[jdk19] RFR: 8290250: Shenandoah: disable Loom for iu mode

[Y. Srinivas Ramakrishna]

On Wed, 13 Jul 2022 18:39:51 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

> Please review this trivial patch to disable Loom for Shenandoah iu mode (an experimental feature).
> 
> Test:
> - [x] hotspot_gc_shenandoah
> - [x] jdk_loom with Shenandoah + iu
> - [x] hotspot_loom with Shenandoah + iu

CMS collected only old gen, and direct allocations in old gen were grey, and so would updates of black objects in old gen. I assume new objects in Shenandoah would also be grey as would be updates of those objects? (That would be the classical IU scheme in my understanding.)

I should read the Vechev paper though. Is the Shenandoah treatment of new allocations described anywhere for the IU case?

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PR: https://git.openjdk.org/jdk19/pull/140