RFR: 8305895: Implementation: JEP 450: Compact Object Headers (Experimental) [v3]

[Aleksey Shipilev]

On Wed, 10 May 2023 14:25:16 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> src/hotspot/share/gc/shenandoah/shenandoahHeap.inline.hpp line 326:
>> 
>>> 324:   oop copy_val = cast_to_oop(copy);
>>> 325:   if (!copy_val->mark().is_marked()) {
>>> 326:     // If we copied a mark-word that indicates 'forwarded' state, then
>> 
>> Ouch. This is only the problem with `UseCompactObjectHeaders`, right? Can additionally conditionalize on that, so that legacy code path stays the same.
>
> I'm actually thinking to maybe upstream these parts separately? Because it seems a nice improvement to not even try to relativize a stack-chunk if object is not reachable anyway?

Yes, upstreaming this separately would be cleaner for this PR. It would also highlight any problems with adjusting the lifecycle for relativization of stack chunks.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13844#discussion_r1190109483