1 /* 2 * Copyright (c) 2001, 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 #include "precompiled.hpp" 26 #include "gc/parallel/cardTableExtension.hpp" 27 #include "gc/parallel/gcTaskManager.hpp" 28 #include "gc/parallel/parallelScavengeHeap.hpp" 29 #include "gc/parallel/psPromotionManager.inline.hpp" 30 #include "gc/parallel/psScavenge.hpp" 31 #include "gc/parallel/psTasks.hpp" 32 #include "gc/parallel/psYoungGen.hpp" 33 #include "oops/oop.inline.hpp" 34 #include "runtime/prefetch.inline.hpp" 35 36 // Checks an individual oop for missing precise marks. Mark 37 // may be either dirty or newgen. 38 class CheckForUnmarkedOops : public OopClosure { 39 private: 40 PSYoungGen* _young_gen; 41 CardTableExtension* _card_table; 42 HeapWord* _unmarked_addr; 43 jbyte* _unmarked_card; 44 45 protected: 46 template <class T> void do_oop_work(T* p) { 47 oop obj = oopDesc::load_decode_heap_oop(p); 48 if (_young_gen->is_in_reserved(obj) && 49 !_card_table->addr_is_marked_imprecise(p)) { 50 // Don't overwrite the first missing card mark 51 if (_unmarked_addr == NULL) { 52 _unmarked_addr = (HeapWord*)p; 53 _unmarked_card = _card_table->byte_for(p); 54 } 55 } 56 } 57 58 public: 59 CheckForUnmarkedOops(PSYoungGen* young_gen, CardTableExtension* card_table) : 60 _young_gen(young_gen), _card_table(card_table), _unmarked_addr(NULL) { } 61 62 virtual void do_oop(oop* p) { CheckForUnmarkedOops::do_oop_work(p); } 63 virtual void do_oop(narrowOop* p) { CheckForUnmarkedOops::do_oop_work(p); } 64 65 bool has_unmarked_oop() { 66 return _unmarked_addr != NULL; 67 } 68 }; 69 70 // Checks all objects for the existence of some type of mark, 71 // precise or imprecise, dirty or newgen. 72 class CheckForUnmarkedObjects : public ObjectClosure { 73 private: 74 PSYoungGen* _young_gen; 75 CardTableExtension* _card_table; 76 77 public: 78 CheckForUnmarkedObjects() { 79 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap(); 80 _young_gen = heap->young_gen(); 81 _card_table = barrier_set_cast<CardTableExtension>(heap->barrier_set()); 82 // No point in asserting barrier set type here. Need to make CardTableExtension 83 // a unique barrier set type. 84 } 85 86 // Card marks are not precise. The current system can leave us with 87 // a mismatch of precise marks and beginning of object marks. This means 88 // we test for missing precise marks first. If any are found, we don't 89 // fail unless the object head is also unmarked. 90 virtual void do_object(oop obj) { 91 CheckForUnmarkedOops object_check(_young_gen, _card_table); 92 obj->oop_iterate_no_header(&object_check); 93 if (object_check.has_unmarked_oop()) { 94 assert(_card_table->addr_is_marked_imprecise(obj), "Found unmarked young_gen object"); 95 } 96 } 97 }; 98 99 // Checks for precise marking of oops as newgen. 100 class CheckForPreciseMarks : public OopClosure { 101 private: 102 PSYoungGen* _young_gen; 103 CardTableExtension* _card_table; 104 105 protected: 106 template <class T> void do_oop_work(T* p) { 107 oop obj = oopDesc::load_decode_heap_oop_not_null(p); 108 if (_young_gen->is_in_reserved(obj)) { 109 assert(_card_table->addr_is_marked_precise(p), "Found unmarked precise oop"); 110 _card_table->set_card_newgen(p); 111 } 112 } 113 114 public: 115 CheckForPreciseMarks( PSYoungGen* young_gen, CardTableExtension* card_table ) : 116 _young_gen(young_gen), _card_table(card_table) { } 117 118 virtual void do_oop(oop* p) { CheckForPreciseMarks::do_oop_work(p); } 119 virtual void do_oop(narrowOop* p) { CheckForPreciseMarks::do_oop_work(p); } 120 }; 121 122 // We get passed the space_top value to prevent us from traversing into 123 // the old_gen promotion labs, which cannot be safely parsed. 124 125 // Do not call this method if the space is empty. 126 // It is a waste to start tasks and get here only to 127 // do no work. If this method needs to be called 128 // when the space is empty, fix the calculation of 129 // end_card to allow sp_top == sp->bottom(). 130 131 void CardTableExtension::scavenge_contents_parallel(ObjectStartArray* start_array, 132 MutableSpace* sp, 133 HeapWord* space_top, 134 PSPromotionManager* pm, 135 uint stripe_number, 136 uint stripe_total) { 137 int ssize = 128; // Naked constant! Work unit = 64k. 138 int dirty_card_count = 0; 139 140 // It is a waste to get here if empty. 141 assert(sp->bottom() < sp->top(), "Should not be called if empty"); 142 oop* sp_top = (oop*)space_top; 143 jbyte* start_card = byte_for(sp->bottom()); 144 jbyte* end_card = byte_for(sp_top - 1) + 1; 145 oop* last_scanned = NULL; // Prevent scanning objects more than once 146 // The width of the stripe ssize*stripe_total must be 147 // consistent with the number of stripes so that the complete slice 148 // is covered. 149 size_t slice_width = ssize * stripe_total; 150 for (jbyte* slice = start_card; slice < end_card; slice += slice_width) { 151 jbyte* worker_start_card = slice + stripe_number * ssize; 152 if (worker_start_card >= end_card) 153 return; // We're done. 154 155 jbyte* worker_end_card = worker_start_card + ssize; 156 if (worker_end_card > end_card) 157 worker_end_card = end_card; 158 159 // We do not want to scan objects more than once. In order to accomplish 160 // this, we assert that any object with an object head inside our 'slice' 161 // belongs to us. We may need to extend the range of scanned cards if the 162 // last object continues into the next 'slice'. 163 // 164 // Note! ending cards are exclusive! 165 HeapWord* slice_start = addr_for(worker_start_card); 166 HeapWord* slice_end = MIN2((HeapWord*) sp_top, addr_for(worker_end_card)); 167 168 #ifdef ASSERT 169 if (GCWorkerDelayMillis > 0) { 170 // Delay 1 worker so that it proceeds after all the work 171 // has been completed. 172 if (stripe_number < 2) { 173 os::sleep(Thread::current(), GCWorkerDelayMillis, false); 174 } 175 } 176 #endif 177 178 // If there are not objects starting within the chunk, skip it. 179 if (!start_array->object_starts_in_range(slice_start, slice_end)) { 180 continue; 181 } 182 // Update our beginning addr 183 HeapWord* first_object = start_array->object_start(slice_start); 184 debug_only(oop* first_object_within_slice = (oop*) first_object;) 185 if (first_object < slice_start) { 186 last_scanned = (oop*)(first_object + oop(first_object)->size()); 187 debug_only(first_object_within_slice = last_scanned;) 188 worker_start_card = byte_for(last_scanned); 189 } 190 191 // Update the ending addr 192 if (slice_end < (HeapWord*)sp_top) { 193 // The subtraction is important! An object may start precisely at slice_end. 194 HeapWord* last_object = start_array->object_start(slice_end - 1); 195 slice_end = last_object + oop(last_object)->size(); 196 // worker_end_card is exclusive, so bump it one past the end of last_object's 197 // covered span. 198 worker_end_card = byte_for(slice_end) + 1; 199 200 if (worker_end_card > end_card) 201 worker_end_card = end_card; 202 } 203 204 assert(slice_end <= (HeapWord*)sp_top, "Last object in slice crosses space boundary"); 205 assert(is_valid_card_address(worker_start_card), "Invalid worker start card"); 206 assert(is_valid_card_address(worker_end_card), "Invalid worker end card"); 207 // Note that worker_start_card >= worker_end_card is legal, and happens when 208 // an object spans an entire slice. 209 assert(worker_start_card <= end_card, "worker start card beyond end card"); 210 assert(worker_end_card <= end_card, "worker end card beyond end card"); 211 212 jbyte* current_card = worker_start_card; 213 while (current_card < worker_end_card) { 214 // Find an unclean card. 215 while (current_card < worker_end_card && card_is_clean(*current_card)) { 216 current_card++; 217 } 218 jbyte* first_unclean_card = current_card; 219 220 // Find the end of a run of contiguous unclean cards 221 while (current_card < worker_end_card && !card_is_clean(*current_card)) { 222 while (current_card < worker_end_card && !card_is_clean(*current_card)) { 223 current_card++; 224 } 225 226 if (current_card < worker_end_card) { 227 // Some objects may be large enough to span several cards. If such 228 // an object has more than one dirty card, separated by a clean card, 229 // we will attempt to scan it twice. The test against "last_scanned" 230 // prevents the redundant object scan, but it does not prevent newly 231 // marked cards from being cleaned. 232 HeapWord* last_object_in_dirty_region = start_array->object_start(addr_for(current_card)-1); 233 size_t size_of_last_object = oop(last_object_in_dirty_region)->size(); 234 HeapWord* end_of_last_object = last_object_in_dirty_region + size_of_last_object; 235 jbyte* ending_card_of_last_object = byte_for(end_of_last_object); 236 assert(ending_card_of_last_object <= worker_end_card, "ending_card_of_last_object is greater than worker_end_card"); 237 if (ending_card_of_last_object > current_card) { 238 // This means the object spans the next complete card. 239 // We need to bump the current_card to ending_card_of_last_object 240 current_card = ending_card_of_last_object; 241 } 242 } 243 } 244 jbyte* following_clean_card = current_card; 245 246 if (first_unclean_card < worker_end_card) { 247 oop* p = (oop*) start_array->object_start(addr_for(first_unclean_card)); 248 assert((HeapWord*)p <= addr_for(first_unclean_card), "checking"); 249 // "p" should always be >= "last_scanned" because newly GC dirtied 250 // cards are no longer scanned again (see comment at end 251 // of loop on the increment of "current_card"). Test that 252 // hypothesis before removing this code. 253 // If this code is removed, deal with the first time through 254 // the loop when the last_scanned is the object starting in 255 // the previous slice. 256 assert((p >= last_scanned) || 257 (last_scanned == first_object_within_slice), 258 "Should no longer be possible"); 259 if (p < last_scanned) { 260 // Avoid scanning more than once; this can happen because 261 // newgen cards set by GC may a different set than the 262 // originally dirty set 263 p = last_scanned; 264 } 265 oop* to = (oop*)addr_for(following_clean_card); 266 267 // Test slice_end first! 268 if ((HeapWord*)to > slice_end) { 269 to = (oop*)slice_end; 270 } else if (to > sp_top) { 271 to = sp_top; 272 } 273 274 // we know which cards to scan, now clear them 275 if (first_unclean_card <= worker_start_card+1) 276 first_unclean_card = worker_start_card+1; 277 if (following_clean_card >= worker_end_card-1) 278 following_clean_card = worker_end_card-1; 279 280 while (first_unclean_card < following_clean_card) { 281 *first_unclean_card++ = clean_card; 282 } 283 284 const int interval = PrefetchScanIntervalInBytes; 285 // scan all objects in the range 286 if (interval != 0) { 287 while (p < to) { 288 Prefetch::write(p, interval); 289 oop m = oop(p); 290 assert(m->is_oop_or_null(), err_msg("Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m))); 291 pm->push_contents(m); 292 p += m->size(); 293 } 294 pm->drain_stacks_cond_depth(); 295 } else { 296 while (p < to) { 297 oop m = oop(p); 298 assert(m->is_oop_or_null(), err_msg("Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m))); 299 pm->push_contents(m); 300 p += m->size(); 301 } 302 pm->drain_stacks_cond_depth(); 303 } 304 last_scanned = p; 305 } 306 // "current_card" is still the "following_clean_card" or 307 // the current_card is >= the worker_end_card so the 308 // loop will not execute again. 309 assert((current_card == following_clean_card) || 310 (current_card >= worker_end_card), 311 "current_card should only be incremented if it still equals " 312 "following_clean_card"); 313 // Increment current_card so that it is not processed again. 314 // It may now be dirty because a old-to-young pointer was 315 // found on it an updated. If it is now dirty, it cannot be 316 // be safely cleaned in the next iteration. 317 current_card++; 318 } 319 } 320 } 321 322 // This should be called before a scavenge. 323 void CardTableExtension::verify_all_young_refs_imprecise() { 324 CheckForUnmarkedObjects check; 325 326 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap(); 327 PSOldGen* old_gen = heap->old_gen(); 328 329 old_gen->object_iterate(&check); 330 } 331 332 // This should be called immediately after a scavenge, before mutators resume. 333 void CardTableExtension::verify_all_young_refs_precise() { 334 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap(); 335 PSOldGen* old_gen = heap->old_gen(); 336 337 CheckForPreciseMarks check( 338 heap->young_gen(), 339 barrier_set_cast<CardTableExtension>(heap->barrier_set())); 340 341 old_gen->oop_iterate_no_header(&check); 342 343 verify_all_young_refs_precise_helper(old_gen->object_space()->used_region()); 344 } 345 346 void CardTableExtension::verify_all_young_refs_precise_helper(MemRegion mr) { 347 CardTableExtension* card_table = 348 barrier_set_cast<CardTableExtension>(ParallelScavengeHeap::heap()->barrier_set()); 349 350 jbyte* bot = card_table->byte_for(mr.start()); 351 jbyte* top = card_table->byte_for(mr.end()); 352 while(bot <= top) { 353 assert(*bot == clean_card || *bot == verify_card, "Found unwanted or unknown card mark"); 354 if (*bot == verify_card) 355 *bot = youngergen_card; 356 bot++; 357 } 358 } 359 360 bool CardTableExtension::addr_is_marked_imprecise(void *addr) { 361 jbyte* p = byte_for(addr); 362 jbyte val = *p; 363 364 if (card_is_dirty(val)) 365 return true; 366 367 if (card_is_newgen(val)) 368 return true; 369 370 if (card_is_clean(val)) 371 return false; 372 373 assert(false, "Found unhandled card mark type"); 374 375 return false; 376 } 377 378 // Also includes verify_card 379 bool CardTableExtension::addr_is_marked_precise(void *addr) { 380 jbyte* p = byte_for(addr); 381 jbyte val = *p; 382 383 if (card_is_newgen(val)) 384 return true; 385 386 if (card_is_verify(val)) 387 return true; 388 389 if (card_is_clean(val)) 390 return false; 391 392 if (card_is_dirty(val)) 393 return false; 394 395 assert(false, "Found unhandled card mark type"); 396 397 return false; 398 } 399 400 // Assumes that only the base or the end changes. This allows indentification 401 // of the region that is being resized. The 402 // CardTableModRefBS::resize_covered_region() is used for the normal case 403 // where the covered regions are growing or shrinking at the high end. 404 // The method resize_covered_region_by_end() is analogous to 405 // CardTableModRefBS::resize_covered_region() but 406 // for regions that grow or shrink at the low end. 407 void CardTableExtension::resize_covered_region(MemRegion new_region) { 408 409 for (int i = 0; i < _cur_covered_regions; i++) { 410 if (_covered[i].start() == new_region.start()) { 411 // Found a covered region with the same start as the 412 // new region. The region is growing or shrinking 413 // from the start of the region. 414 resize_covered_region_by_start(new_region); 415 return; 416 } 417 if (_covered[i].start() > new_region.start()) { 418 break; 419 } 420 } 421 422 int changed_region = -1; 423 for (int j = 0; j < _cur_covered_regions; j++) { 424 if (_covered[j].end() == new_region.end()) { 425 changed_region = j; 426 // This is a case where the covered region is growing or shrinking 427 // at the start of the region. 428 assert(changed_region != -1, "Don't expect to add a covered region"); 429 assert(_covered[changed_region].byte_size() != new_region.byte_size(), 430 "The sizes should be different here"); 431 resize_covered_region_by_end(changed_region, new_region); 432 return; 433 } 434 } 435 // This should only be a new covered region (where no existing 436 // covered region matches at the start or the end). 437 assert(_cur_covered_regions < _max_covered_regions, 438 "An existing region should have been found"); 439 resize_covered_region_by_start(new_region); 440 } 441 442 void CardTableExtension::resize_covered_region_by_start(MemRegion new_region) { 443 CardTableModRefBS::resize_covered_region(new_region); 444 debug_only(verify_guard();) 445 } 446 447 void CardTableExtension::resize_covered_region_by_end(int changed_region, 448 MemRegion new_region) { 449 assert(SafepointSynchronize::is_at_safepoint(), 450 "Only expect an expansion at the low end at a GC"); 451 debug_only(verify_guard();) 452 #ifdef ASSERT 453 for (int k = 0; k < _cur_covered_regions; k++) { 454 if (_covered[k].end() == new_region.end()) { 455 assert(changed_region == k, "Changed region is incorrect"); 456 break; 457 } 458 } 459 #endif 460 461 // Commit new or uncommit old pages, if necessary. 462 if (resize_commit_uncommit(changed_region, new_region)) { 463 // Set the new start of the committed region 464 resize_update_committed_table(changed_region, new_region); 465 } 466 467 // Update card table entries 468 resize_update_card_table_entries(changed_region, new_region); 469 470 // Update the covered region 471 resize_update_covered_table(changed_region, new_region); 472 473 if (TraceCardTableModRefBS) { 474 int ind = changed_region; 475 gclog_or_tty->print_cr("CardTableModRefBS::resize_covered_region: "); 476 gclog_or_tty->print_cr(" " 477 " _covered[%d].start(): " INTPTR_FORMAT 478 " _covered[%d].last(): " INTPTR_FORMAT, 479 ind, p2i(_covered[ind].start()), 480 ind, p2i(_covered[ind].last())); 481 gclog_or_tty->print_cr(" " 482 " _committed[%d].start(): " INTPTR_FORMAT 483 " _committed[%d].last(): " INTPTR_FORMAT, 484 ind, p2i(_committed[ind].start()), 485 ind, p2i(_committed[ind].last())); 486 gclog_or_tty->print_cr(" " 487 " byte_for(start): " INTPTR_FORMAT 488 " byte_for(last): " INTPTR_FORMAT, 489 p2i(byte_for(_covered[ind].start())), 490 p2i(byte_for(_covered[ind].last()))); 491 gclog_or_tty->print_cr(" " 492 " addr_for(start): " INTPTR_FORMAT 493 " addr_for(last): " INTPTR_FORMAT, 494 p2i(addr_for((jbyte*) _committed[ind].start())), 495 p2i(addr_for((jbyte*) _committed[ind].last()))); 496 } 497 debug_only(verify_guard();) 498 } 499 500 bool CardTableExtension::resize_commit_uncommit(int changed_region, 501 MemRegion new_region) { 502 bool result = false; 503 // Commit new or uncommit old pages, if necessary. 504 MemRegion cur_committed = _committed[changed_region]; 505 assert(_covered[changed_region].end() == new_region.end(), 506 "The ends of the regions are expected to match"); 507 // Extend the start of this _committed region to 508 // to cover the start of any previous _committed region. 509 // This forms overlapping regions, but never interior regions. 510 HeapWord* min_prev_start = lowest_prev_committed_start(changed_region); 511 if (min_prev_start < cur_committed.start()) { 512 // Only really need to set start of "cur_committed" to 513 // the new start (min_prev_start) but assertion checking code 514 // below use cur_committed.end() so make it correct. 515 MemRegion new_committed = 516 MemRegion(min_prev_start, cur_committed.end()); 517 cur_committed = new_committed; 518 } 519 #ifdef ASSERT 520 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap(); 521 assert(cur_committed.start() == 522 (HeapWord*) align_size_up((uintptr_t) cur_committed.start(), 523 os::vm_page_size()), 524 "Starts should have proper alignment"); 525 #endif 526 527 jbyte* new_start = byte_for(new_region.start()); 528 // Round down because this is for the start address 529 HeapWord* new_start_aligned = 530 (HeapWord*)align_size_down((uintptr_t)new_start, os::vm_page_size()); 531 // The guard page is always committed and should not be committed over. 532 // This method is used in cases where the generation is growing toward 533 // lower addresses but the guard region is still at the end of the 534 // card table. That still makes sense when looking for writes 535 // off the end of the card table. 536 if (new_start_aligned < cur_committed.start()) { 537 // Expand the committed region 538 // 539 // Case A 540 // |+ guard +| 541 // |+ cur committed +++++++++| 542 // |+ new committed +++++++++++++++++| 543 // 544 // Case B 545 // |+ guard +| 546 // |+ cur committed +| 547 // |+ new committed +++++++| 548 // 549 // These are not expected because the calculation of the 550 // cur committed region and the new committed region 551 // share the same end for the covered region. 552 // Case C 553 // |+ guard +| 554 // |+ cur committed +| 555 // |+ new committed +++++++++++++++++| 556 // Case D 557 // |+ guard +| 558 // |+ cur committed +++++++++++| 559 // |+ new committed +++++++| 560 561 HeapWord* new_end_for_commit = 562 MIN2(cur_committed.end(), _guard_region.start()); 563 if(new_start_aligned < new_end_for_commit) { 564 MemRegion new_committed = 565 MemRegion(new_start_aligned, new_end_for_commit); 566 os::commit_memory_or_exit((char*)new_committed.start(), 567 new_committed.byte_size(), !ExecMem, 568 "card table expansion"); 569 } 570 result = true; 571 } else if (new_start_aligned > cur_committed.start()) { 572 // Shrink the committed region 573 #if 0 // uncommitting space is currently unsafe because of the interactions 574 // of growing and shrinking regions. One region A can uncommit space 575 // that it owns but which is being used by another region B (maybe). 576 // Region B has not committed the space because it was already 577 // committed by region A. 578 MemRegion uncommit_region = committed_unique_to_self(changed_region, 579 MemRegion(cur_committed.start(), new_start_aligned)); 580 if (!uncommit_region.is_empty()) { 581 if (!os::uncommit_memory((char*)uncommit_region.start(), 582 uncommit_region.byte_size())) { 583 // If the uncommit fails, ignore it. Let the 584 // committed table resizing go even though the committed 585 // table will over state the committed space. 586 } 587 } 588 #else 589 assert(!result, "Should be false with current workaround"); 590 #endif 591 } 592 assert(_committed[changed_region].end() == cur_committed.end(), 593 "end should not change"); 594 return result; 595 } 596 597 void CardTableExtension::resize_update_committed_table(int changed_region, 598 MemRegion new_region) { 599 600 jbyte* new_start = byte_for(new_region.start()); 601 // Set the new start of the committed region 602 HeapWord* new_start_aligned = 603 (HeapWord*)align_size_down((uintptr_t)new_start, 604 os::vm_page_size()); 605 MemRegion new_committed = MemRegion(new_start_aligned, 606 _committed[changed_region].end()); 607 _committed[changed_region] = new_committed; 608 _committed[changed_region].set_start(new_start_aligned); 609 } 610 611 void CardTableExtension::resize_update_card_table_entries(int changed_region, 612 MemRegion new_region) { 613 debug_only(verify_guard();) 614 MemRegion original_covered = _covered[changed_region]; 615 // Initialize the card entries. Only consider the 616 // region covered by the card table (_whole_heap) 617 jbyte* entry; 618 if (new_region.start() < _whole_heap.start()) { 619 entry = byte_for(_whole_heap.start()); 620 } else { 621 entry = byte_for(new_region.start()); 622 } 623 jbyte* end = byte_for(original_covered.start()); 624 // If _whole_heap starts at the original covered regions start, 625 // this loop will not execute. 626 while (entry < end) { *entry++ = clean_card; } 627 } 628 629 void CardTableExtension::resize_update_covered_table(int changed_region, 630 MemRegion new_region) { 631 // Update the covered region 632 _covered[changed_region].set_start(new_region.start()); 633 _covered[changed_region].set_word_size(new_region.word_size()); 634 635 // reorder regions. There should only be at most 1 out 636 // of order. 637 for (int i = _cur_covered_regions-1 ; i > 0; i--) { 638 if (_covered[i].start() < _covered[i-1].start()) { 639 MemRegion covered_mr = _covered[i-1]; 640 _covered[i-1] = _covered[i]; 641 _covered[i] = covered_mr; 642 MemRegion committed_mr = _committed[i-1]; 643 _committed[i-1] = _committed[i]; 644 _committed[i] = committed_mr; 645 break; 646 } 647 } 648 #ifdef ASSERT 649 for (int m = 0; m < _cur_covered_regions-1; m++) { 650 assert(_covered[m].start() <= _covered[m+1].start(), 651 "Covered regions out of order"); 652 assert(_committed[m].start() <= _committed[m+1].start(), 653 "Committed regions out of order"); 654 } 655 #endif 656 } 657 658 // Returns the start of any committed region that is lower than 659 // the target committed region (index ind) and that intersects the 660 // target region. If none, return start of target region. 661 // 662 // ------------- 663 // | | 664 // ------------- 665 // ------------ 666 // | target | 667 // ------------ 668 // ------------- 669 // | | 670 // ------------- 671 // ^ returns this 672 // 673 // ------------- 674 // | | 675 // ------------- 676 // ------------ 677 // | target | 678 // ------------ 679 // ------------- 680 // | | 681 // ------------- 682 // ^ returns this 683 684 HeapWord* CardTableExtension::lowest_prev_committed_start(int ind) const { 685 assert(_cur_covered_regions >= 0, "Expecting at least on region"); 686 HeapWord* min_start = _committed[ind].start(); 687 for (int j = 0; j < ind; j++) { 688 HeapWord* this_start = _committed[j].start(); 689 if ((this_start < min_start) && 690 !(_committed[j].intersection(_committed[ind])).is_empty()) { 691 min_start = this_start; 692 } 693 } 694 return min_start; 695 }