1 /*
   2  * Copyright (c) 2003, 2018, 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
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  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_GC_PARALLEL_ADJOININGVIRTUALSPACES_HPP
  26 #define SHARE_VM_GC_PARALLEL_ADJOININGVIRTUALSPACES_HPP
  27 
  28 #include "gc/parallel/psVirtualspace.hpp"
  29 
  30 
  31 // Contains two virtual spaces that each can individually span
  32 // most of the reserved region but committed parts of which
  33 // cannot overlap.
  34 //
  35 //      +-------+ <--- high_boundary for H
  36 //      |       |
  37 //      |   H   |
  38 //      |       |
  39 //      |       |
  40 //      |       |
  41 //      --------- <--- low for H
  42 //      |       |
  43 //      ========= <--- low_boundary for H, high_boundary for L
  44 //      |       |
  45 //      |       |
  46 //      |       |
  47 //      --------- <--- high for L
  48 //      |       |
  49 //      |   L   |
  50 //      |       |
  51 //      |       |
  52 //      |       |
  53 //      +-------+ <--- low_boundary for L
  54 //
  55 // Each virtual space in the AdjoiningVirtualSpaces grows and shrink
  56 // within its reserved region (between the low_boundary and the
  57 // boundary) independently.  If L want to grow above its high_boundary,
  58 // then the high_boundary of L and the low_boundary of H must be
  59 // moved up consistently.  AdjoiningVirtualSpaces provide the
  60 // interfaces for moving the this boundary.
  61 
  62 class AdjoiningVirtualSpaces {
  63   // space at the high end and the low end, respectively
  64   PSVirtualSpace*    _high;
  65   PSVirtualSpace*    _low;
  66 
  67   // The reserved space spanned by the two spaces.
  68   ReservedSpace      _reserved_space;
  69 
  70   // The minimum byte size for the low space.  It will not
  71   // be shrunk below this value.
  72   size_t _min_low_byte_size;
  73   // Same for the high space
  74   size_t _min_high_byte_size;
  75 
  76   const size_t _alignment;
  77 
  78   int _nvdimm_fd;
  79 
  80  public:
  81   // Allocates two virtual spaces that will be located at the
  82   // high and low ends.  Does no initialization.
  83   AdjoiningVirtualSpaces(ReservedSpace rs,
  84                          size_t min_low_byte_size,
  85                          size_t min_high_byte_size,
  86                          size_t alignment);
  87 
  88   // accessors
  89   PSVirtualSpace* high() { return _high; }
  90   PSVirtualSpace* low()  { return _low; }
  91   ReservedSpace reserved_space() { return _reserved_space; }
  92   size_t min_low_byte_size() { return _min_low_byte_size; }
  93   size_t min_high_byte_size() { return _min_high_byte_size; }
  94   size_t alignment() const { return _alignment; }
  95 
  96   // move boundary between the two spaces up
  97   bool adjust_boundary_up(size_t size_in_bytes);
  98   // and down
  99   bool adjust_boundary_down(size_t size_in_bytes);
 100 
 101   // Maximum byte size for the high space.
 102   size_t high_byte_size_limit() {
 103     return _reserved_space.size() - _min_low_byte_size;
 104   }
 105   // Maximum byte size for the low space.
 106   size_t low_byte_size_limit() {
 107     return _reserved_space.size() - _min_high_byte_size;
 108   }
 109 
 110   // Sets the boundaries for the virtual spaces and commits and
 111   // initial size;
 112   void initialize(size_t max_low_byte_size,
 113                   size_t init_low_byte_size,
 114                   size_t init_high_byte_size);
 115   void setup_fd(int fd) {_nvdimm_fd = fd;   }
 116   int nvdimm_fd() const {return _nvdimm_fd; }
 117 };
 118 
 119 #endif // SHARE_VM_GC_PARALLEL_ADJOININGVIRTUALSPACES_HPP