1 /*
   2  * Copyright (c) 2001, 2020, 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/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::DefNew, "Expected the young generation here");
  69 }
  70 
  71 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
  72   return cast_from_oop<HeapWord*>(p) >= _young_gen->reserved().end() || p->is_forwarded();
  73 }
  74 
  75 DefNewGeneration::KeepAliveClosure::
  76 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
  77   _rs = GenCollectedHeap::heap()->rem_set();
  78 }
  79 
  80 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  81 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  82 
  83 
  84 DefNewGeneration::FastKeepAliveClosure::
  85 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
  86   DefNewGeneration::KeepAliveClosure(cl) {
  87   _boundary = g->reserved().end();
  88 }
  89 
  90 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  91 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  92 
  93 DefNewGeneration::FastEvacuateFollowersClosure::
  94 FastEvacuateFollowersClosure(SerialHeap* heap,
  95                              FastScanClosure* cur,
  96                              FastScanClosure* older) :
  97   _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older)
  98 {
  99 }
 100 
 101 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
 102   do {
 103     _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older);
 104   } while (!_heap->no_allocs_since_save_marks());
 105   guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
 106 }
 107 
 108 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
 109     OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 110 {
 111   _boundary = _g->reserved().end();
 112 }
 113 
 114 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
 115   NOT_PRODUCT(ResourceMark rm);
 116   log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
 117                                   p2i(cld),
 118                                   cld->loader_name_and_id(),
 119                                   cld->has_modified_oops() ? "true" : "false");
 120 
 121   // If the cld has not been dirtied we know that there's
 122   // no references into  the young gen and we can skip it.
 123   if (cld->has_modified_oops()) {
 124     if (_accumulate_modified_oops) {
 125       cld->accumulate_modified_oops();
 126     }
 127 
 128     // Tell the closure which CLD is being scanned so that it can be dirtied
 129     // if oops are left pointing into the young gen.
 130     _scavenge_closure->set_scanned_cld(cld);
 131 
 132     // Clean the cld since we're going to scavenge all the metadata.
 133     cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
 134 
 135     _scavenge_closure->set_scanned_cld(NULL);
 136   }
 137 }
 138 
 139 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
 140   _g(g)
 141 {
 142   _boundary = _g->reserved().end();
 143 }
 144 
 145 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
 146                                    size_t initial_size,
 147                                    size_t min_size,
 148                                    size_t max_size,
 149                                    const char* policy)
 150   : Generation(rs, initial_size),
 151     _preserved_marks_set(false /* in_c_heap */),
 152     _promo_failure_drain_in_progress(false),
 153     _should_allocate_from_space(false)
 154 {
 155   MemRegion cmr((HeapWord*)_virtual_space.low(),
 156                 (HeapWord*)_virtual_space.high());
 157   GenCollectedHeap* gch = GenCollectedHeap::heap();
 158 
 159   gch->rem_set()->resize_covered_region(cmr);
 160 
 161   _eden_space = new ContiguousSpace();
 162   _from_space = new ContiguousSpace();
 163   _to_space   = new ContiguousSpace();
 164 
 165   // Compute the maximum eden and survivor space sizes. These sizes
 166   // are computed assuming the entire reserved space is committed.
 167   // These values are exported as performance counters.
 168   uintx size = _virtual_space.reserved_size();
 169   _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
 170   _max_eden_size = size - (2*_max_survivor_size);
 171 
 172   // allocate the performance counters
 173 
 174   // Generation counters -- generation 0, 3 subspaces
 175   _gen_counters = new GenerationCounters("new", 0, 3,
 176       min_size, max_size, &_virtual_space);
 177   _gc_counters = new CollectorCounters(policy, 0);
 178 
 179   _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
 180                                       _gen_counters);
 181   _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
 182                                       _gen_counters);
 183   _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
 184                                     _gen_counters);
 185 
 186   compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
 187   update_counters();
 188   _old_gen = NULL;
 189   _tenuring_threshold = MaxTenuringThreshold;
 190   _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
 191 
 192   _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
 193 }
 194 
 195 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
 196                                                 bool clear_space,
 197                                                 bool mangle_space) {
 198   // If the spaces are being cleared (only done at heap initialization
 199   // currently), the survivor spaces need not be empty.
 200   // Otherwise, no care is taken for used areas in the survivor spaces
 201   // so check.
 202   assert(clear_space || (to()->is_empty() && from()->is_empty()),
 203     "Initialization of the survivor spaces assumes these are empty");
 204 
 205   // Compute sizes
 206   uintx size = _virtual_space.committed_size();
 207   uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
 208   uintx eden_size = size - (2*survivor_size);
 209   assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 210 
 211   if (eden_size < minimum_eden_size) {
 212     // May happen due to 64Kb rounding, if so adjust eden size back up
 213     minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
 214     uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
 215     uintx unaligned_survivor_size =
 216       align_down(maximum_survivor_size, SpaceAlignment);
 217     survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
 218     eden_size = size - (2*survivor_size);
 219     assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 220     assert(eden_size >= minimum_eden_size, "just checking");
 221   }
 222 
 223   char *eden_start = _virtual_space.low();
 224   char *from_start = eden_start + eden_size;
 225   char *to_start   = from_start + survivor_size;
 226   char *to_end     = to_start   + survivor_size;
 227 
 228   assert(to_end == _virtual_space.high(), "just checking");
 229   assert(Space::is_aligned(eden_start), "checking alignment");
 230   assert(Space::is_aligned(from_start), "checking alignment");
 231   assert(Space::is_aligned(to_start),   "checking alignment");
 232 
 233   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
 234   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
 235   MemRegion toMR  ((HeapWord*)to_start, (HeapWord*)to_end);
 236 
 237   // A minimum eden size implies that there is a part of eden that
 238   // is being used and that affects the initialization of any
 239   // newly formed eden.
 240   bool live_in_eden = minimum_eden_size > 0;
 241 
 242   // If not clearing the spaces, do some checking to verify that
 243   // the space are already mangled.
 244   if (!clear_space) {
 245     // Must check mangling before the spaces are reshaped.  Otherwise,
 246     // the bottom or end of one space may have moved into another
 247     // a failure of the check may not correctly indicate which space
 248     // is not properly mangled.
 249     if (ZapUnusedHeapArea) {
 250       HeapWord* limit = (HeapWord*) _virtual_space.high();
 251       eden()->check_mangled_unused_area(limit);
 252       from()->check_mangled_unused_area(limit);
 253         to()->check_mangled_unused_area(limit);
 254     }
 255   }
 256 
 257   // Reset the spaces for their new regions.
 258   eden()->initialize(edenMR,
 259                      clear_space && !live_in_eden,
 260                      SpaceDecorator::Mangle);
 261   // If clear_space and live_in_eden, we will not have cleared any
 262   // portion of eden above its top. This can cause newly
 263   // expanded space not to be mangled if using ZapUnusedHeapArea.
 264   // We explicitly do such mangling here.
 265   if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
 266     eden()->mangle_unused_area();
 267   }
 268   from()->initialize(fromMR, clear_space, mangle_space);
 269   to()->initialize(toMR, clear_space, mangle_space);
 270 
 271   // Set next compaction spaces.
 272   eden()->set_next_compaction_space(from());
 273   // The to-space is normally empty before a compaction so need
 274   // not be considered.  The exception is during promotion
 275   // failure handling when to-space can contain live objects.
 276   from()->set_next_compaction_space(NULL);
 277 }
 278 
 279 void DefNewGeneration::swap_spaces() {
 280   ContiguousSpace* s = from();
 281   _from_space        = to();
 282   _to_space          = s;
 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   if (UsePerfData) {
 290     CSpaceCounters* c = _from_counters;
 291     _from_counters = _to_counters;
 292     _to_counters = c;
 293   }
 294 }
 295 
 296 bool DefNewGeneration::expand(size_t bytes) {
 297   MutexLocker x(ExpandHeap_lock);
 298   HeapWord* prev_high = (HeapWord*) _virtual_space.high();
 299   bool success = _virtual_space.expand_by(bytes);
 300   if (success && ZapUnusedHeapArea) {
 301     // Mangle newly committed space immediately because it
 302     // can be done here more simply that after the new
 303     // spaces have been computed.
 304     HeapWord* new_high = (HeapWord*) _virtual_space.high();
 305     MemRegion mangle_region(prev_high, new_high);
 306     SpaceMangler::mangle_region(mangle_region);
 307   }
 308 
 309   // Do not attempt an expand-to-the reserve size.  The
 310   // request should properly observe the maximum size of
 311   // the generation so an expand-to-reserve should be
 312   // unnecessary.  Also a second call to expand-to-reserve
 313   // value potentially can cause an undue expansion.
 314   // For example if the first expand fail for unknown reasons,
 315   // but the second succeeds and expands the heap to its maximum
 316   // value.
 317   if (GCLocker::is_active()) {
 318     log_debug(gc)("Garbage collection disabled, expanded heap instead");
 319   }
 320 
 321   return success;
 322 }
 323 
 324 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
 325                                                     size_t new_size_before,
 326                                                     size_t alignment) const {
 327   size_t desired_new_size = new_size_before;
 328 
 329   if (NewSizeThreadIncrease > 0) {
 330     int threads_count;
 331     size_t thread_increase_size = 0;
 332 
 333     // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
 334     threads_count = Threads::number_of_non_daemon_threads();
 335     if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
 336       thread_increase_size = threads_count * NewSizeThreadIncrease;
 337 
 338       // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
 339       if (new_size_candidate <= max_uintx - thread_increase_size) {
 340         new_size_candidate += thread_increase_size;
 341 
 342         // 3. Check an overflow at 'align_up'.
 343         size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
 344         if (new_size_candidate <= aligned_max) {
 345           desired_new_size = align_up(new_size_candidate, alignment);
 346         }
 347       }
 348     }
 349   }
 350 
 351   return desired_new_size;
 352 }
 353 
 354 void DefNewGeneration::compute_new_size() {
 355   // This is called after a GC that includes the old generation, so from-space
 356   // will normally be empty.
 357   // Note that we check both spaces, since if scavenge failed they revert roles.
 358   // If not we bail out (otherwise we would have to relocate the objects).
 359   if (!from()->is_empty() || !to()->is_empty()) {
 360     return;
 361   }
 362 
 363   GenCollectedHeap* gch = GenCollectedHeap::heap();
 364 
 365   size_t old_size = gch->old_gen()->capacity();
 366   size_t new_size_before = _virtual_space.committed_size();
 367   size_t min_new_size = initial_size();
 368   size_t max_new_size = reserved().byte_size();
 369   assert(min_new_size <= new_size_before &&
 370          new_size_before <= max_new_size,
 371          "just checking");
 372   // All space sizes must be multiples of Generation::GenGrain.
 373   size_t alignment = Generation::GenGrain;
 374 
 375   int threads_count = 0;
 376   size_t thread_increase_size = 0;
 377 
 378   size_t new_size_candidate = old_size / NewRatio;
 379   // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
 380   // and reverts to previous value if any overflow happens
 381   size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
 382 
 383   // Adjust new generation size
 384   desired_new_size = clamp(desired_new_size, min_new_size, max_new_size);
 385   assert(desired_new_size <= max_new_size, "just checking");
 386 
 387   bool changed = false;
 388   if (desired_new_size > new_size_before) {
 389     size_t change = desired_new_size - new_size_before;
 390     assert(change % alignment == 0, "just checking");
 391     if (expand(change)) {
 392        changed = true;
 393     }
 394     // If the heap failed to expand to the desired size,
 395     // "changed" will be false.  If the expansion failed
 396     // (and at this point it was expected to succeed),
 397     // ignore the failure (leaving "changed" as false).
 398   }
 399   if (desired_new_size < new_size_before && eden()->is_empty()) {
 400     // bail out of shrinking if objects in eden
 401     size_t change = new_size_before - desired_new_size;
 402     assert(change % alignment == 0, "just checking");
 403     _virtual_space.shrink_by(change);
 404     changed = true;
 405   }
 406   if (changed) {
 407     // The spaces have already been mangled at this point but
 408     // may not have been cleared (set top = bottom) and should be.
 409     // Mangling was done when the heap was being expanded.
 410     compute_space_boundaries(eden()->used(),
 411                              SpaceDecorator::Clear,
 412                              SpaceDecorator::DontMangle);
 413     MemRegion cmr((HeapWord*)_virtual_space.low(),
 414                   (HeapWord*)_virtual_space.high());
 415     gch->rem_set()->resize_covered_region(cmr);
 416 
 417     log_debug(gc, ergo, heap)(
 418         "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
 419         new_size_before/K, _virtual_space.committed_size()/K,
 420         eden()->capacity()/K, from()->capacity()/K);
 421     log_trace(gc, ergo, heap)(
 422         "  [allowed " SIZE_FORMAT "K extra for %d threads]",
 423           thread_increase_size/K, threads_count);
 424       }
 425 }
 426 
 427 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
 428   assert(false, "NYI -- are you sure you want to call this?");
 429 }
 430 
 431 
 432 size_t DefNewGeneration::capacity() const {
 433   return eden()->capacity()
 434        + from()->capacity();  // to() is only used during scavenge
 435 }
 436 
 437 
 438 size_t DefNewGeneration::used() const {
 439   return eden()->used()
 440        + from()->used();      // to() is only used during scavenge
 441 }
 442 
 443 
 444 size_t DefNewGeneration::free() const {
 445   return eden()->free()
 446        + from()->free();      // to() is only used during scavenge
 447 }
 448 
 449 size_t DefNewGeneration::max_capacity() const {
 450   const size_t reserved_bytes = reserved().byte_size();
 451   return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
 452 }
 453 
 454 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
 455   return eden()->free();
 456 }
 457 
 458 size_t DefNewGeneration::capacity_before_gc() const {
 459   return eden()->capacity();
 460 }
 461 
 462 size_t DefNewGeneration::contiguous_available() const {
 463   return eden()->free();
 464 }
 465 
 466 
 467 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
 468 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
 469 
 470 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
 471   eden()->object_iterate(blk);
 472   from()->object_iterate(blk);
 473 }
 474 
 475 
 476 void DefNewGeneration::space_iterate(SpaceClosure* blk,
 477                                      bool usedOnly) {
 478   blk->do_space(eden());
 479   blk->do_space(from());
 480   blk->do_space(to());
 481 }
 482 
 483 // The last collection bailed out, we are running out of heap space,
 484 // so we try to allocate the from-space, too.
 485 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
 486   bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
 487 
 488   // If the Heap_lock is not locked by this thread, this will be called
 489   // again later with the Heap_lock held.
 490   bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
 491 
 492   HeapWord* result = NULL;
 493   if (do_alloc) {
 494     result = from()->allocate(size);
 495   }
 496 
 497   log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):  will_fail: %s  heap_lock: %s  free: " SIZE_FORMAT "%s%s returns %s",
 498                         size,
 499                         GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
 500                           "true" : "false",
 501                         Heap_lock->is_locked() ? "locked" : "unlocked",
 502                         from()->free(),
 503                         should_try_alloc ? "" : "  should_allocate_from_space: NOT",
 504                         do_alloc ? "  Heap_lock is not owned by self" : "",
 505                         result == NULL ? "NULL" : "object");
 506 
 507   return result;
 508 }
 509 
 510 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
 511                                                 bool   is_tlab,
 512                                                 bool   parallel) {
 513   // We don't attempt to expand the young generation (but perhaps we should.)
 514   return allocate(size, is_tlab);
 515 }
 516 
 517 void DefNewGeneration::adjust_desired_tenuring_threshold() {
 518   // Set the desired survivor size to half the real survivor space
 519   size_t const survivor_capacity = to()->capacity() / HeapWordSize;
 520   size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
 521 
 522   _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
 523 
 524   if (UsePerfData) {
 525     GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
 526     gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
 527     gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
 528   }
 529 
 530   age_table()->print_age_table(_tenuring_threshold);
 531 }
 532 
 533 void DefNewGeneration::collect(bool   full,
 534                                bool   clear_all_soft_refs,
 535                                size_t size,
 536                                bool   is_tlab) {
 537   assert(full || size > 0, "otherwise we don't want to collect");
 538 
 539   SerialHeap* heap = SerialHeap::heap();
 540 
 541   _gc_timer->register_gc_start();
 542   DefNewTracer gc_tracer;
 543   gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
 544 
 545   _old_gen = heap->old_gen();
 546 
 547   // If the next generation is too full to accommodate promotion
 548   // from this generation, pass on collection; let the next generation
 549   // do it.
 550   if (!collection_attempt_is_safe()) {
 551     log_trace(gc)(":: Collection attempt not safe ::");
 552     heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
 553     return;
 554   }
 555   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 556 
 557   init_assuming_no_promotion_failure();
 558 
 559   GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause());
 560 
 561   heap->trace_heap_before_gc(&gc_tracer);
 562 
 563   // These can be shared for all code paths
 564   IsAliveClosure is_alive(this);
 565   ScanWeakRefClosure scan_weak_ref(this);
 566 
 567   age_table()->clear();
 568   to()->clear(SpaceDecorator::Mangle);
 569   // The preserved marks should be empty at the start of the GC.
 570   _preserved_marks_set.init(1);
 571 
 572   heap->rem_set()->prepare_for_younger_refs_iterate(false);
 573 
 574   assert(heap->no_allocs_since_save_marks(),
 575          "save marks have not been newly set.");
 576 
 577   FastScanClosure fsc_with_no_gc_barrier(this, false);
 578   FastScanClosure fsc_with_gc_barrier(this, true);
 579 
 580   CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier,
 581                                   heap->rem_set()->cld_rem_set()->accumulate_modified_oops());
 582 
 583   set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
 584   FastEvacuateFollowersClosure evacuate_followers(heap,
 585                                                   &fsc_with_no_gc_barrier,
 586                                                   &fsc_with_gc_barrier);
 587 
 588   assert(heap->no_allocs_since_save_marks(),
 589          "save marks have not been newly set.");
 590 
 591   {
 592     // DefNew needs to run with n_threads == 0, to make sure the serial
 593     // version of the card table scanning code is used.
 594     // See: CardTableRS::non_clean_card_iterate_possibly_parallel.
 595     StrongRootsScope srs(0);
 596 
 597     heap->young_process_roots(&srs,
 598                               &fsc_with_no_gc_barrier,
 599                               &fsc_with_gc_barrier,
 600                               &cld_scan_closure);
 601   }
 602 
 603   // "evacuate followers".
 604   evacuate_followers.do_void();
 605 
 606   FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
 607   ReferenceProcessor* rp = ref_processor();
 608   rp->setup_policy(clear_all_soft_refs);
 609   ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
 610   const ReferenceProcessorStats& stats =
 611   rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
 612                                     NULL, &pt);
 613   gc_tracer.report_gc_reference_stats(stats);
 614   gc_tracer.report_tenuring_threshold(tenuring_threshold());
 615   pt.print_all_references();
 616 
 617   assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
 618 
 619   WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
 620 
 621   // Verify that the usage of keep_alive didn't copy any objects.
 622   assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
 623 
 624   if (!_promotion_failed) {
 625     // Swap the survivor spaces.
 626     eden()->clear(SpaceDecorator::Mangle);
 627     from()->clear(SpaceDecorator::Mangle);
 628     if (ZapUnusedHeapArea) {
 629       // This is now done here because of the piece-meal mangling which
 630       // can check for valid mangling at intermediate points in the
 631       // collection(s).  When a young collection fails to collect
 632       // sufficient space resizing of the young generation can occur
 633       // an redistribute the spaces in the young generation.  Mangle
 634       // here so that unzapped regions don't get distributed to
 635       // other spaces.
 636       to()->mangle_unused_area();
 637     }
 638     swap_spaces();
 639 
 640     assert(to()->is_empty(), "to space should be empty now");
 641 
 642     adjust_desired_tenuring_threshold();
 643 
 644     // A successful scavenge should restart the GC time limit count which is
 645     // for full GC's.
 646     AdaptiveSizePolicy* size_policy = heap->size_policy();
 647     size_policy->reset_gc_overhead_limit_count();
 648     assert(!heap->incremental_collection_failed(), "Should be clear");
 649   } else {
 650     assert(_promo_failure_scan_stack.is_empty(), "post condition");
 651     _promo_failure_scan_stack.clear(true); // Clear cached segments.
 652 
 653     remove_forwarding_pointers();
 654     log_info(gc, promotion)("Promotion failed");
 655     // Add to-space to the list of space to compact
 656     // when a promotion failure has occurred.  In that
 657     // case there can be live objects in to-space
 658     // as a result of a partial evacuation of eden
 659     // and from-space.
 660     swap_spaces();   // For uniformity wrt ParNewGeneration.
 661     from()->set_next_compaction_space(to());
 662     heap->set_incremental_collection_failed();
 663 
 664     // Inform the next generation that a promotion failure occurred.
 665     _old_gen->promotion_failure_occurred();
 666     gc_tracer.report_promotion_failed(_promotion_failed_info);
 667 
 668     // Reset the PromotionFailureALot counters.
 669     NOT_PRODUCT(heap->reset_promotion_should_fail();)
 670   }
 671   // We should have processed and cleared all the preserved marks.
 672   _preserved_marks_set.reclaim();
 673   // set new iteration safe limit for the survivor spaces
 674   from()->set_concurrent_iteration_safe_limit(from()->top());
 675   to()->set_concurrent_iteration_safe_limit(to()->top());
 676 
 677   heap->trace_heap_after_gc(&gc_tracer);
 678 
 679   _gc_timer->register_gc_end();
 680 
 681   gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
 682 }
 683 
 684 void DefNewGeneration::init_assuming_no_promotion_failure() {
 685   _promotion_failed = false;
 686   _promotion_failed_info.reset();
 687   from()->set_next_compaction_space(NULL);
 688 }
 689 
 690 void DefNewGeneration::remove_forwarding_pointers() {
 691   RemoveForwardedPointerClosure rspc;
 692   eden()->object_iterate(&rspc);
 693   from()->object_iterate(&rspc);
 694   restore_preserved_marks();
 695 }
 696 
 697 void DefNewGeneration::restore_preserved_marks() {
 698   _preserved_marks_set.restore(NULL);
 699 }
 700 
 701 void DefNewGeneration::handle_promotion_failure(oop old) {
 702   log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
 703 
 704   _promotion_failed = true;
 705   _promotion_failed_info.register_copy_failure(old->size());
 706   _preserved_marks_set.get()->push_if_necessary(old, old->mark_raw());
 707   // forward to self
 708   old->forward_to(old);
 709 
 710   _promo_failure_scan_stack.push(old);
 711 
 712   if (!_promo_failure_drain_in_progress) {
 713     // prevent recursion in copy_to_survivor_space()
 714     _promo_failure_drain_in_progress = true;
 715     drain_promo_failure_scan_stack();
 716     _promo_failure_drain_in_progress = false;
 717   }
 718 }
 719 
 720 oop DefNewGeneration::copy_to_survivor_space(oop old) {
 721   assert(is_in_reserved(old) && !old->is_forwarded(),
 722          "shouldn't be scavenging this oop");
 723   size_t s = old->size();
 724   oop obj = NULL;
 725 
 726   // Try allocating obj in to-space (unless too old)
 727   if (old->age() < tenuring_threshold()) {
 728     obj = (oop) to()->allocate_aligned(s);
 729   }
 730 
 731   // Otherwise try allocating obj tenured
 732   if (obj == NULL) {
 733     obj = _old_gen->promote(old, s);
 734     if (obj == NULL) {
 735       handle_promotion_failure(old);
 736       return old;
 737     }
 738   } else {
 739     // Prefetch beyond obj
 740     const intx interval = PrefetchCopyIntervalInBytes;
 741     Prefetch::write(obj, interval);
 742 
 743     // Copy obj
 744     Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
 745 
 746     // Increment age if obj still in new generation
 747     obj->incr_age();
 748     age_table()->add(obj, s);
 749   }
 750 
 751   // Done, insert forward pointer to obj in this header
 752   old->forward_to(obj);
 753 
 754   return obj;
 755 }
 756 
 757 void DefNewGeneration::drain_promo_failure_scan_stack() {
 758   while (!_promo_failure_scan_stack.is_empty()) {
 759      oop obj = _promo_failure_scan_stack.pop();
 760      obj->oop_iterate(_promo_failure_scan_stack_closure);
 761   }
 762 }
 763 
 764 void DefNewGeneration::save_marks() {
 765   eden()->set_saved_mark();
 766   to()->set_saved_mark();
 767   from()->set_saved_mark();
 768 }
 769 
 770 
 771 void DefNewGeneration::reset_saved_marks() {
 772   eden()->reset_saved_mark();
 773   to()->reset_saved_mark();
 774   from()->reset_saved_mark();
 775 }
 776 
 777 
 778 bool DefNewGeneration::no_allocs_since_save_marks() {
 779   assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
 780   assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
 781   return to()->saved_mark_at_top();
 782 }
 783 
 784 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
 785                                          size_t max_alloc_words) {
 786   if (requestor == this || _promotion_failed) {
 787     return;
 788   }
 789   assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
 790 
 791   /* $$$ Assert this?  "trace" is a "MarkSweep" function so that's not appropriate.
 792   if (to_space->top() > to_space->bottom()) {
 793     trace("to_space not empty when contribute_scratch called");
 794   }
 795   */
 796 
 797   ContiguousSpace* to_space = to();
 798   assert(to_space->end() >= to_space->top(), "pointers out of order");
 799   size_t free_words = pointer_delta(to_space->end(), to_space->top());
 800   if (free_words >= MinFreeScratchWords) {
 801     ScratchBlock* sb = (ScratchBlock*)to_space->top();
 802     sb->num_words = free_words;
 803     sb->next = list;
 804     list = sb;
 805   }
 806 }
 807 
 808 void DefNewGeneration::reset_scratch() {
 809   // If contributing scratch in to_space, mangle all of
 810   // to_space if ZapUnusedHeapArea.  This is needed because
 811   // top is not maintained while using to-space as scratch.
 812   if (ZapUnusedHeapArea) {
 813     to()->mangle_unused_area_complete();
 814   }
 815 }
 816 
 817 bool DefNewGeneration::collection_attempt_is_safe() {
 818   if (!to()->is_empty()) {
 819     log_trace(gc)(":: to is not empty ::");
 820     return false;
 821   }
 822   if (_old_gen == NULL) {
 823     GenCollectedHeap* gch = GenCollectedHeap::heap();
 824     _old_gen = gch->old_gen();
 825   }
 826   return _old_gen->promotion_attempt_is_safe(used());
 827 }
 828 
 829 void DefNewGeneration::gc_epilogue(bool full) {
 830   DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
 831 
 832   assert(!GCLocker::is_active(), "We should not be executing here");
 833   // Check if the heap is approaching full after a collection has
 834   // been done.  Generally the young generation is empty at
 835   // a minimum at the end of a collection.  If it is not, then
 836   // the heap is approaching full.
 837   GenCollectedHeap* gch = GenCollectedHeap::heap();
 838   if (full) {
 839     DEBUG_ONLY(seen_incremental_collection_failed = false;)
 840     if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
 841       log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
 842                             GCCause::to_string(gch->gc_cause()));
 843       gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
 844       set_should_allocate_from_space(); // we seem to be running out of space
 845     } else {
 846       log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
 847                             GCCause::to_string(gch->gc_cause()));
 848       gch->clear_incremental_collection_failed(); // We just did a full collection
 849       clear_should_allocate_from_space(); // if set
 850     }
 851   } else {
 852 #ifdef ASSERT
 853     // It is possible that incremental_collection_failed() == true
 854     // here, because an attempted scavenge did not succeed. The policy
 855     // is normally expected to cause a full collection which should
 856     // clear that condition, so we should not be here twice in a row
 857     // with incremental_collection_failed() == true without having done
 858     // a full collection in between.
 859     if (!seen_incremental_collection_failed &&
 860         gch->incremental_collection_failed()) {
 861       log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
 862                             GCCause::to_string(gch->gc_cause()));
 863       seen_incremental_collection_failed = true;
 864     } else if (seen_incremental_collection_failed) {
 865       log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
 866                             GCCause::to_string(gch->gc_cause()));
 867       assert(gch->gc_cause() == GCCause::_scavenge_alot ||
 868              !gch->incremental_collection_failed(),
 869              "Twice in a row");
 870       seen_incremental_collection_failed = false;
 871     }
 872 #endif // ASSERT
 873   }
 874 
 875   if (ZapUnusedHeapArea) {
 876     eden()->check_mangled_unused_area_complete();
 877     from()->check_mangled_unused_area_complete();
 878     to()->check_mangled_unused_area_complete();
 879   }
 880 
 881   if (!CleanChunkPoolAsync) {
 882     Chunk::clean_chunk_pool();
 883   }
 884 
 885   // update the generation and space performance counters
 886   update_counters();
 887   gch->counters()->update_counters();
 888 }
 889 
 890 void DefNewGeneration::record_spaces_top() {
 891   assert(ZapUnusedHeapArea, "Not mangling unused space");
 892   eden()->set_top_for_allocations();
 893   to()->set_top_for_allocations();
 894   from()->set_top_for_allocations();
 895 }
 896 
 897 void DefNewGeneration::ref_processor_init() {
 898   Generation::ref_processor_init();
 899 }
 900 
 901 
 902 void DefNewGeneration::update_counters() {
 903   if (UsePerfData) {
 904     _eden_counters->update_all();
 905     _from_counters->update_all();
 906     _to_counters->update_all();
 907     _gen_counters->update_all();
 908   }
 909 }
 910 
 911 void DefNewGeneration::verify() {
 912   eden()->verify();
 913   from()->verify();
 914     to()->verify();
 915 }
 916 
 917 void DefNewGeneration::print_on(outputStream* st) const {
 918   Generation::print_on(st);
 919   st->print("  eden");
 920   eden()->print_on(st);
 921   st->print("  from");
 922   from()->print_on(st);
 923   st->print("  to  ");
 924   to()->print_on(st);
 925 }
 926 
 927 
 928 const char* DefNewGeneration::name() const {
 929   return "def new generation";
 930 }
 931 
 932 // Moved from inline file as they are not called inline
 933 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
 934   return eden();
 935 }
 936 
 937 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
 938   // This is the slow-path allocation for the DefNewGeneration.
 939   // Most allocations are fast-path in compiled code.
 940   // We try to allocate from the eden.  If that works, we are happy.
 941   // Note that since DefNewGeneration supports lock-free allocation, we
 942   // have to use it here, as well.
 943   HeapWord* result = eden()->par_allocate(word_size);
 944   if (result != NULL) {
 945     if (_old_gen != NULL) {
 946       _old_gen->sample_eden_chunk();
 947     }
 948   } else {
 949     // If the eden is full and the last collection bailed out, we are running
 950     // out of heap space, and we try to allocate the from-space, too.
 951     // allocate_from_space can't be inlined because that would introduce a
 952     // circular dependency at compile time.
 953     result = allocate_from_space(word_size);
 954   }
 955   return result;
 956 }
 957 
 958 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
 959                                          bool is_tlab) {
 960   HeapWord* res = eden()->par_allocate(word_size);
 961   if (_old_gen != NULL) {
 962     _old_gen->sample_eden_chunk();
 963   }
 964   return res;
 965 }
 966 
 967 size_t DefNewGeneration::tlab_capacity() const {
 968   return eden()->capacity();
 969 }
 970 
 971 size_t DefNewGeneration::tlab_used() const {
 972   return eden()->used();
 973 }
 974 
 975 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
 976   return unsafe_max_alloc_nogc();
 977 }