1 /* 2 * Copyright (c) 2017, 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_SHARED_CARDTABLE_HPP 26 #define SHARE_VM_GC_SHARED_CARDTABLE_HPP 27 28 #include "memory/memRegion.hpp" 29 30 class CardTable: public CHeapObj<mtGC> { 31 friend class VMStructs; 32 protected: 33 // The declaration order of these const fields is important; see the 34 // constructor before changing. 35 const bool _scanned_concurrently; 36 const MemRegion _whole_heap; // the region covered by the card table 37 size_t _guard_index; // index of very last element in the card 38 // table; it is set to a guard value 39 // (last_card) and should never be modified 40 size_t _last_valid_index; // index of the last valid element 41 const size_t _page_size; // page size used when mapping _byte_map 42 size_t _byte_map_size; // in bytes 43 jbyte* _byte_map; // the card marking array 44 jbyte* _byte_map_base; 45 46 int _cur_covered_regions; 47 // The covered regions should be in address order. 48 MemRegion* _covered; 49 // The committed regions correspond one-to-one to the covered regions. 50 // They represent the card-table memory that has been committed to service 51 // the corresponding covered region. It may be that committed region for 52 // one covered region corresponds to a larger region because of page-size 53 // roundings. Thus, a committed region for one covered region may 54 // actually extend onto the card-table space for the next covered region. 55 MemRegion* _committed; 56 57 // The last card is a guard card, and we commit the page for it so 58 // we can use the card for verification purposes. We make sure we never 59 // uncommit the MemRegion for that page. 60 MemRegion _guard_region; 61 62 inline size_t compute_byte_map_size(); 63 64 // Finds and return the index of the region, if any, to which the given 65 // region would be contiguous. If none exists, assign a new region and 66 // returns its index. Requires that no more than the maximum number of 67 // covered regions defined in the constructor are ever in use. 68 int find_covering_region_by_base(HeapWord* base); 69 70 // Same as above, but finds the region containing the given address 71 // instead of starting at a given base address. 72 int find_covering_region_containing(HeapWord* addr); 73 74 // Returns the leftmost end of a committed region corresponding to a 75 // covered region before covered region "ind", or else "NULL" if "ind" is 76 // the first covered region. 77 HeapWord* largest_prev_committed_end(int ind) const; 78 79 // Returns the part of the region mr that doesn't intersect with 80 // any committed region other than self. Used to prevent uncommitting 81 // regions that are also committed by other regions. Also protects 82 // against uncommitting the guard region. 83 MemRegion committed_unique_to_self(int self, MemRegion mr) const; 84 85 // Some barrier sets create tables whose elements correspond to parts of 86 // the heap; the CardTableModRefBS is an example. Such barrier sets will 87 // normally reserve space for such tables, and commit parts of the table 88 // "covering" parts of the heap that are committed. At most one covered 89 // region per generation is needed. 90 static const int _max_covered_regions = 2; 91 92 enum CardValues { 93 clean_card = -1, 94 // The mask contains zeros in places for all other values. 95 clean_card_mask = clean_card - 31, 96 97 dirty_card = 0, 98 precleaned_card = 1, 99 claimed_card = 2, 100 deferred_card = 4, 101 last_card = 8, 102 CT_MR_BS_last_reserved = 16 103 }; 104 105 // a word's worth (row) of clean card values 106 static const intptr_t clean_card_row = (intptr_t)(-1); 107 108 public: 109 CardTable(MemRegion whole_heap, bool conc_scan); 110 virtual ~CardTable(); 111 virtual void initialize(); 112 113 // The kinds of precision a CardTableModRefBS may offer. 114 enum PrecisionStyle { 115 Precise, 116 ObjHeadPreciseArray 117 }; 118 119 // Tells what style of precision this card table offers. 120 PrecisionStyle precision() { 121 return ObjHeadPreciseArray; // Only one supported for now. 122 } 123 124 // *** Barrier set functions. 125 126 // Initialization utilities; covered_words is the size of the covered region 127 // in, um, words. 128 inline size_t cards_required(size_t covered_words) { 129 // Add one for a guard card, used to detect errors. 130 const size_t words = align_size_up(covered_words, card_size_in_words); 131 return words / card_size_in_words + 1; 132 } 133 134 // Dirty the bytes corresponding to "mr" (not all of which must be 135 // covered.) 136 void dirty_MemRegion(MemRegion mr); 137 138 // Clear (to clean_card) the bytes entirely contained within "mr" (not 139 // all of which must be covered.) 140 void clear_MemRegion(MemRegion mr); 141 142 // Return true if "p" is at the start of a card. 143 bool is_card_aligned(HeapWord* p) { 144 jbyte* pcard = byte_for(p); 145 return (addr_for(pcard) == p); 146 } 147 148 // Mapping from address to card marking array entry 149 jbyte* byte_for(const void* p) const { 150 assert(_whole_heap.contains(p), 151 "Attempt to access p = " PTR_FORMAT " out of bounds of " 152 " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")", 153 p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end())); 154 jbyte* result = &_byte_map_base[uintptr_t(p) >> card_shift]; 155 assert(result >= _byte_map && result < _byte_map + _byte_map_size, 156 "out of bounds accessor for card marking array"); 157 return result; 158 } 159 160 // The card table byte one after the card marking array 161 // entry for argument address. Typically used for higher bounds 162 // for loops iterating through the card table. 163 jbyte* byte_after(const void* p) const { 164 return byte_for(p) + 1; 165 } 166 167 virtual void invalidate(MemRegion mr); 168 void clear(MemRegion mr); 169 void dirty(MemRegion mr); 170 171 // Provide read-only access to the card table array. 172 const jbyte* byte_for_const(const void* p) const { 173 return byte_for(p); 174 } 175 const jbyte* byte_after_const(const void* p) const { 176 return byte_after(p); 177 } 178 179 // Mapping from card marking array entry to address of first word 180 HeapWord* addr_for(const jbyte* p) const { 181 assert(p >= _byte_map && p < _byte_map + _byte_map_size, 182 "out of bounds access to card marking array"); 183 size_t delta = pointer_delta(p, _byte_map_base, sizeof(jbyte)); 184 HeapWord* result = (HeapWord*) (delta << card_shift); 185 assert(_whole_heap.contains(result), 186 "Returning result = " PTR_FORMAT " out of bounds of " 187 " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")", 188 p2i(result), p2i(_whole_heap.start()), p2i(_whole_heap.end())); 189 return result; 190 } 191 192 // Mapping from address to card marking array index. 193 size_t index_for(void* p) { 194 assert(_whole_heap.contains(p), 195 "Attempt to access p = " PTR_FORMAT " out of bounds of " 196 " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")", 197 p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end())); 198 return byte_for(p) - _byte_map; 199 } 200 201 const jbyte* byte_for_index(const size_t card_index) const { 202 return _byte_map + card_index; 203 } 204 205 // Resize one of the regions covered by the remembered set. 206 virtual void resize_covered_region(MemRegion new_region); 207 208 // *** Card-table-RemSet-specific things. 209 210 static uintx ct_max_alignment_constraint(); 211 212 // Apply closure "cl" to the dirty cards containing some part of 213 // MemRegion "mr". 214 void dirty_card_iterate(MemRegion mr, MemRegionClosure* cl); 215 216 // Return the MemRegion corresponding to the first maximal run 217 // of dirty cards lying completely within MemRegion mr. 218 // If reset is "true", then sets those card table entries to the given 219 // value. 220 MemRegion dirty_card_range_after_reset(MemRegion mr, bool reset, 221 int reset_val); 222 void verify(); 223 224 void verify_guard(); 225 226 // val_equals -> it will check that all cards covered by mr equal val 227 // !val_equals -> it will check that all cards covered by mr do not equal val 228 void verify_region(MemRegion mr, jbyte val, bool val_equals) PRODUCT_RETURN; 229 void verify_not_dirty_region(MemRegion mr) PRODUCT_RETURN; 230 void verify_dirty_region(MemRegion mr) PRODUCT_RETURN; 231 232 // Print a description of the memory for the card table 233 virtual void print_on(outputStream* st) const; 234 235 // Constants 236 enum SomePublicConstants { 237 card_shift = 9, 238 card_size = 1 << card_shift, 239 card_size_in_words = card_size / sizeof(HeapWord) 240 }; 241 242 static jbyte clean_card_val() { return clean_card; } 243 static jbyte clean_card_mask_val() { return clean_card_mask; } 244 static jbyte dirty_card_val() { return dirty_card; } 245 static jbyte claimed_card_val() { return claimed_card; } 246 static jbyte precleaned_card_val() { return precleaned_card; } 247 static jbyte deferred_card_val() { return deferred_card; } 248 static intptr_t clean_card_row_val() { return clean_card_row; } 249 250 // Card marking array base (adjusted for heap low boundary) 251 // This would be the 0th element of _byte_map, if the heap started at 0x0. 252 // But since the heap starts at some higher address, this points to somewhere 253 // before the beginning of the actual _byte_map. 254 jbyte* byte_map_base() const { return _byte_map_base; } 255 bool scanned_concurrently() const { return _scanned_concurrently; } 256 257 virtual bool is_in_young(void* addr) const = 0; 258 }; 259 260 #endif // SHARE_VM_GC_SHARED_CARDTABLE_HPP