RFR: Load balance remembered set scanning [v2]

[Kelvin Nilsen]

On Thu, 28 Jul 2022 19:18:20 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> This branch divides remembered set scanning into smaller units of work so that multiple cores can more effectively share the workload between them.  The benefit is to reduce concurrent scan remembered set times and to increase the parallelism of this phase.
>
> Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Respond to reviewer comments

I should also emphasize that there are other benefits besides reduced coordination overhead to scanning larger numbers of chunks at a time.  For example, the code that Ramki is working on can cache the starting location of a large object that spans multiple chunks most easily if the starting location is within the range of its current work assignment.

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PR: https://git.openjdk.org/shenandoah/pull/153