3 ms·

A win on the board for ARC? Can anyone with more deep GC knowledge explain why this might be, considering the tweaks they made to G1? Is this a specific workloa

• username223 1y ago
  It has been a long time, but I worked on GC at one point. My guess is that it’s the memory footprint (and loss of cache locality) that’s to blame. Copying or mark/sweep can be fast, but only if you give them lots of extra memory to accumulate garbage between GC passes. ARC does a little extra CPU work all the time, but it has good locality, and doesn’t need the extra memory.
• adamwk 1y ago
  The way to write performant Swift is classless so without ARC, but classes have been necessary for many areas. Recently, Swift’s been leveraging a lot of ownership features similar to Rust to make it possible to do more without classes, and I’d guess Apple teams would be using those
  • sunnybeetroot 1y ago
    What areas are classes necessary assuming you’re talking about pure Swift and not iOS?
    • adamwk 1y ago
      Where copying is expensive (most Swift collections are backed by classes for COW semantics). Where location stability is necessary (where you need a mutex). Resource allocation. Those are the primary examples that noncopyable types are meant to address.
      • sunnybeetroot 1y ago
        Ah yes great examples, thank you for explaining.