RFR: 8320710: Adjust heap size when close to compressed oops limit [v3]

[Oli Gillespie]

On Mon, 27 Nov 2023 11:32:28 GMT, Oli Gillespie <ogillespie at openjdk.org> wrote:

>> When the heap is between 0 and 2% larger than the compressed oops limit, lower it enough to enable compressed oops. See [issue](https://bugs.openjdk.org/browse/JDK-8320710) for more details.
>> 
>> This is just one way of doing it to show the idea, any other ideas welcome.
>> 
>> Before:
>> 
>> java -Xmx32G -XX:+UseCompressedOops -version
>> OpenJDK 64-Bit Server VM warning: Max heap size too large for Compressed Oops
>> 
>> After:
>> 
>> java -Xmx32G -XX:+UseCompressedOops -version
>> OpenJDK 64-Bit Server VM warning: Heap size lowered from 32G to 32256M to accommodate Compressed Oops
>
> Oli Gillespie has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Fix whitespace
>  - Print human readable heap size

Bumping this after the holidays - I'd appreciate if anyone can take a look.

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PR Comment: https://git.openjdk.org/jdk/pull/16813#issuecomment-1893708244