I concede that my arguments were directed primarily at Haskell and actually more about data structure reuse than about GC. The threading model and task affinity

I concede that my arguments were directed primarily at Haskell and actually more about data structure reuse than about GC. The threading model and task affinity is also relevant: if a compacting GC moves a hot data structure to a different memory bank, performance can be much slower. In principle, a runtime (with kernel support, libnuma may be sufficient on Linux) could set thread affinity, trace the page table for each (core,thread) pairs, and then have the compacting GC migrate threads and memory so that threads tended to use local memory. In principle, this could give better performance than most static distribution schemes, but this tracing costs something and to my knowledge, this sort of NUMA-aware GC is still a research topic.