1 /* 2 * Copyright (c) 2014, 2015, 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_G1_G1INCSETSTATE_HPP 26 #define SHARE_VM_GC_G1_G1INCSETSTATE_HPP 27 28 #include "gc/g1/g1BiasedArray.hpp" 29 #include "gc/g1/heapRegion.hpp" 30 #include "memory/allocation.hpp" 31 32 // Per-region state during garbage collection. 33 struct InCSetState { 34 public: 35 // We use different types to represent the state value. Particularly SPARC puts 36 // values in structs from "left to right", i.e. MSB to LSB. This results in many 37 // unnecessary shift operations when loading and storing values of this type. 38 // This degrades performance significantly (>10%) on that platform. 39 // Other tested ABIs do not seem to have this problem, and actually tend to 40 // favor smaller types, so we use the smallest usable type there. 41 #ifdef SPARC 42 #define CSETSTATE_FORMAT INTPTR_FORMAT 43 typedef intptr_t in_cset_state_t; 44 #else 45 #define CSETSTATE_FORMAT "%d" 46 typedef int8_t in_cset_state_t; 47 #endif 48 private: 49 in_cset_state_t _value; 50 public: 51 enum { 52 // Selection of the values were driven to micro-optimize the encoding and 53 // frequency of the checks. 54 // The most common check is whether the region is in the collection set or not. 55 // This encoding allows us to use an != 0 check which in some architectures 56 // (x86*) can be encoded slightly more efficently than a normal comparison 57 // against zero. 58 // The same situation occurs when checking whether the region is humongous 59 // or not, which is encoded by values < 0. 60 // The other values are simply encoded in increasing generation order, which 61 // makes getting the next generation fast by a simple increment. 62 Humongous = -1, // The region is humongous - note that actually any value < 0 would be possible here. 63 NotInCSet = 0, // The region is not in the collection set. 64 Young = 1, // The region is in the collection set and a young region. 65 Old = 2, // The region is in the collection set and an old region. 66 Num 67 }; 68 69 InCSetState(in_cset_state_t value = NotInCSet) : _value(value) { 70 assert(is_valid(), err_msg("Invalid state %d", _value)); 71 } 72 73 in_cset_state_t value() const { return _value; } 74 75 void set_old() { _value = Old; } 76 77 bool is_in_cset_or_humongous() const { return _value != NotInCSet; } 78 bool is_in_cset() const { return _value > NotInCSet; } 79 bool is_humongous() const { return _value < NotInCSet; } 80 bool is_young() const { return _value == Young; } 81 bool is_old() const { return _value == Old; } 82 83 // Converts the given InCSetState value into a generation number from 0 (Young) 84 // to 1 (Old). 85 static int to_gen_number(InCSetState value) { 86 assert(value.is_valid_gen(), err_msg("Cannot convert CSet state " CSETSTATE_FORMAT" to generation number.", value.value())); 87 return (int)(value.value() - Young); 88 } 89 90 #ifdef ASSERT 91 bool is_default() const { return !is_in_cset_or_humongous(); } 92 bool is_valid() const { return (_value >= Humongous) && (_value < Num); } 93 bool is_valid_gen() const { return (_value >= Young && _value <= Old); } 94 #endif 95 }; 96 97 // Instances of this class are used for quick tests on whether a reference points 98 // into the collection set and into which generation or is a humongous object 99 // 100 // Each of the array's elements indicates whether the corresponding region is in 101 // the collection set and if so in which generation, or a humongous region. 102 // 103 // We use this to speed up reference processing during young collection and 104 // quickly reclaim humongous objects. For the latter, by making a humongous region 105 // succeed this test, we sort-of add it to the collection set. During the reference 106 // iteration closures, when we see a humongous region, we then simply mark it as 107 // referenced, i.e. live. 108 class G1InCSetStateFastTestBiasedMappedArray : public G1BiasedMappedArray<InCSetState> { 109 protected: 110 InCSetState default_value() const { return InCSetState::NotInCSet; } 111 public: 112 void set_humongous(uintptr_t index) { 113 assert(get_by_index(index).is_default(), 114 err_msg("State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value())); 115 set_by_index(index, InCSetState::Humongous); 116 } 117 118 void clear_humongous(uintptr_t index) { 119 set_by_index(index, InCSetState::NotInCSet); 120 } 121 122 void set_in_young(uintptr_t index) { 123 assert(get_by_index(index).is_default(), 124 err_msg("State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value())); 125 set_by_index(index, InCSetState::Young); 126 } 127 128 void set_in_old(uintptr_t index) { 129 assert(get_by_index(index).is_default(), 130 err_msg("State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value())); 131 set_by_index(index, InCSetState::Old); 132 } 133 134 bool is_in_cset_or_humongous(HeapWord* addr) const { return at(addr).is_in_cset_or_humongous(); } 135 bool is_in_cset(HeapWord* addr) const { return at(addr).is_in_cset(); } 136 bool is_in_cset(const HeapRegion* hr) const { return get_by_index(hr->hrm_index()).is_in_cset(); } 137 InCSetState at(HeapWord* addr) const { return get_by_address(addr); } 138 void clear() { G1BiasedMappedArray<InCSetState>::clear(); } 139 void clear(const HeapRegion* hr) { return set_by_index(hr->hrm_index(), InCSetState::NotInCSet); } 140 }; 141 142 #endif // SHARE_VM_GC_G1_G1INCSETSTATE_HPP