1 /*
   2  * Copyright (c) 1997, 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 "classfile/systemDictionary.hpp"
  27 #include "classfile/vmSymbols.hpp"
  28 #include "gc/serial/defNewGeneration.hpp"
  29 #include "gc/shared/blockOffsetTable.inline.hpp"
  30 #include "gc/shared/collectedHeap.inline.hpp"
  31 #include "gc/shared/genCollectedHeap.hpp"
  32 #include "gc/shared/genOopClosures.inline.hpp"
  33 #include "gc/shared/space.hpp"
  34 #include "gc/shared/space.inline.hpp"
  35 #include "gc/shared/spaceDecorator.hpp"
  36 #include "memory/universe.inline.hpp"
  37 #include "oops/oop.inline.hpp"
  38 #include "runtime/atomic.inline.hpp"
  39 #include "runtime/java.hpp"
  40 #include "runtime/orderAccess.inline.hpp"
  41 #include "runtime/prefetch.inline.hpp"
  42 #include "runtime/safepoint.hpp"
  43 #include "utilities/copy.hpp"
  44 #include "utilities/globalDefinitions.hpp"
  45 #include "utilities/macros.hpp"
  46 
  47 HeapWord* DirtyCardToOopClosure::get_actual_top(HeapWord* top,
  48                                                 HeapWord* top_obj) {
  49   if (top_obj != NULL) {
  50     if (_sp->block_is_obj(top_obj)) {
  51       if (_precision == CardTableModRefBS::ObjHeadPreciseArray) {
  52         if (oop(top_obj)->is_objArray() || oop(top_obj)->is_typeArray()) {
  53           // An arrayOop is starting on the dirty card - since we do exact
  54           // store checks for objArrays we are done.
  55         } else {
  56           // Otherwise, it is possible that the object starting on the dirty
  57           // card spans the entire card, and that the store happened on a
  58           // later card.  Figure out where the object ends.
  59           // Use the block_size() method of the space over which
  60           // the iteration is being done.  That space (e.g. CMS) may have
  61           // specific requirements on object sizes which will
  62           // be reflected in the block_size() method.
  63           top = top_obj + oop(top_obj)->size();
  64         }
  65       }
  66     } else {
  67       top = top_obj;
  68     }
  69   } else {
  70     assert(top == _sp->end(), "only case where top_obj == NULL");
  71   }
  72   return top;
  73 }
  74 
  75 void DirtyCardToOopClosure::walk_mem_region(MemRegion mr,
  76                                             HeapWord* bottom,
  77                                             HeapWord* top) {
  78   // 1. Blocks may or may not be objects.
  79   // 2. Even when a block_is_obj(), it may not entirely
  80   //    occupy the block if the block quantum is larger than
  81   //    the object size.
  82   // We can and should try to optimize by calling the non-MemRegion
  83   // version of oop_iterate() for all but the extremal objects
  84   // (for which we need to call the MemRegion version of
  85   // oop_iterate()) To be done post-beta XXX
  86   for (; bottom < top; bottom += _sp->block_size(bottom)) {
  87     // As in the case of contiguous space above, we'd like to
  88     // just use the value returned by oop_iterate to increment the
  89     // current pointer; unfortunately, that won't work in CMS because
  90     // we'd need an interface change (it seems) to have the space
  91     // "adjust the object size" (for instance pad it up to its
  92     // block alignment or minimum block size restrictions. XXX
  93     if (_sp->block_is_obj(bottom) &&
  94         !_sp->obj_allocated_since_save_marks(oop(bottom))) {
  95       oop(bottom)->oop_iterate(_cl, mr);
  96     }
  97   }
  98 }
  99 
 100 // We get called with "mr" representing the dirty region
 101 // that we want to process. Because of imprecise marking,
 102 // we may need to extend the incoming "mr" to the right,
 103 // and scan more. However, because we may already have
 104 // scanned some of that extended region, we may need to
 105 // trim its right-end back some so we do not scan what
 106 // we (or another worker thread) may already have scanned
 107 // or planning to scan.
 108 void DirtyCardToOopClosure::do_MemRegion(MemRegion mr) {
 109 
 110   // Some collectors need to do special things whenever their dirty
 111   // cards are processed. For instance, CMS must remember mutator updates
 112   // (i.e. dirty cards) so as to re-scan mutated objects.
 113   // Such work can be piggy-backed here on dirty card scanning, so as to make
 114   // it slightly more efficient than doing a complete non-destructive pre-scan
 115   // of the card table.
 116   MemRegionClosure* pCl = _sp->preconsumptionDirtyCardClosure();
 117   if (pCl != NULL) {
 118     pCl->do_MemRegion(mr);
 119   }
 120 
 121   HeapWord* bottom = mr.start();
 122   HeapWord* last = mr.last();
 123   HeapWord* top = mr.end();
 124   HeapWord* bottom_obj;
 125   HeapWord* top_obj;
 126 
 127   assert(_precision == CardTableModRefBS::ObjHeadPreciseArray ||
 128          _precision == CardTableModRefBS::Precise,
 129          "Only ones we deal with for now.");
 130 
 131   assert(_precision != CardTableModRefBS::ObjHeadPreciseArray ||
 132          _cl->idempotent() || _last_bottom == NULL ||
 133          top <= _last_bottom,
 134          "Not decreasing");
 135   NOT_PRODUCT(_last_bottom = mr.start());
 136 
 137   bottom_obj = _sp->block_start(bottom);
 138   top_obj    = _sp->block_start(last);
 139 
 140   assert(bottom_obj <= bottom, "just checking");
 141   assert(top_obj    <= top,    "just checking");
 142 
 143   // Given what we think is the top of the memory region and
 144   // the start of the object at the top, get the actual
 145   // value of the top.
 146   top = get_actual_top(top, top_obj);
 147 
 148   // If the previous call did some part of this region, don't redo.
 149   if (_precision == CardTableModRefBS::ObjHeadPreciseArray &&
 150       _min_done != NULL &&
 151       _min_done < top) {
 152     top = _min_done;
 153   }
 154 
 155   // Top may have been reset, and in fact may be below bottom,
 156   // e.g. the dirty card region is entirely in a now free object
 157   // -- something that could happen with a concurrent sweeper.
 158   bottom = MIN2(bottom, top);
 159   MemRegion extended_mr = MemRegion(bottom, top);
 160   assert(bottom <= top &&
 161          (_precision != CardTableModRefBS::ObjHeadPreciseArray ||
 162           _min_done == NULL ||
 163           top <= _min_done),
 164          "overlap!");
 165 
 166   // Walk the region if it is not empty; otherwise there is nothing to do.
 167   if (!extended_mr.is_empty()) {
 168     walk_mem_region(extended_mr, bottom_obj, top);
 169   }
 170 
 171   // An idempotent closure might be applied in any order, so we don't
 172   // record a _min_done for it.
 173   if (!_cl->idempotent()) {
 174     _min_done = bottom;
 175   } else {
 176     assert(_min_done == _last_explicit_min_done,
 177            "Don't update _min_done for idempotent cl");
 178   }
 179 }
 180 
 181 DirtyCardToOopClosure* Space::new_dcto_cl(ExtendedOopClosure* cl,
 182                                           CardTableModRefBS::PrecisionStyle precision,
 183                                           HeapWord* boundary,
 184                                           bool parallel) {
 185   return new DirtyCardToOopClosure(this, cl, precision, boundary);
 186 }
 187 
 188 HeapWord* ContiguousSpaceDCTOC::get_actual_top(HeapWord* top,
 189                                                HeapWord* top_obj) {
 190   if (top_obj != NULL && top_obj < (_sp->toContiguousSpace())->top()) {
 191     if (_precision == CardTableModRefBS::ObjHeadPreciseArray) {
 192       if (oop(top_obj)->is_objArray() || oop(top_obj)->is_typeArray()) {
 193         // An arrayOop is starting on the dirty card - since we do exact
 194         // store checks for objArrays we are done.
 195       } else {
 196         // Otherwise, it is possible that the object starting on the dirty
 197         // card spans the entire card, and that the store happened on a
 198         // later card.  Figure out where the object ends.
 199         assert(_sp->block_size(top_obj) == (size_t) oop(top_obj)->size(),
 200           "Block size and object size mismatch");
 201         top = top_obj + oop(top_obj)->size();
 202       }
 203     }
 204   } else {
 205     top = (_sp->toContiguousSpace())->top();
 206   }
 207   return top;
 208 }
 209 
 210 void FilteringDCTOC::walk_mem_region(MemRegion mr,
 211                                      HeapWord* bottom,
 212                                      HeapWord* top) {
 213   // Note that this assumption won't hold if we have a concurrent
 214   // collector in this space, which may have freed up objects after
 215   // they were dirtied and before the stop-the-world GC that is
 216   // examining cards here.
 217   assert(bottom < top, "ought to be at least one obj on a dirty card.");
 218 
 219   if (_boundary != NULL) {
 220     // We have a boundary outside of which we don't want to look
 221     // at objects, so create a filtering closure around the
 222     // oop closure before walking the region.
 223     FilteringClosure filter(_boundary, _cl);
 224     walk_mem_region_with_cl(mr, bottom, top, &filter);
 225   } else {
 226     // No boundary, simply walk the heap with the oop closure.
 227     walk_mem_region_with_cl(mr, bottom, top, _cl);
 228   }
 229 
 230 }
 231 
 232 // We must replicate this so that the static type of "FilteringClosure"
 233 // (see above) is apparent at the oop_iterate calls.
 234 #define ContiguousSpaceDCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \
 235 void ContiguousSpaceDCTOC::walk_mem_region_with_cl(MemRegion mr,        \
 236                                                    HeapWord* bottom,    \
 237                                                    HeapWord* top,       \
 238                                                    ClosureType* cl) {   \
 239   bottom += oop(bottom)->oop_iterate_size(cl, mr);                      \
 240   if (bottom < top) {                                                   \
 241     HeapWord* next_obj = bottom + oop(bottom)->size();                  \
 242     while (next_obj < top) {                                            \
 243       /* Bottom lies entirely below top, so we can call the */          \
 244       /* non-memRegion version of oop_iterate below. */                 \
 245       oop(bottom)->oop_iterate(cl);                                     \
 246       bottom = next_obj;                                                \
 247       next_obj = bottom + oop(bottom)->size();                          \
 248     }                                                                   \
 249     /* Last object. */                                                  \
 250     oop(bottom)->oop_iterate(cl, mr);                                   \
 251   }                                                                     \
 252 }
 253 
 254 // (There are only two of these, rather than N, because the split is due
 255 // only to the introduction of the FilteringClosure, a local part of the
 256 // impl of this abstraction.)
 257 ContiguousSpaceDCTOC__walk_mem_region_with_cl_DEFN(ExtendedOopClosure)
 258 ContiguousSpaceDCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure)
 259 
 260 DirtyCardToOopClosure*
 261 ContiguousSpace::new_dcto_cl(ExtendedOopClosure* cl,
 262                              CardTableModRefBS::PrecisionStyle precision,
 263                              HeapWord* boundary,
 264                              bool parallel) {
 265   return new ContiguousSpaceDCTOC(this, cl, precision, boundary);
 266 }
 267 
 268 void Space::initialize(MemRegion mr,
 269                        bool clear_space,
 270                        bool mangle_space) {
 271   HeapWord* bottom = mr.start();
 272   HeapWord* end    = mr.end();
 273   assert(Universe::on_page_boundary(bottom) && Universe::on_page_boundary(end),
 274          "invalid space boundaries");
 275   set_bottom(bottom);
 276   set_end(end);
 277   if (clear_space) clear(mangle_space);
 278 }
 279 
 280 void Space::clear(bool mangle_space) {
 281   if (ZapUnusedHeapArea && mangle_space) {
 282     mangle_unused_area();
 283   }
 284 }
 285 
 286 ContiguousSpace::ContiguousSpace(): CompactibleSpace(), _top(NULL),
 287     _concurrent_iteration_safe_limit(NULL) {
 288   _mangler = new GenSpaceMangler(this);
 289 }
 290 
 291 ContiguousSpace::~ContiguousSpace() {
 292   delete _mangler;
 293 }
 294 
 295 void ContiguousSpace::initialize(MemRegion mr,
 296                                  bool clear_space,
 297                                  bool mangle_space)
 298 {
 299   CompactibleSpace::initialize(mr, clear_space, mangle_space);
 300   set_concurrent_iteration_safe_limit(top());
 301 }
 302 
 303 void ContiguousSpace::clear(bool mangle_space) {
 304   set_top(bottom());
 305   set_saved_mark();
 306   CompactibleSpace::clear(mangle_space);
 307 }
 308 
 309 bool ContiguousSpace::is_free_block(const HeapWord* p) const {
 310   return p >= _top;
 311 }
 312 
 313 void OffsetTableContigSpace::clear(bool mangle_space) {
 314   ContiguousSpace::clear(mangle_space);
 315   _offsets.initialize_threshold();
 316 }
 317 
 318 void OffsetTableContigSpace::set_bottom(HeapWord* new_bottom) {
 319   Space::set_bottom(new_bottom);
 320   _offsets.set_bottom(new_bottom);
 321 }
 322 
 323 void OffsetTableContigSpace::set_end(HeapWord* new_end) {
 324   // Space should not advertise an increase in size
 325   // until after the underlying offset table has been enlarged.
 326   _offsets.resize(pointer_delta(new_end, bottom()));
 327   Space::set_end(new_end);
 328 }
 329 
 330 #ifndef PRODUCT
 331 
 332 void ContiguousSpace::set_top_for_allocations(HeapWord* v) {
 333   mangler()->set_top_for_allocations(v);
 334 }
 335 void ContiguousSpace::set_top_for_allocations() {
 336   mangler()->set_top_for_allocations(top());
 337 }
 338 void ContiguousSpace::check_mangled_unused_area(HeapWord* limit) {
 339   mangler()->check_mangled_unused_area(limit);
 340 }
 341 
 342 void ContiguousSpace::check_mangled_unused_area_complete() {
 343   mangler()->check_mangled_unused_area_complete();
 344 }
 345 
 346 // Mangled only the unused space that has not previously
 347 // been mangled and that has not been allocated since being
 348 // mangled.
 349 void ContiguousSpace::mangle_unused_area() {
 350   mangler()->mangle_unused_area();
 351 }
 352 void ContiguousSpace::mangle_unused_area_complete() {
 353   mangler()->mangle_unused_area_complete();
 354 }
 355 #endif  // NOT_PRODUCT
 356 
 357 void CompactibleSpace::initialize(MemRegion mr,
 358                                   bool clear_space,
 359                                   bool mangle_space) {
 360   Space::initialize(mr, clear_space, mangle_space);
 361   set_compaction_top(bottom());
 362   _next_compaction_space = NULL;
 363 }
 364 
 365 void CompactibleSpace::clear(bool mangle_space) {
 366   Space::clear(mangle_space);
 367   _compaction_top = bottom();
 368 }
 369 
 370 HeapWord* CompactibleSpace::forward(oop q, size_t size,
 371                                     CompactPoint* cp, HeapWord* compact_top) {
 372   // q is alive
 373   // First check if we should switch compaction space
 374   assert(this == cp->space, "'this' should be current compaction space.");
 375   size_t compaction_max_size = pointer_delta(end(), compact_top);
 376   while (size > compaction_max_size) {
 377     // switch to next compaction space
 378     cp->space->set_compaction_top(compact_top);
 379     cp->space = cp->space->next_compaction_space();
 380     if (cp->space == NULL) {
 381       cp->gen = GenCollectedHeap::heap()->young_gen();
 382       assert(cp->gen != NULL, "compaction must succeed");
 383       cp->space = cp->gen->first_compaction_space();
 384       assert(cp->space != NULL, "generation must have a first compaction space");
 385     }
 386     compact_top = cp->space->bottom();
 387     cp->space->set_compaction_top(compact_top);
 388     cp->threshold = cp->space->initialize_threshold();
 389     compaction_max_size = pointer_delta(cp->space->end(), compact_top);
 390   }
 391 
 392   // store the forwarding pointer into the mark word
 393   if ((HeapWord*)q != compact_top) {
 394     q->forward_to(oop(compact_top));
 395     assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");
 396   } else {
 397     // if the object isn't moving we can just set the mark to the default
 398     // mark and handle it specially later on.
 399     q->init_mark();
 400     assert(q->forwardee() == NULL, "should be forwarded to NULL");
 401   }
 402 
 403   compact_top += size;
 404 
 405   // we need to update the offset table so that the beginnings of objects can be
 406   // found during scavenge.  Note that we are updating the offset table based on
 407   // where the object will be once the compaction phase finishes.
 408   if (compact_top > cp->threshold)
 409     cp->threshold =
 410       cp->space->cross_threshold(compact_top - size, compact_top);
 411   return compact_top;
 412 }
 413 
 414 
 415 bool CompactibleSpace::insert_deadspace(size_t& allowed_deadspace_words,
 416                                         HeapWord* q, size_t deadlength) {
 417   if (allowed_deadspace_words >= deadlength) {
 418     allowed_deadspace_words -= deadlength;
 419     CollectedHeap::fill_with_object(q, deadlength);
 420     oop(q)->set_mark(oop(q)->mark()->set_marked());
 421     assert((int) deadlength == oop(q)->size(), "bad filler object size");
 422     // Recall that we required "q == compaction_top".
 423     return true;
 424   } else {
 425     allowed_deadspace_words = 0;
 426     return false;
 427   }
 428 }
 429 
 430 void ContiguousSpace::prepare_for_compaction(CompactPoint* cp) {
 431   scan_and_forward(this, cp);
 432 }
 433 
 434 void CompactibleSpace::adjust_pointers() {
 435   // Check first is there is any work to do.
 436   if (used() == 0) {
 437     return;   // Nothing to do.
 438   }
 439 
 440   scan_and_adjust_pointers(this);
 441 }
 442 
 443 void CompactibleSpace::compact() {
 444   scan_and_compact(this);
 445 }
 446 
 447 void Space::print_short() const { print_short_on(tty); }
 448 
 449 void Space::print_short_on(outputStream* st) const {
 450   st->print(" space " SIZE_FORMAT "K, %3d%% used", capacity() / K,
 451               (int) ((double) used() * 100 / capacity()));
 452 }
 453 
 454 void Space::print() const { print_on(tty); }
 455 
 456 void Space::print_on(outputStream* st) const {
 457   print_short_on(st);
 458   st->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ")",
 459                 p2i(bottom()), p2i(end()));
 460 }
 461 
 462 void ContiguousSpace::print_on(outputStream* st) const {
 463   print_short_on(st);
 464   st->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
 465                 p2i(bottom()), p2i(top()), p2i(end()));
 466 }
 467 
 468 void OffsetTableContigSpace::print_on(outputStream* st) const {
 469   print_short_on(st);
 470   st->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", "
 471                 INTPTR_FORMAT ", " INTPTR_FORMAT ")",
 472               p2i(bottom()), p2i(top()), p2i(_offsets.threshold()), p2i(end()));
 473 }
 474 
 475 void ContiguousSpace::verify() const {
 476   HeapWord* p = bottom();
 477   HeapWord* t = top();
 478   HeapWord* prev_p = NULL;
 479   while (p < t) {
 480     oop(p)->verify();
 481     prev_p = p;
 482     p += oop(p)->size();
 483   }
 484   guarantee(p == top(), "end of last object must match end of space");
 485   if (top() != end()) {
 486     guarantee(top() == block_start_const(end()-1) &&
 487               top() == block_start_const(top()),
 488               "top should be start of unallocated block, if it exists");
 489   }
 490 }
 491 
 492 void Space::oop_iterate(ExtendedOopClosure* blk) {
 493   ObjectToOopClosure blk2(blk);
 494   object_iterate(&blk2);
 495 }
 496 
 497 bool Space::obj_is_alive(const HeapWord* p) const {
 498   assert (block_is_obj(p), "The address should point to an object");
 499   return true;
 500 }
 501 
 502 #if INCLUDE_ALL_GCS
 503 #define ContigSpace_PAR_OOP_ITERATE_DEFN(OopClosureType, nv_suffix)         \
 504                                                                             \
 505   void ContiguousSpace::par_oop_iterate(MemRegion mr, OopClosureType* blk) {\
 506     HeapWord* obj_addr = mr.start();                                        \
 507     HeapWord* t = mr.end();                                                 \
 508     while (obj_addr < t) {                                                  \
 509       assert(oop(obj_addr)->is_oop(), "Should be an oop");                  \
 510       obj_addr += oop(obj_addr)->oop_iterate_size(blk);                     \
 511     }                                                                       \
 512   }
 513 
 514   ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DEFN)
 515 
 516 #undef ContigSpace_PAR_OOP_ITERATE_DEFN
 517 #endif // INCLUDE_ALL_GCS
 518 
 519 void ContiguousSpace::oop_iterate(ExtendedOopClosure* blk) {
 520   if (is_empty()) return;
 521   HeapWord* obj_addr = bottom();
 522   HeapWord* t = top();
 523   // Could call objects iterate, but this is easier.
 524   while (obj_addr < t) {
 525     obj_addr += oop(obj_addr)->oop_iterate_size(blk);
 526   }
 527 }
 528 
 529 void ContiguousSpace::object_iterate(ObjectClosure* blk) {
 530   if (is_empty()) return;
 531   object_iterate_from(bottom(), blk);
 532 }
 533 
 534 // For a ContiguousSpace object_iterate() and safe_object_iterate()
 535 // are the same.
 536 void ContiguousSpace::safe_object_iterate(ObjectClosure* blk) {
 537   object_iterate(blk);
 538 }
 539 
 540 void ContiguousSpace::object_iterate_from(HeapWord* mark, ObjectClosure* blk) {
 541   while (mark < top()) {
 542     blk->do_object(oop(mark));
 543     mark += oop(mark)->size();
 544   }
 545 }
 546 
 547 HeapWord*
 548 ContiguousSpace::object_iterate_careful(ObjectClosureCareful* blk) {
 549   HeapWord * limit = concurrent_iteration_safe_limit();
 550   assert(limit <= top(), "sanity check");
 551   for (HeapWord* p = bottom(); p < limit;) {
 552     size_t size = blk->do_object_careful(oop(p));
 553     if (size == 0) {
 554       return p;  // failed at p
 555     } else {
 556       p += size;
 557     }
 558   }
 559   return NULL; // all done
 560 }
 561 
 562 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix)  \
 563                                                                           \
 564 void ContiguousSpace::                                                    \
 565 oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk) {            \
 566   HeapWord* t;                                                            \
 567   HeapWord* p = saved_mark_word();                                        \
 568   assert(p != NULL, "expected saved mark");                               \
 569                                                                           \
 570   const intx interval = PrefetchScanIntervalInBytes;                      \
 571   do {                                                                    \
 572     t = top();                                                            \
 573     while (p < t) {                                                       \
 574       Prefetch::write(p, interval);                                       \
 575       debug_only(HeapWord* prev = p);                                     \
 576       oop m = oop(p);                                                     \
 577       p += m->oop_iterate_size(blk);                                      \
 578     }                                                                     \
 579   } while (t < top());                                                    \
 580                                                                           \
 581   set_saved_mark_word(p);                                                 \
 582 }
 583 
 584 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DEFN)
 585 
 586 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DEFN
 587 
 588 // Very general, slow implementation.
 589 HeapWord* ContiguousSpace::block_start_const(const void* p) const {
 590   assert(MemRegion(bottom(), end()).contains(p),
 591          "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
 592          p2i(p), p2i(bottom()), p2i(end()));
 593   if (p >= top()) {
 594     return top();
 595   } else {
 596     HeapWord* last = bottom();
 597     HeapWord* cur = last;
 598     while (cur <= p) {
 599       last = cur;
 600       cur += oop(cur)->size();
 601     }
 602     assert(oop(last)->is_oop(), PTR_FORMAT " should be an object start", p2i(last));
 603     return last;
 604   }
 605 }
 606 
 607 size_t ContiguousSpace::block_size(const HeapWord* p) const {
 608   assert(MemRegion(bottom(), end()).contains(p),
 609          "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
 610          p2i(p), p2i(bottom()), p2i(end()));
 611   HeapWord* current_top = top();
 612   assert(p <= current_top,
 613          "p > current top - p: " PTR_FORMAT ", current top: " PTR_FORMAT,
 614          p2i(p), p2i(current_top));
 615   assert(p == current_top || oop(p)->is_oop(),
 616          "p (" PTR_FORMAT ") is not a block start - "
 617          "current_top: " PTR_FORMAT ", is_oop: %s",
 618          p2i(p), p2i(current_top), BOOL_TO_STR(oop(p)->is_oop()));
 619   if (p < current_top) {
 620     return oop(p)->size();
 621   } else {
 622     assert(p == current_top, "just checking");
 623     return pointer_delta(end(), (HeapWord*) p);
 624   }
 625 }
 626 
 627 // This version requires locking.
 628 inline HeapWord* ContiguousSpace::allocate_impl(size_t size) {
 629   assert(Heap_lock->owned_by_self() ||
 630          (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()),
 631          "not locked");
 632   HeapWord* obj = top();
 633   if (pointer_delta(end(), obj) >= size) {
 634     HeapWord* new_top = obj + size;
 635     set_top(new_top);
 636     assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
 637     return obj;
 638   } else {
 639     return NULL;
 640   }
 641 }
 642 
 643 // This version is lock-free.
 644 inline HeapWord* ContiguousSpace::par_allocate_impl(size_t size) {
 645   do {
 646     HeapWord* obj = top();
 647     if (pointer_delta(end(), obj) >= size) {
 648       HeapWord* new_top = obj + size;
 649       HeapWord* result = (HeapWord*)Atomic::cmpxchg_ptr(new_top, top_addr(), obj);
 650       // result can be one of two:
 651       //  the old top value: the exchange succeeded
 652       //  otherwise: the new value of the top is returned.
 653       if (result == obj) {
 654         assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
 655         return obj;
 656       }
 657     } else {
 658       return NULL;
 659     }
 660   } while (true);
 661 }
 662 
 663 HeapWord* ContiguousSpace::allocate_aligned(size_t size) {
 664   assert(Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()), "not locked");
 665   HeapWord* end_value = end();
 666 
 667   HeapWord* obj = CollectedHeap::align_allocation_or_fail(top(), end_value, SurvivorAlignmentInBytes);
 668   if (obj == NULL) {
 669     return NULL;
 670   }
 671 
 672   if (pointer_delta(end_value, obj) >= size) {
 673     HeapWord* new_top = obj + size;
 674     set_top(new_top);
 675     assert(is_ptr_aligned(obj, SurvivorAlignmentInBytes) && is_aligned(new_top),
 676       "checking alignment");
 677     return obj;
 678   } else {
 679     set_top(obj);
 680     return NULL;
 681   }
 682 }
 683 
 684 // Requires locking.
 685 HeapWord* ContiguousSpace::allocate(size_t size) {
 686   return allocate_impl(size);
 687 }
 688 
 689 // Lock-free.
 690 HeapWord* ContiguousSpace::par_allocate(size_t size) {
 691   return par_allocate_impl(size);
 692 }
 693 
 694 void ContiguousSpace::allocate_temporary_filler(int factor) {
 695   // allocate temporary type array decreasing free size with factor 'factor'
 696   assert(factor >= 0, "just checking");
 697   size_t size = pointer_delta(end(), top());
 698 
 699   // if space is full, return
 700   if (size == 0) return;
 701 
 702   if (factor > 0) {
 703     size -= size/factor;
 704   }
 705   size = align_object_size(size);
 706 
 707   const size_t array_header_size = typeArrayOopDesc::header_size(T_INT);
 708   if (size >= (size_t)align_object_size(array_header_size)) {
 709     size_t length = (size - array_header_size) * (HeapWordSize / sizeof(jint));
 710     // allocate uninitialized int array
 711     typeArrayOop t = (typeArrayOop) allocate(size);
 712     assert(t != NULL, "allocation should succeed");
 713     t->set_mark(markOopDesc::prototype());
 714     t->set_klass(Universe::intArrayKlassObj());
 715     t->set_length((int)length);
 716   } else {
 717     assert(size == CollectedHeap::min_fill_size(),
 718            "size for smallest fake object doesn't match");
 719     instanceOop obj = (instanceOop) allocate(size);
 720     obj->set_mark(markOopDesc::prototype());
 721     obj->set_klass_gap(0);
 722     obj->set_klass(SystemDictionary::Object_klass());
 723   }
 724 }
 725 
 726 HeapWord* OffsetTableContigSpace::initialize_threshold() {
 727   return _offsets.initialize_threshold();
 728 }
 729 
 730 HeapWord* OffsetTableContigSpace::cross_threshold(HeapWord* start, HeapWord* end) {
 731   _offsets.alloc_block(start, end);
 732   return _offsets.threshold();
 733 }
 734 
 735 OffsetTableContigSpace::OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
 736                                                MemRegion mr) :
 737   _offsets(sharedOffsetArray, mr),
 738   _par_alloc_lock(Mutex::leaf, "OffsetTableContigSpace par alloc lock", true)
 739 {
 740   _offsets.set_contig_space(this);
 741   initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle);
 742 }
 743 
 744 #define OBJ_SAMPLE_INTERVAL 0
 745 #define BLOCK_SAMPLE_INTERVAL 100
 746 
 747 void OffsetTableContigSpace::verify() const {
 748   HeapWord* p = bottom();
 749   HeapWord* prev_p = NULL;
 750   int objs = 0;
 751   int blocks = 0;
 752 
 753   if (VerifyObjectStartArray) {
 754     _offsets.verify();
 755   }
 756 
 757   while (p < top()) {
 758     size_t size = oop(p)->size();
 759     // For a sampling of objects in the space, find it using the
 760     // block offset table.
 761     if (blocks == BLOCK_SAMPLE_INTERVAL) {
 762       guarantee(p == block_start_const(p + (size/2)),
 763                 "check offset computation");
 764       blocks = 0;
 765     } else {
 766       blocks++;
 767     }
 768 
 769     if (objs == OBJ_SAMPLE_INTERVAL) {
 770       oop(p)->verify();
 771       objs = 0;
 772     } else {
 773       objs++;
 774     }
 775     prev_p = p;
 776     p += size;
 777   }
 778   guarantee(p == top(), "end of last object must match end of space");
 779 }
 780 
 781 
 782 size_t TenuredSpace::allowed_dead_ratio() const {
 783   return MarkSweepDeadRatio;
 784 }