1 /*
   2  * Copyright (c) 2001, 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 "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.hpp"
  27 #include "gc_implementation/parNew/parNewGeneration.hpp"
  28 #include "gc_implementation/parNew/parOopClosures.inline.hpp"
  29 #include "gc_implementation/shared/adaptiveSizePolicy.hpp"
  30 #include "gc_implementation/shared/ageTable.hpp"
  31 #include "gc_implementation/shared/copyFailedInfo.hpp"
  32 #include "gc_implementation/shared/gcHeapSummary.hpp"
  33 #include "gc_implementation/shared/gcTimer.hpp"
  34 #include "gc_implementation/shared/gcTrace.hpp"
  35 #include "gc_implementation/shared/gcTraceTime.hpp"
  36 #include "gc_implementation/shared/parGCAllocBuffer.inline.hpp"
  37 #include "gc_implementation/shared/spaceDecorator.hpp"
  38 #include "memory/defNewGeneration.inline.hpp"
  39 #include "memory/genCollectedHeap.hpp"
  40 #include "memory/genOopClosures.inline.hpp"
  41 #include "memory/generation.hpp"
  42 #include "memory/generation.inline.hpp"
  43 #include "memory/referencePolicy.hpp"
  44 #include "memory/resourceArea.hpp"
  45 #include "memory/sharedHeap.hpp"
  46 #include "memory/space.hpp"
  47 #include "oops/objArrayOop.hpp"
  48 #include "oops/oop.inline.hpp"
  49 #include "oops/oop.pcgc.inline.hpp"
  50 #include "runtime/atomic.inline.hpp"
  51 #include "runtime/handles.hpp"
  52 #include "runtime/handles.inline.hpp"
  53 #include "runtime/java.hpp"
  54 #include "runtime/thread.inline.hpp"
  55 #include "utilities/copy.hpp"
  56 #include "utilities/globalDefinitions.hpp"
  57 #include "utilities/workgroup.hpp"
  58 
  59 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  60 
  61 #ifdef _MSC_VER
  62 #pragma warning( push )
  63 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
  64 #endif
  65 ParScanThreadState::ParScanThreadState(Space* to_space_,
  66                                        ParNewGeneration* gen_,
  67                                        Generation* old_gen_,
  68                                        int thread_num_,
  69                                        ObjToScanQueueSet* work_queue_set_,
  70                                        Stack<oop, mtGC>* overflow_stacks_,
  71                                        size_t desired_plab_sz_,
  72                                        ParallelTaskTerminator& term_) :
  73   _to_space(to_space_), _old_gen(old_gen_), _young_gen(gen_), _thread_num(thread_num_),
  74   _work_queue(work_queue_set_->queue(thread_num_)), _to_space_full(false),
  75   _overflow_stack(overflow_stacks_ ? overflow_stacks_ + thread_num_ : NULL),
  76   _ageTable(false), // false ==> not the global age table, no perf data.
  77   _to_space_alloc_buffer(desired_plab_sz_),
  78   _to_space_closure(gen_, this), _old_gen_closure(gen_, this),
  79   _to_space_root_closure(gen_, this), _old_gen_root_closure(gen_, this),
  80   _older_gen_closure(gen_, this),
  81   _evacuate_followers(this, &_to_space_closure, &_old_gen_closure,
  82                       &_to_space_root_closure, gen_, &_old_gen_root_closure,
  83                       work_queue_set_, &term_),
  84   _is_alive_closure(gen_), _scan_weak_ref_closure(gen_, this),
  85   _keep_alive_closure(&_scan_weak_ref_closure),
  86   _strong_roots_time(0.0), _term_time(0.0)
  87 {
  88   #if TASKQUEUE_STATS
  89   _term_attempts = 0;
  90   _overflow_refills = 0;
  91   _overflow_refill_objs = 0;
  92   #endif // TASKQUEUE_STATS
  93 
  94   _survivor_chunk_array =
  95     (ChunkArray*) old_gen()->get_data_recorder(thread_num());
  96   _hash_seed = 17;  // Might want to take time-based random value.
  97   _start = os::elapsedTime();
  98   _old_gen_closure.set_generation(old_gen_);
  99   _old_gen_root_closure.set_generation(old_gen_);
 100 }
 101 #ifdef _MSC_VER
 102 #pragma warning( pop )
 103 #endif
 104 
 105 void ParScanThreadState::record_survivor_plab(HeapWord* plab_start,
 106                                               size_t plab_word_size) {
 107   ChunkArray* sca = survivor_chunk_array();
 108   if (sca != NULL) {
 109     // A non-null SCA implies that we want the PLAB data recorded.
 110     sca->record_sample(plab_start, plab_word_size);
 111   }
 112 }
 113 
 114 bool ParScanThreadState::should_be_partially_scanned(oop new_obj, oop old_obj) const {
 115   return new_obj->is_objArray() &&
 116          arrayOop(new_obj)->length() > ParGCArrayScanChunk &&
 117          new_obj != old_obj;
 118 }
 119 
 120 void ParScanThreadState::scan_partial_array_and_push_remainder(oop old) {
 121   assert(old->is_objArray(), "must be obj array");
 122   assert(old->is_forwarded(), "must be forwarded");
 123   assert(Universe::heap()->is_in_reserved(old), "must be in heap.");
 124   assert(!old_gen()->is_in(old), "must be in young generation.");
 125 
 126   objArrayOop obj = objArrayOop(old->forwardee());
 127   // Process ParGCArrayScanChunk elements now
 128   // and push the remainder back onto queue
 129   int start     = arrayOop(old)->length();
 130   int end       = obj->length();
 131   int remainder = end - start;
 132   assert(start <= end, "just checking");
 133   if (remainder > 2 * ParGCArrayScanChunk) {
 134     // Test above combines last partial chunk with a full chunk
 135     end = start + ParGCArrayScanChunk;
 136     arrayOop(old)->set_length(end);
 137     // Push remainder.
 138     bool ok = work_queue()->push(old);
 139     assert(ok, "just popped, push must be okay");
 140   } else {
 141     // Restore length so that it can be used if there
 142     // is a promotion failure and forwarding pointers
 143     // must be removed.
 144     arrayOop(old)->set_length(end);
 145   }
 146 
 147   // process our set of indices (include header in first chunk)
 148   // should make sure end is even (aligned to HeapWord in case of compressed oops)
 149   if ((HeapWord *)obj < young_old_boundary()) {
 150     // object is in to_space
 151     obj->oop_iterate_range(&_to_space_closure, start, end);
 152   } else {
 153     // object is in old generation
 154     obj->oop_iterate_range(&_old_gen_closure, start, end);
 155   }
 156 }
 157 
 158 
 159 void ParScanThreadState::trim_queues(int max_size) {
 160   ObjToScanQueue* queue = work_queue();
 161   do {
 162     while (queue->size() > (juint)max_size) {
 163       oop obj_to_scan;
 164       if (queue->pop_local(obj_to_scan)) {
 165         if ((HeapWord *)obj_to_scan < young_old_boundary()) {
 166           if (obj_to_scan->is_objArray() &&
 167               obj_to_scan->is_forwarded() &&
 168               obj_to_scan->forwardee() != obj_to_scan) {
 169             scan_partial_array_and_push_remainder(obj_to_scan);
 170           } else {
 171             // object is in to_space
 172             obj_to_scan->oop_iterate(&_to_space_closure);
 173           }
 174         } else {
 175           // object is in old generation
 176           obj_to_scan->oop_iterate(&_old_gen_closure);
 177         }
 178       }
 179     }
 180     // For the  case of compressed oops, we have a private, non-shared
 181     // overflow stack, so we eagerly drain it so as to more evenly
 182     // distribute load early. Note: this may be good to do in
 183     // general rather than delay for the final stealing phase.
 184     // If applicable, we'll transfer a set of objects over to our
 185     // work queue, allowing them to be stolen and draining our
 186     // private overflow stack.
 187   } while (ParGCTrimOverflow && young_gen()->take_from_overflow_list(this));
 188 }
 189 
 190 bool ParScanThreadState::take_from_overflow_stack() {
 191   assert(ParGCUseLocalOverflow, "Else should not call");
 192   assert(young_gen()->overflow_list() == NULL, "Error");
 193   ObjToScanQueue* queue = work_queue();
 194   Stack<oop, mtGC>* const of_stack = overflow_stack();
 195   const size_t num_overflow_elems = of_stack->size();
 196   const size_t space_available = queue->max_elems() - queue->size();
 197   const size_t num_take_elems = MIN3(space_available / 4,
 198                                      ParGCDesiredObjsFromOverflowList,
 199                                      num_overflow_elems);
 200   // Transfer the most recent num_take_elems from the overflow
 201   // stack to our work queue.
 202   for (size_t i = 0; i != num_take_elems; i++) {
 203     oop cur = of_stack->pop();
 204     oop obj_to_push = cur->forwardee();
 205     assert(Universe::heap()->is_in_reserved(cur), "Should be in heap");
 206     assert(!old_gen()->is_in_reserved(cur), "Should be in young gen");
 207     assert(Universe::heap()->is_in_reserved(obj_to_push), "Should be in heap");
 208     if (should_be_partially_scanned(obj_to_push, cur)) {
 209       assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned");
 210       obj_to_push = cur;
 211     }
 212     bool ok = queue->push(obj_to_push);
 213     assert(ok, "Should have succeeded");
 214   }
 215   assert(young_gen()->overflow_list() == NULL, "Error");
 216   return num_take_elems > 0;  // was something transferred?
 217 }
 218 
 219 void ParScanThreadState::push_on_overflow_stack(oop p) {
 220   assert(ParGCUseLocalOverflow, "Else should not call");
 221   overflow_stack()->push(p);
 222   assert(young_gen()->overflow_list() == NULL, "Error");
 223 }
 224 
 225 HeapWord* ParScanThreadState::alloc_in_to_space_slow(size_t word_sz) {
 226 
 227   // Otherwise, if the object is small enough, try to reallocate the
 228   // buffer.
 229   HeapWord* obj = NULL;
 230   if (!_to_space_full) {
 231     ParGCAllocBuffer* const plab = to_space_alloc_buffer();
 232     Space*            const sp   = to_space();
 233     if (word_sz * 100 <
 234         ParallelGCBufferWastePct * plab->word_sz()) {
 235       // Is small enough; abandon this buffer and start a new one.
 236       plab->retire(false, false);
 237       size_t buf_size = plab->word_sz();
 238       HeapWord* buf_space = sp->par_allocate(buf_size);
 239       if (buf_space == NULL) {
 240         const size_t min_bytes =
 241           ParGCAllocBuffer::min_size() << LogHeapWordSize;
 242         size_t free_bytes = sp->free();
 243         while(buf_space == NULL && free_bytes >= min_bytes) {
 244           buf_size = free_bytes >> LogHeapWordSize;
 245           assert(buf_size == (size_t)align_object_size(buf_size),
 246                  "Invariant");
 247           buf_space  = sp->par_allocate(buf_size);
 248           free_bytes = sp->free();
 249         }
 250       }
 251       if (buf_space != NULL) {
 252         plab->set_word_size(buf_size);
 253         plab->set_buf(buf_space);
 254         record_survivor_plab(buf_space, buf_size);
 255         obj = plab->allocate_aligned(word_sz, SurvivorAlignmentInBytes);
 256         // Note that we cannot compare buf_size < word_sz below
 257         // because of AlignmentReserve (see ParGCAllocBuffer::allocate()).
 258         assert(obj != NULL || plab->words_remaining() < word_sz,
 259                "Else should have been able to allocate");
 260         // It's conceivable that we may be able to use the
 261         // buffer we just grabbed for subsequent small requests
 262         // even if not for this one.
 263       } else {
 264         // We're used up.
 265         _to_space_full = true;
 266       }
 267 
 268     } else {
 269       // Too large; allocate the object individually.
 270       obj = sp->par_allocate(word_sz);
 271     }
 272   }
 273   return obj;
 274 }
 275 
 276 
 277 void ParScanThreadState::undo_alloc_in_to_space(HeapWord* obj,
 278                                                 size_t word_sz) {
 279   // Is the alloc in the current alloc buffer?
 280   if (to_space_alloc_buffer()->contains(obj)) {
 281     assert(to_space_alloc_buffer()->contains(obj + word_sz - 1),
 282            "Should contain whole object.");
 283     to_space_alloc_buffer()->undo_allocation(obj, word_sz);
 284   } else {
 285     CollectedHeap::fill_with_object(obj, word_sz);
 286   }
 287 }
 288 
 289 void ParScanThreadState::print_promotion_failure_size() {
 290   if (_promotion_failed_info.has_failed() && PrintPromotionFailure) {
 291     gclog_or_tty->print(" (%d: promotion failure size = " SIZE_FORMAT ") ",
 292                         _thread_num, _promotion_failed_info.first_size());
 293   }
 294 }
 295 
 296 class ParScanThreadStateSet: private ResourceArray {
 297 public:
 298   // Initializes states for the specified number of threads;
 299   ParScanThreadStateSet(int                     num_threads,
 300                         Space&                  to_space,
 301                         ParNewGeneration&       gen,
 302                         Generation&             old_gen,
 303                         ObjToScanQueueSet&      queue_set,
 304                         Stack<oop, mtGC>*       overflow_stacks_,
 305                         size_t                  desired_plab_sz,
 306                         ParallelTaskTerminator& term);
 307 
 308   ~ParScanThreadStateSet() { TASKQUEUE_STATS_ONLY(reset_stats()); }
 309 
 310   inline ParScanThreadState& thread_state(int i);
 311 
 312   void trace_promotion_failed(YoungGCTracer& gc_tracer);
 313   void reset(int active_workers, bool promotion_failed);
 314   void flush();
 315 
 316   #if TASKQUEUE_STATS
 317   static void
 318     print_termination_stats_hdr(outputStream* const st = gclog_or_tty);
 319   void print_termination_stats(outputStream* const st = gclog_or_tty);
 320   static void
 321     print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 322   void print_taskqueue_stats(outputStream* const st = gclog_or_tty);
 323   void reset_stats();
 324   #endif // TASKQUEUE_STATS
 325 
 326 private:
 327   ParallelTaskTerminator& _term;
 328   ParNewGeneration&       _gen;
 329   Generation&             _next_gen;
 330  public:
 331   bool is_valid(int id) const { return id < length(); }
 332   ParallelTaskTerminator* terminator() { return &_term; }
 333 };
 334 
 335 
 336 ParScanThreadStateSet::ParScanThreadStateSet(
 337   int num_threads, Space& to_space, ParNewGeneration& gen,
 338   Generation& old_gen, ObjToScanQueueSet& queue_set,
 339   Stack<oop, mtGC>* overflow_stacks,
 340   size_t desired_plab_sz, ParallelTaskTerminator& term)
 341   : ResourceArray(sizeof(ParScanThreadState), num_threads),
 342     _gen(gen), _next_gen(old_gen), _term(term)
 343 {
 344   assert(num_threads > 0, "sanity check!");
 345   assert(ParGCUseLocalOverflow == (overflow_stacks != NULL),
 346          "overflow_stack allocation mismatch");
 347   // Initialize states.
 348   for (int i = 0; i < num_threads; ++i) {
 349     new ((ParScanThreadState*)_data + i)
 350         ParScanThreadState(&to_space, &gen, &old_gen, i, &queue_set,
 351                            overflow_stacks, desired_plab_sz, term);
 352   }
 353 }
 354 
 355 inline ParScanThreadState& ParScanThreadStateSet::thread_state(int i)
 356 {
 357   assert(i >= 0 && i < length(), "sanity check!");
 358   return ((ParScanThreadState*)_data)[i];
 359 }
 360 
 361 void ParScanThreadStateSet::trace_promotion_failed(YoungGCTracer& gc_tracer) {
 362   for (int i = 0; i < length(); ++i) {
 363     if (thread_state(i).promotion_failed()) {
 364       gc_tracer.report_promotion_failed(thread_state(i).promotion_failed_info());
 365       thread_state(i).promotion_failed_info().reset();
 366     }
 367   }
 368 }
 369 
 370 void ParScanThreadStateSet::reset(int active_threads, bool promotion_failed)
 371 {
 372   _term.reset_for_reuse(active_threads);
 373   if (promotion_failed) {
 374     for (int i = 0; i < length(); ++i) {
 375       thread_state(i).print_promotion_failure_size();
 376     }
 377   }
 378 }
 379 
 380 #if TASKQUEUE_STATS
 381 void
 382 ParScanThreadState::reset_stats()
 383 {
 384   taskqueue_stats().reset();
 385   _term_attempts = 0;
 386   _overflow_refills = 0;
 387   _overflow_refill_objs = 0;
 388 }
 389 
 390 void ParScanThreadStateSet::reset_stats()
 391 {
 392   for (int i = 0; i < length(); ++i) {
 393     thread_state(i).reset_stats();
 394   }
 395 }
 396 
 397 void
 398 ParScanThreadStateSet::print_termination_stats_hdr(outputStream* const st)
 399 {
 400   st->print_raw_cr("GC Termination Stats");
 401   st->print_raw_cr("     elapsed  --strong roots-- "
 402                    "-------termination-------");
 403   st->print_raw_cr("thr     ms        ms       %   "
 404                    "    ms       %   attempts");
 405   st->print_raw_cr("--- --------- --------- ------ "
 406                    "--------- ------ --------");
 407 }
 408 
 409 void ParScanThreadStateSet::print_termination_stats(outputStream* const st)
 410 {
 411   print_termination_stats_hdr(st);
 412 
 413   for (int i = 0; i < length(); ++i) {
 414     const ParScanThreadState & pss = thread_state(i);
 415     const double elapsed_ms = pss.elapsed_time() * 1000.0;
 416     const double s_roots_ms = pss.strong_roots_time() * 1000.0;
 417     const double term_ms = pss.term_time() * 1000.0;
 418     st->print_cr("%3d %9.2f %9.2f %6.2f "
 419                  "%9.2f %6.2f " SIZE_FORMAT_W(8),
 420                  i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
 421                  term_ms, term_ms * 100 / elapsed_ms, pss.term_attempts());
 422   }
 423 }
 424 
 425 // Print stats related to work queue activity.
 426 void ParScanThreadStateSet::print_taskqueue_stats_hdr(outputStream* const st)
 427 {
 428   st->print_raw_cr("GC Task Stats");
 429   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
 430   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
 431 }
 432 
 433 void ParScanThreadStateSet::print_taskqueue_stats(outputStream* const st)
 434 {
 435   print_taskqueue_stats_hdr(st);
 436 
 437   TaskQueueStats totals;
 438   for (int i = 0; i < length(); ++i) {
 439     const ParScanThreadState & pss = thread_state(i);
 440     const TaskQueueStats & stats = pss.taskqueue_stats();
 441     st->print("%3d ", i); stats.print(st); st->cr();
 442     totals += stats;
 443 
 444     if (pss.overflow_refills() > 0) {
 445       st->print_cr("    " SIZE_FORMAT_W(10) " overflow refills    "
 446                    SIZE_FORMAT_W(10) " overflow objects",
 447                    pss.overflow_refills(), pss.overflow_refill_objs());
 448     }
 449   }
 450   st->print("tot "); totals.print(st); st->cr();
 451 
 452   DEBUG_ONLY(totals.verify());
 453 }
 454 #endif // TASKQUEUE_STATS
 455 
 456 void ParScanThreadStateSet::flush()
 457 {
 458   // Work in this loop should be kept as lightweight as
 459   // possible since this might otherwise become a bottleneck
 460   // to scaling. Should we add heavy-weight work into this
 461   // loop, consider parallelizing the loop into the worker threads.
 462   for (int i = 0; i < length(); ++i) {
 463     ParScanThreadState& par_scan_state = thread_state(i);
 464 
 465     // Flush stats related to To-space PLAB activity and
 466     // retire the last buffer.
 467     par_scan_state.to_space_alloc_buffer()->
 468       flush_stats_and_retire(_gen.plab_stats(),
 469                              true /* end_of_gc */,
 470                              false /* retain */);
 471 
 472     // Every thread has its own age table.  We need to merge
 473     // them all into one.
 474     ageTable *local_table = par_scan_state.age_table();
 475     _gen.age_table()->merge(local_table);
 476 
 477     // Inform old gen that we're done.
 478     _next_gen.par_promote_alloc_done(i);
 479     _next_gen.par_oop_since_save_marks_iterate_done(i);
 480   }
 481 
 482   if (UseConcMarkSweepGC && ParallelGCThreads > 0) {
 483     // We need to call this even when ResizeOldPLAB is disabled
 484     // so as to avoid breaking some asserts. While we may be able
 485     // to avoid this by reorganizing the code a bit, I am loathe
 486     // to do that unless we find cases where ergo leads to bad
 487     // performance.
 488     CFLS_LAB::compute_desired_plab_size();
 489   }
 490 }
 491 
 492 ParScanClosure::ParScanClosure(ParNewGeneration* g,
 493                                ParScanThreadState* par_scan_state) :
 494   OopsInKlassOrGenClosure(g), _par_scan_state(par_scan_state), _g(g)
 495 {
 496   assert(_g->level() == 0, "Optimized for youngest generation");
 497   _boundary = _g->reserved().end();
 498 }
 499 
 500 void ParScanWithBarrierClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, true, false); }
 501 void ParScanWithBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, false); }
 502 
 503 void ParScanWithoutBarrierClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, false, false); }
 504 void ParScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, false); }
 505 
 506 void ParRootScanWithBarrierTwoGensClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, true, true); }
 507 void ParRootScanWithBarrierTwoGensClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, true); }
 508 
 509 void ParRootScanWithoutBarrierClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, false, true); }
 510 void ParRootScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, true); }
 511 
 512 ParScanWeakRefClosure::ParScanWeakRefClosure(ParNewGeneration* g,
 513                                              ParScanThreadState* par_scan_state)
 514   : ScanWeakRefClosure(g), _par_scan_state(par_scan_state)
 515 {}
 516 
 517 void ParScanWeakRefClosure::do_oop(oop* p)       { ParScanWeakRefClosure::do_oop_work(p); }
 518 void ParScanWeakRefClosure::do_oop(narrowOop* p) { ParScanWeakRefClosure::do_oop_work(p); }
 519 
 520 #ifdef WIN32
 521 #pragma warning(disable: 4786) /* identifier was truncated to '255' characters in the browser information */
 522 #endif
 523 
 524 ParEvacuateFollowersClosure::ParEvacuateFollowersClosure(
 525     ParScanThreadState* par_scan_state_,
 526     ParScanWithoutBarrierClosure* to_space_closure_,
 527     ParScanWithBarrierClosure* old_gen_closure_,
 528     ParRootScanWithoutBarrierClosure* to_space_root_closure_,
 529     ParNewGeneration* par_gen_,
 530     ParRootScanWithBarrierTwoGensClosure* old_gen_root_closure_,
 531     ObjToScanQueueSet* task_queues_,
 532     ParallelTaskTerminator* terminator_) :
 533 
 534     _par_scan_state(par_scan_state_),
 535     _to_space_closure(to_space_closure_),
 536     _old_gen_closure(old_gen_closure_),
 537     _to_space_root_closure(to_space_root_closure_),
 538     _old_gen_root_closure(old_gen_root_closure_),
 539     _par_gen(par_gen_),
 540     _task_queues(task_queues_),
 541     _terminator(terminator_)
 542 {}
 543 
 544 void ParEvacuateFollowersClosure::do_void() {
 545   ObjToScanQueue* work_q = par_scan_state()->work_queue();
 546 
 547   while (true) {
 548 
 549     // Scan to-space and old-gen objs until we run out of both.
 550     oop obj_to_scan;
 551     par_scan_state()->trim_queues(0);
 552 
 553     // We have no local work, attempt to steal from other threads.
 554 
 555     // attempt to steal work from promoted.
 556     if (task_queues()->steal(par_scan_state()->thread_num(),
 557                              par_scan_state()->hash_seed(),
 558                              obj_to_scan)) {
 559       bool res = work_q->push(obj_to_scan);
 560       assert(res, "Empty queue should have room for a push.");
 561 
 562       //   if successful, goto Start.
 563       continue;
 564 
 565       // try global overflow list.
 566     } else if (par_gen()->take_from_overflow_list(par_scan_state())) {
 567       continue;
 568     }
 569 
 570     // Otherwise, offer termination.
 571     par_scan_state()->start_term_time();
 572     if (terminator()->offer_termination()) break;
 573     par_scan_state()->end_term_time();
 574   }
 575   assert(par_gen()->_overflow_list == NULL && par_gen()->_num_par_pushes == 0,
 576          "Broken overflow list?");
 577   // Finish the last termination pause.
 578   par_scan_state()->end_term_time();
 579 }
 580 
 581 ParNewGenTask::ParNewGenTask(ParNewGeneration* gen, Generation* next_gen,
 582                 HeapWord* young_old_boundary, ParScanThreadStateSet* state_set) :
 583     AbstractGangTask("ParNewGeneration collection"),
 584     _gen(gen), _next_gen(next_gen),
 585     _young_old_boundary(young_old_boundary),
 586     _state_set(state_set)
 587   {}
 588 
 589 // Reset the terminator for the given number of
 590 // active threads.
 591 void ParNewGenTask::set_for_termination(int active_workers) {
 592   _state_set->reset(active_workers, _gen->promotion_failed());
 593   // Should the heap be passed in?  There's only 1 for now so
 594   // grab it instead.
 595   GenCollectedHeap* gch = GenCollectedHeap::heap();
 596   gch->set_n_termination(active_workers);
 597 }
 598 
 599 void ParNewGenTask::work(uint worker_id) {
 600   GenCollectedHeap* gch = GenCollectedHeap::heap();
 601   // Since this is being done in a separate thread, need new resource
 602   // and handle marks.
 603   ResourceMark rm;
 604   HandleMark hm;
 605   // We would need multiple old-gen queues otherwise.
 606   assert(gch->n_gens() == 2, "Par young collection currently only works with one older gen.");
 607 
 608   Generation* old_gen = gch->next_gen(_gen);
 609 
 610   ParScanThreadState& par_scan_state = _state_set->thread_state(worker_id);
 611   assert(_state_set->is_valid(worker_id), "Should not have been called");
 612 
 613   par_scan_state.set_young_old_boundary(_young_old_boundary);
 614 
 615   KlassScanClosure klass_scan_closure(&par_scan_state.to_space_root_closure(),
 616                                       gch->rem_set()->klass_rem_set());
 617   CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
 618                                            &par_scan_state.to_space_root_closure(),
 619                                            false);
 620 
 621   par_scan_state.start_strong_roots();
 622   gch->gen_process_roots(_gen->level(),
 623                          true,  // Process younger gens, if any,
 624                                 // as strong roots.
 625                          false, // no scope; this is parallel code
 626                          SharedHeap::SO_ScavengeCodeCache,
 627                          GenCollectedHeap::StrongAndWeakRoots,
 628                          &par_scan_state.to_space_root_closure(),
 629                          &par_scan_state.older_gen_closure(),
 630                          &cld_scan_closure);
 631 
 632   par_scan_state.end_strong_roots();
 633 
 634   // "evacuate followers".
 635   par_scan_state.evacuate_followers_closure().do_void();
 636 }
 637 
 638 #ifdef _MSC_VER
 639 #pragma warning( push )
 640 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 641 #endif
 642 ParNewGeneration::
 643 ParNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level)
 644   : DefNewGeneration(rs, initial_byte_size, level, "PCopy"),
 645   _overflow_list(NULL),
 646   _is_alive_closure(this),
 647   _plab_stats(YoungPLABSize, PLABWeight)
 648 {
 649   NOT_PRODUCT(_overflow_counter = ParGCWorkQueueOverflowInterval;)
 650   NOT_PRODUCT(_num_par_pushes = 0;)
 651   _task_queues = new ObjToScanQueueSet(ParallelGCThreads);
 652   guarantee(_task_queues != NULL, "task_queues allocation failure.");
 653 
 654   for (uint i1 = 0; i1 < ParallelGCThreads; i1++) {
 655     ObjToScanQueue *q = new ObjToScanQueue();
 656     guarantee(q != NULL, "work_queue Allocation failure.");
 657     _task_queues->register_queue(i1, q);
 658   }
 659 
 660   for (uint i2 = 0; i2 < ParallelGCThreads; i2++)
 661     _task_queues->queue(i2)->initialize();
 662 
 663   _overflow_stacks = NULL;
 664   if (ParGCUseLocalOverflow) {
 665 
 666     // typedef to workaround NEW_C_HEAP_ARRAY macro, which can not deal
 667     // with ','
 668     typedef Stack<oop, mtGC> GCOopStack;
 669 
 670     _overflow_stacks = NEW_C_HEAP_ARRAY(GCOopStack, ParallelGCThreads, mtGC);
 671     for (size_t i = 0; i < ParallelGCThreads; ++i) {
 672       new (_overflow_stacks + i) Stack<oop, mtGC>();
 673     }
 674   }
 675 
 676   if (UsePerfData) {
 677     EXCEPTION_MARK;
 678     ResourceMark rm;
 679 
 680     const char* cname =
 681          PerfDataManager::counter_name(_gen_counters->name_space(), "threads");
 682     PerfDataManager::create_constant(SUN_GC, cname, PerfData::U_None,
 683                                      ParallelGCThreads, CHECK);
 684   }
 685 }
 686 #ifdef _MSC_VER
 687 #pragma warning( pop )
 688 #endif
 689 
 690 // ParNewGeneration::
 691 ParKeepAliveClosure::ParKeepAliveClosure(ParScanWeakRefClosure* cl) :
 692   DefNewGeneration::KeepAliveClosure(cl), _par_cl(cl) {}
 693 
 694 template <class T>
 695 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop_work(T* p) {
 696 #ifdef ASSERT
 697   {
 698     assert(!oopDesc::is_null(*p), "expected non-null ref");
 699     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
 700     // We never expect to see a null reference being processed
 701     // as a weak reference.
 702     assert(obj->is_oop(), "expected an oop while scanning weak refs");
 703   }
 704 #endif // ASSERT
 705 
 706   _par_cl->do_oop_nv(p);
 707 
 708   if (Universe::heap()->is_in_reserved(p)) {
 709     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
 710     _rs->write_ref_field_gc_par(p, obj);
 711   }
 712 }
 713 
 714 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(oop* p)       { ParKeepAliveClosure::do_oop_work(p); }
 715 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(narrowOop* p) { ParKeepAliveClosure::do_oop_work(p); }
 716 
 717 // ParNewGeneration::
 718 KeepAliveClosure::KeepAliveClosure(ScanWeakRefClosure* cl) :
 719   DefNewGeneration::KeepAliveClosure(cl) {}
 720 
 721 template <class T>
 722 void /*ParNewGeneration::*/KeepAliveClosure::do_oop_work(T* p) {
 723 #ifdef ASSERT
 724   {
 725     assert(!oopDesc::is_null(*p), "expected non-null ref");
 726     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
 727     // We never expect to see a null reference being processed
 728     // as a weak reference.
 729     assert(obj->is_oop(), "expected an oop while scanning weak refs");
 730   }
 731 #endif // ASSERT
 732 
 733   _cl->do_oop_nv(p);
 734 
 735   if (Universe::heap()->is_in_reserved(p)) {
 736     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
 737     _rs->write_ref_field_gc_par(p, obj);
 738   }
 739 }
 740 
 741 void /*ParNewGeneration::*/KeepAliveClosure::do_oop(oop* p)       { KeepAliveClosure::do_oop_work(p); }
 742 void /*ParNewGeneration::*/KeepAliveClosure::do_oop(narrowOop* p) { KeepAliveClosure::do_oop_work(p); }
 743 
 744 template <class T> void ScanClosureWithParBarrier::do_oop_work(T* p) {
 745   T heap_oop = oopDesc::load_heap_oop(p);
 746   if (!oopDesc::is_null(heap_oop)) {
 747     oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
 748     if ((HeapWord*)obj < _boundary) {
 749       assert(!_g->to()->is_in_reserved(obj), "Scanning field twice?");
 750       oop new_obj = obj->is_forwarded()
 751                       ? obj->forwardee()
 752                       : _g->DefNewGeneration::copy_to_survivor_space(obj);
 753       oopDesc::encode_store_heap_oop_not_null(p, new_obj);
 754     }
 755     if (_gc_barrier) {
 756       // If p points to a younger generation, mark the card.
 757       if ((HeapWord*)obj < _gen_boundary) {
 758         _rs->write_ref_field_gc_par(p, obj);
 759       }
 760     }
 761   }
 762 }
 763 
 764 void ScanClosureWithParBarrier::do_oop(oop* p)       { ScanClosureWithParBarrier::do_oop_work(p); }
 765 void ScanClosureWithParBarrier::do_oop(narrowOop* p) { ScanClosureWithParBarrier::do_oop_work(p); }
 766 
 767 class ParNewRefProcTaskProxy: public AbstractGangTask {
 768   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
 769 public:
 770   ParNewRefProcTaskProxy(ProcessTask& task, ParNewGeneration& gen,
 771                          Generation& next_gen,
 772                          HeapWord* young_old_boundary,
 773                          ParScanThreadStateSet& state_set);
 774 
 775 private:
 776   virtual void work(uint worker_id);
 777   virtual void set_for_termination(int active_workers) {
 778     _state_set.terminator()->reset_for_reuse(active_workers);
 779   }
 780 private:
 781   ParNewGeneration&      _gen;
 782   ProcessTask&           _task;
 783   Generation&            _next_gen;
 784   HeapWord*              _young_old_boundary;
 785   ParScanThreadStateSet& _state_set;
 786 };
 787 
 788 ParNewRefProcTaskProxy::ParNewRefProcTaskProxy(
 789     ProcessTask& task, ParNewGeneration& gen,
 790     Generation& next_gen,
 791     HeapWord* young_old_boundary,
 792     ParScanThreadStateSet& state_set)
 793   : AbstractGangTask("ParNewGeneration parallel reference processing"),
 794     _gen(gen),
 795     _task(task),
 796     _next_gen(next_gen),
 797     _young_old_boundary(young_old_boundary),
 798     _state_set(state_set)
 799 {
 800 }
 801 
 802 void ParNewRefProcTaskProxy::work(uint worker_id)
 803 {
 804   ResourceMark rm;
 805   HandleMark hm;
 806   ParScanThreadState& par_scan_state = _state_set.thread_state(worker_id);
 807   par_scan_state.set_young_old_boundary(_young_old_boundary);
 808   _task.work(worker_id, par_scan_state.is_alive_closure(),
 809              par_scan_state.keep_alive_closure(),
 810              par_scan_state.evacuate_followers_closure());
 811 }
 812 
 813 class ParNewRefEnqueueTaskProxy: public AbstractGangTask {
 814   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
 815   EnqueueTask& _task;
 816 
 817 public:
 818   ParNewRefEnqueueTaskProxy(EnqueueTask& task)
 819     : AbstractGangTask("ParNewGeneration parallel reference enqueue"),
 820       _task(task)
 821   { }
 822 
 823   virtual void work(uint worker_id)
 824   {
 825     _task.work(worker_id);
 826   }
 827 };
 828 
 829 
 830 void ParNewRefProcTaskExecutor::execute(ProcessTask& task)
 831 {
 832   GenCollectedHeap* gch = GenCollectedHeap::heap();
 833   assert(gch->kind() == CollectedHeap::GenCollectedHeap,
 834          "not a generational heap");
 835   FlexibleWorkGang* workers = gch->workers();
 836   assert(workers != NULL, "Need parallel worker threads.");
 837   _state_set.reset(workers->active_workers(), _generation.promotion_failed());
 838   ParNewRefProcTaskProxy rp_task(task, _generation, *_generation.next_gen(),
 839                                  _generation.reserved().end(), _state_set);
 840   workers->run_task(&rp_task);
 841   _state_set.reset(0 /* bad value in debug if not reset */,
 842                    _generation.promotion_failed());
 843 }
 844 
 845 void ParNewRefProcTaskExecutor::execute(EnqueueTask& task)
 846 {
 847   GenCollectedHeap* gch = GenCollectedHeap::heap();
 848   FlexibleWorkGang* workers = gch->workers();
 849   assert(workers != NULL, "Need parallel worker threads.");
 850   ParNewRefEnqueueTaskProxy enq_task(task);
 851   workers->run_task(&enq_task);
 852 }
 853 
 854 void ParNewRefProcTaskExecutor::set_single_threaded_mode()
 855 {
 856   _state_set.flush();
 857   GenCollectedHeap* gch = GenCollectedHeap::heap();
 858   gch->set_par_threads(0);  // 0 ==> non-parallel.
 859   gch->save_marks();
 860 }
 861 
 862 ScanClosureWithParBarrier::
 863 ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier) :
 864   ScanClosure(g, gc_barrier) {}
 865 
 866 EvacuateFollowersClosureGeneral::
 867 EvacuateFollowersClosureGeneral(GenCollectedHeap* gch, int level,
 868                                 OopsInGenClosure* cur,
 869                                 OopsInGenClosure* older) :
 870   _gch(gch), _level(level),
 871   _scan_cur_or_nonheap(cur), _scan_older(older)
 872 {}
 873 
 874 void EvacuateFollowersClosureGeneral::do_void() {
 875   do {
 876     // Beware: this call will lead to closure applications via virtual
 877     // calls.
 878     _gch->oop_since_save_marks_iterate(_level,
 879                                        _scan_cur_or_nonheap,
 880                                        _scan_older);
 881   } while (!_gch->no_allocs_since_save_marks(_level));
 882 }
 883 
 884 
 885 // A Generation that does parallel young-gen collection.
 886 
 887 bool ParNewGeneration::_avoid_promotion_undo = false;
 888 
 889 void ParNewGeneration::handle_promotion_failed(GenCollectedHeap* gch, ParScanThreadStateSet& thread_state_set, ParNewTracer& gc_tracer) {
 890   assert(_promo_failure_scan_stack.is_empty(), "post condition");
 891   _promo_failure_scan_stack.clear(true); // Clear cached segments.
 892 
 893   remove_forwarding_pointers();
 894   if (PrintGCDetails) {
 895     gclog_or_tty->print(" (promotion failed)");
 896   }
 897   // All the spaces are in play for mark-sweep.
 898   swap_spaces();  // Make life simpler for CMS || rescan; see 6483690.
 899   from()->set_next_compaction_space(to());
 900   gch->set_incremental_collection_failed();
 901   // Inform the next generation that a promotion failure occurred.
 902   _next_gen->promotion_failure_occurred();
 903 
 904   // Trace promotion failure in the parallel GC threads
 905   thread_state_set.trace_promotion_failed(gc_tracer);
 906   // Single threaded code may have reported promotion failure to the global state
 907   if (_promotion_failed_info.has_failed()) {
 908     gc_tracer.report_promotion_failed(_promotion_failed_info);
 909   }
 910   // Reset the PromotionFailureALot counters.
 911   NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
 912 }
 913 
 914 void ParNewGeneration::collect(bool   full,
 915                                bool   clear_all_soft_refs,
 916                                size_t size,
 917                                bool   is_tlab) {
 918   assert(full || size > 0, "otherwise we don't want to collect");
 919 
 920   GenCollectedHeap* gch = GenCollectedHeap::heap();
 921 
 922   _gc_timer->register_gc_start();
 923 
 924   assert(gch->kind() == CollectedHeap::GenCollectedHeap,
 925     "not a CMS generational heap");
 926   AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
 927   FlexibleWorkGang* workers = gch->workers();
 928   assert(workers != NULL, "Need workgang for parallel work");
 929   int active_workers =
 930       AdaptiveSizePolicy::calc_active_workers(workers->total_workers(),
 931                                    workers->active_workers(),
 932                                    Threads::number_of_non_daemon_threads());
 933   workers->set_active_workers(active_workers);
 934   assert(gch->n_gens() == 2,
 935          "Par collection currently only works with single older gen.");
 936   _next_gen = gch->next_gen(this);
 937   // Do we have to avoid promotion_undo?
 938   if (gch->collector_policy()->is_concurrent_mark_sweep_policy()) {
 939     set_avoid_promotion_undo(true);
 940   }
 941 
 942   // If the next generation is too full to accommodate worst-case promotion
 943   // from this generation, pass on collection; let the next generation
 944   // do it.
 945   if (!collection_attempt_is_safe()) {
 946     gch->set_incremental_collection_failed();  // slight lie, in that we did not even attempt one
 947     return;
 948   }
 949   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 950 
 951   ParNewTracer gc_tracer;
 952   gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
 953   gch->trace_heap_before_gc(&gc_tracer);
 954 
 955   init_assuming_no_promotion_failure();
 956 
 957   if (UseAdaptiveSizePolicy) {
 958     set_survivor_overflow(false);
 959     size_policy->minor_collection_begin();
 960   }
 961 
 962   GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id());
 963   // Capture heap used before collection (for printing).
 964   size_t gch_prev_used = gch->used();
 965 
 966   SpecializationStats::clear();
 967 
 968   age_table()->clear();
 969   to()->clear(SpaceDecorator::Mangle);
 970 
 971   gch->save_marks();
 972   assert(workers != NULL, "Need parallel worker threads.");
 973   int n_workers = active_workers;
 974 
 975   // Set the correct parallelism (number of queues) in the reference processor
 976   ref_processor()->set_active_mt_degree(n_workers);
 977 
 978   // Always set the terminator for the active number of workers
 979   // because only those workers go through the termination protocol.
 980   ParallelTaskTerminator _term(n_workers, task_queues());
 981   ParScanThreadStateSet thread_state_set(workers->active_workers(),
 982                                          *to(), *this, *_next_gen, *task_queues(),
 983                                          _overflow_stacks, desired_plab_sz(), _term);
 984 
 985   ParNewGenTask tsk(this, _next_gen, reserved().end(), &thread_state_set);
 986   gch->set_par_threads(n_workers);
 987   gch->rem_set()->prepare_for_younger_refs_iterate(true);
 988   // It turns out that even when we're using 1 thread, doing the work in a
 989   // separate thread causes wide variance in run times.  We can't help this
 990   // in the multi-threaded case, but we special-case n=1 here to get
 991   // repeatable measurements of the 1-thread overhead of the parallel code.
 992   if (n_workers > 1) {
 993     GenCollectedHeap::StrongRootsScope srs(gch);
 994     workers->run_task(&tsk);
 995   } else {
 996     GenCollectedHeap::StrongRootsScope srs(gch);
 997     tsk.work(0);
 998   }
 999   thread_state_set.reset(0 /* Bad value in debug if not reset */,
1000                          promotion_failed());
1001 
1002   // Process (weak) reference objects found during scavenge.
1003   ReferenceProcessor* rp = ref_processor();
1004   IsAliveClosure is_alive(this);
1005   ScanWeakRefClosure scan_weak_ref(this);
1006   KeepAliveClosure keep_alive(&scan_weak_ref);
1007   ScanClosure               scan_without_gc_barrier(this, false);
1008   ScanClosureWithParBarrier scan_with_gc_barrier(this, true);
1009   set_promo_failure_scan_stack_closure(&scan_without_gc_barrier);
1010   EvacuateFollowersClosureGeneral evacuate_followers(gch, _level,
1011     &scan_without_gc_barrier, &scan_with_gc_barrier);
1012   rp->setup_policy(clear_all_soft_refs);
1013   // Can  the mt_degree be set later (at run_task() time would be best)?
1014   rp->set_active_mt_degree(active_workers);
1015   ReferenceProcessorStats stats;
1016   if (rp->processing_is_mt()) {
1017     ParNewRefProcTaskExecutor task_executor(*this, thread_state_set);
1018     stats = rp->process_discovered_references(&is_alive, &keep_alive,
1019                                               &evacuate_followers, &task_executor,
1020                                               _gc_timer, gc_tracer.gc_id());
1021   } else {
1022     thread_state_set.flush();
1023     gch->set_par_threads(0);  // 0 ==> non-parallel.
1024     gch->save_marks();
1025     stats = rp->process_discovered_references(&is_alive, &keep_alive,
1026                                               &evacuate_followers, NULL,
1027                                               _gc_timer, gc_tracer.gc_id());
1028   }
1029   gc_tracer.report_gc_reference_stats(stats);
1030   if (!promotion_failed()) {
1031     // Swap the survivor spaces.
1032     eden()->clear(SpaceDecorator::Mangle);
1033     from()->clear(SpaceDecorator::Mangle);
1034     if (ZapUnusedHeapArea) {
1035       // This is now done here because of the piece-meal mangling which
1036       // can check for valid mangling at intermediate points in the
1037       // collection(s).  When a minor collection fails to collect
1038       // sufficient space resizing of the young generation can occur
1039       // an redistribute the spaces in the young generation.  Mangle
1040       // here so that unzapped regions don't get distributed to
1041       // other spaces.
1042       to()->mangle_unused_area();
1043     }
1044     swap_spaces();
1045 
1046     // A successful scavenge should restart the GC time limit count which is
1047     // for full GC's.
1048     size_policy->reset_gc_overhead_limit_count();
1049 
1050     assert(to()->is_empty(), "to space should be empty now");
1051 
1052     adjust_desired_tenuring_threshold();
1053   } else {
1054     handle_promotion_failed(gch, thread_state_set, gc_tracer);
1055   }
1056   // set new iteration safe limit for the survivor spaces
1057   from()->set_concurrent_iteration_safe_limit(from()->top());
1058   to()->set_concurrent_iteration_safe_limit(to()->top());
1059 
1060   if (ResizePLAB) {
1061     plab_stats()->adjust_desired_plab_sz(n_workers);
1062   }
1063 
1064   if (PrintGC && !PrintGCDetails) {
1065     gch->print_heap_change(gch_prev_used);
1066   }
1067 
1068   TASKQUEUE_STATS_ONLY(if (PrintTerminationStats) thread_state_set.print_termination_stats());
1069   TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) thread_state_set.print_taskqueue_stats());


1070 
1071   if (UseAdaptiveSizePolicy) {
1072     size_policy->minor_collection_end(gch->gc_cause());
1073     size_policy->avg_survived()->sample(from()->used());
1074   }
1075 
1076   // We need to use a monotonically non-decreasing time in ms
1077   // or we will see time-warp warnings and os::javaTimeMillis()
1078   // does not guarantee monotonicity.
1079   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
1080   update_time_of_last_gc(now);
1081 
1082   SpecializationStats::print();
1083 
1084   rp->set_enqueuing_is_done(true);
1085   if (rp->processing_is_mt()) {
1086     ParNewRefProcTaskExecutor task_executor(*this, thread_state_set);
1087     rp->enqueue_discovered_references(&task_executor);
1088   } else {
1089     rp->enqueue_discovered_references(NULL);
1090   }
1091   rp->verify_no_references_recorded();
1092 
1093   gch->trace_heap_after_gc(&gc_tracer);
1094   gc_tracer.report_tenuring_threshold(tenuring_threshold());
1095 
1096   _gc_timer->register_gc_end();
1097 
1098   gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
1099 }
1100 
1101 static int sum;
1102 void ParNewGeneration::waste_some_time() {
1103   for (int i = 0; i < 100; i++) {
1104     sum += i;
1105   }
1106 }
1107 
1108 static const oop ClaimedForwardPtr = cast_to_oop<intptr_t>(0x4);
1109 
1110 // Because of concurrency, there are times where an object for which
1111 // "is_forwarded()" is true contains an "interim" forwarding pointer
1112 // value.  Such a value will soon be overwritten with a real value.
1113 // This method requires "obj" to have a forwarding pointer, and waits, if
1114 // necessary for a real one to be inserted, and returns it.
1115 
1116 oop ParNewGeneration::real_forwardee(oop obj) {
1117   oop forward_ptr = obj->forwardee();
1118   if (forward_ptr != ClaimedForwardPtr) {
1119     return forward_ptr;
1120   } else {
1121     return real_forwardee_slow(obj);
1122   }
1123 }
1124 
1125 oop ParNewGeneration::real_forwardee_slow(oop obj) {
1126   // Spin-read if it is claimed but not yet written by another thread.
1127   oop forward_ptr = obj->forwardee();
1128   while (forward_ptr == ClaimedForwardPtr) {
1129     waste_some_time();
1130     assert(obj->is_forwarded(), "precondition");
1131     forward_ptr = obj->forwardee();
1132   }
1133   return forward_ptr;
1134 }
1135 
1136 #ifdef ASSERT
1137 bool ParNewGeneration::is_legal_forward_ptr(oop p) {
1138   return
1139     (_avoid_promotion_undo && p == ClaimedForwardPtr)
1140     || Universe::heap()->is_in_reserved(p);
1141 }
1142 #endif
1143 
1144 void ParNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
1145   if (m->must_be_preserved_for_promotion_failure(obj)) {
1146     // We should really have separate per-worker stacks, rather
1147     // than use locking of a common pair of stacks.
1148     MutexLocker ml(ParGCRareEvent_lock);
1149     preserve_mark(obj, m);
1150   }
1151 }
1152 
1153 // Multiple GC threads may try to promote an object.  If the object
1154 // is successfully promoted, a forwarding pointer will be installed in
1155 // the object in the young generation.  This method claims the right
1156 // to install the forwarding pointer before it copies the object,
1157 // thus avoiding the need to undo the copy as in
1158 // copy_to_survivor_space_avoiding_with_undo.
1159 
1160 oop ParNewGeneration::copy_to_survivor_space_avoiding_promotion_undo(
1161         ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) {
1162   // In the sequential version, this assert also says that the object is
1163   // not forwarded.  That might not be the case here.  It is the case that
1164   // the caller observed it to be not forwarded at some time in the past.
1165   assert(is_in_reserved(old), "shouldn't be scavenging this oop");
1166 
1167   // The sequential code read "old->age()" below.  That doesn't work here,
1168   // since the age is in the mark word, and that might be overwritten with
1169   // a forwarding pointer by a parallel thread.  So we must save the mark
1170   // word in a local and then analyze it.
1171   oopDesc dummyOld;
1172   dummyOld.set_mark(m);
1173   assert(!dummyOld.is_forwarded(),
1174          "should not be called with forwarding pointer mark word.");
1175 
1176   oop new_obj = NULL;
1177   oop forward_ptr;
1178 
1179   // Try allocating obj in to-space (unless too old)
1180   if (dummyOld.age() < tenuring_threshold()) {
1181     new_obj = (oop)par_scan_state->alloc_in_to_space(sz);
1182     if (new_obj == NULL) {
1183       set_survivor_overflow(true);
1184     }
1185   }
1186 
1187   if (new_obj == NULL) {
1188     // Either to-space is full or we decided to promote
1189     // try allocating obj tenured
1190 
1191     // Attempt to install a null forwarding pointer (atomically),
1192     // to claim the right to install the real forwarding pointer.
1193     forward_ptr = old->forward_to_atomic(ClaimedForwardPtr);
1194     if (forward_ptr != NULL) {
1195       // someone else beat us to it.
1196         return real_forwardee(old);
1197     }
1198 
1199     new_obj = _next_gen->par_promote(par_scan_state->thread_num(),
1200                                        old, m, sz);
1201 
1202     if (new_obj == NULL) {
1203       // promotion failed, forward to self
1204       _promotion_failed = true;
1205       new_obj = old;
1206 
1207       preserve_mark_if_necessary(old, m);
1208       par_scan_state->register_promotion_failure(sz);
1209     }
1210 
1211     old->forward_to(new_obj);
1212     forward_ptr = NULL;
1213   } else {
1214     // Is in to-space; do copying ourselves.
1215     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz);
1216     forward_ptr = old->forward_to_atomic(new_obj);
1217     // Restore the mark word copied above.
1218     new_obj->set_mark(m);
1219     // Increment age if obj still in new generation
1220     new_obj->incr_age();
1221     par_scan_state->age_table()->add(new_obj, sz);
1222   }
1223   assert(new_obj != NULL, "just checking");
1224 
1225 #ifndef PRODUCT
1226   // This code must come after the CAS test, or it will print incorrect
1227   // information.
1228   if (TraceScavenge) {
1229     gclog_or_tty->print_cr("{%s %s " PTR_FORMAT " -> " PTR_FORMAT " (%d)}",
1230        is_in_reserved(new_obj) ? "copying" : "tenuring",
1231        new_obj->klass()->internal_name(), (void *)old, (void *)new_obj, new_obj->size());
1232   }
1233 #endif
1234 
1235   if (forward_ptr == NULL) {
1236     oop obj_to_push = new_obj;
1237     if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) {
1238       // Length field used as index of next element to be scanned.
1239       // Real length can be obtained from real_forwardee()
1240       arrayOop(old)->set_length(0);
1241       obj_to_push = old;
1242       assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push,
1243              "push forwarded object");
1244     }
1245     // Push it on one of the queues of to-be-scanned objects.
1246     bool simulate_overflow = false;
1247     NOT_PRODUCT(
1248       if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) {
1249         // simulate a stack overflow
1250         simulate_overflow = true;
1251       }
1252     )
1253     if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) {
1254       // Add stats for overflow pushes.
1255       if (Verbose && PrintGCDetails) {
1256         gclog_or_tty->print("queue overflow!\n");
1257       }
1258       push_on_overflow_list(old, par_scan_state);
1259       TASKQUEUE_STATS_ONLY(par_scan_state->taskqueue_stats().record_overflow(0));
1260     }
1261 
1262     return new_obj;
1263   }
1264 
1265   // Oops.  Someone beat us to it.  Undo the allocation.  Where did we
1266   // allocate it?
1267   if (is_in_reserved(new_obj)) {
1268     // Must be in to_space.
1269     assert(to()->is_in_reserved(new_obj), "Checking");
1270     if (forward_ptr == ClaimedForwardPtr) {
1271       // Wait to get the real forwarding pointer value.
1272       forward_ptr = real_forwardee(old);
1273     }
1274     par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz);
1275   }
1276 
1277   return forward_ptr;
1278 }
1279 
1280 
1281 // Multiple GC threads may try to promote the same object.  If two
1282 // or more GC threads copy the object, only one wins the race to install
1283 // the forwarding pointer.  The other threads have to undo their copy.
1284 
1285 oop ParNewGeneration::copy_to_survivor_space_with_undo(
1286         ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) {
1287 
1288   // In the sequential version, this assert also says that the object is
1289   // not forwarded.  That might not be the case here.  It is the case that
1290   // the caller observed it to be not forwarded at some time in the past.
1291   assert(is_in_reserved(old), "shouldn't be scavenging this oop");
1292 
1293   // The sequential code read "old->age()" below.  That doesn't work here,
1294   // since the age is in the mark word, and that might be overwritten with
1295   // a forwarding pointer by a parallel thread.  So we must save the mark
1296   // word here, install it in a local oopDesc, and then analyze it.
1297   oopDesc dummyOld;
1298   dummyOld.set_mark(m);
1299   assert(!dummyOld.is_forwarded(),
1300          "should not be called with forwarding pointer mark word.");
1301 
1302   bool failed_to_promote = false;
1303   oop new_obj = NULL;
1304   oop forward_ptr;
1305 
1306   // Try allocating obj in to-space (unless too old)
1307   if (dummyOld.age() < tenuring_threshold()) {
1308     new_obj = (oop)par_scan_state->alloc_in_to_space(sz);
1309     if (new_obj == NULL) {
1310       set_survivor_overflow(true);
1311     }
1312   }
1313 
1314   if (new_obj == NULL) {
1315     // Either to-space is full or we decided to promote
1316     // try allocating obj tenured
1317     new_obj = _next_gen->par_promote(par_scan_state->thread_num(),
1318                                        old, m, sz);
1319 
1320     if (new_obj == NULL) {
1321       // promotion failed, forward to self
1322       forward_ptr = old->forward_to_atomic(old);
1323       new_obj = old;
1324 
1325       if (forward_ptr != NULL) {
1326         return forward_ptr;   // someone else succeeded
1327       }
1328 
1329       _promotion_failed = true;
1330       failed_to_promote = true;
1331 
1332       preserve_mark_if_necessary(old, m);
1333       par_scan_state->register_promotion_failure(sz);
1334     }
1335   } else {
1336     // Is in to-space; do copying ourselves.
1337     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz);
1338     // Restore the mark word copied above.
1339     new_obj->set_mark(m);
1340     // Increment age if new_obj still in new generation
1341     new_obj->incr_age();
1342     par_scan_state->age_table()->add(new_obj, sz);
1343   }
1344   assert(new_obj != NULL, "just checking");
1345 
1346 #ifndef PRODUCT
1347   // This code must come after the CAS test, or it will print incorrect
1348   // information.
1349   if (TraceScavenge) {
1350     gclog_or_tty->print_cr("{%s %s " PTR_FORMAT " -> " PTR_FORMAT " (%d)}",
1351        is_in_reserved(new_obj) ? "copying" : "tenuring",
1352        new_obj->klass()->internal_name(), (void *)old, (void *)new_obj, new_obj->size());
1353   }
1354 #endif
1355 
1356   // Now attempt to install the forwarding pointer (atomically).
1357   // We have to copy the mark word before overwriting with forwarding
1358   // ptr, so we can restore it below in the copy.
1359   if (!failed_to_promote) {
1360     forward_ptr = old->forward_to_atomic(new_obj);
1361   }
1362 
1363   if (forward_ptr == NULL) {
1364     oop obj_to_push = new_obj;
1365     if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) {
1366       // Length field used as index of next element to be scanned.
1367       // Real length can be obtained from real_forwardee()
1368       arrayOop(old)->set_length(0);
1369       obj_to_push = old;
1370       assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push,
1371              "push forwarded object");
1372     }
1373     // Push it on one of the queues of to-be-scanned objects.
1374     bool simulate_overflow = false;
1375     NOT_PRODUCT(
1376       if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) {
1377         // simulate a stack overflow
1378         simulate_overflow = true;
1379       }
1380     )
1381     if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) {
1382       // Add stats for overflow pushes.
1383       push_on_overflow_list(old, par_scan_state);
1384       TASKQUEUE_STATS_ONLY(par_scan_state->taskqueue_stats().record_overflow(0));
1385     }
1386 
1387     return new_obj;
1388   }
1389 
1390   // Oops.  Someone beat us to it.  Undo the allocation.  Where did we
1391   // allocate it?
1392   if (is_in_reserved(new_obj)) {
1393     // Must be in to_space.
1394     assert(to()->is_in_reserved(new_obj), "Checking");
1395     par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz);
1396   } else {
1397     assert(!_avoid_promotion_undo, "Should not be here if avoiding.");
1398     _next_gen->par_promote_alloc_undo(par_scan_state->thread_num(),
1399                                       (HeapWord*)new_obj, sz);
1400   }
1401 
1402   return forward_ptr;
1403 }
1404 
1405 #ifndef PRODUCT
1406 // It's OK to call this multi-threaded;  the worst thing
1407 // that can happen is that we'll get a bunch of closely
1408 // spaced simulated overflows, but that's OK, in fact
1409 // probably good as it would exercise the overflow code
1410 // under contention.
1411 bool ParNewGeneration::should_simulate_overflow() {
1412   if (_overflow_counter-- <= 0) { // just being defensive
1413     _overflow_counter = ParGCWorkQueueOverflowInterval;
1414     return true;
1415   } else {
1416     return false;
1417   }
1418 }
1419 #endif
1420 
1421 // In case we are using compressed oops, we need to be careful.
1422 // If the object being pushed is an object array, then its length
1423 // field keeps track of the "grey boundary" at which the next
1424 // incremental scan will be done (see ParGCArrayScanChunk).
1425 // When using compressed oops, this length field is kept in the
1426 // lower 32 bits of the erstwhile klass word and cannot be used
1427 // for the overflow chaining pointer (OCP below). As such the OCP
1428 // would itself need to be compressed into the top 32-bits in this
1429 // case. Unfortunately, see below, in the event that we have a
1430 // promotion failure, the node to be pushed on the list can be
1431 // outside of the Java heap, so the heap-based pointer compression
1432 // would not work (we would have potential aliasing between C-heap
1433 // and Java-heap pointers). For this reason, when using compressed
1434 // oops, we simply use a worker-thread-local, non-shared overflow
1435 // list in the form of a growable array, with a slightly different
1436 // overflow stack draining strategy. If/when we start using fat
1437 // stacks here, we can go back to using (fat) pointer chains
1438 // (although some performance comparisons would be useful since
1439 // single global lists have their own performance disadvantages
1440 // as we were made painfully aware not long ago, see 6786503).
1441 #define BUSY (cast_to_oop<intptr_t>(0x1aff1aff))
1442 void ParNewGeneration::push_on_overflow_list(oop from_space_obj, ParScanThreadState* par_scan_state) {
1443   assert(is_in_reserved(from_space_obj), "Should be from this generation");
1444   if (ParGCUseLocalOverflow) {
1445     // In the case of compressed oops, we use a private, not-shared
1446     // overflow stack.
1447     par_scan_state->push_on_overflow_stack(from_space_obj);
1448   } else {
1449     assert(!UseCompressedOops, "Error");
1450     // if the object has been forwarded to itself, then we cannot
1451     // use the klass pointer for the linked list.  Instead we have
1452     // to allocate an oopDesc in the C-Heap and use that for the linked list.
1453     // XXX This is horribly inefficient when a promotion failure occurs
1454     // and should be fixed. XXX FIX ME !!!
1455 #ifndef PRODUCT
1456     Atomic::inc_ptr(&_num_par_pushes);
1457     assert(_num_par_pushes > 0, "Tautology");
1458 #endif
1459     if (from_space_obj->forwardee() == from_space_obj) {
1460       oopDesc* listhead = NEW_C_HEAP_ARRAY(oopDesc, 1, mtGC);
1461       listhead->forward_to(from_space_obj);
1462       from_space_obj = listhead;
1463     }
1464     oop observed_overflow_list = _overflow_list;
1465     oop cur_overflow_list;
1466     do {
1467       cur_overflow_list = observed_overflow_list;
1468       if (cur_overflow_list != BUSY) {
1469         from_space_obj->set_klass_to_list_ptr(cur_overflow_list);
1470       } else {
1471         from_space_obj->set_klass_to_list_ptr(NULL);
1472       }
1473       observed_overflow_list =
1474         (oop)Atomic::cmpxchg_ptr(from_space_obj, &_overflow_list, cur_overflow_list);
1475     } while (cur_overflow_list != observed_overflow_list);
1476   }
1477 }
1478 
1479 bool ParNewGeneration::take_from_overflow_list(ParScanThreadState* par_scan_state) {
1480   bool res;
1481 
1482   if (ParGCUseLocalOverflow) {
1483     res = par_scan_state->take_from_overflow_stack();
1484   } else {
1485     assert(!UseCompressedOops, "Error");
1486     res = take_from_overflow_list_work(par_scan_state);
1487   }
1488   return res;
1489 }
1490 
1491 
1492 // *NOTE*: The overflow list manipulation code here and
1493 // in CMSCollector:: are very similar in shape,
1494 // except that in the CMS case we thread the objects
1495 // directly into the list via their mark word, and do
1496 // not need to deal with special cases below related
1497 // to chunking of object arrays and promotion failure
1498 // handling.
1499 // CR 6797058 has been filed to attempt consolidation of
1500 // the common code.
1501 // Because of the common code, if you make any changes in
1502 // the code below, please check the CMS version to see if
1503 // similar changes might be needed.
1504 // See CMSCollector::par_take_from_overflow_list() for
1505 // more extensive documentation comments.
1506 bool ParNewGeneration::take_from_overflow_list_work(ParScanThreadState* par_scan_state) {
1507   ObjToScanQueue* work_q = par_scan_state->work_queue();
1508   // How many to take?
1509   size_t objsFromOverflow = MIN2((size_t)(work_q->max_elems() - work_q->size())/4,
1510                                  (size_t)ParGCDesiredObjsFromOverflowList);
1511 
1512   assert(!UseCompressedOops, "Error");
1513   assert(par_scan_state->overflow_stack() == NULL, "Error");
1514   if (_overflow_list == NULL) return false;
1515 
1516   // Otherwise, there was something there; try claiming the list.
1517   oop prefix = cast_to_oop(Atomic::xchg_ptr(BUSY, &_overflow_list));
1518   // Trim off a prefix of at most objsFromOverflow items
1519   Thread* tid = Thread::current();
1520   size_t spin_count = (size_t)ParallelGCThreads;
1521   size_t sleep_time_millis = MAX2((size_t)1, objsFromOverflow/100);
1522   for (size_t spin = 0; prefix == BUSY && spin < spin_count; spin++) {
1523     // someone grabbed it before we did ...
1524     // ... we spin for a short while...
1525     os::sleep(tid, sleep_time_millis, false);
1526     if (_overflow_list == NULL) {
1527       // nothing left to take
1528       return false;
1529     } else if (_overflow_list != BUSY) {
1530      // try and grab the prefix
1531      prefix = cast_to_oop(Atomic::xchg_ptr(BUSY, &_overflow_list));
1532     }
1533   }
1534   if (prefix == NULL || prefix == BUSY) {
1535      // Nothing to take or waited long enough
1536      if (prefix == NULL) {
1537        // Write back the NULL in case we overwrote it with BUSY above
1538        // and it is still the same value.
1539        (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY);
1540      }
1541      return false;
1542   }
1543   assert(prefix != NULL && prefix != BUSY, "Error");
1544   size_t i = 1;
1545   oop cur = prefix;
1546   while (i < objsFromOverflow && cur->klass_or_null() != NULL) {
1547     i++; cur = cur->list_ptr_from_klass();
1548   }
1549 
1550   // Reattach remaining (suffix) to overflow list
1551   if (cur->klass_or_null() == NULL) {
1552     // Write back the NULL in lieu of the BUSY we wrote
1553     // above and it is still the same value.
1554     if (_overflow_list == BUSY) {
1555       (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY);
1556     }
1557   } else {
1558     assert(cur->klass_or_null() != (Klass*)(address)BUSY, "Error");
1559     oop suffix = cur->list_ptr_from_klass();       // suffix will be put back on global list
1560     cur->set_klass_to_list_ptr(NULL);     // break off suffix
1561     // It's possible that the list is still in the empty(busy) state
1562     // we left it in a short while ago; in that case we may be
1563     // able to place back the suffix.
1564     oop observed_overflow_list = _overflow_list;
1565     oop cur_overflow_list = observed_overflow_list;
1566     bool attached = false;
1567     while (observed_overflow_list == BUSY || observed_overflow_list == NULL) {
1568       observed_overflow_list =
1569         (oop) Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list);
1570       if (cur_overflow_list == observed_overflow_list) {
1571         attached = true;
1572         break;
1573       } else cur_overflow_list = observed_overflow_list;
1574     }
1575     if (!attached) {
1576       // Too bad, someone else got in in between; we'll need to do a splice.
1577       // Find the last item of suffix list
1578       oop last = suffix;
1579       while (last->klass_or_null() != NULL) {
1580         last = last->list_ptr_from_klass();
1581       }
1582       // Atomically prepend suffix to current overflow list
1583       observed_overflow_list = _overflow_list;
1584       do {
1585         cur_overflow_list = observed_overflow_list;
1586         if (cur_overflow_list != BUSY) {
1587           // Do the splice ...
1588           last->set_klass_to_list_ptr(cur_overflow_list);
1589         } else { // cur_overflow_list == BUSY
1590           last->set_klass_to_list_ptr(NULL);
1591         }
1592         observed_overflow_list =
1593           (oop)Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list);
1594       } while (cur_overflow_list != observed_overflow_list);
1595     }
1596   }
1597 
1598   // Push objects on prefix list onto this thread's work queue
1599   assert(prefix != NULL && prefix != BUSY, "program logic");
1600   cur = prefix;
1601   ssize_t n = 0;
1602   while (cur != NULL) {
1603     oop obj_to_push = cur->forwardee();
1604     oop next        = cur->list_ptr_from_klass();
1605     cur->set_klass(obj_to_push->klass());
1606     // This may be an array object that is self-forwarded. In that case, the list pointer
1607     // space, cur, is not in the Java heap, but rather in the C-heap and should be freed.
1608     if (!is_in_reserved(cur)) {
1609       // This can become a scaling bottleneck when there is work queue overflow coincident
1610       // with promotion failure.
1611       oopDesc* f = cur;
1612       FREE_C_HEAP_ARRAY(oopDesc, f, mtGC);
1613     } else if (par_scan_state->should_be_partially_scanned(obj_to_push, cur)) {
1614       assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned");
1615       obj_to_push = cur;
1616     }
1617     bool ok = work_q->push(obj_to_push);
1618     assert(ok, "Should have succeeded");
1619     cur = next;
1620     n++;
1621   }
1622   TASKQUEUE_STATS_ONLY(par_scan_state->note_overflow_refill(n));
1623 #ifndef PRODUCT
1624   assert(_num_par_pushes >= n, "Too many pops?");
1625   Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes);
1626 #endif
1627   return true;
1628 }
1629 #undef BUSY
1630 
1631 void ParNewGeneration::ref_processor_init() {
1632   if (_ref_processor == NULL) {
1633     // Allocate and initialize a reference processor
1634     _ref_processor =
1635       new ReferenceProcessor(_reserved,                  // span
1636                              ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
1637                              (int) ParallelGCThreads,    // mt processing degree
1638                              refs_discovery_is_mt(),     // mt discovery
1639                              (int) ParallelGCThreads,    // mt discovery degree
1640                              refs_discovery_is_atomic(), // atomic_discovery
1641                              NULL);                      // is_alive_non_header
1642   }
1643 }
1644 
1645 const char* ParNewGeneration::name() const {
1646   return "par new generation";
1647 }
--- EOF ---