1 /*
   2  * Copyright (c) 2000, 2016, 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/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc_implementation/shared/collectorCounters.hpp"
  32 #include "gc_implementation/shared/gcTrace.hpp"
  33 #include "gc_implementation/shared/gcTraceTime.hpp"
  34 #include "gc_implementation/shared/vmGCOperations.hpp"
  35 #include "gc_interface/collectedHeap.inline.hpp"
  36 #include "memory/filemap.hpp"
  37 #include "memory/gcLocker.inline.hpp"
  38 #include "memory/genCollectedHeap.hpp"
  39 #include "memory/genOopClosures.inline.hpp"
  40 #include "memory/generation.inline.hpp"
  41 #include "memory/generationSpec.hpp"
  42 #include "memory/resourceArea.hpp"
  43 #include "memory/sharedHeap.hpp"
  44 #include "memory/space.hpp"
  45 #include "oops/oop.inline.hpp"
  46 #include "oops/oop.inline2.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/management.hpp"
  54 #include "services/memoryService.hpp"
  55 #include "utilities/vmError.hpp"
  56 #include "utilities/workgroup.hpp"
  57 #include "utilities/macros.hpp"
  58 #if INCLUDE_ALL_GCS
  59 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
  60 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp"
  61 #endif // INCLUDE_ALL_GCS
  62 
  63 GenCollectedHeap* GenCollectedHeap::_gch;
  64 NOT_PRODUCT(size_t GenCollectedHeap::_skip_header_HeapWords = 0;)
  65 
  66 // The set of potentially parallel tasks in root scanning.
  67 enum GCH_strong_roots_tasks {
  68   GCH_PS_Universe_oops_do,
  69   GCH_PS_JNIHandles_oops_do,
  70   GCH_PS_ObjectSynchronizer_oops_do,
  71   GCH_PS_FlatProfiler_oops_do,
  72   GCH_PS_Management_oops_do,
  73   GCH_PS_SystemDictionary_oops_do,
  74   GCH_PS_ClassLoaderDataGraph_oops_do,
  75   GCH_PS_jvmti_oops_do,
  76   GCH_PS_CodeCache_oops_do,
  77   GCH_PS_younger_gens,
  78   // Leave this one last.
  79   GCH_PS_NumElements
  80 };
  81 
  82 GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy) :
  83   SharedHeap(policy),
  84   _gen_policy(policy),
  85   _process_strong_tasks(new SubTasksDone(GCH_PS_NumElements)),
  86   _full_collections_completed(0)
  87 {
  88   assert(policy != NULL, "Sanity check");
  89 }
  90 
  91 jint GenCollectedHeap::initialize() {
  92   CollectedHeap::pre_initialize();
  93 
  94   int i;
  95   _n_gens = gen_policy()->number_of_generations();
  96 
  97   // While there are no constraints in the GC code that HeapWordSize
  98   // be any particular value, there are multiple other areas in the
  99   // system which believe this to be true (e.g. oop->object_size in some
 100   // cases incorrectly returns the size in wordSize units rather than
 101   // HeapWordSize).
 102   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
 103 
 104   // The heap must be at least as aligned as generations.
 105   size_t gen_alignment = Generation::GenGrain;
 106 
 107   _gen_specs = gen_policy()->generations();
 108 
 109   // Make sure the sizes are all aligned.
 110   for (i = 0; i < _n_gens; i++) {
 111     _gen_specs[i]->align(gen_alignment);
 112   }
 113 
 114   // Allocate space for the heap.
 115 
 116   char* heap_address;
 117   size_t total_reserved = 0;
 118   int n_covered_regions = 0;
 119   ReservedSpace heap_rs;
 120 
 121   size_t heap_alignment = collector_policy()->heap_alignment();
 122 
 123   heap_address = allocate(heap_alignment, &total_reserved,
 124                           &n_covered_regions, &heap_rs);
 125 
 126   if (!heap_rs.is_reserved()) {
 127     vm_shutdown_during_initialization(
 128       "Could not reserve enough space for object heap");
 129     return JNI_ENOMEM;
 130   }
 131 
 132   _reserved = MemRegion((HeapWord*)heap_rs.base(),
 133                         (HeapWord*)(heap_rs.base() + heap_rs.size()));
 134 
 135   // It is important to do this in a way such that concurrent readers can't
 136   // temporarily think somethings in the heap.  (Seen this happen in asserts.)
 137   _reserved.set_word_size(0);
 138   _reserved.set_start((HeapWord*)heap_rs.base());
 139   size_t actual_heap_size = heap_rs.size();
 140   _reserved.set_end((HeapWord*)(heap_rs.base() + actual_heap_size));
 141 
 142   _rem_set = collector_policy()->create_rem_set(_reserved, n_covered_regions);
 143   set_barrier_set(rem_set()->bs());
 144 
 145   _gch = this;
 146 
 147   for (i = 0; i < _n_gens; i++) {
 148     ReservedSpace this_rs = heap_rs.first_part(_gen_specs[i]->max_size(), false, false);
 149     _gens[i] = _gen_specs[i]->init(this_rs, i, rem_set());
 150     heap_rs = heap_rs.last_part(_gen_specs[i]->max_size());
 151   }
 152   clear_incremental_collection_failed();
 153 
 154 #if INCLUDE_ALL_GCS
 155   // If we are running CMS, create the collector responsible
 156   // for collecting the CMS generations.
 157   if (collector_policy()->is_concurrent_mark_sweep_policy()) {
 158     bool success = create_cms_collector();
 159     if (!success) return JNI_ENOMEM;
 160   }
 161 #endif // INCLUDE_ALL_GCS
 162 
 163   return JNI_OK;
 164 }
 165 
 166 
 167 char* GenCollectedHeap::allocate(size_t alignment,
 168                                  size_t* _total_reserved,
 169                                  int* _n_covered_regions,
 170                                  ReservedSpace* heap_rs){
 171   const char overflow_msg[] = "The size of the object heap + VM data exceeds "
 172     "the maximum representable size";
 173 
 174   // Now figure out the total size.
 175   size_t total_reserved = 0;
 176   int n_covered_regions = 0;
 177   const size_t pageSize = UseLargePages ?
 178       os::large_page_size() : os::vm_page_size();
 179 
 180   assert(alignment % pageSize == 0, "Must be");
 181 
 182   for (int i = 0; i < _n_gens; i++) {
 183     total_reserved += _gen_specs[i]->max_size();
 184     if (total_reserved < _gen_specs[i]->max_size()) {
 185       vm_exit_during_initialization(overflow_msg);
 186     }
 187     n_covered_regions += _gen_specs[i]->n_covered_regions();
 188   }
 189   assert(total_reserved % alignment == 0,
 190          err_msg("Gen size; total_reserved=" SIZE_FORMAT ", alignment="
 191                  SIZE_FORMAT, total_reserved, alignment));
 192 
 193   // Needed until the cardtable is fixed to have the right number
 194   // of covered regions.
 195   n_covered_regions += 2;
 196 
 197   *_total_reserved = total_reserved;
 198   *_n_covered_regions = n_covered_regions;
 199 
 200   *heap_rs = Universe::reserve_heap(total_reserved, alignment);
 201   return heap_rs->base();
 202 }
 203 
 204 
 205 void GenCollectedHeap::post_initialize() {
 206   SharedHeap::post_initialize();
 207   TwoGenerationCollectorPolicy *policy =
 208     (TwoGenerationCollectorPolicy *)collector_policy();
 209   guarantee(policy->is_two_generation_policy(), "Illegal policy type");
 210   DefNewGeneration* def_new_gen = (DefNewGeneration*) get_gen(0);
 211   assert(def_new_gen->kind() == Generation::DefNew ||
 212          def_new_gen->kind() == Generation::ParNew ||
 213          def_new_gen->kind() == Generation::ASParNew,
 214          "Wrong generation kind");
 215 
 216   Generation* old_gen = get_gen(1);
 217   assert(old_gen->kind() == Generation::ConcurrentMarkSweep ||
 218          old_gen->kind() == Generation::ASConcurrentMarkSweep ||
 219          old_gen->kind() == Generation::MarkSweepCompact,
 220     "Wrong generation kind");
 221 
 222   policy->initialize_size_policy(def_new_gen->eden()->capacity(),
 223                                  old_gen->capacity(),
 224                                  def_new_gen->from()->capacity());
 225   policy->initialize_gc_policy_counters();
 226 }
 227 
 228 void GenCollectedHeap::ref_processing_init() {
 229   SharedHeap::ref_processing_init();
 230   for (int i = 0; i < _n_gens; i++) {
 231     _gens[i]->ref_processor_init();
 232   }
 233 }
 234 
 235 size_t GenCollectedHeap::capacity() const {
 236   size_t res = 0;
 237   for (int i = 0; i < _n_gens; i++) {
 238     res += _gens[i]->capacity();
 239   }
 240   return res;
 241 }
 242 
 243 size_t GenCollectedHeap::used() const {
 244   size_t res = 0;
 245   for (int i = 0; i < _n_gens; i++) {
 246     res += _gens[i]->used();
 247   }
 248   return res;
 249 }
 250 
 251 // Save the "used_region" for generations level and lower.
 252 void GenCollectedHeap::save_used_regions(int level) {
 253   assert(level < _n_gens, "Illegal level parameter");
 254   for (int i = level; i >= 0; i--) {
 255     _gens[i]->save_used_region();
 256   }
 257 }
 258 
 259 size_t GenCollectedHeap::max_capacity() const {
 260   size_t res = 0;
 261   for (int i = 0; i < _n_gens; i++) {
 262     res += _gens[i]->max_capacity();
 263   }
 264   return res;
 265 }
 266 
 267 // Update the _full_collections_completed counter
 268 // at the end of a stop-world full GC.
 269 unsigned int GenCollectedHeap::update_full_collections_completed() {
 270   MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 271   assert(_full_collections_completed <= _total_full_collections,
 272          "Can't complete more collections than were started");
 273   _full_collections_completed = _total_full_collections;
 274   ml.notify_all();
 275   return _full_collections_completed;
 276 }
 277 
 278 // Update the _full_collections_completed counter, as appropriate,
 279 // at the end of a concurrent GC cycle. Note the conditional update
 280 // below to allow this method to be called by a concurrent collector
 281 // without synchronizing in any manner with the VM thread (which
 282 // may already have initiated a STW full collection "concurrently").
 283 unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) {
 284   MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 285   assert((_full_collections_completed <= _total_full_collections) &&
 286          (count <= _total_full_collections),
 287          "Can't complete more collections than were started");
 288   if (count > _full_collections_completed) {
 289     _full_collections_completed = count;
 290     ml.notify_all();
 291   }
 292   return _full_collections_completed;
 293 }
 294 
 295 
 296 #ifndef PRODUCT
 297 // Override of memory state checking method in CollectedHeap:
 298 // Some collectors (CMS for example) can't have badHeapWordVal written
 299 // in the first two words of an object. (For instance , in the case of
 300 // CMS these words hold state used to synchronize between certain
 301 // (concurrent) GC steps and direct allocating mutators.)
 302 // The skip_header_HeapWords() method below, allows us to skip
 303 // over the requisite number of HeapWord's. Note that (for
 304 // generational collectors) this means that those many words are
 305 // skipped in each object, irrespective of the generation in which
 306 // that object lives. The resultant loss of precision seems to be
 307 // harmless and the pain of avoiding that imprecision appears somewhat
 308 // higher than we are prepared to pay for such rudimentary debugging
 309 // support.
 310 void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr,
 311                                                          size_t size) {
 312   if (CheckMemoryInitialization && ZapUnusedHeapArea) {
 313     // We are asked to check a size in HeapWords,
 314     // but the memory is mangled in juint words.
 315     juint* start = (juint*) (addr + skip_header_HeapWords());
 316     juint* end   = (juint*) (addr + size);
 317     for (juint* slot = start; slot < end; slot += 1) {
 318       assert(*slot == badHeapWordVal,
 319              "Found non badHeapWordValue in pre-allocation check");
 320     }
 321   }
 322 }
 323 #endif
 324 
 325 HeapWord* GenCollectedHeap::attempt_allocation(size_t size,
 326                                                bool is_tlab,
 327                                                bool first_only) {
 328   HeapWord* res;
 329   for (int i = 0; i < _n_gens; i++) {
 330     if (_gens[i]->should_allocate(size, is_tlab)) {
 331       res = _gens[i]->allocate(size, is_tlab);
 332       if (res != NULL) return res;
 333       else if (first_only) break;
 334     }
 335   }
 336   // Otherwise...
 337   return NULL;
 338 }
 339 
 340 HeapWord* GenCollectedHeap::mem_allocate(size_t size,
 341                                          bool* gc_overhead_limit_was_exceeded) {
 342   return collector_policy()->mem_allocate_work(size,
 343                                                false /* is_tlab */,
 344                                                gc_overhead_limit_was_exceeded);
 345 }
 346 
 347 bool GenCollectedHeap::must_clear_all_soft_refs() {
 348   return _gc_cause == GCCause::_last_ditch_collection;
 349 }
 350 
 351 bool GenCollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
 352   return UseConcMarkSweepGC &&
 353          ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
 354           (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent));
 355 }
 356 
 357 void GenCollectedHeap::do_collection(bool  full,
 358                                      bool   clear_all_soft_refs,
 359                                      size_t size,
 360                                      bool   is_tlab,
 361                                      int    max_level) {
 362   bool prepared_for_verification = false;
 363   ResourceMark rm;
 364   DEBUG_ONLY(Thread* my_thread = Thread::current();)
 365 
 366   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 367   assert(my_thread->is_VM_thread() ||
 368          my_thread->is_ConcurrentGC_thread(),
 369          "incorrect thread type capability");
 370   assert(Heap_lock->is_locked(),
 371          "the requesting thread should have the Heap_lock");
 372   guarantee(!is_gc_active(), "collection is not reentrant");
 373   assert(max_level < n_gens(), "sanity check");
 374 
 375   if (GC_locker::check_active_before_gc()) {
 376     return; // GC is disabled (e.g. JNI GetXXXCritical operation)
 377   }
 378 
 379   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
 380                           collector_policy()->should_clear_all_soft_refs();
 381 
 382   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
 383 
 384   const size_t metadata_prev_used = MetaspaceAux::used_bytes();
 385 
 386   print_heap_before_gc();
 387 
 388   {
 389     FlagSetting fl(_is_gc_active, true);
 390 
 391     bool complete = full && (max_level == (n_gens()-1));
 392     const char* gc_cause_prefix = complete ? "Full GC" : "GC";
 393     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
 394     // The PrintGCDetails logging starts before we have incremented the GC id. We will do that later
 395     // so we can assume here that the next GC id is what we want.
 396     GCTraceTime t(GCCauseString(gc_cause_prefix, gc_cause()), PrintGCDetails, false, NULL, GCId::peek());
 397 
 398     gc_prologue(complete);
 399     increment_total_collections(complete);
 400 
 401     size_t gch_prev_used = used();
 402 
 403     int starting_level = 0;
 404     if (full) {
 405       // Search for the oldest generation which will collect all younger
 406       // generations, and start collection loop there.
 407       for (int i = max_level; i >= 0; i--) {
 408         if (_gens[i]->full_collects_younger_generations()) {
 409           starting_level = i;
 410           break;
 411         }
 412       }
 413     }
 414 
 415     bool must_restore_marks_for_biased_locking = false;
 416 
 417     int max_level_collected = starting_level;
 418     for (int i = starting_level; i <= max_level; i++) {
 419       if (_gens[i]->should_collect(full, size, is_tlab)) {
 420         if (i == n_gens() - 1) {  // a major collection is to happen
 421           if (!complete) {
 422             // The full_collections increment was missed above.
 423             increment_total_full_collections();
 424           }
 425           pre_full_gc_dump(NULL);    // do any pre full gc dumps
 426         }
 427         // Timer for individual generations. Last argument is false: no CR
 428         // FIXME: We should try to start the timing earlier to cover more of the GC pause
 429         // The PrintGCDetails logging starts before we have incremented the GC id. We will do that later
 430         // so we can assume here that the next GC id is what we want.
 431         GCTraceTime t1(_gens[i]->short_name(), PrintGCDetails, false, NULL, GCId::peek());
 432         TraceCollectorStats tcs(_gens[i]->counters());
 433         TraceMemoryManagerStats tmms(_gens[i]->kind(),gc_cause());
 434 
 435         size_t prev_used = _gens[i]->used();
 436         _gens[i]->stat_record()->invocations++;
 437         _gens[i]->stat_record()->accumulated_time.start();
 438 
 439         // Must be done anew before each collection because
 440         // a previous collection will do mangling and will
 441         // change top of some spaces.
 442         record_gen_tops_before_GC();
 443 
 444         if (PrintGC && Verbose) {
 445           gclog_or_tty->print("level=%d invoke=%d size=" SIZE_FORMAT,
 446                      i,
 447                      _gens[i]->stat_record()->invocations,
 448                      size*HeapWordSize);
 449         }
 450 
 451         if (VerifyBeforeGC && i >= VerifyGCLevel &&
 452             total_collections() >= VerifyGCStartAt) {
 453           HandleMark hm;  // Discard invalid handles created during verification
 454           if (!prepared_for_verification) {
 455             prepare_for_verify();
 456             prepared_for_verification = true;
 457           }
 458           Universe::verify(" VerifyBeforeGC:");
 459         }
 460         COMPILER2_PRESENT(DerivedPointerTable::clear());
 461 
 462         if (!must_restore_marks_for_biased_locking &&
 463             _gens[i]->performs_in_place_marking()) {
 464           // We perform this mark word preservation work lazily
 465           // because it's only at this point that we know whether we
 466           // absolutely have to do it; we want to avoid doing it for
 467           // scavenge-only collections where it's unnecessary
 468           must_restore_marks_for_biased_locking = true;
 469           BiasedLocking::preserve_marks();
 470         }
 471 
 472         // Do collection work
 473         {
 474           // Note on ref discovery: For what appear to be historical reasons,
 475           // GCH enables and disabled (by enqueing) refs discovery.
 476           // In the future this should be moved into the generation's
 477           // collect method so that ref discovery and enqueueing concerns
 478           // are local to a generation. The collect method could return
 479           // an appropriate indication in the case that notification on
 480           // the ref lock was needed. This will make the treatment of
 481           // weak refs more uniform (and indeed remove such concerns
 482           // from GCH). XXX
 483 
 484           HandleMark hm;  // Discard invalid handles created during gc
 485           save_marks();   // save marks for all gens
 486           // We want to discover references, but not process them yet.
 487           // This mode is disabled in process_discovered_references if the
 488           // generation does some collection work, or in
 489           // enqueue_discovered_references if the generation returns
 490           // without doing any work.
 491           ReferenceProcessor* rp = _gens[i]->ref_processor();
 492           // If the discovery of ("weak") refs in this generation is
 493           // atomic wrt other collectors in this configuration, we
 494           // are guaranteed to have empty discovered ref lists.
 495           if (rp->discovery_is_atomic()) {
 496             rp->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
 497             rp->setup_policy(do_clear_all_soft_refs);
 498           } else {
 499             // collect() below will enable discovery as appropriate
 500           }
 501           _gens[i]->collect(full, do_clear_all_soft_refs, size, is_tlab);
 502           if (!rp->enqueuing_is_done()) {
 503             rp->enqueue_discovered_references();
 504           } else {
 505             rp->set_enqueuing_is_done(false);
 506           }
 507           rp->verify_no_references_recorded();
 508         }
 509         max_level_collected = i;
 510 
 511         // Determine if allocation request was met.
 512         if (size > 0) {
 513           if (!is_tlab || _gens[i]->supports_tlab_allocation()) {
 514             if (size*HeapWordSize <= _gens[i]->unsafe_max_alloc_nogc()) {
 515               size = 0;
 516             }
 517           }
 518         }
 519 
 520         COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
 521 
 522         _gens[i]->stat_record()->accumulated_time.stop();
 523 
 524         update_gc_stats(i, full);
 525 
 526         if (VerifyAfterGC && i >= VerifyGCLevel &&
 527             total_collections() >= VerifyGCStartAt) {
 528           HandleMark hm;  // Discard invalid handles created during verification
 529           Universe::verify(" VerifyAfterGC:");
 530         }
 531 
 532         if (PrintGCDetails) {
 533           gclog_or_tty->print(":");
 534           _gens[i]->print_heap_change(prev_used);
 535         }
 536       }
 537     }
 538 
 539     // Update "complete" boolean wrt what actually transpired --
 540     // for instance, a promotion failure could have led to
 541     // a whole heap collection.
 542     complete = complete || (max_level_collected == n_gens() - 1);
 543 
 544     if (complete) { // We did a "major" collection
 545       // FIXME: See comment at pre_full_gc_dump call
 546       post_full_gc_dump(NULL);   // do any post full gc dumps
 547     }
 548 
 549     if (PrintGCDetails) {
 550       print_heap_change(gch_prev_used);
 551 
 552       // Print metaspace info for full GC with PrintGCDetails flag.
 553       if (complete) {
 554         MetaspaceAux::print_metaspace_change(metadata_prev_used);
 555       }
 556     }
 557 
 558     for (int j = max_level_collected; j >= 0; j -= 1) {
 559       // Adjust generation sizes.
 560       _gens[j]->compute_new_size();
 561     }
 562 
 563     if (complete) {
 564       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
 565       ClassLoaderDataGraph::purge();
 566       MetaspaceAux::verify_metrics();
 567       // Resize the metaspace capacity after full collections
 568       MetaspaceGC::compute_new_size();
 569       update_full_collections_completed();
 570     }
 571 
 572     // Track memory usage and detect low memory after GC finishes
 573     MemoryService::track_memory_usage();
 574 
 575     gc_epilogue(complete);
 576 
 577     if (must_restore_marks_for_biased_locking) {
 578       BiasedLocking::restore_marks();
 579     }
 580   }
 581 
 582   AdaptiveSizePolicy* sp = gen_policy()->size_policy();
 583   AdaptiveSizePolicyOutput(sp, total_collections());
 584 
 585   print_heap_after_gc();
 586 
 587 #ifdef TRACESPINNING
 588   ParallelTaskTerminator::print_termination_counts();
 589 #endif
 590 }
 591 
 592 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
 593   return collector_policy()->satisfy_failed_allocation(size, is_tlab);
 594 }
 595 
 596 void GenCollectedHeap::set_par_threads(uint t) {
 597   SharedHeap::set_par_threads(t);
 598   set_n_termination(t);
 599 }
 600 
 601 void GenCollectedHeap::set_n_termination(uint t) {
 602   _process_strong_tasks->set_n_threads(t);
 603 }
 604 
 605 #ifdef ASSERT
 606 class AssertNonScavengableClosure: public OopClosure {
 607 public:
 608   virtual void do_oop(oop* p) {
 609     assert(!Universe::heap()->is_in_partial_collection(*p),
 610       "Referent should not be scavengable.");  }
 611   virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
 612 };
 613 static AssertNonScavengableClosure assert_is_non_scavengable_closure;
 614 #endif
 615 
 616 void GenCollectedHeap::process_roots(bool activate_scope,
 617                                      ScanningOption so,
 618                                      OopClosure* strong_roots,
 619                                      OopClosure* weak_roots,
 620                                      CLDClosure* strong_cld_closure,
 621                                      CLDClosure* weak_cld_closure,
 622                                      CodeBlobToOopClosure* code_roots) {
 623   StrongRootsScope srs(this, activate_scope);
 624 
 625   // General roots.
 626   assert(_strong_roots_parity != 0, "must have called prologue code");
 627   assert(code_roots != NULL, "code root closure should always be set");
 628   // _n_termination for _process_strong_tasks should be set up stream
 629   // in a method not running in a GC worker.  Otherwise the GC worker
 630   // could be trying to change the termination condition while the task
 631   // is executing in another GC worker.
 632 
 633   if (!_process_strong_tasks->is_task_claimed(GCH_PS_ClassLoaderDataGraph_oops_do)) {
 634     ClassLoaderDataGraph::roots_cld_do(strong_cld_closure, weak_cld_closure);
 635   }
 636 
 637   // Some CLDs contained in the thread frames should be considered strong.
 638   // Don't process them if they will be processed during the ClassLoaderDataGraph phase.
 639   CLDClosure* roots_from_clds_p = (strong_cld_closure != weak_cld_closure) ? strong_cld_closure : NULL;
 640   // Only process code roots from thread stacks if we aren't visiting the entire CodeCache anyway
 641   CodeBlobToOopClosure* roots_from_code_p = (so & SO_AllCodeCache) ? NULL : code_roots;
 642 
 643   Threads::possibly_parallel_oops_do(strong_roots, roots_from_clds_p, roots_from_code_p);
 644 
 645   if (!_process_strong_tasks->is_task_claimed(GCH_PS_Universe_oops_do)) {
 646     Universe::oops_do(strong_roots);
 647   }
 648   // Global (strong) JNI handles
 649   if (!_process_strong_tasks->is_task_claimed(GCH_PS_JNIHandles_oops_do)) {
 650     JNIHandles::oops_do(strong_roots);
 651   }
 652 
 653   if (!_process_strong_tasks->is_task_claimed(GCH_PS_ObjectSynchronizer_oops_do)) {
 654     ObjectSynchronizer::oops_do(strong_roots);
 655   }
 656   if (!_process_strong_tasks->is_task_claimed(GCH_PS_FlatProfiler_oops_do)) {
 657     FlatProfiler::oops_do(strong_roots);
 658   }
 659   if (!_process_strong_tasks->is_task_claimed(GCH_PS_Management_oops_do)) {
 660     Management::oops_do(strong_roots);
 661   }
 662   if (!_process_strong_tasks->is_task_claimed(GCH_PS_jvmti_oops_do)) {
 663     JvmtiExport::oops_do(strong_roots);
 664   }
 665 
 666   if (!_process_strong_tasks->is_task_claimed(GCH_PS_SystemDictionary_oops_do)) {
 667     SystemDictionary::roots_oops_do(strong_roots, weak_roots);
 668   }
 669 
 670   // All threads execute the following. A specific chunk of buckets
 671   // from the StringTable are the individual tasks.
 672   if (weak_roots != NULL) {
 673     if (CollectedHeap::use_parallel_gc_threads()) {
 674       StringTable::possibly_parallel_oops_do(weak_roots);
 675     } else {
 676       StringTable::oops_do(weak_roots);
 677     }
 678   }
 679 
 680   if (!_process_strong_tasks->is_task_claimed(GCH_PS_CodeCache_oops_do)) {
 681     if (so & SO_ScavengeCodeCache) {
 682       assert(code_roots != NULL, "must supply closure for code cache");
 683 
 684       // We only visit parts of the CodeCache when scavenging.
 685       CodeCache::scavenge_root_nmethods_do(code_roots);
 686     }
 687     if (so & SO_AllCodeCache) {
 688       assert(code_roots != NULL, "must supply closure for code cache");
 689 
 690       // CMSCollector uses this to do intermediate-strength collections.
 691       // We scan the entire code cache, since CodeCache::do_unloading is not called.
 692       CodeCache::blobs_do(code_roots);
 693     }
 694     // Verify that the code cache contents are not subject to
 695     // movement by a scavenging collection.
 696     DEBUG_ONLY(CodeBlobToOopClosure assert_code_is_non_scavengable(&assert_is_non_scavengable_closure, !CodeBlobToOopClosure::FixRelocations));
 697     DEBUG_ONLY(CodeCache::asserted_non_scavengable_nmethods_do(&assert_code_is_non_scavengable));
 698   }
 699 
 700 }
 701 
 702 void GenCollectedHeap::gen_process_roots(int level,
 703                                          bool younger_gens_as_roots,
 704                                          bool activate_scope,
 705                                          ScanningOption so,
 706                                          bool only_strong_roots,
 707                                          OopsInGenClosure* not_older_gens,
 708                                          OopsInGenClosure* older_gens,
 709                                          CLDClosure* cld_closure) {
 710   const bool is_adjust_phase = !only_strong_roots && !younger_gens_as_roots;
 711 
 712   bool is_moving_collection = false;
 713   if (level == 0 || is_adjust_phase) {
 714     // young collections are always moving
 715     is_moving_collection = true;
 716   }
 717 
 718   MarkingCodeBlobClosure mark_code_closure(not_older_gens, is_moving_collection);
 719   OopsInGenClosure* weak_roots = only_strong_roots ? NULL : not_older_gens;
 720   CLDClosure* weak_cld_closure = only_strong_roots ? NULL : cld_closure;
 721 
 722   process_roots(activate_scope, so,
 723                 not_older_gens, weak_roots,
 724                 cld_closure, weak_cld_closure,
 725                 &mark_code_closure);
 726 
 727   if (younger_gens_as_roots) {
 728     if (!_process_strong_tasks->is_task_claimed(GCH_PS_younger_gens)) {
 729       for (int i = 0; i < level; i++) {
 730         not_older_gens->set_generation(_gens[i]);
 731         _gens[i]->oop_iterate(not_older_gens);
 732       }
 733       not_older_gens->reset_generation();
 734     }
 735   }
 736   // When collection is parallel, all threads get to cooperate to do
 737   // older-gen scanning.
 738   for (int i = level+1; i < _n_gens; i++) {
 739     older_gens->set_generation(_gens[i]);
 740     rem_set()->younger_refs_iterate(_gens[i], older_gens);
 741     older_gens->reset_generation();
 742   }
 743 
 744   _process_strong_tasks->all_tasks_completed();
 745 }
 746 
 747 
 748 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure) {
 749   JNIHandles::weak_oops_do(root_closure);
 750   for (int i = 0; i < _n_gens; i++) {
 751     _gens[i]->ref_processor()->weak_oops_do(root_closure);
 752   }
 753 }
 754 
 755 #define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix)    \
 756 void GenCollectedHeap::                                                 \
 757 oop_since_save_marks_iterate(int level,                                 \
 758                              OopClosureType* cur,                       \
 759                              OopClosureType* older) {                   \
 760   _gens[level]->oop_since_save_marks_iterate##nv_suffix(cur);           \
 761   for (int i = level+1; i < n_gens(); i++) {                            \
 762     _gens[i]->oop_since_save_marks_iterate##nv_suffix(older);           \
 763   }                                                                     \
 764 }
 765 
 766 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN)
 767 
 768 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN
 769 
 770 bool GenCollectedHeap::no_allocs_since_save_marks(int level) {
 771   for (int i = level; i < _n_gens; i++) {
 772     if (!_gens[i]->no_allocs_since_save_marks()) return false;
 773   }
 774   return true;
 775 }
 776 
 777 bool GenCollectedHeap::supports_inline_contig_alloc() const {
 778   return _gens[0]->supports_inline_contig_alloc();
 779 }
 780 
 781 HeapWord** GenCollectedHeap::top_addr() const {
 782   return _gens[0]->top_addr();
 783 }
 784 
 785 HeapWord** GenCollectedHeap::end_addr() const {
 786   return _gens[0]->end_addr();
 787 }
 788 
 789 // public collection interfaces
 790 
 791 void GenCollectedHeap::collect(GCCause::Cause cause) {
 792   if (should_do_concurrent_full_gc(cause)) {
 793 #if INCLUDE_ALL_GCS
 794     // mostly concurrent full collection
 795     collect_mostly_concurrent(cause);
 796 #else  // INCLUDE_ALL_GCS
 797     ShouldNotReachHere();
 798 #endif // INCLUDE_ALL_GCS
 799   } else if (cause == GCCause::_wb_young_gc) {
 800     // minor collection for WhiteBox API
 801     collect(cause, 0);
 802   } else {
 803 #ifdef ASSERT
 804   if (cause == GCCause::_scavenge_alot) {
 805     // minor collection only
 806     collect(cause, 0);
 807   } else {
 808     // Stop-the-world full collection
 809     collect(cause, n_gens() - 1);
 810   }
 811 #else
 812     // Stop-the-world full collection
 813     collect(cause, n_gens() - 1);
 814 #endif
 815   }
 816 }
 817 
 818 void GenCollectedHeap::collect(GCCause::Cause cause, int max_level) {
 819   // The caller doesn't have the Heap_lock
 820   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
 821   MutexLocker ml(Heap_lock);
 822   collect_locked(cause, max_level);
 823 }
 824 
 825 void GenCollectedHeap::collect_locked(GCCause::Cause cause) {
 826   // The caller has the Heap_lock
 827   assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock");
 828   collect_locked(cause, n_gens() - 1);
 829 }
 830 
 831 // this is the private collection interface
 832 // The Heap_lock is expected to be held on entry.
 833 
 834 void GenCollectedHeap::collect_locked(GCCause::Cause cause, int max_level) {
 835   // Read the GC count while holding the Heap_lock
 836   unsigned int gc_count_before      = total_collections();
 837   unsigned int full_gc_count_before = total_full_collections();
 838   {
 839     MutexUnlocker mu(Heap_lock);  // give up heap lock, execute gets it back
 840     VM_GenCollectFull op(gc_count_before, full_gc_count_before,
 841                          cause, max_level);
 842     VMThread::execute(&op);
 843   }
 844 }
 845 
 846 #if INCLUDE_ALL_GCS
 847 bool GenCollectedHeap::create_cms_collector() {
 848 
 849   assert(((_gens[1]->kind() == Generation::ConcurrentMarkSweep) ||
 850          (_gens[1]->kind() == Generation::ASConcurrentMarkSweep)),
 851          "Unexpected generation kinds");
 852   // Skip two header words in the block content verification
 853   NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();)
 854   CMSCollector* collector = new CMSCollector(
 855     (ConcurrentMarkSweepGeneration*)_gens[1],
 856     _rem_set->as_CardTableRS(),
 857     (ConcurrentMarkSweepPolicy*) collector_policy());
 858 
 859   if (collector == NULL || !collector->completed_initialization()) {
 860     if (collector) {
 861       delete collector;  // Be nice in embedded situation
 862     }
 863     vm_shutdown_during_initialization("Could not create CMS collector");
 864     return false;
 865   }
 866   return true;  // success
 867 }
 868 
 869 void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) {
 870   assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock");
 871 
 872   MutexLocker ml(Heap_lock);
 873   // Read the GC counts while holding the Heap_lock
 874   unsigned int full_gc_count_before = total_full_collections();
 875   unsigned int gc_count_before      = total_collections();
 876   {
 877     MutexUnlocker mu(Heap_lock);
 878     VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause);
 879     VMThread::execute(&op);
 880   }
 881 }
 882 #endif // INCLUDE_ALL_GCS
 883 
 884 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs) {
 885    do_full_collection(clear_all_soft_refs, _n_gens - 1);
 886 }
 887 
 888 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
 889                                           int max_level) {
 890   int local_max_level;
 891   if (!incremental_collection_will_fail(false /* don't consult_young */) &&
 892       gc_cause() == GCCause::_gc_locker) {
 893     local_max_level = 0;
 894   } else {
 895     local_max_level = max_level;
 896   }
 897 
 898   do_collection(true                 /* full */,
 899                 clear_all_soft_refs  /* clear_all_soft_refs */,
 900                 0                    /* size */,
 901                 false                /* is_tlab */,
 902                 local_max_level      /* max_level */);
 903   // Hack XXX FIX ME !!!
 904   // A scavenge may not have been attempted, or may have
 905   // been attempted and failed, because the old gen was too full
 906   if (local_max_level == 0 && gc_cause() == GCCause::_gc_locker &&
 907       incremental_collection_will_fail(false /* don't consult_young */)) {
 908     if (PrintGCDetails) {
 909       gclog_or_tty->print_cr("GC locker: Trying a full collection "
 910                              "because scavenge failed");
 911     }
 912     // This time allow the old gen to be collected as well
 913     do_collection(true                 /* full */,
 914                   clear_all_soft_refs  /* clear_all_soft_refs */,
 915                   0                    /* size */,
 916                   false                /* is_tlab */,
 917                   n_gens() - 1         /* max_level */);
 918   }
 919 }
 920 
 921 bool GenCollectedHeap::is_in_young(oop p) {
 922   bool result = ((HeapWord*)p) < _gens[_n_gens - 1]->reserved().start();
 923   assert(result == _gens[0]->is_in_reserved(p),
 924          err_msg("incorrect test - result=%d, p=" PTR_FORMAT, result, p2i((void*)p)));
 925   return result;
 926 }
 927 
 928 // Returns "TRUE" iff "p" points into the committed areas of the heap.
 929 bool GenCollectedHeap::is_in(const void* p) const {
 930   #ifndef ASSERT
 931   guarantee(VerifyBeforeGC      ||
 932             VerifyDuringGC      ||
 933             VerifyBeforeExit    ||
 934             VerifyDuringStartup ||
 935             PrintAssembly       ||
 936             tty->count() != 0   ||   // already printing
 937             VerifyAfterGC       ||
 938     VMError::fatal_error_in_progress(), "too expensive");
 939 
 940   #endif
 941   // This might be sped up with a cache of the last generation that
 942   // answered yes.
 943   for (int i = 0; i < _n_gens; i++) {
 944     if (_gens[i]->is_in(p)) return true;
 945   }
 946   // Otherwise...
 947   return false;
 948 }
 949 
 950 #ifdef ASSERT
 951 // Don't implement this by using is_in_young().  This method is used
 952 // in some cases to check that is_in_young() is correct.
 953 bool GenCollectedHeap::is_in_partial_collection(const void* p) {
 954   assert(is_in_reserved(p) || p == NULL,
 955     "Does not work if address is non-null and outside of the heap");
 956   return p < _gens[_n_gens - 2]->reserved().end() && p != NULL;
 957 }
 958 #endif
 959 
 960 void GenCollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
 961   for (int i = 0; i < _n_gens; i++) {
 962     _gens[i]->oop_iterate(cl);
 963   }
 964 }
 965 
 966 void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
 967   for (int i = 0; i < _n_gens; i++) {
 968     _gens[i]->object_iterate(cl);
 969   }
 970 }
 971 
 972 void GenCollectedHeap::safe_object_iterate(ObjectClosure* cl) {
 973   for (int i = 0; i < _n_gens; i++) {
 974     _gens[i]->safe_object_iterate(cl);
 975   }
 976 }
 977 
 978 Space* GenCollectedHeap::space_containing(const void* addr) const {
 979   for (int i = 0; i < _n_gens; i++) {
 980     Space* res = _gens[i]->space_containing(addr);
 981     if (res != NULL) return res;
 982   }
 983   // Otherwise...
 984   assert(false, "Could not find containing space");
 985   return NULL;
 986 }
 987 
 988 
 989 HeapWord* GenCollectedHeap::block_start(const void* addr) const {
 990   assert(is_in_reserved(addr), "block_start of address outside of heap");
 991   for (int i = 0; i < _n_gens; i++) {
 992     if (_gens[i]->is_in_reserved(addr)) {
 993       assert(_gens[i]->is_in(addr),
 994              "addr should be in allocated part of generation");
 995       return _gens[i]->block_start(addr);
 996     }
 997   }
 998   assert(false, "Some generation should contain the address");
 999   return NULL;
1000 }
1001 
1002 size_t GenCollectedHeap::block_size(const HeapWord* addr) const {
1003   assert(is_in_reserved(addr), "block_size of address outside of heap");
1004   for (int i = 0; i < _n_gens; i++) {
1005     if (_gens[i]->is_in_reserved(addr)) {
1006       assert(_gens[i]->is_in(addr),
1007              "addr should be in allocated part of generation");
1008       return _gens[i]->block_size(addr);
1009     }
1010   }
1011   assert(false, "Some generation should contain the address");
1012   return 0;
1013 }
1014 
1015 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
1016   assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
1017   assert(block_start(addr) == addr, "addr must be a block start");
1018   for (int i = 0; i < _n_gens; i++) {
1019     if (_gens[i]->is_in_reserved(addr)) {
1020       return _gens[i]->block_is_obj(addr);
1021     }
1022   }
1023   assert(false, "Some generation should contain the address");
1024   return false;
1025 }
1026 
1027 bool GenCollectedHeap::supports_tlab_allocation() const {
1028   for (int i = 0; i < _n_gens; i += 1) {
1029     if (_gens[i]->supports_tlab_allocation()) {
1030       return true;
1031     }
1032   }
1033   return false;
1034 }
1035 
1036 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
1037   size_t result = 0;
1038   for (int i = 0; i < _n_gens; i += 1) {
1039     if (_gens[i]->supports_tlab_allocation()) {
1040       result += _gens[i]->tlab_capacity();
1041     }
1042   }
1043   return result;
1044 }
1045 
1046 size_t GenCollectedHeap::tlab_used(Thread* thr) const {
1047   size_t result = 0;
1048   for (int i = 0; i < _n_gens; i += 1) {
1049     if (_gens[i]->supports_tlab_allocation()) {
1050       result += _gens[i]->tlab_used();
1051     }
1052   }
1053   return result;
1054 }
1055 
1056 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
1057   size_t result = 0;
1058   for (int i = 0; i < _n_gens; i += 1) {
1059     if (_gens[i]->supports_tlab_allocation()) {
1060       result += _gens[i]->unsafe_max_tlab_alloc();
1061     }
1062   }
1063   return result;
1064 }
1065 
1066 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) {
1067   bool gc_overhead_limit_was_exceeded;
1068   return collector_policy()->mem_allocate_work(size /* size */,
1069                                                true /* is_tlab */,
1070                                                &gc_overhead_limit_was_exceeded);
1071 }
1072 
1073 // Requires "*prev_ptr" to be non-NULL.  Deletes and a block of minimal size
1074 // from the list headed by "*prev_ptr".
1075 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
1076   bool first = true;
1077   size_t min_size = 0;   // "first" makes this conceptually infinite.
1078   ScratchBlock **smallest_ptr, *smallest;
1079   ScratchBlock  *cur = *prev_ptr;
1080   while (cur) {
1081     assert(*prev_ptr == cur, "just checking");
1082     if (first || cur->num_words < min_size) {
1083       smallest_ptr = prev_ptr;
1084       smallest     = cur;
1085       min_size     = smallest->num_words;
1086       first        = false;
1087     }
1088     prev_ptr = &cur->next;
1089     cur     =  cur->next;
1090   }
1091   smallest      = *smallest_ptr;
1092   *smallest_ptr = smallest->next;
1093   return smallest;
1094 }
1095 
1096 // Sort the scratch block list headed by res into decreasing size order,
1097 // and set "res" to the result.
1098 static void sort_scratch_list(ScratchBlock*& list) {
1099   ScratchBlock* sorted = NULL;
1100   ScratchBlock* unsorted = list;
1101   while (unsorted) {
1102     ScratchBlock *smallest = removeSmallestScratch(&unsorted);
1103     smallest->next  = sorted;
1104     sorted          = smallest;
1105   }
1106   list = sorted;
1107 }
1108 
1109 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
1110                                                size_t max_alloc_words) {
1111   ScratchBlock* res = NULL;
1112   for (int i = 0; i < _n_gens; i++) {
1113     _gens[i]->contribute_scratch(res, requestor, max_alloc_words);
1114   }
1115   sort_scratch_list(res);
1116   return res;
1117 }
1118 
1119 void GenCollectedHeap::release_scratch() {
1120   for (int i = 0; i < _n_gens; i++) {
1121     _gens[i]->reset_scratch();
1122   }
1123 }
1124 
1125 class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure {
1126   void do_generation(Generation* gen) {
1127     gen->prepare_for_verify();
1128   }
1129 };
1130 
1131 void GenCollectedHeap::prepare_for_verify() {
1132   ensure_parsability(false);        // no need to retire TLABs
1133   GenPrepareForVerifyClosure blk;
1134   generation_iterate(&blk, false);
1135 }
1136 
1137 
1138 void GenCollectedHeap::generation_iterate(GenClosure* cl,
1139                                           bool old_to_young) {
1140   if (old_to_young) {
1141     for (int i = _n_gens-1; i >= 0; i--) {
1142       cl->do_generation(_gens[i]);
1143     }
1144   } else {
1145     for (int i = 0; i < _n_gens; i++) {
1146       cl->do_generation(_gens[i]);
1147     }
1148   }
1149 }
1150 
1151 void GenCollectedHeap::space_iterate(SpaceClosure* cl) {
1152   for (int i = 0; i < _n_gens; i++) {
1153     _gens[i]->space_iterate(cl, true);
1154   }
1155 }
1156 
1157 bool GenCollectedHeap::is_maximal_no_gc() const {
1158   for (int i = 0; i < _n_gens; i++) {
1159     if (!_gens[i]->is_maximal_no_gc()) {
1160       return false;
1161     }
1162   }
1163   return true;
1164 }
1165 
1166 void GenCollectedHeap::save_marks() {
1167   for (int i = 0; i < _n_gens; i++) {
1168     _gens[i]->save_marks();
1169   }
1170 }
1171 
1172 GenCollectedHeap* GenCollectedHeap::heap() {
1173   assert(_gch != NULL, "Uninitialized access to GenCollectedHeap::heap()");
1174   assert(_gch->kind() == CollectedHeap::GenCollectedHeap, "not a generational heap");
1175   return _gch;
1176 }
1177 
1178 
1179 void GenCollectedHeap::prepare_for_compaction() {
1180   guarantee(_n_gens = 2, "Wrong number of generations");
1181   Generation* old_gen = _gens[1];
1182   // Start by compacting into same gen.
1183   CompactPoint cp(old_gen);
1184   old_gen->prepare_for_compaction(&cp);
1185   Generation* young_gen = _gens[0];
1186   young_gen->prepare_for_compaction(&cp);
1187 }
1188 
1189 GCStats* GenCollectedHeap::gc_stats(int level) const {
1190   return _gens[level]->gc_stats();
1191 }
1192 
1193 void GenCollectedHeap::verify(bool silent, VerifyOption option /* ignored */) {
1194   for (int i = _n_gens-1; i >= 0; i--) {
1195     Generation* g = _gens[i];
1196     if (!silent) {
1197       gclog_or_tty->print("%s", g->name());
1198       gclog_or_tty->print(" ");
1199     }
1200     g->verify();
1201   }
1202   if (!silent) {
1203     gclog_or_tty->print("remset ");
1204   }
1205   rem_set()->verify();
1206 }
1207 
1208 void GenCollectedHeap::print_on(outputStream* st) const {
1209   for (int i = 0; i < _n_gens; i++) {
1210     _gens[i]->print_on(st);
1211   }
1212   MetaspaceAux::print_on(st);
1213 }
1214 
1215 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
1216   if (workers() != NULL) {
1217     workers()->threads_do(tc);
1218   }
1219 #if INCLUDE_ALL_GCS
1220   if (UseConcMarkSweepGC) {
1221     ConcurrentMarkSweepThread::threads_do(tc);
1222   }
1223 #endif // INCLUDE_ALL_GCS
1224 }
1225 
1226 void GenCollectedHeap::print_gc_threads_on(outputStream* st) const {
1227 #if INCLUDE_ALL_GCS
1228   if (UseParNewGC) {
1229     workers()->print_worker_threads_on(st);
1230   }
1231   if (UseConcMarkSweepGC) {
1232     ConcurrentMarkSweepThread::print_all_on(st);
1233   }
1234 #endif // INCLUDE_ALL_GCS
1235 }
1236 
1237 void GenCollectedHeap::print_on_error(outputStream* st) const {
1238   this->CollectedHeap::print_on_error(st);
1239 
1240 #if INCLUDE_ALL_GCS
1241   if (UseConcMarkSweepGC) {
1242     st->cr();
1243     CMSCollector::print_on_error(st);
1244   }
1245 #endif // INCLUDE_ALL_GCS
1246 }
1247 
1248 void GenCollectedHeap::print_tracing_info() const {
1249   if (TraceGen0Time) {
1250     get_gen(0)->print_summary_info();
1251   }
1252   if (TraceGen1Time) {
1253     get_gen(1)->print_summary_info();
1254   }
1255 }
1256 
1257 void GenCollectedHeap::print_heap_change(size_t prev_used) const {
1258   if (PrintGCDetails && Verbose) {
1259     gclog_or_tty->print(" "  SIZE_FORMAT
1260                         "->" SIZE_FORMAT
1261                         "("  SIZE_FORMAT ")",
1262                         prev_used, used(), capacity());
1263   } else {
1264     gclog_or_tty->print(" "  SIZE_FORMAT "K"
1265                         "->" SIZE_FORMAT "K"
1266                         "("  SIZE_FORMAT "K)",
1267                         prev_used / K, used() / K, capacity() / K);
1268   }
1269 }
1270 
1271 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
1272  private:
1273   bool _full;
1274  public:
1275   void do_generation(Generation* gen) {
1276     gen->gc_prologue(_full);
1277   }
1278   GenGCPrologueClosure(bool full) : _full(full) {};
1279 };
1280 
1281 void GenCollectedHeap::gc_prologue(bool full) {
1282   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
1283 
1284   always_do_update_barrier = false;
1285   // Fill TLAB's and such
1286   CollectedHeap::accumulate_statistics_all_tlabs();
1287   ensure_parsability(true);   // retire TLABs
1288 
1289   // Walk generations
1290   GenGCPrologueClosure blk(full);
1291   generation_iterate(&blk, false);  // not old-to-young.
1292 };
1293 
1294 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
1295  private:
1296   bool _full;
1297  public:
1298   void do_generation(Generation* gen) {
1299     gen->gc_epilogue(_full);
1300   }
1301   GenGCEpilogueClosure(bool full) : _full(full) {};
1302 };
1303 
1304 void GenCollectedHeap::gc_epilogue(bool full) {
1305 #ifdef COMPILER2
1306   assert(DerivedPointerTable::is_empty(), "derived pointer present");
1307   size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr()));
1308   guarantee(actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps");
1309 #endif /* COMPILER2 */
1310 
1311   resize_all_tlabs();
1312 
1313   GenGCEpilogueClosure blk(full);
1314   generation_iterate(&blk, false);  // not old-to-young.
1315 
1316   if (!CleanChunkPoolAsync) {
1317     Chunk::clean_chunk_pool();
1318   }
1319 
1320   MetaspaceCounters::update_performance_counters();
1321   CompressedClassSpaceCounters::update_performance_counters();
1322 
1323   always_do_update_barrier = UseConcMarkSweepGC;
1324 };
1325 
1326 #ifndef PRODUCT
1327 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure {
1328  private:
1329  public:
1330   void do_generation(Generation* gen) {
1331     gen->record_spaces_top();
1332   }
1333 };
1334 
1335 void GenCollectedHeap::record_gen_tops_before_GC() {
1336   if (ZapUnusedHeapArea) {
1337     GenGCSaveTopsBeforeGCClosure blk;
1338     generation_iterate(&blk, false);  // not old-to-young.
1339   }
1340 }
1341 #endif  // not PRODUCT
1342 
1343 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
1344  public:
1345   void do_generation(Generation* gen) {
1346     gen->ensure_parsability();
1347   }
1348 };
1349 
1350 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
1351   CollectedHeap::ensure_parsability(retire_tlabs);
1352   GenEnsureParsabilityClosure ep_cl;
1353   generation_iterate(&ep_cl, false);
1354 }
1355 
1356 oop GenCollectedHeap::handle_failed_promotion(Generation* old_gen,
1357                                               oop obj,
1358                                               size_t obj_size) {
1359   guarantee(old_gen->level() == 1, "We only get here with an old generation");
1360   assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1361   HeapWord* result = NULL;
1362 
1363   result = old_gen->expand_and_allocate(obj_size, false);
1364 
1365   if (result != NULL) {
1366     Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);
1367   }
1368   return oop(result);
1369 }
1370 
1371 class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure {
1372   jlong _time;   // in ms
1373   jlong _now;    // in ms
1374 
1375  public:
1376   GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { }
1377 
1378   jlong time() { return _time; }
1379 
1380   void do_generation(Generation* gen) {
1381     _time = MIN2(_time, gen->time_of_last_gc(_now));
1382   }
1383 };
1384 
1385 jlong GenCollectedHeap::millis_since_last_gc() {
1386   // We need a monotonically non-deccreasing time in ms but
1387   // os::javaTimeMillis() does not guarantee monotonicity.
1388   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
1389   GenTimeOfLastGCClosure tolgc_cl(now);
1390   // iterate over generations getting the oldest
1391   // time that a generation was collected
1392   generation_iterate(&tolgc_cl, false);
1393 
1394   // javaTimeNanos() is guaranteed to be monotonically non-decreasing
1395   // provided the underlying platform provides such a time source
1396   // (and it is bug free). So we still have to guard against getting
1397   // back a time later than 'now'.
1398   jlong retVal = now - tolgc_cl.time();
1399   if (retVal < 0) {
1400     NOT_PRODUCT(warning("time warp: "INT64_FORMAT, (int64_t) retVal);)
1401     return 0;
1402   }
1403   return retVal;
1404 }