviceable (with SSE2). The ARM transition has set the bar at 64-bit architecture for every CPU (since Apple had earlier dumped 32-bit on the iPhone side).
Windows/Intel has developed in a more evolutionary than revolutionary manner, which is easy to see if you look, for example, at all the legacy cruft in the Intel ISA. It's a sad sight. Supporting all that makes instruction decoding a nightmare. In theory, Intel/AMD could reinvent a new sleeker ISA if they could get Microsoft to commit to supplying a performant emulator for the old one? But I'm not holding my breath.
Apple can be much more heavy handed than Apple can. Apple controls their hardware ecosystem. They make everybody buy the architecture they want. They make the OS stop working on older hardware. They set minimum OS requirements for application writers. So, all the software ( from everybody - not just Apple ) gets moved to the new architecture quickly. It does not take long before being on the new architecture is all that makes sense.
Windows on the other hand does not control the hardware. They are trying. They make their own now so they can at least seed the new ecosystem. However most Windows users buy their Windows hardware from somebody other than Microsoft. It makes sense for most hardware to target the larger application audience and that will be the old architecture. It makes sense for application devs to target the older architecture. For a long, long time, the older arch makes the most sense for almost everybody in the ecosystem. Only early adopters make the switch ( both users and application sellers ). In practice, that means that moving to the new arch means not having native apps in many cases which means the new arch will, in practice, be worse than the old one.