I made a mistake in my pinned-cset change recently. As it is, mark-compact would happily compact pinned-cset regions (because they are also cset). This fixes it: http://cr.openjdk.java.net/~rkennke/pinned-mark-compact/webrev.00/ <http://cr.openjdk.java.net/%7Erkennke/pinned-mark-compact/webrev.00/> Passes hotspot_gc_shenandoah. Ok?