1 /*
   2  * Copyright (c) 2001, 2018, 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/gcHeapSummary.hpp"
  34 #include "gc/shared/gcLocker.hpp"
  35 #include "gc/shared/gcPolicyCounters.hpp"
  36 #include "gc/shared/gcTimer.hpp"
  37 #include "gc/shared/gcTrace.hpp"
  38 #include "gc/shared/gcTraceTime.inline.hpp"
  39 #include "gc/shared/genOopClosures.inline.hpp"
  40 #include "gc/shared/generationSpec.hpp"
  41 #include "gc/shared/preservedMarks.inline.hpp"
  42 #include "gc/shared/referencePolicy.hpp"
  43 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
  44 #include "gc/shared/space.inline.hpp"
  45 #include "gc/shared/spaceDecorator.hpp"
  46 #include "gc/shared/strongRootsScope.hpp"
  47 #include "gc/shared/weakProcessor.hpp"
  48 #include "logging/log.hpp"
  49 #include "memory/iterator.inline.hpp"
  50 #include "memory/resourceArea.hpp"
  51 #include "oops/instanceRefKlass.hpp"
  52 #include "oops/oop.inline.hpp"
  53 #include "runtime/atomic.hpp"
  54 #include "runtime/java.hpp"
  55 #include "runtime/prefetch.inline.hpp"
  56 #include "runtime/thread.inline.hpp"
  57 #include "utilities/align.hpp"
  58 #include "utilities/copy.hpp"
  59 #include "utilities/globalDefinitions.hpp"
  60 #include "utilities/stack.inline.hpp"
  61 
  62 //
  63 // DefNewGeneration functions.
  64 
  65 // Methods of protected closure types.
  66 
  67 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
  68   assert(_young_gen->kind() == Generation::ParNew ||
  69          _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, false, /*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                                    const char* policy)
 155   : Generation(rs, initial_size),
 156     _preserved_marks_set(false /* in_c_heap */),
 157     _promo_failure_drain_in_progress(false),
 158     _should_allocate_from_space(false)
 159 {
 160   MemRegion cmr((HeapWord*)_virtual_space.low(),
 161                 (HeapWord*)_virtual_space.high());
 162   GenCollectedHeap* gch = GenCollectedHeap::heap();
 163 
 164   gch->rem_set()->resize_covered_region(cmr);
 165 
 166   _eden_space = new ContiguousSpace();
 167   _from_space = new ContiguousSpace();
 168   _to_space   = new ContiguousSpace();
 169 
 170   if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
 171     vm_exit_during_initialization("Could not allocate a new gen space");
 172   }
 173 
 174   // Compute the maximum eden and survivor space sizes. These sizes
 175   // are computed assuming the entire reserved space is committed.
 176   // These values are exported as performance counters.
 177   uintx alignment = gch->collector_policy()->space_alignment();
 178   uintx size = _virtual_space.reserved_size();
 179   _max_survivor_size = compute_survivor_size(size, alignment);
 180   _max_eden_size = size - (2*_max_survivor_size);
 181 
 182   // allocate the performance counters
 183   GenCollectorPolicy* gcp = gch->gen_policy();
 184 
 185   // Generation counters -- generation 0, 3 subspaces
 186   _gen_counters = new GenerationCounters("new", 0, 3,
 187       gcp->min_young_size(), gcp->max_young_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   uintx alignment =
 210     GenCollectedHeap::heap()->collector_policy()->space_alignment();
 211 
 212   // If the spaces are being cleared (only done at heap initialization
 213   // currently), the survivor spaces need not be empty.
 214   // Otherwise, no care is taken for used areas in the survivor spaces
 215   // so check.
 216   assert(clear_space || (to()->is_empty() && from()->is_empty()),
 217     "Initialization of the survivor spaces assumes these are empty");
 218 
 219   // Compute sizes
 220   uintx size = _virtual_space.committed_size();
 221   uintx survivor_size = compute_survivor_size(size, alignment);
 222   uintx eden_size = size - (2*survivor_size);
 223   assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 224 
 225   if (eden_size < minimum_eden_size) {
 226     // May happen due to 64Kb rounding, if so adjust eden size back up
 227     minimum_eden_size = align_up(minimum_eden_size, alignment);
 228     uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
 229     uintx unaligned_survivor_size =
 230       align_down(maximum_survivor_size, alignment);
 231     survivor_size = MAX2(unaligned_survivor_size, alignment);
 232     eden_size = size - (2*survivor_size);
 233     assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 234     assert(eden_size >= minimum_eden_size, "just checking");
 235   }
 236 
 237   char *eden_start = _virtual_space.low();
 238   char *from_start = eden_start + eden_size;
 239   char *to_start   = from_start + survivor_size;
 240   char *to_end     = to_start   + survivor_size;
 241 
 242   assert(to_end == _virtual_space.high(), "just checking");
 243   assert(Space::is_aligned(eden_start), "checking alignment");
 244   assert(Space::is_aligned(from_start), "checking alignment");
 245   assert(Space::is_aligned(to_start),   "checking alignment");
 246 
 247   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
 248   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
 249   MemRegion toMR  ((HeapWord*)to_start, (HeapWord*)to_end);
 250 
 251   // A minimum eden size implies that there is a part of eden that
 252   // is being used and that affects the initialization of any
 253   // newly formed eden.
 254   bool live_in_eden = minimum_eden_size > 0;
 255 
 256   // If not clearing the spaces, do some checking to verify that
 257   // the space are already mangled.
 258   if (!clear_space) {
 259     // Must check mangling before the spaces are reshaped.  Otherwise,
 260     // the bottom or end of one space may have moved into another
 261     // a failure of the check may not correctly indicate which space
 262     // is not properly mangled.
 263     if (ZapUnusedHeapArea) {
 264       HeapWord* limit = (HeapWord*) _virtual_space.high();
 265       eden()->check_mangled_unused_area(limit);
 266       from()->check_mangled_unused_area(limit);
 267         to()->check_mangled_unused_area(limit);
 268     }
 269   }
 270 
 271   // Reset the spaces for their new regions.
 272   eden()->initialize(edenMR,
 273                      clear_space && !live_in_eden,
 274                      SpaceDecorator::Mangle);
 275   // If clear_space and live_in_eden, we will not have cleared any
 276   // portion of eden above its top. This can cause newly
 277   // expanded space not to be mangled if using ZapUnusedHeapArea.
 278   // We explicitly do such mangling here.
 279   if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
 280     eden()->mangle_unused_area();
 281   }
 282   from()->initialize(fromMR, clear_space, mangle_space);
 283   to()->initialize(toMR, clear_space, mangle_space);
 284 
 285   // Set next compaction spaces.
 286   eden()->set_next_compaction_space(from());
 287   // The to-space is normally empty before a compaction so need
 288   // not be considered.  The exception is during promotion
 289   // failure handling when to-space can contain live objects.
 290   from()->set_next_compaction_space(NULL);
 291 }
 292 
 293 void DefNewGeneration::swap_spaces() {
 294   ContiguousSpace* s = from();
 295   _from_space        = to();
 296   _to_space          = s;
 297   eden()->set_next_compaction_space(from());
 298   // The to-space is normally empty before a compaction so need
 299   // not be considered.  The exception is during promotion
 300   // failure handling when to-space can contain live objects.
 301   from()->set_next_compaction_space(NULL);
 302 
 303   if (UsePerfData) {
 304     CSpaceCounters* c = _from_counters;
 305     _from_counters = _to_counters;
 306     _to_counters = c;
 307   }
 308 }
 309 
 310 bool DefNewGeneration::expand(size_t bytes) {
 311   MutexLocker x(ExpandHeap_lock);
 312   HeapWord* prev_high = (HeapWord*) _virtual_space.high();
 313   bool success = _virtual_space.expand_by(bytes);
 314   if (success && ZapUnusedHeapArea) {
 315     // Mangle newly committed space immediately because it
 316     // can be done here more simply that after the new
 317     // spaces have been computed.
 318     HeapWord* new_high = (HeapWord*) _virtual_space.high();
 319     MemRegion mangle_region(prev_high, new_high);
 320     SpaceMangler::mangle_region(mangle_region);
 321   }
 322 
 323   // Do not attempt an expand-to-the reserve size.  The
 324   // request should properly observe the maximum size of
 325   // the generation so an expand-to-reserve should be
 326   // unnecessary.  Also a second call to expand-to-reserve
 327   // value potentially can cause an undue expansion.
 328   // For example if the first expand fail for unknown reasons,
 329   // but the second succeeds and expands the heap to its maximum
 330   // value.
 331   if (GCLocker::is_active()) {
 332     log_debug(gc)("Garbage collection disabled, expanded heap instead");
 333   }
 334 
 335   return success;
 336 }
 337 
 338 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
 339                                                     size_t new_size_before,
 340                                                     size_t alignment) const {
 341   size_t desired_new_size = new_size_before;
 342 
 343   if (NewSizeThreadIncrease > 0) {
 344     int threads_count;
 345     size_t thread_increase_size = 0;
 346 
 347     // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
 348     threads_count = Threads::number_of_non_daemon_threads();
 349     if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
 350       thread_increase_size = threads_count * NewSizeThreadIncrease;
 351 
 352       // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
 353       if (new_size_candidate <= max_uintx - thread_increase_size) {
 354         new_size_candidate += thread_increase_size;
 355 
 356         // 3. Check an overflow at 'align_up'.
 357         size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
 358         if (new_size_candidate <= aligned_max) {
 359           desired_new_size = align_up(new_size_candidate, alignment);
 360         }
 361       }
 362     }
 363   }
 364 
 365   return desired_new_size;
 366 }
 367 
 368 void DefNewGeneration::compute_new_size() {
 369   // This is called after a GC that includes the old generation, so from-space
 370   // will normally be empty.
 371   // Note that we check both spaces, since if scavenge failed they revert roles.
 372   // If not we bail out (otherwise we would have to relocate the objects).
 373   if (!from()->is_empty() || !to()->is_empty()) {
 374     return;
 375   }
 376 
 377   GenCollectedHeap* gch = GenCollectedHeap::heap();
 378 
 379   size_t old_size = gch->old_gen()->capacity();
 380   size_t new_size_before = _virtual_space.committed_size();
 381   size_t min_new_size = initial_size();
 382   size_t max_new_size = reserved().byte_size();
 383   assert(min_new_size <= new_size_before &&
 384          new_size_before <= max_new_size,
 385          "just checking");
 386   // All space sizes must be multiples of Generation::GenGrain.
 387   size_t alignment = Generation::GenGrain;
 388 
 389   int threads_count = 0;
 390   size_t thread_increase_size = 0;
 391 
 392   size_t new_size_candidate = old_size / NewRatio;
 393   // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
 394   // and reverts to previous value if any overflow happens
 395   size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
 396 
 397   // Adjust new generation size
 398   desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
 399   assert(desired_new_size <= max_new_size, "just checking");
 400 
 401   bool changed = false;
 402   if (desired_new_size > new_size_before) {
 403     size_t change = desired_new_size - new_size_before;
 404     assert(change % alignment == 0, "just checking");
 405     if (expand(change)) {
 406        changed = true;
 407     }
 408     // If the heap failed to expand to the desired size,
 409     // "changed" will be false.  If the expansion failed
 410     // (and at this point it was expected to succeed),
 411     // ignore the failure (leaving "changed" as false).
 412   }
 413   if (desired_new_size < new_size_before && eden()->is_empty()) {
 414     // bail out of shrinking if objects in eden
 415     size_t change = new_size_before - desired_new_size;
 416     assert(change % alignment == 0, "just checking");
 417     _virtual_space.shrink_by(change);
 418     changed = true;
 419   }
 420   if (changed) {
 421     // The spaces have already been mangled at this point but
 422     // may not have been cleared (set top = bottom) and should be.
 423     // Mangling was done when the heap was being expanded.
 424     compute_space_boundaries(eden()->used(),
 425                              SpaceDecorator::Clear,
 426                              SpaceDecorator::DontMangle);
 427     MemRegion cmr((HeapWord*)_virtual_space.low(),
 428                   (HeapWord*)_virtual_space.high());
 429     gch->rem_set()->resize_covered_region(cmr);
 430 
 431     log_debug(gc, ergo, heap)(
 432         "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
 433         new_size_before/K, _virtual_space.committed_size()/K,
 434         eden()->capacity()/K, from()->capacity()/K);
 435     log_trace(gc, ergo, heap)(
 436         "  [allowed " SIZE_FORMAT "K extra for %d threads]",
 437           thread_increase_size/K, threads_count);
 438       }
 439 }
 440 
 441 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
 442   assert(false, "NYI -- are you sure you want to call this?");
 443 }
 444 
 445 
 446 size_t DefNewGeneration::capacity() const {
 447   return eden()->capacity()
 448        + from()->capacity();  // to() is only used during scavenge
 449 }
 450 
 451 
 452 size_t DefNewGeneration::used() const {
 453   return eden()->used()
 454        + from()->used();      // to() is only used during scavenge
 455 }
 456 
 457 
 458 size_t DefNewGeneration::free() const {
 459   return eden()->free()
 460        + from()->free();      // to() is only used during scavenge
 461 }
 462 
 463 size_t DefNewGeneration::max_capacity() const {
 464   const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
 465   const size_t reserved_bytes = reserved().byte_size();
 466   return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
 467 }
 468 
 469 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
 470   return eden()->free();
 471 }
 472 
 473 size_t DefNewGeneration::capacity_before_gc() const {
 474   return eden()->capacity();
 475 }
 476 
 477 size_t DefNewGeneration::contiguous_available() const {
 478   return eden()->free();
 479 }
 480 
 481 
 482 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
 483 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
 484 
 485 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
 486   eden()->object_iterate(blk);
 487   from()->object_iterate(blk);
 488 }
 489 
 490 
 491 void DefNewGeneration::space_iterate(SpaceClosure* blk,
 492                                      bool usedOnly) {
 493   blk->do_space(eden());
 494   blk->do_space(from());
 495   blk->do_space(to());
 496 }
 497 
 498 // The last collection bailed out, we are running out of heap space,
 499 // so we try to allocate the from-space, too.
 500 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
 501   bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
 502 
 503   // If the Heap_lock is not locked by this thread, this will be called
 504   // again later with the Heap_lock held.
 505   bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
 506 
 507   HeapWord* result = NULL;
 508   if (do_alloc) {
 509     result = from()->allocate(size);
 510   }
 511 
 512   log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):  will_fail: %s  heap_lock: %s  free: " SIZE_FORMAT "%s%s returns %s",
 513                         size,
 514                         GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
 515                           "true" : "false",
 516                         Heap_lock->is_locked() ? "locked" : "unlocked",
 517                         from()->free(),
 518                         should_try_alloc ? "" : "  should_allocate_from_space: NOT",
 519                         do_alloc ? "  Heap_lock is not owned by self" : "",
 520                         result == NULL ? "NULL" : "object");
 521 
 522   return result;
 523 }
 524 
 525 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
 526                                                 bool   is_tlab,
 527                                                 bool   parallel) {
 528   // We don't attempt to expand the young generation (but perhaps we should.)
 529   return allocate(size, is_tlab);
 530 }
 531 
 532 void DefNewGeneration::adjust_desired_tenuring_threshold() {
 533   // Set the desired survivor size to half the real survivor space
 534   size_t const survivor_capacity = to()->capacity() / HeapWordSize;
 535   size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
 536 
 537   _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
 538 
 539   if (UsePerfData) {
 540     GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
 541     gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
 542     gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
 543   }
 544 
 545   age_table()->print_age_table(_tenuring_threshold);
 546 }
 547 
 548 void DefNewGeneration::collect(bool   full,
 549                                bool   clear_all_soft_refs,
 550                                size_t size,
 551                                bool   is_tlab) {
 552   assert(full || size > 0, "otherwise we don't want to collect");
 553 
 554   SerialHeap* heap = SerialHeap::heap();
 555 
 556   _gc_timer->register_gc_start();
 557   DefNewTracer gc_tracer;
 558   gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
 559 
 560   _old_gen = heap->old_gen();
 561 
 562   // If the next generation is too full to accommodate promotion
 563   // from this generation, pass on collection; let the next generation
 564   // do it.
 565   if (!collection_attempt_is_safe()) {
 566     log_trace(gc)(":: Collection attempt not safe ::");
 567     heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
 568     return;
 569   }
 570   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 571 
 572   init_assuming_no_promotion_failure();
 573 
 574   GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause());
 575 
 576   heap->trace_heap_before_gc(&gc_tracer);
 577 
 578   // These can be shared for all code paths
 579   IsAliveClosure is_alive(this);
 580   ScanWeakRefClosure scan_weak_ref(this);
 581 
 582   age_table()->clear();
 583   to()->clear(SpaceDecorator::Mangle);
 584   // The preserved marks should be empty at the start of the GC.
 585   _preserved_marks_set.init(1);
 586 
 587   heap->rem_set()->prepare_for_younger_refs_iterate(false);
 588 
 589   assert(heap->no_allocs_since_save_marks(),
 590          "save marks have not been newly set.");
 591 
 592   FastScanClosure fsc_with_no_gc_barrier(this, false);
 593   FastScanClosure fsc_with_gc_barrier(this, true);
 594 
 595   CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier,
 596                                   heap->rem_set()->cld_rem_set()->accumulate_modified_oops());
 597 
 598   set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
 599   FastEvacuateFollowersClosure evacuate_followers(heap,
 600                                                   &fsc_with_no_gc_barrier,
 601                                                   &fsc_with_gc_barrier);
 602 
 603   assert(heap->no_allocs_since_save_marks(),
 604          "save marks have not been newly set.");
 605 
 606   {
 607     // DefNew needs to run with n_threads == 0, to make sure the serial
 608     // version of the card table scanning code is used.
 609     // See: CardTableRS::non_clean_card_iterate_possibly_parallel.
 610     StrongRootsScope srs(0);
 611 
 612     heap->young_process_roots(&srs,
 613                               &fsc_with_no_gc_barrier,
 614                               &fsc_with_gc_barrier,
 615                               &cld_scan_closure);
 616   }
 617 
 618   // "evacuate followers".
 619   evacuate_followers.do_void();
 620 
 621   FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
 622   ReferenceProcessor* rp = ref_processor();
 623   rp->setup_policy(clear_all_soft_refs);
 624   ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
 625   const ReferenceProcessorStats& stats =
 626   rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
 627                                     NULL, &pt);
 628   gc_tracer.report_gc_reference_stats(stats);
 629   gc_tracer.report_tenuring_threshold(tenuring_threshold());
 630   pt.print_all_references();
 631 
 632   assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
 633 
 634   WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
 635 
 636   // Verify that the usage of keep_alive didn't copy any objects.
 637   assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
 638 
 639   if (!_promotion_failed) {
 640     // Swap the survivor spaces.
 641     eden()->clear(SpaceDecorator::Mangle);
 642     from()->clear(SpaceDecorator::Mangle);
 643     if (ZapUnusedHeapArea) {
 644       // This is now done here because of the piece-meal mangling which
 645       // can check for valid mangling at intermediate points in the
 646       // collection(s).  When a young collection fails to collect
 647       // sufficient space resizing of the young generation can occur
 648       // an redistribute the spaces in the young generation.  Mangle
 649       // here so that unzapped regions don't get distributed to
 650       // other spaces.
 651       to()->mangle_unused_area();
 652     }
 653     swap_spaces();
 654 
 655     assert(to()->is_empty(), "to space should be empty now");
 656 
 657     adjust_desired_tenuring_threshold();
 658 
 659     // A successful scavenge should restart the GC time limit count which is
 660     // for full GC's.
 661     AdaptiveSizePolicy* size_policy = heap->size_policy();
 662     size_policy->reset_gc_overhead_limit_count();
 663     assert(!heap->incremental_collection_failed(), "Should be clear");
 664   } else {
 665     assert(_promo_failure_scan_stack.is_empty(), "post condition");
 666     _promo_failure_scan_stack.clear(true); // Clear cached segments.
 667 
 668     remove_forwarding_pointers();
 669     log_info(gc, promotion)("Promotion failed");
 670     // Add to-space to the list of space to compact
 671     // when a promotion failure has occurred.  In that
 672     // case there can be live objects in to-space
 673     // as a result of a partial evacuation of eden
 674     // and from-space.
 675     swap_spaces();   // For uniformity wrt ParNewGeneration.
 676     from()->set_next_compaction_space(to());
 677     heap->set_incremental_collection_failed();
 678 
 679     // Inform the next generation that a promotion failure occurred.
 680     _old_gen->promotion_failure_occurred();
 681     gc_tracer.report_promotion_failed(_promotion_failed_info);
 682 
 683     // Reset the PromotionFailureALot counters.
 684     NOT_PRODUCT(heap->reset_promotion_should_fail();)
 685   }
 686   // We should have processed and cleared all the preserved marks.
 687   _preserved_marks_set.reclaim();
 688   // set new iteration safe limit for the survivor spaces
 689   from()->set_concurrent_iteration_safe_limit(from()->top());
 690   to()->set_concurrent_iteration_safe_limit(to()->top());
 691 
 692   // We need to use a monotonically non-decreasing time in ms
 693   // or we will see time-warp warnings and os::javaTimeMillis()
 694   // does not guarantee monotonicity.
 695   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 696   update_time_of_last_gc(now);
 697 
 698   heap->trace_heap_after_gc(&gc_tracer);
 699 
 700   _gc_timer->register_gc_end();
 701 
 702   gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
 703 }
 704 
 705 void DefNewGeneration::init_assuming_no_promotion_failure() {
 706   _promotion_failed = false;
 707   _promotion_failed_info.reset();
 708   from()->set_next_compaction_space(NULL);
 709 }
 710 
 711 void DefNewGeneration::remove_forwarding_pointers() {
 712   RemoveForwardedPointerClosure rspc;
 713   eden()->object_iterate(&rspc);
 714   from()->object_iterate(&rspc);
 715   restore_preserved_marks();
 716 }
 717 
 718 void DefNewGeneration::restore_preserved_marks() {
 719   SharedRestorePreservedMarksTaskExecutor task_executor(NULL);
 720   _preserved_marks_set.restore(&task_executor);
 721 }
 722 
 723 void DefNewGeneration::handle_promotion_failure(oop old) {
 724   log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
 725 
 726   _promotion_failed = true;
 727   _promotion_failed_info.register_copy_failure(old->size());
 728   _preserved_marks_set.get()->push_if_necessary(old, old->mark_raw());
 729   // forward to self
 730   old->forward_to(old);
 731 
 732   _promo_failure_scan_stack.push(old);
 733 
 734   if (!_promo_failure_drain_in_progress) {
 735     // prevent recursion in copy_to_survivor_space()
 736     _promo_failure_drain_in_progress = true;
 737     drain_promo_failure_scan_stack();
 738     _promo_failure_drain_in_progress = false;
 739   }
 740 }
 741 
 742 oop DefNewGeneration::copy_to_survivor_space(oop old) {
 743   assert(is_in_reserved(old) && !old->is_forwarded(),
 744          "shouldn't be scavenging this oop");
 745   size_t s = old->size();
 746   oop obj = NULL;
 747 
 748   // Try allocating obj in to-space (unless too old)
 749   if (old->age() < tenuring_threshold()) {
 750     obj = (oop) to()->allocate_aligned(s);
 751   }
 752 
 753   // Otherwise try allocating obj tenured
 754   if (obj == NULL) {
 755     obj = _old_gen->promote(old, s);
 756     if (obj == NULL) {
 757       handle_promotion_failure(old);
 758       return old;
 759     }
 760   } else {
 761     // Prefetch beyond obj
 762     const intx interval = PrefetchCopyIntervalInBytes;
 763     Prefetch::write(obj, interval);
 764 
 765     // Copy obj
 766     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
 767 
 768     // Increment age if obj still in new generation
 769     obj->incr_age();
 770     age_table()->add(obj, s);
 771   }
 772 
 773   // Done, insert forward pointer to obj in this header
 774   old->forward_to(obj);
 775 
 776   return obj;
 777 }
 778 
 779 void DefNewGeneration::drain_promo_failure_scan_stack() {
 780   while (!_promo_failure_scan_stack.is_empty()) {
 781      oop obj = _promo_failure_scan_stack.pop();
 782      obj->oop_iterate(_promo_failure_scan_stack_closure);
 783   }
 784 }
 785 
 786 void DefNewGeneration::save_marks() {
 787   eden()->set_saved_mark();
 788   to()->set_saved_mark();
 789   from()->set_saved_mark();
 790 }
 791 
 792 
 793 void DefNewGeneration::reset_saved_marks() {
 794   eden()->reset_saved_mark();
 795   to()->reset_saved_mark();
 796   from()->reset_saved_mark();
 797 }
 798 
 799 
 800 bool DefNewGeneration::no_allocs_since_save_marks() {
 801   assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
 802   assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
 803   return to()->saved_mark_at_top();
 804 }
 805 
 806 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
 807                                          size_t max_alloc_words) {
 808   if (requestor == this || _promotion_failed) {
 809     return;
 810   }
 811   assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
 812 
 813   /* $$$ Assert this?  "trace" is a "MarkSweep" function so that's not appropriate.
 814   if (to_space->top() > to_space->bottom()) {
 815     trace("to_space not empty when contribute_scratch called");
 816   }
 817   */
 818 
 819   ContiguousSpace* to_space = to();
 820   assert(to_space->end() >= to_space->top(), "pointers out of order");
 821   size_t free_words = pointer_delta(to_space->end(), to_space->top());
 822   if (free_words >= MinFreeScratchWords) {
 823     ScratchBlock* sb = (ScratchBlock*)to_space->top();
 824     sb->num_words = free_words;
 825     sb->next = list;
 826     list = sb;
 827   }
 828 }
 829 
 830 void DefNewGeneration::reset_scratch() {
 831   // If contributing scratch in to_space, mangle all of
 832   // to_space if ZapUnusedHeapArea.  This is needed because
 833   // top is not maintained while using to-space as scratch.
 834   if (ZapUnusedHeapArea) {
 835     to()->mangle_unused_area_complete();
 836   }
 837 }
 838 
 839 bool DefNewGeneration::collection_attempt_is_safe() {
 840   if (!to()->is_empty()) {
 841     log_trace(gc)(":: to is not empty ::");
 842     return false;
 843   }
 844   if (_old_gen == NULL) {
 845     GenCollectedHeap* gch = GenCollectedHeap::heap();
 846     _old_gen = gch->old_gen();
 847   }
 848   return _old_gen->promotion_attempt_is_safe(used());
 849 }
 850 
 851 void DefNewGeneration::gc_epilogue(bool full) {
 852   DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
 853 
 854   assert(!GCLocker::is_active(), "We should not be executing here");
 855   // Check if the heap is approaching full after a collection has
 856   // been done.  Generally the young generation is empty at
 857   // a minimum at the end of a collection.  If it is not, then
 858   // the heap is approaching full.
 859   GenCollectedHeap* gch = GenCollectedHeap::heap();
 860   if (full) {
 861     DEBUG_ONLY(seen_incremental_collection_failed = false;)
 862     if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
 863       log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
 864                             GCCause::to_string(gch->gc_cause()));
 865       gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
 866       set_should_allocate_from_space(); // we seem to be running out of space
 867     } else {
 868       log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
 869                             GCCause::to_string(gch->gc_cause()));
 870       gch->clear_incremental_collection_failed(); // We just did a full collection
 871       clear_should_allocate_from_space(); // if set
 872     }
 873   } else {
 874 #ifdef ASSERT
 875     // It is possible that incremental_collection_failed() == true
 876     // here, because an attempted scavenge did not succeed. The policy
 877     // is normally expected to cause a full collection which should
 878     // clear that condition, so we should not be here twice in a row
 879     // with incremental_collection_failed() == true without having done
 880     // a full collection in between.
 881     if (!seen_incremental_collection_failed &&
 882         gch->incremental_collection_failed()) {
 883       log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
 884                             GCCause::to_string(gch->gc_cause()));
 885       seen_incremental_collection_failed = true;
 886     } else if (seen_incremental_collection_failed) {
 887       log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
 888                             GCCause::to_string(gch->gc_cause()));
 889       assert(gch->gc_cause() == GCCause::_scavenge_alot ||
 890              (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
 891              !gch->incremental_collection_failed(),
 892              "Twice in a row");
 893       seen_incremental_collection_failed = false;
 894     }
 895 #endif // ASSERT
 896   }
 897 
 898   if (ZapUnusedHeapArea) {
 899     eden()->check_mangled_unused_area_complete();
 900     from()->check_mangled_unused_area_complete();
 901     to()->check_mangled_unused_area_complete();
 902   }
 903 
 904   if (!CleanChunkPoolAsync) {
 905     Chunk::clean_chunk_pool();
 906   }
 907 
 908   // update the generation and space performance counters
 909   update_counters();
 910   gch->counters()->update_counters();
 911 }
 912 
 913 void DefNewGeneration::record_spaces_top() {
 914   assert(ZapUnusedHeapArea, "Not mangling unused space");
 915   eden()->set_top_for_allocations();
 916   to()->set_top_for_allocations();
 917   from()->set_top_for_allocations();
 918 }
 919 
 920 void DefNewGeneration::ref_processor_init() {
 921   Generation::ref_processor_init();
 922 }
 923 
 924 
 925 void DefNewGeneration::update_counters() {
 926   if (UsePerfData) {
 927     _eden_counters->update_all();
 928     _from_counters->update_all();
 929     _to_counters->update_all();
 930     _gen_counters->update_all();
 931   }
 932 }
 933 
 934 void DefNewGeneration::verify() {
 935   eden()->verify();
 936   from()->verify();
 937     to()->verify();
 938 }
 939 
 940 void DefNewGeneration::print_on(outputStream* st) const {
 941   Generation::print_on(st);
 942   st->print("  eden");
 943   eden()->print_on(st);
 944   st->print("  from");
 945   from()->print_on(st);
 946   st->print("  to  ");
 947   to()->print_on(st);
 948 }
 949 
 950 
 951 const char* DefNewGeneration::name() const {
 952   return "def new generation";
 953 }
 954 
 955 // Moved from inline file as they are not called inline
 956 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
 957   return eden();
 958 }
 959 
 960 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
 961   // This is the slow-path allocation for the DefNewGeneration.
 962   // Most allocations are fast-path in compiled code.
 963   // We try to allocate from the eden.  If that works, we are happy.
 964   // Note that since DefNewGeneration supports lock-free allocation, we
 965   // have to use it here, as well.
 966   HeapWord* result = eden()->par_allocate(word_size);
 967   if (result != NULL) {
 968     if (_old_gen != NULL) {
 969       _old_gen->sample_eden_chunk();
 970     }
 971   } else {
 972     // If the eden is full and the last collection bailed out, we are running
 973     // out of heap space, and we try to allocate the from-space, too.
 974     // allocate_from_space can't be inlined because that would introduce a
 975     // circular dependency at compile time.
 976     result = allocate_from_space(word_size);
 977   }
 978   return result;
 979 }
 980 
 981 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
 982                                          bool is_tlab) {
 983   HeapWord* res = eden()->par_allocate(word_size);
 984   if (_old_gen != NULL) {
 985     _old_gen->sample_eden_chunk();
 986   }
 987   return res;
 988 }
 989 
 990 size_t DefNewGeneration::tlab_capacity() const {
 991   return eden()->capacity();
 992 }
 993 
 994 size_t DefNewGeneration::tlab_used() const {
 995   return eden()->used();
 996 }
 997 
 998 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
 999   return unsafe_max_alloc_nogc();
1000 }