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. 33struct 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. 56 // The positive values are encoded in increasing generation order, which 57 // makes getting the next generation fast by a simple increment. They are also 58 // used to index into arrays. 59 // The negative values are used for objects requiring various special cases, 60 // for example eager reclamation of humongous objects. 61 Ext = -2, // Extension point 62 Humongous = -1, // The region is humongous 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(), "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 is_in_cset() || is_humongous(); } 78 bool is_in_cset() const { return _value > NotInCSet; } 79 80 bool is_humongous() const { return _value == Humongous; } 81 bool is_young() const { return _value == Young; } 82 bool is_old() const { return _value == Old; } 83 bool is_ext() const { return _value == Ext; } 84 85#ifdef ASSERT 86 bool is_default() const { return _value == NotInCSet; } 87 bool is_valid() const { return (_value >= Ext) && (_value < Num); } 88 bool is_valid_gen() const { return (_value >= Young && _value <= Old); } 89#endif 90}; 91 92// Instances of this class are used for quick tests on whether a reference points 93// into the collection set and into which generation or is a humongous object 94// 95// Each of the array's elements indicates whether the corresponding region is in 96// the collection set and if so in which generation, or a humongous region. 97// 98// We use this to speed up reference processing during young collection and 99// quickly reclaim humongous objects. For the latter, by making a humongous region 100// succeed this test, we sort-of add it to the collection set. During the reference 101// iteration closures, when we see a humongous region, we then simply mark it as 102// referenced, i.e. live. 103class G1InCSetStateFastTestBiasedMappedArray : public G1BiasedMappedArray<InCSetState> { 104 protected: 105 InCSetState default_value() const { return InCSetState::NotInCSet; } 106 public: 107 void set_humongous(uintptr_t index) { 108 assert(get_by_index(index).is_default(), 109 "State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value()); 110 set_by_index(index, InCSetState::Humongous); 111 } 112 113 void set_ext(uintptr_t index) { 114 assert(get_by_index(index).is_default(), 115 "State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value()); 116 set_by_index(index, InCSetState::Ext); 117 } 118 119 void clear_humongous(uintptr_t index) { 120 set_by_index(index, InCSetState::NotInCSet); 121 } 122 123 void set_in_young(uintptr_t index) { 124 assert(get_by_index(index).is_default(), 125 "State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value()); 126 set_by_index(index, InCSetState::Young); 127 } 128 129 void set_in_old(uintptr_t index) { 130 assert(get_by_index(index).is_default(), 131 "State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value()); 132 set_by_index(index, InCSetState::Old); 133 } 134 135 bool is_in_cset_or_humongous(HeapWord* addr) const { return at(addr).is_in_cset_or_humongous(); } 136 bool is_in_cset(HeapWord* addr) const { return at(addr).is_in_cset(); } 137 bool is_in_cset(const HeapRegion* hr) const { return get_by_index(hr->hrm_index()).is_in_cset(); } 138 InCSetState at(HeapWord* addr) const { return get_by_address(addr); } 139 void clear() { G1BiasedMappedArray<InCSetState>::clear(); } 140 void clear(const HeapRegion* hr) { return set_by_index(hr->hrm_index(), InCSetState::NotInCSet); } 141}; 142 143#endif // SHARE_VM_GC_G1_G1INCSETSTATE_HPP 144