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

[Thomas Stuefe]

On Wed, 11 Sep 2024 12:27:14 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

>> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix FullGCForwarding initialization
>
> src/hotspot/share/memory/classLoaderMetaspace.cpp line 87:
> 
>> 85:         klass_alignment_words,
>> 86:         "class arena");
>> 87:   }
> 
> As per my comment in the header file, change the code to this:
> 
> ```c++
> if (class_context != nullptr) {
>   // ... Same as in PR
> } else {
>   _class_space_arena = _non_class_space_arena;
> }

Rather not, see reasoning under https://github.com/openjdk/jdk/pull/20677/files#r1754330432

> src/hotspot/share/memory/classLoaderMetaspace.cpp line 118:
> 
>> 116: #ifdef ASSERT
>> 117:   if (result.is_nonempty()) {
>> 118:     const bool in_class_arena = class_space_arena() != nullptr ? class_space_arena()->contains(result) : false;
> 
> Unnecessary nullptr check if you take my suggestion, or you should switch to `have_class_space_arena`.

See reasoning under https://github.com/openjdk/jdk/pull/20677/files#r1754335269

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1765113297
PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1765113850