P4
SATB queue filtering involves two predicates: (1) does the object need to be marked, and (2) is the object marked.
The first involves getting the object's containing region and comparing the object against the region's TAMS.
A possibly faster, though less precise, test could be made using the card table. The G1 card table has g1_young_card_val() in the cards for young regions. Rather than comparing against the object's region's TAMS, we could filter out just young objects using the card table.
In particular, this approach might be inlined into compiled Java code, sharing some code with the inlined post-barrier, e.g. obtaining the card table.
The first involves getting the object's containing region and comparing the object against the region's TAMS.
A possibly faster, though less precise, test could be made using the card table. The G1 card table has g1_young_card_val() in the cards for young regions. Rather than comparing against the object's region's TAMS, we could filter out just young objects using the card table.
In particular, this approach might be inlined into compiled Java code, sharing some code with the inlined post-barrier, e.g. obtaining the card table.