1 /*
   2  * Copyright (c) 2000, 2011, 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/symbolTable.hpp"
  27 #include "classfile/systemDictionary.hpp"
  28 #include "classfile/vmSymbols.hpp"
  29 #include "code/icBuffer.hpp"
  30 #include "gc_implementation/shared/collectorCounters.hpp"
  31 #include "gc_implementation/shared/vmGCOperations.hpp"
  32 #include "gc_interface/collectedHeap.inline.hpp"
  33 #include "memory/compactPermGen.hpp"
  34 #include "memory/filemap.hpp"
  35 #include "memory/gcLocker.inline.hpp"
  36 #include "memory/genCollectedHeap.hpp"
  37 #include "memory/genOopClosures.inline.hpp"
  38 #include "memory/generation.inline.hpp"
  39 #include "memory/generationSpec.hpp"
  40 #include "memory/permGen.hpp"
  41 #include "memory/resourceArea.hpp"
  42 #include "memory/sharedHeap.hpp"
  43 #include "memory/space.hpp"
  44 #include "oops/oop.inline.hpp"
  45 #include "oops/oop.inline2.hpp"
  46 #include "runtime/aprofiler.hpp"
  47 #include "runtime/biasedLocking.hpp"
  48 #include "runtime/fprofiler.hpp"
  49 #include "runtime/handles.hpp"
  50 #include "runtime/handles.inline.hpp"
  51 #include "runtime/java.hpp"
  52 #include "runtime/vmThread.hpp"
  53 #include "services/memoryService.hpp"
  54 #include "utilities/vmError.hpp"
  55 #include "utilities/workgroup.hpp"
  56 #ifndef SERIALGC
  57 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
  58 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp"
  59 #endif
  60 
  61 GenCollectedHeap* GenCollectedHeap::_gch;
  62 NOT_PRODUCT(size_t GenCollectedHeap::_skip_header_HeapWords = 0;)
  63 
  64 // The set of potentially parallel tasks in strong root scanning.
  65 enum GCH_process_strong_roots_tasks {
  66   // We probably want to parallelize both of these internally, but for now...
  67   GCH_PS_younger_gens,
  68   // Leave this one last.
  69   GCH_PS_NumElements
  70 };
  71 
  72 GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy) :
  73   SharedHeap(policy),
  74   _gen_policy(policy),
  75   _gen_process_strong_tasks(new SubTasksDone(GCH_PS_NumElements)),
  76   _full_collections_completed(0)
  77 {
  78   if (_gen_process_strong_tasks == NULL ||
  79       !_gen_process_strong_tasks->valid()) {
  80     vm_exit_during_initialization("Failed necessary allocation.");
  81   }
  82   assert(policy != NULL, "Sanity check");
  83   _preloading_shared_classes = false;
  84 }
  85 
  86 jint GenCollectedHeap::initialize() {
  87   CollectedHeap::pre_initialize();
  88 
  89   int i;
  90   _n_gens = gen_policy()->number_of_generations();
  91 
  92   // While there are no constraints in the GC code that HeapWordSize
  93   // be any particular value, there are multiple other areas in the
  94   // system which believe this to be true (e.g. oop->object_size in some
  95   // cases incorrectly returns the size in wordSize units rather than
  96   // HeapWordSize).
  97   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
  98 
  99   // The heap must be at least as aligned as generations.
 100   size_t alignment = Generation::GenGrain;
 101 
 102   _gen_specs = gen_policy()->generations();
 103   PermanentGenerationSpec *perm_gen_spec =
 104                                 collector_policy()->permanent_generation();
 105 
 106   // Make sure the sizes are all aligned.
 107   for (i = 0; i < _n_gens; i++) {
 108     _gen_specs[i]->align(alignment);
 109   }
 110   perm_gen_spec->align(alignment);
 111 
 112   // If we are dumping the heap, then allocate a wasted block of address
 113   // space in order to push the heap to a lower address.  This extra
 114   // address range allows for other (or larger) libraries to be loaded
 115   // without them occupying the space required for the shared spaces.
 116 
 117   if (DumpSharedSpaces) {
 118     uintx reserved = 0;
 119     uintx block_size = 64*1024*1024;
 120     while (reserved < SharedDummyBlockSize) {
 121       char* dummy = os::reserve_memory(block_size);
 122       reserved += block_size;
 123     }
 124   }
 125 
 126   // Allocate space for the heap.
 127 
 128   char* heap_address;
 129   size_t total_reserved = 0;
 130   int n_covered_regions = 0;
 131   ReservedSpace heap_rs(0);
 132 
 133   heap_address = allocate(alignment, perm_gen_spec, &total_reserved,
 134                           &n_covered_regions, &heap_rs);
 135 
 136   if (UseSharedSpaces) {
 137     if (!heap_rs.is_reserved() || heap_address != heap_rs.base()) {
 138       if (heap_rs.is_reserved()) {
 139         heap_rs.release();
 140       }
 141       FileMapInfo* mapinfo = FileMapInfo::current_info();
 142       mapinfo->fail_continue("Unable to reserve shared region.");
 143       allocate(alignment, perm_gen_spec, &total_reserved, &n_covered_regions,
 144                &heap_rs);
 145     }
 146   }
 147 
 148   if (!heap_rs.is_reserved()) {
 149     vm_shutdown_during_initialization(
 150       "Could not reserve enough space for object heap");
 151     return JNI_ENOMEM;
 152   }
 153 
 154   _reserved = MemRegion((HeapWord*)heap_rs.base(),
 155                         (HeapWord*)(heap_rs.base() + heap_rs.size()));
 156 
 157   // It is important to do this in a way such that concurrent readers can't
 158   // temporarily think somethings in the heap.  (Seen this happen in asserts.)
 159   _reserved.set_word_size(0);
 160   _reserved.set_start((HeapWord*)heap_rs.base());
 161   size_t actual_heap_size = heap_rs.size() - perm_gen_spec->misc_data_size()
 162                                            - perm_gen_spec->misc_code_size();
 163   _reserved.set_end((HeapWord*)(heap_rs.base() + actual_heap_size));
 164 
 165   _rem_set = collector_policy()->create_rem_set(_reserved, n_covered_regions);
 166   set_barrier_set(rem_set()->bs());
 167 
 168   _gch = this;
 169 
 170   for (i = 0; i < _n_gens; i++) {
 171     ReservedSpace this_rs = heap_rs.first_part(_gen_specs[i]->max_size(),
 172                                               UseSharedSpaces, UseSharedSpaces);
 173     _gens[i] = _gen_specs[i]->init(this_rs, i, rem_set());
 174     heap_rs = heap_rs.last_part(_gen_specs[i]->max_size());
 175   }
 176   _perm_gen = perm_gen_spec->init(heap_rs, PermSize, rem_set());
 177 
 178   clear_incremental_collection_failed();
 179 
 180 #ifndef SERIALGC
 181   // If we are running CMS, create the collector responsible
 182   // for collecting the CMS generations.
 183   if (collector_policy()->is_concurrent_mark_sweep_policy()) {
 184     bool success = create_cms_collector();
 185     if (!success) return JNI_ENOMEM;
 186   }
 187 #endif // SERIALGC
 188 
 189   return JNI_OK;
 190 }
 191 
 192 
 193 char* GenCollectedHeap::allocate(size_t alignment,
 194                                  PermanentGenerationSpec* perm_gen_spec,
 195                                  size_t* _total_reserved,
 196                                  int* _n_covered_regions,
 197                                  ReservedSpace* heap_rs){
 198   const char overflow_msg[] = "The size of the object heap + VM data exceeds "
 199     "the maximum representable size";
 200 
 201   // Now figure out the total size.
 202   size_t total_reserved = 0;
 203   int n_covered_regions = 0;
 204   const size_t pageSize = UseLargePages ?
 205       os::large_page_size() : os::vm_page_size();
 206 
 207   for (int i = 0; i < _n_gens; i++) {
 208     total_reserved += _gen_specs[i]->max_size();
 209     if (total_reserved < _gen_specs[i]->max_size()) {
 210       vm_exit_during_initialization(overflow_msg);
 211     }
 212     n_covered_regions += _gen_specs[i]->n_covered_regions();
 213   }
 214   assert(total_reserved % pageSize == 0,
 215          err_msg("Gen size; total_reserved=" SIZE_FORMAT ", pageSize="
 216                  SIZE_FORMAT, total_reserved, pageSize));
 217   total_reserved += perm_gen_spec->max_size();
 218   assert(total_reserved % pageSize == 0,
 219          err_msg("Perm size; total_reserved=" SIZE_FORMAT ", pageSize="
 220                  SIZE_FORMAT ", perm gen max=" SIZE_FORMAT, total_reserved,
 221                  pageSize, perm_gen_spec->max_size()));
 222 
 223   if (total_reserved < perm_gen_spec->max_size()) {
 224     vm_exit_during_initialization(overflow_msg);
 225   }
 226   n_covered_regions += perm_gen_spec->n_covered_regions();
 227 
 228   // Add the size of the data area which shares the same reserved area
 229   // as the heap, but which is not actually part of the heap.
 230   size_t s = perm_gen_spec->misc_data_size() + perm_gen_spec->misc_code_size();
 231 
 232   total_reserved += s;
 233   if (total_reserved < s) {
 234     vm_exit_during_initialization(overflow_msg);
 235   }
 236 
 237   if (UseLargePages) {
 238     assert(total_reserved != 0, "total_reserved cannot be 0");
 239     total_reserved = round_to(total_reserved, os::large_page_size());
 240     if (total_reserved < os::large_page_size()) {
 241       vm_exit_during_initialization(overflow_msg);
 242     }
 243   }
 244 
 245   // Calculate the address at which the heap must reside in order for
 246   // the shared data to be at the required address.
 247 
 248   char* heap_address;
 249   if (UseSharedSpaces) {
 250 
 251     // Calculate the address of the first word beyond the heap.
 252     FileMapInfo* mapinfo = FileMapInfo::current_info();
 253     int lr = CompactingPermGenGen::n_regions - 1;
 254     size_t capacity = align_size_up(mapinfo->space_capacity(lr), alignment);
 255     heap_address = mapinfo->region_base(lr) + capacity;
 256 
 257     // Calculate the address of the first word of the heap.
 258     heap_address -= total_reserved;
 259   } else {
 260     heap_address = NULL;  // any address will do.
 261     if (UseCompressedOops) {
 262       heap_address = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
 263       *_total_reserved = total_reserved;
 264       *_n_covered_regions = n_covered_regions;
 265       *heap_rs = ReservedHeapSpace(total_reserved, alignment,
 266                                    UseLargePages, heap_address);
 267 
 268       if (heap_address != NULL && !heap_rs->is_reserved()) {
 269         // Failed to reserve at specified address - the requested memory
 270         // region is taken already, for example, by 'java' launcher.
 271         // Try again to reserver heap higher.
 272         heap_address = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
 273         *heap_rs = ReservedHeapSpace(total_reserved, alignment,
 274                                      UseLargePages, heap_address);
 275 
 276         if (heap_address != NULL && !heap_rs->is_reserved()) {
 277           // Failed to reserve at specified address again - give up.
 278           heap_address = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
 279           assert(heap_address == NULL, "");
 280           *heap_rs = ReservedHeapSpace(total_reserved, alignment,
 281                                        UseLargePages, heap_address);
 282         }
 283       }
 284       return heap_address;
 285     }
 286   }
 287 
 288   *_total_reserved = total_reserved;
 289   *_n_covered_regions = n_covered_regions;
 290   *heap_rs = ReservedHeapSpace(total_reserved, alignment,
 291                                UseLargePages, heap_address);
 292 
 293   return heap_address;
 294 }
 295 
 296 
 297 void GenCollectedHeap::post_initialize() {
 298   SharedHeap::post_initialize();
 299   TwoGenerationCollectorPolicy *policy =
 300     (TwoGenerationCollectorPolicy *)collector_policy();
 301   guarantee(policy->is_two_generation_policy(), "Illegal policy type");
 302   DefNewGeneration* def_new_gen = (DefNewGeneration*) get_gen(0);
 303   assert(def_new_gen->kind() == Generation::DefNew ||
 304          def_new_gen->kind() == Generation::ParNew ||
 305          def_new_gen->kind() == Generation::ASParNew,
 306          "Wrong generation kind");
 307 
 308   Generation* old_gen = get_gen(1);
 309   assert(old_gen->kind() == Generation::ConcurrentMarkSweep ||
 310          old_gen->kind() == Generation::ASConcurrentMarkSweep ||
 311          old_gen->kind() == Generation::MarkSweepCompact,
 312     "Wrong generation kind");
 313 
 314   policy->initialize_size_policy(def_new_gen->eden()->capacity(),
 315                                  old_gen->capacity(),
 316                                  def_new_gen->from()->capacity());
 317   policy->initialize_gc_policy_counters();
 318 }
 319 
 320 void GenCollectedHeap::ref_processing_init() {
 321   SharedHeap::ref_processing_init();
 322   for (int i = 0; i < _n_gens; i++) {
 323     _gens[i]->ref_processor_init();
 324   }
 325 }
 326 
 327 size_t GenCollectedHeap::capacity() const {
 328   size_t res = 0;
 329   for (int i = 0; i < _n_gens; i++) {
 330     res += _gens[i]->capacity();
 331   }
 332   return res;
 333 }
 334 
 335 size_t GenCollectedHeap::used() const {
 336   size_t res = 0;
 337   for (int i = 0; i < _n_gens; i++) {
 338     res += _gens[i]->used();
 339   }
 340   return res;
 341 }
 342 
 343 // Save the "used_region" for generations level and lower,
 344 // and, if perm is true, for perm gen.
 345 void GenCollectedHeap::save_used_regions(int level, bool perm) {
 346   assert(level < _n_gens, "Illegal level parameter");
 347   for (int i = level; i >= 0; i--) {
 348     _gens[i]->save_used_region();
 349   }
 350   if (perm) {
 351     perm_gen()->save_used_region();
 352   }
 353 }
 354 
 355 size_t GenCollectedHeap::max_capacity() const {
 356   size_t res = 0;
 357   for (int i = 0; i < _n_gens; i++) {
 358     res += _gens[i]->max_capacity();
 359   }
 360   return res;
 361 }
 362 
 363 // Update the _full_collections_completed counter
 364 // at the end of a stop-world full GC.
 365 unsigned int GenCollectedHeap::update_full_collections_completed() {
 366   MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 367   assert(_full_collections_completed <= _total_full_collections,
 368          "Can't complete more collections than were started");
 369   _full_collections_completed = _total_full_collections;
 370   ml.notify_all();
 371   return _full_collections_completed;
 372 }
 373 
 374 // Update the _full_collections_completed counter, as appropriate,
 375 // at the end of a concurrent GC cycle. Note the conditional update
 376 // below to allow this method to be called by a concurrent collector
 377 // without synchronizing in any manner with the VM thread (which
 378 // may already have initiated a STW full collection "concurrently").
 379 unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) {
 380   MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 381   assert((_full_collections_completed <= _total_full_collections) &&
 382          (count <= _total_full_collections),
 383          "Can't complete more collections than were started");
 384   if (count > _full_collections_completed) {
 385     _full_collections_completed = count;
 386     ml.notify_all();
 387   }
 388   return _full_collections_completed;
 389 }
 390 
 391 
 392 #ifndef PRODUCT
 393 // Override of memory state checking method in CollectedHeap:
 394 // Some collectors (CMS for example) can't have badHeapWordVal written
 395 // in the first two words of an object. (For instance , in the case of
 396 // CMS these words hold state used to synchronize between certain
 397 // (concurrent) GC steps and direct allocating mutators.)
 398 // The skip_header_HeapWords() method below, allows us to skip
 399 // over the requisite number of HeapWord's. Note that (for
 400 // generational collectors) this means that those many words are
 401 // skipped in each object, irrespective of the generation in which
 402 // that object lives. The resultant loss of precision seems to be
 403 // harmless and the pain of avoiding that imprecision appears somewhat
 404 // higher than we are prepared to pay for such rudimentary debugging
 405 // support.
 406 void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr,
 407                                                          size_t size) {
 408   if (CheckMemoryInitialization && ZapUnusedHeapArea) {
 409     // We are asked to check a size in HeapWords,
 410     // but the memory is mangled in juint words.
 411     juint* start = (juint*) (addr + skip_header_HeapWords());
 412     juint* end   = (juint*) (addr + size);
 413     for (juint* slot = start; slot < end; slot += 1) {
 414       assert(*slot == badHeapWordVal,
 415              "Found non badHeapWordValue in pre-allocation check");
 416     }
 417   }
 418 }
 419 #endif
 420 
 421 HeapWord* GenCollectedHeap::attempt_allocation(size_t size,
 422                                                bool is_tlab,
 423                                                bool first_only) {
 424   HeapWord* res;
 425   for (int i = 0; i < _n_gens; i++) {
 426     if (_gens[i]->should_allocate(size, is_tlab)) {
 427       res = _gens[i]->allocate(size, is_tlab);
 428       if (res != NULL) return res;
 429       else if (first_only) break;
 430     }
 431   }
 432   // Otherwise...
 433   return NULL;
 434 }
 435 
 436 HeapWord* GenCollectedHeap::mem_allocate(size_t size,
 437                                          bool* gc_overhead_limit_was_exceeded) {
 438   return collector_policy()->mem_allocate_work(size,
 439                                                false /* is_tlab */,
 440                                                gc_overhead_limit_was_exceeded);
 441 }
 442 
 443 bool GenCollectedHeap::must_clear_all_soft_refs() {
 444   return _gc_cause == GCCause::_last_ditch_collection;
 445 }
 446 
 447 bool GenCollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
 448   return UseConcMarkSweepGC &&
 449          ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
 450           (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent));
 451 }
 452 
 453 void GenCollectedHeap::do_collection(bool  full,
 454                                      bool   clear_all_soft_refs,
 455                                      size_t size,
 456                                      bool   is_tlab,
 457                                      int    max_level) {
 458   bool prepared_for_verification = false;
 459   ResourceMark rm;
 460   DEBUG_ONLY(Thread* my_thread = Thread::current();)
 461 
 462   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 463   assert(my_thread->is_VM_thread() ||
 464          my_thread->is_ConcurrentGC_thread(),
 465          "incorrect thread type capability");
 466   assert(Heap_lock->is_locked(),
 467          "the requesting thread should have the Heap_lock");
 468   guarantee(!is_gc_active(), "collection is not reentrant");
 469   assert(max_level < n_gens(), "sanity check");
 470 
 471   if (GC_locker::check_active_before_gc()) {
 472     return; // GC is disabled (e.g. JNI GetXXXCritical operation)
 473   }
 474 
 475   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
 476                           collector_policy()->should_clear_all_soft_refs();
 477 
 478   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
 479 
 480   const size_t perm_prev_used = perm_gen()->used();
 481 
 482   if (PrintHeapAtGC) {
 483     Universe::print_heap_before_gc();
 484     if (Verbose) {
 485       gclog_or_tty->print_cr("GC Cause: %s", GCCause::to_string(gc_cause()));
 486     }
 487   }
 488 
 489   {
 490     FlagSetting fl(_is_gc_active, true);
 491 
 492     bool complete = full && (max_level == (n_gens()-1));
 493     const char* gc_cause_str = "GC ";
 494     if (complete) {
 495       GCCause::Cause cause = gc_cause();
 496       if (cause == GCCause::_java_lang_system_gc) {
 497         gc_cause_str = "Full GC (System) ";
 498       } else {
 499         gc_cause_str = "Full GC ";
 500       }
 501     }
 502     gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
 503     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
 504     TraceTime t(gc_cause_str, PrintGCDetails, false, gclog_or_tty);
 505 
 506     gc_prologue(complete);
 507     increment_total_collections(complete);
 508 
 509     size_t gch_prev_used = used();
 510 
 511     int starting_level = 0;
 512     if (full) {
 513       // Search for the oldest generation which will collect all younger
 514       // generations, and start collection loop there.
 515       for (int i = max_level; i >= 0; i--) {
 516         if (_gens[i]->full_collects_younger_generations()) {
 517           starting_level = i;
 518           break;
 519         }
 520       }
 521     }
 522 
 523     bool must_restore_marks_for_biased_locking = false;
 524 
 525     int max_level_collected = starting_level;
 526     for (int i = starting_level; i <= max_level; i++) {
 527       if (_gens[i]->should_collect(full, size, is_tlab)) {
 528         if (i == n_gens() - 1) {  // a major collection is to happen
 529           if (!complete) {
 530             // The full_collections increment was missed above.
 531             increment_total_full_collections();
 532           }
 533           pre_full_gc_dump();    // do any pre full gc dumps
 534         }
 535         // Timer for individual generations. Last argument is false: no CR
 536         TraceTime t1(_gens[i]->short_name(), PrintGCDetails, false, gclog_or_tty);
 537         TraceCollectorStats tcs(_gens[i]->counters());
 538         TraceMemoryManagerStats tmms(_gens[i]->kind(),gc_cause());
 539 
 540         size_t prev_used = _gens[i]->used();
 541         _gens[i]->stat_record()->invocations++;
 542         _gens[i]->stat_record()->accumulated_time.start();
 543 
 544         // Must be done anew before each collection because
 545         // a previous collection will do mangling and will
 546         // change top of some spaces.
 547         record_gen_tops_before_GC();
 548 
 549         if (PrintGC && Verbose) {
 550           gclog_or_tty->print("level=%d invoke=%d size=" SIZE_FORMAT,
 551                      i,
 552                      _gens[i]->stat_record()->invocations,
 553                      size*HeapWordSize);
 554         }
 555 
 556         if (VerifyBeforeGC && i >= VerifyGCLevel &&
 557             total_collections() >= VerifyGCStartAt) {
 558           HandleMark hm;  // Discard invalid handles created during verification
 559           if (!prepared_for_verification) {
 560             prepare_for_verify();
 561             prepared_for_verification = true;
 562           }
 563           gclog_or_tty->print(" VerifyBeforeGC:");
 564           Universe::verify(true);
 565         }
 566         COMPILER2_PRESENT(DerivedPointerTable::clear());
 567 
 568         if (!must_restore_marks_for_biased_locking &&
 569             _gens[i]->performs_in_place_marking()) {
 570           // We perform this mark word preservation work lazily
 571           // because it's only at this point that we know whether we
 572           // absolutely have to do it; we want to avoid doing it for
 573           // scavenge-only collections where it's unnecessary
 574           must_restore_marks_for_biased_locking = true;
 575           BiasedLocking::preserve_marks();
 576         }
 577 
 578         // Do collection work
 579         {
 580           // Note on ref discovery: For what appear to be historical reasons,
 581           // GCH enables and disabled (by enqueing) refs discovery.
 582           // In the future this should be moved into the generation's
 583           // collect method so that ref discovery and enqueueing concerns
 584           // are local to a generation. The collect method could return
 585           // an appropriate indication in the case that notification on
 586           // the ref lock was needed. This will make the treatment of
 587           // weak refs more uniform (and indeed remove such concerns
 588           // from GCH). XXX
 589 
 590           HandleMark hm;  // Discard invalid handles created during gc
 591           save_marks();   // save marks for all gens
 592           // We want to discover references, but not process them yet.
 593           // This mode is disabled in process_discovered_references if the
 594           // generation does some collection work, or in
 595           // enqueue_discovered_references if the generation returns
 596           // without doing any work.
 597           ReferenceProcessor* rp = _gens[i]->ref_processor();
 598           // If the discovery of ("weak") refs in this generation is
 599           // atomic wrt other collectors in this configuration, we
 600           // are guaranteed to have empty discovered ref lists.
 601           if (rp->discovery_is_atomic()) {
 602             rp->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
 603             rp->setup_policy(do_clear_all_soft_refs);
 604           } else {
 605             // collect() below will enable discovery as appropriate
 606           }
 607           _gens[i]->collect(full, do_clear_all_soft_refs, size, is_tlab);
 608           if (!rp->enqueuing_is_done()) {
 609             rp->enqueue_discovered_references();
 610           } else {
 611             rp->set_enqueuing_is_done(false);
 612           }
 613           rp->verify_no_references_recorded();
 614         }
 615         max_level_collected = i;
 616 
 617         // Determine if allocation request was met.
 618         if (size > 0) {
 619           if (!is_tlab || _gens[i]->supports_tlab_allocation()) {
 620             if (size*HeapWordSize <= _gens[i]->unsafe_max_alloc_nogc()) {
 621               size = 0;
 622             }
 623           }
 624         }
 625 
 626         COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
 627 
 628         _gens[i]->stat_record()->accumulated_time.stop();
 629 
 630         update_gc_stats(i, full);
 631 
 632         if (VerifyAfterGC && i >= VerifyGCLevel &&
 633             total_collections() >= VerifyGCStartAt) {
 634           HandleMark hm;  // Discard invalid handles created during verification
 635           gclog_or_tty->print(" VerifyAfterGC:");
 636           Universe::verify(false);
 637         }
 638 
 639         if (PrintGCDetails) {
 640           gclog_or_tty->print(":");
 641           _gens[i]->print_heap_change(prev_used);
 642         }
 643       }
 644     }
 645 
 646     // Update "complete" boolean wrt what actually transpired --
 647     // for instance, a promotion failure could have led to
 648     // a whole heap collection.
 649     complete = complete || (max_level_collected == n_gens() - 1);
 650 
 651     if (complete) { // We did a "major" collection
 652       post_full_gc_dump();   // do any post full gc dumps
 653     }
 654 
 655     if (PrintGCDetails) {
 656       print_heap_change(gch_prev_used);
 657 
 658       // Print perm gen info for full GC with PrintGCDetails flag.
 659       if (complete) {
 660         print_perm_heap_change(perm_prev_used);
 661       }
 662     }
 663 
 664     for (int j = max_level_collected; j >= 0; j -= 1) {
 665       // Adjust generation sizes.
 666       _gens[j]->compute_new_size();
 667     }
 668 
 669     if (complete) {
 670       // Ask the permanent generation to adjust size for full collections
 671       perm()->compute_new_size();
 672       update_full_collections_completed();
 673     }
 674 
 675     // Track memory usage and detect low memory after GC finishes
 676     MemoryService::track_memory_usage();
 677 
 678     gc_epilogue(complete);
 679 
 680     if (must_restore_marks_for_biased_locking) {
 681       BiasedLocking::restore_marks();
 682     }
 683   }
 684 
 685   AdaptiveSizePolicy* sp = gen_policy()->size_policy();
 686   AdaptiveSizePolicyOutput(sp, total_collections());
 687 
 688   if (PrintHeapAtGC) {
 689     Universe::print_heap_after_gc();
 690   }
 691 
 692 #ifdef TRACESPINNING
 693   ParallelTaskTerminator::print_termination_counts();
 694 #endif
 695 
 696   if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) {
 697     tty->print_cr("Stopping after GC #%d", ExitAfterGCNum);
 698     vm_exit(-1);
 699   }
 700 }
 701 
 702 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
 703   return collector_policy()->satisfy_failed_allocation(size, is_tlab);
 704 }
 705 
 706 void GenCollectedHeap::set_par_threads(int t) {
 707   SharedHeap::set_par_threads(t);
 708   _gen_process_strong_tasks->set_n_threads(t);
 709 }
 710 
 711 void GenCollectedHeap::
 712 gen_process_strong_roots(int level,
 713                          bool younger_gens_as_roots,
 714                          bool activate_scope,
 715                          bool collecting_perm_gen,
 716                          SharedHeap::ScanningOption so,
 717                          OopsInGenClosure* not_older_gens,
 718                          bool do_code_roots,
 719                          OopsInGenClosure* older_gens) {
 720   // General strong roots.
 721 
 722   if (!do_code_roots) {
 723     SharedHeap::process_strong_roots(activate_scope, collecting_perm_gen, so,
 724                                      not_older_gens, NULL, older_gens);
 725   } else {
 726     bool do_code_marking = (activate_scope || nmethod::oops_do_marking_is_active());
 727     CodeBlobToOopClosure code_roots(not_older_gens, /*do_marking=*/ do_code_marking);
 728     SharedHeap::process_strong_roots(activate_scope, collecting_perm_gen, so,
 729                                      not_older_gens, &code_roots, older_gens);
 730   }
 731 
 732   if (younger_gens_as_roots) {
 733     if (!_gen_process_strong_tasks->is_task_claimed(GCH_PS_younger_gens)) {
 734       for (int i = 0; i < level; i++) {
 735         not_older_gens->set_generation(_gens[i]);
 736         _gens[i]->oop_iterate(not_older_gens);
 737       }
 738       not_older_gens->reset_generation();
 739     }
 740   }
 741   // When collection is parallel, all threads get to cooperate to do
 742   // older-gen scanning.
 743   for (int i = level+1; i < _n_gens; i++) {
 744     older_gens->set_generation(_gens[i]);
 745     rem_set()->younger_refs_iterate(_gens[i], older_gens);
 746     older_gens->reset_generation();
 747   }
 748 
 749   _gen_process_strong_tasks->all_tasks_completed();
 750 }
 751 
 752 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure,
 753                                               CodeBlobClosure* code_roots,
 754                                               OopClosure* non_root_closure) {
 755   SharedHeap::process_weak_roots(root_closure, code_roots, non_root_closure);
 756   // "Local" "weak" refs
 757   for (int i = 0; i < _n_gens; i++) {
 758     _gens[i]->ref_processor()->weak_oops_do(root_closure);
 759   }
 760 }
 761 
 762 #define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix)    \
 763 void GenCollectedHeap::                                                 \
 764 oop_since_save_marks_iterate(int level,                                 \
 765                              OopClosureType* cur,                       \
 766                              OopClosureType* older) {                   \
 767   _gens[level]->oop_since_save_marks_iterate##nv_suffix(cur);           \
 768   for (int i = level+1; i < n_gens(); i++) {                            \
 769     _gens[i]->oop_since_save_marks_iterate##nv_suffix(older);           \
 770   }                                                                     \
 771   perm_gen()->oop_since_save_marks_iterate##nv_suffix(older);           \
 772 }
 773 
 774 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN)
 775 
 776 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN
 777 
 778 bool GenCollectedHeap::no_allocs_since_save_marks(int level) {
 779   for (int i = level; i < _n_gens; i++) {
 780     if (!_gens[i]->no_allocs_since_save_marks()) return false;
 781   }
 782   return perm_gen()->no_allocs_since_save_marks();
 783 }
 784 
 785 bool GenCollectedHeap::supports_inline_contig_alloc() const {
 786   return _gens[0]->supports_inline_contig_alloc();
 787 }
 788 
 789 HeapWord** GenCollectedHeap::top_addr() const {
 790   return _gens[0]->top_addr();
 791 }
 792 
 793 HeapWord** GenCollectedHeap::end_addr() const {
 794   return _gens[0]->end_addr();
 795 }
 796 
 797 size_t GenCollectedHeap::unsafe_max_alloc() {
 798   return _gens[0]->unsafe_max_alloc_nogc();
 799 }
 800 
 801 // public collection interfaces
 802 
 803 void GenCollectedHeap::collect(GCCause::Cause cause) {
 804   if (should_do_concurrent_full_gc(cause)) {
 805 #ifndef SERIALGC
 806     // mostly concurrent full collection
 807     collect_mostly_concurrent(cause);
 808 #else  // SERIALGC
 809     ShouldNotReachHere();
 810 #endif // SERIALGC
 811   } else {
 812 #ifdef ASSERT
 813     if (cause == GCCause::_scavenge_alot) {
 814       // minor collection only
 815       collect(cause, 0);
 816     } else {
 817       // Stop-the-world full collection
 818       collect(cause, n_gens() - 1);
 819     }
 820 #else
 821     // Stop-the-world full collection
 822     collect(cause, n_gens() - 1);
 823 #endif
 824   }
 825 }
 826 
 827 void GenCollectedHeap::collect(GCCause::Cause cause, int max_level) {
 828   // The caller doesn't have the Heap_lock
 829   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
 830   MutexLocker ml(Heap_lock);
 831   collect_locked(cause, max_level);
 832 }
 833 
 834 // This interface assumes that it's being called by the
 835 // vm thread. It collects the heap assuming that the
 836 // heap lock is already held and that we are executing in
 837 // the context of the vm thread.
 838 void GenCollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
 839   assert(Thread::current()->is_VM_thread(), "Precondition#1");
 840   assert(Heap_lock->is_locked(), "Precondition#2");
 841   GCCauseSetter gcs(this, cause);
 842   switch (cause) {
 843     case GCCause::_heap_inspection:
 844     case GCCause::_heap_dump: {
 845       HandleMark hm;
 846       do_full_collection(false,         // don't clear all soft refs
 847                          n_gens() - 1);
 848       break;
 849     }
 850     default: // XXX FIX ME
 851       ShouldNotReachHere(); // Unexpected use of this function
 852   }
 853 }
 854 
 855 void GenCollectedHeap::collect_locked(GCCause::Cause cause) {
 856   // The caller has the Heap_lock
 857   assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock");
 858   collect_locked(cause, n_gens() - 1);
 859 }
 860 
 861 // this is the private collection interface
 862 // The Heap_lock is expected to be held on entry.
 863 
 864 void GenCollectedHeap::collect_locked(GCCause::Cause cause, int max_level) {
 865   if (_preloading_shared_classes) {
 866     report_out_of_shared_space(SharedPermGen);
 867   }
 868   // Read the GC count while holding the Heap_lock
 869   unsigned int gc_count_before      = total_collections();
 870   unsigned int full_gc_count_before = total_full_collections();
 871   {
 872     MutexUnlocker mu(Heap_lock);  // give up heap lock, execute gets it back
 873     VM_GenCollectFull op(gc_count_before, full_gc_count_before,
 874                          cause, max_level);
 875     VMThread::execute(&op);
 876   }
 877 }
 878 
 879 #ifndef SERIALGC
 880 bool GenCollectedHeap::create_cms_collector() {
 881 
 882   assert(((_gens[1]->kind() == Generation::ConcurrentMarkSweep) ||
 883          (_gens[1]->kind() == Generation::ASConcurrentMarkSweep)) &&
 884          _perm_gen->as_gen()->kind() == Generation::ConcurrentMarkSweep,
 885          "Unexpected generation kinds");
 886   // Skip two header words in the block content verification
 887   NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();)
 888   CMSCollector* collector = new CMSCollector(
 889     (ConcurrentMarkSweepGeneration*)_gens[1],
 890     (ConcurrentMarkSweepGeneration*)_perm_gen->as_gen(),
 891     _rem_set->as_CardTableRS(),
 892     (ConcurrentMarkSweepPolicy*) collector_policy());
 893 
 894   if (collector == NULL || !collector->completed_initialization()) {
 895     if (collector) {
 896       delete collector;  // Be nice in embedded situation
 897     }
 898     vm_shutdown_during_initialization("Could not create CMS collector");
 899     return false;
 900   }
 901   return true;  // success
 902 }
 903 
 904 void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) {
 905   assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock");
 906 
 907   MutexLocker ml(Heap_lock);
 908   // Read the GC counts while holding the Heap_lock
 909   unsigned int full_gc_count_before = total_full_collections();
 910   unsigned int gc_count_before      = total_collections();
 911   {
 912     MutexUnlocker mu(Heap_lock);
 913     VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause);
 914     VMThread::execute(&op);
 915   }
 916 }
 917 #endif // SERIALGC
 918 
 919 
 920 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
 921                                           int max_level) {
 922   int local_max_level;
 923   if (!incremental_collection_will_fail(false /* don't consult_young */) &&
 924       gc_cause() == GCCause::_gc_locker) {
 925     local_max_level = 0;
 926   } else {
 927     local_max_level = max_level;
 928   }
 929 
 930   do_collection(true                 /* full */,
 931                 clear_all_soft_refs  /* clear_all_soft_refs */,
 932                 0                    /* size */,
 933                 false                /* is_tlab */,
 934                 local_max_level      /* max_level */);
 935   // Hack XXX FIX ME !!!
 936   // A scavenge may not have been attempted, or may have
 937   // been attempted and failed, because the old gen was too full
 938   if (local_max_level == 0 && gc_cause() == GCCause::_gc_locker &&
 939       incremental_collection_will_fail(false /* don't consult_young */)) {
 940     if (PrintGCDetails) {
 941       gclog_or_tty->print_cr("GC locker: Trying a full collection "
 942                              "because scavenge failed");
 943     }
 944     // This time allow the old gen to be collected as well
 945     do_collection(true                 /* full */,
 946                   clear_all_soft_refs  /* clear_all_soft_refs */,
 947                   0                    /* size */,
 948                   false                /* is_tlab */,
 949                   n_gens() - 1         /* max_level */);
 950   }
 951 }
 952 
 953 bool GenCollectedHeap::is_in_young(oop p) {
 954   bool result = ((HeapWord*)p) < _gens[_n_gens - 1]->reserved().start();
 955   assert(result == _gens[0]->is_in_reserved(p),
 956          err_msg("incorrect test - result=%d, p=" PTR_FORMAT, result, (void*)p));
 957   return result;
 958 }
 959 
 960 // Returns "TRUE" iff "p" points into the allocated area of the heap.
 961 bool GenCollectedHeap::is_in(const void* p) const {
 962   #ifndef ASSERT
 963   guarantee(VerifyBeforeGC   ||
 964             VerifyDuringGC   ||
 965             VerifyBeforeExit ||
 966             PrintAssembly    ||
 967             tty->count() != 0 ||   // already printing
 968             VerifyAfterGC    ||
 969     VMError::fatal_error_in_progress(), "too expensive");
 970 
 971   #endif
 972   // This might be sped up with a cache of the last generation that
 973   // answered yes.
 974   for (int i = 0; i < _n_gens; i++) {
 975     if (_gens[i]->is_in(p)) return true;
 976   }
 977   if (_perm_gen->as_gen()->is_in(p)) return true;
 978   // Otherwise...
 979   return false;
 980 }
 981 
 982 #ifdef ASSERT
 983 // Don't implement this by using is_in_young().  This method is used
 984 // in some cases to check that is_in_young() is correct.
 985 bool GenCollectedHeap::is_in_partial_collection(const void* p) {
 986   assert(is_in_reserved(p) || p == NULL,
 987     "Does not work if address is non-null and outside of the heap");
 988   // The order of the generations is young (low addr), old, perm (high addr)
 989   return p < _gens[_n_gens - 2]->reserved().end() && p != NULL;
 990 }
 991 #endif
 992 
 993 void GenCollectedHeap::oop_iterate(OopClosure* cl) {
 994   for (int i = 0; i < _n_gens; i++) {
 995     _gens[i]->oop_iterate(cl);
 996   }
 997 }
 998 
 999 void GenCollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl) {
1000   for (int i = 0; i < _n_gens; i++) {
1001     _gens[i]->oop_iterate(mr, cl);
1002   }
1003 }
1004 
1005 void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
1006   for (int i = 0; i < _n_gens; i++) {
1007     _gens[i]->object_iterate(cl);
1008   }
1009   perm_gen()->object_iterate(cl);
1010 }
1011 
1012 void GenCollectedHeap::safe_object_iterate(ObjectClosure* cl) {
1013   for (int i = 0; i < _n_gens; i++) {
1014     _gens[i]->safe_object_iterate(cl);
1015   }
1016   perm_gen()->safe_object_iterate(cl);
1017 }
1018 
1019 void GenCollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
1020   for (int i = 0; i < _n_gens; i++) {
1021     _gens[i]->object_iterate_since_last_GC(cl);
1022   }
1023 }
1024 
1025 Space* GenCollectedHeap::space_containing(const void* addr) const {
1026   for (int i = 0; i < _n_gens; i++) {
1027     Space* res = _gens[i]->space_containing(addr);
1028     if (res != NULL) return res;
1029   }
1030   Space* res = perm_gen()->space_containing(addr);
1031   if (res != NULL) return res;
1032   // Otherwise...
1033   assert(false, "Could not find containing space");
1034   return NULL;
1035 }
1036 
1037 
1038 HeapWord* GenCollectedHeap::block_start(const void* addr) const {
1039   assert(is_in_reserved(addr), "block_start of address outside of heap");
1040   for (int i = 0; i < _n_gens; i++) {
1041     if (_gens[i]->is_in_reserved(addr)) {
1042       assert(_gens[i]->is_in(addr),
1043              "addr should be in allocated part of generation");
1044       return _gens[i]->block_start(addr);
1045     }
1046   }
1047   if (perm_gen()->is_in_reserved(addr)) {
1048     assert(perm_gen()->is_in(addr),
1049            "addr should be in allocated part of perm gen");
1050     return perm_gen()->block_start(addr);
1051   }
1052   assert(false, "Some generation should contain the address");
1053   return NULL;
1054 }
1055 
1056 size_t GenCollectedHeap::block_size(const HeapWord* addr) const {
1057   assert(is_in_reserved(addr), "block_size of address outside of heap");
1058   for (int i = 0; i < _n_gens; i++) {
1059     if (_gens[i]->is_in_reserved(addr)) {
1060       assert(_gens[i]->is_in(addr),
1061              "addr should be in allocated part of generation");
1062       return _gens[i]->block_size(addr);
1063     }
1064   }
1065   if (perm_gen()->is_in_reserved(addr)) {
1066     assert(perm_gen()->is_in(addr),
1067            "addr should be in allocated part of perm gen");
1068     return perm_gen()->block_size(addr);
1069   }
1070   assert(false, "Some generation should contain the address");
1071   return 0;
1072 }
1073 
1074 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
1075   assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
1076   assert(block_start(addr) == addr, "addr must be a block start");
1077   for (int i = 0; i < _n_gens; i++) {
1078     if (_gens[i]->is_in_reserved(addr)) {
1079       return _gens[i]->block_is_obj(addr);
1080     }
1081   }
1082   if (perm_gen()->is_in_reserved(addr)) {
1083     return perm_gen()->block_is_obj(addr);
1084   }
1085   assert(false, "Some generation should contain the address");
1086   return false;
1087 }
1088 
1089 bool GenCollectedHeap::supports_tlab_allocation() const {
1090   for (int i = 0; i < _n_gens; i += 1) {
1091     if (_gens[i]->supports_tlab_allocation()) {
1092       return true;
1093     }
1094   }
1095   return false;
1096 }
1097 
1098 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
1099   size_t result = 0;
1100   for (int i = 0; i < _n_gens; i += 1) {
1101     if (_gens[i]->supports_tlab_allocation()) {
1102       result += _gens[i]->tlab_capacity();
1103     }
1104   }
1105   return result;
1106 }
1107 
1108 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
1109   size_t result = 0;
1110   for (int i = 0; i < _n_gens; i += 1) {
1111     if (_gens[i]->supports_tlab_allocation()) {
1112       result += _gens[i]->unsafe_max_tlab_alloc();
1113     }
1114   }
1115   return result;
1116 }
1117 
1118 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) {
1119   bool gc_overhead_limit_was_exceeded;
1120   return collector_policy()->mem_allocate_work(size /* size */,
1121                                                true /* is_tlab */,
1122                                                &gc_overhead_limit_was_exceeded);
1123 }
1124 
1125 // Requires "*prev_ptr" to be non-NULL.  Deletes and a block of minimal size
1126 // from the list headed by "*prev_ptr".
1127 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
1128   bool first = true;
1129   size_t min_size = 0;   // "first" makes this conceptually infinite.
1130   ScratchBlock **smallest_ptr, *smallest;
1131   ScratchBlock  *cur = *prev_ptr;
1132   while (cur) {
1133     assert(*prev_ptr == cur, "just checking");
1134     if (first || cur->num_words < min_size) {
1135       smallest_ptr = prev_ptr;
1136       smallest     = cur;
1137       min_size     = smallest->num_words;
1138       first        = false;
1139     }
1140     prev_ptr = &cur->next;
1141     cur     =  cur->next;
1142   }
1143   smallest      = *smallest_ptr;
1144   *smallest_ptr = smallest->next;
1145   return smallest;
1146 }
1147 
1148 // Sort the scratch block list headed by res into decreasing size order,
1149 // and set "res" to the result.
1150 static void sort_scratch_list(ScratchBlock*& list) {
1151   ScratchBlock* sorted = NULL;
1152   ScratchBlock* unsorted = list;
1153   while (unsorted) {
1154     ScratchBlock *smallest = removeSmallestScratch(&unsorted);
1155     smallest->next  = sorted;
1156     sorted          = smallest;
1157   }
1158   list = sorted;
1159 }
1160 
1161 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
1162                                                size_t max_alloc_words) {
1163   ScratchBlock* res = NULL;
1164   for (int i = 0; i < _n_gens; i++) {
1165     _gens[i]->contribute_scratch(res, requestor, max_alloc_words);
1166   }
1167   sort_scratch_list(res);
1168   return res;
1169 }
1170 
1171 void GenCollectedHeap::release_scratch() {
1172   for (int i = 0; i < _n_gens; i++) {
1173     _gens[i]->reset_scratch();
1174   }
1175 }
1176 
1177 class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure {
1178   void do_generation(Generation* gen) {
1179     gen->prepare_for_verify();
1180   }
1181 };
1182 
1183 void GenCollectedHeap::prepare_for_verify() {
1184   ensure_parsability(false);        // no need to retire TLABs
1185   GenPrepareForVerifyClosure blk;
1186   generation_iterate(&blk, false);
1187   perm_gen()->prepare_for_verify();
1188 }
1189 
1190 
1191 void GenCollectedHeap::generation_iterate(GenClosure* cl,
1192                                           bool old_to_young) {
1193   if (old_to_young) {
1194     for (int i = _n_gens-1; i >= 0; i--) {
1195       cl->do_generation(_gens[i]);
1196     }
1197   } else {
1198     for (int i = 0; i < _n_gens; i++) {
1199       cl->do_generation(_gens[i]);
1200     }
1201   }
1202 }
1203 
1204 void GenCollectedHeap::space_iterate(SpaceClosure* cl) {
1205   for (int i = 0; i < _n_gens; i++) {
1206     _gens[i]->space_iterate(cl, true);
1207   }
1208   perm_gen()->space_iterate(cl, true);
1209 }
1210 
1211 bool GenCollectedHeap::is_maximal_no_gc() const {
1212   for (int i = 0; i < _n_gens; i++) {  // skip perm gen
1213     if (!_gens[i]->is_maximal_no_gc()) {
1214       return false;
1215     }
1216   }
1217   return true;
1218 }
1219 
1220 void GenCollectedHeap::save_marks() {
1221   for (int i = 0; i < _n_gens; i++) {
1222     _gens[i]->save_marks();
1223   }
1224   perm_gen()->save_marks();
1225 }
1226 
1227 void GenCollectedHeap::compute_new_generation_sizes(int collectedGen) {
1228   for (int i = 0; i <= collectedGen; i++) {
1229     _gens[i]->compute_new_size();
1230   }
1231 }
1232 
1233 GenCollectedHeap* GenCollectedHeap::heap() {
1234   assert(_gch != NULL, "Uninitialized access to GenCollectedHeap::heap()");
1235   assert(_gch->kind() == CollectedHeap::GenCollectedHeap, "not a generational heap");
1236   return _gch;
1237 }
1238 
1239 
1240 void GenCollectedHeap::prepare_for_compaction() {
1241   Generation* scanning_gen = _gens[_n_gens-1];
1242   // Start by compacting into same gen.
1243   CompactPoint cp(scanning_gen, NULL, NULL);
1244   while (scanning_gen != NULL) {
1245     scanning_gen->prepare_for_compaction(&cp);
1246     scanning_gen = prev_gen(scanning_gen);
1247   }
1248 }
1249 
1250 GCStats* GenCollectedHeap::gc_stats(int level) const {
1251   return _gens[level]->gc_stats();
1252 }
1253 
1254 void GenCollectedHeap::verify(bool allow_dirty, bool silent, VerifyOption option /* ignored */) {
1255   if (!silent) {
1256     gclog_or_tty->print("permgen ");
1257   }
1258   perm_gen()->verify(allow_dirty);
1259   for (int i = _n_gens-1; i >= 0; i--) {
1260     Generation* g = _gens[i];
1261     if (!silent) {
1262       gclog_or_tty->print(g->name());
1263       gclog_or_tty->print(" ");
1264     }
1265     g->verify(allow_dirty);
1266   }
1267   if (!silent) {
1268     gclog_or_tty->print("remset ");
1269   }
1270   rem_set()->verify();
1271 }
1272 
1273 void GenCollectedHeap::print_on(outputStream* st) const {
1274   for (int i = 0; i < _n_gens; i++) {
1275     _gens[i]->print_on(st);
1276   }
1277   perm_gen()->print_on(st);
1278 }
1279 
1280 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
1281   if (workers() != NULL) {
1282     workers()->threads_do(tc);
1283   }
1284 #ifndef SERIALGC
1285   if (UseConcMarkSweepGC) {
1286     ConcurrentMarkSweepThread::threads_do(tc);
1287   }
1288 #endif // SERIALGC
1289 }
1290 
1291 void GenCollectedHeap::print_gc_threads_on(outputStream* st) const {
1292 #ifndef SERIALGC
1293   if (UseParNewGC) {
1294     workers()->print_worker_threads_on(st);
1295   }
1296   if (UseConcMarkSweepGC) {
1297     ConcurrentMarkSweepThread::print_all_on(st);
1298   }
1299 #endif // SERIALGC
1300 }
1301 
1302 void GenCollectedHeap::print_tracing_info() const {
1303   if (TraceGen0Time) {
1304     get_gen(0)->print_summary_info();
1305   }
1306   if (TraceGen1Time) {
1307     get_gen(1)->print_summary_info();
1308   }
1309 }
1310 
1311 void GenCollectedHeap::print_heap_change(size_t prev_used) const {
1312   if (PrintGCDetails && Verbose) {
1313     gclog_or_tty->print(" "  SIZE_FORMAT
1314                         "->" SIZE_FORMAT
1315                         "("  SIZE_FORMAT ")",
1316                         prev_used, used(), capacity());
1317   } else {
1318     gclog_or_tty->print(" "  SIZE_FORMAT "K"
1319                         "->" SIZE_FORMAT "K"
1320                         "("  SIZE_FORMAT "K)",
1321                         prev_used / K, used() / K, capacity() / K);
1322   }
1323 }
1324 
1325 //New method to print perm gen info with PrintGCDetails flag
1326 void GenCollectedHeap::print_perm_heap_change(size_t perm_prev_used) const {
1327   gclog_or_tty->print(", [%s :", perm_gen()->short_name());
1328   perm_gen()->print_heap_change(perm_prev_used);
1329   gclog_or_tty->print("]");
1330 }
1331 
1332 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
1333  private:
1334   bool _full;
1335  public:
1336   void do_generation(Generation* gen) {
1337     gen->gc_prologue(_full);
1338   }
1339   GenGCPrologueClosure(bool full) : _full(full) {};
1340 };
1341 
1342 void GenCollectedHeap::gc_prologue(bool full) {
1343   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
1344 
1345   always_do_update_barrier = false;
1346   // Fill TLAB's and such
1347   CollectedHeap::accumulate_statistics_all_tlabs();
1348   ensure_parsability(true);   // retire TLABs
1349 
1350   // Call allocation profiler
1351   AllocationProfiler::iterate_since_last_gc();
1352   // Walk generations
1353   GenGCPrologueClosure blk(full);
1354   generation_iterate(&blk, false);  // not old-to-young.
1355   perm_gen()->gc_prologue(full);
1356 };
1357 
1358 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
1359  private:
1360   bool _full;
1361  public:
1362   void do_generation(Generation* gen) {
1363     gen->gc_epilogue(_full);
1364   }
1365   GenGCEpilogueClosure(bool full) : _full(full) {};
1366 };
1367 
1368 void GenCollectedHeap::gc_epilogue(bool full) {
1369 #ifdef COMPILER2
1370   assert(DerivedPointerTable::is_empty(), "derived pointer present");
1371   size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr()));
1372   guarantee(actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps");
1373 #endif /* COMPILER2 */
1374 
1375   resize_all_tlabs();
1376 
1377   GenGCEpilogueClosure blk(full);
1378   generation_iterate(&blk, false);  // not old-to-young.
1379   perm_gen()->gc_epilogue(full);
1380 
1381   if (!CleanChunkPoolAsync) {
1382     Chunk::clean_chunk_pool();
1383   }
1384 
1385   always_do_update_barrier = UseConcMarkSweepGC;
1386 };
1387 
1388 #ifndef PRODUCT
1389 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure {
1390  private:
1391  public:
1392   void do_generation(Generation* gen) {
1393     gen->record_spaces_top();
1394   }
1395 };
1396 
1397 void GenCollectedHeap::record_gen_tops_before_GC() {
1398   if (ZapUnusedHeapArea) {
1399     GenGCSaveTopsBeforeGCClosure blk;
1400     generation_iterate(&blk, false);  // not old-to-young.
1401     perm_gen()->record_spaces_top();
1402   }
1403 }
1404 #endif  // not PRODUCT
1405 
1406 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
1407  public:
1408   void do_generation(Generation* gen) {
1409     gen->ensure_parsability();
1410   }
1411 };
1412 
1413 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
1414   CollectedHeap::ensure_parsability(retire_tlabs);
1415   GenEnsureParsabilityClosure ep_cl;
1416   generation_iterate(&ep_cl, false);
1417   perm_gen()->ensure_parsability();
1418 }
1419 
1420 oop GenCollectedHeap::handle_failed_promotion(Generation* gen,
1421                                               oop obj,
1422                                               size_t obj_size) {
1423   assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1424   HeapWord* result = NULL;
1425 
1426   // First give each higher generation a chance to allocate the promoted object.
1427   Generation* allocator = next_gen(gen);
1428   if (allocator != NULL) {
1429     do {
1430       result = allocator->allocate(obj_size, false);
1431     } while (result == NULL && (allocator = next_gen(allocator)) != NULL);
1432   }
1433 
1434   if (result == NULL) {
1435     // Then give gen and higher generations a chance to expand and allocate the
1436     // object.
1437     do {
1438       result = gen->expand_and_allocate(obj_size, false);
1439     } while (result == NULL && (gen = next_gen(gen)) != NULL);
1440   }
1441 
1442   if (result != NULL) {
1443     Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);
1444   }
1445   return oop(result);
1446 }
1447 
1448 class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure {
1449   jlong _time;   // in ms
1450   jlong _now;    // in ms
1451 
1452  public:
1453   GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { }
1454 
1455   jlong time() { return _time; }
1456 
1457   void do_generation(Generation* gen) {
1458     _time = MIN2(_time, gen->time_of_last_gc(_now));
1459   }
1460 };
1461 
1462 jlong GenCollectedHeap::millis_since_last_gc() {
1463   // We need a montonically increasing time in ms but os::javaTimeMillis()
1464   // does not guarantee montonicity.
1465   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
1466   GenTimeOfLastGCClosure tolgc_cl(now);
1467   // iterate over generations getting the oldest
1468   // time that a generation was collected
1469   generation_iterate(&tolgc_cl, false);
1470   tolgc_cl.do_generation(perm_gen());
1471   
1472   // javaTimeNanos() is guaranteed to be monotonically non-decreasing
1473   // provided the underlying platform provides such a time source
1474   // (and it is bug free). So we still have to guard against getting
1475   // back a time later than 'now'.
1476   jlong retVal = now - tolgc_cl.time();
1477   if (retVal < 0) {
1478     NOT_PRODUCT(warning("time warp: "INT64_FORMAT, retVal);)
1479     return 0;
1480   }
1481   return retVal;
1482 }