RFR: 8356716: ZGC: Cleanup Uncommit Logic [v3]

[Axel Boldt-Christmas]

On Mon, 26 May 2025 13:45:03 GMT, Joel Sikström <jsikstro at openjdk.org> wrote:

>> Axel Boldt-Christmas 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 18 additional commits since the last revision:
>> 
>>  - Merge remote-tracking branch 'upstream_jdk/master' into JDK-8356716
>>  - Wrong too
>>  - Less archaic spelling of complete
>>  - Cleanup and simplify
>>  - Move all uncommit logic to zUncommitter
>>  - Log time spent uncommitting
>>  - Split reset_uncommit_cycle and add headroom
>>  - Rename _min_last_uncommit_cycle to _min_size_watermark
>>  - Use milliseconds instead of seconds
>>  - Improve events and statistics
>>  - ... and 8 more: https://git.openjdk.org/jdk/compare/6ee4af7a...43c0795a
>
> src/hotspot/share/gc/z/zUncommitter.cpp line 116:
> 
>> 114:         // Done
>> 115:         break;
>> 116:       }
> 
> Is it possible to convert this to something like the following to make it clearer that this is the "end condition" of the cycle? From what I can see, 2/3 paths that return 0 in `uncommit()` calls `cancel_uncommit_cycle()`.
> Suggestion:
> 
>       if (uncommit_cycle_is_canceled() || uncommit_cycle_is_finished()) {
>         // No more work, cycle is done.
>         break;
>       }

It is used as a proxy to not have to retake the lock. Will add a comment.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25198#discussion_r2108258237