1 /*
   2  * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/serial/defNewGeneration.inline.hpp"
  27 #include "gc/serial/serialHeap.inline.hpp"
  28 #include "gc/serial/tenuredGeneration.hpp"
  29 #include "gc/shared/adaptiveSizePolicy.hpp"
  30 #include "gc/shared/ageTable.inline.hpp"
  31 #include "gc/shared/cardTableRS.hpp"
  32 #include "gc/shared/collectorCounters.hpp"
  33 #include "gc/shared/gcArguments.hpp"
  34 #include "gc/shared/gcHeapSummary.hpp"
  35 #include "gc/shared/gcLocker.hpp"
  36 #include "gc/shared/gcPolicyCounters.hpp"
  37 #include "gc/shared/gcTimer.hpp"
  38 #include "gc/shared/gcTrace.hpp"
  39 #include "gc/shared/gcTraceTime.inline.hpp"
  40 #include "gc/shared/genOopClosures.inline.hpp"
  41 #include "gc/shared/generationSpec.hpp"
  42 #include "gc/shared/preservedMarks.inline.hpp"
  43 #include "gc/shared/referencePolicy.hpp"
  44 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
  45 #include "gc/shared/space.inline.hpp"
  46 #include "gc/shared/spaceDecorator.inline.hpp"
  47 #include "gc/shared/strongRootsScope.hpp"
  48 #include "gc/shared/weakProcessor.hpp"
  49 #include "logging/log.hpp"
  50 #include "memory/iterator.inline.hpp"
  51 #include "memory/resourceArea.hpp"
  52 #include "oops/instanceRefKlass.hpp"
  53 #include "oops/oop.inline.hpp"
  54 #include "runtime/atomic.hpp"
  55 #include "runtime/java.hpp"
  56 #include "runtime/prefetch.inline.hpp"
  57 #include "runtime/thread.inline.hpp"
  58 #include "utilities/align.hpp"
  59 #include "utilities/copy.hpp"
  60 #include "utilities/globalDefinitions.hpp"
  61 #include "utilities/stack.inline.hpp"
  62 
  63 //
  64 // DefNewGeneration functions.
  65 
  66 // Methods of protected closure types.
  67 
  68 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
  69   assert(_young_gen->kind() == Generation::DefNew, "Expected the young generation here");
  70 }
  71 
  72 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
  73   return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded();
  74 }
  75 
  76 DefNewGeneration::KeepAliveClosure::
  77 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
  78   _rs = GenCollectedHeap::heap()->rem_set();
  79 }
  80 
  81 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  82 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  83 
  84 
  85 DefNewGeneration::FastKeepAliveClosure::
  86 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
  87   DefNewGeneration::KeepAliveClosure(cl) {
  88   _boundary = g->reserved().end();
  89 }
  90 
  91 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  92 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  93 
  94 DefNewGeneration::FastEvacuateFollowersClosure::
  95 FastEvacuateFollowersClosure(SerialHeap* heap,
  96                              FastScanClosure* cur,
  97                              FastScanClosure* older) :
  98   _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older)
  99 {
 100 }
 101 
 102 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
 103   do {
 104     _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older);
 105   } while (!_heap->no_allocs_since_save_marks());
 106   guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
 107 }
 108 
 109 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
 110     OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 111 {
 112   _boundary = _g->reserved().end();
 113 }
 114 
 115 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
 116     OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 117 {
 118   _boundary = _g->reserved().end();
 119 }
 120 
 121 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
 122   NOT_PRODUCT(ResourceMark rm);
 123   log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
 124                                   p2i(cld),
 125                                   cld->loader_name_and_id(),
 126                                   cld->has_modified_oops() ? "true" : "false");
 127 
 128   // If the cld has not been dirtied we know that there's
 129   // no references into  the young gen and we can skip it.
 130   if (cld->has_modified_oops()) {
 131     if (_accumulate_modified_oops) {
 132       cld->accumulate_modified_oops();
 133     }
 134 
 135     // Tell the closure which CLD is being scanned so that it can be dirtied
 136     // if oops are left pointing into the young gen.
 137     _scavenge_closure->set_scanned_cld(cld);
 138 
 139     // Clean the cld since we're going to scavenge all the metadata.
 140     cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
 141 
 142     _scavenge_closure->set_scanned_cld(NULL);
 143   }
 144 }
 145 
 146 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
 147   _g(g)
 148 {
 149   _boundary = _g->reserved().end();
 150 }
 151 
 152 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
 153                                    size_t initial_size,
 154                                    size_t min_size,
 155                                    size_t max_size,
 156                                    const char* policy)
 157   : Generation(rs, initial_size),
 158     _preserved_marks_set(false /* in_c_heap */),
 159     _promo_failure_drain_in_progress(false),
 160     _should_allocate_from_space(false)
 161 {
 162   MemRegion cmr((HeapWord*)_virtual_space.low(),
 163                 (HeapWord*)_virtual_space.high());
 164   GenCollectedHeap* gch = GenCollectedHeap::heap();
 165 
 166   gch->rem_set()->resize_covered_region(cmr);
 167 
 168   _eden_space = new ContiguousSpace();
 169   _from_space = new ContiguousSpace();
 170   _to_space   = new ContiguousSpace();
 171 
 172   if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
 173     vm_exit_during_initialization("Could not allocate a new gen space");
 174   }
 175 
 176   // Compute the maximum eden and survivor space sizes. These sizes
 177   // are computed assuming the entire reserved space is committed.
 178   // These values are exported as performance counters.
 179   uintx size = _virtual_space.reserved_size();
 180   _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
 181   _max_eden_size = size - (2*_max_survivor_size);
 182 
 183   // allocate the performance counters
 184 
 185   // Generation counters -- generation 0, 3 subspaces
 186   _gen_counters = new GenerationCounters("new", 0, 3,
 187       min_size, max_size, &_virtual_space);
 188   _gc_counters = new CollectorCounters(policy, 0);
 189 
 190   _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
 191                                       _gen_counters);
 192   _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
 193                                       _gen_counters);
 194   _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
 195                                     _gen_counters);
 196 
 197   compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
 198   update_counters();
 199   _old_gen = NULL;
 200   _tenuring_threshold = MaxTenuringThreshold;
 201   _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
 202 
 203   _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
 204 }
 205 
 206 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
 207                                                 bool clear_space,
 208                                                 bool mangle_space) {
 209   // If the spaces are being cleared (only done at heap initialization
 210   // currently), the survivor spaces need not be empty.
 211   // Otherwise, no care is taken for used areas in the survivor spaces
 212   // so check.
 213   assert(clear_space || (to()->is_empty() && from()->is_empty()),
 214     "Initialization of the survivor spaces assumes these are empty");
 215 
 216   // Compute sizes
 217   uintx size = _virtual_space.committed_size();
 218   uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
 219   uintx eden_size = size - (2*survivor_size);
 220   assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 221 
 222   if (eden_size < minimum_eden_size) {
 223     // May happen due to 64Kb rounding, if so adjust eden size back up
 224     minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
 225     uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
 226     uintx unaligned_survivor_size =
 227       align_down(maximum_survivor_size, SpaceAlignment);
 228     survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
 229     eden_size = size - (2*survivor_size);
 230     assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 231     assert(eden_size >= minimum_eden_size, "just checking");
 232   }
 233 
 234   char *eden_start = _virtual_space.low();
 235   char *from_start = eden_start + eden_size;
 236   char *to_start   = from_start + survivor_size;
 237   char *to_end     = to_start   + survivor_size;
 238 
 239   assert(to_end == _virtual_space.high(), "just checking");
 240   assert(Space::is_aligned(eden_start), "checking alignment");
 241   assert(Space::is_aligned(from_start), "checking alignment");
 242   assert(Space::is_aligned(to_start),   "checking alignment");
 243 
 244   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
 245   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
 246   MemRegion toMR  ((HeapWord*)to_start, (HeapWord*)to_end);
 247 
 248   // A minimum eden size implies that there is a part of eden that
 249   // is being used and that affects the initialization of any
 250   // newly formed eden.
 251   bool live_in_eden = minimum_eden_size > 0;
 252 
 253   // If not clearing the spaces, do some checking to verify that
 254   // the space are already mangled.
 255   if (!clear_space) {
 256     // Must check mangling before the spaces are reshaped.  Otherwise,
 257     // the bottom or end of one space may have moved into another
 258     // a failure of the check may not correctly indicate which space
 259     // is not properly mangled.
 260     if (ZapUnusedHeapArea) {
 261       HeapWord* limit = (HeapWord*) _virtual_space.high();
 262       eden()->check_mangled_unused_area(limit);
 263       from()->check_mangled_unused_area(limit);
 264         to()->check_mangled_unused_area(limit);
 265     }
 266   }
 267 
 268   // Reset the spaces for their new regions.
 269   eden()->initialize(edenMR,
 270                      clear_space && !live_in_eden,
 271                      SpaceDecorator::Mangle);
 272   // If clear_space and live_in_eden, we will not have cleared any
 273   // portion of eden above its top. This can cause newly
 274   // expanded space not to be mangled if using ZapUnusedHeapArea.
 275   // We explicitly do such mangling here.
 276   if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
 277     eden()->mangle_unused_area();
 278   }
 279   from()->initialize(fromMR, clear_space, mangle_space);
 280   to()->initialize(toMR, clear_space, mangle_space);
 281 
 282   // Set next compaction spaces.
 283   eden()->set_next_compaction_space(from());
 284   // The to-space is normally empty before a compaction so need
 285   // not be considered.  The exception is during promotion
 286   // failure handling when to-space can contain live objects.
 287   from()->set_next_compaction_space(NULL);
 288 }
 289 
 290 void DefNewGeneration::swap_spaces() {
 291   ContiguousSpace* s = from();
 292   _from_space        = to();
 293   _to_space          = s;
 294   eden()->set_next_compaction_space(from());
 295   // The to-space is normally empty before a compaction so need
 296   // not be considered.  The exception is during promotion
 297   // failure handling when to-space can contain live objects.
 298   from()->set_next_compaction_space(NULL);
 299 
 300   if (UsePerfData) {
 301     CSpaceCounters* c = _from_counters;
 302     _from_counters = _to_counters;
 303     _to_counters = c;
 304   }
 305 }
 306 
 307 bool DefNewGeneration::expand(size_t bytes) {
 308   MutexLocker x(ExpandHeap_lock);
 309   HeapWord* prev_high = (HeapWord*) _virtual_space.high();
 310   bool success = _virtual_space.expand_by(bytes);
 311   if (success && ZapUnusedHeapArea) {
 312     // Mangle newly committed space immediately because it
 313     // can be done here more simply that after the new
 314     // spaces have been computed.
 315     HeapWord* new_high = (HeapWord*) _virtual_space.high();
 316     MemRegion mangle_region(prev_high, new_high);
 317     SpaceMangler::mangle_region(mangle_region);
 318   }
 319 
 320   // Do not attempt an expand-to-the reserve size.  The
 321   // request should properly observe the maximum size of
 322   // the generation so an expand-to-reserve should be
 323   // unnecessary.  Also a second call to expand-to-reserve
 324   // value potentially can cause an undue expansion.
 325   // For example if the first expand fail for unknown reasons,
 326   // but the second succeeds and expands the heap to its maximum
 327   // value.
 328   if (GCLocker::is_active()) {
 329     log_debug(gc)("Garbage collection disabled, expanded heap instead");
 330   }
 331 
 332   return success;
 333 }
 334 
 335 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
 336                                                     size_t new_size_before,
 337                                                     size_t alignment) const {
 338   size_t desired_new_size = new_size_before;
 339 
 340   if (NewSizeThreadIncrease > 0) {
 341     int threads_count;
 342     size_t thread_increase_size = 0;
 343 
 344     // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
 345     threads_count = Threads::number_of_non_daemon_threads();
 346     if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
 347       thread_increase_size = threads_count * NewSizeThreadIncrease;
 348 
 349       // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
 350       if (new_size_candidate <= max_uintx - thread_increase_size) {
 351         new_size_candidate += thread_increase_size;
 352 
 353         // 3. Check an overflow at 'align_up'.
 354         size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
 355         if (new_size_candidate <= aligned_max) {
 356           desired_new_size = align_up(new_size_candidate, alignment);
 357         }
 358       }
 359     }
 360   }
 361 
 362   return desired_new_size;
 363 }
 364 
 365 void DefNewGeneration::compute_new_size() {
 366   // This is called after a GC that includes the old generation, so from-space
 367   // will normally be empty.
 368   // Note that we check both spaces, since if scavenge failed they revert roles.
 369   // If not we bail out (otherwise we would have to relocate the objects).
 370   if (!from()->is_empty() || !to()->is_empty()) {
 371     return;
 372   }
 373 
 374   GenCollectedHeap* gch = GenCollectedHeap::heap();
 375 
 376   size_t old_size = gch->old_gen()->capacity();
 377   size_t new_size_before = _virtual_space.committed_size();
 378   size_t min_new_size = initial_size();
 379   size_t max_new_size = reserved().byte_size();
 380   assert(min_new_size <= new_size_before &&
 381          new_size_before <= max_new_size,
 382          "just checking");
 383   // All space sizes must be multiples of Generation::GenGrain.
 384   size_t alignment = Generation::GenGrain;
 385 
 386   int threads_count = 0;
 387   size_t thread_increase_size = 0;
 388 
 389   size_t new_size_candidate = old_size / NewRatio;
 390   // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
 391   // and reverts to previous value if any overflow happens
 392   size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
 393 
 394   // Adjust new generation size
 395   desired_new_size = clamp(desired_new_size, min_new_size, max_new_size);
 396   assert(desired_new_size <= max_new_size, "just checking");
 397 
 398   bool changed = false;
 399   if (desired_new_size > new_size_before) {
 400     size_t change = desired_new_size - new_size_before;
 401     assert(change % alignment == 0, "just checking");
 402     if (expand(change)) {
 403        changed = true;
 404     }
 405     // If the heap failed to expand to the desired size,
 406     // "changed" will be false.  If the expansion failed
 407     // (and at this point it was expected to succeed),
 408     // ignore the failure (leaving "changed" as false).
 409   }
 410   if (desired_new_size < new_size_before && eden()->is_empty()) {
 411     // bail out of shrinking if objects in eden
 412     size_t change = new_size_before - desired_new_size;
 413     assert(change % alignment == 0, "just checking");
 414     _virtual_space.shrink_by(change);
 415     changed = true;
 416   }
 417   if (changed) {
 418     // The spaces have already been mangled at this point but
 419     // may not have been cleared (set top = bottom) and should be.
 420     // Mangling was done when the heap was being expanded.
 421     compute_space_boundaries(eden()->used(),
 422                              SpaceDecorator::Clear,
 423                              SpaceDecorator::DontMangle);
 424     MemRegion cmr((HeapWord*)_virtual_space.low(),
 425                   (HeapWord*)_virtual_space.high());
 426     gch->rem_set()->resize_covered_region(cmr);
 427 
 428     log_debug(gc, ergo, heap)(
 429         "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
 430         new_size_before/K, _virtual_space.committed_size()/K,
 431         eden()->capacity()/K, from()->capacity()/K);
 432     log_trace(gc, ergo, heap)(
 433         "  [allowed " SIZE_FORMAT "K extra for %d threads]",
 434           thread_increase_size/K, threads_count);
 435       }
 436 }
 437 
 438 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
 439   assert(false, "NYI -- are you sure you want to call this?");
 440 }
 441 
 442 
 443 size_t DefNewGeneration::capacity() const {
 444   return eden()->capacity()
 445        + from()->capacity();  // to() is only used during scavenge
 446 }
 447 
 448 
 449 size_t DefNewGeneration::used() const {
 450   return eden()->used()
 451        + from()->used();      // to() is only used during scavenge
 452 }
 453 
 454 
 455 size_t DefNewGeneration::free() const {
 456   return eden()->free()
 457        + from()->free();      // to() is only used during scavenge
 458 }
 459 
 460 size_t DefNewGeneration::max_capacity() const {
 461   const size_t reserved_bytes = reserved().byte_size();
 462   return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
 463 }
 464 
 465 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
 466   return eden()->free();
 467 }
 468 
 469 size_t DefNewGeneration::capacity_before_gc() const {
 470   return eden()->capacity();
 471 }
 472 
 473 size_t DefNewGeneration::contiguous_available() const {
 474   return eden()->free();
 475 }
 476 
 477 
 478 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
 479 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
 480 
 481 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
 482   eden()->object_iterate(blk);
 483   from()->object_iterate(blk);
 484 }
 485 
 486 
 487 void DefNewGeneration::space_iterate(SpaceClosure* blk,
 488                                      bool usedOnly) {
 489   blk->do_space(eden());
 490   blk->do_space(from());
 491   blk->do_space(to());
 492 }
 493 
 494 // The last collection bailed out, we are running out of heap space,
 495 // so we try to allocate the from-space, too.
 496 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
 497   bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
 498 
 499   // If the Heap_lock is not locked by this thread, this will be called
 500   // again later with the Heap_lock held.
 501   bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
 502 
 503   HeapWord* result = NULL;
 504   if (do_alloc) {
 505     result = from()->allocate(size);
 506   }
 507 
 508   log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):  will_fail: %s  heap_lock: %s  free: " SIZE_FORMAT "%s%s returns %s",
 509                         size,
 510                         GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
 511                           "true" : "false",
 512                         Heap_lock->is_locked() ? "locked" : "unlocked",
 513                         from()->free(),
 514                         should_try_alloc ? "" : "  should_allocate_from_space: NOT",
 515                         do_alloc ? "  Heap_lock is not owned by self" : "",
 516                         result == NULL ? "NULL" : "object");
 517 
 518   return result;
 519 }
 520 
 521 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
 522                                                 bool   is_tlab,
 523                                                 bool   parallel) {
 524   // We don't attempt to expand the young generation (but perhaps we should.)
 525   return allocate(size, is_tlab);
 526 }
 527 
 528 void DefNewGeneration::adjust_desired_tenuring_threshold() {
 529   // Set the desired survivor size to half the real survivor space
 530   size_t const survivor_capacity = to()->capacity() / HeapWordSize;
 531   size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
 532 
 533   _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
 534 
 535   if (UsePerfData) {
 536     GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
 537     gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
 538     gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
 539   }
 540 
 541   age_table()->print_age_table(_tenuring_threshold);
 542 }
 543 
 544 void DefNewGeneration::collect(bool   full,
 545                                bool   clear_all_soft_refs,
 546                                size_t size,
 547                                bool   is_tlab) {
 548   assert(full || size > 0, "otherwise we don't want to collect");
 549 
 550   SerialHeap* heap = SerialHeap::heap();
 551 
 552   _gc_timer->register_gc_start();
 553   DefNewTracer gc_tracer;
 554   gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
 555 
 556   _old_gen = heap->old_gen();
 557 
 558   // If the next generation is too full to accommodate promotion
 559   // from this generation, pass on collection; let the next generation
 560   // do it.
 561   if (!collection_attempt_is_safe()) {
 562     log_trace(gc)(":: Collection attempt not safe ::");
 563     heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
 564     return;
 565   }
 566   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 567 
 568   init_assuming_no_promotion_failure();
 569 
 570   GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause());
 571 
 572   heap->trace_heap_before_gc(&gc_tracer);
 573 
 574   // These can be shared for all code paths
 575   IsAliveClosure is_alive(this);
 576   ScanWeakRefClosure scan_weak_ref(this);
 577 
 578   age_table()->clear();
 579   to()->clear(SpaceDecorator::Mangle);
 580   // The preserved marks should be empty at the start of the GC.
 581   _preserved_marks_set.init(1);
 582 
 583   heap->rem_set()->prepare_for_younger_refs_iterate(false);
 584 
 585   assert(heap->no_allocs_since_save_marks(),
 586          "save marks have not been newly set.");
 587 
 588   FastScanClosure fsc_with_no_gc_barrier(this, false);
 589   FastScanClosure fsc_with_gc_barrier(this, true);
 590 
 591   CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier,
 592                                   heap->rem_set()->cld_rem_set()->accumulate_modified_oops());
 593 
 594   set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
 595   FastEvacuateFollowersClosure evacuate_followers(heap,
 596                                                   &fsc_with_no_gc_barrier,
 597                                                   &fsc_with_gc_barrier);
 598 
 599   assert(heap->no_allocs_since_save_marks(),
 600          "save marks have not been newly set.");
 601 
 602   {
 603     // DefNew needs to run with n_threads == 0, to make sure the serial
 604     // version of the card table scanning code is used.
 605     // See: CardTableRS::non_clean_card_iterate_possibly_parallel.
 606     StrongRootsScope srs(0);
 607 
 608     heap->young_process_roots(&srs,
 609                               &fsc_with_no_gc_barrier,
 610                               &fsc_with_gc_barrier,
 611                               &cld_scan_closure);
 612   }
 613 
 614   // "evacuate followers".
 615   evacuate_followers.do_void();
 616 
 617   FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
 618   ReferenceProcessor* rp = ref_processor();
 619   rp->setup_policy(clear_all_soft_refs);
 620   ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
 621   const ReferenceProcessorStats& stats =
 622   rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
 623                                     NULL, &pt);
 624   gc_tracer.report_gc_reference_stats(stats);
 625   gc_tracer.report_tenuring_threshold(tenuring_threshold());
 626   pt.print_all_references();
 627 
 628   assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
 629 
 630   WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
 631 
 632   // Verify that the usage of keep_alive didn't copy any objects.
 633   assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
 634 
 635   if (!_promotion_failed) {
 636     // Swap the survivor spaces.
 637     eden()->clear(SpaceDecorator::Mangle);
 638     from()->clear(SpaceDecorator::Mangle);
 639     if (ZapUnusedHeapArea) {
 640       // This is now done here because of the piece-meal mangling which
 641       // can check for valid mangling at intermediate points in the
 642       // collection(s).  When a young collection fails to collect
 643       // sufficient space resizing of the young generation can occur
 644       // an redistribute the spaces in the young generation.  Mangle
 645       // here so that unzapped regions don't get distributed to
 646       // other spaces.
 647       to()->mangle_unused_area();
 648     }
 649     swap_spaces();
 650 
 651     assert(to()->is_empty(), "to space should be empty now");
 652 
 653     adjust_desired_tenuring_threshold();
 654 
 655     // A successful scavenge should restart the GC time limit count which is
 656     // for full GC's.
 657     AdaptiveSizePolicy* size_policy = heap->size_policy();
 658     size_policy->reset_gc_overhead_limit_count();
 659     assert(!heap->incremental_collection_failed(), "Should be clear");
 660   } else {
 661     assert(_promo_failure_scan_stack.is_empty(), "post condition");
 662     _promo_failure_scan_stack.clear(true); // Clear cached segments.
 663 
 664     remove_forwarding_pointers();
 665     log_info(gc, promotion)("Promotion failed");
 666     // Add to-space to the list of space to compact
 667     // when a promotion failure has occurred.  In that
 668     // case there can be live objects in to-space
 669     // as a result of a partial evacuation of eden
 670     // and from-space.
 671     swap_spaces();   // For uniformity wrt ParNewGeneration.
 672     from()->set_next_compaction_space(to());
 673     heap->set_incremental_collection_failed();
 674 
 675     // Inform the next generation that a promotion failure occurred.
 676     _old_gen->promotion_failure_occurred();
 677     gc_tracer.report_promotion_failed(_promotion_failed_info);
 678 
 679     // Reset the PromotionFailureALot counters.
 680     NOT_PRODUCT(heap->reset_promotion_should_fail();)
 681   }
 682   // We should have processed and cleared all the preserved marks.
 683   _preserved_marks_set.reclaim();
 684   // set new iteration safe limit for the survivor spaces
 685   from()->set_concurrent_iteration_safe_limit(from()->top());
 686   to()->set_concurrent_iteration_safe_limit(to()->top());
 687 
 688   // We need to use a monotonically non-decreasing time in ms
 689   // or we will see time-warp warnings and os::javaTimeMillis()
 690   // does not guarantee monotonicity.
 691   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 692   update_time_of_last_gc(now);
 693 
 694   heap->trace_heap_after_gc(&gc_tracer);
 695 
 696   _gc_timer->register_gc_end();
 697 
 698   gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
 699 }
 700 
 701 void DefNewGeneration::init_assuming_no_promotion_failure() {
 702   _promotion_failed = false;
 703   _promotion_failed_info.reset();
 704   from()->set_next_compaction_space(NULL);
 705 }
 706 
 707 void DefNewGeneration::remove_forwarding_pointers() {
 708   RemoveForwardedPointerClosure rspc;
 709   eden()->object_iterate(&rspc);
 710   from()->object_iterate(&rspc);
 711   restore_preserved_marks();
 712 }
 713 
 714 void DefNewGeneration::restore_preserved_marks() {
 715   SharedRestorePreservedMarksTaskExecutor task_executor(NULL);
 716   _preserved_marks_set.restore(&task_executor);
 717 }
 718 
 719 void DefNewGeneration::handle_promotion_failure(oop old) {
 720   log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
 721 
 722   _promotion_failed = true;
 723   _promotion_failed_info.register_copy_failure(old->size());
 724   _preserved_marks_set.get()->push_if_necessary(old, old->mark_raw());
 725   // forward to self
 726   old->forward_to(old);
 727 
 728   _promo_failure_scan_stack.push(old);
 729 
 730   if (!_promo_failure_drain_in_progress) {
 731     // prevent recursion in copy_to_survivor_space()
 732     _promo_failure_drain_in_progress = true;
 733     drain_promo_failure_scan_stack();
 734     _promo_failure_drain_in_progress = false;
 735   }
 736 }
 737 
 738 oop DefNewGeneration::copy_to_survivor_space(oop old) {
 739   assert(is_in_reserved(old) && !old->is_forwarded(),
 740          "shouldn't be scavenging this oop");
 741   size_t s = old->size();
 742   oop obj = NULL;
 743 
 744   // Try allocating obj in to-space (unless too old)
 745   if (old->age() < tenuring_threshold()) {
 746     obj = (oop) to()->allocate_aligned(s);
 747   }
 748 
 749   // Otherwise try allocating obj tenured
 750   if (obj == NULL) {
 751     obj = _old_gen->promote(old, s);
 752     if (obj == NULL) {
 753       handle_promotion_failure(old);
 754       return old;
 755     }
 756   } else {
 757     // Prefetch beyond obj
 758     const intx interval = PrefetchCopyIntervalInBytes;
 759     Prefetch::write(obj, interval);
 760 
 761     // Copy obj
 762     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
 763 
 764     // Increment age if obj still in new generation
 765     obj->incr_age();
 766     age_table()->add(obj, s);
 767   }
 768 
 769   // Done, insert forward pointer to obj in this header
 770   old->forward_to(obj);
 771 
 772   return obj;
 773 }
 774 
 775 void DefNewGeneration::drain_promo_failure_scan_stack() {
 776   while (!_promo_failure_scan_stack.is_empty()) {
 777      oop obj = _promo_failure_scan_stack.pop();
 778      obj->oop_iterate(_promo_failure_scan_stack_closure);
 779   }
 780 }
 781 
 782 void DefNewGeneration::save_marks() {
 783   eden()->set_saved_mark();
 784   to()->set_saved_mark();
 785   from()->set_saved_mark();
 786 }
 787 
 788 
 789 void DefNewGeneration::reset_saved_marks() {
 790   eden()->reset_saved_mark();
 791   to()->reset_saved_mark();
 792   from()->reset_saved_mark();
 793 }
 794 
 795 
 796 bool DefNewGeneration::no_allocs_since_save_marks() {
 797   assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
 798   assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
 799   return to()->saved_mark_at_top();
 800 }
 801 
 802 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
 803                                          size_t max_alloc_words) {
 804   if (requestor == this || _promotion_failed) {
 805     return;
 806   }
 807   assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
 808 
 809   /* $$$ Assert this?  "trace" is a "MarkSweep" function so that's not appropriate.
 810   if (to_space->top() > to_space->bottom()) {
 811     trace("to_space not empty when contribute_scratch called");
 812   }
 813   */
 814 
 815   ContiguousSpace* to_space = to();
 816   assert(to_space->end() >= to_space->top(), "pointers out of order");
 817   size_t free_words = pointer_delta(to_space->end(), to_space->top());
 818   if (free_words >= MinFreeScratchWords) {
 819     ScratchBlock* sb = (ScratchBlock*)to_space->top();
 820     sb->num_words = free_words;
 821     sb->next = list;
 822     list = sb;
 823   }
 824 }
 825 
 826 void DefNewGeneration::reset_scratch() {
 827   // If contributing scratch in to_space, mangle all of
 828   // to_space if ZapUnusedHeapArea.  This is needed because
 829   // top is not maintained while using to-space as scratch.
 830   if (ZapUnusedHeapArea) {
 831     to()->mangle_unused_area_complete();
 832   }
 833 }
 834 
 835 bool DefNewGeneration::collection_attempt_is_safe() {
 836   if (!to()->is_empty()) {
 837     log_trace(gc)(":: to is not empty ::");
 838     return false;
 839   }
 840   if (_old_gen == NULL) {
 841     GenCollectedHeap* gch = GenCollectedHeap::heap();
 842     _old_gen = gch->old_gen();
 843   }
 844   return _old_gen->promotion_attempt_is_safe(used());
 845 }
 846 
 847 void DefNewGeneration::gc_epilogue(bool full) {
 848   DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
 849 
 850   assert(!GCLocker::is_active(), "We should not be executing here");
 851   // Check if the heap is approaching full after a collection has
 852   // been done.  Generally the young generation is empty at
 853   // a minimum at the end of a collection.  If it is not, then
 854   // the heap is approaching full.
 855   GenCollectedHeap* gch = GenCollectedHeap::heap();
 856   if (full) {
 857     DEBUG_ONLY(seen_incremental_collection_failed = false;)
 858     if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
 859       log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
 860                             GCCause::to_string(gch->gc_cause()));
 861       gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
 862       set_should_allocate_from_space(); // we seem to be running out of space
 863     } else {
 864       log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
 865                             GCCause::to_string(gch->gc_cause()));
 866       gch->clear_incremental_collection_failed(); // We just did a full collection
 867       clear_should_allocate_from_space(); // if set
 868     }
 869   } else {
 870 #ifdef ASSERT
 871     // It is possible that incremental_collection_failed() == true
 872     // here, because an attempted scavenge did not succeed. The policy
 873     // is normally expected to cause a full collection which should
 874     // clear that condition, so we should not be here twice in a row
 875     // with incremental_collection_failed() == true without having done
 876     // a full collection in between.
 877     if (!seen_incremental_collection_failed &&
 878         gch->incremental_collection_failed()) {
 879       log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
 880                             GCCause::to_string(gch->gc_cause()));
 881       seen_incremental_collection_failed = true;
 882     } else if (seen_incremental_collection_failed) {
 883       log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
 884                             GCCause::to_string(gch->gc_cause()));
 885       assert(gch->gc_cause() == GCCause::_scavenge_alot ||
 886              !gch->incremental_collection_failed(),
 887              "Twice in a row");
 888       seen_incremental_collection_failed = false;
 889     }
 890 #endif // ASSERT
 891   }
 892 
 893   if (ZapUnusedHeapArea) {
 894     eden()->check_mangled_unused_area_complete();
 895     from()->check_mangled_unused_area_complete();
 896     to()->check_mangled_unused_area_complete();
 897   }
 898 
 899   if (!CleanChunkPoolAsync) {
 900     Chunk::clean_chunk_pool();
 901   }
 902 
 903   // update the generation and space performance counters
 904   update_counters();
 905   gch->counters()->update_counters();
 906 }
 907 
 908 void DefNewGeneration::record_spaces_top() {
 909   assert(ZapUnusedHeapArea, "Not mangling unused space");
 910   eden()->set_top_for_allocations();
 911   to()->set_top_for_allocations();
 912   from()->set_top_for_allocations();
 913 }
 914 
 915 void DefNewGeneration::ref_processor_init() {
 916   Generation::ref_processor_init();
 917 }
 918 
 919 
 920 void DefNewGeneration::update_counters() {
 921   if (UsePerfData) {
 922     _eden_counters->update_all();
 923     _from_counters->update_all();
 924     _to_counters->update_all();
 925     _gen_counters->update_all();
 926   }
 927 }
 928 
 929 void DefNewGeneration::verify() {
 930   eden()->verify();
 931   from()->verify();
 932     to()->verify();
 933 }
 934 
 935 void DefNewGeneration::print_on(outputStream* st) const {
 936   Generation::print_on(st);
 937   st->print("  eden");
 938   eden()->print_on(st);
 939   st->print("  from");
 940   from()->print_on(st);
 941   st->print("  to  ");
 942   to()->print_on(st);
 943 }
 944 
 945 
 946 const char* DefNewGeneration::name() const {
 947   return "def new generation";
 948 }
 949 
 950 // Moved from inline file as they are not called inline
 951 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
 952   return eden();
 953 }
 954 
 955 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
 956   // This is the slow-path allocation for the DefNewGeneration.
 957   // Most allocations are fast-path in compiled code.
 958   // We try to allocate from the eden.  If that works, we are happy.
 959   // Note that since DefNewGeneration supports lock-free allocation, we
 960   // have to use it here, as well.
 961   HeapWord* result = eden()->par_allocate(word_size);
 962   if (result != NULL) {
 963     if (_old_gen != NULL) {
 964       _old_gen->sample_eden_chunk();
 965     }
 966   } else {
 967     // If the eden is full and the last collection bailed out, we are running
 968     // out of heap space, and we try to allocate the from-space, too.
 969     // allocate_from_space can't be inlined because that would introduce a
 970     // circular dependency at compile time.
 971     result = allocate_from_space(word_size);
 972   }
 973   return result;
 974 }
 975 
 976 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
 977                                          bool is_tlab) {
 978   HeapWord* res = eden()->par_allocate(word_size);
 979   if (_old_gen != NULL) {
 980     _old_gen->sample_eden_chunk();
 981   }
 982   return res;
 983 }
 984 
 985 size_t DefNewGeneration::tlab_capacity() const {
 986   return eden()->capacity();
 987 }
 988 
 989 size_t DefNewGeneration::tlab_used() const {
 990   return eden()->used();
 991 }
 992 
 993 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
 994   return unsafe_max_alloc_nogc();
 995 }