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/handles.hpp"
  51 #include "runtime/handles.inline.hpp"
  52 #include "runtime/java.hpp"
  53 #include "runtime/thread.inline.hpp"
  54 #include "utilities/copy.hpp"
  55 #include "utilities/globalDefinitions.hpp"
  56 #include "utilities/workgroup.hpp"
  57 
  58 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  59 
  60 #ifdef _MSC_VER
  61 #pragma warning( push )
  62 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
  63 #endif
  64 ParScanThreadState::ParScanThreadState(Space* to_space_,
  65                                        ParNewGeneration* gen_,
  66                                        Generation* old_gen_,
  67                                        int thread_num_,
  68                                        ObjToScanQueueSet* work_queue_set_,
  69                                        Stack<oop, mtGC>* overflow_stacks_,
  70                                        size_t desired_plab_sz_,
  71                                        ParallelTaskTerminator& term_) :
  72   _to_space(to_space_), _old_gen(old_gen_), _young_gen(gen_), _thread_num(thread_num_),
  73   _work_queue(work_queue_set_->queue(thread_num_)), _to_space_full(false),
  74   _overflow_stack(overflow_stacks_ ? overflow_stacks_ + thread_num_ : NULL),
  75   _ageTable(false), // false ==> not the global age table, no perf data.
  76   _to_space_alloc_buffer(desired_plab_sz_),
  77   _to_space_closure(gen_, this), _old_gen_closure(gen_, this),
  78   _to_space_root_closure(gen_, this), _old_gen_root_closure(gen_, this),
  79   _older_gen_closure(gen_, this),
  80   _evacuate_followers(this, &_to_space_closure, &_old_gen_closure,
  81                       &_to_space_root_closure, gen_, &_old_gen_root_closure,
  82                       work_queue_set_, &term_),
  83   _is_alive_closure(gen_), _scan_weak_ref_closure(gen_, this),
  84   _keep_alive_closure(&_scan_weak_ref_closure),
  85   _strong_roots_time(0.0), _term_time(0.0)
  86 {
  87   #if TASKQUEUE_STATS
  88   _term_attempts = 0;
  89   _overflow_refills = 0;
  90   _overflow_refill_objs = 0;
  91   #endif // TASKQUEUE_STATS
  92 
  93   _survivor_chunk_array =
  94     (ChunkArray*) old_gen()->get_data_recorder(thread_num());
  95   _hash_seed = 17;  // Might want to take time-based random value.
  96   _start = os::elapsedTime();
  97   _old_gen_closure.set_generation(old_gen_);
  98   _old_gen_root_closure.set_generation(old_gen_);
  99 }
 100 #ifdef _MSC_VER
 101 #pragma warning( pop )
 102 #endif
 103 
 104 void ParScanThreadState::record_survivor_plab(HeapWord* plab_start,
 105                                               size_t plab_word_size) {
 106   ChunkArray* sca = survivor_chunk_array();
 107   if (sca != NULL) {
 108     // A non-null SCA implies that we want the PLAB data recorded.
 109     sca->record_sample(plab_start, plab_word_size);
 110   }
 111 }
 112 
 113 bool ParScanThreadState::should_be_partially_scanned(oop new_obj, oop old_obj) const {
 114   return new_obj->is_objArray() &&
 115          arrayOop(new_obj)->length() > ParGCArrayScanChunk &&
 116          new_obj != old_obj;
 117 }
 118 
 119 void ParScanThreadState::scan_partial_array_and_push_remainder(oop old) {
 120   assert(old->is_objArray(), "must be obj array");
 121   assert(old->is_forwarded(), "must be forwarded");
 122   assert(Universe::heap()->is_in_reserved(old), "must be in heap.");
 123   assert(!old_gen()->is_in(old), "must be in young generation.");
 124 
 125   objArrayOop obj = objArrayOop(old->forwardee());
 126   // Process ParGCArrayScanChunk elements now
 127   // and push the remainder back onto queue
 128   int start     = arrayOop(old)->length();
 129   int end       = obj->length();
 130   int remainder = end - start;
 131   assert(start <= end, "just checking");
 132   if (remainder > 2 * ParGCArrayScanChunk) {
 133     // Test above combines last partial chunk with a full chunk
 134     end = start + ParGCArrayScanChunk;
 135     arrayOop(old)->set_length(end);
 136     // Push remainder.
 137     bool ok = work_queue()->push(old);
 138     assert(ok, "just popped, push must be okay");
 139   } else {
 140     // Restore length so that it can be used if there
 141     // is a promotion failure and forwarding pointers
 142     // must be removed.
 143     arrayOop(old)->set_length(end);
 144   }
 145 
 146   // process our set of indices (include header in first chunk)
 147   // should make sure end is even (aligned to HeapWord in case of compressed oops)
 148   if ((HeapWord *)obj < young_old_boundary()) {
 149     // object is in to_space
 150     obj->oop_iterate_range(&_to_space_closure, start, end);
 151   } else {
 152     // object is in old generation
 153     obj->oop_iterate_range(&_old_gen_closure, start, end);
 154   }
 155 }
 156 
 157 
 158 void ParScanThreadState::trim_queues(int max_size) {
 159   ObjToScanQueue* queue = work_queue();
 160   do {
 161     while (queue->size() > (juint)max_size) {
 162       oop obj_to_scan;
 163       if (queue->pop_local(obj_to_scan)) {
 164         if ((HeapWord *)obj_to_scan < young_old_boundary()) {
 165           if (obj_to_scan->is_objArray() &&
 166               obj_to_scan->is_forwarded() &&
 167               obj_to_scan->forwardee() != obj_to_scan) {
 168             scan_partial_array_and_push_remainder(obj_to_scan);
 169           } else {
 170             // object is in to_space
 171             obj_to_scan->oop_iterate(&_to_space_closure);
 172           }
 173         } else {
 174           // object is in old generation
 175           obj_to_scan->oop_iterate(&_old_gen_closure);
 176         }
 177       }
 178     }
 179     // For the  case of compressed oops, we have a private, non-shared
 180     // overflow stack, so we eagerly drain it so as to more evenly
 181     // distribute load early. Note: this may be good to do in
 182     // general rather than delay for the final stealing phase.
 183     // If applicable, we'll transfer a set of objects over to our
 184     // work queue, allowing them to be stolen and draining our
 185     // private overflow stack.
 186   } while (ParGCTrimOverflow && young_gen()->take_from_overflow_list(this));
 187 }
 188 
 189 bool ParScanThreadState::take_from_overflow_stack() {
 190   assert(ParGCUseLocalOverflow, "Else should not call");
 191   assert(young_gen()->overflow_list() == NULL, "Error");
 192   ObjToScanQueue* queue = work_queue();
 193   Stack<oop, mtGC>* const of_stack = overflow_stack();
 194   const size_t num_overflow_elems = of_stack->size();
 195   const size_t space_available = queue->max_elems() - queue->size();
 196   const size_t num_take_elems = MIN3(space_available / 4,
 197                                      ParGCDesiredObjsFromOverflowList,
 198                                      num_overflow_elems);
 199   // Transfer the most recent num_take_elems from the overflow
 200   // stack to our work queue.
 201   for (size_t i = 0; i != num_take_elems; i++) {
 202     oop cur = of_stack->pop();
 203     oop obj_to_push = cur->forwardee();
 204     assert(Universe::heap()->is_in_reserved(cur), "Should be in heap");
 205     assert(!old_gen()->is_in_reserved(cur), "Should be in young gen");
 206     assert(Universe::heap()->is_in_reserved(obj_to_push), "Should be in heap");
 207     if (should_be_partially_scanned(obj_to_push, cur)) {
 208       assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned");
 209       obj_to_push = cur;
 210     }
 211     bool ok = queue->push(obj_to_push);
 212     assert(ok, "Should have succeeded");
 213   }
 214   assert(young_gen()->overflow_list() == NULL, "Error");
 215   return num_take_elems > 0;  // was something transferred?
 216 }
 217 
 218 void ParScanThreadState::push_on_overflow_stack(oop p) {
 219   assert(ParGCUseLocalOverflow, "Else should not call");
 220   overflow_stack()->push(p);
 221   assert(young_gen()->overflow_list() == NULL, "Error");
 222 }
 223 
 224 HeapWord* ParScanThreadState::alloc_in_to_space_slow(size_t word_sz) {
 225 
 226   // Otherwise, if the object is small enough, try to reallocate the
 227   // buffer.
 228   HeapWord* obj = NULL;
 229   if (!_to_space_full) {
 230     ParGCAllocBuffer* const plab = to_space_alloc_buffer();
 231     Space*            const sp   = to_space();
 232     if (word_sz * 100 <
 233         ParallelGCBufferWastePct * plab->word_sz()) {
 234       // Is small enough; abandon this buffer and start a new one.
 235       plab->retire(false, false);
 236       size_t buf_size = plab->word_sz();
 237       HeapWord* buf_space = sp->par_allocate(buf_size);
 238       if (buf_space == NULL) {
 239         const size_t min_bytes =
 240           ParGCAllocBuffer::min_size() << LogHeapWordSize;
 241         size_t free_bytes = sp->free();
 242         while(buf_space == NULL && free_bytes >= min_bytes) {
 243           buf_size = free_bytes >> LogHeapWordSize;
 244           assert(buf_size == (size_t)align_object_size(buf_size),
 245                  "Invariant");
 246           buf_space  = sp->par_allocate(buf_size);
 247           free_bytes = sp->free();
 248         }
 249       }
 250       if (buf_space != NULL) {
 251         plab->set_word_size(buf_size);
 252         plab->set_buf(buf_space);
 253         record_survivor_plab(buf_space, buf_size);
 254         obj = plab->allocate_aligned(word_sz, SurvivorAlignmentInBytes);
 255         // Note that we cannot compare buf_size < word_sz below
 256         // because of AlignmentReserve (see ParGCAllocBuffer::allocate()).
 257         assert(obj != NULL || plab->words_remaining() < word_sz,
 258                "Else should have been able to allocate");
 259         // It's conceivable that we may be able to use the
 260         // buffer we just grabbed for subsequent small requests
 261         // even if not for this one.
 262       } else {
 263         // We're used up.
 264         _to_space_full = true;
 265       }
 266 
 267     } else {
 268       // Too large; allocate the object individually.
 269       obj = sp->par_allocate(word_sz);
 270     }
 271   }
 272   return obj;
 273 }
 274 
 275 
 276 void ParScanThreadState::undo_alloc_in_to_space(HeapWord* obj,
 277                                                 size_t word_sz) {
 278   // Is the alloc in the current alloc buffer?
 279   if (to_space_alloc_buffer()->contains(obj)) {
 280     assert(to_space_alloc_buffer()->contains(obj + word_sz - 1),
 281            "Should contain whole object.");
 282     to_space_alloc_buffer()->undo_allocation(obj, word_sz);
 283   } else {
 284     CollectedHeap::fill_with_object(obj, word_sz);
 285   }
 286 }
 287 
 288 void ParScanThreadState::print_promotion_failure_size() {
 289   if (_promotion_failed_info.has_failed() && PrintPromotionFailure) {
 290     gclog_or_tty->print(" (%d: promotion failure size = " SIZE_FORMAT ") ",
 291                         _thread_num, _promotion_failed_info.first_size());
 292   }
 293 }
 294 
 295 class ParScanThreadStateSet: private ResourceArray {
 296 public:
 297   // Initializes states for the specified number of threads;
 298   ParScanThreadStateSet(int                     num_threads,
 299                         Space&                  to_space,
 300                         ParNewGeneration&       gen,
 301                         Generation&             old_gen,
 302                         ObjToScanQueueSet&      queue_set,
 303                         Stack<oop, mtGC>*       overflow_stacks_,
 304                         size_t                  desired_plab_sz,
 305                         ParallelTaskTerminator& term);
 306 
 307   ~ParScanThreadStateSet() { TASKQUEUE_STATS_ONLY(reset_stats()); }
 308 
 309   inline ParScanThreadState& thread_state(int i);
 310 
 311   void trace_promotion_failed(YoungGCTracer& gc_tracer);
 312   void reset(int active_workers, bool promotion_failed);
 313   void flush();
 314 
 315   #if TASKQUEUE_STATS
 316   static void
 317     print_termination_stats_hdr(outputStream* const st = gclog_or_tty);
 318   void print_termination_stats(outputStream* const st = gclog_or_tty);
 319   static void
 320     print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 321   void print_taskqueue_stats(outputStream* const st = gclog_or_tty);
 322   void reset_stats();
 323   #endif // TASKQUEUE_STATS
 324 
 325 private:
 326   ParallelTaskTerminator& _term;
 327   ParNewGeneration&       _gen;
 328   Generation&             _next_gen;
 329  public:
 330   bool is_valid(int id) const { return id < length(); }
 331   ParallelTaskTerminator* terminator() { return &_term; }
 332 };
 333 
 334 
 335 ParScanThreadStateSet::ParScanThreadStateSet(
 336   int num_threads, Space& to_space, ParNewGeneration& gen,
 337   Generation& old_gen, ObjToScanQueueSet& queue_set,
 338   Stack<oop, mtGC>* overflow_stacks,
 339   size_t desired_plab_sz, ParallelTaskTerminator& term)
 340   : ResourceArray(sizeof(ParScanThreadState), num_threads),
 341     _gen(gen), _next_gen(old_gen), _term(term)
 342 {
 343   assert(num_threads > 0, "sanity check!");
 344   assert(ParGCUseLocalOverflow == (overflow_stacks != NULL),
 345          "overflow_stack allocation mismatch");
 346   // Initialize states.
 347   for (int i = 0; i < num_threads; ++i) {
 348     new ((ParScanThreadState*)_data + i)
 349         ParScanThreadState(&to_space, &gen, &old_gen, i, &queue_set,
 350                            overflow_stacks, desired_plab_sz, term);
 351   }
 352 }
 353 
 354 inline ParScanThreadState& ParScanThreadStateSet::thread_state(int i)
 355 {
 356   assert(i >= 0 && i < length(), "sanity check!");
 357   return ((ParScanThreadState*)_data)[i];
 358 }
 359 
 360 void ParScanThreadStateSet::trace_promotion_failed(YoungGCTracer& gc_tracer) {
 361   for (int i = 0; i < length(); ++i) {
 362     if (thread_state(i).promotion_failed()) {
 363       gc_tracer.report_promotion_failed(thread_state(i).promotion_failed_info());
 364       thread_state(i).promotion_failed_info().reset();
 365     }
 366   }
 367 }
 368 
 369 void ParScanThreadStateSet::reset(int active_threads, bool promotion_failed)
 370 {
 371   _term.reset_for_reuse(active_threads);
 372   if (promotion_failed) {
 373     for (int i = 0; i < length(); ++i) {
 374       thread_state(i).print_promotion_failure_size();
 375     }
 376   }
 377 }
 378 
 379 #if TASKQUEUE_STATS
 380 void
 381 ParScanThreadState::reset_stats()
 382 {
 383   taskqueue_stats().reset();
 384   _term_attempts = 0;
 385   _overflow_refills = 0;
 386   _overflow_refill_objs = 0;
 387 }
 388 
 389 void ParScanThreadStateSet::reset_stats()
 390 {
 391   for (int i = 0; i < length(); ++i) {
 392     thread_state(i).reset_stats();
 393   }
 394 }
 395 
 396 void
 397 ParScanThreadStateSet::print_termination_stats_hdr(outputStream* const st)
 398 {
 399   st->print_raw_cr("GC Termination Stats");
 400   st->print_raw_cr("     elapsed  --strong roots-- "
 401                    "-------termination-------");
 402   st->print_raw_cr("thr     ms        ms       %   "
 403                    "    ms       %   attempts");
 404   st->print_raw_cr("--- --------- --------- ------ "
 405                    "--------- ------ --------");
 406 }
 407 
 408 void ParScanThreadStateSet::print_termination_stats(outputStream* const st)
 409 {
 410   print_termination_stats_hdr(st);
 411 
 412   for (int i = 0; i < length(); ++i) {
 413     const ParScanThreadState & pss = thread_state(i);
 414     const double elapsed_ms = pss.elapsed_time() * 1000.0;
 415     const double s_roots_ms = pss.strong_roots_time() * 1000.0;
 416     const double term_ms = pss.term_time() * 1000.0;
 417     st->print_cr("%3d %9.2f %9.2f %6.2f "
 418                  "%9.2f %6.2f " SIZE_FORMAT_W(8),
 419                  i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
 420                  term_ms, term_ms * 100 / elapsed_ms, pss.term_attempts());
 421   }
 422 }
 423 
 424 // Print stats related to work queue activity.
 425 void ParScanThreadStateSet::print_taskqueue_stats_hdr(outputStream* const st)
 426 {
 427   st->print_raw_cr("GC Task Stats");
 428   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
 429   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
 430 }
 431 
 432 void ParScanThreadStateSet::print_taskqueue_stats(outputStream* const st)
 433 {
 434   print_taskqueue_stats_hdr(st);
 435 
 436   TaskQueueStats totals;
 437   for (int i = 0; i < length(); ++i) {
 438     const ParScanThreadState & pss = thread_state(i);
 439     const TaskQueueStats & stats = pss.taskqueue_stats();
 440     st->print("%3d ", i); stats.print(st); st->cr();
 441     totals += stats;
 442 
 443     if (pss.overflow_refills() > 0) {
 444       st->print_cr("    " SIZE_FORMAT_W(10) " overflow refills    "
 445                    SIZE_FORMAT_W(10) " overflow objects",
 446                    pss.overflow_refills(), pss.overflow_refill_objs());
 447     }
 448   }
 449   st->print("tot "); totals.print(st); st->cr();
 450 
 451   DEBUG_ONLY(totals.verify());
 452 }
 453 #endif // TASKQUEUE_STATS
 454 
 455 void ParScanThreadStateSet::flush()
 456 {
 457   // Work in this loop should be kept as lightweight as
 458   // possible since this might otherwise become a bottleneck
 459   // to scaling. Should we add heavy-weight work into this
 460   // loop, consider parallelizing the loop into the worker threads.
 461   for (int i = 0; i < length(); ++i) {
 462     ParScanThreadState& par_scan_state = thread_state(i);
 463 
 464     // Flush stats related to To-space PLAB activity and
 465     // retire the last buffer.
 466     par_scan_state.to_space_alloc_buffer()->
 467       flush_stats_and_retire(_gen.plab_stats(),
 468                              true /* end_of_gc */,
 469                              false /* retain */);
 470 
 471     // Every thread has its own age table.  We need to merge
 472     // them all into one.
 473     ageTable *local_table = par_scan_state.age_table();
 474     _gen.age_table()->merge(local_table);
 475 
 476     // Inform old gen that we're done.
 477     _next_gen.par_promote_alloc_done(i);
 478     _next_gen.par_oop_since_save_marks_iterate_done(i);
 479   }
 480 
 481   if (UseConcMarkSweepGC && ParallelGCThreads > 0) {
 482     // We need to call this even when ResizeOldPLAB is disabled
 483     // so as to avoid breaking some asserts. While we may be able
 484     // to avoid this by reorganizing the code a bit, I am loathe
 485     // to do that unless we find cases where ergo leads to bad
 486     // performance.
 487     CFLS_LAB::compute_desired_plab_size();
 488   }
 489 }
 490 
 491 ParScanClosure::ParScanClosure(ParNewGeneration* g,
 492                                ParScanThreadState* par_scan_state) :
 493   OopsInKlassOrGenClosure(g), _par_scan_state(par_scan_state), _g(g)
 494 {
 495   assert(_g->level() == 0, "Optimized for youngest generation");
 496   _boundary = _g->reserved().end();
 497 }
 498 
 499 void ParScanWithBarrierClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, true, false); }
 500 void ParScanWithBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, false); }
 501 
 502 void ParScanWithoutBarrierClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, false, false); }
 503 void ParScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, false); }
 504 
 505 void ParRootScanWithBarrierTwoGensClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, true, true); }
 506 void ParRootScanWithBarrierTwoGensClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, true); }
 507 
 508 void ParRootScanWithoutBarrierClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, false, true); }
 509 void ParRootScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, true); }
 510 
 511 ParScanWeakRefClosure::ParScanWeakRefClosure(ParNewGeneration* g,
 512                                              ParScanThreadState* par_scan_state)
 513   : ScanWeakRefClosure(g), _par_scan_state(par_scan_state)
 514 {}
 515 
 516 void ParScanWeakRefClosure::do_oop(oop* p)       { ParScanWeakRefClosure::do_oop_work(p); }
 517 void ParScanWeakRefClosure::do_oop(narrowOop* p) { ParScanWeakRefClosure::do_oop_work(p); }
 518 
 519 #ifdef WIN32
 520 #pragma warning(disable: 4786) /* identifier was truncated to '255' characters in the browser information */
 521 #endif
 522 
 523 ParEvacuateFollowersClosure::ParEvacuateFollowersClosure(
 524     ParScanThreadState* par_scan_state_,
 525     ParScanWithoutBarrierClosure* to_space_closure_,
 526     ParScanWithBarrierClosure* old_gen_closure_,
 527     ParRootScanWithoutBarrierClosure* to_space_root_closure_,
 528     ParNewGeneration* par_gen_,
 529     ParRootScanWithBarrierTwoGensClosure* old_gen_root_closure_,
 530     ObjToScanQueueSet* task_queues_,
 531     ParallelTaskTerminator* terminator_) :
 532 
 533     _par_scan_state(par_scan_state_),
 534     _to_space_closure(to_space_closure_),
 535     _old_gen_closure(old_gen_closure_),
 536     _to_space_root_closure(to_space_root_closure_),
 537     _old_gen_root_closure(old_gen_root_closure_),
 538     _par_gen(par_gen_),
 539     _task_queues(task_queues_),
 540     _terminator(terminator_)
 541 {}
 542 
 543 void ParEvacuateFollowersClosure::do_void() {
 544   ObjToScanQueue* work_q = par_scan_state()->work_queue();
 545 
 546   while (true) {
 547 
 548     // Scan to-space and old-gen objs until we run out of both.
 549     oop obj_to_scan;
 550     par_scan_state()->trim_queues(0);
 551 
 552     // We have no local work, attempt to steal from other threads.
 553 
 554     // attempt to steal work from promoted.
 555     if (task_queues()->steal(par_scan_state()->thread_num(),
 556                              par_scan_state()->hash_seed(),
 557                              obj_to_scan)) {
 558       bool res = work_q->push(obj_to_scan);
 559       assert(res, "Empty queue should have room for a push.");
 560 
 561       //   if successful, goto Start.
 562       continue;
 563 
 564       // try global overflow list.
 565     } else if (par_gen()->take_from_overflow_list(par_scan_state())) {
 566       continue;
 567     }
 568 
 569     // Otherwise, offer termination.
 570     par_scan_state()->start_term_time();
 571     if (terminator()->offer_termination()) break;
 572     par_scan_state()->end_term_time();
 573   }
 574   assert(par_gen()->_overflow_list == NULL && par_gen()->_num_par_pushes == 0,
 575          "Broken overflow list?");
 576   // Finish the last termination pause.
 577   par_scan_state()->end_term_time();
 578 }
 579 
 580 ParNewGenTask::ParNewGenTask(ParNewGeneration* gen, Generation* next_gen,
 581                 HeapWord* young_old_boundary, ParScanThreadStateSet* state_set) :
 582     AbstractGangTask("ParNewGeneration collection"),
 583     _gen(gen), _next_gen(next_gen),
 584     _young_old_boundary(young_old_boundary),
 585     _state_set(state_set)
 586   {}
 587 
 588 // Reset the terminator for the given number of
 589 // active threads.
 590 void ParNewGenTask::set_for_termination(int active_workers) {
 591   _state_set->reset(active_workers, _gen->promotion_failed());
 592   // Should the heap be passed in?  There's only 1 for now so
 593   // grab it instead.
 594   GenCollectedHeap* gch = GenCollectedHeap::heap();
 595   gch->set_n_termination(active_workers);
 596 }
 597 
 598 void ParNewGenTask::work(uint worker_id) {
 599   GenCollectedHeap* gch = GenCollectedHeap::heap();
 600   // Since this is being done in a separate thread, need new resource
 601   // and handle marks.
 602   ResourceMark rm;
 603   HandleMark hm;
 604   // We would need multiple old-gen queues otherwise.
 605   assert(gch->n_gens() == 2, "Par young collection currently only works with one older gen.");
 606 
 607   Generation* old_gen = gch->next_gen(_gen);
 608 
 609   ParScanThreadState& par_scan_state = _state_set->thread_state(worker_id);
 610   assert(_state_set->is_valid(worker_id), "Should not have been called");
 611 
 612   par_scan_state.set_young_old_boundary(_young_old_boundary);
 613 
 614   KlassScanClosure klass_scan_closure(&par_scan_state.to_space_root_closure(),
 615                                       gch->rem_set()->klass_rem_set());
 616   CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
 617                                            &par_scan_state.to_space_root_closure(),
 618                                            false);
 619 
 620   par_scan_state.start_strong_roots();
 621   gch->gen_process_roots(_gen->level(),
 622                          true,  // Process younger gens, if any,
 623                                 // as strong roots.
 624                          false, // no scope; this is parallel code
 625                          GenCollectedHeap::SO_ScavengeCodeCache,
 626                          GenCollectedHeap::StrongAndWeakRoots,
 627                          &par_scan_state.to_space_root_closure(),
 628                          &par_scan_state.older_gen_closure(),
 629                          &cld_scan_closure);
 630 
 631   par_scan_state.end_strong_roots();
 632 
 633   // "evacuate followers".
 634   par_scan_state.evacuate_followers_closure().do_void();
 635 }
 636 
 637 #ifdef _MSC_VER
 638 #pragma warning( push )
 639 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 640 #endif
 641 ParNewGeneration::
 642 ParNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level)
 643   : DefNewGeneration(rs, initial_byte_size, level, "PCopy"),
 644   _overflow_list(NULL),
 645   _is_alive_closure(this),
 646   _plab_stats(YoungPLABSize, PLABWeight)
 647 {
 648   NOT_PRODUCT(_overflow_counter = ParGCWorkQueueOverflowInterval;)
 649   NOT_PRODUCT(_num_par_pushes = 0;)
 650   _task_queues = new ObjToScanQueueSet(ParallelGCThreads);
 651   guarantee(_task_queues != NULL, "task_queues allocation failure.");
 652 
 653   for (uint i1 = 0; i1 < ParallelGCThreads; i1++) {
 654     ObjToScanQueue *q = new ObjToScanQueue();
 655     guarantee(q != NULL, "work_queue Allocation failure.");
 656     _task_queues->register_queue(i1, q);
 657   }
 658 
 659   for (uint i2 = 0; i2 < ParallelGCThreads; i2++)
 660     _task_queues->queue(i2)->initialize();
 661 
 662   _overflow_stacks = NULL;
 663   if (ParGCUseLocalOverflow) {
 664 
 665     // typedef to workaround NEW_C_HEAP_ARRAY macro, which can not deal
 666     // with ','
 667     typedef Stack<oop, mtGC> GCOopStack;
 668 
 669     _overflow_stacks = NEW_C_HEAP_ARRAY(GCOopStack, ParallelGCThreads, mtGC);
 670     for (size_t i = 0; i < ParallelGCThreads; ++i) {
 671       new (_overflow_stacks + i) Stack<oop, mtGC>();
 672     }
 673   }
 674 
 675   if (UsePerfData) {
 676     EXCEPTION_MARK;
 677     ResourceMark rm;
 678 
 679     const char* cname =
 680          PerfDataManager::counter_name(_gen_counters->name_space(), "threads");
 681     PerfDataManager::create_constant(SUN_GC, cname, PerfData::U_None,
 682                                      ParallelGCThreads, CHECK);
 683   }
 684 }
 685 #ifdef _MSC_VER
 686 #pragma warning( pop )
 687 #endif
 688 
 689 // ParNewGeneration::
 690 ParKeepAliveClosure::ParKeepAliveClosure(ParScanWeakRefClosure* cl) :
 691   DefNewGeneration::KeepAliveClosure(cl), _par_cl(cl) {}
 692 
 693 template <class T>
 694 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop_work(T* p) {
 695 #ifdef ASSERT
 696   {
 697     assert(!oopDesc::is_null(*p), "expected non-null ref");
 698     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
 699     // We never expect to see a null reference being processed
 700     // as a weak reference.
 701     assert(obj->is_oop(), "expected an oop while scanning weak refs");
 702   }
 703 #endif // ASSERT
 704 
 705   _par_cl->do_oop_nv(p);
 706 
 707   if (Universe::heap()->is_in_reserved(p)) {
 708     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
 709     _rs->write_ref_field_gc_par(p, obj);
 710   }
 711 }
 712 
 713 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(oop* p)       { ParKeepAliveClosure::do_oop_work(p); }
 714 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(narrowOop* p) { ParKeepAliveClosure::do_oop_work(p); }
 715 
 716 // ParNewGeneration::
 717 KeepAliveClosure::KeepAliveClosure(ScanWeakRefClosure* cl) :
 718   DefNewGeneration::KeepAliveClosure(cl) {}
 719 
 720 template <class T>
 721 void /*ParNewGeneration::*/KeepAliveClosure::do_oop_work(T* p) {
 722 #ifdef ASSERT
 723   {
 724     assert(!oopDesc::is_null(*p), "expected non-null ref");
 725     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
 726     // We never expect to see a null reference being processed
 727     // as a weak reference.
 728     assert(obj->is_oop(), "expected an oop while scanning weak refs");
 729   }
 730 #endif // ASSERT
 731 
 732   _cl->do_oop_nv(p);
 733 
 734   if (Universe::heap()->is_in_reserved(p)) {
 735     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
 736     _rs->write_ref_field_gc_par(p, obj);
 737   }
 738 }
 739 
 740 void /*ParNewGeneration::*/KeepAliveClosure::do_oop(oop* p)       { KeepAliveClosure::do_oop_work(p); }
 741 void /*ParNewGeneration::*/KeepAliveClosure::do_oop(narrowOop* p) { KeepAliveClosure::do_oop_work(p); }
 742 
 743 template <class T> void ScanClosureWithParBarrier::do_oop_work(T* p) {
 744   T heap_oop = oopDesc::load_heap_oop(p);
 745   if (!oopDesc::is_null(heap_oop)) {
 746     oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
 747     if ((HeapWord*)obj < _boundary) {
 748       assert(!_g->to()->is_in_reserved(obj), "Scanning field twice?");
 749       oop new_obj = obj->is_forwarded()
 750                       ? obj->forwardee()
 751                       : _g->DefNewGeneration::copy_to_survivor_space(obj);
 752       oopDesc::encode_store_heap_oop_not_null(p, new_obj);
 753     }
 754     if (_gc_barrier) {
 755       // If p points to a younger generation, mark the card.
 756       if ((HeapWord*)obj < _gen_boundary) {
 757         _rs->write_ref_field_gc_par(p, obj);
 758       }
 759     }
 760   }
 761 }
 762 
 763 void ScanClosureWithParBarrier::do_oop(oop* p)       { ScanClosureWithParBarrier::do_oop_work(p); }
 764 void ScanClosureWithParBarrier::do_oop(narrowOop* p) { ScanClosureWithParBarrier::do_oop_work(p); }
 765 
 766 class ParNewRefProcTaskProxy: public AbstractGangTask {
 767   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
 768 public:
 769   ParNewRefProcTaskProxy(ProcessTask& task, ParNewGeneration& gen,
 770                          Generation& next_gen,
 771                          HeapWord* young_old_boundary,
 772                          ParScanThreadStateSet& state_set);
 773 
 774 private:
 775   virtual void work(uint worker_id);
 776   virtual void set_for_termination(int active_workers) {
 777     _state_set.terminator()->reset_for_reuse(active_workers);
 778   }
 779 private:
 780   ParNewGeneration&      _gen;
 781   ProcessTask&           _task;
 782   Generation&            _next_gen;
 783   HeapWord*              _young_old_boundary;
 784   ParScanThreadStateSet& _state_set;
 785 };
 786 
 787 ParNewRefProcTaskProxy::ParNewRefProcTaskProxy(
 788     ProcessTask& task, ParNewGeneration& gen,
 789     Generation& next_gen,
 790     HeapWord* young_old_boundary,
 791     ParScanThreadStateSet& state_set)
 792   : AbstractGangTask("ParNewGeneration parallel reference processing"),
 793     _gen(gen),
 794     _task(task),
 795     _next_gen(next_gen),
 796     _young_old_boundary(young_old_boundary),
 797     _state_set(state_set)
 798 {
 799 }
 800 
 801 void ParNewRefProcTaskProxy::work(uint worker_id)
 802 {
 803   ResourceMark rm;
 804   HandleMark hm;
 805   ParScanThreadState& par_scan_state = _state_set.thread_state(worker_id);
 806   par_scan_state.set_young_old_boundary(_young_old_boundary);
 807   _task.work(worker_id, par_scan_state.is_alive_closure(),
 808              par_scan_state.keep_alive_closure(),
 809              par_scan_state.evacuate_followers_closure());
 810 }
 811 
 812 class ParNewRefEnqueueTaskProxy: public AbstractGangTask {
 813   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
 814   EnqueueTask& _task;
 815 
 816 public:
 817   ParNewRefEnqueueTaskProxy(EnqueueTask& task)
 818     : AbstractGangTask("ParNewGeneration parallel reference enqueue"),
 819       _task(task)
 820   { }
 821 
 822   virtual void work(uint worker_id)
 823   {
 824     _task.work(worker_id);
 825   }
 826 };
 827 
 828 
 829 void ParNewRefProcTaskExecutor::execute(ProcessTask& task)
 830 {
 831   GenCollectedHeap* gch = GenCollectedHeap::heap();
 832   assert(gch->kind() == CollectedHeap::GenCollectedHeap,
 833          "not a generational heap");
 834   FlexibleWorkGang* workers = gch->workers();
 835   assert(workers != NULL, "Need parallel worker threads.");
 836   _state_set.reset(workers->active_workers(), _generation.promotion_failed());
 837   ParNewRefProcTaskProxy rp_task(task, _generation, *_generation.next_gen(),
 838                                  _generation.reserved().end(), _state_set);
 839   workers->run_task(&rp_task);
 840   _state_set.reset(0 /* bad value in debug if not reset */,
 841                    _generation.promotion_failed());
 842 }
 843 
 844 void ParNewRefProcTaskExecutor::execute(EnqueueTask& task)
 845 {
 846   GenCollectedHeap* gch = GenCollectedHeap::heap();
 847   FlexibleWorkGang* workers = gch->workers();
 848   assert(workers != NULL, "Need parallel worker threads.");
 849   ParNewRefEnqueueTaskProxy enq_task(task);
 850   workers->run_task(&enq_task);
 851 }
 852 
 853 void ParNewRefProcTaskExecutor::set_single_threaded_mode()
 854 {
 855   _state_set.flush();
 856   GenCollectedHeap* gch = GenCollectedHeap::heap();
 857   gch->set_par_threads(0);  // 0 ==> non-parallel.
 858   gch->save_marks();
 859 }
 860 
 861 ScanClosureWithParBarrier::
 862 ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier) :
 863   ScanClosure(g, gc_barrier) {}
 864 
 865 EvacuateFollowersClosureGeneral::
 866 EvacuateFollowersClosureGeneral(GenCollectedHeap* gch, int level,
 867                                 OopsInGenClosure* cur,
 868                                 OopsInGenClosure* older) :
 869   _gch(gch), _level(level),
 870   _scan_cur_or_nonheap(cur), _scan_older(older)
 871 {}
 872 
 873 void EvacuateFollowersClosureGeneral::do_void() {
 874   do {
 875     // Beware: this call will lead to closure applications via virtual
 876     // calls.
 877     _gch->oop_since_save_marks_iterate(_level,
 878                                        _scan_cur_or_nonheap,
 879                                        _scan_older);
 880   } while (!_gch->no_allocs_since_save_marks(_level));
 881 }
 882 
 883 
 884 // A Generation that does parallel young-gen collection.
 885 
 886 bool ParNewGeneration::_avoid_promotion_undo = false;
 887 
 888 void ParNewGeneration::handle_promotion_failed(GenCollectedHeap* gch, ParScanThreadStateSet& thread_state_set, ParNewTracer& gc_tracer) {
 889   assert(_promo_failure_scan_stack.is_empty(), "post condition");
 890   _promo_failure_scan_stack.clear(true); // Clear cached segments.
 891 
 892   remove_forwarding_pointers();
 893   if (PrintGCDetails) {
 894     gclog_or_tty->print(" (promotion failed)");
 895   }
 896   // All the spaces are in play for mark-sweep.
 897   swap_spaces();  // Make life simpler for CMS || rescan; see 6483690.
 898   from()->set_next_compaction_space(to());
 899   gch->set_incremental_collection_failed();
 900   // Inform the next generation that a promotion failure occurred.
 901   _next_gen->promotion_failure_occurred();
 902 
 903   // Trace promotion failure in the parallel GC threads
 904   thread_state_set.trace_promotion_failed(gc_tracer);
 905   // Single threaded code may have reported promotion failure to the global state
 906   if (_promotion_failed_info.has_failed()) {
 907     gc_tracer.report_promotion_failed(_promotion_failed_info);
 908   }
 909   // Reset the PromotionFailureALot counters.
 910   NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
 911 }
 912 
 913 void ParNewGeneration::collect(bool   full,
 914                                bool   clear_all_soft_refs,
 915                                size_t size,
 916                                bool   is_tlab) {
 917   assert(full || size > 0, "otherwise we don't want to collect");
 918 
 919   GenCollectedHeap* gch = GenCollectedHeap::heap();
 920 
 921   _gc_timer->register_gc_start();
 922 
 923   assert(gch->kind() == CollectedHeap::GenCollectedHeap,
 924     "not a CMS generational heap");
 925   AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
 926   FlexibleWorkGang* workers = gch->workers();
 927   assert(workers != NULL, "Need workgang for parallel work");
 928   int active_workers =
 929       AdaptiveSizePolicy::calc_active_workers(workers->total_workers(),
 930                                    workers->active_workers(),
 931                                    Threads::number_of_non_daemon_threads());
 932   workers->set_active_workers(active_workers);
 933   assert(gch->n_gens() == 2,
 934          "Par collection currently only works with single older gen.");
 935   _next_gen = gch->next_gen(this);
 936   // Do we have to avoid promotion_undo?
 937   if (gch->collector_policy()->is_concurrent_mark_sweep_policy()) {
 938     set_avoid_promotion_undo(true);
 939   }
 940 
 941   // If the next generation is too full to accommodate worst-case promotion
 942   // from this generation, pass on collection; let the next generation
 943   // do it.
 944   if (!collection_attempt_is_safe()) {
 945     gch->set_incremental_collection_failed();  // slight lie, in that we did not even attempt one
 946     return;
 947   }
 948   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 949 
 950   ParNewTracer gc_tracer;
 951   gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
 952   gch->trace_heap_before_gc(&gc_tracer);
 953 
 954   init_assuming_no_promotion_failure();
 955 
 956   if (UseAdaptiveSizePolicy) {
 957     set_survivor_overflow(false);
 958     size_policy->minor_collection_begin();
 959   }
 960 
 961   GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id());
 962   // Capture heap used before collection (for printing).
 963   size_t gch_prev_used = gch->used();
 964 
 965   SpecializationStats::clear();
 966 
 967   age_table()->clear();
 968   to()->clear(SpaceDecorator::Mangle);
 969 
 970   gch->save_marks();
 971   assert(workers != NULL, "Need parallel worker threads.");
 972   int n_workers = active_workers;
 973 
 974   // Set the correct parallelism (number of queues) in the reference processor
 975   ref_processor()->set_active_mt_degree(n_workers);
 976 
 977   // Always set the terminator for the active number of workers
 978   // because only those workers go through the termination protocol.
 979   ParallelTaskTerminator _term(n_workers, task_queues());
 980   ParScanThreadStateSet thread_state_set(workers->active_workers(),
 981                                          *to(), *this, *_next_gen, *task_queues(),
 982                                          _overflow_stacks, desired_plab_sz(), _term);
 983 
 984   ParNewGenTask tsk(this, _next_gen, reserved().end(), &thread_state_set);
 985   gch->set_par_threads(n_workers);
 986   gch->rem_set()->prepare_for_younger_refs_iterate(true);
 987   // It turns out that even when we're using 1 thread, doing the work in a
 988   // separate thread causes wide variance in run times.  We can't help this
 989   // in the multi-threaded case, but we special-case n=1 here to get
 990   // repeatable measurements of the 1-thread overhead of the parallel code.
 991   if (n_workers > 1) {
 992     GenCollectedHeap::StrongRootsScope srs(gch);
 993     workers->run_task(&tsk);
 994   } else {
 995     GenCollectedHeap::StrongRootsScope srs(gch);
 996     tsk.work(0);
 997   }
 998   thread_state_set.reset(0 /* Bad value in debug if not reset */,
 999                          promotion_failed());
1000 
1001   // Process (weak) reference objects found during scavenge.
1002   ReferenceProcessor* rp = ref_processor();
1003   IsAliveClosure is_alive(this);
1004   ScanWeakRefClosure scan_weak_ref(this);
1005   KeepAliveClosure keep_alive(&scan_weak_ref);
1006   ScanClosure               scan_without_gc_barrier(this, false);
1007   ScanClosureWithParBarrier scan_with_gc_barrier(this, true);
1008   set_promo_failure_scan_stack_closure(&scan_without_gc_barrier);
1009   EvacuateFollowersClosureGeneral evacuate_followers(gch, _level,
1010     &scan_without_gc_barrier, &scan_with_gc_barrier);
1011   rp->setup_policy(clear_all_soft_refs);
1012   // Can  the mt_degree be set later (at run_task() time would be best)?
1013   rp->set_active_mt_degree(active_workers);
1014   ReferenceProcessorStats stats;
1015   if (rp->processing_is_mt()) {
1016     ParNewRefProcTaskExecutor task_executor(*this, thread_state_set);
1017     stats = rp->process_discovered_references(&is_alive, &keep_alive,
1018                                               &evacuate_followers, &task_executor,
1019                                               _gc_timer, gc_tracer.gc_id());
1020   } else {
1021     thread_state_set.flush();
1022     gch->set_par_threads(0);  // 0 ==> non-parallel.
1023     gch->save_marks();
1024     stats = rp->process_discovered_references(&is_alive, &keep_alive,
1025                                               &evacuate_followers, NULL,
1026                                               _gc_timer, gc_tracer.gc_id());
1027   }
1028   gc_tracer.report_gc_reference_stats(stats);
1029   if (!promotion_failed()) {
1030     // Swap the survivor spaces.
1031     eden()->clear(SpaceDecorator::Mangle);
1032     from()->clear(SpaceDecorator::Mangle);
1033     if (ZapUnusedHeapArea) {
1034       // This is now done here because of the piece-meal mangling which
1035       // can check for valid mangling at intermediate points in the
1036       // collection(s).  When a minor collection fails to collect
1037       // sufficient space resizing of the young generation can occur
1038       // an redistribute the spaces in the young generation.  Mangle
1039       // here so that unzapped regions don't get distributed to
1040       // other spaces.
1041       to()->mangle_unused_area();
1042     }
1043     swap_spaces();
1044 
1045     // A successful scavenge should restart the GC time limit count which is
1046     // for full GC's.
1047     size_policy->reset_gc_overhead_limit_count();
1048 
1049     assert(to()->is_empty(), "to space should be empty now");
1050 
1051     adjust_desired_tenuring_threshold(gc_tracer);
1052   } else {
1053     handle_promotion_failed(gch, thread_state_set, gc_tracer);
1054   }
1055   // set new iteration safe limit for the survivor spaces
1056   from()->set_concurrent_iteration_safe_limit(from()->top());
1057   to()->set_concurrent_iteration_safe_limit(to()->top());
1058 
1059   if (ResizePLAB) {
1060     plab_stats()->adjust_desired_plab_sz(n_workers);
1061   }
1062 
1063   if (PrintGC && !PrintGCDetails) {
1064     gch->print_heap_change(gch_prev_used);
1065   }
1066 
1067   if (PrintGCDetails && ParallelGCVerbose) {
1068     TASKQUEUE_STATS_ONLY(thread_state_set.print_termination_stats());
1069     TASKQUEUE_STATS_ONLY(thread_state_set.print_taskqueue_stats());
1070   }
1071 
1072   if (UseAdaptiveSizePolicy) {
1073     size_policy->minor_collection_end(gch->gc_cause());
1074     size_policy->avg_survived()->sample(from()->used());
1075   }
1076 
1077   // We need to use a monotonically non-deccreasing time in ms
1078   // or we will see time-warp warnings and os::javaTimeMillis()
1079   // does not guarantee monotonicity.
1080   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
1081   update_time_of_last_gc(now);
1082 
1083   SpecializationStats::print();
1084 
1085   rp->set_enqueuing_is_done(true);
1086   if (rp->processing_is_mt()) {
1087     ParNewRefProcTaskExecutor task_executor(*this, thread_state_set);
1088     rp->enqueue_discovered_references(&task_executor);
1089   } else {
1090     rp->enqueue_discovered_references(NULL);
1091   }
1092   rp->verify_no_references_recorded();
1093 
1094   gch->trace_heap_after_gc(&gc_tracer);
1095   gc_tracer.report_tenuring_threshold(tenuring_threshold());
1096 
1097   _gc_timer->register_gc_end();
1098 
1099   gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
1100 }
1101 
1102 static int sum;
1103 void ParNewGeneration::waste_some_time() {
1104   for (int i = 0; i < 100; i++) {
1105     sum += i;
1106   }
1107 }
1108 
1109 static const oop ClaimedForwardPtr = cast_to_oop<intptr_t>(0x4);
1110 
1111 // Because of concurrency, there are times where an object for which
1112 // "is_forwarded()" is true contains an "interim" forwarding pointer
1113 // value.  Such a value will soon be overwritten with a real value.
1114 // This method requires "obj" to have a forwarding pointer, and waits, if
1115 // necessary for a real one to be inserted, and returns it.
1116 
1117 oop ParNewGeneration::real_forwardee(oop obj) {
1118   oop forward_ptr = obj->forwardee();
1119   if (forward_ptr != ClaimedForwardPtr) {
1120     return forward_ptr;
1121   } else {
1122     return real_forwardee_slow(obj);
1123   }
1124 }
1125 
1126 oop ParNewGeneration::real_forwardee_slow(oop obj) {
1127   // Spin-read if it is claimed but not yet written by another thread.
1128   oop forward_ptr = obj->forwardee();
1129   while (forward_ptr == ClaimedForwardPtr) {
1130     waste_some_time();
1131     assert(obj->is_forwarded(), "precondition");
1132     forward_ptr = obj->forwardee();
1133   }
1134   return forward_ptr;
1135 }
1136 
1137 #ifdef ASSERT
1138 bool ParNewGeneration::is_legal_forward_ptr(oop p) {
1139   return
1140     (_avoid_promotion_undo && p == ClaimedForwardPtr)
1141     || Universe::heap()->is_in_reserved(p);
1142 }
1143 #endif
1144 
1145 void ParNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
1146   if (m->must_be_preserved_for_promotion_failure(obj)) {
1147     // We should really have separate per-worker stacks, rather
1148     // than use locking of a common pair of stacks.
1149     MutexLocker ml(ParGCRareEvent_lock);
1150     preserve_mark(obj, m);
1151   }
1152 }
1153 
1154 // Multiple GC threads may try to promote an object.  If the object
1155 // is successfully promoted, a forwarding pointer will be installed in
1156 // the object in the young generation.  This method claims the right
1157 // to install the forwarding pointer before it copies the object,
1158 // thus avoiding the need to undo the copy as in
1159 // copy_to_survivor_space_avoiding_with_undo.
1160 
1161 oop ParNewGeneration::copy_to_survivor_space_avoiding_promotion_undo(
1162         ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) {
1163   // In the sequential version, this assert also says that the object is
1164   // not forwarded.  That might not be the case here.  It is the case that
1165   // the caller observed it to be not forwarded at some time in the past.
1166   assert(is_in_reserved(old), "shouldn't be scavenging this oop");
1167 
1168   // The sequential code read "old->age()" below.  That doesn't work here,
1169   // since the age is in the mark word, and that might be overwritten with
1170   // a forwarding pointer by a parallel thread.  So we must save the mark
1171   // word in a local and then analyze it.
1172   oopDesc dummyOld;
1173   dummyOld.set_mark(m);
1174   assert(!dummyOld.is_forwarded(),
1175          "should not be called with forwarding pointer mark word.");
1176 
1177   oop new_obj = NULL;
1178   oop forward_ptr;
1179 
1180   // Try allocating obj in to-space (unless too old)
1181   if (dummyOld.age() < tenuring_threshold()) {
1182     new_obj = (oop)par_scan_state->alloc_in_to_space(sz);
1183     if (new_obj == NULL) {
1184       set_survivor_overflow(true);
1185     }
1186   }
1187 
1188   if (new_obj == NULL) {
1189     // Either to-space is full or we decided to promote
1190     // try allocating obj tenured
1191 
1192     // Attempt to install a null forwarding pointer (atomically),
1193     // to claim the right to install the real forwarding pointer.
1194     forward_ptr = old->forward_to_atomic(ClaimedForwardPtr);
1195     if (forward_ptr != NULL) {
1196       // someone else beat us to it.
1197         return real_forwardee(old);
1198     }
1199 
1200     if (!_promotion_failed) {
1201       new_obj = _next_gen->par_promote(par_scan_state->thread_num(),
1202                                         old, m, sz);
1203     }
1204 
1205     if (new_obj == NULL) {
1206       // promotion failed, forward to self
1207       _promotion_failed = true;
1208       new_obj = old;
1209 
1210       preserve_mark_if_necessary(old, m);
1211       par_scan_state->register_promotion_failure(sz);
1212     }
1213 
1214     old->forward_to(new_obj);
1215     forward_ptr = NULL;
1216   } else {
1217     // Is in to-space; do copying ourselves.
1218     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz);
1219     forward_ptr = old->forward_to_atomic(new_obj);
1220     // Restore the mark word copied above.
1221     new_obj->set_mark(m);
1222     // Increment age if obj still in new generation
1223     new_obj->incr_age();
1224     par_scan_state->age_table()->add(new_obj, sz);
1225   }
1226   assert(new_obj != NULL, "just checking");
1227 
1228 #ifndef PRODUCT
1229   // This code must come after the CAS test, or it will print incorrect
1230   // information.
1231   if (TraceScavenge) {
1232     gclog_or_tty->print_cr("{%s %s " PTR_FORMAT " -> " PTR_FORMAT " (%d)}",
1233        is_in_reserved(new_obj) ? "copying" : "tenuring",
1234        new_obj->klass()->internal_name(), (void *)old, (void *)new_obj, new_obj->size());
1235   }
1236 #endif
1237 
1238   if (forward_ptr == NULL) {
1239     oop obj_to_push = new_obj;
1240     if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) {
1241       // Length field used as index of next element to be scanned.
1242       // Real length can be obtained from real_forwardee()
1243       arrayOop(old)->set_length(0);
1244       obj_to_push = old;
1245       assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push,
1246              "push forwarded object");
1247     }
1248     // Push it on one of the queues of to-be-scanned objects.
1249     bool simulate_overflow = false;
1250     NOT_PRODUCT(
1251       if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) {
1252         // simulate a stack overflow
1253         simulate_overflow = true;
1254       }
1255     )
1256     if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) {
1257       // Add stats for overflow pushes.
1258       if (Verbose && PrintGCDetails) {
1259         gclog_or_tty->print("queue overflow!\n");
1260       }
1261       push_on_overflow_list(old, par_scan_state);
1262       TASKQUEUE_STATS_ONLY(par_scan_state->taskqueue_stats().record_overflow(0));
1263     }
1264 
1265     return new_obj;
1266   }
1267 
1268   // Oops.  Someone beat us to it.  Undo the allocation.  Where did we
1269   // allocate it?
1270   if (is_in_reserved(new_obj)) {
1271     // Must be in to_space.
1272     assert(to()->is_in_reserved(new_obj), "Checking");
1273     if (forward_ptr == ClaimedForwardPtr) {
1274       // Wait to get the real forwarding pointer value.
1275       forward_ptr = real_forwardee(old);
1276     }
1277     par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz);
1278   }
1279 
1280   return forward_ptr;
1281 }
1282 
1283 
1284 // Multiple GC threads may try to promote the same object.  If two
1285 // or more GC threads copy the object, only one wins the race to install
1286 // the forwarding pointer.  The other threads have to undo their copy.
1287 
1288 oop ParNewGeneration::copy_to_survivor_space_with_undo(
1289         ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) {
1290 
1291   // In the sequential version, this assert also says that the object is
1292   // not forwarded.  That might not be the case here.  It is the case that
1293   // the caller observed it to be not forwarded at some time in the past.
1294   assert(is_in_reserved(old), "shouldn't be scavenging this oop");
1295 
1296   // The sequential code read "old->age()" below.  That doesn't work here,
1297   // since the age is in the mark word, and that might be overwritten with
1298   // a forwarding pointer by a parallel thread.  So we must save the mark
1299   // word here, install it in a local oopDesc, and then analyze it.
1300   oopDesc dummyOld;
1301   dummyOld.set_mark(m);
1302   assert(!dummyOld.is_forwarded(),
1303          "should not be called with forwarding pointer mark word.");
1304 
1305   bool failed_to_promote = false;
1306   oop new_obj = NULL;
1307   oop forward_ptr;
1308 
1309   // Try allocating obj in to-space (unless too old)
1310   if (dummyOld.age() < tenuring_threshold()) {
1311     new_obj = (oop)par_scan_state->alloc_in_to_space(sz);
1312     if (new_obj == NULL) {
1313       set_survivor_overflow(true);
1314     }
1315   }
1316 
1317   if (new_obj == NULL) {
1318     // Either to-space is full or we decided to promote
1319     // try allocating obj tenured
1320     new_obj = _next_gen->par_promote(par_scan_state->thread_num(),
1321                                        old, m, sz);
1322 
1323     if (new_obj == NULL) {
1324       // promotion failed, forward to self
1325       forward_ptr = old->forward_to_atomic(old);
1326       new_obj = old;
1327 
1328       if (forward_ptr != NULL) {
1329         return forward_ptr;   // someone else succeeded
1330       }
1331 
1332       _promotion_failed = true;
1333       failed_to_promote = true;
1334 
1335       preserve_mark_if_necessary(old, m);
1336       par_scan_state->register_promotion_failure(sz);
1337     }
1338   } else {
1339     // Is in to-space; do copying ourselves.
1340     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz);
1341     // Restore the mark word copied above.
1342     new_obj->set_mark(m);
1343     // Increment age if new_obj still in new generation
1344     new_obj->incr_age();
1345     par_scan_state->age_table()->add(new_obj, sz);
1346   }
1347   assert(new_obj != NULL, "just checking");
1348 
1349 #ifndef PRODUCT
1350   // This code must come after the CAS test, or it will print incorrect
1351   // information.
1352   if (TraceScavenge) {
1353     gclog_or_tty->print_cr("{%s %s " PTR_FORMAT " -> " PTR_FORMAT " (%d)}",
1354        is_in_reserved(new_obj) ? "copying" : "tenuring",
1355        new_obj->klass()->internal_name(), (void *)old, (void *)new_obj, new_obj->size());
1356   }
1357 #endif
1358 
1359   // Now attempt to install the forwarding pointer (atomically).
1360   // We have to copy the mark word before overwriting with forwarding
1361   // ptr, so we can restore it below in the copy.
1362   if (!failed_to_promote) {
1363     forward_ptr = old->forward_to_atomic(new_obj);
1364   }
1365 
1366   if (forward_ptr == NULL) {
1367     oop obj_to_push = new_obj;
1368     if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) {
1369       // Length field used as index of next element to be scanned.
1370       // Real length can be obtained from real_forwardee()
1371       arrayOop(old)->set_length(0);
1372       obj_to_push = old;
1373       assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push,
1374              "push forwarded object");
1375     }
1376     // Push it on one of the queues of to-be-scanned objects.
1377     bool simulate_overflow = false;
1378     NOT_PRODUCT(
1379       if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) {
1380         // simulate a stack overflow
1381         simulate_overflow = true;
1382       }
1383     )
1384     if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) {
1385       // Add stats for overflow pushes.
1386       push_on_overflow_list(old, par_scan_state);
1387       TASKQUEUE_STATS_ONLY(par_scan_state->taskqueue_stats().record_overflow(0));
1388     }
1389 
1390     return new_obj;
1391   }
1392 
1393   // Oops.  Someone beat us to it.  Undo the allocation.  Where did we
1394   // allocate it?
1395   if (is_in_reserved(new_obj)) {
1396     // Must be in to_space.
1397     assert(to()->is_in_reserved(new_obj), "Checking");
1398     par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz);
1399   } else {
1400     assert(!_avoid_promotion_undo, "Should not be here if avoiding.");
1401     _next_gen->par_promote_alloc_undo(par_scan_state->thread_num(),
1402                                       (HeapWord*)new_obj, sz);
1403   }
1404 
1405   return forward_ptr;
1406 }
1407 
1408 #ifndef PRODUCT
1409 // It's OK to call this multi-threaded;  the worst thing
1410 // that can happen is that we'll get a bunch of closely
1411 // spaced simulated oveflows, but that's OK, in fact
1412 // probably good as it would exercise the overflow code
1413 // under contention.
1414 bool ParNewGeneration::should_simulate_overflow() {
1415   if (_overflow_counter-- <= 0) { // just being defensive
1416     _overflow_counter = ParGCWorkQueueOverflowInterval;
1417     return true;
1418   } else {
1419     return false;
1420   }
1421 }
1422 #endif
1423 
1424 // In case we are using compressed oops, we need to be careful.
1425 // If the object being pushed is an object array, then its length
1426 // field keeps track of the "grey boundary" at which the next
1427 // incremental scan will be done (see ParGCArrayScanChunk).
1428 // When using compressed oops, this length field is kept in the
1429 // lower 32 bits of the erstwhile klass word and cannot be used
1430 // for the overflow chaining pointer (OCP below). As such the OCP
1431 // would itself need to be compressed into the top 32-bits in this
1432 // case. Unfortunately, see below, in the event that we have a
1433 // promotion failure, the node to be pushed on the list can be
1434 // outside of the Java heap, so the heap-based pointer compression
1435 // would not work (we would have potential aliasing between C-heap
1436 // and Java-heap pointers). For this reason, when using compressed
1437 // oops, we simply use a worker-thread-local, non-shared overflow
1438 // list in the form of a growable array, with a slightly different
1439 // overflow stack draining strategy. If/when we start using fat
1440 // stacks here, we can go back to using (fat) pointer chains
1441 // (although some performance comparisons would be useful since
1442 // single global lists have their own performance disadvantages
1443 // as we were made painfully aware not long ago, see 6786503).
1444 #define BUSY (cast_to_oop<intptr_t>(0x1aff1aff))
1445 void ParNewGeneration::push_on_overflow_list(oop from_space_obj, ParScanThreadState* par_scan_state) {
1446   assert(is_in_reserved(from_space_obj), "Should be from this generation");
1447   if (ParGCUseLocalOverflow) {
1448     // In the case of compressed oops, we use a private, not-shared
1449     // overflow stack.
1450     par_scan_state->push_on_overflow_stack(from_space_obj);
1451   } else {
1452     assert(!UseCompressedOops, "Error");
1453     // if the object has been forwarded to itself, then we cannot
1454     // use the klass pointer for the linked list.  Instead we have
1455     // to allocate an oopDesc in the C-Heap and use that for the linked list.
1456     // XXX This is horribly inefficient when a promotion failure occurs
1457     // and should be fixed. XXX FIX ME !!!
1458 #ifndef PRODUCT
1459     Atomic::inc_ptr(&_num_par_pushes);
1460     assert(_num_par_pushes > 0, "Tautology");
1461 #endif
1462     if (from_space_obj->forwardee() == from_space_obj) {
1463       oopDesc* listhead = NEW_C_HEAP_ARRAY(oopDesc, 1, mtGC);
1464       listhead->forward_to(from_space_obj);
1465       from_space_obj = listhead;
1466     }
1467     oop observed_overflow_list = _overflow_list;
1468     oop cur_overflow_list;
1469     do {
1470       cur_overflow_list = observed_overflow_list;
1471       if (cur_overflow_list != BUSY) {
1472         from_space_obj->set_klass_to_list_ptr(cur_overflow_list);
1473       } else {
1474         from_space_obj->set_klass_to_list_ptr(NULL);
1475       }
1476       observed_overflow_list =
1477         (oop)Atomic::cmpxchg_ptr(from_space_obj, &_overflow_list, cur_overflow_list);
1478     } while (cur_overflow_list != observed_overflow_list);
1479   }
1480 }
1481 
1482 bool ParNewGeneration::take_from_overflow_list(ParScanThreadState* par_scan_state) {
1483   bool res;
1484 
1485   if (ParGCUseLocalOverflow) {
1486     res = par_scan_state->take_from_overflow_stack();
1487   } else {
1488     assert(!UseCompressedOops, "Error");
1489     res = take_from_overflow_list_work(par_scan_state);
1490   }
1491   return res;
1492 }
1493 
1494 
1495 // *NOTE*: The overflow list manipulation code here and
1496 // in CMSCollector:: are very similar in shape,
1497 // except that in the CMS case we thread the objects
1498 // directly into the list via their mark word, and do
1499 // not need to deal with special cases below related
1500 // to chunking of object arrays and promotion failure
1501 // handling.
1502 // CR 6797058 has been filed to attempt consolidation of
1503 // the common code.
1504 // Because of the common code, if you make any changes in
1505 // the code below, please check the CMS version to see if
1506 // similar changes might be needed.
1507 // See CMSCollector::par_take_from_overflow_list() for
1508 // more extensive documentation comments.
1509 bool ParNewGeneration::take_from_overflow_list_work(ParScanThreadState* par_scan_state) {
1510   ObjToScanQueue* work_q = par_scan_state->work_queue();
1511   // How many to take?
1512   size_t objsFromOverflow = MIN2((size_t)(work_q->max_elems() - work_q->size())/4,
1513                                  (size_t)ParGCDesiredObjsFromOverflowList);
1514 
1515   assert(!UseCompressedOops, "Error");
1516   assert(par_scan_state->overflow_stack() == NULL, "Error");
1517   if (_overflow_list == NULL) return false;
1518 
1519   // Otherwise, there was something there; try claiming the list.
1520   oop prefix = cast_to_oop(Atomic::xchg_ptr(BUSY, &_overflow_list));
1521   // Trim off a prefix of at most objsFromOverflow items
1522   Thread* tid = Thread::current();
1523   size_t spin_count = (size_t)ParallelGCThreads;
1524   size_t sleep_time_millis = MAX2((size_t)1, objsFromOverflow/100);
1525   for (size_t spin = 0; prefix == BUSY && spin < spin_count; spin++) {
1526     // someone grabbed it before we did ...
1527     // ... we spin for a short while...
1528     os::sleep(tid, sleep_time_millis, false);
1529     if (_overflow_list == NULL) {
1530       // nothing left to take
1531       return false;
1532     } else if (_overflow_list != BUSY) {
1533      // try and grab the prefix
1534      prefix = cast_to_oop(Atomic::xchg_ptr(BUSY, &_overflow_list));
1535     }
1536   }
1537   if (prefix == NULL || prefix == BUSY) {
1538      // Nothing to take or waited long enough
1539      if (prefix == NULL) {
1540        // Write back the NULL in case we overwrote it with BUSY above
1541        // and it is still the same value.
1542        (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY);
1543      }
1544      return false;
1545   }
1546   assert(prefix != NULL && prefix != BUSY, "Error");
1547   size_t i = 1;
1548   oop cur = prefix;
1549   while (i < objsFromOverflow && cur->klass_or_null() != NULL) {
1550     i++; cur = cur->list_ptr_from_klass();
1551   }
1552 
1553   // Reattach remaining (suffix) to overflow list
1554   if (cur->klass_or_null() == NULL) {
1555     // Write back the NULL in lieu of the BUSY we wrote
1556     // above and it is still the same value.
1557     if (_overflow_list == BUSY) {
1558       (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY);
1559     }
1560   } else {
1561     assert(cur->klass_or_null() != (Klass*)(address)BUSY, "Error");
1562     oop suffix = cur->list_ptr_from_klass();       // suffix will be put back on global list
1563     cur->set_klass_to_list_ptr(NULL);     // break off suffix
1564     // It's possible that the list is still in the empty(busy) state
1565     // we left it in a short while ago; in that case we may be
1566     // able to place back the suffix.
1567     oop observed_overflow_list = _overflow_list;
1568     oop cur_overflow_list = observed_overflow_list;
1569     bool attached = false;
1570     while (observed_overflow_list == BUSY || observed_overflow_list == NULL) {
1571       observed_overflow_list =
1572         (oop) Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list);
1573       if (cur_overflow_list == observed_overflow_list) {
1574         attached = true;
1575         break;
1576       } else cur_overflow_list = observed_overflow_list;
1577     }
1578     if (!attached) {
1579       // Too bad, someone else got in in between; we'll need to do a splice.
1580       // Find the last item of suffix list
1581       oop last = suffix;
1582       while (last->klass_or_null() != NULL) {
1583         last = last->list_ptr_from_klass();
1584       }
1585       // Atomically prepend suffix to current overflow list
1586       observed_overflow_list = _overflow_list;
1587       do {
1588         cur_overflow_list = observed_overflow_list;
1589         if (cur_overflow_list != BUSY) {
1590           // Do the splice ...
1591           last->set_klass_to_list_ptr(cur_overflow_list);
1592         } else { // cur_overflow_list == BUSY
1593           last->set_klass_to_list_ptr(NULL);
1594         }
1595         observed_overflow_list =
1596           (oop)Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list);
1597       } while (cur_overflow_list != observed_overflow_list);
1598     }
1599   }
1600 
1601   // Push objects on prefix list onto this thread's work queue
1602   assert(prefix != NULL && prefix != BUSY, "program logic");
1603   cur = prefix;
1604   ssize_t n = 0;
1605   while (cur != NULL) {
1606     oop obj_to_push = cur->forwardee();
1607     oop next        = cur->list_ptr_from_klass();
1608     cur->set_klass(obj_to_push->klass());
1609     // This may be an array object that is self-forwarded. In that case, the list pointer
1610     // space, cur, is not in the Java heap, but rather in the C-heap and should be freed.
1611     if (!is_in_reserved(cur)) {
1612       // This can become a scaling bottleneck when there is work queue overflow coincident
1613       // with promotion failure.
1614       oopDesc* f = cur;
1615       FREE_C_HEAP_ARRAY(oopDesc, f, mtGC);
1616     } else if (par_scan_state->should_be_partially_scanned(obj_to_push, cur)) {
1617       assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned");
1618       obj_to_push = cur;
1619     }
1620     bool ok = work_q->push(obj_to_push);
1621     assert(ok, "Should have succeeded");
1622     cur = next;
1623     n++;
1624   }
1625   TASKQUEUE_STATS_ONLY(par_scan_state->note_overflow_refill(n));
1626 #ifndef PRODUCT
1627   assert(_num_par_pushes >= n, "Too many pops?");
1628   Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes);
1629 #endif
1630   return true;
1631 }
1632 #undef BUSY
1633 
1634 void ParNewGeneration::ref_processor_init() {
1635   if (_ref_processor == NULL) {
1636     // Allocate and initialize a reference processor
1637     _ref_processor =
1638       new ReferenceProcessor(_reserved,                  // span
1639                              ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
1640                              (int) ParallelGCThreads,    // mt processing degree
1641                              refs_discovery_is_mt(),     // mt discovery
1642                              (int) ParallelGCThreads,    // mt discovery degree
1643                              refs_discovery_is_atomic(), // atomic_discovery
1644                              NULL);                      // is_alive_non_header
1645   }
1646 }
1647 
1648 const char* ParNewGeneration::name() const {
1649   return "par new generation";
1650 }