RFR: 8274178: G1: Occupancy value in IHOP logging and JFR event is inaccurate [v4]

[Thomas Schatzl]

On Tue, 11 Nov 2025 15:08:23 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Hi all,
>> 
>>   please review this change that modifies heap occupancy reporting for IHOP to use the actual occupancy value the IHOP calculation actually uses.
>> 
>> I.e. previously IHOP logging used to report `G1CollectedHeap::used()` as occupancy (which is correct at a general level), but for IHOP/marking that value is not interesting, but the "occupancy" value used for comparing against the current heap occupancy threshold.
>> 
>> Testing: tier1-3, GHA
>> 
>> Thomas
>
> Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:
> 
>   * fix compilation on osx

Please hold off further reviewing it seems like the changes for [JDK-8371635](https://bugs.openjdk.org/browse/JDK-8371635) I rolled into this PR cause different concurrent mark starts. I'll separate it out again if it does.

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PR Comment: https://git.openjdk.org/jdk/pull/28175#issuecomment-3517366887