1 /*
   2  * Copyright (c) 2001, 2015, 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/serial/defNewGeneration.inline.hpp"
  27 #include "gc/shared/collectorCounters.hpp"
  28 #include "gc/shared/gcHeapSummary.hpp"
  29 #include "gc/shared/gcLocker.inline.hpp"
  30 #include "gc/shared/gcPolicyCounters.hpp"
  31 #include "gc/shared/gcTimer.hpp"
  32 #include "gc/shared/gcTrace.hpp"
  33 #include "gc/shared/gcTraceTime.hpp"
  34 #include "gc/shared/genCollectedHeap.hpp"
  35 #include "gc/shared/genOopClosures.inline.hpp"
  36 #include "gc/shared/genRemSet.hpp"
  37 #include "gc/shared/generationSpec.hpp"
  38 #include "gc/shared/referencePolicy.hpp"
  39 #include "gc/shared/space.inline.hpp"
  40 #include "gc/shared/spaceDecorator.hpp"
  41 #include "gc/shared/strongRootsScope.hpp"
  42 #include "memory/iterator.hpp"
  43 #include "oops/instanceRefKlass.hpp"
  44 #include "oops/oop.inline.hpp"
  45 #include "runtime/atomic.inline.hpp"
  46 #include "runtime/java.hpp"
  47 #include "runtime/prefetch.inline.hpp"
  48 #include "runtime/thread.inline.hpp"
  49 #include "utilities/copy.hpp"
  50 #include "utilities/globalDefinitions.hpp"
  51 #include "utilities/stack.inline.hpp"
  52 #if INCLUDE_ALL_GCS
  53 #include "gc/cms/parOopClosures.hpp"
  54 #endif
  55 
  56 //
  57 // DefNewGeneration functions.
  58 
  59 // Methods of protected closure types.
  60 
  61 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
  62   assert(_young_gen->kind() == Generation::ParNew ||
  63          _young_gen->kind() == Generation::DefNew, "Expected the young generation here");
  64 }
  65 
  66 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
  67   return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded();
  68 }
  69 
  70 DefNewGeneration::KeepAliveClosure::
  71 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
  72   GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
  73   _rs = (CardTableRS*)rs;
  74 }
  75 
  76 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  77 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  78 
  79 
  80 DefNewGeneration::FastKeepAliveClosure::
  81 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
  82   DefNewGeneration::KeepAliveClosure(cl) {
  83   _boundary = g->reserved().end();
  84 }
  85 
  86 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  87 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  88 
  89 DefNewGeneration::EvacuateFollowersClosure::
  90 EvacuateFollowersClosure(GenCollectedHeap* gch,
  91                          ScanClosure* cur,
  92                          ScanClosure* older) :
  93   _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
  94 {}
  95 
  96 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
  97   do {
  98     _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
  99   } while (!_gch->no_allocs_since_save_marks());
 100 }
 101 
 102 DefNewGeneration::FastEvacuateFollowersClosure::
 103 FastEvacuateFollowersClosure(GenCollectedHeap* gch,
 104                              FastScanClosure* cur,
 105                              FastScanClosure* older) :
 106   _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
 107 {
 108   assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew");
 109   _young_gen = (DefNewGeneration*)_gch->young_gen();
 110 }
 111 
 112 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
 113   do {
 114     _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
 115   } while (!_gch->no_allocs_since_save_marks());
 116   guarantee(_young_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
 117 }
 118 
 119 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
 120     OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 121 {
 122   _boundary = _g->reserved().end();
 123 }
 124 
 125 void ScanClosure::do_oop(oop* p)       { ScanClosure::do_oop_work(p); }
 126 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
 127 
 128 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
 129     OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 130 {
 131   _boundary = _g->reserved().end();
 132 }
 133 
 134 void FastScanClosure::do_oop(oop* p)       { FastScanClosure::do_oop_work(p); }
 135 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
 136 
 137 void KlassScanClosure::do_klass(Klass* klass) {
 138 #ifndef PRODUCT
 139   if (TraceScavenge) {
 140     ResourceMark rm;
 141     gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
 142                            p2i(klass),
 143                            klass->external_name(),
 144                            klass->has_modified_oops() ? "true" : "false");
 145   }
 146 #endif
 147 
 148   // If the klass has not been dirtied we know that there's
 149   // no references into  the young gen and we can skip it.
 150   if (klass->has_modified_oops()) {
 151     if (_accumulate_modified_oops) {
 152       klass->accumulate_modified_oops();
 153     }
 154 
 155     // Clear this state since we're going to scavenge all the metadata.
 156     klass->clear_modified_oops();
 157 
 158     // Tell the closure which Klass is being scanned so that it can be dirtied
 159     // if oops are left pointing into the young gen.
 160     _scavenge_closure->set_scanned_klass(klass);
 161 
 162     klass->oops_do(_scavenge_closure);
 163 
 164     _scavenge_closure->set_scanned_klass(NULL);
 165   }
 166 }
 167 
 168 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
 169   _g(g)
 170 {
 171   _boundary = _g->reserved().end();
 172 }
 173 
 174 void ScanWeakRefClosure::do_oop(oop* p)       { ScanWeakRefClosure::do_oop_work(p); }
 175 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
 176 
 177 void FilteringClosure::do_oop(oop* p)       { FilteringClosure::do_oop_work(p); }
 178 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
 179 
 180 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
 181                                    KlassRemSet* klass_rem_set)
 182     : _scavenge_closure(scavenge_closure),
 183       _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
 184 
 185 
 186 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
 187                                    size_t initial_size,
 188                                    const char* policy)
 189   : Generation(rs, initial_size),
 190     _promo_failure_drain_in_progress(false),
 191     _should_allocate_from_space(false)
 192 {
 193   MemRegion cmr((HeapWord*)_virtual_space.low(),
 194                 (HeapWord*)_virtual_space.high());
 195   GenCollectedHeap* gch = GenCollectedHeap::heap();
 196 
 197   gch->barrier_set()->resize_covered_region(cmr);
 198 
 199   _eden_space = new ContiguousSpace();
 200   _from_space = new ContiguousSpace();
 201   _to_space   = new ContiguousSpace();
 202 
 203   if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
 204     vm_exit_during_initialization("Could not allocate a new gen space");
 205   }
 206 
 207   // Compute the maximum eden and survivor space sizes. These sizes
 208   // are computed assuming the entire reserved space is committed.
 209   // These values are exported as performance counters.
 210   uintx alignment = gch->collector_policy()->space_alignment();
 211   uintx size = _virtual_space.reserved_size();
 212   _max_survivor_size = compute_survivor_size(size, alignment);
 213   _max_eden_size = size - (2*_max_survivor_size);
 214 
 215   // allocate the performance counters
 216   GenCollectorPolicy* gcp = gch->gen_policy();
 217 
 218   // Generation counters -- generation 0, 3 subspaces
 219   _gen_counters = new GenerationCounters("new", 0, 3,
 220       gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
 221   _gc_counters = new CollectorCounters(policy, 0);
 222 
 223   _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
 224                                       _gen_counters);
 225   _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
 226                                       _gen_counters);
 227   _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
 228                                     _gen_counters);
 229 
 230   compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
 231   update_counters();
 232   _old_gen = NULL;
 233   _tenuring_threshold = MaxTenuringThreshold;
 234   _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
 235 
 236   _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
 237 }
 238 
 239 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
 240                                                 bool clear_space,
 241                                                 bool mangle_space) {
 242   uintx alignment =
 243     GenCollectedHeap::heap()->collector_policy()->space_alignment();
 244 
 245   // If the spaces are being cleared (only done at heap initialization
 246   // currently), the survivor spaces need not be empty.
 247   // Otherwise, no care is taken for used areas in the survivor spaces
 248   // so check.
 249   assert(clear_space || (to()->is_empty() && from()->is_empty()),
 250     "Initialization of the survivor spaces assumes these are empty");
 251 
 252   // Compute sizes
 253   uintx size = _virtual_space.committed_size();
 254   uintx survivor_size = compute_survivor_size(size, alignment);
 255   uintx eden_size = size - (2*survivor_size);
 256   assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 257 
 258   if (eden_size < minimum_eden_size) {
 259     // May happen due to 64Kb rounding, if so adjust eden size back up
 260     minimum_eden_size = align_size_up(minimum_eden_size, alignment);
 261     uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
 262     uintx unaligned_survivor_size =
 263       align_size_down(maximum_survivor_size, alignment);
 264     survivor_size = MAX2(unaligned_survivor_size, alignment);
 265     eden_size = size - (2*survivor_size);
 266     assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 267     assert(eden_size >= minimum_eden_size, "just checking");
 268   }
 269 
 270   char *eden_start = _virtual_space.low();
 271   char *from_start = eden_start + eden_size;
 272   char *to_start   = from_start + survivor_size;
 273   char *to_end     = to_start   + survivor_size;
 274 
 275   assert(to_end == _virtual_space.high(), "just checking");
 276   assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
 277   assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
 278   assert(Space::is_aligned((HeapWord*)to_start),   "checking alignment");
 279 
 280   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
 281   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
 282   MemRegion toMR  ((HeapWord*)to_start, (HeapWord*)to_end);
 283 
 284   // A minimum eden size implies that there is a part of eden that
 285   // is being used and that affects the initialization of any
 286   // newly formed eden.
 287   bool live_in_eden = minimum_eden_size > 0;
 288 
 289   // If not clearing the spaces, do some checking to verify that
 290   // the space are already mangled.
 291   if (!clear_space) {
 292     // Must check mangling before the spaces are reshaped.  Otherwise,
 293     // the bottom or end of one space may have moved into another
 294     // a failure of the check may not correctly indicate which space
 295     // is not properly mangled.
 296     if (ZapUnusedHeapArea) {
 297       HeapWord* limit = (HeapWord*) _virtual_space.high();
 298       eden()->check_mangled_unused_area(limit);
 299       from()->check_mangled_unused_area(limit);
 300         to()->check_mangled_unused_area(limit);
 301     }
 302   }
 303 
 304   // Reset the spaces for their new regions.
 305   eden()->initialize(edenMR,
 306                      clear_space && !live_in_eden,
 307                      SpaceDecorator::Mangle);
 308   // If clear_space and live_in_eden, we will not have cleared any
 309   // portion of eden above its top. This can cause newly
 310   // expanded space not to be mangled if using ZapUnusedHeapArea.
 311   // We explicitly do such mangling here.
 312   if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
 313     eden()->mangle_unused_area();
 314   }
 315   from()->initialize(fromMR, clear_space, mangle_space);
 316   to()->initialize(toMR, clear_space, mangle_space);
 317 
 318   // Set next compaction spaces.
 319   eden()->set_next_compaction_space(from());
 320   // The to-space is normally empty before a compaction so need
 321   // not be considered.  The exception is during promotion
 322   // failure handling when to-space can contain live objects.
 323   from()->set_next_compaction_space(NULL);
 324 }
 325 
 326 void DefNewGeneration::swap_spaces() {
 327   ContiguousSpace* s = from();
 328   _from_space        = to();
 329   _to_space          = s;
 330   eden()->set_next_compaction_space(from());
 331   // The to-space is normally empty before a compaction so need
 332   // not be considered.  The exception is during promotion
 333   // failure handling when to-space can contain live objects.
 334   from()->set_next_compaction_space(NULL);
 335 
 336   if (UsePerfData) {
 337     CSpaceCounters* c = _from_counters;
 338     _from_counters = _to_counters;
 339     _to_counters = c;
 340   }
 341 }
 342 
 343 bool DefNewGeneration::expand(size_t bytes) {
 344   MutexLocker x(ExpandHeap_lock);
 345   HeapWord* prev_high = (HeapWord*) _virtual_space.high();
 346   bool success = _virtual_space.expand_by(bytes);
 347   if (success && ZapUnusedHeapArea) {
 348     // Mangle newly committed space immediately because it
 349     // can be done here more simply that after the new
 350     // spaces have been computed.
 351     HeapWord* new_high = (HeapWord*) _virtual_space.high();
 352     MemRegion mangle_region(prev_high, new_high);
 353     SpaceMangler::mangle_region(mangle_region);
 354   }
 355 
 356   // Do not attempt an expand-to-the reserve size.  The
 357   // request should properly observe the maximum size of
 358   // the generation so an expand-to-reserve should be
 359   // unnecessary.  Also a second call to expand-to-reserve
 360   // value potentially can cause an undue expansion.
 361   // For example if the first expand fail for unknown reasons,
 362   // but the second succeeds and expands the heap to its maximum
 363   // value.
 364   if (GC_locker::is_active()) {
 365     if (PrintGC && Verbose) {
 366       gclog_or_tty->print_cr("Garbage collection disabled, "
 367         "expanded heap instead");
 368     }
 369   }
 370 
 371   return success;
 372 }
 373 
 374 void DefNewGeneration::compute_new_size() {
 375   // This is called after a GC that includes the old generation, so from-space
 376   // will normally be empty.
 377   // Note that we check both spaces, since if scavenge failed they revert roles.
 378   // If not we bail out (otherwise we would have to relocate the objects).
 379   if (!from()->is_empty() || !to()->is_empty()) {
 380     return;
 381   }
 382 
 383   GenCollectedHeap* gch = GenCollectedHeap::heap();
 384 
 385   size_t old_size = gch->old_gen()->capacity();
 386   size_t new_size_before = _virtual_space.committed_size();
 387   size_t min_new_size = initial_size();
 388   size_t max_new_size = reserved().byte_size();
 389   assert(min_new_size <= new_size_before &&
 390          new_size_before <= max_new_size,
 391          "just checking");
 392   // All space sizes must be multiples of Generation::GenGrain.
 393   size_t alignment = Generation::GenGrain;
 394 
 395   // Compute desired new generation size based on NewRatio and
 396   // NewSizeThreadIncrease
 397   size_t desired_new_size = old_size/NewRatio;
 398   int threads_count = Threads::number_of_non_daemon_threads();
 399   size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
 400   desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
 401 
 402   // Adjust new generation size
 403   desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
 404   assert(desired_new_size <= max_new_size, "just checking");
 405 
 406   bool changed = false;
 407   if (desired_new_size > new_size_before) {
 408     size_t change = desired_new_size - new_size_before;
 409     assert(change % alignment == 0, "just checking");
 410     if (expand(change)) {
 411        changed = true;
 412     }
 413     // If the heap failed to expand to the desired size,
 414     // "changed" will be false.  If the expansion failed
 415     // (and at this point it was expected to succeed),
 416     // ignore the failure (leaving "changed" as false).
 417   }
 418   if (desired_new_size < new_size_before && eden()->is_empty()) {
 419     // bail out of shrinking if objects in eden
 420     size_t change = new_size_before - desired_new_size;
 421     assert(change % alignment == 0, "just checking");
 422     _virtual_space.shrink_by(change);
 423     changed = true;
 424   }
 425   if (changed) {
 426     // The spaces have already been mangled at this point but
 427     // may not have been cleared (set top = bottom) and should be.
 428     // Mangling was done when the heap was being expanded.
 429     compute_space_boundaries(eden()->used(),
 430                              SpaceDecorator::Clear,
 431                              SpaceDecorator::DontMangle);
 432     MemRegion cmr((HeapWord*)_virtual_space.low(),
 433                   (HeapWord*)_virtual_space.high());
 434     gch->barrier_set()->resize_covered_region(cmr);
 435     if (Verbose && PrintGC) {
 436       size_t new_size_after  = _virtual_space.committed_size();
 437       size_t eden_size_after = eden()->capacity();
 438       size_t survivor_size_after = from()->capacity();
 439       gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
 440         SIZE_FORMAT "K [eden="
 441         SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
 442         new_size_before/K, new_size_after/K,
 443         eden_size_after/K, survivor_size_after/K);
 444       if (WizardMode) {
 445         gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
 446           thread_increase_size/K, threads_count);
 447       }
 448       gclog_or_tty->cr();
 449     }
 450   }
 451 }
 452 
 453 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
 454   assert(false, "NYI -- are you sure you want to call this?");
 455 }
 456 
 457 
 458 size_t DefNewGeneration::capacity() const {
 459   return eden()->capacity()
 460        + from()->capacity();  // to() is only used during scavenge
 461 }
 462 
 463 
 464 size_t DefNewGeneration::used() const {
 465   return eden()->used()
 466        + from()->used();      // to() is only used during scavenge
 467 }
 468 
 469 
 470 size_t DefNewGeneration::free() const {
 471   return eden()->free()
 472        + from()->free();      // to() is only used during scavenge
 473 }
 474 
 475 size_t DefNewGeneration::max_capacity() const {
 476   const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
 477   const size_t reserved_bytes = reserved().byte_size();
 478   return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
 479 }
 480 
 481 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
 482   return eden()->free();
 483 }
 484 
 485 size_t DefNewGeneration::capacity_before_gc() const {
 486   return eden()->capacity();
 487 }
 488 
 489 size_t DefNewGeneration::contiguous_available() const {
 490   return eden()->free();
 491 }
 492 
 493 
 494 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
 495 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
 496 
 497 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
 498   eden()->object_iterate(blk);
 499   from()->object_iterate(blk);
 500 }
 501 
 502 
 503 void DefNewGeneration::space_iterate(SpaceClosure* blk,
 504                                      bool usedOnly) {
 505   blk->do_space(eden());
 506   blk->do_space(from());
 507   blk->do_space(to());
 508 }
 509 
 510 // The last collection bailed out, we are running out of heap space,
 511 // so we try to allocate the from-space, too.
 512 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
 513   HeapWord* result = NULL;
 514   if (Verbose && PrintGCDetails) {
 515     gclog_or_tty->print("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):"
 516                         "  will_fail: %s"
 517                         "  heap_lock: %s"
 518                         "  free: " SIZE_FORMAT,
 519                         size,
 520                         GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
 521                           "true" : "false",
 522                         Heap_lock->is_locked() ? "locked" : "unlocked",
 523                         from()->free());
 524   }
 525   if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
 526     if (Heap_lock->owned_by_self() ||
 527         (SafepointSynchronize::is_at_safepoint() &&
 528          Thread::current()->is_VM_thread())) {
 529       // If the Heap_lock is not locked by this thread, this will be called
 530       // again later with the Heap_lock held.
 531       result = from()->allocate(size);
 532     } else if (PrintGC && Verbose) {
 533       gclog_or_tty->print_cr("  Heap_lock is not owned by self");
 534     }
 535   } else if (PrintGC && Verbose) {
 536     gclog_or_tty->print_cr("  should_allocate_from_space: NOT");
 537   }
 538   if (PrintGC && Verbose) {
 539     gclog_or_tty->print_cr("  returns %s", result == NULL ? "NULL" : "object");
 540   }
 541   return result;
 542 }
 543 
 544 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
 545                                                 bool   is_tlab,
 546                                                 bool   parallel) {
 547   // We don't attempt to expand the young generation (but perhaps we should.)
 548   return allocate(size, is_tlab);
 549 }
 550 
 551 void DefNewGeneration::adjust_desired_tenuring_threshold() {
 552   // Set the desired survivor size to half the real survivor space
 553   GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->collector_policy()->counters();
 554   _tenuring_threshold =
 555     age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, gc_counters);
 556 }
 557 
 558 void DefNewGeneration::collect(bool   full,
 559                                bool   clear_all_soft_refs,
 560                                size_t size,
 561                                bool   is_tlab) {
 562   assert(full || size > 0, "otherwise we don't want to collect");
 563 
 564   GenCollectedHeap* gch = GenCollectedHeap::heap();
 565 
 566   _gc_timer->register_gc_start();
 567   DefNewTracer gc_tracer;
 568   gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
 569 
 570   _old_gen = gch->old_gen();
 571 
 572   // If the next generation is too full to accommodate promotion
 573   // from this generation, pass on collection; let the next generation
 574   // do it.
 575   if (!collection_attempt_is_safe()) {
 576     if (Verbose && PrintGCDetails) {
 577       gclog_or_tty->print(" :: Collection attempt not safe :: ");
 578     }
 579     gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
 580     return;
 581   }
 582   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 583 
 584   init_assuming_no_promotion_failure();
 585 
 586   GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL);
 587   // Capture heap used before collection (for printing).
 588   size_t gch_prev_used = gch->used();
 589 
 590   gch->trace_heap_before_gc(&gc_tracer);
 591 
 592   // These can be shared for all code paths
 593   IsAliveClosure is_alive(this);
 594   ScanWeakRefClosure scan_weak_ref(this);
 595 
 596   age_table()->clear();
 597   to()->clear(SpaceDecorator::Mangle);
 598 
 599   gch->rem_set()->prepare_for_younger_refs_iterate(false);
 600 
 601   assert(gch->no_allocs_since_save_marks(),
 602          "save marks have not been newly set.");
 603 
 604   // Not very pretty.
 605   CollectorPolicy* cp = gch->collector_policy();
 606 
 607   FastScanClosure fsc_with_no_gc_barrier(this, false);
 608   FastScanClosure fsc_with_gc_barrier(this, true);
 609 
 610   KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
 611                                       gch->rem_set()->klass_rem_set());
 612   CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
 613                                            &fsc_with_no_gc_barrier,
 614                                            false);
 615 
 616   set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
 617   FastEvacuateFollowersClosure evacuate_followers(gch,
 618                                                   &fsc_with_no_gc_barrier,
 619                                                   &fsc_with_gc_barrier);
 620 
 621   assert(gch->no_allocs_since_save_marks(),
 622          "save marks have not been newly set.");
 623 
 624   {
 625     // DefNew needs to run with n_threads == 0, to make sure the serial
 626     // version of the card table scanning code is used.
 627     // See: CardTableModRefBSForCTRS::non_clean_card_iterate_possibly_parallel.
 628     StrongRootsScope srs(0);
 629 
 630     gch->young_process_roots(&srs,
 631                              &fsc_with_no_gc_barrier,
 632                              &fsc_with_gc_barrier,
 633                              &cld_scan_closure);
 634   }
 635 
 636   // "evacuate followers".
 637   evacuate_followers.do_void();
 638 
 639   FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
 640   ReferenceProcessor* rp = ref_processor();
 641   rp->setup_policy(clear_all_soft_refs);
 642   const ReferenceProcessorStats& stats =
 643   rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
 644                                     NULL, _gc_timer);
 645   gc_tracer.report_gc_reference_stats(stats);
 646 
 647   if (!_promotion_failed) {
 648     // Swap the survivor spaces.
 649     eden()->clear(SpaceDecorator::Mangle);
 650     from()->clear(SpaceDecorator::Mangle);
 651     if (ZapUnusedHeapArea) {
 652       // This is now done here because of the piece-meal mangling which
 653       // can check for valid mangling at intermediate points in the
 654       // collection(s).  When a young collection fails to collect
 655       // sufficient space resizing of the young generation can occur
 656       // an redistribute the spaces in the young generation.  Mangle
 657       // here so that unzapped regions don't get distributed to
 658       // other spaces.
 659       to()->mangle_unused_area();
 660     }
 661     swap_spaces();
 662 
 663     assert(to()->is_empty(), "to space should be empty now");
 664 
 665     adjust_desired_tenuring_threshold();
 666 
 667     // A successful scavenge should restart the GC time limit count which is
 668     // for full GC's.
 669     AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
 670     size_policy->reset_gc_overhead_limit_count();
 671     assert(!gch->incremental_collection_failed(), "Should be clear");
 672   } else {
 673     assert(_promo_failure_scan_stack.is_empty(), "post condition");
 674     _promo_failure_scan_stack.clear(true); // Clear cached segments.
 675 
 676     remove_forwarding_pointers();
 677     if (PrintGCDetails) {
 678       gclog_or_tty->print(" (promotion failed) ");
 679     }
 680     // Add to-space to the list of space to compact
 681     // when a promotion failure has occurred.  In that
 682     // case there can be live objects in to-space
 683     // as a result of a partial evacuation of eden
 684     // and from-space.
 685     swap_spaces();   // For uniformity wrt ParNewGeneration.
 686     from()->set_next_compaction_space(to());
 687     gch->set_incremental_collection_failed();
 688 
 689     // Inform the next generation that a promotion failure occurred.
 690     _old_gen->promotion_failure_occurred();
 691     gc_tracer.report_promotion_failed(_promotion_failed_info);
 692 
 693     // Reset the PromotionFailureALot counters.
 694     NOT_PRODUCT(gch->reset_promotion_should_fail();)
 695   }
 696   if (PrintGC && !PrintGCDetails) {
 697     gch->print_heap_change(gch_prev_used);
 698   }
 699   // set new iteration safe limit for the survivor spaces
 700   from()->set_concurrent_iteration_safe_limit(from()->top());
 701   to()->set_concurrent_iteration_safe_limit(to()->top());
 702 
 703   // We need to use a monotonically non-decreasing time in ms
 704   // or we will see time-warp warnings and os::javaTimeMillis()
 705   // does not guarantee monotonicity.
 706   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 707   update_time_of_last_gc(now);
 708 
 709   gch->trace_heap_after_gc(&gc_tracer);
 710   gc_tracer.report_tenuring_threshold(tenuring_threshold());
 711 
 712   _gc_timer->register_gc_end();
 713 
 714   gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
 715 }
 716 
 717 class RemoveForwardPointerClosure: public ObjectClosure {
 718 public:
 719   void do_object(oop obj) {
 720     obj->init_mark();
 721   }
 722 };
 723 
 724 void DefNewGeneration::init_assuming_no_promotion_failure() {
 725   _promotion_failed = false;
 726   _promotion_failed_info.reset();
 727   from()->set_next_compaction_space(NULL);
 728 }
 729 
 730 void DefNewGeneration::remove_forwarding_pointers() {
 731   RemoveForwardPointerClosure rspc;
 732   eden()->object_iterate(&rspc);
 733   from()->object_iterate(&rspc);
 734 
 735   // Now restore saved marks, if any.
 736   assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
 737          "should be the same");
 738   while (!_objs_with_preserved_marks.is_empty()) {
 739     oop obj   = _objs_with_preserved_marks.pop();
 740     markOop m = _preserved_marks_of_objs.pop();
 741     obj->set_mark(m);
 742   }
 743   _objs_with_preserved_marks.clear(true);
 744   _preserved_marks_of_objs.clear(true);
 745 }
 746 
 747 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
 748   assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
 749          "Oversaving!");
 750   _objs_with_preserved_marks.push(obj);
 751   _preserved_marks_of_objs.push(m);
 752 }
 753 
 754 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
 755   if (m->must_be_preserved_for_promotion_failure(obj)) {
 756     preserve_mark(obj, m);
 757   }
 758 }
 759 
 760 void DefNewGeneration::handle_promotion_failure(oop old) {
 761   if (PrintPromotionFailure && !_promotion_failed) {
 762     gclog_or_tty->print(" (promotion failure size = %d) ",
 763                         old->size());
 764   }
 765   _promotion_failed = true;
 766   _promotion_failed_info.register_copy_failure(old->size());
 767   preserve_mark_if_necessary(old, old->mark());
 768   // forward to self
 769   old->forward_to(old);
 770 
 771   _promo_failure_scan_stack.push(old);
 772 
 773   if (!_promo_failure_drain_in_progress) {
 774     // prevent recursion in copy_to_survivor_space()
 775     _promo_failure_drain_in_progress = true;
 776     drain_promo_failure_scan_stack();
 777     _promo_failure_drain_in_progress = false;
 778   }
 779 }
 780 
 781 oop DefNewGeneration::copy_to_survivor_space(oop old) {
 782   assert(is_in_reserved(old) && !old->is_forwarded(),
 783          "shouldn't be scavenging this oop");
 784   size_t s = old->size();
 785   oop obj = NULL;
 786 
 787   // Try allocating obj in to-space (unless too old)
 788   if (old->age() < tenuring_threshold()) {
 789     obj = (oop) to()->allocate_aligned(s);
 790   }
 791 
 792   // Otherwise try allocating obj tenured
 793   if (obj == NULL) {
 794     obj = _old_gen->promote(old, s);
 795     if (obj == NULL) {
 796       handle_promotion_failure(old);
 797       return old;
 798     }
 799   } else {
 800     // Prefetch beyond obj
 801     const intx interval = PrefetchCopyIntervalInBytes;
 802     Prefetch::write(obj, interval);
 803 
 804     // Copy obj
 805     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
 806 
 807     // Increment age if obj still in new generation
 808     obj->incr_age();
 809     age_table()->add(obj, s);
 810   }
 811 
 812   // Done, insert forward pointer to obj in this header
 813   old->forward_to(obj);
 814 
 815   return obj;
 816 }
 817 
 818 void DefNewGeneration::drain_promo_failure_scan_stack() {
 819   while (!_promo_failure_scan_stack.is_empty()) {
 820      oop obj = _promo_failure_scan_stack.pop();
 821      obj->oop_iterate(_promo_failure_scan_stack_closure);
 822   }
 823 }
 824 
 825 void DefNewGeneration::save_marks() {
 826   eden()->set_saved_mark();
 827   to()->set_saved_mark();
 828   from()->set_saved_mark();
 829 }
 830 
 831 
 832 void DefNewGeneration::reset_saved_marks() {
 833   eden()->reset_saved_mark();
 834   to()->reset_saved_mark();
 835   from()->reset_saved_mark();
 836 }
 837 
 838 
 839 bool DefNewGeneration::no_allocs_since_save_marks() {
 840   assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
 841   assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
 842   return to()->saved_mark_at_top();
 843 }
 844 
 845 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
 846                                                                 \
 847 void DefNewGeneration::                                         \
 848 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) {   \
 849   cl->assert_generation(this);                                  \
 850   eden()->oop_since_save_marks_iterate##nv_suffix(cl);          \
 851   to()->oop_since_save_marks_iterate##nv_suffix(cl);            \
 852   from()->oop_since_save_marks_iterate##nv_suffix(cl);          \
 853   save_marks();                                                 \
 854 }
 855 
 856 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
 857 
 858 #undef DefNew_SINCE_SAVE_MARKS_DEFN
 859 
 860 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
 861                                          size_t max_alloc_words) {
 862   if (requestor == this || _promotion_failed) {
 863     return;
 864   }
 865   assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
 866 
 867   /* $$$ Assert this?  "trace" is a "MarkSweep" function so that's not appropriate.
 868   if (to_space->top() > to_space->bottom()) {
 869     trace("to_space not empty when contribute_scratch called");
 870   }
 871   */
 872 
 873   ContiguousSpace* to_space = to();
 874   assert(to_space->end() >= to_space->top(), "pointers out of order");
 875   size_t free_words = pointer_delta(to_space->end(), to_space->top());
 876   if (free_words >= MinFreeScratchWords) {
 877     ScratchBlock* sb = (ScratchBlock*)to_space->top();
 878     sb->num_words = free_words;
 879     sb->next = list;
 880     list = sb;
 881   }
 882 }
 883 
 884 void DefNewGeneration::reset_scratch() {
 885   // If contributing scratch in to_space, mangle all of
 886   // to_space if ZapUnusedHeapArea.  This is needed because
 887   // top is not maintained while using to-space as scratch.
 888   if (ZapUnusedHeapArea) {
 889     to()->mangle_unused_area_complete();
 890   }
 891 }
 892 
 893 bool DefNewGeneration::collection_attempt_is_safe() {
 894   if (!to()->is_empty()) {
 895     if (Verbose && PrintGCDetails) {
 896       gclog_or_tty->print(" :: to is not empty :: ");
 897     }
 898     return false;
 899   }
 900   if (_old_gen == NULL) {
 901     GenCollectedHeap* gch = GenCollectedHeap::heap();
 902     _old_gen = gch->old_gen();
 903   }
 904   return _old_gen->promotion_attempt_is_safe(used());
 905 }
 906 
 907 void DefNewGeneration::gc_epilogue(bool full) {
 908   DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
 909 
 910   assert(!GC_locker::is_active(), "We should not be executing here");
 911   // Check if the heap is approaching full after a collection has
 912   // been done.  Generally the young generation is empty at
 913   // a minimum at the end of a collection.  If it is not, then
 914   // the heap is approaching full.
 915   GenCollectedHeap* gch = GenCollectedHeap::heap();
 916   if (full) {
 917     DEBUG_ONLY(seen_incremental_collection_failed = false;)
 918     if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
 919       if (Verbose && PrintGCDetails) {
 920         gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
 921                             GCCause::to_string(gch->gc_cause()));
 922       }
 923       gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
 924       set_should_allocate_from_space(); // we seem to be running out of space
 925     } else {
 926       if (Verbose && PrintGCDetails) {
 927         gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
 928                             GCCause::to_string(gch->gc_cause()));
 929       }
 930       gch->clear_incremental_collection_failed(); // We just did a full collection
 931       clear_should_allocate_from_space(); // if set
 932     }
 933   } else {
 934 #ifdef ASSERT
 935     // It is possible that incremental_collection_failed() == true
 936     // here, because an attempted scavenge did not succeed. The policy
 937     // is normally expected to cause a full collection which should
 938     // clear that condition, so we should not be here twice in a row
 939     // with incremental_collection_failed() == true without having done
 940     // a full collection in between.
 941     if (!seen_incremental_collection_failed &&
 942         gch->incremental_collection_failed()) {
 943       if (Verbose && PrintGCDetails) {
 944         gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
 945                             GCCause::to_string(gch->gc_cause()));
 946       }
 947       seen_incremental_collection_failed = true;
 948     } else if (seen_incremental_collection_failed) {
 949       if (Verbose && PrintGCDetails) {
 950         gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
 951                             GCCause::to_string(gch->gc_cause()));
 952       }
 953       assert(gch->gc_cause() == GCCause::_scavenge_alot ||
 954              (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
 955              !gch->incremental_collection_failed(),
 956              "Twice in a row");
 957       seen_incremental_collection_failed = false;
 958     }
 959 #endif // ASSERT
 960   }
 961 
 962   if (ZapUnusedHeapArea) {
 963     eden()->check_mangled_unused_area_complete();
 964     from()->check_mangled_unused_area_complete();
 965     to()->check_mangled_unused_area_complete();
 966   }
 967 
 968   if (!CleanChunkPoolAsync) {
 969     Chunk::clean_chunk_pool();
 970   }
 971 
 972   // update the generation and space performance counters
 973   update_counters();
 974   gch->collector_policy()->counters()->update_counters();
 975 }
 976 
 977 void DefNewGeneration::record_spaces_top() {
 978   assert(ZapUnusedHeapArea, "Not mangling unused space");
 979   eden()->set_top_for_allocations();
 980   to()->set_top_for_allocations();
 981   from()->set_top_for_allocations();
 982 }
 983 
 984 void DefNewGeneration::ref_processor_init() {
 985   Generation::ref_processor_init();
 986 }
 987 
 988 
 989 void DefNewGeneration::update_counters() {
 990   if (UsePerfData) {
 991     _eden_counters->update_all();
 992     _from_counters->update_all();
 993     _to_counters->update_all();
 994     _gen_counters->update_all();
 995   }
 996 }
 997 
 998 void DefNewGeneration::verify() {
 999   eden()->verify();
1000   from()->verify();
1001     to()->verify();
1002 }
1003 
1004 void DefNewGeneration::print_on(outputStream* st) const {
1005   Generation::print_on(st);
1006   st->print("  eden");
1007   eden()->print_on(st);
1008   st->print("  from");
1009   from()->print_on(st);
1010   st->print("  to  ");
1011   to()->print_on(st);
1012 }
1013 
1014 
1015 const char* DefNewGeneration::name() const {
1016   return "def new generation";
1017 }
1018 
1019 // Moved from inline file as they are not called inline
1020 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1021   return eden();
1022 }
1023 
1024 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1025   // This is the slow-path allocation for the DefNewGeneration.
1026   // Most allocations are fast-path in compiled code.
1027   // We try to allocate from the eden.  If that works, we are happy.
1028   // Note that since DefNewGeneration supports lock-free allocation, we
1029   // have to use it here, as well.
1030   HeapWord* result = eden()->par_allocate(word_size);
1031   if (result != NULL) {
1032     if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1033       _old_gen->sample_eden_chunk();
1034     }
1035   } else {
1036     // If the eden is full and the last collection bailed out, we are running
1037     // out of heap space, and we try to allocate the from-space, too.
1038     // allocate_from_space can't be inlined because that would introduce a
1039     // circular dependency at compile time.
1040     result = allocate_from_space(word_size);
1041   }
1042   return result;
1043 }
1044 
1045 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1046                                          bool is_tlab) {
1047   HeapWord* res = eden()->par_allocate(word_size);
1048   if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1049     _old_gen->sample_eden_chunk();
1050   }
1051   return res;
1052 }
1053 
1054 size_t DefNewGeneration::tlab_capacity() const {
1055   return eden()->capacity();
1056 }
1057 
1058 size_t DefNewGeneration::tlab_used() const {
1059   return eden()->used();
1060 }
1061 
1062 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1063   return unsafe_max_alloc_nogc();
1064 }