1 /* 2 * Copyright (c) 2001, 2014, 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_implementation/parallelScavenge/cardTableExtension.hpp" 27 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp" 28 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp" 29 #include "gc_implementation/parallelScavenge/psPromotionManager.hpp" 30 #include "gc_implementation/parallelScavenge/psScavenge.hpp" 31 #include "gc_implementation/parallelScavenge/psTasks.hpp" 32 #include "gc_implementation/parallelScavenge/psYoungGen.hpp" 33 #include "oops/oop.inline.hpp" 34 #include "oops/oop.psgc.inline.hpp" 35 #include "runtime/prefetch.inline.hpp" 36 37 // Checks an individual oop for missing precise marks. Mark 38 // may be either dirty or newgen. 39 class CheckForUnmarkedOops : public OopClosure { 40 private: 41 PSYoungGen* _young_gen; 42 CardTableExtension* _card_table; 43 HeapWord* _unmarked_addr; 44 jbyte* _unmarked_card; 45 46 protected: 47 template <class T> void do_oop_work(T* p) { 48 oop obj = oopDesc::load_decode_heap_oop(p); 49 if (_young_gen->is_in_reserved(obj) && 50 !_card_table->addr_is_marked_imprecise(p)) { 51 // Don't overwrite the first missing card mark 52 if (_unmarked_addr == NULL) { 53 _unmarked_addr = (HeapWord*)p; 54 _unmarked_card = _card_table->byte_for(p); 55 } 56 } 57 } 58 59 public: 60 CheckForUnmarkedOops(PSYoungGen* young_gen, CardTableExtension* card_table) : 61 _young_gen(young_gen), _card_table(card_table), _unmarked_addr(NULL) { } 62 63 virtual void do_oop(oop* p) { CheckForUnmarkedOops::do_oop_work(p); } 64 virtual void do_oop(narrowOop* p) { CheckForUnmarkedOops::do_oop_work(p); } 65 66 bool has_unmarked_oop() { 67 return _unmarked_addr != NULL; 68 } 69 }; 70 71 // Checks all objects for the existence of some type of mark, 72 // precise or imprecise, dirty or newgen. 73 class CheckForUnmarkedObjects : public ObjectClosure { 74 private: 75 PSYoungGen* _young_gen; 76 CardTableExtension* _card_table; 77 78 public: 79 CheckForUnmarkedObjects() { 80 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 81 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 82 83 _young_gen = heap->young_gen(); 84 _card_table = (CardTableExtension*)heap->barrier_set(); 85 // No point in asserting barrier set type here. Need to make CardTableExtension 86 // a unique barrier set type. 87 } 88 89 // Card marks are not precise. The current system can leave us with 90 // a mismatch of precise marks and beginning of object marks. This means 91 // we test for missing precise marks first. If any are found, we don't 92 // fail unless the object head is also unmarked. 93 virtual void do_object(oop obj) { 94 CheckForUnmarkedOops object_check(_young_gen, _card_table); 95 obj->oop_iterate_no_header(&object_check); 96 if (object_check.has_unmarked_oop()) { 97 assert(_card_table->addr_is_marked_imprecise(obj), "Found unmarked young_gen object"); 98 } 99 } 100 }; 101 102 // Checks for precise marking of oops as newgen. 103 class CheckForPreciseMarks : public OopClosure { 104 private: 105 PSYoungGen* _young_gen; 106 CardTableExtension* _card_table; 107 108 protected: 109 template <class T> void do_oop_work(T* p) { 110 oop obj = oopDesc::load_decode_heap_oop_not_null(p); 111 if (_young_gen->is_in_reserved(obj)) { 112 assert(_card_table->addr_is_marked_precise(p), "Found unmarked precise oop"); 113 _card_table->set_card_newgen(p); 114 } 115 } 116 117 public: 118 CheckForPreciseMarks( PSYoungGen* young_gen, CardTableExtension* card_table ) : 119 _young_gen(young_gen), _card_table(card_table) { } 120 121 virtual void do_oop(oop* p) { CheckForPreciseMarks::do_oop_work(p); } 122 virtual void do_oop(narrowOop* p) { CheckForPreciseMarks::do_oop_work(p); } 123 }; 124 125 // We get passed the space_top value to prevent us from traversing into 126 // the old_gen promotion labs, which cannot be safely parsed. 127 128 // Do not call this method if the space is empty. 129 // It is a waste to start tasks and get here only to 130 // do no work. If this method needs to be called 131 // when the space is empty, fix the calculation of 132 // end_card to allow sp_top == sp->bottom(). 133 134 void CardTableExtension::scavenge_contents_parallel(ObjectStartArray* start_array, 135 MutableSpace* sp, 136 HeapWord* space_top, 137 PSPromotionManager* pm, 138 uint stripe_number, 139 uint stripe_total) { 140 int ssize = 128; // Naked constant! Work unit = 64k. 141 int dirty_card_count = 0; 142 143 // It is a waste to get here if empty. 144 assert(sp->bottom() < sp->top(), "Should not be called if empty"); 145 oop* sp_top = (oop*)space_top; 146 jbyte* start_card = byte_for(sp->bottom()); 147 jbyte* end_card = byte_for(sp_top - 1) + 1; 148 oop* last_scanned = NULL; // Prevent scanning objects more than once 149 // The width of the stripe ssize*stripe_total must be 150 // consistent with the number of stripes so that the complete slice 151 // is covered. 152 size_t slice_width = ssize * stripe_total; 153 for (jbyte* slice = start_card; slice < end_card; slice += slice_width) { 154 jbyte* worker_start_card = slice + stripe_number * ssize; 155 if (worker_start_card >= end_card) 156 return; // We're done. 157 158 jbyte* worker_end_card = worker_start_card + ssize; 159 if (worker_end_card > end_card) 160 worker_end_card = end_card; 161 162 // We do not want to scan objects more than once. In order to accomplish 163 // this, we assert that any object with an object head inside our 'slice' 164 // belongs to us. We may need to extend the range of scanned cards if the 165 // last object continues into the next 'slice'. 166 // 167 // Note! ending cards are exclusive! 168 HeapWord* slice_start = addr_for(worker_start_card); 169 HeapWord* slice_end = MIN2((HeapWord*) sp_top, addr_for(worker_end_card)); 170 171 #ifdef ASSERT 172 if (GCWorkerDelayMillis > 0) { 173 // Delay 1 worker so that it proceeds after all the work 174 // has been completed. 175 if (stripe_number < 2) { 176 os::sleep(Thread::current(), GCWorkerDelayMillis, false); 177 } 178 } 179 #endif 180 181 // If there are not objects starting within the chunk, skip it. 182 if (!start_array->object_starts_in_range(slice_start, slice_end)) { 183 continue; 184 } 185 // Update our beginning addr 186 HeapWord* first_object = start_array->object_start(slice_start); 187 debug_only(oop* first_object_within_slice = (oop*) first_object;) 188 if (first_object < slice_start) { 189 last_scanned = (oop*)(first_object + oop(first_object)->size()); 190 debug_only(first_object_within_slice = last_scanned;) 191 worker_start_card = byte_for(last_scanned); 192 } 193 194 // Update the ending addr 195 if (slice_end < (HeapWord*)sp_top) { 196 // The subtraction is important! An object may start precisely at slice_end. 197 HeapWord* last_object = start_array->object_start(slice_end - 1); 198 slice_end = last_object + oop(last_object)->size(); 199 // worker_end_card is exclusive, so bump it one past the end of last_object's 200 // covered span. 201 worker_end_card = byte_for(slice_end) + 1; 202 203 if (worker_end_card > end_card) 204 worker_end_card = end_card; 205 } 206 207 assert(slice_end <= (HeapWord*)sp_top, "Last object in slice crosses space boundary"); 208 assert(is_valid_card_address(worker_start_card), "Invalid worker start card"); 209 assert(is_valid_card_address(worker_end_card), "Invalid worker end card"); 210 // Note that worker_start_card >= worker_end_card is legal, and happens when 211 // an object spans an entire slice. 212 assert(worker_start_card <= end_card, "worker start card beyond end card"); 213 assert(worker_end_card <= end_card, "worker end card beyond end card"); 214 215 jbyte* current_card = worker_start_card; 216 while (current_card < worker_end_card) { 217 // Find an unclean card. 218 while (current_card < worker_end_card && card_is_clean(*current_card)) { 219 current_card++; 220 } 221 jbyte* first_unclean_card = current_card; 222 223 // Find the end of a run of contiguous unclean cards 224 while (current_card < worker_end_card && !card_is_clean(*current_card)) { 225 while (current_card < worker_end_card && !card_is_clean(*current_card)) { 226 current_card++; 227 } 228 229 if (current_card < worker_end_card) { 230 // Some objects may be large enough to span several cards. If such 231 // an object has more than one dirty card, separated by a clean card, 232 // we will attempt to scan it twice. The test against "last_scanned" 233 // prevents the redundant object scan, but it does not prevent newly 234 // marked cards from being cleaned. 235 HeapWord* last_object_in_dirty_region = start_array->object_start(addr_for(current_card)-1); 236 size_t size_of_last_object = oop(last_object_in_dirty_region)->size(); 237 HeapWord* end_of_last_object = last_object_in_dirty_region + size_of_last_object; 238 jbyte* ending_card_of_last_object = byte_for(end_of_last_object); 239 assert(ending_card_of_last_object <= worker_end_card, "ending_card_of_last_object is greater than worker_end_card"); 240 if (ending_card_of_last_object > current_card) { 241 // This means the object spans the next complete card. 242 // We need to bump the current_card to ending_card_of_last_object 243 current_card = ending_card_of_last_object; 244 } 245 } 246 } 247 jbyte* following_clean_card = current_card; 248 249 if (first_unclean_card < worker_end_card) { 250 oop* p = (oop*) start_array->object_start(addr_for(first_unclean_card)); 251 assert((HeapWord*)p <= addr_for(first_unclean_card), "checking"); 252 // "p" should always be >= "last_scanned" because newly GC dirtied 253 // cards are no longer scanned again (see comment at end 254 // of loop on the increment of "current_card"). Test that 255 // hypothesis before removing this code. 256 // If this code is removed, deal with the first time through 257 // the loop when the last_scanned is the object starting in 258 // the previous slice. 259 assert((p >= last_scanned) || 260 (last_scanned == first_object_within_slice), 261 "Should no longer be possible"); 262 if (p < last_scanned) { 263 // Avoid scanning more than once; this can happen because 264 // newgen cards set by GC may a different set than the 265 // originally dirty set 266 p = last_scanned; 267 } 268 oop* to = (oop*)addr_for(following_clean_card); 269 270 // Test slice_end first! 271 if ((HeapWord*)to > slice_end) { 272 to = (oop*)slice_end; 273 } else if (to > sp_top) { 274 to = sp_top; 275 } 276 277 // we know which cards to scan, now clear them 278 if (first_unclean_card <= worker_start_card+1) 279 first_unclean_card = worker_start_card+1; 280 if (following_clean_card >= worker_end_card-1) 281 following_clean_card = worker_end_card-1; 282 283 while (first_unclean_card < following_clean_card) { 284 *first_unclean_card++ = clean_card; 285 } 286 287 const int interval = PrefetchScanIntervalInBytes; 288 // scan all objects in the range 289 if (interval != 0) { 290 while (p < to) { 291 Prefetch::write(p, interval); 292 oop m = oop(p); 293 assert(m->is_oop_or_null(), err_msg("Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m))); 294 m->push_contents(pm); 295 p += m->size(); 296 } 297 pm->drain_stacks_cond_depth(); 298 } else { 299 while (p < to) { 300 oop m = oop(p); 301 assert(m->is_oop_or_null(), err_msg("Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m))); 302 m->push_contents(pm); 303 p += m->size(); 304 } 305 pm->drain_stacks_cond_depth(); 306 } 307 last_scanned = p; 308 } 309 // "current_card" is still the "following_clean_card" or 310 // the current_card is >= the worker_end_card so the 311 // loop will not execute again. 312 assert((current_card == following_clean_card) || 313 (current_card >= worker_end_card), 314 "current_card should only be incremented if it still equals " 315 "following_clean_card"); 316 // Increment current_card so that it is not processed again. 317 // It may now be dirty because a old-to-young pointer was 318 // found on it an updated. If it is now dirty, it cannot be 319 // be safely cleaned in the next iteration. 320 current_card++; 321 } 322 } 323 } 324 325 // This should be called before a scavenge. 326 void CardTableExtension::verify_all_young_refs_imprecise() { 327 CheckForUnmarkedObjects check; 328 329 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 330 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 331 332 PSOldGen* old_gen = heap->old_gen(); 333 334 old_gen->object_iterate(&check); 335 } 336 337 // This should be called immediately after a scavenge, before mutators resume. 338 void CardTableExtension::verify_all_young_refs_precise() { 339 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 340 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); 341 342 PSOldGen* old_gen = heap->old_gen(); 343 344 CheckForPreciseMarks check(heap->young_gen(), (CardTableExtension*)heap->barrier_set()); 345 346 old_gen->oop_iterate_no_header(&check); 347 348 verify_all_young_refs_precise_helper(old_gen->object_space()->used_region()); 349 } 350 351 void CardTableExtension::verify_all_young_refs_precise_helper(MemRegion mr) { 352 CardTableExtension* card_table = (CardTableExtension*)Universe::heap()->barrier_set(); 353 // FIX ME ASSERT HERE 354 355 jbyte* bot = card_table->byte_for(mr.start()); 356 jbyte* top = card_table->byte_for(mr.end()); 357 while(bot <= top) { 358 assert(*bot == clean_card || *bot == verify_card, "Found unwanted or unknown card mark"); 359 if (*bot == verify_card) 360 *bot = youngergen_card; 361 bot++; 362 } 363 } 364 365 bool CardTableExtension::addr_is_marked_imprecise(void *addr) { 366 jbyte* p = byte_for(addr); 367 jbyte val = *p; 368 369 if (card_is_dirty(val)) 370 return true; 371 372 if (card_is_newgen(val)) 373 return true; 374 375 if (card_is_clean(val)) 376 return false; 377 378 assert(false, "Found unhandled card mark type"); 379 380 return false; 381 } 382 383 // Also includes verify_card 384 bool CardTableExtension::addr_is_marked_precise(void *addr) { 385 jbyte* p = byte_for(addr); 386 jbyte val = *p; 387 388 if (card_is_newgen(val)) 389 return true; 390 391 if (card_is_verify(val)) 392 return true; 393 394 if (card_is_clean(val)) 395 return false; 396 397 if (card_is_dirty(val)) 398 return false; 399 400 assert(false, "Found unhandled card mark type"); 401 402 return false; 403 } 404 405 // Assumes that only the base or the end changes. This allows indentification 406 // of the region that is being resized. The 407 // CardTableModRefBS::resize_covered_region() is used for the normal case 408 // where the covered regions are growing or shrinking at the high end. 409 // The method resize_covered_region_by_end() is analogous to 410 // CardTableModRefBS::resize_covered_region() but 411 // for regions that grow or shrink at the low end. 412 void CardTableExtension::resize_covered_region(MemRegion new_region) { 413 414 for (int i = 0; i < _cur_covered_regions; i++) { 415 if (_covered[i].start() == new_region.start()) { 416 // Found a covered region with the same start as the 417 // new region. The region is growing or shrinking 418 // from the start of the region. 419 resize_covered_region_by_start(new_region); 420 return; 421 } 422 if (_covered[i].start() > new_region.start()) { 423 break; 424 } 425 } 426 427 int changed_region = -1; 428 for (int j = 0; j < _cur_covered_regions; j++) { 429 if (_covered[j].end() == new_region.end()) { 430 changed_region = j; 431 // This is a case where the covered region is growing or shrinking 432 // at the start of the region. 433 assert(changed_region != -1, "Don't expect to add a covered region"); 434 assert(_covered[changed_region].byte_size() != new_region.byte_size(), 435 "The sizes should be different here"); 436 resize_covered_region_by_end(changed_region, new_region); 437 return; 438 } 439 } 440 // This should only be a new covered region (where no existing 441 // covered region matches at the start or the end). 442 assert(_cur_covered_regions < _max_covered_regions, 443 "An existing region should have been found"); 444 resize_covered_region_by_start(new_region); 445 } 446 447 void CardTableExtension::resize_covered_region_by_start(MemRegion new_region) { 448 CardTableModRefBS::resize_covered_region(new_region); 449 debug_only(verify_guard();) 450 } 451 452 void CardTableExtension::resize_covered_region_by_end(int changed_region, 453 MemRegion new_region) { 454 assert(SafepointSynchronize::is_at_safepoint(), 455 "Only expect an expansion at the low end at a GC"); 456 debug_only(verify_guard();) 457 #ifdef ASSERT 458 for (int k = 0; k < _cur_covered_regions; k++) { 459 if (_covered[k].end() == new_region.end()) { 460 assert(changed_region == k, "Changed region is incorrect"); 461 break; 462 } 463 } 464 #endif 465 466 // Commit new or uncommit old pages, if necessary. 467 if (resize_commit_uncommit(changed_region, new_region)) { 468 // Set the new start of the committed region 469 resize_update_committed_table(changed_region, new_region); 470 } 471 472 // Update card table entries 473 resize_update_card_table_entries(changed_region, new_region); 474 475 // Update the covered region 476 resize_update_covered_table(changed_region, new_region); 477 478 if (TraceCardTableModRefBS) { 479 int ind = changed_region; 480 gclog_or_tty->print_cr("CardTableModRefBS::resize_covered_region: "); 481 gclog_or_tty->print_cr(" " 482 " _covered[%d].start(): " INTPTR_FORMAT 483 " _covered[%d].last(): " INTPTR_FORMAT, 484 ind, p2i(_covered[ind].start()), 485 ind, p2i(_covered[ind].last())); 486 gclog_or_tty->print_cr(" " 487 " _committed[%d].start(): " INTPTR_FORMAT 488 " _committed[%d].last(): " INTPTR_FORMAT, 489 ind, p2i(_committed[ind].start()), 490 ind, p2i(_committed[ind].last())); 491 gclog_or_tty->print_cr(" " 492 " byte_for(start): " INTPTR_FORMAT 493 " byte_for(last): " INTPTR_FORMAT, 494 p2i(byte_for(_covered[ind].start())), 495 p2i(byte_for(_covered[ind].last()))); 496 gclog_or_tty->print_cr(" " 497 " addr_for(start): " INTPTR_FORMAT 498 " addr_for(last): " INTPTR_FORMAT, 499 p2i(addr_for((jbyte*) _committed[ind].start())), 500 p2i(addr_for((jbyte*) _committed[ind].last()))); 501 } 502 debug_only(verify_guard();) 503 } 504 505 bool CardTableExtension::resize_commit_uncommit(int changed_region, 506 MemRegion new_region) { 507 bool result = false; 508 // Commit new or uncommit old pages, if necessary. 509 MemRegion cur_committed = _committed[changed_region]; 510 assert(_covered[changed_region].end() == new_region.end(), 511 "The ends of the regions are expected to match"); 512 // Extend the start of this _committed region to 513 // to cover the start of any previous _committed region. 514 // This forms overlapping regions, but never interior regions. 515 HeapWord* min_prev_start = lowest_prev_committed_start(changed_region); 516 if (min_prev_start < cur_committed.start()) { 517 // Only really need to set start of "cur_committed" to 518 // the new start (min_prev_start) but assertion checking code 519 // below use cur_committed.end() so make it correct. 520 MemRegion new_committed = 521 MemRegion(min_prev_start, cur_committed.end()); 522 cur_committed = new_committed; 523 } 524 #ifdef ASSERT 525 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); 526 assert(cur_committed.start() == 527 (HeapWord*) align_size_up((uintptr_t) cur_committed.start(), 528 os::vm_page_size()), 529 "Starts should have proper alignment"); 530 #endif 531 532 jbyte* new_start = byte_for(new_region.start()); 533 // Round down because this is for the start address 534 HeapWord* new_start_aligned = 535 (HeapWord*)align_size_down((uintptr_t)new_start, os::vm_page_size()); 536 // The guard page is always committed and should not be committed over. 537 // This method is used in cases where the generation is growing toward 538 // lower addresses but the guard region is still at the end of the 539 // card table. That still makes sense when looking for writes 540 // off the end of the card table. 541 if (new_start_aligned < cur_committed.start()) { 542 // Expand the committed region 543 // 544 // Case A 545 // |+ guard +| 546 // |+ cur committed +++++++++| 547 // |+ new committed +++++++++++++++++| 548 // 549 // Case B 550 // |+ guard +| 551 // |+ cur committed +| 552 // |+ new committed +++++++| 553 // 554 // These are not expected because the calculation of the 555 // cur committed region and the new committed region 556 // share the same end for the covered region. 557 // Case C 558 // |+ guard +| 559 // |+ cur committed +| 560 // |+ new committed +++++++++++++++++| 561 // Case D 562 // |+ guard +| 563 // |+ cur committed +++++++++++| 564 // |+ new committed +++++++| 565 566 HeapWord* new_end_for_commit = 567 MIN2(cur_committed.end(), _guard_region.start()); 568 if(new_start_aligned < new_end_for_commit) { 569 MemRegion new_committed = 570 MemRegion(new_start_aligned, new_end_for_commit); 571 os::commit_memory_or_exit((char*)new_committed.start(), 572 new_committed.byte_size(), !ExecMem, 573 "card table expansion"); 574 } 575 result = true; 576 } else if (new_start_aligned > cur_committed.start()) { 577 // Shrink the committed region 578 #if 0 // uncommitting space is currently unsafe because of the interactions 579 // of growing and shrinking regions. One region A can uncommit space 580 // that it owns but which is being used by another region B (maybe). 581 // Region B has not committed the space because it was already 582 // committed by region A. 583 MemRegion uncommit_region = committed_unique_to_self(changed_region, 584 MemRegion(cur_committed.start(), new_start_aligned)); 585 if (!uncommit_region.is_empty()) { 586 if (!os::uncommit_memory((char*)uncommit_region.start(), 587 uncommit_region.byte_size())) { 588 // If the uncommit fails, ignore it. Let the 589 // committed table resizing go even though the committed 590 // table will over state the committed space. 591 } 592 } 593 #else 594 assert(!result, "Should be false with current workaround"); 595 #endif 596 } 597 assert(_committed[changed_region].end() == cur_committed.end(), 598 "end should not change"); 599 return result; 600 } 601 602 void CardTableExtension::resize_update_committed_table(int changed_region, 603 MemRegion new_region) { 604 605 jbyte* new_start = byte_for(new_region.start()); 606 // Set the new start of the committed region 607 HeapWord* new_start_aligned = 608 (HeapWord*)align_size_down((uintptr_t)new_start, 609 os::vm_page_size()); 610 MemRegion new_committed = MemRegion(new_start_aligned, 611 _committed[changed_region].end()); 612 _committed[changed_region] = new_committed; 613 _committed[changed_region].set_start(new_start_aligned); 614 } 615 616 void CardTableExtension::resize_update_card_table_entries(int changed_region, 617 MemRegion new_region) { 618 debug_only(verify_guard();) 619 MemRegion original_covered = _covered[changed_region]; 620 // Initialize the card entries. Only consider the 621 // region covered by the card table (_whole_heap) 622 jbyte* entry; 623 if (new_region.start() < _whole_heap.start()) { 624 entry = byte_for(_whole_heap.start()); 625 } else { 626 entry = byte_for(new_region.start()); 627 } 628 jbyte* end = byte_for(original_covered.start()); 629 // If _whole_heap starts at the original covered regions start, 630 // this loop will not execute. 631 while (entry < end) { *entry++ = clean_card; } 632 } 633 634 void CardTableExtension::resize_update_covered_table(int changed_region, 635 MemRegion new_region) { 636 // Update the covered region 637 _covered[changed_region].set_start(new_region.start()); 638 _covered[changed_region].set_word_size(new_region.word_size()); 639 640 // reorder regions. There should only be at most 1 out 641 // of order. 642 for (int i = _cur_covered_regions-1 ; i > 0; i--) { 643 if (_covered[i].start() < _covered[i-1].start()) { 644 MemRegion covered_mr = _covered[i-1]; 645 _covered[i-1] = _covered[i]; 646 _covered[i] = covered_mr; 647 MemRegion committed_mr = _committed[i-1]; 648 _committed[i-1] = _committed[i]; 649 _committed[i] = committed_mr; 650 break; 651 } 652 } 653 #ifdef ASSERT 654 for (int m = 0; m < _cur_covered_regions-1; m++) { 655 assert(_covered[m].start() <= _covered[m+1].start(), 656 "Covered regions out of order"); 657 assert(_committed[m].start() <= _committed[m+1].start(), 658 "Committed regions out of order"); 659 } 660 #endif 661 } 662 663 // Returns the start of any committed region that is lower than 664 // the target committed region (index ind) and that intersects the 665 // target region. If none, return start of target region. 666 // 667 // ------------- 668 // | | 669 // ------------- 670 // ------------ 671 // | target | 672 // ------------ 673 // ------------- 674 // | | 675 // ------------- 676 // ^ returns this 677 // 678 // ------------- 679 // | | 680 // ------------- 681 // ------------ 682 // | target | 683 // ------------ 684 // ------------- 685 // | | 686 // ------------- 687 // ^ returns this 688 689 HeapWord* CardTableExtension::lowest_prev_committed_start(int ind) const { 690 assert(_cur_covered_regions >= 0, "Expecting at least on region"); 691 HeapWord* min_start = _committed[ind].start(); 692 for (int j = 0; j < ind; j++) { 693 HeapWord* this_start = _committed[j].start(); 694 if ((this_start < min_start) && 695 !(_committed[j].intersection(_committed[ind])).is_empty()) { 696 min_start = this_start; 697 } 698 } 699 return min_start; 700 }