1 /*
   2  * Copyright (c) 2001, 2017, 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/cms/compactibleFreeListSpace.hpp"
  27 #include "gc/cms/concurrentMarkSweepGeneration.hpp"
  28 #include "gc/cms/parNewGeneration.inline.hpp"
  29 #include "gc/cms/parOopClosures.inline.hpp"
  30 #include "gc/serial/defNewGeneration.inline.hpp"
  31 #include "gc/shared/adaptiveSizePolicy.hpp"
  32 #include "gc/shared/ageTable.inline.hpp"
  33 #include "gc/shared/copyFailedInfo.hpp"
  34 #include "gc/shared/gcHeapSummary.hpp"
  35 #include "gc/shared/gcTimer.hpp"
  36 #include "gc/shared/gcTrace.hpp"
  37 #include "gc/shared/gcTraceTime.inline.hpp"
  38 #include "gc/shared/genCollectedHeap.hpp"
  39 #include "gc/shared/genOopClosures.inline.hpp"
  40 #include "gc/shared/generation.hpp"
  41 #include "gc/shared/plab.inline.hpp"
  42 #include "gc/shared/preservedMarks.inline.hpp"
  43 #include "gc/shared/referencePolicy.hpp"
  44 #include "gc/shared/space.hpp"
  45 #include "gc/shared/spaceDecorator.hpp"
  46 #include "gc/shared/strongRootsScope.hpp"
  47 #include "gc/shared/taskqueue.inline.hpp"
  48 #include "gc/shared/workgroup.hpp"
  49 #include "logging/log.hpp"
  50 #include "memory/resourceArea.hpp"
  51 #include "oops/objArrayOop.hpp"
  52 #include "oops/oop.inline.hpp"
  53 #include "runtime/atomic.hpp"
  54 #include "runtime/handles.hpp"
  55 #include "runtime/handles.inline.hpp"
  56 #include "runtime/java.hpp"
  57 #include "runtime/thread.inline.hpp"
  58 #include "utilities/copy.hpp"
  59 #include "utilities/globalDefinitions.hpp"
  60 #include "utilities/stack.inline.hpp"
  61 
  62 ParScanThreadState::ParScanThreadState(Space* to_space_,
  63                                        ParNewGeneration* young_gen_,
  64                                        Generation* old_gen_,
  65                                        int thread_num_,
  66                                        ObjToScanQueueSet* work_queue_set_,
  67                                        Stack<oop, mtGC>* overflow_stacks_,
  68                                        PreservedMarks* preserved_marks_,
  69                                        size_t desired_plab_sz_,
  70                                        ParallelTaskTerminator& term_) :
  71   _to_space(to_space_),
  72   _old_gen(old_gen_),
  73   _young_gen(young_gen_),
  74   _thread_num(thread_num_),
  75   _work_queue(work_queue_set_->queue(thread_num_)),
  76   _to_space_full(false),
  77   _overflow_stack(overflow_stacks_ ? overflow_stacks_ + thread_num_ : NULL),
  78   _preserved_marks(preserved_marks_),
  79   _ageTable(false), // false ==> not the global age table, no perf data.
  80   _to_space_alloc_buffer(desired_plab_sz_),
  81   _to_space_closure(young_gen_, this),
  82   _old_gen_closure(young_gen_, this),
  83   _to_space_root_closure(young_gen_, this),
  84   _old_gen_root_closure(young_gen_, this),
  85   _older_gen_closure(young_gen_, this),
  86   _evacuate_followers(this, &_to_space_closure, &_old_gen_closure,
  87                       &_to_space_root_closure, young_gen_, &_old_gen_root_closure,
  88                       work_queue_set_, &term_),
  89   _is_alive_closure(young_gen_),
  90   _scan_weak_ref_closure(young_gen_, this),
  91   _keep_alive_closure(&_scan_weak_ref_closure),
  92   _strong_roots_time(0.0),
  93   _term_time(0.0)
  94 {
  95   #if TASKQUEUE_STATS
  96   _term_attempts = 0;
  97   _overflow_refills = 0;
  98   _overflow_refill_objs = 0;
  99   #endif // TASKQUEUE_STATS
 100 
 101   _survivor_chunk_array = (ChunkArray*) old_gen()->get_data_recorder(thread_num());
 102   _hash_seed = 17;  // Might want to take time-based random value.
 103   _start = os::elapsedTime();
 104   _old_gen_closure.set_generation(old_gen_);
 105   _old_gen_root_closure.set_generation(old_gen_);
 106 }
 107 
 108 void ParScanThreadState::record_survivor_plab(HeapWord* plab_start,
 109                                               size_t plab_word_size) {
 110   ChunkArray* sca = survivor_chunk_array();
 111   if (sca != NULL) {
 112     // A non-null SCA implies that we want the PLAB data recorded.
 113     sca->record_sample(plab_start, plab_word_size);
 114   }
 115 }
 116 
 117 bool ParScanThreadState::should_be_partially_scanned(oop new_obj, oop old_obj) const {
 118   return new_obj->is_objArray() &&
 119          arrayOop(new_obj)->length() > ParGCArrayScanChunk &&
 120          new_obj != old_obj;
 121 }
 122 
 123 void ParScanThreadState::scan_partial_array_and_push_remainder(oop old) {
 124   assert(old->is_objArray(), "must be obj array");
 125   assert(old->is_forwarded(), "must be forwarded");
 126   assert(GenCollectedHeap::heap()->is_in_reserved(old), "must be in heap.");
 127   assert(!old_gen()->is_in(old), "must be in young generation.");
 128 
 129   objArrayOop obj = objArrayOop(old->forwardee());
 130   // Process ParGCArrayScanChunk elements now
 131   // and push the remainder back onto queue
 132   int start     = arrayOop(old)->length();
 133   int end       = obj->length();
 134   int remainder = end - start;
 135   assert(start <= end, "just checking");
 136   if (remainder > 2 * ParGCArrayScanChunk) {
 137     // Test above combines last partial chunk with a full chunk
 138     end = start + ParGCArrayScanChunk;
 139     arrayOop(old)->set_length(end);
 140     // Push remainder.
 141     bool ok = work_queue()->push(old);
 142     assert(ok, "just popped, push must be okay");
 143   } else {
 144     // Restore length so that it can be used if there
 145     // is a promotion failure and forwarding pointers
 146     // must be removed.
 147     arrayOop(old)->set_length(end);
 148   }
 149 
 150   // process our set of indices (include header in first chunk)
 151   // should make sure end is even (aligned to HeapWord in case of compressed oops)
 152   if ((HeapWord *)obj < young_old_boundary()) {
 153     // object is in to_space
 154     obj->oop_iterate_range(&_to_space_closure, start, end);
 155   } else {
 156     // object is in old generation
 157     obj->oop_iterate_range(&_old_gen_closure, start, end);
 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(GenCollectedHeap::heap()->is_in_reserved(cur), "Should be in heap");
 208     assert(!old_gen()->is_in_reserved(cur), "Should be in young gen");
 209     assert(GenCollectedHeap::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   // If the object is small enough, try to reallocate the buffer.
 229   HeapWord* obj = NULL;
 230   if (!_to_space_full) {
 231     PLAB* const plab = to_space_alloc_buffer();
 232     Space* const sp  = to_space();
 233     if (word_sz * 100 < ParallelGCBufferWastePct * plab->word_sz()) {
 234       // Is small enough; abandon this buffer and start a new one.
 235       plab->retire();
 236       // The minimum size has to be twice SurvivorAlignmentInBytes to
 237       // allow for padding used in the alignment of 1 word.  A padding
 238       // of 1 is too small for a filler word so the padding size will
 239       // be increased by SurvivorAlignmentInBytes.
 240       size_t min_usable_size = 2 * static_cast<size_t>(SurvivorAlignmentInBytes >> LogHeapWordSize);
 241       size_t buf_size = MAX2(plab->word_sz(), min_usable_size);
 242       HeapWord* buf_space = sp->par_allocate(buf_size);
 243       if (buf_space == NULL) {
 244         const size_t min_bytes = MAX2(PLAB::min_size(), min_usable_size) << LogHeapWordSize;
 245         size_t free_bytes = sp->free();
 246         while(buf_space == NULL && free_bytes >= min_bytes) {
 247           buf_size = free_bytes >> LogHeapWordSize;
 248           assert(buf_size == (size_t)align_object_size(buf_size), "Invariant");
 249           buf_space  = sp->par_allocate(buf_size);
 250           free_bytes = sp->free();
 251         }
 252       }
 253       if (buf_space != NULL) {
 254         plab->set_buf(buf_space, buf_size);
 255         record_survivor_plab(buf_space, buf_size);
 256         obj = plab->allocate_aligned(word_sz, SurvivorAlignmentInBytes);
 257         // Note that we cannot compare buf_size < word_sz below
 258         // because of AlignmentReserve (see PLAB::allocate()).
 259         assert(obj != NULL || plab->words_remaining() < word_sz,
 260                "Else should have been able to allocate requested object size "
 261                SIZE_FORMAT ", PLAB size " SIZE_FORMAT ", SurvivorAlignmentInBytes "
 262                SIZE_FORMAT ", words_remaining " SIZE_FORMAT,
 263                word_sz, buf_size, SurvivorAlignmentInBytes, plab->words_remaining());
 264         // It's conceivable that we may be able to use the
 265         // buffer we just grabbed for subsequent small requests
 266         // even if not for this one.
 267       } else {
 268         // We're used up.
 269         _to_space_full = true;
 270       }
 271     } else {
 272       // Too large; allocate the object individually.
 273       obj = sp->par_allocate(word_sz);
 274     }
 275   }
 276   return obj;
 277 }
 278 
 279 void ParScanThreadState::undo_alloc_in_to_space(HeapWord* obj, size_t word_sz) {
 280   to_space_alloc_buffer()->undo_allocation(obj, word_sz);
 281 }
 282 
 283 void ParScanThreadState::print_promotion_failure_size() {
 284   if (_promotion_failed_info.has_failed()) {
 285     log_trace(gc, promotion)(" (%d: promotion failure size = " SIZE_FORMAT ") ",
 286                              _thread_num, _promotion_failed_info.first_size());
 287   }
 288 }
 289 
 290 class ParScanThreadStateSet: StackObj {
 291 public:
 292   // Initializes states for the specified number of threads;
 293   ParScanThreadStateSet(int                     num_threads,
 294                         Space&                  to_space,
 295                         ParNewGeneration&       young_gen,
 296                         Generation&             old_gen,
 297                         ObjToScanQueueSet&      queue_set,
 298                         Stack<oop, mtGC>*       overflow_stacks_,
 299                         PreservedMarksSet&      preserved_marks_set,
 300                         size_t                  desired_plab_sz,
 301                         ParallelTaskTerminator& term);
 302 
 303   ~ParScanThreadStateSet() { TASKQUEUE_STATS_ONLY(reset_stats()); }
 304 
 305   inline ParScanThreadState& thread_state(int i);
 306 
 307   void trace_promotion_failed(const YoungGCTracer* gc_tracer);
 308   void reset(uint active_workers, bool promotion_failed);
 309   void flush();
 310 
 311   #if TASKQUEUE_STATS
 312   static void
 313     print_termination_stats_hdr(outputStream* const st);
 314   void print_termination_stats();
 315   static void
 316     print_taskqueue_stats_hdr(outputStream* const st);
 317   void print_taskqueue_stats();
 318   void reset_stats();
 319   #endif // TASKQUEUE_STATS
 320 
 321 private:
 322   ParallelTaskTerminator& _term;
 323   ParNewGeneration&       _young_gen;
 324   Generation&             _old_gen;
 325   ParScanThreadState*     _per_thread_states;
 326   const int               _num_threads;
 327  public:
 328   bool is_valid(int id) const { return id < _num_threads; }
 329   ParallelTaskTerminator* terminator() { return &_term; }
 330 };
 331 
 332 ParScanThreadStateSet::ParScanThreadStateSet(int num_threads,
 333                                              Space& to_space,
 334                                              ParNewGeneration& young_gen,
 335                                              Generation& old_gen,
 336                                              ObjToScanQueueSet& queue_set,
 337                                              Stack<oop, mtGC>* overflow_stacks,
 338                                              PreservedMarksSet& preserved_marks_set,
 339                                              size_t desired_plab_sz,
 340                                              ParallelTaskTerminator& term)
 341   : _young_gen(young_gen),
 342     _old_gen(old_gen),
 343     _term(term),
 344     _per_thread_states(NEW_RESOURCE_ARRAY(ParScanThreadState, num_threads)),
 345     _num_threads(num_threads)
 346 {
 347   assert(num_threads > 0, "sanity check!");
 348   assert(ParGCUseLocalOverflow == (overflow_stacks != NULL),
 349          "overflow_stack allocation mismatch");
 350   // Initialize states.
 351   for (int i = 0; i < num_threads; ++i) {
 352     new(_per_thread_states + i)
 353       ParScanThreadState(&to_space, &young_gen, &old_gen, i, &queue_set,
 354                          overflow_stacks, preserved_marks_set.get(i),
 355                          desired_plab_sz, term);
 356   }
 357 }
 358 
 359 inline ParScanThreadState& ParScanThreadStateSet::thread_state(int i) {
 360   assert(i >= 0 && i < _num_threads, "sanity check!");
 361   return _per_thread_states[i];
 362 }
 363 
 364 void ParScanThreadStateSet::trace_promotion_failed(const YoungGCTracer* gc_tracer) {
 365   for (int i = 0; i < _num_threads; ++i) {
 366     if (thread_state(i).promotion_failed()) {
 367       gc_tracer->report_promotion_failed(thread_state(i).promotion_failed_info());
 368       thread_state(i).promotion_failed_info().reset();
 369     }
 370   }
 371 }
 372 
 373 void ParScanThreadStateSet::reset(uint active_threads, bool promotion_failed) {
 374   _term.reset_for_reuse(active_threads);
 375   if (promotion_failed) {
 376     for (int i = 0; i < _num_threads; ++i) {
 377       thread_state(i).print_promotion_failure_size();
 378     }
 379   }
 380 }
 381 
 382 #if TASKQUEUE_STATS
 383 void ParScanThreadState::reset_stats() {
 384   taskqueue_stats().reset();
 385   _term_attempts = 0;
 386   _overflow_refills = 0;
 387   _overflow_refill_objs = 0;
 388 }
 389 
 390 void ParScanThreadStateSet::reset_stats() {
 391   for (int i = 0; i < _num_threads; ++i) {
 392     thread_state(i).reset_stats();
 393   }
 394 }
 395 
 396 void ParScanThreadStateSet::print_termination_stats_hdr(outputStream* const st) {
 397   st->print_raw_cr("GC Termination Stats");
 398   st->print_raw_cr("     elapsed  --strong roots-- -------termination-------");
 399   st->print_raw_cr("thr     ms        ms       %       ms       %   attempts");
 400   st->print_raw_cr("--- --------- --------- ------ --------- ------ --------");
 401 }
 402 
 403 void ParScanThreadStateSet::print_termination_stats() {
 404   Log(gc, task, stats) log;
 405   if (!log.is_debug()) {
 406     return;
 407   }
 408 
 409   ResourceMark rm;
 410   outputStream* st = log.debug_stream();
 411 
 412   print_termination_stats_hdr(st);
 413 
 414   for (int i = 0; i < _num_threads; ++i) {
 415     const ParScanThreadState & pss = thread_state(i);
 416     const double elapsed_ms = pss.elapsed_time() * 1000.0;
 417     const double s_roots_ms = pss.strong_roots_time() * 1000.0;
 418     const double term_ms = pss.term_time() * 1000.0;
 419     st->print_cr("%3d %9.2f %9.2f %6.2f %9.2f %6.2f " SIZE_FORMAT_W(8),
 420                  i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
 421                  term_ms, term_ms * 100 / elapsed_ms, pss.term_attempts());
 422   }
 423 }
 424 
 425 // Print stats related to work queue activity.
 426 void ParScanThreadStateSet::print_taskqueue_stats_hdr(outputStream* const st) {
 427   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() {
 433   if (!log_develop_is_enabled(Trace, gc, task, stats)) {
 434     return;
 435   }
 436   Log(gc, task, stats) log;
 437   ResourceMark rm;
 438   outputStream* st = log.trace_stream();
 439   print_taskqueue_stats_hdr(st);
 440 
 441   TaskQueueStats totals;
 442   for (int i = 0; i < _num_threads; ++i) {
 443     const ParScanThreadState & pss = thread_state(i);
 444     const TaskQueueStats & stats = pss.taskqueue_stats();
 445     st->print("%3d ", i); stats.print(st); st->cr();
 446     totals += stats;
 447 
 448     if (pss.overflow_refills() > 0) {
 449       st->print_cr("    " SIZE_FORMAT_W(10) " overflow refills    "
 450                    SIZE_FORMAT_W(10) " overflow objects",
 451                    pss.overflow_refills(), pss.overflow_refill_objs());
 452     }
 453   }
 454   st->print("tot "); totals.print(st); st->cr();
 455 
 456   DEBUG_ONLY(totals.verify());
 457 }
 458 #endif // TASKQUEUE_STATS
 459 
 460 void ParScanThreadStateSet::flush() {
 461   // Work in this loop should be kept as lightweight as
 462   // possible since this might otherwise become a bottleneck
 463   // to scaling. Should we add heavy-weight work into this
 464   // loop, consider parallelizing the loop into the worker threads.
 465   for (int i = 0; i < _num_threads; ++i) {
 466     ParScanThreadState& par_scan_state = thread_state(i);
 467 
 468     // Flush stats related to To-space PLAB activity and
 469     // retire the last buffer.
 470     par_scan_state.to_space_alloc_buffer()->flush_and_retire_stats(_young_gen.plab_stats());
 471 
 472     // Every thread has its own age table.  We need to merge
 473     // them all into one.
 474     AgeTable *local_table = par_scan_state.age_table();
 475     _young_gen.age_table()->merge(local_table);
 476 
 477     // Inform old gen that we're done.
 478     _old_gen.par_promote_alloc_done(i);
 479   }
 480 
 481   if (UseConcMarkSweepGC) {
 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     CompactibleFreeListSpaceLAB::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   _boundary = _g->reserved().end();
 495 }
 496 
 497 void ParScanWithBarrierClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, true, false); }
 498 void ParScanWithBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, false); }
 499 
 500 void ParScanWithoutBarrierClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, false, false); }
 501 void ParScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, false); }
 502 
 503 void ParRootScanWithBarrierTwoGensClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, true, true); }
 504 void ParRootScanWithBarrierTwoGensClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, true); }
 505 
 506 void ParRootScanWithoutBarrierClosure::do_oop(oop* p)       { ParScanClosure::do_oop_work(p, false, true); }
 507 void ParRootScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, true); }
 508 
 509 ParScanWeakRefClosure::ParScanWeakRefClosure(ParNewGeneration* g,
 510                                              ParScanThreadState* par_scan_state)
 511   : ScanWeakRefClosure(g), _par_scan_state(par_scan_state)
 512 {}
 513 
 514 void ParScanWeakRefClosure::do_oop(oop* p)       { ParScanWeakRefClosure::do_oop_work(p); }
 515 void ParScanWeakRefClosure::do_oop(narrowOop* p) { ParScanWeakRefClosure::do_oop_work(p); }
 516 
 517 #ifdef WIN32
 518 #pragma warning(disable: 4786) /* identifier was truncated to '255' characters in the browser information */
 519 #endif
 520 
 521 ParEvacuateFollowersClosure::ParEvacuateFollowersClosure(
 522     ParScanThreadState* par_scan_state_,
 523     ParScanWithoutBarrierClosure* to_space_closure_,
 524     ParScanWithBarrierClosure* old_gen_closure_,
 525     ParRootScanWithoutBarrierClosure* to_space_root_closure_,
 526     ParNewGeneration* par_gen_,
 527     ParRootScanWithBarrierTwoGensClosure* old_gen_root_closure_,
 528     ObjToScanQueueSet* task_queues_,
 529     ParallelTaskTerminator* terminator_) :
 530 
 531     _par_scan_state(par_scan_state_),
 532     _to_space_closure(to_space_closure_),
 533     _old_gen_closure(old_gen_closure_),
 534     _to_space_root_closure(to_space_root_closure_),
 535     _old_gen_root_closure(old_gen_root_closure_),
 536     _par_gen(par_gen_),
 537     _task_queues(task_queues_),
 538     _terminator(terminator_)
 539 {}
 540 
 541 void ParEvacuateFollowersClosure::do_void() {
 542   ObjToScanQueue* work_q = par_scan_state()->work_queue();
 543 
 544   while (true) {
 545     // Scan to-space and old-gen objs until we run out of both.
 546     oop obj_to_scan;
 547     par_scan_state()->trim_queues(0);
 548 
 549     // We have no local work, attempt to steal from other threads.
 550 
 551     // Attempt to steal work from promoted.
 552     if (task_queues()->steal(par_scan_state()->thread_num(),
 553                              par_scan_state()->hash_seed(),
 554                              obj_to_scan)) {
 555       bool res = work_q->push(obj_to_scan);
 556       assert(res, "Empty queue should have room for a push.");
 557 
 558       // If successful, goto Start.
 559       continue;
 560 
 561       // Try global overflow list.
 562     } else if (par_gen()->take_from_overflow_list(par_scan_state())) {
 563       continue;
 564     }
 565 
 566     // Otherwise, offer termination.
 567     par_scan_state()->start_term_time();
 568     if (terminator()->offer_termination()) break;
 569     par_scan_state()->end_term_time();
 570   }
 571   assert(par_gen()->_overflow_list == NULL && par_gen()->_num_par_pushes == 0,
 572          "Broken overflow list?");
 573   // Finish the last termination pause.
 574   par_scan_state()->end_term_time();
 575 }
 576 
 577 ParNewGenTask::ParNewGenTask(ParNewGeneration* young_gen,
 578                              Generation* old_gen,
 579                              HeapWord* young_old_boundary,
 580                              ParScanThreadStateSet* state_set,
 581                              StrongRootsScope* strong_roots_scope) :
 582     AbstractGangTask("ParNewGeneration collection"),
 583     _young_gen(young_gen), _old_gen(old_gen),
 584     _young_old_boundary(young_old_boundary),
 585     _state_set(state_set),
 586     _strong_roots_scope(strong_roots_scope)
 587 {}
 588 
 589 void ParNewGenTask::work(uint worker_id) {
 590   GenCollectedHeap* gch = GenCollectedHeap::heap();
 591   // Since this is being done in a separate thread, need new resource
 592   // and handle marks.
 593   ResourceMark rm;
 594   HandleMark hm;
 595 
 596   ParScanThreadState& par_scan_state = _state_set->thread_state(worker_id);
 597   assert(_state_set->is_valid(worker_id), "Should not have been called");
 598 
 599   par_scan_state.set_young_old_boundary(_young_old_boundary);
 600 
 601   KlassScanClosure klass_scan_closure(&par_scan_state.to_space_root_closure(),
 602                                       gch->rem_set()->klass_rem_set());
 603   CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
 604                                            &par_scan_state.to_space_root_closure(),
 605                                            false);
 606 
 607   par_scan_state.start_strong_roots();
 608   gch->young_process_roots(_strong_roots_scope,
 609                            &par_scan_state.to_space_root_closure(),
 610                            &par_scan_state.older_gen_closure(),
 611                            &cld_scan_closure);
 612 
 613   par_scan_state.end_strong_roots();
 614 
 615   // "evacuate followers".
 616   par_scan_state.evacuate_followers_closure().do_void();
 617 
 618   // This will collapse this worker's promoted object list that's
 619   // created during the main ParNew parallel phase of ParNew. This has
 620   // to be called after all workers have finished promoting objects
 621   // and scanning promoted objects. It should be safe calling it from
 622   // here, given that we can only reach here after all thread have
 623   // offered termination, i.e., after there is no more work to be
 624   // done. It will also disable promotion tracking for the rest of
 625   // this GC as it's not necessary to be on during reference processing.
 626   _old_gen->par_oop_since_save_marks_iterate_done((int) worker_id);
 627 }
 628 
 629 ParNewGeneration::ParNewGeneration(ReservedSpace rs, size_t initial_byte_size)
 630   : DefNewGeneration(rs, initial_byte_size, "PCopy"),
 631   _overflow_list(NULL),
 632   _is_alive_closure(this),
 633   _plab_stats("Young", YoungPLABSize, PLABWeight)
 634 {
 635   NOT_PRODUCT(_overflow_counter = ParGCWorkQueueOverflowInterval;)
 636   NOT_PRODUCT(_num_par_pushes = 0;)
 637   _task_queues = new ObjToScanQueueSet(ParallelGCThreads);
 638   guarantee(_task_queues != NULL, "task_queues allocation failure.");
 639 
 640   for (uint i = 0; i < ParallelGCThreads; i++) {
 641     ObjToScanQueue *q = new ObjToScanQueue();
 642     guarantee(q != NULL, "work_queue Allocation failure.");
 643     _task_queues->register_queue(i, q);
 644   }
 645 
 646   for (uint i = 0; i < ParallelGCThreads; i++) {
 647     _task_queues->queue(i)->initialize();
 648   }
 649 
 650   _overflow_stacks = NULL;
 651   if (ParGCUseLocalOverflow) {
 652     // typedef to workaround NEW_C_HEAP_ARRAY macro, which can not deal with ','
 653     typedef Stack<oop, mtGC> GCOopStack;
 654 
 655     _overflow_stacks = NEW_C_HEAP_ARRAY(GCOopStack, ParallelGCThreads, mtGC);
 656     for (size_t i = 0; i < ParallelGCThreads; ++i) {
 657       new (_overflow_stacks + i) Stack<oop, mtGC>();
 658     }
 659   }
 660 
 661   if (UsePerfData) {
 662     EXCEPTION_MARK;
 663     ResourceMark rm;
 664 
 665     const char* cname =
 666          PerfDataManager::counter_name(_gen_counters->name_space(), "threads");
 667     PerfDataManager::create_constant(SUN_GC, cname, PerfData::U_None,
 668                                      ParallelGCThreads, CHECK);
 669   }
 670 }
 671 
 672 // ParNewGeneration::
 673 ParKeepAliveClosure::ParKeepAliveClosure(ParScanWeakRefClosure* cl) :
 674   DefNewGeneration::KeepAliveClosure(cl), _par_cl(cl) {}
 675 
 676 template <class T>
 677 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop_work(T* p) {
 678 #ifdef ASSERT
 679   {
 680     assert(!oopDesc::is_null(*p), "expected non-null ref");
 681     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
 682     // We never expect to see a null reference being processed
 683     // as a weak reference.
 684     assert(obj->is_oop(), "expected an oop while scanning weak refs");
 685   }
 686 #endif // ASSERT
 687 
 688   _par_cl->do_oop_nv(p);
 689 
 690   if (GenCollectedHeap::heap()->is_in_reserved(p)) {
 691     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
 692     _rs->write_ref_field_gc_par(p, obj);
 693   }
 694 }
 695 
 696 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(oop* p)       { ParKeepAliveClosure::do_oop_work(p); }
 697 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(narrowOop* p) { ParKeepAliveClosure::do_oop_work(p); }
 698 
 699 // ParNewGeneration::
 700 KeepAliveClosure::KeepAliveClosure(ScanWeakRefClosure* cl) :
 701   DefNewGeneration::KeepAliveClosure(cl) {}
 702 
 703 template <class T>
 704 void /*ParNewGeneration::*/KeepAliveClosure::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   _cl->do_oop_nv(p);
 716 
 717   if (GenCollectedHeap::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::*/KeepAliveClosure::do_oop(oop* p)       { KeepAliveClosure::do_oop_work(p); }
 724 void /*ParNewGeneration::*/KeepAliveClosure::do_oop(narrowOop* p) { KeepAliveClosure::do_oop_work(p); }
 725 
 726 template <class T> void ScanClosureWithParBarrier::do_oop_work(T* p) {
 727   T heap_oop = oopDesc::load_heap_oop(p);
 728   if (!oopDesc::is_null(heap_oop)) {
 729     oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
 730     if ((HeapWord*)obj < _boundary) {
 731       assert(!_g->to()->is_in_reserved(obj), "Scanning field twice?");
 732       oop new_obj = obj->is_forwarded()
 733                       ? obj->forwardee()
 734                       : _g->DefNewGeneration::copy_to_survivor_space(obj);
 735       oopDesc::encode_store_heap_oop_not_null(p, new_obj);
 736     }
 737     if (_gc_barrier) {
 738       // If p points to a younger generation, mark the card.
 739       if ((HeapWord*)obj < _gen_boundary) {
 740         _rs->write_ref_field_gc_par(p, obj);
 741       }
 742     }
 743   }
 744 }
 745 
 746 void ScanClosureWithParBarrier::do_oop(oop* p)       { ScanClosureWithParBarrier::do_oop_work(p); }
 747 void ScanClosureWithParBarrier::do_oop(narrowOop* p) { ScanClosureWithParBarrier::do_oop_work(p); }
 748 
 749 class ParNewRefProcTaskProxy: public AbstractGangTask {
 750   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
 751 public:
 752   ParNewRefProcTaskProxy(ProcessTask& task,
 753                          ParNewGeneration& young_gen,
 754                          Generation& old_gen,
 755                          HeapWord* young_old_boundary,
 756                          ParScanThreadStateSet& state_set);
 757 
 758 private:
 759   virtual void work(uint worker_id);
 760 private:
 761   ParNewGeneration&      _young_gen;
 762   ProcessTask&           _task;
 763   Generation&            _old_gen;
 764   HeapWord*              _young_old_boundary;
 765   ParScanThreadStateSet& _state_set;
 766 };
 767 
 768 ParNewRefProcTaskProxy::ParNewRefProcTaskProxy(ProcessTask& task,
 769                                                ParNewGeneration& young_gen,
 770                                                Generation& old_gen,
 771                                                HeapWord* young_old_boundary,
 772                                                ParScanThreadStateSet& state_set)
 773   : AbstractGangTask("ParNewGeneration parallel reference processing"),
 774     _young_gen(young_gen),
 775     _task(task),
 776     _old_gen(old_gen),
 777     _young_old_boundary(young_old_boundary),
 778     _state_set(state_set)
 779 { }
 780 
 781 void ParNewRefProcTaskProxy::work(uint worker_id) {
 782   ResourceMark rm;
 783   HandleMark hm;
 784   ParScanThreadState& par_scan_state = _state_set.thread_state(worker_id);
 785   par_scan_state.set_young_old_boundary(_young_old_boundary);
 786   _task.work(worker_id, par_scan_state.is_alive_closure(),
 787              par_scan_state.keep_alive_closure(),
 788              par_scan_state.evacuate_followers_closure());
 789 }
 790 
 791 class ParNewRefEnqueueTaskProxy: public AbstractGangTask {
 792   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
 793   EnqueueTask& _task;
 794 
 795 public:
 796   ParNewRefEnqueueTaskProxy(EnqueueTask& task)
 797     : AbstractGangTask("ParNewGeneration parallel reference enqueue"),
 798       _task(task)
 799   { }
 800 
 801   virtual void work(uint worker_id) {
 802     _task.work(worker_id);
 803   }
 804 };
 805 
 806 void ParNewRefProcTaskExecutor::execute(ProcessTask& task) {
 807   GenCollectedHeap* gch = GenCollectedHeap::heap();
 808   WorkGang* workers = gch->workers();
 809   assert(workers != NULL, "Need parallel worker threads.");
 810   _state_set.reset(workers->active_workers(), _young_gen.promotion_failed());
 811   ParNewRefProcTaskProxy rp_task(task, _young_gen, _old_gen,
 812                                  _young_gen.reserved().end(), _state_set);
 813   workers->run_task(&rp_task);
 814   _state_set.reset(0 /* bad value in debug if not reset */,
 815                    _young_gen.promotion_failed());
 816 }
 817 
 818 void ParNewRefProcTaskExecutor::execute(EnqueueTask& task) {
 819   GenCollectedHeap* gch = GenCollectedHeap::heap();
 820   WorkGang* workers = gch->workers();
 821   assert(workers != NULL, "Need parallel worker threads.");
 822   ParNewRefEnqueueTaskProxy enq_task(task);
 823   workers->run_task(&enq_task);
 824 }
 825 
 826 void ParNewRefProcTaskExecutor::set_single_threaded_mode() {
 827   _state_set.flush();
 828   GenCollectedHeap* gch = GenCollectedHeap::heap();
 829   gch->save_marks();
 830 }
 831 
 832 ScanClosureWithParBarrier::
 833 ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier) :
 834   ScanClosure(g, gc_barrier)
 835 { }
 836 
 837 EvacuateFollowersClosureGeneral::
 838 EvacuateFollowersClosureGeneral(GenCollectedHeap* gch,
 839                                 OopsInGenClosure* cur,
 840                                 OopsInGenClosure* older) :
 841   _gch(gch),
 842   _scan_cur_or_nonheap(cur), _scan_older(older)
 843 { }
 844 
 845 void EvacuateFollowersClosureGeneral::do_void() {
 846   do {
 847     // Beware: this call will lead to closure applications via virtual
 848     // calls.
 849     _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen,
 850                                        _scan_cur_or_nonheap,
 851                                        _scan_older);
 852   } while (!_gch->no_allocs_since_save_marks());
 853 }
 854 
 855 // A Generation that does parallel young-gen collection.
 856 
 857 void ParNewGeneration::handle_promotion_failed(GenCollectedHeap* gch, ParScanThreadStateSet& thread_state_set) {
 858   assert(_promo_failure_scan_stack.is_empty(), "post condition");
 859   _promo_failure_scan_stack.clear(true); // Clear cached segments.
 860 
 861   remove_forwarding_pointers();
 862   log_info(gc, promotion)("Promotion failed");
 863   // All the spaces are in play for mark-sweep.
 864   swap_spaces();  // Make life simpler for CMS || rescan; see 6483690.
 865   from()->set_next_compaction_space(to());
 866   gch->set_incremental_collection_failed();
 867   // Inform the next generation that a promotion failure occurred.
 868   _old_gen->promotion_failure_occurred();
 869 
 870   // Trace promotion failure in the parallel GC threads
 871   thread_state_set.trace_promotion_failed(gc_tracer());
 872   // Single threaded code may have reported promotion failure to the global state
 873   if (_promotion_failed_info.has_failed()) {
 874     _gc_tracer.report_promotion_failed(_promotion_failed_info);
 875   }
 876   // Reset the PromotionFailureALot counters.
 877   NOT_PRODUCT(gch->reset_promotion_should_fail();)
 878 }
 879 
 880 void ParNewGeneration::collect(bool   full,
 881                                bool   clear_all_soft_refs,
 882                                size_t size,
 883                                bool   is_tlab) {
 884   assert(full || size > 0, "otherwise we don't want to collect");
 885 
 886   GenCollectedHeap* gch = GenCollectedHeap::heap();
 887 
 888   _gc_timer->register_gc_start();
 889 
 890   AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
 891   WorkGang* workers = gch->workers();
 892   assert(workers != NULL, "Need workgang for parallel work");
 893   uint active_workers =
 894        AdaptiveSizePolicy::calc_active_workers(workers->total_workers(),
 895                                                workers->active_workers(),
 896                                                Threads::number_of_non_daemon_threads());
 897   active_workers = workers->update_active_workers(active_workers);
 898   log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers->total_workers());
 899 
 900   _old_gen = gch->old_gen();
 901 
 902   // If the next generation is too full to accommodate worst-case promotion
 903   // from this generation, pass on collection; let the next generation
 904   // do it.
 905   if (!collection_attempt_is_safe()) {
 906     gch->set_incremental_collection_failed();  // slight lie, in that we did not even attempt one
 907     return;
 908   }
 909   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 910 
 911   _gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
 912   gch->trace_heap_before_gc(gc_tracer());
 913 
 914   init_assuming_no_promotion_failure();
 915 
 916   if (UseAdaptiveSizePolicy) {
 917     set_survivor_overflow(false);
 918     size_policy->minor_collection_begin();
 919   }
 920 
 921   GCTraceTime(Trace, gc, phases) t1("ParNew", NULL, gch->gc_cause());
 922 
 923   age_table()->clear();
 924   to()->clear(SpaceDecorator::Mangle);
 925 
 926   gch->save_marks();
 927 
 928   // Set the correct parallelism (number of queues) in the reference processor
 929   ref_processor()->set_active_mt_degree(active_workers);
 930 
 931   // Need to initialize the preserved marks before the ThreadStateSet c'tor.
 932   _preserved_marks_set.init(active_workers);
 933 
 934   // Always set the terminator for the active number of workers
 935   // because only those workers go through the termination protocol.
 936   ParallelTaskTerminator _term(active_workers, task_queues());
 937   ParScanThreadStateSet thread_state_set(active_workers,
 938                                          *to(), *this, *_old_gen, *task_queues(),
 939                                          _overflow_stacks, _preserved_marks_set,
 940                                          desired_plab_sz(), _term);
 941 
 942   thread_state_set.reset(active_workers, promotion_failed());
 943 
 944   {
 945     StrongRootsScope srs(active_workers);
 946 
 947     ParNewGenTask tsk(this, _old_gen, reserved().end(), &thread_state_set, &srs);
 948     gch->rem_set()->prepare_for_younger_refs_iterate(true);
 949     // It turns out that even when we're using 1 thread, doing the work in a
 950     // separate thread causes wide variance in run times.  We can't help this
 951     // in the multi-threaded case, but we special-case n=1 here to get
 952     // repeatable measurements of the 1-thread overhead of the parallel code.
 953     // Might multiple workers ever be used?  If yes, initialization
 954     // has been done such that the single threaded path should not be used.
 955     if (workers->total_workers() > 1) {
 956       workers->run_task(&tsk);
 957     } else {
 958       tsk.work(0);
 959     }
 960   }
 961 
 962   thread_state_set.reset(0 /* Bad value in debug if not reset */,
 963                          promotion_failed());
 964 
 965   // Trace and reset failed promotion info.
 966   if (promotion_failed()) {
 967     thread_state_set.trace_promotion_failed(gc_tracer());
 968   }
 969 
 970   // Process (weak) reference objects found during scavenge.
 971   ReferenceProcessor* rp = ref_processor();
 972   IsAliveClosure is_alive(this);
 973   ScanWeakRefClosure scan_weak_ref(this);
 974   KeepAliveClosure keep_alive(&scan_weak_ref);
 975   ScanClosure               scan_without_gc_barrier(this, false);
 976   ScanClosureWithParBarrier scan_with_gc_barrier(this, true);
 977   set_promo_failure_scan_stack_closure(&scan_without_gc_barrier);
 978   EvacuateFollowersClosureGeneral evacuate_followers(gch,
 979     &scan_without_gc_barrier, &scan_with_gc_barrier);
 980   rp->setup_policy(clear_all_soft_refs);
 981   // Can  the mt_degree be set later (at run_task() time would be best)?
 982   rp->set_active_mt_degree(active_workers);
 983   ReferenceProcessorStats stats;
 984   if (rp->processing_is_mt()) {
 985     ParNewRefProcTaskExecutor task_executor(*this, *_old_gen, thread_state_set);
 986     stats = rp->process_discovered_references(&is_alive, &keep_alive,
 987                                               &evacuate_followers, &task_executor,
 988                                               _gc_timer);
 989   } else {
 990     thread_state_set.flush();
 991     gch->save_marks();
 992     stats = rp->process_discovered_references(&is_alive, &keep_alive,
 993                                               &evacuate_followers, NULL,
 994                                               _gc_timer);
 995   }
 996   _gc_tracer.report_gc_reference_stats(stats);
 997   _gc_tracer.report_tenuring_threshold(tenuring_threshold());
 998 
 999   if (!promotion_failed()) {
1000     // Swap the survivor spaces.
1001     eden()->clear(SpaceDecorator::Mangle);
1002     from()->clear(SpaceDecorator::Mangle);
1003     if (ZapUnusedHeapArea) {
1004       // This is now done here because of the piece-meal mangling which
1005       // can check for valid mangling at intermediate points in the
1006       // collection(s).  When a young collection fails to collect
1007       // sufficient space resizing of the young generation can occur
1008       // and redistribute the spaces in the young generation.  Mangle
1009       // here so that unzapped regions don't get distributed to
1010       // other spaces.
1011       to()->mangle_unused_area();
1012     }
1013     swap_spaces();
1014 
1015     // A successful scavenge should restart the GC time limit count which is
1016     // for full GC's.
1017     size_policy->reset_gc_overhead_limit_count();
1018 
1019     assert(to()->is_empty(), "to space should be empty now");
1020 
1021     adjust_desired_tenuring_threshold();
1022   } else {
1023     handle_promotion_failed(gch, thread_state_set);
1024   }
1025   _preserved_marks_set.reclaim();
1026   // set new iteration safe limit for the survivor spaces
1027   from()->set_concurrent_iteration_safe_limit(from()->top());
1028   to()->set_concurrent_iteration_safe_limit(to()->top());
1029 
1030   plab_stats()->adjust_desired_plab_sz();
1031 
1032   TASKQUEUE_STATS_ONLY(thread_state_set.print_termination_stats());
1033   TASKQUEUE_STATS_ONLY(thread_state_set.print_taskqueue_stats());
1034 
1035   if (UseAdaptiveSizePolicy) {
1036     size_policy->minor_collection_end(gch->gc_cause());
1037     size_policy->avg_survived()->sample(from()->used());
1038   }
1039 
1040   // We need to use a monotonically non-decreasing time in ms
1041   // or we will see time-warp warnings and os::javaTimeMillis()
1042   // does not guarantee monotonicity.
1043   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
1044   update_time_of_last_gc(now);
1045 
1046   rp->set_enqueuing_is_done(true);
1047   if (rp->processing_is_mt()) {
1048     ParNewRefProcTaskExecutor task_executor(*this, *_old_gen, thread_state_set);
1049     rp->enqueue_discovered_references(&task_executor, _gc_timer);
1050   } else {
1051     rp->enqueue_discovered_references(NULL);
1052   }
1053   rp->verify_no_references_recorded();
1054 
1055   gch->trace_heap_after_gc(gc_tracer());
1056 
1057   _gc_timer->register_gc_end();
1058 
1059   _gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
1060 }
1061 
1062 size_t ParNewGeneration::desired_plab_sz() {
1063   return _plab_stats.desired_plab_sz(GenCollectedHeap::heap()->workers()->active_workers());
1064 }
1065 
1066 static int sum;
1067 void ParNewGeneration::waste_some_time() {
1068   for (int i = 0; i < 100; i++) {
1069     sum += i;
1070   }
1071 }
1072 
1073 static const oop ClaimedForwardPtr = cast_to_oop<intptr_t>(0x4);
1074 
1075 // Because of concurrency, there are times where an object for which
1076 // "is_forwarded()" is true contains an "interim" forwarding pointer
1077 // value.  Such a value will soon be overwritten with a real value.
1078 // This method requires "obj" to have a forwarding pointer, and waits, if
1079 // necessary for a real one to be inserted, and returns it.
1080 
1081 oop ParNewGeneration::real_forwardee(oop obj) {
1082   oop forward_ptr = obj->forwardee();
1083   if (forward_ptr != ClaimedForwardPtr) {
1084     return forward_ptr;
1085   } else {
1086     return real_forwardee_slow(obj);
1087   }
1088 }
1089 
1090 oop ParNewGeneration::real_forwardee_slow(oop obj) {
1091   // Spin-read if it is claimed but not yet written by another thread.
1092   oop forward_ptr = obj->forwardee();
1093   while (forward_ptr == ClaimedForwardPtr) {
1094     waste_some_time();
1095     assert(obj->is_forwarded(), "precondition");
1096     forward_ptr = obj->forwardee();
1097   }
1098   return forward_ptr;
1099 }
1100 
1101 // Multiple GC threads may try to promote an object.  If the object
1102 // is successfully promoted, a forwarding pointer will be installed in
1103 // the object in the young generation.  This method claims the right
1104 // to install the forwarding pointer before it copies the object,
1105 // thus avoiding the need to undo the copy as in
1106 // copy_to_survivor_space_avoiding_with_undo.
1107 
1108 oop ParNewGeneration::copy_to_survivor_space(ParScanThreadState* par_scan_state,
1109                                              oop old,
1110                                              size_t sz,
1111                                              markOop m) {
1112   // In the sequential version, this assert also says that the object is
1113   // not forwarded.  That might not be the case here.  It is the case that
1114   // the caller observed it to be not forwarded at some time in the past.
1115   assert(is_in_reserved(old), "shouldn't be scavenging this oop");
1116 
1117   // The sequential code read "old->age()" below.  That doesn't work here,
1118   // since the age is in the mark word, and that might be overwritten with
1119   // a forwarding pointer by a parallel thread.  So we must save the mark
1120   // word in a local and then analyze it.
1121   oopDesc dummyOld;
1122   dummyOld.set_mark(m);
1123   assert(!dummyOld.is_forwarded(),
1124          "should not be called with forwarding pointer mark word.");
1125 
1126   oop new_obj = NULL;
1127   oop forward_ptr;
1128 
1129   // Try allocating obj in to-space (unless too old)
1130   if (dummyOld.age() < tenuring_threshold()) {
1131     new_obj = (oop)par_scan_state->alloc_in_to_space(sz);
1132     if (new_obj == NULL) {
1133       set_survivor_overflow(true);
1134     }
1135   }
1136 
1137   if (new_obj == NULL) {
1138     // Either to-space is full or we decided to promote try allocating obj tenured
1139 
1140     // Attempt to install a null forwarding pointer (atomically),
1141     // to claim the right to install the real forwarding pointer.
1142     forward_ptr = old->forward_to_atomic(ClaimedForwardPtr);
1143     if (forward_ptr != NULL) {
1144       // someone else beat us to it.
1145         return real_forwardee(old);
1146     }
1147 
1148     if (!_promotion_failed) {
1149       new_obj = _old_gen->par_promote(par_scan_state->thread_num(),
1150                                       old, m, sz);
1151     }
1152 
1153     if (new_obj == NULL) {
1154       // promotion failed, forward to self
1155       _promotion_failed = true;
1156       new_obj = old;
1157 
1158       par_scan_state->preserved_marks()->push_if_necessary(old, m);
1159       par_scan_state->register_promotion_failure(sz);
1160     }
1161 
1162     old->forward_to(new_obj);
1163     forward_ptr = NULL;
1164   } else {
1165     // Is in to-space; do copying ourselves.
1166     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz);
1167     assert(GenCollectedHeap::heap()->is_in_reserved(new_obj), "illegal forwarding pointer value.");
1168     forward_ptr = old->forward_to_atomic(new_obj);
1169     // Restore the mark word copied above.
1170     new_obj->set_mark(m);
1171     // Increment age if obj still in new generation
1172     new_obj->incr_age();
1173     par_scan_state->age_table()->add(new_obj, sz);
1174   }
1175   assert(new_obj != NULL, "just checking");
1176 
1177   // This code must come after the CAS test, or it will print incorrect
1178   // information.
1179   log_develop_trace(gc, scavenge)("{%s %s " PTR_FORMAT " -> " PTR_FORMAT " (%d)}",
1180                                   is_in_reserved(new_obj) ? "copying" : "tenuring",
1181                                   new_obj->klass()->internal_name(), p2i(old), p2i(new_obj), new_obj->size());
1182 
1183   if (forward_ptr == NULL) {
1184     oop obj_to_push = new_obj;
1185     if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) {
1186       // Length field used as index of next element to be scanned.
1187       // Real length can be obtained from real_forwardee()
1188       arrayOop(old)->set_length(0);
1189       obj_to_push = old;
1190       assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push,
1191              "push forwarded object");
1192     }
1193     // Push it on one of the queues of to-be-scanned objects.
1194     bool simulate_overflow = false;
1195     NOT_PRODUCT(
1196       if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) {
1197         // simulate a stack overflow
1198         simulate_overflow = true;
1199       }
1200     )
1201     if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) {
1202       // Add stats for overflow pushes.
1203       log_develop_trace(gc)("Queue Overflow");
1204       push_on_overflow_list(old, par_scan_state);
1205       TASKQUEUE_STATS_ONLY(par_scan_state->taskqueue_stats().record_overflow(0));
1206     }
1207 
1208     return new_obj;
1209   }
1210 
1211   // Oops.  Someone beat us to it.  Undo the allocation.  Where did we
1212   // allocate it?
1213   if (is_in_reserved(new_obj)) {
1214     // Must be in to_space.
1215     assert(to()->is_in_reserved(new_obj), "Checking");
1216     if (forward_ptr == ClaimedForwardPtr) {
1217       // Wait to get the real forwarding pointer value.
1218       forward_ptr = real_forwardee(old);
1219     }
1220     par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz);
1221   }
1222 
1223   return forward_ptr;
1224 }
1225 
1226 #ifndef PRODUCT
1227 // It's OK to call this multi-threaded;  the worst thing
1228 // that can happen is that we'll get a bunch of closely
1229 // spaced simulated overflows, but that's OK, in fact
1230 // probably good as it would exercise the overflow code
1231 // under contention.
1232 bool ParNewGeneration::should_simulate_overflow() {
1233   if (_overflow_counter-- <= 0) { // just being defensive
1234     _overflow_counter = ParGCWorkQueueOverflowInterval;
1235     return true;
1236   } else {
1237     return false;
1238   }
1239 }
1240 #endif
1241 
1242 // In case we are using compressed oops, we need to be careful.
1243 // If the object being pushed is an object array, then its length
1244 // field keeps track of the "grey boundary" at which the next
1245 // incremental scan will be done (see ParGCArrayScanChunk).
1246 // When using compressed oops, this length field is kept in the
1247 // lower 32 bits of the erstwhile klass word and cannot be used
1248 // for the overflow chaining pointer (OCP below). As such the OCP
1249 // would itself need to be compressed into the top 32-bits in this
1250 // case. Unfortunately, see below, in the event that we have a
1251 // promotion failure, the node to be pushed on the list can be
1252 // outside of the Java heap, so the heap-based pointer compression
1253 // would not work (we would have potential aliasing between C-heap
1254 // and Java-heap pointers). For this reason, when using compressed
1255 // oops, we simply use a worker-thread-local, non-shared overflow
1256 // list in the form of a growable array, with a slightly different
1257 // overflow stack draining strategy. If/when we start using fat
1258 // stacks here, we can go back to using (fat) pointer chains
1259 // (although some performance comparisons would be useful since
1260 // single global lists have their own performance disadvantages
1261 // as we were made painfully aware not long ago, see 6786503).
1262 #define BUSY (cast_to_oop<intptr_t>(0x1aff1aff))
1263 void ParNewGeneration::push_on_overflow_list(oop from_space_obj, ParScanThreadState* par_scan_state) {
1264   assert(is_in_reserved(from_space_obj), "Should be from this generation");
1265   if (ParGCUseLocalOverflow) {
1266     // In the case of compressed oops, we use a private, not-shared
1267     // overflow stack.
1268     par_scan_state->push_on_overflow_stack(from_space_obj);
1269   } else {
1270     assert(!UseCompressedOops, "Error");
1271     // if the object has been forwarded to itself, then we cannot
1272     // use the klass pointer for the linked list.  Instead we have
1273     // to allocate an oopDesc in the C-Heap and use that for the linked list.
1274     // XXX This is horribly inefficient when a promotion failure occurs
1275     // and should be fixed. XXX FIX ME !!!
1276 #ifndef PRODUCT
1277     Atomic::inc_ptr(&_num_par_pushes);
1278     assert(_num_par_pushes > 0, "Tautology");
1279 #endif
1280     if (from_space_obj->forwardee() == from_space_obj) {
1281       oopDesc* listhead = NEW_C_HEAP_ARRAY(oopDesc, 1, mtGC);
1282       listhead->forward_to(from_space_obj);
1283       from_space_obj = listhead;
1284     }
1285     oop observed_overflow_list = _overflow_list;
1286     oop cur_overflow_list;
1287     do {
1288       cur_overflow_list = observed_overflow_list;
1289       if (cur_overflow_list != BUSY) {
1290         from_space_obj->set_klass_to_list_ptr(cur_overflow_list);
1291       } else {
1292         from_space_obj->set_klass_to_list_ptr(NULL);
1293       }
1294       observed_overflow_list =
1295         (oop)Atomic::cmpxchg_ptr(from_space_obj, &_overflow_list, cur_overflow_list);
1296     } while (cur_overflow_list != observed_overflow_list);
1297   }
1298 }
1299 
1300 bool ParNewGeneration::take_from_overflow_list(ParScanThreadState* par_scan_state) {
1301   bool res;
1302 
1303   if (ParGCUseLocalOverflow) {
1304     res = par_scan_state->take_from_overflow_stack();
1305   } else {
1306     assert(!UseCompressedOops, "Error");
1307     res = take_from_overflow_list_work(par_scan_state);
1308   }
1309   return res;
1310 }
1311 
1312 
1313 // *NOTE*: The overflow list manipulation code here and
1314 // in CMSCollector:: are very similar in shape,
1315 // except that in the CMS case we thread the objects
1316 // directly into the list via their mark word, and do
1317 // not need to deal with special cases below related
1318 // to chunking of object arrays and promotion failure
1319 // handling.
1320 // CR 6797058 has been filed to attempt consolidation of
1321 // the common code.
1322 // Because of the common code, if you make any changes in
1323 // the code below, please check the CMS version to see if
1324 // similar changes might be needed.
1325 // See CMSCollector::par_take_from_overflow_list() for
1326 // more extensive documentation comments.
1327 bool ParNewGeneration::take_from_overflow_list_work(ParScanThreadState* par_scan_state) {
1328   ObjToScanQueue* work_q = par_scan_state->work_queue();
1329   // How many to take?
1330   size_t objsFromOverflow = MIN2((size_t)(work_q->max_elems() - work_q->size())/4,
1331                                  (size_t)ParGCDesiredObjsFromOverflowList);
1332 
1333   assert(!UseCompressedOops, "Error");
1334   assert(par_scan_state->overflow_stack() == NULL, "Error");
1335   if (_overflow_list == NULL) return false;
1336 
1337   // Otherwise, there was something there; try claiming the list.
1338   oop prefix = cast_to_oop(Atomic::xchg_ptr(BUSY, &_overflow_list));
1339   // Trim off a prefix of at most objsFromOverflow items
1340   Thread* tid = Thread::current();
1341   size_t spin_count = ParallelGCThreads;
1342   size_t sleep_time_millis = MAX2((size_t)1, objsFromOverflow/100);
1343   for (size_t spin = 0; prefix == BUSY && spin < spin_count; spin++) {
1344     // someone grabbed it before we did ...
1345     // ... we spin for a short while...
1346     os::sleep(tid, sleep_time_millis, false);
1347     if (_overflow_list == NULL) {
1348       // nothing left to take
1349       return false;
1350     } else if (_overflow_list != BUSY) {
1351      // try and grab the prefix
1352      prefix = cast_to_oop(Atomic::xchg_ptr(BUSY, &_overflow_list));
1353     }
1354   }
1355   if (prefix == NULL || prefix == BUSY) {
1356      // Nothing to take or waited long enough
1357      if (prefix == NULL) {
1358        // Write back the NULL in case we overwrote it with BUSY above
1359        // and it is still the same value.
1360        (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY);
1361      }
1362      return false;
1363   }
1364   assert(prefix != NULL && prefix != BUSY, "Error");
1365   oop cur = prefix;
1366   for (size_t i = 1; i < objsFromOverflow; ++i) {
1367     oop next = cur->list_ptr_from_klass();
1368     if (next == NULL) break;
1369     cur = next;
1370   }
1371   assert(cur != NULL, "Loop postcondition");
1372 
1373   // Reattach remaining (suffix) to overflow list
1374   oop suffix = cur->list_ptr_from_klass();
1375   if (suffix == NULL) {
1376     // Write back the NULL in lieu of the BUSY we wrote
1377     // above and it is still the same value.
1378     if (_overflow_list == BUSY) {
1379       (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY);
1380     }
1381   } else {
1382     assert(suffix != BUSY, "Error");
1383     // suffix will be put back on global list
1384     cur->set_klass_to_list_ptr(NULL);     // break off suffix
1385     // It's possible that the list is still in the empty(busy) state
1386     // we left it in a short while ago; in that case we may be
1387     // able to place back the suffix.
1388     oop observed_overflow_list = _overflow_list;
1389     oop cur_overflow_list = observed_overflow_list;
1390     bool attached = false;
1391     while (observed_overflow_list == BUSY || observed_overflow_list == NULL) {
1392       observed_overflow_list =
1393         (oop) Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list);
1394       if (cur_overflow_list == observed_overflow_list) {
1395         attached = true;
1396         break;
1397       } else cur_overflow_list = observed_overflow_list;
1398     }
1399     if (!attached) {
1400       // Too bad, someone else got in in between; we'll need to do a splice.
1401       // Find the last item of suffix list
1402       oop last = suffix;
1403       while (true) {
1404         oop next = last->list_ptr_from_klass();
1405         if (next == NULL) break;
1406         last = next;
1407       }
1408       // Atomically prepend suffix to current overflow list
1409       observed_overflow_list = _overflow_list;
1410       do {
1411         cur_overflow_list = observed_overflow_list;
1412         if (cur_overflow_list != BUSY) {
1413           // Do the splice ...
1414           last->set_klass_to_list_ptr(cur_overflow_list);
1415         } else { // cur_overflow_list == BUSY
1416           last->set_klass_to_list_ptr(NULL);
1417         }
1418         observed_overflow_list =
1419           (oop)Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list);
1420       } while (cur_overflow_list != observed_overflow_list);
1421     }
1422   }
1423 
1424   // Push objects on prefix list onto this thread's work queue
1425   assert(prefix != NULL && prefix != BUSY, "program logic");
1426   cur = prefix;
1427   ssize_t n = 0;
1428   while (cur != NULL) {
1429     oop obj_to_push = cur->forwardee();
1430     oop next        = cur->list_ptr_from_klass();
1431     cur->set_klass(obj_to_push->klass());
1432     // This may be an array object that is self-forwarded. In that case, the list pointer
1433     // space, cur, is not in the Java heap, but rather in the C-heap and should be freed.
1434     if (!is_in_reserved(cur)) {
1435       // This can become a scaling bottleneck when there is work queue overflow coincident
1436       // with promotion failure.
1437       oopDesc* f = cur;
1438       FREE_C_HEAP_ARRAY(oopDesc, f);
1439     } else if (par_scan_state->should_be_partially_scanned(obj_to_push, cur)) {
1440       assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned");
1441       obj_to_push = cur;
1442     }
1443     bool ok = work_q->push(obj_to_push);
1444     assert(ok, "Should have succeeded");
1445     cur = next;
1446     n++;
1447   }
1448   TASKQUEUE_STATS_ONLY(par_scan_state->note_overflow_refill(n));
1449 #ifndef PRODUCT
1450   assert(_num_par_pushes >= n, "Too many pops?");
1451   Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes);
1452 #endif
1453   return true;
1454 }
1455 #undef BUSY
1456 
1457 void ParNewGeneration::ref_processor_init() {
1458   if (_ref_processor == NULL) {
1459     // Allocate and initialize a reference processor
1460     _ref_processor =
1461       new ReferenceProcessor(_reserved,                  // span
1462                              ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
1463                              ParallelGCThreads,          // mt processing degree
1464                              refs_discovery_is_mt(),     // mt discovery
1465                              ParallelGCThreads,          // mt discovery degree
1466                              refs_discovery_is_atomic(), // atomic_discovery
1467                              NULL);                      // is_alive_non_header
1468   }
1469 }
1470 
1471 const char* ParNewGeneration::name() const {
1472   return "par new generation";
1473 }