This backports the per-region seqnum tracking, which is used by the traversal GC. It doesn't come with a bug-ID because it pre-dates Shenandoah upstreaming. I'd push it together with the Traversal GC backport. Webrev: http://cr.openjdk.java.net/~rkennke/shjdk8-seqnum/webrev.01/ Testing: hotspot_gc_shenandoah Ok? Roman