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hotspot/src/share/vm/gc_implementation/parallelScavenge/adjoiningGenerations.hpp

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+/*
+ * Copyright 2003 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+
+// Contains two generations that both use an AdjoiningVirtualSpaces.
+// The two generations are adjacent in the reserved space for the
+// heap.  Each generation has a virtual space and shrinking and
+// expanding of the generations can still be down with that
+// virtual space as was previously done.  If expanding of reserved
+// size of a generation is required, the adjacent generation
+// must be shrunk.  Adjusting the boundary between the generations
+// is called for in this class.
+
+class AdjoiningGenerations : public CHeapObj {
+  friend class VMStructs;
+ private:
+  // The young generation and old generation, respectively
+  PSYoungGen* _young_gen;
+  PSOldGen* _old_gen;
+
+  // The spaces used by the two generations.
+  AdjoiningVirtualSpaces _virtual_spaces;
+
+  // Move boundary up to expand old gen.  Checks are made to
+  // determine if the move can be done with specified limits.
+  void request_old_gen_expansion(size_t desired_change_in_bytes);
+  // Move boundary down to expand young gen.
+  bool request_young_gen_expansion(size_t desired_change_in_bytes);
+
+ public:
+  AdjoiningGenerations(ReservedSpace rs,
+                       size_t init_low_byte_size,
+                       size_t min_low_byte_size,
+                       size_t max_low_byte_size,
+                       size_t init_high_byte_size,
+                       size_t min_high_byte_size,
+                       size_t max_high_bytes_size,
+                       size_t alignment);
+
+  // Accessors
+  PSYoungGen* young_gen() { return _young_gen; }
+  PSOldGen* old_gen() { return _old_gen; }
+
+  AdjoiningVirtualSpaces* virtual_spaces() { return &_virtual_spaces; }
+
+  // Additional space is needed in the old generation.  Check
+  // the available space and attempt to move the boundary if more space
+  // is needed.  The growth is not guaranteed to occur.
+  void adjust_boundary_for_old_gen_needs(size_t desired_change_in_bytes);
+  // Similary for a growth of the young generation.
+  void adjust_boundary_for_young_gen_needs(size_t eden_size, size_t survivor_size);
+
+  // Return the total byte size of the reserved space
+  // for the adjoining generations.
+  size_t reserved_byte_size();
+};