Question

How Generational GC works ?
Totally what is Generational GC ?

thanks

Answer 1

Wikipedia’s explanation.

A generational GC (also known as
ephemeral GC) divides objects into
generations and, on most cycles, will
place only the objects of a subset of
generations into the initial white
(condemned) set. Furthermore, the
runtime system maintains knowledge of
when references cross generations by
observing the creation and overwriting
of references. When the garbage
collector runs, it may be able to use
this knowledge to prove that some
objects in the initial white set are
unreachable without having to traverse
the entire reference tree. If the
generational hypothesis holds, this
results in much faster collection
cycles while still reclaiming most
unreachable objects.

Basically, it’s a heuristic approach. The Garbage collection puts newly created objects in a memory region (called white set), when this set is full, those objects that are still referenced are moved to another region, and the white set is cleared and populated with fresh new objects. The white set is the hypothesis that the objects found there are generally unreachable.

For further reading on JVM Fine-Tuning of Garbage Collection.