1 /*
   2  * Copyright (c) 2001, 2012, 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/spaceDecorator.hpp"
  29 #include "memory/defNewGeneration.inline.hpp"
  30 #include "memory/gcLocker.inline.hpp"
  31 #include "memory/genCollectedHeap.hpp"
  32 #include "memory/genOopClosures.inline.hpp"
  33 #include "memory/genRemSet.hpp"
  34 #include "memory/generationSpec.hpp"
  35 #include "memory/iterator.hpp"
  36 #include "memory/referencePolicy.hpp"
  37 #include "memory/space.inline.hpp"
  38 #include "oops/instanceRefKlass.hpp"
  39 #include "oops/oop.inline.hpp"
  40 #include "runtime/java.hpp"
  41 #include "runtime/thread.inline.hpp"
  42 #include "utilities/copy.hpp"
  43 #include "utilities/stack.inline.hpp"
  44 
  45 //
  46 // DefNewGeneration functions.
  47 
  48 // Methods of protected closure types.
  49 
  50 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
  51   assert(g->level() == 0, "Optimized for youngest gen.");
  52 }
  53 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
  54   return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
  55 }
  56 
  57 DefNewGeneration::KeepAliveClosure::
  58 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
  59   GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
  60   assert(rs->rs_kind() == GenRemSet::CardTable, "Wrong rem set kind.");
  61   _rs = (CardTableRS*)rs;
  62 }
  63 
  64 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  65 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  66 
  67 
  68 DefNewGeneration::FastKeepAliveClosure::
  69 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
  70   DefNewGeneration::KeepAliveClosure(cl) {
  71   _boundary = g->reserved().end();
  72 }
  73 
  74 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  75 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  76 
  77 DefNewGeneration::EvacuateFollowersClosure::
  78 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
  79                          ScanClosure* cur, ScanClosure* older) :
  80   _gch(gch), _level(level),
  81   _scan_cur_or_nonheap(cur), _scan_older(older)
  82 {}
  83 
  84 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
  85   do {
  86     _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
  87                                        _scan_older);
  88   } while (!_gch->no_allocs_since_save_marks(_level));
  89 }
  90 
  91 DefNewGeneration::FastEvacuateFollowersClosure::
  92 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
  93                              DefNewGeneration* gen,
  94                              FastScanClosure* cur, FastScanClosure* older) :
  95   _gch(gch), _level(level), _gen(gen),
  96   _scan_cur_or_nonheap(cur), _scan_older(older)
  97 {}
  98 
  99 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
 100   do {
 101     _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
 102                                        _scan_older);
 103   } while (!_gch->no_allocs_since_save_marks(_level));
 104   guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
 105 }
 106 
 107 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
 108     OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 109 {
 110   assert(_g->level() == 0, "Optimized for youngest generation");
 111   _boundary = _g->reserved().end();
 112 }
 113 
 114 void ScanClosure::do_oop(oop* p)       { ScanClosure::do_oop_work(p); }
 115 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
 116 
 117 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
 118     OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 119 {
 120   assert(_g->level() == 0, "Optimized for youngest generation");
 121   _boundary = _g->reserved().end();
 122 }
 123 
 124 void FastScanClosure::do_oop(oop* p)       { FastScanClosure::do_oop_work(p); }
 125 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
 126 
 127 void KlassScanClosure::do_klass(Klass* klass) {
 128 #ifndef PRODUCT
 129   if (TraceScavenge) {
 130     ResourceMark rm;
 131     gclog_or_tty->print_cr("KlassScanClosure::do_klass %p, %s, dirty: %s",
 132                            klass,
 133                            klass->external_name(),
 134                            klass->has_modified_oops() ? "true" : "false");
 135   }
 136 #endif
 137 
 138   // If the klass has not been dirtied we know that there's
 139   // no references into  the young gen and we can skip it.
 140   if (klass->has_modified_oops()) {
 141     if (_accumulate_modified_oops) {
 142       klass->accumulate_modified_oops();
 143     }
 144 
 145     // Clear this state since we're going to scavenge all the metadata.
 146     klass->clear_modified_oops();
 147 
 148     // Tell the closure which Klass is being scanned so that it can be dirtied
 149     // if oops are left pointing into the young gen.
 150     _scavenge_closure->set_scanned_klass(klass);
 151 
 152     klass->oops_do(_scavenge_closure);
 153 
 154     _scavenge_closure->set_scanned_klass(NULL);
 155   }
 156 }
 157 
 158 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
 159   _g(g)
 160 {
 161   assert(_g->level() == 0, "Optimized for youngest generation");
 162   _boundary = _g->reserved().end();
 163 }
 164 
 165 void ScanWeakRefClosure::do_oop(oop* p)       { ScanWeakRefClosure::do_oop_work(p); }
 166 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
 167 
 168 void FilteringClosure::do_oop(oop* p)       { FilteringClosure::do_oop_work(p); }
 169 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
 170 
 171 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
 172                                    KlassRemSet* klass_rem_set)
 173     : _scavenge_closure(scavenge_closure),
 174       _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
 175 
 176 
 177 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
 178                                    size_t initial_size,
 179                                    int level,
 180                                    const char* policy)
 181   : Generation(rs, initial_size, level),
 182     _promo_failure_drain_in_progress(false),
 183     _should_allocate_from_space(false)
 184 {
 185   MemRegion cmr((HeapWord*)_virtual_space.low(),
 186                 (HeapWord*)_virtual_space.high());
 187   Universe::heap()->barrier_set()->resize_covered_region(cmr);
 188 
 189   if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) {
 190     _eden_space = new ConcEdenSpace(this);
 191   } else {
 192     _eden_space = new EdenSpace(this);
 193   }
 194   _from_space = new ContiguousSpace();
 195   _to_space   = new ContiguousSpace();
 196 
 197   if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
 198     vm_exit_during_initialization("Could not allocate a new gen space");
 199 
 200   // Compute the maximum eden and survivor space sizes. These sizes
 201   // are computed assuming the entire reserved space is committed.
 202   // These values are exported as performance counters.
 203   uintx alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();
 204   uintx size = _virtual_space.reserved_size();
 205   _max_survivor_size = compute_survivor_size(size, alignment);
 206   _max_eden_size = size - (2*_max_survivor_size);
 207 
 208   // allocate the performance counters
 209 
 210   // Generation counters -- generation 0, 3 subspaces
 211   _gen_counters = new GenerationCounters("new", 0, 3, &_virtual_space);
 212   _gc_counters = new CollectorCounters(policy, 0);
 213 
 214   _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
 215                                       _gen_counters);
 216   _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
 217                                       _gen_counters);
 218   _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
 219                                     _gen_counters);
 220 
 221   compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
 222   update_counters();
 223   _next_gen = NULL;
 224   _tenuring_threshold = MaxTenuringThreshold;
 225   _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
 226 }
 227 
 228 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
 229                                                 bool clear_space,
 230                                                 bool mangle_space) {
 231   uintx alignment =
 232     GenCollectedHeap::heap()->collector_policy()->min_alignment();
 233 
 234   // If the spaces are being cleared (only done at heap initialization
 235   // currently), the survivor spaces need not be empty.
 236   // Otherwise, no care is taken for used areas in the survivor spaces
 237   // so check.
 238   assert(clear_space || (to()->is_empty() && from()->is_empty()),
 239     "Initialization of the survivor spaces assumes these are empty");
 240 
 241   // Compute sizes
 242   uintx size = _virtual_space.committed_size();
 243   uintx survivor_size = compute_survivor_size(size, alignment);
 244   uintx eden_size = size - (2*survivor_size);
 245   assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 246 
 247   if (eden_size < minimum_eden_size) {
 248     // May happen due to 64Kb rounding, if so adjust eden size back up
 249     minimum_eden_size = align_size_up(minimum_eden_size, alignment);
 250     uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
 251     uintx unaligned_survivor_size =
 252       align_size_down(maximum_survivor_size, alignment);
 253     survivor_size = MAX2(unaligned_survivor_size, alignment);
 254     eden_size = size - (2*survivor_size);
 255     assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 256     assert(eden_size >= minimum_eden_size, "just checking");
 257   }
 258 
 259   char *eden_start = _virtual_space.low();
 260   char *from_start = eden_start + eden_size;
 261   char *to_start   = from_start + survivor_size;
 262   char *to_end     = to_start   + survivor_size;
 263 
 264   assert(to_end == _virtual_space.high(), "just checking");
 265   assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
 266   assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
 267   assert(Space::is_aligned((HeapWord*)to_start),   "checking alignment");
 268 
 269   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
 270   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
 271   MemRegion toMR  ((HeapWord*)to_start, (HeapWord*)to_end);
 272 
 273   // A minimum eden size implies that there is a part of eden that
 274   // is being used and that affects the initialization of any
 275   // newly formed eden.
 276   bool live_in_eden = minimum_eden_size > 0;
 277 
 278   // If not clearing the spaces, do some checking to verify that
 279   // the space are already mangled.
 280   if (!clear_space) {
 281     // Must check mangling before the spaces are reshaped.  Otherwise,
 282     // the bottom or end of one space may have moved into another
 283     // a failure of the check may not correctly indicate which space
 284     // is not properly mangled.
 285     if (ZapUnusedHeapArea) {
 286       HeapWord* limit = (HeapWord*) _virtual_space.high();
 287       eden()->check_mangled_unused_area(limit);
 288       from()->check_mangled_unused_area(limit);
 289         to()->check_mangled_unused_area(limit);
 290     }
 291   }
 292 
 293   // Reset the spaces for their new regions.
 294   eden()->initialize(edenMR,
 295                      clear_space && !live_in_eden,
 296                      SpaceDecorator::Mangle);
 297   // If clear_space and live_in_eden, we will not have cleared any
 298   // portion of eden above its top. This can cause newly
 299   // expanded space not to be mangled if using ZapUnusedHeapArea.
 300   // We explicitly do such mangling here.
 301   if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
 302     eden()->mangle_unused_area();
 303   }
 304   from()->initialize(fromMR, clear_space, mangle_space);
 305   to()->initialize(toMR, clear_space, mangle_space);
 306 
 307   // Set next compaction spaces.
 308   eden()->set_next_compaction_space(from());
 309   // The to-space is normally empty before a compaction so need
 310   // not be considered.  The exception is during promotion
 311   // failure handling when to-space can contain live objects.
 312   from()->set_next_compaction_space(NULL);
 313 }
 314 
 315 void DefNewGeneration::swap_spaces() {
 316   ContiguousSpace* s = from();
 317   _from_space        = to();
 318   _to_space          = s;
 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   if (UsePerfData) {
 326     CSpaceCounters* c = _from_counters;
 327     _from_counters = _to_counters;
 328     _to_counters = c;
 329   }
 330 }
 331 
 332 bool DefNewGeneration::expand(size_t bytes) {
 333   MutexLocker x(ExpandHeap_lock);
 334   HeapWord* prev_high = (HeapWord*) _virtual_space.high();
 335   bool success = _virtual_space.expand_by(bytes);
 336   if (success && ZapUnusedHeapArea) {
 337     // Mangle newly committed space immediately because it
 338     // can be done here more simply that after the new
 339     // spaces have been computed.
 340     HeapWord* new_high = (HeapWord*) _virtual_space.high();
 341     MemRegion mangle_region(prev_high, new_high);
 342     SpaceMangler::mangle_region(mangle_region);
 343   }
 344 
 345   // Do not attempt an expand-to-the reserve size.  The
 346   // request should properly observe the maximum size of
 347   // the generation so an expand-to-reserve should be
 348   // unnecessary.  Also a second call to expand-to-reserve
 349   // value potentially can cause an undue expansion.
 350   // For example if the first expand fail for unknown reasons,
 351   // but the second succeeds and expands the heap to its maximum
 352   // value.
 353   if (GC_locker::is_active()) {
 354     if (PrintGC && Verbose) {
 355       gclog_or_tty->print_cr("Garbage collection disabled, "
 356         "expanded heap instead");
 357     }
 358   }
 359 
 360   return success;
 361 }
 362 
 363 
 364 void DefNewGeneration::compute_new_size() {
 365   // This is called after a gc that includes the following generation
 366   // (which is required to exist.)  So from-space will normally be empty.
 367   // Note that we check both spaces, since if scavenge failed they revert roles.
 368   // If not we bail out (otherwise we would have to relocate the objects)
 369   if (!from()->is_empty() || !to()->is_empty()) {
 370     return;
 371   }
 372 
 373   int next_level = level() + 1;
 374   GenCollectedHeap* gch = GenCollectedHeap::heap();
 375   assert(next_level < gch->_n_gens,
 376          "DefNewGeneration cannot be an oldest gen");
 377 
 378   Generation* next_gen = gch->_gens[next_level];
 379   size_t old_size = next_gen->capacity();
 380   size_t new_size_before = _virtual_space.committed_size();
 381   size_t min_new_size = spec()->init_size();
 382   size_t max_new_size = reserved().byte_size();
 383   assert(min_new_size <= new_size_before &&
 384          new_size_before <= max_new_size,
 385          "just checking");
 386   // All space sizes must be multiples of Generation::GenGrain.
 387   size_t alignment = Generation::GenGrain;
 388 
 389   // Compute desired new generation size based on NewRatio and
 390   // NewSizeThreadIncrease
 391   size_t desired_new_size = old_size/NewRatio;
 392   int threads_count = Threads::number_of_non_daemon_threads();
 393   size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
 394   desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
 395 
 396   // Adjust new generation size
 397   desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
 398   assert(desired_new_size <= max_new_size, "just checking");
 399 
 400   bool changed = false;
 401   if (desired_new_size > new_size_before) {
 402     size_t change = desired_new_size - new_size_before;
 403     assert(change % alignment == 0, "just checking");
 404     if (expand(change)) {
 405        changed = true;
 406     }
 407     // If the heap failed to expand to the desired size,
 408     // "changed" will be false.  If the expansion failed
 409     // (and at this point it was expected to succeed),
 410     // ignore the failure (leaving "changed" as false).
 411   }
 412   if (desired_new_size < new_size_before && eden()->is_empty()) {
 413     // bail out of shrinking if objects in eden
 414     size_t change = new_size_before - desired_new_size;
 415     assert(change % alignment == 0, "just checking");
 416     _virtual_space.shrink_by(change);
 417     changed = true;
 418   }
 419   if (changed) {
 420     // The spaces have already been mangled at this point but
 421     // may not have been cleared (set top = bottom) and should be.
 422     // Mangling was done when the heap was being expanded.
 423     compute_space_boundaries(eden()->used(),
 424                              SpaceDecorator::Clear,
 425                              SpaceDecorator::DontMangle);
 426     MemRegion cmr((HeapWord*)_virtual_space.low(),
 427                   (HeapWord*)_virtual_space.high());
 428     Universe::heap()->barrier_set()->resize_covered_region(cmr);
 429     if (Verbose && PrintGC) {
 430       size_t new_size_after  = _virtual_space.committed_size();
 431       size_t eden_size_after = eden()->capacity();
 432       size_t survivor_size_after = from()->capacity();
 433       gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
 434         SIZE_FORMAT "K [eden="
 435         SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
 436         new_size_before/K, new_size_after/K,
 437         eden_size_after/K, survivor_size_after/K);
 438       if (WizardMode) {
 439         gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
 440           thread_increase_size/K, threads_count);
 441       }
 442       gclog_or_tty->cr();
 443     }
 444   }
 445 }
 446 
 447 void DefNewGeneration::object_iterate_since_last_GC(ObjectClosure* cl) {
 448   // $$$ This may be wrong in case of "scavenge failure"?
 449   eden()->object_iterate(cl);
 450 }
 451 
 452 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
 453   assert(false, "NYI -- are you sure you want to call this?");
 454 }
 455 
 456 
 457 size_t DefNewGeneration::capacity() const {
 458   return eden()->capacity()
 459        + from()->capacity();  // to() is only used during scavenge
 460 }
 461 
 462 
 463 size_t DefNewGeneration::used() const {
 464   return eden()->used()
 465        + from()->used();      // to() is only used during scavenge
 466 }
 467 
 468 
 469 size_t DefNewGeneration::free() const {
 470   return eden()->free()
 471        + from()->free();      // to() is only used during scavenge
 472 }
 473 
 474 size_t DefNewGeneration::max_capacity() const {
 475   const size_t alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();
 476   const size_t reserved_bytes = reserved().byte_size();
 477   return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
 478 }
 479 
 480 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
 481   return eden()->free();
 482 }
 483 
 484 size_t DefNewGeneration::capacity_before_gc() const {
 485   return eden()->capacity();
 486 }
 487 
 488 size_t DefNewGeneration::contiguous_available() const {
 489   return eden()->free();
 490 }
 491 
 492 
 493 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
 494 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
 495 
 496 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
 497   eden()->object_iterate(blk);
 498   from()->object_iterate(blk);
 499 }
 500 
 501 
 502 void DefNewGeneration::space_iterate(SpaceClosure* blk,
 503                                      bool usedOnly) {
 504   blk->do_space(eden());
 505   blk->do_space(from());
 506   blk->do_space(to());
 507 }
 508 
 509 // The last collection bailed out, we are running out of heap space,
 510 // so we try to allocate the from-space, too.
 511 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
 512   HeapWord* result = NULL;
 513   if (Verbose && PrintGCDetails) {
 514     gclog_or_tty->print("DefNewGeneration::allocate_from_space(%u):"
 515                         "  will_fail: %s"
 516                         "  heap_lock: %s"
 517                         "  free: " SIZE_FORMAT,
 518                         size,
 519                         GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
 520                           "true" : "false",
 521                         Heap_lock->is_locked() ? "locked" : "unlocked",
 522                         from()->free());
 523   }
 524   if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
 525     if (Heap_lock->owned_by_self() ||
 526         (SafepointSynchronize::is_at_safepoint() &&
 527          Thread::current()->is_VM_thread())) {
 528       // If the Heap_lock is not locked by this thread, this will be called
 529       // again later with the Heap_lock held.
 530       result = from()->allocate(size);
 531     } else if (PrintGC && Verbose) {
 532       gclog_or_tty->print_cr("  Heap_lock is not owned by self");
 533     }
 534   } else if (PrintGC && Verbose) {
 535     gclog_or_tty->print_cr("  should_allocate_from_space: NOT");
 536   }
 537   if (PrintGC && Verbose) {
 538     gclog_or_tty->print_cr("  returns %s", result == NULL ? "NULL" : "object");
 539   }
 540   return result;
 541 }
 542 
 543 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
 544                                                 bool   is_tlab,
 545                                                 bool   parallel) {
 546   // We don't attempt to expand the young generation (but perhaps we should.)
 547   return allocate(size, is_tlab);
 548 }
 549 
 550 void DefNewGeneration::adjust_desired_tenuring_threshold() {
 551   // Set the desired survivor size to half the real survivor space
 552   _tenuring_threshold =
 553     age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
 554 }
 555 
 556 void DefNewGeneration::collect(bool   full,
 557                                bool   clear_all_soft_refs,
 558                                size_t size,
 559                                bool   is_tlab) {
 560   assert(full || size > 0, "otherwise we don't want to collect");
 561   GenCollectedHeap* gch = GenCollectedHeap::heap();
 562   _next_gen = gch->next_gen(this);
 563   assert(_next_gen != NULL,
 564     "This must be the youngest gen, and not the only gen");
 565 
 566   // If the next generation is too full to accomodate promotion
 567   // from this generation, pass on collection; let the next generation
 568   // do it.
 569   if (!collection_attempt_is_safe()) {
 570     if (Verbose && PrintGCDetails) {
 571       gclog_or_tty->print(" :: Collection attempt not safe :: ");
 572     }
 573     gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
 574     return;
 575   }
 576   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 577 
 578   init_assuming_no_promotion_failure();
 579 
 580   TraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, gclog_or_tty);
 581   // Capture heap used before collection (for printing).
 582   size_t gch_prev_used = gch->used();
 583 
 584   SpecializationStats::clear();
 585 
 586   // These can be shared for all code paths
 587   IsAliveClosure is_alive(this);
 588   ScanWeakRefClosure scan_weak_ref(this);
 589 
 590   age_table()->clear();
 591   to()->clear(SpaceDecorator::Mangle);
 592 
 593   gch->rem_set()->prepare_for_younger_refs_iterate(false);
 594 
 595   assert(gch->no_allocs_since_save_marks(0),
 596          "save marks have not been newly set.");
 597 
 598   // Not very pretty.
 599   CollectorPolicy* cp = gch->collector_policy();
 600 
 601   FastScanClosure fsc_with_no_gc_barrier(this, false);
 602   FastScanClosure fsc_with_gc_barrier(this, true);
 603 
 604   KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
 605                                       gch->rem_set()->klass_rem_set());
 606 
 607   set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
 608   FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
 609                                                   &fsc_with_no_gc_barrier,
 610                                                   &fsc_with_gc_barrier);
 611 
 612   assert(gch->no_allocs_since_save_marks(0),
 613          "save marks have not been newly set.");
 614 
 615   int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
 616 
 617   gch->gen_process_strong_roots(_level,
 618                                 true,  // Process younger gens, if any,
 619                                        // as strong roots.
 620                                 true,  // activate StrongRootsScope
 621                                 true,  // is scavenging
 622                                 SharedHeap::ScanningOption(so),
 623                                 &fsc_with_no_gc_barrier,
 624                                 true,   // walk *all* scavengable nmethods
 625                                 &fsc_with_gc_barrier,
 626                                 &klass_scan_closure);
 627 
 628   // "evacuate followers".
 629   evacuate_followers.do_void();
 630 
 631   FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
 632   ReferenceProcessor* rp = ref_processor();
 633   rp->setup_policy(clear_all_soft_refs);
 634   rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
 635                                     NULL);
 636   if (!promotion_failed()) {
 637     // Swap the survivor spaces.
 638     eden()->clear(SpaceDecorator::Mangle);
 639     from()->clear(SpaceDecorator::Mangle);
 640     if (ZapUnusedHeapArea) {
 641       // This is now done here because of the piece-meal mangling which
 642       // can check for valid mangling at intermediate points in the
 643       // collection(s).  When a minor collection fails to collect
 644       // sufficient space resizing of the young generation can occur
 645       // an redistribute the spaces in the young generation.  Mangle
 646       // here so that unzapped regions don't get distributed to
 647       // other spaces.
 648       to()->mangle_unused_area();
 649     }
 650     swap_spaces();
 651 
 652     assert(to()->is_empty(), "to space should be empty now");
 653 
 654     adjust_desired_tenuring_threshold();
 655 
 656     // A successful scavenge should restart the GC time limit count which is
 657     // for full GC's.
 658     AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
 659     size_policy->reset_gc_overhead_limit_count();
 660     if (PrintGC && !PrintGCDetails) {
 661       gch->print_heap_change(gch_prev_used);
 662     }
 663     assert(!gch->incremental_collection_failed(), "Should be clear");
 664   } else {
 665     assert(_promo_failure_scan_stack.is_empty(), "post condition");
 666     _promo_failure_scan_stack.clear(true); // Clear cached segments.
 667 
 668     remove_forwarding_pointers();
 669     if (PrintGCDetails) {
 670       gclog_or_tty->print(" (promotion failed) ");
 671     }
 672     // Add to-space to the list of space to compact
 673     // when a promotion failure has occurred.  In that
 674     // case there can be live objects in to-space
 675     // as a result of a partial evacuation of eden
 676     // and from-space.
 677     swap_spaces();   // For uniformity wrt ParNewGeneration.
 678     from()->set_next_compaction_space(to());
 679     gch->set_incremental_collection_failed();
 680 
 681     // Inform the next generation that a promotion failure occurred.
 682     _next_gen->promotion_failure_occurred();
 683 
 684     // Reset the PromotionFailureALot counters.
 685     NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
 686   }
 687   // set new iteration safe limit for the survivor spaces
 688   from()->set_concurrent_iteration_safe_limit(from()->top());
 689   to()->set_concurrent_iteration_safe_limit(to()->top());
 690   SpecializationStats::print();
 691 
 692   // We need to use a monotonically non-deccreasing time in ms
 693   // or we will see time-warp warnings and os::javaTimeMillis()
 694   // does not guarantee monotonicity.
 695   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 696   update_time_of_last_gc(now);
 697 }
 698 
 699 class RemoveForwardPointerClosure: public ObjectClosure {
 700 public:
 701   void do_object(oop obj) {
 702     obj->init_mark();
 703   }
 704 };
 705 
 706 void DefNewGeneration::init_assuming_no_promotion_failure() {
 707   _promotion_failed = false;
 708   from()->set_next_compaction_space(NULL);
 709 }
 710 
 711 void DefNewGeneration::remove_forwarding_pointers() {
 712   RemoveForwardPointerClosure rspc;
 713   eden()->object_iterate(&rspc);
 714   from()->object_iterate(&rspc);
 715 
 716   // Now restore saved marks, if any.
 717   assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
 718          "should be the same");
 719   while (!_objs_with_preserved_marks.is_empty()) {
 720     oop obj   = _objs_with_preserved_marks.pop();
 721     markOop m = _preserved_marks_of_objs.pop();
 722     obj->set_mark(m);
 723   }
 724   _objs_with_preserved_marks.clear(true);
 725   _preserved_marks_of_objs.clear(true);
 726 }
 727 
 728 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
 729   assert(promotion_failed() && m->must_be_preserved_for_promotion_failure(obj),
 730          "Oversaving!");
 731   _objs_with_preserved_marks.push(obj);
 732   _preserved_marks_of_objs.push(m);
 733 }
 734 
 735 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
 736   if (m->must_be_preserved_for_promotion_failure(obj)) {
 737     preserve_mark(obj, m);
 738   }
 739 }
 740 
 741 void DefNewGeneration::handle_promotion_failure(oop old) {
 742   if (PrintPromotionFailure && !_promotion_failed) {
 743     gclog_or_tty->print(" (promotion failure size = " SIZE_FORMAT ") ",
 744                         old->size());
 745   }
 746   _promotion_failed = true;
 747   preserve_mark_if_necessary(old, old->mark());
 748   // forward to self
 749   old->forward_to(old);
 750 
 751   _promo_failure_scan_stack.push(old);
 752 
 753   if (!_promo_failure_drain_in_progress) {
 754     // prevent recursion in copy_to_survivor_space()
 755     _promo_failure_drain_in_progress = true;
 756     drain_promo_failure_scan_stack();
 757     _promo_failure_drain_in_progress = false;
 758   }
 759 }
 760 
 761 oop DefNewGeneration::copy_to_survivor_space(oop old) {
 762   assert(is_in_reserved(old) && !old->is_forwarded(),
 763          "shouldn't be scavenging this oop");
 764   size_t s = old->size();
 765   oop obj = NULL;
 766 
 767   // Try allocating obj in to-space (unless too old)
 768   if (old->age() < tenuring_threshold()) {
 769     obj = (oop) to()->allocate(s);
 770   }
 771 
 772   // Otherwise try allocating obj tenured
 773   if (obj == NULL) {
 774     obj = _next_gen->promote(old, s);
 775     if (obj == NULL) {
 776       handle_promotion_failure(old);
 777       return old;
 778     }
 779   } else {
 780     // Prefetch beyond obj
 781     const intx interval = PrefetchCopyIntervalInBytes;
 782     Prefetch::write(obj, interval);
 783 
 784     // Copy obj
 785     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
 786 
 787     // Increment age if obj still in new generation
 788     obj->incr_age();
 789     age_table()->add(obj, s);
 790   }
 791 
 792   // Done, insert forward pointer to obj in this header
 793   old->forward_to(obj);
 794 
 795   return obj;
 796 }
 797 
 798 void DefNewGeneration::drain_promo_failure_scan_stack() {
 799   while (!_promo_failure_scan_stack.is_empty()) {
 800      oop obj = _promo_failure_scan_stack.pop();
 801      obj->oop_iterate(_promo_failure_scan_stack_closure);
 802   }
 803 }
 804 
 805 void DefNewGeneration::save_marks() {
 806   eden()->set_saved_mark();
 807   to()->set_saved_mark();
 808   from()->set_saved_mark();
 809 }
 810 
 811 
 812 void DefNewGeneration::reset_saved_marks() {
 813   eden()->reset_saved_mark();
 814   to()->reset_saved_mark();
 815   from()->reset_saved_mark();
 816 }
 817 
 818 
 819 bool DefNewGeneration::no_allocs_since_save_marks() {
 820   assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
 821   assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
 822   return to()->saved_mark_at_top();
 823 }
 824 
 825 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
 826                                                                 \
 827 void DefNewGeneration::                                         \
 828 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) {   \
 829   cl->set_generation(this);                                     \
 830   eden()->oop_since_save_marks_iterate##nv_suffix(cl);          \
 831   to()->oop_since_save_marks_iterate##nv_suffix(cl);            \
 832   from()->oop_since_save_marks_iterate##nv_suffix(cl);          \
 833   cl->reset_generation();                                       \
 834   save_marks();                                                 \
 835 }
 836 
 837 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
 838 
 839 #undef DefNew_SINCE_SAVE_MARKS_DEFN
 840 
 841 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
 842                                          size_t max_alloc_words) {
 843   if (requestor == this || _promotion_failed) return;
 844   assert(requestor->level() > level(), "DefNewGeneration must be youngest");
 845 
 846   /* $$$ Assert this?  "trace" is a "MarkSweep" function so that's not appropriate.
 847   if (to_space->top() > to_space->bottom()) {
 848     trace("to_space not empty when contribute_scratch called");
 849   }
 850   */
 851 
 852   ContiguousSpace* to_space = to();
 853   assert(to_space->end() >= to_space->top(), "pointers out of order");
 854   size_t free_words = pointer_delta(to_space->end(), to_space->top());
 855   if (free_words >= MinFreeScratchWords) {
 856     ScratchBlock* sb = (ScratchBlock*)to_space->top();
 857     sb->num_words = free_words;
 858     sb->next = list;
 859     list = sb;
 860   }
 861 }
 862 
 863 void DefNewGeneration::reset_scratch() {
 864   // If contributing scratch in to_space, mangle all of
 865   // to_space if ZapUnusedHeapArea.  This is needed because
 866   // top is not maintained while using to-space as scratch.
 867   if (ZapUnusedHeapArea) {
 868     to()->mangle_unused_area_complete();
 869   }
 870 }
 871 
 872 bool DefNewGeneration::collection_attempt_is_safe() {
 873   if (!to()->is_empty()) {
 874     if (Verbose && PrintGCDetails) {
 875       gclog_or_tty->print(" :: to is not empty :: ");
 876     }
 877     return false;
 878   }
 879   if (_next_gen == NULL) {
 880     GenCollectedHeap* gch = GenCollectedHeap::heap();
 881     _next_gen = gch->next_gen(this);
 882     assert(_next_gen != NULL,
 883            "This must be the youngest gen, and not the only gen");
 884   }
 885   return _next_gen->promotion_attempt_is_safe(used());
 886 }
 887 
 888 void DefNewGeneration::gc_epilogue(bool full) {
 889   DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
 890 
 891   assert(!GC_locker::is_active(), "We should not be executing here");
 892   // Check if the heap is approaching full after a collection has
 893   // been done.  Generally the young generation is empty at
 894   // a minimum at the end of a collection.  If it is not, then
 895   // the heap is approaching full.
 896   GenCollectedHeap* gch = GenCollectedHeap::heap();
 897   if (full) {
 898     DEBUG_ONLY(seen_incremental_collection_failed = false;)
 899     if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
 900       if (Verbose && PrintGCDetails) {
 901         gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
 902                             GCCause::to_string(gch->gc_cause()));
 903       }
 904       gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
 905       set_should_allocate_from_space(); // we seem to be running out of space
 906     } else {
 907       if (Verbose && PrintGCDetails) {
 908         gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
 909                             GCCause::to_string(gch->gc_cause()));
 910       }
 911       gch->clear_incremental_collection_failed(); // We just did a full collection
 912       clear_should_allocate_from_space(); // if set
 913     }
 914   } else {
 915 #ifdef ASSERT
 916     // It is possible that incremental_collection_failed() == true
 917     // here, because an attempted scavenge did not succeed. The policy
 918     // is normally expected to cause a full collection which should
 919     // clear that condition, so we should not be here twice in a row
 920     // with incremental_collection_failed() == true without having done
 921     // a full collection in between.
 922     if (!seen_incremental_collection_failed &&
 923         gch->incremental_collection_failed()) {
 924       if (Verbose && PrintGCDetails) {
 925         gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
 926                             GCCause::to_string(gch->gc_cause()));
 927       }
 928       seen_incremental_collection_failed = true;
 929     } else if (seen_incremental_collection_failed) {
 930       if (Verbose && PrintGCDetails) {
 931         gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
 932                             GCCause::to_string(gch->gc_cause()));
 933       }
 934       assert(gch->gc_cause() == GCCause::_scavenge_alot ||
 935              (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
 936              !gch->incremental_collection_failed(),
 937              "Twice in a row");
 938       seen_incremental_collection_failed = false;
 939     }
 940 #endif // ASSERT
 941   }
 942 
 943   if (ZapUnusedHeapArea) {
 944     eden()->check_mangled_unused_area_complete();
 945     from()->check_mangled_unused_area_complete();
 946     to()->check_mangled_unused_area_complete();
 947   }
 948 
 949   if (!CleanChunkPoolAsync) {
 950     Chunk::clean_chunk_pool();
 951   }
 952 
 953   // update the generation and space performance counters
 954   update_counters();
 955   gch->collector_policy()->counters()->update_counters();
 956 }
 957 
 958 void DefNewGeneration::record_spaces_top() {
 959   assert(ZapUnusedHeapArea, "Not mangling unused space");
 960   eden()->set_top_for_allocations();
 961   to()->set_top_for_allocations();
 962   from()->set_top_for_allocations();
 963 }
 964 
 965 
 966 void DefNewGeneration::update_counters() {
 967   if (UsePerfData) {
 968     _eden_counters->update_all();
 969     _from_counters->update_all();
 970     _to_counters->update_all();
 971     _gen_counters->update_all();
 972   }
 973 }
 974 
 975 void DefNewGeneration::verify() {
 976   eden()->verify();
 977   from()->verify();
 978     to()->verify();
 979 }
 980 
 981 void DefNewGeneration::print_on(outputStream* st) const {
 982   Generation::print_on(st);
 983   st->print("  eden");
 984   eden()->print_on(st);
 985   st->print("  from");
 986   from()->print_on(st);
 987   st->print("  to  ");
 988   to()->print_on(st);
 989 }
 990 
 991 
 992 const char* DefNewGeneration::name() const {
 993   return "def new generation";
 994 }
 995 
 996 // Moved from inline file as they are not called inline
 997 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
 998   return eden();
 999 }
1000 
1001 HeapWord* DefNewGeneration::allocate(size_t word_size,
1002                                      bool is_tlab) {
1003   // This is the slow-path allocation for the DefNewGeneration.
1004   // Most allocations are fast-path in compiled code.
1005   // We try to allocate from the eden.  If that works, we are happy.
1006   // Note that since DefNewGeneration supports lock-free allocation, we
1007   // have to use it here, as well.
1008   HeapWord* result = eden()->par_allocate(word_size);
1009   if (result != NULL) {
1010     return result;
1011   }
1012   do {
1013     HeapWord* old_limit = eden()->soft_end();
1014     if (old_limit < eden()->end()) {
1015       // Tell the next generation we reached a limit.
1016       HeapWord* new_limit =
1017         next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size);
1018       if (new_limit != NULL) {
1019         Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);
1020       } else {
1021         assert(eden()->soft_end() == eden()->end(),
1022                "invalid state after allocation_limit_reached returned null");
1023       }
1024     } else {
1025       // The allocation failed and the soft limit is equal to the hard limit,
1026       // there are no reasons to do an attempt to allocate
1027       assert(old_limit == eden()->end(), "sanity check");
1028       break;
1029     }
1030     // Try to allocate until succeeded or the soft limit can't be adjusted
1031     result = eden()->par_allocate(word_size);
1032   } while (result == NULL);
1033 
1034   // If the eden is full and the last collection bailed out, we are running
1035   // out of heap space, and we try to allocate the from-space, too.
1036   // allocate_from_space can't be inlined because that would introduce a
1037   // circular dependency at compile time.
1038   if (result == NULL) {
1039     result = allocate_from_space(word_size);
1040   }
1041   return result;
1042 }
1043 
1044 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1045                                          bool is_tlab) {
1046   return eden()->par_allocate(word_size);
1047 }
1048 
1049 void DefNewGeneration::gc_prologue(bool full) {
1050   // Ensure that _end and _soft_end are the same in eden space.
1051   eden()->set_soft_end(eden()->end());
1052 }
1053 
1054 size_t DefNewGeneration::tlab_capacity() const {
1055   return eden()->capacity();
1056 }
1057 
1058 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1059   return unsafe_max_alloc_nogc();
1060 }