--- old/src/share/vm/gc/g1/collectionSetChooser.cpp	2017-03-21 16:20:02.689431778 -0400
+++ new/src/share/vm/gc/g1/collectionSetChooser.cpp	2017-03-21 16:20:01.477361756 -0400
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -210,45 +210,42 @@
   _remaining_reclaimable_bytes = 0;
 }
 
-class ParKnownGarbageHRClosure: public HeapRegionClosure {
-  G1CollectedHeap* _g1h;
-  CSetChooserParUpdater _cset_updater;
-
-public:
-  ParKnownGarbageHRClosure(CollectionSetChooser* hrSorted,
-                           uint chunk_size) :
-    _g1h(G1CollectedHeap::heap()),
-    _cset_updater(hrSorted, true /* parallel */, chunk_size) { }
-
-  bool doHeapRegion(HeapRegion* r) {
-    // Do we have any marking information for this region?
-    if (r->is_marked()) {
-      // We will skip any region that's currently used as an old GC
-      // alloc region (we should not consider those for collection
-      // before we fill them up).
-      if (_cset_updater.should_add(r) && !_g1h->is_old_gc_alloc_region(r)) {
-        _cset_updater.add_region(r);
+class ParKnownGarbageTask: public G1ParallelizeByRegionsTask {
+  class ParKnownGarbageHRClosure: public HeapRegionClosure {
+    G1CollectedHeap* _g1h;
+    CSetChooserParUpdater _cset_updater;
+
+  public:
+    ParKnownGarbageHRClosure(CollectionSetChooser* hrSorted,
+                             uint chunk_size) :
+      _g1h(G1CollectedHeap::heap()),
+      _cset_updater(hrSorted, true /* parallel */, chunk_size) { }
+
+    bool doHeapRegion(HeapRegion* r) {
+      // Do we have any marking information for this region?
+      if (r->is_marked()) {
+        // We will skip any region that's currently used as an old GC
+        // alloc region (we should not consider those for collection
+        // before we fill them up).
+        if (_cset_updater.should_add(r) && !_g1h->is_old_gc_alloc_region(r)) {
+          _cset_updater.add_region(r);
+        }
       }
+      return false;
     }
-    return false;
-  }
-};
+  };
 
-class ParKnownGarbageTask: public AbstractGangTask {
   CollectionSetChooser* _hrSorted;
   uint _chunk_size;
-  G1CollectedHeap* _g1;
-  HeapRegionClaimer _hrclaimer;
 
 public:
   ParKnownGarbageTask(CollectionSetChooser* hrSorted, uint chunk_size, uint n_workers) :
-      AbstractGangTask("ParKnownGarbageTask"),
-      _hrSorted(hrSorted), _chunk_size(chunk_size),
-      _g1(G1CollectedHeap::heap()), _hrclaimer(n_workers) {}
+      G1ParallelizeByRegionsTask("ParKnownGarbageTask", n_workers),
+      _hrSorted(hrSorted), _chunk_size(chunk_size) {}
 
   void work(uint worker_id) {
     ParKnownGarbageHRClosure parKnownGarbageCl(_hrSorted, _chunk_size);
-    _g1->heap_region_par_iterate(&parKnownGarbageCl, worker_id, &_hrclaimer);
+    all_heap_regions_work(&parKnownGarbageCl, worker_id);
   }
 };