1 /*
   2  * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc_implementation/shared/collectorCounters.hpp"
  27 #include "gc_implementation/shared/gcPolicyCounters.hpp"
  28 #include "gc_implementation/shared/gcHeapSummary.hpp"
  29 #include "gc_implementation/shared/gcTimer.hpp"
  30 #include "gc_implementation/shared/gcTraceTime.hpp"
  31 #include "gc_implementation/shared/gcTrace.hpp"
  32 #include "gc_implementation/shared/spaceDecorator.hpp"
  33 #include "memory/defNewGeneration.inline.hpp"
  34 #include "memory/gcLocker.inline.hpp"
  35 #include "memory/genCollectedHeap.hpp"
  36 #include "memory/genOopClosures.inline.hpp"
  37 #include "memory/genRemSet.hpp"
  38 #include "memory/generationSpec.hpp"
  39 #include "memory/iterator.hpp"
  40 #include "memory/referencePolicy.hpp"
  41 #include "memory/space.inline.hpp"
  42 #include "oops/instanceRefKlass.hpp"
  43 #include "oops/oop.inline.hpp"
  44 #include "runtime/java.hpp"
  45 #include "runtime/thread.inline.hpp"
  46 #include "utilities/copy.hpp"
  47 #include "utilities/stack.inline.hpp"
  48 
  49 //
  50 // DefNewGeneration functions.
  51 
  52 // Methods of protected closure types.
  53 
  54 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
  55   assert(g->level() == 0, "Optimized for youngest gen.");
  56 }
  57 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
  58   return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
  59 }
  60 
  61 DefNewGeneration::KeepAliveClosure::
  62 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
  63   GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
  64   assert(rs->rs_kind() == GenRemSet::CardTable, "Wrong rem set kind.");
  65   _rs = (CardTableRS*)rs;
  66 }
  67 
  68 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  69 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  70 
  71 
  72 DefNewGeneration::FastKeepAliveClosure::
  73 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
  74   DefNewGeneration::KeepAliveClosure(cl) {
  75   _boundary = g->reserved().end();
  76 }
  77 
  78 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  79 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  80 
  81 DefNewGeneration::EvacuateFollowersClosure::
  82 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
  83                          ScanClosure* cur, ScanClosure* older) :
  84   _gch(gch), _level(level),
  85   _scan_cur_or_nonheap(cur), _scan_older(older)
  86 {}
  87 
  88 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
  89   do {
  90     _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
  91                                        _scan_older);
  92   } while (!_gch->no_allocs_since_save_marks(_level));
  93 }
  94 
  95 DefNewGeneration::FastEvacuateFollowersClosure::
  96 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
  97                              DefNewGeneration* gen,
  98                              FastScanClosure* cur, FastScanClosure* older) :
  99   _gch(gch), _level(level), _gen(gen),
 100   _scan_cur_or_nonheap(cur), _scan_older(older)
 101 {}
 102 
 103 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
 104   do {
 105     _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
 106                                        _scan_older);
 107   } while (!_gch->no_allocs_since_save_marks(_level));
 108   guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
 109 }
 110 
 111 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
 112     OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 113 {
 114   assert(_g->level() == 0, "Optimized for youngest generation");
 115   _boundary = _g->reserved().end();
 116 }
 117 
 118 void ScanClosure::do_oop(oop* p)       { ScanClosure::do_oop_work(p); }
 119 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
 120 
 121 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
 122     OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 123 {
 124   assert(_g->level() == 0, "Optimized for youngest generation");
 125   _boundary = _g->reserved().end();
 126 }
 127 
 128 void FastScanClosure::do_oop(oop* p)       { FastScanClosure::do_oop_work(p); }
 129 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
 130 
 131 void KlassScanClosure::do_klass(Klass* klass) {
 132 #ifndef PRODUCT
 133   if (TraceScavenge) {
 134     ResourceMark rm;
 135     gclog_or_tty->print_cr("KlassScanClosure::do_klass %p, %s, dirty: %s",
 136                            klass,
 137                            klass->external_name(),
 138                            klass->has_modified_oops() ? "true" : "false");
 139   }
 140 #endif
 141 
 142   // If the klass has not been dirtied we know that there's
 143   // no references into  the young gen and we can skip it.
 144   if (klass->has_modified_oops()) {
 145     if (_accumulate_modified_oops) {
 146       klass->accumulate_modified_oops();
 147     }
 148 
 149     // Clear this state since we're going to scavenge all the metadata.
 150     klass->clear_modified_oops();
 151 
 152     // Tell the closure which Klass is being scanned so that it can be dirtied
 153     // if oops are left pointing into the young gen.
 154     _scavenge_closure->set_scanned_klass(klass);
 155 
 156     klass->oops_do(_scavenge_closure);
 157 
 158     _scavenge_closure->set_scanned_klass(NULL);
 159   }
 160 }
 161 
 162 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
 163   _g(g)
 164 {
 165   assert(_g->level() == 0, "Optimized for youngest generation");
 166   _boundary = _g->reserved().end();
 167 }
 168 
 169 void ScanWeakRefClosure::do_oop(oop* p)       { ScanWeakRefClosure::do_oop_work(p); }
 170 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
 171 
 172 void FilteringClosure::do_oop(oop* p)       { FilteringClosure::do_oop_work(p); }
 173 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
 174 
 175 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
 176                                    KlassRemSet* klass_rem_set)
 177     : _scavenge_closure(scavenge_closure),
 178       _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
 179 
 180 
 181 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
 182                                    size_t initial_size,
 183                                    int level,
 184                                    const char* policy)
 185   : Generation(rs, initial_size, level),
 186     _promo_failure_drain_in_progress(false),
 187     _should_allocate_from_space(false)
 188 {
 189   MemRegion cmr((HeapWord*)_virtual_space.low(),
 190                 (HeapWord*)_virtual_space.high());
 191   Universe::heap()->barrier_set()->resize_covered_region(cmr);
 192 
 193   if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) {
 194     _eden_space = new ConcEdenSpace(this);
 195   } else {
 196     _eden_space = new EdenSpace(this);
 197   }
 198   _from_space = new ContiguousSpace();
 199   _to_space   = new ContiguousSpace();
 200 
 201   if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
 202     vm_exit_during_initialization("Could not allocate a new gen space");
 203 
 204   // Compute the maximum eden and survivor space sizes. These sizes
 205   // are computed assuming the entire reserved space is committed.
 206   // These values are exported as performance counters.
 207   uintx alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();
 208   uintx size = _virtual_space.reserved_size();
 209   _max_survivor_size = compute_survivor_size(size, alignment);
 210   _max_eden_size = size - (2*_max_survivor_size);
 211 
 212   // allocate the performance counters
 213 
 214   // Generation counters -- generation 0, 3 subspaces
 215   _gen_counters = new GenerationCounters("new", 0, 3, &_virtual_space);
 216   _gc_counters = new CollectorCounters(policy, 0);
 217 
 218   _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
 219                                       _gen_counters);
 220   _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
 221                                       _gen_counters);
 222   _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
 223                                     _gen_counters);
 224 
 225   compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
 226   update_counters();
 227   _next_gen = NULL;
 228   _tenuring_threshold = MaxTenuringThreshold;
 229   _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
 230 
 231   _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
 232 }
 233 
 234 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
 235                                                 bool clear_space,
 236                                                 bool mangle_space) {
 237   uintx alignment =
 238     GenCollectedHeap::heap()->collector_policy()->min_alignment();
 239 
 240   // If the spaces are being cleared (only done at heap initialization
 241   // currently), the survivor spaces need not be empty.
 242   // Otherwise, no care is taken for used areas in the survivor spaces
 243   // so check.
 244   assert(clear_space || (to()->is_empty() && from()->is_empty()),
 245     "Initialization of the survivor spaces assumes these are empty");
 246 
 247   // Compute sizes
 248   uintx size = _virtual_space.committed_size();
 249   uintx survivor_size = compute_survivor_size(size, alignment);
 250   uintx eden_size = size - (2*survivor_size);
 251   assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 252 
 253   if (eden_size < minimum_eden_size) {
 254     // May happen due to 64Kb rounding, if so adjust eden size back up
 255     minimum_eden_size = align_size_up(minimum_eden_size, alignment);
 256     uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
 257     uintx unaligned_survivor_size =
 258       align_size_down(maximum_survivor_size, alignment);
 259     survivor_size = MAX2(unaligned_survivor_size, alignment);
 260     eden_size = size - (2*survivor_size);
 261     assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 262     assert(eden_size >= minimum_eden_size, "just checking");
 263   }
 264 
 265   char *eden_start = _virtual_space.low();
 266   char *from_start = eden_start + eden_size;
 267   char *to_start   = from_start + survivor_size;
 268   char *to_end     = to_start   + survivor_size;
 269 
 270   assert(to_end == _virtual_space.high(), "just checking");
 271   assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
 272   assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
 273   assert(Space::is_aligned((HeapWord*)to_start),   "checking alignment");
 274 
 275   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
 276   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
 277   MemRegion toMR  ((HeapWord*)to_start, (HeapWord*)to_end);
 278 
 279   // A minimum eden size implies that there is a part of eden that
 280   // is being used and that affects the initialization of any
 281   // newly formed eden.
 282   bool live_in_eden = minimum_eden_size > 0;
 283 
 284   // If not clearing the spaces, do some checking to verify that
 285   // the space are already mangled.
 286   if (!clear_space) {
 287     // Must check mangling before the spaces are reshaped.  Otherwise,
 288     // the bottom or end of one space may have moved into another
 289     // a failure of the check may not correctly indicate which space
 290     // is not properly mangled.
 291     if (ZapUnusedHeapArea) {
 292       HeapWord* limit = (HeapWord*) _virtual_space.high();
 293       eden()->check_mangled_unused_area(limit);
 294       from()->check_mangled_unused_area(limit);
 295         to()->check_mangled_unused_area(limit);
 296     }
 297   }
 298 
 299   // Reset the spaces for their new regions.
 300   eden()->initialize(edenMR,
 301                      clear_space && !live_in_eden,
 302                      SpaceDecorator::Mangle);
 303   // If clear_space and live_in_eden, we will not have cleared any
 304   // portion of eden above its top. This can cause newly
 305   // expanded space not to be mangled if using ZapUnusedHeapArea.
 306   // We explicitly do such mangling here.
 307   if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
 308     eden()->mangle_unused_area();
 309   }
 310   from()->initialize(fromMR, clear_space, mangle_space);
 311   to()->initialize(toMR, clear_space, mangle_space);
 312 
 313   // Set next compaction spaces.
 314   eden()->set_next_compaction_space(from());
 315   // The to-space is normally empty before a compaction so need
 316   // not be considered.  The exception is during promotion
 317   // failure handling when to-space can contain live objects.
 318   from()->set_next_compaction_space(NULL);
 319 }
 320 
 321 void DefNewGeneration::swap_spaces() {
 322   ContiguousSpace* s = from();
 323   _from_space        = to();
 324   _to_space          = s;
 325   eden()->set_next_compaction_space(from());
 326   // The to-space is normally empty before a compaction so need
 327   // not be considered.  The exception is during promotion
 328   // failure handling when to-space can contain live objects.
 329   from()->set_next_compaction_space(NULL);
 330 
 331   if (UsePerfData) {
 332     CSpaceCounters* c = _from_counters;
 333     _from_counters = _to_counters;
 334     _to_counters = c;
 335   }
 336 }
 337 
 338 bool DefNewGeneration::expand(size_t bytes) {
 339   MutexLocker x(ExpandHeap_lock);
 340   HeapWord* prev_high = (HeapWord*) _virtual_space.high();
 341   bool success = _virtual_space.expand_by(bytes);
 342   if (success && ZapUnusedHeapArea) {
 343     // Mangle newly committed space immediately because it
 344     // can be done here more simply that after the new
 345     // spaces have been computed.
 346     HeapWord* new_high = (HeapWord*) _virtual_space.high();
 347     MemRegion mangle_region(prev_high, new_high);
 348     SpaceMangler::mangle_region(mangle_region);
 349   }
 350 
 351   // Do not attempt an expand-to-the reserve size.  The
 352   // request should properly observe the maximum size of
 353   // the generation so an expand-to-reserve should be
 354   // unnecessary.  Also a second call to expand-to-reserve
 355   // value potentially can cause an undue expansion.
 356   // For example if the first expand fail for unknown reasons,
 357   // but the second succeeds and expands the heap to its maximum
 358   // value.
 359   if (GC_locker::is_active()) {
 360     if (PrintGC && Verbose) {
 361       gclog_or_tty->print_cr("Garbage collection disabled, "
 362         "expanded heap instead");
 363     }
 364   }
 365 
 366   return success;
 367 }
 368 
 369 
 370 void DefNewGeneration::compute_new_size() {
 371   // This is called after a gc that includes the following generation
 372   // (which is required to exist.)  So from-space will normally be empty.
 373   // Note that we check both spaces, since if scavenge failed they revert roles.
 374   // If not we bail out (otherwise we would have to relocate the objects)
 375   if (!from()->is_empty() || !to()->is_empty()) {
 376     return;
 377   }
 378 
 379   int next_level = level() + 1;
 380   GenCollectedHeap* gch = GenCollectedHeap::heap();
 381   assert(next_level < gch->_n_gens,
 382          "DefNewGeneration cannot be an oldest gen");
 383 
 384   Generation* next_gen = gch->_gens[next_level];
 385   size_t old_size = next_gen->capacity();
 386   size_t new_size_before = _virtual_space.committed_size();
 387   size_t min_new_size = spec()->init_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     Universe::heap()->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::object_iterate_since_last_GC(ObjectClosure* cl) {
 454   // $$$ This may be wrong in case of "scavenge failure"?
 455   eden()->object_iterate(cl);
 456 }
 457 
 458 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
 459   assert(false, "NYI -- are you sure you want to call this?");
 460 }
 461 
 462 
 463 size_t DefNewGeneration::capacity() const {
 464   return eden()->capacity()
 465        + from()->capacity();  // to() is only used during scavenge
 466 }
 467 
 468 
 469 size_t DefNewGeneration::used() const {
 470   return eden()->used()
 471        + from()->used();      // to() is only used during scavenge
 472 }
 473 
 474 
 475 size_t DefNewGeneration::free() const {
 476   return eden()->free()
 477        + from()->free();      // to() is only used during scavenge
 478 }
 479 
 480 size_t DefNewGeneration::max_capacity() const {
 481   const size_t alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();
 482   const size_t reserved_bytes = reserved().byte_size();
 483   return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
 484 }
 485 
 486 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
 487   return eden()->free();
 488 }
 489 
 490 size_t DefNewGeneration::capacity_before_gc() const {
 491   return eden()->capacity();
 492 }
 493 
 494 size_t DefNewGeneration::contiguous_available() const {
 495   return eden()->free();
 496 }
 497 
 498 
 499 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
 500 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
 501 
 502 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
 503   eden()->object_iterate(blk);
 504   from()->object_iterate(blk);
 505 }
 506 
 507 
 508 void DefNewGeneration::space_iterate(SpaceClosure* blk,
 509                                      bool usedOnly) {
 510   blk->do_space(eden());
 511   blk->do_space(from());
 512   blk->do_space(to());
 513 }
 514 
 515 // The last collection bailed out, we are running out of heap space,
 516 // so we try to allocate the from-space, too.
 517 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
 518   HeapWord* result = NULL;
 519   if (Verbose && PrintGCDetails) {
 520     gclog_or_tty->print("DefNewGeneration::allocate_from_space(%u):"
 521                         "  will_fail: %s"
 522                         "  heap_lock: %s"
 523                         "  free: " SIZE_FORMAT,
 524                         size,
 525                         GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
 526                           "true" : "false",
 527                         Heap_lock->is_locked() ? "locked" : "unlocked",
 528                         from()->free());
 529   }
 530   if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
 531     if (Heap_lock->owned_by_self() ||
 532         (SafepointSynchronize::is_at_safepoint() &&
 533          Thread::current()->is_VM_thread())) {
 534       // If the Heap_lock is not locked by this thread, this will be called
 535       // again later with the Heap_lock held.
 536       result = from()->allocate(size);
 537     } else if (PrintGC && Verbose) {
 538       gclog_or_tty->print_cr("  Heap_lock is not owned by self");
 539     }
 540   } else if (PrintGC && Verbose) {
 541     gclog_or_tty->print_cr("  should_allocate_from_space: NOT");
 542   }
 543   if (PrintGC && Verbose) {
 544     gclog_or_tty->print_cr("  returns %s", result == NULL ? "NULL" : "object");
 545   }
 546   return result;
 547 }
 548 
 549 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
 550                                                 bool   is_tlab,
 551                                                 bool   parallel) {
 552   // We don't attempt to expand the young generation (but perhaps we should.)
 553   return allocate(size, is_tlab);
 554 }
 555 
 556 void DefNewGeneration::adjust_desired_tenuring_threshold() {
 557   // Set the desired survivor size to half the real survivor space
 558   _tenuring_threshold =
 559     age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
 560 }
 561 
 562 void DefNewGeneration::collect(bool   full,
 563                                bool   clear_all_soft_refs,
 564                                size_t size,
 565                                bool   is_tlab) {
 566   assert(full || size > 0, "otherwise we don't want to collect");
 567 
 568   GenCollectedHeap* gch = GenCollectedHeap::heap();
 569 
 570   _gc_timer->register_gc_start(os::elapsed_counter());
 571   DefNewTracer gc_tracer;
 572   gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
 573 
 574   _next_gen = gch->next_gen(this);
 575   assert(_next_gen != NULL,
 576     "This must be the youngest gen, and not the only gen");
 577 
 578   // If the next generation is too full to accommodate promotion
 579   // from this generation, pass on collection; let the next generation
 580   // do it.
 581   if (!collection_attempt_is_safe()) {
 582     if (Verbose && PrintGCDetails) {
 583       gclog_or_tty->print(" :: Collection attempt not safe :: ");
 584     }
 585     gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
 586     return;
 587   }
 588   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 589 
 590   init_assuming_no_promotion_failure();
 591 
 592   GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL);
 593   // Capture heap used before collection (for printing).
 594   size_t gch_prev_used = gch->used();
 595 
 596   gch->trace_heap_before_gc(&gc_tracer);
 597 
 598   SpecializationStats::clear();
 599 
 600   // These can be shared for all code paths
 601   IsAliveClosure is_alive(this);
 602   ScanWeakRefClosure scan_weak_ref(this);
 603 
 604   age_table()->clear();
 605   to()->clear(SpaceDecorator::Mangle);
 606 
 607   gch->rem_set()->prepare_for_younger_refs_iterate(false);
 608 
 609   assert(gch->no_allocs_since_save_marks(0),
 610          "save marks have not been newly set.");
 611 
 612   // Not very pretty.
 613   CollectorPolicy* cp = gch->collector_policy();
 614 
 615   FastScanClosure fsc_with_no_gc_barrier(this, false);
 616   FastScanClosure fsc_with_gc_barrier(this, true);
 617 
 618   KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
 619                                       gch->rem_set()->klass_rem_set());
 620 
 621   set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
 622   FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
 623                                                   &fsc_with_no_gc_barrier,
 624                                                   &fsc_with_gc_barrier);
 625 
 626   assert(gch->no_allocs_since_save_marks(0),
 627          "save marks have not been newly set.");
 628 
 629   int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
 630 
 631   gch->gen_process_strong_roots(_level,
 632                                 true,  // Process younger gens, if any,
 633                                        // as strong roots.
 634                                 true,  // activate StrongRootsScope
 635                                 true,  // is scavenging
 636                                 SharedHeap::ScanningOption(so),
 637                                 &fsc_with_no_gc_barrier,
 638                                 true,   // walk *all* scavengable nmethods
 639                                 &fsc_with_gc_barrier,
 640                                 &klass_scan_closure);
 641 
 642   // "evacuate followers".
 643   evacuate_followers.do_void();
 644 
 645   FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
 646   ReferenceProcessor* rp = ref_processor();
 647   rp->setup_policy(clear_all_soft_refs);
 648   const ReferenceProcessorStats& stats =
 649   rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
 650                                     NULL, _gc_timer);
 651   gc_tracer.report_gc_reference_stats(stats);
 652 
 653   if (!_promotion_failed) {
 654     // Swap the survivor spaces.
 655     eden()->clear(SpaceDecorator::Mangle);
 656     from()->clear(SpaceDecorator::Mangle);
 657     if (ZapUnusedHeapArea) {
 658       // This is now done here because of the piece-meal mangling which
 659       // can check for valid mangling at intermediate points in the
 660       // collection(s).  When a minor collection fails to collect
 661       // sufficient space resizing of the young generation can occur
 662       // an redistribute the spaces in the young generation.  Mangle
 663       // here so that unzapped regions don't get distributed to
 664       // other spaces.
 665       to()->mangle_unused_area();
 666     }
 667     swap_spaces();
 668 
 669     assert(to()->is_empty(), "to space should be empty now");
 670 
 671     adjust_desired_tenuring_threshold();
 672 
 673     // A successful scavenge should restart the GC time limit count which is
 674     // for full GC's.
 675     AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
 676     size_policy->reset_gc_overhead_limit_count();
 677     if (PrintGC && !PrintGCDetails) {
 678       gch->print_heap_change(gch_prev_used);
 679     }
 680     assert(!gch->incremental_collection_failed(), "Should be clear");
 681   } else {
 682     assert(_promo_failure_scan_stack.is_empty(), "post condition");
 683     _promo_failure_scan_stack.clear(true); // Clear cached segments.
 684 
 685     remove_forwarding_pointers();
 686     if (PrintGCDetails) {
 687       gclog_or_tty->print(" (promotion failed) ");
 688     }
 689     // Add to-space to the list of space to compact
 690     // when a promotion failure has occurred.  In that
 691     // case there can be live objects in to-space
 692     // as a result of a partial evacuation of eden
 693     // and from-space.
 694     swap_spaces();   // For uniformity wrt ParNewGeneration.
 695     from()->set_next_compaction_space(to());
 696     gch->set_incremental_collection_failed();
 697 
 698     // Inform the next generation that a promotion failure occurred.
 699     _next_gen->promotion_failure_occurred();
 700     gc_tracer.report_promotion_failed(_promotion_failed_info);
 701 
 702     // Reset the PromotionFailureALot counters.
 703     NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
 704   }
 705   // set new iteration safe limit for the survivor spaces
 706   from()->set_concurrent_iteration_safe_limit(from()->top());
 707   to()->set_concurrent_iteration_safe_limit(to()->top());
 708   SpecializationStats::print();
 709 
 710   // We need to use a monotonically non-decreasing time in ms
 711   // or we will see time-warp warnings and os::javaTimeMillis()
 712   // does not guarantee monotonicity.
 713   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 714   update_time_of_last_gc(now);
 715 
 716   gch->trace_heap_after_gc(&gc_tracer);
 717   gc_tracer.report_tenuring_threshold(tenuring_threshold());
 718 
 719   _gc_timer->register_gc_end(os::elapsed_counter());
 720 
 721   gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
 722 }
 723 
 724 class RemoveForwardPointerClosure: public ObjectClosure {
 725 public:
 726   void do_object(oop obj) {
 727     obj->init_mark();
 728   }
 729 };
 730 
 731 void DefNewGeneration::init_assuming_no_promotion_failure() {
 732   _promotion_failed = false;
 733   _promotion_failed_info.reset();
 734   from()->set_next_compaction_space(NULL);
 735 }
 736 
 737 void DefNewGeneration::remove_forwarding_pointers() {
 738   RemoveForwardPointerClosure rspc;
 739   eden()->object_iterate(&rspc);
 740   from()->object_iterate(&rspc);
 741 
 742   // Now restore saved marks, if any.
 743   assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
 744          "should be the same");
 745   while (!_objs_with_preserved_marks.is_empty()) {
 746     oop obj   = _objs_with_preserved_marks.pop();
 747     markOop m = _preserved_marks_of_objs.pop();
 748     obj->set_mark(m);
 749   }
 750   _objs_with_preserved_marks.clear(true);
 751   _preserved_marks_of_objs.clear(true);
 752 }
 753 
 754 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
 755   assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
 756          "Oversaving!");
 757   _objs_with_preserved_marks.push(obj);
 758   _preserved_marks_of_objs.push(m);
 759 }
 760 
 761 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
 762   if (m->must_be_preserved_for_promotion_failure(obj)) {
 763     preserve_mark(obj, m);
 764   }
 765 }
 766 
 767 void DefNewGeneration::handle_promotion_failure(oop old) {
 768   if (PrintPromotionFailure && !_promotion_failed) {
 769     gclog_or_tty->print(" (promotion failure size = " SIZE_FORMAT ") ",
 770                         old->size());
 771   }
 772   _promotion_failed = true;
 773   _promotion_failed_info.register_copy_failure(old->size());
 774   preserve_mark_if_necessary(old, old->mark());
 775   // forward to self
 776   old->forward_to(old);
 777 
 778   _promo_failure_scan_stack.push(old);
 779 
 780   if (!_promo_failure_drain_in_progress) {
 781     // prevent recursion in copy_to_survivor_space()
 782     _promo_failure_drain_in_progress = true;
 783     drain_promo_failure_scan_stack();
 784     _promo_failure_drain_in_progress = false;
 785   }
 786 }
 787 
 788 oop DefNewGeneration::copy_to_survivor_space(oop old) {
 789   assert(is_in_reserved(old) && !old->is_forwarded(),
 790          "shouldn't be scavenging this oop");
 791   size_t s = old->size();
 792   oop obj = NULL;
 793 
 794   // Try allocating obj in to-space (unless too old)
 795   if (old->age() < tenuring_threshold()) {
 796     obj = (oop) to()->allocate(s);
 797   }
 798 
 799   // Otherwise try allocating obj tenured
 800   if (obj == NULL) {
 801     obj = _next_gen->promote(old, s);
 802     if (obj == NULL) {
 803       handle_promotion_failure(old);
 804       return old;
 805     }
 806   } else {
 807     // Prefetch beyond obj
 808     const intx interval = PrefetchCopyIntervalInBytes;
 809     Prefetch::write(obj, interval);
 810 
 811     // Copy obj
 812     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
 813 
 814     // Increment age if obj still in new generation
 815     obj->incr_age();
 816     age_table()->add(obj, s);
 817   }
 818 
 819   // Done, insert forward pointer to obj in this header
 820   old->forward_to(obj);
 821 
 822   return obj;
 823 }
 824 
 825 void DefNewGeneration::drain_promo_failure_scan_stack() {
 826   while (!_promo_failure_scan_stack.is_empty()) {
 827      oop obj = _promo_failure_scan_stack.pop();
 828      obj->oop_iterate(_promo_failure_scan_stack_closure);
 829   }
 830 }
 831 
 832 void DefNewGeneration::save_marks() {
 833   eden()->set_saved_mark();
 834   to()->set_saved_mark();
 835   from()->set_saved_mark();
 836 }
 837 
 838 
 839 void DefNewGeneration::reset_saved_marks() {
 840   eden()->reset_saved_mark();
 841   to()->reset_saved_mark();
 842   from()->reset_saved_mark();
 843 }
 844 
 845 
 846 bool DefNewGeneration::no_allocs_since_save_marks() {
 847   assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
 848   assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
 849   return to()->saved_mark_at_top();
 850 }
 851 
 852 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
 853                                                                 \
 854 void DefNewGeneration::                                         \
 855 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) {   \
 856   cl->set_generation(this);                                     \
 857   eden()->oop_since_save_marks_iterate##nv_suffix(cl);          \
 858   to()->oop_since_save_marks_iterate##nv_suffix(cl);            \
 859   from()->oop_since_save_marks_iterate##nv_suffix(cl);          \
 860   cl->reset_generation();                                       \
 861   save_marks();                                                 \
 862 }
 863 
 864 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
 865 
 866 #undef DefNew_SINCE_SAVE_MARKS_DEFN
 867 
 868 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
 869                                          size_t max_alloc_words) {
 870   if (requestor == this || _promotion_failed) return;
 871   assert(requestor->level() > level(), "DefNewGeneration must be youngest");
 872 
 873   /* $$$ Assert this?  "trace" is a "MarkSweep" function so that's not appropriate.
 874   if (to_space->top() > to_space->bottom()) {
 875     trace("to_space not empty when contribute_scratch called");
 876   }
 877   */
 878 
 879   ContiguousSpace* to_space = to();
 880   assert(to_space->end() >= to_space->top(), "pointers out of order");
 881   size_t free_words = pointer_delta(to_space->end(), to_space->top());
 882   if (free_words >= MinFreeScratchWords) {
 883     ScratchBlock* sb = (ScratchBlock*)to_space->top();
 884     sb->num_words = free_words;
 885     sb->next = list;
 886     list = sb;
 887   }
 888 }
 889 
 890 void DefNewGeneration::reset_scratch() {
 891   // If contributing scratch in to_space, mangle all of
 892   // to_space if ZapUnusedHeapArea.  This is needed because
 893   // top is not maintained while using to-space as scratch.
 894   if (ZapUnusedHeapArea) {
 895     to()->mangle_unused_area_complete();
 896   }
 897 }
 898 
 899 bool DefNewGeneration::collection_attempt_is_safe() {
 900   if (!to()->is_empty()) {
 901     if (Verbose && PrintGCDetails) {
 902       gclog_or_tty->print(" :: to is not empty :: ");
 903     }
 904     return false;
 905   }
 906   if (_next_gen == NULL) {
 907     GenCollectedHeap* gch = GenCollectedHeap::heap();
 908     _next_gen = gch->next_gen(this);
 909     assert(_next_gen != NULL,
 910            "This must be the youngest gen, and not the only gen");
 911   }
 912   return _next_gen->promotion_attempt_is_safe(used());
 913 }
 914 
 915 void DefNewGeneration::gc_epilogue(bool full) {
 916   DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
 917 
 918   assert(!GC_locker::is_active(), "We should not be executing here");
 919   // Check if the heap is approaching full after a collection has
 920   // been done.  Generally the young generation is empty at
 921   // a minimum at the end of a collection.  If it is not, then
 922   // the heap is approaching full.
 923   GenCollectedHeap* gch = GenCollectedHeap::heap();
 924   if (full) {
 925     DEBUG_ONLY(seen_incremental_collection_failed = false;)
 926     if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
 927       if (Verbose && PrintGCDetails) {
 928         gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
 929                             GCCause::to_string(gch->gc_cause()));
 930       }
 931       gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
 932       set_should_allocate_from_space(); // we seem to be running out of space
 933     } else {
 934       if (Verbose && PrintGCDetails) {
 935         gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
 936                             GCCause::to_string(gch->gc_cause()));
 937       }
 938       gch->clear_incremental_collection_failed(); // We just did a full collection
 939       clear_should_allocate_from_space(); // if set
 940     }
 941   } else {
 942 #ifdef ASSERT
 943     // It is possible that incremental_collection_failed() == true
 944     // here, because an attempted scavenge did not succeed. The policy
 945     // is normally expected to cause a full collection which should
 946     // clear that condition, so we should not be here twice in a row
 947     // with incremental_collection_failed() == true without having done
 948     // a full collection in between.
 949     if (!seen_incremental_collection_failed &&
 950         gch->incremental_collection_failed()) {
 951       if (Verbose && PrintGCDetails) {
 952         gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
 953                             GCCause::to_string(gch->gc_cause()));
 954       }
 955       seen_incremental_collection_failed = true;
 956     } else if (seen_incremental_collection_failed) {
 957       if (Verbose && PrintGCDetails) {
 958         gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
 959                             GCCause::to_string(gch->gc_cause()));
 960       }
 961       assert(gch->gc_cause() == GCCause::_scavenge_alot ||
 962              (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
 963              !gch->incremental_collection_failed(),
 964              "Twice in a row");
 965       seen_incremental_collection_failed = false;
 966     }
 967 #endif // ASSERT
 968   }
 969 
 970   if (ZapUnusedHeapArea) {
 971     eden()->check_mangled_unused_area_complete();
 972     from()->check_mangled_unused_area_complete();
 973     to()->check_mangled_unused_area_complete();
 974   }
 975 
 976   if (!CleanChunkPoolAsync) {
 977     Chunk::clean_chunk_pool();
 978   }
 979 
 980   // update the generation and space performance counters
 981   update_counters();
 982   gch->collector_policy()->counters()->update_counters();
 983 }
 984 
 985 void DefNewGeneration::record_spaces_top() {
 986   assert(ZapUnusedHeapArea, "Not mangling unused space");
 987   eden()->set_top_for_allocations();
 988   to()->set_top_for_allocations();
 989   from()->set_top_for_allocations();
 990 }
 991 
 992 void DefNewGeneration::ref_processor_init() {
 993   Generation::ref_processor_init();
 994 }
 995 
 996 
 997 void DefNewGeneration::update_counters() {
 998   if (UsePerfData) {
 999     _eden_counters->update_all();
1000     _from_counters->update_all();
1001     _to_counters->update_all();
1002     _gen_counters->update_all();
1003   }
1004 }
1005 
1006 void DefNewGeneration::verify() {
1007   eden()->verify();
1008   from()->verify();
1009     to()->verify();
1010 }
1011 
1012 void DefNewGeneration::print_on(outputStream* st) const {
1013   Generation::print_on(st);
1014   st->print("  eden");
1015   eden()->print_on(st);
1016   st->print("  from");
1017   from()->print_on(st);
1018   st->print("  to  ");
1019   to()->print_on(st);
1020 }
1021 
1022 
1023 const char* DefNewGeneration::name() const {
1024   return "def new generation";
1025 }
1026 
1027 // Moved from inline file as they are not called inline
1028 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1029   return eden();
1030 }
1031 
1032 HeapWord* DefNewGeneration::allocate(size_t word_size,
1033                                      bool is_tlab) {
1034   // This is the slow-path allocation for the DefNewGeneration.
1035   // Most allocations are fast-path in compiled code.
1036   // We try to allocate from the eden.  If that works, we are happy.
1037   // Note that since DefNewGeneration supports lock-free allocation, we
1038   // have to use it here, as well.
1039   HeapWord* result = eden()->par_allocate(word_size);
1040   if (result != NULL) {
1041     return result;
1042   }
1043   do {
1044     HeapWord* old_limit = eden()->soft_end();
1045     if (old_limit < eden()->end()) {
1046       // Tell the next generation we reached a limit.
1047       HeapWord* new_limit =
1048         next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size);
1049       if (new_limit != NULL) {
1050         Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);
1051       } else {
1052         assert(eden()->soft_end() == eden()->end(),
1053                "invalid state after allocation_limit_reached returned null");
1054       }
1055     } else {
1056       // The allocation failed and the soft limit is equal to the hard limit,
1057       // there are no reasons to do an attempt to allocate
1058       assert(old_limit == eden()->end(), "sanity check");
1059       break;
1060     }
1061     // Try to allocate until succeeded or the soft limit can't be adjusted
1062     result = eden()->par_allocate(word_size);
1063   } while (result == NULL);
1064 
1065   // If the eden is full and the last collection bailed out, we are running
1066   // out of heap space, and we try to allocate the from-space, too.
1067   // allocate_from_space can't be inlined because that would introduce a
1068   // circular dependency at compile time.
1069   if (result == NULL) {
1070     result = allocate_from_space(word_size);
1071   }
1072   return result;
1073 }
1074 
1075 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1076                                          bool is_tlab) {
1077   return eden()->par_allocate(word_size);
1078 }
1079 
1080 void DefNewGeneration::gc_prologue(bool full) {
1081   // Ensure that _end and _soft_end are the same in eden space.
1082   eden()->set_soft_end(eden()->end());
1083 }
1084 
1085 size_t DefNewGeneration::tlab_capacity() const {
1086   return eden()->capacity();
1087 }
1088 
1089 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1090   return unsafe_max_alloc_nogc();
1091 }