--- old/src/hotspot/share/gc/parallel/psParallelCompact.cpp	2018-05-02 11:09:00.071066481 +0200
+++ new/src/hotspot/share/gc/parallel/psParallelCompact.cpp	2018-05-02 11:08:59.785057708 +0200
@@ -117,6 +117,7 @@
 
 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
 
+SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
 ReferenceProcessor* PSParallelCompact::_ref_processor = NULL;
 
 double PSParallelCompact::_dwl_mean;
@@ -843,14 +844,14 @@
 
 void PSParallelCompact::post_initialize() {
   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
-  MemRegion mr = heap->reserved_region();
+  _span_based_discoverer.set_span(heap->reserved_region());
   _ref_processor =
-    new ReferenceProcessor(mr,            // span
+    new ReferenceProcessor(&_span_based_discoverer,
                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
-                           ParallelGCThreads, // mt processing degree
-                           true,              // mt discovery
-                           ParallelGCThreads, // mt discovery degree
-                           true,              // atomic_discovery
+                           ParallelGCThreads,   // mt processing degree
+                           true,                // mt discovery
+                           ParallelGCThreads,   // mt discovery degree
+                           true,                // atomic_discovery
                            &_is_alive_closure); // non-header is alive closure
   _counters = new CollectorCounters("PSParallelCompact", 1);