>Write barriers are not necessary if an object is in a nursery, which is true for most objects per the generational hypothesis. This is trivial to check based o

>Write barriers are not necessary if an object is in a nursery, which is true for most objects per the generational hypothesis. This is trivial to check based on the pointer value. Yes but what when it leaves it? You have to update all pointers to another location. When it passes to the Gen2 slab all references that point to it need to be updated, and those changes need to propagate to all threads, and all cores. The simplest way to do this is a memory barrier. Well the real simplest way is just "never multi-thread" and this is OCaml's GC is so fast. No write barriers, 1 thread only, final destination.