--- /dev/null	2019-01-23 10:08:26.972556532 +0100
+++ new/src/hotspot/share/gc/g1/g1CollectionSetCandidates.hpp	2019-01-23 10:44:03.012913501 +0100
@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2019, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_GC_G1_G1COLLECTIONSETCANDIDATES_HPP
+#define SHARE_GC_G1_G1COLLECTIONSETCANDIDATES_HPP
+
+#include "gc/g1/g1CollectionSetCandidates.hpp"
+#include "gc/shared/workgroup.hpp"
+#include "memory/allocation.hpp"
+#include "runtime/globals.hpp"
+
+class HeapRegion;
+class HeapRegionClosure;
+
+// Set of collection set candidates, i.e. all old gen regions we consider worth
+// collecting in the remainder of the current mixed phase. Regions are sorted by decreasing
+// gc efficiency.
+// Maintains a cursor into the list that specifies the next collection set candidate
+// to put into the current collection set.
+class G1CollectionSetCandidates : public CHeapObj<mtGC> {
+  HeapRegion** _regions;
+  uint _num_regions; // Total number of regions in the collection set candidate set.
+
+  // The sum of bytes that can be reclaimed in the remaining set of collection
+  // set candidates.
+  size_t _remaining_reclaimable_bytes;
+  // The index of the next candidate old region to be considered for
+  // addition to the current collection set.
+  uint _front_idx;
+
+public:
+  G1CollectionSetCandidates(HeapRegion** regions, uint num_regions, size_t remaining_reclaimable_bytes) :
+    _regions(regions),
+    _num_regions(num_regions),
+    _remaining_reclaimable_bytes(remaining_reclaimable_bytes),
+    _front_idx(0) { }
+
+  ~G1CollectionSetCandidates() {
+    FREE_C_HEAP_ARRAY(HeapRegion*, _regions);
+  }
+
+  // Returns the total number of collection set candidate old regions added.
+  uint num_regions() { return _num_regions; }
+
+  // Return the candidate region at the cursor position to be considered for collection without
+  // removing it.
+  HeapRegion* peek_front() {
+    HeapRegion* res = NULL;
+    if (_front_idx < _num_regions) {
+      res = _regions[_front_idx];
+      assert(res != NULL, "Unexpected NULL HeapRegion at index %u", _front_idx);
+    }
+    return res;
+  }
+
+  // Remove the given region from the candidates set and move the cursor to the next one.
+  HeapRegion* pop_front();
+
+  // Add the given HeapRegion to the front of the collection set candidate set again.
+  void push_front(HeapRegion* hr);
+
+  // Iterate over all remaining collection set candidate regions.
+  void iterate(HeapRegionClosure* cl);
+
+  // Return the number of candidate regions remaining.
+  uint num_remaining() { return _num_regions - _front_idx; }
+
+  bool is_empty() { return num_remaining() == 0; }
+
+  // Return the amount of reclaimable bytes that may be collected by the remaining
+  // candidate regions.
+  size_t remaining_reclaimable_bytes() { return _remaining_reclaimable_bytes; }
+
+  void verify() const PRODUCT_RETURN;
+};
+
+#endif /* SHARE_GC_G1_G1COLLECTIONSETCANDIDATES_HPP */
+