I would like to have more insight in what ParallelCleanupTask is doing: http://cr.openjdk.java.net/~shade/shenandoah/stats-parallelclean/webrev.01/ Produces output like this: http://cr.openjdk.java.net/~shade/shenandoah/stats-parallelclean/stats.txt Testing: hotspot_gc_shenandoah, some benchmarks Thanks, -Aleksey