RFR: 8256302: releasing oopStorage when deflating allows for faster deleting [v5]

[Daniel D. Daugherty]

On Sun, 4 Jun 2023 14:18:41 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

>> Releasing ObjectMonitor oopStorage earlier when deflating allows ObjectMonitor
>> deletion by a JavaThread (usually the MonitorDeflationThread) to happen while a
>> ThreadBlockInVM helper is in place. This should improve time-to-safepoint.
>
> Daniel D. Daugherty has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:
> 
>  - Merge tag 'jdk-21+25' into JDK-8256302
>    
>    Added tag jdk-21+25 for changeset a46b5acc
>  - Allow ObjectMonitor::_object to be reset to nullptr when it is released which allows the code to be cleaner.
>  - Merge tag 'jdk-21+23' into JDK-8256302
>    
>    Added tag jdk-21+23 for changeset 6d4782bc
>  - address the easy dholmes and kimbarrett CR comments
>  - 8256302: releasing oopStorage when deflating allows for faster deleting

Eric Caspole did another round of perf testing on these bits, I did some analysis on the
perf results and Eric wrote in the bug:

> IMO the performance of Dan's build is within the range of variation in a normal promo build,
> and there are no important regressions or improvements requiring further investigation.
> This result seems good to me.

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PR Comment: https://git.openjdk.org/jdk/pull/11296#issuecomment-1581424422