RFR: 8305895: Implementation: JEP 450: Compact Object Headers (Experimental) [v11]

[Roman Kennke]

On Fri, 12 May 2023 09:22:01 GMT, Erik Österlund <eosterlund at openjdk.org> wrote:

>> Roman Kennke has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Fix some uses of klass_offset_in_bytes()
>>  - Fix args checking
>
> src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp line 253:
> 
>> 251:     // The copy above is not atomic. Make sure we have seen the proper mark
>> 252:     // and re-install it into the copy, so that Klass* is guaranteed to be correct.
>> 253:     markWord mark = o->mark_acquire();
> 
> I don't think we need the acquire here, do we?

Right. An atomic load would be sufficient, which is what oopDesc::mark() already does. I change those code paths to use just mark().

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PR Review Comment: https://git.openjdk.org/jdk/pull/13844#discussion_r1192208296