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by mojuba 1454 days ago
I'm not familiar with the details but it is said that Swift's ARC is several times faster than ObjC's, it somehow doesn't always require atomic inc/dec. It also got even better specifically on the M1 processors. As for GC's, with each cycle there's always overhead of going over the same objects that are not disposable.

Someone also conducted tests, for the same tasks and on equivalent CPU's Android requires 30% more energy and 2x RAM compared to iOS. Presumably the culprit is the GC.
1 comments
kaba0 1454 days ago
That’s a very strong presumably, on a very niche use case of mobile devices.

It is not an accident that on powerful server machines all FAANG companies use managed languages for their critical web services, and there is no change on the horizon.

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mojuba 1454 days ago
It might be because on the server side they usually don't care about energy or RAM much. The StackOverflow dev team has an interesting blog post somewhere, where they explain that they figured at one point C#'s GC was the bottleneck and they had to do a lot of optimizations at the expense of extra code complexity to minimize the GC overhead.

It is actually quite rare that companies think of their infrastructure costs, it's usually just taken for granted, plus that there aren't many ARC languages around.

Anyway I'm now rewriting one of my server projects from PHP to Swift (on Linux) and there's already a world of difference in terms of performance. For multiple reasons of course, not just ARC vs. GC, but still.

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kaba0 1454 days ago
With all due respect, (big) servers care about energy costs a lot, at least as much as mobile phones. By the way, out of the manages languages Java has the lowest energy consumption. RAM takes the same energy whether filled or not.

Just because GC can be a bottleneck doesn’t mean it is bad or that alternatives wouldn’t have an analog bottleneck. Of course one should try to decrease the number of allocations (the same way you have to do in case of RC as well), but there are certain allocation types that simply have to be managed. For those a modern GC is the best choice in most use case.

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