1 /*
   2  * Copyright (c) 2000, 2014, 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   if (!UseConcMarkSweepGC) {
 353     return false;
 354   }
 355 
 356   switch (cause) {
 357     case GCCause::_gc_locker:           return GCLockerInvokesConcurrent;
 358     case GCCause::_java_lang_system_gc:
 359     case GCCause::_dcmd_gc_run:         return ExplicitGCInvokesConcurrent;
 360     default:                            return false;
 361   }
 362 }
 363 
 364 void GenCollectedHeap::do_collection(bool  full,
 365                                      bool   clear_all_soft_refs,
 366                                      size_t size,
 367                                      bool   is_tlab,
 368                                      int    max_level) {
 369   bool prepared_for_verification = false;
 370   ResourceMark rm;
 371   DEBUG_ONLY(Thread* my_thread = Thread::current();)
 372 
 373   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 374   assert(my_thread->is_VM_thread() ||
 375          my_thread->is_ConcurrentGC_thread(),
 376          "incorrect thread type capability");
 377   assert(Heap_lock->is_locked(),
 378          "the requesting thread should have the Heap_lock");
 379   guarantee(!is_gc_active(), "collection is not reentrant");
 380   assert(max_level < n_gens(), "sanity check");
 381 
 382   if (GC_locker::check_active_before_gc()) {
 383     return; // GC is disabled (e.g. JNI GetXXXCritical operation)
 384   }
 385 
 386   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
 387                           collector_policy()->should_clear_all_soft_refs();
 388 
 389   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
 390 
 391   const size_t metadata_prev_used = MetaspaceAux::used_bytes();
 392 
 393   print_heap_before_gc();
 394 
 395   {
 396     FlagSetting fl(_is_gc_active, true);
 397 
 398     bool complete = full && (max_level == (n_gens()-1));
 399     const char* gc_cause_prefix = complete ? "Full GC" : "GC";
 400     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
 401     // The PrintGCDetails logging starts before we have incremented the GC id. We will do that later
 402     // so we can assume here that the next GC id is what we want.
 403     GCTraceTime t(GCCauseString(gc_cause_prefix, gc_cause()), PrintGCDetails, false, NULL, GCId::peek());
 404 
 405     gc_prologue(complete);
 406     increment_total_collections(complete);
 407 
 408     size_t gch_prev_used = used();
 409 
 410     int starting_level = 0;
 411     if (full) {
 412       // Search for the oldest generation which will collect all younger
 413       // generations, and start collection loop there.
 414       for (int i = max_level; i >= 0; i--) {
 415         if (_gens[i]->full_collects_younger_generations()) {
 416           starting_level = i;
 417           break;
 418         }
 419       }
 420     }
 421 
 422     bool must_restore_marks_for_biased_locking = false;
 423 
 424     int max_level_collected = starting_level;
 425     for (int i = starting_level; i <= max_level; i++) {
 426       if (_gens[i]->should_collect(full, size, is_tlab)) {
 427         if (i == n_gens() - 1) {  // a major collection is to happen
 428           if (!complete) {
 429             // The full_collections increment was missed above.
 430             increment_total_full_collections();
 431           }
 432           pre_full_gc_dump(NULL);    // do any pre full gc dumps
 433         }
 434         // Timer for individual generations. Last argument is false: no CR
 435         // FIXME: We should try to start the timing earlier to cover more of the GC pause
 436         // The PrintGCDetails logging starts before we have incremented the GC id. We will do that later
 437         // so we can assume here that the next GC id is what we want.
 438         GCTraceTime t1(_gens[i]->short_name(), PrintGCDetails, false, NULL, GCId::peek());
 439         TraceCollectorStats tcs(_gens[i]->counters());
 440         TraceMemoryManagerStats tmms(_gens[i]->kind(),gc_cause());
 441 
 442         size_t prev_used = _gens[i]->used();
 443         _gens[i]->stat_record()->invocations++;
 444         _gens[i]->stat_record()->accumulated_time.start();
 445 
 446         // Must be done anew before each collection because
 447         // a previous collection will do mangling and will
 448         // change top of some spaces.
 449         record_gen_tops_before_GC();
 450 
 451         if (PrintGC && Verbose) {
 452           gclog_or_tty->print("level=%d invoke=%d size=" SIZE_FORMAT,
 453                      i,
 454                      _gens[i]->stat_record()->invocations,
 455                      size*HeapWordSize);
 456         }
 457 
 458         if (VerifyBeforeGC && i >= VerifyGCLevel &&
 459             total_collections() >= VerifyGCStartAt) {
 460           HandleMark hm;  // Discard invalid handles created during verification
 461           if (!prepared_for_verification) {
 462             prepare_for_verify();
 463             prepared_for_verification = true;
 464           }
 465           Universe::verify(" VerifyBeforeGC:");
 466         }
 467         COMPILER2_PRESENT(DerivedPointerTable::clear());
 468 
 469         if (!must_restore_marks_for_biased_locking &&
 470             _gens[i]->performs_in_place_marking()) {
 471           // We perform this mark word preservation work lazily
 472           // because it's only at this point that we know whether we
 473           // absolutely have to do it; we want to avoid doing it for
 474           // scavenge-only collections where it's unnecessary
 475           must_restore_marks_for_biased_locking = true;
 476           BiasedLocking::preserve_marks();
 477         }
 478 
 479         // Do collection work
 480         {
 481           // Note on ref discovery: For what appear to be historical reasons,
 482           // GCH enables and disabled (by enqueing) refs discovery.
 483           // In the future this should be moved into the generation's
 484           // collect method so that ref discovery and enqueueing concerns
 485           // are local to a generation. The collect method could return
 486           // an appropriate indication in the case that notification on
 487           // the ref lock was needed. This will make the treatment of
 488           // weak refs more uniform (and indeed remove such concerns
 489           // from GCH). XXX
 490 
 491           HandleMark hm;  // Discard invalid handles created during gc
 492           save_marks();   // save marks for all gens
 493           // We want to discover references, but not process them yet.
 494           // This mode is disabled in process_discovered_references if the
 495           // generation does some collection work, or in
 496           // enqueue_discovered_references if the generation returns
 497           // without doing any work.
 498           ReferenceProcessor* rp = _gens[i]->ref_processor();
 499           // If the discovery of ("weak") refs in this generation is
 500           // atomic wrt other collectors in this configuration, we
 501           // are guaranteed to have empty discovered ref lists.
 502           if (rp->discovery_is_atomic()) {
 503             rp->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
 504             rp->setup_policy(do_clear_all_soft_refs);
 505           } else {
 506             // collect() below will enable discovery as appropriate
 507           }
 508           _gens[i]->collect(full, do_clear_all_soft_refs, size, is_tlab);
 509           if (!rp->enqueuing_is_done()) {
 510             rp->enqueue_discovered_references();
 511           } else {
 512             rp->set_enqueuing_is_done(false);
 513           }
 514           rp->verify_no_references_recorded();
 515         }
 516         max_level_collected = i;
 517 
 518         // Determine if allocation request was met.
 519         if (size > 0) {
 520           if (!is_tlab || _gens[i]->supports_tlab_allocation()) {
 521             if (size*HeapWordSize <= _gens[i]->unsafe_max_alloc_nogc()) {
 522               size = 0;
 523             }
 524           }
 525         }
 526 
 527         COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
 528 
 529         _gens[i]->stat_record()->accumulated_time.stop();
 530 
 531         update_gc_stats(i, full);
 532 
 533         if (VerifyAfterGC && i >= VerifyGCLevel &&
 534             total_collections() >= VerifyGCStartAt) {
 535           HandleMark hm;  // Discard invalid handles created during verification
 536           Universe::verify(" VerifyAfterGC:");
 537         }
 538 
 539         if (PrintGCDetails) {
 540           gclog_or_tty->print(":");
 541           _gens[i]->print_heap_change(prev_used);
 542         }
 543       }
 544     }
 545 
 546     // Update "complete" boolean wrt what actually transpired --
 547     // for instance, a promotion failure could have led to
 548     // a whole heap collection.
 549     complete = complete || (max_level_collected == n_gens() - 1);
 550 
 551     if (complete) { // We did a "major" collection
 552       // FIXME: See comment at pre_full_gc_dump call
 553       post_full_gc_dump(NULL);   // do any post full gc dumps
 554     }
 555 
 556     if (PrintGCDetails) {
 557       print_heap_change(gch_prev_used);
 558 
 559       // Print metaspace info for full GC with PrintGCDetails flag.
 560       if (complete) {
 561         MetaspaceAux::print_metaspace_change(metadata_prev_used);
 562       }
 563     }
 564 
 565     for (int j = max_level_collected; j >= 0; j -= 1) {
 566       // Adjust generation sizes.
 567       _gens[j]->compute_new_size();
 568     }
 569 
 570     if (complete) {
 571       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
 572       ClassLoaderDataGraph::purge();
 573       MetaspaceAux::verify_metrics();
 574       // Resize the metaspace capacity after full collections
 575       MetaspaceGC::compute_new_size();
 576       update_full_collections_completed();
 577     }
 578 
 579     // Track memory usage and detect low memory after GC finishes
 580     MemoryService::track_memory_usage();
 581 
 582     gc_epilogue(complete);
 583 
 584     if (must_restore_marks_for_biased_locking) {
 585       BiasedLocking::restore_marks();
 586     }
 587   }
 588 
 589   AdaptiveSizePolicy* sp = gen_policy()->size_policy();
 590   AdaptiveSizePolicyOutput(sp, total_collections());
 591 
 592   print_heap_after_gc();
 593 
 594 #ifdef TRACESPINNING
 595   ParallelTaskTerminator::print_termination_counts();
 596 #endif
 597 }
 598 
 599 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
 600   return collector_policy()->satisfy_failed_allocation(size, is_tlab);
 601 }
 602 
 603 void GenCollectedHeap::set_par_threads(uint t) {
 604   SharedHeap::set_par_threads(t);
 605   set_n_termination(t);
 606 }
 607 
 608 void GenCollectedHeap::set_n_termination(uint t) {
 609   _process_strong_tasks->set_n_threads(t);
 610 }
 611 
 612 #ifdef ASSERT
 613 class AssertNonScavengableClosure: public OopClosure {
 614 public:
 615   virtual void do_oop(oop* p) {
 616     assert(!Universe::heap()->is_in_partial_collection(*p),
 617       "Referent should not be scavengable.");  }
 618   virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
 619 };
 620 static AssertNonScavengableClosure assert_is_non_scavengable_closure;
 621 #endif
 622 
 623 void GenCollectedHeap::process_roots(bool activate_scope,
 624                                      ScanningOption so,
 625                                      OopClosure* strong_roots,
 626                                      OopClosure* weak_roots,
 627                                      CLDClosure* strong_cld_closure,
 628                                      CLDClosure* weak_cld_closure,
 629                                      CodeBlobClosure* code_roots) {
 630   StrongRootsScope srs(this, activate_scope);
 631 
 632   // General roots.
 633   assert(_strong_roots_parity != 0, "must have called prologue code");
 634   assert(code_roots != NULL, "code root closure should always be set");
 635   // _n_termination for _process_strong_tasks should be set up stream
 636   // in a method not running in a GC worker.  Otherwise the GC worker
 637   // could be trying to change the termination condition while the task
 638   // is executing in another GC worker.
 639 
 640   if (!_process_strong_tasks->is_task_claimed(GCH_PS_ClassLoaderDataGraph_oops_do)) {
 641     ClassLoaderDataGraph::roots_cld_do(strong_cld_closure, weak_cld_closure);
 642   }
 643 
 644   // Some CLDs contained in the thread frames should be considered strong.
 645   // Don't process them if they will be processed during the ClassLoaderDataGraph phase.
 646   CLDClosure* roots_from_clds_p = (strong_cld_closure != weak_cld_closure) ? strong_cld_closure : NULL;
 647   // Only process code roots from thread stacks if we aren't visiting the entire CodeCache anyway
 648   CodeBlobClosure* roots_from_code_p = (so & SO_AllCodeCache) ? NULL : code_roots;
 649 
 650   Threads::possibly_parallel_oops_do(strong_roots, roots_from_clds_p, roots_from_code_p);
 651 
 652   if (!_process_strong_tasks->is_task_claimed(GCH_PS_Universe_oops_do)) {
 653     Universe::oops_do(strong_roots);
 654   }
 655   // Global (strong) JNI handles
 656   if (!_process_strong_tasks->is_task_claimed(GCH_PS_JNIHandles_oops_do)) {
 657     JNIHandles::oops_do(strong_roots);
 658   }
 659 
 660   if (!_process_strong_tasks->is_task_claimed(GCH_PS_ObjectSynchronizer_oops_do)) {
 661     ObjectSynchronizer::oops_do(strong_roots);
 662   }
 663   if (!_process_strong_tasks->is_task_claimed(GCH_PS_FlatProfiler_oops_do)) {
 664     FlatProfiler::oops_do(strong_roots);
 665   }
 666   if (!_process_strong_tasks->is_task_claimed(GCH_PS_Management_oops_do)) {
 667     Management::oops_do(strong_roots);
 668   }
 669   if (!_process_strong_tasks->is_task_claimed(GCH_PS_jvmti_oops_do)) {
 670     JvmtiExport::oops_do(strong_roots);
 671   }
 672 
 673   if (!_process_strong_tasks->is_task_claimed(GCH_PS_SystemDictionary_oops_do)) {
 674     SystemDictionary::roots_oops_do(strong_roots, weak_roots);
 675   }
 676 
 677   // All threads execute the following. A specific chunk of buckets
 678   // from the StringTable are the individual tasks.
 679   if (weak_roots != NULL) {
 680     if (CollectedHeap::use_parallel_gc_threads()) {
 681       StringTable::possibly_parallel_oops_do(weak_roots);
 682     } else {
 683       StringTable::oops_do(weak_roots);
 684     }
 685   }
 686 
 687   if (!_process_strong_tasks->is_task_claimed(GCH_PS_CodeCache_oops_do)) {
 688     if (so & SO_ScavengeCodeCache) {
 689       assert(code_roots != NULL, "must supply closure for code cache");
 690 
 691       // We only visit parts of the CodeCache when scavenging.
 692       CodeCache::scavenge_root_nmethods_do(code_roots);
 693     }
 694     if (so & SO_AllCodeCache) {
 695       assert(code_roots != NULL, "must supply closure for code cache");
 696 
 697       // CMSCollector uses this to do intermediate-strength collections.
 698       // We scan the entire code cache, since CodeCache::do_unloading is not called.
 699       CodeCache::blobs_do(code_roots);
 700     }
 701     // Verify that the code cache contents are not subject to
 702     // movement by a scavenging collection.
 703     DEBUG_ONLY(CodeBlobToOopClosure assert_code_is_non_scavengable(&assert_is_non_scavengable_closure, !CodeBlobToOopClosure::FixRelocations));
 704     DEBUG_ONLY(CodeCache::asserted_non_scavengable_nmethods_do(&assert_code_is_non_scavengable));
 705   }
 706 
 707 }
 708 
 709 void GenCollectedHeap::gen_process_roots(int level,
 710                                          bool younger_gens_as_roots,
 711                                          bool activate_scope,
 712                                          ScanningOption so,
 713                                          bool only_strong_roots,
 714                                          OopsInGenClosure* not_older_gens,
 715                                          OopsInGenClosure* older_gens,
 716                                          CLDClosure* cld_closure) {
 717   const bool is_adjust_phase = !only_strong_roots && !younger_gens_as_roots;
 718 
 719   bool is_moving_collection = false;
 720   if (level == 0 || is_adjust_phase) {
 721     // young collections are always moving
 722     is_moving_collection = true;
 723   }
 724 
 725   MarkingCodeBlobClosure mark_code_closure(not_older_gens, is_moving_collection);
 726   OopsInGenClosure* weak_roots = only_strong_roots ? NULL : not_older_gens;
 727   CLDClosure* weak_cld_closure = only_strong_roots ? NULL : cld_closure;
 728 
 729   process_roots(activate_scope, so,
 730                 not_older_gens, weak_roots,
 731                 cld_closure, weak_cld_closure,
 732                 &mark_code_closure);
 733 
 734   if (younger_gens_as_roots) {
 735     if (!_process_strong_tasks->is_task_claimed(GCH_PS_younger_gens)) {
 736       for (int i = 0; i < level; i++) {
 737         not_older_gens->set_generation(_gens[i]);
 738         _gens[i]->oop_iterate(not_older_gens);
 739       }
 740       not_older_gens->reset_generation();
 741     }
 742   }
 743   // When collection is parallel, all threads get to cooperate to do
 744   // older-gen scanning.
 745   for (int i = level+1; i < _n_gens; i++) {
 746     older_gens->set_generation(_gens[i]);
 747     rem_set()->younger_refs_iterate(_gens[i], older_gens);
 748     older_gens->reset_generation();
 749   }
 750 
 751   _process_strong_tasks->all_tasks_completed();
 752 }
 753 
 754 
 755 class AlwaysTrueClosure: public BoolObjectClosure {
 756 public:
 757   bool do_object_b(oop p) { return true; }
 758 };
 759 static AlwaysTrueClosure always_true;
 760 
 761 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure) {
 762   JNIHandles::weak_oops_do(&always_true, root_closure);
 763   for (int i = 0; i < _n_gens; i++) {
 764     _gens[i]->ref_processor()->weak_oops_do(root_closure);
 765   }
 766 }
 767 
 768 #define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix)    \
 769 void GenCollectedHeap::                                                 \
 770 oop_since_save_marks_iterate(int level,                                 \
 771                              OopClosureType* cur,                       \
 772                              OopClosureType* older) {                   \
 773   _gens[level]->oop_since_save_marks_iterate##nv_suffix(cur);           \
 774   for (int i = level+1; i < n_gens(); i++) {                            \
 775     _gens[i]->oop_since_save_marks_iterate##nv_suffix(older);           \
 776   }                                                                     \
 777 }
 778 
 779 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN)
 780 
 781 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN
 782 
 783 bool GenCollectedHeap::no_allocs_since_save_marks(int level) {
 784   for (int i = level; i < _n_gens; i++) {
 785     if (!_gens[i]->no_allocs_since_save_marks()) return false;
 786   }
 787   return true;
 788 }
 789 
 790 bool GenCollectedHeap::supports_inline_contig_alloc() const {
 791   return _gens[0]->supports_inline_contig_alloc();
 792 }
 793 
 794 HeapWord** GenCollectedHeap::top_addr() const {
 795   return _gens[0]->top_addr();
 796 }
 797 
 798 HeapWord** GenCollectedHeap::end_addr() const {
 799   return _gens[0]->end_addr();
 800 }
 801 
 802 // public collection interfaces
 803 
 804 void GenCollectedHeap::collect(GCCause::Cause cause) {
 805   if (should_do_concurrent_full_gc(cause)) {
 806 #if INCLUDE_ALL_GCS
 807     // mostly concurrent full collection
 808     collect_mostly_concurrent(cause);
 809 #else  // INCLUDE_ALL_GCS
 810     ShouldNotReachHere();
 811 #endif // INCLUDE_ALL_GCS
 812   } else if (cause == GCCause::_wb_young_gc) {
 813     // minor collection for WhiteBox API
 814     collect(cause, 0);
 815   } else {
 816 #ifdef ASSERT
 817   if (cause == GCCause::_scavenge_alot) {
 818     // minor collection only
 819     collect(cause, 0);
 820   } else {
 821     // Stop-the-world full collection
 822     collect(cause, n_gens() - 1);
 823   }
 824 #else
 825     // Stop-the-world full collection
 826     collect(cause, n_gens() - 1);
 827 #endif
 828   }
 829 }
 830 
 831 void GenCollectedHeap::collect(GCCause::Cause cause, int max_level) {
 832   // The caller doesn't have the Heap_lock
 833   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
 834   MutexLocker ml(Heap_lock);
 835   collect_locked(cause, max_level);
 836 }
 837 
 838 void GenCollectedHeap::collect_locked(GCCause::Cause cause) {
 839   // The caller has the Heap_lock
 840   assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock");
 841   collect_locked(cause, n_gens() - 1);
 842 }
 843 
 844 // this is the private collection interface
 845 // The Heap_lock is expected to be held on entry.
 846 
 847 void GenCollectedHeap::collect_locked(GCCause::Cause cause, int max_level) {
 848   // Read the GC count while holding the Heap_lock
 849   unsigned int gc_count_before      = total_collections();
 850   unsigned int full_gc_count_before = total_full_collections();
 851   {
 852     MutexUnlocker mu(Heap_lock);  // give up heap lock, execute gets it back
 853     VM_GenCollectFull op(gc_count_before, full_gc_count_before,
 854                          cause, max_level);
 855     VMThread::execute(&op);
 856   }
 857 }
 858 
 859 #if INCLUDE_ALL_GCS
 860 bool GenCollectedHeap::create_cms_collector() {
 861 
 862   assert(((_gens[1]->kind() == Generation::ConcurrentMarkSweep) ||
 863          (_gens[1]->kind() == Generation::ASConcurrentMarkSweep)),
 864          "Unexpected generation kinds");
 865   // Skip two header words in the block content verification
 866   NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();)
 867   CMSCollector* collector = new CMSCollector(
 868     (ConcurrentMarkSweepGeneration*)_gens[1],
 869     _rem_set->as_CardTableRS(),
 870     (ConcurrentMarkSweepPolicy*) collector_policy());
 871 
 872   if (collector == NULL || !collector->completed_initialization()) {
 873     if (collector) {
 874       delete collector;  // Be nice in embedded situation
 875     }
 876     vm_shutdown_during_initialization("Could not create CMS collector");
 877     return false;
 878   }
 879   return true;  // success
 880 }
 881 
 882 void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) {
 883   assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock");
 884 
 885   MutexLocker ml(Heap_lock);
 886   // Read the GC counts while holding the Heap_lock
 887   unsigned int full_gc_count_before = total_full_collections();
 888   unsigned int gc_count_before      = total_collections();
 889   {
 890     MutexUnlocker mu(Heap_lock);
 891     VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause);
 892     VMThread::execute(&op);
 893   }
 894 }
 895 #endif // INCLUDE_ALL_GCS
 896 
 897 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs) {
 898    do_full_collection(clear_all_soft_refs, _n_gens - 1);
 899 }
 900 
 901 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
 902                                           int max_level) {
 903   int local_max_level;
 904   if (!incremental_collection_will_fail(false /* don't consult_young */) &&
 905       gc_cause() == GCCause::_gc_locker) {
 906     local_max_level = 0;
 907   } else {
 908     local_max_level = max_level;
 909   }
 910 
 911   do_collection(true                 /* full */,
 912                 clear_all_soft_refs  /* clear_all_soft_refs */,
 913                 0                    /* size */,
 914                 false                /* is_tlab */,
 915                 local_max_level      /* max_level */);
 916   // Hack XXX FIX ME !!!
 917   // A scavenge may not have been attempted, or may have
 918   // been attempted and failed, because the old gen was too full
 919   if (local_max_level == 0 && gc_cause() == GCCause::_gc_locker &&
 920       incremental_collection_will_fail(false /* don't consult_young */)) {
 921     if (PrintGCDetails) {
 922       gclog_or_tty->print_cr("GC locker: Trying a full collection "
 923                              "because scavenge failed");
 924     }
 925     // This time allow the old gen to be collected as well
 926     do_collection(true                 /* full */,
 927                   clear_all_soft_refs  /* clear_all_soft_refs */,
 928                   0                    /* size */,
 929                   false                /* is_tlab */,
 930                   n_gens() - 1         /* max_level */);
 931   }
 932 }
 933 
 934 bool GenCollectedHeap::is_in_young(oop p) {
 935   bool result = ((HeapWord*)p) < _gens[_n_gens - 1]->reserved().start();
 936   assert(result == _gens[0]->is_in_reserved(p),
 937          err_msg("incorrect test - result=%d, p=" PTR_FORMAT, result, p2i((void*)p)));
 938   return result;
 939 }
 940 
 941 // Returns "TRUE" iff "p" points into the committed areas of the heap.
 942 bool GenCollectedHeap::is_in(const void* p) const {
 943   #ifndef ASSERT
 944   guarantee(VerifyBeforeGC      ||
 945             VerifyDuringGC      ||
 946             VerifyBeforeExit    ||
 947             VerifyDuringStartup ||
 948             PrintAssembly       ||
 949             tty->count() != 0   ||   // already printing
 950             VerifyAfterGC       ||
 951     VMError::fatal_error_in_progress(), "too expensive");
 952 
 953   #endif
 954   // This might be sped up with a cache of the last generation that
 955   // answered yes.
 956   for (int i = 0; i < _n_gens; i++) {
 957     if (_gens[i]->is_in(p)) return true;
 958   }
 959   // Otherwise...
 960   return false;
 961 }
 962 
 963 #ifdef ASSERT
 964 // Don't implement this by using is_in_young().  This method is used
 965 // in some cases to check that is_in_young() is correct.
 966 bool GenCollectedHeap::is_in_partial_collection(const void* p) {
 967   assert(is_in_reserved(p) || p == NULL,
 968     "Does not work if address is non-null and outside of the heap");
 969   return p < _gens[_n_gens - 2]->reserved().end() && p != NULL;
 970 }
 971 #endif
 972 
 973 void GenCollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
 974   for (int i = 0; i < _n_gens; i++) {
 975     _gens[i]->oop_iterate(cl);
 976   }
 977 }
 978 
 979 void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
 980   for (int i = 0; i < _n_gens; i++) {
 981     _gens[i]->object_iterate(cl);
 982   }
 983 }
 984 
 985 void GenCollectedHeap::safe_object_iterate(ObjectClosure* cl) {
 986   for (int i = 0; i < _n_gens; i++) {
 987     _gens[i]->safe_object_iterate(cl);
 988   }
 989 }
 990 
 991 Space* GenCollectedHeap::space_containing(const void* addr) const {
 992   for (int i = 0; i < _n_gens; i++) {
 993     Space* res = _gens[i]->space_containing(addr);
 994     if (res != NULL) return res;
 995   }
 996   // Otherwise...
 997   assert(false, "Could not find containing space");
 998   return NULL;
 999 }
1000 
1001 
1002 HeapWord* GenCollectedHeap::block_start(const void* addr) const {
1003   assert(is_in_reserved(addr), "block_start 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_start(addr);
1009     }
1010   }
1011   assert(false, "Some generation should contain the address");
1012   return NULL;
1013 }
1014 
1015 size_t GenCollectedHeap::block_size(const HeapWord* addr) const {
1016   assert(is_in_reserved(addr), "block_size of address outside of heap");
1017   for (int i = 0; i < _n_gens; i++) {
1018     if (_gens[i]->is_in_reserved(addr)) {
1019       assert(_gens[i]->is_in(addr),
1020              "addr should be in allocated part of generation");
1021       return _gens[i]->block_size(addr);
1022     }
1023   }
1024   assert(false, "Some generation should contain the address");
1025   return 0;
1026 }
1027 
1028 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
1029   assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
1030   assert(block_start(addr) == addr, "addr must be a block start");
1031   for (int i = 0; i < _n_gens; i++) {
1032     if (_gens[i]->is_in_reserved(addr)) {
1033       return _gens[i]->block_is_obj(addr);
1034     }
1035   }
1036   assert(false, "Some generation should contain the address");
1037   return false;
1038 }
1039 
1040 bool GenCollectedHeap::supports_tlab_allocation() const {
1041   for (int i = 0; i < _n_gens; i += 1) {
1042     if (_gens[i]->supports_tlab_allocation()) {
1043       return true;
1044     }
1045   }
1046   return false;
1047 }
1048 
1049 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
1050   size_t result = 0;
1051   for (int i = 0; i < _n_gens; i += 1) {
1052     if (_gens[i]->supports_tlab_allocation()) {
1053       result += _gens[i]->tlab_capacity();
1054     }
1055   }
1056   return result;
1057 }
1058 
1059 size_t GenCollectedHeap::tlab_used(Thread* thr) const {
1060   size_t result = 0;
1061   for (int i = 0; i < _n_gens; i += 1) {
1062     if (_gens[i]->supports_tlab_allocation()) {
1063       result += _gens[i]->tlab_used();
1064     }
1065   }
1066   return result;
1067 }
1068 
1069 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
1070   size_t result = 0;
1071   for (int i = 0; i < _n_gens; i += 1) {
1072     if (_gens[i]->supports_tlab_allocation()) {
1073       result += _gens[i]->unsafe_max_tlab_alloc();
1074     }
1075   }
1076   return result;
1077 }
1078 
1079 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) {
1080   bool gc_overhead_limit_was_exceeded;
1081   return collector_policy()->mem_allocate_work(size /* size */,
1082                                                true /* is_tlab */,
1083                                                &gc_overhead_limit_was_exceeded);
1084 }
1085 
1086 // Requires "*prev_ptr" to be non-NULL.  Deletes and a block of minimal size
1087 // from the list headed by "*prev_ptr".
1088 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
1089   bool first = true;
1090   size_t min_size = 0;   // "first" makes this conceptually infinite.
1091   ScratchBlock **smallest_ptr, *smallest;
1092   ScratchBlock  *cur = *prev_ptr;
1093   while (cur) {
1094     assert(*prev_ptr == cur, "just checking");
1095     if (first || cur->num_words < min_size) {
1096       smallest_ptr = prev_ptr;
1097       smallest     = cur;
1098       min_size     = smallest->num_words;
1099       first        = false;
1100     }
1101     prev_ptr = &cur->next;
1102     cur     =  cur->next;
1103   }
1104   smallest      = *smallest_ptr;
1105   *smallest_ptr = smallest->next;
1106   return smallest;
1107 }
1108 
1109 // Sort the scratch block list headed by res into decreasing size order,
1110 // and set "res" to the result.
1111 static void sort_scratch_list(ScratchBlock*& list) {
1112   ScratchBlock* sorted = NULL;
1113   ScratchBlock* unsorted = list;
1114   while (unsorted) {
1115     ScratchBlock *smallest = removeSmallestScratch(&unsorted);
1116     smallest->next  = sorted;
1117     sorted          = smallest;
1118   }
1119   list = sorted;
1120 }
1121 
1122 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
1123                                                size_t max_alloc_words) {
1124   ScratchBlock* res = NULL;
1125   for (int i = 0; i < _n_gens; i++) {
1126     _gens[i]->contribute_scratch(res, requestor, max_alloc_words);
1127   }
1128   sort_scratch_list(res);
1129   return res;
1130 }
1131 
1132 void GenCollectedHeap::release_scratch() {
1133   for (int i = 0; i < _n_gens; i++) {
1134     _gens[i]->reset_scratch();
1135   }
1136 }
1137 
1138 class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure {
1139   void do_generation(Generation* gen) {
1140     gen->prepare_for_verify();
1141   }
1142 };
1143 
1144 void GenCollectedHeap::prepare_for_verify() {
1145   ensure_parsability(false);        // no need to retire TLABs
1146   GenPrepareForVerifyClosure blk;
1147   generation_iterate(&blk, false);
1148 }
1149 
1150 
1151 void GenCollectedHeap::generation_iterate(GenClosure* cl,
1152                                           bool old_to_young) {
1153   if (old_to_young) {
1154     for (int i = _n_gens-1; i >= 0; i--) {
1155       cl->do_generation(_gens[i]);
1156     }
1157   } else {
1158     for (int i = 0; i < _n_gens; i++) {
1159       cl->do_generation(_gens[i]);
1160     }
1161   }
1162 }
1163 
1164 void GenCollectedHeap::space_iterate(SpaceClosure* cl) {
1165   for (int i = 0; i < _n_gens; i++) {
1166     _gens[i]->space_iterate(cl, true);
1167   }
1168 }
1169 
1170 bool GenCollectedHeap::is_maximal_no_gc() const {
1171   for (int i = 0; i < _n_gens; i++) {
1172     if (!_gens[i]->is_maximal_no_gc()) {
1173       return false;
1174     }
1175   }
1176   return true;
1177 }
1178 
1179 void GenCollectedHeap::save_marks() {
1180   for (int i = 0; i < _n_gens; i++) {
1181     _gens[i]->save_marks();
1182   }
1183 }
1184 
1185 GenCollectedHeap* GenCollectedHeap::heap() {
1186   assert(_gch != NULL, "Uninitialized access to GenCollectedHeap::heap()");
1187   assert(_gch->kind() == CollectedHeap::GenCollectedHeap, "not a generational heap");
1188   return _gch;
1189 }
1190 
1191 
1192 void GenCollectedHeap::prepare_for_compaction() {
1193   guarantee(_n_gens = 2, "Wrong number of generations");
1194   Generation* old_gen = _gens[1];
1195   // Start by compacting into same gen.
1196   CompactPoint cp(old_gen);
1197   old_gen->prepare_for_compaction(&cp);
1198   Generation* young_gen = _gens[0];
1199   young_gen->prepare_for_compaction(&cp);
1200 }
1201 
1202 GCStats* GenCollectedHeap::gc_stats(int level) const {
1203   return _gens[level]->gc_stats();
1204 }
1205 
1206 void GenCollectedHeap::verify(bool silent, VerifyOption option /* ignored */) {
1207   for (int i = _n_gens-1; i >= 0; i--) {
1208     Generation* g = _gens[i];
1209     if (!silent) {
1210       gclog_or_tty->print("%s", g->name());
1211       gclog_or_tty->print(" ");
1212     }
1213     g->verify();
1214   }
1215   if (!silent) {
1216     gclog_or_tty->print("remset ");
1217   }
1218   rem_set()->verify();
1219 }
1220 
1221 void GenCollectedHeap::print_on(outputStream* st) const {
1222   for (int i = 0; i < _n_gens; i++) {
1223     _gens[i]->print_on(st);
1224   }
1225   MetaspaceAux::print_on(st);
1226 }
1227 
1228 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
1229   if (workers() != NULL) {
1230     workers()->threads_do(tc);
1231   }
1232 #if INCLUDE_ALL_GCS
1233   if (UseConcMarkSweepGC) {
1234     ConcurrentMarkSweepThread::threads_do(tc);
1235   }
1236 #endif // INCLUDE_ALL_GCS
1237 }
1238 
1239 void GenCollectedHeap::print_gc_threads_on(outputStream* st) const {
1240 #if INCLUDE_ALL_GCS
1241   if (UseParNewGC) {
1242     workers()->print_worker_threads_on(st);
1243   }
1244   if (UseConcMarkSweepGC) {
1245     ConcurrentMarkSweepThread::print_all_on(st);
1246   }
1247 #endif // INCLUDE_ALL_GCS
1248 }
1249 
1250 void GenCollectedHeap::print_on_error(outputStream* st) const {
1251   this->CollectedHeap::print_on_error(st);
1252 
1253 #if INCLUDE_ALL_GCS
1254   if (UseConcMarkSweepGC) {
1255     st->cr();
1256     CMSCollector::print_on_error(st);
1257   }
1258 #endif // INCLUDE_ALL_GCS
1259 }
1260 
1261 void GenCollectedHeap::print_tracing_info() const {
1262   if (TraceGen0Time) {
1263     get_gen(0)->print_summary_info();
1264   }
1265   if (TraceGen1Time) {
1266     get_gen(1)->print_summary_info();
1267   }
1268 }
1269 
1270 void GenCollectedHeap::print_heap_change(size_t prev_used) const {
1271   if (PrintGCDetails && Verbose) {
1272     gclog_or_tty->print(" "  SIZE_FORMAT
1273                         "->" SIZE_FORMAT
1274                         "("  SIZE_FORMAT ")",
1275                         prev_used, used(), capacity());
1276   } else {
1277     gclog_or_tty->print(" "  SIZE_FORMAT "K"
1278                         "->" SIZE_FORMAT "K"
1279                         "("  SIZE_FORMAT "K)",
1280                         prev_used / K, used() / K, capacity() / K);
1281   }
1282 }
1283 
1284 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
1285  private:
1286   bool _full;
1287  public:
1288   void do_generation(Generation* gen) {
1289     gen->gc_prologue(_full);
1290   }
1291   GenGCPrologueClosure(bool full) : _full(full) {};
1292 };
1293 
1294 void GenCollectedHeap::gc_prologue(bool full) {
1295   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
1296 
1297   always_do_update_barrier = false;
1298   // Fill TLAB's and such
1299   CollectedHeap::accumulate_statistics_all_tlabs();
1300   ensure_parsability(true);   // retire TLABs
1301 
1302   // Walk generations
1303   GenGCPrologueClosure blk(full);
1304   generation_iterate(&blk, false);  // not old-to-young.
1305 };
1306 
1307 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
1308  private:
1309   bool _full;
1310  public:
1311   void do_generation(Generation* gen) {
1312     gen->gc_epilogue(_full);
1313   }
1314   GenGCEpilogueClosure(bool full) : _full(full) {};
1315 };
1316 
1317 void GenCollectedHeap::gc_epilogue(bool full) {
1318 #ifdef COMPILER2
1319   assert(DerivedPointerTable::is_empty(), "derived pointer present");
1320   size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr()));
1321   guarantee(actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps");
1322 #endif /* COMPILER2 */
1323 
1324   resize_all_tlabs();
1325 
1326   GenGCEpilogueClosure blk(full);
1327   generation_iterate(&blk, false);  // not old-to-young.
1328 
1329   if (!CleanChunkPoolAsync) {
1330     Chunk::clean_chunk_pool();
1331   }
1332 
1333   MetaspaceCounters::update_performance_counters();
1334   CompressedClassSpaceCounters::update_performance_counters();
1335 
1336   always_do_update_barrier = UseConcMarkSweepGC;
1337 };
1338 
1339 #ifndef PRODUCT
1340 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure {
1341  private:
1342  public:
1343   void do_generation(Generation* gen) {
1344     gen->record_spaces_top();
1345   }
1346 };
1347 
1348 void GenCollectedHeap::record_gen_tops_before_GC() {
1349   if (ZapUnusedHeapArea) {
1350     GenGCSaveTopsBeforeGCClosure blk;
1351     generation_iterate(&blk, false);  // not old-to-young.
1352   }
1353 }
1354 #endif  // not PRODUCT
1355 
1356 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
1357  public:
1358   void do_generation(Generation* gen) {
1359     gen->ensure_parsability();
1360   }
1361 };
1362 
1363 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
1364   CollectedHeap::ensure_parsability(retire_tlabs);
1365   GenEnsureParsabilityClosure ep_cl;
1366   generation_iterate(&ep_cl, false);
1367 }
1368 
1369 oop GenCollectedHeap::handle_failed_promotion(Generation* old_gen,
1370                                               oop obj,
1371                                               size_t obj_size) {
1372   guarantee(old_gen->level() == 1, "We only get here with an old generation");
1373   assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1374   HeapWord* result = NULL;
1375 
1376   result = old_gen->expand_and_allocate(obj_size, false);
1377 
1378   if (result != NULL) {
1379     Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);
1380   }
1381   return oop(result);
1382 }
1383 
1384 class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure {
1385   jlong _time;   // in ms
1386   jlong _now;    // in ms
1387 
1388  public:
1389   GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { }
1390 
1391   jlong time() { return _time; }
1392 
1393   void do_generation(Generation* gen) {
1394     _time = MIN2(_time, gen->time_of_last_gc(_now));
1395   }
1396 };
1397 
1398 jlong GenCollectedHeap::millis_since_last_gc() {
1399   // We need a monotonically non-deccreasing time in ms but
1400   // os::javaTimeMillis() does not guarantee monotonicity.
1401   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
1402   GenTimeOfLastGCClosure tolgc_cl(now);
1403   // iterate over generations getting the oldest
1404   // time that a generation was collected
1405   generation_iterate(&tolgc_cl, false);
1406 
1407   // javaTimeNanos() is guaranteed to be monotonically non-decreasing
1408   // provided the underlying platform provides such a time source
1409   // (and it is bug free). So we still have to guard against getting
1410   // back a time later than 'now'.
1411   jlong retVal = now - tolgc_cl.time();
1412   if (retVal < 0) {
1413     NOT_PRODUCT(warning("time warp: "INT64_FORMAT, (int64_t) retVal);)
1414     return 0;
1415   }
1416   return retVal;
1417 }