diff -r 4ebc2e2fb97c -r 71c04702a3d5 src/hotspot/share/gc/g1/g1YoungGenSizer.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/g1/g1YoungGenSizer.hpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,109 @@
+/*
+ * Copyright (c) 2016, 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_G1_G1YOUNGGENSIZER_HPP
+#define SHARE_VM_GC_G1_G1YOUNGGENSIZER_HPP
+
+#include "memory/allocation.hpp"
+
+// There are three command line options related to the young gen size:
+// NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is
+// just a short form for NewSize==MaxNewSize). G1 will use its internal
+// heuristics to calculate the actual young gen size, so these options
+// basically only limit the range within which G1 can pick a young gen
+// size. Also, these are general options taking byte sizes. G1 will
+// internally work with a number of regions instead. So, some rounding
+// will occur.
+//
+// If nothing related to the the young gen size is set on the command
+// line we should allow the young gen to be between G1NewSizePercent
+// and G1MaxNewSizePercent of the heap size. This means that every time
+// the heap size changes, the limits for the young gen size will be
+// recalculated.
+//
+// If only -XX:NewSize is set we should use the specified value as the
+// minimum size for young gen. Still using G1MaxNewSizePercent of the
+// heap as maximum.
+//
+// If only -XX:MaxNewSize is set we should use the specified value as the
+// maximum size for young gen. Still using G1NewSizePercent of the heap
+// as minimum.
+//
+// If -XX:NewSize and -XX:MaxNewSize are both specified we use these values.
+// No updates when the heap size changes. There is a special case when
+// NewSize==MaxNewSize. This is interpreted as "fixed" and will use a
+// different heuristic for calculating the collection set when we do mixed
+// collection.
+//
+// If only -XX:NewRatio is set we should use the specified ratio of the heap
+// as both min and max. This will be interpreted as "fixed" just like the
+// NewSize==MaxNewSize case above. But we will update the min and max
+// every time the heap size changes.
+//
+// NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is
+// combined with either NewSize or MaxNewSize. (A warning message is printed.)
+class G1YoungGenSizer VALUE_OBJ_CLASS_SPEC {
+private:
+  enum SizerKind {
+    SizerDefaults,
+    SizerNewSizeOnly,
+    SizerMaxNewSizeOnly,
+    SizerMaxAndNewSize,
+    SizerNewRatio
+  };
+  SizerKind _sizer_kind;
+  uint _min_desired_young_length;
+  uint _max_desired_young_length;
+
+  // False when using a fixed young generation size due to command-line options,
+  // true otherwise.
+  bool _adaptive_size;
+
+  uint calculate_default_min_length(uint new_number_of_heap_regions);
+  uint calculate_default_max_length(uint new_number_of_heap_regions);
+
+  // Update the given values for minimum and maximum young gen length in regions
+  // given the number of heap regions depending on the kind of sizing algorithm.
+  void recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length);
+
+public:
+  G1YoungGenSizer();
+  // Calculate the maximum length of the young gen given the number of regions
+  // depending on the sizing algorithm.
+  void adjust_max_new_size(uint number_of_heap_regions);
+
+  void heap_size_changed(uint new_number_of_heap_regions);
+  uint min_desired_young_length() const {
+    return _min_desired_young_length;
+  }
+  uint max_desired_young_length() const {
+    return _max_desired_young_length;
+  }
+
+  bool adaptive_young_list_length() const {
+    return _adaptive_size;
+  }
+};
+
+#endif // SHARE_VM_GC_G1_G1YOUNGGENSIZER_HPP