RFR: 8310946: G1: Refactor G1Policy::next_gc_should_be_mixed

[Kim Barrett]

On Tue, 27 Jun 2023 11:58:34 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Simple restructuring around `next_gc_should_be_mixed`.
> 
> (After such refactoring, I also tend to think this predicate makes more sense in the caller context, i.e. `bool is_next_gc_mixed = has_marking_candidates();`. For example, one of the call site even asserts `assert(!candidates()->has_more_marking_candidates(),`. Ofc, this is rather subjective.)
> 
> Test: hotspot_gc

Looks good.

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Marked as reviewed by kbarrett (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/14673#pullrequestreview-1506647322