RFR: 8367240: Parallel: Refactor PSScavengeCLDClosure

[Stefan Karlsson]

On Tue, 9 Sep 2025 08:59:10 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Refactor `PSScavengeCLDClosure` and its "enclosing" `PSScavengeFromCLDClosure` so that all CLD logic is encapsulated in the CLD closure, without polluting the oop closure.
> 
> Test: tier1-3

src/hotspot/share/gc/parallel/psClosure.inline.hpp line 118:

> 116:     if (cld->has_modified_oops()) {
> 117:       // Reset before iterating oops.
> 118:       _oop_closure._has_oop_into_young_gen = false;

I wonder if this wouldn't be cleaner if you set up a new `PSScavengeFromCLDClosure` here instead. Then you wouldn't have to explicitly reset _has_oop_into_young_gen here. 

    if (cld->has_modified_oops()) {
      PSScavengeFromCLDClosure oop_closure(_pm);

      // Clean the cld since we're going to scavenge all the metadata.
      cld->oops_do(&oop_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);

      if (oop_closure.has_oops_into_young_gen()) {
        cld->record_modified_oops();
      }
    }


Maybe you don't have to hide `PSScavengeFromCLDClosure` inside `PSScavengeCLDClosure`. I find it more distracting that what we had before. If you don't agree with that, maybe the PSScavengeCLDClosure name could be changed so that we don't repeat the PSScavenge prefix for the internal class.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27165#discussion_r2333135554