[KMag]

Minor nit: the description above is true for copying GCs, but non-copying mark-sweep collectors generally still touch the header words of both live and dead objects in the heap in order to add dead objects to free lists. Mark-sweep-compact collectors also end up reading all of the mark words in the object headers of both live and dead objects in order to find the holes to be filled by compaction.

It's also not uncommon to have a copying young generation and a mark-sweep-compact tenured generation. That way, you get the advantages of not needing to scan the huge numbers of young dead objects, but the space savings of not needing 2x space for the older generation.