RFR: 8338977: Parallel: Improve heap resizing heuristics [v2]

[Albert Mingkun Yang]

On Sun, 18 May 2025 13:53:53 GMT, Guoxiong Li <gli at openjdk.org> wrote:

>> Albert Mingkun Yang 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 three additional commits since the last revision:
>> 
>>  - review
>>  - Merge branch 'master' into pgc-size-policy
>>  - pgc-size-policy
>
> src/hotspot/share/gc/parallel/psAdaptiveSizePolicy.cpp line 232:
> 
>> 230:     // Major times are too long, so we want less promotion.
>> 231:     incr_tenuring_threshold = true;
>> 232:   }
> 
> You keep the condition `minor_cost > major_cost * _threshold_tolerance_percent` of the previous code. But it will be strange when we only read the new code (in the future). What about removing the condition `minor_cost > major_cost * _threshold_tolerance_percent` and moving the comment `we prefer young-gc over full-gc` to another place?

I keep it this way because I find the structure to be more symmetric, but I don't have a strong opinion on this. If you prefer, I can remove the empty if-branch. (The resulting asm should be identical.)

> When is_survivor_overflow is false, the promoted is 0

That's not true; objs that live long enough will be promoted as well, even when the survivor-space has plenty of free-space.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25000#discussion_r2094855103
PR Review Comment: https://git.openjdk.org/jdk/pull/25000#discussion_r2094856261