1 /*
   2  * Copyright (c) 2000, 2013, 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 "memory/allocation.inline.hpp"
  27 #include "memory/cardTableModRefBS.hpp"
  28 #include "memory/cardTableRS.hpp"
  29 #include "memory/sharedHeap.hpp"
  30 #include "memory/space.hpp"
  31 #include "memory/space.inline.hpp"
  32 #include "memory/universe.hpp"
  33 #include "runtime/java.hpp"
  34 #include "runtime/mutexLocker.hpp"
  35 #include "runtime/virtualspace.hpp"
  36 #include "services/memTracker.hpp"
  37 #include "utilities/macros.hpp"
  38 #ifdef COMPILER1
  39 #include "c1/c1_LIR.hpp"
  40 #include "c1/c1_LIRGenerator.hpp"
  41 #endif
  42 
  43 // This kind of "BarrierSet" allows a "CollectedHeap" to detect and
  44 // enumerate ref fields that have been modified (since the last
  45 // enumeration.)
  46 
  47 size_t CardTableModRefBS::cards_required(size_t covered_words)
  48 {
  49   // Add one for a guard card, used to detect errors.
  50   const size_t words = align_size_up(covered_words, card_size_in_words);
  51   return words / card_size_in_words + 1;
  52 }
  53 
  54 size_t CardTableModRefBS::compute_byte_map_size()
  55 {
  56   assert(_guard_index == cards_required(_whole_heap.word_size()) - 1,
  57                                         "unitialized, check declaration order");
  58   assert(_page_size != 0, "unitialized, check declaration order");
  59   const size_t granularity = os::vm_allocation_granularity();
  60   return align_size_up(_guard_index + 1, MAX2(_page_size, granularity));
  61 }
  62 
  63 CardTableModRefBS::CardTableModRefBS(MemRegion whole_heap,
  64                                      int max_covered_regions):
  65   ModRefBarrierSet(max_covered_regions),
  66   _whole_heap(whole_heap),
  67   _guard_index(cards_required(whole_heap.word_size()) - 1),
  68   _last_valid_index(_guard_index - 1),
  69   _page_size(os::vm_page_size()),
  70   _byte_map_size(compute_byte_map_size())
  71 {
  72   _kind = BarrierSet::CardTableModRef;
  73 
  74   HeapWord* low_bound  = _whole_heap.start();
  75   HeapWord* high_bound = _whole_heap.end();
  76   assert((uintptr_t(low_bound)  & (card_size - 1))  == 0, "heap must start at card boundary");
  77   assert((uintptr_t(high_bound) & (card_size - 1))  == 0, "heap must end at card boundary");
  78 
  79   assert(card_size <= 512, "card_size must be less than 512"); // why?
  80 
  81   _covered   = new MemRegion[max_covered_regions];
  82   _committed = new MemRegion[max_covered_regions];
  83   if (_covered == NULL || _committed == NULL) {
  84     vm_exit_during_initialization("couldn't alloc card table covered region set.");
  85   }
  86 
  87   _cur_covered_regions = 0;
  88   const size_t rs_align = _page_size == (size_t) os::vm_page_size() ? 0 :
  89     MAX2(_page_size, (size_t) os::vm_allocation_granularity());
  90   ReservedSpace heap_rs(_byte_map_size, rs_align, false);
  91 
  92   MemTracker::record_virtual_memory_type((address)heap_rs.base(), mtGC);
  93 
  94   os::trace_page_sizes("card table", _guard_index + 1, _guard_index + 1,
  95                        _page_size, heap_rs.base(), heap_rs.size());
  96   if (!heap_rs.is_reserved()) {
  97     vm_exit_during_initialization("Could not reserve enough space for the "
  98                                   "card marking array");
  99   }
 100 
 101   // The assember store_check code will do an unsigned shift of the oop,
 102   // then add it to byte_map_base, i.e.
 103   //
 104   //   _byte_map = byte_map_base + (uintptr_t(low_bound) >> card_shift)
 105   _byte_map = (jbyte*) heap_rs.base();
 106   byte_map_base = _byte_map - (uintptr_t(low_bound) >> card_shift);
 107   assert(byte_for(low_bound) == &_byte_map[0], "Checking start of map");
 108   assert(byte_for(high_bound-1) <= &_byte_map[_last_valid_index], "Checking end of map");
 109 
 110   jbyte* guard_card = &_byte_map[_guard_index];
 111   uintptr_t guard_page = align_size_down((uintptr_t)guard_card, _page_size);
 112   _guard_region = MemRegion((HeapWord*)guard_page, _page_size);
 113   os::commit_memory_or_exit((char*)guard_page, _page_size, _page_size,
 114                             !ExecMem, "card table last card");
 115   *guard_card = last_card;
 116 
 117    _lowest_non_clean =
 118     NEW_C_HEAP_ARRAY(CardArr, max_covered_regions, mtGC);
 119   _lowest_non_clean_chunk_size =
 120     NEW_C_HEAP_ARRAY(size_t, max_covered_regions, mtGC);
 121   _lowest_non_clean_base_chunk_index =
 122     NEW_C_HEAP_ARRAY(uintptr_t, max_covered_regions, mtGC);
 123   _last_LNC_resizing_collection =
 124     NEW_C_HEAP_ARRAY(int, max_covered_regions, mtGC);
 125   if (_lowest_non_clean == NULL
 126       || _lowest_non_clean_chunk_size == NULL
 127       || _lowest_non_clean_base_chunk_index == NULL
 128       || _last_LNC_resizing_collection == NULL)
 129     vm_exit_during_initialization("couldn't allocate an LNC array.");
 130   for (int i = 0; i < max_covered_regions; i++) {
 131     _lowest_non_clean[i] = NULL;
 132     _lowest_non_clean_chunk_size[i] = 0;
 133     _last_LNC_resizing_collection[i] = -1;
 134   }
 135 
 136   if (TraceCardTableModRefBS) {
 137     gclog_or_tty->print_cr("CardTableModRefBS::CardTableModRefBS: ");
 138     gclog_or_tty->print_cr("  "
 139                   "  &_byte_map[0]: " INTPTR_FORMAT
 140                   "  &_byte_map[_last_valid_index]: " INTPTR_FORMAT,
 141                   &_byte_map[0],
 142                   &_byte_map[_last_valid_index]);
 143     gclog_or_tty->print_cr("  "
 144                   "  byte_map_base: " INTPTR_FORMAT,
 145                   byte_map_base);
 146   }
 147 }
 148 
 149 CardTableModRefBS::~CardTableModRefBS() {
 150   if (_covered) {
 151     delete[] _covered;
 152     _covered = NULL;
 153   }
 154   if (_committed) {
 155     delete[] _committed;
 156     _committed = NULL;
 157   }
 158   if (_lowest_non_clean) {
 159     FREE_C_HEAP_ARRAY(CardArr, _lowest_non_clean, mtGC);
 160     _lowest_non_clean = NULL;
 161   }
 162   if (_lowest_non_clean_chunk_size) {
 163     FREE_C_HEAP_ARRAY(size_t, _lowest_non_clean_chunk_size, mtGC);
 164     _lowest_non_clean_chunk_size = NULL;
 165   }
 166   if (_lowest_non_clean_base_chunk_index) {
 167     FREE_C_HEAP_ARRAY(uintptr_t, _lowest_non_clean_base_chunk_index, mtGC);
 168     _lowest_non_clean_base_chunk_index = NULL;
 169   }
 170   if (_last_LNC_resizing_collection) {
 171     FREE_C_HEAP_ARRAY(int, _last_LNC_resizing_collection, mtGC);
 172     _last_LNC_resizing_collection = NULL;
 173   }
 174 }
 175 
 176 int CardTableModRefBS::find_covering_region_by_base(HeapWord* base) {
 177   int i;
 178   for (i = 0; i < _cur_covered_regions; i++) {
 179     if (_covered[i].start() == base) return i;
 180     if (_covered[i].start() > base) break;
 181   }
 182   // If we didn't find it, create a new one.
 183   assert(_cur_covered_regions < _max_covered_regions,
 184          "too many covered regions");
 185   // Move the ones above up, to maintain sorted order.
 186   for (int j = _cur_covered_regions; j > i; j--) {
 187     _covered[j] = _covered[j-1];
 188     _committed[j] = _committed[j-1];
 189   }
 190   int res = i;
 191   _cur_covered_regions++;
 192   _covered[res].set_start(base);
 193   _covered[res].set_word_size(0);
 194   jbyte* ct_start = byte_for(base);
 195   uintptr_t ct_start_aligned = align_size_down((uintptr_t)ct_start, _page_size);
 196   _committed[res].set_start((HeapWord*)ct_start_aligned);
 197   _committed[res].set_word_size(0);
 198   return res;
 199 }
 200 
 201 int CardTableModRefBS::find_covering_region_containing(HeapWord* addr) {
 202   for (int i = 0; i < _cur_covered_regions; i++) {
 203     if (_covered[i].contains(addr)) {
 204       return i;
 205     }
 206   }
 207   assert(0, "address outside of heap?");
 208   return -1;
 209 }
 210 
 211 HeapWord* CardTableModRefBS::largest_prev_committed_end(int ind) const {
 212   HeapWord* max_end = NULL;
 213   for (int j = 0; j < ind; j++) {
 214     HeapWord* this_end = _committed[j].end();
 215     if (this_end > max_end) max_end = this_end;
 216   }
 217   return max_end;
 218 }
 219 
 220 MemRegion CardTableModRefBS::committed_unique_to_self(int self,
 221                                                       MemRegion mr) const {
 222   MemRegion result = mr;
 223   for (int r = 0; r < _cur_covered_regions; r += 1) {
 224     if (r != self) {
 225       result = result.minus(_committed[r]);
 226     }
 227   }
 228   // Never include the guard page.
 229   result = result.minus(_guard_region);
 230   return result;
 231 }
 232 
 233 void CardTableModRefBS::resize_covered_region(MemRegion new_region) {
 234   // We don't change the start of a region, only the end.
 235   assert(_whole_heap.contains(new_region),
 236            "attempt to cover area not in reserved area");
 237   debug_only(verify_guard();)
 238   // collided is true if the expansion would push into another committed region
 239   debug_only(bool collided = false;)
 240   int const ind = find_covering_region_by_base(new_region.start());
 241   MemRegion const old_region = _covered[ind];
 242   assert(old_region.start() == new_region.start(), "just checking");
 243   if (new_region.word_size() != old_region.word_size()) {
 244     // Commit new or uncommit old pages, if necessary.
 245     MemRegion cur_committed = _committed[ind];
 246     // Extend the end of this _commited region
 247     // to cover the end of any lower _committed regions.
 248     // This forms overlapping regions, but never interior regions.
 249     HeapWord* const max_prev_end = largest_prev_committed_end(ind);
 250     if (max_prev_end > cur_committed.end()) {
 251       cur_committed.set_end(max_prev_end);
 252     }
 253     // Align the end up to a page size (starts are already aligned).
 254     jbyte* const new_end = byte_after(new_region.last());
 255     HeapWord* new_end_aligned =
 256       (HeapWord*) align_size_up((uintptr_t)new_end, _page_size);
 257     assert(new_end_aligned >= (HeapWord*) new_end,
 258            "align up, but less");
 259     // Check the other regions (excludes "ind") to ensure that
 260     // the new_end_aligned does not intrude onto the committed
 261     // space of another region.
 262     int ri = 0;
 263     for (ri = 0; ri < _cur_covered_regions; ri++) {
 264       if (ri != ind) {
 265         if (_committed[ri].contains(new_end_aligned)) {
 266           // The prior check included in the assert
 267           // (new_end_aligned >= _committed[ri].start())
 268           // is redundant with the "contains" test.
 269           // Any region containing the new end
 270           // should start at or beyond the region found (ind)
 271           // for the new end (committed regions are not expected to
 272           // be proper subsets of other committed regions).
 273           assert(_committed[ri].start() >= _committed[ind].start(),
 274                  "New end of committed region is inconsistent");
 275           new_end_aligned = _committed[ri].start();
 276           // new_end_aligned can be equal to the start of its
 277           // committed region (i.e., of "ind") if a second
 278           // region following "ind" also start at the same location
 279           // as "ind".
 280           assert(new_end_aligned >= _committed[ind].start(),
 281             "New end of committed region is before start");
 282           debug_only(collided = true;)
 283           // Should only collide with 1 region
 284           break;
 285         }
 286       }
 287     }
 288 #ifdef ASSERT
 289     for (++ri; ri < _cur_covered_regions; ri++) {
 290       assert(!_committed[ri].contains(new_end_aligned),
 291         "New end of committed region is in a second committed region");
 292     }
 293 #endif
 294     // The guard page is always committed and should not be committed over.
 295     // "guarded" is used for assertion checking below and recalls the fact
 296     // that the would-be end of the new committed region would have
 297     // penetrated the guard page.
 298     HeapWord* new_end_for_commit = new_end_aligned;
 299 
 300     DEBUG_ONLY(bool guarded = false;)
 301     if (new_end_for_commit > _guard_region.start()) {
 302       new_end_for_commit = _guard_region.start();
 303       DEBUG_ONLY(guarded = true;)
 304     }
 305 
 306     if (new_end_for_commit > cur_committed.end()) {
 307       // Must commit new pages.
 308       MemRegion const new_committed =
 309         MemRegion(cur_committed.end(), new_end_for_commit);
 310 
 311       assert(!new_committed.is_empty(), "Region should not be empty here");
 312       os::commit_memory_or_exit((char*)new_committed.start(),
 313                                 new_committed.byte_size(), _page_size,
 314                                 !ExecMem, "card table expansion");
 315     // Use new_end_aligned (as opposed to new_end_for_commit) because
 316     // the cur_committed region may include the guard region.
 317     } else if (new_end_aligned < cur_committed.end()) {
 318       // Must uncommit pages.
 319       MemRegion const uncommit_region =
 320         committed_unique_to_self(ind, MemRegion(new_end_aligned,
 321                                                 cur_committed.end()));
 322       if (!uncommit_region.is_empty()) {
 323         // It is not safe to uncommit cards if the boundary between
 324         // the generations is moving.  A shrink can uncommit cards
 325         // owned by generation A but being used by generation B.
 326         if (!UseAdaptiveGCBoundary) {
 327           if (!os::uncommit_memory((char*)uncommit_region.start(),
 328                                    uncommit_region.byte_size())) {
 329             assert(false, "Card table contraction failed");
 330             // The call failed so don't change the end of the
 331             // committed region.  This is better than taking the
 332             // VM down.
 333             new_end_aligned = _committed[ind].end();
 334           }
 335         } else {
 336           new_end_aligned = _committed[ind].end();
 337         }
 338       }
 339     }
 340     // In any case, we can reset the end of the current committed entry.
 341     _committed[ind].set_end(new_end_aligned);
 342 
 343 #ifdef ASSERT
 344     // Check that the last card in the new region is committed according
 345     // to the tables.
 346     bool covered = false;
 347     for (int cr = 0; cr < _cur_covered_regions; cr++) {
 348       if (_committed[cr].contains(new_end - 1)) {
 349         covered = true;
 350         break;
 351       }
 352     }
 353     assert(covered, "Card for end of new region not committed");
 354 #endif
 355 
 356     // The default of 0 is not necessarily clean cards.
 357     jbyte* entry;
 358     if (old_region.last() < _whole_heap.start()) {
 359       entry = byte_for(_whole_heap.start());
 360     } else {
 361       entry = byte_after(old_region.last());
 362     }
 363     assert(index_for(new_region.last()) <  _guard_index,
 364       "The guard card will be overwritten");
 365     // This line commented out cleans the newly expanded region and
 366     // not the aligned up expanded region.
 367     // jbyte* const end = byte_after(new_region.last());
 368     jbyte* const end = (jbyte*) new_end_for_commit;
 369     assert((end >= byte_after(new_region.last())) || collided || guarded,
 370       "Expect to be beyond new region unless impacting another region");
 371     // do nothing if we resized downward.
 372 #ifdef ASSERT
 373     for (int ri = 0; ri < _cur_covered_regions; ri++) {
 374       if (ri != ind) {
 375         // The end of the new committed region should not
 376         // be in any existing region unless it matches
 377         // the start of the next region.
 378         assert(!_committed[ri].contains(end) ||
 379                (_committed[ri].start() == (HeapWord*) end),
 380                "Overlapping committed regions");
 381       }
 382     }
 383 #endif
 384     if (entry < end) {
 385       memset(entry, clean_card, pointer_delta(end, entry, sizeof(jbyte)));
 386     }
 387   }
 388   // In any case, the covered size changes.
 389   _covered[ind].set_word_size(new_region.word_size());
 390   if (TraceCardTableModRefBS) {
 391     gclog_or_tty->print_cr("CardTableModRefBS::resize_covered_region: ");
 392     gclog_or_tty->print_cr("  "
 393                   "  _covered[%d].start(): " INTPTR_FORMAT
 394                   "  _covered[%d].last(): " INTPTR_FORMAT,
 395                   ind, _covered[ind].start(),
 396                   ind, _covered[ind].last());
 397     gclog_or_tty->print_cr("  "
 398                   "  _committed[%d].start(): " INTPTR_FORMAT
 399                   "  _committed[%d].last(): " INTPTR_FORMAT,
 400                   ind, _committed[ind].start(),
 401                   ind, _committed[ind].last());
 402     gclog_or_tty->print_cr("  "
 403                   "  byte_for(start): " INTPTR_FORMAT
 404                   "  byte_for(last): " INTPTR_FORMAT,
 405                   byte_for(_covered[ind].start()),
 406                   byte_for(_covered[ind].last()));
 407     gclog_or_tty->print_cr("  "
 408                   "  addr_for(start): " INTPTR_FORMAT
 409                   "  addr_for(last): " INTPTR_FORMAT,
 410                   addr_for((jbyte*) _committed[ind].start()),
 411                   addr_for((jbyte*) _committed[ind].last()));
 412   }
 413   // Touch the last card of the covered region to show that it
 414   // is committed (or SEGV).
 415   debug_only((void) (*byte_for(_covered[ind].last()));)
 416   debug_only(verify_guard();)
 417 }
 418 
 419 // Note that these versions are precise!  The scanning code has to handle the
 420 // fact that the write barrier may be either precise or imprecise.
 421 
 422 void CardTableModRefBS::write_ref_field_work(void* field, oop newVal) {
 423   inline_write_ref_field(field, newVal);
 424 }
 425 
 426 
 427 void CardTableModRefBS::non_clean_card_iterate_possibly_parallel(Space* sp,
 428                                                                  MemRegion mr,
 429                                                                  OopsInGenClosure* cl,
 430                                                                  CardTableRS* ct) {
 431   if (!mr.is_empty()) {
 432     // Caller (process_strong_roots()) claims that all GC threads
 433     // execute this call.  With UseDynamicNumberOfGCThreads now all
 434     // active GC threads execute this call.  The number of active GC
 435     // threads needs to be passed to par_non_clean_card_iterate_work()
 436     // to get proper partitioning and termination.
 437     //
 438     // This is an example of where n_par_threads() is used instead
 439     // of workers()->active_workers().  n_par_threads can be set to 0 to
 440     // turn off parallelism.  For example when this code is called as
 441     // part of verification and SharedHeap::process_strong_roots() is being
 442     // used, then n_par_threads() may have been set to 0.  active_workers
 443     // is not overloaded with the meaning that it is a switch to disable
 444     // parallelism and so keeps the meaning of the number of
 445     // active gc workers.  If parallelism has not been shut off by
 446     // setting n_par_threads to 0, then n_par_threads should be
 447     // equal to active_workers.  When a different mechanism for shutting
 448     // off parallelism is used, then active_workers can be used in
 449     // place of n_par_threads.
 450     //  This is an example of a path where n_par_threads is
 451     // set to 0 to turn off parallism.
 452     //  [7] CardTableModRefBS::non_clean_card_iterate()
 453     //  [8] CardTableRS::younger_refs_in_space_iterate()
 454     //  [9] Generation::younger_refs_in_space_iterate()
 455     //  [10] OneContigSpaceCardGeneration::younger_refs_iterate()
 456     //  [11] CompactingPermGenGen::younger_refs_iterate()
 457     //  [12] CardTableRS::younger_refs_iterate()
 458     //  [13] SharedHeap::process_strong_roots()
 459     //  [14] G1CollectedHeap::verify()
 460     //  [15] Universe::verify()
 461     //  [16] G1CollectedHeap::do_collection_pause_at_safepoint()
 462     //
 463     int n_threads =  SharedHeap::heap()->n_par_threads();
 464     bool is_par = n_threads > 0;
 465     if (is_par) {
 466 #if INCLUDE_ALL_GCS
 467       assert(SharedHeap::heap()->n_par_threads() ==
 468              SharedHeap::heap()->workers()->active_workers(), "Mismatch");
 469       non_clean_card_iterate_parallel_work(sp, mr, cl, ct, n_threads);
 470 #else  // INCLUDE_ALL_GCS
 471       fatal("Parallel gc not supported here.");
 472 #endif // INCLUDE_ALL_GCS
 473     } else {
 474       // We do not call the non_clean_card_iterate_serial() version below because
 475       // we want to clear the cards (which non_clean_card_iterate_serial() does not
 476       // do for us): clear_cl here does the work of finding contiguous dirty ranges
 477       // of cards to process and clear.
 478 
 479       DirtyCardToOopClosure* dcto_cl = sp->new_dcto_cl(cl, precision(),
 480                                                        cl->gen_boundary());
 481       ClearNoncleanCardWrapper clear_cl(dcto_cl, ct);
 482 
 483       clear_cl.do_MemRegion(mr);
 484     }
 485   }
 486 }
 487 
 488 // The iterator itself is not MT-aware, but
 489 // MT-aware callers and closures can use this to
 490 // accomplish dirty card iteration in parallel. The
 491 // iterator itself does not clear the dirty cards, or
 492 // change their values in any manner.
 493 void CardTableModRefBS::non_clean_card_iterate_serial(MemRegion mr,
 494                                                       MemRegionClosure* cl) {
 495   bool is_par = (SharedHeap::heap()->n_par_threads() > 0);
 496   assert(!is_par ||
 497           (SharedHeap::heap()->n_par_threads() ==
 498           SharedHeap::heap()->workers()->active_workers()), "Mismatch");
 499   for (int i = 0; i < _cur_covered_regions; i++) {
 500     MemRegion mri = mr.intersection(_covered[i]);
 501     if (mri.word_size() > 0) {
 502       jbyte* cur_entry = byte_for(mri.last());
 503       jbyte* limit = byte_for(mri.start());
 504       while (cur_entry >= limit) {
 505         jbyte* next_entry = cur_entry - 1;
 506         if (*cur_entry != clean_card) {
 507           size_t non_clean_cards = 1;
 508           // Should the next card be included in this range of dirty cards.
 509           while (next_entry >= limit && *next_entry != clean_card) {
 510             non_clean_cards++;
 511             cur_entry = next_entry;
 512             next_entry--;
 513           }
 514           // The memory region may not be on a card boundary.  So that
 515           // objects beyond the end of the region are not processed, make
 516           // cur_cards precise with regard to the end of the memory region.
 517           MemRegion cur_cards(addr_for(cur_entry),
 518                               non_clean_cards * card_size_in_words);
 519           MemRegion dirty_region = cur_cards.intersection(mri);
 520           cl->do_MemRegion(dirty_region);
 521         }
 522         cur_entry = next_entry;
 523       }
 524     }
 525   }
 526 }
 527 
 528 void CardTableModRefBS::dirty_MemRegion(MemRegion mr) {
 529   assert((HeapWord*)align_size_down((uintptr_t)mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
 530   assert((HeapWord*)align_size_up  ((uintptr_t)mr.end(),   HeapWordSize) == mr.end(),   "Unaligned end"  );
 531   jbyte* cur  = byte_for(mr.start());
 532   jbyte* last = byte_after(mr.last());
 533   while (cur < last) {
 534     *cur = dirty_card;
 535     cur++;
 536   }
 537 }
 538 
 539 void CardTableModRefBS::invalidate(MemRegion mr, bool whole_heap) {
 540   assert((HeapWord*)align_size_down((uintptr_t)mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
 541   assert((HeapWord*)align_size_up  ((uintptr_t)mr.end(),   HeapWordSize) == mr.end(),   "Unaligned end"  );
 542   for (int i = 0; i < _cur_covered_regions; i++) {
 543     MemRegion mri = mr.intersection(_covered[i]);
 544     if (!mri.is_empty()) dirty_MemRegion(mri);
 545   }
 546 }
 547 
 548 void CardTableModRefBS::clear_MemRegion(MemRegion mr) {
 549   // Be conservative: only clean cards entirely contained within the
 550   // region.
 551   jbyte* cur;
 552   if (mr.start() == _whole_heap.start()) {
 553     cur = byte_for(mr.start());
 554   } else {
 555     assert(mr.start() > _whole_heap.start(), "mr is not covered.");
 556     cur = byte_after(mr.start() - 1);
 557   }
 558   jbyte* last = byte_after(mr.last());
 559   memset(cur, clean_card, pointer_delta(last, cur, sizeof(jbyte)));
 560 }
 561 
 562 void CardTableModRefBS::clear(MemRegion mr) {
 563   for (int i = 0; i < _cur_covered_regions; i++) {
 564     MemRegion mri = mr.intersection(_covered[i]);
 565     if (!mri.is_empty()) clear_MemRegion(mri);
 566   }
 567 }
 568 
 569 void CardTableModRefBS::dirty(MemRegion mr) {
 570   jbyte* first = byte_for(mr.start());
 571   jbyte* last  = byte_after(mr.last());
 572   memset(first, dirty_card, last-first);
 573 }
 574 
 575 // Unlike several other card table methods, dirty_card_iterate()
 576 // iterates over dirty cards ranges in increasing address order.
 577 void CardTableModRefBS::dirty_card_iterate(MemRegion mr,
 578                                            MemRegionClosure* cl) {
 579   for (int i = 0; i < _cur_covered_regions; i++) {
 580     MemRegion mri = mr.intersection(_covered[i]);
 581     if (!mri.is_empty()) {
 582       jbyte *cur_entry, *next_entry, *limit;
 583       for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
 584            cur_entry <= limit;
 585            cur_entry  = next_entry) {
 586         next_entry = cur_entry + 1;
 587         if (*cur_entry == dirty_card) {
 588           size_t dirty_cards;
 589           // Accumulate maximal dirty card range, starting at cur_entry
 590           for (dirty_cards = 1;
 591                next_entry <= limit && *next_entry == dirty_card;
 592                dirty_cards++, next_entry++);
 593           MemRegion cur_cards(addr_for(cur_entry),
 594                               dirty_cards*card_size_in_words);
 595           cl->do_MemRegion(cur_cards);
 596         }
 597       }
 598     }
 599   }
 600 }
 601 
 602 MemRegion CardTableModRefBS::dirty_card_range_after_reset(MemRegion mr,
 603                                                           bool reset,
 604                                                           int reset_val) {
 605   for (int i = 0; i < _cur_covered_regions; i++) {
 606     MemRegion mri = mr.intersection(_covered[i]);
 607     if (!mri.is_empty()) {
 608       jbyte* cur_entry, *next_entry, *limit;
 609       for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
 610            cur_entry <= limit;
 611            cur_entry  = next_entry) {
 612         next_entry = cur_entry + 1;
 613         if (*cur_entry == dirty_card) {
 614           size_t dirty_cards;
 615           // Accumulate maximal dirty card range, starting at cur_entry
 616           for (dirty_cards = 1;
 617                next_entry <= limit && *next_entry == dirty_card;
 618                dirty_cards++, next_entry++);
 619           MemRegion cur_cards(addr_for(cur_entry),
 620                               dirty_cards*card_size_in_words);
 621           if (reset) {
 622             for (size_t i = 0; i < dirty_cards; i++) {
 623               cur_entry[i] = reset_val;
 624             }
 625           }
 626           return cur_cards;
 627         }
 628       }
 629     }
 630   }
 631   return MemRegion(mr.end(), mr.end());
 632 }
 633 
 634 uintx CardTableModRefBS::ct_max_alignment_constraint() {
 635   return card_size * os::vm_page_size();
 636 }
 637 
 638 void CardTableModRefBS::verify_guard() {
 639   // For product build verification
 640   guarantee(_byte_map[_guard_index] == last_card,
 641             "card table guard has been modified");
 642 }
 643 
 644 void CardTableModRefBS::verify() {
 645   verify_guard();
 646 }
 647 
 648 #ifndef PRODUCT
 649 void CardTableModRefBS::verify_region(MemRegion mr,
 650                                       jbyte val, bool val_equals) {
 651   jbyte* start    = byte_for(mr.start());
 652   jbyte* end      = byte_for(mr.last());
 653   bool   failures = false;
 654   for (jbyte* curr = start; curr <= end; ++curr) {
 655     jbyte curr_val = *curr;
 656     bool failed = (val_equals) ? (curr_val != val) : (curr_val == val);
 657     if (failed) {
 658       if (!failures) {
 659         tty->cr();
 660         tty->print_cr("== CT verification failed: ["PTR_FORMAT","PTR_FORMAT"]", start, end);
 661         tty->print_cr("==   %sexpecting value: %d",
 662                       (val_equals) ? "" : "not ", val);
 663         failures = true;
 664       }
 665       tty->print_cr("==   card "PTR_FORMAT" ["PTR_FORMAT","PTR_FORMAT"], "
 666                     "val: %d", curr, addr_for(curr),
 667                     (HeapWord*) (((size_t) addr_for(curr)) + card_size),
 668                     (int) curr_val);
 669     }
 670   }
 671   guarantee(!failures, "there should not have been any failures");
 672 }
 673 
 674 void CardTableModRefBS::verify_not_dirty_region(MemRegion mr) {
 675   verify_region(mr, dirty_card, false /* val_equals */);
 676 }
 677 
 678 void CardTableModRefBS::verify_dirty_region(MemRegion mr) {
 679   verify_region(mr, dirty_card, true /* val_equals */);
 680 }
 681 #endif
 682 
 683 void CardTableModRefBS::print_on(outputStream* st) const {
 684   st->print_cr("Card table byte_map: [" INTPTR_FORMAT "," INTPTR_FORMAT "] byte_map_base: " INTPTR_FORMAT,
 685                _byte_map, _byte_map + _byte_map_size, byte_map_base);
 686 }
 687 
 688 bool CardTableModRefBSForCTRS::card_will_be_scanned(jbyte cv) {
 689   return
 690     CardTableModRefBS::card_will_be_scanned(cv) ||
 691     _rs->is_prev_nonclean_card_val(cv);
 692 };
 693 
 694 bool CardTableModRefBSForCTRS::card_may_have_been_dirty(jbyte cv) {
 695   return
 696     cv != clean_card &&
 697     (CardTableModRefBS::card_may_have_been_dirty(cv) ||
 698      CardTableRS::youngergen_may_have_been_dirty(cv));
 699 };