RFR: 8338977: Parallel: Improve heap resizing heuristics [v3]

[Albert Mingkun Yang]

On Sun, 18 May 2025 18:06:15 GMT, Guoxiong Li <gli at openjdk.org> wrote:

>> src/hotspot/share/gc/parallel/parallelScavengeHeap.cpp line 343:
>> 
>>> 341:       if (_gc_overhead_counter >= GCOverheadLimitThreshold) {
>>> 342:         return nullptr;
>>> 343:       }
>> 
>> Returning `nullptr` means the `OutOfMemoryError` will be thrown later. Is it good to add a `error` level log here?
>
> And notice: we can't identify whether the `OutOfMemoryError` is because of `gc overhead limit exceeded`.
> 
> As I pointed out before: `the field MemAllocator::Allocation::_overhead_limit_exceeded are not used now`.

The one inside the safepoint will print sth `log_info(gc)("GCOverheadLimitThreshold ...`. There can be multiple concurrent mutators reaching here; printing here is undesirable.

I don't think throwing OOM, from gc's perspective, is an "error".

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PR Review Comment: https://git.openjdk.org/jdk/pull/25000#discussion_r2094899794