Periodic plug of David Bacon’s “A Unified Theory of Garbage Collection”, an excellent paper that changed my view on GC: https://courses.cs.washington.edu/courses/cse590p/05au/p50-bacon.pdf …
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tl;dr: Reference counting and mark/sweep are just extreme points on a *continuum* of GC approaches. Optimizations of RC tend to give it characteristics of tracing, and vice versa.
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One very interesting insight: The write barrier for a generational GC is a form of reference counting. Thus a generational GC is actually just a hybrid of reference counting and tracing GC!
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Replying to @pcwalton
I think that's not quite right: the write barrier is used to implement a 0/1 reference count.
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Replying to @samth
Not sure how that differs what I said; could you explain?
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Replying to @pcwalton
The write barrier is just a bit of code executed for every write; you can do a variety of things with it. Similarly you could implement the reference count with other things than a write barrier, for example some systems use page protection (although in a sense that's a barrier).
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Oh, that was just sloppy language on my part. By “the write barrier” I just meant “the portion of the generational GC algorithm that is usually implemented with a write barrier”.
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