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What is the need of three garbage collector generation? Where are these generations located(physical or logical)?
Different generations need to manage different kinds of objects. Small objects created locally in functions have small live time and small size. They should be controlled in different way comparing to big objects with high live time. Number of generations depends on GC realization. Physical or logical - I do not understand exactly what do you mean, but if GC uses virtual memory it can be considered as logical.