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@startuml
skinparam monochrome true
title G1: garbage collection flow
:Process not processed cards from CardTable to fill RemSets;
:Add all Eden regions to the Collection Set;
if (Mixed) then(Yes)
    :Select and add some old regions to the Collection Set
     We can use these metrics for selection:
     - last time when this region participated in GC or when it was created
     - number of GCs it survived
     - occupied space;
endif
:Collect Roots for regions in the Collection Set:
Roots from stack
Class roots, string roots etc
__Heap roots collected via RemSets__;
:Mark objects by traversing object stack obtained from the roots;
:Compact: copy marked/alive objects to the old regions(create new if required)
Note: only if occupied by alive objects space in region < some threshold;
:Update references to the moved objects;
:Update RemSets(remove freed regions from RemSets, mark cards with moved objects as "dirty");
:Return freed regions to region space;
stop
@enduml