On Fri, 30 Aug 2024 11:15:23 GMT, Stefan Karlsson <stef...@openjdk.org> wrote:
>> I was thinking the same, but there's a problem with that. If we get a >> promotion failure in the young gen, we are leaving the dead objects marked >> as forwarded. Then when the Full GC scans these regions with dead objects it >> will mistakenly think that they have been marked alive because >> `is_forwarded() == is_gc_marked()`. The code in `phase2_calculate_new_addr` >> will then break when it looks for `is_gc_marked` objects. > > FWIW, the ParallelGC does something very similar to what you propose, except > that it walks bitmaps instead of paring the space to find the self-forwarded > objects. It then has a check inside object_iterate to make sure that it > doesn't expose the dead objects (in eden and the from space) to heap dumpers > and histogram printers. > > Because of the the code above, the SerialGC clears away the information about > what objects are dead in eden and the from space, so heap dumpers and > histogram printers will include these dead objects. We might want to fix that > as a future RFE. > If we get a promotion failure in the young gen, we are leaving the dead > objects marked as forwarded. True; need to do sth like `obj->init_mark();` for the non-self-forwarded case. The postcondition is that no forwarded objs in eden/from. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1739218189
