--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/parallel/adjoiningGenerationsForHeteroHeap.hpp	Fri Dec 21 08:23:55 2018 -0800
@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 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
+ * 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_VM_GC_PARALLEL_ADJOININGGENERATIONSFORHETEROHEAP_HPP
+#define SHARE_VM_GC_PARALLEL_ADJOININGGENERATIONSFORHETEROHEAP_HPP
+
+#include "gc/parallel/adjoiningGenerations.hpp"
+
+class AdjoiningGenerationsForHeteroHeap : public AdjoiningGenerations {
+  friend class VMStructs;
+private:
+  // Maximum total size of the generations. This is equal to the heap size specified by user.
+  // When adjusting young and old generation sizes, we need ensure that sum of the generation sizes does not exceed this.
+  size_t _total_size_limit;
+
+  size_t total_size_limit() const {
+    return _total_size_limit;
+  }
+
+  // HeteroVirtualSpaces creates non-overlapping virtual spaces. Here _low and _high do not share a reserved space, i.e. there is no boundary
+  // separating the two virtual spaces.
+  class HeteroVirtualSpaces : public AdjoiningVirtualSpaces {
+    size_t _max_total_size;
+    size_t _min_old_byte_size;
+    size_t _min_young_byte_size;
+    size_t _max_old_byte_size;
+    size_t _max_young_byte_size;
+
+    // Internally we access the virtual spaces using these methods. It increases readability, since we were not really
+    // dealing with adjoining virtual spaces separated by a boundary as is the case in base class.
+    // Externally they are accessed using low() and high() methods of base class.
+    PSVirtualSpace* young_vs() { return high(); }
+    PSVirtualSpace* old_vs() { return low(); }
+
+  public:
+    HeteroVirtualSpaces(ReservedSpace rs,
+                        size_t min_old_byte_size,
+                        size_t min_young_byte_size, size_t max_total_size,
+                        size_t alignment);
+
+    // Increase old generation size and decrease young generation size by same amount
+    bool adjust_boundary_up(size_t size_in_bytes);
+    // Increase young generation size and decrease old generation size by same amount
+    bool adjust_boundary_down(size_t size_in_bytes);
+
+    size_t max_young_size() const { return _max_young_byte_size; }
+    size_t max_old_size() const { return _max_old_byte_size; }
+
+    void initialize(size_t initial_old_reserved_size, size_t init_low_byte_size,
+                    size_t init_high_byte_size);
+  };
+
+public:
+  AdjoiningGenerationsForHeteroHeap(ReservedSpace rs, GenerationSizer* policy, size_t alignment);
+
+  // Given the size policy, calculate the total amount of memory that needs to be reserved.
+  // We need to reserve more memory than Xmx, since we use non-overlapping virtual spaces for the young and old generations.
+  static size_t required_reserved_memory(GenerationSizer* policy);
+
+  // Return the total byte size of the reserved space
+  size_t reserved_byte_size();
+};
+#endif // SHARE_VM_GC_PARALLEL_ADJOININGGENERATIONSFORHETEROHEAP_HPP
+