diff -r ca5978b8378b -r 784f3f2dea14 src/hotspot/share/gc/g1/collectionSetChooser.hpp
--- a/src/hotspot/share/gc/g1/collectionSetChooser.hpp	Mon Mar 26 16:51:41 2018 +0200
+++ b/src/hotspot/share/gc/g1/collectionSetChooser.hpp	Mon Mar 26 16:51:43 2018 +0200
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2018, 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
@@ -101,17 +101,18 @@
 
   CollectionSetChooser();
 
+  static size_t mixed_gc_live_threshold_bytes() {
+    return HeapRegion::GrainBytes * (size_t) G1MixedGCLiveThresholdPercent / 100;
+  }
+
+  static bool region_occupancy_low_enough_for_evac(size_t live_bytes);
+
   void sort_regions();
 
   // Determine whether to add the given region to the CSet chooser or
   // not. Currently, we skip pinned regions and regions whose live
   // bytes are over the threshold. Humongous regions may be reclaimed during cleanup.
-  bool should_add(HeapRegion* hr) {
-    assert(hr->is_marked(), "pre-condition");
-    assert(!hr->is_young(), "should never consider young regions");
-    return !hr->is_pinned() &&
-            hr->live_bytes() < _region_live_threshold_bytes;
-  }
+  bool should_add(HeapRegion* hr) const;
 
   // Returns the number candidate old regions added
   uint length() { return _end; }
@@ -133,6 +134,9 @@
   // and the amount of reclaimable bytes by reclaimable_bytes.
   void update_totals(uint region_num, size_t reclaimable_bytes);
 
+  // Iterate over all collection set candidate regions.
+  void iterate(HeapRegionClosure* cl);
+
   void clear();
 
   void rebuild(WorkGang* workers, uint n_regions);