RFR: 8305895: Implement JEP 450: Compact Object Headers (Experimental) [v21]

[Thomas Stuefe]

On Thu, 19 Sep 2024 05:44:42 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

>> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   JVMCI support
>
> src/hotspot/share/oops/compressedKlass.cpp line 231:
> 
>> 229:     // The reason is that we want to avoid, if possible, shifts larger than
>> 230:     // a cacheline size.
>> 231:     _base = addr;
> 
> Why is this important?

It lessens the cache effects of Klass hyperaligning.

> src/hotspot/share/oops/compressedKlass.hpp line 261:
> 
>> 259:   }
>> 260: 
>> 261: };
> 
> Missing blank line before `#endif`

Fixed

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

PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1766684016
PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1766684491