1 /*
   2  * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc_implementation/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/prefetch.inline.hpp"
  46 #include "runtime/thread.inline.hpp"
  47 #include "utilities/copy.hpp"
  48 #include "utilities/stack.inline.hpp"
  49 
  50 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  51 
  52 //
  53 // DefNewGeneration functions.
  54 
  55 // Methods of protected closure types.
  56 
  57 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
  58   assert(g->level() == 0, "Optimized for youngest gen.");
  59 }
  60 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
  61   return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
  62 }
  63 
  64 DefNewGeneration::KeepAliveClosure::
  65 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
  66   GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
  67   assert(rs->rs_kind() == GenRemSet::CardTable, "Wrong rem set kind.");
  68   _rs = (CardTableRS*)rs;
  69 }
  70 
  71 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  72 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  73 
  74 
  75 DefNewGeneration::FastKeepAliveClosure::
  76 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
  77   DefNewGeneration::KeepAliveClosure(cl) {
  78   _boundary = g->reserved().end();
  79 }
  80 
  81 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  82 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  83 
  84 DefNewGeneration::EvacuateFollowersClosure::
  85 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
  86                          ScanClosure* cur, ScanClosure* older) :
  87   _gch(gch), _level(level),
  88   _scan_cur_or_nonheap(cur), _scan_older(older)
  89 {}
  90 
  91 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
  92   do {
  93     _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
  94                                        _scan_older);
  95   } while (!_gch->no_allocs_since_save_marks(_level));
  96 }
  97 
  98 DefNewGeneration::FastEvacuateFollowersClosure::
  99 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
 100                              DefNewGeneration* gen,
 101                              FastScanClosure* cur, FastScanClosure* older) :
 102   _gch(gch), _level(level), _gen(gen),
 103   _scan_cur_or_nonheap(cur), _scan_older(older)
 104 {}
 105 
 106 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
 107   do {
 108     _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
 109                                        _scan_older);
 110   } while (!_gch->no_allocs_since_save_marks(_level));
 111   guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
 112 }
 113 
 114 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
 115     OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 116 {
 117   assert(_g->level() == 0, "Optimized for youngest generation");
 118   _boundary = _g->reserved().end();
 119 }
 120 
 121 void ScanClosure::do_oop(oop* p)       { ScanClosure::do_oop_work(p); }
 122 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
 123 
 124 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
 125     OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 126 {
 127   assert(_g->level() == 0, "Optimized for youngest generation");
 128   _boundary = _g->reserved().end();
 129 }
 130 
 131 void FastScanClosure::do_oop(oop* p)       { FastScanClosure::do_oop_work(p); }
 132 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
 133 
 134 void KlassScanClosure::do_klass(Klass* klass) {
 135 #ifndef PRODUCT
 136   if (TraceScavenge) {
 137     ResourceMark rm;
 138     gclog_or_tty->print_cr("KlassScanClosure::do_klass %p, %s, dirty: %s",
 139                            klass,
 140                            klass->external_name(),
 141                            klass->has_modified_oops() ? "true" : "false");
 142   }
 143 #endif
 144 
 145   // If the klass has not been dirtied we know that there's
 146   // no references into  the young gen and we can skip it.
 147   if (klass->has_modified_oops()) {
 148     if (_accumulate_modified_oops) {
 149       klass->accumulate_modified_oops();
 150     }
 151 
 152     // Clear this state since we're going to scavenge all the metadata.
 153     klass->clear_modified_oops();
 154 
 155     // Tell the closure which Klass is being scanned so that it can be dirtied
 156     // if oops are left pointing into the young gen.
 157     _scavenge_closure->set_scanned_klass(klass);
 158 
 159     klass->oops_do(_scavenge_closure);
 160 
 161     _scavenge_closure->set_scanned_klass(NULL);
 162   }
 163 }
 164 
 165 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
 166   _g(g)
 167 {
 168   assert(_g->level() == 0, "Optimized for youngest generation");
 169   _boundary = _g->reserved().end();
 170 }
 171 
 172 void ScanWeakRefClosure::do_oop(oop* p)       { ScanWeakRefClosure::do_oop_work(p); }
 173 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
 174 
 175 void FilteringClosure::do_oop(oop* p)       { FilteringClosure::do_oop_work(p); }
 176 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
 177 
 178 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
 179                                    KlassRemSet* klass_rem_set)
 180     : _scavenge_closure(scavenge_closure),
 181       _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
 182 
 183 
 184 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
 185                                    size_t initial_size,
 186                                    int level,
 187                                    const char* policy)
 188   : Generation(rs, initial_size, level),
 189     _promo_failure_drain_in_progress(false),
 190     _should_allocate_from_space(false)
 191 {
 192   MemRegion cmr((HeapWord*)_virtual_space.low(),
 193                 (HeapWord*)_virtual_space.high());
 194   Universe::heap()->barrier_set()->resize_covered_region(cmr);
 195 
 196   if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) {
 197     _eden_space = new ConcEdenSpace(this);
 198   } else {
 199     _eden_space = new EdenSpace(this);
 200   }
 201   _from_space = new ContiguousSpace();
 202   _to_space   = new ContiguousSpace();
 203 
 204   if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
 205     vm_exit_during_initialization("Could not allocate a new gen space");
 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 = GenCollectedHeap::heap()->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 
 217   // Generation counters -- generation 0, 3 subspaces
 218   _gen_counters = new GenerationCounters("new", 0, 3, &_virtual_space);
 219   _gc_counters = new CollectorCounters(policy, 0);
 220 
 221   _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
 222                                       _gen_counters);
 223   _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
 224                                       _gen_counters);
 225   _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
 226                                     _gen_counters);
 227 
 228   compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
 229   update_counters();
 230   _next_gen = NULL;
 231   _tenuring_threshold = MaxTenuringThreshold;
 232   _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
 233 
 234   _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
 235 }
 236 
 237 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
 238                                                 bool clear_space,
 239                                                 bool mangle_space) {
 240   uintx alignment =
 241     GenCollectedHeap::heap()->collector_policy()->space_alignment();
 242 
 243   // If the spaces are being cleared (only done at heap initialization
 244   // currently), the survivor spaces need not be empty.
 245   // Otherwise, no care is taken for used areas in the survivor spaces
 246   // so check.
 247   assert(clear_space || (to()->is_empty() && from()->is_empty()),
 248     "Initialization of the survivor spaces assumes these are empty");
 249 
 250   // Compute sizes
 251   uintx size = _virtual_space.committed_size();
 252   uintx survivor_size = compute_survivor_size(size, alignment);
 253   uintx eden_size = size - (2*survivor_size);
 254   assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 255 
 256   if (eden_size < minimum_eden_size) {
 257     // May happen due to 64Kb rounding, if so adjust eden size back up
 258     minimum_eden_size = align_size_up(minimum_eden_size, alignment);
 259     uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
 260     uintx unaligned_survivor_size =
 261       align_size_down(maximum_survivor_size, alignment);
 262     survivor_size = MAX2(unaligned_survivor_size, alignment);
 263     eden_size = size - (2*survivor_size);
 264     assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 265     assert(eden_size >= minimum_eden_size, "just checking");
 266   }
 267 
 268   char *eden_start = _virtual_space.low();
 269   char *from_start = eden_start + eden_size;
 270   char *to_start   = from_start + survivor_size;
 271   char *to_end     = to_start   + survivor_size;
 272 
 273   assert(to_end == _virtual_space.high(), "just checking");
 274   assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
 275   assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
 276   assert(Space::is_aligned((HeapWord*)to_start),   "checking alignment");
 277 
 278   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
 279   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
 280   MemRegion toMR  ((HeapWord*)to_start, (HeapWord*)to_end);
 281 
 282   // A minimum eden size implies that there is a part of eden that
 283   // is being used and that affects the initialization of any
 284   // newly formed eden.
 285   bool live_in_eden = minimum_eden_size > 0;
 286 
 287   // If not clearing the spaces, do some checking to verify that
 288   // the space are already mangled.
 289   if (!clear_space) {
 290     // Must check mangling before the spaces are reshaped.  Otherwise,
 291     // the bottom or end of one space may have moved into another
 292     // a failure of the check may not correctly indicate which space
 293     // is not properly mangled.
 294     if (ZapUnusedHeapArea) {
 295       HeapWord* limit = (HeapWord*) _virtual_space.high();
 296       eden()->check_mangled_unused_area(limit);
 297       from()->check_mangled_unused_area(limit);
 298         to()->check_mangled_unused_area(limit);
 299     }
 300   }
 301 
 302   // Reset the spaces for their new regions.
 303   eden()->initialize(edenMR,
 304                      clear_space && !live_in_eden,
 305                      SpaceDecorator::Mangle);
 306   // If clear_space and live_in_eden, we will not have cleared any
 307   // portion of eden above its top. This can cause newly
 308   // expanded space not to be mangled if using ZapUnusedHeapArea.
 309   // We explicitly do such mangling here.
 310   if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
 311     eden()->mangle_unused_area();
 312   }
 313   from()->initialize(fromMR, clear_space, mangle_space);
 314   to()->initialize(toMR, clear_space, mangle_space);
 315 
 316   // Set next compaction spaces.
 317   eden()->set_next_compaction_space(from());
 318   // The to-space is normally empty before a compaction so need
 319   // not be considered.  The exception is during promotion
 320   // failure handling when to-space can contain live objects.
 321   from()->set_next_compaction_space(NULL);
 322 }
 323 
 324 void DefNewGeneration::swap_spaces() {
 325   ContiguousSpace* s = from();
 326   _from_space        = to();
 327   _to_space          = s;
 328   eden()->set_next_compaction_space(from());
 329   // The to-space is normally empty before a compaction so need
 330   // not be considered.  The exception is during promotion
 331   // failure handling when to-space can contain live objects.
 332   from()->set_next_compaction_space(NULL);
 333 
 334   if (UsePerfData) {
 335     CSpaceCounters* c = _from_counters;
 336     _from_counters = _to_counters;
 337     _to_counters = c;
 338   }
 339 }
 340 
 341 bool DefNewGeneration::expand(size_t bytes) {
 342   MutexLocker x(ExpandHeap_lock);
 343   HeapWord* prev_high = (HeapWord*) _virtual_space.high();
 344   bool success = _virtual_space.expand_by(bytes);
 345   if (success && ZapUnusedHeapArea) {
 346     // Mangle newly committed space immediately because it
 347     // can be done here more simply that after the new
 348     // spaces have been computed.
 349     HeapWord* new_high = (HeapWord*) _virtual_space.high();
 350     MemRegion mangle_region(prev_high, new_high);
 351     SpaceMangler::mangle_region(mangle_region);
 352   }
 353 
 354   // Do not attempt an expand-to-the reserve size.  The
 355   // request should properly observe the maximum size of
 356   // the generation so an expand-to-reserve should be
 357   // unnecessary.  Also a second call to expand-to-reserve
 358   // value potentially can cause an undue expansion.
 359   // For example if the first expand fail for unknown reasons,
 360   // but the second succeeds and expands the heap to its maximum
 361   // value.
 362   if (GC_locker::is_active()) {
 363     if (PrintGC && Verbose) {
 364       gclog_or_tty->print_cr("Garbage collection disabled, "
 365         "expanded heap instead");
 366     }
 367   }
 368 
 369   return success;
 370 }
 371 
 372 
 373 void DefNewGeneration::compute_new_size() {
 374   // This is called after a gc that includes the following generation
 375   // (which is required to exist.)  So from-space will normally be empty.
 376   // Note that we check both spaces, since if scavenge failed they revert roles.
 377   // If not we bail out (otherwise we would have to relocate the objects)
 378   if (!from()->is_empty() || !to()->is_empty()) {
 379     return;
 380   }
 381 
 382   int next_level = level() + 1;
 383   GenCollectedHeap* gch = GenCollectedHeap::heap();
 384   assert(next_level < gch->_n_gens,
 385          "DefNewGeneration cannot be an oldest gen");
 386 
 387   Generation* next_gen = gch->_gens[next_level];
 388   size_t old_size = next_gen->capacity();
 389   size_t new_size_before = _virtual_space.committed_size();
 390   size_t min_new_size = spec()->init_size();
 391   size_t max_new_size = reserved().byte_size();
 392   assert(min_new_size <= new_size_before &&
 393          new_size_before <= max_new_size,
 394          "just checking");
 395   // All space sizes must be multiples of Generation::GenGrain.
 396   size_t alignment = Generation::GenGrain;
 397 
 398   // Compute desired new generation size based on NewRatio and
 399   // NewSizeThreadIncrease
 400   size_t desired_new_size = old_size/NewRatio;
 401   int threads_count = Threads::number_of_non_daemon_threads();
 402   size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
 403   desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
 404 
 405   // Adjust new generation size
 406   desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
 407   assert(desired_new_size <= max_new_size, "just checking");
 408 
 409   bool changed = false;
 410   if (desired_new_size > new_size_before) {
 411     size_t change = desired_new_size - new_size_before;
 412     assert(change % alignment == 0, "just checking");
 413     if (expand(change)) {
 414        changed = true;
 415     }
 416     // If the heap failed to expand to the desired size,
 417     // "changed" will be false.  If the expansion failed
 418     // (and at this point it was expected to succeed),
 419     // ignore the failure (leaving "changed" as false).
 420   }
 421   if (desired_new_size < new_size_before && eden()->is_empty()) {
 422     // bail out of shrinking if objects in eden
 423     size_t change = new_size_before - desired_new_size;
 424     assert(change % alignment == 0, "just checking");
 425     _virtual_space.shrink_by(change);
 426     changed = true;
 427   }
 428   if (changed) {
 429     // The spaces have already been mangled at this point but
 430     // may not have been cleared (set top = bottom) and should be.
 431     // Mangling was done when the heap was being expanded.
 432     compute_space_boundaries(eden()->used(),
 433                              SpaceDecorator::Clear,
 434                              SpaceDecorator::DontMangle);
 435     MemRegion cmr((HeapWord*)_virtual_space.low(),
 436                   (HeapWord*)_virtual_space.high());
 437     Universe::heap()->barrier_set()->resize_covered_region(cmr);
 438     if (Verbose && PrintGC) {
 439       size_t new_size_after  = _virtual_space.committed_size();
 440       size_t eden_size_after = eden()->capacity();
 441       size_t survivor_size_after = from()->capacity();
 442       gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
 443         SIZE_FORMAT "K [eden="
 444         SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
 445         new_size_before/K, new_size_after/K,
 446         eden_size_after/K, survivor_size_after/K);
 447       if (WizardMode) {
 448         gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
 449           thread_increase_size/K, threads_count);
 450       }
 451       gclog_or_tty->cr();
 452     }
 453   }
 454 }
 455 
 456 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
 457   assert(false, "NYI -- are you sure you want to call this?");
 458 }
 459 
 460 
 461 size_t DefNewGeneration::capacity() const {
 462   return eden()->capacity()
 463        + from()->capacity();  // to() is only used during scavenge
 464 }
 465 
 466 
 467 size_t DefNewGeneration::used() const {
 468   return eden()->used()
 469        + from()->used();      // to() is only used during scavenge
 470 }
 471 
 472 
 473 size_t DefNewGeneration::free() const {
 474   return eden()->free()
 475        + from()->free();      // to() is only used during scavenge
 476 }
 477 
 478 size_t DefNewGeneration::max_capacity() const {
 479   const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
 480   const size_t reserved_bytes = reserved().byte_size();
 481   return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
 482 }
 483 
 484 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
 485   return eden()->free();
 486 }
 487 
 488 size_t DefNewGeneration::capacity_before_gc() const {
 489   return eden()->capacity();
 490 }
 491 
 492 size_t DefNewGeneration::contiguous_available() const {
 493   return eden()->free();
 494 }
 495 
 496 
 497 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
 498 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
 499 
 500 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
 501   eden()->object_iterate(blk);
 502   from()->object_iterate(blk);
 503 }
 504 
 505 
 506 void DefNewGeneration::space_iterate(SpaceClosure* blk,
 507                                      bool usedOnly) {
 508   blk->do_space(eden());
 509   blk->do_space(from());
 510   blk->do_space(to());
 511 }
 512 
 513 // The last collection bailed out, we are running out of heap space,
 514 // so we try to allocate the from-space, too.
 515 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
 516   HeapWord* result = NULL;
 517   if (Verbose && PrintGCDetails) {
 518     gclog_or_tty->print("DefNewGeneration::allocate_from_space(%u):"
 519                         "  will_fail: %s"
 520                         "  heap_lock: %s"
 521                         "  free: " SIZE_FORMAT,
 522                         size,
 523                         GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
 524                           "true" : "false",
 525                         Heap_lock->is_locked() ? "locked" : "unlocked",
 526                         from()->free());
 527   }
 528   if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
 529     if (Heap_lock->owned_by_self() ||
 530         (SafepointSynchronize::is_at_safepoint() &&
 531          Thread::current()->is_VM_thread())) {
 532       // If the Heap_lock is not locked by this thread, this will be called
 533       // again later with the Heap_lock held.
 534       result = from()->allocate(size);
 535     } else if (PrintGC && Verbose) {
 536       gclog_or_tty->print_cr("  Heap_lock is not owned by self");
 537     }
 538   } else if (PrintGC && Verbose) {
 539     gclog_or_tty->print_cr("  should_allocate_from_space: NOT");
 540   }
 541   if (PrintGC && Verbose) {
 542     gclog_or_tty->print_cr("  returns %s", result == NULL ? "NULL" : "object");
 543   }
 544   return result;
 545 }
 546 
 547 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
 548                                                 bool   is_tlab,
 549                                                 bool   parallel) {
 550   // We don't attempt to expand the young generation (but perhaps we should.)
 551   return allocate(size, is_tlab);
 552 }
 553 
 554 void DefNewGeneration::adjust_desired_tenuring_threshold(GCTracer &tracer) {
 555   // Set the desired survivor size to half the real survivor space
 556   _tenuring_threshold =
 557     age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, tracer);
 558 }
 559 
 560 void DefNewGeneration::collect(bool   full,
 561                                bool   clear_all_soft_refs,
 562                                size_t size,
 563                                bool   is_tlab) {
 564   assert(full || size > 0, "otherwise we don't want to collect");
 565 
 566   GenCollectedHeap* gch = GenCollectedHeap::heap();
 567 
 568   _gc_timer->register_gc_start();
 569   DefNewTracer gc_tracer;
 570   gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
 571 
 572   _next_gen = gch->next_gen(this);
 573 
 574   // If the next generation is too full to accommodate promotion
 575   // from this generation, pass on collection; let the next generation
 576   // do it.
 577   if (!collection_attempt_is_safe()) {
 578     if (Verbose && PrintGCDetails) {
 579       gclog_or_tty->print(" :: Collection attempt not safe :: ");
 580     }
 581     gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
 582     return;
 583   }
 584   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 585 
 586   init_assuming_no_promotion_failure();
 587 
 588   GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id());
 589   // Capture heap used before collection (for printing).
 590   size_t gch_prev_used = gch->used();
 591 
 592   gch->trace_heap_before_gc(&gc_tracer);
 593 
 594   SpecializationStats::clear();
 595 
 596   // These can be shared for all code paths
 597   IsAliveClosure is_alive(this);
 598   ScanWeakRefClosure scan_weak_ref(this);
 599 
 600   age_table()->clear();
 601   to()->clear(SpaceDecorator::Mangle);
 602 
 603   gch->rem_set()->prepare_for_younger_refs_iterate(false);
 604 
 605   assert(gch->no_allocs_since_save_marks(0),
 606          "save marks have not been newly set.");
 607 
 608   // Not very pretty.
 609   CollectorPolicy* cp = gch->collector_policy();
 610 
 611   FastScanClosure fsc_with_no_gc_barrier(this, false);
 612   FastScanClosure fsc_with_gc_barrier(this, true);
 613 
 614   KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
 615                                       gch->rem_set()->klass_rem_set());
 616   CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
 617                                            &fsc_with_no_gc_barrier,
 618                                            false);
 619 
 620   set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
 621   FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
 622                                                   &fsc_with_no_gc_barrier,
 623                                                   &fsc_with_gc_barrier);
 624 
 625   assert(gch->no_allocs_since_save_marks(0),
 626          "save marks have not been newly set.");
 627 
 628   gch->gen_process_roots(_level,
 629                          true,  // Process younger gens, if any,
 630                                 // as strong roots.
 631                          true,  // activate StrongRootsScope
 632                          GenCollectedHeap::SO_ScavengeCodeCache,
 633                          GenCollectedHeap::StrongAndWeakRoots,
 634                          &fsc_with_no_gc_barrier,
 635                          &fsc_with_gc_barrier,
 636                          &cld_scan_closure);
 637 
 638   // "evacuate followers".
 639   evacuate_followers.do_void();
 640 
 641   FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
 642   ReferenceProcessor* rp = ref_processor();
 643   rp->setup_policy(clear_all_soft_refs);
 644   const ReferenceProcessorStats& stats =
 645   rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
 646                                     NULL, _gc_timer, gc_tracer.gc_id());
 647   gc_tracer.report_gc_reference_stats(stats);
 648 
 649   if (!_promotion_failed) {
 650     // Swap the survivor spaces.
 651     eden()->clear(SpaceDecorator::Mangle);
 652     from()->clear(SpaceDecorator::Mangle);
 653     if (ZapUnusedHeapArea) {
 654       // This is now done here because of the piece-meal mangling which
 655       // can check for valid mangling at intermediate points in the
 656       // collection(s).  When a minor collection fails to collect
 657       // sufficient space resizing of the young generation can occur
 658       // an redistribute the spaces in the young generation.  Mangle
 659       // here so that unzapped regions don't get distributed to
 660       // other spaces.
 661       to()->mangle_unused_area();
 662     }
 663     swap_spaces();
 664 
 665     assert(to()->is_empty(), "to space should be empty now");
 666 
 667     adjust_desired_tenuring_threshold(gc_tracer);
 668 
 669     // A successful scavenge should restart the GC time limit count which is
 670     // for full GC's.
 671     AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
 672     size_policy->reset_gc_overhead_limit_count();
 673     if (PrintGC && !PrintGCDetails) {
 674       gch->print_heap_change(gch_prev_used);
 675     }
 676     assert(!gch->incremental_collection_failed(), "Should be clear");
 677   } else {
 678     assert(_promo_failure_scan_stack.is_empty(), "post condition");
 679     _promo_failure_scan_stack.clear(true); // Clear cached segments.
 680 
 681     remove_forwarding_pointers();
 682     if (PrintGCDetails) {
 683       gclog_or_tty->print(" (promotion failed) ");
 684     }
 685     // Add to-space to the list of space to compact
 686     // when a promotion failure has occurred.  In that
 687     // case there can be live objects in to-space
 688     // as a result of a partial evacuation of eden
 689     // and from-space.
 690     swap_spaces();   // For uniformity wrt ParNewGeneration.
 691     from()->set_next_compaction_space(to());
 692     gch->set_incremental_collection_failed();
 693 
 694     // Inform the next generation that a promotion failure occurred.
 695     _next_gen->promotion_failure_occurred();
 696     gc_tracer.report_promotion_failed(_promotion_failed_info);
 697 
 698     // Reset the PromotionFailureALot counters.
 699     NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
 700   }
 701   // set new iteration safe limit for the survivor spaces
 702   from()->set_concurrent_iteration_safe_limit(from()->top());
 703   to()->set_concurrent_iteration_safe_limit(to()->top());
 704   SpecializationStats::print();
 705 
 706   // We need to use a monotonically non-decreasing time in ms
 707   // or we will see time-warp warnings and os::javaTimeMillis()
 708   // does not guarantee monotonicity.
 709   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 710   update_time_of_last_gc(now);
 711 
 712   gch->trace_heap_after_gc(&gc_tracer);
 713   gc_tracer.report_tenuring_threshold(tenuring_threshold());
 714 
 715   _gc_timer->register_gc_end();
 716 
 717   gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
 718 }
 719 
 720 class RemoveForwardPointerClosure: public ObjectClosure {
 721 public:
 722   void do_object(oop obj) {
 723     obj->init_mark();
 724   }
 725 };
 726 
 727 void DefNewGeneration::init_assuming_no_promotion_failure() {
 728   _promotion_failed = false;
 729   _promotion_failed_info.reset();
 730   from()->set_next_compaction_space(NULL);
 731 }
 732 
 733 void DefNewGeneration::remove_forwarding_pointers() {
 734   RemoveForwardPointerClosure rspc;
 735   eden()->object_iterate(&rspc);
 736   from()->object_iterate(&rspc);
 737 
 738   // Now restore saved marks, if any.
 739   assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
 740          "should be the same");
 741   while (!_objs_with_preserved_marks.is_empty()) {
 742     oop obj   = _objs_with_preserved_marks.pop();
 743     markOop m = _preserved_marks_of_objs.pop();
 744     obj->set_mark(m);
 745   }
 746   _objs_with_preserved_marks.clear(true);
 747   _preserved_marks_of_objs.clear(true);
 748 }
 749 
 750 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
 751   assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
 752          "Oversaving!");
 753   _objs_with_preserved_marks.push(obj);
 754   _preserved_marks_of_objs.push(m);
 755 }
 756 
 757 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
 758   if (m->must_be_preserved_for_promotion_failure(obj)) {
 759     preserve_mark(obj, m);
 760   }
 761 }
 762 
 763 void DefNewGeneration::handle_promotion_failure(oop old) {
 764   if (PrintPromotionFailure && !_promotion_failed) {
 765     gclog_or_tty->print(" (promotion failure size = " SIZE_FORMAT ") ",
 766                         old->size());
 767   }
 768   _promotion_failed = true;
 769   _promotion_failed_info.register_copy_failure(old->size());
 770   preserve_mark_if_necessary(old, old->mark());
 771   // forward to self
 772   old->forward_to(old);
 773 
 774   _promo_failure_scan_stack.push(old);
 775 
 776   if (!_promo_failure_drain_in_progress) {
 777     // prevent recursion in copy_to_survivor_space()
 778     _promo_failure_drain_in_progress = true;
 779     drain_promo_failure_scan_stack();
 780     _promo_failure_drain_in_progress = false;
 781   }
 782 }
 783 
 784 oop DefNewGeneration::copy_to_survivor_space(oop old) {
 785   assert(is_in_reserved(old) && !old->is_forwarded(),
 786          "shouldn't be scavenging this oop");
 787   size_t s = old->size();
 788   oop obj = NULL;
 789 
 790   // Try allocating obj in to-space (unless too old)
 791   if (old->age() < tenuring_threshold()) {
 792     obj = (oop) to()->allocate_aligned(s);
 793   }
 794 
 795   // Otherwise try allocating obj tenured
 796   if (obj == NULL) {
 797     obj = _next_gen->promote(old, s);
 798     if (obj == NULL) {
 799       handle_promotion_failure(old);
 800       return old;
 801     }
 802   } else {
 803     // Prefetch beyond obj
 804     const intx interval = PrefetchCopyIntervalInBytes;
 805     Prefetch::write(obj, interval);
 806 
 807     // Copy obj
 808     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
 809 
 810     // Increment age if obj still in new generation
 811     obj->incr_age();
 812     age_table()->add(obj, s);
 813   }
 814 
 815   // Done, insert forward pointer to obj in this header
 816   old->forward_to(obj);
 817 
 818   return obj;
 819 }
 820 
 821 void DefNewGeneration::drain_promo_failure_scan_stack() {
 822   while (!_promo_failure_scan_stack.is_empty()) {
 823      oop obj = _promo_failure_scan_stack.pop();
 824      obj->oop_iterate(_promo_failure_scan_stack_closure);
 825   }
 826 }
 827 
 828 void DefNewGeneration::save_marks() {
 829   eden()->set_saved_mark();
 830   to()->set_saved_mark();
 831   from()->set_saved_mark();
 832 }
 833 
 834 
 835 void DefNewGeneration::reset_saved_marks() {
 836   eden()->reset_saved_mark();
 837   to()->reset_saved_mark();
 838   from()->reset_saved_mark();
 839 }
 840 
 841 
 842 bool DefNewGeneration::no_allocs_since_save_marks() {
 843   assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
 844   assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
 845   return to()->saved_mark_at_top();
 846 }
 847 
 848 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
 849                                                                 \
 850 void DefNewGeneration::                                         \
 851 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) {   \
 852   cl->set_generation(this);                                     \
 853   eden()->oop_since_save_marks_iterate##nv_suffix(cl);          \
 854   to()->oop_since_save_marks_iterate##nv_suffix(cl);            \
 855   from()->oop_since_save_marks_iterate##nv_suffix(cl);          \
 856   cl->reset_generation();                                       \
 857   save_marks();                                                 \
 858 }
 859 
 860 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
 861 
 862 #undef DefNew_SINCE_SAVE_MARKS_DEFN
 863 
 864 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
 865                                          size_t max_alloc_words) {
 866   if (requestor == this || _promotion_failed) return;
 867   assert(requestor->level() > level(), "DefNewGeneration must be youngest");
 868 
 869   /* $$$ Assert this?  "trace" is a "MarkSweep" function so that's not appropriate.
 870   if (to_space->top() > to_space->bottom()) {
 871     trace("to_space not empty when contribute_scratch called");
 872   }
 873   */
 874 
 875   ContiguousSpace* to_space = to();
 876   assert(to_space->end() >= to_space->top(), "pointers out of order");
 877   size_t free_words = pointer_delta(to_space->end(), to_space->top());
 878   if (free_words >= MinFreeScratchWords) {
 879     ScratchBlock* sb = (ScratchBlock*)to_space->top();
 880     sb->num_words = free_words;
 881     sb->next = list;
 882     list = sb;
 883   }
 884 }
 885 
 886 void DefNewGeneration::reset_scratch() {
 887   // If contributing scratch in to_space, mangle all of
 888   // to_space if ZapUnusedHeapArea.  This is needed because
 889   // top is not maintained while using to-space as scratch.
 890   if (ZapUnusedHeapArea) {
 891     to()->mangle_unused_area_complete();
 892   }
 893 }
 894 
 895 bool DefNewGeneration::collection_attempt_is_safe() {
 896   if (!to()->is_empty()) {
 897     if (Verbose && PrintGCDetails) {
 898       gclog_or_tty->print(" :: to is not empty :: ");
 899     }
 900     return false;
 901   }
 902   if (_next_gen == NULL) {
 903     GenCollectedHeap* gch = GenCollectedHeap::heap();
 904     _next_gen = gch->next_gen(this);
 905   }
 906   return _next_gen->promotion_attempt_is_safe(used());
 907 }
 908 
 909 void DefNewGeneration::gc_epilogue(bool full) {
 910   DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
 911 
 912   assert(!GC_locker::is_active(), "We should not be executing here");
 913   // Check if the heap is approaching full after a collection has
 914   // been done.  Generally the young generation is empty at
 915   // a minimum at the end of a collection.  If it is not, then
 916   // the heap is approaching full.
 917   GenCollectedHeap* gch = GenCollectedHeap::heap();
 918   if (full) {
 919     DEBUG_ONLY(seen_incremental_collection_failed = false;)
 920     if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
 921       if (Verbose && PrintGCDetails) {
 922         gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
 923                             GCCause::to_string(gch->gc_cause()));
 924       }
 925       gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
 926       set_should_allocate_from_space(); // we seem to be running out of space
 927     } else {
 928       if (Verbose && PrintGCDetails) {
 929         gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
 930                             GCCause::to_string(gch->gc_cause()));
 931       }
 932       gch->clear_incremental_collection_failed(); // We just did a full collection
 933       clear_should_allocate_from_space(); // if set
 934     }
 935   } else {
 936 #ifdef ASSERT
 937     // It is possible that incremental_collection_failed() == true
 938     // here, because an attempted scavenge did not succeed. The policy
 939     // is normally expected to cause a full collection which should
 940     // clear that condition, so we should not be here twice in a row
 941     // with incremental_collection_failed() == true without having done
 942     // a full collection in between.
 943     if (!seen_incremental_collection_failed &&
 944         gch->incremental_collection_failed()) {
 945       if (Verbose && PrintGCDetails) {
 946         gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
 947                             GCCause::to_string(gch->gc_cause()));
 948       }
 949       seen_incremental_collection_failed = true;
 950     } else if (seen_incremental_collection_failed) {
 951       if (Verbose && PrintGCDetails) {
 952         gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
 953                             GCCause::to_string(gch->gc_cause()));
 954       }
 955       assert(gch->gc_cause() == GCCause::_scavenge_alot ||
 956              (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
 957              !gch->incremental_collection_failed(),
 958              "Twice in a row");
 959       seen_incremental_collection_failed = false;
 960     }
 961 #endif // ASSERT
 962   }
 963 
 964   if (ZapUnusedHeapArea) {
 965     eden()->check_mangled_unused_area_complete();
 966     from()->check_mangled_unused_area_complete();
 967     to()->check_mangled_unused_area_complete();
 968   }
 969 
 970   if (!CleanChunkPoolAsync) {
 971     Chunk::clean_chunk_pool();
 972   }
 973 
 974   // update the generation and space performance counters
 975   update_counters();
 976   gch->collector_policy()->counters()->update_counters();
 977 }
 978 
 979 void DefNewGeneration::record_spaces_top() {
 980   assert(ZapUnusedHeapArea, "Not mangling unused space");
 981   eden()->set_top_for_allocations();
 982   to()->set_top_for_allocations();
 983   from()->set_top_for_allocations();
 984 }
 985 
 986 void DefNewGeneration::ref_processor_init() {
 987   Generation::ref_processor_init();
 988 }
 989 
 990 
 991 void DefNewGeneration::update_counters() {
 992   if (UsePerfData) {
 993     _eden_counters->update_all();
 994     _from_counters->update_all();
 995     _to_counters->update_all();
 996     _gen_counters->update_all();
 997   }
 998 }
 999 
1000 void DefNewGeneration::verify() {
1001   eden()->verify();
1002   from()->verify();
1003     to()->verify();
1004 }
1005 
1006 void DefNewGeneration::print_on(outputStream* st) const {
1007   Generation::print_on(st);
1008   st->print("  eden");
1009   eden()->print_on(st);
1010   st->print("  from");
1011   from()->print_on(st);
1012   st->print("  to  ");
1013   to()->print_on(st);
1014 }
1015 
1016 
1017 const char* DefNewGeneration::name() const {
1018   return "def new generation";
1019 }
1020 
1021 // Moved from inline file as they are not called inline
1022 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1023   return eden();
1024 }
1025 
1026 HeapWord* DefNewGeneration::allocate(size_t word_size,
1027                                      bool is_tlab) {
1028   // This is the slow-path allocation for the DefNewGeneration.
1029   // Most allocations are fast-path in compiled code.
1030   // We try to allocate from the eden.  If that works, we are happy.
1031   // Note that since DefNewGeneration supports lock-free allocation, we
1032   // have to use it here, as well.
1033   HeapWord* result = eden()->par_allocate(word_size);
1034   if (result != NULL) {
1035     if (CMSEdenChunksRecordAlways && _next_gen != NULL) {
1036       _next_gen->sample_eden_chunk();
1037     }
1038     return result;
1039   }
1040   do {
1041     HeapWord* old_limit = eden()->soft_end();
1042     if (old_limit < eden()->end()) {
1043       // Tell the next generation we reached a limit.
1044       HeapWord* new_limit =
1045         next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size);
1046       if (new_limit != NULL) {
1047         Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);
1048       } else {
1049         assert(eden()->soft_end() == eden()->end(),
1050                "invalid state after allocation_limit_reached returned null");
1051       }
1052     } else {
1053       // The allocation failed and the soft limit is equal to the hard limit,
1054       // there are no reasons to do an attempt to allocate
1055       assert(old_limit == eden()->end(), "sanity check");
1056       break;
1057     }
1058     // Try to allocate until succeeded or the soft limit can't be adjusted
1059     result = eden()->par_allocate(word_size);
1060   } while (result == NULL);
1061 
1062   // If the eden is full and the last collection bailed out, we are running
1063   // out of heap space, and we try to allocate the from-space, too.
1064   // allocate_from_space can't be inlined because that would introduce a
1065   // circular dependency at compile time.
1066   if (result == NULL) {
1067     result = allocate_from_space(word_size);
1068   } else if (CMSEdenChunksRecordAlways && _next_gen != NULL) {
1069     _next_gen->sample_eden_chunk();
1070   }
1071   return result;
1072 }
1073 
1074 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1075                                          bool is_tlab) {
1076   HeapWord* res = eden()->par_allocate(word_size);
1077   if (CMSEdenChunksRecordAlways && _next_gen != NULL) {
1078     _next_gen->sample_eden_chunk();
1079   }
1080   return res;
1081 }
1082 
1083 void DefNewGeneration::gc_prologue(bool full) {
1084   // Ensure that _end and _soft_end are the same in eden space.
1085   eden()->set_soft_end(eden()->end());
1086 }
1087 
1088 size_t DefNewGeneration::tlab_capacity() const {
1089   return eden()->capacity();
1090 }
1091 
1092 size_t DefNewGeneration::tlab_used() const {
1093   return eden()->used();
1094 }
1095 
1096 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1097   return unsafe_max_alloc_nogc();
1098 }