RFR: 8315031: YoungPLABSize and OldPLABSize not aligned by ObjectAlignmentInBytes

[Thomas Schatzl]

On Mon, 25 Sep 2023 12:26:26 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Simple fix around unaligned PLAB size. Due to a circular dependency between the heap and PLAB initialization in G1, `_default_plab_size` picks up unaligned PLAB sizes, hence the additional alignment there.

Changes requested by tschatzl (Reviewer).

src/hotspot/share/gc/g1/g1EvacStats.cpp line 136:

> 134: size_t G1EvacStats::desired_plab_size(uint no_of_gc_workers) const {
> 135:   if (!ResizePLAB) {
> 136:       return align_object_size(_default_plab_size);

Maybe a comment about that circular dependency should be added here; please also fix the indentation.

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PR Review: https://git.openjdk.org/jdk/pull/15901#pullrequestreview-1648148860
PR Review Comment: https://git.openjdk.org/jdk/pull/15901#discussion_r1339702168