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/shared/adaptiveSizePolicy.hpp"
  28 #include "gc/shared/ageTable.inline.hpp"
  29 #include "gc/shared/cardTableRS.hpp"
  30 #include "gc/shared/collectorCounters.hpp"
  31 #include "gc/shared/gcHeapSummary.hpp"
  32 #include "gc/shared/gcLocker.hpp"
  33 #include "gc/shared/gcPolicyCounters.hpp"
  34 #include "gc/shared/gcTimer.hpp"
  35 #include "gc/shared/gcTrace.hpp"
  36 #include "gc/shared/gcTraceTime.inline.hpp"
  37 #include "gc/shared/genCollectedHeap.hpp"
  38 #include "gc/shared/genOopClosures.inline.hpp"
  39 #include "gc/shared/generationSpec.hpp"
  40 #include "gc/shared/preservedMarks.inline.hpp"
  41 #include "gc/shared/referencePolicy.hpp"
  42 #include "gc/shared/space.inline.hpp"
  43 #include "gc/shared/spaceDecorator.hpp"
  44 #include "gc/shared/strongRootsScope.hpp"
  45 #include "gc/shared/weakProcessor.hpp"
  46 #include "logging/log.hpp"
  47 #include "memory/iterator.hpp"
  48 #include "memory/resourceArea.hpp"
  49 #include "oops/instanceRefKlass.hpp"
  50 #include "oops/oop.inline.hpp"
  51 #include "runtime/atomic.hpp"
  52 #include "runtime/java.hpp"
  53 #include "runtime/prefetch.inline.hpp"
  54 #include "runtime/thread.inline.hpp"
  55 #include "utilities/align.hpp"
  56 #include "utilities/copy.hpp"
  57 #include "utilities/globalDefinitions.hpp"
  58 #include "utilities/stack.inline.hpp"
  59 #if INCLUDE_ALL_GCS
  60 #include "gc/cms/parOopClosures.hpp"
  61 #endif
  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::ParNew ||
  70          _young_gen->kind() == Generation::DefNew, "Expected the young generation here");
  71 }
  72 
  73 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
  74   return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded();
  75 }
  76 
  77 DefNewGeneration::KeepAliveClosure::
  78 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
  79   _rs = GenCollectedHeap::heap()->rem_set();
  80 }
  81 
  82 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  83 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  84 
  85 
  86 DefNewGeneration::FastKeepAliveClosure::
  87 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
  88   DefNewGeneration::KeepAliveClosure(cl) {
  89   _boundary = g->reserved().end();
  90 }
  91 
  92 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  93 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  94 
  95 DefNewGeneration::EvacuateFollowersClosure::
  96 EvacuateFollowersClosure(GenCollectedHeap* gch,
  97                          ScanClosure* cur,
  98                          ScanClosure* older) :
  99   _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
 100 {}
 101 
 102 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
 103   do {
 104     _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
 105   } while (!_gch->no_allocs_since_save_marks());
 106 }
 107 
 108 DefNewGeneration::FastEvacuateFollowersClosure::
 109 FastEvacuateFollowersClosure(GenCollectedHeap* gch,
 110                              FastScanClosure* cur,
 111                              FastScanClosure* older) :
 112   _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
 113 {
 114   assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew");
 115   _young_gen = (DefNewGeneration*)_gch->young_gen();
 116 }
 117 
 118 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
 119   do {
 120     _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
 121   } while (!_gch->no_allocs_since_save_marks());
 122   guarantee(_young_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
 123 }
 124 
 125 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
 126     OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 127 {
 128   _boundary = _g->reserved().end();
 129 }
 130 
 131 void ScanClosure::do_oop(oop* p)       { ScanClosure::do_oop_work(p); }
 132 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
 133 
 134 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
 135     OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 136 {
 137   _boundary = _g->reserved().end();
 138 }
 139 
 140 void FastScanClosure::do_oop(oop* p)       { FastScanClosure::do_oop_work(p); }
 141 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
 142 
 143 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
 144   NOT_PRODUCT(ResourceMark rm);
 145   log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
 146                                   p2i(cld),
 147                                   cld->loader_name(),
 148                                   cld->has_modified_oops() ? "true" : "false");
 149 
 150   // If the cld has not been dirtied we know that there's
 151   // no references into  the young gen and we can skip it.
 152   if (cld->has_modified_oops()) {
 153     if (_accumulate_modified_oops) {
 154       cld->accumulate_modified_oops();
 155     }
 156 
 157     // Tell the closure which CLD is being scanned so that it can be dirtied
 158     // if oops are left pointing into the young gen.
 159     _scavenge_closure->set_scanned_cld(cld);
 160 
 161     // Clean the cld since we're going to scavenge all the metadata.
 162     cld->oops_do(_scavenge_closure, false, /*clear_modified_oops*/true);
 163 
 164     _scavenge_closure->set_scanned_cld(NULL);
 165   }
 166 }
 167 
 168 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
 169   _g(g)
 170 {
 171   _boundary = _g->reserved().end();
 172 }
 173 
 174 void ScanWeakRefClosure::do_oop(oop* p)       { ScanWeakRefClosure::do_oop_work(p); }
 175 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
 176 
 177 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
 178                                    size_t initial_size,
 179                                    const char* policy)
 180   : Generation(rs, initial_size),
 181     _preserved_marks_set(false /* in_c_heap */),
 182     _promo_failure_drain_in_progress(false),
 183     _should_allocate_from_space(false)
 184 {
 185   MemRegion cmr((HeapWord*)_virtual_space.low(),
 186                 (HeapWord*)_virtual_space.high());
 187   GenCollectedHeap* gch = GenCollectedHeap::heap();
 188 
 189   gch->rem_set()->resize_covered_region(cmr);
 190 
 191   _eden_space = new ContiguousSpace();
 192   _from_space = new ContiguousSpace();
 193   _to_space   = new ContiguousSpace();
 194 
 195   if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
 196     vm_exit_during_initialization("Could not allocate a new gen space");
 197   }
 198 
 199   // Compute the maximum eden and survivor space sizes. These sizes
 200   // are computed assuming the entire reserved space is committed.
 201   // These values are exported as performance counters.
 202   uintx alignment = gch->collector_policy()->space_alignment();
 203   uintx size = _virtual_space.reserved_size();
 204   _max_survivor_size = compute_survivor_size(size, alignment);
 205   _max_eden_size = size - (2*_max_survivor_size);
 206 
 207   // allocate the performance counters
 208   GenCollectorPolicy* gcp = gch->gen_policy();
 209 
 210   // Generation counters -- generation 0, 3 subspaces
 211   _gen_counters = new GenerationCounters("new", 0, 3,
 212       gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
 213   _gc_counters = new CollectorCounters(policy, 0);
 214 
 215   _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
 216                                       _gen_counters);
 217   _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
 218                                       _gen_counters);
 219   _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
 220                                     _gen_counters);
 221 
 222   compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
 223   update_counters();
 224   _old_gen = NULL;
 225   _tenuring_threshold = MaxTenuringThreshold;
 226   _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
 227 
 228   _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
 229 }
 230 
 231 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
 232                                                 bool clear_space,
 233                                                 bool mangle_space) {
 234   uintx alignment =
 235     GenCollectedHeap::heap()->collector_policy()->space_alignment();
 236 
 237   // If the spaces are being cleared (only done at heap initialization
 238   // currently), the survivor spaces need not be empty.
 239   // Otherwise, no care is taken for used areas in the survivor spaces
 240   // so check.
 241   assert(clear_space || (to()->is_empty() && from()->is_empty()),
 242     "Initialization of the survivor spaces assumes these are empty");
 243 
 244   // Compute sizes
 245   uintx size = _virtual_space.committed_size();
 246   uintx survivor_size = compute_survivor_size(size, alignment);
 247   uintx eden_size = size - (2*survivor_size);
 248   assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 249 
 250   if (eden_size < minimum_eden_size) {
 251     // May happen due to 64Kb rounding, if so adjust eden size back up
 252     minimum_eden_size = align_up(minimum_eden_size, alignment);
 253     uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
 254     uintx unaligned_survivor_size =
 255       align_down(maximum_survivor_size, alignment);
 256     survivor_size = MAX2(unaligned_survivor_size, alignment);
 257     eden_size = size - (2*survivor_size);
 258     assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 259     assert(eden_size >= minimum_eden_size, "just checking");
 260   }
 261 
 262   char *eden_start = _virtual_space.low();
 263   char *from_start = eden_start + eden_size;
 264   char *to_start   = from_start + survivor_size;
 265   char *to_end     = to_start   + survivor_size;
 266 
 267   assert(to_end == _virtual_space.high(), "just checking");
 268   assert(Space::is_aligned(eden_start), "checking alignment");
 269   assert(Space::is_aligned(from_start), "checking alignment");
 270   assert(Space::is_aligned(to_start),   "checking alignment");
 271 
 272   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
 273   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
 274   MemRegion toMR  ((HeapWord*)to_start, (HeapWord*)to_end);
 275 
 276   // A minimum eden size implies that there is a part of eden that
 277   // is being used and that affects the initialization of any
 278   // newly formed eden.
 279   bool live_in_eden = minimum_eden_size > 0;
 280 
 281   // If not clearing the spaces, do some checking to verify that
 282   // the space are already mangled.
 283   if (!clear_space) {
 284     // Must check mangling before the spaces are reshaped.  Otherwise,
 285     // the bottom or end of one space may have moved into another
 286     // a failure of the check may not correctly indicate which space
 287     // is not properly mangled.
 288     if (ZapUnusedHeapArea) {
 289       HeapWord* limit = (HeapWord*) _virtual_space.high();
 290       eden()->check_mangled_unused_area(limit);
 291       from()->check_mangled_unused_area(limit);
 292         to()->check_mangled_unused_area(limit);
 293     }
 294   }
 295 
 296   // Reset the spaces for their new regions.
 297   eden()->initialize(edenMR,
 298                      clear_space && !live_in_eden,
 299                      SpaceDecorator::Mangle);
 300   // If clear_space and live_in_eden, we will not have cleared any
 301   // portion of eden above its top. This can cause newly
 302   // expanded space not to be mangled if using ZapUnusedHeapArea.
 303   // We explicitly do such mangling here.
 304   if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
 305     eden()->mangle_unused_area();
 306   }
 307   from()->initialize(fromMR, clear_space, mangle_space);
 308   to()->initialize(toMR, clear_space, mangle_space);
 309 
 310   // Set next compaction spaces.
 311   eden()->set_next_compaction_space(from());
 312   // The to-space is normally empty before a compaction so need
 313   // not be considered.  The exception is during promotion
 314   // failure handling when to-space can contain live objects.
 315   from()->set_next_compaction_space(NULL);
 316 }
 317 
 318 void DefNewGeneration::swap_spaces() {
 319   ContiguousSpace* s = from();
 320   _from_space        = to();
 321   _to_space          = s;
 322   eden()->set_next_compaction_space(from());
 323   // The to-space is normally empty before a compaction so need
 324   // not be considered.  The exception is during promotion
 325   // failure handling when to-space can contain live objects.
 326   from()->set_next_compaction_space(NULL);
 327 
 328   if (UsePerfData) {
 329     CSpaceCounters* c = _from_counters;
 330     _from_counters = _to_counters;
 331     _to_counters = c;
 332   }
 333 }
 334 
 335 bool DefNewGeneration::expand(size_t bytes) {
 336   MutexLocker x(ExpandHeap_lock);
 337   HeapWord* prev_high = (HeapWord*) _virtual_space.high();
 338   bool success = _virtual_space.expand_by(bytes);
 339   if (success && ZapUnusedHeapArea) {
 340     // Mangle newly committed space immediately because it
 341     // can be done here more simply that after the new
 342     // spaces have been computed.
 343     HeapWord* new_high = (HeapWord*) _virtual_space.high();
 344     MemRegion mangle_region(prev_high, new_high);
 345     SpaceMangler::mangle_region(mangle_region);
 346   }
 347 
 348   // Do not attempt an expand-to-the reserve size.  The
 349   // request should properly observe the maximum size of
 350   // the generation so an expand-to-reserve should be
 351   // unnecessary.  Also a second call to expand-to-reserve
 352   // value potentially can cause an undue expansion.
 353   // For example if the first expand fail for unknown reasons,
 354   // but the second succeeds and expands the heap to its maximum
 355   // value.
 356   if (GCLocker::is_active()) {
 357     log_debug(gc)("Garbage collection disabled, expanded heap instead");
 358   }
 359 
 360   return success;
 361 }
 362 
 363 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
 364                                                     size_t new_size_before,
 365                                                     size_t alignment) const {
 366   size_t desired_new_size = new_size_before;
 367 
 368   if (NewSizeThreadIncrease > 0) {
 369     int threads_count;
 370     size_t thread_increase_size = 0;
 371 
 372     // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
 373     threads_count = Threads::number_of_non_daemon_threads();
 374     if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
 375       thread_increase_size = threads_count * NewSizeThreadIncrease;
 376 
 377       // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
 378       if (new_size_candidate <= max_uintx - thread_increase_size) {
 379         new_size_candidate += thread_increase_size;
 380 
 381         // 3. Check an overflow at 'align_up'.
 382         size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
 383         if (new_size_candidate <= aligned_max) {
 384           desired_new_size = align_up(new_size_candidate, alignment);
 385         }
 386       }
 387     }
 388   }
 389 
 390   return desired_new_size;
 391 }
 392 
 393 void DefNewGeneration::compute_new_size() {
 394   // This is called after a GC that includes the old generation, so from-space
 395   // will normally be empty.
 396   // Note that we check both spaces, since if scavenge failed they revert roles.
 397   // If not we bail out (otherwise we would have to relocate the objects).
 398   if (!from()->is_empty() || !to()->is_empty()) {
 399     return;
 400   }
 401 
 402   GenCollectedHeap* gch = GenCollectedHeap::heap();
 403 
 404   size_t old_size = gch->old_gen()->capacity();
 405   size_t new_size_before = _virtual_space.committed_size();
 406   size_t min_new_size = initial_size();
 407   size_t max_new_size = reserved().byte_size();
 408   assert(min_new_size <= new_size_before &&
 409          new_size_before <= max_new_size,
 410          "just checking");
 411   // All space sizes must be multiples of Generation::GenGrain.
 412   size_t alignment = Generation::GenGrain;
 413 
 414   int threads_count = 0;
 415   size_t thread_increase_size = 0;
 416 
 417   size_t new_size_candidate = old_size / NewRatio;
 418   // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
 419   // and reverts to previous value if any overflow happens
 420   size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
 421 
 422   // Adjust new generation size
 423   desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
 424   assert(desired_new_size <= max_new_size, "just checking");
 425 
 426   bool changed = false;
 427   if (desired_new_size > new_size_before) {
 428     size_t change = desired_new_size - new_size_before;
 429     assert(change % alignment == 0, "just checking");
 430     if (expand(change)) {
 431        changed = true;
 432     }
 433     // If the heap failed to expand to the desired size,
 434     // "changed" will be false.  If the expansion failed
 435     // (and at this point it was expected to succeed),
 436     // ignore the failure (leaving "changed" as false).
 437   }
 438   if (desired_new_size < new_size_before && eden()->is_empty()) {
 439     // bail out of shrinking if objects in eden
 440     size_t change = new_size_before - desired_new_size;
 441     assert(change % alignment == 0, "just checking");
 442     _virtual_space.shrink_by(change);
 443     changed = true;
 444   }
 445   if (changed) {
 446     // The spaces have already been mangled at this point but
 447     // may not have been cleared (set top = bottom) and should be.
 448     // Mangling was done when the heap was being expanded.
 449     compute_space_boundaries(eden()->used(),
 450                              SpaceDecorator::Clear,
 451                              SpaceDecorator::DontMangle);
 452     MemRegion cmr((HeapWord*)_virtual_space.low(),
 453                   (HeapWord*)_virtual_space.high());
 454     gch->rem_set()->resize_covered_region(cmr);
 455 
 456     log_debug(gc, ergo, heap)(
 457         "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
 458         new_size_before/K, _virtual_space.committed_size()/K,
 459         eden()->capacity()/K, from()->capacity()/K);
 460     log_trace(gc, ergo, heap)(
 461         "  [allowed " SIZE_FORMAT "K extra for %d threads]",
 462           thread_increase_size/K, threads_count);
 463       }
 464 }
 465 
 466 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
 467   assert(false, "NYI -- are you sure you want to call this?");
 468 }
 469 
 470 
 471 size_t DefNewGeneration::capacity() const {
 472   return eden()->capacity()
 473        + from()->capacity();  // to() is only used during scavenge
 474 }
 475 
 476 
 477 size_t DefNewGeneration::used() const {
 478   return eden()->used()
 479        + from()->used();      // to() is only used during scavenge
 480 }
 481 
 482 
 483 size_t DefNewGeneration::free() const {
 484   return eden()->free()
 485        + from()->free();      // to() is only used during scavenge
 486 }
 487 
 488 size_t DefNewGeneration::max_capacity() const {
 489   const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
 490   const size_t reserved_bytes = reserved().byte_size();
 491   return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
 492 }
 493 
 494 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
 495   return eden()->free();
 496 }
 497 
 498 size_t DefNewGeneration::capacity_before_gc() const {
 499   return eden()->capacity();
 500 }
 501 
 502 size_t DefNewGeneration::contiguous_available() const {
 503   return eden()->free();
 504 }
 505 
 506 
 507 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
 508 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
 509 
 510 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
 511   eden()->object_iterate(blk);
 512   from()->object_iterate(blk);
 513 }
 514 
 515 
 516 void DefNewGeneration::space_iterate(SpaceClosure* blk,
 517                                      bool usedOnly) {
 518   blk->do_space(eden());
 519   blk->do_space(from());
 520   blk->do_space(to());
 521 }
 522 
 523 // The last collection bailed out, we are running out of heap space,
 524 // so we try to allocate the from-space, too.
 525 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
 526   bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
 527 
 528   // If the Heap_lock is not locked by this thread, this will be called
 529   // again later with the Heap_lock held.
 530   bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
 531 
 532   HeapWord* result = NULL;
 533   if (do_alloc) {
 534     result = from()->allocate(size);
 535   }
 536 
 537   log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):  will_fail: %s  heap_lock: %s  free: " SIZE_FORMAT "%s%s returns %s",
 538                         size,
 539                         GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
 540                           "true" : "false",
 541                         Heap_lock->is_locked() ? "locked" : "unlocked",
 542                         from()->free(),
 543                         should_try_alloc ? "" : "  should_allocate_from_space: NOT",
 544                         do_alloc ? "  Heap_lock is not owned by self" : "",
 545                         result == NULL ? "NULL" : "object");
 546 
 547   return result;
 548 }
 549 
 550 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
 551                                                 bool   is_tlab,
 552                                                 bool   parallel) {
 553   // We don't attempt to expand the young generation (but perhaps we should.)
 554   return allocate(size, is_tlab);
 555 }
 556 
 557 void DefNewGeneration::adjust_desired_tenuring_threshold() {
 558   // Set the desired survivor size to half the real survivor space
 559   size_t const survivor_capacity = to()->capacity() / HeapWordSize;
 560   size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
 561 
 562   _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
 563 
 564   if (UsePerfData) {
 565     GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
 566     gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
 567     gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
 568   }
 569 
 570   age_table()->print_age_table(_tenuring_threshold);
 571 }
 572 
 573 void DefNewGeneration::collect(bool   full,
 574                                bool   clear_all_soft_refs,
 575                                size_t size,
 576                                bool   is_tlab) {
 577   assert(full || size > 0, "otherwise we don't want to collect");
 578 
 579   GenCollectedHeap* gch = GenCollectedHeap::heap();
 580 
 581   _gc_timer->register_gc_start();
 582   DefNewTracer gc_tracer;
 583   gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
 584 
 585   _old_gen = gch->old_gen();
 586 
 587   // If the next generation is too full to accommodate promotion
 588   // from this generation, pass on collection; let the next generation
 589   // do it.
 590   if (!collection_attempt_is_safe()) {
 591     log_trace(gc)(":: Collection attempt not safe ::");
 592     gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
 593     return;
 594   }
 595   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 596 
 597   init_assuming_no_promotion_failure();
 598 
 599   GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, gch->gc_cause());
 600 
 601   gch->trace_heap_before_gc(&gc_tracer);
 602 
 603   // These can be shared for all code paths
 604   IsAliveClosure is_alive(this);
 605   ScanWeakRefClosure scan_weak_ref(this);
 606 
 607   age_table()->clear();
 608   to()->clear(SpaceDecorator::Mangle);
 609   // The preserved marks should be empty at the start of the GC.
 610   _preserved_marks_set.init(1);
 611 
 612   gch->rem_set()->prepare_for_younger_refs_iterate(false);
 613 
 614   assert(gch->no_allocs_since_save_marks(),
 615          "save marks have not been newly set.");
 616 
 617   FastScanClosure fsc_with_no_gc_barrier(this, false);
 618   FastScanClosure fsc_with_gc_barrier(this, true);
 619 
 620   CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier,
 621                                   gch->rem_set()->cld_rem_set()->accumulate_modified_oops());
 622 
 623   set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
 624   FastEvacuateFollowersClosure evacuate_followers(gch,
 625                                                   &fsc_with_no_gc_barrier,
 626                                                   &fsc_with_gc_barrier);
 627 
 628   assert(gch->no_allocs_since_save_marks(),
 629          "save marks have not been newly set.");
 630 
 631   {
 632     // DefNew needs to run with n_threads == 0, to make sure the serial
 633     // version of the card table scanning code is used.
 634     // See: CardTableRS::non_clean_card_iterate_possibly_parallel.
 635     StrongRootsScope srs(0);
 636 
 637     gch->young_process_roots(&srs,
 638                              &fsc_with_no_gc_barrier,
 639                              &fsc_with_gc_barrier,
 640                              &cld_scan_closure);
 641   }
 642 
 643   // "evacuate followers".
 644   evacuate_followers.do_void();
 645 
 646   FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
 647   ReferenceProcessor* rp = ref_processor();
 648   rp->setup_policy(clear_all_soft_refs);
 649   ReferenceProcessorPhaseTimes pt(_gc_timer, rp->num_q());
 650   const ReferenceProcessorStats& stats =
 651   rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
 652                                     NULL, &pt);
 653   gc_tracer.report_gc_reference_stats(stats);
 654   gc_tracer.report_tenuring_threshold(tenuring_threshold());
 655   pt.print_all_references();
 656 
 657   assert(gch->no_allocs_since_save_marks(), "save marks have not been newly set.");
 658 
 659   WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
 660 
 661   // Verify that the usage of keep_alive didn't copy any objects.
 662   assert(gch->no_allocs_since_save_marks(), "save marks have not been newly set.");
 663 
 664   if (!_promotion_failed) {
 665     // Swap the survivor spaces.
 666     eden()->clear(SpaceDecorator::Mangle);
 667     from()->clear(SpaceDecorator::Mangle);
 668     if (ZapUnusedHeapArea) {
 669       // This is now done here because of the piece-meal mangling which
 670       // can check for valid mangling at intermediate points in the
 671       // collection(s).  When a young collection fails to collect
 672       // sufficient space resizing of the young generation can occur
 673       // an redistribute the spaces in the young generation.  Mangle
 674       // here so that unzapped regions don't get distributed to
 675       // other spaces.
 676       to()->mangle_unused_area();
 677     }
 678     swap_spaces();
 679 
 680     assert(to()->is_empty(), "to space should be empty now");
 681 
 682     adjust_desired_tenuring_threshold();
 683 
 684     // A successful scavenge should restart the GC time limit count which is
 685     // for full GC's.
 686     AdaptiveSizePolicy* size_policy = gch->size_policy();
 687     size_policy->reset_gc_overhead_limit_count();
 688     assert(!gch->incremental_collection_failed(), "Should be clear");
 689   } else {
 690     assert(_promo_failure_scan_stack.is_empty(), "post condition");
 691     _promo_failure_scan_stack.clear(true); // Clear cached segments.
 692 
 693     remove_forwarding_pointers();
 694     log_info(gc, promotion)("Promotion failed");
 695     // Add to-space to the list of space to compact
 696     // when a promotion failure has occurred.  In that
 697     // case there can be live objects in to-space
 698     // as a result of a partial evacuation of eden
 699     // and from-space.
 700     swap_spaces();   // For uniformity wrt ParNewGeneration.
 701     from()->set_next_compaction_space(to());
 702     gch->set_incremental_collection_failed();
 703 
 704     // Inform the next generation that a promotion failure occurred.
 705     _old_gen->promotion_failure_occurred();
 706     gc_tracer.report_promotion_failed(_promotion_failed_info);
 707 
 708     // Reset the PromotionFailureALot counters.
 709     NOT_PRODUCT(gch->reset_promotion_should_fail();)
 710   }
 711   // We should have processed and cleared all the preserved marks.
 712   _preserved_marks_set.reclaim();
 713   // set new iteration safe limit for the survivor spaces
 714   from()->set_concurrent_iteration_safe_limit(from()->top());
 715   to()->set_concurrent_iteration_safe_limit(to()->top());
 716 
 717   // We need to use a monotonically non-decreasing time in ms
 718   // or we will see time-warp warnings and os::javaTimeMillis()
 719   // does not guarantee monotonicity.
 720   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 721   update_time_of_last_gc(now);
 722 
 723   gch->trace_heap_after_gc(&gc_tracer);
 724 
 725   _gc_timer->register_gc_end();
 726 
 727   gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
 728 }
 729 
 730 void DefNewGeneration::init_assuming_no_promotion_failure() {
 731   _promotion_failed = false;
 732   _promotion_failed_info.reset();
 733   from()->set_next_compaction_space(NULL);
 734 }
 735 
 736 void DefNewGeneration::remove_forwarding_pointers() {
 737   RemoveForwardedPointerClosure rspc;
 738   eden()->object_iterate(&rspc);
 739   from()->object_iterate(&rspc);
 740   restore_preserved_marks();
 741 }
 742 
 743 void DefNewGeneration::restore_preserved_marks() {
 744   SharedRestorePreservedMarksTaskExecutor task_executor(NULL);
 745   _preserved_marks_set.restore(&task_executor);
 746 }
 747 
 748 void DefNewGeneration::handle_promotion_failure(oop old) {
 749   log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
 750 
 751   _promotion_failed = true;
 752   _promotion_failed_info.register_copy_failure(old->size());
 753   _preserved_marks_set.get()->push_if_necessary(old, old->mark());
 754   // forward to self
 755   old->forward_to(old);
 756 
 757   _promo_failure_scan_stack.push(old);
 758 
 759   if (!_promo_failure_drain_in_progress) {
 760     // prevent recursion in copy_to_survivor_space()
 761     _promo_failure_drain_in_progress = true;
 762     drain_promo_failure_scan_stack();
 763     _promo_failure_drain_in_progress = false;
 764   }
 765 }
 766 
 767 oop DefNewGeneration::copy_to_survivor_space(oop old) {
 768   assert(is_in_reserved(old) && !old->is_forwarded(),
 769          "shouldn't be scavenging this oop");
 770   size_t s = old->size();
 771   oop obj = NULL;
 772 
 773   // Try allocating obj in to-space (unless too old)
 774   if (old->age() < tenuring_threshold()) {
 775     obj = (oop) to()->allocate_aligned(s);
 776   }
 777 
 778   // Otherwise try allocating obj tenured
 779   if (obj == NULL) {
 780     obj = _old_gen->promote(old, s);
 781     if (obj == NULL) {
 782       handle_promotion_failure(old);
 783       return old;
 784     }
 785   } else {
 786     // Prefetch beyond obj
 787     const intx interval = PrefetchCopyIntervalInBytes;
 788     Prefetch::write(obj, interval);
 789 
 790     // Copy obj
 791     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
 792 
 793     // Increment age if obj still in new generation
 794     obj->incr_age();
 795     age_table()->add(obj, s);
 796   }
 797 
 798   // Done, insert forward pointer to obj in this header
 799   old->forward_to(obj);
 800 
 801   return obj;
 802 }
 803 
 804 void DefNewGeneration::drain_promo_failure_scan_stack() {
 805   while (!_promo_failure_scan_stack.is_empty()) {
 806      oop obj = _promo_failure_scan_stack.pop();
 807      obj->oop_iterate(_promo_failure_scan_stack_closure);
 808   }
 809 }
 810 
 811 void DefNewGeneration::save_marks() {
 812   eden()->set_saved_mark();
 813   to()->set_saved_mark();
 814   from()->set_saved_mark();
 815 }
 816 
 817 
 818 void DefNewGeneration::reset_saved_marks() {
 819   eden()->reset_saved_mark();
 820   to()->reset_saved_mark();
 821   from()->reset_saved_mark();
 822 }
 823 
 824 
 825 bool DefNewGeneration::no_allocs_since_save_marks() {
 826   assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
 827   assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
 828   return to()->saved_mark_at_top();
 829 }
 830 
 831 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
 832                                                                 \
 833 void DefNewGeneration::                                         \
 834 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) {   \
 835   cl->set_generation(this);                                     \
 836   eden()->oop_since_save_marks_iterate##nv_suffix(cl);          \
 837   to()->oop_since_save_marks_iterate##nv_suffix(cl);            \
 838   from()->oop_since_save_marks_iterate##nv_suffix(cl);          \
 839   cl->reset_generation();                                       \
 840   save_marks();                                                 \
 841 }
 842 
 843 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
 844 
 845 #undef DefNew_SINCE_SAVE_MARKS_DEFN
 846 
 847 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
 848                                          size_t max_alloc_words) {
 849   if (requestor == this || _promotion_failed) {
 850     return;
 851   }
 852   assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
 853 
 854   /* $$$ Assert this?  "trace" is a "MarkSweep" function so that's not appropriate.
 855   if (to_space->top() > to_space->bottom()) {
 856     trace("to_space not empty when contribute_scratch called");
 857   }
 858   */
 859 
 860   ContiguousSpace* to_space = to();
 861   assert(to_space->end() >= to_space->top(), "pointers out of order");
 862   size_t free_words = pointer_delta(to_space->end(), to_space->top());
 863   if (free_words >= MinFreeScratchWords) {
 864     ScratchBlock* sb = (ScratchBlock*)to_space->top();
 865     sb->num_words = free_words;
 866     sb->next = list;
 867     list = sb;
 868   }
 869 }
 870 
 871 void DefNewGeneration::reset_scratch() {
 872   // If contributing scratch in to_space, mangle all of
 873   // to_space if ZapUnusedHeapArea.  This is needed because
 874   // top is not maintained while using to-space as scratch.
 875   if (ZapUnusedHeapArea) {
 876     to()->mangle_unused_area_complete();
 877   }
 878 }
 879 
 880 bool DefNewGeneration::collection_attempt_is_safe() {
 881   if (!to()->is_empty()) {
 882     log_trace(gc)(":: to is not empty ::");
 883     return false;
 884   }
 885   if (_old_gen == NULL) {
 886     GenCollectedHeap* gch = GenCollectedHeap::heap();
 887     _old_gen = gch->old_gen();
 888   }
 889   return _old_gen->promotion_attempt_is_safe(used());
 890 }
 891 
 892 void DefNewGeneration::gc_epilogue(bool full) {
 893   DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
 894 
 895   assert(!GCLocker::is_active(), "We should not be executing here");
 896   // Check if the heap is approaching full after a collection has
 897   // been done.  Generally the young generation is empty at
 898   // a minimum at the end of a collection.  If it is not, then
 899   // the heap is approaching full.
 900   GenCollectedHeap* gch = GenCollectedHeap::heap();
 901   if (full) {
 902     DEBUG_ONLY(seen_incremental_collection_failed = false;)
 903     if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
 904       log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
 905                             GCCause::to_string(gch->gc_cause()));
 906       gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
 907       set_should_allocate_from_space(); // we seem to be running out of space
 908     } else {
 909       log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
 910                             GCCause::to_string(gch->gc_cause()));
 911       gch->clear_incremental_collection_failed(); // We just did a full collection
 912       clear_should_allocate_from_space(); // if set
 913     }
 914   } else {
 915 #ifdef ASSERT
 916     // It is possible that incremental_collection_failed() == true
 917     // here, because an attempted scavenge did not succeed. The policy
 918     // is normally expected to cause a full collection which should
 919     // clear that condition, so we should not be here twice in a row
 920     // with incremental_collection_failed() == true without having done
 921     // a full collection in between.
 922     if (!seen_incremental_collection_failed &&
 923         gch->incremental_collection_failed()) {
 924       log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
 925                             GCCause::to_string(gch->gc_cause()));
 926       seen_incremental_collection_failed = true;
 927     } else if (seen_incremental_collection_failed) {
 928       log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
 929                             GCCause::to_string(gch->gc_cause()));
 930       assert(gch->gc_cause() == GCCause::_scavenge_alot ||
 931              (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
 932              !gch->incremental_collection_failed(),
 933              "Twice in a row");
 934       seen_incremental_collection_failed = false;
 935     }
 936 #endif // ASSERT
 937   }
 938 
 939   if (ZapUnusedHeapArea) {
 940     eden()->check_mangled_unused_area_complete();
 941     from()->check_mangled_unused_area_complete();
 942     to()->check_mangled_unused_area_complete();
 943   }
 944 
 945   if (!CleanChunkPoolAsync) {
 946     Chunk::clean_chunk_pool();
 947   }
 948 
 949   // update the generation and space performance counters
 950   update_counters();
 951   gch->counters()->update_counters();
 952 }
 953 
 954 void DefNewGeneration::record_spaces_top() {
 955   assert(ZapUnusedHeapArea, "Not mangling unused space");
 956   eden()->set_top_for_allocations();
 957   to()->set_top_for_allocations();
 958   from()->set_top_for_allocations();
 959 }
 960 
 961 void DefNewGeneration::ref_processor_init() {
 962   Generation::ref_processor_init();
 963 }
 964 
 965 
 966 void DefNewGeneration::update_counters() {
 967   if (UsePerfData) {
 968     _eden_counters->update_all();
 969     _from_counters->update_all();
 970     _to_counters->update_all();
 971     _gen_counters->update_all();
 972   }
 973 }
 974 
 975 void DefNewGeneration::verify() {
 976   eden()->verify();
 977   from()->verify();
 978     to()->verify();
 979 }
 980 
 981 void DefNewGeneration::print_on(outputStream* st) const {
 982   Generation::print_on(st);
 983   st->print("  eden");
 984   eden()->print_on(st);
 985   st->print("  from");
 986   from()->print_on(st);
 987   st->print("  to  ");
 988   to()->print_on(st);
 989 }
 990 
 991 
 992 const char* DefNewGeneration::name() const {
 993   return "def new generation";
 994 }
 995 
 996 // Moved from inline file as they are not called inline
 997 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
 998   return eden();
 999 }
1000 
1001 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1002   // This is the slow-path allocation for the DefNewGeneration.
1003   // Most allocations are fast-path in compiled code.
1004   // We try to allocate from the eden.  If that works, we are happy.
1005   // Note that since DefNewGeneration supports lock-free allocation, we
1006   // have to use it here, as well.
1007   HeapWord* result = eden()->par_allocate(word_size);
1008   if (result != NULL) {
1009     if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1010       _old_gen->sample_eden_chunk();
1011     }
1012   } else {
1013     // If the eden is full and the last collection bailed out, we are running
1014     // out of heap space, and we try to allocate the from-space, too.
1015     // allocate_from_space can't be inlined because that would introduce a
1016     // circular dependency at compile time.
1017     result = allocate_from_space(word_size);
1018   }
1019   return result;
1020 }
1021 
1022 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1023                                          bool is_tlab) {
1024   HeapWord* res = eden()->par_allocate(word_size);
1025   if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1026     _old_gen->sample_eden_chunk();
1027   }
1028   return res;
1029 }
1030 
1031 size_t DefNewGeneration::tlab_capacity() const {
1032   return eden()->capacity();
1033 }
1034 
1035 size_t DefNewGeneration::tlab_used() const {
1036   return eden()->used();
1037 }
1038 
1039 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1040   return unsafe_max_alloc_nogc();
1041 }