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