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/atomic.inline.hpp"
  45 #include "runtime/java.hpp"
  46 #include "runtime/prefetch.inline.hpp"
  47 #include "runtime/thread.inline.hpp"
  48 #include "utilities/copy.hpp"
  49 #include "utilities/globalDefinitions.hpp"
  50 #include "utilities/stack.inline.hpp"
  51 
  52 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  53 
  54 //
  55 // DefNewGeneration functions.
  56 
  57 // Methods of protected closure types.
  58 
  59 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
  60   assert(g->level() == 0, "Optimized for youngest gen.");
  61 }
  62 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
  63   return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
  64 }
  65 
  66 DefNewGeneration::KeepAliveClosure::
  67 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
  68   GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
  69   _rs = (CardTableRS*)rs;
  70 }
  71 
  72 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  73 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  74 
  75 
  76 DefNewGeneration::FastKeepAliveClosure::
  77 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
  78   DefNewGeneration::KeepAliveClosure(cl) {
  79   _boundary = g->reserved().end();
  80 }
  81 
  82 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  83 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  84 
  85 DefNewGeneration::EvacuateFollowersClosure::
  86 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
  87                          ScanClosure* cur, ScanClosure* older) :
  88   _gch(gch), _level(level),
  89   _scan_cur_or_nonheap(cur), _scan_older(older)
  90 {}
  91 
  92 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
  93   do {
  94     _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
  95                                        _scan_older);
  96   } while (!_gch->no_allocs_since_save_marks(_level));
  97 }
  98 
  99 DefNewGeneration::FastEvacuateFollowersClosure::
 100 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
 101                              DefNewGeneration* gen,
 102                              FastScanClosure* cur, FastScanClosure* older) :
 103   _gch(gch), _level(level), _gen(gen),
 104   _scan_cur_or_nonheap(cur), _scan_older(older)
 105 {}
 106 
 107 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
 108   do {
 109     _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
 110                                        _scan_older);
 111   } while (!_gch->no_allocs_since_save_marks(_level));
 112   guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
 113 }
 114 
 115 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
 116     OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 117 {
 118   assert(_g->level() == 0, "Optimized for youngest generation");
 119   _boundary = _g->reserved().end();
 120 }
 121 
 122 void ScanClosure::do_oop(oop* p)       { ScanClosure::do_oop_work(p); }
 123 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
 124 
 125 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
 126     OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 127 {
 128   assert(_g->level() == 0, "Optimized for youngest generation");
 129   _boundary = _g->reserved().end();
 130 }
 131 
 132 void FastScanClosure::do_oop(oop* p)       { FastScanClosure::do_oop_work(p); }
 133 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
 134 
 135 void KlassScanClosure::do_klass(Klass* klass) {
 136 #ifndef PRODUCT
 137   if (TraceScavenge) {
 138     ResourceMark rm;
 139     gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
 140                            klass,
 141                            klass->external_name(),
 142                            klass->has_modified_oops() ? "true" : "false");
 143   }
 144 #endif
 145 
 146   // If the klass has not been dirtied we know that there's
 147   // no references into  the young gen and we can skip it.
 148   if (klass->has_modified_oops()) {
 149     if (_accumulate_modified_oops) {
 150       klass->accumulate_modified_oops();
 151     }
 152 
 153     // Clear this state since we're going to scavenge all the metadata.
 154     klass->clear_modified_oops();
 155 
 156     // Tell the closure which Klass is being scanned so that it can be dirtied
 157     // if oops are left pointing into the young gen.
 158     _scavenge_closure->set_scanned_klass(klass);
 159 
 160     klass->oops_do(_scavenge_closure);
 161 
 162     _scavenge_closure->set_scanned_klass(NULL);
 163   }
 164 }
 165 
 166 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
 167   _g(g)
 168 {
 169   assert(_g->level() == 0, "Optimized for youngest generation");
 170   _boundary = _g->reserved().end();
 171 }
 172 
 173 void ScanWeakRefClosure::do_oop(oop* p)       { ScanWeakRefClosure::do_oop_work(p); }
 174 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
 175 
 176 void FilteringClosure::do_oop(oop* p)       { FilteringClosure::do_oop_work(p); }
 177 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
 178 
 179 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
 180                                    KlassRemSet* klass_rem_set)
 181     : _scavenge_closure(scavenge_closure),
 182       _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
 183 
 184 
 185 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
 186                                    size_t initial_size,
 187                                    int level,
 188                                    const char* policy)
 189   : Generation(rs, initial_size, level),
 190     _promo_failure_drain_in_progress(false),
 191     _should_allocate_from_space(false)
 192 {
 193   MemRegion cmr((HeapWord*)_virtual_space.low(),
 194                 (HeapWord*)_virtual_space.high());
 195   Universe::heap()->barrier_set()->resize_covered_region(cmr);
 196 
 197   if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) {
 198     _eden_space = new ConcEdenSpace(this);
 199   } else {
 200     _eden_space = new EdenSpace(this);
 201   }
 202   _from_space = new ContiguousSpace();
 203   _to_space   = new ContiguousSpace();
 204 
 205   if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
 206     vm_exit_during_initialization("Could not allocate a new gen space");
 207 
 208   // Compute the maximum eden and survivor space sizes. These sizes
 209   // are computed assuming the entire reserved space is committed.
 210   // These values are exported as performance counters.
 211   uintx alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
 212   uintx size = _virtual_space.reserved_size();
 213   _max_survivor_size = compute_survivor_size(size, alignment);
 214   _max_eden_size = size - (2*_max_survivor_size);
 215 
 216   // allocate the performance counters
 217 
 218   // Generation counters -- generation 0, 3 subspaces
 219   _gen_counters = new GenerationCounters("new", 0, 3, &_virtual_space);
 220   _gc_counters = new CollectorCounters(policy, 0);
 221 
 222   _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
 223                                       _gen_counters);
 224   _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
 225                                       _gen_counters);
 226   _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
 227                                     _gen_counters);
 228 
 229   compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
 230   update_counters();
 231   _next_gen = NULL;
 232   _tenuring_threshold = MaxTenuringThreshold;
 233   _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
 234 
 235   _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
 236 }
 237 
 238 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
 239                                                 bool clear_space,
 240                                                 bool mangle_space) {
 241   uintx alignment =
 242     GenCollectedHeap::heap()->collector_policy()->space_alignment();
 243 
 244   // If the spaces are being cleared (only done at heap initialization
 245   // currently), the survivor spaces need not be empty.
 246   // Otherwise, no care is taken for used areas in the survivor spaces
 247   // so check.
 248   assert(clear_space || (to()->is_empty() && from()->is_empty()),
 249     "Initialization of the survivor spaces assumes these are empty");
 250 
 251   // Compute sizes
 252   uintx size = _virtual_space.committed_size();
 253   uintx survivor_size = compute_survivor_size(size, alignment);
 254   uintx eden_size = size - (2*survivor_size);
 255   assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 256 
 257   if (eden_size < minimum_eden_size) {
 258     // May happen due to 64Kb rounding, if so adjust eden size back up
 259     minimum_eden_size = align_size_up(minimum_eden_size, alignment);
 260     uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
 261     uintx unaligned_survivor_size =
 262       align_size_down(maximum_survivor_size, alignment);
 263     survivor_size = MAX2(unaligned_survivor_size, alignment);
 264     eden_size = size - (2*survivor_size);
 265     assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 266     assert(eden_size >= minimum_eden_size, "just checking");
 267   }
 268 
 269   char *eden_start = _virtual_space.low();
 270   char *from_start = eden_start + eden_size;
 271   char *to_start   = from_start + survivor_size;
 272   char *to_end     = to_start   + survivor_size;
 273 
 274   assert(to_end == _virtual_space.high(), "just checking");
 275   assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
 276   assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
 277   assert(Space::is_aligned((HeapWord*)to_start),   "checking alignment");
 278 
 279   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
 280   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
 281   MemRegion toMR  ((HeapWord*)to_start, (HeapWord*)to_end);
 282 
 283   // A minimum eden size implies that there is a part of eden that
 284   // is being used and that affects the initialization of any
 285   // newly formed eden.
 286   bool live_in_eden = minimum_eden_size > 0;
 287 
 288   // If not clearing the spaces, do some checking to verify that
 289   // the space are already mangled.
 290   if (!clear_space) {
 291     // Must check mangling before the spaces are reshaped.  Otherwise,
 292     // the bottom or end of one space may have moved into another
 293     // a failure of the check may not correctly indicate which space
 294     // is not properly mangled.
 295     if (ZapUnusedHeapArea) {
 296       HeapWord* limit = (HeapWord*) _virtual_space.high();
 297       eden()->check_mangled_unused_area(limit);
 298       from()->check_mangled_unused_area(limit);
 299         to()->check_mangled_unused_area(limit);
 300     }
 301   }
 302 
 303   // Reset the spaces for their new regions.
 304   eden()->initialize(edenMR,
 305                      clear_space && !live_in_eden,
 306                      SpaceDecorator::Mangle);
 307   // If clear_space and live_in_eden, we will not have cleared any
 308   // portion of eden above its top. This can cause newly
 309   // expanded space not to be mangled if using ZapUnusedHeapArea.
 310   // We explicitly do such mangling here.
 311   if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
 312     eden()->mangle_unused_area();
 313   }
 314   from()->initialize(fromMR, clear_space, mangle_space);
 315   to()->initialize(toMR, clear_space, mangle_space);
 316 
 317   // Set next compaction spaces.
 318   eden()->set_next_compaction_space(from());
 319   // The to-space is normally empty before a compaction so need
 320   // not be considered.  The exception is during promotion
 321   // failure handling when to-space can contain live objects.
 322   from()->set_next_compaction_space(NULL);
 323 }
 324 
 325 void DefNewGeneration::swap_spaces() {
 326   ContiguousSpace* s = from();
 327   _from_space        = to();
 328   _to_space          = s;
 329   eden()->set_next_compaction_space(from());
 330   // The to-space is normally empty before a compaction so need
 331   // not be considered.  The exception is during promotion
 332   // failure handling when to-space can contain live objects.
 333   from()->set_next_compaction_space(NULL);
 334 
 335   if (UsePerfData) {
 336     CSpaceCounters* c = _from_counters;
 337     _from_counters = _to_counters;
 338     _to_counters = c;
 339   }
 340 }
 341 
 342 bool DefNewGeneration::expand(size_t bytes) {
 343   MutexLocker x(ExpandHeap_lock);
 344   HeapWord* prev_high = (HeapWord*) _virtual_space.high();
 345   bool success = _virtual_space.expand_by(bytes);
 346   if (success && ZapUnusedHeapArea) {
 347     // Mangle newly committed space immediately because it
 348     // can be done here more simply that after the new
 349     // spaces have been computed.
 350     HeapWord* new_high = (HeapWord*) _virtual_space.high();
 351     MemRegion mangle_region(prev_high, new_high);
 352     SpaceMangler::mangle_region(mangle_region);
 353   }
 354 
 355   // Do not attempt an expand-to-the reserve size.  The
 356   // request should properly observe the maximum size of
 357   // the generation so an expand-to-reserve should be
 358   // unnecessary.  Also a second call to expand-to-reserve
 359   // value potentially can cause an undue expansion.
 360   // For example if the first expand fail for unknown reasons,
 361   // but the second succeeds and expands the heap to its maximum
 362   // value.
 363   if (GC_locker::is_active()) {
 364     if (PrintGC && Verbose) {
 365       gclog_or_tty->print_cr("Garbage collection disabled, "
 366         "expanded heap instead");
 367     }
 368   }
 369 
 370   return success;
 371 }
 372 
 373 
 374 void DefNewGeneration::compute_new_size() {
 375   // This is called after a gc that includes the following generation
 376   // (which is required to exist.)  So from-space will normally be empty.
 377   // Note that we check both spaces, since if scavenge failed they revert roles.
 378   // If not we bail out (otherwise we would have to relocate the objects)
 379   if (!from()->is_empty() || !to()->is_empty()) {
 380     return;
 381   }
 382 
 383   int next_level = level() + 1;
 384   GenCollectedHeap* gch = GenCollectedHeap::heap();
 385   assert(next_level < gch->_n_gens,
 386          "DefNewGeneration cannot be an oldest gen");
 387 
 388   Generation* next_gen = gch->_gens[next_level];
 389   size_t old_size = next_gen->capacity();
 390   size_t new_size_before = _virtual_space.committed_size();
 391   size_t min_new_size = spec()->init_size();
 392   size_t max_new_size = reserved().byte_size();
 393   assert(min_new_size <= new_size_before &&
 394          new_size_before <= max_new_size,
 395          "just checking");
 396   // All space sizes must be multiples of Generation::GenGrain.
 397   size_t alignment = Generation::GenGrain;
 398 
 399   // Compute desired new generation size based on NewRatio and
 400   // NewSizeThreadIncrease
 401   size_t desired_new_size = old_size/NewRatio;
 402   int threads_count = Threads::number_of_non_daemon_threads();
 403   size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
 404   desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
 405 
 406   // Adjust new generation size
 407   desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
 408   assert(desired_new_size <= max_new_size, "just checking");
 409 
 410   bool changed = false;
 411   if (desired_new_size > new_size_before) {
 412     size_t change = desired_new_size - new_size_before;
 413     assert(change % alignment == 0, "just checking");
 414     if (expand(change)) {
 415        changed = true;
 416     }
 417     // If the heap failed to expand to the desired size,
 418     // "changed" will be false.  If the expansion failed
 419     // (and at this point it was expected to succeed),
 420     // ignore the failure (leaving "changed" as false).
 421   }
 422   if (desired_new_size < new_size_before && eden()->is_empty()) {
 423     // bail out of shrinking if objects in eden
 424     size_t change = new_size_before - desired_new_size;
 425     assert(change % alignment == 0, "just checking");
 426     _virtual_space.shrink_by(change);
 427     changed = true;
 428   }
 429   if (changed) {
 430     // The spaces have already been mangled at this point but
 431     // may not have been cleared (set top = bottom) and should be.
 432     // Mangling was done when the heap was being expanded.
 433     compute_space_boundaries(eden()->used(),
 434                              SpaceDecorator::Clear,
 435                              SpaceDecorator::DontMangle);
 436     MemRegion cmr((HeapWord*)_virtual_space.low(),
 437                   (HeapWord*)_virtual_space.high());
 438     Universe::heap()->barrier_set()->resize_covered_region(cmr);
 439     if (Verbose && PrintGC) {
 440       size_t new_size_after  = _virtual_space.committed_size();
 441       size_t eden_size_after = eden()->capacity();
 442       size_t survivor_size_after = from()->capacity();
 443       gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
 444         SIZE_FORMAT "K [eden="
 445         SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
 446         new_size_before/K, new_size_after/K,
 447         eden_size_after/K, survivor_size_after/K);
 448       if (WizardMode) {
 449         gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
 450           thread_increase_size/K, threads_count);
 451       }
 452       gclog_or_tty->cr();
 453     }
 454   }
 455 }
 456 
 457 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
 458   assert(false, "NYI -- are you sure you want to call this?");
 459 }
 460 
 461 
 462 size_t DefNewGeneration::capacity() const {
 463   return eden()->capacity()
 464        + from()->capacity();  // to() is only used during scavenge
 465 }
 466 
 467 
 468 size_t DefNewGeneration::used() const {
 469   return eden()->used()
 470        + from()->used();      // to() is only used during scavenge
 471 }
 472 
 473 
 474 size_t DefNewGeneration::free() const {
 475   return eden()->free()
 476        + from()->free();      // to() is only used during scavenge
 477 }
 478 
 479 size_t DefNewGeneration::max_capacity() const {
 480   const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
 481   const size_t reserved_bytes = reserved().byte_size();
 482   return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
 483 }
 484 
 485 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
 486   return eden()->free();
 487 }
 488 
 489 size_t DefNewGeneration::capacity_before_gc() const {
 490   return eden()->capacity();
 491 }
 492 
 493 size_t DefNewGeneration::contiguous_available() const {
 494   return eden()->free();
 495 }
 496 
 497 
 498 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
 499 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
 500 
 501 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
 502   eden()->object_iterate(blk);
 503   from()->object_iterate(blk);
 504 }
 505 
 506 
 507 void DefNewGeneration::space_iterate(SpaceClosure* blk,
 508                                      bool usedOnly) {
 509   blk->do_space(eden());
 510   blk->do_space(from());
 511   blk->do_space(to());
 512 }
 513 
 514 // The last collection bailed out, we are running out of heap space,
 515 // so we try to allocate the from-space, too.
 516 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
 517   HeapWord* result = NULL;
 518   if (Verbose && PrintGCDetails) {
 519     gclog_or_tty->print("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):"
 520                         "  will_fail: %s"
 521                         "  heap_lock: %s"
 522                         "  free: " SIZE_FORMAT,
 523                         size,
 524                         GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
 525                           "true" : "false",
 526                         Heap_lock->is_locked() ? "locked" : "unlocked",
 527                         from()->free());
 528   }
 529   if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
 530     if (Heap_lock->owned_by_self() ||
 531         (SafepointSynchronize::is_at_safepoint() &&
 532          Thread::current()->is_VM_thread())) {
 533       // If the Heap_lock is not locked by this thread, this will be called
 534       // again later with the Heap_lock held.
 535       result = from()->allocate(size);
 536     } else if (PrintGC && Verbose) {
 537       gclog_or_tty->print_cr("  Heap_lock is not owned by self");
 538     }
 539   } else if (PrintGC && Verbose) {
 540     gclog_or_tty->print_cr("  should_allocate_from_space: NOT");
 541   }
 542   if (PrintGC && Verbose) {
 543     gclog_or_tty->print_cr("  returns %s", result == NULL ? "NULL" : "object");
 544   }
 545   return result;
 546 }
 547 
 548 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
 549                                                 bool   is_tlab,
 550                                                 bool   parallel) {
 551   // We don't attempt to expand the young generation (but perhaps we should.)
 552   return allocate(size, is_tlab);
 553 }
 554 
 555 void DefNewGeneration::adjust_desired_tenuring_threshold() {
 556   // Set the desired survivor size to half the real survivor space
 557   _tenuring_threshold =
 558     age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
 559 }
 560 
 561 void DefNewGeneration::collect(bool   full,
 562                                bool   clear_all_soft_refs,
 563                                size_t size,
 564                                bool   is_tlab) {
 565   assert(full || size > 0, "otherwise we don't want to collect");
 566 
 567   GenCollectedHeap* gch = GenCollectedHeap::heap();
 568 
 569   _gc_timer->register_gc_start();
 570   DefNewTracer gc_tracer;
 571   gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
 572 
 573   _next_gen = gch->next_gen(this);
 574 
 575   // If the next generation is too full to accommodate promotion
 576   // from this generation, pass on collection; let the next generation
 577   // do it.
 578   if (!collection_attempt_is_safe()) {
 579     if (Verbose && PrintGCDetails) {
 580       gclog_or_tty->print(" :: Collection attempt not safe :: ");
 581     }
 582     gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
 583     return;
 584   }
 585   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 586 
 587   init_assuming_no_promotion_failure();
 588 
 589   GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id());
 590   // Capture heap used before collection (for printing).
 591   size_t gch_prev_used = gch->used();
 592 
 593   gch->trace_heap_before_gc(&gc_tracer);
 594 
 595   SpecializationStats::clear();
 596 
 597   // These can be shared for all code paths
 598   IsAliveClosure is_alive(this);
 599   ScanWeakRefClosure scan_weak_ref(this);
 600 
 601   age_table()->clear();
 602   to()->clear(SpaceDecorator::Mangle);
 603 
 604   gch->rem_set()->prepare_for_younger_refs_iterate(false);
 605 
 606   assert(gch->no_allocs_since_save_marks(0),
 607          "save marks have not been newly set.");
 608 
 609   // Not very pretty.
 610   CollectorPolicy* cp = gch->collector_policy();
 611 
 612   FastScanClosure fsc_with_no_gc_barrier(this, false);
 613   FastScanClosure fsc_with_gc_barrier(this, true);
 614 
 615   KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
 616                                       gch->rem_set()->klass_rem_set());
 617   CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
 618                                            &fsc_with_no_gc_barrier,
 619                                            false);
 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   gch->gen_process_roots(_level,
 630                          true,  // Process younger gens, if any,
 631                                 // as strong roots.
 632                          true,  // activate StrongRootsScope
 633                          SharedHeap::SO_ScavengeCodeCache,
 634                          GenCollectedHeap::StrongAndWeakRoots,
 635                          &fsc_with_no_gc_barrier,
 636                          &fsc_with_gc_barrier,
 637                          &cld_scan_closure);
 638 
 639   // "evacuate followers".
 640   evacuate_followers.do_void();
 641 
 642   FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
 643   ReferenceProcessor* rp = ref_processor();
 644   rp->setup_policy(clear_all_soft_refs);
 645   const ReferenceProcessorStats& stats =
 646   rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
 647                                     NULL, _gc_timer, gc_tracer.gc_id());
 648   gc_tracer.report_gc_reference_stats(stats);
 649 
 650   if (!_promotion_failed) {
 651     // Swap the survivor spaces.
 652     eden()->clear(SpaceDecorator::Mangle);
 653     from()->clear(SpaceDecorator::Mangle);
 654     if (ZapUnusedHeapArea) {
 655       // This is now done here because of the piece-meal mangling which
 656       // can check for valid mangling at intermediate points in the
 657       // collection(s).  When a minor collection fails to collect
 658       // sufficient space resizing of the young generation can occur
 659       // an redistribute the spaces in the young generation.  Mangle
 660       // here so that unzapped regions don't get distributed to
 661       // other spaces.
 662       to()->mangle_unused_area();
 663     }
 664     swap_spaces();
 665 
 666     assert(to()->is_empty(), "to space should be empty now");
 667 
 668     adjust_desired_tenuring_threshold();
 669 
 670     // A successful scavenge should restart the GC time limit count which is
 671     // for full GC's.
 672     AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
 673     size_policy->reset_gc_overhead_limit_count();
 674     assert(!gch->incremental_collection_failed(), "Should be clear");
 675   } else {
 676     assert(_promo_failure_scan_stack.is_empty(), "post condition");
 677     _promo_failure_scan_stack.clear(true); // Clear cached segments.
 678 
 679     remove_forwarding_pointers();
 680     if (PrintGCDetails) {
 681       gclog_or_tty->print(" (promotion failed) ");
 682     }
 683     // Add to-space to the list of space to compact
 684     // when a promotion failure has occurred.  In that
 685     // case there can be live objects in to-space
 686     // as a result of a partial evacuation of eden
 687     // and from-space.
 688     swap_spaces();   // For uniformity wrt ParNewGeneration.
 689     from()->set_next_compaction_space(to());
 690     gch->set_incremental_collection_failed();
 691 
 692     // Inform the next generation that a promotion failure occurred.
 693     _next_gen->promotion_failure_occurred();
 694     gc_tracer.report_promotion_failed(_promotion_failed_info);
 695 
 696     // Reset the PromotionFailureALot counters.
 697     NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
 698   }
 699   if (PrintGC && !PrintGCDetails) {
 700     gch->print_heap_change(gch_prev_used);
 701   }
 702   // set new iteration safe limit for the survivor spaces
 703   from()->set_concurrent_iteration_safe_limit(from()->top());
 704   to()->set_concurrent_iteration_safe_limit(to()->top());
 705   SpecializationStats::print();
 706 
 707   // We need to use a monotonically non-decreasing time in ms
 708   // or we will see time-warp warnings and os::javaTimeMillis()
 709   // does not guarantee monotonicity.
 710   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 711   update_time_of_last_gc(now);
 712 
 713   gch->trace_heap_after_gc(&gc_tracer);
 714   gc_tracer.report_tenuring_threshold(tenuring_threshold());
 715 
 716   _gc_timer->register_gc_end();
 717 
 718   gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
 719 }
 720 
 721 class RemoveForwardPointerClosure: public ObjectClosure {
 722 public:
 723   void do_object(oop obj) {
 724     obj->init_mark();
 725   }
 726 };
 727 
 728 void DefNewGeneration::init_assuming_no_promotion_failure() {
 729   _promotion_failed = false;
 730   _promotion_failed_info.reset();
 731   from()->set_next_compaction_space(NULL);
 732 }
 733 
 734 void DefNewGeneration::remove_forwarding_pointers() {
 735   RemoveForwardPointerClosure rspc;
 736   eden()->object_iterate(&rspc);
 737   from()->object_iterate(&rspc);
 738 
 739   // Now restore saved marks, if any.
 740   assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
 741          "should be the same");
 742   while (!_objs_with_preserved_marks.is_empty()) {
 743     oop obj   = _objs_with_preserved_marks.pop();
 744     markOop m = _preserved_marks_of_objs.pop();
 745     obj->set_mark(m);
 746   }
 747   _objs_with_preserved_marks.clear(true);
 748   _preserved_marks_of_objs.clear(true);
 749 }
 750 
 751 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
 752   assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
 753          "Oversaving!");
 754   _objs_with_preserved_marks.push(obj);
 755   _preserved_marks_of_objs.push(m);
 756 }
 757 
 758 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
 759   if (m->must_be_preserved_for_promotion_failure(obj)) {
 760     preserve_mark(obj, m);
 761   }
 762 }
 763 
 764 void DefNewGeneration::handle_promotion_failure(oop old) {
 765   if (PrintPromotionFailure && !_promotion_failed) {
 766     gclog_or_tty->print(" (promotion failure size = %d) ",
 767                         old->size());
 768   }
 769   _promotion_failed = true;
 770   _promotion_failed_info.register_copy_failure(old->size());
 771   preserve_mark_if_necessary(old, old->mark());
 772   // forward to self
 773   old->forward_to(old);
 774 
 775   _promo_failure_scan_stack.push(old);
 776 
 777   if (!_promo_failure_drain_in_progress) {
 778     // prevent recursion in copy_to_survivor_space()
 779     _promo_failure_drain_in_progress = true;
 780     drain_promo_failure_scan_stack();
 781     _promo_failure_drain_in_progress = false;
 782   }
 783 }
 784 
 785 oop DefNewGeneration::copy_to_survivor_space(oop old) {
 786   assert(is_in_reserved(old) && !old->is_forwarded(),
 787          "shouldn't be scavenging this oop");
 788   size_t s = old->size();
 789   oop obj = NULL;
 790 
 791   // Try allocating obj in to-space (unless too old)
 792   if (old->age() < tenuring_threshold()) {
 793     obj = (oop) to()->allocate_aligned(s);
 794   }
 795 
 796   // Otherwise try allocating obj tenured
 797   if (obj == NULL) {
 798     obj = _next_gen->promote(old, s);
 799     if (obj == NULL) {
 800       handle_promotion_failure(old);
 801       return old;
 802     }
 803   } else {
 804     // Prefetch beyond obj
 805     const intx interval = PrefetchCopyIntervalInBytes;
 806     Prefetch::write(obj, interval);
 807 
 808     // Copy obj
 809     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
 810 
 811     // Increment age if obj still in new generation
 812     obj->incr_age();
 813     age_table()->add(obj, s);
 814   }
 815 
 816   // Done, insert forward pointer to obj in this header
 817   old->forward_to(obj);
 818 
 819   return obj;
 820 }
 821 
 822 void DefNewGeneration::drain_promo_failure_scan_stack() {
 823   while (!_promo_failure_scan_stack.is_empty()) {
 824      oop obj = _promo_failure_scan_stack.pop();
 825      obj->oop_iterate(_promo_failure_scan_stack_closure);
 826   }
 827 }
 828 
 829 void DefNewGeneration::save_marks() {
 830   eden()->set_saved_mark();
 831   to()->set_saved_mark();
 832   from()->set_saved_mark();
 833 }
 834 
 835 
 836 void DefNewGeneration::reset_saved_marks() {
 837   eden()->reset_saved_mark();
 838   to()->reset_saved_mark();
 839   from()->reset_saved_mark();
 840 }
 841 
 842 
 843 bool DefNewGeneration::no_allocs_since_save_marks() {
 844   assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
 845   assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
 846   return to()->saved_mark_at_top();
 847 }
 848 
 849 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
 850                                                                 \
 851 void DefNewGeneration::                                         \
 852 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) {   \
 853   cl->set_generation(this);                                     \
 854   eden()->oop_since_save_marks_iterate##nv_suffix(cl);          \
 855   to()->oop_since_save_marks_iterate##nv_suffix(cl);            \
 856   from()->oop_since_save_marks_iterate##nv_suffix(cl);          \
 857   cl->reset_generation();                                       \
 858   save_marks();                                                 \
 859 }
 860 
 861 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
 862 
 863 #undef DefNew_SINCE_SAVE_MARKS_DEFN
 864 
 865 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
 866                                          size_t max_alloc_words) {
 867   if (requestor == this || _promotion_failed) return;
 868   assert(requestor->level() > level(), "DefNewGeneration must be youngest");
 869 
 870   /* $$$ Assert this?  "trace" is a "MarkSweep" function so that's not appropriate.
 871   if (to_space->top() > to_space->bottom()) {
 872     trace("to_space not empty when contribute_scratch called");
 873   }
 874   */
 875 
 876   ContiguousSpace* to_space = to();
 877   assert(to_space->end() >= to_space->top(), "pointers out of order");
 878   size_t free_words = pointer_delta(to_space->end(), to_space->top());
 879   if (free_words >= MinFreeScratchWords) {
 880     ScratchBlock* sb = (ScratchBlock*)to_space->top();
 881     sb->num_words = free_words;
 882     sb->next = list;
 883     list = sb;
 884   }
 885 }
 886 
 887 void DefNewGeneration::reset_scratch() {
 888   // If contributing scratch in to_space, mangle all of
 889   // to_space if ZapUnusedHeapArea.  This is needed because
 890   // top is not maintained while using to-space as scratch.
 891   if (ZapUnusedHeapArea) {
 892     to()->mangle_unused_area_complete();
 893   }
 894 }
 895 
 896 bool DefNewGeneration::collection_attempt_is_safe() {
 897   if (!to()->is_empty()) {
 898     if (Verbose && PrintGCDetails) {
 899       gclog_or_tty->print(" :: to is not empty :: ");
 900     }
 901     return false;
 902   }
 903   if (_next_gen == NULL) {
 904     GenCollectedHeap* gch = GenCollectedHeap::heap();
 905     _next_gen = gch->next_gen(this);
 906   }
 907   return _next_gen->promotion_attempt_is_safe(used());
 908 }
 909 
 910 void DefNewGeneration::gc_epilogue(bool full) {
 911   DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
 912 
 913   assert(!GC_locker::is_active(), "We should not be executing here");
 914   // Check if the heap is approaching full after a collection has
 915   // been done.  Generally the young generation is empty at
 916   // a minimum at the end of a collection.  If it is not, then
 917   // the heap is approaching full.
 918   GenCollectedHeap* gch = GenCollectedHeap::heap();
 919   if (full) {
 920     DEBUG_ONLY(seen_incremental_collection_failed = false;)
 921     if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
 922       if (Verbose && PrintGCDetails) {
 923         gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
 924                             GCCause::to_string(gch->gc_cause()));
 925       }
 926       gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
 927       set_should_allocate_from_space(); // we seem to be running out of space
 928     } else {
 929       if (Verbose && PrintGCDetails) {
 930         gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
 931                             GCCause::to_string(gch->gc_cause()));
 932       }
 933       gch->clear_incremental_collection_failed(); // We just did a full collection
 934       clear_should_allocate_from_space(); // if set
 935     }
 936   } else {
 937 #ifdef ASSERT
 938     // It is possible that incremental_collection_failed() == true
 939     // here, because an attempted scavenge did not succeed. The policy
 940     // is normally expected to cause a full collection which should
 941     // clear that condition, so we should not be here twice in a row
 942     // with incremental_collection_failed() == true without having done
 943     // a full collection in between.
 944     if (!seen_incremental_collection_failed &&
 945         gch->incremental_collection_failed()) {
 946       if (Verbose && PrintGCDetails) {
 947         gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
 948                             GCCause::to_string(gch->gc_cause()));
 949       }
 950       seen_incremental_collection_failed = true;
 951     } else if (seen_incremental_collection_failed) {
 952       if (Verbose && PrintGCDetails) {
 953         gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
 954                             GCCause::to_string(gch->gc_cause()));
 955       }
 956       assert(gch->gc_cause() == GCCause::_scavenge_alot ||
 957              (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
 958              !gch->incremental_collection_failed(),
 959              "Twice in a row");
 960       seen_incremental_collection_failed = false;
 961     }
 962 #endif // ASSERT
 963   }
 964 
 965   if (ZapUnusedHeapArea) {
 966     eden()->check_mangled_unused_area_complete();
 967     from()->check_mangled_unused_area_complete();
 968     to()->check_mangled_unused_area_complete();
 969   }
 970 
 971   if (!CleanChunkPoolAsync) {
 972     Chunk::clean_chunk_pool();
 973   }
 974 
 975   // update the generation and space performance counters
 976   update_counters();
 977   gch->collector_policy()->counters()->update_counters();
 978 }
 979 
 980 void DefNewGeneration::record_spaces_top() {
 981   assert(ZapUnusedHeapArea, "Not mangling unused space");
 982   eden()->set_top_for_allocations();
 983   to()->set_top_for_allocations();
 984   from()->set_top_for_allocations();
 985 }
 986 
 987 void DefNewGeneration::ref_processor_init() {
 988   Generation::ref_processor_init();
 989 }
 990 
 991 
 992 void DefNewGeneration::update_counters() {
 993   if (UsePerfData) {
 994     _eden_counters->update_all();
 995     _from_counters->update_all();
 996     _to_counters->update_all();
 997     _gen_counters->update_all();
 998   }
 999 }
1000 
1001 void DefNewGeneration::verify() {
1002   eden()->verify();
1003   from()->verify();
1004     to()->verify();
1005 }
1006 
1007 void DefNewGeneration::print_on(outputStream* st) const {
1008   Generation::print_on(st);
1009   st->print("  eden");
1010   eden()->print_on(st);
1011   st->print("  from");
1012   from()->print_on(st);
1013   st->print("  to  ");
1014   to()->print_on(st);
1015 }
1016 
1017 
1018 const char* DefNewGeneration::name() const {
1019   return "def new generation";
1020 }
1021 
1022 // Moved from inline file as they are not called inline
1023 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1024   return eden();
1025 }
1026 
1027 HeapWord* DefNewGeneration::allocate(size_t word_size,
1028                                      bool is_tlab) {
1029   // This is the slow-path allocation for the DefNewGeneration.
1030   // Most allocations are fast-path in compiled code.
1031   // We try to allocate from the eden.  If that works, we are happy.
1032   // Note that since DefNewGeneration supports lock-free allocation, we
1033   // have to use it here, as well.
1034   HeapWord* result = eden()->par_allocate(word_size);
1035   if (result != NULL) {
1036     if (CMSEdenChunksRecordAlways && _next_gen != NULL) {
1037       _next_gen->sample_eden_chunk();
1038     }
1039     return result;
1040   }
1041   do {
1042     HeapWord* old_limit = eden()->soft_end();
1043     if (old_limit < eden()->end()) {
1044       // Tell the next generation we reached a limit.
1045       HeapWord* new_limit =
1046         next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size);
1047       if (new_limit != NULL) {
1048         Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);
1049       } else {
1050         assert(eden()->soft_end() == eden()->end(),
1051                "invalid state after allocation_limit_reached returned null");
1052       }
1053     } else {
1054       // The allocation failed and the soft limit is equal to the hard limit,
1055       // there are no reasons to do an attempt to allocate
1056       assert(old_limit == eden()->end(), "sanity check");
1057       break;
1058     }
1059     // Try to allocate until succeeded or the soft limit can't be adjusted
1060     result = eden()->par_allocate(word_size);
1061   } while (result == NULL);
1062 
1063   // If the eden is full and the last collection bailed out, we are running
1064   // out of heap space, and we try to allocate the from-space, too.
1065   // allocate_from_space can't be inlined because that would introduce a
1066   // circular dependency at compile time.
1067   if (result == NULL) {
1068     result = allocate_from_space(word_size);
1069   } else if (CMSEdenChunksRecordAlways && _next_gen != NULL) {
1070     _next_gen->sample_eden_chunk();
1071   }
1072   return result;
1073 }
1074 
1075 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1076                                          bool is_tlab) {
1077   HeapWord* res = eden()->par_allocate(word_size);
1078   if (CMSEdenChunksRecordAlways && _next_gen != NULL) {
1079     _next_gen->sample_eden_chunk();
1080   }
1081   return res;
1082 }
1083 
1084 void DefNewGeneration::gc_prologue(bool full) {
1085   // Ensure that _end and _soft_end are the same in eden space.
1086   eden()->set_soft_end(eden()->end());
1087 }
1088 
1089 size_t DefNewGeneration::tlab_capacity() const {
1090   return eden()->capacity();
1091 }
1092 
1093 size_t DefNewGeneration::tlab_used() const {
1094   return eden()->used();
1095 }
1096 
1097 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1098   return unsafe_max_alloc_nogc();
1099 }