1 /* 2 * Copyright (c) 2014, 2019, 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_GC_G1_G1HEAPREGIONATTR_HPP 26 #define SHARE_GC_G1_G1HEAPREGIONATTR_HPP 27 28 #include "gc/g1/g1BiasedArray.hpp" 29 #include "gc/g1/heapRegion.hpp" 30 31 // Per-region attributes often used during garbage collection to avoid costly 32 // lookups for that information all over the place. 33 struct G1HeapRegionAttr { 34 public: 35 typedef int8_t region_type_t; 36 typedef uint8_t needs_remset_update_t; 37 38 private: 39 needs_remset_update_t _needs_remset_update; 40 region_type_t _type; 41 42 public: 43 // Selection of the values for the _type field were driven to micro-optimize the 44 // encoding and frequency of the checks. 45 // The most common check for a given reference is whether the region is in the 46 // collection set or not, and which generation this region is in. 47 // The selected encoding allows us to use a single check (> NotInCSet) for the 48 // former. 49 // 50 // The other values are used for objects in regions requiring various special handling, 51 // eager reclamation of humongous objects or optional regions. 52 static const region_type_t Optional = -3; // The region is optional not in the current collection set. 53 static const region_type_t Humongous = -2; // The region is a humongous candidate not in the current collection set. 54 static const region_type_t NotInCSet = -1; // The region is not in the collection set. 55 static const region_type_t Young = 0; // The region is in the collection set and a young region. 56 static const region_type_t Old = 1; // The region is in the collection set and an old region. 57 static const region_type_t Num = 2; 58 59 G1HeapRegionAttr(region_type_t type = NotInCSet, bool needs_remset_update = false) : 60 _needs_remset_update(needs_remset_update), _type(type) { 61 62 assert(is_valid(), "Invalid type %d", _type); 63 } 64 65 region_type_t type() const { return _type; } 66 67 const char* get_type_str() const { 68 switch (type()) { 69 case Optional: return "Optional"; 70 case Humongous: return "Humongous"; 71 case NotInCSet: return "NotInCSet"; 72 case Young: return "Young"; 73 case Old: return "Old"; 74 default: ShouldNotReachHere(); return ""; 75 } 76 } 77 78 bool needs_remset_update() const { return _needs_remset_update != 0; } 79 80 void set_old() { _type = Old; } 81 void clear_humongous() { 82 assert(is_humongous() || !is_in_cset(), "must be"); 83 _type = NotInCSet; 84 } 85 void set_has_remset(bool value) { _needs_remset_update = value ? 1 : 0; } 86 87 bool is_in_cset_or_humongous() const { return is_in_cset() || is_humongous(); } 88 bool is_in_cset() const { return type() >= Young; } 89 90 bool is_humongous() const { return type() == Humongous; } 91 bool is_young() const { return type() == Young; } 92 bool is_old() const { return type() == Old; } 93 bool is_optional() const { return type() == Optional; } 94 95 #ifdef ASSERT 96 bool is_default() const { return type() == NotInCSet; } 97 bool is_valid() const { return (type() >= Optional && type() < Num); } 98 bool is_valid_gen() const { return (type() >= Young && type() <= Old); } 99 #endif 100 }; 101 102 // Table for all regions in the heap for above. 103 // 104 // We use this to speed up reference processing during young collection and 105 // quickly reclaim humongous objects. For the latter, at the start of GC, by adding 106 // it as a humongous region we enable special handling for that region. During the 107 // reference iteration closures, when we see a humongous region, we then simply mark 108 // it as referenced, i.e. live, and remove it from this table to prevent further 109 // processing on it. 110 // 111 // This means that this does NOT completely correspond to the information stored 112 // in a HeapRegion, but only to what is interesting for the current young collection. 113 class G1HeapRegionAttrBiasedMappedArray : public G1BiasedMappedArray<G1HeapRegionAttr> { 114 protected: 115 G1HeapRegionAttr default_value() const { return G1HeapRegionAttr(G1HeapRegionAttr::NotInCSet); } 116 public: 117 void set_optional(uintptr_t index, bool needs_remset_update) { 118 assert(get_by_index(index).is_default(), 119 "Region attributes at index " INTPTR_FORMAT " should be default but is %s", index, get_by_index(index).get_type_str()); 120 set_by_index(index, G1HeapRegionAttr(G1HeapRegionAttr::Optional, needs_remset_update)); 121 } 122 123 void set_humongous(uintptr_t index, bool needs_remset_update) { 124 assert(get_by_index(index).is_default(), 125 "Region attributes at index " INTPTR_FORMAT " should be default but is %s", index, get_by_index(index).get_type_str()); 126 set_by_index(index, G1HeapRegionAttr(G1HeapRegionAttr::Humongous, needs_remset_update)); 127 } 128 129 void clear_humongous(uintptr_t index) { 130 get_ref_by_index(index)->clear_humongous(); 131 } 132 133 void set_has_remset(uintptr_t index, bool needs_remset_update) { 134 get_ref_by_index(index)->set_has_remset(needs_remset_update); 135 } 136 137 void set_in_young(uintptr_t index) { 138 assert(get_by_index(index).is_default(), 139 "Region attributes at index " INTPTR_FORMAT " should be default but is %s", index, get_by_index(index).get_type_str()); 140 set_by_index(index, G1HeapRegionAttr(G1HeapRegionAttr::Young, true)); 141 } 142 143 void set_in_old(uintptr_t index, bool needs_remset_update) { 144 assert(get_by_index(index).is_default(), 145 "Region attributes at index " INTPTR_FORMAT " should be default but is %s", index, get_by_index(index).get_type_str()); 146 set_by_index(index, G1HeapRegionAttr(G1HeapRegionAttr::Old, needs_remset_update)); 147 } 148 149 bool is_in_cset_or_humongous(HeapWord* addr) const { return at(addr).is_in_cset_or_humongous(); } 150 bool is_in_cset(HeapWord* addr) const { return at(addr).is_in_cset(); } 151 bool is_in_cset(const HeapRegion* hr) const { return get_by_index(hr->hrm_index()).is_in_cset(); } 152 G1HeapRegionAttr at(HeapWord* addr) const { return get_by_address(addr); } 153 void clear() { G1BiasedMappedArray<G1HeapRegionAttr>::clear(); } 154 void clear(const HeapRegion* hr) { return set_by_index(hr->hrm_index(), G1HeapRegionAttr(G1HeapRegionAttr::NotInCSet)); } 155 }; 156 157 #endif // SHARE_GC_G1_G1HEAPREGIONATTR_HPP