The generation number affected.
The number of garbage collections survived by objects in that generation, before promotion. If count is
nil
, the function returns the current promotion count setting.
Specifies which segment of the generation is to be affected. The default is the lowest segment of the generation.
Controls how many garbage collections an object in a segment must survive before promotion to the next generation.
block-promotion
clean-generation-0
collect-generation-2
collect-highest-generation
expand-generation-1