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0 pointsdvt13y ago0 comments

> So... how would you have handled it, out of curiosity.

Imo separate heaps is the first big mistake. Even implementations like Erjang (Erlang on the JVM using the Kilim microthreading library -- which I've also contributed to) improve on the copy-from-heap mechanism prevalent in vanilla Erlang. Not only that, but Erlang's memory allocator isn't that well-suited for multi-threaded allocations, which also means that Erlang doesn't (can't?) take advantage of tcmalloc, umem, hoard, etc.

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wrboyce13y ago

Maybe I am missing something, but aren't separate heaps (i.e., no shared memory between processes) one of the things that makes concurrency such a "joy" in Erlang?

Why do you feel the major selling point was the first big mistake?

EvanMiller13y ago

Well, technically there is a difference between separate heaps and no shared memory. Data in Erlang is immutable, so processes could use a combined heap, but they still wouldn't have read-write shared memory.

However, in my opinion separate heaps was absolutely 100% the correct design decision. The main benefit is not having to worry about the effects of a long-running, stop-the-world garbage collection, which can have catastrophic effects on user interaction, server response times, request queue lengths, etc. An additional benefit is that the language implementers can use "dumb" algorithms for garbage collection and avoid a large class of difficult-to-track bugs.

Robert Virding talked about these issues at some length at this year's Erlang Factory; hopefully the video will be posted soon.

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