1 /*
   2  * Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 
  26 // Contains two generations that both use an AdjoiningVirtualSpaces.
  27 // The two generations are adjacent in the reserved space for the
  28 // heap.  Each generation has a virtual space and shrinking and
  29 // expanding of the generations can still be down with that
  30 // virtual space as was previously done.  If expanding of reserved
  31 // size of a generation is required, the adjacent generation
  32 // must be shrunk.  Adjusting the boundary between the generations
  33 // is called for in this class.
  34 
  35 class AdjoiningGenerations : public CHeapObj {
  36   friend class VMStructs;
  37  private:
  38   // The young generation and old generation, respectively
  39   PSYoungGen* _young_gen;
  40   PSOldGen* _old_gen;
  41 
  42   // The spaces used by the two generations.
  43   AdjoiningVirtualSpaces _virtual_spaces;
  44 
  45   // Move boundary up to expand old gen.  Checks are made to
  46   // determine if the move can be done with specified limits.
  47   void request_old_gen_expansion(size_t desired_change_in_bytes);
  48   // Move boundary down to expand young gen.
  49   bool request_young_gen_expansion(size_t desired_change_in_bytes);
  50 
  51  public:
  52   AdjoiningGenerations(ReservedSpace rs,
  53                        size_t init_low_byte_size,
  54                        size_t min_low_byte_size,
  55                        size_t max_low_byte_size,
  56                        size_t init_high_byte_size,
  57                        size_t min_high_byte_size,
  58                        size_t max_high_bytes_size,
  59                        size_t alignment);
  60 
  61   // Accessors
  62   PSYoungGen* young_gen() { return _young_gen; }
  63   PSOldGen* old_gen() { return _old_gen; }
  64 
  65   AdjoiningVirtualSpaces* virtual_spaces() { return &_virtual_spaces; }
  66 
  67   // Additional space is needed in the old generation.  Check
  68   // the available space and attempt to move the boundary if more space
  69   // is needed.  The growth is not guaranteed to occur.
  70   void adjust_boundary_for_old_gen_needs(size_t desired_change_in_bytes);
  71   // Similary for a growth of the young generation.
  72   void adjust_boundary_for_young_gen_needs(size_t eden_size, size_t survivor_size);
  73 
  74   // Return the total byte size of the reserved space
  75   // for the adjoining generations.
  76   size_t reserved_byte_size();
  77 };