1 /* 2 * Copyright (c) 2001, 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_G1CARDTABLE_HPP 26 #define SHARE_GC_G1_G1CARDTABLE_HPP 27 28 #include "gc/g1/g1RegionToSpaceMapper.hpp" 29 #include "gc/shared/cardTable.hpp" 30 #include "oops/oopsHierarchy.hpp" 31 #include "utilities/macros.hpp" 32 33 class G1CardTable; 34 class G1RegionToSpaceMapper; 35 36 class G1CardTableChangedListener : public G1MappingChangedListener { 37 private: 38 G1CardTable* _card_table; 39 public: G1CardTableChangedListener()40 G1CardTableChangedListener() : _card_table(NULL) { } 41 set_card_table(G1CardTable * card_table)42 void set_card_table(G1CardTable* card_table) { _card_table = card_table; } 43 44 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 45 }; 46 47 class G1CardTable : public CardTable { 48 friend class VMStructs; 49 friend class G1CardTableChangedListener; 50 51 G1CardTableChangedListener _listener; 52 53 public: 54 enum G1CardValues { 55 g1_young_gen = CT_MR_BS_last_reserved << 1, 56 57 // During evacuation we use the card table to consolidate the cards we need to 58 // scan for roots onto the card table from the various sources. Further it is 59 // used to record already completely scanned cards to avoid re-scanning them 60 // when incrementally evacuating the old gen regions of a collection set. 61 // This means that already scanned cards should be preserved. 62 // 63 // The merge at the start of each evacuation round simply sets cards to dirty 64 // that are clean; scanned cards are set to 0x1. 65 // 66 // This means that the LSB determines what to do with the card during evacuation 67 // given the following possible values: 68 // 69 // 11111111 - clean, do not scan 70 // 00000001 - already scanned, do not scan 71 // 00000000 - dirty, needs to be scanned. 72 // 73 g1_card_already_scanned = 0x1 74 }; 75 76 static const size_t WordAllClean = SIZE_MAX; 77 static const size_t WordAllDirty = 0; 78 79 STATIC_ASSERT(BitsPerByte == 8); 80 static const size_t WordAlreadyScanned = (SIZE_MAX / 255) * g1_card_already_scanned; 81 G1CardTable(MemRegion whole_heap)82 G1CardTable(MemRegion whole_heap): CardTable(whole_heap, /* scanned concurrently */ true), _listener() { 83 _listener.set_card_table(this); 84 } 85 g1_young_card_val()86 static CardValue g1_young_card_val() { return g1_young_gen; } 87 88 void verify_g1_young_region(MemRegion mr) PRODUCT_RETURN; 89 void g1_mark_as_young(const MemRegion& mr); 90 index_for_cardvalue(CardValue const * p) const91 size_t index_for_cardvalue(CardValue const* p) const { 92 return pointer_delta(p, _byte_map, sizeof(CardValue)); 93 } 94 95 // Mark the given card as Dirty if it is Clean. Returns the number of dirtied 96 // cards that were not yet dirty. This result may be inaccurate as it does not 97 // perform the dirtying atomically. 98 inline size_t mark_clean_as_dirty(size_t card_index); 99 100 // Change Clean cards in a (large) area on the card table as Dirty, preserving 101 // already scanned cards. Assumes that most cards in that area are Clean. 102 // Returns the number of dirtied cards that were not yet dirty. This result may 103 // be inaccurate as it does not perform the dirtying atomically. 104 inline size_t mark_region_dirty(size_t start_card_index, size_t num_cards); 105 106 // Mark the given range of cards as Scanned. All of these cards must be Dirty. 107 inline void mark_as_scanned(size_t start_card_index, size_t num_cards); 108 109 inline uint region_idx_for(CardValue* p); 110 compute_size(size_t mem_region_size_in_words)111 static size_t compute_size(size_t mem_region_size_in_words) { 112 size_t number_of_slots = (mem_region_size_in_words / card_size_in_words); 113 return ReservedSpace::allocation_align_size_up(number_of_slots); 114 } 115 116 // Returns how many bytes of the heap a single byte of the Card Table corresponds to. heap_map_factor()117 static size_t heap_map_factor() { return card_size; } 118 initialize()119 void initialize() {} 120 void initialize(G1RegionToSpaceMapper* mapper); 121 resize_covered_region(MemRegion new_region)122 virtual void resize_covered_region(MemRegion new_region) { ShouldNotReachHere(); } 123 124 virtual bool is_in_young(oop obj) const; 125 }; 126 127 #endif // SHARE_GC_G1_G1CARDTABLE_HPP 128