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1 /* |
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2 * Copyright (c) 2014, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
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22 * |
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23 */ |
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24 |
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25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1INCSETSTATE_HPP |
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26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1INCSETSTATE_HPP |
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27 |
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28 #include "gc_implementation/g1/g1BiasedArray.hpp" |
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29 #include "memory/allocation.hpp" |
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30 |
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31 // Per-region state during garbage collection. |
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32 struct InCSetState { |
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33 public: |
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34 // We use different types to represent the state value. Particularly SPARC puts |
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35 // values in structs from "left to right", i.e. MSB to LSB. This results in many |
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36 // unnecessary shift operations when loading and storing values of this type. |
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37 // This degrades performance significantly (>10%) on that platform. |
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38 // Other tested ABIs do not seem to have this problem, and actually tend to |
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39 // favor smaller types, so we use the smallest usable type there. |
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40 #ifdef SPARC |
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41 #define CSETSTATE_FORMAT INTPTR_FORMAT |
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42 typedef intptr_t in_cset_state_t; |
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43 #else |
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44 #define CSETSTATE_FORMAT "%d" |
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45 typedef int8_t in_cset_state_t; |
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46 #endif |
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47 private: |
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48 in_cset_state_t _value; |
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49 public: |
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50 enum { |
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51 // Selection of the values were driven to micro-optimize the encoding and |
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52 // frequency of the checks. |
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53 // The most common check is whether the region is in the collection set or not. |
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54 // This encoding allows us to use an != 0 check which in some architectures |
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55 // (x86*) can be encoded slightly more efficently than a normal comparison |
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56 // against zero. |
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57 // The same situation occurs when checking whether the region is humongous |
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58 // or not, which is encoded by values < 0. |
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59 // The other values are simply encoded in increasing generation order, which |
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60 // makes getting the next generation fast by a simple increment. |
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61 Humongous = -1, // The region is humongous - note that actually any value < 0 would be possible here. |
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62 NotInCSet = 0, // The region is not in the collection set. |
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63 Young = 1, // The region is in the collection set and a young region. |
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64 Old = 2, // The region is in the collection set and an old region. |
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65 Num |
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66 }; |
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67 |
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68 InCSetState(in_cset_state_t value = NotInCSet) : _value(value) { |
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69 assert(is_valid(), err_msg("Invalid state %d", _value)); |
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70 } |
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71 |
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72 in_cset_state_t value() const { return _value; } |
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73 |
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74 void set_old() { _value = Old; } |
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75 |
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76 bool is_in_cset_or_humongous() const { return _value != NotInCSet; } |
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77 bool is_in_cset() const { return _value > NotInCSet; } |
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78 bool is_humongous() const { return _value < NotInCSet; } |
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79 bool is_young() const { return _value == Young; } |
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80 bool is_old() const { return _value == Old; } |
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81 |
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82 #ifdef ASSERT |
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83 bool is_default() const { return !is_in_cset_or_humongous(); } |
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84 bool is_valid() const { return (_value >= Humongous) && (_value < Num); } |
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85 bool is_valid_gen() const { return (_value >= Young && _value <= Old); } |
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86 #endif |
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87 }; |
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88 |
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89 // Instances of this class are used for quick tests on whether a reference points |
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90 // into the collection set and into which generation or is a humongous object |
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91 // |
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92 // Each of the array's elements indicates whether the corresponding region is in |
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93 // the collection set and if so in which generation, or a humongous region. |
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94 // |
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95 // We use this to speed up reference processing during young collection and |
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96 // quickly reclaim humongous objects. For the latter, by making a humongous region |
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97 // succeed this test, we sort-of add it to the collection set. During the reference |
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98 // iteration closures, when we see a humongous region, we then simply mark it as |
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99 // referenced, i.e. live. |
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100 class G1InCSetStateFastTestBiasedMappedArray : public G1BiasedMappedArray<InCSetState> { |
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101 protected: |
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102 InCSetState default_value() const { return InCSetState::NotInCSet; } |
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103 public: |
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104 void set_humongous(uintptr_t index) { |
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105 assert(get_by_index(index).is_default(), |
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106 err_msg("State at index " INTPTR_FORMAT" should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value())); |
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107 set_by_index(index, InCSetState::Humongous); |
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108 } |
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109 |
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110 void clear_humongous(uintptr_t index) { |
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111 set_by_index(index, InCSetState::NotInCSet); |
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112 } |
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113 |
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114 void set_in_young(uintptr_t index) { |
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115 assert(get_by_index(index).is_default(), |
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116 err_msg("State at index " INTPTR_FORMAT" should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value())); |
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117 set_by_index(index, InCSetState::Young); |
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118 } |
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119 |
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120 void set_in_old(uintptr_t index) { |
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121 assert(get_by_index(index).is_default(), |
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122 err_msg("State at index " INTPTR_FORMAT" should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value())); |
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123 set_by_index(index, InCSetState::Old); |
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124 } |
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125 |
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126 bool is_in_cset_or_humongous(HeapWord* addr) const { return at(addr).is_in_cset_or_humongous(); } |
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127 bool is_in_cset(HeapWord* addr) const { return at(addr).is_in_cset(); } |
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128 InCSetState at(HeapWord* addr) const { return get_by_address(addr); } |
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129 void clear() { G1BiasedMappedArray<InCSetState>::clear(); } |
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130 }; |
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131 |
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132 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1INCSETSTATE_HPP |