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->verify_no_references_recorded();
 603             rp->enable_discovery();
 604             rp->setup_policy(do_clear_all_soft_refs);
 605           } else {
 606             // collect() below will enable discovery as appropriate
 607           }
 608           _gens[i]->collect(full, do_clear_all_soft_refs, size, is_tlab);
 609           if (!rp->enqueuing_is_done()) {
 610             rp->enqueue_discovered_references();
 611           } else {
 612             rp->set_enqueuing_is_done(false);
 613           }
 614           rp->verify_no_references_recorded();
 615         }
 616         max_level_collected = i;
 617 
 618         // Determine if allocation request was met.
 619         if (size > 0) {
 620           if (!is_tlab || _gens[i]->supports_tlab_allocation()) {
 621             if (size*HeapWordSize <= _gens[i]->unsafe_max_alloc_nogc()) {
 622               size = 0;
 623             }
 624           }
 625         }
 626 
 627         COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
 628 
 629         _gens[i]->stat_record()->accumulated_time.stop();
 630 
 631         update_gc_stats(i, full);
 632 
 633         if (VerifyAfterGC && i >= VerifyGCLevel &&
 634             total_collections() >= VerifyGCStartAt) {
 635           HandleMark hm;  // Discard invalid handles created during verification
 636           gclog_or_tty->print(" VerifyAfterGC:");
 637           Universe::verify(false);
 638         }
 639 
 640         if (PrintGCDetails) {
 641           gclog_or_tty->print(":");
 642           _gens[i]->print_heap_change(prev_used);
 643         }
 644       }
 645     }
 646 
 647     // Update "complete" boolean wrt what actually transpired --
 648     // for instance, a promotion failure could have led to
 649     // a whole heap collection.
 650     complete = complete || (max_level_collected == n_gens() - 1);
 651 
 652     if (complete) { // We did a "major" collection
 653       post_full_gc_dump();   // do any post full gc dumps
 654     }
 655 
 656     if (PrintGCDetails) {
 657       print_heap_change(gch_prev_used);
 658 
 659       // Print perm gen info for full GC with PrintGCDetails flag.
 660       if (complete) {
 661         print_perm_heap_change(perm_prev_used);
 662       }
 663     }
 664 
 665     for (int j = max_level_collected; j >= 0; j -= 1) {
 666       // Adjust generation sizes.
 667       _gens[j]->compute_new_size();
 668     }
 669 
 670     if (complete) {
 671       // Ask the permanent generation to adjust size for full collections
 672       perm()->compute_new_size();
 673       update_full_collections_completed();
 674     }
 675 
 676     // Track memory usage and detect low memory after GC finishes
 677     MemoryService::track_memory_usage();
 678 
 679     gc_epilogue(complete);
 680 
 681     if (must_restore_marks_for_biased_locking) {
 682       BiasedLocking::restore_marks();
 683     }
 684   }
 685 
 686   AdaptiveSizePolicy* sp = gen_policy()->size_policy();
 687   AdaptiveSizePolicyOutput(sp, total_collections());
 688 
 689   if (PrintHeapAtGC) {
 690     Universe::print_heap_after_gc();
 691   }
 692 
 693 #ifdef TRACESPINNING
 694   ParallelTaskTerminator::print_termination_counts();
 695 #endif
 696 
 697   if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) {
 698     tty->print_cr("Stopping after GC #%d", ExitAfterGCNum);
 699     vm_exit(-1);
 700   }
 701 }
 702 
 703 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
 704   return collector_policy()->satisfy_failed_allocation(size, is_tlab);
 705 }
 706 
 707 void GenCollectedHeap::set_par_threads(int t) {
 708   SharedHeap::set_par_threads(t);
 709   _gen_process_strong_tasks->set_n_threads(t);
 710 }
 711 
 712 void GenCollectedHeap::
 713 gen_process_strong_roots(int level,
 714                          bool younger_gens_as_roots,
 715                          bool activate_scope,
 716                          bool collecting_perm_gen,
 717                          SharedHeap::ScanningOption so,
 718                          OopsInGenClosure* not_older_gens,
 719                          bool do_code_roots,
 720                          OopsInGenClosure* older_gens) {
 721   // General strong roots.
 722 
 723   if (!do_code_roots) {
 724     SharedHeap::process_strong_roots(activate_scope, collecting_perm_gen, so,
 725                                      not_older_gens, NULL, older_gens);
 726   } else {
 727     bool do_code_marking = (activate_scope || nmethod::oops_do_marking_is_active());
 728     CodeBlobToOopClosure code_roots(not_older_gens, /*do_marking=*/ do_code_marking);
 729     SharedHeap::process_strong_roots(activate_scope, collecting_perm_gen, so,
 730                                      not_older_gens, &code_roots, older_gens);
 731   }
 732 
 733   if (younger_gens_as_roots) {
 734     if (!_gen_process_strong_tasks->is_task_claimed(GCH_PS_younger_gens)) {
 735       for (int i = 0; i < level; i++) {
 736         not_older_gens->set_generation(_gens[i]);
 737         _gens[i]->oop_iterate(not_older_gens);
 738       }
 739       not_older_gens->reset_generation();
 740     }
 741   }
 742   // When collection is parallel, all threads get to cooperate to do
 743   // older-gen scanning.
 744   for (int i = level+1; i < _n_gens; i++) {
 745     older_gens->set_generation(_gens[i]);
 746     rem_set()->younger_refs_iterate(_gens[i], older_gens);
 747     older_gens->reset_generation();
 748   }
 749 
 750   _gen_process_strong_tasks->all_tasks_completed();
 751 }
 752 
 753 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure,
 754                                               CodeBlobClosure* code_roots,
 755                                               OopClosure* non_root_closure) {
 756   SharedHeap::process_weak_roots(root_closure, code_roots, non_root_closure);
 757   // "Local" "weak" refs
 758   for (int i = 0; i < _n_gens; i++) {
 759     _gens[i]->ref_processor()->weak_oops_do(root_closure);
 760   }
 761 }
 762 
 763 #define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix)    \
 764 void GenCollectedHeap::                                                 \
 765 oop_since_save_marks_iterate(int level,                                 \
 766                              OopClosureType* cur,                       \
 767                              OopClosureType* older) {                   \
 768   _gens[level]->oop_since_save_marks_iterate##nv_suffix(cur);           \
 769   for (int i = level+1; i < n_gens(); i++) {                            \
 770     _gens[i]->oop_since_save_marks_iterate##nv_suffix(older);           \
 771   }                                                                     \
 772   perm_gen()->oop_since_save_marks_iterate##nv_suffix(older);           \
 773 }
 774 
 775 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN)
 776 
 777 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN
 778 
 779 bool GenCollectedHeap::no_allocs_since_save_marks(int level) {
 780   for (int i = level; i < _n_gens; i++) {
 781     if (!_gens[i]->no_allocs_since_save_marks()) return false;
 782   }
 783   return perm_gen()->no_allocs_since_save_marks();
 784 }
 785 
 786 bool GenCollectedHeap::supports_inline_contig_alloc() const {
 787   return _gens[0]->supports_inline_contig_alloc();
 788 }
 789 
 790 HeapWord** GenCollectedHeap::top_addr() const {
 791   return _gens[0]->top_addr();
 792 }
 793 
 794 HeapWord** GenCollectedHeap::end_addr() const {
 795   return _gens[0]->end_addr();
 796 }
 797 
 798 size_t GenCollectedHeap::unsafe_max_alloc() {
 799   return _gens[0]->unsafe_max_alloc_nogc();
 800 }
 801 
 802 // public collection interfaces
 803 
 804 void GenCollectedHeap::collect(GCCause::Cause cause) {
 805   if (should_do_concurrent_full_gc(cause)) {
 806 #ifndef SERIALGC
 807     // mostly concurrent full collection
 808     collect_mostly_concurrent(cause);
 809 #else  // SERIALGC
 810     ShouldNotReachHere();
 811 #endif // SERIALGC
 812   } else {
 813 #ifdef ASSERT
 814     if (cause == GCCause::_scavenge_alot) {
 815       // minor collection only
 816       collect(cause, 0);
 817     } else {
 818       // Stop-the-world full collection
 819       collect(cause, n_gens() - 1);
 820     }
 821 #else
 822     // Stop-the-world full collection
 823     collect(cause, n_gens() - 1);
 824 #endif
 825   }
 826 }
 827 
 828 void GenCollectedHeap::collect(GCCause::Cause cause, int max_level) {
 829   // The caller doesn't have the Heap_lock
 830   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
 831   MutexLocker ml(Heap_lock);
 832   collect_locked(cause, max_level);
 833 }
 834 
 835 // This interface assumes that it's being called by the
 836 // vm thread. It collects the heap assuming that the
 837 // heap lock is already held and that we are executing in
 838 // the context of the vm thread.
 839 void GenCollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
 840   assert(Thread::current()->is_VM_thread(), "Precondition#1");
 841   assert(Heap_lock->is_locked(), "Precondition#2");
 842   GCCauseSetter gcs(this, cause);
 843   switch (cause) {
 844     case GCCause::_heap_inspection:
 845     case GCCause::_heap_dump: {
 846       HandleMark hm;
 847       do_full_collection(false,         // don't clear all soft refs
 848                          n_gens() - 1);
 849       break;
 850     }
 851     default: // XXX FIX ME
 852       ShouldNotReachHere(); // Unexpected use of this function
 853   }
 854 }
 855 
 856 void GenCollectedHeap::collect_locked(GCCause::Cause cause) {
 857   // The caller has the Heap_lock
 858   assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock");
 859   collect_locked(cause, n_gens() - 1);
 860 }
 861 
 862 // this is the private collection interface
 863 // The Heap_lock is expected to be held on entry.
 864 
 865 void GenCollectedHeap::collect_locked(GCCause::Cause cause, int max_level) {
 866   if (_preloading_shared_classes) {
 867     report_out_of_shared_space(SharedPermGen);
 868   }
 869   // Read the GC count while holding the Heap_lock
 870   unsigned int gc_count_before      = total_collections();
 871   unsigned int full_gc_count_before = total_full_collections();
 872   {
 873     MutexUnlocker mu(Heap_lock);  // give up heap lock, execute gets it back
 874     VM_GenCollectFull op(gc_count_before, full_gc_count_before,
 875                          cause, max_level);
 876     VMThread::execute(&op);
 877   }
 878 }
 879 
 880 #ifndef SERIALGC
 881 bool GenCollectedHeap::create_cms_collector() {
 882 
 883   assert(((_gens[1]->kind() == Generation::ConcurrentMarkSweep) ||
 884          (_gens[1]->kind() == Generation::ASConcurrentMarkSweep)) &&
 885          _perm_gen->as_gen()->kind() == Generation::ConcurrentMarkSweep,
 886          "Unexpected generation kinds");
 887   // Skip two header words in the block content verification
 888   NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();)
 889   CMSCollector* collector = new CMSCollector(
 890     (ConcurrentMarkSweepGeneration*)_gens[1],
 891     (ConcurrentMarkSweepGeneration*)_perm_gen->as_gen(),
 892     _rem_set->as_CardTableRS(),
 893     (ConcurrentMarkSweepPolicy*) collector_policy());
 894 
 895   if (collector == NULL || !collector->completed_initialization()) {
 896     if (collector) {
 897       delete collector;  // Be nice in embedded situation
 898     }
 899     vm_shutdown_during_initialization("Could not create CMS collector");
 900     return false;
 901   }
 902   return true;  // success
 903 }
 904 
 905 void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) {
 906   assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock");
 907 
 908   MutexLocker ml(Heap_lock);
 909   // Read the GC counts while holding the Heap_lock
 910   unsigned int full_gc_count_before = total_full_collections();
 911   unsigned int gc_count_before      = total_collections();
 912   {
 913     MutexUnlocker mu(Heap_lock);
 914     VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause);
 915     VMThread::execute(&op);
 916   }
 917 }
 918 #endif // SERIALGC
 919 
 920 
 921 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
 922                                           int max_level) {
 923   int local_max_level;
 924   if (!incremental_collection_will_fail(false /* don't consult_young */) &&
 925       gc_cause() == GCCause::_gc_locker) {
 926     local_max_level = 0;
 927   } else {
 928     local_max_level = max_level;
 929   }
 930 
 931   do_collection(true                 /* full */,
 932                 clear_all_soft_refs  /* clear_all_soft_refs */,
 933                 0                    /* size */,
 934                 false                /* is_tlab */,
 935                 local_max_level      /* max_level */);
 936   // Hack XXX FIX ME !!!
 937   // A scavenge may not have been attempted, or may have
 938   // been attempted and failed, because the old gen was too full
 939   if (local_max_level == 0 && gc_cause() == GCCause::_gc_locker &&
 940       incremental_collection_will_fail(false /* don't consult_young */)) {
 941     if (PrintGCDetails) {
 942       gclog_or_tty->print_cr("GC locker: Trying a full collection "
 943                              "because scavenge failed");
 944     }
 945     // This time allow the old gen to be collected as well
 946     do_collection(true                 /* full */,
 947                   clear_all_soft_refs  /* clear_all_soft_refs */,
 948                   0                    /* size */,
 949                   false                /* is_tlab */,
 950                   n_gens() - 1         /* max_level */);
 951   }
 952 }
 953 
 954 bool GenCollectedHeap::is_in_young(oop p) {
 955   bool result = ((HeapWord*)p) < _gens[_n_gens - 1]->reserved().start();
 956   assert(result == _gens[0]->is_in_reserved(p),
 957          err_msg("incorrect test - result=%d, p=" PTR_FORMAT, result, (void*)p));
 958   return result;
 959 }
 960 
 961 // Returns "TRUE" iff "p" points into the allocated area of the heap.
 962 bool GenCollectedHeap::is_in(const void* p) const {
 963   #ifndef ASSERT
 964   guarantee(VerifyBeforeGC   ||
 965             VerifyDuringGC   ||
 966             VerifyBeforeExit ||
 967             PrintAssembly    ||
 968             tty->count() != 0 ||   // already printing
 969             VerifyAfterGC    ||
 970     VMError::fatal_error_in_progress(), "too expensive");
 971 
 972   #endif
 973   // This might be sped up with a cache of the last generation that
 974   // answered yes.
 975   for (int i = 0; i < _n_gens; i++) {
 976     if (_gens[i]->is_in(p)) return true;
 977   }
 978   if (_perm_gen->as_gen()->is_in(p)) return true;
 979   // Otherwise...
 980   return false;
 981 }
 982 
 983 #ifdef ASSERT
 984 // Don't implement this by using is_in_young().  This method is used
 985 // in some cases to check that is_in_young() is correct.
 986 bool GenCollectedHeap::is_in_partial_collection(const void* p) {
 987   assert(is_in_reserved(p) || p == NULL,
 988     "Does not work if address is non-null and outside of the heap");
 989   // The order of the generations is young (low addr), old, perm (high addr)
 990   return p < _gens[_n_gens - 2]->reserved().end() && p != NULL;
 991 }
 992 #endif
 993 
 994 void GenCollectedHeap::oop_iterate(OopClosure* cl) {
 995   for (int i = 0; i < _n_gens; i++) {
 996     _gens[i]->oop_iterate(cl);
 997   }
 998 }
 999 
1000 void GenCollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl) {
1001   for (int i = 0; i < _n_gens; i++) {
1002     _gens[i]->oop_iterate(mr, cl);
1003   }
1004 }
1005 
1006 void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
1007   for (int i = 0; i < _n_gens; i++) {
1008     _gens[i]->object_iterate(cl);
1009   }
1010   perm_gen()->object_iterate(cl);
1011 }
1012 
1013 void GenCollectedHeap::safe_object_iterate(ObjectClosure* cl) {
1014   for (int i = 0; i < _n_gens; i++) {
1015     _gens[i]->safe_object_iterate(cl);
1016   }
1017   perm_gen()->safe_object_iterate(cl);
1018 }
1019 
1020 void GenCollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
1021   for (int i = 0; i < _n_gens; i++) {
1022     _gens[i]->object_iterate_since_last_GC(cl);
1023   }
1024 }
1025 
1026 Space* GenCollectedHeap::space_containing(const void* addr) const {
1027   for (int i = 0; i < _n_gens; i++) {
1028     Space* res = _gens[i]->space_containing(addr);
1029     if (res != NULL) return res;
1030   }
1031   Space* res = perm_gen()->space_containing(addr);
1032   if (res != NULL) return res;
1033   // Otherwise...
1034   assert(false, "Could not find containing space");
1035   return NULL;
1036 }
1037 
1038 
1039 HeapWord* GenCollectedHeap::block_start(const void* addr) const {
1040   assert(is_in_reserved(addr), "block_start of address outside of heap");
1041   for (int i = 0; i < _n_gens; i++) {
1042     if (_gens[i]->is_in_reserved(addr)) {
1043       assert(_gens[i]->is_in(addr),
1044              "addr should be in allocated part of generation");
1045       return _gens[i]->block_start(addr);
1046     }
1047   }
1048   if (perm_gen()->is_in_reserved(addr)) {
1049     assert(perm_gen()->is_in(addr),
1050            "addr should be in allocated part of perm gen");
1051     return perm_gen()->block_start(addr);
1052   }
1053   assert(false, "Some generation should contain the address");
1054   return NULL;
1055 }
1056 
1057 size_t GenCollectedHeap::block_size(const HeapWord* addr) const {
1058   assert(is_in_reserved(addr), "block_size of address outside of heap");
1059   for (int i = 0; i < _n_gens; i++) {
1060     if (_gens[i]->is_in_reserved(addr)) {
1061       assert(_gens[i]->is_in(addr),
1062              "addr should be in allocated part of generation");
1063       return _gens[i]->block_size(addr);
1064     }
1065   }
1066   if (perm_gen()->is_in_reserved(addr)) {
1067     assert(perm_gen()->is_in(addr),
1068            "addr should be in allocated part of perm gen");
1069     return perm_gen()->block_size(addr);
1070   }
1071   assert(false, "Some generation should contain the address");
1072   return 0;
1073 }
1074 
1075 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
1076   assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
1077   assert(block_start(addr) == addr, "addr must be a block start");
1078   for (int i = 0; i < _n_gens; i++) {
1079     if (_gens[i]->is_in_reserved(addr)) {
1080       return _gens[i]->block_is_obj(addr);
1081     }
1082   }
1083   if (perm_gen()->is_in_reserved(addr)) {
1084     return perm_gen()->block_is_obj(addr);
1085   }
1086   assert(false, "Some generation should contain the address");
1087   return false;
1088 }
1089 
1090 bool GenCollectedHeap::supports_tlab_allocation() const {
1091   for (int i = 0; i < _n_gens; i += 1) {
1092     if (_gens[i]->supports_tlab_allocation()) {
1093       return true;
1094     }
1095   }
1096   return false;
1097 }
1098 
1099 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
1100   size_t result = 0;
1101   for (int i = 0; i < _n_gens; i += 1) {
1102     if (_gens[i]->supports_tlab_allocation()) {
1103       result += _gens[i]->tlab_capacity();
1104     }
1105   }
1106   return result;
1107 }
1108 
1109 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
1110   size_t result = 0;
1111   for (int i = 0; i < _n_gens; i += 1) {
1112     if (_gens[i]->supports_tlab_allocation()) {
1113       result += _gens[i]->unsafe_max_tlab_alloc();
1114     }
1115   }
1116   return result;
1117 }
1118 
1119 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) {
1120   bool gc_overhead_limit_was_exceeded;
1121   return collector_policy()->mem_allocate_work(size /* size */,
1122                                                true /* is_tlab */,
1123                                                &gc_overhead_limit_was_exceeded);
1124 }
1125 
1126 // Requires "*prev_ptr" to be non-NULL.  Deletes and a block of minimal size
1127 // from the list headed by "*prev_ptr".
1128 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
1129   bool first = true;
1130   size_t min_size = 0;   // "first" makes this conceptually infinite.
1131   ScratchBlock **smallest_ptr, *smallest;
1132   ScratchBlock  *cur = *prev_ptr;
1133   while (cur) {
1134     assert(*prev_ptr == cur, "just checking");
1135     if (first || cur->num_words < min_size) {
1136       smallest_ptr = prev_ptr;
1137       smallest     = cur;
1138       min_size     = smallest->num_words;
1139       first        = false;
1140     }
1141     prev_ptr = &cur->next;
1142     cur     =  cur->next;
1143   }
1144   smallest      = *smallest_ptr;
1145   *smallest_ptr = smallest->next;
1146   return smallest;
1147 }
1148 
1149 // Sort the scratch block list headed by res into decreasing size order,
1150 // and set "res" to the result.
1151 static void sort_scratch_list(ScratchBlock*& list) {
1152   ScratchBlock* sorted = NULL;
1153   ScratchBlock* unsorted = list;
1154   while (unsorted) {
1155     ScratchBlock *smallest = removeSmallestScratch(&unsorted);
1156     smallest->next  = sorted;
1157     sorted          = smallest;
1158   }
1159   list = sorted;
1160 }
1161 
1162 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
1163                                                size_t max_alloc_words) {
1164   ScratchBlock* res = NULL;
1165   for (int i = 0; i < _n_gens; i++) {
1166     _gens[i]->contribute_scratch(res, requestor, max_alloc_words);
1167   }
1168   sort_scratch_list(res);
1169   return res;
1170 }
1171 
1172 void GenCollectedHeap::release_scratch() {
1173   for (int i = 0; i < _n_gens; i++) {
1174     _gens[i]->reset_scratch();
1175   }
1176 }
1177 
1178 class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure {
1179   void do_generation(Generation* gen) {
1180     gen->prepare_for_verify();
1181   }
1182 };
1183 
1184 void GenCollectedHeap::prepare_for_verify() {
1185   ensure_parsability(false);        // no need to retire TLABs
1186   GenPrepareForVerifyClosure blk;
1187   generation_iterate(&blk, false);
1188   perm_gen()->prepare_for_verify();
1189 }
1190 
1191 
1192 void GenCollectedHeap::generation_iterate(GenClosure* cl,
1193                                           bool old_to_young) {
1194   if (old_to_young) {
1195     for (int i = _n_gens-1; i >= 0; i--) {
1196       cl->do_generation(_gens[i]);
1197     }
1198   } else {
1199     for (int i = 0; i < _n_gens; i++) {
1200       cl->do_generation(_gens[i]);
1201     }
1202   }
1203 }
1204 
1205 void GenCollectedHeap::space_iterate(SpaceClosure* cl) {
1206   for (int i = 0; i < _n_gens; i++) {
1207     _gens[i]->space_iterate(cl, true);
1208   }
1209   perm_gen()->space_iterate(cl, true);
1210 }
1211 
1212 bool GenCollectedHeap::is_maximal_no_gc() const {
1213   for (int i = 0; i < _n_gens; i++) {  // skip perm gen
1214     if (!_gens[i]->is_maximal_no_gc()) {
1215       return false;
1216     }
1217   }
1218   return true;
1219 }
1220 
1221 void GenCollectedHeap::save_marks() {
1222   for (int i = 0; i < _n_gens; i++) {
1223     _gens[i]->save_marks();
1224   }
1225   perm_gen()->save_marks();
1226 }
1227 
1228 void GenCollectedHeap::compute_new_generation_sizes(int collectedGen) {
1229   for (int i = 0; i <= collectedGen; i++) {
1230     _gens[i]->compute_new_size();
1231   }
1232 }
1233 
1234 GenCollectedHeap* GenCollectedHeap::heap() {
1235   assert(_gch != NULL, "Uninitialized access to GenCollectedHeap::heap()");
1236   assert(_gch->kind() == CollectedHeap::GenCollectedHeap, "not a generational heap");
1237   return _gch;
1238 }
1239 
1240 
1241 void GenCollectedHeap::prepare_for_compaction() {
1242   Generation* scanning_gen = _gens[_n_gens-1];
1243   // Start by compacting into same gen.
1244   CompactPoint cp(scanning_gen, NULL, NULL);
1245   while (scanning_gen != NULL) {
1246     scanning_gen->prepare_for_compaction(&cp);
1247     scanning_gen = prev_gen(scanning_gen);
1248   }
1249 }
1250 
1251 GCStats* GenCollectedHeap::gc_stats(int level) const {
1252   return _gens[level]->gc_stats();
1253 }
1254 
1255 void GenCollectedHeap::verify(bool allow_dirty, bool silent, VerifyOption option /* ignored */) {
1256   if (!silent) {
1257     gclog_or_tty->print("permgen ");
1258   }
1259   perm_gen()->verify(allow_dirty);
1260   for (int i = _n_gens-1; i >= 0; i--) {
1261     Generation* g = _gens[i];
1262     if (!silent) {
1263       gclog_or_tty->print(g->name());
1264       gclog_or_tty->print(" ");
1265     }
1266     g->verify(allow_dirty);
1267   }
1268   if (!silent) {
1269     gclog_or_tty->print("remset ");
1270   }
1271   rem_set()->verify();
1272 }
1273 
1274 void GenCollectedHeap::print() const { print_on(tty); }
1275 void GenCollectedHeap::print_on(outputStream* st) const {
1276   for (int i = 0; i < _n_gens; i++) {
1277     _gens[i]->print_on(st);
1278   }
1279   perm_gen()->print_on(st);
1280 }
1281 
1282 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
1283   if (workers() != NULL) {
1284     workers()->threads_do(tc);
1285   }
1286 #ifndef SERIALGC
1287   if (UseConcMarkSweepGC) {
1288     ConcurrentMarkSweepThread::threads_do(tc);
1289   }
1290 #endif // SERIALGC
1291 }
1292 
1293 void GenCollectedHeap::print_gc_threads_on(outputStream* st) const {
1294 #ifndef SERIALGC
1295   if (UseParNewGC) {
1296     workers()->print_worker_threads_on(st);
1297   }
1298   if (UseConcMarkSweepGC) {
1299     ConcurrentMarkSweepThread::print_all_on(st);
1300   }
1301 #endif // SERIALGC
1302 }
1303 
1304 void GenCollectedHeap::print_tracing_info() const {
1305   if (TraceGen0Time) {
1306     get_gen(0)->print_summary_info();
1307   }
1308   if (TraceGen1Time) {
1309     get_gen(1)->print_summary_info();
1310   }
1311 }
1312 
1313 void GenCollectedHeap::print_heap_change(size_t prev_used) const {
1314   if (PrintGCDetails && Verbose) {
1315     gclog_or_tty->print(" "  SIZE_FORMAT
1316                         "->" SIZE_FORMAT
1317                         "("  SIZE_FORMAT ")",
1318                         prev_used, used(), capacity());
1319   } else {
1320     gclog_or_tty->print(" "  SIZE_FORMAT "K"
1321                         "->" SIZE_FORMAT "K"
1322                         "("  SIZE_FORMAT "K)",
1323                         prev_used / K, used() / K, capacity() / K);
1324   }
1325 }
1326 
1327 //New method to print perm gen info with PrintGCDetails flag
1328 void GenCollectedHeap::print_perm_heap_change(size_t perm_prev_used) const {
1329   gclog_or_tty->print(", [%s :", perm_gen()->short_name());
1330   perm_gen()->print_heap_change(perm_prev_used);
1331   gclog_or_tty->print("]");
1332 }
1333 
1334 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
1335  private:
1336   bool _full;
1337  public:
1338   void do_generation(Generation* gen) {
1339     gen->gc_prologue(_full);
1340   }
1341   GenGCPrologueClosure(bool full) : _full(full) {};
1342 };
1343 
1344 void GenCollectedHeap::gc_prologue(bool full) {
1345   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
1346 
1347   always_do_update_barrier = false;
1348   // Fill TLAB's and such
1349   CollectedHeap::accumulate_statistics_all_tlabs();
1350   ensure_parsability(true);   // retire TLABs
1351 
1352   // Call allocation profiler
1353   AllocationProfiler::iterate_since_last_gc();
1354   // Walk generations
1355   GenGCPrologueClosure blk(full);
1356   generation_iterate(&blk, false);  // not old-to-young.
1357   perm_gen()->gc_prologue(full);
1358 };
1359 
1360 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
1361  private:
1362   bool _full;
1363  public:
1364   void do_generation(Generation* gen) {
1365     gen->gc_epilogue(_full);
1366   }
1367   GenGCEpilogueClosure(bool full) : _full(full) {};
1368 };
1369 
1370 void GenCollectedHeap::gc_epilogue(bool full) {
1371 #ifdef COMPILER2
1372   assert(DerivedPointerTable::is_empty(), "derived pointer present");
1373   size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr()));
1374   guarantee(actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps");
1375 #endif /* COMPILER2 */
1376 
1377   resize_all_tlabs();
1378 
1379   GenGCEpilogueClosure blk(full);
1380   generation_iterate(&blk, false);  // not old-to-young.
1381   perm_gen()->gc_epilogue(full);
1382 
1383   if (!CleanChunkPoolAsync) {
1384     Chunk::clean_chunk_pool();
1385   }
1386 
1387   always_do_update_barrier = UseConcMarkSweepGC;
1388 };
1389 
1390 #ifndef PRODUCT
1391 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure {
1392  private:
1393  public:
1394   void do_generation(Generation* gen) {
1395     gen->record_spaces_top();
1396   }
1397 };
1398 
1399 void GenCollectedHeap::record_gen_tops_before_GC() {
1400   if (ZapUnusedHeapArea) {
1401     GenGCSaveTopsBeforeGCClosure blk;
1402     generation_iterate(&blk, false);  // not old-to-young.
1403     perm_gen()->record_spaces_top();
1404   }
1405 }
1406 #endif  // not PRODUCT
1407 
1408 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
1409  public:
1410   void do_generation(Generation* gen) {
1411     gen->ensure_parsability();
1412   }
1413 };
1414 
1415 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
1416   CollectedHeap::ensure_parsability(retire_tlabs);
1417   GenEnsureParsabilityClosure ep_cl;
1418   generation_iterate(&ep_cl, false);
1419   perm_gen()->ensure_parsability();
1420 }
1421 
1422 oop GenCollectedHeap::handle_failed_promotion(Generation* gen,
1423                                               oop obj,
1424                                               size_t obj_size) {
1425   assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1426   HeapWord* result = NULL;
1427 
1428   // First give each higher generation a chance to allocate the promoted object.
1429   Generation* allocator = next_gen(gen);
1430   if (allocator != NULL) {
1431     do {
1432       result = allocator->allocate(obj_size, false);
1433     } while (result == NULL && (allocator = next_gen(allocator)) != NULL);
1434   }
1435 
1436   if (result == NULL) {
1437     // Then give gen and higher generations a chance to expand and allocate the
1438     // object.
1439     do {
1440       result = gen->expand_and_allocate(obj_size, false);
1441     } while (result == NULL && (gen = next_gen(gen)) != NULL);
1442   }
1443 
1444   if (result != NULL) {
1445     Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);
1446   }
1447   return oop(result);
1448 }
1449 
1450 class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure {
1451   jlong _time;   // in ms
1452   jlong _now;    // in ms
1453 
1454  public:
1455   GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { }
1456 
1457   jlong time() { return _time; }
1458 
1459   void do_generation(Generation* gen) {
1460     _time = MIN2(_time, gen->time_of_last_gc(_now));
1461   }
1462 };
1463 
1464 jlong GenCollectedHeap::millis_since_last_gc() {
1465   jlong now = os::javaTimeMillis();
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   // XXX Despite the assert above, since javaTimeMillis()
1472   // doesnot guarantee monotonically increasing return
1473   // values (note, i didn't say "strictly monotonic"),
1474   // we need to guard against getting back a time
1475   // later than now. This should be fixed by basing
1476   // on someting like gethrtime() which guarantees
1477   // monotonicity. Note that cond_wait() is susceptible
1478   // to a similar problem, because its interface is
1479   // based on absolute time in the form of the
1480   // system time's notion of UCT. See also 4506635
1481   // for yet another problem of similar nature. XXX
1482   jlong retVal = now - tolgc_cl.time();
1483   if (retVal < 0) {
1484     NOT_PRODUCT(warning("time warp: %d", retVal);)
1485     return 0;
1486   }
1487   return retVal;
1488 }