RFR: 8345732: Provide helpers for using PartialArrayState [v2]

[Kim Barrett]

On Fri, 13 Dec 2024 08:44:13 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Kim Barrett 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 branch 'master' into pa-splitter
>>  - parallel uses PartialArraySplitter
>>  - g1 uses PartialArraySplitter
>>  - add PartialArraySplitter
>>  - add PartialArrayTaskStats
>
> src/hotspot/share/gc/shared/partialArraySplitter.inline.hpp line 45:
> 
>> 43:   PartialArrayTaskStepper::Step step = _stepper.start(length);
>> 44:   // Push any needed partial scan tasks.  Pushed before processing the initial
>> 45:   // chunk to allow other workers to steal while we're processing.
> 
> This comment (last two lines) now imo better belongs to where this method is called. Same with similar comment in `step()`.

I was going to suggest the comment does belong here, but could perhaps be
written more clearly. But on further consideration, I don't think this comment
is needed at all. That behavior is the whole point of the splitter class, as
somewhat discussed in the comments in the header. I've expanded the comments
there to be more explicit.

Also, I really don't want to need to be adding comments about this to each
current and future caller. Part of the point of this class is to minimize the
amount of duplication among clients, and needing (near) duplicated comments
would count against that.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22622#discussion_r1884397894