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0 pointslambdaelite10y ago0 comments

Why are concurrent GCs rare?

0 comments

Mostly because there are very very few people in the world who are able to develop such a complex thing for Lisp (or similar runtimes). Since the market is relatively small and many applications are not overly concurrent, there is very little money to support the development.

0xCMP10y ago

I am guessing[1] that GCs are easier to code correctly without the concurrency and that a GC language is already expected to be slower so it doesn't make sense to do a concurrent GC. Also possibly, the language doesn't support concurrency well. Like a Python or Ruby.

[1] just an educated guess. I have no real knowledge of GCs other than skimming how they work in articles and runtime/language docs.

vseloved10y ago

are there many platforms, besides JVM and .Net, that have good-quality concurrent GCs?

fredyr10y ago

The Erlang Vm (BEAM), is another one at least.

the_why_of_y10y ago

It doesn't actually implement concurrent GC, although what it does implement is far simpler and has a similar effect (low latencies) as concurrent GC.

Each Erlang process has a separate heap that is collected independently; because the process heap is usually small a stop-the-process collection does not take much time.

The downside is that sending messages between processes requires copying all the data that is sent between process heaps.

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