The G1 garbage collector further reduces remembered set memory overhead and pause-time by allowing multiple regions to share a single internal structure (G1CardSet) when they are likely to be collected together during a Mixed GC.

Previously, each region maintained its own G1CardSet, resulting in high memory overhead and redundant tracking of references between regions that would eventually be collected as a group. In the new design, regions expected to be evacuated together are grouped after the Remark phase and assigned a shared G1CardSet, eliminating the need to track references between them individually.

This improves memory efficiency and reduces merge time during collection pauses.