1 /* 2 * Copyright (c) 2000, 2023, 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 #include "precompiled.hpp" 26 #include "gc/shared/cardTable.hpp" 27 #include "gc/shared/collectedHeap.hpp" 28 #include "gc/shared/gcLogPrecious.hpp" 29 #include "gc/shared/gc_globals.hpp" 30 #include "gc/shared/space.inline.hpp" 31 #include "logging/log.hpp" 32 #include "memory/virtualspace.hpp" 33 #include "runtime/java.hpp" 34 #include "runtime/os.hpp" 35 #include "services/memTracker.hpp" 36 #include "utilities/align.hpp" 37 #if INCLUDE_PARALLELGC 38 #include "gc/parallel/objectStartArray.hpp" 39 #endif 40 41 uint CardTable::_card_shift = 0; 42 uint CardTable::_card_size = 0; 43 uint CardTable::_card_size_in_words = 0; 44 45 void CardTable::initialize_card_size() { 46 assert(UseG1GC || UseParallelGC || UseSerialGC || UseShenandoahGC, 47 "Initialize card size should only be called by card based collectors."); 48 49 _card_size = GCCardSizeInBytes; 50 _card_shift = log2i_exact(_card_size); 51 _card_size_in_words = _card_size / sizeof(HeapWord); 52 53 // Set blockOffsetTable size based on card table entry size 54 BOTConstants::initialize_bot_size(_card_shift); 55 56 #if INCLUDE_PARALLELGC 57 // Set ObjectStartArray block size based on card table entry size 58 ObjectStartArray::initialize_block_size(_card_shift); 59 #endif 60 61 log_info_p(gc, init)("CardTable entry size: " UINT32_FORMAT, _card_size); 62 } 63 64 size_t CardTable::compute_byte_map_size(size_t num_bytes) { 65 assert(_page_size != 0, "uninitialized, check declaration order"); 66 const size_t granularity = os::vm_allocation_granularity(); 67 return align_up(num_bytes, MAX2(_page_size, granularity)); 68 } 69 70 CardTable::CardTable(MemRegion whole_heap) : 71 _whole_heap(whole_heap), 72 _page_size(os::vm_page_size()), 73 _byte_map_size(0), 74 _byte_map(nullptr), 75 _byte_map_base(nullptr), 76 _cur_covered_regions(0), 77 _covered(MemRegion::create_array(_max_covered_regions, mtGC)), 78 _committed(MemRegion::create_array(_max_covered_regions, mtGC)), 79 _guard_region() 80 { 81 assert((uintptr_t(_whole_heap.start()) & (_card_size - 1)) == 0, "heap must start at card boundary"); 82 assert((uintptr_t(_whole_heap.end()) & (_card_size - 1)) == 0, "heap must end at card boundary"); 83 } 84 85 CardTable::~CardTable() { 86 MemRegion::destroy_array(_covered, _max_covered_regions); 87 MemRegion::destroy_array(_committed, _max_covered_regions); 88 } 89 90 void CardTable::initialize() { 91 size_t num_cards = cards_required(_whole_heap.word_size()); 92 93 // each card takes 1 byte; + 1 for the guard card 94 size_t num_bytes = num_cards + 1; 95 _byte_map_size = compute_byte_map_size(num_bytes); 96 97 HeapWord* low_bound = _whole_heap.start(); 98 HeapWord* high_bound = _whole_heap.end(); 99 100 _cur_covered_regions = 0; 101 102 const size_t rs_align = _page_size == os::vm_page_size() ? 0 : 103 MAX2(_page_size, os::vm_allocation_granularity()); 104 ReservedSpace heap_rs(_byte_map_size, rs_align, _page_size); 105 106 MemTracker::record_virtual_memory_type((address)heap_rs.base(), mtGC); 107 108 os::trace_page_sizes("Card Table", num_bytes, num_bytes, 109 _page_size, heap_rs.base(), heap_rs.size()); 110 if (!heap_rs.is_reserved()) { 111 vm_exit_during_initialization("Could not reserve enough space for the " 112 "card marking array"); 113 } 114 115 // The assembler store_check code will do an unsigned shift of the oop, 116 // then add it to _byte_map_base, i.e. 117 // 118 // _byte_map = _byte_map_base + (uintptr_t(low_bound) >> card_shift) 119 _byte_map = (CardValue*) heap_rs.base(); 120 _byte_map_base = _byte_map - (uintptr_t(low_bound) >> _card_shift); 121 assert(byte_for(low_bound) == &_byte_map[0], "Checking start of map"); 122 assert(byte_for(high_bound-1) <= &_byte_map[last_valid_index()], "Checking end of map"); 123 124 CardValue* guard_card = &_byte_map[num_cards]; 125 assert(is_aligned(guard_card, _page_size), "must be on its own OS page"); 126 _guard_region = MemRegion((HeapWord*)guard_card, _page_size); 127 128 log_trace(gc, barrier)("CardTable::CardTable: "); 129 log_trace(gc, barrier)(" &_byte_map[0]: " PTR_FORMAT " &_byte_map[last_valid_index()]: " PTR_FORMAT, 130 p2i(&_byte_map[0]), p2i(&_byte_map[last_valid_index()])); 131 log_trace(gc, barrier)(" _byte_map_base: " PTR_FORMAT, p2i(_byte_map_base)); 132 } 133 134 int CardTable::find_covering_region_by_base(HeapWord* base) { 135 int i; 136 for (i = 0; i < _cur_covered_regions; i++) { 137 if (_covered[i].start() == base) return i; 138 if (_covered[i].start() > base) break; 139 } 140 // If we didn't find it, create a new one. 141 assert(_cur_covered_regions < _max_covered_regions, 142 "too many covered regions"); 143 // Move the ones above up, to maintain sorted order. 144 for (int j = _cur_covered_regions; j > i; j--) { 145 _covered[j] = _covered[j-1]; 146 _committed[j] = _committed[j-1]; 147 } 148 int res = i; 149 _cur_covered_regions++; 150 _covered[res].set_start(base); 151 _covered[res].set_word_size(0); 152 CardValue* ct_start = byte_for(base); 153 HeapWord* ct_start_aligned = align_down((HeapWord*)ct_start, _page_size); 154 _committed[res].set_start(ct_start_aligned); 155 _committed[res].set_word_size(0); 156 return res; 157 } 158 159 HeapWord* CardTable::largest_prev_committed_end(int ind) const { 160 HeapWord* max_end = nullptr; 161 for (int j = 0; j < ind; j++) { 162 HeapWord* this_end = _committed[j].end(); 163 if (this_end > max_end) max_end = this_end; 164 } 165 return max_end; 166 } 167 168 MemRegion CardTable::committed_unique_to_self(int self, MemRegion mr) const { 169 assert(mr.intersection(_guard_region).is_empty(), "precondition"); 170 MemRegion result = mr; 171 for (int r = 0; r < _cur_covered_regions; r += 1) { 172 if (r != self) { 173 result = result.minus(_committed[r]); 174 } 175 } 176 return result; 177 } 178 179 void CardTable::resize_covered_region(MemRegion new_region) { 180 // We don't change the start of a region, only the end. 181 assert(_whole_heap.contains(new_region), 182 "attempt to cover area not in reserved area"); 183 // collided is true if the expansion would push into another committed region 184 debug_only(bool collided = false;) 185 int const ind = find_covering_region_by_base(new_region.start()); 186 MemRegion const old_region = _covered[ind]; 187 assert(old_region.start() == new_region.start(), "just checking"); 188 if (new_region.word_size() != old_region.word_size()) { 189 // Commit new or uncommit old pages, if necessary. 190 MemRegion cur_committed = _committed[ind]; 191 // Extend the end of this _committed region 192 // to cover the end of any lower _committed regions. 193 // This forms overlapping regions, but never interior regions. 194 HeapWord* const max_prev_end = largest_prev_committed_end(ind); 195 if (max_prev_end > cur_committed.end()) { 196 cur_committed.set_end(max_prev_end); 197 } 198 // Align the end up to a page size (starts are already aligned). 199 HeapWord* new_end = (HeapWord*) byte_after(new_region.last()); 200 HeapWord* new_end_aligned = align_up(new_end, _page_size); 201 assert(new_end_aligned >= new_end, "align up, but less"); 202 // Check the other regions (excludes "ind") to ensure that 203 // the new_end_aligned does not intrude onto the committed 204 // space of another region. 205 int ri = 0; 206 for (ri = ind + 1; ri < _cur_covered_regions; ri++) { 207 if (new_end_aligned > _committed[ri].start()) { 208 assert(new_end_aligned <= _committed[ri].end(), 209 "An earlier committed region can't cover a later committed region"); 210 // Any region containing the new end 211 // should start at or beyond the region found (ind) 212 // for the new end (committed regions are not expected to 213 // be proper subsets of other committed regions). 214 assert(_committed[ri].start() >= _committed[ind].start(), 215 "New end of committed region is inconsistent"); 216 new_end_aligned = _committed[ri].start(); 217 // new_end_aligned can be equal to the start of its 218 // committed region (i.e., of "ind") if a second 219 // region following "ind" also start at the same location 220 // as "ind". 221 assert(new_end_aligned >= _committed[ind].start(), 222 "New end of committed region is before start"); 223 debug_only(collided = true;) 224 // Should only collide with 1 region 225 break; 226 } 227 } 228 #ifdef ASSERT 229 for (++ri; ri < _cur_covered_regions; ri++) { 230 assert(!_committed[ri].contains(new_end_aligned), 231 "New end of committed region is in a second committed region"); 232 } 233 #endif 234 // The guard page is always committed and should not be committed over. 235 // "guarded" is used for assertion checking below and recalls the fact 236 // that the would-be end of the new committed region would have 237 // penetrated the guard page. 238 HeapWord* new_end_for_commit = new_end_aligned; 239 240 DEBUG_ONLY(bool guarded = false;) 241 if (new_end_for_commit > _guard_region.start()) { 242 new_end_for_commit = _guard_region.start(); 243 DEBUG_ONLY(guarded = true;) 244 } 245 246 if (new_end_for_commit > cur_committed.end()) { 247 // Must commit new pages. 248 MemRegion const new_committed = 249 MemRegion(cur_committed.end(), new_end_for_commit); 250 251 assert(!new_committed.is_empty(), "Region should not be empty here"); 252 os::commit_memory_or_exit((char*)new_committed.start(), 253 new_committed.byte_size(), _page_size, 254 !ExecMem, "card table expansion"); 255 // Use new_end_aligned (as opposed to new_end_for_commit) because 256 // the cur_committed region may include the guard region. 257 } else if (new_end_aligned < cur_committed.end()) { 258 // Must uncommit pages. 259 MemRegion const uncommit_region = 260 committed_unique_to_self(ind, MemRegion(new_end_aligned, 261 cur_committed.end())); 262 if (!uncommit_region.is_empty()) { 263 if (!os::uncommit_memory((char*)uncommit_region.start(), 264 uncommit_region.byte_size())) { 265 assert(false, "Card table contraction failed"); 266 // The call failed so don't change the end of the 267 // committed region. This is better than taking the 268 // VM down. 269 new_end_aligned = _committed[ind].end(); 270 } 271 } 272 } 273 // In any case, we can reset the end of the current committed entry. 274 _committed[ind].set_end(new_end_aligned); 275 276 #ifdef ASSERT 277 // Check that the last card in the new region is committed according 278 // to the tables. 279 bool covered = false; 280 for (int cr = 0; cr < _cur_covered_regions; cr++) { 281 if (_committed[cr].contains(new_end - 1)) { 282 covered = true; 283 break; 284 } 285 } 286 assert(covered, "Card for end of new region not committed"); 287 #endif 288 289 // The default of 0 is not necessarily clean cards. 290 CardValue* entry; 291 if (old_region.last() < _whole_heap.start()) { 292 entry = byte_for(_whole_heap.start()); 293 } else { 294 entry = byte_after(old_region.last()); 295 } 296 assert(index_for(new_region.last()) <= last_valid_index(), 297 "The guard card will be overwritten"); 298 // This line commented out cleans the newly expanded region and 299 // not the aligned up expanded region. 300 // CardValue* const end = byte_after(new_region.last()); 301 CardValue* const end = (CardValue*) new_end_for_commit; 302 assert((end >= byte_after(new_region.last())) || collided || guarded, 303 "Expect to be beyond new region unless impacting another region"); 304 // do nothing if we resized downward. 305 #ifdef ASSERT 306 for (int ri = 0; ri < _cur_covered_regions; ri++) { 307 if (ri != ind) { 308 // The end of the new committed region should not 309 // be in any existing region unless it matches 310 // the start of the next region. 311 assert(!_committed[ri].contains(end) || 312 (_committed[ri].start() == (HeapWord*) end), 313 "Overlapping committed regions"); 314 } 315 } 316 #endif 317 if (entry < end) { 318 memset(entry, clean_card, pointer_delta(end, entry, sizeof(CardValue))); 319 } 320 } 321 // In any case, the covered size changes. 322 _covered[ind].set_word_size(new_region.word_size()); 323 324 log_trace(gc, barrier)("CardTable::resize_covered_region: "); 325 log_trace(gc, barrier)(" _covered[%d].start(): " PTR_FORMAT " _covered[%d].last(): " PTR_FORMAT, 326 ind, p2i(_covered[ind].start()), ind, p2i(_covered[ind].last())); 327 log_trace(gc, barrier)(" _committed[%d].start(): " PTR_FORMAT " _committed[%d].last(): " PTR_FORMAT, 328 ind, p2i(_committed[ind].start()), ind, p2i(_committed[ind].last())); 329 log_trace(gc, barrier)(" byte_for(start): " PTR_FORMAT " byte_for(last): " PTR_FORMAT, 330 p2i(byte_for(_covered[ind].start())), p2i(byte_for(_covered[ind].last()))); 331 log_trace(gc, barrier)(" addr_for(start): " PTR_FORMAT " addr_for(last): " PTR_FORMAT, 332 p2i(addr_for((CardValue*) _committed[ind].start())), p2i(addr_for((CardValue*) _committed[ind].last()))); 333 334 // Touch the last card of the covered region to show that it 335 // is committed (or SEGV). 336 debug_only((void) (*byte_for(_covered[ind].last()));) 337 } 338 339 // Note that these versions are precise! The scanning code has to handle the 340 // fact that the write barrier may be either precise or imprecise. 341 void CardTable::dirty_MemRegion(MemRegion mr) { 342 assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start"); 343 assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" ); 344 CardValue* cur = byte_for(mr.start()); 345 CardValue* last = byte_after(mr.last()); 346 while (cur < last) { 347 *cur = dirty_card; 348 cur++; 349 } 350 } 351 352 void CardTable::clear_MemRegion(MemRegion mr) { 353 // Be conservative: only clean cards entirely contained within the 354 // region. 355 CardValue* cur; 356 if (mr.start() == _whole_heap.start()) { 357 cur = byte_for(mr.start()); 358 } else { 359 assert(mr.start() > _whole_heap.start(), "mr is not covered."); 360 cur = byte_after(mr.start() - 1); 361 } 362 CardValue* last = byte_after(mr.last()); 363 memset(cur, clean_card, pointer_delta(last, cur, sizeof(CardValue))); 364 } 365 366 void CardTable::clear(MemRegion mr) { 367 for (int i = 0; i < _cur_covered_regions; i++) { 368 MemRegion mri = mr.intersection(_covered[i]); 369 if (!mri.is_empty()) clear_MemRegion(mri); 370 } 371 } 372 373 uintx CardTable::ct_max_alignment_constraint() { 374 // Calculate maximum alignment using GCCardSizeInBytes as card_size hasn't been set yet 375 return GCCardSizeInBytes * os::vm_page_size(); 376 } 377 378 void CardTable::invalidate(MemRegion mr) { 379 assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start"); 380 assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" ); 381 for (int i = 0; i < _cur_covered_regions; i++) { 382 MemRegion mri = mr.intersection(_covered[i]); 383 if (!mri.is_empty()) dirty_MemRegion(mri); 384 } 385 } 386 387 #ifndef PRODUCT 388 void CardTable::verify_region(MemRegion mr, CardValue val, bool val_equals) { 389 CardValue* start = byte_for(mr.start()); 390 CardValue* end = byte_for(mr.last()); 391 bool failures = false; 392 for (CardValue* curr = start; curr <= end; ++curr) { 393 CardValue curr_val = *curr; 394 bool failed = (val_equals) ? (curr_val != val) : (curr_val == val); 395 if (failed) { 396 if (!failures) { 397 log_error(gc, verify)("== CT verification failed: [" PTR_FORMAT "," PTR_FORMAT "]", p2i(start), p2i(end)); 398 log_error(gc, verify)("== %sexpecting value: %d", (val_equals) ? "" : "not ", val); 399 failures = true; 400 } 401 log_error(gc, verify)("== card " PTR_FORMAT " [" PTR_FORMAT "," PTR_FORMAT "], val: %d", 402 p2i(curr), p2i(addr_for(curr)), 403 p2i((HeapWord*) (((size_t) addr_for(curr)) + _card_size)), 404 (int) curr_val); 405 } 406 } 407 guarantee(!failures, "there should not have been any failures"); 408 } 409 410 void CardTable::verify_not_dirty_region(MemRegion mr) { 411 verify_region(mr, dirty_card, false /* val_equals */); 412 } 413 414 void CardTable::verify_dirty_region(MemRegion mr) { 415 verify_region(mr, dirty_card, true /* val_equals */); 416 } 417 #endif 418 419 void CardTable::print_on(outputStream* st) const { 420 st->print_cr("Card table byte_map: [" PTR_FORMAT "," PTR_FORMAT "] _byte_map_base: " PTR_FORMAT, 421 p2i(_byte_map), p2i(_byte_map + _byte_map_size), p2i(_byte_map_base)); 422 }