rev 11970 : [mq]: base_volatiles

   1 /*
   2  * Copyright (c) 2001, 2016, 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/ageTable.inline.hpp"
  28 #include "gc/shared/cardTableRS.hpp"
  29 #include "gc/shared/collectorCounters.hpp"
  30 #include "gc/shared/gcHeapSummary.hpp"
  31 #include "gc/shared/gcLocker.inline.hpp"
  32 #include "gc/shared/gcPolicyCounters.hpp"
  33 #include "gc/shared/gcTimer.hpp"
  34 #include "gc/shared/gcTrace.hpp"
  35 #include "gc/shared/gcTraceTime.inline.hpp"
  36 #include "gc/shared/genCollectedHeap.hpp"
  37 #include "gc/shared/genOopClosures.inline.hpp"
  38 #include "gc/shared/generationSpec.hpp"
  39 #include "gc/shared/preservedMarks.inline.hpp"
  40 #include "gc/shared/referencePolicy.hpp"
  41 #include "gc/shared/space.inline.hpp"
  42 #include "gc/shared/spaceDecorator.hpp"
  43 #include "gc/shared/strongRootsScope.hpp"
  44 #include "logging/log.hpp"
  45 #include "memory/iterator.hpp"
  46 #include "memory/resourceArea.hpp"
  47 #include "oops/instanceRefKlass.hpp"
  48 #include "oops/oop.inline.hpp"
  49 #include "runtime/atomic.hpp"
  50 #include "runtime/java.hpp"
  51 #include "runtime/prefetch.inline.hpp"
  52 #include "runtime/thread.inline.hpp"
  53 #include "utilities/copy.hpp"
  54 #include "utilities/globalDefinitions.hpp"
  55 #include "utilities/stack.inline.hpp"
  56 #if INCLUDE_ALL_GCS
  57 #include "gc/cms/parOopClosures.hpp"
  58 #endif
  59 
  60 //
  61 // DefNewGeneration functions.
  62 
  63 // Methods of protected closure types.
  64 
  65 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
  66   assert(_young_gen->kind() == Generation::ParNew ||
  67          _young_gen->kind() == Generation::DefNew, "Expected the young generation here");
  68 }
  69 
  70 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
  71   return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded();
  72 }
  73 
  74 DefNewGeneration::KeepAliveClosure::
  75 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
  76   _rs = GenCollectedHeap::heap()->rem_set();
  77 }
  78 
  79 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  80 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  81 
  82 
  83 DefNewGeneration::FastKeepAliveClosure::
  84 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
  85   DefNewGeneration::KeepAliveClosure(cl) {
  86   _boundary = g->reserved().end();
  87 }
  88 
  89 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  90 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  91 
  92 DefNewGeneration::EvacuateFollowersClosure::
  93 EvacuateFollowersClosure(GenCollectedHeap* gch,
  94                          ScanClosure* cur,
  95                          ScanClosure* older) :
  96   _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
  97 {}
  98 
  99 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
 100   do {
 101     _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
 102   } while (!_gch->no_allocs_since_save_marks());
 103 }
 104 
 105 DefNewGeneration::FastEvacuateFollowersClosure::
 106 FastEvacuateFollowersClosure(GenCollectedHeap* gch,
 107                              FastScanClosure* cur,
 108                              FastScanClosure* older) :
 109   _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
 110 {
 111   assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew");
 112   _young_gen = (DefNewGeneration*)_gch->young_gen();
 113 }
 114 
 115 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
 116   do {
 117     _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
 118   } while (!_gch->no_allocs_since_save_marks());
 119   guarantee(_young_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
 120 }
 121 
 122 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
 123     OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 124 {
 125   _boundary = _g->reserved().end();
 126 }
 127 
 128 void ScanClosure::do_oop(oop* p)       { ScanClosure::do_oop_work(p); }
 129 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
 130 
 131 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
 132     OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 133 {
 134   _boundary = _g->reserved().end();
 135 }
 136 
 137 void FastScanClosure::do_oop(oop* p)       { FastScanClosure::do_oop_work(p); }
 138 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
 139 
 140 void KlassScanClosure::do_klass(Klass* klass) {
 141   NOT_PRODUCT(ResourceMark rm);
 142   log_develop_trace(gc, scavenge)("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
 143                                   p2i(klass),
 144                                   klass->external_name(),
 145                                   klass->has_modified_oops() ? "true" : "false");
 146 
 147   // If the klass has not been dirtied we know that there's
 148   // no references into  the young gen and we can skip it.
 149   if (klass->has_modified_oops()) {
 150     if (_accumulate_modified_oops) {
 151       klass->accumulate_modified_oops();
 152     }
 153 
 154     // Clear this state since we're going to scavenge all the metadata.
 155     klass->clear_modified_oops();
 156 
 157     // Tell the closure which Klass is being scanned so that it can be dirtied
 158     // if oops are left pointing into the young gen.
 159     _scavenge_closure->set_scanned_klass(klass);
 160 
 161     klass->oops_do(_scavenge_closure);
 162 
 163     _scavenge_closure->set_scanned_klass(NULL);
 164   }
 165 }
 166 
 167 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
 168   _g(g)
 169 {
 170   _boundary = _g->reserved().end();
 171 }
 172 
 173 void ScanWeakRefClosure::do_oop(oop* p)       { ScanWeakRefClosure::do_oop_work(p); }
 174 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
 175 
 176 void FilteringClosure::do_oop(oop* p)       { FilteringClosure::do_oop_work(p); }
 177 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
 178 
 179 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
 180                                    KlassRemSet* klass_rem_set)
 181     : _scavenge_closure(scavenge_closure),
 182       _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
 183 
 184 
 185 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
 186                                    size_t initial_size,
 187                                    const char* policy)
 188   : Generation(rs, initial_size),
 189     _preserved_marks_set(false /* in_c_heap */),
 190     _promo_failure_drain_in_progress(false),
 191     _should_allocate_from_space(false)
 192 {
 193   MemRegion cmr((HeapWord*)_virtual_space.low(),
 194                 (HeapWord*)_virtual_space.high());
 195   GenCollectedHeap* gch = GenCollectedHeap::heap();
 196 
 197   gch->barrier_set()->resize_covered_region(cmr);
 198 
 199   _eden_space = new ContiguousSpace();
 200   _from_space = new ContiguousSpace();
 201   _to_space   = new ContiguousSpace();
 202 
 203   if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
 204     vm_exit_during_initialization("Could not allocate a new gen space");
 205   }
 206 
 207   // Compute the maximum eden and survivor space sizes. These sizes
 208   // are computed assuming the entire reserved space is committed.
 209   // These values are exported as performance counters.
 210   uintx alignment = gch->collector_policy()->space_alignment();
 211   uintx size = _virtual_space.reserved_size();
 212   _max_survivor_size = compute_survivor_size(size, alignment);
 213   _max_eden_size = size - (2*_max_survivor_size);
 214 
 215   // allocate the performance counters
 216   GenCollectorPolicy* gcp = gch->gen_policy();
 217 
 218   // Generation counters -- generation 0, 3 subspaces
 219   _gen_counters = new GenerationCounters("new", 0, 3,
 220       gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
 221   _gc_counters = new CollectorCounters(policy, 0);
 222 
 223   _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
 224                                       _gen_counters);
 225   _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
 226                                       _gen_counters);
 227   _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
 228                                     _gen_counters);
 229 
 230   compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
 231   update_counters();
 232   _old_gen = NULL;
 233   _tenuring_threshold = MaxTenuringThreshold;
 234   _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
 235 
 236   _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
 237 }
 238 
 239 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
 240                                                 bool clear_space,
 241                                                 bool mangle_space) {
 242   uintx alignment =
 243     GenCollectedHeap::heap()->collector_policy()->space_alignment();
 244 
 245   // If the spaces are being cleared (only done at heap initialization
 246   // currently), the survivor spaces need not be empty.
 247   // Otherwise, no care is taken for used areas in the survivor spaces
 248   // so check.
 249   assert(clear_space || (to()->is_empty() && from()->is_empty()),
 250     "Initialization of the survivor spaces assumes these are empty");
 251 
 252   // Compute sizes
 253   uintx size = _virtual_space.committed_size();
 254   uintx survivor_size = compute_survivor_size(size, alignment);
 255   uintx eden_size = size - (2*survivor_size);
 256   assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 257 
 258   if (eden_size < minimum_eden_size) {
 259     // May happen due to 64Kb rounding, if so adjust eden size back up
 260     minimum_eden_size = align_size_up(minimum_eden_size, alignment);
 261     uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
 262     uintx unaligned_survivor_size =
 263       align_size_down(maximum_survivor_size, alignment);
 264     survivor_size = MAX2(unaligned_survivor_size, alignment);
 265     eden_size = size - (2*survivor_size);
 266     assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 267     assert(eden_size >= minimum_eden_size, "just checking");
 268   }
 269 
 270   char *eden_start = _virtual_space.low();
 271   char *from_start = eden_start + eden_size;
 272   char *to_start   = from_start + survivor_size;
 273   char *to_end     = to_start   + survivor_size;
 274 
 275   assert(to_end == _virtual_space.high(), "just checking");
 276   assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
 277   assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
 278   assert(Space::is_aligned((HeapWord*)to_start),   "checking alignment");
 279 
 280   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
 281   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
 282   MemRegion toMR  ((HeapWord*)to_start, (HeapWord*)to_end);
 283 
 284   // A minimum eden size implies that there is a part of eden that
 285   // is being used and that affects the initialization of any
 286   // newly formed eden.
 287   bool live_in_eden = minimum_eden_size > 0;
 288 
 289   // If not clearing the spaces, do some checking to verify that
 290   // the space are already mangled.
 291   if (!clear_space) {
 292     // Must check mangling before the spaces are reshaped.  Otherwise,
 293     // the bottom or end of one space may have moved into another
 294     // a failure of the check may not correctly indicate which space
 295     // is not properly mangled.
 296     if (ZapUnusedHeapArea) {
 297       HeapWord* limit = (HeapWord*) _virtual_space.high();
 298       eden()->check_mangled_unused_area(limit);
 299       from()->check_mangled_unused_area(limit);
 300         to()->check_mangled_unused_area(limit);
 301     }
 302   }
 303 
 304   // Reset the spaces for their new regions.
 305   eden()->initialize(edenMR,
 306                      clear_space && !live_in_eden,
 307                      SpaceDecorator::Mangle);
 308   // If clear_space and live_in_eden, we will not have cleared any
 309   // portion of eden above its top. This can cause newly
 310   // expanded space not to be mangled if using ZapUnusedHeapArea.
 311   // We explicitly do such mangling here.
 312   if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
 313     eden()->mangle_unused_area();
 314   }
 315   from()->initialize(fromMR, clear_space, mangle_space);
 316   to()->initialize(toMR, clear_space, mangle_space);
 317 
 318   // Set next compaction spaces.
 319   eden()->set_next_compaction_space(from());
 320   // The to-space is normally empty before a compaction so need
 321   // not be considered.  The exception is during promotion
 322   // failure handling when to-space can contain live objects.
 323   from()->set_next_compaction_space(NULL);
 324 }
 325 
 326 void DefNewGeneration::swap_spaces() {
 327   ContiguousSpace* s = from();
 328   _from_space        = to();
 329   _to_space          = s;
 330   eden()->set_next_compaction_space(from());
 331   // The to-space is normally empty before a compaction so need
 332   // not be considered.  The exception is during promotion
 333   // failure handling when to-space can contain live objects.
 334   from()->set_next_compaction_space(NULL);
 335 
 336   if (UsePerfData) {
 337     CSpaceCounters* c = _from_counters;
 338     _from_counters = _to_counters;
 339     _to_counters = c;
 340   }
 341 }
 342 
 343 bool DefNewGeneration::expand(size_t bytes) {
 344   MutexLocker x(ExpandHeap_lock);
 345   HeapWord* prev_high = (HeapWord*) _virtual_space.high();
 346   bool success = _virtual_space.expand_by(bytes);
 347   if (success && ZapUnusedHeapArea) {
 348     // Mangle newly committed space immediately because it
 349     // can be done here more simply that after the new
 350     // spaces have been computed.
 351     HeapWord* new_high = (HeapWord*) _virtual_space.high();
 352     MemRegion mangle_region(prev_high, new_high);
 353     SpaceMangler::mangle_region(mangle_region);
 354   }
 355 
 356   // Do not attempt an expand-to-the reserve size.  The
 357   // request should properly observe the maximum size of
 358   // the generation so an expand-to-reserve should be
 359   // unnecessary.  Also a second call to expand-to-reserve
 360   // value potentially can cause an undue expansion.
 361   // For example if the first expand fail for unknown reasons,
 362   // but the second succeeds and expands the heap to its maximum
 363   // value.
 364   if (GCLocker::is_active()) {
 365     log_debug(gc)("Garbage collection disabled, expanded heap instead");
 366   }
 367 
 368   return success;
 369 }
 370 
 371 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
 372                                                     size_t new_size_before,
 373                                                     size_t alignment) const {
 374   size_t desired_new_size = new_size_before;
 375 
 376   if (NewSizeThreadIncrease > 0) {
 377     int threads_count;
 378     size_t thread_increase_size = 0;
 379 
 380     // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
 381     threads_count = Threads::number_of_non_daemon_threads();
 382     if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
 383       thread_increase_size = threads_count * NewSizeThreadIncrease;
 384 
 385       // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
 386       if (new_size_candidate <= max_uintx - thread_increase_size) {
 387         new_size_candidate += thread_increase_size;
 388 
 389         // 3. Check an overflow at 'align_size_up'.
 390         size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
 391         if (new_size_candidate <= aligned_max) {
 392           desired_new_size = align_size_up(new_size_candidate, alignment);
 393         }
 394       }
 395     }
 396   }
 397 
 398   return desired_new_size;
 399 }
 400 
 401 void DefNewGeneration::compute_new_size() {
 402   // This is called after a GC that includes the old generation, so from-space
 403   // will normally be empty.
 404   // Note that we check both spaces, since if scavenge failed they revert roles.
 405   // If not we bail out (otherwise we would have to relocate the objects).
 406   if (!from()->is_empty() || !to()->is_empty()) {
 407     return;
 408   }
 409 
 410   GenCollectedHeap* gch = GenCollectedHeap::heap();
 411 
 412   size_t old_size = gch->old_gen()->capacity();
 413   size_t new_size_before = _virtual_space.committed_size();
 414   size_t min_new_size = initial_size();
 415   size_t max_new_size = reserved().byte_size();
 416   assert(min_new_size <= new_size_before &&
 417          new_size_before <= max_new_size,
 418          "just checking");
 419   // All space sizes must be multiples of Generation::GenGrain.
 420   size_t alignment = Generation::GenGrain;
 421 
 422   int threads_count = 0;
 423   size_t thread_increase_size = 0;
 424 
 425   size_t new_size_candidate = old_size / NewRatio;
 426   // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
 427   // and reverts to previous value if any overflow happens
 428   size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
 429 
 430   // Adjust new generation size
 431   desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
 432   assert(desired_new_size <= max_new_size, "just checking");
 433 
 434   bool changed = false;
 435   if (desired_new_size > new_size_before) {
 436     size_t change = desired_new_size - new_size_before;
 437     assert(change % alignment == 0, "just checking");
 438     if (expand(change)) {
 439        changed = true;
 440     }
 441     // If the heap failed to expand to the desired size,
 442     // "changed" will be false.  If the expansion failed
 443     // (and at this point it was expected to succeed),
 444     // ignore the failure (leaving "changed" as false).
 445   }
 446   if (desired_new_size < new_size_before && eden()->is_empty()) {
 447     // bail out of shrinking if objects in eden
 448     size_t change = new_size_before - desired_new_size;
 449     assert(change % alignment == 0, "just checking");
 450     _virtual_space.shrink_by(change);
 451     changed = true;
 452   }
 453   if (changed) {
 454     // The spaces have already been mangled at this point but
 455     // may not have been cleared (set top = bottom) and should be.
 456     // Mangling was done when the heap was being expanded.
 457     compute_space_boundaries(eden()->used(),
 458                              SpaceDecorator::Clear,
 459                              SpaceDecorator::DontMangle);
 460     MemRegion cmr((HeapWord*)_virtual_space.low(),
 461                   (HeapWord*)_virtual_space.high());
 462     gch->barrier_set()->resize_covered_region(cmr);
 463 
 464     log_debug(gc, ergo, heap)(
 465         "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
 466         new_size_before/K, _virtual_space.committed_size()/K,
 467         eden()->capacity()/K, from()->capacity()/K);
 468     log_trace(gc, ergo, heap)(
 469         "  [allowed " SIZE_FORMAT "K extra for %d threads]",
 470           thread_increase_size/K, threads_count);
 471       }
 472 }
 473 
 474 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
 475   assert(false, "NYI -- are you sure you want to call this?");
 476 }
 477 
 478 
 479 size_t DefNewGeneration::capacity() const {
 480   return eden()->capacity()
 481        + from()->capacity();  // to() is only used during scavenge
 482 }
 483 
 484 
 485 size_t DefNewGeneration::used() const {
 486   return eden()->used()
 487        + from()->used();      // to() is only used during scavenge
 488 }
 489 
 490 
 491 size_t DefNewGeneration::free() const {
 492   return eden()->free()
 493        + from()->free();      // to() is only used during scavenge
 494 }
 495 
 496 size_t DefNewGeneration::max_capacity() const {
 497   const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
 498   const size_t reserved_bytes = reserved().byte_size();
 499   return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
 500 }
 501 
 502 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
 503   return eden()->free();
 504 }
 505 
 506 size_t DefNewGeneration::capacity_before_gc() const {
 507   return eden()->capacity();
 508 }
 509 
 510 size_t DefNewGeneration::contiguous_available() const {
 511   return eden()->free();
 512 }
 513 
 514 
 515 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
 516 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
 517 
 518 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
 519   eden()->object_iterate(blk);
 520   from()->object_iterate(blk);
 521 }
 522 
 523 
 524 void DefNewGeneration::space_iterate(SpaceClosure* blk,
 525                                      bool usedOnly) {
 526   blk->do_space(eden());
 527   blk->do_space(from());
 528   blk->do_space(to());
 529 }
 530 
 531 // The last collection bailed out, we are running out of heap space,
 532 // so we try to allocate the from-space, too.
 533 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
 534   bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
 535 
 536   // If the Heap_lock is not locked by this thread, this will be called
 537   // again later with the Heap_lock held.
 538   bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
 539 
 540   HeapWord* result = NULL;
 541   if (do_alloc) {
 542     result = from()->allocate(size);
 543   }
 544 
 545   log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):  will_fail: %s  heap_lock: %s  free: " SIZE_FORMAT "%s%s returns %s",
 546                         size,
 547                         GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
 548                           "true" : "false",
 549                         Heap_lock->is_locked() ? "locked" : "unlocked",
 550                         from()->free(),
 551                         should_try_alloc ? "" : "  should_allocate_from_space: NOT",
 552                         do_alloc ? "  Heap_lock is not owned by self" : "",
 553                         result == NULL ? "NULL" : "object");
 554 
 555   return result;
 556 }
 557 
 558 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
 559                                                 bool   is_tlab,
 560                                                 bool   parallel) {
 561   // We don't attempt to expand the young generation (but perhaps we should.)
 562   return allocate(size, is_tlab);
 563 }
 564 
 565 void DefNewGeneration::adjust_desired_tenuring_threshold() {
 566   // Set the desired survivor size to half the real survivor space
 567   size_t const survivor_capacity = to()->capacity() / HeapWordSize;
 568   size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
 569 
 570   _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
 571 
 572   if (UsePerfData) {
 573     GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->gen_policy()->counters();
 574     gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
 575     gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
 576   }
 577 
 578   age_table()->print_age_table(_tenuring_threshold);
 579 }
 580 
 581 void DefNewGeneration::collect(bool   full,
 582                                bool   clear_all_soft_refs,
 583                                size_t size,
 584                                bool   is_tlab) {
 585   assert(full || size > 0, "otherwise we don't want to collect");
 586 
 587   GenCollectedHeap* gch = GenCollectedHeap::heap();
 588 
 589   _gc_timer->register_gc_start();
 590   DefNewTracer gc_tracer;
 591   gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
 592 
 593   _old_gen = gch->old_gen();
 594 
 595   // If the next generation is too full to accommodate promotion
 596   // from this generation, pass on collection; let the next generation
 597   // do it.
 598   if (!collection_attempt_is_safe()) {
 599     log_trace(gc)(":: Collection attempt not safe ::");
 600     gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
 601     return;
 602   }
 603   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 604 
 605   init_assuming_no_promotion_failure();
 606 
 607   GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, gch->gc_cause());
 608 
 609   gch->trace_heap_before_gc(&gc_tracer);
 610 
 611   // These can be shared for all code paths
 612   IsAliveClosure is_alive(this);
 613   ScanWeakRefClosure scan_weak_ref(this);
 614 
 615   age_table()->clear();
 616   to()->clear(SpaceDecorator::Mangle);
 617   // The preserved marks should be empty at the start of the GC.
 618   _preserved_marks_set.init(1);
 619 
 620   gch->rem_set()->prepare_for_younger_refs_iterate(false);
 621 
 622   assert(gch->no_allocs_since_save_marks(),
 623          "save marks have not been newly set.");
 624 
 625   // Not very pretty.
 626   CollectorPolicy* cp = gch->collector_policy();
 627 
 628   FastScanClosure fsc_with_no_gc_barrier(this, false);
 629   FastScanClosure fsc_with_gc_barrier(this, true);
 630 
 631   KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
 632                                       gch->rem_set()->klass_rem_set());
 633   CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
 634                                            &fsc_with_no_gc_barrier,
 635                                            false);
 636 
 637   set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
 638   FastEvacuateFollowersClosure evacuate_followers(gch,
 639                                                   &fsc_with_no_gc_barrier,
 640                                                   &fsc_with_gc_barrier);
 641 
 642   assert(gch->no_allocs_since_save_marks(),
 643          "save marks have not been newly set.");
 644 
 645   {
 646     // DefNew needs to run with n_threads == 0, to make sure the serial
 647     // version of the card table scanning code is used.
 648     // See: CardTableModRefBSForCTRS::non_clean_card_iterate_possibly_parallel.
 649     StrongRootsScope srs(0);
 650 
 651     gch->gen_process_roots(&srs,
 652                            GenCollectedHeap::YoungGen,
 653                            true,  // Process younger gens, if any,
 654                                   // as strong roots.
 655                            GenCollectedHeap::SO_ScavengeCodeCache,
 656                            GenCollectedHeap::StrongAndWeakRoots,
 657                            &fsc_with_no_gc_barrier,
 658                            &fsc_with_gc_barrier,
 659                            &cld_scan_closure);
 660   }
 661 
 662   // "evacuate followers".
 663   evacuate_followers.do_void();
 664 
 665   FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
 666   ReferenceProcessor* rp = ref_processor();
 667   rp->setup_policy(clear_all_soft_refs);
 668   const ReferenceProcessorStats& stats =
 669   rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
 670                                     NULL, _gc_timer);
 671   gc_tracer.report_gc_reference_stats(stats);
 672   gc_tracer.report_tenuring_threshold(tenuring_threshold());
 673 
 674   if (!_promotion_failed) {
 675     // Swap the survivor spaces.
 676     eden()->clear(SpaceDecorator::Mangle);
 677     from()->clear(SpaceDecorator::Mangle);
 678     if (ZapUnusedHeapArea) {
 679       // This is now done here because of the piece-meal mangling which
 680       // can check for valid mangling at intermediate points in the
 681       // collection(s).  When a young collection fails to collect
 682       // sufficient space resizing of the young generation can occur
 683       // an redistribute the spaces in the young generation.  Mangle
 684       // here so that unzapped regions don't get distributed to
 685       // other spaces.
 686       to()->mangle_unused_area();
 687     }
 688     swap_spaces();
 689 
 690     assert(to()->is_empty(), "to space should be empty now");
 691 
 692     adjust_desired_tenuring_threshold();
 693 
 694     // A successful scavenge should restart the GC time limit count which is
 695     // for full GC's.
 696     AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
 697     size_policy->reset_gc_overhead_limit_count();
 698     assert(!gch->incremental_collection_failed(), "Should be clear");
 699   } else {
 700     assert(_promo_failure_scan_stack.is_empty(), "post condition");
 701     _promo_failure_scan_stack.clear(true); // Clear cached segments.
 702 
 703     remove_forwarding_pointers();
 704     log_info(gc, promotion)("Promotion failed");
 705     // Add to-space to the list of space to compact
 706     // when a promotion failure has occurred.  In that
 707     // case there can be live objects in to-space
 708     // as a result of a partial evacuation of eden
 709     // and from-space.
 710     swap_spaces();   // For uniformity wrt ParNewGeneration.
 711     from()->set_next_compaction_space(to());
 712     gch->set_incremental_collection_failed();
 713 
 714     // Inform the next generation that a promotion failure occurred.
 715     _old_gen->promotion_failure_occurred();
 716     gc_tracer.report_promotion_failed(_promotion_failed_info);
 717 
 718     // Reset the PromotionFailureALot counters.
 719     NOT_PRODUCT(gch->reset_promotion_should_fail();)
 720   }
 721   // We should have processed and cleared all the preserved marks.
 722   _preserved_marks_set.reclaim();
 723   // set new iteration safe limit for the survivor spaces
 724   from()->set_concurrent_iteration_safe_limit(from()->top());
 725   to()->set_concurrent_iteration_safe_limit(to()->top());
 726 
 727   // We need to use a monotonically non-decreasing time in ms
 728   // or we will see time-warp warnings and os::javaTimeMillis()
 729   // does not guarantee monotonicity.
 730   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 731   update_time_of_last_gc(now);
 732 
 733   gch->trace_heap_after_gc(&gc_tracer);
 734 
 735   _gc_timer->register_gc_end();
 736 
 737   gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
 738 }
 739 
 740 void DefNewGeneration::init_assuming_no_promotion_failure() {
 741   _promotion_failed = false;
 742   _promotion_failed_info.reset();
 743   from()->set_next_compaction_space(NULL);
 744 }
 745 
 746 void DefNewGeneration::remove_forwarding_pointers() {
 747   RemoveForwardedPointerClosure rspc;
 748   eden()->object_iterate(&rspc);
 749   from()->object_iterate(&rspc);
 750 
 751   SharedRestorePreservedMarksTaskExecutor task_executor(GenCollectedHeap::heap()->workers());
 752   _preserved_marks_set.restore(&task_executor);
 753 }
 754 
 755 void DefNewGeneration::handle_promotion_failure(oop old) {
 756   log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
 757 
 758   _promotion_failed = true;
 759   _promotion_failed_info.register_copy_failure(old->size());
 760   _preserved_marks_set.get()->push_if_necessary(old, old->mark());
 761   // forward to self
 762   old->forward_to(old);
 763 
 764   _promo_failure_scan_stack.push(old);
 765 
 766   if (!_promo_failure_drain_in_progress) {
 767     // prevent recursion in copy_to_survivor_space()
 768     _promo_failure_drain_in_progress = true;
 769     drain_promo_failure_scan_stack();
 770     _promo_failure_drain_in_progress = false;
 771   }
 772 }
 773 
 774 oop DefNewGeneration::copy_to_survivor_space(oop old) {
 775   assert(is_in_reserved(old) && !old->is_forwarded(),
 776          "shouldn't be scavenging this oop");
 777   size_t s = old->size();
 778   oop obj = NULL;
 779 
 780   // Try allocating obj in to-space (unless too old)
 781   if (old->age() < tenuring_threshold()) {
 782     obj = (oop) to()->allocate_aligned(s);
 783   }
 784 
 785   // Otherwise try allocating obj tenured
 786   if (obj == NULL) {
 787     obj = _old_gen->promote(old, s);
 788     if (obj == NULL) {
 789       handle_promotion_failure(old);
 790       return old;
 791     }
 792   } else {
 793     // Prefetch beyond obj
 794     const intx interval = PrefetchCopyIntervalInBytes;
 795     Prefetch::write(obj, interval);
 796 
 797     // Copy obj
 798     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
 799 
 800     // Increment age if obj still in new generation
 801     obj->incr_age();
 802     age_table()->add(obj, s);
 803   }
 804 
 805   // Done, insert forward pointer to obj in this header
 806   old->forward_to(obj);
 807 
 808   return obj;
 809 }
 810 
 811 void DefNewGeneration::drain_promo_failure_scan_stack() {
 812   while (!_promo_failure_scan_stack.is_empty()) {
 813      oop obj = _promo_failure_scan_stack.pop();
 814      obj->oop_iterate(_promo_failure_scan_stack_closure);
 815   }
 816 }
 817 
 818 void DefNewGeneration::save_marks() {
 819   eden()->set_saved_mark();
 820   to()->set_saved_mark();
 821   from()->set_saved_mark();
 822 }
 823 
 824 
 825 void DefNewGeneration::reset_saved_marks() {
 826   eden()->reset_saved_mark();
 827   to()->reset_saved_mark();
 828   from()->reset_saved_mark();
 829 }
 830 
 831 
 832 bool DefNewGeneration::no_allocs_since_save_marks() {
 833   assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
 834   assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
 835   return to()->saved_mark_at_top();
 836 }
 837 
 838 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
 839                                                                 \
 840 void DefNewGeneration::                                         \
 841 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) {   \
 842   cl->set_generation(this);                                     \
 843   eden()->oop_since_save_marks_iterate##nv_suffix(cl);          \
 844   to()->oop_since_save_marks_iterate##nv_suffix(cl);            \
 845   from()->oop_since_save_marks_iterate##nv_suffix(cl);          \
 846   cl->reset_generation();                                       \
 847   save_marks();                                                 \
 848 }
 849 
 850 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
 851 
 852 #undef DefNew_SINCE_SAVE_MARKS_DEFN
 853 
 854 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
 855                                          size_t max_alloc_words) {
 856   if (requestor == this || _promotion_failed) {
 857     return;
 858   }
 859   assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
 860 
 861   /* $$$ Assert this?  "trace" is a "MarkSweep" function so that's not appropriate.
 862   if (to_space->top() > to_space->bottom()) {
 863     trace("to_space not empty when contribute_scratch called");
 864   }
 865   */
 866 
 867   ContiguousSpace* to_space = to();
 868   assert(to_space->end() >= to_space->top(), "pointers out of order");
 869   size_t free_words = pointer_delta(to_space->end(), to_space->top());
 870   if (free_words >= MinFreeScratchWords) {
 871     ScratchBlock* sb = (ScratchBlock*)to_space->top();
 872     sb->num_words = free_words;
 873     sb->next = list;
 874     list = sb;
 875   }
 876 }
 877 
 878 void DefNewGeneration::reset_scratch() {
 879   // If contributing scratch in to_space, mangle all of
 880   // to_space if ZapUnusedHeapArea.  This is needed because
 881   // top is not maintained while using to-space as scratch.
 882   if (ZapUnusedHeapArea) {
 883     to()->mangle_unused_area_complete();
 884   }
 885 }
 886 
 887 bool DefNewGeneration::collection_attempt_is_safe() {
 888   if (!to()->is_empty()) {
 889     log_trace(gc)(":: to is not empty ::");
 890     return false;
 891   }
 892   if (_old_gen == NULL) {
 893     GenCollectedHeap* gch = GenCollectedHeap::heap();
 894     _old_gen = gch->old_gen();
 895   }
 896   return _old_gen->promotion_attempt_is_safe(used());
 897 }
 898 
 899 void DefNewGeneration::gc_epilogue(bool full) {
 900   DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
 901 
 902   assert(!GCLocker::is_active(), "We should not be executing here");
 903   // Check if the heap is approaching full after a collection has
 904   // been done.  Generally the young generation is empty at
 905   // a minimum at the end of a collection.  If it is not, then
 906   // the heap is approaching full.
 907   GenCollectedHeap* gch = GenCollectedHeap::heap();
 908   if (full) {
 909     DEBUG_ONLY(seen_incremental_collection_failed = false;)
 910     if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
 911       log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
 912                             GCCause::to_string(gch->gc_cause()));
 913       gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
 914       set_should_allocate_from_space(); // we seem to be running out of space
 915     } else {
 916       log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
 917                             GCCause::to_string(gch->gc_cause()));
 918       gch->clear_incremental_collection_failed(); // We just did a full collection
 919       clear_should_allocate_from_space(); // if set
 920     }
 921   } else {
 922 #ifdef ASSERT
 923     // It is possible that incremental_collection_failed() == true
 924     // here, because an attempted scavenge did not succeed. The policy
 925     // is normally expected to cause a full collection which should
 926     // clear that condition, so we should not be here twice in a row
 927     // with incremental_collection_failed() == true without having done
 928     // a full collection in between.
 929     if (!seen_incremental_collection_failed &&
 930         gch->incremental_collection_failed()) {
 931       log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
 932                             GCCause::to_string(gch->gc_cause()));
 933       seen_incremental_collection_failed = true;
 934     } else if (seen_incremental_collection_failed) {
 935       log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
 936                             GCCause::to_string(gch->gc_cause()));
 937       assert(gch->gc_cause() == GCCause::_scavenge_alot ||
 938              (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
 939              !gch->incremental_collection_failed(),
 940              "Twice in a row");
 941       seen_incremental_collection_failed = false;
 942     }
 943 #endif // ASSERT
 944   }
 945 
 946   if (ZapUnusedHeapArea) {
 947     eden()->check_mangled_unused_area_complete();
 948     from()->check_mangled_unused_area_complete();
 949     to()->check_mangled_unused_area_complete();
 950   }
 951 
 952   if (!CleanChunkPoolAsync) {
 953     Chunk::clean_chunk_pool();
 954   }
 955 
 956   // update the generation and space performance counters
 957   update_counters();
 958   gch->gen_policy()->counters()->update_counters();
 959 }
 960 
 961 void DefNewGeneration::record_spaces_top() {
 962   assert(ZapUnusedHeapArea, "Not mangling unused space");
 963   eden()->set_top_for_allocations();
 964   to()->set_top_for_allocations();
 965   from()->set_top_for_allocations();
 966 }
 967 
 968 void DefNewGeneration::ref_processor_init() {
 969   Generation::ref_processor_init();
 970 }
 971 
 972 
 973 void DefNewGeneration::update_counters() {
 974   if (UsePerfData) {
 975     _eden_counters->update_all();
 976     _from_counters->update_all();
 977     _to_counters->update_all();
 978     _gen_counters->update_all();
 979   }
 980 }
 981 
 982 void DefNewGeneration::verify() {
 983   eden()->verify();
 984   from()->verify();
 985     to()->verify();
 986 }
 987 
 988 void DefNewGeneration::print_on(outputStream* st) const {
 989   Generation::print_on(st);
 990   st->print("  eden");
 991   eden()->print_on(st);
 992   st->print("  from");
 993   from()->print_on(st);
 994   st->print("  to  ");
 995   to()->print_on(st);
 996 }
 997 
 998 
 999 const char* DefNewGeneration::name() const {
1000   return "def new generation";
1001 }
1002 
1003 // Moved from inline file as they are not called inline
1004 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1005   return eden();
1006 }
1007 
1008 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1009   // This is the slow-path allocation for the DefNewGeneration.
1010   // Most allocations are fast-path in compiled code.
1011   // We try to allocate from the eden.  If that works, we are happy.
1012   // Note that since DefNewGeneration supports lock-free allocation, we
1013   // have to use it here, as well.
1014   HeapWord* result = eden()->par_allocate(word_size);
1015   if (result != NULL) {
1016     if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1017       _old_gen->sample_eden_chunk();
1018     }
1019   } else {
1020     // If the eden is full and the last collection bailed out, we are running
1021     // out of heap space, and we try to allocate the from-space, too.
1022     // allocate_from_space can't be inlined because that would introduce a
1023     // circular dependency at compile time.
1024     result = allocate_from_space(word_size);
1025   }
1026   return result;
1027 }
1028 
1029 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1030                                          bool is_tlab) {
1031   HeapWord* res = eden()->par_allocate(word_size);
1032   if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1033     _old_gen->sample_eden_chunk();
1034   }
1035   return res;
1036 }
1037 
1038 size_t DefNewGeneration::tlab_capacity() const {
1039   return eden()->capacity();
1040 }
1041 
1042 size_t DefNewGeneration::tlab_used() const {
1043   return eden()->used();
1044 }
1045 
1046 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1047   return unsafe_max_alloc_nogc();
1048 }
--- EOF ---