RFR: 8361055: Serial: Inline SerialHeap::process_roots

[Stefan Karlsson]

On Mon, 30 Jun 2025 08:25:09 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Refactor roots processing in Serial (young-gc and full-gc) to clean up the control-flow and make is clearer what roots and closures are used in each context.
> 
> Test: tier1-8

Changes requested by stefank (Reviewer).

src/hotspot/share/gc/serial/defNewGeneration.cpp line 619:

> 617: 
> 618:     _old_gen->scan_old_to_young_refs(_old_gen->space()->top());
> 619:     // During young-gc, visit all (strong+weak) clds with the same closure.

Suggestion:

    _old_gen->scan_old_to_young_refs(_old_gen->space()->top());

    // During young-gc, visit all (strong+weak) clds with the same closure.


I also wonder if the previous placement of `scan_old_to_young_refs` after the other roots were intentional and this PR changes that?

src/hotspot/share/gc/serial/serialFullGC.cpp line 492:

> 490:                                             true);
> 491: 
> 492:     ClassLoaderDataGraph::always_strong_cld_do(&follow_cld_closure);

The old code treated `!ClassUnloading` differently. It's not clear to me why this change is correct.

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PR Review: https://git.openjdk.org/jdk/pull/26038#pullrequestreview-2970440186
PR Review Comment: https://git.openjdk.org/jdk/pull/26038#discussion_r2174571747
PR Review Comment: https://git.openjdk.org/jdk/pull/26038#discussion_r2174574043