RFR: 8314100: G1: Improve collection set candidate selection code

[Albert Mingkun Yang]

On Fri, 11 Aug 2023 07:36:23 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   discussions during review of [JDK-8140326](https://bugs.openjdk.org/browse/JDK-8140326) indicated that he code surrounding selecting candidates after marking/rebuild for the collection set could be improved.
> 
> Testing: gha
> 
> Thanks,
>   Thomas

src/hotspot/share/gc/g1/g1CollectionSetChooser.cpp line 161:

> 159:         !G1CollectedHeap::heap()->is_old_gc_alloc_region(r) &&
> 160:         G1CollectionSetChooser::region_occupancy_low_enough_for_evac(r->live_bytes()) &&
> 161:         r->rem_set()->is_complete();

Does this work?


assert(!r->rem_set()->is_updating(), "inv");
if (!r->rem_set()->is_complete()) {
  return false;
}
if (G1CollectionSetChooser::region_occupancy_low_enough_for_evac(r->live_bytes())) {
  add_region(r);
} else {
  r->rem_set()->clear(true /* only_cardset */);
}

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/15243#discussion_r1291394499