Currently the remembered set eager reclaim threshold is based on G1RSetSparseRegionEntries. I.e. otherwise eligible humongous objects are only considered candidates for eager reclaim if their remembered set has less than G1RSetSparseRegionEntries entries.

The reason for this limitation has been that before JDK-8233919 (in JDK14) it has been very expensive to get a remembered set size estimate if the remembered set for that heap region had expanded to fine tables.

This is not the case any more, and there are situation where you want to set this threshold (much) larger than the number of sparse table entries.

By default, this new value should still be based on the current value.