So we are agreed that mixing tracing GCs with any other form of memory management (including another GC) is an unsolved problem. Good. Swift is a disaster, al

So we are agreed that mixing tracing GCs with any other form of memory management (including another GC) is an unsolved problem. Good. Swift is a disaster, also agreed. So? For the rest: actual research disagrees with your forceful but unsubstantiated assertion: https://2013.splashcon.org/details/oopsla-2013-papers/21/Taking-Off-the-Gloves-with-Reference-Counting-Immix https://2013.splashcon.org/details/oopsla-2013-papers/21/Tak... And once again, tracing GCs do well in microbenchmarks where you only check the cost of local operations. They are horrible when you take the global effects into account, with those local/benchmarking advantages not translating into real world use. https://people.cs.umass.edu/~emery/pubs/gcvsmalloc.pdf https://people.cs.umass.edu/~emery/pubs/gcvsmalloc.pdf Very similar to JITs, which also do massively better in microbenchmarks than in production code: http://blog.metaobject.com/2015/10/jitterdammerung.html http://blog.metaobject.com/2015/10/jitterdammerung.html Oh, and integrating well and without high cost to fast languages where you have even more control is actually an important feature.