RFR: Initial sizing refactor [v2]

[William Kemper]

On Wed, 21 Dec 2022 22:17:54 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> William Kemper has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Improve assertions and comments
>
> src/hotspot/share/gc/shenandoah/shenandoahYoungGeneration.hpp line 57:
> 
>> 55:   // Returns true if the young generation is configured to enqueue old
>> 56:   // oops for the old generation mark queues.
>> 57:   bool is_bootstrap_cycle() {
> 
> Why is this called a `bootstrap cycle`? I must be missing some big picture background of nomenclature here.

Every old generation cycle is preceded by a young collection. We call this a bootstrap cycle because it populates the old generation mark queues with old objects it encountered during the marking of young. Otherwise, we'd have to maintain a reverse-remembered set for young->old pointers.

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PR: https://git.openjdk.org/shenandoah/pull/185