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1 /*
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2 * Copyright 2003 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25
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26 // Contains two virtual spaces that each can individually span
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27 // most of the reserved region but committed parts of which
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28 // cannot overlap.
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29 //
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30 // +-------+ <--- high_boundary for H
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31 // | |
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32 // | H |
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33 // | |
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34 // | |
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35 // | |
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36 // --------- <--- low for H
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37 // | |
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38 // ========= <--- low_boundary for H, high_boundary for L
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39 // | |
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40 // | |
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41 // | |
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42 // --------- <--- high for L
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43 // | |
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44 // | L |
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45 // | |
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46 // | |
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47 // | |
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48 // +-------+ <--- low_boundary for L
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49 //
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50 // Each virtual space in the AdjoiningVirtualSpaces grows and shrink
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51 // within its reserved region (between the low_boundary and the
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52 // boundary) independently. If L want to grow above its high_boundary,
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53 // then the high_boundary of L and the low_boundary of H must be
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54 // moved up consistently. AdjoiningVirtualSpaces provide the
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55 // interfaces for moving the this boundary.
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56
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57 class AdjoiningVirtualSpaces {
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58 // space at the high end and the low end, respectively
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59 PSVirtualSpace* _high;
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60 PSVirtualSpace* _low;
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61
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62 // The reserved space spanned by the two spaces.
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63 ReservedSpace _reserved_space;
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64
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65 // The minimum byte size for the low space. It will not
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66 // be shrunk below this value.
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67 size_t _min_low_byte_size;
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68 // Same for the high space
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69 size_t _min_high_byte_size;
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70
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71 const size_t _alignment;
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72
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73 public:
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74 // Allocates two virtual spaces that will be located at the
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75 // high and low ends. Does no initialization.
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76 AdjoiningVirtualSpaces(ReservedSpace rs,
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77 size_t min_low_byte_size,
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78 size_t min_high_byte_size,
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79 size_t alignment);
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80
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81 // accessors
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82 PSVirtualSpace* high() { return _high; }
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83 PSVirtualSpace* low() { return _low; }
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84 ReservedSpace reserved_space() { return _reserved_space; }
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85 size_t min_low_byte_size() { return _min_low_byte_size; }
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86 size_t min_high_byte_size() { return _min_high_byte_size; }
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87 size_t alignment() const { return _alignment; }
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88
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89 // move boundary between the two spaces up
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90 bool adjust_boundary_up(size_t size_in_bytes);
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91 // and down
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92 bool adjust_boundary_down(size_t size_in_bytes);
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93
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94 // Maximum byte size for the high space.
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95 size_t high_byte_size_limit() {
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96 return _reserved_space.size() - _min_low_byte_size;
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97 }
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98 // Maximum byte size for the low space.
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99 size_t low_byte_size_limit() {
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100 return _reserved_space.size() - _min_high_byte_size;
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101 }
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102
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103 // Sets the boundaries for the virtual spaces and commits and
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104 // initial size;
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105 void initialize(size_t max_low_byte_size,
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106 size_t init_low_byte_size,
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107 size_t init_high_byte_size);
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108 };
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