Except that Java already has G1GC[0], a region-based collector. And if you're willing to shell out money there even is a pauseless, fully concurrent collector[1] scaling to hundreds of gigabytes.
Shenandoah[0]. From what I've read it's contributed to openjdk by redhat. Their claims about pause times aren't quite as strong as those of Azul, but <100ms pauses for 100GB+ heaps will still be leagues ahead of most GCs.
It's probably also be less CPU-efficient than azul's, since it uses forwarding pointers instead of page table trickery. But if you have such a large heap you'll also have many cores. Here's a performance comparison to G1[1].
[0] https://docs.oracle.com/javase/8/docs/technotes/guides/vm/gc... [1] https://www.azul.com/products/zing/pgc/