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                                        ParNewTracer* gc_tracer,
  73                                        ParallelTaskTerminator& term_) :
  74   _to_space(to_space_), _old_gen(old_gen_), _young_gen(gen_), _thread_num(thread_num_),
  75   _work_queue(work_queue_set_->queue(thread_num_)), _to_space_full(false),
  76   _overflow_stack(overflow_stacks_ ? overflow_stacks_ + thread_num_ : NULL),
  77   _ageTable(false), // false ==> not the global age table, no perf data.
  78   _to_space_alloc_buffer(desired_plab_sz_),
  79   _to_space_closure(gen_, this), _old_gen_closure(gen_, this),
  80   _to_space_root_closure(gen_, this), _old_gen_root_closure(gen_, this),
  81   _older_gen_closure(gen_, this),
  82   _evacuate_followers(this, &_to_space_closure, &_old_gen_closure,
  83                       &_to_space_root_closure, gen_, &_old_gen_root_closure,
  84                       work_queue_set_, &term_),
  85   _is_alive_closure(gen_), _scan_weak_ref_closure(gen_, this),
  86   _keep_alive_closure(&_scan_weak_ref_closure),
  87   _gc_tracer(gc_tracer),
  88   _strong_roots_time(0.0), _term_time(0.0)
  89 {
  90   #if TASKQUEUE_STATS
  91   _term_attempts = 0;
  92   _overflow_refills = 0;
  93   _overflow_refill_objs = 0;
  94   #endif // TASKQUEUE_STATS
  95 
  96   _survivor_chunk_array =
  97     (ChunkArray*) old_gen()->get_data_recorder(thread_num());
  98   _hash_seed = 17;  // Might want to take time-based random value.
  99   _start = os::elapsedTime();
 100   _old_gen_closure.set_generation(old_gen_);
 101   _old_gen_root_closure.set_generation(old_gen_);
 102 }
 103 #ifdef _MSC_VER
 104 #pragma warning( pop )
 105 #endif
 106 
 107 void ParScanThreadState::record_survivor_plab(HeapWord* plab_start,
 108                                               size_t plab_word_size) {
 109   ChunkArray* sca = survivor_chunk_array();
 110   if (sca != NULL) {
 111     // A non-null SCA implies that we want the PLAB data recorded.
 112     sca->record_sample(plab_start, plab_word_size);
 113   }
 114 }
 115 
 116 bool ParScanThreadState::should_be_partially_scanned(oop new_obj, oop old_obj) const {
 117   return new_obj->is_objArray() &&
 118          arrayOop(new_obj)->length() > ParGCArrayScanChunk &&
 119          new_obj != old_obj;
 120 }
 121 
 122 void ParScanThreadState::scan_partial_array_and_push_remainder(oop old) {
 123   assert(old->is_objArray(), "must be obj array");
 124   assert(old->is_forwarded(), "must be forwarded");
 125   assert(Universe::heap()->is_in_reserved(old), "must be in heap.");
 126   assert(!old_gen()->is_in(old), "must be in young generation.");
 127 
 128   objArrayOop obj = objArrayOop(old->forwardee());
 129   // Process ParGCArrayScanChunk elements now
 130   // and push the remainder back onto queue
 131   int start     = arrayOop(old)->length();
 132   int end       = obj->length();
 133   int remainder = end - start;
 134   assert(start <= end, "just checking");
 135   if (remainder > 2 * ParGCArrayScanChunk) {
 136     // Test above combines last partial chunk with a full chunk
 137     end = start + ParGCArrayScanChunk;
 138     arrayOop(old)->set_length(end);
 139     // Push remainder.
 140     bool ok = work_queue()->push(old);
 141     assert(ok, "just popped, push must be okay");
 142   } else {
 143     // Restore length so that it can be used if there
 144     // is a promotion failure and forwarding pointers
 145     // must be removed.
 146     arrayOop(old)->set_length(end);
 147   }
 148 
 149   // process our set of indices (include header in first chunk)
 150   // should make sure end is even (aligned to HeapWord in case of compressed oops)
 151   if ((HeapWord *)obj < young_old_boundary()) {
 152     // object is in to_space
 153     obj->oop_iterate_range(&_to_space_closure, start, end);
 154   } else {
 155     // object is in old generation
 156     obj->oop_iterate_range(&_old_gen_closure, start, end);
 157   }
 158 }
 159 
 160 
 161 void ParScanThreadState::trim_queues(int max_size) {
 162   ObjToScanQueue* queue = work_queue();
 163   do {
 164     while (queue->size() > (juint)max_size) {
 165       oop obj_to_scan;
 166       if (queue->pop_local(obj_to_scan)) {
 167         if ((HeapWord *)obj_to_scan < young_old_boundary()) {
 168           if (obj_to_scan->is_objArray() &&
 169               obj_to_scan->is_forwarded() &&
 170               obj_to_scan->forwardee() != obj_to_scan) {
 171             scan_partial_array_and_push_remainder(obj_to_scan);
 172           } else {
 173             // object is in to_space
 174             obj_to_scan->oop_iterate(&_to_space_closure);
 175           }
 176         } else {
 177           // object is in old generation
 178           obj_to_scan->oop_iterate(&_old_gen_closure);
 179         }
 180       }
 181     }
 182     // For the  case of compressed oops, we have a private, non-shared
 183     // overflow stack, so we eagerly drain it so as to more evenly
 184     // distribute load early. Note: this may be good to do in
 185     // general rather than delay for the final stealing phase.
 186     // If applicable, we'll transfer a set of objects over to our
 187     // work queue, allowing them to be stolen and draining our
 188     // private overflow stack.
 189   } while (ParGCTrimOverflow && young_gen()->take_from_overflow_list(this));
 190 }
 191 
 192 bool ParScanThreadState::take_from_overflow_stack() {
 193   assert(ParGCUseLocalOverflow, "Else should not call");
 194   assert(young_gen()->overflow_list() == NULL, "Error");
 195   ObjToScanQueue* queue = work_queue();
 196   Stack<oop, mtGC>* const of_stack = overflow_stack();
 197   const size_t num_overflow_elems = of_stack->size();
 198   const size_t space_available = queue->max_elems() - queue->size();
 199   const size_t num_take_elems = MIN3(space_available / 4,
 200                                      ParGCDesiredObjsFromOverflowList,
 201                                      num_overflow_elems);
 202   // Transfer the most recent num_take_elems from the overflow
 203   // stack to our work queue.
 204   for (size_t i = 0; i != num_take_elems; i++) {
 205     oop cur = of_stack->pop();
 206     oop obj_to_push = cur->forwardee();
 207     assert(Universe::heap()->is_in_reserved(cur), "Should be in heap");
 208     assert(!old_gen()->is_in_reserved(cur), "Should be in young gen");
 209     assert(Universe::heap()->is_in_reserved(obj_to_push), "Should be in heap");
 210     if (should_be_partially_scanned(obj_to_push, cur)) {
 211       assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned");
 212       obj_to_push = cur;
 213     }
 214     bool ok = queue->push(obj_to_push);
 215     assert(ok, "Should have succeeded");
 216   }
 217   assert(young_gen()->overflow_list() == NULL, "Error");
 218   return num_take_elems > 0;  // was something transferred?
 219 }
 220 
 221 void ParScanThreadState::push_on_overflow_stack(oop p) {
 222   assert(ParGCUseLocalOverflow, "Else should not call");
 223   overflow_stack()->push(p);
 224   assert(young_gen()->overflow_list() == NULL, "Error");
 225 }
 226 
 227 HeapWord* ParScanThreadState::alloc_in_to_space_slow(size_t word_sz, 
 228                                                      const oop old, 
 229                                                      const uint age) {
 230 
 231   // Otherwise, if the object is small enough, try to reallocate the
 232   // buffer.
 233   HeapWord* obj = NULL;
 234   if (!_to_space_full) {
 235     ParGCAllocBuffer* const plab = to_space_alloc_buffer();
 236     Space*            const sp   = to_space();
 237     if (word_sz * 100 <
 238         ParallelGCBufferWastePct * plab->word_sz()) {
 239       // Is small enough; abandon this buffer and start a new one.
 240       plab->retire(false, false);
 241       size_t buf_size = plab->word_sz();
 242       HeapWord* buf_space = sp->par_allocate(buf_size);
 243       if (buf_space == NULL) {
 244         const size_t min_bytes =
 245           ParGCAllocBuffer::min_size() << LogHeapWordSize;
 246         size_t free_bytes = sp->free();
 247         while(buf_space == NULL && free_bytes >= min_bytes) {
 248           buf_size = free_bytes >> LogHeapWordSize;
 249           assert(buf_size == (size_t)align_object_size(buf_size),
 250                  "Invariant");
 251           buf_space  = sp->par_allocate(buf_size);
 252           free_bytes = sp->free();
 253         }
 254       }
 255       if (buf_space != NULL) {
 256         plab->set_word_size(buf_size);
 257         plab->set_buf(buf_space);
 258         record_survivor_plab(buf_space, buf_size);
 259         gc_tracer()->report_promotion_in_new_plab_event(old, word_sz, age, false,
 260                                                         buf_size);
 261         obj = plab->allocate_aligned(word_sz, SurvivorAlignmentInBytes);
 262         // Note that we cannot compare buf_size < word_sz below
 263         // because of AlignmentReserve (see ParGCAllocBuffer::allocate()).
 264         assert(obj != NULL || plab->words_remaining() < word_sz,
 265                "Else should have been able to allocate");
 266         // It's conceivable that we may be able to use the
 267         // buffer we just grabbed for subsequent small requests
 268         // even if not for this one.
 269       } else {
 270         // We're used up.
 271         _to_space_full = true;
 272       }
 273 
 274     } else {
 275       // Too large; allocate the object individually.
 276       gc_tracer()->report_promotion_outside_plab_event(old, word_sz, age, false);
 277       obj = sp->par_allocate(word_sz);
 278     }
 279   }
 280   return obj;
 281 }
 282 
 283 
 284 void ParScanThreadState::undo_alloc_in_to_space(HeapWord* obj,
 285                                                 size_t word_sz) {
 286   // Is the alloc in the current alloc buffer?
 287   if (to_space_alloc_buffer()->contains(obj)) {
 288     assert(to_space_alloc_buffer()->contains(obj + word_sz - 1),
 289            "Should contain whole object.");
 290     to_space_alloc_buffer()->undo_allocation(obj, word_sz);
 291   } else {
 292     CollectedHeap::fill_with_object(obj, word_sz);
 293   }
 294 }
 295 
 296 void ParScanThreadState::print_promotion_failure_size() {
 297   if (_promotion_failed_info.has_failed() && PrintPromotionFailure) {
 298     gclog_or_tty->print(" (%d: promotion failure size = " SIZE_FORMAT ") ",
 299                         _thread_num, _promotion_failed_info.first_size());
 300   }
 301 }
 302 
 303 class ParScanThreadStateSet: private ResourceArray {
 304 public:
 305   // Initializes states for the specified number of threads;
 306   ParScanThreadStateSet(int                     num_threads,
 307                         Space&                  to_space,
 308                         ParNewGeneration&       gen,
 309                         Generation&             old_gen,
 310                         ObjToScanQueueSet&      queue_set,
 311                         Stack<oop, mtGC>*       overflow_stacks_,
 312                         size_t                  desired_plab_sz,
 313                         ParNewTracer*           gc_tracer,
 314                         ParallelTaskTerminator& term);
 315 
 316   ~ParScanThreadStateSet() { TASKQUEUE_STATS_ONLY(reset_stats()); }
 317 
 318   inline ParScanThreadState& thread_state(int i);
 319 
 320   void trace_promotion_failed(YoungGCTracer& gc_tracer);
 321   void reset(int active_workers, bool promotion_failed);
 322   void flush();
 323 
 324   #if TASKQUEUE_STATS
 325   static void
 326     print_termination_stats_hdr(outputStream* const st = gclog_or_tty);
 327   void print_termination_stats(outputStream* const st = gclog_or_tty);
 328   static void
 329     print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 330   void print_taskqueue_stats(outputStream* const st = gclog_or_tty);
 331   void reset_stats();
 332   #endif // TASKQUEUE_STATS
 333 
 334 private:
 335   ParallelTaskTerminator& _term;
 336   ParNewGeneration&       _gen;
 337   Generation&             _next_gen;
 338  public:
 339   bool is_valid(int id) const { return id < length(); }
 340   ParallelTaskTerminator* terminator() { return &_term; }
 341 };
 342 
 343 
 344 ParScanThreadStateSet::ParScanThreadStateSet(
 345   int num_threads, Space& to_space, ParNewGeneration& gen,
 346   Generation& old_gen, ObjToScanQueueSet& queue_set,
 347   Stack<oop, mtGC>* overflow_stacks,
 348   size_t desired_plab_sz, ParNewTracer* gc_tracer, 
 349   ParallelTaskTerminator& term)
 350   : ResourceArray(sizeof(ParScanThreadState), num_threads),
 351     _gen(gen), _next_gen(old_gen), _term(term)
 352 {
 353   assert(num_threads > 0, "sanity check!");
 354   assert(ParGCUseLocalOverflow == (overflow_stacks != NULL),
 355          "overflow_stack allocation mismatch");
 356   // Initialize states.
 357   for (int i = 0; i < num_threads; ++i) {
 358     new ((ParScanThreadState*)_data + i)
 359         ParScanThreadState(&to_space, &gen, &old_gen, i, &queue_set,
 360                            overflow_stacks, desired_plab_sz, gc_tracer, term);
 361   }
 362 }
 363 
 364 inline ParScanThreadState& ParScanThreadStateSet::thread_state(int i)
 365 {
 366   assert(i >= 0 && i < length(), "sanity check!");
 367   return ((ParScanThreadState*)_data)[i];
 368 }
 369 
 370 void ParScanThreadStateSet::trace_promotion_failed(YoungGCTracer& gc_tracer) {
 371   for (int i = 0; i < length(); ++i) {
 372     if (thread_state(i).promotion_failed()) {
 373       gc_tracer.report_promotion_failed(thread_state(i).promotion_failed_info());
 374       thread_state(i).promotion_failed_info().reset();
 375     }
 376   }
 377 }
 378 
 379 void ParScanThreadStateSet::reset(int active_threads, bool promotion_failed)
 380 {
 381   _term.reset_for_reuse(active_threads);
 382   if (promotion_failed) {
 383     for (int i = 0; i < length(); ++i) {
 384       thread_state(i).print_promotion_failure_size();
 385     }
 386   }
 387 }
 388 
 389 #if TASKQUEUE_STATS
 390 void
 391 ParScanThreadState::reset_stats()
 392 {
 393   taskqueue_stats().reset();
 394   _term_attempts = 0;
 395   _overflow_refills = 0;
 396   _overflow_refill_objs = 0;
 397 }
 398 
 399 void ParScanThreadStateSet::reset_stats()
 400 {
 401   for (int i = 0; i < length(); ++i) {
 402     thread_state(i).reset_stats();
 403   }
 404 }
 405 
 406 void
 407 ParScanThreadStateSet::print_termination_stats_hdr(outputStream* const st)
 408 {
 409   st->print_raw_cr("GC Termination Stats");
 410   st->print_raw_cr("     elapsed  --strong roots-- "
 411                    "-------termination-------");
 412   st->print_raw_cr("thr     ms        ms       %   "
 413                    "    ms       %   attempts");
 414   st->print_raw_cr("--- --------- --------- ------ "
 415                    "--------- ------ --------");
 416 }
 417 
 418 void ParScanThreadStateSet::print_termination_stats(outputStream* const st)
 419 {
 420   print_termination_stats_hdr(st);
 421 
 422   for (int i = 0; i < length(); ++i) {
 423     const ParScanThreadState & pss = thread_state(i);
 424     const double elapsed_ms = pss.elapsed_time() * 1000.0;
 425     const double s_roots_ms = pss.strong_roots_time() * 1000.0;
 426     const double term_ms = pss.term_time() * 1000.0;
 427     st->print_cr("%3d %9.2f %9.2f %6.2f "
 428                  "%9.2f %6.2f " SIZE_FORMAT_W(8),
 429                  i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
 430                  term_ms, term_ms * 100 / elapsed_ms, pss.term_attempts());
 431   }
 432 }
 433 
 434 // Print stats related to work queue activity.
 435 void ParScanThreadStateSet::print_taskqueue_stats_hdr(outputStream* const st)
 436 {
 437   st->print_raw_cr("GC Task Stats");
 438   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
 439   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
 440 }
 441 
 442 void ParScanThreadStateSet::print_taskqueue_stats(outputStream* const st)
 443 {
 444   print_taskqueue_stats_hdr(st);
 445 
 446   TaskQueueStats totals;
 447   for (int i = 0; i < length(); ++i) {
 448     const ParScanThreadState & pss = thread_state(i);
 449     const TaskQueueStats & stats = pss.taskqueue_stats();
 450     st->print("%3d ", i); stats.print(st); st->cr();
 451     totals += stats;
 452 
 453     if (pss.overflow_refills() > 0) {
 454       st->print_cr("    " SIZE_FORMAT_W(10) " overflow refills    "
 455                    SIZE_FORMAT_W(10) " overflow objects",
 456                    pss.overflow_refills(), pss.overflow_refill_objs());
 457     }
 458   }
 459   st->print("tot "); totals.print(st); st->cr();
 460 
 461   DEBUG_ONLY(totals.verify());
 462 }
 463 #endif // TASKQUEUE_STATS
 464 
 465 void ParScanThreadStateSet::flush()
 466 {
 467   // Work in this loop should be kept as lightweight as
 468   // possible since this might otherwise become a bottleneck
 469   // to scaling. Should we add heavy-weight work into this
 470   // loop, consider parallelizing the loop into the worker threads.
 471   for (int i = 0; i < length(); ++i) {
 472     ParScanThreadState& par_scan_state = thread_state(i);
 473 
 474     // Flush stats related to To-space PLAB activity and
 475     // retire the last buffer.
 476     par_scan_state.to_space_alloc_buffer()->
 477       flush_stats_and_retire(_gen.plab_stats(),
 478                              true /* end_of_gc */,
 479                              false /* retain */);
 480 
 481     // Every thread has its own age table.  We need to merge
 482     // them all into one.
 483     ageTable *local_table = par_scan_state.age_table();
 484     _gen.age_table()->merge(local_table);
 485 
 486     // Inform old gen that we're done.
 487     _next_gen.par_promote_alloc_done(i);
 488     _next_gen.par_oop_since_save_marks_iterate_done(i);
 489   }
 490 
 491   if (UseConcMarkSweepGC) {
 492     // We need to call this even when ResizeOldPLAB is disabled
 493     // so as to avoid breaking some asserts. While we may be able
 494     // to avoid this by reorganizing the code a bit, I am loathe
 495     // to do that unless we find cases where ergo leads to bad
 496     // performance.
 497     CFLS_LAB::compute_desired_plab_size();
 498   }
 499 }
 500 
 501 ParScanClosure::ParScanClosure(ParNewGeneration* g,
 502                                ParScanThreadState* par_scan_state) :
 503   OopsInKlassOrGenClosure(g), _par_scan_state(par_scan_state), _g(g)
 504 {
 505   assert(_g->level() == 0, "Optimized for youngest generation");
 506   _boundary = _g->reserved().end();
 507 }
 508 
 509 void ParScanWithBarrierClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, true, false); }
 510 void ParScanWithBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, false); }
 511 
 512 void ParScanWithoutBarrierClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, false, false); }
 513 void ParScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, false); }
 514 
 515 void ParRootScanWithBarrierTwoGensClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, true, true); }
 516 void ParRootScanWithBarrierTwoGensClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, true); }
 517 
 518 void ParRootScanWithoutBarrierClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, false, true); }
 519 void ParRootScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, true); }
 520 
 521 ParScanWeakRefClosure::ParScanWeakRefClosure(ParNewGeneration* g,
 522                                              ParScanThreadState* par_scan_state)
 523   : ScanWeakRefClosure(g), _par_scan_state(par_scan_state)
 524 {}
 525 
 526 void ParScanWeakRefClosure::do_oop(oop* p)       { ParScanWeakRefClosure::do_oop_work(p); }
 527 void ParScanWeakRefClosure::do_oop(narrowOop* p) { ParScanWeakRefClosure::do_oop_work(p); }
 528 
 529 #ifdef WIN32
 530 #pragma warning(disable: 4786) /* identifier was truncated to '255' characters in the browser information */
 531 #endif
 532 
 533 ParEvacuateFollowersClosure::ParEvacuateFollowersClosure(
 534     ParScanThreadState* par_scan_state_,
 535     ParScanWithoutBarrierClosure* to_space_closure_,
 536     ParScanWithBarrierClosure* old_gen_closure_,
 537     ParRootScanWithoutBarrierClosure* to_space_root_closure_,
 538     ParNewGeneration* par_gen_,
 539     ParRootScanWithBarrierTwoGensClosure* old_gen_root_closure_,
 540     ObjToScanQueueSet* task_queues_,
 541     ParallelTaskTerminator* terminator_) :
 542 
 543     _par_scan_state(par_scan_state_),
 544     _to_space_closure(to_space_closure_),
 545     _old_gen_closure(old_gen_closure_),
 546     _to_space_root_closure(to_space_root_closure_),
 547     _old_gen_root_closure(old_gen_root_closure_),
 548     _par_gen(par_gen_),
 549     _task_queues(task_queues_),
 550     _terminator(terminator_)
 551 {}
 552 
 553 void ParEvacuateFollowersClosure::do_void() {
 554   ObjToScanQueue* work_q = par_scan_state()->work_queue();
 555 
 556   while (true) {
 557 
 558     // Scan to-space and old-gen objs until we run out of both.
 559     oop obj_to_scan;
 560     par_scan_state()->trim_queues(0);
 561 
 562     // We have no local work, attempt to steal from other threads.
 563 
 564     // attempt to steal work from promoted.
 565     if (task_queues()->steal(par_scan_state()->thread_num(),
 566                              par_scan_state()->hash_seed(),
 567                              obj_to_scan)) {
 568       bool res = work_q->push(obj_to_scan);
 569       assert(res, "Empty queue should have room for a push.");
 570 
 571       //   if successful, goto Start.
 572       continue;
 573 
 574       // try global overflow list.
 575     } else if (par_gen()->take_from_overflow_list(par_scan_state())) {
 576       continue;
 577     }
 578 
 579     // Otherwise, offer termination.
 580     par_scan_state()->start_term_time();
 581     if (terminator()->offer_termination()) break;
 582     par_scan_state()->end_term_time();
 583   }
 584   assert(par_gen()->_overflow_list == NULL && par_gen()->_num_par_pushes == 0,
 585          "Broken overflow list?");
 586   // Finish the last termination pause.
 587   par_scan_state()->end_term_time();
 588 }
 589 
 590 ParNewGenTask::ParNewGenTask(ParNewGeneration* gen, Generation* next_gen,
 591                 HeapWord* young_old_boundary, ParScanThreadStateSet* state_set) :
 592     AbstractGangTask("ParNewGeneration collection"),
 593     _gen(gen), _next_gen(next_gen),
 594     _young_old_boundary(young_old_boundary),
 595     _state_set(state_set)
 596   {}
 597 
 598 // Reset the terminator for the given number of
 599 // active threads.
 600 void ParNewGenTask::set_for_termination(int active_workers) {
 601   _state_set->reset(active_workers, _gen->promotion_failed());
 602   // Should the heap be passed in?  There's only 1 for now so
 603   // grab it instead.
 604   GenCollectedHeap* gch = GenCollectedHeap::heap();
 605   gch->set_n_termination(active_workers);
 606 }
 607 
 608 void ParNewGenTask::work(uint worker_id) {
 609   GenCollectedHeap* gch = GenCollectedHeap::heap();
 610   // Since this is being done in a separate thread, need new resource
 611   // and handle marks.
 612   ResourceMark rm;
 613   HandleMark hm;
 614   // We would need multiple old-gen queues otherwise.
 615   assert(gch->n_gens() == 2, "Par young collection currently only works with one older gen.");
 616 
 617   Generation* old_gen = gch->next_gen(_gen);
 618 
 619   ParScanThreadState& par_scan_state = _state_set->thread_state(worker_id);
 620   assert(_state_set->is_valid(worker_id), "Should not have been called");
 621 
 622   par_scan_state.set_young_old_boundary(_young_old_boundary);
 623 
 624   KlassScanClosure klass_scan_closure(&par_scan_state.to_space_root_closure(),
 625                                       gch->rem_set()->klass_rem_set());
 626   CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
 627                                            &par_scan_state.to_space_root_closure(),
 628                                            false);
 629 
 630   par_scan_state.start_strong_roots();
 631   gch->gen_process_roots(_gen->level(),
 632                          true,  // Process younger gens, if any,
 633                                 // as strong roots.
 634                          false, // no scope; this is parallel code
 635                          SharedHeap::SO_ScavengeCodeCache,
 636                          GenCollectedHeap::StrongAndWeakRoots,
 637                          &par_scan_state.to_space_root_closure(),
 638                          &par_scan_state.older_gen_closure(),
 639                          &cld_scan_closure);
 640 
 641   par_scan_state.end_strong_roots();
 642 
 643   // "evacuate followers".
 644   par_scan_state.evacuate_followers_closure().do_void();
 645 }
 646 
 647 #ifdef _MSC_VER
 648 #pragma warning( push )
 649 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 650 #endif
 651 ParNewGeneration::
 652 ParNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level)
 653   : DefNewGeneration(rs, initial_byte_size, level, "PCopy"),
 654   _overflow_list(NULL),
 655   _is_alive_closure(this),
 656   _plab_stats(YoungPLABSize, PLABWeight)
 657 {
 658   NOT_PRODUCT(_overflow_counter = ParGCWorkQueueOverflowInterval;)
 659   NOT_PRODUCT(_num_par_pushes = 0;)
 660   _task_queues = new ObjToScanQueueSet(ParallelGCThreads);
 661   guarantee(_task_queues != NULL, "task_queues allocation failure.");
 662 
 663   for (uint i1 = 0; i1 < ParallelGCThreads; i1++) {
 664     ObjToScanQueue *q = new ObjToScanQueue();
 665     guarantee(q != NULL, "work_queue Allocation failure.");
 666     _task_queues->register_queue(i1, q);
 667   }
 668 
 669   for (uint i2 = 0; i2 < ParallelGCThreads; i2++)
 670     _task_queues->queue(i2)->initialize();
 671 
 672   _overflow_stacks = NULL;
 673   if (ParGCUseLocalOverflow) {
 674 
 675     // typedef to workaround NEW_C_HEAP_ARRAY macro, which can not deal
 676     // with ','
 677     typedef Stack<oop, mtGC> GCOopStack;
 678 
 679     _overflow_stacks = NEW_C_HEAP_ARRAY(GCOopStack, ParallelGCThreads, mtGC);
 680     for (size_t i = 0; i < ParallelGCThreads; ++i) {
 681       new (_overflow_stacks + i) Stack<oop, mtGC>();
 682     }
 683   }
 684 
 685   if (UsePerfData) {
 686     EXCEPTION_MARK;
 687     ResourceMark rm;
 688 
 689     const char* cname =
 690          PerfDataManager::counter_name(_gen_counters->name_space(), "threads");
 691     PerfDataManager::create_constant(SUN_GC, cname, PerfData::U_None,
 692                                      ParallelGCThreads, CHECK);
 693   }
 694 }
 695 #ifdef _MSC_VER
 696 #pragma warning( pop )
 697 #endif
 698 
 699 // ParNewGeneration::
 700 ParKeepAliveClosure::ParKeepAliveClosure(ParScanWeakRefClosure* cl) :
 701   DefNewGeneration::KeepAliveClosure(cl), _par_cl(cl) {}
 702 
 703 template <class T>
 704 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop_work(T* p) {
 705 #ifdef ASSERT
 706   {
 707     assert(!oopDesc::is_null(*p), "expected non-null ref");
 708     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
 709     // We never expect to see a null reference being processed
 710     // as a weak reference.
 711     assert(obj->is_oop(), "expected an oop while scanning weak refs");
 712   }
 713 #endif // ASSERT
 714 
 715   _par_cl->do_oop_nv(p);
 716 
 717   if (Universe::heap()->is_in_reserved(p)) {
 718     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
 719     _rs->write_ref_field_gc_par(p, obj);
 720   }
 721 }
 722 
 723 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(oop* p)       { ParKeepAliveClosure::do_oop_work(p); }
 724 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(narrowOop* p) { ParKeepAliveClosure::do_oop_work(p); }
 725 
 726 // ParNewGeneration::
 727 KeepAliveClosure::KeepAliveClosure(ScanWeakRefClosure* cl) :
 728   DefNewGeneration::KeepAliveClosure(cl) {}
 729 
 730 template <class T>
 731 void /*ParNewGeneration::*/KeepAliveClosure::do_oop_work(T* p) {
 732 #ifdef ASSERT
 733   {
 734     assert(!oopDesc::is_null(*p), "expected non-null ref");
 735     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
 736     // We never expect to see a null reference being processed
 737     // as a weak reference.
 738     assert(obj->is_oop(), "expected an oop while scanning weak refs");
 739   }
 740 #endif // ASSERT
 741 
 742   _cl->do_oop_nv(p);
 743 
 744   if (Universe::heap()->is_in_reserved(p)) {
 745     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
 746     _rs->write_ref_field_gc_par(p, obj);
 747   }
 748 }
 749 
 750 void /*ParNewGeneration::*/KeepAliveClosure::do_oop(oop* p)       { KeepAliveClosure::do_oop_work(p); }
 751 void /*ParNewGeneration::*/KeepAliveClosure::do_oop(narrowOop* p) { KeepAliveClosure::do_oop_work(p); }
 752 
 753 template <class T> void ScanClosureWithParBarrier::do_oop_work(T* p) {
 754   T heap_oop = oopDesc::load_heap_oop(p);
 755   if (!oopDesc::is_null(heap_oop)) {
 756     oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
 757     if ((HeapWord*)obj < _boundary) {
 758       assert(!_g->to()->is_in_reserved(obj), "Scanning field twice?");
 759       oop new_obj = obj->is_forwarded()
 760                       ? obj->forwardee()
 761                       : _g->DefNewGeneration::copy_to_survivor_space(obj);
 762       oopDesc::encode_store_heap_oop_not_null(p, new_obj);
 763     }
 764     if (_gc_barrier) {
 765       // If p points to a younger generation, mark the card.
 766       if ((HeapWord*)obj < _gen_boundary) {
 767         _rs->write_ref_field_gc_par(p, obj);
 768       }
 769     }
 770   }
 771 }
 772 
 773 void ScanClosureWithParBarrier::do_oop(oop* p)       { ScanClosureWithParBarrier::do_oop_work(p); }
 774 void ScanClosureWithParBarrier::do_oop(narrowOop* p) { ScanClosureWithParBarrier::do_oop_work(p); }
 775 
 776 class ParNewRefProcTaskProxy: public AbstractGangTask {
 777   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
 778 public:
 779   ParNewRefProcTaskProxy(ProcessTask& task, ParNewGeneration& gen,
 780                          Generation& next_gen,
 781                          HeapWord* young_old_boundary,
 782                          ParScanThreadStateSet& state_set);
 783 
 784 private:
 785   virtual void work(uint worker_id);
 786   virtual void set_for_termination(int active_workers) {
 787     _state_set.terminator()->reset_for_reuse(active_workers);
 788   }
 789 private:
 790   ParNewGeneration&      _gen;
 791   ProcessTask&           _task;
 792   Generation&            _next_gen;
 793   HeapWord*              _young_old_boundary;
 794   ParScanThreadStateSet& _state_set;
 795 };
 796 
 797 ParNewRefProcTaskProxy::ParNewRefProcTaskProxy(
 798     ProcessTask& task, ParNewGeneration& gen,
 799     Generation& next_gen,
 800     HeapWord* young_old_boundary,
 801     ParScanThreadStateSet& state_set)
 802   : AbstractGangTask("ParNewGeneration parallel reference processing"),
 803     _gen(gen),
 804     _task(task),
 805     _next_gen(next_gen),
 806     _young_old_boundary(young_old_boundary),
 807     _state_set(state_set)
 808 {
 809 }
 810 
 811 void ParNewRefProcTaskProxy::work(uint worker_id)
 812 {
 813   ResourceMark rm;
 814   HandleMark hm;
 815   ParScanThreadState& par_scan_state = _state_set.thread_state(worker_id);
 816   par_scan_state.set_young_old_boundary(_young_old_boundary);
 817   _task.work(worker_id, par_scan_state.is_alive_closure(),
 818              par_scan_state.keep_alive_closure(),
 819              par_scan_state.evacuate_followers_closure());
 820 }
 821 
 822 class ParNewRefEnqueueTaskProxy: public AbstractGangTask {
 823   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
 824   EnqueueTask& _task;
 825 
 826 public:
 827   ParNewRefEnqueueTaskProxy(EnqueueTask& task)
 828     : AbstractGangTask("ParNewGeneration parallel reference enqueue"),
 829       _task(task)
 830   { }
 831 
 832   virtual void work(uint worker_id)
 833   {
 834     _task.work(worker_id);
 835   }
 836 };
 837 
 838 
 839 void ParNewRefProcTaskExecutor::execute(ProcessTask& task)
 840 {
 841   GenCollectedHeap* gch = GenCollectedHeap::heap();
 842   assert(gch->kind() == CollectedHeap::GenCollectedHeap,
 843          "not a generational heap");
 844   FlexibleWorkGang* workers = gch->workers();
 845   assert(workers != NULL, "Need parallel worker threads.");
 846   _state_set.reset(workers->active_workers(), _generation.promotion_failed());
 847   ParNewRefProcTaskProxy rp_task(task, _generation, *_generation.next_gen(),
 848                                  _generation.reserved().end(), _state_set);
 849   workers->run_task(&rp_task);
 850   _state_set.reset(0 /* bad value in debug if not reset */,
 851                    _generation.promotion_failed());
 852 }
 853 
 854 void ParNewRefProcTaskExecutor::execute(EnqueueTask& task)
 855 {
 856   GenCollectedHeap* gch = GenCollectedHeap::heap();
 857   FlexibleWorkGang* workers = gch->workers();
 858   assert(workers != NULL, "Need parallel worker threads.");
 859   ParNewRefEnqueueTaskProxy enq_task(task);
 860   workers->run_task(&enq_task);
 861 }
 862 
 863 void ParNewRefProcTaskExecutor::set_single_threaded_mode()
 864 {
 865   _state_set.flush();
 866   GenCollectedHeap* gch = GenCollectedHeap::heap();
 867   gch->set_par_threads(0);  // 0 ==> non-parallel.
 868   gch->save_marks();
 869 }
 870 
 871 ScanClosureWithParBarrier::
 872 ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier) :
 873   ScanClosure(g, gc_barrier) {}
 874 
 875 EvacuateFollowersClosureGeneral::
 876 EvacuateFollowersClosureGeneral(GenCollectedHeap* gch, int level,
 877                                 OopsInGenClosure* cur,
 878                                 OopsInGenClosure* older) :
 879   _gch(gch), _level(level),
 880   _scan_cur_or_nonheap(cur), _scan_older(older)
 881 {}
 882 
 883 void EvacuateFollowersClosureGeneral::do_void() {
 884   do {
 885     // Beware: this call will lead to closure applications via virtual
 886     // calls.
 887     _gch->oop_since_save_marks_iterate(_level,
 888                                        _scan_cur_or_nonheap,
 889                                        _scan_older);
 890   } while (!_gch->no_allocs_since_save_marks(_level));
 891 }
 892 
 893 
 894 // A Generation that does parallel young-gen collection.
 895 
 896 bool ParNewGeneration::_avoid_promotion_undo = false;
 897 
 898 void ParNewGeneration::handle_promotion_failed(GenCollectedHeap* gch, ParScanThreadStateSet& thread_state_set, ParNewTracer& gc_tracer) {
 899   assert(_promo_failure_scan_stack.is_empty(), "post condition");
 900   _promo_failure_scan_stack.clear(true); // Clear cached segments.
 901 
 902   remove_forwarding_pointers();
 903   if (PrintGCDetails) {
 904     gclog_or_tty->print(" (promotion failed)");
 905   }
 906   // All the spaces are in play for mark-sweep.
 907   swap_spaces();  // Make life simpler for CMS || rescan; see 6483690.
 908   from()->set_next_compaction_space(to());
 909   gch->set_incremental_collection_failed();
 910   // Inform the next generation that a promotion failure occurred.
 911   _next_gen->promotion_failure_occurred();
 912 
 913   // Trace promotion failure in the parallel GC threads
 914   thread_state_set.trace_promotion_failed(gc_tracer);
 915   // Single threaded code may have reported promotion failure to the global state
 916   if (_promotion_failed_info.has_failed()) {
 917     gc_tracer.report_promotion_failed(_promotion_failed_info);
 918   }
 919   // Reset the PromotionFailureALot counters.
 920   NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
 921 }
 922 
 923 void ParNewGeneration::collect(bool   full,
 924                                bool   clear_all_soft_refs,
 925                                size_t size,
 926                                bool   is_tlab) {
 927   assert(full || size > 0, "otherwise we don't want to collect");
 928 
 929   GenCollectedHeap* gch = GenCollectedHeap::heap();
 930 
 931   _gc_timer->register_gc_start();
 932 
 933   assert(gch->kind() == CollectedHeap::GenCollectedHeap,
 934     "not a CMS generational heap");
 935   AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
 936   FlexibleWorkGang* workers = gch->workers();
 937   assert(workers != NULL, "Need workgang for parallel work");
 938   int active_workers =
 939       AdaptiveSizePolicy::calc_active_workers(workers->total_workers(),
 940                                    workers->active_workers(),
 941                                    Threads::number_of_non_daemon_threads());
 942   workers->set_active_workers(active_workers);
 943   assert(gch->n_gens() == 2,
 944          "Par collection currently only works with single older gen.");
 945   _next_gen = gch->next_gen(this);
 946   // Do we have to avoid promotion_undo?
 947   if (gch->collector_policy()->is_concurrent_mark_sweep_policy()) {
 948     set_avoid_promotion_undo(true);
 949   }
 950 
 951   // If the next generation is too full to accommodate worst-case promotion
 952   // from this generation, pass on collection; let the next generation
 953   // do it.
 954   if (!collection_attempt_is_safe()) {
 955     gch->set_incremental_collection_failed();  // slight lie, in that we did not even attempt one
 956     return;
 957   }
 958   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 959 
 960   ParNewTracer gc_tracer;
 961   gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
 962   gch->trace_heap_before_gc(&gc_tracer);
 963 
 964   init_assuming_no_promotion_failure();
 965 
 966   if (UseAdaptiveSizePolicy) {
 967     set_survivor_overflow(false);
 968     size_policy->minor_collection_begin();
 969   }
 970 
 971   GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id());
 972   // Capture heap used before collection (for printing).
 973   size_t gch_prev_used = gch->used();
 974 
 975   SpecializationStats::clear();
 976 
 977   age_table()->clear();
 978   to()->clear(SpaceDecorator::Mangle);
 979 
 980   gch->save_marks();
 981   assert(workers != NULL, "Need parallel worker threads.");
 982   int n_workers = active_workers;
 983 
 984   // Set the correct parallelism (number of queues) in the reference processor
 985   ref_processor()->set_active_mt_degree(n_workers);
 986 
 987   // Always set the terminator for the active number of workers
 988   // because only those workers go through the termination protocol.
 989   ParallelTaskTerminator _term(n_workers, task_queues());
 990   ParScanThreadStateSet thread_state_set(workers->active_workers(),
 991                                          *to(), *this, *_next_gen, *task_queues(),
 992                                          _overflow_stacks, desired_plab_sz(), 
 993                                          &gc_tracer, _term);
 994 
 995   ParNewGenTask tsk(this, _next_gen, reserved().end(), &thread_state_set);
 996   gch->set_par_threads(n_workers);
 997   gch->rem_set()->prepare_for_younger_refs_iterate(true);
 998   // It turns out that even when we're using 1 thread, doing the work in a
 999   // separate thread causes wide variance in run times.  We can't help this
1000   // in the multi-threaded case, but we special-case n=1 here to get
1001   // repeatable measurements of the 1-thread overhead of the parallel code.
1002   if (n_workers > 1) {
1003     GenCollectedHeap::StrongRootsScope srs(gch);
1004     workers->run_task(&tsk);
1005   } else {
1006     GenCollectedHeap::StrongRootsScope srs(gch);
1007     tsk.work(0);
1008   }
1009   thread_state_set.reset(0 /* Bad value in debug if not reset */,
1010                          promotion_failed());
1011 
1012   // Process (weak) reference objects found during scavenge.
1013   ReferenceProcessor* rp = ref_processor();
1014   IsAliveClosure is_alive(this);
1015   ScanWeakRefClosure scan_weak_ref(this);
1016   KeepAliveClosure keep_alive(&scan_weak_ref);
1017   ScanClosure               scan_without_gc_barrier(this, false);
1018   ScanClosureWithParBarrier scan_with_gc_barrier(this, true);
1019   set_promo_failure_scan_stack_closure(&scan_without_gc_barrier);
1020   EvacuateFollowersClosureGeneral evacuate_followers(gch, _level,
1021     &scan_without_gc_barrier, &scan_with_gc_barrier);
1022   rp->setup_policy(clear_all_soft_refs);
1023   // Can  the mt_degree be set later (at run_task() time would be best)?
1024   rp->set_active_mt_degree(active_workers);
1025   ReferenceProcessorStats stats;
1026   if (rp->processing_is_mt()) {
1027     ParNewRefProcTaskExecutor task_executor(*this, thread_state_set);
1028     stats = rp->process_discovered_references(&is_alive, &keep_alive,
1029                                               &evacuate_followers, &task_executor,
1030                                               _gc_timer, gc_tracer.gc_id());
1031   } else {
1032     thread_state_set.flush();
1033     gch->set_par_threads(0);  // 0 ==> non-parallel.
1034     gch->save_marks();
1035     stats = rp->process_discovered_references(&is_alive, &keep_alive,
1036                                               &evacuate_followers, NULL,
1037                                               _gc_timer, gc_tracer.gc_id());
1038   }
1039   gc_tracer.report_gc_reference_stats(stats);
1040   if (!promotion_failed()) {
1041     // Swap the survivor spaces.
1042     eden()->clear(SpaceDecorator::Mangle);
1043     from()->clear(SpaceDecorator::Mangle);
1044     if (ZapUnusedHeapArea) {
1045       // This is now done here because of the piece-meal mangling which
1046       // can check for valid mangling at intermediate points in the
1047       // collection(s).  When a minor collection fails to collect
1048       // sufficient space resizing of the young generation can occur
1049       // an redistribute the spaces in the young generation.  Mangle
1050       // here so that unzapped regions don't get distributed to
1051       // other spaces.
1052       to()->mangle_unused_area();
1053     }
1054     swap_spaces();
1055 
1056     // A successful scavenge should restart the GC time limit count which is
1057     // for full GC's.
1058     size_policy->reset_gc_overhead_limit_count();
1059 
1060     assert(to()->is_empty(), "to space should be empty now");
1061 
1062     adjust_desired_tenuring_threshold();
1063   } else {
1064     handle_promotion_failed(gch, thread_state_set, gc_tracer);
1065   }
1066   // set new iteration safe limit for the survivor spaces
1067   from()->set_concurrent_iteration_safe_limit(from()->top());
1068   to()->set_concurrent_iteration_safe_limit(to()->top());
1069 
1070   if (ResizePLAB) {
1071     plab_stats()->adjust_desired_plab_sz(n_workers);
1072   }
1073 
1074   if (PrintGC && !PrintGCDetails) {
1075     gch->print_heap_change(gch_prev_used);
1076   }
1077 
1078   TASKQUEUE_STATS_ONLY(if (PrintTerminationStats) thread_state_set.print_termination_stats());
1079   TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) thread_state_set.print_taskqueue_stats());
1080 
1081   if (UseAdaptiveSizePolicy) {
1082     size_policy->minor_collection_end(gch->gc_cause());
1083     size_policy->avg_survived()->sample(from()->used());
1084   }
1085 
1086   // We need to use a monotonically non-decreasing time in ms
1087   // or we will see time-warp warnings and os::javaTimeMillis()
1088   // does not guarantee monotonicity.
1089   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
1090   update_time_of_last_gc(now);
1091 
1092   SpecializationStats::print();
1093 
1094   rp->set_enqueuing_is_done(true);
1095   if (rp->processing_is_mt()) {
1096     ParNewRefProcTaskExecutor task_executor(*this, thread_state_set);
1097     rp->enqueue_discovered_references(&task_executor);
1098   } else {
1099     rp->enqueue_discovered_references(NULL);
1100   }
1101   rp->verify_no_references_recorded();
1102 
1103   gch->trace_heap_after_gc(&gc_tracer);
1104   gc_tracer.report_tenuring_threshold(tenuring_threshold());
1105 
1106   _gc_timer->register_gc_end();
1107 
1108   gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
1109 }
1110 
1111 static int sum;
1112 void ParNewGeneration::waste_some_time() {
1113   for (int i = 0; i < 100; i++) {
1114     sum += i;
1115   }
1116 }
1117 
1118 static const oop ClaimedForwardPtr = cast_to_oop<intptr_t>(0x4);
1119 
1120 // Because of concurrency, there are times where an object for which
1121 // "is_forwarded()" is true contains an "interim" forwarding pointer
1122 // value.  Such a value will soon be overwritten with a real value.
1123 // This method requires "obj" to have a forwarding pointer, and waits, if
1124 // necessary for a real one to be inserted, and returns it.
1125 
1126 oop ParNewGeneration::real_forwardee(oop obj) {
1127   oop forward_ptr = obj->forwardee();
1128   if (forward_ptr != ClaimedForwardPtr) {
1129     return forward_ptr;
1130   } else {
1131     return real_forwardee_slow(obj);
1132   }
1133 }
1134 
1135 oop ParNewGeneration::real_forwardee_slow(oop obj) {
1136   // Spin-read if it is claimed but not yet written by another thread.
1137   oop forward_ptr = obj->forwardee();
1138   while (forward_ptr == ClaimedForwardPtr) {
1139     waste_some_time();
1140     assert(obj->is_forwarded(), "precondition");
1141     forward_ptr = obj->forwardee();
1142   }
1143   return forward_ptr;
1144 }
1145 
1146 #ifdef ASSERT
1147 bool ParNewGeneration::is_legal_forward_ptr(oop p) {
1148   return
1149     (_avoid_promotion_undo && p == ClaimedForwardPtr)
1150     || Universe::heap()->is_in_reserved(p);
1151 }
1152 #endif
1153 
1154 void ParNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
1155   if (m->must_be_preserved_for_promotion_failure(obj)) {
1156     // We should really have separate per-worker stacks, rather
1157     // than use locking of a common pair of stacks.
1158     MutexLocker ml(ParGCRareEvent_lock);
1159     preserve_mark(obj, m);
1160   }
1161 }
1162 
1163 // Multiple GC threads may try to promote an object.  If the object
1164 // is successfully promoted, a forwarding pointer will be installed in
1165 // the object in the young generation.  This method claims the right
1166 // to install the forwarding pointer before it copies the object,
1167 // thus avoiding the need to undo the copy as in
1168 // copy_to_survivor_space_avoiding_with_undo.
1169 
1170 oop ParNewGeneration::copy_to_survivor_space_avoiding_promotion_undo(
1171         ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) {
1172   // In the sequential version, this assert also says that the object is
1173   // not forwarded.  That might not be the case here.  It is the case that
1174   // the caller observed it to be not forwarded at some time in the past.
1175   assert(is_in_reserved(old), "shouldn't be scavenging this oop");
1176 
1177   // The sequential code read "old->age()" below.  That doesn't work here,
1178   // since the age is in the mark word, and that might be overwritten with
1179   // a forwarding pointer by a parallel thread.  So we must save the mark
1180   // word in a local and then analyze it.
1181   oopDesc dummyOld;
1182   dummyOld.set_mark(m);
1183   assert(!dummyOld.is_forwarded(),
1184          "should not be called with forwarding pointer mark word.");
1185 
1186   oop new_obj = NULL;
1187   oop forward_ptr;
1188 
1189   // Try allocating obj in to-space (unless too old)
1190   if (dummyOld.age() < tenuring_threshold()) {
1191     new_obj = (oop)par_scan_state->alloc_in_to_space(sz, old, dummyOld.age());
1192     if (new_obj == NULL) {
1193       set_survivor_overflow(true);
1194     }
1195   }
1196 
1197   if (new_obj == NULL) {
1198     // Either to-space is full or we decided to promote
1199     // try allocating obj tenured
1200 
1201     // Attempt to install a null forwarding pointer (atomically),
1202     // to claim the right to install the real forwarding pointer.
1203     forward_ptr = old->forward_to_atomic(ClaimedForwardPtr);
1204     if (forward_ptr != NULL) {
1205       // someone else beat us to it.
1206         return real_forwardee(old);
1207     }
1208 
1209     new_obj = _next_gen->par_promote(par_scan_state->gc_tracer(),
1210                                      par_scan_state->thread_num(),
1211                                      old, m, sz);
1212 
1213     if (new_obj == NULL) {
1214       // promotion failed, forward to self
1215       _promotion_failed = true;
1216       new_obj = old;
1217 
1218       preserve_mark_if_necessary(old, m);
1219       par_scan_state->register_promotion_failure(sz);
1220     }
1221 
1222     old->forward_to(new_obj);
1223     forward_ptr = NULL;
1224   } else {
1225     // Is in to-space; do copying ourselves.
1226     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz);
1227     forward_ptr = old->forward_to_atomic(new_obj);
1228     // Restore the mark word copied above.
1229     new_obj->set_mark(m);
1230     // Increment age if obj still in new generation
1231     new_obj->incr_age();
1232     par_scan_state->age_table()->add(new_obj, sz);
1233   }
1234   assert(new_obj != NULL, "just checking");
1235 
1236 #ifndef PRODUCT
1237   // This code must come after the CAS test, or it will print incorrect
1238   // information.
1239   if (TraceScavenge) {
1240     gclog_or_tty->print_cr("{%s %s " PTR_FORMAT " -> " PTR_FORMAT " (%d)}",
1241        is_in_reserved(new_obj) ? "copying" : "tenuring",
1242        new_obj->klass()->internal_name(), (void *)old, (void *)new_obj, new_obj->size());
1243   }
1244 #endif
1245 
1246   if (forward_ptr == NULL) {
1247     oop obj_to_push = new_obj;
1248     if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) {
1249       // Length field used as index of next element to be scanned.
1250       // Real length can be obtained from real_forwardee()
1251       arrayOop(old)->set_length(0);
1252       obj_to_push = old;
1253       assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push,
1254              "push forwarded object");
1255     }
1256     // Push it on one of the queues of to-be-scanned objects.
1257     bool simulate_overflow = false;
1258     NOT_PRODUCT(
1259       if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) {
1260         // simulate a stack overflow
1261         simulate_overflow = true;
1262       }
1263     )
1264     if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) {
1265       // Add stats for overflow pushes.
1266       if (Verbose && PrintGCDetails) {
1267         gclog_or_tty->print("queue overflow!\n");
1268       }
1269       push_on_overflow_list(old, par_scan_state);
1270       TASKQUEUE_STATS_ONLY(par_scan_state->taskqueue_stats().record_overflow(0));
1271     }
1272 
1273     return new_obj;
1274   }
1275 
1276   // Oops.  Someone beat us to it.  Undo the allocation.  Where did we
1277   // allocate it?
1278   if (is_in_reserved(new_obj)) {
1279     // Must be in to_space.
1280     assert(to()->is_in_reserved(new_obj), "Checking");
1281     if (forward_ptr == ClaimedForwardPtr) {
1282       // Wait to get the real forwarding pointer value.
1283       forward_ptr = real_forwardee(old);
1284     }
1285     par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz);
1286   }
1287 
1288   return forward_ptr;
1289 }
1290 
1291 
1292 // Multiple GC threads may try to promote the same object.  If two
1293 // or more GC threads copy the object, only one wins the race to install
1294 // the forwarding pointer.  The other threads have to undo their copy.
1295 
1296 oop ParNewGeneration::copy_to_survivor_space_with_undo(
1297         ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) {
1298 
1299   // In the sequential version, this assert also says that the object is
1300   // not forwarded.  That might not be the case here.  It is the case that
1301   // the caller observed it to be not forwarded at some time in the past.
1302   assert(is_in_reserved(old), "shouldn't be scavenging this oop");
1303 
1304   // The sequential code read "old->age()" below.  That doesn't work here,
1305   // since the age is in the mark word, and that might be overwritten with
1306   // a forwarding pointer by a parallel thread.  So we must save the mark
1307   // word here, install it in a local oopDesc, and then analyze it.
1308   oopDesc dummyOld;
1309   dummyOld.set_mark(m);
1310   assert(!dummyOld.is_forwarded(),
1311          "should not be called with forwarding pointer mark word.");
1312 
1313   bool failed_to_promote = false;
1314   oop new_obj = NULL;
1315   oop forward_ptr;
1316 
1317   // Try allocating obj in to-space (unless too old)
1318   if (dummyOld.age() < tenuring_threshold()) {
1319     new_obj = (oop)par_scan_state->alloc_in_to_space(sz, old, dummyOld.age());
1320     if (new_obj == NULL) {
1321       set_survivor_overflow(true);
1322     }
1323   }
1324 
1325   if (new_obj == NULL) {
1326     // Either to-space is full or we decided to promote
1327     // try allocating obj tenured
1328     new_obj = _next_gen->par_promote(par_scan_state->gc_tracer(),
1329                                      par_scan_state->thread_num(),
1330                                      old, m, sz);
1331 
1332     if (new_obj == NULL) {
1333       // promotion failed, forward to self
1334       forward_ptr = old->forward_to_atomic(old);
1335       new_obj = old;
1336 
1337       if (forward_ptr != NULL) {
1338         return forward_ptr;   // someone else succeeded
1339       }
1340 
1341       _promotion_failed = true;
1342       failed_to_promote = true;
1343 
1344       preserve_mark_if_necessary(old, m);
1345       par_scan_state->register_promotion_failure(sz);
1346     }
1347   } else {
1348     // Is in to-space; do copying ourselves.
1349     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz);
1350     // Restore the mark word copied above.
1351     new_obj->set_mark(m);
1352     // Increment age if new_obj still in new generation
1353     new_obj->incr_age();
1354     par_scan_state->age_table()->add(new_obj, sz);
1355   }
1356   assert(new_obj != NULL, "just checking");
1357 
1358 #ifndef PRODUCT
1359   // This code must come after the CAS test, or it will print incorrect
1360   // information.
1361   if (TraceScavenge) {
1362     gclog_or_tty->print_cr("{%s %s " PTR_FORMAT " -> " PTR_FORMAT " (%d)}",
1363        is_in_reserved(new_obj) ? "copying" : "tenuring",
1364        new_obj->klass()->internal_name(), (void *)old, (void *)new_obj, new_obj->size());
1365   }
1366 #endif
1367 
1368   // Now attempt to install the forwarding pointer (atomically).
1369   // We have to copy the mark word before overwriting with forwarding
1370   // ptr, so we can restore it below in the copy.
1371   if (!failed_to_promote) {
1372     forward_ptr = old->forward_to_atomic(new_obj);
1373   }
1374 
1375   if (forward_ptr == NULL) {
1376     oop obj_to_push = new_obj;
1377     if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) {
1378       // Length field used as index of next element to be scanned.
1379       // Real length can be obtained from real_forwardee()
1380       arrayOop(old)->set_length(0);
1381       obj_to_push = old;
1382       assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push,
1383              "push forwarded object");
1384     }
1385     // Push it on one of the queues of to-be-scanned objects.
1386     bool simulate_overflow = false;
1387     NOT_PRODUCT(
1388       if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) {
1389         // simulate a stack overflow
1390         simulate_overflow = true;
1391       }
1392     )
1393     if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) {
1394       // Add stats for overflow pushes.
1395       push_on_overflow_list(old, par_scan_state);
1396       TASKQUEUE_STATS_ONLY(par_scan_state->taskqueue_stats().record_overflow(0));
1397     }
1398 
1399     return new_obj;
1400   }
1401 
1402   // Oops.  Someone beat us to it.  Undo the allocation.  Where did we
1403   // allocate it?
1404   if (is_in_reserved(new_obj)) {
1405     // Must be in to_space.
1406     assert(to()->is_in_reserved(new_obj), "Checking");
1407     par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz);
1408   } else {
1409     assert(!_avoid_promotion_undo, "Should not be here if avoiding.");
1410     _next_gen->par_promote_alloc_undo(par_scan_state->thread_num(),
1411                                       (HeapWord*)new_obj, sz);
1412   }
1413 
1414   return forward_ptr;
1415 }
1416 
1417 #ifndef PRODUCT
1418 // It's OK to call this multi-threaded;  the worst thing
1419 // that can happen is that we'll get a bunch of closely
1420 // spaced simulated overflows, but that's OK, in fact
1421 // probably good as it would exercise the overflow code
1422 // under contention.
1423 bool ParNewGeneration::should_simulate_overflow() {
1424   if (_overflow_counter-- <= 0) { // just being defensive
1425     _overflow_counter = ParGCWorkQueueOverflowInterval;
1426     return true;
1427   } else {
1428     return false;
1429   }
1430 }
1431 #endif
1432 
1433 // In case we are using compressed oops, we need to be careful.
1434 // If the object being pushed is an object array, then its length
1435 // field keeps track of the "grey boundary" at which the next
1436 // incremental scan will be done (see ParGCArrayScanChunk).
1437 // When using compressed oops, this length field is kept in the
1438 // lower 32 bits of the erstwhile klass word and cannot be used
1439 // for the overflow chaining pointer (OCP below). As such the OCP
1440 // would itself need to be compressed into the top 32-bits in this
1441 // case. Unfortunately, see below, in the event that we have a
1442 // promotion failure, the node to be pushed on the list can be
1443 // outside of the Java heap, so the heap-based pointer compression
1444 // would not work (we would have potential aliasing between C-heap
1445 // and Java-heap pointers). For this reason, when using compressed
1446 // oops, we simply use a worker-thread-local, non-shared overflow
1447 // list in the form of a growable array, with a slightly different
1448 // overflow stack draining strategy. If/when we start using fat
1449 // stacks here, we can go back to using (fat) pointer chains
1450 // (although some performance comparisons would be useful since
1451 // single global lists have their own performance disadvantages
1452 // as we were made painfully aware not long ago, see 6786503).
1453 #define BUSY (cast_to_oop<intptr_t>(0x1aff1aff))
1454 void ParNewGeneration::push_on_overflow_list(oop from_space_obj, ParScanThreadState* par_scan_state) {
1455   assert(is_in_reserved(from_space_obj), "Should be from this generation");
1456   if (ParGCUseLocalOverflow) {
1457     // In the case of compressed oops, we use a private, not-shared
1458     // overflow stack.
1459     par_scan_state->push_on_overflow_stack(from_space_obj);
1460   } else {
1461     assert(!UseCompressedOops, "Error");
1462     // if the object has been forwarded to itself, then we cannot
1463     // use the klass pointer for the linked list.  Instead we have
1464     // to allocate an oopDesc in the C-Heap and use that for the linked list.
1465     // XXX This is horribly inefficient when a promotion failure occurs
1466     // and should be fixed. XXX FIX ME !!!
1467 #ifndef PRODUCT
1468     Atomic::inc_ptr(&_num_par_pushes);
1469     assert(_num_par_pushes > 0, "Tautology");
1470 #endif
1471     if (from_space_obj->forwardee() == from_space_obj) {
1472       oopDesc* listhead = NEW_C_HEAP_ARRAY(oopDesc, 1, mtGC);
1473       listhead->forward_to(from_space_obj);
1474       from_space_obj = listhead;
1475     }
1476     oop observed_overflow_list = _overflow_list;
1477     oop cur_overflow_list;
1478     do {
1479       cur_overflow_list = observed_overflow_list;
1480       if (cur_overflow_list != BUSY) {
1481         from_space_obj->set_klass_to_list_ptr(cur_overflow_list);
1482       } else {
1483         from_space_obj->set_klass_to_list_ptr(NULL);
1484       }
1485       observed_overflow_list =
1486         (oop)Atomic::cmpxchg_ptr(from_space_obj, &_overflow_list, cur_overflow_list);
1487     } while (cur_overflow_list != observed_overflow_list);
1488   }
1489 }
1490 
1491 bool ParNewGeneration::take_from_overflow_list(ParScanThreadState* par_scan_state) {
1492   bool res;
1493 
1494   if (ParGCUseLocalOverflow) {
1495     res = par_scan_state->take_from_overflow_stack();
1496   } else {
1497     assert(!UseCompressedOops, "Error");
1498     res = take_from_overflow_list_work(par_scan_state);
1499   }
1500   return res;
1501 }
1502 
1503 
1504 // *NOTE*: The overflow list manipulation code here and
1505 // in CMSCollector:: are very similar in shape,
1506 // except that in the CMS case we thread the objects
1507 // directly into the list via their mark word, and do
1508 // not need to deal with special cases below related
1509 // to chunking of object arrays and promotion failure
1510 // handling.
1511 // CR 6797058 has been filed to attempt consolidation of
1512 // the common code.
1513 // Because of the common code, if you make any changes in
1514 // the code below, please check the CMS version to see if
1515 // similar changes might be needed.
1516 // See CMSCollector::par_take_from_overflow_list() for
1517 // more extensive documentation comments.
1518 bool ParNewGeneration::take_from_overflow_list_work(ParScanThreadState* par_scan_state) {
1519   ObjToScanQueue* work_q = par_scan_state->work_queue();
1520   // How many to take?
1521   size_t objsFromOverflow = MIN2((size_t)(work_q->max_elems() - work_q->size())/4,
1522                                  (size_t)ParGCDesiredObjsFromOverflowList);
1523 
1524   assert(!UseCompressedOops, "Error");
1525   assert(par_scan_state->overflow_stack() == NULL, "Error");
1526   if (_overflow_list == NULL) return false;
1527 
1528   // Otherwise, there was something there; try claiming the list.
1529   oop prefix = cast_to_oop(Atomic::xchg_ptr(BUSY, &_overflow_list));
1530   // Trim off a prefix of at most objsFromOverflow items
1531   Thread* tid = Thread::current();
1532   size_t spin_count = (size_t)ParallelGCThreads;
1533   size_t sleep_time_millis = MAX2((size_t)1, objsFromOverflow/100);
1534   for (size_t spin = 0; prefix == BUSY && spin < spin_count; spin++) {
1535     // someone grabbed it before we did ...
1536     // ... we spin for a short while...
1537     os::sleep(tid, sleep_time_millis, false);
1538     if (_overflow_list == NULL) {
1539       // nothing left to take
1540       return false;
1541     } else if (_overflow_list != BUSY) {
1542      // try and grab the prefix
1543      prefix = cast_to_oop(Atomic::xchg_ptr(BUSY, &_overflow_list));
1544     }
1545   }
1546   if (prefix == NULL || prefix == BUSY) {
1547      // Nothing to take or waited long enough
1548      if (prefix == NULL) {
1549        // Write back the NULL in case we overwrote it with BUSY above
1550        // and it is still the same value.
1551        (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY);
1552      }
1553      return false;
1554   }
1555   assert(prefix != NULL && prefix != BUSY, "Error");
1556   size_t i = 1;
1557   oop cur = prefix;
1558   while (i < objsFromOverflow && cur->klass_or_null() != NULL) {
1559     i++; cur = cur->list_ptr_from_klass();
1560   }
1561 
1562   // Reattach remaining (suffix) to overflow list
1563   if (cur->klass_or_null() == NULL) {
1564     // Write back the NULL in lieu of the BUSY we wrote
1565     // above and it is still the same value.
1566     if (_overflow_list == BUSY) {
1567       (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY);
1568     }
1569   } else {
1570     assert(cur->klass_or_null() != (Klass*)(address)BUSY, "Error");
1571     oop suffix = cur->list_ptr_from_klass();       // suffix will be put back on global list
1572     cur->set_klass_to_list_ptr(NULL);     // break off suffix
1573     // It's possible that the list is still in the empty(busy) state
1574     // we left it in a short while ago; in that case we may be
1575     // able to place back the suffix.
1576     oop observed_overflow_list = _overflow_list;
1577     oop cur_overflow_list = observed_overflow_list;
1578     bool attached = false;
1579     while (observed_overflow_list == BUSY || observed_overflow_list == NULL) {
1580       observed_overflow_list =
1581         (oop) Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list);
1582       if (cur_overflow_list == observed_overflow_list) {
1583         attached = true;
1584         break;
1585       } else cur_overflow_list = observed_overflow_list;
1586     }
1587     if (!attached) {
1588       // Too bad, someone else got in in between; we'll need to do a splice.
1589       // Find the last item of suffix list
1590       oop last = suffix;
1591       while (last->klass_or_null() != NULL) {
1592         last = last->list_ptr_from_klass();
1593       }
1594       // Atomically prepend suffix to current overflow list
1595       observed_overflow_list = _overflow_list;
1596       do {
1597         cur_overflow_list = observed_overflow_list;
1598         if (cur_overflow_list != BUSY) {
1599           // Do the splice ...
1600           last->set_klass_to_list_ptr(cur_overflow_list);
1601         } else { // cur_overflow_list == BUSY
1602           last->set_klass_to_list_ptr(NULL);
1603         }
1604         observed_overflow_list =
1605           (oop)Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list);
1606       } while (cur_overflow_list != observed_overflow_list);
1607     }
1608   }
1609 
1610   // Push objects on prefix list onto this thread's work queue
1611   assert(prefix != NULL && prefix != BUSY, "program logic");
1612   cur = prefix;
1613   ssize_t n = 0;
1614   while (cur != NULL) {
1615     oop obj_to_push = cur->forwardee();
1616     oop next        = cur->list_ptr_from_klass();
1617     cur->set_klass(obj_to_push->klass());
1618     // This may be an array object that is self-forwarded. In that case, the list pointer
1619     // space, cur, is not in the Java heap, but rather in the C-heap and should be freed.
1620     if (!is_in_reserved(cur)) {
1621       // This can become a scaling bottleneck when there is work queue overflow coincident
1622       // with promotion failure.
1623       oopDesc* f = cur;
1624       FREE_C_HEAP_ARRAY(oopDesc, f, mtGC);
1625     } else if (par_scan_state->should_be_partially_scanned(obj_to_push, cur)) {
1626       assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned");
1627       obj_to_push = cur;
1628     }
1629     bool ok = work_q->push(obj_to_push);
1630     assert(ok, "Should have succeeded");
1631     cur = next;
1632     n++;
1633   }
1634   TASKQUEUE_STATS_ONLY(par_scan_state->note_overflow_refill(n));
1635 #ifndef PRODUCT
1636   assert(_num_par_pushes >= n, "Too many pops?");
1637   Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes);
1638 #endif
1639   return true;
1640 }
1641 #undef BUSY
1642 
1643 void ParNewGeneration::ref_processor_init() {
1644   if (_ref_processor == NULL) {
1645     // Allocate and initialize a reference processor
1646     _ref_processor =
1647       new ReferenceProcessor(_reserved,                  // span
1648                              ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
1649                              (int) ParallelGCThreads,    // mt processing degree
1650                              refs_discovery_is_mt(),     // mt discovery
1651                              (int) ParallelGCThreads,    // mt discovery degree
1652                              refs_discovery_is_atomic(), // atomic_discovery
1653                              NULL);                      // is_alive_non_header
1654   }
1655 }
1656 
1657 const char* ParNewGeneration::name() const {
1658   return "par new generation";
1659 }