What is the difference between mark-and-sweep GC and generational GC in Ruby architecture?

Mark-and-sweep is the base algorithm; generational GC is an optimization layered on top.

Mark-and-sweep traverses all reachable objects and frees unreachable ones. Generational GC improves this by splitting heap into young and old generations. Most allocations occur in young space, making GC cycles cheaper. Write barriers maintain cross-generation references. Ruby combines both approaches with incremental marking to reduce pause times.